JPS62268737A - Power transmission device for 4-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To shorten an oil passage for supplying compressed oil to a clutch and to simplify a hydraulic circuit, by disposing a hydraulic pressure clutch for driving a front wheel in the vicinity of the wall surface of a transmission case provided with a hydraulic pressure pump driven in association with an input shaft. CONSTITUTION:A transmission case 4 has an input shaft, second main speed changing shafts S1, S2, an auxiliary speed changing shaft S3, a PTO shaft S4 and a front wheel drive shaft S5 disposed therein in parallel. Engine power from the input shaft 7 is transmitted to the a first main speed changing shaft S1 through a chain trained around sprockets 16, 18 and a main clutch 17. A front wheel drive shaft 61 is pivotally engaged with the front wheel drive shaft S5 through a bearing 65 and a front wheel drive hydraulic clutch 66 is interposed between both the drive shafts 61, S5. The hydraulic clutch 66 is disposed in the vicinity of the wall surface of the transmission case provided with a gear pump driven in association with the input shaft. Oil discharged from the pump 68 is supplied to a front wheel driving oil passage 67 formed at the shaft center of the front wheel drive shaft 61.

Description

[Detailed description of the invention] L1 upper summer and ■±1 The present invention is a front width drive that can transmit the power of the prime mover to the rear wheels, and also connects the power of the prime mover to the 01f wheels in an intermittent manner as necessary. The present invention relates to a transmission device for a four-wheel drive vehicle equipped with a hydraulic clutch.

1. In the conventional transmission device of this type of four-wheel drive vehicle,
The front wheel drive clutch was located away from the transmission case.

n (゛shi ~U) In the transmission system of the conventional four-wheel drive vehicle described above, when the front wheel drive clutch is a hydraulic clutch, pressure oil is supplied to the hydraulic clutch from a hydraulic pump normally attached to the engine. As oil passages became better, it was necessary to connect them with hydraulic hoses, etc., making the hydraulic circuit more complex and increasing the number of parts, which inevitably increased costs.

. The present invention relates to an improvement of a transmission device for a four-wheel drive vehicle that overcomes the above-mentioned difficulties, and is directed to a transmission device for a four-wheel drive vehicle that transmits the power of a prime mover to the front wheels and rear wheels. The vehicle has independent brakes for each of the left and right rear wheels, and is configured to brake the original fJJ in conjunction with unilateral braking of the left and right rear wheel brakes.
The front wheel drive clutch in the power transmission path from Ii to the front wheels! In the transmission device for a four-wheel drive vehicle, the front wheel drive clutch is configured with a hydraulic wet multi-disc clutch, and the front wheel drive hydraulic clutch is located near a wall surface of a transmission case where a hydraulic pump is disposed. With this arrangement, the hydraulic path from the hydraulic pump to the front wheel drive hydraulic clutch can be shortened.

Point JLJ Hereinafter, a description will be given of an embodiment shown in FIGS. 1 to 8 in which the present invention is applied to an agricultural tractor.

The agricultural tractor is equipped with front wheels 1 and rear wheels 2 at the front and rear, an engine 3 is mounted on the front part of the vehicle body, and a multi-stage gear transmission 1114 is mounted on the rear part of the engine 3.

Further, the output shaft of the engine 3 is connected to a propeller shaft 6 via a reduction gear 5, and the propeller shaft 6 extends rearward from the lower part of the vehicle body and is connected to an input @7 of the multi-gear transmission 4.

Further, the multi-stage gear transmission 4 is fixed to a vehicle body frame 8, a part of which is partially shown, and the engine power input to the input shaft 7 is appropriately shifted through the multi-stage gear transmission 14, and then Rear axle 9, P through differential that is not
The power is output to the TO axis (power take-off shaft) S4 and the front wheel drive shaft S5, the PTo axis S4 transmits power to a working machine such as a rotary working machine (not shown) connected to the rear of the tractor, and the front wheel drive shaft S5 transmits power to the front wheel drive shaft S5. Power is transmitted to the front wheels 1 via a drive propeller shaft 10.

Furthermore, a hydraulic cylinder 11 is attached to the rear of the vehicle body frame 8, and is adapted to raise and lower the working machine up and down via a lift arm 12, and the tractor is equipped with a seat 13 and a handle 14.

Details of the multi-stage gear shift 8!14 are shown in FIG. 2, and as shown, the input shaft 7, the first main shift shaft S1,';
The two main transmission shafts S2, auxiliary transmission shafts S3, PTO shafts S4, and front wheel drive shafts S5 are arranged parallel to each other, and as is clear from FIG. 3, these axes are arranged along one plane. For example, the first main transmission shaft S1 and the second main transmission shaft S
2 are arranged side by side on the left and right at approximately the same height, and the sub-shift shaft S
3 and the front wheel drive shaft S5 are also at approximately the same height as the first main transmission @S.
1. They are arranged side by side slightly to the lower left of the second main transmission shaft S2, and PTO@S4 is arranged at the uppermost position.

Further, the input #A7 connected to the propeller shaft 6 is rotatably supported by the multi-stage gear transmission 4 and the clutch housing 15 fixed thereto via a bearing.
A sprocket 16 is fixed to this input shaft 7, and the input shaft 7 transmits engine power to a sprocket 18 provided on a main clutch 11 of a hot type multi-disc type via a chain.

Roughly, the main clutch 17 is a clutch shaft 2 that is pivotally supported to the mission case of the multi-gear transmission 4 via a ball bearing 19.
0, and the sprocket 18 has this clutch shaft 20
The sprocket 18 is relatively rotatably supported via a needle bearing 21, and a bottomed cylindrical drive member 23 is attached to the sprocket 18 via a spring member 22 to absorb the impact when the clutch is connected.
is fixed to the drive member 23, and a plurality of drive clutch plates 24 are received on the inner peripheral surface of the drive member 23 via splines so as to be displaceable in the axial direction.

Furthermore, a driven member 25 in the shape of a cylinder with a bottom is integrally fixed to the clutch shaft 20. A plurality of driven clutch plates 26 are received on the outer circumferential surface of the driven member 25 via splines so as to be displaceable in the axial direction, and these driven clutch plates 26 and the driving clutch plates 24 are arranged alternately. The disc-shaped pressure contact plates 27, which are arranged and have approximately the same diameter as the flange 25a provided at the end of the driven member 25, rotate integrally with the driven member 25 and can be relatively displaced in the axial direction. It is set in.

The press plate 27 also has a post 28 that protrudes through a hole provided in the bottom wall of the driven member 25. A lifter plate 29 is fixed to the end surface of the boss 28, and the lifter plate 29 and the driven member A coil spring 30 is sandwiched between the bottom wall surface of the member 25 and the direction in which the flange 25a of the driven member 25 and the pressure plate 21 are brought closer together, that is, the drive clutch plate 24 and the driven clutch plate 26 A biasing force is applied in the direction of crimping the two.

Roughly, the lifter plate 29 is received from behind by an actuating piece 32 via a ball bearing 31, and this actuating piece 3
2 along the clutch shaft 20 against the coil spring 30, the pressure contact plate 21 moves away from the flange 25a of the driven member 25, and the drive clutch plate 24 and the driven member 25 are moved away from each other. Drive clutch plate 2
6 is released. That is, the main clutch 17
becomes detached.

Furthermore, a gear G13 is integrally formed at the end of the clutch shaft 20 that protrudes into the multi-gear transmission 4, and an end of the first main transmission shaft S1 is coaxially connected to the end, and a needle bearing is provided at the end. The first main transmission shaft S1 is supported in a relatively rotatable manner via a ball bearing 35 at the other end and an intermediate portion thereof.
．． 35... and extends back and forth within the multi-stage gear transmission 4.

Next, a second main transmission shaft S2 is arranged adjacent to and parallel to the first main transmission shaft S1, and this second main transmission shaft S2 is connected to the mission case front wall 80 of the multi-stage gear transmission 4 and the multi-stage gear transmission A ball bearing 37.3 is mounted on the bearing wall 36 provided on the machine 4, respectively.
8 and is rotatably supported.

A gear G23 that constantly meshes with the gear G13 of the clutch shaft 20 is fixed to the front end of the second main transmission shaft S2,
Gear G 1 and gear G 23 have the same diameter, so that when the main clutch 11 is engaged, the second main transmission shaft S 2 moves from the clutch shaft 20 to gear G 13 . It is rotationally driven at the same rotational speed as the clutch shaft 20 via G23.

Further, a low speed (first speed) speed change clutch 39 is provided at the other end of the second main speed change shaft S2, that is, the end that penetrates the bearing wall 36 and protrudes rearward, in close proximity to the bearing wall 36. Clutch 39, as shown in more detail in FIG.
A cylindrical drive member 40 with a bottom fixed to the second main transmission shaft S2
A ring-shaped receiver plate 41 is fixed to the open end surface of the drive member 40.

A plurality of drive clutch plates 42 similar to the drive clutch plates 24 in the main clutch 17 are received on the inner circumferential surface of the receiver so as to be displaceable in the axial direction, facing the plate 41 via splines.

Further, the drive member 40 has a peripheral wall portion 40a and a bottom wall portion 40.
b and a boss portion 40c attached to the second main transmission shaft S2.
An annular cylinder portion 43 is formed, and an actuating member 44 is fitted into the cylinder portion 43 in the shape of a piston, and is biased toward the bottom wall portion 40b by a spring 45, so that the actuating member 44 and the driving member 40 are An oil passage 46 is provided in the boss part 40c so that hydraulic pressure can be supplied between it and the bottom wall part 40b. It communicates with a clutch oil passage 47 through which oil is supplied.

Furthermore, a low speed change drive gear G21 is rotatably mounted on the second main speed change shaft S2 adjacent to the drive member 40 via a needle bearing 48, and the driven member 49 of the low speed hydraulic speed change clutch 39 is attached to the gear G21. is integrally formed and enters into the cylinder portion 43 of the drive member 40. A plurality of driven clutch plates 50 are received on the outer circumferential surface of the driven member 49 via splines so as to be displaceable in the axial direction, and these driven clutch plates 50 and the driving clutch plates 42 are arranged alternately. Arranged.

Since the low-speed hydraulic shift clutch 39 is constructed as described above, oil flows into the clutch oil passage 4 during the shift operation.
7. When oil is supplied behind the actuating member 4A through the oil passage 46, the actuating member 44 is pushed forward by the hydraulic pressure, and the driving clutch plate 42 and the driven clutch plate 50 are pressed against each other, so that the second main shift shaft S2 The rotation of the drive member 40. Drive clutch plate 42, driven clutch plate 50, driven member 4
9 to the gear G21, and the gear G21 rotates integrally with the second main transmission shaft S2. Since the gear G21 meshes with the low-speed variable driven gear "11" fixed to the first main transmission shaft S1, the engagement of the low-speed hydraulic transmission clutch 39 causes the first main transmission shaft S1 to shift between the gear G and the gear G11. When the low-speed hydraulic transmission clutch 39 is disengaged, the gear G21 is rotated at a reduction ratio corresponding to the number of teeth.
11 from the first main transmission shaft S1 side, and rotates freely around the second main transmission shaft S2.

Further, a 2-speed hydraulic transmission clutch 51 and a 3-speed hydraulic transmission clutch 52 are provided at the front end of the first main transmission shaft S1. These hydraulic speed change clutches 51, 52 are all constructed in exactly the same way as the low speed hydraulic speed change clutch 39. However, the drive members 51a and 52b of these clutches are integrated, and each cylinder portion is formed back to back on this integrated drive member.

Furthermore, the driven member 49a of the second-speed hydraulic transmission clutch 51 is integral with a tooth 1'aG12 rotatably mounted on the first main transmission shaft S1 via a needle bearing 53,
2 meshes with the gear G22 fixed to the second main transmission shaft S2, and when the 2nd speed hydraulic transmission clutch 51 engages in the manner described for the low speed hydraulic transmission clutch 39,
The rotation of the second main transmission shaft S2 is the gear G tooth! 1G12, the driven member 49a, and the driving member Sta to the first main transmission shaft S1, and the first main transmission shaft S1 rotates at a transmission ratio according to the number of teeth of the gear G22 and the gear G12. Strictly speaking, regarding the clutches 51 and 52, the driving member 51a1 and the driving member 52b are the driven members, and the driven member 49 is the driven member.
a, the driven member 49b is the drive side member, and each part is named like this to match the name of the low-speed hydraulic speed change clutch 39.

Furthermore, the driven member 49 of the third-speed hydraulic transmission clutch 52
b is formed integrally with the gear G13, and when the clutch 52 is engaged, the rotation of the clutch shaft 20 is caused by the gear G13.
, is transmitted to the first main transmission shaft S1 through the driven member 49b1 and the driving member 52b, and the first main transmission shaft S1 has a rotational speed equal to that of the second main transmission shaft S2, and in the opposite direction to the second main transmission shaft S2. Rotationally driven.

Furthermore, a 4-speed/reverse hydraulic transmission clutch 54 having the same configuration as each of the hydraulic transmission clutches 39, 51, and 52 is provided at the intermediate portion of the second main transmission shaft S2, with its driving member attached to the second main transmission shaft S2. The driven member of the clutch 54 is a second
It is formed integrally with a gear G24 rotatably mounted on the main transmission shaft S2 via a needle bearing 55, and the gear G24 is also integral with a reverse drive gear G2R.

On the other hand, the first main transmission shaft S1 has a gear G that meshes with the gear G24.
14 is rotatably mounted via a needle bearing 56, and a reverse driven gear G1° that engages with the gear 02R via an idle gear 57 (FIG. 3) is attached to the needle bearing 5.
It is rotatably mounted via 8.

Further, the gear G14 and the gear G1R have boss portions facing each other and having the same diameter, and a connecting member 59 having the same diameter and annular shape is provided between these boss portions. Both gears 014. Splines are carved on the outer circumferential surface of each of the boss portions of the GlR and on the outer circumferential surface of the connecting member 59, respectively, and the splines fit into the splines to move back and forth on both the boss portions and the connecting member 59! An annular selector 60 is provided.

When the selector 60 is in a position straddling the gear G14 and the connecting member 59, the gear G14 is connected to the first main transmission shaft S1 via the connecting member 59, and the selector 60 is in a position straddling the gear G1R and the connecting member 59. Teeth when in! T! When G1R is connected to the first main transmission shaft S1 and the selector 60 is on the connecting member 59, the gear G
Both the gear G1R and the gear G1R can freely rotate with respect to the first main transmission shaft S1.

Therefore, when the selector 60 is moved to the gear G, 4 side and the clutch 54 is engaged, the rotation of the second main shift 'Nl52 is changed between the clutch 54, the gear G1, the gear G14, and the selector.
60, the speed is increased via the connecting member 59 and the first main shift IP*
131. When the selector 60 is moved to the gear IIG1R side and the clutch 54 is engaged, the rotation of the second main shift @S2 is changed to the clutch 54, the gear G24, and the gear 9.
The signal is transmitted to the first main transmission shaft S1 via the idle gear 57, the gear G1R, the selector 2R'60, and the connecting member 59, and the first main transmission shaft S1 is rotationally driven in the reverse direction.

As can be seen from the above, engine power is transmitted to the second main transmission shaft S2 via the main clutch 11, and by selectively engaging the hydraulic transmission clutches 39, 51, and 54, the engine power is transmitted to the second main transmission shaft S2 at a predetermined transmission ratio. It is transmitted from the second main shift shaft S2 to the first main shift shaft S1. Furthermore, when the 3rd speed hydraulic transmission clutch 52 is engaged, power is directly transmitted from the clutch shaft 20 to the first main transmission shaft S1 via the gear G13, and when the 4th speed and reverse hydraulic transmission clutch 54 is engaged, power is transmitted directly from the clutch shaft 20 to the first main transmission shaft S1 via the gear G13. , gear G211,
The first main transmission shaft S1 can also be driven in the reverse direction from the second main transmission shaft S2 at a predetermined reduction ratio through the idle tooth 1157 and the gear G1R.
1 is given a speed change rotation of four forward speeds and one reverse speed.

The rotation of the first main transmission shaft S1 is further configured to be transmitted to the auxiliary transmission shaft S3 at three speed reduction ratios. In other words, 3 teeth "G61.62.63 on the first main shift @S1
is fixed, the gear G61 meshes with the gear G rotatably mounted on the sub-transmission shaft S3 via the needle shaft in the same manner as described above, and the gear "63 is similarly rotatably mounted on the sub-transmission shaft S3. The gear G6□ meshes with the boss portion of the gear G31, the n1 shift shaft S3, and the gear G33 by a spline mechanism similar to that of the selector 60.
It is designed so that it can mesh with a gear G32 that can slide back and forth across the boss portion.

Therefore, when the gear G32 is meshing with the gear G62 as shown in the figure, the rotation of the first main transmission shaft S1 is decelerated and transmitted to the auxiliary transmission 'N153 through the gear G and the gear G32, and the gear G is meshed with the tooth rIG62. Get away from it [G31
When the first main transmission shaft S1 is moved to a position straddling the sub transmission shaft S3, the rotation of the first main transmission shaft S1 is transmitted to the n1 transmission shaft S3 at an increased speed through the gear G61 and the gear G31. When the gear G3□ moves to the gear G33 side, the rotation of the first main transmission shaft S1 is decelerated and transmitted to the auxiliary transmission shaft S3 through the gear G and the gear G33. 01
The transmission shaft S3 is connected to the rear axle 9 (FIG. 1) via an operating gear and a final reduction gear (not shown), thus providing 12 forward speeds and 3 reverse speeds.

As can be seen from FIG. 3, the front wheel drive shaft S5 is arranged adjacent to the auxiliary transmission shaft S3, and has a gear G fixed to the n1 transmission shaft S3.
34 meshes with a tooth IhG5 integral with the front wheel drive input shaft 61.

PTO shaft S shaft rotation 43As explained in Fig. 43, it is arranged at the uppermost position in the multi-stage gear transmission 4, and its rear end protrudes outward from the multi-stage gear transmission 4 and is connected to the drive system of the work machine. It is now possible to do so.

In other words, this PTO shaft S axis rotation 43 gears "41, G4
2. Gear G43 is rotatably mounted via a needle bearing in the same way as the gears described above, and gear G41 is connected to the second main transmission shaft S.
A gear G22.2 which is integral with the gear G22 fixed to the gear G22 and has a smaller diameter than the gear G2. The gear G41 is always in mesh with the PTO shaft S, and the gear G41 is rotated out of the PTO shaft S by the selector 62.

In addition, the gear G42 and the gear ``43'' are always in mesh with the gear IJIG2□ and the gear 023, respectively, and these gears G42 and ``43 are selectively connected to the PTO@S4 by moving the selector 64 back and forth. can do.

With this configuration, the PTO shaft S shaft rotates 4 gears G SG
Alternatively, by connecting either G43 to the PTo shaft 54, it can be driven by engine power via the second main transmission shaft S2 at three rotational speeds: low, medium, and high.

Further, the front drive shaft 61 is rotatably fitted to the front wheel drive shaft $5 via a needle bearing 65.
A front wheel drive hydraulic clutch 66 having a structure similar to the low speed hydraulic transmission clutch 39 shown in FIG. 4 is interposed between the front wheel drive shaft S5 and the front wheel drive shaft S5. Only when the power is supplied, the front wheel drive hydraulic clutch 66 is engaged and power is transmitted from the front drive shaft 61 to the front drive shaft S5.

Furthermore, the multi-stage gear transmission 4 has the above-mentioned shafts 7, 20°Sl.
...In addition to S5, a pump shaft SP is arranged roughly parallel to each of the above-mentioned axes, and a gear G is fixed to this pump shaft SP, and the gear G is fixed to the input shaft P7. It is constantly meshing with the tooth iG7. The front end of the pump shaft SP is connected to an oil pump 68, for example, a gear pump, disposed in the multi-gear transmission 4.
The pump 68 is driven by a pump shaft SP.

Furthermore, the discharge passage 69 and the return passage 70.71 of the oil pump 68 are connected to the 6-bot 3-position electromagnetic switching valve 72 via the 6-bot 3-position electromagnetic switching valve 72. Oil passages 73, 7
The oil passages 73 and 74 are respectively connected to the switching valves 7 and 7.
6 to oil passages 77 and 78, and the oil passage 75
．． 77 and 78 are combined into one oil passage 79, and this oil passage 79 is a multi-stage gear shifting! 14 mission case front wall 80
The end of the oil passage 79 is connected to a connecting joint 81.
The front wheel drive hydraulic clutch 66 is connected to the front wheel drive hydraulic clutch 66 via a hydraulic hose 82 and a front wheel drive oil passage 67.

Therefore, the switching valve 76 is a right switching valve 76R and a left switching valve 76L.
Therefore, the right brake pedal 1s3R and the left brake pedal 83L are connected to the right brake pedal 83R and the left brake pedal 83L, which are arranged on the front floor of the vehicle body frame 8. In this case, the oil passage 73 and the oil passage 77 are communicated with each other,
Conversely, the right brake pedal 83R and the left brake pedal 8
When only one of the 3L is depressed, the oil passage 73 and the oil passage 77 are spaced apart by 'lX1g1.

In addition, a speed detector 84 is attached to the front drive shaft 61, and when the front drive shaft 61 exceeds a predetermined rotational speed, an output from the speed detector 84 causes 6 points and 3rd position W1 electromagnetic switching. Valve 72 is adapted to assume the C position.

Furthermore, the discharge passage 69 of the oil pump 68 passes through a suitable passage provided along the wall of the mission case of the multi-stage gear transmission 8!4, and then passes through the respective first main transmission shafts S1. 2nd main transmission shaft S2...Front wheel drive shaft 85 etc. are fed under pressure to a lubricant passage 85 provided in the axial direction at the center, and through each oil passage branched from these f71 slip passages 85, to each of the above-mentioned needles. It is designed to lubricate the bearing part of the bearing.

The right brake pedal 83R and the left brake pedal 83L are respectively connected to left and right brakes that are not attached to the rear wheels 9R, 9L, and the brake pedals 83R,
When you step on 83L, the left and right brakes operate accordingly.

Since the embodiment shown in FIGS. 1 to 8 is constructed as described above, the 6-bottom 3-position electromagnetic switching valve 12 is set to the A position in FIG. 6, and the brake pedal 83R and the brake pedal 83L are not depressed or are depressed at the same time, the pressure oil from the oil pump 68 is discharged through the discharge passage 69.6 port 3 position 1!1 switching valve 12. Oil passage 73. The oil is supplied to the front wheel drive hydraulic clutch 66 through the switching valve 76 and oil passages 77, 79, the front wheel drive hydraulic clutch 66 is engaged, the front drive shaft 61 is integrally connected to the front drive shaft S5, and the rear wheel drive shaft 61 is integrally connected to the front drive shaft S5. Not only the front wheels 2 but also the front wheels 1 are driven.

In addition, when the 6-bottom 3rd position ffi electromagnetic switching valve 72 is set to the A position and one-wheel braking is performed by depressing either the brake pedal 83R or the brake pedal 831, the oil passage 73 and the oil passage 77 Since the communication between the oil passage 78 and the oil passage 74 is interrupted, the pressure oil in the front wheel drive hydraulic clutch 66 is transferred to the oil passage 79.78 degree switching valve 76,
The oil is discharged to the drain via the oil passage 74, 6-bot 3rd position @ electromagnetic switching valve 72, and the return passage 70, the engagement of the front wheel drive hydraulic clutch 66 is released, and the front wheel drive shaft 61 and the front wheel drive shaft S5 are The connection is cut off, @wheel 1 is not driven, and only rear wheel 2 is driven. Then, by depressing either the brake pedal 83R or the brake pedal 831, the rear wheel 2 is braked on one side and a turn is performed.

Next, when the 6-point, 3-position electromagnetic switching valve 72 is set to the 8th position as shown in FIG. Since pressure oil is not supplied to the hydraulic clutch 66, the front wheel drive hydraulic clutch 66 is not engaged and the front wheel drive shaft S5
is cut off from the front axle drive @61, so the switching valve 76R
, 76L, only the rear wheels 2 are driven in two-wheel drive.

Furthermore, when the tractor exceeds a predetermined running speed and the speed detector 84 operates, the 6-boat 3-position electromagnetic switching valve 72 is switched to the C position in FIG. 8, and the switching valves 76R, 7
Regardless of whether or not the wheel pump 68 is depressed, the pressure oil from the wheel pump 68 flows through the discharge passage 69.6 and the 3-position electromagnetic switching valve 72.6. The oil is constantly supplied to the front wheel drive hydraulic clutch 66 through the oil passages 75 and 79, the front wheel drive hydraulic clutch 6G is in an engaged state, and the front wheel drive shaft S5 is connected to the front axle drive shaft 61, resulting in a four-wheel rfA dynamic state. .

In the embodiments shown in FIGS. 1 to 8, when the vehicle is running at high speed, the four-wheel drive mode is automatically activated, or when the vehicle is running at a low speed, only the rear wheels 2 are in the two-wheel drive mode and the rear wheels 2 are in the four-wheel drive mode. Even if the vehicle is in four-wheel drive mode, if one wheel brake is applied, the vehicle is automatically switched to two-wheel drive mode, allowing for corner turns with a small turning radius.

Further, since the oil passage 79 is formed in the front wall 80 of the transmission case, the number of parts in the hydraulic circuit is reduced, assembly processing is simplified, and costs can be reduced.

In the embodiment shown in FIGS. 1 to 8, the front wheel drive hydraulic clutch 66 is configured to be supplied with pressure oil and the front wheel drive hydraulic clutch 6G is in a disconnected state, but FIG. As shown in FIG. 9, a front wheel drive hydraulic clutch 86 is engaged when no pressure oil is supplied, and is disconnected when pressure oil is supplied, and a hydraulic circuit is configured as shown in FIG. Good too.

In FIG. 9, the coil of the 2-point, 2-position electromagnetic switching valve 87 is connected to the speed detector 84, and when the tractor is steered to a predetermined running speed, the 2-point, 2-position electromagnetic switching valve 87 is connected to the 2-point, 2-position electromagnetic switching valve 87 using the output from the speed detector 38. When the 2-position Ti magnetic switching valve 87 is operated, the oil passage of the oil bong 768 is cut off, and the front wheel drive shaft S5 becomes front axle drive regardless of the depression operation of the brake pedal 83! 'J
It is always connected to l@61 and becomes a four-wheel drive state.

Moreover, when the 2-bot-1-2-position manual switching valve 88 is switched from the state shown in FIG.
9 is activated to block the passage, and the front wheel drive shaft $5 is cut off from the front drive shaft 61, completely unrelated to the traveling speed or the depression operation of the brake pedal 83, resulting in a two-wheel drive state.

Thus, in the present invention, the hydraulic pump can be communicated with the front wheel drive hydraulic clutch via the oil passage formed in the front wall of the transmission case, and the oil passage can be shortened. Moreover, it is possible to simplify the hydraulic circuit and reduce the number of parts, thereby reducing costs.

[Brief explanation of the drawing]

Fig. 1 is a side view of an agricultural tractor to which the present invention is applied, Fig. 2 is a sectional view of the same tractor without showing the power transmission device, and Fig. 3 is a drawing showing the actual arrangement of each shaft of the power transmission device. FIGS. 4 and 5 are partially enlarged views of FIG. 2, FIGS. 6 to 8 are detailed views of the hydraulic circuit, and FIG. The figure is a hydraulic circuit diagram of another embodiment of the present invention. 1...front wheel, 2...rear wheel, 3...engine,
4...Multi-stage gear transmission, 5...Reduction gear, 6...
Propeller shaft, 7... Input shaft, 8... Vehicle body frame, 9... (Vine axle, 10... Front wheel drive propeller shaft, 11... Hydraulic cylinder, 12... Lift arm, 13...・・Seat, 14・・Steering wheel, 15・
...Clutch housing, 16...Sprocket, 1
7... Main clutch, 18... Sprocket, 19...
... Ball bearing, 20 ... Clutch shaft, 21 ... Needle bearing, 22 ... Spring member, 23 ... Drive member, 2
4... Drive clutch plate, 25... Driven member, 26
... Driven clutch plate, 27... Pressure contact plate, 28...
・Boss, 29... Lifter plate, 30... Coil spring, 31... Ball bearing, 32... Operating piece, 33.
... Lever, 34 ... Needle bearing, 35 ... Ball bearing, 36 ... Bearing wall, 37° 38 ... Ball bearing, 39
...Low speed hydraulic transmission clutch, 40...Drive member, 4
1...Buffer plate, 42...Drive clutch plate, 43...
- Cylinder part, 44... Operating member, 45... Spring, 46... Oil passage, 47... Clutch oil passage,
48... Needle bearing, 49... Driven member, 50
. . . Driven clutch plate, 51 . . . 2-speed hydraulic transmission clutch, 52 . . . 3-speed hydraulic transmission clutch, 53 . . . needle bearing, 54 . . . 4-speed and reverse hydraulic transmission clutch,
55.56... Needle bearing, 57... Idle gear, 58... Needle bearing, 59... Connection member, 6
0... Selector, 61... Front axle drive shaft, 62...
・Selector, 63...Boss, 64...Selector, 65...Needle 'T'1l15, 66...Front wheel drive hydraulic clutch, 67...Front wheel drive oil path, 68...
・Oil pump, 69...Discharge passage, 70.71...
・Return passage, 72... 6-bottom 3rd position @ solenoid switching valve, 73° 74, 75... Oil passage, 76... switching valve,
77, 78.79...Oil passage, 80...Mission case front wall, 81...Connection joint, 82...Hydraulic hose 82.83...Brake pedal, 84...
Speed detector, 85... Lubrication passage, 86... Front wheel drive hydraulic clutch, 87... 2-bottom 2-position electromagnetic switching valve,
88...2-bottom 2-position manual switching valve, 89...2-bottom 2-position electromagnetic switching valve, SL...1st main shift shaft, SP...2nd main shift shaft, S
3... Sub-transmission shaft, S4... PTO axis, S5... Front wheel drive shaft, G... Gear, SP... Pump shaft.

Claims (1)

[Scope of Claims] 1. A vehicle such as a four-wheel drive agricultural tractor that transmits the power of a prime mover to front wheels and rear wheels, wherein the left and right rear wheels each have independent brakes, and In a transmission device for a four-wheel drive vehicle, the front wheel drive clutch in a power transmission path from the prime mover to the front wheels is disconnected in conjunction with one-sided braking of the brake, the front wheel drive clutch being a hydraulic wet multi-disc clutch. A transmission device for a four-wheel drive vehicle, characterized in that the front wheel drive hydraulic clutch is arranged near a wall surface of a mission case in which a hydraulic pump is disposed. 2. The front wheel drive hydraulic clutch is provided at the front lower part of the transmission case, and the oil passage in the front wall of the transmission case leading to the front wheel drive hydraulic clutch is communicated with the hydraulic clutch provided on the transmission shaft. A transmission device for a four-wheel drive vehicle according to claim 1. 3. The first aspect of the present invention is characterized in that the front wheel drive hydraulic clutch is disengaged only when the vehicle speed is below a certain constant and the left and right rear wheel brakes are braked on one side.
A transmission device for a four-wheel drive vehicle as described in 2.