JPH11180174A - Front wheel transmission system for four wheel drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain four wheel drive state irrespective of trouble occurred in a hydraulic system or the like by engaging a first hydraulic clutch that can drive front wheels at a speed substantially equal to the speed for driving rear wheels by means of a hydraulic force supplied to one hydraulic chamber and an biasing force of spring means, and by disengaging the first hydraulic clutch by means of a hydraulic force supplied to the other hydraulic chamber. SOLUTION: A piston 46 is disposed in a clutch case 45 for compressing friction plates 43, 44, which is accommodated in a cylinder of double acting type. This cylinder has a first hydraulic chamber C1 forward of the piston 46 and a second hydraulic chamber C2 rearward of the piston 46. A spring 47 that biases the piston 46 toward compression direction is accommodated within the first hydraulic chamber C1 that brings the piston 46 into press contact with the friction plates 43, 44. Hydraulic passages 48, 49 pierced through a front output shaft 40 and the hydraulic chambers C1, C2 provided forward and rearward of the piston 46 are communicated with each other so as to constitute a first hydraulic clutch. By this, four wheel drive state can be maintained by the biasing force of the spring 47 in spite of the trouble occurred in the hydraulic system or an electromagnetic valve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front-wheel transmission for switching between front-wheel drive and standard-drive in which front and rear wheels have substantially the same speed in a four-wheel drive vehicle. Regarding the configuration.

[0002]

2. Description of the Related Art Conventionally, when tilling work is performed by a four-wheel drive agricultural tractor, when the front wheel and the rear wheel make a sharp turn at substantially the same speed when rotating at the edge of the field, the rear wheel inside the turning direction is centered. Therefore, the rotation of the front wheels cannot follow the rotation of the body, and the rotation is delayed, thereby damaging the field. Therefore,
In recent years, at the time of work, when turning, the number of rotations of the front wheels has been increased to follow the turning of the body, so as not to damage the field. The front wheel speed increasing mechanism is configured to mechanically turn on the speed increasing clutch by the turning force of the steering wheel when the steering wheel of the driver's seat is turned by more than a set angle, or a sensor in the steering drive path to the steering wheel or the front wheel. And the actuator is actuated by detecting the angle to turn on the speed-increasing clutch when it rotates by more than the set angle.

[0003]

However, if the configuration is such that the front wheel speed increase and the same speed drive are mechanically switched, the operation of the steering wheel requires a large operation force, and labor is required at the time of turning. When the turning angle is detected by the sensor and the clutch is turned on, the clutch uses two hydraulic clutches that are easily controlled.When the hydraulic clutch is turned on, the hydraulic pressure is used. When the "off" operation is performed, the operation is performed by urging the spring by draining the pressure oil. However, when a trouble occurs in the electric system or the hydraulic system, the two hydraulic clutches are disengaged, so that a two-wheel drive state occurs, and there is a disadvantage that the traction performance is reduced. Also,
A certain amount of clutch capacity is required to transmit the driving force to the front wheels, and the hydraulic clutch is relatively large, and its installation space tends to be large.

[0004]

Means for Solving the Problems The present invention is configured as follows to solve the above-mentioned problems. That is, the front wheel drive system includes a first hydraulic clutch capable of driving the front wheels at a speed substantially equal to the rear wheel drive speed and a second hydraulic clutch capable of driving the front wheels at a speed greater than the rear wheel drive speed. In the device, the "on" operation of the first hydraulic clutch is performed by the hydraulic pressure supplied to one of the oil chambers and the biasing force of the spring means, while the "off" operation of the first hydraulic clutch is performed by the other hydraulic device. This is configured to be performed by the oil pressure supplied into the room.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of an embodiment in which the front wheel transmission of the present invention is applied to a tractor as a four-wheel drive vehicle will be described below. 1 is an overall side view of a tractor on which the front wheel transmission of the present invention is mounted, FIG. 2 is a skeleton diagram showing a power transmission mechanism in a transmission case, FIG. 3 is a side sectional view of the front wheel transmission, and FIG. FIG. 5, FIG. 5 is a front sectional view showing a piping configuration between the front wheel transmission and the electromagnetic valve, FIG. 6 is a perspective view of an upper portion of a transmission case showing an arrangement of the electromagnetic valve,
7 is a hydraulic circuit diagram of the front wheel transmission, FIG. 8 is a hydraulic circuit diagram showing another embodiment of the same, and FIG. 9 is an electric circuit diagram of the front wheel transmission.

Referring to FIG. 1, the entire configuration of a tractor having the front wheel transmission according to the present invention will be described. An engine 2 is housed in a hood 1 on the front of the fuselage, and power is input from the engine 2 to an input shaft 20 in a transmission case 5 via a flywheel 4 (FIG. 2) with a damper joint in a clutch housing 3. doing. A dashboard 6 is provided at the rear of the hood 1, and a handle 7 is arranged on the dashboard 6. A seat 8 is arranged on the transmission case 5 behind the handle 7, and a main shift lever 9, an elevating lever of a work implement mounting device, and the like are arranged on the side of the seat 8. Front frame 1 for supporting the engine 2
A front wheel 12 is supported by a front axle case 11 via a front axle case 11, and a rear wheel 14 is supported by a rear axle case 13 protruding from both sides of the transmission case 5.
A hydraulic lift case 15a of the work implement mounting device 15 is disposed on the rear upper surface of the transmission case 5.

Next, the configuration inside the transmission case 5 will be described with reference to FIG. Power is transmitted to a rear portion of the input shaft 20 supported by the transmission case 5 via a PTO transmission shaft 21, a PTO clutch 22, and a PTO transmission 23 to a rear PTO shaft 24 projecting rearward from the rear surface of the transmission case 5. .

A hollow traveling input shaft 25 is externally fitted to the input shaft 20 and connected so that power from an engine is transmitted through the damper joint. A power reverser 26 is arranged on the rear,
In the case of reverse rotation drive, the reverse rotation clutch 2 of the power reverser 26
Power is transmitted to gear 27 from 6R, and counter shaft 2
8. The power is transmitted to the hollow transmission shaft 30 via the respective gears on the reverse rotation shaft 29. In the case of forward rotation drive, the power is transmitted directly to the speed change transmission shaft 30 from the forward rotation clutch 26F. A plurality of fixed gears are provided on the speed change transmission shaft 30, and the plurality of fixed gears are respectively meshed with a plurality of loosely fitted gears loosely fitted on the main speed change shaft 31. A mesh-type main transmission 19 is configured to enable four-speed shifting. Then, the power transmitted to the main transmission shaft 31 is shifted by an auxiliary transmission device 32 disposed at the rear thereof to transmit the power to an output shaft 35, and transmitted from a pinion 33 at the rear end of the output shaft 35 via a differential device 34. The rear wheel 14 is driven.

Power is transmitted from a power take-out gear 36 fixed on the output shaft 35 to a front wheel transmission 39 of the present invention via a gear 38 loosely fitted on an intermediate shaft 37. Two-wheel drive for driving only the rear wheel 14 by the front wheel transmission 39, four-wheel same-speed drive for driving the front wheel 12 and the rear wheel 14 at substantially the same drive speed, or driving the front wheel 12 for the rear wheel 14 It is possible to switch to front wheel speed-up driving that drives at a speed greater than the speed. In the case of four-wheel equal-speed drive and front-wheel speed-increasing drive, power is transmitted from the front axle case 11 to the front wheels 12 from the front wheel output shaft 40 via a universal joint.

The structure of the front wheel transmission 39 of the present invention is shown in FIG.
As shown in FIG. 4, a transmission case 41 is fixed to the lower surface of the transmission case 5, and an intermediate shaft 37 is pivotally supported on the upper portion of the transmission case 41 and faces the transmission case 5. The front surface of the transmission case 41 is closed by a lid 59, and the front wheel output shaft 40 and the counter shaft 56 are supported between the lid 59 and the transmission case 41 in a parallel and rotatable manner in the front-rear direction. . A double gear 38 is rotatably supported on the intermediate shaft 37 via a bearing, and one gear 38a of the double gear 38 is meshed with a power take-out gear 36 fixed on the output shaft 35, and Gear 38b is meshed with a gear 42 loosely fitted on the front wheel output shaft 40. A friction plate 43 is provided on the outer periphery of the boss 42a of the gear 42.
Are fixed on the front wheel output shaft 40, and a friction plate 44 is provided on the cylindrical portion of the clutch case 45 so as to overlap with the friction plate 43.
・ 44 ... are locked.

A piston 46 for pressing the friction plates 43 and 44 is provided in the clutch case 45, and is housed in a double-acting cylinder. This cylinder has a first oil chamber C1 formed in front of the piston 46 and a second oil chamber C2 formed in the rear.
A spring 47 for urging the piston 46 in the press-contact direction is housed in the first oil chamber C1 that presses against the friction plates 43 and 44,
Inside the oil chambers C1 and C2 before and after the piston 46 and the front wheel output shaft 4
The oil passages 48 and 49 formed in the cylinder 0 communicate with each other. Thus, the first hydraulic clutch 16 is configured,
When oil is supplied to the second oil chamber C2, the first hydraulic clutch 16 is operated to "disengage", and when oil is supplied to the first oil chamber C1, the first hydraulic clutch 16 is operated "on" to connect the gear 42 to the front wheel output shaft 40. Engage.

A gear 50 is loosely fitted on the front wheel output shaft 40 on the front side of the clutch case 45, and friction plates 51 are locked on a boss 50a of the gear 50.
Further, friction plates 52, 52,... Are engaged with the cylinder portion of the clutch case 45 so as to overlap with the friction plate 51. Further, a friction plate 51 is provided in the clutch case 45.
A piston 53 for pressing the piston 52 is provided and housed in a single-acting cylinder. The piston 53 is urged by a spring 54 disposed outside the cylinder to a side where the friction plates 51 and 52 are not pressed. Oil chamber C of the cylinder
Reference numeral 3 communicates with an oil passage 55 formed in the shaft center of the front wheel output shaft 40. In this manner, the second hydraulic clutch 17 serving as the front wheel speed increasing clutch is configured. When the oil is supplied to the oil chamber C3, the second hydraulic clutch 17 is operated to “on”, and when the hydraulic oil is released from the oil chamber C3, the second hydraulic clutch 17 is released. The clutch 17 is "disengaged". Further, gears 57 and 58 are fixed to the front and rear on a counter shaft 56 arranged in parallel with the front wheel output shaft 40, and mesh with the gears 42 and 50, respectively. The gear ratio is set so that the peripheral speed ratio of the front wheels 12 is about twice as large as that of the rear wheels 14.

In such a configuration, when pressure oil is supplied to the oil passage 49, the piston 46 slides in the direction of pressing the friction plates 43 and 44 together with the urging force of the spring 47, and the output power is increased. From the shaft 35 to the intermediate shaft 37 and the gears 38a and 38
The power transmitted via the first hydraulic clutch 1
When the “6” is turned on, the front wheel 12 and the rear wheel 14 are transmitted to the front wheel output shaft 40 to be driven at substantially the same speed, so that the four wheels are driven at the same speed. Further, when pressure oil is supplied to the oil passage 48, the piston 46 slides in the direction of releasing the pressure contact of the friction plates 43 and 44 against the spring 47, and the first hydraulic clutch 16 is turned off. Thus, a two-wheel drive state in which only the rear wheel 14 is driven is established.

When pressure oil is supplied to the oil passage 55 in the "disengaged" state of the first hydraulic clutch 16, the piston 53 slides against the urging force of the spring 54 to press the friction plates 51 and 52 against each other. Then, the second hydraulic clutch 17 is engaged, and the power transmitted to the gear 42 is transmitted to the gear 57, the counter shaft 56, the gear 58, the gear 50, and the front wheel output shaft 40, thereby increasing the speed of the front wheel 12 and driving it. The front wheel is in a speed-up state.

Each of the rotary joints for the oil passages 48, 49 and 55 formed at the rear end of the front wheel output shaft 40 has an oil passage disposed outside the transmission case 41 as shown in FIGS. The oil passages 60, 61, 62 are connected to an electromagnetic valve 63 disposed above the hydraulic lift case 15a. The electromagnetic valve 63 is connected to a hydraulic pump 65 via an oil passage 64, and the hydraulic pump 65 is disposed on a hydraulic lift case 15a behind the electromagnetic valve 63, and as shown in FIG. 21 is driven via a gear train. 66 is an electromagnetic valve for operating the PTO clutch 22.

As shown in FIG. 7, a hydraulic circuit for controlling the first clutch 16 and the second clutch 17 branches an oil passage 64 on the discharge side of a hydraulic pump 65 in two directions. The other is connected to the electromagnetic valve 63,
It is connected to the oil supply circuit of the TO drive. Solenoid valve 6
The pressure oil which is selectively introduced into the oil passages 60, 61 and 62 connected to the respective output ports of No. 6 is set by a relief valve 67, and the excess oil exceeding the set pressure is actuated by the relief valve 67 to operate the PTO drive device. Oil is supplied to the oil supply circuit. By switching the electromagnetic valve 63, the first hydraulic clutch 16 and the second hydraulic clutch 17 of the front wheel transmission 39 are actuated, so that two-wheel drive, four-wheel same-speed drive, or four-wheel drive front wheel speed-up drive can be selected. I have to.

The electromagnetic valve 63 uses a three-position switching electromagnetic valve. However, as shown in FIG. 8, the two-position switching electromagnetic valves 70 and 7 are used instead of the electromagnetic valve 63.
1 are connected in series and the electromagnetic valve 70 is switched to enable switching between four-wheel constant-speed driving and front-wheel speed-up driving of four-wheel driving. By switching the electromagnetic valve 71, two-wheel driving and four-wheel constant-speed driving are performed. Can be switched.

The primary side and the secondary side of the relief valve 67 are connected to an electromagnetic valve 66, and one of two output ports of the electromagnetic valve 66 is connected to the PTO clutch 22 and the other is a PTO brake 69. It is connected to the. The operating pressure of the PTO clutch 22 is defined by a delay relief valve 68, and the secondary side of the delay relief valve 68 is connected to a clutch lubrication circuit 77. The PTO brake 69 presses the housing of the PTO clutch 22 by the urging force of the spring to perform braking, and sets the electromagnetic valve 66 to the OFF position shown in FIG.
When the O-clutch 22 is not operated, the rear PTO shaft 2
When the electromagnetic valve 66 is shifted leftward from the position shown in the figure by turning the PTO lever or operating the clutch pedal (not shown), the PTO brake 6 is braked.
After the hydraulic oil is supplied to the oil chamber 9 and the braking is released, the PTO is slightly delayed by the operation of the delay relief valve 68.
The clutch 22 is set to "on".

Next, the control circuit of the electromagnetic valve 63 is shown in FIG.
A more detailed description will be given. A power supply circuit for driving one of the solenoids 63a of the electromagnetic valve 63 includes a switch 72 that is turned on when the rotation angle of the front wheel 12 by the operation of the handle 7 is turned to the left or right by more than a set angle (for example, 35 degrees).
A switch 73 that artificially switches so as not to increase the speed of the front wheels even when turning, and a switch 74 that does not increase the speed of the front wheels other than during work traveling are connected in series. It is connected. The other solenoid 63b of the electromagnetic valve 63 is connected to the second output terminal of the front wheel drive changeover switch 75. By switching the front wheel drive changeover switch 75, the power from the battery 76 is supplied to the solenoid 63a or 63b. It is working.

The switch 72 is normally open and the switch 7
3.74 is a normally closed switch. However, the switch 72 can be arranged on a transmission path for rotating the front wheel 12 from the handle 7 and its position is not limited. In this embodiment, the switch 72 is arranged above the front axle case 11 as shown in FIG. Is placed on the steering cylinder. Instead of the switch 72, the turning angle of the front wheel 12 itself may be detected by a sensor, and the switch may be turned on when the turning angle exceeds the set angle.

With this configuration, when the front-wheel drive switch 75 is switched to the two-wheel drive position, the solenoid 63b is excited, and the electromagnetic valve 63 shown in FIG. The oil is sent from the oil passage 60 to the oil chamber C2 of the first hydraulic clutch 16 via the oil passage 48, and the piston 46 is slid to the right in FIG. 3 to release the pressure contact between the friction plates 43 and 44. And the gear 42
Therefore, the power is not engaged with the front wheel output shaft 40 and only the rear wheels 14 are driven.

When the front wheel drive switch 75 is switched to the four-wheel drive position and the front wheel 12 is rotated by a predetermined angle or more, the switch 72 is turned on, the solenoid 63a is excited, and the electromagnetic valve 63 is moved to the left. Switched,
Pressure oil from the hydraulic pump 65 is supplied from the oil passage 62 to the oil passage 48 via the oil passage 55 and the check valve 76, and the pressure oil sent to the oil passage 48 is supplied to the first clutch as described above. At the same time as being introduced into the oil chamber C2 of 16 and sliding the piston 46 to release the pressure contact between the friction plates 43 and 44, the pressure oil from the oil passage 55 is sent to the oil chamber C3 of the second hydraulic clutch 17. Then, the piston 53 is slid to the right in FIG. 3 to press the friction plates 51 and 52 against each other. Thus, the gear 50 is engaged with the front wheel output shaft 40 to drive the front wheel 12 at an increased speed.

At this time, if the above-mentioned switch 73 is pressed or the switch 74 is opened during traveling on the road, the solenoid 63a is not excited, and the electromagnetic valve 63 returns to the neutral position shown in FIG. The oil is supplied to the oil chamber C1 of the first hydraulic clutch 16 via the oil passage 61 and the oil passage 49, and the piston 46 is slid to the left in FIG. 3 to press the friction plates 43 and 44 against each other. The power from the gear 42 is engaged with the front wheel output shaft 40, and the front wheel 12 and the rear wheel 14 are driven at substantially the same speed.

[0024]

As described above, the present invention has the following advantages. That is, since the "on" operation of the first hydraulic clutch is performed by the combined force of the hydraulic pressure and the urging force of the spring, the clutch capacity can be reduced, the front wheel transmission can be configured compact, and the arrangement space can be reduced. Can be. Further, even if a trouble occurs in the hydraulic system or the electromagnetic valve, the four-wheel drive state continues due to the urging force of the spring means in one oil chamber of the first hydraulic clutch, so that the traction performance does not decrease. In addition, since the two-wheel drive position is performed without draining the circuit pressure of both hydraulic clutches, the circuit pressure is always maintained at the set pressure, and the switching response of the hydraulic clutch is improved.

[Brief description of the drawings]

FIG. 1 is an overall side view of a tractor equipped with a front wheel transmission according to the present invention.

FIG. 2 is a skeleton diagram showing a power transmission mechanism in a transmission case.

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

FIG. 4 is a front sectional view of the same.

FIG. 5 is a front sectional view showing a configuration of an oil passage between a front wheel transmission and an electromagnetic valve.

FIG. 6 is a perspective view of an upper portion of a transmission case showing an arrangement of an electromagnetic valve.

FIG. 7 is a hydraulic circuit diagram of the front wheel transmission.

FIG. 8 is a hydraulic circuit diagram showing another embodiment.

FIG. 9 is an electric circuit diagram of the front wheel transmission.

[Explanation of symbols]

 C1 First oil chamber C2 Second oil chamber C3 Third oil chamber 12 Front wheel 14 Rear wheel 16 First hydraulic clutch 17 Second hydraulic clutch 39 Front wheel transmission 47 Spring

Claims (1)

[Claims] 1. A front wheel drive system comprising a first hydraulic clutch capable of driving a front wheel at a speed substantially equal to a rear wheel drive speed, and a second hydraulic clutch capable of driving a front wheel at a speed greater than the rear wheel drive speed. In the front wheel transmission, while the "on" operation of the first hydraulic clutch is performed by the hydraulic pressure supplied to one of the oil chambers and the urging force of the spring means,
A front wheel transmission for a four-wheel drive vehicle, wherein the "disengagement" operation of the first hydraulic clutch is performed by hydraulic pressure supplied to the other oil chamber.