JPH056182Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a four-wheel drive type working vehicle, typified by an agricultural tractor.

[Conventional technology]

Some agricultural tractors, which are an example of four-wheel drive working vehicles, have a structure as disclosed in, for example, Japanese Utility Model Application Publication No. 60-62378.

In other words, it is equipped with a front wheel transmission that can be freely switched between a standard drive state in which the front wheels and rear wheels are driven at approximately the same speed, and an increased speed drive state in which the front wheels are driven at a higher speed than the rear wheels. is equipped with a steering sensor that detects the steering angle of the front wheels. Based on the signal from this steering sensor, when the front wheels are steered beyond a set angle from a straight-ahead position, the front wheel transmission is shifted to the speed-up drive state. It has a structure that allows automatic switching.

In this way, by increasing the speed of the front wheels when turning, it is possible to turn smoothly without disturbing the field.

Generally, such agricultural tractors are often equipped with a differential lock means that can lock the differential mechanisms for the left and right rear wheels. In the structure of the above-mentioned publication, it is considered that the deflock means is configured to be operated manually.

For the above structure, for example, JP-A-58-
There is a structure as disclosed in Japanese Patent No. 199224.

This system is equipped with a rotation speed sensor that detects the rotation speed of each of the left and right rear wheels, and when driving straight, if the difference in rotation speed between the left and right rear wheels exceeds a set value and one of the rear wheels slips, The differential mechanism for the left and right rear wheels is configured to be automatically switched to the differential side.

In this case, it is determined that the vehicle is traveling straight if the pair of left and right hand brakes for the rear wheels are not both operated to the braking side.

[The problem that the idea attempts to solve]

As mentioned above, if the structure of JP-A-58-199224 is added to the structure of JP-A-60-62378 mentioned above, a front wheel transmission is equipped and an automatic rear wheel differential lock operation structure is installed. A four-wheel drive work vehicle equipped with the following features is obtained.

However, in this four-wheel drive type work vehicle, a pair of contact switches detect whether or not the handbrake pedal is depressed (structure disclosed in Japanese Patent Application Laid-open No. 199224/1983).

Therefore, there are wires from the pair of contact switches of the handbrake pedal and wires from the steering sensor, which increases the overall number of wires. This results in an increase in the number of parts and a complicated structure, and at the same time leads to an increase in failures and a decrease in reliability in four-wheel drive working vehicles that travel on rough terrain.

Furthermore, when turning, it is not always necessary to press the handbrake pedal on the inside of the turn, and there are cases where the vehicle turns only by steering the front wheels without pressing the handbrake pedal.

In this case, the above-mentioned four-wheel-drive work vehicle performs automatic defroster operation based only on the rotational speed difference between the left and right rear wheels, so if a turn is made only by steering the front wheels, it is determined that the vehicle is traveling straight. In some cases, the defrock may be automatically operated. If the defrock is operated in this manner when turning, smooth turning cannot be achieved.

The present invention suppresses an increase in the number of parts and complication of the structure when obtaining a four-wheel drive working vehicle equipped with a front wheel transmission and an automatic rear wheel differential lock operation structure, and also reduces the number of parts when turning. The purpose is to prevent situations where the defrock is operated.

[Means to solve the problem]

The feature of the present invention is that the above-mentioned four-wheel drive type work vehicle is configured as follows. In other words, it is equipped with a steering sensor that detects the steering angle of the front wheels, and a rotation speed sensor that detects the rotation speed of each of the left and right rear wheels.Based on the signal from the steering sensor, the front wheels move from a straight-ahead position to a set angle or more. When the steering operation is performed, the steering angle of the front wheels is set to the straight-ahead position based on signals from the first switching means that automatically switches the front wheel transmission to the speed-increasing drive state, the steering sensor, and the rotation speed sensor. a second switching means for automatically switching the differential mechanism for the left and right rear wheels to the differential side when the rotation speed difference between the left and right rear wheels is within a set angle from It is equipped with

[Effect]

With the configuration described above, when the front wheels are steered from the straight-ahead position to a predetermined angle or more, the front wheel transmission is automatically switched to the speed-increasing drive state based on the signal from the steering sensor. This allows for smooth turning without disturbing the field.

Then, based on the signal from the steering sensor, if the steering angle of the front wheels is within a set angle from the straight-ahead position, it is determined that the vehicle is not in a turning state but in a straight-ahead state. In this state, if the difference in rotation speed between the left and right rear wheels is greater than the set value based on the signal from the rotation speed sensor, it is determined that one of the rear wheels is slipping, and the differential mechanism of the left and right rear wheels is activated. The differential lock means is automatically switched to the differential lock side.

As described above, the determination as to whether the vehicle is traveling straight or turning is made by the steering sensor that detects the steering angle of the front wheels. in this way,
By using the steering sensor for the front wheel transmission also for the differential lock operation, the contact switch for the handbrake pedal in the conventional structure can be omitted.

In addition, since it determines whether the vehicle is going straight or turning based on the steering angle of the front wheels, rather than by pressing the handbrake pedal, it can be used when turning with the handbrake and when turning without using the handbrake. It is determined that the turning state is correct at both times.

This prevents automatic deflock operation from being performed due to the rotational speed difference between the left and right rear wheels that occurs when turning.

[Effect of idea]

As described above, by using the steering sensor for the front wheel transmission also for differential lock operation and omitting the contact switch for the handbrake pedal, the overall number of wiring can be reduced, resulting in an increase in the number of parts and a complicated structure. We were able to suppress the or,
It was also possible to suppress an increase in failures and a decrease in reliability due to an increase in the total number of wiring lines.

And when turning without using the handbrake,
Since it is possible to prevent a situation in which an automatic deflock operation is performed, smooth turning can be always performed without any hindrance due to the speed increasing action of the front wheel transmission.

〔Example〕

Below, an example of the present invention will be described.
The explanation will be based on an agricultural tractor.

As shown in FIG. 4, an engine 4, a main clutch 5, a transmission case 6, and a control unit 7 are mounted on a fuselage frame 3 that supports a pair of left and right steering type front wheels 1 and rear wheels 2 in a freely drivable manner. , a lift arm 8 at the rear of the aircraft that lifts and lowers various work devices such as a rotary tiller, and transmits power to the work devices.
A PTO shaft 28 is provided to constitute a four-wheel drive type agricultural tractor.

Next, the power transmission system and front wheel transmission 10 of the agricultural tractor will be explained. As shown in FIGS. 4 and 3, the power from the engine 4 is transmitted to the transmission case 6 via the main clutch 5 and the power transmission shaft 11.
Main transmission (not shown) and sub-transmission 1
2, a gear change operation is performed, and the transmission is transmitted to the rear wheel differential mechanism 2a. Then, the gear 12 of the sub-transmission device 12
The power branched from a is sent from the intermediate shaft 9 in the front wheel transmission 10 to the first hydraulic clutch 13 or the second hydraulic clutch 14, and from the front wheel output shaft 15 to the front wheel differential mechanism 1a.

When the first hydraulic clutch 13 is in the engaged state, the driving speed of the front wheels 1 and the rear wheels 2 are approximately equal to each other, and when the second hydraulic clutch 14 is in the engaged state, the driving speed of the front wheels 1 becomes the rear wheel. An increased speed driving state is established, which is higher than the driving speed of the wheels 2. In this speed-up driving state, sharp turns can be easily made even in soft fields without disturbing the fields.

As shown in FIG. 2, the front wheel transmission 10 is operated by detecting the steering angle of the pitman arm 16 for steering the front wheels 1 by a potentiometer-type steering sensor 17, and by receiving this detection signal by a control device 18. This is done by operating the electromagnetic control valve 19 (corresponding to the first switching means) that supplies and discharges pressure oil to and from the first and second hydraulic clutches 13 and 14. This electromagnetic control valve 19 is biased by a spring 20 toward the pressure oil supply side to the first hydraulic clutch 13, and is normally in a standard operating state.

The deflock operation of the rear wheels 2 is performed by a shift member 21 having an engaging portion on the rear axle 2b, as shown in FIG.
The shift member 21 is engaged with the casing of the differential mechanism 2a by a hydraulic cylinder 23 (corresponding to a second switching means) via a balance-type operating arm 22. The electromagnetic control valve 24 that supplies and discharges pressure oil to and from the hydraulic cylinder 23 is operated by a signal from the control device 18. And operation arm 2
2 and the electromagnetic control valve 24 are biased toward the defrock release side by springs 25 and 26, and normally the deflock is not operated.

Next, the flow of control within the control device 18 will be explained. As shown in the flowchart of FIG. 1, a rotation speed sensor 27R is attached to the rear axle 2b and detects the rotation speed of each of the left and right rear wheels 2.
A signal from 27L is input to the control device 18, and the vehicle speed V is calculated based on this signal in step _S1 and displayed in step ₂ .

Then, if the front wheel speed increase switch 29 that causes the front wheels 1 to appear in the speed increase drive state during a turning operation is in the ON state, and the vehicle speed V is below the upper limit set speed ₀ ,
The process moves from steps S ₃ and S ₄ to step S ₅ .

In step _S5 , the rotational speed difference ratio S between the left and right rear wheels 2 is calculated, and the rotational speed difference ratio is lower than the lower limit differential rotational speed ratio _S0 , which requires front wheel speed increase operation or rear wheel 2 deflock operation. If S is large, the process moves to step _S6 . If the steering angle θ of the front wheel 1 at that time is larger than the steering angle θ ₀ of the front wheel speed increasing operation, it means that a sharp turn is to be started, and the steps start from step _S6 .
At _S7 , the front wheel transmission 10 is operated to the speed increasing drive side. This state continues until the turning is completed in the loop of steps _S7 and _S8 , and when the turning is completed, the process moves to step _S9 , where the front wheel transmission 10 is returned to the standard drive side and steered.

Also, the steering angle θ of the front wheel 1 is the steering angle θ ₀ of the front wheel speed increasing operation and the steering angle θ ₁ of the rear wheel 2 deflock operation.
If it is smaller than both, it means that one of the rear wheels 2 is slipping even though the vehicle is traveling straight, so the process moves from steps S ₆ and S ₁₀ to step S ₁₁ , and the vehicle is driven only for the set time. The differential mechanism 2a of the rear wheels 2 is operated to deflock.

Note that although reference numerals are written in the claims section of the utility model registration for convenience of comparison with the drawings, the present invention is not limited to the structure of the attached drawings by such entry.

[Brief explanation of drawings]

The drawings show an embodiment of a four-wheel drive type work vehicle according to the present invention, and Fig. 1 is a flowchart showing the flow of operation, and Fig. 2 shows the cooperation between the control device, front wheel transmission, and rear wheel differential mechanism. FIG. 3 is a schematic diagram of the auxiliary transmission and front wheel transmission, and FIG. 4 is an overall side view of the agricultural tractor. DESCRIPTION OF SYMBOLS 1... Front wheel, 2... Rear wheel, 2a... Rear wheel differential mechanism, 10... Front wheel transmission, 17... Steering sensor, 19... First switching means, 21...
Defrot locking means, 23...Second switching means, 27
R, 27L...Rotation speed sensor.

Claims (1)

[Claims for Utility Model Registration] It is possible to freely switch between a standard drive state in which the front wheels 1 and rear wheels 2 are driven at approximately the same speed, and an increased speed drive state in which the front wheels 1 are driven at a higher speed than the rear wheels 2. A four-wheel drive working vehicle is provided with a front wheel transmission 10 and a differential locking means 21 capable of locking the differential mechanism 2a for the left and right rear wheels 2, which detects the steering angle of the front wheels 1. It includes a steering sensor 17 and rotation speed sensors 27R and 27L that detect the rotation speed of each of the left and right rear wheels 2, and based on a signal from the steering sensor 17, the front wheels 1 move from a straight-ahead position to a set angle or more. a first switching means 19 that automatically switches the front wheel transmission 10 to a speed-increasing drive state when a steering operation is performed; and based on signals from the steering sensor 17 and rotation speed sensors 27R and 27L, When the steering angle of the front wheels 1 is within a set angle from the straight-ahead position, and when the difference in rotational speed between the left and right rear wheels 2 is greater than or equal to the set value, the differential mechanism 2a of the left and right rear wheels 2 is activated. A four-wheel drive type working vehicle is provided with a second switching means 23 for automatically switching the switch 21 to the differential lock side.