JPH048256B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a standard drive state in which power is transmitted to the steerable front wheels at a drive speed approximately equal to the rear wheel drive speed, and a standard drive state in which power is transmitted to the steerable front wheels at a drive speed approximately equal to the rear wheel drive speed. The present invention relates to a running transmission structure for an agricultural tractor equipped with a clutch-type front wheel transmission that switches to an increased speed driving state in which transmission is performed at a high driving speed.

[Conventional technology]

A clutch-type structure for switching the front wheels of an agricultural tractor between the standard drive state and the accelerated drive state as described above is disclosed, for example, in Japanese Utility Model Application Publication No. 102133/1983, but this is a permanent-bit type structure. This mechanism is composed of a gear mechanism and two hydraulic friction clutches, and changes the path of the engine power transmitted through the full-length gear mechanism by turning on and off the friction clutches to operate the gear change. However, this had the following problems.

[Problem that the invention seeks to solve]

In the above-mentioned conventional structure, a hydraulic friction clutch was used for shifting operations in both the standard and increased speed driving states, because the gear shifting operation could be performed quickly with one operation, and from the structural point of view. However, in agricultural tractors, the front wheels are shifted to an increased speed drive state when changing direction with a small turning radius at the edge of a ridge, or when making a sharp turn to avoid an immediate danger, so it is important to change this shift position. Generally used infrequently.
On the other hand, shifting the front wheels to the standard drive state is done during normal work, and in such cases there are generally few opportunities to shift gears quickly, but for the reasons mentioned above, it is generally costly. Moreover, because a hydraulic friction clutch was used, which tends to complicate the overall structure of the device due to its hydraulic path, etc., this resulted in problems such as high cost and complicated structure of the front wheel transmission.

An object of the present invention is to reduce the cost and simplify the structure of the front wheel transmission without reducing its operability.

[Means for solving problems]

The feature of the present invention is that the above-mentioned running power transmission structure for an agricultural tractor is configured as follows. In other words, power from the engine is transmitted in parallel to the first passive gear on the standard drive side and the second passive gear on the speed-up drive side through a set of hydraulic friction clutches.
A shift member for transmitting power to the front wheels is arranged between the front wheel and the second passive gear, and when the shift member is engaged with the first passive gear, the standard drive state is achieved, and when the shift member is engaged with the second passive gear, the drive state is increased. The front wheel transmission is constructed so as to be in a high-speed drive state, and includes an actuator that slides the shift member between a position where the shift member engages with the first passive gear and a position where the shift member engages with the second passive gear. Follow the signal of
After disengaging the friction clutch, the actuator slides the shift member, and then,
A sequence mechanism is provided that is configured to engage and operate the friction clutch.

[Effect]

With the above configuration, a standard drive state and an increased speed drive state can be obtained by sliding the shift member to engage the first passive gear or the second passive gear.

Therefore, in a front wheel transmission system that conventionally used two sets of hydraulic friction clutches, one set of friction clutches can be replaced with a simple gear transmission structure as described above. This results in
The hydraulic path for one set of friction clutches, etc. can be omitted.

Further, since the sliding operation of the shift member by the actuator and the on/off operation of the friction clutch are automatically performed by the sequence mechanism, operability is also improved.

〔Effect of the invention〕

As explained above, in an agricultural tractor equipped with a front wheel transmission, it is possible to reduce the cost and simplify the structure of the front wheel transmission without reducing its operability.

In addition, in the conventional structure using two hydraulic friction clutches, there was a risk that both clutches would be accidentally engaged at the same time, resulting in damage to the device, but the gear type transmission mechanism and sequence mechanism of the present invention As a result, the risk of such an accident occurring has disappeared.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An agricultural tractor that is an embodiment of the present invention will be described below based on the drawings.

As shown in FIG. 3, a fuselage frame 3 that supports a pair of left and right steering type front wheels 1, 1 and rear wheels 2, 2 in a freely drivable manner includes an engine 4, a main clutch 5, a transmission case 6, and a control section. 7, a lift arm 8 that can be driven up and down to freely swing up and down to connect various work devices such as a rotary tiller to the rear of the aircraft, and a PTO that transmits power to the work devices.
A four-wheel drive agricultural tractor is constructed by providing a shaft 9.

Next, the power transmission system and front wheel transmission 10 of the agricultural tractor will be described in detail. As shown in FIGS. The main transmission (not shown) in 6 and the sub-transmission 1
The power branched from the auxiliary transmission 12 is transmitted to the hydraulic friction clutch 1 in the front wheel transmission 10 and is transmitted to the front wheel transmission 10 to drive the rear wheels 2 and 2.
3 to the gear type transmission mechanism 14 for gear change operation, and the front wheel output shaft 15 to the front wheel differential mechanism 1a.
It is configured to be sent to and drive the front wheels 1, 1.

The gear type transmission mechanism 14 in the front wheel transmission 10 will be described in detail as shown in FIG.
A first passive gear 17 and a second passive gear 18 that mesh with gears 16a and 16b of a rotating shaft 16 having a friction clutch 13 at one end are loosely fitted to the front wheel output shaft 15, and the first and second passive gears 17 , 18 is provided with a shift member 19 having a spline structure and capable of rotating integrally with the front wheel output shaft 15 and movable in the axial direction. This shift member 19 is moved in the axial direction by a pair of hydraulic cylinders, which are actuators 20, and the first and second passive gears 17, 18
A speed change operation is performed by engaging engaging portions 17a and 18a that protrude like claws from the sides. When the shift member 19 engages with the first passive gear 17, it becomes a standard drive state, and when it engages with the second passive gear 18, it becomes an increased speed drive state.

Next, the sequence mechanism that controls the operation of the front wheel transmission 10 will be described in detail. As shown in FIG. 2, steering rotation angle detection detects when the steering mechanism (not shown) is operated beyond a set angle. A sensor 22, a right brake detection switch 23 of a limit switch type that detects depression of left and right side brake pedals (not shown) capable of independently braking one side of the left and right rear wheels 2, 2, a left brake detection switch 24, and the shift switch. A limit switch type standard speed change detection switch 3 that detects that the member 19 is being changed to standard or increased speed.
0, a speed increase detection switch 31 is provided, and signals from the five devices 22, 23, 24, 30, and 31 are input to the control circuit 25. On the other hand, the friction clutch 13 and the hydraulic cylinder 20 of the front wheel transmission 10
are operated by pressure oil supplied from the pump 26 via operating valves 27 and 28, and the operating valves 27 and 28 are automatically operated by the control circuit 25.

Normally, the hydraulic cylinder 20 is operated to the standard drive side by the control circuit 25, and when turning with a small turning radius, the steering rotation angle detection sensor 22
When the right or left brake detection switches 23, 24 detect that the steering mechanism has been operated at an angle greater than or equal to the set angle, and the right or left brake detection switches 23, 24 detect that only one of the right or left side brake pedals has been depressed, the control circuit 25 detects the operation. The valve 27 is closed, the friction clutch 13 is disconnected, and the operating valve 28 is used to operate the hydraulic cylinder 20 to the speed-increasing drive side. Thereafter, when the speed increase detection switch 31 enters the detection state and receives a signal confirming that it has been operated to the speed increase drive side, the operating valve 27 is opened and the friction clutch 13 is engaged.

After that, the turning is completed, and the steering rotation angle detection sensor 22, left and right brake detection switch 2
When either 3 or 24 becomes non-detected,
The control circuit 25 operates the hydraulic cylinder 20 to the standard drive side in the same order as described above.

Further, the control circuit 25 can switch the above-mentioned automatic operation toward the speed increasing drive side between an active state and a non-active state using a DT switch 29 provided in a control section (not shown).

[Brief explanation of drawings]

The drawings show an embodiment of the running transmission structure for an agricultural tractor according to the present invention, in which FIG. 1 is a partially cutaway plan view of the front wheel transmission and the vicinity of the auxiliary transmission, FIG. 2 is a control system diagram of the front wheel transmission, and FIG. Figure 3 is an overall side view of the agricultural tractor. DESCRIPTION OF SYMBOLS 1... Front wheel, 4... Engine, 10... Front wheel transmission, 13... Friction clutch, 17... First passive gear, 18... Second passive gear, 19... Shift member, 20... Actuator.

Claims (1)

[Claims] 1 A clutch that switches the transmission system to the freely steerable front wheels 1, 1 between a standard drive state in which power is transmitted at a drive speed approximately equal to the rear wheel drive speed, and an increased speed drive state in which power is transmitted at a drive speed greater than the rear wheel drive speed. This is a running transmission structure for an agricultural tractor equipped with a front wheel transmission 10 of the type shown in FIG. Transmitted in parallel to the second driven gear 18 on the driving side, and the first and second driven gears 1
A shift member 19 for transmitting power to the front wheels 1, 1 is disposed between 7 and 18, and the shift member 19 is connected to the first
The front wheel transmission 10 is configured such that when the shift member 19 is engaged with the second passive gear 17, the standard drive state is set, and when the shift member 19 is engaged with the second passive gear 18, the speed-up drive state is set. The actuator 20 is provided with an actuator 20 that slides between a position where it engages with the first passive gear 17 and a position where it engages with the second passive gear 18. The actuator 20 is operated to disengage the friction clutch 13 according to a signal from an operation system, and then the actuator A running transmission structure for an agricultural tractor, which is equipped with a sequence mechanism configured to slide a shift member 19 by a lever 20 and then engage and operate a friction clutch 13.