JPH0456634A - Hydraulic circuit structure for working vehicle - Google Patents

Abstract

PURPOSE:To perform rapid disengagement of a hydraulic clutch by discharging working oil of a hydraulic clutch through the drain part of the operation member for a shift gear of a forward reverse shifting device by means of a logic valve when operation of a forward reverse shift lever is started. CONSTITUTION:A working vehicle, such as an agricultural tractor, is provided with a forward reverse shifting device and a transmission device for each of gears on both sides for running, and a hydraulic circuit is provided with actuators 11-13 to perform shift operation of the transmission device for each gear and a hydraulic clutch 3 for running transmission. In this case, logic valves 22b-22d to bleed working oil for clutch engaging operation from the hydraulic clutch 3 in linkage with shift operation of the transmission device for each gear are located in a hydraulic circuit. In an operation member 17 to effect shift operation of the forward reverse shift device, a drain part 17a to bleed working oil from the hydraulic clutch 3 is located between a forward position F and a reverse position R. A logic valve 22a to feed working oil to the hydraulic clutch 3 in linkage with completion of shift operation of the transmission device for each gear and the forward reverse shift device is provided.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a gear shift type forward/reverse switching device, a gear transmission device for traveling, an actuator for operating the gear changing device, and a gear transmission device for traveling transmission. The present invention relates to a hydraulic circuit structure for a work vehicle equipped with a hydraulic clutch.

[Conventional technology]

As one of the above-mentioned work vehicles, for example, JP-A-2-4
There is something like the one disclosed in Japanese Patent No. 6325.

That is, the actuator ((11A) of the above publication).

(IIB), (13)) When the gear shift operation of the gear transmission is started, the pilot pressure disappears and the logic valve ((17B), (17C), (17D) in the above publication) is operated to the drain side. Hydraulic clutch ((C) in the above publication)
Hydraulic oil is removed from the pump and the hydraulic clutch is disengaged.

Then, when the shift operation by the actuator is completed,
Pilot pressure is generated and the logic valve is operated to the hydraulic oil supply side. This causes the hydraulic clutch to be engaged and operated.

The same applies to the forward/reverse switching device; for example, when the forward/reverse switching lever ((18) in the above publication) is started to be operated from the forward position to the reverse side, the pilot pressure disappears at an intermediate position and the logic valve ( (17A)) of the above publication is operated to the drain side.

Then, when you finish operating the forward/reverse switching lever to the reverse position,
Pilot pressure is generated and operated on the logic valve or the hydraulic oil supply side, which engages and operates the hydraulic clutch.

As described above, with the above-mentioned structure, the gear shift operation and forward/reverse switching can be performed by simply operating the actuator control valve ((1) of the above publication and the forward/reverse switching lever) without stepping on the clutch pedal. can be done.

[Invention or problem to be solved]

In the above-mentioned structure, the pilot pressure disappears when the actuator and forward/reverse switching lever start operating, and the logic valve is operated to the drain side to drain the hydraulic oil from the hydraulic clutch, so there is a slight delay from the start of operation. The situation is such that the hydraulic clutch is disengaged.

When changing the speed of the gear transmission, the transmission ratio is changed within the forward or reverse range, so the change in the transmission ratio is not very large. Therefore, even if there is a slight delay in disengaging the hydraulic clutch, the gear change operation (sliding operation of the shift gear) can be performed without any particular problem.

However, when switching the forward/reverse switching device, the power is completely reversed, so if the disengagement of the hydraulic clutch is delayed, the hydraulic clutch will not be able to fully operate, especially when performing a quick forward/reverse switching operation. In an uncut state,
This creates a situation where the shift gear is forced to engage with the gear that is in reverse. As a result, in the constant mesh type, there is a risk of gear noise due to the shift gears not meshing with each other, and in the synchronized mesh type, there is a risk of seizure due to overload on the synchronizer ring for synchronizing the rotation.

It is an object of the present invention to reduce the above-mentioned problems when switching between forward and backward motions.

[Means to solve the problem]

The feature of the present invention is that the hydraulic circuit structure for a work vehicle as described above is configured as follows. In other words, [a] A logic valve that drains the hydraulic oil for clutch engagement operation from the hydraulic clutch in conjunction with the start of the shift operation of the gear transmission device by the actuator.

[mouth] In the part between the forward position and the reverse position of the operating member that slides the shift gear of the forward/reverse switching device,
A drain portion is provided for draining hydraulic oil for clutch engagement operation from the hydraulic clutch, so that the hydraulic oil of the hydraulic clutch is drained from the drain portion during operation of the operating member from one operating position to the other operating position. Configure.

[C] A logic valve that supplies hydraulic oil for clutch engagement operation to the hydraulic clutch in conjunction with the completion of the shift operation of the gear transmission device and the completion of the switching operation of the forward/reverse switching device.

When configured as described above, its functions and effects are as follows.

[For production]

With the configuration described above, when the forward/reverse switching lever (16) is started to be operated as shown in FIG. etc.) drain part (1
7a), the hydraulic oil of the hydraulic clutch (3) or the logic valve (
22a) It is directly pulled out and cut without going through it.

In other words, compared to the conventional structure where the pilot pressure disappears during the operation of the forward/reverse switching lever and is operated to the logic valve or drain side,
The hydraulic clutch is disengaged quickly.

Furthermore, when the actuator performs a gear change operation, the hydraulic clutch is disengaged by the logic valve, and when the actuator completes the shift operation and the forward/backward switching is completed, the hydraulic clutch is engaged by the logic valve.

〔Effect of the invention〕

As described above, it is now possible to quickly disengage the hydraulic clutch when switching between forward and reverse, suppress gear noise and burn-in of the synchronizer ring when switching between forward and reverse, and improve the speed of the forward/reverse switching device. We were able to improve durability.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

As shown in Fig. 2, power from the engine (1) is transmitted through the main clutch (2) to the main gear transmission (A), the multi-disc hydraulic clutch (3), the auxiliary gear transmission (B), and the gear shift. It sequentially transmits the power from the auxiliary gear transmission (B) to the forward/reverse switching device (C) of the model, and also transmits the power from the auxiliary gear transmission (B) to the differential mechanism (4a) of the rear wheels (4), and branches from just before the differential mechanism (4a). The generated power is transferred to the front wheels (5) via the front wheel transmission (D).
A travel transmission system is configured such that the transmission is transmitted to the differential mechanism (5a). The power transmitted through the main clutch (2) is sequentially transmitted to the PTO transmission (6) and the one-way rotation clutch (7) to drive the PTO shaft (8). It constitutes the drive system of a four-wheel drive agricultural tractor.

The main gear transmission (A) has two sets of shift gears (9).

(10), configured in a synchromesh type with 4
It is possible to change the speed. In addition, the auxiliary gear transmission (B) with two high and low speeds and the forward/reverse switching device (C) are similarly constructed of a synchromesh type equipped with shift gears (30) and (31), and these same devices (B) , (C) are configured to share some of the gears.

As shown in the figure, shift gears (9), (10), (3) of the main gear transmission (A) and the auxiliary gear transmission (B) are shown.
0) are two hydraulic cylinders (11) and (12), respectively.
(corresponding to an actuator), and one hydraulic cylinder (
13) (corresponding to an actuator) is configured to be slid. These three hydraulic cylinders (11
), (12), and (13) are operated by supplying hydraulic oil from the pump (15) via the control valve (14) for speed change operation, as shown in Fig. 1, and this control valve (14
) 8-speed shifting is possible by supplying and discharging hydraulic oil from the

As shown in FIG. 1, a hydraulic cylinder (11).

(12) and (13) have their operating parts as switching valves (lla).
, (12a).

(13a), and is configured to generate pilot pressure when each is operated to a position other than neutral. Hydraulic cylinder (1) for auxiliary gear transmission (B)
3) can be operated only in two positions, low speed position (L) and high speed position (H), and the neutral position of the switching valve (13a) of this hydraulic cylinder (13) functions only during operation.

The shift gear (31) of the forward/reverse switching device (C) is slid by a swingable forward/reverse switching lever (16). In this case, the shift shaft (17) of the shift fork (not shown) that slides the shift gear (31)
(corresponding to the operating member), a control valve function is incorporated therein, and is configured to generate pilot pressure in the forward position (F) or the reverse position (R).
Between the forward position (F) and the reverse position (R), a drain part (
17a) is provided.

The hydraulic clutch (3) is configured to be engaged when hydraulic oil is supplied, and the oil path (18) from the pump (15) is branched into two to connect the control valve (14). An oil passage (19) and a hydraulic oil supply passage (20) for the hydraulic clutch (3) are formed.

The hydraulic clutch (3) is automatically disconnected when either the main gear transmission (A), the auxiliary gear transmission (B), or the forward/reverse switching device (C) is shifted or switched. When the main clutch (2) is finished, it is configured to be automatically engaged again, and the gear shifting operation can be performed without disengaging the main clutch (2).

As shown in Fig. 1, the hydraulic oil supply path (20) for the hydraulic clutch (3) includes a normally open first on-off valve (21) that is closed when the secondary oil pressure exceeds a first set value. , a normally closed second on-off valve (27) that is opened when the secondary oil pressure exceeds a second set value that is higher than the first set value, and a throttle section (28).
are connected in parallel. And the hydraulic cylinder (
11), (12).

(13) switching valve (lla), (12a), (13)
Four logic valves (22a), (22b), (22c), which are operated by the pilot pressure of a) and the pilot pressure from the shift shaft (17) of the forward/reverse switching device (C).
An accumulator (23) is provided to suppress a sudden increase in pressure acting on the logic valve group (22) and the hydraulic clutch (3).

As a result, when the main gear transmission (A) etc. are set to a state in which the aircraft is running as shown in FIG. 1 (FIG. 1 is the aforementioned 1st speed state), the logic valve group (22) becomes in a communicating state, The hydraulic clutch (3) is maintained in the engaged state. Then, when the main gear transmission (A) and the auxiliary gear transmission (B) are operated to change gears while the aircraft is running, the switching valves (lla), (12a), (13a) are activated at the neutral position during operation. The pilot pressure of any one of the logic valves (22b), (22c), (22d) of the logic valve group (22) decreases.
cuts off the hydraulic oil from the pump (15), and at the same time drains the hydraulic oil of the hydraulic clutch (3) into the drain oil path (24) to disengage the hydraulic clutch (3).

Next, when the gear shift operation is completed, the switching valve (lla) is activated.

Pilot pressure is generated from (12a) and (13a), the logic valve group (22) is again set in a communicating state, and the hydraulic clutch (3) is engaged and operated. In this case, a sudden increase in the pressure of the hydraulic oil supplied to the hydraulic clutch (3) is suppressed. In other words, the first on-off valve (21) is open until the pressure reaches a relatively low first set value from zero, and when the pressure reaches the first set value, the first on-off valve (21) closes and operates. Oil is supplied through the throttle part (28), and the pressure of the hydraulic clutch (3) gradually increases due to the pressure accumulation action of the accumulator (23). Then, when the pressure reaches a relatively high second set value, the second on-off valve (27) opens.

Next, the switching operation of the forward/reverse switching device (C) will be explained. As shown in FIG. 1, it is connected to an oil passage (29) between the hydraulic clutch (3) and the accumulator (23) or to a shift shaft (17) of a forward/reverse switching device (C).

As a result, for example, when the forward/reverse switching lever (16) is operated from the forward position (F) to the reverse side, during the operation, the hydraulic oil of the hydraulic clutch (3) or the oil passage (29) and the shift shaft ( 17) is removed from the drain portion C17a), and the hydraulic clutch (3) is quickly operated to disengage the clutch.

Further, the pilot pressure from the shift shaft (17) also disappears, and the logic valve (22a) is also operated to the drain oil path (24) side.

After that, when the forward/reverse switching lever (16) is moved to the reverse position (R), the oil passage (29) is shut off, pilot pressure is generated at the shift shaft (17), and the logic valve (22) is closed.
a) is switched to the hydraulic oil supply side, and the hydraulic clutch (3
) is operated to engage the clutch. In this case as well, the first
and second on-off valve (21), (27), throttle part (28)
and the accumulator (23) operate in the same manner as described above.

As shown in Figure 1, this hydraulic circuit includes a hydraulic cylinder (
In order to reduce the inconvenience caused when 11), (12), and (13) operate at high speed, the pressure on the downstream side of the oil passage (18) from the pump (15) is reduced. An on-off valve (25) is provided which closes when the temperature rises above a predetermined value. Also provided is a relief valve (26) that sends excess oil to the power steering mechanism (32) via the oil path (18a).

In the above-described embodiment, the shift gear (31) of the forward/reverse switching device (C) is configured to be slid by the forward/backward switching lever (16), or the main and auxiliary gear transmissions (A),
Similarly to (B), the structure may be such that the shift gear (31) is slid by an actuator.

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of the drawing]

The drawings show an embodiment of the hydraulic circuit structure of a working vehicle according to the present invention, with FIG. 1 being a hydraulic circuit diagram for speed change operation, and FIG. 2 being a schematic diagram of a transmission system. (3)...Hydraulic clutch, (11), (12
), (13)...actuator, (17)
......Operation member, (17a)...Drain part of operation member, (22a), (22b), (22c
). (22d)...Logical logic, (31)...
Shift gear of forward/reverse switching device, (A), (B)...
... Gear transmission device, (C) ... Forward/forward switching device.

Claims (1)

[Claims] A gear shift type forward/reverse switching device (C), a traveling gear transmission device (A), (B), and this gear transmission device (A).
, (B) actuators (11), (1
2), (13) and a hydraulic clutch (3) for traveling transmission, the hydraulic circuit structure of a working vehicle is as follows [A]
A hydraulic circuit structure of a work vehicle equipped with the configuration described in ~[C]. [B] The actuators (11), (12), (13)
), the logic valves (22b), (22c) remove the hydraulic oil for clutch engagement operation from the hydraulic clutch (3) in conjunction with the start of the shift operation of the gear transmission devices (A), (B).
), (22d). [B] Shift gear (31) of the forward/reverse switching device (C)
A drain part (17a) for draining the hydraulic oil for clutch engagement operation from the hydraulic clutch (3) is provided between the forward position (F) and the reverse position (R) in the operating member (17) for sliding operation. The hydraulic clutch (3) is configured such that the hydraulic oil of the hydraulic clutch (3) escapes from the drain portion (17a) during operation of the operating member (17) from one operating position to the other operating position. [C] In conjunction with the completion of the gear shifting operations of the gear transmission devices (A) and (B) and the completion of the switching operation of the forward/reverse switching device (C), the hydraulic clutch (3) is activated for clutch engagement operation. Logic valves (22a), (22b), (
22c), (22d).