JPH0684137B2 - Hydraulic circuit structure of work vehicle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic circuit structure for forward / reverse switching operation in a work vehicle.

[Conventional technology]

Some agricultural tractors having a gear shift type forward / reverse switching device have a structure as disclosed in, for example, Japanese Patent Application Laid-Open No. 62-80133.

In this structure, when a voltage clutch is provided in the traveling power transmission system and, for example, when the forward / reverse switching lever at the forward position is started to be moved to the reverse position, the hydraulic clutch is automatically drained and the hydraulic clutch is disengaged. When the forward / reverse switching lever is operated to the reverse position, hydraulic oil is again supplied from the pump to the hydraulic clutch, the hydraulic clutch is turned on and operated, and power is transmitted via the hydraulic clutch.

[Problems to be Solved by the Invention]

With the above-described configuration, the forward / reverse switching operation can be performed with one touch without performing an artificial clutch input operation with the clutch pedal.

However, if, for example, the forward / reverse switching lever is suddenly operated to the reverse side while moving forward at a certain speed, a shock will occur when the reverse power is transmitted. You have to artificially brake and slow down the aircraft. In this way, it is necessary to separately operate the brake when switching between forward and reverse, so
There was room for improvement in terms of operability.

An object of the present invention is to improve the operability when switching between forward and backward movement.

[Means for Solving the Problems]

A feature of the present invention is that the hydraulic circuit structure for a work vehicle as described above is configured as follows.

It is equipped with a hydraulic clutch that transmits power to the traveling system, a gear-shifting forward / reverse switching device, and a traveling brake.The hydraulic oil from the pump is passed through a pressure control mechanism that smoothly raises the pressure on the lower side. , Is configured to supply to the hydraulic clutch, and between the pressure control mechanism and the hydraulic clutch, the hydraulic oil from the pressure control mechanism is supplied to the hydraulic clutch to enter and operate it to drain the traveling brake. As a result, the operating position is switched to the operating position and the operating position is supplied by supplying hydraulic oil from the pressure control mechanism to the traveling brake, and the hydraulic clutch is operated in the oil draining state. It is equipped with a free switching valve, and in conjunction with the switching operation of the forward / reverse switching device from one shift state to the other shift state, the switching valve is switched from the traveling position to the braking position to switch the forward / reverse switching device. In conjunction with the operation ends, it is provided with operating means for switching the operation to the running position switching valve from the braking position.

[Work]

(I) For example, as shown in FIG. 1, it is assumed that the forward / reverse switching device is started to be switched to the reverse side during traveling while the forward / reverse switching device is operated to the forward side.

In this case, with the configuration of the present invention, the operating means (17) supplies hydraulic oil to the traveling position (hydraulic clutch (3) in FIG. 1 with the start of the switching device to the reverse side, and the traveling brake). Switch valve (22)
2) is switched to the braking position as shown in FIG.

At the braking position of the switching valve (22a), the hydraulic clutch (3) is drained and is turned off, and the hydraulic oil from the pressure control mechanism (21) is supplied to the traveling brake (34). At this time, since the hydraulic oil is supplied to the traveling brake (34) while the pressure control mechanism (21) is operating, the traveling brake (34) is relatively controlled while suppressing a rapid increase in pressure. The vehicle enters a smooth entering state and brakes the forward movement of the aircraft.

(Ii) Next, when the backward switching operation of the forward / reverse switching device is completed, the switching valve (22a) is switched to the traveling position as shown in FIG. 1 by the operating means (17).

As a result, the traveling brake (34) is drained to be turned off, and the hydraulic oil from the pressure control mechanism (21) is supplied to the hydraulic clutch (3). At this time, since the hydraulic oil is supplied to the hydraulic clutch (3) while the pressure control mechanism (21) is operating, the hydraulic clutch (3) is relatively smooth while suppressing a rapid increase in pressure. When the aircraft is in the on-state, the aircraft smoothly transitions to the reverse state with less shock.

(Iii) As described above, the switching valve (22a), the hydraulic clutch (3), and the traveling brake (3) are provided on the lower side of the pressure control mechanism (21).
4) is arranged, the above-mentioned one pressure control mechanism (21) causes the hydraulic clutch (3) and the traveling brake (34) when the switching valve (22a) is switched to the traveling position and the braking position.
As a result, the pressures of the hydraulic clutch (3) and the traveling brake (34) rise smoothly.

As a result, one pressure control mechanism (21) can be shared by both the hydraulic clutch (3) and the traveling brake (34).

〔The invention's effect〕

As described above, by effectively utilizing the hydraulic oil for the hydraulic clutch that was drained during the forward / reverse switching operation for the traveling brake, automatic operation is possible without manual braking during the forward / reverse switching operation. Thus, a structure in which the braking operation is performed is obtained, and the operability during the forward / reverse switching operation can be improved.

Further, the braking operation during the forward / reverse switching operation and the subsequent hydraulic clutch engagement operation are performed smoothly by the pressure control mechanism with less shock, so that the riding comfort of the work vehicle during the forward / reverse switching operation can be improved. It was

Moreover, since one pressure control mechanism is shared by both the hydraulic clutch and the traveling brake, it is advantageous in terms of simplification of the structure.

〔Example〕

Hereinafter, an agricultural tractor using the hydraulic circuit structure of the present invention will be described with reference to the drawings.

As shown in FIG. 4, the power from the engine (1) is transmitted through the main clutch (2) to the main transmission (A), the multi-plate hydraulic clutch (3), the forward / reverse switching device (C), and the auxiliary shift. The power from the auxiliary transmission device (B) is sequentially transmitted to the device (B) and is transmitted to the differential mechanism (4a) of the rear wheel (4), and the power branched from immediately before the differential mechanism (4a) is transmitted to the front wheel (5). The drive transmission system is configured so as to be transmitted to the differential mechanism (5a). Further, the power transmitted through the main clutch (2) is sequentially transmitted to the transmission (6) and the one-way rotation clutch (7), and the PTO
The drive system of the four-wheel drive type agricultural tractor is configured by driving the shaft (8).

As shown in FIG. 4, the main transmission (A) is composed of two sets of synchromesh type gear transmissions (9) and (10), and is capable of shifting in four stages. The sub transmission (B) and the forward / reverse switching device (C) are also composed of synchromesh type gear mechanisms, and share some gears of the sub transmission (B) and the forward / reverse switching device (C). Each is configured as follows.

The main transmission device (A) and the auxiliary transmission device (B) have two hydraulic cylinders (11) and (12) and one hydraulic cylinder (1).
3) is configured to be shifted, and the three hydraulic cylinders (11), (12) and (13) are connected via a control valve (14) for traveling speed selection as shown in FIG. , Pump (1
It operates by supplying hydraulic oil from 5).

The control valve (14) is a rotary type, and as shown in FIG.
It is bolted to the inner surface of the side cover (27) of the machine body, the rotor operation part (14a) projects outward, and the pulley (28) is attached to this rotor operation part (14a). The pulley (28) has two wires (29a), (29
b) is wound, and the wires (29a) and (29b) are wound around the pulley (not shown) of the speed change lever (not shown), and the speed change lever moves the rotor operation part (14a) of the control valve (14). It is configured so that it can be rotated. The end of the pulley (28) is connected to the outer casing (31) through the bearing (30).
The inner diameter of the casing (31) is set slightly larger than the outer diameter of the bearing (30) so that there is play between the bearing (30) and the casing (31). There is.

As shown in FIG. 1, the hydraulic cylinders (11) and (12) of the main transmission (A) have their operating portions configured as switching valves, and when each is operated to a position other than neutral, the pilot pressure is reduced. Is configured to generate. The hydraulic cylinder (13) of the auxiliary transmission (B) can be operated only in two positions, the low speed operation position (L) and the high speed operation device (H), and the neutral position of the switching valve of the operating portion of the hydraulic cylinder (13). The position only works during operation.

The forward / reverse switching device (C) is manually operated by an oscillating forward / backward switching lever (16), and a control valve mechanism (17) (corresponding to operating means) is interposed in the manual operation system. The control valve mechanism (17) is configured to generate pilot pressure when the forward / reverse switching device (C) is set to the forward operating device (F) or the reverse operating position (R).

The hydraulic clutch (3) is configured to be turned on and operated when hydraulic oil is supplied. The oil passage (18) from the pump (15) is branched into two to form an oil passage (19) for the control valve (14) and an oil passage (20) for the hydraulic clutch (3).

The hydraulic clutch (3) is automatically disengaged when any one of the main transmission (A), the sub transmission (B), and the forward / reverse switching device (C) is operated, and when the operation is completed, ,
It is configured so that it can be automatically entered and operated again, and the gear shifting operation can be performed without disengaging the main clutch (2).

The oil passage (20) for the hydraulic clutch (3) includes a low-pass valve (21a), a high-pass valve (21b) and a throttle valve (21).
c) Pressure control mechanism (21), 4 logical valves (2
2a) (corresponding to a switching valve), (22b), (22c), and (22d) are installed in the logic valve (22), and the oil on the hydraulic clutch (3) side of the logic valve group (22) is installed. In the road, an accumulator (2 that suppresses a sudden increase in pressure acting on the hydraulic clutch (3)
3) is provided.

With the above structure, when the main transmission (A) or the like is set in a state in which the aircraft is traveling (the front speed is the first speed state in FIG. 1), the logical valve group (22) is in the communication state and the hydraulic clutch (3) Is kept in a closed state. Then, when any one of the main transmission (A), the sub transmission (B), and the forward / reverse switching device (C) is switched in this state, the pilot pressure from the switching operation system decreases at the neutral position during the switching operation. Then, one of the logical valves (22a), (22b), (22) of the logical valve group (22) is
c) and (22d) shut off the hydraulic oil from the pump (15), and at the same time the hydraulic oil from the hydraulic clutch (3) is drained to the drain oil passage (2
Drain oil to 4) and disengage the hydraulic clutch (3). Next, when the shift change operation is completed, the logical valve group (22) is set to the communicating state again, and the hydraulic clutch (3) is operated.

In this case, in the pressure control mechanism (21), a rapid increase in the pressure of the hydraulic oil supplied to the hydraulic clutch (3) is suppressed. That is, the low-pass valve (21a) is open until the pressure reaches a relatively low first set pressure, and when the pressure reaches the first set pressure, the low-pass valve (21a) is closed.
The hydraulic oil is supplied through the throttle valve (21c) and the pressure gradually rises. Then, when the pressure reaches the relatively high second set pressure, the high pass valve (21b) is opened.

In addition, this hydraulic circuit has hydraulic cylinders (11), (1
In order to reduce the inconvenience that occurs when 2) and (13) operate at high speed, for the oil passage (18) from the pump (15),
An on-off valve (25) is provided which closes when the pressure on the lower side of the oil passage (18) rises above a predetermined value. In addition, excess hydraulic oil is passed through the oil passage (18a) to the power steering mechanism (32).
There is also a relief valve (26) for sending to.

Next, a configuration in which braking is automatically applied when switching between forward and backward travel will be described. FIG. 1 shows a state in which the forward / reverse switching lever (16) is operated by the forward operating device (F) and the control valve (14) is operated by the first speed position (F ₁ ). In this state,
Control valve mechanism (17) and hydraulic cylinders (11), (12),
By the pilot pressure from the switching valve of (13), each logical valve (22a), (22b), (22c), (22d) is located on the hydraulic oil supply side to the hydraulic clutch (3) (logical valve (22a )), The hydraulic clutch (3) is in the engaged state, and the aircraft is moving forward.

When the forward / reverse switching lever (16) is first operated to the neutral position in order to switch from the forward drive state to the reverse drive state, the pilot pressure from the control valve mechanism (17) disappears as shown in FIG. (22a) operates the hydraulic clutch (3) to the draining state, and connects the oil passage (33) from the pressure control mechanism (21) to the wet multi-plate traveling brake (34) (logic) Equivalent to the braking position of the valve (22a)).

At this time, the hydraulic clutch (3) is disengaged, the pressure in the oil passage (33) is reduced, and the low-pass valve (21a) of the pressure control mechanism (21) is opened from the state shown in FIG. 1 and the high-pass valve (21b) is opened. ) Closed or high pass valve (21b)
Only the state is closed. As a result, the traveling brake (34) is operated by the action of the pressure control mechanism (21) described above.
While the rapid increase in the pressure on the vehicle is suppressed, the traveling brake (34) enters a relatively smooth state and the forward braking is applied.

Next, when the forward / reverse switching lever (16) is operated to the reverse operation position (R), pilot pressure is generated again from the control valve mechanism (17), and the logical valve (22a) causes the hydraulic pressure as shown in FIG. The hydraulic oil is supplied to the clutch (3) and the traveling brake (34) is operated to the oil draining state (the logical valve (22
Equivalent to the driving position in a)). As a result, the traveling brake (34) is disengaged, the hydraulic clutch (3) is engaged, and the machine body is in the reverse drive state.

In addition, a manual switching valve (35) for shutting off the oil passage (36) to the traveling brake (34) is also provided so that a state in which the above-mentioned control action does not appear is obtained. .

[Another embodiment]

In the above-described embodiment, the forward / reverse switching device (C) was manually operated by the forward / reverse switching lever (16), but as shown in FIG. 5, a hydraulic cylinder for operating the forward / reverse switching device (C). (Not shown), a control valve mechanism (17) for generating pilot pressure is incorporated in the hydraulic cylinder, an electromagnetic control valve (37) for the hydraulic cylinder is provided, and a push button type forward / reverse selector switch ( A structure in which the control device (39) switches the control valve (37) on the basis of a signal from 38) can also be adopted.

In this case, the control valve (37) is not immediately operated even when the forward / reverse selector switch (38) is operated, but is held in the neutral position for a short time so that the traveling brake (34 ) Control operation is performed sufficiently.

It should be noted that reference numerals are added to the claims for convenience of comparison with the drawings, but the present invention is not limited to the structures of the accompanying drawings by the entry.

[Brief description of drawings]

The drawings show an embodiment of the hydraulic circuit structure of a work vehicle according to the present invention. Fig. 1 is a hydraulic circuit diagram showing the state of each valve in the first forward speed state, and Fig. 2 is a front and rear view from the state shown in Fig. 1. FIG. 4 is a hydraulic circuit diagram showing the state of each valve when the advance switching lever is operated to the neutral position, FIG. 3 is a sectional view showing the structure of the operating portion of the control valve,
FIG. 5 is a schematic diagram showing a power transmission system to the front and rear wheels, and FIG. 5 is a hydraulic circuit diagram in another embodiment. (3) …… hydraulic clutch, (15) …… pump, (17)…
... Operating means, (21) ... pressure control mechanism, (22a) ... switching valve, (34) ... traveling brake, (C) ... forward / reverse switching device.

Claims (1)

[Claims] A hydraulic clutch (3) for transmitting power to a traveling system, a gear shift type forward / reverse switching device (C), and a traveling brake (34), and a hydraulic oil from a pump (15). Is configured to be supplied to the hydraulic clutch (3) through a pressure control mechanism (21) that smoothly increases the pressure on the lower side, and the pressure control mechanism (21) and the hydraulic clutch (3) are connected to each other. In the meantime, the hydraulic oil from the pressure control mechanism (21) is supplied to the hydraulic clutch (3) to operate the hydraulic clutch (3), and the traveling brake (34) is set in the oil draining state to cut and operate the traveling. Position and braking position where hydraulic oil from the pressure control mechanism (21) is supplied to the traveling brake (34) to operate the hydraulic brake (34), and the hydraulic clutch (3) is in an oil-discharging state to turn it off. And a switching valve (22a) capable of switching operation, and The switching valve (22a) is interlocked with the switching operation of the forward / reverse switching device (C) from one speed change state to the other speed change state.
Is switched from the traveling position to the braking position, and in conjunction with the completion of the switching operation of the forward / reverse switching device (C), the switching valve (22
Operation means (1) for switching a) from the braking position to the traveling position
7) equipped with hydraulic circuit structure of work vehicle.