JP3784505B2 - Hydraulic circuit of work vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a work vehicle, in particular, in an excavation work vehicle such as a backhoe, in which a hydraulic circuit for operating a work machine is provided with an impact prevention circuit for eliminating an impact generated when starting the work machine part .
[0002]
[Prior art]
In the conventional excavation work vehicle, the working machine operating hydraulic circuit is not provided with an impact prevention circuit constituted by an automatic switching valve as shown in the prior art drawing shown in FIG.
[0003]
The impact at the start of the work machine is avoided by the opening characteristics of the control valve spool, and the impact on the hydraulic motor at the start of traveling is avoided to some extent by tuning the counter balance valve.
[0004]
[Problems to be solved by the invention]
In the excavation work vehicle, the construction is such that the impact can be eliminated and the engine can be started smoothly at the start of the operation of the work machine part, thereby facilitating the operation.
[0005]
[Means for Solving the Problems]
The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.
[0006]
It is configured to supply pressure oil from multiple hydraulic pumps to each cylinder via an automatic switching valve, travel valve, swing operation valve, arm operation valve, boom operation valve, or bucket operation valve. The switching valve is switched by a switch between a pilot pump and the automatic switching valve in a hydraulic circuit configuration in which a spool is moved by an urging spring and pressure oil from the plurality of hydraulic pumps escapes to an oil tank. And a throttle is provided between the solenoid valve and the automatic switching valve, and another throttle is provided on the pilot line constructed between the throttle and the automatic switching valve .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described.
FIG. 1 is a side view of an excavation work vehicle showing a lock mechanism of a traveling operation lever 1, FIG. 2 is also a side view of an excavation work vehicle showing a lock mechanism of only a conventional work machine operation lever, and FIG. FIG. 3 is a hydraulic circuit diagram showing a configuration in which an impact prevention circuit G is interposed.
[0008]
4 is a hydraulic circuit diagram of a conventional excavating work vehicle that does not incorporate an impact prevention circuit, FIG. 5 is a hydraulic circuit diagram showing a specific configuration and operation of the impact prevention circuit G, and FIG. 6 is provided with an impact prevention circuit. It is a hydraulic circuit diagram which shows the concrete structure and effect | action when there is no.
[0009]
In the conventional working machine operating hydraulic circuit shown in FIG. 4, the technology of the impact prevention circuit G and the automatic switching valve 4 is not interposed.
In the present invention, the impact prevention circuit G is provided at the inlet portion of the pressure oil from the hydraulic pumps P1 and P2.
[0010]
A circuit through the diaphragm A constitutes a pilot line PG for an impact prevention circuit. The throttle D needs to be interposed in order to apply pressure necessary for operation to the left remote control valve 12L and the right remote control valve 12R even when the pressure of the pilot line PG is the same as the pressure of the hydraulic oil tank. is there.
[0012]
The throttle A is for securing the pressure of the pilot pump P4 necessary for the remote control valves 12L and 12R and at the same time for adjusting the switching speed of the spool of the automatic switching valve 4 constituting the impact prevention circuit G. .
When the work machine operation levers 10 and 11 are not operated in a normal state, the automatic switching valve 4 moves the spool against the biasing spring, and the hydraulic oil from the hydraulic pumps P1 and P2 is used as the hydraulic oil. It is a circuit to escape to the tank.
[0013]
The left and right traveling valves 28L and 28R or any one of the arm operating valve 15, the swing operating valve 16, the boom operating valve 13, the bucket operating valve 14, the blade operating valve 17, and the turning operating valve 18 by the work implement operating levers 10 and 11. Is switched, the pilot line PG is blocked at the position of the valve operated by the work implement operating levers 10 and 11.
As a result, a pressure is generated in the pilot line PG, and the spool of the automatic switching valve 4 constituting the impact prevention circuit G is slid and switched by this pressure.
[0014]
By switching the spool of the automatic switching valve 4, the circuit for returning from the hydraulic oil from the hydraulic pumps P1 and P2 to the hydraulic oil tank is gradually throttled, and at the same time, the left and right traveling valves 28L and 28R, or the arm operation valve 15, the hydraulic oil of the hydraulic pumps P1 and P2 is supplied to the hydraulic motor and the cylinder through any one of the swing operation valve 16, the boom operation valve 13, the bucket operation valve 14, the blade operation valve 17 and the turning operation valve 18. . The pressure oil to the cylinder and the motor is gradually increased according to the degree of restriction of the restriction A.
[0015]
By gradually supplying the pressure oil to the hydraulic motor and cylinder, a sudden rise in pressure is avoided to prevent impact when starting the work machine.
When the spool of the automatic switching valve 4 constituting the impact prevention circuit G reaches the stroke end, the entire amount of hydraulic oil from the hydraulic pumps P1 and P2 flows to the cylinder or motor.
[0016]
By pulling out the pressure oil of the automatic switching valve 4 constituting the impact prevention circuit G by the electromagnetic valve 5 operated by the lifting / lowering state detection switch 6 as described above, the lever stand 2 is rotated and the working machine of the working machine is operated. When the travel operation lever 1 is operated as shown in FIG. 5 together with the operation of locking the operation levers 10 and 11, the pressure oil of the hydraulic pumps P1 and P2 does not reach the left and right travel valves 28L and 28R. The lever 1 is also locked at the same time.
Conventionally, as shown in FIG. 2, the operation lever is locked so that the boom operation lever, the arm operation lever, the bucket operation lever, and the turning operation lever are locked when the operator stands up from the seat. There was a drive control lever that could not be locked.
Therefore, even if the work lever is locked when getting on and off, there is a problem that the excavation work vehicle starts to move when the traveling operation lever is touched.
Further, as shown in FIG. 1, when the lever stand 2 is turned, the lifting / lowering state detection switch 6 is turned off, the bell crank 3 is turned by the electromagnetic solenoid SO, and the engaging protrusion 20 is moved to the engaging protrusion insertion recess 21. There was also a mechanism for locking the travel control lever 1 by locking.
[0017]
A conventional mechanical locking mechanism will be described with reference to FIG.
At a position where the operator passes by the side of the seat S at the time of getting on and off, a lever stand 2 is arranged that can be switched up and down between the driving posture and the raising and lowering posture. A lift state detection switch 6 for detecting the lift of the operator is provided at the base of the lever stand 2. When the lifting / lowering state detection switch 6 detects the lifting / lowering of the operator, the lifting / lowering state detection switch 6 is turned off. By turning off the lift state detection switch 6, the solenoid valve 5 is opened and the pressure oil of the pilot pump P4 that supplies pressure oil to the left remote control valve 12L and the right remote control valve 12R is fully relieved, as shown in FIG. No pressure is generated on the dotted pilot line PL.
[0018]
As a result, the left remote control valve 12L and the right remote control valve 12R cannot be operated, so that the work machine is in a locked state.
However, in the conventional hydraulic circuit shown in FIG. 6, the left traveling hydraulic valve 28L that supplies pressure oil to the left and right traveling hydraulic motors and the hydraulic pumps P1 and P2 that supply pressure oil to the right traveling hydraulic valve 28R are pilots. Since the pressure oil is supplied regardless of the line PL, if the traveling operation lever 1 is erroneously operated, the traveling hydraulic motor is rotationally driven, and a situation occurs in which the gas advances. T is a battery.
[0019]
In FIG. 1, the configuration of another prior art will be described.
An electromagnetic valve 5 that locks a work implement operating lever that is opened / closed by the lifting / lowering state detection switch 6 is provided. In addition, as shown in FIG. 1, a mechanism for locking the travel operation lever 1 via the electromagnetic solenoid SO when the lift state detection switch 6 is turned off is configured.
That is, when the lift state detection switch 6 is turned OFF, the electromagnetic valve 5 is opened, and at the same time, the electromagnetic solenoid SO is turned ON by the power supply from the battery T, and the bell crank 3 is rotated to be provided on the bell crank 3. The engaging projection 20 is configured to be fitted into an engaging projection fitting recess 21 provided at the base of the traveling operation lever 1.
[0020]
With this configuration, when the lever stand 2 is rotated upward and it is detected that the operator is moving up and down, the work implement operation lever is locked and the traveling operation lever 1 is also locked. In this case, the excavation work vehicle 1 is configured not to erroneously travel by operating the travel operation lever 1 by an erroneous operation.
The above is a conventional mechanical lock mechanism, but it is necessary to separately provide parts, and the operation may be uncertain.
In the present invention, an impact prevention circuit G at the time of starting the work machine is provided, and the automatic switching valve 4 of the impact prevention circuit G is also used to constitute a hydraulic travel control lever 1 locking mechanism.
Next, referring to FIG. 5, a lock mechanism for the travel operation lever 1 in the case of a hydraulic type will be described.
In this case, when the lifting / lowering state detection switch 6 is turned off to the automatic switching valve 4 constituting the impact prevention circuit G provided to avoid the impact at the time of starting the work machine, the hydraulic pumps P1, The pressure oil from P2 is configured to pass through a circuit that recirculates directly to the hydraulic oil tank, and it becomes impossible to supply the pressure oil from the hydraulic pumps P1 and P2 to the travel drive motor. The hydraulic motor of the excavation work vehicle was not driven, and there was no erroneous gas travel.
[0021]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
In other words, since the spool of the automatic switching valve 4 is switched, the circuit for returning the hydraulic oil from the hydraulic pumps P1 and P2 to the hydraulic oil tank is gradually throttled, and at the same time, The pressures of the hydraulic pumps P1 and P2 through the travel valves 28L and 28R or any one of the arm operation valve 15, the swing operation valve 16, the boom operation valve 13, the bucket operation valve 14, the blade operation valve 17, and the swing operation valve 18. Oil is supplied to the hydraulic motor and cylinder. The pressure oil to the cylinder and the motor is gradually increased according to the degree of restriction of the restriction A. By gradually supplying the pressure oil to the hydraulic motor and the cylinder, it is possible to avoid a sudden rise in pressure and prevent an impact when starting the work machine.
[Brief description of the drawings]
FIG. 1 is a side view of an excavation work vehicle showing a lock mechanism of a conventional travel operation lever 1;
FIG. 2 is a side view of an excavation work vehicle showing a conventional lock mechanism using only a work machine operation lever.
FIG. 3 is a hydraulic circuit diagram showing a configuration in which an impact prevention circuit G is interposed in a working machine hydraulic circuit.
FIG. 4 is a hydraulic circuit diagram of a conventional excavation work vehicle that does not incorporate an impact prevention circuit.
FIG. 5 is a hydraulic circuit diagram showing a specific configuration and operation of an impact prevention circuit G.
FIG. 6 is a hydraulic circuit diagram showing a specific configuration and operation when no impact prevention circuit is arranged.
[Explanation of symbols]
A, D Aperture G Impact prevention circuit 1 Traveling operation lever 2 Lever stand 3 Bell crank 4 Automatic switching valve 5 Solenoid valve 6 Elevating state detection switch 7 Stopper 10, 11 Work machine operation lever 12L, 12R Remote control valve 101 Pilot pressure supply circuit 102 Drain tank circuit

Claims (1)

Configured to supply pressure oil from multiple hydraulic pumps to each cylinder via either automatic switching valve, travel valve, swing operation valve, arm operation valve, boom operation valve, bucket operation valve,
In the configuration of the hydraulic circuit, the automatic switching valve has a circuit in which a spool is moved by an urging spring and pressure oil from the plurality of hydraulic pumps escapes to an oil tank.
A solenoid valve that is switched by a switch is provided between the pilot pump and the automatic switching valve, a throttle is provided between the solenoid valve and the automatic switching valve, and another pilot line is provided between the throttle and the automatic switching valve. A hydraulic circuit for a work vehicle, characterized in that a throttle is provided.

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