JPS6216467Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a hydraulic control device for a crane, and particularly relates to a hydraulic control device for a crane that always operates a boom actuator at a controlled speed.

The actuator of the boom cylinder in the hydraulic circuit appropriately controls the depression of the boom body, which is driven by switching the unit valve for the boom, so it is possible to operate the lever of the unit valve without being affected by load pressure. It must be operated at a suitable speed.

A typical example of a conventional crane hydraulic control device will be described with reference to FIG. 1 has unit valves 5 and 6 that control boom and telescopic actuators 3 and 4 with one multiple control valve. 2 is the other multiple control valve and has unit valves 9 and 10 that control actuators 7 and 8 for the auxiliary winding and the main winding. The selector valves 11 and 12 are connected to the multiple control valve 1 depending on their switching positions.
The rear chamber 14 of the logic valve 13 provided in the tank 15
By cutting off the connection to pump P1, the oil discharged from pump P1 is merged into pump P2. Furthermore, a pressure compensation flow control valve (hereinafter simply referred to as a flow control valve) interposed between the unit valve 5 and the pump P1 in the multiple control valve 1
16 is a unit valve 5 for the boom actuator 3.
The flow rate is supplied according to the amount of operation.

When the unit valve 5 is operated independently, the flow rate control valve 16 is automatically controlled so as to keep the differential pressure between the front and rear constant, which is caused by the opening degree of a variable orifice (not shown) provided in the unit valve 5. The flow rate according to the degree of opening is the cylinder port 17 or 1.
8 to one side of the actuator 3 of the boom to actuate said actuator 3.

However, when the actuators 3, 7, and 8 of the boom, auxiliary hoist, and main hoist are operated simultaneously, the load pressure of the actuators 7, 8 of the multiple control valve 2 is transferred to the downstream circuit of the flow control valve 16 via the circuit 23. It is pressurized to 20. At this time, if the load pressure of the actuators 7 and 8 fluctuates, the output flow rate of the unit valve 5 fluctuates until the flow control valve 16 stabilizes. The output flow rate to the actuator 3 changes instantaneously over a short period of 0.1 to 0.2 seconds, and the boom actuator 3 operates at a steady speed, acceleration, deceleration, or Steady speed or vice versa operation resulted in the boom body wobbling and preventing proper operation of the device.

The present invention was conceived in view of the above-mentioned problems, and its purpose is to provide a hydraulic control system for a crane that increases the reliability of boom actuator operation during multiple operations.

FIG. 2, which shows an embodiment of the present invention, will be described below. Note that the same reference numerals are used for the same parts as in FIG. 1, detailed explanation is omitted, and only the different parts will be explained.

A selector valve 22 that operates in conjunction with the unit valve 5 is provided at the end of the unit valve 5 of the multiple control valve 1. The rear chamber 14 is configured to be connected to or disconnected from the tank 15 via the circuit 21,
When the unit valve 5 is in the neutral state and the unit valves 9 and/or 10 are operated to the operating position, the logic valve 13 is closed and oil from the pump P1 is supplied to the multiple control valve 2, and the unit valve 5 is operated. At this time, the logic valve 13 is opened and the remainder of the oil discharged from the pump P1 used to drive the boom actuator is returned to the tank.

Next, the operation of the present invention will be explained. In the illustrated state in which all the unit valves linked to the selector valve are neutral, the selector valve 22 linked to the boom unit valve 5 is shut off, but the selector valves 11 and 12 connect the rear chamber 14 of the logic valve 13 to the tank 15. Therefore, the oil discharged from the pump P1 flows back to the tank 15 via the logic valve 13. When the unit valve 5 is neutral as shown in the figure and at least one unit valve of the control valve 2 is in the switching position, the selector valve 22 is linked to the boom unit valve 5, the selector valve 11 is linked to the unit valves 9 and 10, 12, the connection between the rear chamber 14 of the logic valve 13 and the tank 15 is cut off. Therefore, the oil discharged from the pump P1 can be supplied to the multiple control valve 2.

During a combined operation in which the boom unit valve 5 and the auxiliary hoisting unit valve 9 or/and the main hoisting unit valve 10 are moved to the upper or lower position in the figure, the rear chamber 14 of the logic valve 13 is moved to one of the selector valves 11 or/
and 12, the connection to the tank 15 is cut off, but since the other selector valve 22 connects to the tank 15, the rear chamber 14 is at tank pressure.
At this time, the logic valve 13 is in an unloaded state, and the load pressure of the auxiliary winding and main winding actuators 7 and 8 does not act on the downstream circuit 20 of the flow rate control valve 16 via the circuit 23. Therefore, the discharge oil of the pump P1 is supplied to one side of the actuator 3 from the cylinder port 17 or 18 at an output flow rate corresponding to the opening degree of the variable orifice generated in response to the operation amount of the unit valve 5, and the return oil is supplied to one side of the actuator 3 from the cylinder port 18. Or it is returned to the tank 15 from 17. Therefore, the actuator 3 is operated at a constant speed unless the lever of the unit valve 5 is moved, so even if the loads on the actuators 7 and 8 of the auxiliary winding and the main winding fluctuate, shaking of the boom body is completely prevented. Can be done.

As described above, according to the present invention, the rear chamber of the logic valve provided in the multiple control valve is disconnected from the tank when the selector valve linked to the boom unit valve is in neutral, and connected to the tank when activated. Although the structure is simple, it is possible to cut off the fluctuating load pressure that occurs on the auxiliary winding and main winding actuators from acting on the boom actuator, so the boom actuator can be controlled appropriately. This has the effect of increasing the credibility of what is being done.

[Brief explanation of the drawing]

FIG. 1 is a conventional hydraulic circuit diagram, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. 1, 2... Multiple control valve, 3, 4, 7, 8... Actuator, 5, 6, 9, 10... Unit valve, 1
1, 12, 22... Selector valve, 13... Logic valve, 14... Rear chamber, 21... Circuit, P1, P2
……pump.

Claims (1)

[Scope of utility model registration request] A multiple control valve is connected to each of the two pumps,
One unit valve of one of the multiple control valves controls the boom actuator with the required amount of oil discharged from one pump, and the remaining discharged oil is passed downstream of the center bypass passage of the unit valve to control the other pump. A hydraulic system for a crane equipped with a circuit supplying a valve includes a logic valve that communicates and cuts off the downstream of the center bypass passage of one control valve to the tank by communicating and cutting off the rear chamber to the tank; A selector valve is provided to communicate and shut off the rear chamber to the tank, and is switched in conjunction with the unit valve that controls the boom actuator of one of the control valves, shutting off at the neutral position and communicating at the operating position, and the other control valve. A hydraulic system for a crane, characterized in that the selector valve is switched in conjunction with a unit valve of a control valve, communicates in a neutral position and shuts off in an operating position, and is provided to form a parallel circuit with the selector valve. .