JPS595163B2 - Speed control circuit for cranes, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed control circuit for cranes, pile drivers, etc., and particularly to a very low speed control circuit for hoisting, turning, and traveling hydraulic circuits.

In recent years, as the work range of cranes has expanded, winch hoisting control has become possible by using variable capacity cedar hydraulic pumps to control speed over a wide range from low speeds to high speeds. It has been improved.

A conventional hoisting speed control circuit will be explained with reference to FIG.

1 is a variable displacement cedar hydraulic pump (hereinafter referred to as hydraulic pump) driven by an engine (not shown), and on the upstream side of the hydraulic pump 1 there is a directional switching valve 2 for switching and controlling the discharge oil, and an IJ IJ- for setting the circuit pressure. A valve 3 is provided.

The directional control valve 2 is connected to drive circuits 5, 6 of the hoisting hydraulic motor 4, and a counterbalance valve 7 is installed in the drive circuit 5.6.

8 is a return circuit.

A control circuit for the hoisting drive circuit configured as described above will be explained next.

9 is a hydraulic pump for operation, and a biloft valve 10 and a relief valve 20 are installed on the upstream side thereof.

The secondary pipe line 11.12 of the pyro 714100 is connected to the inlet side of the shuttle valve 130, and is also connected to the pressure receiving parts 2a and 2b of the directional control valve 2.

The outlet side of the shuttle valve 13 is connected to the control section 1a of the hydraulic pump 1 via a conduit 14.

In FIG. 1, the operating lever 10 of the pilot valve 10 is now
When a is swung in the direction of the arrow, hydraulic pressure corresponding to the amount of operation is generated in the secondary pipe line 11, and the hydraulic pressure is applied to the shuttle valve 13.
It flows into the control unit 1a through the pipe line 14, and the discharge pressure flow rate of the hydraulic pump 1 is controlled.

On the other hand, the pressure oil generated in the secondary pipe line 11 flows into the pressure receiving part 2a, switches the directional control valve 2, and rotates the hydraulic motor 4 in the direction of the arrow.

In this way, by controlling the flow rate of the hydraulic pump 1, stable mid-to-high speed hoisting control of the suspended load can be performed.

On the other hand, a crane is used as a pile driver by attaching a pile driver attenment to its main body.

When this pile driver performs an auger action, the hoisting speed of this auger needs to be controlled over a wide range from a very low speed range to a high speed range depending on the soil quality, mortar injection speed, etc.

In this case, the conventional hoisting speed control circuit described above is designed to be capable of hoisting at high speeds, and therefore does not have sufficient controllability in a low speed range.

Therefore, when the operator needs to wind the winding in a low speed range (particularly in a very low speed range), he/she performs the work by repeatedly turning the winding lever on and off.

However, since auger work generally requires about 30 minutes of continuous operation, frequent turning on and off of the hoisting lever has the disadvantage of increasing operator fatigue.

In addition, in the conventional hoisting speed control circuit shown in FIG. 1, the discharge flow rate of the hydraulic pump 1 and the switching control of the directional control valve 2 are performed simultaneously, so the discharge flow rate of the hydraulic pump 1 is set to a small value. Then, the directional control valve 2 also enters the -off state, resulting in a disadvantage that control of the hoisting speed becomes unstable.

The present invention has been made in view of the above circumstances, and its purpose is, of course, to be able to perform stable medium to high speed hoisting control, but also to be able to perform very low speed control. To provide a control circuit that can perform stable very low speed control even when a lever is operated at a full stroke, for example, without frequently turning the lever on and off.

In order to achieve the above-mentioned object, the present invention has a pilot valve that switches and controls the discharge oil of the operating hydraulic pump,
The speed of a crane, etc. is configured to control the discharge oil of a variable displacement cedar hydraulic pump by the secondary pressure of the pilot valve, and to operate a directional control valve that switches and controls the discharge oil in accordance with the operation of the pilot valve. In the control circuit, a 2-position switching valve is provided in the middle of the pipe line that leads the secondary pressure of the pilot valve to the control part of the variable displacement cedar hydraulic pump, and connects or shuts off the pipe line regardless of the operation of the pilot valve. At the cutoff position of the switching valve, the control section of the variable displacement cedar hydraulic pump is to be communicated with the secondary side conduit of a pressure reducing valve provided separately from the pilot valve, and at the communication position of the two-position switching valve, medium-high speed control is performed. The present invention is characterized in that it performs very low speed control at the cutoff position.

An embodiment of the present invention will be described below with reference to FIGS. 2 to 5.

FIG. 2 shows the hoisting speed control circuit of the present invention, and the same reference numerals as in FIG. 1 represent the same or equivalent components.

The secondary pressure of the pilot valve 10 is controlled by the control unit 1 of the hydraulic pump 1.
A switching valve 15 is inserted in the middle of the pipe line 14 leading to the pipe line 14 for communicating or blocking the pipe line 14.

The switching valve 15 is a 2-position, 3-port electromagnetic valve, and a pressure reducing valve 160 secondary side conduit 17 is connected to its b port.

One end of the solenoid of the changeover valve 15 is connected to one end of a changeover switch 18 installed in the driver's cab, and the other end of the changeover switch 18 is grounded via a power source 19.

The other end of the solenoid of the switching valve 15 is grounded.

Therefore, the switching valve 15 can be switched by operating the switching switch 18 regardless of the operation of the pilot valve 10.

The pressure reducing valve 16 is provided on the upstream side of the operating hydraulic pump 9 in parallel with the pilot valve 10, and its secondary pressure can obtain the flow rate necessary for very low speed control of the hydraulic pump 1. It is set near the set pressure, and the set value of the secondary pressure can be changed by adjusting the threaded part.

FIG. 3 is an explanatory diagram of the operation when the switching valve 15 is switched.

When the switching valve 15 is switched from the communication side shown in FIG. 2 to the cutoff side shown in FIG.
It communicates with the next pipe line 17.

Next, the present invention will be explained in detail.

When the switching valve 15 is in the communication side as shown in FIG. 2 due to its spring pressure, stable medium-high speed hoisting control can be performed in the same way as the conventional hoisting speed control circuit shown in FIG. 1.

That is, when the operating lever 10a of the pilot valve 10 is swung in the direction of the arrow, hydraulic pressure is generated in the secondary pipe line 11,
The pressure oil is supplied to the shuttle valve 13 pipe line 14 and the solenoid valve 150.
The oil is supplied to the control section 1a of the hydraulic pump 10 through the ae port, and the discharge oil of the hydraulic pump 1 is controlled, and is also supplied to the pressure receiving section 2a of the directional switching valve 2, so that the hydraulic motor 4 rotates in the direction of the arrow.

In this way, hoisting control of the suspended load is performed.

At this time, if the operating lever 10a of the pilot valve 10 is operated to a full stroke, the hydraulic pump 1 will discharge the maximum flow rate and the directional control valve 2 will be completely switched.

Therefore, if the operating lever 10a is operated in this state, the hydraulic motor 4 can perform stable medium-high speed control by controlling the flow rate of the hydraulic pump 1.

Next, when stable very low speed control is desired, the changeover switch 18 is turned on as shown in FIG.

Then, the solenoid of the switching valve 15 is energized, and the pressure oil in the secondary pipe line 17 of the pressure reduction 16, which is set to the oil pressure corresponding to the flow rate required for very low speed control of the hydraulic pump 1, is transferred to the switching valve 15.
is supplied to the control unit 1a through the be port.

On the other hand, even if the operating lever 10a is operated in this state, the secondary pressure of the pilot valve 10 guided to the switching valve 15 will not be guided to the control unit 1a since the switching valve 15 has been switched to the cutoff side. There isn't.

Therefore, the secondary pressure of the pressure reducing valve 160 and the control pressure Pp of the hydraulic pump 10 are equal, so if the discharge flow rate of the hydraulic pump 1 is Q, the flow rate control diagram of the hydraulic pump 1 when the load pressure is constant is It will look like Figure 4.

Further, since the secondary pressure of the pilot valve 10 and the directional control valve 20 control pressure PC are equal, if the secondary flow rate of the directional control valve 20 is Qc, the flow rate control diagram of the directional control valve 2 is the fifth
It will look like the figure.

Conventionally, in FIGS. 4 and 5, the secondary flow rate Q is obtained when the pressure Pc of the directional control valve 2 is controlled to a half pressure of PC□ in an attempt to perform very low speed control.

However, in the present invention, when the load pressure P changes from P1 to P3 (P3>P2>Pt), it changes from Qcz to Qca, making stable flow control impossible. However, in the present invention, the pump 10 control pressure P, Since the directional control valves 20 and 20 foot pressures Pc are independent from each other, in FIG.
The control pressure Pc of the directional control valve 20 is set to P c 2 so as not to be affected by this, and the flow rate at that time is set to Qc=Qp.

In this state, the hydraulic pump 1 in Fig. 4! IJ# Pressure P Pressure machine Pressure machine Low speed control flow rate Qp If set to 3, Qc
=Q, 3.

Therefore, even when the operating lever 10a is operated at a full stroke, the oil discharged from the hydraulic pump 1 is not maintained at the pilot valve 10.
The flow rate Q3 necessary for very low speed control can be maintained by the secondary pressure of the pressure reducing valve 16 which is provided separately, and thereby stable very low speed control can be performed.

Although the above explanation has been made as a hoisting speed control circuit for a crane, the present invention can also be applied to positioning work by turning or traveling.

As described above, according to the speed control circuit of the present invention, two
In the communication position of the position switching valve, stable medium-high speed control can be performed in exactly the same way as before, and if you want to perform very low speed control, you can switch the 2-position switching valve to the cutoff position to achieve stable very low speed control. Thus, stable speed control can be performed from a high speed range to a low speed range in a hoisting, turning, and traveling device such as a crane.

Particularly when auger work with a pile driver requires very low speed control over a long period of time, the control lever is turned on frequently like in the past.

There is no need to keep turning it off, and for example, the operating lever can be operated in a full stroke and detented as necessary, so work efficiency and operability can be greatly improved.

In the above embodiment, the secondary pressure of the pilot valve 10 is configured to act as a control pressure for switching the directional control valve 2, but the control lever 10 of the pilot valve 10
It is also possible to mechanically switch the directional control valve 2 by attaching a rod and a link to the control lever 1.
The movement of 0a may be detected by a microsinch and switched electrically.

Furthermore, the electromagnetic valve 15 may have any configuration as long as it is an on/off valve.

[Brief explanation of the drawing]

Fig. 1 is a conventional speed control circuit diagram, Fig. 2 is a speed control circuit diagram of the present invention, Fig. 3 is an action explanatory diagram of Fig. 2, and Figs. 4 and 5 are flow control lines according to the present invention. It is a diagram. 1...Variable capacity expansion hydraulic pump, 1a...
・Control unit, 2... Directional switching valve, 9...
Hydraulic pump for operation, 10...Pilot valve, 1
0a... Operation lever, 11.12.14...
...Pipeline, 13...Shuttle valve, 15...
...Switching valve, 16...Reducing valve.

Claims (1)

[Claims] 1 It has a viroft valve that switches and controls the discharge oil of the operating hydraulic pump, and controls the discharge oil of the variable displacement cedar hydraulic pump by the secondary pressure of the viroft valve, and also has a directional switching valve that switches and controls the discharge oil. In a speed control circuit for a crane or the like that is configured to operate in response to the operation of the viroft valve, a pipe line that leads the secondary pressure of the viroft valve to the control section of the variable displacement cedar hydraulic pump is connected in accordance with the operation of the viroft valve. A two-position switching valve is provided to communicate or cut off the pipeline independently, and in the blocking position of the switching valve, a control section of the variable displacement cedar hydraulic pump is provided on the secondary side of a pressure reducing valve separately from the viroft valve. A speed control circuit for a crane or the like, characterized in that the two-position switching valve is configured to communicate with a pipe, and performs medium-high speed control in the communication position, and performs very low-speed control in the cut-off position.