JP2589528B2 - Safety device when the spool of the directional control valve is stuck - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an open hydraulic circuit used for a truck crane, a power shovel and the like.

[Conventional technology]

In general spool valves, the machining accuracy and assembly accuracy of the spool and its fitting hole are low, or the spool valve is distorted by its mounting or hydraulic pressure, or the gap between the spool and the fitting hole wall is small. If oil leakage from the gap becomes uneven over the circumference due to clogging of garbage or the like, the pressure distribution on the outer periphery of the spool becomes unbalanced. As described in the Hydraulic Technology Handbook, published on January 30, pages 380 to 381, the fluid sticking phenomenon of the spool may occur, but there has been no decisive way to completely prevent the fluid sticking phenomenon in the past.

[Problems to be solved by the invention]

For this reason, in an open hydraulic circuit that operates each actuator such as a truck crane and a power shovel, if a fluid sticking phenomenon occurs in the spool of the directional control valve, the directional control valve cannot be returned to the neutral position while the actuator is driven. In this case, the actuator may run away, causing damage to surrounding buildings and equipment, or causing personal injury.

The present invention addresses this problem. The pump is operated under no load by conducting the vent circuit of the pilot operated relief valve only when the directional control valve that is driving the actuator cannot return to the neutral position due to the fluid sticking phenomenon. (Unload)
Accordingly, it is an object to stop the driving of the actuator.

[Means for solving the problem]

The present invention achieves this object by providing an operating lever (10).
A directional control valve (11), which is operated by a solenoid or a pilot and the output port and the tank port communicate with each other at a neutral position, and an actuator controlled by the directional control valve. Pilot operated relief valve (1
In the open hydraulic circuit connected to 3), the relief valve (1
The normally closed solenoid valve (14) is inserted into the vent circuit (52) between the vent chamber and the tank in 3), and it is electrically detected that the operating lever is at the actuator driving position, and is normally closed. A first switch control device (16) for connecting an operation relay (41) of the first switch (15) to a power source, and a directional control valve (1).
The second switch control device (18) detects that the actuator 1 is at the actuator drive position by increasing the actuator drive hydraulic pressure at its output side and closes the normally open second switch (17) by the detected hydraulic pressure. When the first and second switches are inserted in series into the operation circuit (58) of the solenoid (14a) for opening the solenoid valve and the operation lever at the actuator driving position is returned to the neutral position, 2 switches (17)
So that the first switch (15) closes after the first
The charge / discharge circuit of the capacitor (20) is connected to the circuit between the switch control device (16) and the operation relay, and the spool of the directional control valve is fluid-fixed to operate the solenoid valve opening solenoid operation circuit (58). ) Is provided with means for holding the second switch (17) or the solenoid (14a) for opening the solenoid valve in a conductive state during the no-load operation of the pump with the conductive state.

This means includes the second step even during the no-load operation of the pump.
The detected hydraulic pressure for operating the second switch control device (18) is set low or the operating circuit (58) is connected in parallel with the solenoid (14a) for opening the electromagnetic valve so that the switch is kept closed. A relay (63) is connected, and a relay self-holding circuit (65) in which a normally open contact (63a) of the relay and a normally closed reset switch (64) are inserted in series is connected to the first and second relays. It is connected to the operating circuit (58) in parallel with the switch.

The capacitor charging / discharging circuit includes a diode (19) inserted in a circuit between the first switch control device (16) and the operation relay (41), and a resistor (56) connected to the input side and the output side of the diode, respectively. ) And (55), and a capacitor (20) grounded on the non-connection side and a resistor (57) grounded on the input side of the diode.

[Action]

According to the above configuration, when the operation lever (10) is in the neutral position, the output port of the directional control valve (11) communicates with the tank port, and the operating oil pressure of the second switch control device (18) is generated. No, the second switch (17) is open,
The operation circuit (58) of the solenoid (14a) does not conduct.

When the operation lever is rotated from the neutral position to either the left or right actuator driving position for driving the actuator, the first
By the switch control device (16), the operation relay (41) is turned on to open the first switch (15), and the directional control valve is switched to the actuator driving position. This is detected by an increase in the actuator driving hydraulic pressure at the output side of the direction switching valve, and the second switch control device (18) closes the second switch (17). The two switches are closed and the operating circuit (58)
Does not conduct.

On the other hand, the first switch (1) is controlled by the first switch control device.
As soon as 5) is opened, the capacitor is charged by the charge / discharge circuit of the capacitor (20). Therefore, the operating lever is returned from the actuator driving position to the neutral position, and the operation relay (1) is operated by the first switch control device. When the power supply to 41) is cut off, the discharging power of the capacitor is supplied to the activation relay, delaying the return of the first switch to the closed position. As a result, the directional control valve returns to the neutral position, and the hydraulic pressure of the second switch control device (18) is discharged from the directional control valve to the tank, whereby the second switch (17) returns to the open position. After that, the first switch (15) will be closed, and the solenoid operating circuit (58) will not be conducting either.

Therefore, when the directional control valve is normally switched between the neutral position and the actuator moving position by operating the operation lever, the operation circuit (58) is not always conducted, and the solenoid valve (14) is closed. In some cases, the relief valve (13) is not opened and the pump (2) is not operated under no load, and the actuator can be controlled freely.

However, when the operating lever is returned to the neutral position while the actuator is being driven and the spool of the directional control valve is fixed at the actuator driving position due to the fluid fixing phenomenon, the second switch (17) remains closed. Since the first switch (15) returns to the closed position (normal position), the operation circuit (58) conducts and opens the solenoid valve (14), and accordingly the relief valve (13) opens to operate the pump under no load. (Unload). Since the means for holding the second switch or the solenoid (14a) for opening the electromagnetic valve in the conductive state is provided during the no-load operation of the pump, the actuator is maintained in the drive stopped state and there is no danger of runaway.

As this means, the second pressure is detected by detecting the hydraulic pressure of the direction switching valve at the actuator driving position when the pump is unloaded.
Obviously, if the operating oil pressure of the second switch control device is set low so that the switch is closed, the solenoid (14a) is kept conductive.

As the above means, a relay (63) is connected to the operating circuit (58) in parallel with the solenoid (14a) for opening the solenoid valve, and if the solenoid valve (14) is opened by conduction of the above-mentioned operating circuit, the relay is simultaneously opened. (63) is activated, the normally open contact (63a) is closed by the signal and the self-holding circuit (65) is turned on to hold the solenoid (14a) in a conductive state. The self-holding action is released by opening the normally closed reset switch (64). When the directional control valve is normally switched by operating the operation lever, the operation circuit (58) does not conduct as described above, so that the relay (63) operates at an emergency and the self-holding circuit (65).
There is no danger of conduction.

The second switch control device (18) detects that the direction switching valve is at the actuator driving position by increasing the actuator driving oil pressure at its output port, and closes the second switch by the detected oil pressure. It is clear that the runaway of the actuator can be prevented even if the spool of the directional valve has a fluid stuck phenomenon in any half-switching state between the neutral position and the maximum sliding limit of the actuator driving position.

The capacitor charge / discharge circuit connects a capacitor (20) to a circuit between the first switch control device (16) and the operation relay (41) via a resistor (55) for adjusting a time constant. Although a conventionally well-known configuration in which the non-connection side of the capacitor is grounded may be used, the charging voltage of the capacitor is reduced by half due to the voltage dividing phenomenon due to grounding, which complicates the configuration of the amplifier and returns the first switch to the closed position. Is slightly inaccurate.
Therefore, a diode (19) is inserted in a circuit between the first switch control device and the operation relay, and resistors (56) and (55) for adjusting the time constant are provided on the input side and the output side of the diode, respectively.
If the capacitor (20) is connected via the capacitor, the non-connection side of the capacitor is grounded, and the input side of the diode is grounded via the resistor (57), the operation lever is turned to the actuator driving position to operate. When the relay (41) is turned on, the input side and the output side of the diode charge the capacitor via the resistors (56) and (55), respectively, so that the resistor reduces the power consumed for charging the capacitor. As a result, the first switch (15) is quickly opened, and the charging voltage of the capacitor is increased.

Accordingly, when the operation lever is returned to the neutral position and the supply of power to the operation relay (41) by the first switch control device is stopped, the discharge power of the capacitor is supplied to the operation relay via the resistor (55). At the same time, since a part of the discharged power is discharged to the ground via the resistors (56) and (57) in sequence, the return of the first switch (15) to the closed position is delayed for a certain time, and immediately after the second switch is opened. The first switch can be closed.

〔Example〕

FIG. 1 shows an embodiment of the present invention. When the operating lever 10 is turned to a left or right actuator driving position from a neutral position shown in the drawing, a potentiometer controlled thereby is controlled.
The output of 40 is subjected to processing such as amplification, and the directional control valve 11 for solenoid control pilot operation is switched to the left or right actuator drive position, and the oil passage 4 connected to its output port
The supply of the discharge pressure oil of the pump 12 to the actuator (not shown) via 6, 47 and the discharge of oil from the actuator to the tank T are performed.

The output port of the direction switching valve 11 communicates with the tank port at the neutral position shown. For this reason, when a load always acts on the actuator, the two oil passages 46, 4 on the actuator side are used.
Of course, a check valve (holding valve) that opens by the pilot pressure from the other oil path may be attached to one of the 7, so that the load oil pressure does not act on the output port of the directional switching valve in the neutral position. It is.

The first switch 15 is a normally closed contact of the operation relay 41,
The first switch control device 16 includes an electromagnetic coil 42 of the relay.
The switches 45a and 45b that close when the operation lever 10 is switched to the left and right actuator driving positions are connected in parallel in an electric circuit 44 that connects the power supply 43 to the power supply 43.

The second switch 17 is a normally open contact of the pressure switch 48, and the second switch control device 18 has the following configuration.
A pilot oil passage 49 communicating with the output port at the neutral position and communicating with the output port on the high pressure side at the actuator driving position is connected to the directional control valve 11, and the pilot oil taken out from the pilot oil passage 49 is connected. By pressure,
The hydro switching valve 50 which normally returns the operating portion of the pressure switch 48 to the position connecting the tank T can be switched to the position connecting the operating portion of the pressure switch 48 to a low-pressure hydraulic source 51 such as a pilot pump. To be configured.

The reason why the pressure switch 48 is not directly operated by the pilot pressure of the oil passage 49 is that a special pressure-resistant pressure switch is required because the maximum discharge pressure of the pump 12 or the set pressure of the relief valve 13 due to the load is extremely high. It is.

Also, the operating part of the pressure switch 48 has a low pressure due to the pilot pressure in the oil passage 49 during the no-load operation of the pump in which the operating circuit 58 of the solenoid valve opening solenoid 14a is in conduction with the spool of the directional control valve being fluidly fixed. Connected to the hydraulic source 51,
The pilot pressure for operating the switching valve 50 of the second switch control device 18 is set low (about 3 to 5 kg / cm 2) so as to maintain the second switch 17 in the closed position.

For this reason, when the resistance of the return circuit 53 to the tank T is larger than that of the directional control valve 11, the pressure difference between the output port of the directional control valve and the tank port is set as shown in FIG. It is configured as a differential pressure control valve that is switched to the upper position when pressure is reached. Reference numeral 54 denotes a pilot oil passage for transmitting the pressure of the tank port or the back pressure of the return circuit 53 to the switching valve 50.

A capacitor charging / discharging circuit including a diode 19, an electrolytic capacitor 20, and resistors 55, 56, 57 is provided by a first switch control device.
It is inserted into the electric circuit 44 between the 16 switches 45a and 45b and the amplifier 62.

In the figure, 59 is an alarm lamp connected in parallel to the solenoid valve opening solenoid 14a to the operating circuit 58, 60 is an oil passage between the discharge port of the pump 12 and the pressure port of the directional control valve 11, and 61 is an oil passage. 3 shows an oil passage connecting the relief valve 13.

FIG. 2 shows the above-mentioned relay 63 as means for holding the solenoid 14a for opening the electromagnetic valve in the conductive state during the no-load operation of the pump in which the circuit 58 including the first and second switches 15 and 17 is conductive. Normally open relay contact 63a and reset switch 64
This is another embodiment of the present invention in which a device including a self-holding circuit 65 including a device is provided. In the embodiment shown in FIG. 2, parts denoted by the same reference numerals as those in the embodiment shown in FIG. 1 indicate corresponding parts, and a directional control valve, a relief valve, and a second switch control not shown in FIG. The construction of the device is the same as that of FIG. 1, but the pilot set pressure for switching the hydro switching valve 50 does not need to be reduced as in the embodiment of FIG.

According to the present invention, the second switch control device (18) in the embodiment shown in FIG. 1 or FIG. 2 is provided with a pressure-resistant pressure switch directly operated by the pilot pressure of the pilot oil passage 49,
Alternatively, it is needless to say that a pressure-sensitive differential pressure switch operated by the pilot pressure of the pilot oil passages 49 and 54 may be included.

〔The invention's effect〕

According to the present invention, when the operation lever is switched from the neutral position to the actuator driving position, the first switch that opens earlier by the electric operation and the second switch that closes later by the hydraulic operation
The switch prevents the solenoid valve opening solenoid operating circuit (58) from conducting, and when the operating lever is returned from the actuator driving position to the neutral position, the electric charge charged to the capacitor during the actuator driving is discharged. Since the closing of the first switch is delayed later than the opening of the second switch to prevent conduction of the operating circuit, there is no danger of causing any trouble in controlling the directional control valve by the operating lever. Detected by a second switch that is closed by the actuator drive hydraulic pressure on the output side of the switching valve, and when a fluid sticking phenomenon occurs in the spool, the first switch and the second switch that are closed when the operation lever returns to the neutral position generate a signal. Open the solenoid valve quickly, operate the pump under no load regardless of the opening of the directional control valve, and always check for runaway of the actuator. It is possible to prevent the.

Further, if the charge / discharge circuit of the capacitor is configured as described in claim (3), the accuracy of the delay time for returning the closed position of the first switch when returning the neutral position of the operating lever is increased, and the first switch is opened immediately after the opening of the second switch. The switch can be closed, and it becomes easy to repeat the inching operation of the actuator (the operation of slightly operating the actuator).

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention, and FIG. 2 is a circuit diagram of another embodiment. 43 ... power supply, 44 ... electric circuit, 45a, 45b ... switch, 4
8… Pressure switch, 49,54 …… Pilot oil passage, 50 ……
Hydro switching valve, 51 ... Pilot pump.

Claims (3)

(57) [Claims] A directional control valve (11) that is operated by a solenoid or a pilot by an operation lever (10) and that communicates with an output port and a tank port at a neutral position, and an actuator controlled by the directional control valve; In an open hydraulic circuit in which a pilot-operated relief valve (13) is connected to an oil passage between the directional control valve and the discharge port of the pump (12), a valve between the vent chamber of the relief valve (13) and the tank is provided. The normally closed solenoid valve (14) is inserted into the vent circuit (52), and the operation lever (41) of the normally closed first switch (15) is electrically detected by detecting that the operation lever is at the actuator driving position. ) To a power supply, and detecting that the direction switching valve (11) is at the actuator driving position by detecting an increase in the actuator driving oil pressure at the output side thereof. A second switch control device (18) for closing the normally open second switch (17) by the detected oil pressure is provided, and the first and second switches are operated by a solenoid valve opening solenoid (14a) operating circuit (14a). 58) when the operating lever at the actuator driving position is returned to the neutral position, the first switch control device is so arranged that the first switch (15) closes after the second switch (17) opens. (16)
A charge / discharge circuit for a capacitor (20) is connected to the circuit between the pump and the actuation relay, and the spool of the directional control valve is fluidly fixed and the actuation circuit (58) of the solenoid for opening the solenoid valve is turned on. The detection oil pressure for operating the second switch control device (18) is set low so that the second switch (17) is kept closed during a load operation. Safety device. 2. A directional control valve (11) which is operated by a solenoid or a pilot by an operation lever (10), and in which the output port and the tank port communicate with each other at a neutral position, and an actuator controlled by the directional control valve. In an open hydraulic circuit in which a pilot-operated relief valve (13) is connected to an oil passage between the directional control valve and the discharge port of the pump (12), a valve between the vent chamber of the relief valve (13) and the tank is provided. The normally closed solenoid valve (14) is inserted into the vent circuit (52), and the operation lever (41) of the normally closed first switch (15) is electrically detected by detecting that the operation lever is at the actuator driving position. ) To a power supply, and detecting that the direction switching valve (11) is at the actuator driving position by detecting an increase in the actuator driving oil pressure at the output side thereof. A second switch control device (18) for closing the normally open second switch (17) by the detected oil pressure is provided, and the first and second switches are operated by a solenoid valve opening solenoid (14a) operating circuit (14a). 58) when the operating lever at the actuator driving position is returned to the neutral position, the first switch control device is so arranged that the first switch (15) closes after the second switch (17) opens. (16)
A charge / discharge circuit for a capacitor (20) is connected to the circuit between the pump and the actuation relay, and the spool of the directional control valve is fluidly fixed and the actuation circuit (58) of the solenoid for opening the solenoid valve is turned on. An operation circuit (58) of a solenoid (14a) for opening a solenoid valve in which first and second switches are inserted in series so that the solenoid valve (14) is kept open during a load operation.
A relay (63) is connected in parallel with the solenoid for opening the solenoid valve, and a normally open contact (63a) of the relay and a normally closed reset switch (64) are inserted in series. 65) is connected to the operating circuit (58) in parallel with the first and second switches. 3. A capacitor charging / discharging circuit includes a diode (19) inserted in a circuit between the first switch control device (16) and an operation relay (41), and an input side and an output side of the diode. A capacitor (20) connected via resistors (56) and (55) and grounded on the non-connection side, and a resistor (57) grounded on the input side of the diode.
Alternatively, the safety device when the spool of the directional control valve according to (2) is fixed.