阅读说明：本技术 用于检测电磁换向阀卡阀的装置和方法 (Device and method for detecting jamming of electromagnetic directional valve ) 是由 陈家豪 彭敏 于 2019-07-02 设计创作，主要内容包括：用于检测电磁换向阀卡阀的装置和方法,电流检测单元对电磁线圈的得电过程、连续得电过程和失电过程中的电流变化趋势和大小进行采样处理；卡阀判断单元与预设参数作对比,若在预设参数范围内,输出正常信号；若超出,则输出故障信号；逻辑控制单元控制功率开关器件的通断；检测电磁换向阀卡阀的方法：对电磁线圈的回路电流的变化趋势和大小进行采样；若为故障,则断开电磁线圈；若不属于故障,保持导通。本发明采用直接检测电磁线圈回路电流的方法,通过对比电磁换向阀作动正常和异常时其电磁线圈回路电流变化的趋势和大小,来达到检测电磁换向阀作动是否正常的目的。(The device and the method for detecting the valve clamping of the electromagnetic reversing valve are characterized in that a current detection unit samples the current change trend and magnitude in the power-on process, the continuous power-on process and the power-off process of an electromagnetic coil; the valve clamping judgment unit compares the preset parameters with the valve clamping judgment unit, and if the preset parameters are within the preset parameter range, a normal signal is output; if the voltage exceeds the preset value, outputting a fault signal; the logic control unit controls the on-off of the power switch device; the method for detecting the jamming of the electromagnetic directional valve comprises the following steps: sampling the change trend and the magnitude of the loop current of the electromagnetic coil; if the fault is detected, the electromagnetic coil is disconnected; if not, the circuit is kept on. The invention adopts a method for directly detecting the current of the electromagnetic coil loop, and achieves the purpose of detecting whether the electromagnetic reversing valve is normally actuated or not by comparing the trend and the magnitude of the current change of the electromagnetic coil loop when the electromagnetic reversing valve is normally actuated and abnormal.)

1. The utility model provides a device for detecting solenoid directional valve card valve, solenoid directional valve includes solenoid, electro-magnet, traveller, reset spring, valve body and head etc. its characterized in that: including detecting the return circuit, detecting the return circuit and being equipped with current detection unit, card valve judgement unit, logic control unit and warning output unit, wherein:

the current detection unit samples the current change trend and magnitude in the power-on process, the continuous power-on process and the power-off process of the electromagnetic coil;

the card valve judging unit receives the data collected by the current detecting unit, compares the data with preset parameters, and outputs a normal signal to the logic control unit if the data are within the preset parameter range; if the fault exceeds the preset parameter range, outputting a fault signal to the logic control unit;

the logic control unit sends a control signal and controls the on-off of the power switch device;

the alarm output unit receives the alarm signal sent by the logic control unit and outputs an alarm for the abnormal actuation of the electromagnetic directional valve.

2. The apparatus for detecting a stuck valve of a solenoid directional valve according to claim 1, wherein: still include the major loop, the major loop is including buffer circuit, the voltage stabilizing circuit and the power switch device that are used for filtering clutter, interference signal's filter circuit, regulated voltage that are used for the current-limiting, wherein: the power switch device is connected with the electromagnetic coil and is controlled by the logic control unit, the power switch device is connected with a power supply, and a buffer circuit is arranged on a power supply path; and a filter circuit and a voltage stabilizing circuit are arranged between the anode and the cathode of the power switch device.

3. The apparatus for detecting a stuck valve of an electromagnetic directional valve according to claim 1 or 2, characterized in that: when the logic control unit receives a power-on signal for controlling the electromagnetic coil, the logic control unit sends a control signal to control the power switch device to be conducted, and the electromagnetic coil is powered on;

in the power-on process and the continuous power-on process of the electromagnetic coil, when a normal signal sent by the card valve judging unit is received, the logic control unit keeps the sending control signal unchanged, and the power switch device is continuously conducted; and when a fault signal sent by the card valve judging unit is received, the logic control unit stops sending the control signal, the power switch device is switched off, the electromagnetic coil is powered off, and meanwhile, the logic control unit sends an alarm signal to the alarm output unit.

4. The apparatus for detecting a stuck valve of an electromagnetic directional valve according to claim 1 or 2, characterized in that: when the logic control unit receives a power-off signal for controlling the electromagnetic coil, the logic control unit stops sending the control signal to control the power switch device to be switched off, and the electromagnetic coil is powered off;

in the power-off process of the electromagnetic coil, when a normal signal sent by the card valve judging unit is received, the logic control unit does not change;

and when a fault signal sent by the card valve judging unit is received, the logic control unit sends an alarm signal to the alarm output unit.

5. The apparatus for detecting a stuck valve of a solenoid directional valve according to claim 2, wherein: the power supply supplies electromotive force to the drive detection device and the electromagnetic coil, and the on-off control is performed through the switch SB 1.

6. A method for detecting the valve blockage of an electromagnetic directional valve is characterized by comprising the following steps:

sampling the change trend and the magnitude of loop current in the power-on process, the continuous power-on process and the power-off process of the electromagnetic coil;

comparing the obtained data with preset parameters, and judging whether the data belong to a fault;

if the fault is detected, the electromagnetic coil is disconnected; if not, the circuit is kept on.

7. The method of detecting a stuck valve of a solenoid directional valve according to claim 6, wherein:

collecting the current value of a loop flowing through the electromagnetic coil in a period of time in the process of getting the electromagnetic coil to be electrified, and judging; if the current changes in an increasing trend and then in a decreasing trend, and the decreasing minimum current value Ia is within the range of preset parameters, the current is normal, and the electromagnetic coil is continuously electrified;

if the current changes always or firstly and then gradually decreases, and the minimum current value of the gradual decrease is larger than 1.1Ia, the fault is detected, the electromagnetic coil is de-energized, and the alarm is given.

8. The method of detecting a stuck valve of a solenoid directional valve according to claim 6, wherein: when the current of the electromagnetic coil is on for a period of time, periodically sampling the current value of a loop passing through the electromagnetic coil, if the current Ii is within a preset parameter range, the current is normal, and the electromagnetic coil is continuously on; if the change of the loop current exceeds the range of +/-10% of Ii, the fault is detected, the electromagnetic coil 15 is de-energized, and an alarm is given.

9. The method of detecting a stuck valve of a solenoid directional valve according to claim 6, wherein: continuously collecting the reverse current value flowing through the electromagnetic coil in a period of time in the power-off process of the electromagnetic coil, and if the change of the reverse current is in a descending trend and then in an increasing trend, and the ascending maximum reverse current value Ib is in a preset parameter range, the current is normal; if the change of the reverse current is always in a descending trend or is in a descending trend firstly and then presents an ascending trend, and the ascending reverse minimum current value is less than 0.9Ia, the fault is judged and an alarm is given.

Technical Field

The invention relates to the field of electromagnetic directional valves, in particular to a device and a method for detecting valve clamping of an electromagnetic directional valve.

Background

The electromagnetic directional valve is a hydraulic element capable of controlling the flowing direction and the on-off of media such as hydraulic oil, and is very commonly and indispensably applied to main machines such as injection molding machines, machine tools, engineering machinery and the like. In the working process of the electromagnetic directional valve, due to the influences of factors such as working condition difference of a main machine, aging of media, internal abrasion, external impurity infiltration and the like, a valve core of the electromagnetic directional valve can be clamped, so that the direction can not be changed, and the working condition of the main machine is directly influenced, even fatal influence is caused; therefore, the method is very important for detecting the jamming of the electromagnetic directional valve and giving out fault early warning.

At present, a proximity switch is added to the conventional detection of the jamming of the electromagnetic reversing valve, namely, the proximity switch is triggered by the valve core in the reversing process through the design of the reversing valve structure, so that the on-off of the valve core at a certain position point in the reversing process is detected.

Although the above device can detect the stuck valve fault of the electromagnetic directional valve, the device has many defects:

a proximity switch is additionally arranged, and meanwhile, the structure of the reversing valve needs to be redefined, so that the cost is increased;

the proximity switch is connected with the electromagnetic directional valve, so that the size of the electromagnetic directional valve is increased, and if bidirectional detection is needed, the size is larger, and the installation is inconvenient;

the proximity switch only detects a certain position point of the valve core, so that the detection range is small.

Disclosure of Invention

The invention aims to solve the existing problems and provides a device and a method for detecting the jamming of an electromagnetic directional valve.

In order to achieve the above object, the electromagnetic directional valve of the technical scheme of the invention comprises an electromagnetic coil, an electromagnet, a sliding column, a reset spring, a valve body, a seal head and the like, and comprises a detection loop, wherein the detection loop is provided with a current detection unit, a valve clamping judgment unit, a logic control unit and an alarm output unit, wherein:

the current detection unit samples the current change trend and magnitude in the power-on process, the continuous power-on process and the power-off process of the electromagnetic coil;

the card valve judging unit receives the data collected by the current detecting unit, compares the data with preset parameters, and outputs a normal signal to the logic control unit if the data are within the preset parameter range; if the fault exceeds the preset parameter range, outputting a fault signal to the logic control unit;

the logic control unit sends a control signal and controls the on-off of the power switch device;

the alarm output unit receives the alarm signal sent by the logic control unit and outputs an alarm for the abnormal actuation of the electromagnetic directional valve.

Wherein, still include the major loop, the major loop is including buffer circuit, the voltage stabilizing circuit and the power switch device that are used for filtering clutter, interference signal's filter circuit, regulated voltage that are used for the current-limiting, wherein: the power switch device is connected with the electromagnetic coil and is controlled by the logic control unit, the power switch device is connected with a power supply, and a buffer circuit is arranged on a power supply path; and a filter circuit and a voltage stabilizing circuit are arranged between the anode and the cathode of the power switch device.

When the logic control unit receives a power-on signal for controlling the electromagnetic coil, the logic control unit sends a control signal to control the power switch device to be conducted, and the electromagnetic coil is powered on;

in the power-on process and the continuous power-on process of the electromagnetic coil, when a normal signal sent by the card valve judging unit is received, the logic control unit keeps the sending control signal unchanged, and the power switch device is continuously conducted; and when a fault signal sent by the card valve judging unit is received, the logic control unit stops sending the control signal, the power switch device is switched off, the electromagnetic coil is powered off, and meanwhile, the logic control unit sends an alarm signal to the alarm output unit.

When the logic control unit receives a power-off signal for controlling the electromagnetic coil, the logic control unit stops sending the control signal to control the power switch device to be switched off, and the electromagnetic coil is powered off;

in the power-off process of the electromagnetic coil, when a normal signal sent by the card valve judging unit is received, the logic control unit does not change;

and when a fault signal sent by the card valve judging unit is received, the logic control unit sends an alarm signal to the alarm output unit.

The power supply supplies electromotive force to the drive detection device and the electromagnetic coil, and on-off control is performed through a switch SB 1.

The invention also provides a method for detecting the valve blockage of the electromagnetic directional valve, which comprises the following steps:

sampling the change trend and the magnitude of loop current in the power-on process, the continuous power-on process and the power-off process of the electromagnetic coil;

comparing the obtained data with preset parameters, and judging whether the data belong to a fault;

if the fault is detected, the electromagnetic coil is disconnected; if not, the circuit is kept on.

Further, collecting the current value of a loop flowing through the electromagnetic coil in a period of time in the process of getting the electromagnetic coil to be electrified, and judging; if the current changes in a first increasing trend and then in a decreasing trend, and the decreasing minimum current value Ia is within the preset parameter range, the current is normal, and the electromagnetic coil 15 is continuously electrified;

if the current changes always or firstly and then gradually decreases, and the minimum current value of the gradual decrease is larger than 1.1Ia, the fault is detected, the electromagnetic coil is de-energized, and the alarm is given.

Further, when the power-on time of the electromagnetic coil is longer than a period of time, periodic sampling is adopted for the current value of a loop flowing through the electromagnetic coil, if the current Ii is within a preset parameter range, the current is normal, and the electromagnetic coil is continuously powered on; if the change of the loop current exceeds the range of +/-10% of Ii, the fault is detected, and the electromagnetic coil is de-energized and gives an alarm.

Further, continuously collecting the reverse current value flowing through the electromagnetic coil in a period of time in the power-off process of the electromagnetic coil, if the change of the reverse current is in a descending trend first and then in an increasing trend, and the ascending maximum reverse current value Ib is in a preset parameter range, the current is normal; if the change of the reverse current is always in a descending trend or is in a descending trend firstly and then presents an ascending trend, and the ascending reverse minimum current value is less than 0.9Ia, the fault is judged and an alarm is given.

Compared with the prior art, the invention adopts the method of directly detecting the loop current of the electromagnetic coil, achieves the purpose of detecting whether the electromagnetic reversing valve acts normally or not by comparing the trend and the magnitude of the change of the loop current of the electromagnetic coil when the electromagnetic reversing valve acts normally and abnormally, and can detect the performance of the electromagnetic coil.

The detection device adopts the integrated circuit technology, can be integrated on the plug of the electromagnetic coil, and has the advantages of small volume, low cost and stable performance. The valve is monitored by directly detecting the current change of the electromagnetic coil, so that the stability is good, the performance of the coil can be detected, and the functionality is strong. The change through direct detection solenoid electric current monitors the card valve and carries out fault output, can realize networking control, and degree of automation is high. The range of valve clamping detection of the electromagnetic reversing valve in the reversing process is improved by analyzing and judging a range of loop current change of the electromagnetic coil.

Drawings

FIG. 1 is a schematic structural diagram of one embodiment of the present invention;

fig. 2 is a graph showing the change curve of the loop current and the change curve of the motion stroke s of the armature when the electromagnetic directional valve is in normal operation.

Detailed Description

The invention will now be further described with reference to the accompanying drawings.

Referring to fig. 1, fig. 1 illustrates one embodiment of the present invention. The electromagnetic directional valve 2 in this embodiment is a conventional two-position four-way electromagnetic directional valve, and mainly comprises an electromagnetic coil 15, an electromagnet 16, a spool 18, return springs 19 and 20, a valve body 21, and a seal head 22.

The working principle is that when the electromagnetic coil 15 is electrified, a magnetic field is generated to act on the electromagnet 16, the armature 17 in the electromagnet moves to the left under the action of the magnetic field and pushes the valve core 18, the valve core 18 overcomes the spring force of the return spring 19 to move to the left, a loop is switched, and meanwhile, the movement stroke s of the armature 17 is gradually increased to the left; when the electromagnetic coil 15 is de-energized, the magnetic field disappears, and the valve core 18 moves rightwards under the action of the return spring 19; the circuit is switched, meanwhile, the armature 17 is pushed to move, and the moving stroke s of the armature is gradually reduced towards the right.

The detection device 1 is connected with the electromagnetic coil 15 and used for driving the electromagnetic directional valve 2 to actuate and detecting whether the electromagnetic directional valve actuates normally, and the detection device mainly comprises the following components:

the detection device 1 in the present embodiment is composed of a main circuit 3 and a detection circuit 4:

wherein, the main loop 3 is provided with a buffer circuit 5, a filter circuit 6, a voltage stabilizing circuit 7 and a power switch device 8: the buffer circuit 5 is used for limiting the current flowing through the circuit (such as external impact current, series connection of large current and the like) in the working process of the detection device 1;

the filtering circuit 6 filters noise waves and interference signals of the current flowing through the circuit;

the voltage stabilizing circuit 7 is used for stabilizing the voltage required by driving the load and preventing the voltage fluctuation caused by the factors such as load change, environment change and the like;

the power switch device 8 is connected with the load electromagnetic coil 15 and used for directly controlling the on-off of the electromagnetic coil 15, and the conduction of the power switch device needs an external signal to control.

The detection loop 4 is provided with a current detection unit 9, a card valve judgment unit 10, a logic control unit 11 and an alarm output unit 12:

the current detection unit 9 is used for sampling the change trend and the magnitude of loop current of the electromagnetic coil 15 in the power-on process, the continuous power-on process and the power-off process; in one working cycle of the electromagnetic coil 15, the power-on process and the power-off process are one-time actions, and the continuous power-on process is continuous and depends on the length of the working time; when the current detection unit 9 monitors the power-on signal of the electromagnetic coil 15 (for example, SB2 is closed), the current detection unit 9 takes the rising edge of SB2 closure as a trigger signal, and continuously collects the variation trend and magnitude (for example, 20ms) of the loop current of the electromagnetic coil 15 during a period of time during the power-on process; when the current detection unit 9 monitors a power loss signal of the electromagnetic coil 15 (for example, SB2 is turned off), the current detection unit 9 takes the falling edge of the turn-off of SB2 as a trigger signal, and continuously collects the variation trend and magnitude (for example, 30ms) of the loop current of the electromagnetic coil 15 during a period of the power loss process; when the electromagnetic coil 15 is continuously powered, the current detection unit 9 may periodically sample the loop current (for example, once every 100 ms).

The card valve judging unit 10 receives the change trend and the magnitude data of the loop current of the electromagnetic coil 15 in the power-on process, the continuous power-on process and the power-off process collected by the current detecting unit 9, compares the change trend and the magnitude data with preset parameters, and outputs a normal signal if the collected current change trend and the magnitude data are in the preset parameter range; and if the collected current variation trend and the collected current variation magnitude exceed the preset parameter range, outputting a fault signal.

The logic control unit 11 is used for sending a control signal to control the on-off of the power switch device 8 so as to control the on-off of the electromagnetic coil 15;

when the logic control unit 11 receives an electrifying signal for controlling the electromagnetic coil 15 (if SB2 is closed), the logic control unit 11 sends a control signal to control the power switch device 8 to be conducted, and the electromagnetic coil 15 is electrified; in the power-on process and the continuous power-on process of the electromagnetic coil 15, if a normal signal sent by the card valve judging unit 10 is received, the logic control unit 11 keeps sending the control signal unchanged, and the power switch device 8 is continuously conducted; if a fault signal sent by the card valve judging unit 10 is received, the logic control unit 11 stops sending the control signal, the power switch device 8 is disconnected, the electromagnetic coil 15 is powered off, and meanwhile the logic control unit 11 sends an alarm signal to the alarm output unit 12.

When the logic control unit 11 receives a power-off signal for controlling the electromagnetic coil 15 (if SB2 is disconnected), the logic control unit 11 stops sending the control signal, controls the power switch device 8 to be disconnected, and powers off the electromagnetic coil 15; in the power-off process of the electromagnetic coil 15, if a normal signal sent by the card valve judging unit 10 is received, the logic control unit 11 does not change; if a fault signal sent by the card valve judging unit 10 is received, the logic control unit 11 sends an alarm signal to the alarm output unit 12.

The alarm output unit 12 receives the alarm signal sent by the logic control unit 11, and performs alarm output (such as outputting a switch signal, a power signal, and the like) on the actuation abnormality of the electromagnetic directional valve 2, and a user performs troubleshooting on the electromagnetic directional valve 2 according to the alarm signal.

The power supply 13 is provided as an external device for supplying electromotive force to the drive detection device 1 and the electromagnetic coil 15, and is on/off controlled by a switch SB 1.

The actual measurement shows that when an on-off driving voltage is applied to the electromagnetic coil 15, the electromagnetic directional valve 15 normally operates, and the change curve of the loop current and the change curve of the movement stroke s of the armature 17 are shown in fig. 2 (thick solid line in the figure).

In the power-on process of the electromagnetic coil:

when the solenoid 15 is supplied with a stepped nominal voltage (see the power-up process of the U-t curve), the loop current I of the solenoid increases gradually due to the inductive effect of the solenoid, while the armature 17 is not yet actuated. (see section 1 of the I-t and s-t curves)

When the loop current I of the electromagnetic coil is gradually increased, the armature 17 starts to move to the left and pushes the valve core 18 to do work due to the action of magnetic force, and the motion stroke s of the armature 17 is gradually increased to the left, so that the inductance of the electromagnetic coil 15 is also increased, and the loop current I of the electromagnetic coil is gradually reduced; when the movement path s of the armature 17 reaches the maximum Si, the coil current reaches a minimum value Ia. (see section 2 of the I-t and s-t curves)

When the movement stroke s of the armature 17 reaches the maximum Si and does not change, the inductance of the electromagnetic coil 15 does not change, and the loop current I of the electromagnetic coil gradually increases to the rated current value Ii. (see section 3 of the I-t and s-t curves)

However, when the electromagnetic directional valve 2 is in operation, the valve element 18 may be jammed due to various factors. When the valve core 18 is completely locked, and a step-change rated voltage is applied to the electromagnetic coil 15, the loop current I of the electromagnetic coil is gradually increased due to the inductance effect of the electromagnetic coil; however, since the valve element 18 is completely stuck, the movement stroke s of the armature 17 does not change, and the inductance of the solenoid coil 15 also does not change, the current I of the solenoid coil gradually increases to the rated current Ii (see the segment x of the dashed line of the I-t curve), and a process of current reduction as shown in "section 2" does not occur.

When the valve core 18 is clamped in the moving process, and a step-change rated voltage is applied to the electromagnetic coil 15 at the moment, the current I of the electromagnetic coil is gradually increased due to the inductance effect of the electromagnetic coil; however, since the valve element 18 is jammed during the movement, the maximum movement stroke s < Si of the armature 17, and the inductance of the solenoid coil 15 does not reach the maximum value, although the loop current of the solenoid coil 15 shows a downward trend in "section 2", the inductance does not reach the lowest current Ia (see section u of the I-t curve).

In the continuous power-on process of the electromagnetic coil:

when rated voltage is continuously supplied to the electromagnetic coil 15, the armature 17 pushes the valve core 18 to the maximum position, the electromagnetic directional valve 15 continuously works stably, and the electromagnetic coil 15 reaches the rated current Ii and is stabilized (see section 3 of I-t and s-t curves); if the current value Ii deviates from the stable value due to factors such as short circuit, open circuit and large current entering the electromagnetic coil winding.

In the power loss process of the electromagnetic coil:

the rated voltage of the solenoid 15 is momentarily turned off (see the power-off process of the U-t curve), and due to the inductance effect of the solenoid, the solenoid will momentarily generate a reverse current Ic, which then gradually decreases, while the armature 17 is not yet actuated. (see section 4 of the I-t and s-t curves)

Under the action of the return spring 19, the valve core 18 pushes the armature 17 to move rightwards, the movement stroke s of the armature 17 is gradually reduced rightwards, and the inductance of the electromagnetic coil 15 is also reduced, so that the reverse current I of the electromagnetic coil is gradually increased; when the movement path s of the armature 17 is minimal, the reverse current of the solenoid reaches a maximum value Ib. (see section 5 of the I-t and s-t curves)

When the movement stroke s of the armature 17 reaches the minimum without changing, the inductance of the electromagnetic coil 15 is not changing, and the reverse current I of the electromagnetic coil is gradually reduced to zero. (see section 6 of the I-t and s-t curves)

When the valve core 18 is completely locked, and the rated voltage of the electromagnetic coil 15 is instantly disconnected, the electromagnetic coil can instantly generate a reverse current Ic due to the inductance effect of the electromagnetic coil, and then the reverse current Ic gradually decreases; however, since the valve element 18 is completely stuck, the movement stroke s of the armature 17 does not change, and the inductance of the electromagnetic coil 15 also does not change, the reverse current I of the electromagnetic coil gradually decreases to zero (see the segment y of the dashed line of the I-t curve), and a process of increasing the reverse current shown in "section 5" does not occur.

When the valve core 18 is clamped in the moving process, and the rated voltage of the electromagnetic coil 15 is cut off instantly at the moment, the electromagnetic coil can generate a reverse current Ic instantly due to the inductance effect of the electromagnetic coil, and then the reverse current Ic is gradually reduced; however, since the valve element 18 is locked during the movement, the movement stroke s of the armature 17 is greater than the minimum value, and the inductance of the electromagnetic coil 15 does not reach the minimum value, although the reverse current of the electromagnetic coil 15 shows a reverse ascending trend in the "section 5", the reverse current does not reach the maximum reverse current Ib (see the section w of the I-t curve).

Referring to fig. 1, the detection method of the present embodiment specifically operates as follows.

The power supply 13 is connected to the detection device 1 through a switch SB1, a pin of the electromagnetic coil 15 is connected with the output end of the power switch device 8 of the detection device 1, the on-off command for controlling the electromagnetic coil 15 is sent out through a switch SB2, and the fault output 14 is used for fault alarm.

The switch SB1 is pressed, and the electromotive force of the power supply 13 is connected to the detection device 1; when the button SB2 is pressed, the logic control unit 11 sends out a control signal to turn on the power switch device 8, and at this time, the electromotive force of the power supply 13 is communicated with the electromagnetic coil 15 through the switch SB1, the buffer circuit 5, the filter circuit 6, the voltage stabilizing circuit 7 and the power switch device 8, so that the electromagnetic coil 15 is electrified.

During a period of time (20 ms is adopted in the embodiment) during the power-on process of the electromagnetic coil 15, the current detection unit 9 takes the rising edge of the closed switch SB2 as a trigger signal, continuously collects the loop current value flowing through the electromagnetic coil 15 during the period of time, and transmits the loop current value to the stuck valve judgment unit 10 after conversion processing; the stuck valve judging unit 10 analyzes the data acquired by the current detecting unit 9, if the change of the current obtained by analysis presents an increasing trend and then presents a decreasing trend, and the decreased minimum current value Ia is within a preset parameter range (such as +/-10%), a normal signal is sent to the logic control unit 11, the logic control unit 11 maintains the normal control signal to the power switch device 8, so that the power switch device 8 is continuously conducted, and the electromagnetic coil 15 is continuously electrified; if the current change is always presented with the increasing trend or firstly presented with the increasing trend and then presented with the decreasing trend, but the minimum current value of the decreasing trend is larger than 1.1Ia, a fault signal is sent to the logic control unit 11, the logic control unit 11 stops sending the control signal to the power switch device 8, the power switch device 8 is disconnected, the electromagnetic coil 15 is de-energized, and meanwhile, the logic control unit 11 sends a signal to the alarm output unit 12 to alarm the fault.

When the power-on time of the electromagnetic coil 15 is more than 20ms, the current detection unit 9 adopts a periodic sampling mode (sampling once every 100 ms) for the current value of a loop flowing through the electromagnetic coil 15, the current value is converted and transmitted to the card valve judgment unit 10, the card valve judgment unit 10 analyzes data collected by the current detection unit 9, if the current Ii is obtained in a preset parameter range (plus or minus 10 percent) through analysis, a normal signal is sent to the logic control unit 11, the logic control unit 11 maintains a normal control signal to the power switch device 8, the power switch device 8 is continuously conducted, and the electromagnetic coil 15 is continuously powered on; if the change of the loop current exceeds the range of +/-10% of Ii, a fault signal is sent to the logic control unit 11, the logic control unit 11 stops sending a control signal to the power switch device 8, the power switch device 8 is switched off, the electromagnetic coil 15 is powered off, and meanwhile, the logic control unit 11 sends a signal to the alarm output unit 12 to give out a fault alarm.

When the SB2 button is turned off, the logic control unit 11 cuts off the control signal and the power switch device 8 is turned off, so that the electromagnetic coil 15 is de-energized.

In a period of time (30ms) in the power-off process of the electromagnetic coil 15, the current detection unit 9 takes the falling edge of the switch SB2 as a trigger signal, continuously collects the reverse current value flowing through the electromagnetic coil 15 in the period of time, converts the reverse current value and transmits the reverse current value to the card valve judgment unit 10; the card valve judging unit 10 analyzes the data acquired by the current detecting unit 9, if the change of the reverse current is analyzed to be in a descending trend and then in an ascending trend, and the ascending maximum reverse current value Ib is within a preset parameter range (+ -10%), a normal signal is sent to the logic control unit 11, and the logic control unit 11 does not act; if the analysis shows that the change of the reverse current is always in a descending trend or is in a descending trend firstly, and then presents an ascending trend, but the ascending reverse minimum current value is less than 0.9Ia, a fault signal is sent to the logic control unit 11, and the logic control unit 11 sends a signal to the alarm output unit 12 to carry out fault alarm.

The embodiments of the present invention have been described in conjunction with the accompanying drawings and examples, the structures of which are given by way of illustration and not limitation, and those skilled in the art can make modifications as required, and various changes and modifications can be made within the scope of the appended claims.