CN102586723B - Method for automatically controlling vacuum pressure of ion chemical heat treatment furnace - Google Patents
Method for automatically controlling vacuum pressure of ion chemical heat treatment furnace Download PDFInfo
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- CN102586723B CN102586723B CN201210060706.8A CN201210060706A CN102586723B CN 102586723 B CN102586723 B CN 102586723B CN 201210060706 A CN201210060706 A CN 201210060706A CN 102586723 B CN102586723 B CN 102586723B
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Abstract
The invention provides a method and a device for automatically controlling vacuum pressure of an ion chemical heat treatment furnace, relating to a method and a device for automatically controlling the vacuum pressure of heat treatment equipment. According to the method and the device, a vacuum pressure transmitter, a gas flow transmitter, a frequency converter and a rotary-vane mechanical vacuum pump motor of the ion chemical heat treatment furnace form a closed loop control system. The device comprises the frequency converter, the vacuum pressure transmitter, the mechanical vacuum pump, the gas flow transmitter, a program controller and a control computer, wherein the gas flow transmitter is arranged on a vacuum furnace gas delivery pipeline; a data acquisition terminal of the vacuum pressure transmitter is directly contacted with internal pressure of the heat treatment furnace; the mechanical vacuum pump is arranged at an exhaust port of a furnace body; the program controller is connected with the frequency converter, the vacuum pressure transmitter and the gas flow transmitter respectively through signals; the frequency converter is connected with the mechanical vacuum pump motor through lines; and the control computer is connected with the program controller through signals. According to the method and the device, oil can be prevented from returning from the vacuum pump to the furnace, and the service life of the vacuum pump can be prolonged.
Description
Technical field
The present invention relates to a kind of vacuum pressure autocontrol method and device thereof of equipment for Heating Processing, method and device thereof that especially in the stove of glow ion chemical heat treatment furnace, vacuum pressure closed loop is controlled automatically.
Background technology
Plasma Chemical heat-treatment comprises ionitriding, carburizing, carbonitriding, sulfurizing, metallic cementation, plasma activated chemical vapour deposition etc.It is that the workpiece that wish is processed is placed in the vacuum oven of plasma Chemical heat-treatment stove, and workpiece connects the negative pole of direct current glow discharge power supply, and body of heater connects positive pole.Under DC electric field effect, furnace gas generation glow discharge, the surface of the positive ion bombardment workpiece (negative electrode) generating, workpiece is heated to needed thermo-chemical treatment temperature (generally between 400～600 ℃), gas glow discharge has activated reactant gases simultaneously, at workpiece surface, there is a series of physical-chemical reaction, reach the object that workpiece surface modification is processed.
In plasma Chemical heat-treatment process, gas pressure intensity in vacuum oven is an important processing parameter, requires in whole processing engineering, and in stove, vacuum pressure remains in certain pressure range, and reduce fluctuation of pressure as far as possible, to guarantee the quality conformance of processed workpiece.
In existing plasma Chemical heat-treatment stove, pressure regulates to control and conventionally adopts following three kinds of methods:
(1) opening angle that is arranged on the high vacuum butterfly valve on pump-line by manual adjustment changes the flow resistance bleed, and the pumping speed of vacuum pump is changed along with the variation of flow resistance, finally makes charge flow rate and pumping speed reach a kind of transient equilibrium.The drawback that this control method exists is that the open degree of manual setting butterfly valve repeatedly just can reach predetermined pressure, and control accuracy is lower, once and change the flow of air inlet, need again carry out again manual setting.
(2) opening angle that is arranged on the electric butterfly valve on pump-line by the automatic adjustment of pressure instrument is realized pressure in stove and is automatically controlled.Due to butterfly valve opening angle when smaller pressure regulate obviously, now angle slightly changes and will cause that pressure has larger fluctuation, therefore lower with automatic pressure instrument control ratio of precision processed, the interior fluctuation of pressure of stove is larger.
(3) by the closed-loop control of vacuumometer and frequency transformer, make suction motor according to the difference of actual pressure value in default vacuum pressure value and stove, change the rotating speed (namely changing the pumping speed of vacuum pump) of suction motor, realize pressure in vacuum oven and automatically control (as patent of invention 200410013266.6 and utility model patent 200420064865.6).But, if less toward the interior logical gas flow of vacuum oven, and default vacuum pressure is higher, the rotating speed of vacuum pump just may be very low, even may stop operating, and at this moment likely causes normal atmosphere that vacuum pump oil is pressed in vacuum oven, pollutes vacuum chamber.
Summary of the invention
The object of the invention is to overcome above-mentioned deficiency, provide a kind of can avoiding in stove, to return oily phenomenon because of the too low vacuum pump causing of rotating speed of vacuum pump, and can extend plasma Chemical heat-treatment stove vacuum pressure autocontrol method and the device thereof in the work-ing life of vacuum pump.
Technical solution of the present invention is:
Plasma Chemical heat-treatment stove vacuum pressure autocontrol method, forms a closed loop control system by the vacuum pressure transmitter of plasma Chemical heat-treatment stove, gas flow transmitter, frequency transformer and rotary-vane pump electric motor; Vacuum pressure transmitter is for detection of the pressure in heat treatment furnace body, and detection signal is flowed to sequence controller, control after computer compares computing by vacuum pressure sampled value and set(ting)value and output a control signal to frequency transformer, frequency transformer is the motor speed with change oil-sealed rotary pump according to the voltage of alternating current of the corresponding output of input signal different frequency, thereby change the pumping speed of vacuum pump, make the interior invariablenes pressure of liquid of stove in the pressure values of technique initialization; When the rotating speed of mechanical vacuum pump motor is reduced to a certain given lower value, pressure in heat treatment furnace is still lower than given vacuum pressure value, by controlling computer export one signal, by sequence controller and gas flow transmitter, improve the flow of air inlet, until the pressure in heat treatment furnace reaches given vacuum pressure value.
According to above-mentioned autocontrol method, plasma Chemical heat-treatment stove vacuum pressure automatic control device, it comprises frequency transformer, vacuum pressure transmitter and oil-sealed rotary pump, it is characterized in that: it at least also comprises gas flow transmitter, sequence controller and control computer, gas flow transmitter is arranged on vacuum oven gas pipe line, the data gathering end direct contact heat of vacuum pressure transmitter is processed furnace pressure, oil-sealed rotary pump is arranged on body of heater venting port, sequence controller respectively with frequency transformer, vacuum pressure transmitter, gas flow transducer signal connects, frequency transformer is connected with oil-sealed rotary pump motor line, controlling computer is connected with sequence controller signal.
The present invention has advantages of as follows: 1. due to gas flow transmitter, participated in the automatic control of vacuum pressure in plasma Chemical heat-treatment stove, avoided in stove, returning oily phenomenon because of the too low vacuum pump causing of rotating speed of the vacuum pump that air input is too low, default vacuum pressure occurs when higher.2. in plasma Chemical heat-treatment process, vacuum pump is in middling speed running all the time, has extended the work-ing life of vacuum pump.3. adopt speed control by frequency variation can save electric energy, for long thermo-chemical treatment, power savings is very remarkable.
Accompanying drawing explanation
Fig. 1 is organigram of the present invention.
In figure: 1, the vacuum furnace body of plasma Chemical heat-treatment stove, 2, gas pipe line, 3, put the worktable of workpiece, 4, gas flow transmitter, 5, vacuum pressure transmitter, 6, rotary-vane pump, 7, PLC programmable controller, 8, frequency transformer, 9, industrial control computer.
Below in conjunction with accompanying drawing, the present invention is made to detailed description.
Embodiment
The present embodiment take plasma Chemical heat-treatment stove vacuum furnace body 1 overall dimensions as 1200 * 2000 millimeters of φ be example.
Plasma Chemical heat-treatment stove vacuum pressure automatic control device, it comprises frequency transformer 8, oil-sealed rotary pump 6, vacuum pressure transmitter 5, gas flow transmitter 4, sequence controller 7 and controls computer 9.Oil-sealed rotary pump 6 is selected the rotary-vane pump of 15 liters/second, and suction motor power is 2.2KW.Working gas with ammonia as ionitriding thermo-chemical treatment.Vacuum pressure transmitter 5 is selected capacitance diaphragm absolute manometer, and range is 1～1000Pa.Gas flow transmitter 4 is selected mass-flow gas meter, and maximum ammonia flow is 3 liters/min.Frequency-variable controller adopts 3.7KW frequency transformer 8.Sequence controller is selected PLC programmable controller 7.Control computer 9 and select industrial control computer.Gas flow transmitter 4 is arranged on vacuum oven gas pipe line 2, and vacuum pressure transmitter 5, by pipeline and vacuum furnace body 1 internal communication, is guaranteed its data gathering end direct contact heat processing furnace pressure.Rotary-vane pump 6 is arranged on vacuum furnace body 1 venting port, PLC programmable controller 7 is connected with frequency transformer 8, vacuum pressure transmitter 5, gas flow transmitter 4 signals respectively, frequency transformer 8 is connected with the motor line of rotary-vane pump 6, and industrial control computer 9 is connected with PLC programmable controller 7 signals.
Pending workpiece is placed on worktable 3, when vacuum oven forvacuum is to the about 5Pa of highest attainable vacuum pressure of plasma Chemical heat-treatment stove, under motor speed by the default rotary-vane pumps 6 of industrial control computer 9, be limited to 300 revs/min, and in default stove, vacuum pressure is 260Pa, the flow of ammonia is 1 liter/min, at this moment the motor speed of rotary-vane pump 6 reduces gradually, and in stove, practical vacuum degree starts to level off to gradually 260Pa.When vacuum tightness reaches 220Pa, the motor speed of rotary-vane pump 6 has approached the lower limit rotating speed of preset value, and at this moment ammonia starts to rise gradually from 1 liter/min, and in final stove, vacuum pressure is stabilized in 260Pa gradually, until nitriding process finishes.
Vacuum pressure closed loop automatic control process explanation in plasma Chemical heat-treatment stove: vacuum pressure transmitter 5 is for detection of the pressure in vacuum furnace body 1, and the pressure signal of 4-20mA is sent into PLC programmable controller 7, industrial control computer 9 carries out vacuum pressure sampled value and set(ting)value after PID comparison operation, by PLC programmable controller 7 output 4～20mA control signals, arrive frequency transformer 8, thereby frequency transformer 8 changes the pumping speed of vacuum pump according to the voltage of alternating current of the corresponding output of incoming frequency control signal different frequency to change the motor speed of rotary-vane pump 6, make the interior invariablenes pressure of liquid of stove in technique initialization pressure values.When if the frequency control current reduction that the rotating speed of suction motor is frequency transformer 8 is preset a certain lower-frequency limit value to PLC is interior, pressure in vacuum furnace body is still lower than given vacuum pressure, at this moment do not continue to reduce the rotating speed of rotary-vane pump 6 electric motor, but control gas flow transmitter 4 by PLC programmable controller 7, improve charge flow rate, until the pressure in vacuum furnace body 1 reaches given vacuum pressure value.
Claims (1)
1. plasma Chemical heat-treatment stove vacuum pressure autocontrol method, is characterized in that: the vacuum pressure transmitter of plasma Chemical heat-treatment stove, gas flow transmitter, frequency transformer, rotary-vane pump motor control computing mechanism are formed to a closed loop control system; Vacuum pressure transmitter is for detection of the pressure in heat treatment furnace body, and detection signal is flowed to sequence controller, control after computer compares computing by vacuum pressure sampled value and set(ting)value and output a control signal to frequency transformer, frequency transformer is the motor speed with change oil-sealed rotary pump according to the voltage of alternating current of the corresponding output of input signal different frequency, thereby change the pumping speed of vacuum pump, make the interior invariablenes pressure of liquid of stove in the pressure values of technique initialization; When the rotating speed of mechanical vacuum pump motor is reduced to a certain given lower value, pressure in heat treatment furnace is still lower than given vacuum pressure value, by controlling computer export one signal, by sequence controller and gas flow transmitter, improve the flow of air inlet, until the pressure in heat treatment furnace reaches given vacuum pressure value, frequency transformer and gas flow transmitter jointly participate in vacuum pressure in plasma Chemical heat-treatment stove and automatically control;
Plasma Chemical heat-treatment stove vacuum pressure automatic control device, it comprises frequency transformer, oil-sealed rotary pump, vacuum pressure transmitter, gas flow transmitter, sequence controller and control computer, oil-sealed rotary pump is selected the rotary-vane pump of 15 liters/second, suction motor power is 2.2KW, working gas with ammonia as ionitriding thermo-chemical treatment, vacuum pressure transmitter is selected capacitance diaphragm absolute manometer, range is 1～1000Pa, gas flow transmitter is selected mass-flow gas meter, maximum ammonia flow is 3 liters/min, frequency-variable controller adopts 3.7KW frequency transformer, sequence controller is selected PLC programmable controller, control computer and select industrial control computer, gas flow transmitter is arranged on vacuum oven gas pipe line, vacuum pressure transmitter is by pipeline and vacuum furnace body internal communication, guarantee its data gathering end direct contact heat processing furnace pressure, rotary-vane pump is arranged on vacuum furnace body venting port, PLC programmable controller respectively with frequency transformer, vacuum pressure transmitter, gas flow transducer signal connects, frequency transformer is connected with the motor line of rotary-vane pump, industrial control computer is connected with PLC programmable controller signal, pending workpiece is placed on worktable, when vacuum oven forvacuum is to the about 5Pa of highest attainable vacuum pressure of plasma Chemical heat-treatment stove, by industrial control computer, preset rotary-vane pump motor speed under be limited to 300 revs/min, and in default stove, vacuum pressure is 260Pa, the flow of ammonia is 1 liter/min, at this moment the motor speed of rotary-vane pump reduces gradually, in stove, practical vacuum degree starts to level off to gradually 260Pa, when vacuum tightness reaches 220Pa, the motor speed of rotary-vane pump has approached the lower limit rotating speed of preset value, at this moment ammonia starts to rise gradually from 1 liter/min, in final stove, vacuum pressure is stabilized in 260Pa gradually, until nitriding process finishes,
In plasma Chemical heat-treatment stove, vacuum pressure closed loop automatic control process is as follows: vacuum pressure transmitter is for detection of the pressure in vacuum furnace body, and the pressure signal of 4-20mA is sent into PLC programmable controller, industrial control computer carries out vacuum pressure sampled value and set(ting)value after PID comparison operation, by PLC programmable controller output 4～20mA control signal, arrive frequency transformer, thereby frequency transformer changes the pumping speed of vacuum pump according to the voltage of alternating current of the corresponding output of incoming frequency control signal different frequency to change the motor speed of rotary-vane pump, make the interior invariablenes pressure of liquid of stove in technique initialization pressure values, when if the frequency control current reduction that the rotating speed of suction motor is frequency transformer is preset a certain lower-frequency limit value to PLC is interior, pressure in vacuum furnace body is still lower than given vacuum pressure, at this moment do not continue to reduce the rotating speed of rotary-vane pump electric motor, but control gas flow transmitter by PLC programmable controller, improve charge flow rate, until the pressure in vacuum furnace body reaches given vacuum pressure value.
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| JP6345320B1 (en) * | 2017-07-07 | 2018-06-20 | パーカー熱処理工業株式会社 | Surface hardening processing apparatus and surface hardening processing method |
| CN107308889B (en) * | 2017-08-23 | 2020-04-14 | 中南钻石有限公司 | Method for removing artificial diamond dark particles |
| CN115449601A (en) * | 2022-08-30 | 2022-12-09 | 鞍钢股份有限公司 | Method for controlling vacuum degree by variable frequency speed regulation of RH refining furnace mechanical pump |
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| CN1544714A (en) * | 2003-11-14 | 2004-11-10 | 中国科学院物理研究所 | Automatic pressure control device for SiC single-crystal growth |
| CN1584100A (en) * | 2004-06-04 | 2005-02-23 | 黄健 | Pressure closing-ring automatic controller for glowing ionic azotizing furnace vacuum furnace |
| CN1862435A (en) * | 2006-01-12 | 2006-11-15 | 绵阳西磁科技开发公司 | Device and method for controlling atmosphere content and pressure balance in negative pressure container |
| CN202543299U (en) * | 2012-03-09 | 2012-11-21 | 江苏丰东热技术股份有限公司 | Automatic control device of vacuum pressure of ionic chemical thermal treatment furnace |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP4815538B2 (en) * | 2010-01-15 | 2011-11-16 | シーケーディ株式会社 | Vacuum control system and vacuum control method |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1544714A (en) * | 2003-11-14 | 2004-11-10 | 中国科学院物理研究所 | Automatic pressure control device for SiC single-crystal growth |
| CN1584100A (en) * | 2004-06-04 | 2005-02-23 | 黄健 | Pressure closing-ring automatic controller for glowing ionic azotizing furnace vacuum furnace |
| CN1862435A (en) * | 2006-01-12 | 2006-11-15 | 绵阳西磁科技开发公司 | Device and method for controlling atmosphere content and pressure balance in negative pressure container |
| CN202543299U (en) * | 2012-03-09 | 2012-11-21 | 江苏丰东热技术股份有限公司 | Automatic control device of vacuum pressure of ionic chemical thermal treatment furnace |
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Effective date of registration: 20170330 Address after: Nanxiang Road 224100 Jiangsu province Yancheng City Dafeng Economic Development Zone No. 333 Patentee after: Jiangsu Dong Feng Technology Co., Ltd. Address before: Dafeng City, Jiangsu province 224100 Nanxiang Road, Yancheng City Economic Development Zone No. 333 Patentee before: Jiangsu Fengdong Thermal Technology Co., Ltd. |