JP5145005B2 - Plasma processing furnace and method for measuring temperature of workpiece in plasma processing furnace - Google Patents

Description

The present invention relates to a plasma processing furnace for processing an object to be processed such as a steel material using plasma , and a method for measuring the temperature of the object to be processed in the plasma processing furnace .

For example, in the manufacture of steel products such as crankshafts, a nitriding treatment is performed in which an iron nitride layer is formed on the surface of the steel material in order to improve the wear resistance and corrosion resistance of the steel material. An example of such a nitriding method is plasma nitriding (ion nitriding) (see Patent Document 1). In this method, a processing gas containing nitrogen gas (N ₂ ) is supplied to a processing chamber in which an object to be processed that is a steel product is charged, and the processing object is configured by using the object to be processed that is a steel product as a cathode. Using a conductor such as a furnace body as an anode, glow discharge is generated between the two electrodes, and an ionized process gas (nitrogen ions) is caused to collide with the object to be processed and enter the surface of the object to be processed.

In the processing furnace for performing the nitriding treatment as described above, as a configuration for detecting the temperature of the object to be processed, there is known a structure in which a dummy of the object to be processed is provided in the processing chamber and the temperature of the dummy is measured ( Patent Document 1). In this configuration, a contact thermometer is attached to the surface of the dummy, and the temperature of the dummy is directly measured. Then, the temperature of the object to be processed is estimated from the dummy temperature measurement value and the like, and the heat generation amount of the heater in the processing chamber is adjusted to control the temperature of the object to be processed to a desired nitriding temperature. It has a configuration. As a thermometer for measuring a dummy temperature, for example, a thermometer provided with a thermocouple is known (see Patent Document 2).
JP 2005-2444 A JP-A-9-89682

  However, in the conventional processing furnace, the thermometer for measuring the dummy temperature is affected by the discharge and may be damaged. If the thermometer is damaged, the temperature of the dummy cannot be measured accurately, and further, the temperature of the object to be processed cannot be accurately controlled, and stable processing cannot be performed. In addition, the thermometer has a short life, and the thermometer must be frequently replaced, which may reduce the economy.

The present invention has been made in view of the above points, a plasma processing furnace capable of preventing damage to the thermometer and extending the life of the thermometer, and a method for measuring the temperature of the target object of the plasma processing furnace. The purpose is to provide.

In order to solve the above-described problems, according to the present invention, the object to be processed is accommodated in the processing chamber, and a predetermined voltage is applied between the discharge conductor and the object to be processed, whereby plasma is generated in the processing chamber. A plasma processing furnace for processing the object to be processed, the temperature measuring member including a temperature measuring part of a thermometer at the tip is provided, and the temperature measuring member includes the discharge conductor and the object to be processed. In order to confirm the influence of the discharge from the object to be processed, the tip of the temperature measuring member is disposed at a position at a substantially minimum distance where there is no influence of the discharge from the object to be processed. , A heat-resistant window of the furnace body that can be seen between the tip of the temperature measuring member and the object to be processed, or at least a recorder that records the relationship between the output from the temperature measuring member and the passage of time in that it comprises one means The symptom, the plasma processing reactor is provided.

The minimum distance may be 5 to 30 mm. Further, the thermometer may be a thermocouple, and a junction point of the thermocouple may be built in a tip portion of the temperature measuring member. The temperature measuring member may be electrically insulated from the processing chamber. Moreover, you may have a mechanism which adjusts the distance of the said temperature measurement member from the said to-be-processed object. Moreover, the front-end | tip part of the said temperature measurement member may be colored black. Further, the processing chamber may be a nitriding chamber for nitriding a target object.
Further, accommodating the article to be processed in the processing chamber, by applying a predetermined voltage between the discharge conductor material and the object to be processed, by generating Oite plasma in the processing chamber, the object to be processed A temperature measuring method for an object to be processed of a plasma processing furnace for processing a temperature measuring member including a temperature measuring part of a thermometer at a tip, wherein the temperature measuring member includes the discharge conductor and the object to be processed. electrically insulated from the processed, the tip of the temperature measurement member, the temperature of the object to be processed is measured in a state where the disposed from the workpiece to the position of minimum distance there is no influence of the discharge, the minimum distance View between the tip of the temperature measuring member and the object to be processed from the heat-resistant window provided in the furnace body, or record the relationship between the output from the temperature measuring member and the passage of time with a recorder. , Discharged by at least one of And determining to verify the effects, the temperature measurement method of the object to be processed in a plasma processing furnace.

  According to the present invention, the temperature measuring member incorporating the thermometer is electrically insulated from the discharge conductor and the object to be processed, and the tip of the temperature measuring member is discharged from the object to be processed accommodated in the processing chamber. By disposing at a position at a substantially minimum distance where there is no influence, it is possible to prevent the thermometer from being damaged by the influence of the discharge, and it is possible to extend the life of the thermometer. As a result, it is possible to accurately measure and control the temperature of the object to be processed and perform stable processing.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments according to the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the plasma nitriding system 1 includes three processing chambers that house and process the object 2, that is, a heating chamber S <b> 1 that heats (preheats) the object 2. A nitriding chamber S2 for nitriding the object to be processed 2 heated in the heating chamber S1 by generating plasma, and a cooling chamber S3 for cooling the object to be processed 2 nitrided in the nitriding chamber S2 are provided. The heating chamber S1, the nitriding chamber S2, and the cooling chamber S3 are provided in the heating furnace 3, the nitriding furnace 4 (plasma processing furnace), and the cooling unit 5, respectively, and are arranged in a row in the lateral direction (substantially horizontal direction, transport direction D). These are arranged in this order from the entrance side. In addition, the plasma nitriding system 1 includes a target object transport mechanism 6 that moves the target object 2 in a predetermined transport direction D and transports the heating chamber S1, the nitriding chamber S2, and the cooling chamber S3 in this order. (See FIG. 2). Furthermore, on the entrance side of the heating furnace 3, a carry-in machine 11 for carrying the workpiece 2 into the heating chamber S1 is provided. On the outlet side of the cooling unit 5, a carry-out machine 12 that receives the workpiece 2 carried out from the cooling chamber S <b> 3 is provided. A shutter chamber 15 is provided between the heating furnace 3 and the nitriding furnace 4. A shutter chamber 16 is provided between the nitriding furnace 4 and the cooling unit 5. Outside the heating furnace 3, the nitriding furnace 4, and the cooling unit 5, a control unit 17 that controls the operation of each unit of the plasma nitriding system 1 and a power supply unit 18 that supplies a voltage to each unit of the plasma nitriding system 1 are provided. (See FIG. 1).

  In the present embodiment, the object to be processed 2 is a plurality of metal products such as a crankshaft or a camshaft, for example, and is supported by a support member 2a (a tray or the like) having conductivity such as metal, and the support member 2a. It is designed to be transported integrally. The material of the workpiece 2 is a steel material such as carbon steel or alloy steel in the case of a crankshaft, and is cast iron or the like in the case of a camshaft.

The heating furnace 3 includes a furnace body 21, and the internal space of the furnace body 21 is a heating chamber S1. On the entrance side of the furnace body 21, a carry-in port 22 for the workpiece 2 and a shutter 23 for opening and closing the carry-in port 22 are provided. On the outlet side of the furnace body 21, a carry-out port 25 for the object to be processed 2 and a shutter 26 for opening and closing the carry-out port 25 are provided. The shutter 26 moves in the shutter chamber 15. The heating chamber S1 includes a chain conveyor 31 (see FIG. 2) that conveys the object 2 to be processed in the heating chamber S1, and a heating chamber heater (not shown) that heats the object 2 in the heating chamber S1 by radiant heat. ), A stirring mechanism 34 (fan) for stirring the atmosphere in the heating chamber S1 is provided. Further, in the heating chamber S1, a heating chamber pressure-reducing mechanism 42 that depressurizes (evacuates) the inside of the heating chamber S1, and heating for supplying, for example, nitrogen gas (N ₂ ) as a heating gas or a purge gas into the heating chamber S1. A chamber gas supply path 43 is connected (see FIG. 2).

  The nitriding furnace 4 has a so-called horizontal furnace structure. For example, the nitriding furnace 4 includes a furnace body 51 having a substantially cylindrical shape with the length direction (axial direction) directed in the transport direction D, and the internal space of the furnace body 51 is nitrided. It is chamber S2. The furnace body 51 is made of metal (conductor). On the entrance side of the furnace body 51, a carry-in port 52 for the workpiece 2 and a shutter 53 for opening and closing the carry-in port 52 are provided. The shutter 53 moves in the shutter chamber 15 (see FIG. 2). On the outlet side of the furnace body 51, a carry-out port 55 for the object to be processed 2 and a shutter 56 for opening and closing the carry-out port 55 are provided. The shutter 56 moves in the shutter chamber 16.

  As shown in FIGS. 3 and 4, the nitriding chamber S <b> 2 is provided with a chain conveyor 61 for conveying the object 2 to be processed in the nitriding chamber S <b> 2 and a heater 62 (nitriding chamber heater) for heating the object 2 by radiant heat. It has been. Furthermore, a heat shield 63 (nitriding chamber heat shield) that suppresses the heat generated by the heater 62 from diffusing and being taken away by the furnace body 51 and the like, and an inlet side heat shield that opens and closes an opening portion on the inlet side of the heat shield 63. An exit-side heat shielding door 65 that opens and closes an opening on the exit side of the door 64 and the heat shield 63 is provided. Moreover, the to-be-processed object raising / lowering mechanism 66 which raises / lowers the to-be-processed object 2 with respect to the chain conveyor 61 within the nitriding chamber S2 is provided. The workpiece lifting mechanism 66 is provided with an electrode body 67. The furnace body 51 has a built-in cooling water passage 68 through which cooling water for cooling the furnace body 51 passes.

  The heater 62 is provided inside a heat shield 63 (side walls 63a and 63b described later). In the example shown in the drawing, the heat shield 63 is provided on the side of the object 2 along the inner surface of the heat shield 63, and the object 2 is heated from both sides. AC power is supplied from the power supply unit 18 to the heater 62.

  As shown in FIG. 4, the heat shield 63 is substantially U-shaped when viewed from the conveyance direction D, and is located on the side of the workpiece 2 in a state of being held by the chain conveyor 61 or the workpiece lifting mechanism 66 ( Side walls 63a and 63b provided on both sides in the width direction of the workpiece 2 and an upper plate 63c provided above the workpiece 2 are provided. That is, it is provided around the object to be processed 2 in the nitriding chamber S2 so as to surround the side and upper side of the object to be processed 2. The heat shield 63 may be formed of a highly heat insulating material (heat insulating material).

  An opening 81 is provided in the central portion of the upper plate portion 63c (that is, above the workpiece 2 held by the chain conveyor 61 or the workpiece lifting mechanism 66). In the illustrated example, the opening 81 is provided at a position that overlaps the upper center of the workpiece 2 disposed at a predetermined position when performing nitriding in a plan view viewed from above. An opening wall body 82 is provided at the peripheral edge of the opening 81. The opening wall body 82 is erected from the periphery of the opening 81 toward the outside (above the upper plate portion 63 c), and is provided along the entire periphery of the opening 81. A lid 83 that opens and closes the opening 81 (the upper opening of the opening wall 82) is provided above the opening 81 and the opening wall 82. The lid 83 is supported by a lower end portion of a lid lifting / lowering mechanism 84 (lid moving mechanism) attached to the ceiling of the furnace body 51, and is substantially along the vertical direction by the operation of the lid lifting / lowering mechanism 84. The opening 81 is opened and closed.

  The workpiece lifting mechanism 66 has an electrode body 67 for applying a voltage to the workpiece 2, a lift 112 that lifts and lowers the electrode body 67 in the nitriding chamber S <b> 2, and the electrode body 67 is insulated from the lift 112. And an insulator 113. The electrode body 67 is provided inside the chain conveyor 61 (between the chain belts) in the nitriding chamber S2 (see FIG. 5).

  A cathode (first polarity electrode) of a plasma power supply 115 (DC power supply) provided outside the nitriding chamber S2 is connected to each electrode body 67 via a wiring or the like. On the other hand, the anode (second polarity electrode) of the plasma power supply 115 is connected to the furnace body 51 through wiring or the like, for example. That is, in the present embodiment, the discharge conductor disposed around the object 2 is the furnace body 51. An electrode having a polarity opposite to that of the electrode body 67 (object to be processed 2) is connected to the furnace body 51 serving as a discharge conductor.

  Further, the furnace body 51 and the electrode body 67 are electrically insulated by an insulator 113. That is, by providing the insulator 113, the cathode and the anode of the plasma power supply 115 are short-circuited to reduce the voltage, and abnormal discharge such as arc discharge occurs, thereby reducing the processing efficiency. ing. As shown in FIG. 5, when the object 2 is supported by the electrode body 67 and the insulator 113 and the electrode body 67 are raised by the elevator 112, the object 2 is lifted from the chain conveyor 61, and the electrode body 67. It is the structure which can be made into the state insulated from other parts. The insulator 113 is made of a material having high heat resistance, high electrical insulation, etc., such as ceramics.

  The nitriding furnace 4 is provided with a temperature measuring member 120 for measuring the temperature of the workpiece 2. As shown in FIG. 6, the temperature measuring member 120 has a configuration in which a thermocouple 122 as a thermometer is built in a protective tube (sheath) 121 having a hollow cylindrical shape. The tip of the protective tube 121 (the left end of the protective tube 121 in FIG. 6) is blocked. The protective tube 121 is made of a material having high heat resistance and rigidity, such as metal such as SUS310 or ceramics.

  The thermocouple 122 includes two thermocouple strands 125 and 126 (metal wires). Each thermocouple wire 125, 126 is extended along the length direction of the protective tube 121 inside the protective tube 121. A junction 127, which is a temperature measuring part of the thermocouple 122, is built in the tip of the temperature measuring member 120 (protective tube 121). Note that the tip of the temperature measurement member 120 (protection tube 121) is the tip surface 121 ′ of the protection tube 121 and the peripheral surface portion 121 ″ of the protection tube 121 in the vicinity of the tip surface 121 ′. The entire inside of the tube 121) is filled with an insulating filler 128. Thus, the thermocouple 122 is electrically insulated inside the temperature measuring member 120 (protective tube 121). Is held by.

The proximal end portion of the temperature measuring member 120 (protective tube 121) is supported by the furnace body 51 via the attachment tool 130 and the seal member 131. Inside the furnace body 51, the temperature measuring member 120 (protective tube 121) penetrates the heat shield 63 (side wall portion 63b) and the heater 62 in the thickness direction, and the tip of the temperature measuring member 120 (protective tube 121). Are arranged inside the heat shield 63 and the heater 62. An appropriate seal member 132 is disposed in a penetration portion of the temperature measuring member 120 (protective tube 121) with respect to the heat shield 63 (side wall portion 63b) and the heater 62. Both the sealing member 132 and the sealing member 131 disposed at the base end portion of the temperature measuring member 120 (protective tube 121) are made of an insulating material. Thereby, the temperature measurement member 120 is electrically insulated from the furnace body 51, the heat shield 63, the heater 62, and the like.
Moreover, it is preferable that the temperature measuring member 120 has a mechanism and means capable of adjusting the distance with respect to the object to be processed 2 so as to correspond to various objects to be processed 2. For example, it is preferable that the temperature measuring member 120 and the seal member 132, the attachment tool 130, and the seal member 131 have a slidable mechanism, and the distance from the object to be processed can be adjusted. . Further, the attachment 128 and the seal member 131 are installed, for example, via a vacuum O-ring (not shown) so as to be slidable and airtight .
It is preferable that the distance between the object to be processed 2 and the tip of the temperature measuring member 120 can be adjusted within a substantially minimum distance without influence of discharge, that is, in a range of 5 to 30 mm. Moreover, it is preferable that the said distance from the furnace outside can be adjusted according to a to-be-processed object. Furthermore, the distance may be adjusted easily and accurately using a mechanism such as a rack and pinion gear.
Conventionally, there is no mechanism or means for adjusting the distance, and it has been difficult to accurately measure the temperature close to the object to be processed.

The front end of the temperature measuring member 120 (the front end surface 121 ′ of the protective tube 121) is separated from the surface of the workpiece 2 accommodated in the nitriding chamber S2 by a predetermined distance L, that is, a substantially minimum distance that is not affected by discharge. Placed in position. In this case, the distance L is 5 to 30 mm, preferably 5 to 20 mm, and 5 to 10 mm.
Whether or not there is an influence of discharge, for example, by providing a heat-resistant window (not shown) in the furnace body, it is possible to confirm whether there is no discharge by directly looking between the tip of the temperature measurement member 120 and the object 2 to be processed, This is possible because the relationship between the output from the temperature measuring member 120 and the passage of time is recorded by a recorder and it is confirmed whether there is any abnormal vibration (due to abnormal discharge or the like).
Further, the adjustment and confirmation of the distance can be carried out by confirmation from the heat-resistant window or by setting the distance based on the shape since the shape of the object to be processed is known in advance.

  Moreover, it is preferable that the black coating material 132 is apply | coated to the front-end | tip part of the temperature measurement member 120 (protection tube 121). Thereby, the outer surface of the front end surface 121 ′ of the protective tube 121 and the peripheral surface portion 121 ″ of the protective tube 121 near the front end surface 121 ′ is colored black by the paint 132. In this case, the black paint 132 is applied to the black paint 132. For example, a heat-resistant ink mainly composed of a silicone resin is preferably used. As an example, a heat-resistant and weather-resistant marker (black) manufactured by Okitsumo Co., Ltd. is used.

  The thermocouple 122 (thermocouple wires 125 and 126) built in the temperature measurement member 120 (protection tube 121) is connected to the temperature detection unit 135 installed outside the furnace body 51 via wiring or the like. Are electrically connected. That is, the thermoelectromotive force generated in the thermocouple 122 is detected by the temperature detection unit 135, and based on this, the temperature at the junction 127 of the thermocouple 122 is measured. Further, the measurement value measured by the temperature detection unit 135 is transmitted from the temperature detection unit 135 to the control unit 17.

As shown in FIG. 3, a nitriding chamber pressure reducing path 141 for reducing the pressure in the nitriding chamber S2 (evacuating) is connected to the nitriding chamber S2. The nitridation chamber decompression path 141 is connected to the decompression mechanism 142 (nitridation chamber decompression mechanism) including a vacuum pump or the like outside the nitridation chamber S2. Further, for example, nitrogen gas (N ₂ ), hydrogen gas (H ₂ ), hydrocarbon gas such as propane gas (C ₃ H ₈ ), ammonia gas (NH ₃ ) or the like is treated or purged into the nitriding chamber S2. A nitriding chamber gas supply path 143 is provided as supply gas. The nitriding chamber gas supply path 143 is connected to the nitriding chamber gas supply source unit 145 outside the nitriding chamber S2. The nitriding chamber gas supply source unit 145 is provided with a nitrogen gas supply source 145a, a hydrogen gas supply source 145b, a propane gas supply source 145c, and an ammonia gas supply source 145d.

As shown in FIG. 2, the cooling unit 5 includes a casing 151, and an internal space of the casing 151 is a cooling chamber S <b> 3. On the entrance side of the housing 151, a carry-in port 152 for the workpiece 2 and a shutter 153 for opening and closing the carry-in port 152 are provided. The shutter 153 moves in the shutter chamber 16. On the outlet side of the housing 151, a carry-out port 155 for the object to be processed 2 and a shutter 156 for opening and closing the carry-out port 155 are provided. The cooling chamber S3 is provided with a chain conveyor 161 that conveys the workpiece 2 in the cooling chamber S3 and an agitation mechanism 164 (fan) that agitates the atmosphere in the cooling chamber S3. Further, the cooling chamber S3 includes a cooling chamber decompression mechanism 172 that decompresses (evacuates) the inside of the cooling chamber S3, and a cooling chamber that supplies, for example, nitrogen gas (N ₂ ) as a cooling gas or a purge gas into the cooling chamber S3. A gas supply path 173 is connected.

  As shown in FIG. 2, the workpiece transfer mechanism 6 includes the roller provided in the chain conveyor 31 in the heating chamber S1, the chain conveyor 61 in the nitriding chamber S2, the chain conveyor 161 in the cooling chamber S3, and the shutter chamber 15. 181 and a roller 182 provided in the shutter chamber 16.

  The functional elements of each part of the above-described plasma nitriding system 1 are controlled by commands from the control unit 17 (see FIG. 1). The control unit 17 includes, for example, a general-purpose computer, and is configured to perform control for automatically processing the workpiece 2 according to a predetermined processing recipe. That is, under the control of the control unit 17, a heating process, a nitriding process, and a cooling process described later can be automatically performed.

  As described above, the measurement value of the thermocouple 122 is transmitted from the temperature detection unit 135 to the control unit 17. Based on the measurement value transmitted from the temperature detection unit 135, the control unit 17 generates the amount of heat generated by the heater 62 (voltage of the power supply unit 18), the flow rate of cooling water in the cooling water channel 68, and the lid 83 by the lid lifting mechanism 84. The amount of movement (the opening degree of the opening 81), the voltage of the plasma power source 115, and the like can be adjusted, whereby the temperature of the object 2 in the nitriding chamber S2 can be controlled.

  Although not shown, the plasma nitriding system 1 includes a thermometer and a pressure gauge for detecting the temperature and pressure of the heating chamber S1, the pressure of the nitriding chamber S2, the temperature and pressure in the cooling chamber S3, respectively. Sensors are provided, and their detection values are also transmitted to the control unit 17. That is, the control unit 17 controls each unit of the plasma nitriding system 1 based on the detection value of each detection sensor.

  Next, a plasma nitriding (ion nitriding) processing method using the plasma nitriding processing system 1 configured as described above will be described. First, the workpiece 2 is carried into the heating chamber S1. That is, the workpiece 2 is conveyed from the carry-in machine 11 to the heating chamber S <b> 1 through the carry-in port 22, and is transferred onto the chain conveyor 31.

When the inlet 22 is closed and the inside of the heating chamber S1 is sealed, the inside of the heating chamber S1 is depressurized by the operation of the heating chamber decompression mechanism 42 and is in a substantially vacuum state (for example, about 0.1 Torr (about 13.3 Pa). )). Thereafter, nitrogen gas is supplied into the heating chamber S <b> 1 through the heating chamber gas supply path 43. Thus, the oxidizing atmosphere (O ₂ ) is discharged from the heating chamber S1, the inside of the heating chamber S1 is purged with nitrogen gas, and the processing pressure (pressure in the heating chamber S1) is, for example, about 500 Torr (about 66.7 kPa). Degree). And the to-be-processed object 2 on the chain conveyor 31 is heated to about 500 degreeC by the heat_generation | fever of the heater which is not shown in figure, for example.

  On the other hand, in the nitriding chamber S2, the carrying-in port 52 and the carrying-out port 55 of the nitriding chamber S2 are closed by the shutters 53 and 56, respectively, and the nitriding chamber S2 is closed by the operation of the decompression mechanism 142. The inside of S2 is in a decompressed state (for example, about 1 Torr (about 133.3 Pa)). Further, nitrogen gas is supplied into the nitriding chamber S2 through the nitriding chamber gas supply path 143. That is, the inside of the nitriding chamber S2 is purged with nitrogen gas. Further, the temperature in the nitriding chamber S <b> 2 is raised to a predetermined temperature (for example, about 500 ° C. to 550 ° C.) by the heat generated by the heater 62. The cooling water channel 68 is appropriately supplied with cooling water. That is, the temperature in the nitriding chamber S2 is controlled to a predetermined temperature by adjusting the heat generation amount of the heater 62 and the flow rate of the cooling water in the cooling water channel 68.

  When the heat treatment in the heating chamber S1 is completed, the pressure reducing mechanism 42 is operated again, and the pressure in the heating chamber S1 is reduced to the same level as the pressure in the nitriding chamber S2 (for example, about 1 Torr). Thereafter, the carry-out port 25 and the carry-in port 52 are opened, and the heating chamber S1 and the nitriding chamber S2 are communicated with each other through the shutter chamber 15. In the nitriding chamber S2, the entrance-side heat shielding door 64 is moved, and the entrance side of the heat shield 63 is opened.

  In this state, the workpiece 2 is moved along the transport direction D, and is transported from the heating chamber S1 to the nitriding chamber S2 through the carry-out port 25, the shutter chamber 15, and the carry-in port 52. That is, the workpiece 2 is transferred from the chain conveyor 31 to the chain conveyor 61. When the workpiece 2 is carried into the nitriding chamber S2, the carry-in port 52 of the nitriding chamber S2 is closed, and the inside of the nitriding chamber S2 is again sealed.

The workpiece 2 carried into the nitriding chamber S <b> 2 is transported to a predetermined position inside the heat shield 63 by driving the chain conveyor 61, and is then stopped. The entrance side and the exit side of the heat shield 63 are closed by an entrance side heat shield door 64 and an exit side heat shield door 65, respectively. Further, the electrode body 67 is raised by driving the object lifting mechanism 66, and the object to be processed 2 held on the chain conveyor 61 is pushed up by the electrode body 67. That is, the object to be processed 2 is separated from the chain conveyor 61 upward, and is placed on the electrode body 67 inside the heat shield 63, and the parts other than the electrode body 67 (elevator 112, furnace body 51, It is electrically insulated from the chain conveyor 61 or the like. In this way, the object to be processed 2 is stationary at a predetermined height while being supported by the object lifting mechanism 66, and is surrounded by the heat shield 63, the inlet side heat shield door 64, and the outlet side heat shield door 65. It will be in the state. In this state, the temperature measuring member 120 is disposed on the side of the workpiece 2 and is housed in the tip of the temperature measuring member 120 (tip surface 121 ′ of the protective tube 121) and the nitriding chamber S2. Further, the distance L from the surface of the object 2 to be processed is within a range of 5 to 30 mm, preferably 5 to 20 mm, and more preferably 5 to 10 mm, which is a substantially minimum distance that is not affected by discharge. The adjustment of the distance is performed by a mechanism that adjusts the distance from the object to be processed to the temperature measuring member.
Further, since the tip of the temperature measuring member is colored black, the heat absorption of the tip of the temperature measuring member is good, and the temperature of the object to be processed can be measured with high accuracy.

  When the object to be processed 2 is carried into the nitriding chamber S2, the inlet 52 is closed and the inside of the nitriding chamber S2 is sealed, a processing gas containing nitrogen gas in the nitriding chamber S2 through the nitriding chamber gas supply path 143 ( For example, a mixed fluid such as nitrogen gas, hydrogen gas, propane gas, and ammonia gas) is supplied. Thereby, the pressure in the nitriding chamber S2 is increased to a predetermined processing pressure (for example, about 300 Pa to 400 Pa).

  Thus, in a state where the processing gas is supplied into the nitriding chamber S2 and the workpiece 2 is supported by the electrode body 67, a plasma voltage of 400 V, for example, is applied by the plasma power source 115, and nitriding is performed. That is, the electrode body 67 and the object to be processed 2 serve as a cathode, the furnace body 5 serves as an anode, glow discharge occurs between the two electrodes, and the processing gas in the nitriding chamber S2 is ionized to generate plasma. The ionized processing gas (nitrogen ions) collides with the object to be processed 2 and enters the surface of the object to be processed 2. Thereby, an iron nitride layer is formed on the surface of the workpiece 2.

  Further, during the nitriding process, the processing temperature in the nitriding chamber S2 and the temperature of the object to be processed 2 are measured at the junction 127 of the thermocouple 122 built in the tip of the temperature measuring member 120 (protective tube 121). It is measured and transmitted from the temperature detection unit 135 to the control unit 17. And the emitted-heat amount of the heater 62, etc. are controlled so that the temperature of to-be-processed object 2 may approach target value. Thereby, the actual temperature of the to-be-processed object 2 is adjusted so that it may become a target value (for example, about 500 to 550 degreeC).

  In this case, the distance L between the tip of the temperature measuring member 120 (tip surface 121 ′ of the protective tube 121) and the surface of the workpiece 2 accommodated in the nitriding chamber S2 is in the range of 5 to 30 mm. Since the outer surface of the distal end portion of the protective tube 121 is colored black by the paint 132, the temperature of the object to be processed 2 is efficiently absorbed by the distal end portion of the temperature measuring member 120, and the object 2 to be processed is absorbed by the thermocouple 122. The temperature error can be measured with high accuracy. For example, the temperature error can be suppressed to within 5 ° C. to within several ° C. Thereby, the control part 17 can control the temperature of the to-be-processed object 2 appropriately using the accurate measured value by the thermocouple 122. FIG.

  As described above, when the nitriding process in the nitriding chamber S2 is completed, the supply of voltage by the plasma power source 115 is stopped, and the glow discharge is stopped. Further, the electrode body 67 and the object to be processed 2 are lowered by driving the object to be processed lifting mechanism 66. Then, the workpiece 2 is transferred from the electrode body 67 to the chain conveyor 61, and the electrode body 67 is lowered below the chain conveyor 61 and the workpiece 2. Moreover, the exit side heat shielding door 65 is moved, and the exit side passage port 63e is opened. Furthermore, the carry-out port 55 and the carry-in port 152 are opened, and the nitriding chamber S2 and the cooling chamber S3 are communicated with each other through the shutter chamber 16.

  In this state, the workpiece 2 is moved along the transport direction D, and transported from the inside of the heat shield 63 to the cooling chamber S3 through the outlet side passage port 63e, the transport port 55, the shutter chamber 16, and the transport port 152. Is done. That is, the workpiece 2 is transferred from the chain conveyor 61 to the chain conveyor 161. When the workpiece 2 is carried into the cooling chamber S3, the carry-in port 152 of the cooling chamber S3 is closed, and the inside of the cooling chamber S3 is sealed.

  The object to be processed 2 carried into the cooling chamber S3 is conveyed to a predetermined position in the cooling chamber S3 by the driving of the chain conveyor 161, and is stopped. Further, nitrogen gas is supplied to the cooling chamber S3 through the cooling chamber gas supply path 173, the inside of the cooling chamber S3 is increased to a predetermined processing pressure (for example, about 500 Torr), and cooling processing is performed. The heat radiated from the workpiece 2 is transmitted to cooling water in a cooling water passage (not shown) via nitrogen gas in the cooling chamber S3, the casing 151, and the like, and is exhausted from the cooling unit 5 together with the cooling water. By this cooling treatment, the temperature of the workpiece 2 is lowered from about 500 ° C. to 550 ° C. to about 100 ° C. to 150 ° C.

  When the cooling process is completed, the carry-out port 155 is opened, and the workpiece 2 is transferred from the cooling chamber S3 to the unloader 12 through the carry-out port 155 by driving the chain conveyor 161. As described above, a series of processing steps in the plasma nitriding processing system 1 is completed.

  In the plasma nitriding system 1, a plurality of objects to be processed 2 can be continuously processed in parallel. That is, a plurality of objects to be processed 2 can be processed continuously and efficiently while performing heat treatment in the heating chamber S1, nitriding treatment in the nitriding chamber S2, and cooling treatment in the cooling chamber S1.

  As described above, in the nitriding furnace 4 of the plasma nitriding treatment system 1, the tip of the temperature measuring member 120 is approximately the minimum distance from the surface of the workpiece 2 accommodated in the nitriding chamber S2 that is not affected by discharge. The thermocouple 122 built in the temperature measuring member 120 is electrically insulated from the furnace body 51, the heat shield 63, the heater 62, and the like. 122 can be prevented from being damaged by the influence of discharge. Therefore, the life of the thermocouple 122 can be extended. In addition, since the temperature of the object to be processed 2 can be measured in a non-contact manner by the temperature measuring member 120, it is possible to deal with automated equipment. The substantially minimum distance free from the influence of discharge depends on conditions such as atmosphere, temperature, pressure, and discharge voltage, but may be adjusted within a range of 5 to 30 mm, and preferably about 5 to 10 mm.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to this example. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

  For example, in the above embodiment, a crankshaft made of an iron-based alloy, a camshaft, and the like are illustrated as the object to be processed 2, but the object to be processed 2 is not limited to this, and the present embodiment is applicable to various materials. Applicable to plasma nitriding.

  The shape, arrangement, and the like of the heater 62, the heat shield 63, the opening 81, the opening wall 82, the lid 83, and the like provided in the nitriding furnace 4 are not limited to the above embodiment. For example, the heater 62 may be provided not only on the side of the workpiece 2 in the nitriding chamber S2, but also on the upper side.

  Further, the shape of the temperature measuring member 120 is not limited to the above embodiment. For example, although only the front end portion of the temperature measurement member 120 is colored, the portion other than the front end portion of the temperature measurement member 120 may naturally be colored black.

  The position where the temperature measuring member 120 is disposed is not limited to the side of the object 2 to be processed. For example, it may be above the workpiece 2, that is, between the upper plate portion 63 c and the upper portion of the workpiece 2, or may be below, forward, rearward, etc. of the workpiece 2.

  For example, when the temperature measuring member 120 is provided between the opening 81 and the workpiece 2, the opening degree of the opening 81 (the distance between the lid 83 and the opening 81) is measured by the thermocouple 122. Based on the above, it becomes possible to adjust more suitably. That is, in the nitriding furnace 4, by opening and closing the opening 81, the amount of heat released from the object to be processed 2 to the outside through the opening 81 can be increased or decreased, whereby a portion facing the opening 81 (in the above embodiments) Although the temperature of the upper central portion of the workpiece 2 can be adjusted, a measurement value close to the actual temperature of the portion facing the opening 81 can be detected. And in the control part 17, the suitable opening degree of the opening 81 can be calculated using the measured value. That is, the temperature of the portion facing the opening 81 can be controlled to a desired value. In particular, in the nitriding furnace 4 as in the above-described embodiment, when the opening 81 is small, the temperature of the upper central portion of the object to be processed 2 is another part (the side portion, the lower part, etc. of the object to be processed 2). However, the temperature distribution of the object to be treated 2 can be made uniform by measuring the temperature of the portion that is most likely to become high temperature and adjusting the opening of the opening 81. Can be planned. As a result, the process nonuniformity of the to-be-processed object 2 can be prevented.

Alternatively, the temperature measuring member 120 may be grounded at a plurality of locations in the nitriding chamber S2, and the temperatures at the plurality of locations in the nitriding chamber S2 may be measured. In this case, it is preferable to have a plurality of heaters that can be controlled according to the number of temperature measuring members 120.
Further, a radiation thermometer for the object to be processed that measures the radiation temperature of the object to be processed 2 in a non-contact state is provided, and the actual temperature of the object to be processed 2 is estimated by adding those measured values. good. However, the radiation thermometer is preferably used supplementarily because the measurement accuracy of the radiation thermometer itself is low for the purpose of temperature control of the plasma processing furnace of the present invention.

  Further, in the above embodiment, the anode of the plasma power supply 115 is connected to the furnace body 51, that is, the furnace body 51 is a discharge conductor. You may connect to a member. For example, a discharge conductor is provided inside the furnace body 51 (between the furnace body 51 and the heat shield 63) or inside the heat shield 63 (between the heater 62 and the object to be processed 2). The anode of the plasma power supply 115 may be connected to the discharge conductor. In short, any structure may be used as long as glow discharge is generated between the discharge conductor and the object to be processed 2 and between the discharge conductor and the dummy 120 in the nitriding chamber S2.

  Furthermore, the configuration of the nitriding furnace 4 is a continuous processing system such as the plasma nitriding processing system 1 shown in the above embodiment (including a plurality of processing chambers, such as a heating process, a process using plasma, a cooling process, etc. The present invention is not limited to a system that performs a plurality of types of processing in different processing chambers), and can also be applied to a batch-type plasma processing system (a system that performs a plurality of types of processing in the same processing chamber). That is, for example, the present invention can be applied to a configuration in which heat treatment and nitriding treatment are performed in the same processing chamber, or a configuration in which heating treatment, nitriding treatment, and cooling processing are performed in the same processing chamber.

  Further, the configuration of the nitriding furnace 4 is not limited to the horizontal furnace as described in the above embodiment (a structure in which the object to be processed is moved in the lateral direction and is carried in / out from the side of the processing chamber). The present invention can also be applied to a furnace (a structure in which an object to be processed is moved up and down and carried in and out from below a processing chamber).

  In addition to the plasma nitriding process, the present embodiment can be applied to various processes using plasma such as a plasma carburizing process and a plasma carbonitriding process. That is, the plasma processing furnace is not limited to a nitriding furnace (plasma nitriding furnace), and may be a plasma carburizing furnace, a plasma carbonitriding furnace, or the like.

  The present invention can be applied to a plasma processing furnace and a plasma processing method for performing a surface treatment of a metal product or the like.

It is a schematic plan view of a plasma nitriding system. It is a schematic longitudinal cross-sectional view of a plasma nitriding system. It is a longitudinal cross-sectional view of a nitriding furnace. It is a longitudinal cross-sectional view (schematic cross-sectional view by the II line | wire in FIG. 3) of a nitriding furnace. It is explanatory drawing which expanded and showed the structure of the thermal-shielding body and the to-be-processed object raising / lowering mechanism. It is the longitudinal cross-sectional view which showed structures, such as a temperature measurement member.

Explanation of symbols

D Transport direction S1 Heating chamber S2 Nitriding chamber S3 Cooling chamber 1 Plasma nitriding system 2 Processed object 3 Heating furnace 4 Nitriding furnace 5 Cooling unit 17 Control unit 51 Furnace body 115 Power source for plasma 120 Temperature measuring member 121 Protection tube 122 Thermocouple 127 Joint part 132 Paint 135 Temperature detection part

Claims (8)

Accommodating the article to be processed in the processing chamber, by applying a predetermined voltage between the discharge conductor material and the object, by generating Oite plasma in the processing chamber to process the object to be processed plasma A processing furnace,
Equipped with a temperature measurement member with a built-in thermometer at the tip,
The temperature measuring member is electrically insulated from the discharge conductor and the object to be processed,
The tip of the temperature measurement member is disposed at a position at a substantially minimum distance where there is no influence of discharge from the object to be processed ,
In order to confirm the influence of the discharge from the object to be processed, the heat-resistant window of the furnace body that can be seen between the tip of the temperature measuring member and the object to be processed, or the output from the temperature measuring member A plasma processing furnace comprising at least one of a recorder for recording a relationship with the passage of time . The plasma processing furnace according to claim 1, wherein the minimum distance is 5 to 30 mm . The plasma processing furnace according to claim 1 or 2, wherein the thermometer is a thermocouple, and a junction point of the thermocouple is built in a tip portion of the temperature measurement member . The plasma processing furnace according to claim 1, wherein the temperature measuring member is electrically insulated from the processing chamber . The plasma processing furnace according to claim 1, further comprising a mechanism that adjusts a distance of the temperature measurement member from the object to be processed . The plasma processing furnace according to claim 1, wherein a tip portion of the temperature measuring member is colored black . The plasma processing furnace according to claim 1, wherein the processing chamber is a nitriding chamber for nitriding a target object. Plasma processing for processing the object to be processed by storing the object to be processed in the processing chamber and generating a plasma in the processing chamber by applying a predetermined voltage between the discharge conductor and the object to be processed. A method for measuring the temperature of an object to be processed in a furnace,
  A temperature measuring member including a temperature measuring part of a thermometer at a distal end portion, the temperature measuring member is electrically insulated from the discharge conductor and the object to be processed,
  The tip of the temperature measurement member measures the temperature of the object to be processed in a state where it is disposed at a position at a minimum distance where there is no influence of discharge from the object to be processed,
  The minimum distance is determined by looking between the tip of the temperature measuring member and the object to be processed from a heat-resistant window provided in the furnace body, or by using a recorder to determine the relationship between the output from the temperature measuring member and the passage of time. A method for measuring a temperature of an object to be processed in a plasma processing furnace, wherein the effect of discharge is confirmed and determined by at least one of recording.

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