How to determine the timing of burnout

Abstract

To provide a technique capable of accurately determining execution timing of burnout.SOLUTION: A method for determining the timing to execute burnout in a vacuum carburizing furnace according to the present invention includes: a setting step of setting a reference range for the peak time difference, which is the time difference between the timing of a first pressure peak measured by a first pressure gauge among a plurality of pressure gauges that is equal to or greater than a predetermined threshold pressure, and the timing of a second pressure peak corresponding to the first pressure peak measured by a second pressure gauge different from the first pressure gauge, using the time-varying changes in each measured pressure in the vacuum carburizing furnace measured by the plurality of pressure gauges; an acquisition step of acquiring the time-varying changes in each measured pressure in the vacuum carburizing furnace after the setting step and acquiring the peak time difference; and a determination step of outputting that it is time to execute burnout if the peak time difference acquired in the acquisition step is outside the reference range.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a method for determining burnout implementation timing.

Background Art

[0002] In a vacuum carburizing furnace, it is known to perform burnout to remove soot adhering to the furnace interior. Patent Document 1 describes a technique for monitoring the temperature and pressure inside the furnace and the components of the exhaust gas during burnout and determining the end timing of burnout.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There has been a demand for a technique capable of accurately determining the burnout implementation timing.

Means for Solving the Problems

[0005] The present disclosure has been made to solve the above problems and can be realized in the following forms.

[0006] (1) According to the embodiment of the present disclosure, a method for determining the timing of burnout of a vacuum carburizing furnace is provided. This determination method includes: a setting step of setting a reference range for peak time difference, which is the time difference between the timing of the peak of a first pressure measured by a first pressure gauge among the plurality of pressure gauges that is above a predetermined threshold pressure, and the timing of the peak of a second pressure corresponding to the peak of the first pressure measured by a second pressure gauge different from the first pressure gauge, using the time-dependent changes in each measured pressure in the vacuum carburizing furnace measured by a plurality of pressure gauges; an acquisition step of acquiring the time-dependent changes in each measured pressure of the vacuum carburizing furnace after the setting step and acquiring the peak time difference; and a determination step of outputting that it is the timing to perform the burnout if the peak time difference acquired in the acquisition step is outside the reference range. It is difficult to identify the location of electrical discharges within a carburizing furnace and the resulting pressure changes. This method uses the peak time difference to determine the timing of burnout. Therefore, it can determine the timing of burnout with greater accuracy than simply using pressure values.

[0007] Furthermore, this disclosure can be implemented in various forms, for example, in the form of a vacuum carburizing apparatus or a control method for a vacuum carburizing apparatus. [Brief explanation of the drawing]

[0008] [Figure 1] This is an explanatory diagram showing the configuration of a vacuum carburizing apparatus. [Figure 2] This flowchart shows an example of a timing determination process. [Figure 3] This figure shows an example of a reference range. [Modes for carrying out the invention]

[0009] A. First Embodiment: Figure 1 is an explanatory diagram showing the configuration of the vacuum carburizing apparatus 100 in this embodiment. The vacuum carburizing apparatus 100 comprises a vacuum carburizing furnace 110, a vacuum pump 120, a first pressure gauge 210, a second pressure gauge 220, and a control device 300. The vacuum carburizing apparatus 100 places a workpiece, such as steel, inside the vacuum carburizing furnace 110 under reduced pressure and heating conditions, and performs a carburizing treatment by bringing a carburizing gas into contact with the surface of the workpiece, thereby allowing the carbon from the carburizing gas to penetrate and diffuse from the surface of the workpiece.

[0010] The vacuum pump 120 sucks in the gas inside the vacuum carburizing furnace 110 and discharges it to the outside.

[0011] The first pressure gauge 210 and the second pressure gauge 220 measure the pressure inside the vacuum carburizing furnace 110. The first pressure gauge 210 and the second pressure gauge 220 output the measured pressure to the control device 300. The first pressure gauge 210 and the second pressure gauge 220 are located in different positions. In this embodiment, the first pressure gauge 210 is provided in a measuring pipe that communicates with the inside of the vacuum carburizing furnace 110, and the second pressure gauge 220 is provided in a gas discharge passage that communicates from inside the vacuum carburizing furnace 110 to the vacuum pump 120. Hereinafter, the pressure value measured by the first pressure gauge 210 will also be referred to as the first pressure, and the pressure value measured by the second pressure gauge 220 will also be referred to as the second pressure.

[0012] The control device 300 includes a memory 310 and a CPU 320. The CPU 320 controls the operation of the vacuum pump 120 and a carburizing gas supply device (not shown) by executing a program pre-installed in the memory 310. However, some or all of the functions of these components may be implemented by hardware circuits.

[0013] Figure 2 is a flowchart showing an example of the timing determination process. This process determines whether or not it is the right time for the control device 300 to perform a burnout.

[0014] In step S100, the control device 300 sets a reference range for the peak time difference, which is the time difference between the timing of the first pressure peak and the timing of the second pressure peak corresponding to the first pressure peak. This process is also called the "setting process". The first pressure peak is a peak that is above a predetermined threshold pressure. The threshold pressure is a value that has been experimentally determined in advance and indicates that the pressure generated in the vacuum carburizing furnace 110 due to discharge has changed. In this embodiment, the control device 300 sets the reference range using the time-dependent changes in the measured pressures of the first pressure gauge 210 and the second pressure gauge 220 during the carburizing process, which have been measured. The reference range is also recorded in the memory 310.

[0015] Figure 3 shows an example of a reference range. In the graph shown in Figure 3, the horizontal axis represents the pressure value inside the vacuum carburizing furnace 110 just before the peak occurs, and shows the pressure value measured by the first pressure gauge 210. The vertical axis represents the peak time difference. The pressure value of regression line gr1 is a regression line obtained by regression analysis from measured values. Regression line gr2 is a regression line obtained by shifting regression line gr1 upward by a predetermined first threshold Th1, and indicates the upper limit of the reference range. Regression line gr3 is a regression line obtained by shifting regression line gr1 downward by a predetermined second threshold Th2, and indicates the lower limit of the reference range. The first threshold Th1 and the second threshold Th2 may be the same value.

[0016] The greater the pressure change associated with the discharge, the faster the pressure change propagates, resulting in a shorter peak time difference. Therefore, when the initial pressure immediately before the peak is low, the pressure change associated with the discharge is greater than when the initial pressure immediately before the peak is high, resulting in a shorter peak time and an upward-sloping regression line gr1.

[0017] In step S110 (see FIG. 2), the control device 300 acquires the change over time of the measured pressures of the first pressure gauge 210 and the second pressure gauge 220 during the carburizing process, and acquires the peak time difference. This step is also referred to as the "acquisition step". In the present embodiment, the control device 300 continuously acquires the measured pressures of the first pressure gauge 210 and the second pressure gauge 220 during the carburizing process in time series, acquires the timing of the peak of the first pressure and the timing of the peak of the second pressure, and calculates the peak time difference. Further, the control device 300 stores the first pressure immediately before the peak together with the peak time difference.

[0018] In step S120, the control device 300 determines whether the peak time difference acquired in step S110 is a pressure within the reference range set in step S100. In the present embodiment, the reference range is determined according to the first pressure gauge 210 immediately before the peak occurs. When the peak time difference is within the reference range, the control device 300 ends the timing determination process. On the other hand, when the peak time difference is outside the reference range, the control device 300 proceeds to the process of step S1三十.

[0019] In step S130, the control device outputs the necessity of performing burnout. This step is also referred to as the "output step". Further, the step combining the processes of step S120 and step S130 is also referred to as the "determination step". The control device 300 notifies the necessity of performing burnout via, for example, an output device or a communication device not shown in the figure.

[0020] It is difficult to specify the location where discharge occurs in the vacuum carburizing furnace 110 and the amount of pressure change accompanying the discharge. According to the determination method of this embodiment, the implementation timing of burnout is determined using the peak time difference. Therefore, the implementation timing of burnout can be determined with higher accuracy than when simply using the pressure value.

[0021] B. Other embodiments: (B1) In the above-described embodiment, the first pressure gauge 210 is provided in the vacuum carburizing furnace 110, and the second pressure gauge 220 is provided in the gas discharge passage that communicates from inside the vacuum carburizing furnace 110 to the vacuum pump 120. Not limited to this, the pressure gauge may be provided at a location that conducts into the vacuum carburizing furnace 110. For example, both the first pressure gauge 210 and the second pressure gauge 220 may be provided in the gas discharge passage. The first pressure gauge 210 may be provided upstream of the second pressure gauge 220, and the second pressure gauge 220 may be provided downstream of a valve (not shown). The distance between the first pressure gauge 210 and the second pressure gauge 220 is preferably a distance such that the peak time difference when the amount of change in pressure caused by discharge in the vacuum carburizing furnace 110 is greater than or equal to a predetermined determination value is greater than or equal to a predetermined threshold time. When the first pressure gauge 210 and the second pressure gauge 220 are sufficiently separated, it becomes easier to obtain a significant peak time difference.

[0022] (B2) In the above-described embodiment, the vacuum carburizing apparatus 100 includes two pressure gauges. Not limited to this, the vacuum carburizing apparatus 100 may include three or more pressure gauges. In this case, in the setting step, for example, the control device 300 sets a reference range for each combination of two pressure gauges among the plurality of pressure gauges, and in step S130, when any one or more of the peak times of each combination are outside the reference range, the process of step S130 is performed.

[0023] (B3) In the above-described embodiment, the reference range is determined according to the pressure in the vacuum carburizing furnace 110 immediately before a peak occurs. Not limited to this, the reference range may be determined to be constant regardless of the pressure in the vacuum carburizing furnace 110 immediately before a peak occurs.

[0024] (B4) In the above-described embodiment, in the timing determination process after the first time, the control device 300 may omit the process of step S100. After setting the reference range using the change over time of the measured pressures of the first pressure gauge 210 and the second pressure gauge 220 during the carburizing process actually measured in step S100 once, the control device 300 can execute the process of step S120 using the reference range recorded in the memory 310.

[0025] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve the problems described above or to achieve some or all of the effects described above. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of Symbols]

[0026] 100... Vacuum carburizing apparatus, 110... Vacuum carburizing furnace, 120... Vacuum pump, 210... First pressure gauge, 220... Second pressure gauge, 300... Control device, 310... Memory, 320... CPU

Claims

[Claim 1] A method for determining the timing of burnout in a vacuum carburizing furnace, Setting step: Using the time-dependent changes in each measured pressure within the vacuum carburizing furnace measured by multiple pressure gauges, set a reference range for the peak time difference, which is the time difference between the timing of the peak of the first pressure measured by a first pressure gauge among the multiple pressure gauges that is above a predetermined threshold pressure, and the timing of the peak of the second pressure corresponding to the peak of the first pressure measured by a second pressure gauge different from the first pressure gauge. After the setting step, the acquisition step involves acquiring the time-dependent changes in each of the measured pressures of the vacuum carburizing furnace and acquiring the peak time difference. A determination method comprising: a determination step of outputting that if the peak time difference obtained in the acquisition step is outside the reference range, it is the timing to perform the burnout.

Images