Method of determining burnout execution timing

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, pressure, and exhaust gas components inside the furnace 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-described problems and can be realized in the following forms.

[0006] (1) According to an aspect of the present disclosure, a method for determining the timing of performing burnout in a vacuum carburizing furnace is provided. This determination method uses the change over time of each measured pressure in the vacuum carburizing furnace measured by a plurality of pressure gauges, and among the plurality of pressure gauges that are equal to or higher than a predetermined threshold pressure, the timing of the peak of the first pressure measured by the first pressure gauge, and the timing of the peak of the second pressure corresponding to the peak of the first pressure measured by the second pressure gauge different from the first pressure gauge, a setting step of setting a reference range of the peak time difference, which is the time difference therebetween; an acquisition step of acquiring the change over time of 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 of performing the burnout when the peak time difference acquired in the acquisition step is outside the reference range. It is difficult to specify the location where discharge occurs in the carburizing furnace and the amount of pressure change accompanying the discharge. According to the determination method of this aspect, the timing of performing burnout is determined using the peak time difference. Therefore, the timing of performing burnout can be determined with higher accuracy than when simply using the pressure value.

[0007] Note that the present disclosure can be realized in various forms, for example, it can be realized in forms such as a vacuum carburizing device and a control method of a vacuum carburizing device.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Embodiments 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 the present embodiment. The vacuum carburizing apparatus 100 includes 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 in the vacuum carburizing furnace 110 in a reduced-pressure and heated state, and contacts the surface of the workpiece with carburizing gas, thereby performing a carburizing process in which carbon of the carburizing gas penetrates and diffuses from the surface of the workpiece.

[0010] The vacuum pump 120 sucks the gas in 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 in 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 arranged at different positions. In the present embodiment, the first pressure gauge 210 is provided in a measurement pipe communicating with the inside of the vacuum carburizing furnace 110, and the second pressure gauge 220 is provided in a gas discharge path communicating from the inside of the vacuum carburizing furnace 110 to the vacuum pump 120. Hereinafter, the pressure value measured by the first pressure gauge 210 is also referred to as the first pressure, and the pressure value measured by the second pressure gauge 220 is also referred to as the second pressure.

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

[0013] Figure 2 is a flowchart showing an example of the timing determination process. This process is a process in which the control device 300 determines whether it is the timing for burnout to be performed.

[0014] In step S100, the control device 300 sets a reference range of the peak time difference, which is the time difference between the timing of the peak of the first pressure and the timing of the peak of the second pressure corresponding to the peak of the first pressure. This process is also referred to as the "setting process". The peak of the first pressure is a peak above a predetermined threshold pressure. The threshold pressure is a value determined experimentally in advance and indicates that the pressure generated due to discharge has changed in the vacuum carburizing furnace 110. In the present embodiment, the control device 300 sets 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. Also, the reference range is recorded in the memory 310.

[0015] FIG. 3 is a diagram showing an example of the reference range. In the graph shown in FIG. 3, the horizontal axis represents the pressure value in the vacuum carburizing furnace 110 immediately before the peak occurs and indicates the pressure value measured by the first pressure gauge 210. The vertical axis represents the peak time difference. The pressure value of the regression line gr1 is a regression line obtained by regression analysis from the measured values. The regression line gr2 is a regression line obtained by parallelly moving the regression line gr1 upward by a predetermined first threshold Th1 and indicates the upper limit of the reference range. The regression line gr3 is a regression line obtained by parallelly moving the 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 change in pressure due to discharge, the faster the speed at which the pressure change propagates, and thus the shorter the peak time difference. Therefore, when the first pressure immediately before the peak occurs is low, the change in pressure due to discharge is greater than when the first pressure immediately before the peak occurs is high, so the peak time becomes shorter and the regression line gr1 slopes upward to the right.

[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 in time series during the carburizing process, 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 within the pressure 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 S130.

[0019] In step S130, the control device 300 outputs the necessity of performing burnout. This step is also referred to as the "output step". Further, the steps of step S120 and step S130 combined are 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).

[0020] It is difficult to identify the location where discharge occurs in the vacuum carburizing furnace 110 and the amount of pressure change associated with the discharge. According to the determination method of this form, 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 path that communicates from inside the vacuum carburizing furnace 110 to the vacuum pump 120. However, it is not limited to this, and the pressure gauge may be provided at a location that communicates with the inside of 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 path, 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 equal to or greater than a predetermined determination value is equal to or greater than 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. However, it is not limited to this, and the vacuum carburizing apparatus 100 may include three or more pressure gauges. In this case, for example, in the setting step, 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 inside the vacuum carburizing furnace 110 immediately before a peak occurs. However, it is not limited to this, and the reference range may be determined to be constant regardless of the pressure inside 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 the control device 300 sets the reference range using the temporal changes in 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, it can execute the process of step S120 using the reference range recorded in the memory 310.

[0025] The present disclosure is not limited to the above-described embodiments, and can be implemented in various configurations without departing from the spirit thereof. 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 appropriately replaced or combined in order to solve the above-described problems or to achieve some or all of the above-described effects. Further, if the technical feature is not described as essential in this specification, it can be appropriately deleted.

Description of Reference Numerals

[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 performing burnout of a vacuum carburizing furnace, comprising: a setting step of setting a reference range of a peak time difference, which is a time difference between the timing of a peak of a first pressure measured by a first pressure gauge among the plurality of pressure gauges that are equal to or higher than a predetermined threshold pressure, using the change over time of each measured pressure in the vacuum carburizing furnace measured by the plurality of pressure gauges, and the timing of a 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; an acquisition step of acquiring the change over time of each measured pressure in the vacuum carburizing furnace after the setting step and acquiring the peak time difference; a determination step of outputting that it is the timing for performing the burnout when the peak time difference acquired in the acquisition step is outside the reference range.

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