JP-2026075834-A - How to determine the timing of burnout

JP2026075834AJP 2026075834 AJP2026075834 AJP 2026075834AJP-2026075834-A

Abstract

[Problem] To provide a method for determining the timing of burnout that can accurately determine when burnout should occur. [Solution] A method for determining the timing of burnout in a vacuum carburizing furnace, comprising: temporarily changing the pressure inside the vacuum carburizing furnace with an object of a first weight placed inside, setting a peak time difference reference range for the first weight based on the time difference between the timing when the measured pressure of a first pressure gauge reaches its peak and the timing when the measured pressure of a second pressure gauge reaches its peak; obtaining the peak time difference, which is the time difference between the timing when the measured pressure of a first pressure gauge reaches its peak and the timing when the measured pressure of a second pressure gauge reaches its peak when the pressure inside the vacuum carburizing furnace is temporarily changed while the workpiece is being carburized in the vacuum carburizing furnace, and determining the timing of burnout based on the peak time difference reference range for the first weight and the peak time difference. [Selection Diagram] Figure 2

Inventors

立石浩規
鶴田靖彦

Assignees

トヨタ自動車株式会社

Dates

Publication Date: 20260511
Application Date: 20241023

Claims (2)

A method for determining the timing of burnout in a vacuum carburizing furnace, The steps include: arranging a first pressure gauge and a second pressure gauge in different locations within the vacuum carburizing furnace; A first weight reference range setting step involves placing an object having a predetermined first weight inside the vacuum carburizing furnace, temporarily changing the pressure inside the furnace, and setting a first weight reference range based on the peak time difference, which is the time difference between the timing at which the measured pressure of the first pressure gauge peaks and the timing at which the measured pressure of the second pressure gauge peaks when the pressure is temporarily changed. A peak time difference acquisition step is performed to acquire the peak time difference, which is the time difference between the timing when the measured pressure of the first pressure gauge reaches its peak and the timing when the measured pressure of the second pressure gauge reaches its peak, while the workpiece is being carburized in the vacuum carburizing furnace. The process includes a first weight peak time difference reference range set in the first weight reference range setting step, and a determination step that determines the timing for performing burnout based on the peak time difference acquired in the peak time difference acquisition step, How to determine the timing for burnout.
A second weight reference range setting step involves placing an object of a predetermined second weight, which has a weight different from the first weight, into the vacuum carburizing furnace, temporarily changing the pressure inside the vacuum carburizing furnace, and setting a peak time difference reference range for the second weight based on the peak time difference, which is the time difference between the timing when the measured pressure of the first pressure gauge reaches its peak and the timing when the measured pressure of the second pressure gauge reaches its peak when the pressure is temporarily changed. The process includes a workpiece reference range setting step, which sets a peak time difference reference range for the workpiece based on the weight of the workpiece to be carburized in the vacuum carburizing furnace, the peak time difference reference range of the first weight set in the first weight reference range setting step, and the peak time difference reference range of the second weight set in the second weight reference range setting step, The determination step determines the timing for performing burnout based on the peak time difference reference range of the work set in the work reference range setting step and the peak time difference acquired in the peak time difference acquisition step. A method for determining the timing of burnout implementation according to claim 1.

Description

This disclosure concerns a method for determining the timing of burnout. In vacuum carburizing furnaces, burnout is a known process for burning and removing soot accumulated inside the furnace. Patent Document 1 discloses a technique for monitoring the temperature, pressure, and exhaust gas composition inside the furnace during burnout to determine the timing of its completion. Japanese Patent Publication No. 2007-131936 This is a schematic diagram showing the vacuum carburizing apparatus of Embodiment 1.This flowchart shows an example of a burnout timing determination process.This figure shows an example of a peak time difference reference range. The embodiments of this disclosure will be described below with reference to Figures 1 to 3. Figure 1 is a schematic diagram showing the vacuum carburizing apparatus of Embodiment 1. Figure 2 is a flowchart showing an example of the burnout timing determination process. Figure 3 is a diagram showing an example of the peak time difference reference range. Embodiment 1 Referring to Figure 1, the configuration of the vacuum carburizing apparatus 10 for implementing the burnout timing determination method according to this disclosure will be described. The vacuum carburizing apparatus 10 comprises a vacuum carburizing furnace 11, a vacuum pump 12, a first pressure gauge 20, a second pressure gauge 30, and a control device 50. The vacuum carburizing furnace 11 performs carburizing treatment on a workpiece by supplying carburizing gas under reduced pressure and heating conditions. Workpieces subjected to carburizing treatment include, for example, automobile parts and machine parts made of steel. The vacuum carburizing furnace 11 is equipped with heaters 11a for heating the inside of the furnace. Multiple heaters 11a are arranged on both the upper and lower surfaces of the furnace. The vacuum carburizing furnace 11 is also equipped with a gas inlet (not shown) for introducing combustion gases such as air during burnout. The vacuum pump 12 is connected to the vacuum carburizing furnace 11 via the exhaust port 12a. The vacuum pump 12 sucks gas from inside the vacuum carburizing furnace 11 and discharges it to the outside, thereby reducing the pressure inside the vacuum carburizing furnace 11 to below atmospheric pressure. The vacuum carburizing apparatus 10 has a first pressure gauge 20 and a second pressure gauge 30 located in different positions. The first pressure gauge 20 is located inside the vacuum carburizing furnace 11. The second pressure gauge 30 is located at the exhaust port 12a. The first pressure gauge 20 and the second pressure gauge 30 measure the pressure inside the vacuum carburizing furnace 11. The first pressure gauge 20 and the second pressure gauge 30 output the measured pressure to the control device 50. The first pressure gauge 20 and the second pressure gauge 30 can be located in any position as long as they can measure the pressure inside the vacuum carburizing furnace 11. The control device 50 comprises a memory 51 and a CPU 52. The memory 51 stores programs for executing processes such as carburizing the workpiece and determining the burnout timing (described later). The CPU 52 executes the programs stored in the memory 51 to control the operation of components such as the heater 11a and the vacuum pump 12. The procedure for performing carburizing treatment in the vacuum carburizing apparatus 10 is as follows: First, the workpiece is placed in the vacuum carburizing furnace 11, and the vacuum pump 12 is activated to reduce the pressure inside the vacuum carburizing furnace 11 while heating it with the heater 11a. Once the workpiece reaches a predetermined treatment temperature (for example, 950 degrees Celsius), a carburizing gas is supplied to the vacuum carburizing furnace 11. The carburizing gas is a hydrocarbon gas, such as acetylene gas. Under reduced pressure and high temperature, the hydrocarbon gas decomposes to produce carbon. The resulting carbon diffuses from the surface to the interior of the workpiece, performing the carburizing treatment. Some of the carbon generated from the carburizing gas adheres to the inside of the vacuum carburizing furnace 11 as soot. Soot accumulation inside the vacuum carburizing furnace 11 can lead to malfunctions in the furnace 11 and poor quality of the carburized products. Therefore, if soot accumulates inside the vacuum carburizing furnace 11, a burnout procedure is performed by introducing air into the furnace 11 to burn and remove the soot. Next, we will explain the method for determining the burnout timing. Figure 2 is a flowchart showing an example of the burnout timing determination process performed by the control device 50. In step S1, the vacuum carburizing furnace 11 is emptied. Specifically, only the tray on which the workpiece will be placed during the carburizing process is placed inside the vacuum carburizing furnace 11. In step S2, the vacuum pump 12 is activated to bring the vacuum car