JP-2026074657-A - Quantitative evaluation method for engine oil-derived deposits

Abstract

[Problem] The object of the present invention is to provide an evaluation method that can quantitatively and efficiently evaluate engine oil-derived carbon deposits generated in an environment that simulates all temperature environments within a gasoline engine (intake system temperature environment, combustion chamber temperature environment, exhaust temperature environment). [Solution] The evaluation method is characterized by including a pretreatment step of heating engine oil to 270°C or higher in an inert gas atmosphere and holding it at that temperature for a predetermined time; a deposit generation step of setting the engine oil that has undergone the pretreatment step to a constant temperature in an air atmosphere and holding it at that set temperature for 120 minutes or more to generate deposits; and a deposit generation amount measurement step of measuring the amount of deposit generated in the deposit generation step. [Selection Diagram] Figure 5

Inventors

• 戸邊 祥太
• 志岐 昌美
• 江口 直希
• 橋本 弘平

Assignees

• 株式会社SUBARU

Dates

Publication Date

20260507

Application Date

20241021

Claims (6)

1. A pretreatment step in which engine oil is heated to 270°C or higher under an inert gas atmosphere and held at that temperature for a predetermined time. A quantitative evaluation method for engine oil-derived deposits, characterized by comprising: a deposit generation step, in which the engine oil that has undergone the pretreatment step described above is set to a certain temperature in an air atmosphere and held at that set temperature for 120 minutes or more to generate deposits; and a deposit generation amount measurement step, in which the amount of deposit generated in the deposit generation step is measured.
2. The quantitative evaluation method according to claim 1, characterized in that the pretreatment step, the deposit generation step, and the deposit generation amount measurement step are performed using a TG-DTA apparatus.
3. The quantitative evaluation method according to claim 1, characterized in that the heating temperature in the pretreatment step is maintained for 20 minutes or more.
4. The quantitative evaluation method according to claim 1, characterized in that the set temperature in the deposit generation step is any temperature within the temperature range of 200°C to 700°C.
5. An engine oil weight measurement step is performed in a step prior to the aforementioned pretreatment step, in which the weight of the engine oil provided to the pretreatment step is measured. A deposit generation rate calculation step is performed in a step following the deposit generation amount measurement step, in which the deposit generation rate is calculated using the following formula: [Formula] Amount of deposits measured in the deposit generation amount measurement step / Weight of engine oil measured in the engine oil weight measurement step × 100 The quantitative evaluation method according to claim 1, characterized by including the following.
6. Engine oil weight measurement process, A pretreatment step in which the engine oil is heated to 270°C or higher and 300°C or lower under an inert gas atmosphere, and held at the heated temperature for 20 minutes or more and 40 minutes or less. A deposit generation step in which the engine oil that has undergone the pretreatment step is set to a temperature within the range of 200°C to 700°C under an air atmosphere, and is held at that set temperature for 120 minutes or more to generate deposits. A deposit generation amount measurement step for measuring the amount of deposit generated in the deposit generation step, and a deposit generation rate calculation step for calculating the deposit generation rate using the following formula [formula]. Amount of deposits measured in the deposit generation measurement step / Weight of engine oil measured in the engine oil weight measurement step × 100 Includes, The quantitative evaluation method according to claim 1, characterized in that the pretreatment step, the deposit generation step, and the deposit generation amount measurement step are performed using a TG-DTA apparatus.

Description

This invention relates to a quantitative evaluation method for engine oil-derived deposits, and more particularly to a quantitative evaluation method for engine oil-derived deposits generated under a temperature environment simulating that of a gasoline engine. Engine oil accumulates as carbon deposits in various locations within the engine of internal combustion engine vehicles, and these accumulated carbon deposits are known to have various effects on engine performance and function. Furthermore, there is a societal trend towards switching from petroleum-derived engine oils and fuels to carbon-neutral engine oils and fuels (plant-derived engine oils and fuels) in internal combustion engine vehicles. In line with this trend, it is necessary to evaluate the impact of carbon-neutral engine oils and fuels on engine performance and function. Based on the above points, test methods have been developed to quantitatively evaluate the formation of carbon deposits in an environment simulating a gasoline engine, with the aim of predicting and examining the effects of engine oil-derived and fuel-derived carbon deposits generated within gasoline engines. Examples of such evaluation test methods include the hot tube test and panel coking test described in Patent Document 1, etc. Japanese Patent Application Publication No. 2-45595 This figure compares the appearance after a deposit formation test when no pretreatment step is performed.This diagram shows the deposit state at different temperatures when the heating temperature in the pretreatment process is changed.This figure shows the deposit generation rate and physical state for each holding time in the deposit generation process.This figure shows the FT-IR spectra when the holding time at 300°C was changed during the deposit formation process.This figure shows the deposit formation rate for new oil and used oil at each set temperature in the deposit formation process. <Quantitative evaluation method for deposits derived from engine oil> The quantitative evaluation method for engine oil-derived deposits according to the present invention includes a pretreatment step, a deposit generation step, and a deposit generation amount measurement step, and preferably further includes an engine oil weight measurement step and a deposit generation rate calculation step. [Pre-treatment process] In the pretreatment process, the engine oil is heated to 270°C or higher under an inert gas atmosphere and held at that temperature for a predetermined time. The engine oils subject to the pretreatment process are unused and used engine oils. In the case of unused engine oil, the pretreatment process removes highly volatile components, allowing for a more accurate quantitative evaluation of deposit formation. In the case of used engine oil, the pretreatment process removes gasoline components, preventing the engine oil from overflowing due to the boiling of gasoline components during the deposit formation process. Furthermore, removing highly volatile components allows for a more accurate quantitative evaluation of deposit formation. The inert gas atmosphere is preferably an N2 atmosphere. The lower limit of the heating temperature is 270°C or higher, preferably 280°C or higher, more preferably 290°C or higher, and the upper limit is preferably 300°C or lower. These lower and upper limits can be combined arbitrarily. Setting the lower limit of the heating temperature to 270°C or higher prevents highly volatile components and gasoline components contained in the engine oil from remaining. Setting the upper limit of the heating temperature to 300°C or lower suppresses the influence on components that become solid deposits. The minimum holding time for the heating temperature is preferably 20 minutes or more, more preferably 30 minutes or more, and the maximum holding time is preferably 40 minutes or less. These minimum and maximum values can be combined arbitrarily. When the minimum holding time for the heating temperature is 20 minutes or more, it is possible to prevent highly volatile components in the engine oil and gasoline components from remaining. By setting the maximum holding time for the heating temperature to 40 minutes or less, excessive evaporation of the oil can be suppressed. The apparatus used in the pretreatment process is preferably a TG-DTA apparatus. [Deposit generation process] In the deposit formation process, the engine oil that has undergone the pretreatment process is set to a constant temperature in an air atmosphere and held at that temperature for 120 minutes or more, thereby forming deposits. Considering that the set temperature is an evaluation test of the amount (rate) of deposit formation at each set temperature, limiting the range of the set temperature is basically unnecessary. However, considering that the evaluation test covers all temperature environments within a gasoline engine (including intake system temperature, combustion chamber temperature, and exh