Quantitative evaluation method for engine oil-derived deposits

Abstract

The object of the present invention is to provide an evaluation method that can quantitatively and efficiently evaluate engine oil-derived carbon deposits generated under conditions that simulate 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.

Description

Technical Field

[0001] The present invention relates to a method for quantitatively evaluating engine oil-derived deposits, particularly a method for quantitatively evaluating engine oil-derived deposits generated under a temperature environment simulating that inside a gasoline engine.

Background Art

[0002] Engine oil deposits on various parts inside the engines of vehicles equipped with internal combustion engines, and it is known that the deposited carbon deposits have various effects on the performance and functions of the engine. Further, in vehicles equipped with internal combustion engines, there is a social trend to change from petroleum-derived engine oil and fuel to carbon-neutral engine oil and fuel (plant-derived engine oil and fuel). Along with this trend of change, there is a need to evaluate the effects of carbon-neutral engine oil and fuel on the performance and functions of the engine.

[0003] Based on the above points, conventionally, for the purpose of predicting and examining the effects of engine oil-derived and fuel-derived carbon deposits generated inside a gasoline engine, a test method for quantitatively evaluating the generation of carbon deposits in an environment simulating that inside a gasoline engine has been developed. Examples of the evaluation test methods include the hot tube test and the panel coking test described in Patent Document 1 and the like.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Table 1 below summarizes conventional evaluation test methods, including the hot tube test and panel caulking test described above, in terms of the type of oil targeted for testing, the temperature environment simulating the engine installation environment, whether or not the generated deposit can be collected, whether or not the deposit generation rate can be calculated, and the test time.

[0006] [Table 1]

[0007] As shown in Table 1, conventional evaluation test methods that target only oil (hot tube test, TEOST MHK / 33C, panel coking test, and muffle furnace) cannot perform carbon deposit evaluation tests in all temperature environments (i.e., intake system temperature environment in the low temperature range, combustion chamber temperature environment in the medium temperature range, and exhaust temperature environment in the high temperature range). Specifically, hot tube tests must be conducted at temperatures below 300°C (usually at 250°C and 300°C; the hot tube test described in Patent Document 1 is conducted at 300°C), TEOST MHK / 33C at temperatures below 285°C (usually at 200°C, 250°C, 275°C, and 285°C), panel caulking tests at temperatures below 320°C (usually at 200°C, 250°C, and 300°C; the panel caulking test described in Patent Document 1 is conducted at 320°C), and muffle furnaces at temperatures below 500°C (usually at 300°C and 500°C). Tests cannot be conducted at temperatures exceeding these limits.

[0008] Regarding whether the generated deposit can be collected, the hot tube test and TEOST MHK / 33C evaluation tests use glass test tubes or glass test tubing. To collect the generated deposit, it is necessary to break the glass test tubes or glass test tubing (which are not intended to be broken) for each test, which is not a practical evaluation method.

[0009] Regarding whether the deposit formation rate (amount of deposit formed / amount of sample used in the test × 100) can be calculated, in panel caulking tests, the amount of oil splashed up (amount of sample used in the test) cannot be quantitatively determined, so the deposit formation rate cannot be calculated. In the hot tube test and TEOST MHK / 33C, even if deposits cannot be directly collected, the amount of deposit generated before and after the test can be determined, and the amount of sample used in the test can be determined by flow rate control, etc., so the deposit generation rate can be calculated indirectly. However, it is not possible to directly calculate the deposit generation rate from the amount of deposit actually collected. Therefore, it is evaluated as △ in Table 1 above.

[0010] Autoclave testing of oil and gasoline has the drawback that, being a classic device, it is not easy to implement improvements to efficiently (especially automatically) perform evaluation tests. Furthermore, even with autoclave testing, it is not possible to evaluate carbon deposits in all temperature environments.

[0011] Regarding test duration, the hot tube test takes 960 minutes (16 hours) per test, and the TEOST MHK / 33C test takes 1440 minutes (24 hours) per test. These tests are not efficient because they occupy a large portion of the equipment per test.

[0012] The object of the present invention is to provide an evaluation method that can quantitatively and efficiently evaluate engine oil-derived carbon deposits generated under conditions that simulate all temperature environments within a gasoline engine (intake system temperature environment, combustion chamber temperature environment, exhaust temperature environment). [Means for solving the problem]

[0013] The inventors of the present invention conducted diligent studies to achieve the above objectives, and as a result, they found that the above problems can be solved by performing a specific pretreatment step in the step prior to the deposit generation process, and further by setting the engine oil to a certain temperature in the deposit generation process and holding it at that set temperature for a certain period of time or longer, thus completing the present invention.

[0014] To achieve the above objective, one embodiment of the quantitative evaluation method for engine oil-derived deposits of the present invention is: 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 deposit generation step in which the engine oil that has undergone the pretreatment step is set to a constant temperature in an air atmosphere, and is held at that set temperature for 120 minutes or more to generate deposits, and Deposit generation amount measurement step for measuring the amount of deposit generated in the deposit generation step. It is characterized by including.

[0015] A preferred embodiment of the quantitative evaluation method for engine oil-derived deposits of the present invention is characterized in that the pretreatment step, the deposit generation step, and the deposit generation amount measurement step are performed using a TG-DTA apparatus.

[0016] Another preferred embodiment of the quantitative evaluation method for engine oil-derived deposits of the present invention is characterized in that the heating temperature in the pretreatment step is maintained for 20 minutes or more.

[0017] Another preferred embodiment of the quantitative evaluation method for engine oil-derived deposits of the present invention is characterized in that the set temperature in the deposit generation step is any temperature within the temperature range of 200°C to 700°C.

[0018] A further preferred embodiment of the quantitative evaluation method for engine oil-derived deposits of the present invention is an engine oil weight measurement step in a step prior to the pretreatment step, in which the weight of the engine oil provided to the pretreatment step is measured, and In a subsequent step to the deposit generation amount measurement step, a deposit generation rate calculation step of calculating the deposit generation rate by the following calculation formula [Calculation formula] The deposit generation amount measured in the deposit generation amount measurement step / the weight of the engine oil measured in the engine oil weight measurement step × 100 characterized by including the above.

[0019] Another preferred embodiment of the method for quantitatively evaluating engine oil-derived deposits of the present invention is an engine oil weight measurement step of measuring the weight of engine oil, a pretreatment step of heating the engine oil at 270 °C or higher and 300 °C or lower and holding it for 20 minutes or longer and 40 minutes or shorter at that heating temperature in an inert gas atmosphere, a deposit generation step of setting the engine oil subjected to the pretreatment step to any temperature within the temperature range of 200 °C to 700 °C in an air atmosphere and holding it for 120 minutes or longer at that set temperature to generate deposits, a deposit generation amount measurement step of measuring the deposit generation amount generated in the deposit generation step, and a deposit generation rate calculation step of calculating the deposit generation rate by the following calculation formula [Calculation formula] The deposit generation amount measured in the deposit generation amount measurement step / the weight of the engine oil measured in the engine oil weight measurement step × 100 including the above, characterized in that the pretreatment step, the deposit generation step, and the deposit generation amount measurement step are performed using a TG-DTA apparatus.

Advantages of the Invention

[0020] According to the present invention, it is possible to quantitatively and efficiently evaluate engine oil-derived carbon deposits generated in an environment simulating all temperature environments (intake system temperature environment, combustion chamber temperature environment, exhaust temperature environment) in a gasoline engine.

Brief Description of the Drawings

[0021] [Figure 1] This figure compares the appearance after a deposit formation test when no pretreatment step is performed. [Figure 2] This diagram shows the deposit state at different temperatures when the heating temperature in the pretreatment process is changed. [Figure 3] This figure shows the deposit generation rate and physical state for each holding time in the deposit generation process. [Figure 4] This figure shows the FT-IR spectra obtained when the holding time at 300°C was changed during the deposit formation process. [Figure 5] This figure shows the deposit formation rate for new oil and used oil at each set temperature in the deposit formation process. [Modes for carrying out the invention]

[0022] <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.

[0023] [Pre-treatment process] In the pretreatment process, the engine oil is heated to over 270°C in an inert gas atmosphere and held at that temperature for a predetermined time.

[0024] 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, making it possible to more accurately quantitatively evaluate deposit formation. In the case of used engine oil, the pretreatment process removes gasoline components contained in the used engine oil, preventing the engine oil from overflowing due to the boiling of gasoline components during the deposit formation process. Furthermore, by removing highly volatile components, it becomes possible to more accurately quantitatively evaluate deposit formation.

[0025] 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.

[0026] 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 as desired. When the minimum holding time for the heating temperature is 20 minutes or more, it is possible to prevent highly volatile components contained 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.

[0027] The apparatus used in the pretreatment process is preferably a TG-DTA apparatus.

[0028] [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, during which time deposits are formed.

[0029] While it is generally unnecessary to limit the range of the set temperature considering that this is an evaluation test of the amount (rate) of deposit formation at each set temperature, it is preferable that the range be 200°C to 700°C, considering that this is an evaluation test of all temperature environments inside a gasoline engine (including intake system temperature environment, combustion chamber temperature environment, and exhaust temperature environment) in an environment simulating the inside of a gasoline engine.

[0030] The minimum holding time at the set temperature is 120 minutes or more, preferably 150 minutes or more, and more preferably 180 minutes or more. By holding the set temperature for 120 minutes or more, the deposition process can be stabilized, as will be explained in the examples described later.

[0031] The apparatus used in the deposit generation process is preferably a TG-DTA apparatus.

[0032] [Deposit generation amount measurement process] In the deposit generation amount measurement process, the amount of deposit generated in the deposit generation process is measured.

[0033] The apparatus used in the deposit generation amount measurement process is preferably a TG-DTA apparatus. A TG-DTA apparatus is more preferable because it can measure the amount of deposit generated over time.

[0034] [Engine oil weight measurement process and deposit formation rate calculation process] The quantitative evaluation method for engine oil-derived deposits according to the present invention may include an engine oil weight measurement step and a deposit generation rate calculation step in order to obtain the deposit generation rate.

[0035] The engine oil weight measurement process is performed prior to the pretreatment process, and the weight of the engine oil provided to the pretreatment process is measured. The weight of the engine oil can be measured using known weighing instruments.

[0036] The deposit generation rate calculation process is performed after the deposit generation amount measurement process, and the deposit generation rate is calculated using the following formula. [Calculation formula] The formula is: Amount of deposits generated (g) measured in the deposit generation measurement process / Weight of engine oil (g) measured in the engine oil weight measurement process × 100.

[0037] [others] The engine oil weight measurement process, pretreatment process, deposit generation process, deposit generation amount measurement process, and deposit generation rate calculation process can be performed consecutively without any time intervals between each process, or with time intervals between any of the processes.

[0038] When the pretreatment process, deposit generation process, and deposit generation amount measurement process are performed in the same apparatus, any apparatus capable of heating the engine oil, switching between an inert gas atmosphere and an air atmosphere, and measuring the amount of deposit generated after the heating time can be used. In particular, the TG-DTA apparatus is preferable in terms of work efficiency because it can heat the engine oil, switch between an inert gas atmosphere and an air atmosphere, measure the amount of deposit generated over time during heating, and furthermore, perform the pretreatment process, deposit generation process, and deposit generation amount measurement process automatically and continuously. [Examples]

[0039] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0040] [Investigation of the feasibility of pretreatment by evaluating the effect of gasoline components in deposit formation tests] After use in an actual engine, used oil contains gasoline components because gasoline injected into the cylinder is scraped off and mixed into the crankcase. In other words, if used oil without pretreatment is used directly in the deposit formation test, the effect of gasoline components will also be evaluated. Therefore, in order to confirm whether or not gasoline components have an effect in the deposit formation test, the deposit formation test was conducted on both used oil and new oil without pretreatment. As the engine oil, SUBARU® genuine gasoline engine oil 5W-30 was used (this engine oil was also used in the study described later).

[0041] The test conditions involved using two atmospheric gases, N2 and air, with a heating temperature of 400°C and a heating time of 180 minutes. A differential thermal-thermogravimetric analysis (TG-DTA) system (STA7000 model, Hitachi High-Tech Science Corporation) was used as the experimental equipment. The experimental results are shown in Figure 1. The results revealed that the oil overflowed from the container during heating, making it impossible to accurately evaluate the amount of deposit formation.

[0042] Therefore, it was found that pretreatment (specifically, pretreatment to remove gasoline components from used oil in order to enable deposit formation testing in an air atmosphere) is necessary.

[0043] [Consideration of pretreatment conditions] Using the oil in question, the deposit formation test conditions were fixed at 300°C in an air atmosphere and a holding time of 180 minutes, and the pretreatment conditions were investigated. The pretreatment conditions were set to a holding time of 40 minutes in an N2 atmosphere and a heating rate of 10°C / min, with pretreatment heating temperatures of 200°C, 250°C, and 300°C. The state of the deposits formed in the deposit formation test was confirmed for each temperature pretreatment. A differential thermal-thermogravimetric analysis (TG-DTA) (STA7000 model, Hitachi High-Tech Science Corporation) was used as the experimental equipment. The experimental results are shown in Figure 2. From the experimental results, it was confirmed that when the pretreatment heating temperature was 200°C and 250°C, a membrane-like deposit was formed on the upper side of the container after the deposit formation process. Since this membrane-like deposit was not formed during pretreatment, it is thought that the gasoline contained in the oil is influencing the deposit formation test. On the other hand, when the pretreatment heating temperature was 300°C, no film-like deposits were formed, suggesting that the gasoline contained in the oil did not have an effect in the deposit formation test (i.e., only oil-based deposits were formed).

[0044] Therefore, it was found that the preferred pretreatment conditions were an N2 atmosphere with a heating temperature of 300°C and a holding time of 40 minutes.

[0045] [Study on the state and generation rate of deposits generated in relation to the holding time at the set temperature in deposit generation tests] The pretreatment conditions were set to an N2 atmosphere with a set temperature of 300°C, a heating rate of 10°C / min, and a holding time of 40 minutes. The deposit formation conditions were set to an air atmosphere with a set temperature of 300°C and holding times of 30 minutes, 60 minutes, 120 minutes, 180 minutes, 240 minutes, and 360 minutes. The rate of deposit formation at each holding time was confirmed. The appearance of the deposits was visually classified into two categories: liquid and solid. The experimental results are shown in Figure 3.

[0046] The stability of the depositation reaction was confirmed from the state of the functional groups using a Fourier transform infrared spectrometer (FT-IR) (Agilent Technologies 5500a). The experimental results are shown in Figure 4.

[0047] When the heating temperature was maintained for 30 minutes, the deposit remained in a liquid state, and the FT-IR waveform did not change significantly from the untreated state. Further increasing the heating temperature maintenance time caused the deposit to change from liquid to solid, and the FT-IR waveform changed to 2900 cm⁻¹. -1 The nearby peak has decreased to 1750cm. -1 The following peaks rose. This result is attributed to 2900cm. -1 The decrease in the nearby peak indicates a reduction in the cleaning dispersant, at 1750cm. -1 The following peak increase is due to carbonyl oxide products (COO - This indicates that ) was generated. The holding time for the heating temperature is preferably at least 120 minutes, as the FT-IR waveform stabilizes after 120 minutes, and more preferably 180 minutes, as deposit formation is reliably progressing.

[0048] The results of the above experiments are summarized in Table 2 below.

[0049] [Table 2] *1: In the above [Study on the state and generation rate of deposits generated in relation to the holding time of heating temperature in the deposit generation test], the set temperature is 300°C. In the below [Study on the deposit generation rate in relation to heating temperature in the deposit generation test for new oil and used oil], the set temperature is in the range of 200 to 700°C.

[0050] [Investigation of deposit formation rate in relation to the set temperature for deposit formation tests of new and used oil] The deposition formation rate in relation to heating temperature was investigated for new and used oil (SUBARU® genuine gasoline engine oil, 5W-30 engine oil) in a deposition formation test. Pretreatment was performed in an N2 atmosphere at a heating temperature of 300°C for a holding time of 40 minutes. The deposition formation test was performed in an air atmosphere with a fixed holding time of 180 minutes, and the test was conducted under eight conditions with set temperatures of 200°C, 250°C, 300°C, 350°C, 400°C, 500°C, 600°C, and 700°C. Differential thermal-thermogravimetric analysis (TG-DTA) (STA7000 model, Hitachi High-Tech Science Corporation) was used as the experimental equipment. The experimental results are shown in Figure 5. In the graph showing the test results, liquid deposits are shown in white, and solid deposits are shown in filled. The deposit formation rate was calculated using the following formula: Amount of deposit formed (g) ÷ Weight of engine oil used in the experiment (g) × 100.

[0051] In new oil, deposits exhibited liquid deposit properties (including some solid deposits) at 200-250°C, and solidified above 300°C. The deposit formation rate was 2.0 wt% at 300-350°C. On the other hand, in used oil, deposits exhibited liquid deposit properties (including some solid deposits) at 200-350°C, and solidified above 400°C. At all heating temperatures, used oil had a higher deposit formation rate than new oil. At 500°C, used oil showed a deposit formation rate of 3.9 wt%, which was 13 times higher than that of new oil.

[0052] By using the pretreatment and deposit formation conditions used in this study, we were able to confirm the formation rate and physical properties (liquid or solid state) of deposits derived from new and used oil at various temperatures within the temperature range of 200 to 700°C.

[0053] Furthermore, it was shown that used oil had a higher deposit formation rate than new oil across all temperature ranges, confirming that the condition of the engine oil can affect deposit formation differently. Furthermore, we were able to confirm that the temperature at which engine oil changes from liquid to completely solid differs between new oil and used oil.

[0054] Since the pretreatment and deposit formation tests could be performed using only differential thermal-thermogravimetric (TG-DTA) equipment (capable of automated measurement), the deposit formation rate could be evaluated efficiently.

Claims

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 deposit generation step in which the engine oil that has undergone the above pretreatment step is set to a constant temperature in an air atmosphere, and is held at that set temperature for 120 minutes or more to generate deposits, and Deposit generation amount measurement step for measuring the amount of deposit generated in the deposit generation step. A quantitative evaluation method for engine oil-derived deposits, characterized by including [a specific component].

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. In a step prior to the aforementioned pretreatment step, an engine oil weight measurement step is performed to measure the weight of the engine oil provided to the aforementioned pretreatment step, and A deposit generation rate calculation step is performed in a subsequent step after the deposit generation amount measurement step, in which the deposit generation rate is calculated using the following formula. [Calculation 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 Deposit generation rate calculation process: The deposit generation rate is calculated using the following formula. [Calculation 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 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.

Images