JP4413987B1 - Tire pressure adjustment method - Google Patents

Abstract

Provided is a tire pressure adjusting method that can obtain an adjusted air pressure by simple calculation and can adjust and maintain the tire air pressure with higher accuracy than before, and contributes to improving fuel efficiency and reducing carbon dioxide emissions. .
A tire pressure adjusting method for bringing the air pressure close to a specified air pressure PS after a predetermined period (one month) has elapsed since the air pressure of the tire mounted on the vehicle is adjusted to the adjusted air pressure P0, and depends on temperature changes. The temperature variation PT of the air pressure to be obtained is obtained from the temperature T0 at the time of adjustment and the daily average temperature T2 after the lapse of a predetermined period, and the air pressure leakage reduction PL depending on natural leakage is obtained from the period average temperature TA during the predetermined period. The adjusted air pressure P0 is obtained by adding the temperature variation PT and the leakage reduction PL to the designated air pressure PS. When the vehicle is traveling more than a predetermined distance immediately before the adjustment, the travel increase PR of the air pressure depending on the travel is obtained from the average speed during travel, and the travel increase PR is further added to obtain the adjusted air pressure P0.
[Selection] Figure 1

Description

  The present invention relates to a method for adjusting the air pressure of a tire mounted on a vehicle, and more particularly to a method for correcting an error in air pressure that varies depending on a temperature change, natural leakage, or the like.

  As is well known, maintaining the tire pressure properly is extremely important in terms of safety, stability, comfort, etc. when the vehicle is running. Furthermore, by maintaining the tire pressure properly, fuel consumption can be improved and fuel consumption can be reduced, leading to a reduction in carbon dioxide emissions that cause global warming, which has become a problem in recent years. Is also important in that it can contribute. For this reason, it is recommended to carry out a tire pressure check in a daily check and fill with air if necessary. The proper usage method and inspection method of tires are shown in, for example, “Selection, Use and Maintenance Standards for Automobile Tires” in Non-Patent Document 1. Non-Patent Document 1 is issued by an association composed of five tire manufacturers, and in accordance with this, the inspection and adjustment of tire air pressure are performed at an automobile maintenance shop or a gas station.

  According to Non-Patent Document 1, “Tire pressure is checked with an air gauge when it is cold before driving (when cold) and adjusted to the air pressure specified by the car manufacturer. Therefore, it should be adjusted to the air pressure specified by the car manufacturer at the time of inspection (at least once a month). The air pressure measured by the air gauge is a gauge pressure based on the atmospheric pressure, and the notation follows this. As the designated air pressure, a gauge pressure range of 200 to 250 kPa is shown, and tires of about 220 kPa are widely used. In addition, if the air pressure drops by 10-20 kPa per month due to natural leakage, adjusts to within the specified air pressure + 0-20 kPa or 10% increase during adjustment, or must be adjusted during driving unavoidably It is shown that after adjusting to 10% or 20-30 kPa higher, the inspection is performed again in the cold state. The basis is cold adjustment.

  If the tire pressure is not properly maintained, various functional degradations occur as described in Non-Patent Document 2. That is, when the air pressure is low, damage is likely to occur due to accumulation of deformation fatigue which is repeatedly increased due to deflection. In addition, the portion in contact with the road surface is increased to promote wear and shorten the tire life. Furthermore, the rolling resistance increases and a lot of fuel is consumed. On the other hand, if the air pressure is high, the tension on the surface of the tire increases and it becomes easy to puncture. In addition, the portion in contact with the road surface is localized at the center of the tire width, so that central wear tends to occur. In addition, the role of the cushion is lost, and the ride comfort becomes worse.

  In addition, according to the road transport vehicle law of Non-Patent Document 3, “For private cars, etc., the user himself / herself responds to the advancement of technology and diversification of usage forms. For general vehicles, which are required to be inspected at an appropriate time determined from the above, and to be serviced as necessary. Also, the inspection method for tire air pressure is not specified, and visual inspection is considered basic. However, in flat tires that are frequently used in recent years, the visual pressure check for one month reduces the air pressure. It is impossible to distinguish. Therefore, the current situation is that it is described in the instruction manual such as "Check once a month using a tire pressure gauge."

Published by Japan Automobile Tire Association, selection and use of automobile tires, maintenance standards, 2008 tires for passenger cars Published by Japan Automobile Tire Association, Tire knowledge, July 2007 edition Article 47-2 of the Road Transport Vehicle Law

  By the way, the maintenance standards defined in Non-Patent Documents 1 and 3 are not actually used strictly. Only a fraction of car users perform tire pressure checks once a month using tire pressure gauges. Even car manufacturers, car dealers, car mechanics who are car specialists are not much different from general users. The inventor has confirmed that the daily test is not performed even for the test ride of the store where the customer visits. To guess why the inspections required by law have not been carried out, “Current automobiles rarely break down.” “Even if neglected daily inspections, there will be no accidents immediately.” “Automatic inspections and regular inspections for one year "There are no penalties or fines."

  The degree of consumption of consumable parts of an automobile is roughly proportional to the travel distance. Parts that are consumed even when not driving are the battery and tire pressure. If the battery goes up, you can't start the car, but you can't run, so there's no danger. On the other hand, since the tire air pressure gradually decreases due to natural air leakage even if it is normal, the main purpose of the air pressure adjustment is to supplement the leakage. However, when a tire sticks into the tire or abnormalities of a valve occur, air leakage is promoted more than normal, but it may not be noticed even if the vehicle is running. This is the most dangerous and it is impossible to predict when this will happen. This is the main reason why regular inspections and daily inspections are necessary. It is most dangerous to assume safety.

  The tire inspection condition is “Please adjust to the specified air pressure when it is cold before driving”, but it is not well known to general users. The engine service information label affixed to the inside of the bonnet and referred to by the maintenance engineer is written as valve clearance (cold) intake air ... mm, but it is affixed to the body side where the driver's seat door is opened. “Cold” is not written on the tire pressure label referred to by general users. The instruction manual of the vehicle says “When it is cold”, but it seems that the number of general users who read it is hardly read. In addition, even when it is cold before traveling, traveling to an automobile maintenance factory cannot be avoided, and the air pressure varies depending on the temperature changing in season and time. The amount of decrease in air pressure due to natural leakage is not constant and varies depending on the temperature. These error factors have not been conventionally considered quantitatively.

  The adjustment value is determined to be the designated air pressure. There are no automakers or industry associations that define the range to adjust. Some tire manufacturers stipulate that they are regulated and controlled at a specified air pressure of +0 to 20 kPa, but since all automobile manufacturers, industry groups and governments have not officially established, the amount of air filling is at the discretion of the person who maintains the vehicle. Is entrusted to. Even when correcting for temperature, the calculation based on Boyle-Charles's law is complicated, and the accuracy decreases due to the effect of the phase change between the vapor phase / liquid phase of water vapor contained in the filled air. .

  Auto mechanics tend to adjust air pressure too high during adjustment. The car manufacturer's maintenance manual only states that the tire air pressure matches the reference value (designated air pressure). However, all auto mechanics know that tire air leaks naturally, and adjust the air pressure higher because it can escape. The inventor has confirmed two examples of rental cars owned by dealers that are adjusted to be extremely higher than the designated air pressure. In the first example, when the tire pressure of a substitute car lent on May 11, 2008 was examined, it was 282 to 286 kPa for 4 wheels when cold at 11 ° C in the morning, compared to the specified air pressure of 220 kPa, 30% It was higher (+65 kPa). Furthermore, the air pressure after running at 3 pm was 310 to 312 kPa at a temperature of 21 ° C., which was 40% (+90 kPa) higher. The second example was March 28, 2009, when the tire pressure was 25% higher when cold. Non-Patent Document 1 shows that air pressure during traveling +50 kPa or more is excessive air pressure, but it is estimated that many automobile mechanics do not know this.

  In addition, not all auto mechanics adjust tire pressures constantly. Some people adjust to the specified air pressure at room temperature, and others check and adjust before the tire cools down. Since it takes 30 minutes to 2 hours for the tire to cool down completely, the air pressure varies depending on when the vehicle is inspected. Further, since the temperature is different between the tire on the side exposed to direct sunlight and the tire on the shaded side, an error also occurs here. The inventor has confirmed that a maximum difference of 12 kPa occurs between the solar radiation side and the shade side. Some German manufacturers are giving guidance on adjusting the pressure of tires exposed to direct sunlight. Japanese manufacturers do not give guidance.

  Fluctuation due to air temperature can be calculated using Boyle-Charle's law for 0% humidity air (ideal gas) for tires with a specified air pressure of 220 kPa. fluctuate. The lower the temperature, the larger the fluctuation range per 1 ° C, and the higher the temperature, the smaller the fluctuation range. The air actually filled in the tire is mixed with water vapor, and the fluctuation range is larger than the ideal gas due to the influence of the phase change of the water vapor. As a result of examining many tires by the inventor, it was confirmed that the temperature fluctuated approximately 1.5 kPa at 1 ° C. as will be described later. Of course, automakers, tire makers, and auto mechanics have knowledge of Boyle-Charles's law, but they do not use it for actual inspection or maintenance.

The reason why the tire pressure is not adjusted using Boyle-Charles' law is thought to be due to insufficient understanding of the weather. In Japan, the fluctuation range of the daily temperature is about 10 ° C (± 5 ° C) in clear weather, about 5 ° C (± 2.5 ° C) in cloudy weather, and about 5 ° C (± 2.5 ° C) in cloudy weather. It is said to be 2 ° C (± 1 ° C). The average temperature occurs at 8am to 9am at night. The average temperature is often exceeded during the daytime when car maintenance shops are operating. Therefore, if the air pressure is adjusted to the designated air pressure during daytime maintenance, the tire air pressure will be less than the designated air pressure when the temperature falls to the daily average air temperature.

  Although the temperature fluctuates from day to day, the average daily temperature does not become the same as normal, but in Japan, the average temperature for one month rarely fluctuates by more than 2 ° C from normal. However, the daily fluctuation range is 10 to 15 ° C. in fine weather, but the monthly fluctuation range is 20 to 25 ° C. For example, the maximum temperature in Abashiri, Hokkaido on May 1, 2008 was 30.6 ° C, and the minimum temperature on May 3, two days later, was 2.6 ° C, representing a 28 ° C decrease. When calculating according to Boyle-Charles' law, if the tire air pressure is adjusted to 220 kPa at 30.6 ° C., the air pressure becomes 190.4 kPa at 2.6 ° C. and decreases by 30 kPa. Even if the daily average temperature at this time is 8.5 ° C., the air pressure is 196.6 kPa, which is a decrease of 23 kPa. This is greater than a one month air pressure drop that depends on the monthly average temperature. Such large temperature fluctuations frequently occur in Japan, such as during the Fern phenomenon. However, temperature fluctuations are not taken into account at the actual maintenance site. Even if the temperature temporarily becomes high, the air temperature often settles down to a normal level in a few days, and the air pressure is most stabilized by adjusting using the statistical average temperature announced by the Japan Meteorological Agency. Until now, the relationship between tire pressure and weather phenomena has not been emphasized.

  In addition, vehicle inspections and periodic inspections are conducted in accordance with the inspection record book of the association for automobile maintenance in each prefecture. At this time, the remaining groove of the tire (mm), the running pad remaining thickness (mm), the carbon dioxide exhaust concentration (ppm), etc. are recorded as numerical values, but for the tire pressure, the results of inspection and adjustment values are: There is no record of actual air pressure just by checking “No” or “A” adjustment. Furthermore, the tire pressure column of the daily check in the maintenance note that is always provided for all vehicles does not record the measured value of the tire pressure gauge. As a result of continuing the inspection by the numerical record, the inventor noticed that the air pressure decreased by 5 kPa in only one month from the past numerical records in only one month, and found an abnormality in the tire valve. There is. Even if the tire pressure is checked every month, it is difficult to detect abnormalities early without accurate adjustment and numerical recording.

  The minimum scale of an analog general tire pressure gauge is 10 kPa, and the measurement accuracy is ± 10 kPa. The display value is not always constant and may vary by about 1%. Even in an analog type high precision type gauge, the minimum scale is 5 kPa, the measurement accuracy is ± 3 kPa, and a reading error of about ± 1 kPa is practically inevitable. This high-accuracy type gauge is not widely used at general maintenance sites. Digital gauges that can minimize the reading error with a minimum display unit of 1 kPa are rarely used. In addition, Japanese law imposes a calibration obligation once a year on measuring instruments used for vehicle inspections, but does not impose a calibration obligation on tire pressure gauges and torque wrenches. The tire pressure gauge is a precision instrument, so if you use it for a long time, the measurement error will increase, and it is also vulnerable to shock, so it is fragile.Therefore, regular inspection and adjustment is necessary when using the tire pressure gauge, but as mentioned above Since there is no obligation to calibrate, it is unclear whether calibration is actually being performed, and it is not known whether or not the tire pressure gauges of many car mechanics are accurate and how accurate they are. .

  As described above, the conventional tire pressure adjustment method includes many error factors and may cause an error of about 20 kPa (about 10%), and it has been considered that it is not easy to improve accuracy. If the tire air pressure is not properly maintained, the above-described various functional degradations may occur. In particular, a reduction in fuel consumption caused by a decrease in air pressure is directly related to an increase in carbon dioxide emissions, which has become a problem in recent years, and is an important issue.

  The present invention has been made in view of the above-mentioned background, and it is possible to obtain the adjusted air pressure by simple calculation and adjust the tire air pressure with higher accuracy than before, and to maintain it appropriately, improving fuel consumption and reducing carbon dioxide emissions. To provide a tire pressure adjustment method that contributes to

  In order to solve the above-mentioned problems, the inventor has collected and analyzed a large number of actually measured data, and has arrived at the present invention. That is, the tire pressure adjusting method of the present invention is a tire pressure adjusting method for bringing the air pressure close to the specified air pressure after a predetermined period has elapsed since the pressure of the tire mounted on the vehicle is adjusted to the adjusted air pressure. The temperature variation of the air pressure that depends on the change is obtained from the temperature at the time of adjustment and the daily average temperature after the lapse of the predetermined period, and the decrease in the air pressure that depends on natural leakage is calculated as the period average temperature during the predetermined period. And the adjusted air pressure is obtained by adding the temperature fluctuation and leakage reduction to the designated air pressure.

  Further, when steam-containing air is sealed in the tire, the temperature fluctuation amount is obtained by multiplying the temperature difference obtained by subtracting the daily average temperature after the predetermined period from the temperature at the time of adjustment by a predetermined temperature fluctuation coefficient. It is preferable that it is required.

  Further, the designated air pressure is a gauge pressure of 220 kPa, and the temperature variation coefficient is determined by a temperature zone to which the air temperature at the time of adjustment and the daily average air temperature after the lapse of the predetermined period belong, and the temperature zone is 25 ° C. or less and 1 It is preferable that it is 1.4 kPa at 0.5 kPa, 25-30 degreeC, 1.3 kPa at 30-35 degreeC, and 1.2 kPa at 35-40 degreeC.

  Further, when dry air is sealed in the tire, it is preferable that the temperature variation is obtained based on Boyle-Charles' law.

  Alternatively, when dry air is sealed in the tire, the temperature variation is obtained by multiplying the temperature difference obtained by subtracting the daily average temperature after the predetermined period from the temperature at the time of adjustment by a predetermined temperature variation coefficient during drying. It may be required.

  In addition, for the daily average temperature after adjustment and after the lapse of a predetermined period, a past statistical daily average temperature announced by a public meteorological agency is used, or a corrected daily average temperature obtained by correcting the statistical daily average temperature is used. You may make it use temperature.

  Further, the adjusted air pressure may be described by adding a temperature correction amount obtained by multiplying the temperature difference obtained by subtracting the daily average temperature of the day from the temperature at the time of adjustment by a predetermined temperature variation coefficient.

  The leakage decrease is regarded as zero when the period average temperature is less than or equal to the leak start temperature determined by the properties of the tire, and when the period average temperature exceeds the leak start temperature, a predetermined amount is added to the excess temperature. It is preferable to calculate by multiplying the leakage reduction coefficient.

  Furthermore, it is preferable that the predetermined period is one month, the designated air pressure is a gauge pressure of 220 kPa, the leak start temperature is regarded as 0 ° C., and the leak reduction coefficient is 0.2% of the designated air pressure. .

  Further, when the vehicle is traveling for a predetermined distance or more immediately before adjusting the air pressure, an increase in travel of the air pressure depending on travel is obtained from an average speed during travel, and the adjustment is further performed by adding the travel increase. It is preferable to determine the air pressure.

  Further, the predetermined distance is 10 km, and the travel increase of the front wheels filled with steam-containing air of the front wheel drive vehicle is obtained by multiplying the average speed during travel by 0.1% of the specified air pressure as the travel increase coefficient. Preferably, the travel increase of the rear wheel in which the steam-containing air of the front wheel drive vehicle is sealed is determined by multiplying the travel increase of the front wheel by a predetermined reduction ratio.

  Alternatively, the predetermined distance is 10 km, and the travel increase of the front wheels in which the dry air of the front-wheel drive vehicle is sealed is obtained by multiplying the average speed during travel by 0.07% of the specified air pressure as the travel increase coefficient. The travel increase of the rear wheel in which the dry air of the front wheel drive vehicle is sealed is preferably obtained by multiplying the travel increase of the front wheel by a predetermined reduction ratio.

  The measurement of the air pressure is preferably performed with an analog tire pressure gauge, and the air pressure is adjusted in units of 5 kPa.

  Further, an error between the actual air pressure after the lapse of the predetermined period and the designated air pressure is obtained, and the temperature fluctuation coefficient and the drying temperature fluctuation coefficient, the leakage start temperature and the leakage reduction coefficient so as to reduce the error, You may make it correct | amend at least 1 item of the said predetermined distance and the said driving | running | working increase coefficient, and you may make it use for subsequent air pressure adjustment.

  Further, when the error is 6 kPa or more, at least one of the temperature fluctuation coefficient, the temperature fluctuation coefficient during drying, the leak start temperature, the leak reduction coefficient, the predetermined distance, and the travel increase coefficient is corrected. It may be.

  In the tire air pressure adjusting method of the present invention, the adjusted air pressure is obtained in consideration of the temperature fluctuation and the leakage reduction, so that the actual air pressure after the lapse of a predetermined period can be brought close to the designated air pressure. In addition, in the past, it was decided to adjust to the specified air pressure as a rule, and the value of the adjusted air pressure, which was performed within +0 to 20 kPa or + 10% in consideration of the decrease in air pressure, was changed to the temperature based on the temperature during adjustment. Since the fluctuation and the leakage reduction are accurately obtained, the error factor is removed and the air pressure accuracy is improved. In addition, temperature fluctuation and leakage reduction are simplified using temperature fluctuation coefficient (applied to steam-containing air mixed with water vapor), drying temperature fluctuation coefficient (applied to dry air using an air dryer), and leakage reduction coefficient. These coefficients can be calculated from the measured data and have high practical accuracy.

  Furthermore, in the aspect of calculating the increase in the air pressure in the vehicle travel just before the adjustment, the adjustment air pressure value is obtained accurately by quantitatively taking into account the influence of the heat generation of the tire due to the travel. Further improvement.

  Further, in a mode in which the temperature variation coefficient is corrected from the difference between the actual air pressure and the specified air pressure after the lapse of a predetermined period and used for the subsequent air pressure adjustment, the coefficient most suitable for each vehicle and tire can be used. The air pressure adjustment accuracy is greatly improved.

As a comprehensive effect as described above, it is possible to appropriately maintain the tire air pressure so as not to decrease throughout a predetermined period, and it is possible to contribute to the improvement of fuel consumption and the reduction of carbon dioxide emission.
Furthermore, the number of people who adjust the tire pressure during daily inspections increases, and the following effects occur.

  (1) As human psychology, it is worrisome if it is not made accurate, so the tire pressure is adjusted regularly (every month).

  (2) Both car users and car mechanics recognize that the degree of decrease in air pressure varies according to the season, and conduct daily inspections, especially tire pressure adjustment as an important matter.

  (3) Public relations activities to pay attention to the regulated air pressure can be done according to weather information. For example, it is possible to publicize a forecast that the air pressure will increase or decrease when the Fern phenomenon occurs when the temperature temporarily rises from normal or when a cold wave strikes when the temperature decreases.

  (4) The recognition of the importance of vehicle maintenance will be improved, leading to a reduction in traffic accidents.

  (5) By learning the maintenance method of predicting tire air pressure, it will lead to the improvement of technology and further development of automobile mechanics.

  (6) Environmental awareness will increase further, and other energy-saving methods will be implemented, and the reduction of carbon dioxide emissions will be accelerated.

  (7) If air pressure inspections and adjustments are carried out free of charge at automobile dealers, tire dealers, car supply dealers, gas stations, etc., the number of customer visits will increase due to regular inspections once a month. , Which leads to sales opportunities.

It is a figure explaining the pneumatic pressure adjustment method of the tire of the embodiment of the present invention. It is a figure of the list of the temperature fluctuation coefficient used when calculating | requiring the temperature fluctuation part of an air pressure, and the temperature fluctuation coefficient at the time of drying. It is a figure of the result of the 1st verification experiment which applied the adjustment method of an embodiment to an actual vehicle. It is a figure of the result of the 2nd verification experiment which applied the adjustment method of an embodiment to an actual vehicle. It is a scatter diagram of the actual measurement data of the basic experiment that became the basis for determining the temperature variation coefficient. FIG. 6 is a scatter diagram of measured data of a basic experiment that is a basis for setting a leak start temperature and determining a leak reduction coefficient. It is a figure of the actual measurement data of the basic experiment used as the basis which determines a driving | running | working increase coefficient.

  An embodiment for carrying out the present invention will be described with reference to FIG. FIG. 1 is a diagram for explaining a tire pressure adjusting method according to an embodiment of the present invention. In FIG. 1, (1) air temperature, (2) air pressure temperature fluctuation, (3) air pressure leakage reduction, and (4) tire air pressure are shown, and the horizontal axis represents a common time t. The adjustment method of the embodiment is a method in which the adjustment air pressure P0 is calculated at the time of adjustment to adjust the tire air pressure, and the actual air pressure is made to coincide with the designated air pressure PS at the next adjustment after a predetermined period.

For measurement of the air pressure, a tire pressure gauge having a conventional general minimum scale of 10 kPa can be used, and there is a limitation in measurement accuracy, but the error is within 10 kPa (about 5%) of the minimum scale. It is even better if a high-precision analog gauge with a minimum scale of 5 kPa or a digital gauge with a display of 1 kPa can be used. The measured air pressure is a gauge pressure based on the atmospheric pressure, and the following explanation is also expressed as a gauge pressure. In the present embodiment, an example in which the predetermined period is one month and the designated air pressure PS = 220 kPa is mainly shown, but the same adjustment method can be used for other conditions by application such as changing the coefficient as appropriate.
First, the adjustment air pressure P0 at the time of adjustment is calculated based on the following (Equation 1), as shown in FIG.

Adjusted air pressure P0 = designated air pressure PS + temperature fluctuation PT
+ Leakage reduction PL + Running increase PR (Formula 1)
Here, in order to obtain the temperature variation PT and the leakage reduction PL, the relationship between the temperatures shown in FIG. The adjusted temperature T0 can be measured by using a thermometer at the actual adjustment location. The daily average temperature T2 at the next adjustment can be obtained from past data released by a public meteorological agency such as the Japan Meteorological Agency. At this time, in consideration of the influence of global warming in recent years, a corrected daily average temperature obtained by adding 1 ° C. to past data is adopted (this correction is arbitrarily performed in accordance with the actual situation of the region and past changes). be able to). Then, the temperature difference Td is obtained by subtracting the daily average temperature T2 at the next adjustment from the adjustment temperature T0.

Temperature difference Td = T0−T2 (Formula 2)
Also, the average daily temperature T1, T2 at the time of adjustment and the next adjustment is averaged to obtain a period average temperature TA.

Period average temperature TA = (T1 + T2) ÷ 2 (Formula 3)
Next, the temperature variation PT is obtained by multiplying the temperature difference Td by the temperature variation coefficient. Here, when water vapor-containing air is sealed in the tire, the temperature variation coefficient varies slightly depending on the amount of water vapor in the tire. Therefore, as shown in FIG. 2, the value of the temperature variation coefficient CT = 1.5 to 1.2 (kPa / ° C.) may be properly used according to the temperature zone to which the adjusted temperature T0 and the daily average temperature T2 belong. Alternatively, it may be fixed at 1.5 (kPa / ° C.). In any case, the calculation error is about 3 kPa or less and falls within the minimum scale of 5 kPa of the high-precision type analog gauge. In other words, even if the air pressure is strictly calculated, there is not much meaning because the measurement accuracy cannot follow. Further, when dry air generated using an air dryer is enclosed, it may be considered as an ideal gas and may be calculated based on Boyle-Charles' law, or the temperature variation coefficient during drying CD = 1.1 Calculation using (kPa / ° C.) may also be used.

Temperature variation PT = Td × CT (at the time of air containing steam) (Formula 4)
Or = Td × CD (with dry air)
Next, the air pressure leakage reduction PL is obtained from the period average temperature TA. Here, when the period average temperature TA is equal to or lower than 0 ° C. set as the leak start temperature TL, the leak reduction PL is regarded as zero. When the period average temperature TA exceeds 0 ° C., the period average temperature TA itself, which is the excess temperature, is 0.2% of the specified air pressure as a leakage reduction coefficient CL (kPa / ° C.) (220 × 0.002 = 0.44).

Leakage reduction PL = TA × 0.44 kPa (period average temperature TA> 0 ° C.) (Formula 5)
Or = 0 (period average temperature TA ≦ 0 ℃)
Further, when the vehicle is traveling 10 km or more of the predetermined distance RL immediately before the air pressure is adjusted, the front wheel of the front-wheel drive vehicle in which moisture-containing air is enclosed has an average traveling speed CR (% / (Km / h)) is multiplied by 0.1% (220 × 0.001 = 0.22) of the specified air pressure to determine the travel increase PR.

Travel increase PR = V × 0.22 kPa (with travel of 10 km or more) (Formula 6)
Or = 0 (no driving)
The travel increase PR of the rear wheels of the front wheel drive vehicle is obtained by multiplying the value obtained by (Equation 6) by the reduction ratio 0.9. Further, the travel increase PR of the tire in which dry air is enclosed is obtained using a travel increase coefficient CS obtained by multiplying the travel increase coefficient CR of the tire in which moisture-containing air is enclosed by 0.7.

  Finally, the adjusted air pressure P0 is obtained by substituting the amounts obtained in (Expression 4) to (Expression 6) into (Expression 1). The tire air pressure fluctuates as indicated by a broken line Z in FIG. 1 (4), and it can be predicted that the designated air pressure PS will be reached at the next inspection. Here, numerical records of the adjustment temperature T0 and the adjustment air pressure P0 are left as adjustment records. Alternatively, the adjusted air pressure P0 is expressed by correcting the daily average temperature on the adjustment date. Furthermore, it is preferable to leave numerical records of various amounts used in (Expression 1) to (Expression 6).

Next, an example in which a model case is set and the adjusted air pressure P0 is calculated will be described. The specified air pressure PS in the model case is 220 kPa, the adjustment temperature T0 = 20 ° C., the adjustment daily average temperature T1 = 15 ° C., and the next adjustment daily average temperature T2 = 10 ° C. Shall not. Then, according to (Expression 2) to (Expression 5), the temperature difference Td = 20−10 = 10 ° C.
Period average temperature TA = (15 + 10) ÷ 2 = 12.5 ° C
Temperature fluctuation PT = 10 × 1.5 = 15 kPa
Leakage reduction PL = 12.5 × 0.44 = 5.5 kPa
(Equation 1), adjusted air pressure P0 = 220 + 15 + 5.5 = 240.5 kPa
Is obtained.

Also, if the vehicle is traveling at an average speed of V = 50 (km / h) immediately before the adjustment, the traveling increase PR = 50 × 0.22 = 11 kPa according to (Equation 6).
Is obtained and added to the adjusted air pressure P0.

When the daily average temperature T2 at the next adjustment is higher than the adjustment temperature T0, the temperature fluctuation PT becomes a negative value, and the adjustment air pressure P0 is adjusted to be smaller than the designated air pressure PS.
Next, the results of the first and second verification experiments in which the adjustment method of the above-described embodiment is applied to actual vehicles and tires will be described with reference to FIGS.

  In the first verification experiment, a total of 16 tires 11 to 44 (designated air pressure PS = 200 to 230 kPa) of four passenger car models PUR, PAS, WAG, and FIL were targeted. Then, filling the steam-containing air to adjust the adjusted air pressure P0, and measuring the actual air pressure one month later to obtain the difference from the designated air pressure PS is from August 2008 to January 2009. Repeated for months. FIG. 3 summarizes the difference PD (kPa) obtained by subtracting the designated air pressure PS from the actual air pressure. The positive value is larger for the actual air pressure, and the negative value is larger for the designated air pressure PS. Is shown. As apparent from the list of FIG. 3, the difference PD is within ± 3 kPa in the majority of cases, and is +6 kPa at the maximum. This difference PD is remarkably improved in accuracy as compared with the conventional error of about 20 kPa. Furthermore, the difference PD of ± 3 kPa is only 1% of the absolute pressure 321 kPa of the designated air pressure PS, and it was verified that the air pressure can be adjusted with extremely high accuracy.

  In the second verification experiment, the right front wheel tire (designated air pressure PS = 230 kPa) of the passenger car PUR was targeted. Then, the predicted value of the air pressure after one month is obtained without adjusting the air pressure, and the actual measured value when one month has passed is compared with the predicted value for eight months from January to August 2008. Repeated over. The predicted value was calculated by obtaining the temperature variation PT (Equation 4) and obtaining the leakage reduction PL (Equation 5). FIG. 4 is a graph in which the predicted value and the actual measurement value are plotted and connected. The horizontal axis indicates the time transition from January to August, and the vertical axis indicates the tire air pressure. As shown in FIG. 4, the predicted value and the actually measured value are in good agreement, and the prediction error of the difference between them is 4 kPa at the maximum. Thereby, the validity of (Formula 4) and (Formula 5) was verified.

  The tire pressure adjustment method of the present embodiment is a simple calculation method using the temperature fluctuation coefficient CT, the drying temperature fluctuation coefficient CD, the leakage reduction coefficient CL, and the running increase coefficient CR, and the tire pressure after one month. Can be accommodated within about ± 3 kPa of the designated air pressure PS, and practical accuracy is high. Thereby, the tire air pressure can be properly maintained throughout the month, and safety, stability, and comfort during vehicle travel can be ensured, and fuel efficiency can be improved. Further, according to a trial calculation, when the tire pressure adjustment method of the present invention becomes widespread, fuel is saved and carbon dioxide emissions in the world are reduced by 0.1%.

  It should be noted that the present invention can be realized not only as a simple measurement and calculation by hand, but also as a partly or entirely automated device. For example, input means for inputting measured air temperature and air pressure, past daily average temperature and monthly average temperature data of the Japan Meteorological Agency, and arithmetic means for automatically calculating (Equation 1) to (Equation 6), The tire pressure adjusting method of the tire of the present invention by means of a computer application device comprising storage means for storing past data of the Japan Meteorological Agency and various coefficients CT, CD, CL, CR, etc., and output means for outputting the determined adjusted air pressure P0 It can be performed. In addition, it is possible to construct a computer application system in which measurement is automated by combining a temperature sensor and an air pressure sensor that can exchange data.

  Furthermore, it is possible to operate a so-called “customer pneumatic chart” by utilizing IT technology. Specifically, by providing a communication function to the tire pressure gauge and performing data communication with the customer management system, information including the adjusted air pressure P0 of the tire at each inspection and the predicted air pressure at the next inspection is included. Is stored as a pneumatic chart. Then, this pneumatic chart can be presented to the customer in an easy-to-understand manner and "predicted maintenance" can be performed. Further, by combining with a monitoring camera, not only numerical information such as the adjustment air pressure P0 but also the maintenance status of the vehicle can be remotely monitored at other locations in the store away from the vehicle. Thus, “visualization of maintenance” is performed from the viewpoint of the car owner, and “maintenance to display” can be performed from the viewpoint of the car maintenance factory or the mechanic.

  The above-described computer application apparatus and system, a system combined with IT technology and a monitoring camera can be used in preparation for an automobile maintenance shop, for example.

  Furthermore, it is possible to develop a system in combination with a mobile phone or a car navigation device. For example, vehicle type data and a bar code of the designated air pressure PS are displayed on a label that has been pasted in the vehicle and displays the designated air pressure, and can be read from a mobile phone. Then, in the mobile phone, the inspection place where the air pressure adjustment is performed can be specified by the GPS function or the like, the adjustment temperature T0 at the inspection place can be obtained from AMeDAS of the Japan Meteorological Agency, and the adjusted air pressure P0 using the read designated air pressure PS. Can be calculated and displayed. This function can be similarly realized by a car navigation device having a communication function. Therefore, by providing this function as a service for the general public, anyone can easily calculate the adjusted air pressure P0 anywhere in the country.

  Next, the motivation conceived of the present invention and the basic experiment by data collection supporting the invention will be described.

  The inventor purchased a new hybrid car in October 2003 and recorded the fuel consumption every time during traveling, and it turned out that the fuel consumption was very poor in January 2004. I was wondering about this, and when I measured the air pressure of the tire, it was 50 kPa lower than the specified air pressure, so I immediately adjusted it to an appropriate value. This event occurred as a result of not having performed a daily inspection since we conducted a one-month inspection of the new car in November. When I visited an automobile manufacturer and asked, “Is the air pressure so low?” I was told, “Please check at the dealer,” so we inspected and confirmed that there were no problems with the tires. So I started to investigate the amount of tire pressure drop by myself. I noticed that the air pressure increased or decreased by more than one scale (10 kPa) of the tire pressure gauge due to changes in temperature.

  With this as an opportunity, the first basic experiment was started in February 2004, and the effect of temperature was first investigated. FIG. 5 is a scatter diagram of the actual measurement data of the basic experiment which became the basis for setting the temperature variation coefficient CT to 1.5 (kPa / ° C.) at 25 ° C. or less. The horizontal axis in the figure indicates the number of 104 samples, and the vertical axis indicates the actually measured temperature variation coefficient. The basic experiment is for a tire filled with steam-containing air, and measures the change in air pressure when the temperature changes in a temperature range of 25 ° C. or less, and divides the air pressure change by the temperature change. The change in air pressure per ° C, that is, the temperature variation coefficient was obtained and plotted. As is apparent from FIG. 5, the temperature variation coefficient is dispersed around 1.5 kPa.

  On the other hand, in an ideal gas, the temperature variation coefficient is obtained from Boyle-Charles' law (or gas equation of state) and is 1.1 kPa at 20 ° C. This value was confirmed to be generally applicable to dry air containing almost no water vapor. Therefore, when dry air is sealed in the tire, the temperature variation can be accurately obtained based on Boyle-Charles' law. In addition, since the temperature fluctuation does not fluctuate greatly in the normal temperature range, a large error does not occur even if the temperature fluctuation coefficient CD = 1.1 (kPa / ° C.) during drying is determined and calculated simply.

  In comparison with this, the temperature variation coefficient of the above-mentioned steam-containing air is large, but considering that the water vapor can change between the gas phase and the liquid phase, the temperature variation coefficient of 25 ° C. or less CT = 1. 5 (kPa / ° C.) was determined. Further, at 25 ° C. or higher, the influence of the contained water vapor was reduced and the temperature variation coefficient CT was confirmed to approach that of the ideal gas. Based on this, the temperature variation coefficient in the temperature range 25 to 40 ° C. of FIG. CT = 1.4 to 1.2 (kPa / ° C.) was determined.

  A basic experiment for investigating the influence of running was performed on a front-wheel drive vehicle equipped with a tire in which steam-containing air was sealed at a specified air pressure of 230 kPa. First, the distance traveled until the increase in tire air pressure (travel increase) due to heat generated during travel was stabilized. As a result, it was found that the travel increase was stable after traveling 10 km, increased to about 80% when traveling 5 km, and 20% or less (negligible level) when traveling within 1 km. From this experiment, a predetermined distance RL = 10 km was determined.

  Next, the relationship between travel speed and travel increase was confirmed. In this experiment, the driving speed of the front wheel drive vehicle is set to five conditions of 30 to 90 (km / h), a highway is a highway, a lowway is a general road, and a driving test is performed a plurality of times over a predetermined distance RL = 10 km. Then, the tire air pressure was measured before and after running to determine the average value of the air pressure increase rate. FIG. 7 is actual measurement data of a basic experiment that is a basis for determining the travel increase coefficient CR. In the figure, the horizontal axis indicates the average speed V (km / h), and the vertical axis plots the rate of increase in air pressure actually measured on the front wheels of the front-wheel drive vehicle. As is apparent from FIG. 7, it has been found that the rate of increase in air pressure is approximately proportional to the average speed V. Since the slope of the graph indicating the proportional relationship is an average speed of 100 (km / h) and an increase rate of 10%, the travel increase coefficient CR is set to 0.1% of the designated air pressure. In addition, since a 90% increase in air pressure was recognized for the rear wheels of the front wheel drive vehicle, 0.9 was set as a predetermined reduction ratio.

  Further, the dry travel increase coefficient CS in a tire filled with dry air can be estimated by the following equation using the ratio of the dry temperature fluctuation coefficient CD to the temperature fluctuation coefficient CT.

Driving increase coefficient during drying CS = CR x (CD / CT)
From this formula, it was determined that the dry running increase coefficient CS≈0.07%.

  In addition, it was found that the influence of direct sunlight was a maximum of 12 kPa from winter to spring and about 5 kPa in summer. It was also found that it takes 2 hours or more in humid summer and 30 minutes or more in dry winter before the tire cools down after running and the air pressure returns to the cold value. Furthermore, it was confirmed that the tire air pressure affects the running performance and fuel consumption. For example, on a mountain road curve, it has been found that if the air pressure is different by 20 kPa, there is a difference in travel. It was also found that when the air pressure was reduced by 50 kPa, the fuel consumption was reduced by about 5% (example of a hybrid car). According to a study by the Energy Conservation Center, a decrease in air pressure of 50 kPa corresponds to a decrease in fuel consumption of 2.5% when traveling in an ordinary vehicle.

  In the second basic experiment, the conditions of adjusting the tire air pressure to the specified air pressure when it was cold in the early morning and the conditions adjusted to (specified air pressure +20 kPa) were compared. The effect of the temperature and the effect of traveling were reconfirmed.

  In the next third basic experiment, four outdoor parked vehicles were inspected every month to investigate the effects of leakage. FIG. 6 is a scatter diagram of actual measurement data of a basic experiment which is a basis for setting the leak start temperature TL to 0 ° C. and setting the leak reduction coefficient CL to 0.2% of the designated air pressure. In the figure, (1) is an experiment using a passenger car model PUR (designated air pressure PS = 230 kPa), (2) is an experiment using a passenger car model PAS (designated air pressure PS = 220 kPa), the horizontal axis is the monthly average temperature, and the vertical axis is The air pressure drop for one month is shown. In the basic experiment, we measured the air pressure once a month, corrected the air pressure change from the previous month with the temperature to determine the amount of air pressure decrease due to pure natural leakage, and plotted it on the average temperature of the month for one year. As apparent from the regression line of FIG. 6, the decrease in air pressure due to natural leakage shows a substantially linear temperature dependence. Therefore, 0 ° C. at which the regression line intersects with the air pressure decrease amount zero was set as the leakage start temperature TL. Moreover, since the regression line is a slope that changes by 12 to 13.5 kPas at 30 ° C., it changes by 0.40 to 0.45 kPa per 1 ° C., which is about 0 of the designated air pressure PS (= 220 to 230 kPa). Since this corresponds to 2%, the leakage reduction coefficient CL is set to 0.2% of the designated air pressure.

  The physical reason why the leak start temperature TL coincides with 0 ° C. of the freezing point of water is not clear, but is considered to depend on properties such as the material of the tire.

  Finally, in the first and second verification experiments described above, verification for verifying the air pressure adjustment method of the present invention that performs air pressure prediction by calculation is performed. The results of FIGS. 3 and 4 were obtained. As explained above, based on the basic experiment, the temperature fluctuation coefficient CT, the temperature fluctuation coefficient CD during drying, the leakage start temperature TL, the leakage reduction coefficient CL, the predetermined distance RL, and the traveling increase coefficient CR are determined and validated in the verification experiment. The sex was confirmed. However, while basic experiments and verification experiments are conducted with limited vehicle types and limited tire types, there are a wide variety of practical vehicle types and tire types, and the mileage per month is reduced. There are various forms of usage, including the beginning. For this reason, it is conceivable that an error occurs when the coefficients of the embodiment are uniformly used. Therefore, if each coefficient is corrected so as to be adapted to individual vehicles and tires and used for the subsequent air pressure adjustment, the air pressure adjustment accuracy is remarkably improved.

  Here, considering that the analog tire pressure gauge is a high-precision type and the measurement accuracy is ± 3 kPa, it is desirable to correct when the error is 6 kPa or more. For example, if the temperature variation coefficient CT is corrected from 1.5 to 1.4 by 0.1, the 1 kPa air pressure is corrected per 10 ° C. By adopting this correction, the error can be reduced. The reduction effect can be measured as a significant difference.

  Further, the temperature variation coefficient CT and the leakage reduction coefficient CL can be individually determined for different designated air pressure PS. Alternatively, the leakage start temperature TL and the leakage reduction coefficient CL can be individually determined according to the type of tire. Furthermore, the traveling increase coefficient CR for traveling less than 10 km can be determined. In the above-described embodiment, various coefficients are determined based on the results obtained from data collection and verification in a general passenger car, but the present invention is also applied to large truck and bus tires used at high pressure. it can. Various factors are considered to vary depending on the structure of tire, material, designated air pressure, load change during travel and travel distance. In large vehicle tires, the specified air pressure is 700 to 900 kPa, several times larger than that of passenger cars, and the temperature variation coefficient CT (kPa / ° C.) is relatively large. In addition, the present invention can be applied in various ways.

P0: Adjusted air pressure PS: Designated air pressure PT: Temperature fluctuation PL: Leakage reduction PR: Traveling rise T0: Adjustment temperature T1, T2 day average temperature Td: Temperature difference TA: Period average temperature CT: Temperature fluctuation coefficient CD: Temperature variation coefficient during drying

Claims (15)

A tire pressure adjusting method for bringing the air pressure close to a designated air pressure after a predetermined period of time has elapsed since the air pressure of the tire mounted on the vehicle is adjusted to the adjusted air pressure,
The amount of temperature fluctuation of the air pressure depending on the temperature change is obtained from the temperature at the time of adjustment and the daily average temperature after the predetermined period has passed,
The amount of decrease in air pressure leakage that depends on natural leakage is determined from the average temperature during the predetermined period,
A method for adjusting tire air pressure, wherein the adjusted air pressure is obtained by adding the temperature fluctuation and the leakage reduction to the designated air pressure.   In Claim 1, when steam-containing air is sealed in the tire, the temperature variation is a temperature difference obtained by subtracting the daily average temperature after the predetermined period from the temperature at the time of adjustment. The tire pressure adjustment method required by multiplying by.   In Claim 2, the specified air pressure is a gauge pressure of 220 kPa, and the temperature variation coefficient is determined by a temperature range to which the air temperature at the time of adjustment and the daily average air temperature after the lapse of the predetermined period belong, and the temperature range is 25 ° C. The tire pressure adjusting method is 1.5 kPa, 1.4 kPa at 25-30 ° C., 1.3 kPa at 30-35 ° C., and 1.2 kPa at 35-40 ° C.   2. The tire pressure adjusting method according to claim 1, wherein when the dry air is sealed in the tire, the temperature fluctuation is obtained based on Boyle-Charles' law.   In Claim 1, when dry air is enclosed in the tire, the temperature variation is a temperature difference obtained by subtracting the daily average temperature after the predetermined period from the temperature at the time of adjustment. Tire pressure adjustment method obtained by multiplying by a coefficient.   In any one of Claims 1-5, the past statistical daily average temperature which the public weather organization announced is used for the said daily average temperature after adjustment and the predetermined period progress, or the said statistical The tire pressure adjustment method using the corrected daily average temperature obtained by correcting the daily average temperature.   7. The tire pressure adjusting method according to claim 6, wherein a temperature correction amount obtained by multiplying a temperature difference obtained by subtracting the daily average temperature of the day from the temperature at the time of adjustment by a predetermined temperature variation coefficient is added to express the adjusted air pressure.   The leakage reduction amount according to any one of claims 1 to 7, wherein the leakage reduction amount is regarded as zero when the period average temperature is equal to or less than a leakage start temperature determined by a property of the tire, and the period average temperature exceeds the leakage start temperature. A method for adjusting the tire air pressure, which is obtained by multiplying the excess temperature by a predetermined leakage reduction coefficient when the temperature is over.   9. The tire according to claim 8, wherein the predetermined period is one month, the designated air pressure is a gauge pressure of 220 kPa, the leak start temperature is regarded as 0 ° C., and the leak reduction coefficient is 0.2% of the designated air pressure. Air pressure adjustment method.   In any one of claims 1 to 9, when the vehicle is traveling for a predetermined distance or more immediately before adjusting the air pressure, a traveling increase amount of the air pressure depending on traveling is obtained from an average speed during traveling, A tire pressure adjusting method for obtaining the adjusted air pressure by further adding the travel increase.   11. The predetermined distance is 10 km, and the travel increase of the front wheels filled with water vapor-containing air of a front wheel drive vehicle is 0.1% of the specified air pressure as a travel increase coefficient at an average hourly speed during travel. The tire air pressure adjustment method is obtained by multiplying the travel increase amount of the rear wheel in which steam-containing air of the front wheel drive vehicle is enclosed by multiplying the travel increase amount of the front wheel by a predetermined reduction ratio.   In Claim 10, The said predetermined distance is 10 km, and the said driving | running | working increase of the front wheel with which the dry air of the front-wheel drive vehicle was enclosed has set 0.07% of the said designated air pressure as a driving | running | working increase coefficient to the average speed at the time of driving | running | working. A method for adjusting the tire air pressure obtained by multiplying and calculating the travel increase of the rear wheel in which the dry air of the front wheel drive vehicle is sealed by multiplying the travel increase of the front wheel by a predetermined reduction ratio.   The tire pressure adjusting method according to any one of claims 1 to 12, wherein the air pressure is measured by an analog tire pressure gauge, and the air pressure is adjusted in units of 5 kPa.   In any one of Claims 2-13, the difference between the actual air pressure after the lapse of the predetermined period and the designated air pressure is obtained, and the temperature variation coefficient and the drying temperature variation coefficient so as to reduce the error, A tire pressure adjustment method used for subsequent air pressure adjustment after correcting at least one of the leak start temperature, the leak reduction coefficient, the predetermined distance, and the travel increase coefficient.   15. The correction according to claim 14, wherein when the error is 6 kPa or more, at least one of the temperature fluctuation coefficient, the drying temperature fluctuation coefficient, the leak start temperature, the leak reduction coefficient, the predetermined distance, and the travel increase coefficient is corrected. How to adjust tire pressure.

Images