COOLANT DETERIORATION LEVEL CALCULATION SYSTEM

Abstract

A CPU executes acquisition processing of acquiring a cumulative time for each temperature of a coolant, conversion processing of converting each cumulative time into a converted value which is a cumulative time at a predetermined reference temperature, and calculation processing of calculating a deterioration level of the coolant based on the sum of the converted values.

Claims

1. A coolant deterioration level calculation system that calculates a deterioration level of coolant used for an internal combustion engine, the coolant deterioration level calculation system comprising: an execution unit, wherein the execution unit is configured to execute: acquisition processing of acquiring a cumulative time for each temperature of the coolant; conversion processing of converting cumulative times into converted values, respectively, the converted value being a cumulative time at a predetermined reference temperature; and calculation processing of calculating the deterioration level based on a sum of the converted values.

2. The coolant deterioration level calculation system according to claim 1, wherein, in the acquisition processing, when a temperature of the cumulative time is lower than the reference temperature, the cumulative time is converted such that the converted value is smaller than the cumulative time before conversion.

3. The coolant deterioration level calculation system according to claim 1, wherein, in the acquisition processing, when a temperature of the cumulative time is higher than the reference temperature, the cumulative time is converted such that the converted value is greater than the cumulative time before conversion.

4. The coolant deterioration level calculation system according to claim 1, wherein the execution unit is configured to execute: estimation processing of estimating a temperature change of the coolant while the execution unit has stopped operating, based on stop-time information including a temperature of the coolant at the time when the execution unit stops operating while the engine has stopped, start-time information including a temperature of the coolant at the time when the execution unit starts operating while the engine has started, and a stop time during which the execution unit has stopped operating; and update processing of updating the cumulative time for each temperature based on the estimated temperature of the coolant while the execution unit has stopped operating.

5. The coolant deterioration level calculation system according to claim 1, wherein: a plurality of temperature zones are set; the cumulative time for each temperature of the coolant is a cumulative time for each of the temperature zones; and a temperature range of a higher temperature zone is narrower than a temperature range of a lower temperature zone.

6. The coolant deterioration level calculation system according to claim 1, wherein: a plurality of temperature zones are set; the cumulative time for each temperature of the coolant is a cumulative time for each of the temperature zones; and a temperature range of the temperature zone in which the cumulative time tends to be longer is narrower than a temperature range of the temperature zone in which the cumulative time tends to be shorter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Features, advantages, and technical and industrial significance of exemplary embodiments of the present disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:

[0017] FIG. 1 is a schematic diagram illustrating a configuration of a deterioration level calculation system according to one embodiment;

[0018] FIG. 2 is a flowchart illustrating a procedure of processes executed by a control device according to the same embodiment;

[0019] FIG. 3 is a graph illustrating a temperature zone and a counter value of the same embodiment;

[0020] FIG. 4 is a flowchart illustrating a series of processes executed by the control device according to the same embodiment;

[0021] FIG. 5 is a flowchart illustrating a procedure of processes executed by a data analysis device according to the same embodiment;

[0022] FIG. 6 is a graph illustrating a temperature zone and a converted counter value of the same embodiment; and

[0023] FIG. 7 is a flowchart illustrating the series of processes executed by the data analysis device according to the same embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[0024] System Configuration

[0025] Hereinafter, one embodiment in which the coolant deterioration level calculation system is applied to an internal combustion engine mounted on a vehicle will be described with reference to FIGS. 1 to 7.

[0026] As shown in FIG. 1, a vehicle 500 includes an internal combustion engine 15, a cooling device 10, and the like. The cooling device 10 is a device that cools the internal combustion engine 15 with coolant. A rust inhibitor or the like is added to the coolant.

[0027] The cooling device 10 includes a radiator 12, which is a heat exchanger. A water jacket 15W is formed inside a cylinder block and a cylinder head of the internal combustion engine 15. A coolant outlet of the water jacket 15W and a coolant inlet of the radiator 12 are connected by a first passage 16. A coolant inlet of the water jacket 15W and a coolant outlet of the radiator 12 are connected by a second passage 17. A water pump 18 is provided on a path of the second passage 17.

[0028] The cooling device 10 is provided with a branched passage 20, which is a passage branched from the first passage 16 and connected to the second passage 17 between the coolant outlet of the radiator 12 and the water pump 18. A thermostat 25 is arranged at a connecting portion between the branched passage 20 and the second passage 17. The thermostat 25 is a control valve in which the opening degree of a valve body provided inside varies according to the coolant temperature. When the coolant temperature is low, the coolant flowing out from the water jacket 15W is recirculated by flowing through the branched passage 20 instead of the radiator 12. On the other hand, when the coolant temperature is high, the coolant flowing out of the water jacket 15W is recirculated by flowing through the radiator 12 instead of the branched passage 20.

[0029] The control device 100 performs various controls, including controls for an amount of intake air and an amount of injected fuel of the internal combustion engine 15. The control device 100 includes a central processing unit (hereinafter referred to as a CPU) 110, a memory 120 in which control programs and data are stored, a communication device 130, and the like. The control device 100 performs various controls by executing the program stored in the memory 120 by the CPU 110. Further, the control device 100 is capable of establishing communication with a data analysis device 300 via an external network 200 by the communication device 130. In the present embodiment, a first execution unit is configured by the control device 100 including the CPU 110 and the memory 120.

[0030] The control device 100 refers to various detected values obtained from, for example, a sensor when performing various controls. For example, the control device 100 refers to a coolant temperature THW, which is the coolant temperature detected by a temperature sensor 34, and outside air temperature TH.sub.out detected by an outside air temperature sensor 35.

[0031] The data analysis device 300 analyzes data transmitted from a plurality of vehicles 500, a vehicle 600, and the like. The data analysis device 300 includes a CPU 310, a memory 320, a communication device 330, and the like, and these are capable of establishing communication with each other via a network 200. In the present embodiment, a second execution unit is configured by the data analysis device 300 including the CPU 310 and the memory 320.

[0032] Calculation of Coolant Deterioration Level

[0033] The coolant of the internal combustion engine 15 deteriorates due to oxidation depending on heat receiving temperature and heat receiving time. As the deterioration progresses in this way, the effect of additives such as rust inhibitors decreases. Therefore, in the present embodiment, a deterioration level R of the coolant is calculated.

[0034] In the present embodiment, the deterioration level R indicates that the larger its numerical value is, the more the coolant deteriorates. Further, a hydrogen ion concentration (so-called pH) or conductivity of the coolant is used as a physical quantity for determining the deterioration level in a test. For example, analysis of residual components of the coolant or investigation of rust status in a recalled cooling device are also carried out for verification in the actual vehicle.

[0035] Processes Executed by Control Device 100

[0036] Hereinafter, the calculation of the deterioration level R will be described. FIG. 2 shows a procedure of processes executed by the control device 100. The process shown in FIG. 2 is implemented by executing the program stored in the memory 120 by the CPU 110. The process shown in FIG. 2 is executed when the engine is started.

[0037] Hereinbelow, step numbers are represented by a number prefixed with “S”.

[0038] When this process is started, the CPU 110 transmits a vehicle ID, which is identification information of the vehicle 500, start-time information, and stop-time information to the data analysis device 300 (S10). The start-time information includes an operation start time coolant temperature THW.sub.s, i.e. a coolant temperature THW at a time when the control device 100 starts operating when the engine has started, a start time T.sub.s at which the control device 100 starts operating, and an operation start time outside air temperature TH.sub.outs, i.e. an outside air temperature TH.sub.out at a time when the control device 100 starts operating.

[0039] The stop-time information includes a device downtime coolant temperature THW.sub.e, i.e. a coolant temperature THW at a time when the control device 100 stops operating when the engine has stopped, a device downtime T.sub.e at which the control device 100 stops operating, and a device downtime outside air temperature TH.sub.oute, i.e. an outside air temperature TH.sub.out at the time when the control device 100 stops operating.

[0040] The CPU 110 starts an acquisition process of acquiring operation start time temperature information (S12), and ends the process. The operation start time temperature information is a cumulative time for each temperature as the coolant temperature THW during operation of the internal combustion engine 15, i.e. the control device 100 starts operating.

[0041] FIG. 3 shows one example of the cumulative time for each temperature as the coolant temperature THW acquired in the acquisition process. In the present embodiment, a plurality of temperature zones are set, and the cumulative time for each temperature as the coolant temperature THW is calculated from a counter value C.sub.n indicating the cumulative time for each temperature zone. The counter value C.sub.n is a value counted for each temperature zone described below, and the number “n” indicates the corresponding temperature zone. The cumulative time for each temperature zone can be calculated from the counter value C.sub.n by multiplying the counter value C.sub.n by a sampling cycle of the coolant temperature THW.

[0042] More specifically, 10 temperature zones are set as a first temperature zone R.sub.1 a second temperature zone R.sub.2, a third temperature zone R.sub.3, a fourth temperature zone R.sub.4, a fifth temperature zone R.sub.5, a sixth temperature zone R.sub.6, a seventh temperature zone R.sub.7, an eighth temperature zone R.sub.8, a ninth temperature zone R.sub.9, and a tenth temperature zone R.sub.10, in order from the lowest temperature zone to the highest temperature zone.

[0043] The first temperature zone R.sub.1 is a temperature range lower than a preset first temperature THW.sub.1. The counter value C.sub.n of the first temperature zone R.sub.1 is referred to as a first counter value C.sub.1. The second temperature zone R.sub.2 is a temperature range equal to or higher than the first temperature THW.sub.1 and lower than a second temperature THW.sub.2. The second temperature THW.sub.2 is a temperature obtained by adding a preset first temperature width H.sub.1 to the first temperature THW.sub.1. The counter value C.sub.n of the second temperature zone R.sub.2 is referred to as a second counter value C.sub.2.

[0044] The third temperature zone R.sub.3 is a temperature range equal to or higher than the second temperature THW.sub.2 and lower than a third temperature THW.sub.3. The third temperature THW.sub.3 is a temperature obtained by adding a preset second temperature width H.sub.2 to the second temperature THW.sub.2. The counter value C.sub.n of the third temperature zone R.sub.3 is referred to as a third counter value C.sub.3.

[0045] The fourth temperature zone R.sub.4 is a temperature range equal to or higher than the third temperature THW.sub.3 and lower than a fourth temperature THW.sub.4. The fourth temperature THW.sub.4 is a temperature obtained by adding a preset third temperature width H.sub.3 to the third temperature THW.sub.3. The counter value C.sub.n of the fourth temperature zone R.sub.4 is referred to as a fourth counter value C.sub.4. The fourth temperature zone R.sub.4 is a zone within which a reference temperature THW.sub.b (described below) falls.

[0046] The fifth temperature zone R.sub.5 is a temperature range equal to or higher than the fourth temperature THW.sub.4 and lower than a fifth temperature THW.sub.5. The fifth temperature THW.sub.5 is a temperature obtained by adding a preset fourth temperature width H.sub.4 to the fourth temperature THW.sub.4. The counter value C.sub.n of the fifth temperature zone R.sub.5 is referred to as a fifth counter value C.sub.5.

[0047] The sixth temperature zone R.sub.6 is a temperature range equal to or higher than the fifth temperature THW.sub.5 and lower than a sixth temperature THW.sub.6. The sixth temperature THW.sub.6 is a temperature obtained by adding the fourth temperature width H.sub.4 to the fifth temperature THW.sub.5. The counter value C.sub.n of the sixth temperature zone R.sub.6 is referred to as a sixth counter value C.sub.6.

[0048] The seventh temperature zone R.sub.7 is a temperature range equal to or higher than the sixth temperature THW.sub.6 and lower than a seventh temperature THW.sub.7. The seventh temperature THW.sub.7 is a temperature obtained by adding a preset fifth temperature width H.sub.5 to the sixth temperature THW.sub.6. The counter value C.sub.n of the seventh temperature zone R.sub.7 is referred to as a seventh counter value C.sub.7.

[0049] The eighth temperature zone R.sub.8 is a temperature range equal to or higher than the seventh temperature THW.sub.7 and lower than an eighth temperature THW.sub.8. The eighth temperature THW.sub.8 is a temperature obtained by adding the fifth temperature width H.sub.5 to the seventh temperature THW.sub.7. The counter value C.sub.n of the eighth temperature zone R.sub.8 is referred to as an eighth counter value C.sub.8.

[0050] The ninth temperature zone R.sub.9 is a temperature range equal to or higher than the eighth temperature THW.sub.8 and lower than a ninth temperature THW.sub.9. The ninth temperature THW.sub.9 is a temperature obtained by adding the fifth temperature width H.sub.5 to the eighth temperature THW.sub.8. The counter value C.sub.r, of the ninth temperature zone R.sub.9 is referred to as a ninth counter value C.sub.9.

[0051] The tenth temperature zone R.sub.10 is a temperature range equal to or higher than the ninth temperature THW.sub.9. The counter value C.sub.n of the tenth temperature zone R.sub.10 is referred to as a tenth counter value C.sub.10. The first temperature width H.sub.1 is wider than the second temperature width H.sub.2, and the second temperature width H.sub.2 is wider than the third temperature width H.sub.3. The third temperature width H.sub.3 is wider than the fourth temperature width H.sub.4, and the fourth temperature width H.sub.4 is wider than the fifth temperature width H.sub.5. Since each temperature width is different as stated above, the temperature range of the higher temperature zone (for example, the seventh temperature zone R.sub.7, the eighth temperature zone R.sub.8, and the ninth temperature zone R.sub.9) is narrower than the temperature range of the lower temperature zone.

[0052] Since each temperature width is different as stated above, the temperature range of the temperature zone in which the counter value C.sub.n tends to be higher (for example, the fourth temperature zone R.sub.4, the fifth temperature zone R.sub.5, and the sixth temperature zone R.sub.6) is narrower than the temperature range of the temperature zone in which the counter value C.sub.n tends to be lower.

[0053] When a process of S12 is started, the CPU 110 acquires the coolant temperature THW at each predetermined sampling cycle. A process of increasing the counter value C.sub.n of the temperature zone within which the acquired coolant temperature THW falls by a predetermined value a (for example, 1) is repeatedly executed while the control device 100 is operating. Consequently, the counter value C.sub.n corresponding to the cumulative time for each temperature as the coolant temperature THW is updated for each temperature zone. Each updated counter value C.sub.n is stored in the memory 120.

[0054] FIG. 4 shows a procedure of processes executed by the control device 100 at predetermined intervals. When this process is started, the CPU 110 determines whether or not there is a request for transmitting the operation start time temperature information (S20). For example, the CPU 110 determines that there is a request for transmitting the operation start time temperature information in a case where a predetermined period has elapsed since the last transmission of the operation start time temperature information. The predetermined period includes the start time of the control device 100, the travel distance of the vehicle 500, and the like.

[0055] In a case where it is determined that there is a request for transmitting the operation start time temperature information (S20: YES), the CPU 110 transmits the vehicle ID, which is the identification information of the vehicle 500, and the counter value C.sub.n for each temperature zone constituting the operation start time temperature information to the data analysis device 300 (S22). In a case where the process of S22 is completed or NO is determined in the process of S20, the CPU 110 temporarily ends the series of processes shown in FIG. 4.

[0056] Processes Executed by Data Analysis Device 300

[0057] FIG. 5 shows a procedure of processes executed by the CPU 310 when the data analysis device 300 receives the data transmitted in the process of S22 shown in FIG. 4.

[0058] Upon receiving the vehicle ID and the counter value C.sub.n (operation start time temperature information) transmitted from the control device 100 in S100, the CPU 310 updates each counter value C.sub.n for each temperature zone, stored in the memory 320 in association with the vehicle ID, and thereby stores the updated counter value C.sub.n in the memory 320 (S110). The update of the counter value C.sub.n is performed by adding the received counter value C.sub.n to each counter value C.sub.n for each temperature zone stored in the memory 320. As updated, a value of each counter value C.sub.n for each temperature zone stored in the memory 320 becomes an integrated value of the counter values C.sub.n for each temperature zone which have been received.

[0059] The CPU 310 executes a conversion process of converting each updated counter value Cn into a converted counter value CC.sub.n (S120). The converted counter value CC.sub.n is a converted value obtained by converting each of the counter values C.sub.n for each temperature zone into the counter value C.sub.n corresponding to the cumulative time at the predetermined reference temperature THW.sub.b (for example, about 90° C.). That is, the converted counter value CC.sub.n is a value obtained by converting the counter value C.sub.n for each temperature zone into the counter value assuming that the coolant temperature THW is the reference temperature THW.sub.b. In other words, when the deterioration level corresponding to the counter value C.sub.n for each temperature zone is set to a deterioration level R.sub.n, the counter value C.sub.n required to reach the deterioration level R.sub.n at the reference temperature THW.sub.b is the converted counter value CC.sub.n. The number “n” in the converted counter value CC.sub.n is the same as the number “n” in the counter value C.sub.n, which is a conversion source, and indicates the corresponding temperature zone.

[0060] This conversion process is performed as follows. As shown in FIG. 6, a first representative temperature P.sub.1, a second representative temperature P.sub.2, a third representative temperature P.sub.3, a fourth representative temperature P.sub.4, a fifth representative temperature P.sub.5, a sixth representative temperature P.sub.6, a seventh representative temperature P.sub.7, an eighth representative temperature P.sub.8, a ninth representative temperature P.sub.9, and a tenth representative temperature P.sub.10 are acquired in advance, each of which is a representative temperature for the respective temperature zones from the first temperature zone R.sub.1 to the tenth temperature zone R.sub.10. Hereinbelow, these representative temperatures are collectively referred to as a representative temperature P.sub.n. A number indicating the temperature zone is substituted for “n”.

[0061] The second representative temperature P.sub.2 to the ninth representative temperature P.sub.9 are obtained from the following equation (1). Any value from 2 to 9 is substituted for “n” in the equation (1). Further, a coefficient K is a value larger than “0” and smaller than “1”, for which an optimum value is set in advance for reducing the error of the deterioration level R.

P.sub.n=THW.sub.(n-1)+(THW.sub.n−THW.sub.(n-1))×coefficient K  (1)

[0062] As an example, when the coefficient K is “0.4”, the second representative temperature P.sub.2, which is the representative temperature of the second temperature zone R.sub.2, is obtained from “first temperature THW.sub.1+(second temperature THW.sub.2−first temperature THW.sub.1)×0.4”.

[0063] Further, the first representative temperature P.sub.1 and the tenth representative temperature P.sub.10 are preset as optimum temperatures for reducing the error of the deterioration level R. The lower the coolant temperature THW is, the less likely it is that the coolant will deteriorate. As shown in FIG. 6, in the temperature zone where the representative temperature P.sub.n is lower than the reference temperature THW.sub.b, the counter value C.sub.n is converted such that the converted counter value CC.sub.n (shown by a solid line) is smaller than the counter value C.sub.n before conversion (shown by a two-dot chain line). The higher the coolant temperature THW is, the easier the coolant deteriorates. As shown in FIG. 6, in the temperature zone where the representative temperature P.sub.n is higher than the reference temperature THW.sub.b, the counter value C.sub.n is converted such that the converted counter value CC.sub.n (shown by a solid line) is greater than the counter value C.sub.n before conversion (shown by a two-dot chain line).

[0064] The calculation of the converted counter value CC.sub.n for each temperature zone is performed using a regression equation in which the representative temperature P.sub.n acquired for each temperature zone and the counter value C.sub.n of the temperature zone within which the representative temperature P.sub.n falls are inputs, and the converted counter value CC.sub.n is output.

[0065] The CPU 310 calculates the sum S by adding all converted counter values CC.sub.n calculated for the respective temperature zones (S130). The CPU 310 executes a calculation process for calculating the deterioration level R based on the calculated sum S (S140). A relational expression between the sum S and the deterioration level R is obtained in advance, and the CPU 310 calculates the deterioration level R based on such a relational expression. The deterioration level R is calculated such that the deterioration level R increases as the sum S increases. When the deterioration level R is calculated as stated above, the CPU 310 stores the calculated deterioration level R in the memory 320 (S150).

[0066] The CPU 310 executes a process of calculating expected replacement timing of the coolant based on a change in the deterioration level R (S160). In S160, the CPU 310 performs the following process, for example. The CPU 310 calculates a time and a travel distance by which the deterioration level R reaches the allowable limit value, based on a difference between the deterioration level R calculated a previous time and the deterioration level R calculated this time, and an elapsed period from the previous calculation of the deterioration level R to the current calculation of the deterioration level R (for example, elapsed time or travel distance). The calculated time and travel distance are set as the expected replacement timing. When the process of S160 is completed, the CPU 310 ends the present process.

[0067] FIG. 7 shows a procedure of processes executed by the CPU 310 when the data analysis device 300 receives the data transmitted in the process of S10 shown in FIG. 2. Upon receiving the vehicle ID, the start-time information, and the stop-time information, transmitted from the control device 100 in S200, the CPU 310 calculates a stop time T.sub.sp, which is a time during which the control device 100 has stopped operating, by subtracting the start time T.sub.s included in the start-time information from the device downtime T.sub.e included in the stop-time information. The CPU 310 executes an estimation process of estimating change of the coolant temperature THW while the control device 100 has stopped operating, i.e. the coolant temperature THW at each predetermined elapsed time from a time at which the control device 100 stops operating, based on a model formula in which the stop time T.sub.sp, the operation start time coolant temperature THW.sub.s and the operation start time outside air temperature TH.sub.outs (included in the start-time information), and the device downtime coolant temperature THW.sub.e and the device downtime outside air temperature TH.sub.oute (included in the stop-time information) are inputs (S210).

[0068] The CPU 310 executes an update process of updating each counter value C.sub.n, which is stored in the memory 320 in association with the vehicle ID and the counter value C.sub.n of the temperature zone within which each coolant temperature THW at the elapsed time, estimated in the process of S210, falls.

[0069] The CPU 310 executes an update process of updating the counter value C.sub.n for each temperature zone stored in the memory 320 in association with the vehicle ID, based on the coolant temperature THW at each elapsed time estimated in the process of S210 (S220). This process is then terminated.

[0070] Operation and Effect

[0071] The operation and effect of the present embodiment will be described hereinbelow.

[0072] (1) The longer the cumulative time for each coolant temperature THW is, the more the coolant deteriorates. In a case where the cumulative time is the same but the coolant temperature THW is higher, the coolant deteriorates more as compared with a case where the coolant temperature is lower.

[0073] For calculating the deterioration level of the coolant, it is necessary to take account of the coolant temperature THW and the cumulative time for each temperature zone. In the present embodiment, the process of converting each of the counter values C.sub.n corresponding to the cumulative time acquired for each temperature zone into the counter value C.sub.n corresponding to the cumulative time at the reference temperature THW.sub.b, i.e. the converted counter value CC.sub.n, is executed. Therefore, the counter value C.sub.n for each temperature zone is converted into the counter value C.sub.n assuming that the coolant temperature THW is the reference temperature THW.sub.b. Since the deterioration level R is calculated based on the sum S of the converted counter values CC.sub.n, i.e. the converted counter values C.sub.n, the deterioration level R is calculated using the coolant temperature THW and the cumulative time for each temperature zone. Consequently, the deterioration level R of the coolant can be calculated accurately.

[0074] (2) Because the coolant temperature remains high for a while even though the internal combustion engine 15 has stopped, the coolant keeps deteriorating even while the internal combustion engine 15 has stopped. In a case where the control device 100 stops operating due to the engine stopping, the temperature change of the coolant during the stop cannot be recognized. In the present embodiment, the change of the coolant temperature THW while the control device 100 has stopped operating can be estimated by the estimation process of the coolant temperature THW as stated above. The counter value C.sub.n for each temperature zone is updated based on the coolant temperature THW while the control device 100 has stopped operating. Consequently, the deterioration level R is calculated using the coolant temperature THW while the control device 100 has stopped operating, and thus the estimation accuracy of the deterioration level R is further improved.

[0075] (3) Upon sampling of the coolant temperature THW, the plurality of temperature zones are set, and thus it is possible to reduce a calculation load of the control device 100 as compared with a case where such temperature zones are not set. The temperature range of the higher temperature zone is narrower than the temperature range of the lower temperature zone. Since the temperature range of the temperature zone on the high temperature side, which has a great influence on the deterioration level R, is narrow and the temperature zone has the enhanced resolution, it is possible to reduce an estimation error of the deterioration level R caused by dividing the temperature range.

[0076] (4) The temperature range of the temperature zone in which the counter value C.sub.n tends to be higher is narrower than the temperature range of the temperature zone in which the counter value C.sub.n tends to be lower. As described above, the temperature zone in which the counter value C.sub.n tends to be higher and the deterioration level R is greatly influenced has the narrower temperature range and the enhanced resolution. Therefore, it is also possible to reduce an estimation error of the deterioration level R caused by dividing the temperature range.

MODIFIED EXAMPLE

[0077] The present embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other without departing from the technical scope. [0078] The number of temperature zones for the coolant temperature THW and the temperature width may be appropriately changed. [0079] The counter value C.sub.n may be obtained for each sampled coolant temperature THW without setting the temperature zones. [0080] The timing at which the operation start time temperature information is transmitted may be changed as appropriate. [0081] The process of S160 shown in FIG. 5 may be omitted. [0082] The series of processes shown in FIG. 7 may be omitted. Even in this case, the operation and effect can be obtained except for the outcome stated in (2). [0083] The change of the coolant temperature THW while the control device 100 has stopped operating may be estimated by another aspect. [0084] Although the temperature ranges of the higher temperature zone and the temperature zone in which the counter value C.sub.n tends to be higher are narrowed, the temperature range of either one may be narrowed. [0085] The actual cumulative time may be calculated instead of the counter value C.sub.n. [0086] The conversion process of S120 shown in FIG. 7 may be executed by the control device 100. The converted counter value CC.sub.n may be transmitted instead of the counter value C.sub.n as the operation start time temperature information sent to the data analysis device 300. [0087] The series of processes shown in FIG. 7 may be executed by the control device 100. [0088] All the processes stated above may be executed by the control device 100. [0089] The coolant temperature THW acquired while the control device 100 is operating may be transmitted to the data analysis device 300 in real time. The counter value C.sub.n may be updated by the data analysis device 300. [0090] The execution unit is not limited to one that is provided with the CPU and the memory to execute the software process. For example, a dedicated hardware circuit (for example, ASIC) that processes at least a part of the software processes executed in each embodiment may be provided. That is, the execution unit may have any of the following configurations (a) to (c). (a) A processing device that executes all processes stated above according to a program, and a program storage device such as a memory that stores the program, are provided. (b) A processing device and a program storage device that execute a part of the processes stated above according to a program, and a dedicated hardware circuit that executes the remaining processes, are provided. (c) A dedicated hardware circuit for executing all processes stated above is provided. There may be a plurality of the software processing circuits having a processing device and a program storage device, or a plurality of the dedicated hardware circuits. That is, the process may be executed by a processing circuit including at least one of the software processing circuits and the dedicated hardware circuits.