Coolant degradation detection system

Abstract

To provide a cooling liquid deterioration determination system capable of determining deterioration in cooling liquid accurately.SOLUTION: A cooling liquid deterioration determination system 50 includes: a temperature sensor 31 for measuring a temperature of cooling liquid passing through an engine 10; a concentration sensor 32 for measuring concentration of ethylene glycol contained in the cooling liquid; and a control device 40 for determining deterioration in the cooling liquid. The control device 40 includes: an integrated time counting part 42 for counting integrated time in which the temperature of the cooling liquid measured by the temperature sensor 31 is a specified temperature or higher up to time that the cooling liquid is replaced; a deterioration determination part 43 for determining that the cooling liquid has deteriorated when the integrated time is specified time or more; and a correction part 44 for correcting the specified time on the basis of concentration of the ethylene glycol measured by the concentration sensor 32. The deterioration determination part 43 determines deterioration in the cooling liquid by comparing the specified time corrected by the correction part 44 with the integrated time.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a coolant deterioration determination system.

Background Art

[0002] Conventionally, an internal combustion engine system including an engine as a power source and a control device for controlling the engine has been proposed. When the engine is operating, the engine generates heat at a high temperature by combustion of a mixture of fuel and air. Therefore, a coolant is passed through the engine, and the coolant is circulated by a cooling circulation mechanism and sent to the engine.

[0003] By the way, such a coolant may use one containing ethylene glycol for the purpose of antifreeze. However, ethylene glycol may oxidatively deteriorate in a temperature environment exceeding 80°C. When ethylene glycol oxidatively deteriorates, organic acids such as formic acid or acetic acid are generated in the coolant. The organic acid acts as a corrosive ion. Therefore, when ethylene glycol oxidatively deteriorates and the coolant deteriorates, there is a risk that the metal of the flow path through which the coolant flows corrodes.

[0004] For example, as a system for managing such a coolant, Patent Document 1 discloses a system that integrates the time during which the temperature of the coolant is above a specified temperature and determines that the coolant has deteriorated when this integrated time reaches a specified time.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The oxidative degradation of ethylene glycol depends on the concentration of ethylene glycol in the coolant. However, the system disclosed in Patent Document 1 determines the degradation of the coolant without considering the concentration of ethylene glycol. Therefore, if, for example, the concentration of ethylene glycol is diluted below the specified concentration, the degradation of the coolant cannot be accurately determined.

[0007] The present invention has been made in view of the above, and aims to provide a coolant deterioration determination system that can accurately determine the deterioration of the coolant. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides a coolant deterioration determination system for determining the deterioration of a coolant containing ethylene glycol as a coolant for cooling an engine, comprising: a temperature sensor for measuring the temperature of the coolant that has passed through the engine; a concentration sensor for measuring the concentration of the ethylene glycol contained in the coolant; and a control device for determining the deterioration of the coolant based on the measurement results of the temperature sensor and the concentration sensor, wherein the control device includes an integrated time measuring unit that measures the integrated time during which the temperature of the coolant measured by the temperature sensor is above a specified temperature until the coolant is replaced. A start counting unit that counts the number of cold starts of the engine until the coolant is replaced, If the aforementioned cumulative time is equal to or greater than the specified time Furthermore, the number of cold starts is equal to or greater than the specified number. In this case, the system includes a deterioration determination unit that determines that the coolant has deteriorated, and a correction unit that corrects the specified time based on the concentration of ethylene glycol measured by the concentration sensor. The correction unit calculates a degradation rate coefficient that relatively indicates the degree of oxidative degradation of the ethylene glycol from the concentration of the ethylene glycol measured by the concentration sensor and the temperature of the coolant measured by the temperature sensor, and corrects the specified time by dividing the specified time by the calculated degradation rate coefficient. The deterioration determination unit is characterized by determining the deterioration of the coolant by comparing the specified time corrected by the correction unit with the accumulated time.

[0009] With this configuration, the degradation detection unit can determine the degradation of the coolant by taking into account the concentration of ethylene glycol contained in the coolant. The coolant degradation detection system can easily determine the degradation of the coolant while taking into account the concentration of ethylene glycol. Therefore, the coolant degradation detection system accurately detects the degradation of the coolant. And easy It can be determined that way.

[0010] In a more preferred embodiment, the coolant degradation determination system is incorporated into an internal combustion engine system, the internal combustion engine system comprising the engine and a cooling circulation mechanism that circulates the coolant to the engine while cooling it, the cooling circulation mechanism having a high-temperature passage through which the high-temperature coolant that has passed through the engine flows and a low-temperature passage through which the cooled, low-temperature coolant flows, and the concentration sensor is installed in the high-temperature passage.

[0011] In this configuration, the concentration sensor can accurately measure the concentration of ethylene glycol contained in the high-temperature coolant, which contributes to the accurate determination of coolant degradation. The coolant degradation determination system can reduce the possibility of underestimating the oxidative degradation of ethylene glycol. Therefore, the coolant degradation determination system can accurately and precisely determine the degradation of the coolant.

[0012] In a more preferred embodiment, the coolant deterioration determination system is incorporated into an internal combustion engine system, the internal combustion engine system comprising the engine and a cooling circulation mechanism that circulates the coolant to the engine while cooling it, the cooling circulation mechanism having a discharge port for discharging the coolant that has passed through the engine from the engine, and the temperature sensor and the concentration sensor are installed at the discharge port.

[0013] In this configuration, the concentration sensor can accurately measure the concentration of ethylene glycol contained in the high-temperature coolant, which contributes to the accurate determination of coolant degradation. Therefore, the coolant degradation determination system can determine the degradation of the coolant more accurately.

[0014] In a more preferred embodiment, the concentration sensor comprises a densimeter for measuring the density of the coolant, or a refractometer for measuring the refractive index of the coolant, and a concentration calculation unit that calculates the concentration of ethylene glycol from the density of the coolant measured by the densimeter, or the refractive index of the coolant measured by the refractometer, and the temperature of the coolant measured by the temperature sensor.

[0015] With this aspect, the concentration sensor can accurately measure the concentration of ethylene glycol that depends on the temperature of the coolant. Therefore, the coolant deterioration determination system can more accurately determine the deterioration of the coolant based on the accurately measured concentration of ethylene glycol.

Advantages of the Invention

[0018] According to the present invention, it is possible to provide a coolant deterioration determination system that can accurately determine the deterioration of the coolant.

Brief Description of the Drawings

[0019] [Figure 1] A diagram schematically showing an internal combustion engine system 1 incorporating the coolant deterioration determination system 50 of the present embodiment. [Figure 2] A block diagram showing the configuration of the concentration sensor. [Figure 3] A diagram showing the relationship between the temperature and density of the coolant and the concentration of ethylene glycol. [Figure 4] A diagram explaining the installation locations of the temperature sensor and the concentration sensor. [Figure 5] A block diagram showing the configuration of the control device. [Figure 6] A diagram showing the relationship between the temperature and concentration of the coolant and the deterioration rate coefficient. [Figure 7] A flowchart showing the operation flow of the coolant deterioration determination system.

Modes for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For configurations denoted by the same reference numerals in each embodiment, unless otherwise particularly noted, they have the same functions in each embodiment, and the description thereof will be omitted.

[0021] FIG. 1 is a diagram schematically showing an internal combustion engine system 1 incorporating the coolant deterioration determination system 50 of the present embodiment.

[0022] The coolant degradation determination system 50 is a system that determines the degradation of the coolant containing ethylene glycol, which is used to cool the engine 10. The coolant degradation determination system 50 is incorporated into the internal combustion engine system 1 mounted on the vehicle.

[0023] The internal combustion engine system 1 comprises an engine 10, a cooling circulation mechanism 20, a temperature sensor 31, a concentration sensor 32, a control device 40, a starter 60, and a warning light 70. The temperature sensor 31, the concentration sensor 32, and the control device 40 constitute the coolant deterioration determination system 50.

[0024] The engine 10 is a device that provides power to the vehicle. The engine 10 has a piston slidably arranged in a cylinder block, and an intake valve and an exhaust valve are provided in the cylinder head. In the combustion chamber of the engine 10, a mixture of fuel and intake air is ignited and burned, thereby operating the engine 10. Because this combustion heats the engine 10, in this embodiment, passages for coolant to cool the engine 10 are formed in the cylinder block and cylinder head of the engine 10.

[0025] In this embodiment, the coolant is a liquid to which an additive containing ethylene glycol (hereinafter also referred to as "EG") is added to water. In this embodiment, the coolant may contain 30% to 60% (for example, by mass) of ethylene glycol. By adding ethylene glycol to the coolant, freezing of the coolant can be prevented.

[0026] The coolant that cools the engine 10 is circulated to the engine 10 by a commonly known cooling circulation mechanism 20. The cooling circulation mechanism 20 comprises a pump 21, a heater core 22, a radiator 23, and a reserve tank 24, which are connected via piping 25.

[0027] Pump 21 is installed upstream of engine 10 and pumps coolant to engine 10. When engine 10 is running, it heats up, so the pumping by pump 21 cools engine 10.

[0028] A temperature sensor 31 and a concentration sensor 32 are installed downstream of the engine 10. The temperature sensor 31 measures the temperature of the coolant that has passed through the engine 10. The concentration sensor 32 measures the concentration of ethylene glycol contained in the coolant.

[0029] Downstream of the temperature sensor 31 and the concentration sensor 32, a heater core 22 and a radiator 23 are installed. The heater core 22 absorbs heat from the coolant that has passed through the engine 10 through heat exchange when raising the temperature inside the vehicle. The radiator 23 can cool the coolant that has passed through the engine 10.

[0030] Furthermore, a reserve tank 24 for storing coolant is installed between the radiator 23 and the pump 21. When the amount of coolant supplied to the pump 21 is insufficient, coolant is supplied from the reserve tank 24. In this embodiment, the reserve tank 24 is installed between the radiator 23 and the pump 21, but it may also be installed in the radiator 23, for example.

[0031] In this embodiment, the flow paths formed in the engine (specifically the cylinder block and cylinder head) 10, heater core 22, radiator 23, and pump 21 shown in Figure 1, and the flow paths in the piping 25 connecting them, correspond to the "coolant flow paths" as defined in this invention.

[0032] The control device 40 controls each component of the internal combustion engine system 1. For example, based on the starting signal from the starter 60, the control device 40 controls the starting of the engine 10 and then continues to control the combustion of the engine 10. The control of the engine 10 by the control device 40 is general control for operating the engine 10, such as air-fuel ratio control, and a detailed explanation is omitted.

[0033] Furthermore, the control device 40 determines the deterioration of the coolant based on the measurement results of the temperature sensor 31 and the concentration sensor 32. If the control device 40 determines that the coolant has deteriorated, it controls the system to illuminate a warning light 70 to prompt the replacement of the coolant. The control device 40 is electrically connected to the temperature sensor 31 and receives a measurement signal from the temperature sensor 31 indicating the measurement result of the coolant temperature. The control device 40 is electrically connected to the concentration sensor 32 and receives a measurement signal from the concentration sensor 32 indicating the measurement result of the ethylene glycol concentration. The control device 40 is equipped with a processing unit such as a CPU and storage devices such as RAM and ROM as hardware.

[0034] Figure 2 is a block diagram showing the configuration of the concentration sensor 32. Figure 3 is a diagram showing the relationship between the temperature and density of the coolant and the concentration of ethylene glycol.

[0035] The concentration of ethylene glycol in the coolant can be measured from the density or refractive index of the coolant. The concentration sensor 32 is composed of a densimeter 33 or a refractometer and a concentration calculation unit 34. The densimeter 33 measures the density of the coolant. The refractometer measures the refractive index of the coolant. The concentration calculation unit 34 calculates the concentration of ethylene glycol from the density of the coolant measured by the densimeter 33, or the refractive index of the coolant measured by the refractometer, and the temperature of the coolant measured by the temperature sensor 31. In this embodiment, the concentration sensor 32 is described as having a densimeter 33 and a concentration calculation unit 34.

[0036] The density or refractive index of the coolant depends on the temperature of the coolant. For example, as shown in Figure 3, the density of the coolant decreases as the temperature of the coolant rises. Also, as shown in Figure 3, once the temperature and density of the coolant are determined, the concentration of ethylene glycol can be determined. The concentration calculation unit 34 may have a mathematical model (formula) pre-set that describes the relationship between the temperature and density of the coolant and the concentration of ethylene glycol, as shown in Figure 3. The concentration calculation unit 34 can calculate the concentration of ethylene glycol by inputting the density of the coolant measured by the densimeter 33 and the temperature of the coolant measured by the temperature sensor 31 into this mathematical model. As a result, the concentration sensor 32 can measure the concentration of ethylene glycol. The concentration calculation unit 34 may be part of the control device 40.

[0037] Since the concentration sensor 32 is composed of a densimeter 33 or refractometer and a concentration calculation unit 34, the concentration sensor 32 can accurately measure the concentration of ethylene glycol, which depends on the temperature of the coolant. Therefore, the coolant degradation determination system 50 can more accurately determine the degradation of the coolant based on the accurately measured concentration of ethylene glycol.

[0038] Figure 4 illustrates the installation locations of the temperature sensor 31 and the concentration sensor 32. Figure 4 also shows an example of the engine 10 and the cooling circulation mechanism 20.

[0039] The cooling circulation mechanism 20 has a high-temperature passage 26 through which high-temperature coolant that has passed through the engine 10 flows, and a low-temperature passage 27 through which low-temperature coolant cooled by the heater core 22 or radiator 23 flows. In Figure 4, the high-temperature passage 26 is shown in gray, and the low-temperature passage 27 is shown in a lighter gray than the high-temperature passage 26.

[0040] Since the high-temperature coolant that has passed through the engine 10 flows stably through the high-temperature passage 26, the temperature of the coolant flowing through the high-temperature passage 26 is stable. On the other hand, depending on the operating state of the engine 10, there may be cases where it is not necessary to supply low-temperature coolant to the engine 10, so the coolant may not flow stably through the low-temperature passage 27, and therefore the temperature of the coolant flowing through the low-temperature passage 27 is less stable than that of the high-temperature passage 26. Furthermore, since ethylene glycol is more susceptible to oxidative degradation at higher temperatures, in order to accurately determine the degradation of the coolant, it is desirable to measure the concentration of ethylene glycol used for the degradation determination in relation to the coolant flowing through the high-temperature passage 26. In other words, measuring the concentration of ethylene glycol in relation to the coolant flowing through the low-temperature passage 27 may underestimate the oxidative degradation of ethylene glycol.

[0041] For this reason, the concentration sensor 32 (specifically, the densimeter 33) is installed in the high-temperature flow path 26. This allows the concentration sensor 32 to accurately measure the concentration of ethylene glycol contained in the high-temperature coolant, which contributes to accurate determination of coolant degradation. The coolant degradation determination system 50 can reduce the possibility of underestimating the oxidative degradation of ethylene glycol. Therefore, the coolant degradation determination system 50 can accurately and precisely determine the degradation of the coolant.

[0042] Furthermore, the cooling circulation mechanism 20 has an outlet 28 that discharges the coolant that has passed through the engine 10 from the engine 10. The coolant passing through the outlet 28 is hot before it is cooled by the heater core 22 or radiator 23, etc. The temperature sensor 31 is installed at this outlet 28 and measures the temperature of the hot coolant. As explained using Figure 3, the density of the coolant depends on the temperature of the coolant, so if the installation locations of the concentration sensor 32 and the temperature sensor 31 are different, the measurement error of the concentration sensor 32 will increase.

[0043] For this reason, the concentration sensor 32 is located in the same place as the temperature sensor 31 and is installed at the outlet 28 through which the high-temperature coolant flows. As a result, the concentration sensor 32 can accurately measure the concentration of ethylene glycol contained in the high-temperature coolant, which contributes to accurate determination of coolant degradation. Therefore, the coolant degradation determination system 50 can determine the degradation of the coolant with even greater accuracy.

[0044] In this embodiment, the installation location of the concentration sensor 32 is not limited to the outlet 28. For example, the concentration sensor 32 may be installed at the inlet of the radiator 23, which is one of the high-temperature flow paths 26, or inside the reserve tank 24.

[0045] Figure 5 is a block diagram showing the configuration of the control device 40. Figure 6 is a diagram showing the relationship between the temperature of the coolant, the concentration of ethylene glycol, and the degradation rate coefficient.

[0046] The control device 40 includes a start counting unit 41, an integrated time timing unit 42, a deterioration determination unit 43, and a correction unit 44.

[0047] The start count unit 41 determines whether the engine 10 has been cold-started and counts the number of cold starts until the coolant is replaced. A cold start is when the engine 10 is started at or below the ambient temperature (ambient temperature), and in this embodiment, it is when the engine 10 is started after the heat absorbed from the engine 10 has been completely dissipated from the coolant. For example, a cold start of the engine 10 may be determined by comparing the ambient temperature with the coolant temperature at the time a start signal is received from the starter 60. Alternatively, a cold start of the engine 10 may be determined at the time when the engine 10 starts after the coolant temperature has dropped.

[0048] The cumulative time timing unit 42 measures the cumulative time during which the coolant temperature, as measured by the temperature sensor 31, is above a specified temperature until the coolant is replaced. Here, the specified temperature is the temperature at which ethylene glycol contained in the coolant oxidizes and degrades, generating organic acids such as formic acid or acetic acid in the coolant. The specified temperature is, for example, 80°C.

[0049] The deterioration determination unit 43 determines that the coolant has deteriorated if the cumulative time measured by the cumulative time timing unit 42 is equal to or greater than a specified time. Preferably, the deterioration determination unit 43 determines that the coolant has deteriorated if the cumulative time measured by the cumulative time timing unit 42 is equal to or greater than a specified time AND the number of cold starts counted by the start count unit 41 is equal to or greater than a specified number.

[0050] If the coolant is determined to have deteriorated, the deterioration detection unit 43 transmits a warning signal, which is a control signal for illuminating the warning light 70, to the warning light 70, causing the warning light 70 to illuminate. This allows the control device 40 to prompt the user to replace the coolant at the appropriate time.

[0051] Here, the specified time may be determined, for example, as follows: With a predetermined amount of oxygen dissolved in the coolant, the coolant is heated to the same temperature as the highest temperature of the coolant that has passed through the engine 10, and the heating time at which the amount of organic acid such as formic acid or acetic acid produced from ethylene glycol reaches a predetermined amount is obtained in advance by experimentation or other means. The obtained heating time can be set as the specified time. As a result, if the cumulative time measured by the cumulative time timing unit 42 is equal to or greater than the specified time, it can be considered that the ethylene glycol contained in the coolant is oxidatively degraded. The specified time is, for example, 3,000 hours to 50,000 hours, preferably 5,000 hours to 30,000 hours.

[0052] When the coolant reaches the specified temperature, oxidative degradation of ethylene glycol begins, and the amount of dissolved oxygen in the coolant is consumed. On the other hand, when the engine 10 is cold, the amount of dissolved oxygen in the coolant increases as it is taken in from the gas phase (air) in the cooling circulation mechanism 20, including the reserve tank 24. Therefore, when the engine 10 is cold, oxygen is replenished in the coolant, and the amount of dissolved oxygen becomes saturated in a specified time.

[0053] Therefore, in this embodiment, the deterioration determination unit 43 determines that the coolant has deteriorated when, in addition to the determination condition that the cumulative time is equal to or greater than a specified time, the number of cold starts counted by the start count unit 41 is equal to or greater than a specified number.

[0054] Incidentally, the oxidative degradation of ethylene glycol depends not only on the temperature and dissolved oxygen content of the coolant, but also on the concentration of ethylene glycol. The lower the concentration of ethylene glycol, the more easily the oxidative degradation of ethylene glycol progresses. In other words, the lower the concentration of ethylene glycol, the faster the rate of coolant degradation.

[0055] Figure 6 shows the relationship between the coolant temperature, the ethylene glycol concentration, and the degradation rate coefficient. The degradation rate coefficient is an index that relatively indicates the degree of oxidative degradation of ethylene glycol. Specifically, the degradation rate coefficient is set to 1 when the coolant temperature is 90°C and the ethylene glycol concentration is 50%, and is an index that relatively indicates the degree of oxidative degradation of ethylene glycol at each temperature and concentration. The graph shown in Figure 6 was obtained as follows: As test solutions, aqueous solutions with concentrations of 30% and 50% ethylene glycol were prepared. These test solutions were placed in sealed containers and heated to temperatures of 20°C, 30°C, ..., 110°C, and 120°C. The heating time was 504 hours at each temperature. After that, the amounts of formic acid and glycolic acid produced in the test solutions of each concentration at each temperature were measured. Then, the amount of the component in the test solution at a coolant temperature of 90°C and an ethylene glycol concentration of 50% was set as the degradation rate coefficient = 1, and the degradation rate coefficients for each temperature and concentration of the test solution were calculated from the amount of the component in the test solution.

[0056] As shown in Figure 6, since the oxidative degradation of ethylene glycol depends on the concentration of ethylene glycol, in this embodiment, the degradation of the coolant is determined by taking the concentration of ethylene glycol into consideration. For this purpose, the control device 40 of this embodiment is equipped with a correction unit 44.

[0057] The correction unit 44 corrects the specified time based on the ethylene glycol concentration measured by the concentration sensor 32. Specifically, as shown in Figure 6, once the coolant temperature and the ethylene glycol concentration are determined, the degradation rate coefficient is determined. The correction unit 44 may have a mathematical model (formula) pre-set that describes the relationship between the coolant temperature, the ethylene glycol concentration and the degradation rate coefficient, as shown in Figure 6. The correction unit 44 can calculate the degradation rate coefficient by inputting the ethylene glycol concentration measured by the concentration sensor 32 and the coolant temperature measured by the temperature sensor 31 into this mathematical model. Then, the correction unit 44 corrects the specified time by dividing the specified time by the calculated degradation rate coefficient.

[0058] The deterioration determination unit 43 determines the deterioration of the coolant by comparing the specified time corrected by the correction unit 44 with the accumulated time measured by the accumulated time timing unit 42. As shown in Figure 6, the lower the concentration of ethylene glycol, the larger the deterioration rate coefficient, so the specified time is corrected to a shorter time. The deterioration determination unit 43 determines that the coolant has deteriorated when the accumulated time is equal to or greater than the specified time, so the lower the concentration of ethylene glycol, the easier it is to determine that the coolant has deteriorated.

[0059] In this way, the correction unit 44 calculates the degradation rate coefficient, and by correcting the specified time using the calculated degradation rate coefficient, the coolant degradation determination system 50 can easily determine the degradation of the coolant while taking into account the concentration of ethylene glycol. Therefore, the coolant degradation determination system 50 can accurately and easily determine the degradation of the coolant.

[0060] Furthermore, the degradation determination unit 43 can determine that the coolant has deteriorated if the concentration of ethylene glycol measured by the concentration sensor 32 is outside the specified concentration range. The specified concentration range is, for example, 25% to 70%, preferably 30% to 65%. If the concentration of ethylene glycol is outside the specified concentration range, it is highly likely that the user intentionally diluted the coolant by adding tap water to the reserve tank 24, or intentionally concentrated the coolant by adding ethylene glycol. In this case, the coolant may not be able to perform as desired.

[0061] Therefore, in this embodiment, the deterioration determination unit 43 determines that the coolant has deteriorated if the concentration of ethylene glycol measured by the concentration sensor 32 is outside the specified concentration range. As a result, the control device 40 can prevent a situation in which the coolant is unable to perform as desired.

[0062] Figure 7 is a flowchart showing the operation flow of the coolant degradation detection system 50.

[0063] In step S1, when the control device 40 starts the engine 10, the temperature sensor 31 measures the temperature of the coolant.

[0064] In step S2, the concentration sensor 32 measures the concentration of the coolant.

[0065] In step S3, the degradation determination unit 43 determines whether the concentration of ethylene glycol measured by the concentration sensor 32 is within a specified concentration range. If the concentration of ethylene glycol is within the specified concentration range, the coolant degradation determination system 50 proceeds to step S4. If the concentration of ethylene glycol is outside the specified concentration range, the coolant degradation determination system 50 proceeds to step S13.

[0066] In step S4, the correction unit 44 calculates the degradation rate coefficient from the concentration of ethylene glycol measured by the concentration sensor 32 and the temperature of the coolant measured by the temperature sensor 31.

[0067] In step S5, the correction unit 44 corrects the specified time by dividing the specified time by the calculated degradation rate coefficient.

[0068] In step S6, the temperature sensor 31 measures the temperature of the coolant.

[0069] In step S7, the degradation determination unit 43 determines whether the temperature of the coolant measured by the temperature sensor 31 has reached a specified temperature. If the coolant temperature has reached the specified temperature, the coolant degradation determination system 50 proceeds to step S8. If the coolant temperature has not reached the specified temperature, the coolant degradation determination system 50 proceeds to step S9.

[0070] In step S8, the cumulative time timing unit 42 measures the cumulative time during which the coolant temperature is above a specified temperature. Then, the coolant degradation determination system 50 proceeds to step S10.

[0071] In step S9, the cumulative time timing unit 42 terminates the cumulative time timing if it is currently timing the cumulative time during which the coolant temperature is above the specified temperature, and stores the time that has been timed. After that, the coolant deterioration determination system 50 proceeds to step S6.

[0072] In step S10, the deterioration determination unit 43 determines whether the accumulated time measured by the accumulated time timing unit 42 has reached a specified time. If the accumulated time has reached the specified time, the coolant deterioration determination system 50 proceeds to step S11. If the accumulated time has not reached the specified time, the coolant deterioration determination system 50 proceeds to step S6.

[0073] In step S11, the start counting unit 41 counts the number of cold starts of the engine 10.

[0074] In step S12, the deterioration determination unit 43 determines whether the number of cold starts counted by the start count count unit 41 has reached a specified number. If the number of cold starts has reached the specified number, the coolant deterioration determination system 50 proceeds to step S13. If the number of cold starts has not reached the specified number, the coolant deterioration determination system 50 proceeds to step S6.

[0075] In step S13, the deterioration determination unit 43 transmits a warning signal to the warning light 70 to illuminate it. After that, the operation of the coolant deterioration determination system 50 shown in Figure 7 ends. After the coolant is replaced, the coolant deterioration determination system 50 resets the number of cold starts counted by the start count unit 41 and the accumulated time measured by the accumulated time measurement unit 42, and then performs the operation shown in Figure 7 again.

[0076] As described above, the coolant deterioration determination system 50 is a coolant deterioration determination system that determines the deterioration of coolant containing ethylene glycol as coolant for cooling the engine 10. The coolant deterioration determination system 50 includes a temperature sensor 31 that measures the temperature of the coolant that has passed through the engine 10, a concentration sensor 32 that measures the concentration of ethylene glycol contained in the coolant, and a control device 40 that determines the deterioration of the coolant based on the measurement results of the temperature sensor 31 and the concentration sensor 32. The control device 40 includes an accumulation time measuring unit 42 that measures the accumulated time during which the temperature of the coolant measured by the temperature sensor 31 is above a specified temperature until the coolant is replaced, a deterioration determination unit 43 that determines that the coolant has deteriorated if the accumulated time is above a specified time, and a correction unit 44 that corrects the specified time based on the concentration of ethylene glycol measured by the concentration sensor 32. The deterioration determination unit 43 determines the deterioration of the coolant by comparing the specified time corrected by the correction unit 44 with the accumulated time.

[0077] As a result, the deterioration determination unit 43 can determine the deterioration of the coolant by taking into account the concentration of ethylene glycol contained in the coolant. Therefore, the coolant deterioration determination system 50 can accurately determine the deterioration of the coolant.

[0078] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention as described in the claims. The present invention can be modified by adding the configuration of one embodiment to the configuration of another embodiment, replacing the configuration of one embodiment with that of another embodiment, or deleting a part of the configuration of one embodiment. [Explanation of symbols]

[0079] 1...Internal combustion engine system, 10...Engine, 20...Cooling circulation mechanism, 26...High temperature passage, 27...Low temperature passage, 28...Discharge port, 31...Temperature sensor, 32...Concentration sensor, 33...Densimeter, 34...Concentration calculation unit, 40...Control device, 42...Integrated time timing unit, 43...Degradation determination unit, 44...Correction unit, 50...Coolant degradation determination system

Claims

1. A coolant degradation determination system for determining the degradation of a coolant containing ethylene glycol used to cool an engine, A temperature sensor for measuring the temperature of the coolant that has passed through the engine, A concentration sensor for measuring the concentration of ethylene glycol contained in the coolant, The system includes a control device that determines the deterioration of the coolant based on the measurement results of the temperature sensor and the concentration sensor, The control device is The system includes an integrated time timing unit that measures the cumulative time during which the temperature of the coolant, as measured by the temperature sensor, is above a specified temperature until the coolant is replaced, A start counting unit that counts the number of cold starts of the engine until the coolant is replaced, A deterioration determination unit determines that the coolant has deteriorated if the cumulative time is equal to or greater than a specified time and the number of cold starts is equal to or greater than a specified number. It has a correction unit that corrects the specified time based on the concentration of ethylene glycol measured by the concentration sensor, The correction unit, From the concentration of ethylene glycol measured by the concentration sensor and the temperature of the coolant measured by the temperature sensor, a degradation rate coefficient that relatively indicates the degree of oxidative degradation of the ethylene glycol is calculated. The specified time is corrected by dividing it by the calculated degradation rate coefficient. The deterioration determination unit determines the deterioration of the coolant by comparing the specified time corrected by the correction unit with the accumulated time. A coolant degradation determination system characterized by the following features.

2. The aforementioned coolant degradation detection system is incorporated into the internal combustion engine system. The internal combustion engine system comprises the engine and a cooling circulation mechanism that circulates the coolant to the engine while cooling it. The cooling circulation mechanism has a high-temperature passage through which the high-temperature coolant that has passed through the engine flows, and a low-temperature passage through which the cooled, low-temperature coolant flows. The concentration sensor is installed in the high-temperature flow path. The coolant degradation determination system according to feature 1.

3. The aforementioned coolant degradation detection system is incorporated into the internal combustion engine system. The internal combustion engine system comprises the engine and a cooling circulation mechanism that circulates the coolant to the engine while cooling it. The cooling circulation mechanism has an outlet for discharging the coolant that has passed through the engine from the engine, The temperature sensor and the concentration sensor are installed at the outlet. The coolant degradation determination system according to feature 1.

4. The aforementioned concentration sensor is A densimeter for measuring the density of the coolant, or a refractometer for measuring the refractive index of the coolant, The system comprises: a concentration calculation unit that calculates the concentration of ethylene glycol from the density of the coolant measured by the density meter, or the refractive index of the coolant measured by the refractive index meter, and the temperature of the coolant measured by the temperature sensor; and The coolant degradation determination system according to feature 1.

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