Catalyst state detection device

Abstract

The present invention provides a catalyst state detection device that accurately detects the state of an oxidation catalyst section. The catalyst state detection device includes: a temperature sensor that detects the temperature of exhaust gas heated by the reaction heat of an oxidation catalyst section disposed in an exhaust pipe of a vehicle; a calculation section that sequentially calculates the degree of heat generation of the oxidation catalyst section based on the temperature detected by the temperature sensor and accumulates the same; and a determination section that determines the state of the oxidation catalyst section based on the accumulated value of the degree of heat generation calculated by the calculation section.

Description

Technical Field

[0001] The present invention relates to a catalyst state detection device. Background Art

[0002] Conventionally, for example, in a vehicle such as a commercial vehicle, an oxidation catalyst section that heats exhaust gas using reaction heat is disposed in an exhaust pipe. Generally, the oxidation catalyst section is disposed upstream of a filter that captures particulate matter contained in the exhaust gas, and the exhaust gas is heated to a high temperature using the reaction heat generated by oxidizing fuel supplied to the exhaust pipe. The exhaust gas heated to a high temperature passes through the filter, so that the particulate matter accumulated in the filter can be burned, and the filter can be regenerated.

[0003] Here, the oxidation catalyst section deteriorates due to poisoning, damage, etc., and therefore, suppression of such deterioration is required.

[0004] Therefore, as a technique for suppressing the deterioration of the oxidation catalyst section, for example, Patent Document 1 discloses a control device for an internal combustion engine that can protect the catalyst of an exhaust gas purification device from deterioration and prevent the deterioration of exhaust gas. This device detects an abnormal state of the exhaust gas temperature inside the catalyst by obtaining the temperature difference between the measured exhaust gas temperature and the measured exhaust gas temperature inside the catalyst of the catalyst device, thereby suppressing the deterioration of the catalyst.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2000-257497. Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] However, the device of Patent Document 1 determines the deterioration of the oxidation catalyst section based on the temperature of the exhaust gas. Since the temperature of the exhaust gas varies for various reasons in addition to the deterioration of the oxidation catalyst section, it is difficult to detect the state of the oxidation catalyst section with high accuracy.

[0010] An object of the present invention is to provide a catalyst state detection device that can detect the state of an oxidation catalyst section with high accuracy.

[0011] Solution to the Problem

[0012] The catalyst state detection device of the present invention includes: a temperature sensor that detects the temperature of exhaust gas heated by the reaction heat of an oxidation catalyst section disposed in an exhaust pipe of a vehicle; a calculation unit that sequentially calculates and accumulates the degree of heat generation of the oxidation catalyst section based on the temperature detected by the temperature sensor; and a determination unit that determines the state of the oxidation catalyst section based on the accumulated value of the degree of heat generation calculated by the calculation unit.

[0013] Advantages of the Invention

[0014] According to the present invention, the state of the oxidation catalyst section can be detected with high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 FIG. is a diagram showing the structure of a vehicle equipped with the catalyst state detection device according to Embodiment 1 of the present invention.

[0016] Figure 2 FIG. is a graph showing changes in the heat conversion efficiency of the oxidation catalyst section.

[0017] Figure 3 FIG. is a graph showing a case where the heat conversion efficiency of the oxidation catalyst section is calculated.

[0018] Figure 4 FIG. is a map showing the heat conversion efficiency of the oxidation catalyst section with respect to the engine speed and load.

[0019] Figure 5 FIG. is a graph showing a case where the cumulative measured value of the heat generation amount of the oxidation catalyst section is calculated in Embodiment 3.

[0020] Figure 6 FIG. is a graph showing a case where the cumulative measured value of the ratio with respect to the target heat generation amount of the oxidation catalyst section is calculated in Embodiment 3. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0022] (Embodiment 1)

[0023] Figure 1 FIG. shows the structure of a vehicle equipped with the catalyst state detection device according to Embodiment 1 of the present invention. The vehicle includes: an internal combustion engine 1, an intake pipe 2, an exhaust pipe 3, an internal combustion engine control unit 4, and a purification device 5. It should be noted that, as the vehicle, for example, a commercial vehicle such as a truck can be cited.

[0024] The internal combustion engine 1 is an engine for driving the vehicle, and is constituted by, for example, a so-called four-stroke engine that repeats four strokes of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. As the internal combustion engine 1, for example, a diesel engine can be cited.

[0025] The intake pipe 2 is a flow path that connects the front end portion thereof to the intake port of the internal combustion engine 1 and supplies the air sucked from the outside to the internal combustion engine 1.

[0026] The exhaust pipe 3 is a flow path that is arranged to extend from the exhaust port of the internal combustion engine 1 to the outside and discharges the exhaust gas discharged from the internal combustion engine 1 to the outside.

[0027] The internal combustion engine control unit 4 controls the internal combustion engine 1 and is respectively connected to the internal combustion engine 1 and the regeneration processing control section of the purification device 5. The internal combustion engine control unit 4 controls, for example, the flow rates of air and exhaust gas flowing through the intake pipe 2 and the exhaust pipe 3, the engine speed, and the fuel injection, etc.

[0028] The purification device 5 includes an oxidation catalyst section 6, a filter 7, a differential pressure sensor 8, a valve 9, an injector 10, a regeneration processing control section 11, and a catalyst state detection device 12.

[0029] The oxidation catalyst section 6 is disposed in the exhaust pipe 3 and purifies unburned fuels such as hydrocarbons and carbon monoxide contained in the exhaust gas by oxidizing them. In addition, the oxidation catalyst section 6 heats the exhaust gas to a high temperature by using the reaction heat generated by oxidizing the fuel supplied from the injector 10. The oxidation catalyst section 6 can be composed of, for example, platinum and cerium oxide, etc.

[0030] The filter 7 is disposed in the exhaust pipe 3 on the downstream side of the oxidation catalyst section 6 and captures particulate matters such as soot components and ash. The filter 7 can be of a so-called wall flow type, which is formed by arranging cells made of porous ceramics such as cordierite and silicon carbide in an alternatingly blocked manner at the inlets and outlets. In addition, the filter 7 is provided to include an oxidation catalyst body, which heats the exhaust gas to a high temperature by using the reaction heat generated by oxidizing the fuel supplied from the injector 10.

[0031] The differential pressure sensor 8 is disposed in the exhaust pipe 3 and detects the pressure difference between the upstream side and the downstream side of the filter 7.

[0032] The valve 9 is a so-called exhaust throttle valve that is connected to the regeneration processing control section 11 and adjusts the opening degree of the exhaust pipe 3 under the control of the regeneration processing control section 11. The valve 9 can be configured, for example, to adjust the opening degree of the exhaust pipe 3 by rotating around a rotation axis orthogonal to the exhaust pipe 3. In addition, the valve 9 can be disposed near the internal combustion engine 1 between the internal combustion engine 1 and the temperature sensor 13a, and specifically can be disposed on the downstream side of a turbocharger (not shown).

[0033] The injector 10 is connected to the regeneration processing control section 11 and injects fuel into the exhaust pipe 3 under the control of the regeneration processing control section 11 to supply fuel to the oxidation catalyst section 6. The injector 10 is disposed in the exhaust pipe 3 on the downstream side of the valve 9.

[0034] The regeneration processing control unit 11 is connected to the internal combustion engine control unit 4, the differential pressure sensor 8, and the temperature sensors 13a to 13c of the catalyst state detection device 12. The regeneration processing control unit 11 determines the timing to start the regeneration processing of the filter 7 based on the pressure difference between the upstream side and the downstream side of the filter 7 input from the differential pressure sensor 8. When it is determined to start the regeneration processing, the regeneration processing control unit 11 controls the injector 10 to inject fuel into the exhaust pipe 3 and causes the oxidation catalyst unit 6 to react to heat the exhaust gas. In addition, the regeneration processing control unit 11 controls the valve 9 to close the exhaust pipe 3, thereby increasing the load of the internal combustion engine 1 and raising the temperature of the exhaust gas. At this time, the regeneration processing control unit 11 controls the regeneration processing of the filter 7 based on the temperature information input from the temperature sensors 13a to 13c.

[0035] The catalyst state detection device 12 includes temperature sensors 13a to 13c, a calculation unit 14, a determination unit 15, a notification unit 16, a communication unit 17, and an information providing unit 18. The temperature sensors 13a to 13c are connected to the determination unit 15 via the calculation unit 14. In addition, the calculation unit 14 is also connected to the regeneration processing control unit 11. Moreover, the determination unit 15 is respectively connected to the notification unit 16 and the communication unit 17, and the communication unit 17 is connected to the information providing unit 18 by wireless communication.

[0036] The temperature sensor 13a is arranged on the upstream side of the oxidation catalyst unit 6 in the exhaust pipe 3, and the temperature sensor 13b is arranged between the oxidation catalyst unit 6 and the filter 7 in the exhaust pipe 3. In addition, the temperature sensor 13c is arranged on the downstream side of the filter 7 in the exhaust pipe 3. The temperature sensors 13a and 13b detect the temperature of the exhaust gas flowing through the oxidation catalyst unit 6 and the temperature of the exhaust gas heated by the reaction heat of the oxidation catalyst unit 6 during the regeneration processing of the filter 7. In addition, the temperature sensor 13c detects the temperature of the exhaust gas flowing through the filter 7 and, when there is no reaction heat due to deterioration of the oxidation catalyst unit 6 or the like, detects the temperature of the exhaust gas heated by the reaction heat of the oxidation catalyst body contained in the filter 7.

[0037] The calculation unit 14 sequentially calculates the heat generation amount of the oxidation catalyst unit 6 based on the temperatures detected by the temperature sensors 13a and 13b. For example, the calculation unit 14 can sequentially calculate the heat generation amount of the oxidation catalyst unit 6 based on the following formula (1). Then, the calculation unit 14 accumulates the heat generation amounts of the oxidation catalyst unit 6 calculated sequentially.

[0038] Heat generation amount = (Difference between the temperature of the temperature sensor 13a and the temperature of the temperature sensor 13b) × Flow rate of exhaust gas × Specific heat of exhaust gas …(1)

[0039] In addition, the calculation unit 14 sequentially calculates the supplied heat of the fuel based on the supply amount of the fuel supplied to the oxidation catalyst unit 6. For example, the calculation unit 14 can calculate the supplied heat of the fuel according to the injection amount of the fuel injected from the injector 10 and the lower calorific value of the fuel. Moreover, the calculation unit 14 accumulates the supplied heat of the fuel calculated sequentially.

[0040] The calculation unit 14 calculates the measured value of the heat conversion efficiency of the oxidation catalyst unit 6 based on the cumulative value of the heat generated by the oxidation catalyst unit 6 and the cumulative value of the supplied heat of the fuel.

[0041] In addition, the calculation unit 14 sequentially calculates the reference value of the heat conversion efficiency of the oxidation catalyst unit 6 corresponding to the running of the vehicle based on the heat conversion efficiency of the oxidation catalyst unit 6 preset for the engine speed and load (fuel flow rate). For example, the calculation unit 14 can pre-create a map showing the heat conversion efficiency of the oxidation catalyst unit 6 for the engine speed and load through simulation or the like, and calculate the reference value of the heat conversion efficiency of the oxidation catalyst unit 6 based on this map. Then, the calculation unit 14 calculates the reference value of the heat conversion efficiency corresponding to the measured value of the heat conversion efficiency by averaging the reference values of the heat conversion efficiency of the oxidation catalyst unit 6 calculated sequentially.

[0042] The determination unit 15 compares the measured value and the reference value of the heat conversion efficiency of the oxidation catalyst unit 6 calculated by the calculation unit 14 to determine the state of the oxidation catalyst unit 6.

[0043] The notification unit 16 notifies the determination result determined by the determination unit 15 to the user of the vehicle. The notification unit 16 can be composed of, for example, a display unit and a speaker.

[0044] The communication unit 17 wirelessly transmits the determination result determined by the determination unit 15 to the information providing unit 18.

[0045] The information providing unit 18 provides the maintenance period of the oxidation catalyst unit 6 to the user of the vehicle based on the determination result transmitted from the communication unit 17. The information providing unit 18 can be set, for example, in a vehicle management company, a vehicle repair shop, a dealership, etc.

[0046] It should be noted that the functions of the internal combustion engine control unit 4, the regeneration process control unit 11, the calculation unit 14, and the determination unit 15 can also be realized by a computer program. For example, a reading device of a computer reads the program recorded on a recording medium having a program for realizing the functions of the internal combustion engine control unit 4, the regeneration process control unit 11, the calculation unit 14, and the determination unit 15, and stores it in a storage device. Then, the CPU copies the program stored in the storage device to the RAM, and sequentially reads and executes the commands included in the program from the RAM, thereby enabling the functions of the internal combustion engine control unit 4, the regeneration process control unit 11, the calculation unit 14, and the determination unit 15 to be realized.

[0047] Next, the operation of this embodiment will be described.

[0048] First, as Figure 1 shown, after the internal combustion engine control unit 4 controls the internal combustion engine 1 to make the vehicle travel, the exhaust gas generated by the internal combustion engine 1 flows through the exhaust pipe 3 and is discharged to the outside. At this time, the exhaust gas passes through the filter 7, so that the particulate matter contained in the exhaust gas is captured by the filter 7.

[0049] In this way, particulate matter accumulates on the filter 7, and as the accumulation amount increases, the pressure difference between the upstream side and the downstream side of the filter 7 rises. Therefore, the differential pressure sensor 8 sequentially detects the pressure difference of the filter 7. Then, the regeneration processing control unit 11 determines the start timing of the regeneration processing for burning and removing the particulate matter accumulated on the filter 7 based on the pressure difference detected by the differential pressure sensor 8.

[0050] After the regeneration processing control unit 11 determines to start the regeneration processing of the filter 7, it controls the injector 10 based on the temperatures detected by the temperature sensors 13a to 13c, so that the injector 10 injects fuel, such as light oil, into the exhaust pipe 3. Thereby, the oxidation catalyst unit 6 oxidizes the fuel injected from the injector 10, and uses the reaction heat to heat the exhaust gas to a high temperature. In addition, the regeneration processing control unit 11 closes the exhaust pipe 3 by controlling the valve 9 to raise the temperature of the exhaust gas. In this way, the exhaust gas heated to a high temperature passes through the filter 7, so that the soot component of the particulate matter accumulated on the filter 7 is burned, and the filter 7 is subjected to the regeneration processing.

[0051] At this time, the temperature sensors 13a and 13b detect the temperature of the exhaust gas heated by the reaction heat of the oxidation catalyst unit 6. Then, the calculation unit 14 sequentially calculates the heat generation amount of the oxidation catalyst unit 6 based on the temperatures detected by the temperature sensors 13a and 13b.

[0052] For example, the calculation unit 14 obtains the temperatures at the inlet and outlet of the oxidation catalyst unit 6 from the temperature sensors 13a and 13b, and obtains the flow rate of the exhaust gas from the internal combustion engine control unit 4 via the regeneration processing control unit 11. In addition, the specific heat of the exhaust gas is preset in the calculation unit 14. The calculation unit 14 can calculate the measured value of the heat generation amount of the oxidation catalyst unit 6 according to the above formula (1) based on the obtained temperatures at the inlet and outlet of the oxidation catalyst unit 6, the flow rate of the exhaust gas, and the specific heat of the exhaust gas.

[0053] In addition, the calculation unit 14 sequentially calculates the supply heat of the fuel based on the supply amount of the fuel supplied to the oxidation catalyst unit 6. For example, the calculation unit 14 can obtain the injection amount of the fuel injected from the injector 10 from the regeneration processing control unit 11, and calculate the supply heat of the fuel based on the injection amount of the fuel.

[0054] Thus, the heat generation amount of the oxidation catalyst section 6 and the supplied heat amount of the fuel can be used to calculate the heat conversion efficiency of the oxidation catalyst section 6 according to the following formula (2). Moreover, based on the calculated heat conversion efficiency, the state of the oxidation catalyst section 6, such as deterioration, can be determined.

[0055] Heat conversion efficiency = Heat generation amount of oxidation catalyst section 6 ÷ Supplied heat amount of fuel... (2)

[0056] However, as Figure 2 shown, the heat conversion efficiency varies greatly corresponding to the flow rate of the exhaust gas, etc. Therefore, even if the heat conversion efficiency for a specified time is calculated, it may not be possible to accurately determine the state of the oxidation catalyst section 6 based on this heat conversion efficiency.

[0057] Therefore, the calculation unit 14 accumulates the heat generation amount of the oxidation catalyst section 6 and the supplied heat amount of the fuel calculated successively. Then, the calculation unit 14 calculates the measured value of the heat conversion efficiency of the oxidation catalyst section 6 according to the above formula (2) based on the accumulated value of the heat generation amount of the oxidation catalyst section 6 and the accumulated value of the supplied heat amount of the fuel.

[0058] For example, as Figure 3 shown, the calculation unit 14 successively accumulates and plots the heat generation amount of the oxidation catalyst section 6 with respect to the supplied heat amount of the fuel supplied to the oxidation catalyst section 6, and the heat conversion efficiency of the oxidation catalyst section 6 can be calculated based on the slopes of these multiple curves. That is, the closer the slope is to 1, the higher the heat conversion efficiency of the oxidation catalyst section 6, and the closer the slope is to zero, the lower the heat conversion efficiency of the oxidation catalyst section 6.

[0059] In this way, the calculation unit 14 calculates the measured value of the heat conversion efficiency of the oxidation catalyst section 6 based on the accumulated value of the heat generation amount of the oxidation catalyst section 6 and the accumulated value of the supplied heat amount of the fuel. Therefore, it is possible to suppress the situation where the calculated heat conversion efficiency varies corresponding to the flow rate of the exhaust gas, and the heat conversion efficiency can be accurately calculated.

[0060] In this way, the calculation unit 14 calculates the measured value of the heat conversion efficiency of the oxidation catalyst section 6 during the period when a specified amount of fuel is supplied to the oxidation catalyst section 6, for example, during the period of performing the regeneration process of the filter 7, each time the regeneration process is performed.

[0061] It should be noted that the calculation unit 14 does not need to accumulate all of the heat generation amount of the oxidation catalyst section 6 and the supplied heat amount of the fuel calculated successively, and it is also possible to accumulate the heat generation amount of the oxidation catalyst section 6 and the supplied heat amount of the fuel at a specified interval, for example.

[0062] On the other hand, the calculation unit 14 sequentially calculates a reference value of the heat conversion efficiency corresponding to the vehicle's driving based on the heat conversion efficiency of the oxidation catalyst unit 6 preset for the engine speed and load. For example, as Figure 4 shown, a map representing the heat conversion efficiency of the oxidation catalyst unit 6 for the engine speed and load is preset in the calculation unit 14. For example, this map can be set based on the already deteriorated oxidation catalyst unit 6. That is, the map can be set based on the oxidation catalyst unit 6 in which the generated heat has dropped to a specified value, for example, the lower limit value of the range where the generated heat can burn the particulate matter of the filter 7, and the darker the color, the lower the heat conversion efficiency. The calculation unit 14 obtains the engine speed and load from the internal combustion engine control unit 4 via the regeneration processing control unit 11, and sequentially calculates the reference value of the heat conversion efficiency according to the map based on the obtained engine speed and load. Then, the calculation unit 14 averages the calculated reference values of the multiple heat conversion efficiencies, and calculates the reference value of the heat conversion efficiency corresponding to the measured value of the heat conversion efficiency.

[0063] In this way, the calculation unit 14 sequentially calculates the reference value of the heat conversion efficiency based on the engine speed and load that vary corresponding to the vehicle's driving, rather than based on the reference values that are all preset in advance. Therefore, it is possible to calculate the reference value that corresponds to the measured value of the heat conversion efficiency with high precision.

[0064] The calculation unit 14 outputs the measured value and the reference value of the calculated heat conversion efficiency to the determination unit 15.

[0065] Next, the determination unit 15 compares the measured value and the reference value of the heat conversion efficiency output from the calculation unit 14 to determine the state of the oxidation catalyst unit 6. For example, when the measured value of the heat conversion efficiency is higher than the reference value, the determination unit 15 determines that the oxidation catalyst unit 6 is normal, and when the measured value of the heat conversion efficiency is lower than the reference value, it determines that the oxidation catalyst unit 6 is abnormal and requires maintenance.

[0066] In this way, since the calculation unit 14 calculates the measured value of the heat conversion efficiency of the oxidation catalyst unit 6 based on the cumulative value of the generated heat of the oxidation catalyst unit 6 and the cumulative value of the supplied heat of the fuel, the determination unit 15 can accurately determine the state of the oxidation catalyst unit 6.

[0067] In addition, since the calculation unit 14 calculates the reference value that corresponds to the measured value of the heat conversion efficiency of the oxidation catalyst unit 6 with high precision, the determination unit 15 can accurately determine the state of the oxidation catalyst unit 6.

[0068] In addition, since the determination unit 15 makes a determination based on the measured value and the reference value of the heat conversion efficiency that suppresses the variation corresponding to the exhaust gas flow rate, it is possible to accurately determine the state of the oxidation catalyst unit 6 while the vehicle is running.

[0069] Next, the determination unit 15 outputs the determination result to the notification unit 16 and outputs it to the information providing unit 18 via the communication unit 17. Then, based on the determination result of the determination unit 15, the notification unit 16 notifies the vehicle user by displaying the maintenance period of the oxidation catalyst unit 6 and the like. In addition, based on the determination result of the determination unit 15, the information providing unit 18 associates the maintenance period of the oxidation catalyst unit 6 and provides it to the vehicle user.

[0070] In this way, by providing the maintenance period of the oxidation catalyst unit 6, the vehicle user can efficiently perform maintenance such as replacement of the oxidation catalyst unit 6.

[0071] Moreover, when the temperature detected by the temperature sensors 13a and 13b does not rise to a specified temperature even though the regeneration process of the filter 7 has started, the determination unit 15 can determine whether the cause is an abnormality in the oxidation catalyst unit 6 or an abnormality in the injector 10.

[0072] Specifically, when the temperature detected by the temperature sensor 13b does not rise from the starting temperature and the temperature detected by the temperature sensor 13c rises from the starting temperature, the determination unit 15 determines that the fuel supplied from the injector 10 has reacted in the oxidation catalyst body of the filter 7. Therefore, the determination unit 15 determines that the drive of the injector 10 is normal and the oxidation catalyst unit 6 is abnormal, for example, deterioration of the oxidation catalyst unit 6 and blockage of the front surface have occurred.

[0073] In addition, when the temperatures detected by the temperature sensors 13b and 13c do not rise from the starting temperature, the determination unit 15 determines that there is an abnormality in the injector 10, for example, a specified amount of fuel is not supplied from the injector 10.

[0074] In this way, the determination unit 15 determines the states of the oxidation catalyst unit 6 and the injector 10 based on the temperatures detected by the temperature sensors 13b and 13c. Therefore, when an abnormality occurs during the regeneration process of the filter 7, the cause can be accurately determined.

[0075] According to the present embodiment, the calculation unit 14 calculates the measured value of the heat conversion efficiency of the oxidation catalyst unit 6 based on the cumulative value of the heat generated by the oxidation catalyst unit 6 and the cumulative value of the heat supplied by the fuel. Therefore, the state of the oxidation catalyst unit 6 can be detected with high precision.

[0076] (Embodiment 2)

[0077] Next, Embodiment 2 of the present invention will be described. Here, the description will focus on the differences from the above-described Embodiment 1. For the same points as those in the above-described Embodiment 1, the same reference numerals will be used and their detailed description will be omitted.

[0078] In the above-described Embodiment 1, the calculation unit 14 calculated the reference value of the heat conversion efficiency of the oxidation catalyst unit 6 based on the heat conversion efficiency of the oxidation catalyst unit 6 preset for the engine speed and load. However, it is not limited thereto.

[0079] For example, the calculation unit 14 may calculate the reference value of the heat generation amount of the oxidation catalyst unit 6 based on the reference temperature obtained by subtracting the preset temperature from the temperature detected by the temperature sensor 13b when the vehicle is in a specified driving state. It should be noted that for the specified driving state, for example, it can be determined based on the engine speed and load, that is, it can be determined based on the factors that affect the exhaust gas flow rate and the temperature of the oxidation catalyst unit 6.

[0080] Specifically, when the vehicle is in a specified driving state, the calculation unit 14 obtains the temperatures at the inlet and outlet of the oxidation catalyst unit 6 from the temperature sensors 13a and 13b. At this time, preferably, when the vehicle shows an average driving state, the calculation unit 14 obtains the temperature at the outlet of the oxidation catalyst unit 6. For example, the calculation unit 14 can calculate the average driving state at the initial stage when the vehicle is used, and obtain the temperature at the outlet of the oxidation catalyst unit 6 when the vehicle is in a driving state. In addition, preferably, when the average driving state of the vehicle changes, the calculation unit 14 calculates the average driving state again and obtains the temperature at the outlet of the oxidation catalyst unit 6.

[0081] Then, the calculation unit 14 sequentially calculates the reference temperature obtained by subtracting the preset temperature from the temperature at the outlet of the oxidation catalyst unit 6 obtained from the temperature sensor 13b when the vehicle is in a specified driving state. At this time, for the set temperature, for example, it can be set based on the lower limit value of the activation temperature of the oxidation catalyst unit 6.

[0082] In addition, the calculation unit 14 obtains the exhaust gas flow rate from the internal combustion engine control unit 4 via the regeneration process control unit 11, and the specific heat of the exhaust gas is preset.

[0083] Next, the calculation unit 14 sequentially calculates and accumulates the reference value of the heat generation amount of the oxidation catalyst unit 6 based on the difference between the temperature at the inlet of the oxidation catalyst unit 6 and the reference temperature, the exhaust gas flow rate, and the specific heat of the exhaust gas according to the above formula (1).

[0084] In addition, the calculation unit 14 sequentially calculates and accumulates the supply heat of the fuel supplied to the oxidation catalyst unit 6 when the vehicle is in a specified driving state.

[0085] Next, the calculation unit 14 calculates a reference value of the heat conversion efficiency of the oxidation catalyst unit 6 in a specified driving state based on the cumulative value of the heat generated by the oxidation catalyst unit 6 and the cumulative value of the supplied heat of the fuel. In this way, the calculation unit 14 can calculate a reference value of the heat conversion efficiency corresponding to the driving state of the vehicle, that is, the driving manner and usage mode of the vehicle, etc.

[0086] Then, in the same manner as in the first embodiment, the determination unit 15 compares the measured value and the reference value of the heat conversion efficiency calculated by the calculation unit 14 to determine the state of the oxidation catalyst unit 6.

[0087] According to this embodiment, the calculation unit 14 sequentially calculates and accumulates the reference value of the heat generated by the oxidation catalyst unit 6 based on the reference temperature obtained by subtracting the preset temperature from the temperature detected by the temperature sensor 13b when the vehicle is in a specified driving state. Thereby, a reference value of the heat conversion efficiency corresponding to the driving state of the vehicle can be calculated, and the determination unit 15 can determine the state of the oxidation catalyst unit 6 with higher accuracy.

[0088] (Embodiment 3)

[0089] Next, Embodiment 3 of the present invention will be described. Here, the description will focus on the differences from the above-described Embodiments 1 and 2, and for the same points as those in the above-described Embodiments 1 and 2, the same reference numerals will be used and their detailed descriptions will be omitted.

[0090] In the above-described Embodiments 1 and 2, the calculation unit 14 calculates the measured value of the heat conversion efficiency of the oxidation catalyst unit 6 by respectively accumulating the heat generated by the oxidation catalyst unit 6 and the supplied amount of fuel. However, this is not limited thereto, as long as the state of the oxidation catalyst unit 6 can be determined based on the cumulative value obtained by accumulating the degree of heat generation of the oxidation catalyst unit.

[0091] For example, the calculation unit 14 can sequentially calculate and accumulate the heat generated by the oxidation catalyst unit 6 based on the temperatures detected by the temperature sensors 13a and 13b.

[0092] Specifically, in the same manner as in the first embodiment, the calculation unit 14 obtains the temperatures at the inlet and outlet of the oxidation catalyst unit 6 from the temperature sensors 13a and 13b, and obtains the flow rate of the exhaust gas from the internal combustion engine control unit 4 via the regeneration process control unit 11. In addition, the specific heat of the exhaust gas is preset in the calculation unit 14. The calculation unit 14 sequentially calculates the measured value of the heat generated by the oxidation catalyst unit 6 according to the above formula (1) based on the obtained temperatures at the inlet and outlet of the oxidation catalyst unit 6, the flow rate of the exhaust gas, and the specific heat of the exhaust gas.

[0093] Then, the calculation unit 14 is as Figure 5As shown, the measured values of the heat generation of the oxidation catalyst unit 6 calculated in sequence are accumulated to calculate the cumulative measured value V1a of the heat generation.

[0094] In this way, the calculation unit 14 calculates the cumulative measured value V1a of the heat generation of the oxidation catalyst unit 6. Therefore, it is possible to suppress the case where the calculated cumulative measured value V1a varies corresponding to the flow rate of the exhaust gas, and the heat generation can be accurately calculated.

[0095] On the other hand, the calculation unit 14 sequentially calculates and accumulates the reference value of the heat generation of the oxidation catalyst unit 6 corresponding to the running of the vehicle based on a preset temperature. For example, the calculation unit 14 can set the set temperature to the lower limit value of the target temperature range of the exhaust gas heated due to the reaction heat of the oxidation catalyst unit 6, that is, the lower limit value of the target temperature range of the exhaust gas required for the combustion of the particulate matter accumulated in the filter 7. The lower limit value of this target temperature range can be sequentially calculated, for example, according to the heating-up mapping diagram preset based on the temperature change of the exhaust gas caused by the reaction heat of the oxidation catalyst unit 6.

[0096] Then, the calculation unit 14 sequentially calculates the reference value of the heat generation of the oxidation catalyst unit 6 according to the above formula (1) based on the difference between the temperature at the inlet of the oxidation catalyst unit 6 and the set temperature, the flow rate of the exhaust gas, and the specific heat of the exhaust gas.

[0097] In this way, the calculation unit 14 calculates the reference value of the heat generation of the oxidation catalyst unit 6 based on the engine speed and load that vary corresponding to the running of the vehicle, rather than based on the reference values all preset in advance. Therefore, it is possible to calculate a reference value that corresponds to the measured value of the heat generation with high accuracy.

[0098] The calculation unit 14 accumulates the reference values of the heat generation of the oxidation catalyst unit 6 calculated in sequence to calculate the cumulative reference value V2a of the heat generation.

[0099] Next, the determination unit 15 determines the state of the oxidation catalyst unit 6 based on the cumulative measured value V1a and the cumulative reference value V2a of the heat generation of the oxidation catalyst unit 6 calculated by the calculation unit 14. That is, when the cumulative measured value V1a of the heat generation is higher than the cumulative reference value V2a, the determination unit 15 determines that the oxidation catalyst unit 6 is normal, and when the cumulative measured value V1a of the heat generation is lower than the cumulative reference value V2a, it is determined that the oxidation catalyst unit 6 is abnormal and maintenance is required.

[0100] It should be noted that, in the present embodiment, the calculation unit 14 can calculate the target value of the heat generation amount of the oxidation catalyst unit 6, and calculate the ratio of the measured value of the heat generation amount to the target value. Specifically, the calculation unit 14 obtains the target temperature of the exhaust gas heated by the reaction heat of the oxidation catalyst unit 6 from the regeneration treatment control unit 11, and based on the difference between the temperature at the inlet of the oxidation catalyst unit 6 and the target temperature, the flow rate of the exhaust gas, and the specific heat of the exhaust gas, sequentially calculates the target value of the heat generation amount of the oxidation catalyst unit 6 according to the above formula (1). The calculated target value of the heat generation amount of the oxidation catalyst unit 6 is used as the target heat generation amount.

[0101] As Figure 6 shown, the calculation unit 14 sequentially calculates the ratio of the measured value of the heat generation amount of the oxidation catalyst unit 6 to the target heat generation amount of the oxidation catalyst unit 6, and accumulates this ratio to calculate the cumulative measured value V1b.

[0102] Similarly, the calculation unit 14 sequentially calculates the ratio of the reference value of the heat generation amount of the oxidation catalyst unit 6 to the target heat generation amount of the oxidation catalyst unit 6, and accumulates this ratio to calculate the cumulative reference value V2b.

[0103] In this way, since the calculation unit 14 calculates the ratio with respect to the target heat generation amount of the oxidation catalyst unit 6, the determination unit 15 can more accurately determine the state of the oxidation catalyst unit 6.

[0104] According to the present embodiment, the calculation unit 14 sequentially calculates and accumulates the heat generation amount of the oxidation catalyst unit 6 based on the temperatures detected by the temperature sensors 13a and 13b. Therefore, the determination unit 15 can accurately determine the state of the oxidation catalyst unit 6 based on the calculated cumulative value of the heat generation amount.

[0105] It should be noted that, in the above-described Embodiments 1 to 3, the oxidation catalyst unit 6 is used in the regeneration treatment of the filter 7, but it is not limited thereto, as long as the exhaust gas can be heated to a high temperature using the reaction heat.

[0106] In addition, in the above-described Embodiments 1 to 3, the calculation unit 14 and the determination unit 15 are arranged in the vehicle. However, they can also be arranged externally and send and receive information through a communication line.

[0107] In addition, in the above-described Embodiments 1 to 3, the regeneration treatment control unit controls the injector 10 arranged in the exhaust pipe 3 to heat the exhaust gas to a high temperature. However, it is not limited to being arranged in the exhaust pipe 3, as long as the exhaust gas can be heated to a high temperature using the reaction heat of the oxidation catalyst unit 6.

[0108] For example, the regeneration treatment control unit can perform multi-stage injection control of the injector arranged in the internal combustion engine 1 to cause the oxidation catalyst unit 6 to react.

[0109] It should be noted that the above-described embodiments are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be limited by these embodiments. That is, the present invention can be implemented in various forms without departing from its gist or its main features. For example, the disclosure of the shape, number, etc. of each part described in the above embodiments is only an example, and appropriate changes can be made before implementation.

[0110] This application is based on Japanese Patent Application No. 2020-094330 filed on May 29, 2020, the content of which is incorporated herein by reference.

[0111] Industrial Applicability

[0112] The catalyst state detection device of the present invention can be used in a device in which an oxidation catalyst unit that heats exhaust gas to a high temperature using reaction heat is disposed in an exhaust pipe.

[0113] Explanation of Reference Numerals

[0114] 1 Internal combustion engine

[0115] 2 Intake pipe

[0116] 3 Exhaust pipe

[0117] 4 Internal combustion engine control unit

[0118] 5 Purification device

[0119] 6 Oxidation catalyst unit

[0120] 7 Filter

[0121] 8 Differential pressure sensor

[0122] 9 Valve

[0123] 10 Injector

[0124] 11 Regeneration process control unit

[0125] 12 Catalyst state detection device

[0126] 13a, 13b, 13c Temperature sensor

[0127] 14 Calculation unit

[0128] 15 Judgment unit

[0129] 16 Notification unit

[0130] 17 Communication unit

[0131] 18 Information providing unit

[0132] V1a, V1b Cumulative measured value

[0133] Cumulative reference value of V2a and V2b

Claims

1. A catalyst state detection device, comprising: A temperature sensor that detects the temperature of exhaust gas heated by the reaction heat of an oxidation catalyst portion disposed in an exhaust pipe of a vehicle; A calculation unit that sequentially calculates and accumulates the degree of heat generation of the oxidation catalyst portion based on the temperature detected by the temperature sensor; and A determination unit that determines the state of the oxidation catalyst portion based on the cumulative value of the degree of heat generation calculated by the calculation unit, The calculation unit sequentially calculates and accumulates the heat generation amount of the oxidation catalyst portion based on the temperature detected by the temperature sensor, and sequentially calculates and accumulates the supplied heat amount of the fuel supplied to the oxidation catalyst portion based on the supply amount of the fuel. Based on the cumulative value of the heat generation amount and the cumulative value of the supplied heat amount, the measured value of the heat conversion efficiency of the oxidation catalyst portion is calculated. Further, the calculation unit calculates a reference value of the heat conversion efficiency of the oxidation catalyst portion, which is a value obtained by sequentially calculating the heat conversion efficiency of the oxidation catalyst portion corresponding to the running of the vehicle based on the heat conversion efficiency of the oxidation catalyst portion preset for the engine speed and load and averaging them. The determination unit compares the measured value and the reference value of the heat conversion efficiency of the oxidation catalyst portion calculated by the calculation unit to determine the state of the oxidation catalyst portion.

2. The catalyst state detection device according to claim 1, wherein the temperature sensor is a first temperature sensor, the catalyst state detection device further includes a second temperature sensor that detects the temperature of exhaust gas heated by the reaction heat of an oxidation catalyst body contained in a filter disposed on the downstream side of the oxidation catalyst portion, the determination unit determines the states of the oxidation catalyst portion and an injector that supplies fuel to the oxidation catalyst portion based on the temperatures detected by the first temperature sensor and the second temperature sensor respectively.

3. The catalyst state detection device according to claim 1, wherein it further includes: A communication unit that wirelessly transmits the determination result determined by the determination unit; and An information providing unit that provides the maintenance period of the oxidation catalyst portion to the user of the vehicle based on the determination result transmitted from the communication unit.

4. A catalyst state detection device, comprising: A temperature sensor that detects the temperature of exhaust gas heated by the reaction heat of an oxidation catalyst portion disposed in an exhaust pipe of a vehicle; A calculation unit that sequentially calculates and accumulates the degree of heat generation of the oxidation catalyst portion based on the temperature detected by the temperature sensor; and A determination unit that determines the state of the oxidation catalyst portion based on the cumulative value of the degree of heat generation calculated by the calculation unit, The calculation unit sequentially calculates and accumulates the heat generation amount of the oxidation catalyst unit based on the temperature detected by the temperature sensor, and sequentially calculates and accumulates the supplied heat amount of the fuel supplied to the oxidation catalyst unit. Based on the accumulated value of the heat generation amount and the accumulated value of the supplied heat amount, the calculation unit calculates the measured value of the heat conversion efficiency of the oxidation catalyst unit. Further, the calculation unit sequentially calculates and accumulates the reference value of the heat generation amount of the oxidation catalyst unit based on a reference temperature, and calculates the reference value of the heat conversion efficiency of the oxidation catalyst unit based on the accumulated value of the reference value of the heat generation amount and the accumulated value of the supplied heat amount. The reference temperature is obtained by subtracting a preset temperature from the temperature detected by the temperature sensor when the vehicle is in a specified driving state. The determination unit compares the measured value and the reference value of the heat conversion efficiency of the oxidation catalyst unit calculated by the calculation unit, thereby determining the state of the oxidation catalyst unit.

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