Control device for vehicle

Abstract

To provide a control device for a vehicle capable of determining an oxidation degradation abnormality and a crack abnormality in an electric heating type catalyst.SOLUTION: A control device 40 for a vehicle 1 having an electric heating type catalyst 20 calculates a resistance rise amount due to oxidation degradation of the electric heating type catalyst 20 on the basis of temperature history information of the electric heating type catalyst 20. The control device 40 determines an oxidation degradation abnormality by using the resistance rise amount due to the oxidation degradation. The control device 40 calculates a resistance rise amount due to a crack of the electric heating type catalyst 20 by subtracting the resistance rise amount due to the oxidation degradation from a total resistance rise amount of the electric heating type catalyst 20. The control device 40 determines a crack abnormality by using the resistance rise amount due to the crack.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device. [Background technology]

[0002] Vehicles equipped with an electrically heated catalyst (EHC) that purifies exhaust gas from an internal combustion engine are known. The EHC generates heat when electricity is applied. If an abnormality occurs in such an EHC, the resistance of the EHC increases, which may result in a decrease in the EHC's temperature rise performance. Patent Document 1 discloses an example of determining an abnormality in such an EHC by comparing a target amount of electricity applied with an actual amount of electricity applied. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-115005 Summary of the Invention [Problem to be solved by the invention]

[0004] Examples of abnormalities that cause an increase in the resistance of an EHC include oxidation degradation abnormalities, in which an oxide film forms on the EHC, and crack abnormalities, in which cracks form in the EHC. The method disclosed in Patent Document 1 may not be able to determine the nature of the abnormality occurring in the EHC. [Means for solving the problem]

[0005] A vehicle control device for solving the above problem is a control device for a vehicle equipped with an electrically heated catalyst, which calculates the amount of resistance increase due to oxidative degradation of the electrically heated catalyst based on temperature history information of the electrically heated catalyst, determines an oxidative degradation abnormality using the amount of resistance increase due to oxidative degradation, calculates the amount of resistance increase due to cracks in the electrically heated catalyst by subtracting the amount of resistance increase due to oxidative degradation from the total resistance increase of the electrically heated catalyst, and determines a crack abnormality using the amount of resistance increase due to cracks. [Effects of the Invention]

[0006] According to the above configuration, the amount of resistance increase due to oxidation degradation of the EHC and the amount of resistance increase due to cracks in the EHC are calculated. The amount of resistance increase due to oxidation degradation is used to determine an oxidation degradation abnormality, and the amount of resistance increase due to cracks is used to determine a crack abnormality, so that it is possible to determine an oxidation degradation abnormality and a crack abnormality in the EHC. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram illustrating a configuration of an embodiment of a vehicle control device; [Figure 2] 4 is a graph showing the relationship between bed temperature and resistance of an electrically heated catalyst of one embodiment. [Figure 3] 4 is a flowchart illustrating a procedure of a process executed by a control device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a vehicle control device will be described below with reference to FIGS. 1 to 3. FIG. <Vehicle Overview> Referring to Fig. 1, a vehicle 1 includes an engine 10, an electrically heated catalyst (EHC) 20, a power supply device 30, and a control device 40.

[0009] The engine 10 is an internal combustion engine having a plurality of cylinders 11. The engine 10 has a spark plug for igniting the mixed gas in each cylinder 11. The engine 10 drives the drive wheels of the vehicle 1 by igniting and burning the mixed gas in the plurality of cylinders 11. An exhaust pipe 12 is connected to the engine 10, and exhausts burned gas produced by combustion in the cylinders 11 of the engine 10.

[0010] The EHC 20 is disposed midway through the exhaust pipe 12. The EHC 20 has a catalyst carrier 21 that purifies the exhaust gas, and a case 22 that houses the catalyst carrier 21. The catalyst carrier 21 has a honeycomb structure. The case 22 is disposed midway through the exhaust pipe 12. The exhaust gas passing through the case 22 is purified by passing through the catalyst carrier 21.

[0011] The power supply device 30 supplies power to the EHC 20 by applying a voltage to an electrode 32 connected to the catalyst carrier 21 using power supplied from a battery 31. The electrode 32 is provided in the case 22.

[0012] The catalyst carrier 21 is made of a material whose resistance increases as the bed temperature of the EHC 20, which is the temperature of the catalyst carrier 21, decreases. The catalyst carrier 21 becomes resistant and generates heat when electricity is applied to the EHC 20. Because the catalyst carrier 21 generates heat by supplying electricity to the EHC 20 prior to starting the engine 10, exhaust emissions can be reduced when the engine 10 is started and immediately after it is started.

[0013] Power supply device 30 controls the voltage applied to EHC 20 so that the actual power of EHC 20 becomes the command power for a predetermined period of time. Power supply device 30 is provided with a current sensor 33 that detects the current flowing through EHC 20 and a voltage sensor 34 that detects the voltage applied to EHC 20. Power supply device 30 measures the actual power of EHC 20 from the outputs of current sensor 33 and voltage sensor 34 and performs PID control. Here, the applied voltage has an upper limit voltage depending on the performance of power supply device 30, so if the resistance of EHC 20 is high, the actual power will be smaller than the command power.

[0014] The control device 40 controls the power supply to the EHC 20 by instructing the power supply device 30 to specify the specified power. The control device 40 has a memory for storing programs and a CPU for executing the programs. A bed temperature sensor 41 for detecting the bed temperature of the EHC 20 is provided in the case 22 of the EHC 20. The control device 40 acquires the bed temperature from the bed temperature sensor 41 and instructs the power supply device 30 to specify the specified power based on the bed temperature. Note that because the bed temperature of the EHC 20 tends to be proportional to the actual amount of power, the bed temperature can also be estimated from the outputs of the current sensor 33 and the voltage sensor 34. When the bed temperature of the EHC 20 reaches the target temperature, the control device 40 terminates the power supply to the EHC 20.

[0015] <Conventional abnormality detection> FIG. 2 shows an example in which the resistance of the EHC 20 increases from the initial resistance Rini (solid line) when the EHC 20 is new to resistance R (two-dot chain line). Examples of EHC 20 abnormalities that cause this increase in resistance include oxidation degradation, in which an oxide film forms on the EHC 20, and cracking, in which cracks form on the EHC 20. In oxidation degradation, the EHC 20 becomes hot due to power supply, exhaust, etc., causing the silicon contained in the catalyst carrier 21 to oxidize, resulting in the formation of an oxide film on the catalyst carrier 21. In cracking, cracks occur in the catalyst carrier 21 due to thermal stress caused by the temperature distribution in the catalyst carrier 21 due to exhaust. In FIG. 2, the resistance increase ΔRox due to oxidation degradation corresponds to the difference from the solid line to the one-dot chain line, and the resistance increase ΔRck due to cracking corresponds to the difference from the one-dot chain line to the two-dot chain line. Note that the resistance increase ΔRox tends to increase as the bed temperature of the EHC 20 decreases. The resistance increase amount ΔRck tends to increase in inverse proportion to the reduction in the cross-sectional area of ​​the catalyst carrier 21 due to cracks.

[0016] As the resistance of the EHC 20 increases, the actual amount of power actually supplied to the EHC 20 decreases from the indicated amount of power. Conventional abnormality determination methods determine an abnormality in the EHC 20 when the rate at which the actual amount of power supplied to the EHC 20 reaches the indicated amount of power after a predetermined period of time has elapsed since the start of power supply is below a predetermined value. However, when the bed temperature is low, the decrease in the actual amount of power due to the resistance increase ΔRck caused by cracks tends to be smaller than the decrease in the actual amount of power due to the resistance increase ΔRox caused by oxidation degradation. Therefore, in the case of a crack abnormality, the difference between the indicated amount of power and the actual amount of power is not large enough to allow for a determination over a short period of time. On the other hand, in the case of an oxidation degradation abnormality, a large difference between the indicated amount of power and the actual amount of power occurs over a short period of time. Therefore, if a predetermined value that can determine an oxidation degradation abnormality is set, the crack abnormality will be overlooked. In other words, performing a determination over a short period of time when the bed temperature is low is likely to result in an erroneous determination. If the predetermined period is extended to avoid this erroneous determination so that the deviation between the indicated amount of electric power and the actual amount of electric power becomes large enough even in the case of a crack abnormality, the determination itself may not be possible because the engine 10 starts to start while power is being supplied to the EHC 20. In other words, the opportunity to determine the abnormality is lost.

[0017] <Determining oxidation deterioration abnormalities using a control device> The control device 40 calculates the resistance increase amount ΔRox of the EHC 20 due to oxidation degradation, based on the temperature history information of the EHC 20, assuming that the higher the temperature, the more rapidly the resistance increase due to oxidation. The temperature history information is information regarding the length of time the EHC 20 was exposed to a certain bed temperature. The upper right of FIG. 2 shows a graph indicating the resistance increase rate relative to the time the EHC 20 was exposed to each bed temperature, for calculating the resistance increase amount ΔRox. The example graph in the upper right of FIG. 2 indicates that when the EHC 20 was exposed to 700°C for 80 hours, the resistance increase rate relative to the initial resistance Rini was 1.1 times. The example graph in the upper right of FIG. 2 indicates that when the EHC 20 was exposed to 900°C for 130 hours, the resistance increase rate relative to the initial resistance Rini was 1.4 times. The example graph in the upper right of FIG. 2 indicates that when the EHC 20 was exposed to 1100°C for 150 hours, the resistance increase rate relative to the initial resistance Rini was 2.2 times.

[0018] When the temperature history of EHC20 indicates that it has been exposed to 700°C for 80 hours, 900°C for 130 hours, and 1100°C for 150 hours, the resistance increase amount ΔRox can be calculated by the following formula 1. T (t) is a parameter corresponding to the resistance increase rate in the upper right of Figure 2, and indicates the resistance increase rate when exposed to a bed temperature of T°C for t hours.

[0019]

number

[0020] The control device 40 determines whether an oxidation degradation abnormality has occurred using the resistance increase amount ΔRox. If the resistance increase amount ΔRox is equal to or greater than a first predetermined value, the control device 40 determines that an oxidation degradation abnormality has occurred in the EHC 20 because the resistance has increased due to an oxide film. The first predetermined value is set for each bed temperature, and a value corresponding to the bed temperature at the time of calculating the resistance increase amount ΔRox is selected.

[0021] <Crack abnormality detection by control device> The control device 40 calculates the total resistance increase ΔR of the EHC 20. The total resistance increase ΔR is calculated by subtracting the initial resistance Rini of the EHC 20 at the bed temperature at the time of calculation from the resistance R of the EHC 20. The resistance R of the EHC 20 can be calculated from the power detected by the current sensor 33 and the voltage detected by the voltage sensor 34. Instead of the current sensor 33 and the voltage sensor 34, a resistance meter that can directly measure the resistance R of the EHC 20 may be provided in the power supply device 30.

[0022] The control device 40 calculates the resistance increase amount ΔRck due to cracks in the EHC 20 by subtracting the resistance increase amount ΔRox due to oxidative degradation from the total resistance increase amount ΔR of the EHC 20. The control device 40 determines whether a crack has occurred using the resistance increase amount ΔRck due to the crack. If the resistance increase amount ΔRck is equal to or greater than a second predetermined value, the control device 40 determines that a crack has occurred in the EHC 20 because the resistance has increased due to a crack. The second predetermined value is set for each bed temperature, and a value corresponding to the bed temperature at the time of calculating the resistance increase amount ΔRck is selected.

[0023] <Control device operation flow> The processing by the control device 40 will be described with reference to FIG. 3. When the processing of FIG. 3 is started, if the EHC 20 is new (S10: YES), the control device 40 acquires the initial resistance Rini of the EHC 20 (S11) and ends the processing of FIG. 3. If the EHC 20 is not new (S10: NO), the control device 40 acquires temperature history information of the EHC 20 (S12) and calculates the amount of resistance increase ΔRox due to oxidative degradation (S13). If the amount of resistance increase ΔRox is equal to or greater than a first predetermined value (S14: YES), the control device 40 determines that oxidative degradation is abnormal (S15). If the amount of resistance increase ΔRox is less than the first predetermined value (S14: NO), the control device 40 determines that oxidative degradation is normal (S16). The control device 40 waits until power supply to the EHC 20 starts (S17: NO), and when power supply starts (S17: YES), it calculates the total amount of resistance increase ΔR of the EHC 20 (S18). The control device 40 calculates the resistance increase amount ΔRck due to cracks by subtracting the resistance increase amount ΔRox due to oxidative degradation from the total resistance increase amount ΔR (S19). If the resistance increase amount ΔRck is equal to or greater than a second predetermined value (S20: YES), the control device 40 determines that a crack is abnormal (S21) and ends the processing of Fig. 3. If the resistance increase amount ΔRck is smaller than the second predetermined value (S20: NO), the control device 40 determines that a crack is normal (S22) and ends the processing of Fig. 3.

[0024] <Other abnormality detection> An oxidation degradation abnormality may be determined by comparing the power amount that takes into account only oxidation degradation with the indicated power amount. The resistance Rox that takes into account only oxidation degradation can be calculated by adding the resistance increase ΔRox to the initial resistance Rini, and the voltage that takes into account only oxidation degradation can be calculated using this resistance Rox and the indicated power. The power that takes into account only oxidation degradation can be calculated from the resistance Rox that takes into account only oxidation degradation and the voltage that takes into account only oxidation degradation. The power that takes into account only oxidation degradation can be calculated by integrating this power that takes into account only oxidation degradation over time. If the power amount that takes into account only oxidation degradation is significantly lower than the indicated power amount, it can be determined that there is an oxidation degradation abnormality in the EHC20.

[0025] In addition to the amount of power that takes into account only oxidative degradation, the amount of resistance increase ΔRox due to oxidative degradation may be used to calculate the current or voltage that takes into account only oxidative degradation, and the amount of change in each may be used to determine whether the EHC 20 is abnormal due to oxidative degradation.

[0026] A crack abnormality may be determined by comparing the amount of power that takes only cracks into account with the indicated amount of power. The resistance Rck that takes only cracks into account can be calculated by adding the resistance increase ΔRck to the initial resistance Rini, and the voltage that takes only cracks into account can be calculated using this resistance Rck and the indicated power. The power that takes only cracks into account can be calculated from the resistance Rck that takes only cracks into account and the voltage that takes only cracks into account. The amount of power that takes only cracks into account can be calculated by integrating this power that takes only cracks into account over time. If the amount of power that takes only cracks into account is significantly lower than the indicated amount of power, it can be determined that a crack abnormality has occurred in the EHC20.

[0027] In addition to the amount of power that takes only cracks into consideration, the amount of resistance increase ΔRck due to cracks may be used to calculate the current or voltage that takes only cracks into consideration, and the crack abnormality of the EHC 20 may be determined from the amount of change in each.

[0028] <Effects of this embodiment> The above configuration calculates the resistance increase amount ΔRox due to oxidation degradation of the EHC 20 and the resistance increase amount ΔRck due to cracks in the EHC 20. Since the resistance increase amount ΔRox due to oxidation degradation is used to determine an oxidation degradation abnormality, and the resistance increase amount ΔRck due to cracks is used to determine a crack abnormality, it is possible to determine an oxidation degradation abnormality and a crack abnormality in the EHC 20.

[0029] <Example of change> The control device 40 may calculate the resistance increase amount ΔRox due to oxidative degradation of the EHC 20 according to a temperature range of the bed temperature based on the temperature history information of the EHC 20. For example, the temperature range includes a first range and a second range having a bed temperature higher than that of the first range. As an example, the first range is a bed temperature equal to or higher than 20°C and lower than 40°C, and the second range is a bed temperature equal to or higher than 40°C and lower than 60°C. The control device 40 calculates the resistance increase amount ΔRox so that when the EHC 20 is exposed to a bed temperature in the second range for a predetermined time, the resistance increase amount ΔRox is larger than when the EHC 20 is exposed to a bed temperature in the first range for the same time as that in the second range. [Explanation of symbols]

[0030] 1...vehicle, 10...engine, 11...cylinder, 12...exhaust pipe, 20...electrically heated catalyst (EHC), 21...catalyst carrier, 22...case, 30...power supply unit, 31...battery, 32...electrode, 33...current sensor, 34...voltage sensor, 40...control unit, 41...floor temperature sensor

Claims

[Claim 1] A control device for a vehicle equipped with an electrically heated catalyst, calculating an increase in resistance due to oxidation degradation of the electrically heated catalyst based on temperature history information of the electrically heated catalyst; determining an oxidation degradation abnormality using the amount of resistance increase due to the oxidation degradation; calculating the resistance increase amount due to cracks in the electrically heated catalyst by subtracting the resistance increase amount due to the oxidative degradation from the total resistance increase amount of the electrically heated catalyst; A crack abnormality is determined using the amount of increase in resistance due to the crack. Vehicle control device.

Images