Vehicle control device

Abstract

An electronic control unit for controlling a vehicle equipped with an internal combustion engine in which two catalyst devices, i.e., a front-stage catalyst device and a rear-stage catalyst device, are provided in an exhaust passage is provided, the electronic control unit being provided with a processing circuit. And a processing circuit that performs processing to relax the execution condition of fuel cut of the internal combustion engine when the condition of removal of sulfur accumulated in the preceding-stage catalyst device is satisfied and the subsequent-stage catalyst device is not activated.

Description

Technical Field

[0001] This invention relates to a vehicle control device. Background Technology

[0002] Catalyst devices, which carry precious metal catalysts, are known as exhaust purification devices for internal combustion engines such as those in vehicles. In these devices, sulfur poisoning sometimes occurs, where sulfur components in the exhaust coat the surface of the precious metal catalyst, leading to a decrease in exhaust purification efficiency. Japanese Patent Application Laid-Open No. 2012-117458 describes a control device for an internal combustion engine that cuts off fuel supply to the catalyst device when the catalyst device temperature is high, thereby oxidizing and releasing the sulfur components that have poisoned the precious metal catalyst, thus restoring control of the sulfur poisoning process. Summary of the Invention

[0003] There exists an internal combustion engine with two catalytic converters: a pre-catalytic converter and a post-catalytic converter. In this type of engine, even if the exhaust purification rate of the pre-catalytic converter decreases due to sulfur poisoning, the exhaust purification by the post-catalytic converter can still suppress the deterioration of tailpipe emissions. However, if sulfur poisoning occurs in the pre-catalytic converter while the post-catalytic converter is not preheated, the deterioration of tailpipe emissions cannot be adequately suppressed.

[0004] A control device for a vehicle equipped with an internal combustion engine, the internal combustion engine comprising a pre-catalyst device disposed in an exhaust passage and a post-catalyst device disposed in the exhaust passage further downstream of the pre-catalyst device.

[0005] The vehicle's control device includes processing circuitry.

[0006] The processing circuit is configured as follows: when the conditions for the removal of sulfur accumulated in the pre-catalyst unit are met and the post-catalyst unit is not activated, a process is implemented to change the control settings of the vehicle to facilitate the execution of fuel cut-off of the internal combustion engine.

[0007] The control device of the aforementioned vehicle has the effect of suppressing the deterioration of tailpipe emissions caused by sulfur poisoning of the catalyst device. Attached Figure Description

[0008] Hereinafter, with reference to the accompanying drawings, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described, in which the same reference numerals denote the same elements, and wherein:

[0009] Figure 1 This is a diagram schematically illustrating the structure of a first embodiment of a vehicle control device.

[0010] Figure 2yes Figure 1 The flowchart shows the process of facilitating the execution of poison recovery control by the control device.

[0011] Figure 3 This is a flowchart of the poison recovery control execution promotion process performed by the control device of the vehicle in the second embodiment. Detailed Implementation

[0012] Implementation Method 1

[0013] The following is for reference. Figure 1 and Figure 2 The first embodiment of the vehicle control device will be described in detail.

[0014] Structure of vehicle control device

[0015] First, refer to Figure 1 The structure of the vehicle control device according to this embodiment will be described. Figure 1 As shown, vehicle 10 is configured as a hybrid electric vehicle equipped with an internal combustion engine 11 and an electric motor 12 as the driving source for generating driving force.

[0016] The internal combustion engine 11 includes a combustion chamber 13 for combustion, an intake passage 14 serving as the path for introducing air into the combustion chamber 13, and an exhaust passage 15 serving as the path for exhaust from the combustion chamber 13. Furthermore, the internal combustion engine 11 includes an air flow meter 16 for detecting the intake air volume GA, and a throttle valve 17 for adjusting the intake air volume GA. The internal combustion engine 11 also includes an injector 18 for injecting fuel into the air flowing into the combustion chamber 13, and an ignition device 19 for igniting the air-fuel mixture introduced into the combustion chamber 13 by spark discharge. A pre-catalyst unit 20 is installed in the exhaust passage 15 of the internal combustion engine 11. A post-catalyst unit 21 is installed downstream of the pre-catalyst unit 20 in the exhaust passage 15. Both the pre-catalyst unit 20 and the post-catalyst unit 21 contain precious metal catalysts and function as a three-way catalytic converter to purify exhaust gas by simultaneously oxidizing hydrocarbons and carbon monoxide and reducing nitrogen oxides. Furthermore, the pre-catalyst unit 20 also functions as a filter device for capturing particulate matter in the exhaust gas.

[0017] An electronic control unit 22 as a control device is mounted in a vehicle 10. The electronic control unit 22 includes a storage device 23 and a processing circuit 24. A control program or data is stored in the storage device 23. The processing circuit 24 executes the program read from the storage device 23. The electronic control unit 22 obtains the detection results of various sensors provided in each part of the vehicle 10 such as an internal combustion engine 11. For example, in addition to the intake air amount GA detected by an air flow meter 16, the electronic control unit 22 also obtains the detection results such as the rotational speed NE of the internal combustion engine 11, the coolant temperature THW, the accelerator opening ACC, and the vehicle speed SPD. The accelerator opening ACC indicates the amount of depression of the driver's accelerator pedal. Further, the electronic control unit 22 performs various controls of the vehicle 10 based on these detection results.

[0018] Sulfur poisoning of the catalyst device

[0019] In the pre-stage catalyst device 20 and the post-stage catalyst device 21, sulfur poisoning may occur, which causes a decrease in the exhaust purification rate. Next, the mechanism of sulfur poisoning will be described. In the following description, the pre-stage catalyst device 20 and the post-stage catalyst device 2l are collectively referred to as the catalyst device.

[0020] The catalyst device includes a base material made of a porous material such as ceramics, a coating material coated on the surface of the base material, and a catalyst noble metal supported on the base material via the coating material. In a state where the temperature of the catalyst device is lower than a specified temperature, sulfur components (such as sulfur dioxide) in the exhaust gas accumulate in the coating material. If the temperature of the catalyst device rises above the above-specified temperature and the inside of the catalyst device becomes a rich atmosphere state, the accumulated sulfur components are detached from the coating material. Further, sulfur in the detached sulfur components covers the surface of the catalyst noble metal, thereby causing sulfur poisoning. In the following description, the lower limit value of the temperature range of the catalyst device in which the sulfur components are detached from the coating material is described as the detachment start temperature T1. In addition, the exhaust purification ability of the pre-stage catalyst device 20 having a function as a filter device is lower than that of the post-stage catalyst device 21. Therefore, the pre-stage catalyst device 20 is more likely to be in a state where the exhaust gas cannot be sufficiently purified due to sulfur poisoning than the post-stage catalyst device 21.

[0021] ​​​​​​After a cold start of the internal combustion engine 11, the temperature of the pre-catalyst unit 20 first reaches the temperature range where sulfur components in the exhaust gas accumulate in the coating material, and then reaches the temperature range where sulfur components detach from the coating material and move to the surface of the precious metal catalyst. Therefore, after a cold start of the internal combustion engine 11, a decrease in the exhaust gas purification rate of the pre-catalyst unit 20 due to sulfur poisoning is likely to occur. Even if sulfur poisoning occurs in the pre-catalyst unit 20, as long as the post-catalyst unit 21 is activated, the exhaust gas can be purified before the outside air is discharged, thus preventing the deterioration of tailpipe emissions. However, in low-temperature environments or at high speeds, the temperature of the post-catalyst unit 21 is difficult to rise because a large amount of heat is absorbed by the outside air. In this case, the pre-catalyst unit 20 is poisoned by sulfur, and the post-catalyst unit 21 is not activated, and sometimes both become unable to adequately purify the exhaust gas. The electronic control unit 22 performs poisoning recovery promotion control to suppress the deterioration of tailpipe emissions under this condition.

[0024] Figure 2 The diagram shows the routine procedure performed by the processing circuit 24 to facilitate control of poisoning recovery. The processing circuit 24 repeatedly executes this routine according to each predetermined control cycle.

[0025] If this routine procedure begins, the processing circuit 24 first determines in S100 whether the sulfur buildup in the fore-catalyst unit 20 exceeds a predetermined threshold X. If the processing circuit 24 determines that the sulfur buildup exceeds the threshold X ("Yes"), it proceeds to S110 for processing. If the processing circuit 24 determines that the sulfur buildup is below the threshold X ("No"), it terminates the processing of this routine procedure in the current control cycle. The sulfur buildup amount represents the amount of sulfur content deposited on the coating material of the fore-catalyst unit 20. The processing circuit 24 calculates the increase or decrease in sulfur content in the fore-catalyst unit 20 based on the operating state of the internal combustion engine 11 (e.g., intake air volume GA) and the fore-catalyst temperature THC1. Furthermore, the processing circuit 24 calculates an estimated value for the sulfur buildup amount by accumulating the increase or decrease. The fore-catalyst temperature THC1 represents the temperature of the fore-catalyst unit 20. The processing circuit 24 infers the pre-catalyst temperature THC1 based on the operating status of the internal combustion engine 11 (e.g., intake air volume GA, cooling water temperature THW, ignition timing, etc.).

[0026] In S110, the processing circuit 24 determines whether the sulfur removal condition of the fore-stage catalyst unit 20 is met. If the processing circuit 24 determines that the sulfur removal condition is met ("Yes"), it proceeds to S120 for processing. Conversely, if the processing circuit 24 determines that the sulfur removal condition is not met ("No"), it terminates the processing of this routine procedure in the current control cycle. The meeting of the sulfur removal condition indicates that the fore-stage catalyst unit 20 is in a state where the sulfur components accumulated in the coating material can be removed. In this embodiment, the processing circuit 24 determines that the sulfur removal condition is met based on the fore-stage catalyst temperature THC1 exceeding the removal start temperature T1.

[0027] In S120, the processing circuit 24 determines whether the downstream catalytic converter 21 is activated. If the processing circuit 24 determines that the downstream catalytic converter 21 is activated ("Yes"), it terminates the processing of this routine procedure in the current control cycle. Conversely, if the processing circuit 24 determines that the downstream catalytic converter 21 is not activated ("No"), it proceeds to S130 for processing. In this embodiment, the processing circuit 24 determines that the downstream catalytic converter 21 is activated because the downstream catalytic converter temperature THC2 exceeds the catalytic converter activation temperature T2. The downstream catalytic converter temperature THC2 represents the temperature of the downstream catalytic converter 21. Similar to the upstream catalytic converter temperature THC1, the processing circuit 24 infers the downstream catalytic converter temperature THC2 based on the operating state of the internal combustion engine 11, etc.

[0028] In S130, the processing circuit 24 relaxes the execution conditions for fuel cut-off during deceleration. Furthermore, after processing in S130, the processing circuit 24 terminates the processing of this routine procedure in the current control cycle. In this embodiment, the execution conditions for fuel cut-off during deceleration are set to at least the following conditions: the cooling water temperature THW of the internal combustion engine 11 is above the allowable F / C temperature and the throttle opening ACC is below the F / C starting throttle opening. Moreover, in S130, the processing circuit 24 relaxes the execution conditions for fuel cut-off during deceleration by lowering the allowable F / C temperature to a lower than normal temperature and increasing the F / C starting throttle opening to a larger than normal opening.

[0029] The function of the first implementation method

[0030] exist Figure 2In the poisoning recovery promotion control, the processing circuit 24 relaxes the execution conditions for fuel cut-off during deceleration (S130) when all conditions A to C are met. Condition A is that the sulfur accumulation in the pre-catalyst unit 20 is above the judgment value X (S100: "Yes"). Condition B is that the sulfur removal condition of the pre-catalyst unit 20 is met (S110: "Yes"). Condition C is that the post-catalyst unit 21 is not activated (S120: "No"). It is assumed that when conditions A and B are both met, the pre-catalyst unit 20 may be in a state where the exhaust gas purification rate is reduced due to sulfur poisoning. When condition C is met, the post-catalyst unit 21 is in a state where it cannot adequately purify the exhaust gas. Therefore, when all conditions A to C are met, neither the pre-catalyst unit 20 nor the post-catalyst unit 21 can adequately purify the exhaust gas, and thus tailpipe emissions may deteriorate.

[0031] By relaxing the execution conditions, it becomes easier to obtain the opportunity to execute fuel cut-off during deceleration. Thus, the processing circuit 24 modifies the control settings of the vehicle 10 by relaxing the execution conditions to facilitate the execution of fuel cut-off from the internal combustion engine 11. If fuel cut-off is executed during deceleration, the reduction in exhaust gas purification efficiency of the pre-catalyst unit 20 caused by sulfur poisoning can be eliminated. Therefore, by relaxing the execution conditions, the likelihood of eliminating tailpipe emission degradation in a shorter period increases.

[0032] Effects of the first embodiment

[0033] The control device for the vehicle 10 in this embodiment has the following effects.

[0034] (1) Sulfur poisoning in the pre-catalyst unit 20 can be eliminated in the early stage, thus suppressing the deterioration of tailpipe emissions.

[0035] (2) If the conditions for fuel cut-off during deceleration are relaxed, fuel cut-off will occur even when it is not normally performed, potentially causing drawbacks such as delayed warm-up of the internal combustion engine 11. On the other hand, even if sulfur poisoning occurs in the upstream catalytic converter 20, tailpipe emissions will not worsen as long as the downstream catalytic converter 21 is fully activated. The processing circuit 24 relaxes the conditions for fuel cut-off during deceleration only when the sulfur removal conditions of the upstream catalytic converter 20 are met and the downstream catalytic converter 21 is not activated. Therefore, unnecessary fuel cut-off under inappropriate conditions is prevented.

[0036] (3) The processing circuit 24 is configured to perform fuel cut-off during deceleration under the condition that the cooling water temperature THW is above a predetermined temperature (F / C allowable water temperature). On the other hand, sulfur poisoning of the pre-catalyst unit 20 is prone to occur before the cooling water temperature THW has risen sufficiently after the cold start of the internal combustion engine 11. If the F / C allowable water temperature is not changed, fuel cut-off will not be performed until the cooling water temperature THW has risen sufficiently, so the state of reduced exhaust gas purification efficiency of the pre-catalyst unit 20 may continue for a long time. In contrast, the processing circuit 24 is configured to change the F / C allowable water temperature to a lower temperature than usual in the process of relaxing the execution conditions of fuel cut-off during deceleration. Therefore, it is easier to eliminate the deterioration of tailpipe emissions caused by sulfur poisoning of the pre-catalyst unit 20 in the early stage.

[0037] (4) The processing circuit 24 is configured to perform fuel cut-off during deceleration when the throttle opening ACC is less than a predetermined opening (F / C start opening). Furthermore, the processing circuit 24 is configured to change the F / C start opening to a larger value than usual during deceleration when the fuel cut-off execution condition is relaxed. When the driver releases the accelerator pedal to decelerate the vehicle 10, with the increased F / C start opening, fuel cut-off begins earlier during deceleration compared to when it is not increased. As a result, the fuel cut-off lasts longer than usual, thus easily eliminating sulfur poisoning of the pre-catalyst unit 20 with fewer fuel cut-offs.

[0038] Implementation Method 2

[0039] Next, refer to Figure 3 The second embodiment of the vehicle control device will be described in detail. Furthermore, in this embodiment, structures identical to those in the above-described embodiments are marked with the same symbols and their detailed descriptions are omitted. This embodiment is identical in structure to the first embodiment, except for the processing content related to poison recovery promotion control.

[0040] In the hybrid vehicle 10, the processing circuit 24 calculates the required driving force, for example, based on the throttle opening (ACC) and vehicle speed (SPD). The required driving force represents the driving force of the vehicle 10 requested by the driver when the accelerator pedal is depressed. Furthermore, the processing circuit 24 determines the output distribution of the internal combustion engine 11 and the electric motor 12 in such a way that the driving force of the vehicle 10 corresponding to the required driving force is generated by the internal combustion engine 11 and the electric motor 12 sharing the burden.

[0041] Figure 3 The diagram shows the routine procedure performed by the processing circuit 24 for promoting poison recovery in this embodiment. The processing circuit 24 repeatedly executes this routine according to each predetermined control cycle. Furthermore, Figure 3 The processing of S100 to S120 and Figure 2 The situation is the same. Figure 3 When the processing circuit 24 determines a negative determination in S120 ("No"), the process proceeds to S135 for processing. In this S135, the processing circuit 24 enforces fuel cut-off of the internal combustion engine 11 by compensating for the required driving force solely by the electric motor 12. That is, in S135, the processing circuit 24 performs processing to change the output distribution of the internal combustion engine 11 and the electric motor 12 so that only the electric motor 12 generates a driving force corresponding to the required driving force. As a result, since the internal combustion engine 11 does not need to generate a driving force, fuel cut-off of the internal combustion engine 11 can be performed regardless of the success or failure of the execution condition of fuel cut-off during deceleration.

[0042] In the case of the present embodiment configured as described above, when sulfur poisoning of the pre-stage catalyst device 20 occurs while the post-stage catalyst device 21 is in an unactivated state, fuel cut-off of the internal combustion engine 11 is enforced. Therefore, in the control device of the present embodiment, deterioration of the tailpipe emission can also be suppressed.

[0043] Other embodiments

[0044] The above-described embodiment can be implemented in the following manner. The present embodiment and the following modification examples can be implemented in combination with each other within a range where there is no technical contradiction.

[0045] · The pre-stage catalyst temperature THC1 and the post-stage catalyst temperature THC2 may be estimated in a manner different from the above-described embodiment. Also, temperature sensors may be provided in the pre-stage catalyst device 20 and the post-stage catalyst device 21 to actually measure the pre-stage catalyst temperature THC1 and the post-stage catalyst temperature THC2.

[0046] · The determination as to whether the sulfur desorption condition in Figure 2 and Figure 3 of S110 may be made in a manner different from the above-described embodiment. For example, in addition to the pre-stage catalyst temperature THC1, the determination of S110 may be made based on the operating state of the internal combustion engine 11 such as the air-fuel ratio.

[0047] · The determination as to whether the post-stage catalyst device 21 in Figure 2 and Figure 3 of S120 is activated may be made in a manner different from the above-described embodiment. For example, the determination as to whether the post-stage catalyst device 21 is activated may be made based on the elapsed time after the start of the internal combustion engine 11, the cumulative air amount, and the cumulative fuel injection amount.

[0048] · The determination as to whether Figure 2The execution conditions for fuel cut-off during deceleration in S130 are relaxed. For example, the execution conditions can also be relaxed by changing the threshold values ​​for the engine speed NE and vehicle speed SPD of the internal combustion engine 11 in the elements constituting the execution conditions.

[0049] Notes

[0050] • The control device of the first embodiment can also be applied to non-hybrid vehicles that are not equipped with an electric motor 12.

[0051] Postscript 1

[0052] A control device for a vehicle equipped with an internal combustion engine, the internal combustion engine comprising a pre-catalyst device disposed in an exhaust passage and a post-catalyst device disposed in the exhaust passage further downstream of the pre-catalyst device.

[0053] The vehicle's control device includes processing circuitry.

[0054] The processing circuit is configured as follows: when the conditions for the removal of sulfur accumulated in the pre-catalyst unit are met and the post-catalyst unit is not activated, the processing condition for relaxing the fuel cut-off of the internal combustion engine is performed.

[0055] Appendix 2

[0056] A control device for a vehicle, the vehicle being equipped with an internal combustion engine and an electric motor, the control device including a processing circuit, the internal combustion engine including: a front catalyst device disposed in an exhaust passage; and a rear catalyst device disposed in a portion of the exhaust passage further downstream than the front catalyst device, the vehicle being configured such that the driving force of the vehicle is generated by the internal combustion engine and the electric motor sharing the driving force, the processing circuit being configured to perform the following processing: when the sulfur removal condition accumulated in the front catalyst device is met and the rear catalyst device is not activated, changing the output distribution of the internal combustion engine and the electric motor so that the driving force is generated only by the electric motor.

Claims

1. A control device for a vehicle, the vehicle being equipped with an internal combustion engine, the internal combustion engine comprising a pre-catalyst device disposed in an exhaust passage and a post-catalyst device disposed in the exhaust passage further downstream of the pre-catalyst device, the control device for the vehicle being characterized in that... Equipped with processing circuitry, When the conditions for sulfur removal accumulated in the pre-catalyst unit are met and the post-catalyst unit is not activated, the processing circuit performs a process to change the control settings of the vehicle to facilitate the execution of fuel cut-off of the internal combustion engine.

2. The control device for the vehicle according to claim 1, characterized in that, The process is a process of relaxing the execution conditions for the fuel cut-off of the internal combustion engine.

3. The control device for the vehicle according to claim 2, characterized in that, The internal combustion mechanism is configured to perform the fuel cut-off condition that the cooling water temperature of the internal combustion engine is above a predetermined temperature, and the processing circuit is configured to change the predetermined temperature to a lower temperature in the process of relaxing the execution condition.

4. The control device for the vehicle according to claim 2, characterized in that, The internal combustion mechanism is configured to perform the fuel cut-off condition that the throttle opening is below a predetermined opening, and the processing circuit is configured to change the predetermined opening to a larger value in a process that relaxes the execution condition.

5. The control device for the vehicle according to claim 1, characterized in that, The vehicle is configured such that the driving force of the vehicle is generated by the internal combustion engine and the electric motor, and the process is to change the output distribution of the internal combustion engine and the electric motor so that the driving force is generated only by the electric motor.

Images