JP6871838B2 - Internal combustion engine control device - Google Patents

Description

The present invention relates to a control device for an internal combustion engine provided with a diesel oxidation catalyst.

Conventionally, an internal combustion engine including an exhaust purification device for purifying exhaust gas has been known. Patent Documents 1 and 2 disclose this type of internal combustion engine.

The exhaust gas purification system of Patent Document 1 estimates the amount of unburned hydrocarbon HC accumulated in the carrier of the oxidation catalyst, and when the estimated amount of unburned hydrocarbon HC accumulated exceeds a predetermined determination value, Hydrocarbon removal control is performed to raise the temperature of the exhaust gas to activate the oxidation catalyst, and the accumulated unburned hydrocarbon HC is oxidized and removed.

The exhaust gas purification device of Patent Document 2 increases the injection amount per main injection of fuel when the idling state of the engine continues for a predetermined standby time or longer, and after the exhaust gas can be combusted immediately after the main injection. The exhaust gas is heated to a predetermined temperature or higher by adding an injection.

Japanese Unexamined Patent Publication No. 2004-108320 Japanese Patent No. 4276525

In the configuration of Patent Document 1, the target idle speed is increased and the exhaust gas temperature is raised by performing multi-stage injection. As a result, the operator may feel a sense of discomfort due to the fluctuation of the rotation speed, and may also cause extra fuel consumption.

Further, in the exhaust gas purification system, when the idling state continues, the amount of unburned hydrocarbon HC adsorbed by the oxidation catalyst provided in the exhaust gas purification device gradually increases. Therefore, in the configurations of Patent Documents 1 and 2, for example, when the exhaust gas suddenly increases due to sudden acceleration after the idling state continues for a long time, a large amount of unburned hydrocarbon HC adsorbed on the oxidation catalyst is released at once. There is a possibility that In such a case, the temperature of the oxidation catalyst may rise too much due to the large release of unburned hydrocarbon HC, which may cause problems such as melting damage of the oxidation catalyst due to such excessive temperature rise. ..

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an internal combustion engine capable of avoiding a large amount of unburned hydrocarbon HC adsorbed on an oxidation catalyst being released at once.

Means and effects to solve problems

The problem to be solved by the present invention is as described above, and next, the means for solving this problem and its effect will be described.

According to the viewpoint of the present invention, the following configuration is provided for a control device for an internal combustion engine including an oxidation catalyst. That is, the control device for the internal combustion engine includes a required accelerator opening degree detection unit, an accelerator opening degree correction unit, and an accelerator opening degree control unit. The required accelerator opening degree detecting unit detects the required accelerator opening degree, which is the requested accelerator opening degree. The accelerator opening correction unit opens the required accelerator so as to reduce the responsiveness to a change in the required accelerator opening detected by the required accelerator opening detection unit after the internal combustion engine is operated in low idle. Correct the degree. The accelerator opening degree control unit controls the accelerator opening degree based on the required accelerator opening degree corrected by the accelerator opening degree correction unit. The accelerator opening degree correction unit makes at least one of the presence / absence and the degree of correction of the required accelerator opening degree different depending on the duration of the low idle operation.

As a result, after the low idle operation is continued, the responsiveness to the requested change in the accelerator opening can be lowered, so that it is possible to prevent the exhaust gas from suddenly increasing due to the sudden change in the accelerator opening. As a result, it is possible to avoid an excessive temperature rise of the oxidation catalyst due to a large amount of unburned hydrocarbons adsorbed on the oxidation catalyst being released at once. Further, by a simple process of measuring the time, it is possible to effectively prevent the overheating of the oxidation catalyst while suppressing the deterioration of the operation feeling related to the accelerator.

The internal combustion engine control device preferably has the following configuration. That is, the control device of this internal combustion engine includes an adsorption amount estimation unit that estimates the adsorption amount of unburned hydrocarbons adsorbed on the oxidation catalyst. The accelerator opening degree correction unit makes at least one of the presence / absence and the degree of correction of the required accelerator opening degree different depending on the adsorption amount estimated by the adsorption amount estimation unit.

As a result, the amount of unburned hydrocarbons adsorbed on the oxidation catalyst can be taken into consideration, so that it is possible to reliably avoid overheating of the oxidation catalyst while maintaining the operational feeling.

The internal combustion engine control device preferably has the following configuration. That is, when the adsorption amount estimated by the adsorption amount estimation unit is less than a predetermined value, the accelerator opening degree correction unit corrects the required accelerator opening degree when the internal combustion engine is in low idle operation. To do. When the suction amount estimated by the suction amount estimation unit is equal to or more than a predetermined value, the accelerator opening degree correction unit obtains the required accelerator opening degree regardless of whether or not the internal combustion engine is in low idle operation. to correct.

The amount of unburned hydrocarbon adsorbed varies depending on the state of the oxidation catalyst, operating conditions, and the like. In this regard, in the above configuration, when the estimated amount of unburned hydrocarbons adsorbed is equal to or higher than a predetermined value, the accelerator opening suddenly changes regardless of whether the internal combustion engine is currently in low idle operation. Can be suppressed. As a result, it is possible to more reliably avoid an excessive temperature rise of the oxidation catalyst.

The figure which shows typically the flow of the intake air, the exhaust gas and the fuel supply of the internal combustion engine which concerns on one Embodiment of this invention. The functional block diagram which shows the structure of an ECU. Flow chart used in low idle operation duration count-up processing. Flowchart used for accelerator smoothing control. Conceptual diagram showing accelerator smoothing control. The figure which shows the calculation map of the accelerator smoothing rate α based on the low idle duration and the accelerator opening. The figure which shows the base map of the accelerator smoothing rate β and the low idle duration correction coefficient map. The graph which shows the change rate limit of the accelerator in the accelerator smoothing control of 2nd Embodiment. The figure which shows the state transition time base map of 2nd Embodiment.

Next, an embodiment of the present invention will be described with reference to the drawings. First, an outline of the internal combustion engine 100 will be described with reference to FIGS. 1 and 2. FIG. 1 is a diagram schematically showing the flow of intake air, exhaust gas, and fuel supply of the internal combustion engine 100. FIG. 2 is a functional block diagram showing the configuration of the ECU 90.

The internal combustion engine 100 of the first embodiment is a diesel engine mounted on a vehicle or the like, and is configured as an in-line 4-cylinder engine having four cylinders 30. The internal combustion engine 100 includes an engine main body 10 and an ECU (Engine Control Unit) 90 which is a control device.

The engine body 10 includes an intake unit 2 that sucks air from the outside, a cylinder (not shown) having a combustion chamber 3, and an exhaust unit 4 that exhausts exhaust gas generated in the combustion chamber 3 by combustion of fuel to the outside. Is provided as the main configuration.

The intake unit 2 includes an intake pipe 21 which is an intake passage. Further, the intake unit 2 includes a supercharger 22, a throttle valve 27, and an intake manifold 28, which are arranged in order from the upstream side in the direction in which the intake air flows in the intake pipe 21.

The intake pipe 21 is an intake passage and is configured to connect the supercharger 22, the throttle valve 27, and the intake manifold 28. Air sucked from the outside can flow inside the intake pipe 21.

As shown in FIG. 1, the supercharger 22 includes a turbine 23, a shaft 24, and a compressor 25. One end of the shaft 24 is connected to the turbine 23 and the other end is connected to the compressor 25. The turbine 23 is configured to rotate using exhaust gas. The compressor 25, which is connected to the turbine 23 via the shaft 24, rotates as the turbine 23 rotates. By rotating the compressor 25, the air purified by the air cleaner shown in the figure can be compressed and forcibly sucked.

The throttle valve 27 changes the cross-sectional area of the intake passage by adjusting its opening degree in accordance with a control command from the ECU 90. Thereby, the amount of air supplied to the intake manifold 28 can be adjusted via the throttle valve 27.

The intake manifold 28 is configured so that the air supplied from the intake pipe 21 can be distributed according to the number of cylinders of the engine body 10 and supplied to the combustion chamber 3 of each cylinder.

An intercooler (not shown) is installed on the downstream side of the compressor 25 of the turbocharger 22 to cool the compressed air sucked by the turbocharger 22 by exchanging heat with cooling water or fluidized air (that is, wind). You may.

In the combustion chamber 3, the air supplied from the intake manifold 28 is compressed, and the fuel is injected into the compressed air that has become hot, so that the fuel is spontaneously ignited and burned, and the piston is pushed to move. The power thus obtained is transmitted to an appropriate device on the downstream side of the power via a crankshaft or the like.

The internal combustion engine 100 is provided with a cooling water circulation system (not shown) for preventing the engine body 10 from becoming overheated due to the combustion of fuel. This cooling water circulation system is configured to return the cooling water to a cooling jacket (not shown) formed on the cylinder head or the like of the engine body 10 and exchange heat with the cooling jacket or the like of the engine body 10.

Subsequently, a configuration for supplying and injecting fuel in the internal combustion engine 100 of the present embodiment will be briefly described. As shown in FIG. 1, the internal combustion engine 100 includes a fuel tank 81 for storing fuel, a fuel filter 82, a fuel pump 83, a common rail 84, and an injector 85.

The fuel sucked by the fuel pump 83 passes through the fuel filter 82, whereby dust and dirt mixed in the fuel are removed. After that, fuel is supplied to the common rail 84. The common rail 84 stores fuel at a high pressure and distributes and supplies the fuel to a plurality of injectors 85.

The injector 85 includes a fuel injection valve (not shown) for injecting fuel into the combustion chamber 3 of each cylinder 30. The injector 85 injects fuel into the combustion chamber 3 by opening and closing the fuel injection valve at the timing according to the instruction of the ECU 90. The ECU 90 controls the opening and closing of the fuel injection valve in the injector 85 based on the fuel injection amount according to the operating state of the internal combustion engine 100, the accelerator opening degree, and the like.

Exhaust gas generated by burning fuel in the combustion chamber 3 is discharged from the combustion chamber 3 to the outside of the engine body 10 via the exhaust unit 4.

The exhaust unit 4 includes an exhaust pipe 41 which is a passage for exhaust gas. Further, the exhaust unit 4 includes an exhaust manifold 42 arranged in order from the upstream side in the direction in which the exhaust gas flows in the exhaust pipe 41, and a DPF (Diesel Particulate Filter) 60 which is an exhaust gas purification device.

The exhaust pipe 41 is an exhaust gas passage, and is configured to connect the exhaust manifold 42 and the DPF 60. The exhaust gas discharged from the combustion chamber 3 can flow inside the exhaust pipe 41.

The exhaust manifold 42 collects the exhaust gas generated in each combustion chamber 3 and guides the exhaust gas to the exhaust pipe 41 so as to supply the exhaust gas to the turbine 23 of the supercharger 22. The exhaust manifold 42 is provided with an exhaust gas temperature sensor 71 that detects the temperature of the exhaust gas. The exhaust temperature detected by the exhaust gas temperature sensor 71 is output to the ECU 90. The exhaust gas temperature sensor 71 is not limited to the configuration provided in the exhaust manifold 42, and may be arranged at the inlet of the DPF 60, for example.

Further, the engine body 10 is provided with an EGR (Exhaust Gas Recirculation) device 50, and a part of the exhaust gas can be returned to the intake side via the EGR device 50 as shown in FIG. As a result, for example, the maximum combustion temperature of the internal combustion engine 100 during high-load operation can be lowered, so that the amount of NOx (nitrogen oxide) produced can be reduced.

As shown in FIG. 1, the DPF 60 is provided at the outlet of the exhaust pipe 41. The DPF 60 includes an elongated hollow casing having a substantially cylindrical shape, an oxidation catalyst (DOC: Diesel Oxtion Catalyst) 61, and a suit filter 62.

The oxidation catalyst 61 and the soot filter 62 are arranged inside the casing. Further, the soot filter 62 is arranged on the downstream side of the oxidation catalyst 61 in the direction in which the exhaust gas flows inside the casing. The exhaust gas introduced into the DPF 60 from the exhaust pipe 41 is purified by the suit filter 62 and then discharged to the outside of the internal combustion engine 100.

The soot filter 62 is composed of, for example, a wall flow type filter or a honeycomb structure filter. The suit filter 62 collects particulate matter (PM: Particulate Matter) contained in the exhaust gas treated with the oxidation catalyst 61.

When the accumulated amount of PM in the suit filter 62 exceeds a predetermined amount, the opening degree of the throttle valve 27 is adjusted and the exhaust gas temperature is raised by after-injection of fuel from the injector 85 to increase the accumulated PM. The soot filter 62 is regenerated by forced combustion.

The oxidation catalyst 61 is made of platinum or the like, and can promote the oxidation of carbon monoxide, nitric oxide, etc. contained in the exhaust gas. By the action of the oxidation catalyst 61, nitric oxide in the exhaust gas is oxidized to unstable nitrogen dioxide. Then, the oxygen released when nitrogen dioxide returns to nitric oxide is supplied for the oxidation of PM captured by the soot filter 62 on the downstream side. Further, the oxidation catalyst 61 removes the unburned hydrocarbon HC by promoting the oxidation reaction of the unburned hydrocarbon HC in the exhaust gas.

Generally, during the low idle operation of the engine body 10, the temperature of the exhaust gas is low, so that the temperature of the oxidation catalyst 61 does not reach the activation temperature. Therefore, if the low idle operation continues, the oxidation reaction of the unburned hydrocarbon HC or the like in the exhaust gas is not promoted, and the unburned hydrocarbon HC is adsorbed on the oxidation catalyst 61 and accumulates.

When the exhaust gas suddenly increases due to sudden acceleration or the like after the unburned hydrocarbon HC is adsorbed to some extent after the low idle operation is continued for a considerable period of time, a large amount of the unburned hydrocarbon HC adsorbed on the oxidation catalyst 61 is released at once. As a result, the oxidation catalyst 61 may be overheated and melted.

In consideration of this circumstance, the ECU 90 of the present embodiment responds to sudden acceleration during low idle operation or when the adsorption amount of unburned hydrocarbon HC is equal to or higher than a predetermined value during operation of the engine body 10. The accelerator opening is corrected so as to reduce the responsiveness to the accelerator opening operated by.

The ECU 90 shown in FIGS. 1 and 2 is arranged at or near the engine body 10. The ECU 90 is configured as a known computer, and is mainly composed of a CPU that executes various arithmetic processes and controls, and a ROM and RAM as a storage unit 91.

The ECU 90 can obtain information such as the rotation speed, the intake amount, and the fuel injection amount of the engine body 10 based on the detection values from various sensors that detect the information on the state of the engine body 10.

As shown in FIG. 2, in addition to the storage unit 91, the ECU 90 includes an HC adsorption amount estimation unit (adsorption amount estimation unit) 92, a request accelerator opening degree detection unit 93, an accelerator opening degree correction unit 94, and an accelerator opening degree. A control unit 95 is provided.

The storage unit 91 stores various preset information regarding the control of the operation of the internal combustion engine 100. Examples of the information stored in the storage unit 91 include a calculation map of the accelerator smoothing rate α.

The HC adsorption amount estimation unit 92 estimates the adsorption amount of unburned hydrocarbon HC adsorbed on the oxidation catalyst 61. This estimation can be performed by, for example, the following method. That is, the HC adsorption amount estimation unit 92 is the load of the internal combustion engine 100 based on the required accelerator opening degree detected from the required accelerator opening degree detecting unit 93, and the internal combustion engine 100 detected from the rotation speed detection unit (not shown). The operating state of the internal combustion engine 100 is obtained based on the rotation speed and the like, and the HC emission amount of the internal combustion engine 100 is calculated based on this operating state. Then, the HC adsorption amount estimation unit 92 obtains the HC adsorption amount based on the above-mentioned HC discharge amount, the temperature of the oxidation catalyst 61, the exhaust temperature detected from the exhaust gas temperature sensor 71, and the like. However, the above HC emission amount can also be obtained from a map based on the load and the number of revolutions of the internal combustion engine 100. Further, the exhaust temperature can be obtained from a map based on the load and the rotation speed of the internal combustion engine 100 instead of acquiring from the exhaust gas temperature sensor 71.

The requested accelerator opening degree detecting unit 93 is composed of, for example, an accelerator position sensor (not shown), and detects the opening degree of the accelerator instructed by the operator. In the following description, the opening degree of the accelerator requested by the operator's instruction or the like may be referred to as the required accelerator opening degree.

The accelerator opening degree correction unit 94 changes the required accelerator opening degree detected by the required accelerator opening degree detecting unit 93 using the map or calculation formula stored in the storage unit 91 according to the operating state of the engine body 10. A correction value is obtained by making corrections so as to reduce the responsiveness to.

The accelerator opening degree control unit 95 acquires the control accelerator opening degree from the requested accelerator opening degree detection unit 93 or the accelerator opening degree correction unit 94, and controls the opening and closing of the fuel injection valve of the injector 85. Specifically, for example, when the accelerator opening degree correction unit 94 corrects the required accelerator opening degree, the accelerator opening degree control unit 95 actually adjusts the accelerator opening degree so as to match the corrected required accelerator opening degree. To control. On the other hand, when the required accelerator opening degree is not corrected by the accelerator opening degree correction unit 94, the actual accelerator opening degree is controlled so as to match the required accelerator opening degree.

Next, in the ECU 90 of the present embodiment, when the accelerator of the vehicle on which the internal combustion engine 100 is mounted is operated by the operator during the low idle operation, the correction performed for the accelerator opening degree will be described. In the following description, the control that performs correction so as to reduce the responsiveness to a change in the accelerator opening degree may be referred to as accelerator smoothing control.

First, the specific processing performed by the ECU 90 will be described with reference to FIGS. 3 and 4. FIG. 3 is a flowchart used in the low idle operation duration count-up process. FIG. 4 is a flowchart used in accelerator smoothing control executed when accelerated during low idle operation.

The flow shown in FIG. 3 is always executed during operation of the engine body 10. When this flow starts, the ECU 90 first determines whether or not the rotation speed of the engine body 10 is equal to or lower than a predetermined value (step S101).

If the number of revolutions is larger than the predetermined value in the determination of step S101, the ECU 90 determines that the internal combustion engine 100 is not in the low idle operation, and resets the count value for the duration of the low idle operation to zero (step S102). , Return to step S101. On the other hand, when the rotation speed is a predetermined value or less, the ECU 90 determines whether or not the fuel injection amount indicated value is a predetermined value or less (step S103).

If the fuel injection amount indicated value is equal to or less than the predetermined value in the determination of step S103, the ECU 90 determines that the internal combustion engine 100 is in low idle operation, and adds 1 to the count value of the duration of low idle operation. (Step S104), the process returns to step S101. On the other hand, when the fuel injection amount indicated value is larger than a predetermined value, the ECU 90 determines that the internal combustion engine 100 is not in low idle operation, resets the above count value to zero (step S102), and returns to step S101.

The flow shown in FIG. 4 is always executed during operation of the engine body 10 in parallel with the flow shown in FIG. When this flow starts, the ECU 90 first determines whether or not the HC adsorption amount estimated by the HC adsorption amount estimation unit 92 is equal to or greater than a predetermined threshold value (step S201).

If the HC adsorption amount is equal to or higher than a predetermined threshold value in the judgment of step S201, it means that it is necessary to execute the accelerator smoothing control. Therefore, in this case, the ECU 90 stores for internal processing that the accelerator smoothing control is executed (step S202). However, the process of step S202 may be omitted. After that, the ECU 90 determines whether or not there is an accelerator operation based on whether or not the requested accelerator opening degree detected by the requested accelerator opening degree detecting unit 93 is other than zero (step S203).

If there is an accelerator operation at the judgment of step S203, the accelerator opening degree correction unit 94 corrects the required accelerator opening degree based on the low idle operation duration, the required accelerator opening degree, and the like (step S204). After that, the accelerator opening degree control unit 95 acquires the requested accelerator opening degree corrected by the accelerator opening degree correction unit 94 as the control accelerator opening degree (step S205), and actually based on the acquired control accelerator opening degree. The accelerator opening degree is controlled (step S206). Then, the process returns to step S201.

If there is no accelerator operation at the judgment of step S203, the accelerator opening degree is set to 0% (step S207), and the process proceeds to step S206.

On the other hand, if the HC adsorption amount is less than a predetermined threshold value in the determination of step S201, whether or not the duration of the low idle operation of the engine body 10 is counted up (that is, the low idle operation is in progress). Whether or not) is determined (step S208). This determination can be made based on whether or not the count value described in the flow of FIG. 3 is zero.

If the duration of the low idle operation is zero in the determination of step S208, it means that it is not necessary to execute the accelerator smoothing control. Therefore, in this case, the ECU 90 stores for internal processing that the accelerator smoothing control is not executed (step S209). However, the process of step S209 may be omitted. After that, the ECU 90 determines whether or not the accelerator is operated (step S210).

If there is an accelerator operation in the judgment of step S210, the accelerator opening degree control unit 95 acquires the required accelerator opening degree detected by the request accelerator opening degree detection unit 93 as it is as the control accelerator opening degree (step S211). Then, the accelerator opening degree control unit 95 controls the actual accelerator opening degree based on the acquired control accelerator opening degree (step S206). Then, the process returns to step S201.

If there is no accelerator operation at the judgment of step S210, the ECU 90 assumes that the accelerator opening degree is 0% (step S207), and proceeds to step S206.

On the other hand, according to the judgment of step S208, when the low idle operation is in progress, it is necessary to execute the accelerator smoothing control, so the above-mentioned processes of steps S202 to S207 are performed.

Hereinafter, the effect of executing the above-mentioned flow will be described. FIG. 5 is a conceptual diagram showing accelerator smoothing control.

In FIG. 5, the operator suddenly pushes the accelerator from 0% to 100% at the time t1 which is the timing after the long-time low-idle operation and the time t2 which is the timing after the short-time low-idle operation. The graph shows the change of each value when the operation to open is performed. The horizontal axis of each of the five graphs is time, and the time corresponds to the upper and lower graphs.

The operator rapidly opens the accelerator from 0% to 100% at time t1. At this time t1, the amount of HC adsorbed on the oxidation catalyst 61 is considerably increased due to the long-time low idle operation.

In the sudden acceleration operation at time t1, the accelerator smoothing control is performed. Since low idle operation was performed for a long time until then, the increase in the corrected accelerator opening (control accelerator opening) was slower than the increase in the required accelerator opening, and the engine speed increased accordingly. The rise is also gradual.

Therefore, the amount of HC adsorbed on the oxidation catalyst 61 decreased more slowly in some cases than in the case without accelerator tanning control, which indicates that the release of HC was slower. Therefore, the excessive temperature rise of the oxidation catalyst 61 does not occur.

The operator returns the accelerator to 0% after a while, and suddenly opens the accelerator again to 100% at time t2, which is a timing when a little time has passed.

Accelerator smoothing control is also performed for this sudden acceleration operation, but since the low idle operation until time t2 is short, the accelerator opening is substantially not corrected. Therefore, the control accelerator opening changes in substantially the same manner as the required accelerator opening. However, since the amount of HC adsorbed on the oxidation catalyst 61 was small at time t2, the temperature of the oxidation catalyst 61 did not rise excessively.

As described above, the ECU 90 of the present embodiment can avoid a sudden change in the control accelerator opening degree by correcting the accelerator opening degree input by the operator's operation. As a result, it is possible to avoid a rapid increase in the exhaust gas, so that the unburned hydrocarbon HC adsorbed on the oxidation catalyst 61 is gradually released without being released in large quantities at once. Therefore, it is possible to avoid overheating of the oxidation catalyst 61.

Subsequently, two examples of correcting the detected accelerator opening degree will be described with reference to FIGS. 6 and 7.

An example of the first correction uses the accelerator smoothing rate α shown in FIG. This accelerator smoothing rate α corresponds to how much the increase in the control accelerator opening in the second graph from the top is slowed down with respect to the increase in the required accelerator opening shown in the uppermost graph of FIG. It is a thing. As the accelerator smoothing rate α increases, the slope of the increase in the control accelerator opening becomes closer to horizontal (in other words, the increase becomes slower).

The calculation map of the accelerator smoothing rate α shown in FIG. 6 is for determining the accelerator smoothing rate α according to the low idle operation duration and the required accelerator opening detected by the required accelerator opening detection unit 93. belongs to. As shown in FIG. 6, this calculation map can be expressed as a two-dimensional table in which the smoothing rate α is associated with the combination of the low idle operation duration and the accelerator opening.

As shown in FIG. 6, the accelerator smoothing rate α is set to increase as the duration of low idle operation increases, and to increase as the detected accelerator opening increases. ..

That is, when the low idle operation duration is short, it is highly possible that the amount of unburned hydrocarbon HC adsorbed on the oxidation catalyst 61 is still small, and a large amount of unburned hydrocarbon HC is released due to the change in the accelerator opening. Is unlikely to occur. Further, when the accelerator opening operated by the operator is small, the amount of increase in the exhaust gas is limited, so that it is unlikely that a large amount of unburned hydrocarbon HC is released. In such a case, by setting the smoothing rate α with respect to the accelerator opening to a small value or zero, it is possible to quickly respond to the accelerator opening operated by the operator.

On the other hand, when the low idle operation duration is long and the detected accelerator opening is large, the gradient at which the control accelerator opening changes is reduced by setting a large smoothing rate α with respect to the accelerator opening. Can be done. As a result, it is possible to avoid a large amount of unburned hydrocarbon HC being released at once.

In the second correction example, the accelerator smoothing rate β and the low idle duration correction coefficient shown in FIG. 7 are used.

The base map of the accelerator smoothing rate β shown in FIG. 7 is for determining the accelerator smoothing rate β according to the target rotation speed of the engine main body 10 and the target load factor of the engine main body 10. As shown in FIG. 7, this base map can be expressed as a two-dimensional table in which the smoothing rate β is associated with the combination of the target rotation speed and the target load factor. The target rotation speed and the target load factor can be calculated based on the required accelerator opening.

As shown in FIG. 7, the accelerator smoothing rate β is set to increase with an increase in the target rotation speed and to increase with an increase in the target load factor.

That is, when the target rotation speed and the target load factor are small, the amount of increase in the exhaust gas is limited, so that a large amount of unburned hydrocarbon HC is unlikely to be released. In such a case, a natural feeling of accelerator operation can be realized by setting the smoothing rate β with respect to the accelerator opening to a small value or zero.

On the other hand, when the target rotation speed and the target load factor are large, it is considered that the amount of increase in exhaust gas is also large. Therefore, in this case, the change gradient of the control accelerator opening can be reduced by setting a large smoothing rate β with respect to the accelerator opening. As a result, it is possible to avoid a large amount of unburned hydrocarbon HC being released at once.

As shown in FIG. 7, the low idle duration correction coefficient can be set in association with the low idle duration. That is, the larger the low idle duration, the larger the low idle duration correction coefficient.

As described above, by correcting the accelerator opening degree based on the target rotation speed and the target load factor that better reflect the increase amount of the exhaust gas, an appropriate correction can be realized.

As described above, the ECU 90 of the present embodiment is provided in the internal combustion engine 100 provided with the oxidation catalyst 61. The ECU 90 includes a request accelerator opening degree detection unit 93, an accelerator opening degree correction unit 94, and an accelerator opening degree control unit 95. The requested accelerator opening degree detection unit 93 detects the requested accelerator opening degree. The accelerator opening degree correction unit 94 adjusts the required accelerator opening degree so as to reduce the responsiveness to an increase in the required accelerator opening degree detected by the required accelerator opening degree detecting unit 93 after the internal combustion engine 100 is operated in low idle. to correct. The accelerator opening degree control unit 95 controls the accelerator opening degree based on the requested accelerator opening degree corrected by the accelerator opening degree correction unit 94.

As a result, after the low idle operation is continued, the responsiveness to the required increase in the accelerator opening can be lowered, so that it is possible to prevent the exhaust gas from suddenly increasing due to the sudden change in the actual accelerator opening. it can. As a result, it is possible to avoid an excessive temperature rise of the oxidation catalyst 61 due to the large amount of unburned hydrocarbon HC adsorbed on the oxidation catalyst 61 being released at once.

Further, in the ECU 90 of the present embodiment, the accelerator opening degree correction unit 94 changes the presence or absence of correction of the required accelerator opening degree and the degree of correction according to the duration of the low idle operation.

As a result, it is possible to effectively prevent the oxidation catalyst 61 from being overheated by a simple process of measuring the time while suppressing a decrease in the operation feeling related to the accelerator.

Further, the ECU 90 of the present embodiment includes an HC adsorption amount estimation unit 92 that estimates the adsorption amount of unburned hydrocarbon HC adsorbed on the oxidation catalyst 61. The accelerator opening degree correction unit 94 makes the presence or absence of correction of the required accelerator opening degree different according to the adsorption amount estimated by the HC adsorption amount estimation unit 92.

As a result, the amount of unburned hydrocarbon HC adsorbed on the oxidation catalyst 61 can be taken into consideration, so that the overheating of the oxidation catalyst 61 can be reliably avoided while maintaining the operational feeling.

Further, in the ECU 90 of the present embodiment, when the adsorption amount estimated by the HC adsorption amount estimation unit 92 is less than a predetermined value, the accelerator opening correction unit 94 determines that the internal combustion engine 100 is in low idle operation. The required accelerator opening degree is corrected (steps S201, S208, S202 in FIG. 4). When the adsorption amount estimated by the HC adsorption amount estimation unit 92 is equal to or more than a predetermined value, the accelerator opening correction unit 94 corrects the required accelerator opening regardless of whether the internal combustion engine 100 is in low idle operation. (Steps S201 and S202 in FIG. 4).

That is, the amount of unburned hydrocarbon HC adsorbed varies depending on the state of the oxidation catalyst 61, operating conditions, and the like. In this regard, in the above configuration, when the estimated amount of unburned hydrocarbon HC adsorbed is equal to or higher than a predetermined value, the accelerator opening suddenly increases regardless of whether the internal combustion engine 100 is currently in low idle operation. Changes can be suppressed. As a result, it is possible to more reliably avoid the excessive temperature rise of the oxidation catalyst 61.

Further, in the above-mentioned first correction example, the storage unit 91 included in the ECU 90 stores a map of the smoothing rate α used by the accelerator opening degree correction unit 94. The smoothing rate α is set to increase as the duration of the low idle operation increases, and increases as the accelerator opening degree detected by the required accelerator opening degree detecting unit 93 increases.

Thereby, an appropriate smoothing rate α can be set according to the duration of the low idle operation and the detected accelerator opening degree.

Further, in the second correction example, the storage unit 91 included in the ECU 90 stores a map of the smoothing rate β used by the accelerator opening degree correction unit 94 and a map of the time correction coefficient. The smoothing rate β is set based on the target rotation speed and the target load factor of the internal combustion engine 100 according to the accelerator opening degree detected by the required accelerator opening degree detecting unit 93. The time correction factor is set based on the duration of low idle operation.

Thereby, the correction that appropriately reflects the operating state of the internal combustion engine can be performed.

Next, the second embodiment will be described. FIG. 8 is a graph showing the limit of the rate of change of the accelerator in the accelerator smoothing control of the second embodiment. FIG. 9 is a diagram showing a state transition time base map of the second embodiment. In the description of this embodiment, the same or similar members as those in the above-described embodiment may be designated by the same reference numerals in the drawings, and the description may be omitted.

In the ECU 90 of the present embodiment, when the estimated amount of unburned hydrocarbon HC adsorbed on the oxidation catalyst 61 is equal to or more than a predetermined amount, or when the accelerator is operated during low idle operation, the accelerator opening degree is changed. Accelerator smoothing control is performed for the required accelerator opening so as to limit the rate of change. That is, the time for the control accelerator opening to reach the requested accelerator opening input by the operator's operation is delayed.

Specifically, as shown by a in the graph of FIG. 8, the accelerator opening correction unit 94 multiplies a predetermined state transition time with the required accelerator opening detected by the required accelerator opening detection unit 93 as a target. The accelerator opening is corrected so as to obtain a control accelerator opening that changes linearly.

The above state transition time can be calculated using, for example, the state transition time base map and the low idle duration correction coefficient shown in FIG.

The state transition time base map shown in FIG. 9 is for determining the state transition time according to the target rotation speed of the engine body 10 and the target load factor. As shown in FIG. 9, this state transition time base map can be expressed as a two-dimensional table in which the state transition time is associated with the combination of the target rotation speed and the target load factor.

As shown in FIG. 9, the state transition time is set to increase as the target rotation speed increases and as the target load factor increases.

That is, when the target rotation speed and the target load factor are small, the amount of increase in the exhaust gas is limited, so that a large amount of unburned hydrocarbon HC is unlikely to be released. In such a case, the state transition time with respect to the accelerator opening can be set to a small value or zero.

On the other hand, when the target rotation speed and the target load factor are large, it is considered that the amount of increase in the exhaust gas is also large, so the state transition time with respect to the accelerator opening is set large. As a result, the change gradient of the control accelerator opening becomes small, so that it is possible to avoid a large amount of unburned hydrocarbon HC being released at once.

As shown in FIG. 9, the low idle duration correction coefficient can be set in association with the low idle duration. That is, the larger the low idle duration, the larger the low idle duration correction coefficient.

As a specific calculation example, when the target rotation speed corresponding to the required accelerator opening is 2000 / min, the target load factor is 100%, and the low idle duration is 5 hours, refer to the map of FIG. , The state transition time of the accelerator opening can be calculated as 5 × 0.5 = 2.5 seconds. That is, the time until the control accelerator opening reaches the required accelerator opening is delayed by 2.5 seconds without changing the control accelerator opening in the same manner as the required accelerator opening in FIG.

In this way, by limiting the rate of change of the control accelerator opening degree of the engine body 10 with respect to the requested accelerator opening degree input by the operator's operation, it is possible to avoid a sudden increase in exhaust gas. As a result, it is possible to prevent the oxidation catalyst 61 from being overheated due to the release of a large amount of unburned hydrocarbon HC at once.

How to correct the required accelerator opening is arbitrary, and for example, instead of a in the graph of FIG. 8, it can be corrected so as to show a curvilinear change such as b or c. .. In the correction shown by b or c in FIG. 8, the difference between the required accelerator opening and the current accelerator opening is divided by a predetermined value (smoothing value), and the value added to the current accelerator opening is the control accelerator opening. It can be realized by. This smooth value is determined according to the state transition time. In this case, the rapid increase in exhaust gas can be mitigated without significantly reducing the responsiveness to the required accelerator opening.

Further, the correction for the required accelerator opening degree can also be performed as shown by d in the graph of FIG. The correction shown by d in FIG. 8 was added to the current accelerator opening by multiplying the difference between the required accelerator opening and the current accelerator opening by a function of the amount of change set to increase with time. This can be achieved by setting the value as the control accelerator opening. The function of this amount of change takes a value of 0 or more and 1 or less, and is determined to be 1 when the state transition time elapses.

It should be noted that the equation shown by the part d in the lower part of FIG. 8 can realize not only d but all the accelerator opening curves of a to c by appropriately defining the function of the amount of change.

As described above, the ECU 90 of the present embodiment includes a storage unit 91 that stores the state transition time until the accelerator opening degree detected by the requested accelerator opening degree detecting unit 93 and the time correction coefficient. .. The state transition time is set based on the target rotation speed and the target load factor of the internal combustion engine 100. The time correction factor is set based on the duration of low idle operation. The accelerator opening correction unit 94 corrects the accelerator opening with respect to the accelerator opening detected by the requested accelerator opening detection unit 93 so as to realize a rate of change based on the state transition time and the time correction coefficient. ..

Thereby, by limiting the rate of change of the control accelerator opening degree, it is possible to prevent a large amount of unburned hydrocarbon HC adsorbed on the oxidation catalyst 61 from being released at once.

Although preferred embodiments and modifications of the present invention have been described above, the above configuration can be changed as follows, for example.

In FIG. 2, the HC adsorption amount estimation unit 92 may be omitted. In other words, in the flow of FIG. 4, the determination in step S201 may be omitted, and the determination in step S208 alone may be used to determine whether or not to perform accelerator smoothing control.

It is also possible to change the degree of correction of the required accelerator opening degree according to the magnitude of the HC adsorption amount estimated by the HC adsorption amount estimation unit 92. For example, instead of the map of FIG. 6, it is conceivable to determine a map of the accelerator smoothing rate α so as to be determined by the combination of the required accelerator opening degree and the HC adsorption amount.

When the estimated amount of unburned hydrocarbon HC adsorbed is equal to or greater than a predetermined amount, or when the amount of change in accelerator opening is greater than or equal to a predetermined amount during low idle operation, the ECU 90 executes the above-mentioned accelerator smoothing control. If not, it may be configured not to run.

The smoothing rate α may be set based on, for example, the amount of change in the accelerator opening degree.

Instead of the target load factor for obtaining the smoothing rate β and the state transition time, the fuel injection amount, the intake amount, and the like can be used.

Information on the correction of the required accelerator opening (for example, smoothing rate α, β, state transition time, low idle duration correction coefficient, etc.) is changed so as to be acquired by, for example, a predetermined calculation formula instead of the map or the like. You can also do it.

The ECU 90 can be used for an internal combustion engine for other purposes instead of the internal combustion engine 100 for a vehicle.

90 ECU (control unit)
93 Requested accelerator opening detection unit 94 Accelerator opening correction unit 95 Accelerator opening control unit 100 Internal combustion engine

Claims (3)

A control device for an internal combustion engine equipped with an oxidation catalyst.
A request accelerator opening detection unit that detects the required accelerator opening, which is the requested accelerator opening, and
Accelerator opening correction that corrects the required accelerator opening so as to reduce the responsiveness to the change in the required accelerator opening detected by the required accelerator opening detection unit after the internal combustion engine is operated in low idle. Department and
An accelerator opening control unit that controls the accelerator opening based on the required accelerator opening corrected by the accelerator opening correction unit.
Equipped with a,
The accelerator opening degree correction unit is a control device for an internal combustion engine, characterized in that at least one of the presence / absence of correction and the degree of correction of the required accelerator opening degree is changed according to the duration of the low idle operation. The control device for an internal combustion engine according to claim 1.
Equipped with an adsorption amount estimation unit that estimates the adsorption amount of unburned hydrocarbons adsorbed on the oxidation catalyst.
The internal combustion engine is characterized in that the accelerator opening degree correction unit makes at least one of the presence / absence and the degree of correction of the required accelerator opening degree different according to the adsorption amount estimated by the adsorption amount estimation unit. Engine control device. The control device for an internal combustion engine according to claim 2.
The accelerator opening correction unit
When the adsorption amount estimated by the adsorption amount estimation unit is less than a predetermined value, the required accelerator opening degree is corrected when the internal combustion engine is in low idle operation.
When the adsorption amount estimated by the adsorption amount estimation unit is equal to or greater than a predetermined value, the internal combustion engine is characterized in that the required accelerator opening degree is corrected regardless of whether or not the internal combustion engine is in low idle operation. Engine control device.

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