JP2019074008A - Control device of internal combustion engine - Google Patents

Abstract

To provide an internal combustion engine capable of preventing a large amount of unburned hydrocarbon adsorbed to an oxidation catalyst from being released at once.SOLUTION: An ECU 90 is disposed on an internal combustion engine including an oxidation catalyst. The ECU 90 includes a required accelerator opening detection portion 93, an accelerator opening correction portion 94, and an accelerator opening control portion 95. The required accelerator opening detection portion 93 detects a required accelerator opening as the accelerator opening which is required. The accelerator opening correction portion 94 corrects the required accelerator opening to lower responsiveness to increase of the required accelerator opening detected by the required accelerator opening detection portion 93, after a low idle operation of the internal combustion engine. The accelerator opening control portion 95 controls the accelerator opening on the basis of the required accelerator opening corrected by the accelerator opening correction portion 94.SELECTED DRAWING: Figure 2

Description

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

  BACKGROUND Conventionally, an internal combustion engine provided with an exhaust gas purification device for purifying exhaust gas is known. Patent documents 1 and 2 disclose this kind of internal combustion engine.

  The exhaust gas purification system of Patent Document 1 estimates the amount of unburned hydrocarbon HC accumulated in the support of the oxidation catalyst, and when the accumulated estimated amount of the unburned hydrocarbon HC exceeds a predetermined judgment value, The 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 removed by oxidation.

  The exhaust gas control apparatus of Patent Document 2 increases the injection amount per one main injection of fuel when continuation of the idling state of the engine continues for a predetermined standby time or more, and at the timing after which the combustion can be performed immediately after the main injection. By adding the injection, the exhaust gas is heated up to a predetermined temperature or more.

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

  The configuration of Patent Document 1 raises the temperature of the exhaust gas by performing the multistage injection while raising the target idle speed. As a result, the operator may feel a sense of incongruity due to the fluctuation of the rotational speed, and it also causes an extra consumption of fuel.

  In the exhaust gas purification system, when the idling state continues, the amount of unburned hydrocarbon HC adsorbed to 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 sharply increases due to rapid acceleration after idling for a long time, a large amount of unburned hydrocarbon HC adsorbed to the oxidation catalyst is rapidly released. There is a possibility of In such a case, there is a possibility that the temperature of the oxidation catalyst may rise excessively due to the large release of unburned hydrocarbon HC, and there may be a problem such as dissolution 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 thereof is to provide an internal combustion engine that can avoid large-scale release of unburned hydrocarbon HC adsorbed to an oxidation catalyst at once.

Means and effect for solving the problem

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

  According to an aspect of the present invention, the following configuration is provided for a control device of an internal combustion engine provided with an oxidation catalyst. That is, the control device of the internal combustion engine includes a required accelerator opening degree detecting unit, an accelerator opening degree correcting unit, and an accelerator opening degree control unit. The required accelerator opening degree detecting unit detects a required accelerator opening degree which is a requested accelerator opening degree. The accelerator opening degree correction unit is configured to open the required accelerator so as to reduce responsiveness to a change in the required accelerator opening degree detected by the required accelerator opening degree detection unit after the internal combustion engine is operated at low idle. Correct the degree. The accelerator opening control unit controls the accelerator opening based on the required accelerator opening corrected by the accelerator opening correction unit.

  Thereby, after the low idle operation continues, the responsiveness to the required change in the accelerator opening can be reduced, so that the exhaust gas can be prevented from sharply increasing due to the abrupt change in the accelerator opening. As a result, it is possible to avoid the excessive temperature rise of the oxidation catalyst caused by the rapid release of a large amount of unburned hydrocarbon adsorbed to the oxidation catalyst.

  In the control device of the internal combustion engine, the accelerator opening correction unit may change at least one of the presence or absence of the correction of the required accelerator opening and the degree of the correction according to the duration of the low idle operation. Is preferred.

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

  In the control device for an internal combustion engine described above, the following configuration is preferable. That is, the control device of the internal combustion engine includes an adsorption amount estimation unit that estimates the adsorption amount of unburned hydrocarbon adsorbed to the oxidation catalyst. The accelerator opening degree correction unit makes at least one of the presence or absence of the correction of the required accelerator opening degree and the degree of the correction different according to the adsorption amount estimated by the adsorption amount estimation unit.

  As a result, the amount of adsorption of unburned hydrocarbons on the oxidation catalyst can be taken into consideration, so that the excessive rise in temperature of the oxidation catalyst can be reliably avoided while maintaining the operation feeling.

  In the control device for an internal combustion engine described above, the following configuration is preferable. That is, the accelerator opening correction unit corrects the required accelerator opening when the internal combustion engine is in a low idle operation when the adsorption amount estimated by the adsorption amount estimation unit is less than a predetermined amount. Do. The accelerator opening degree correction unit determines the required accelerator opening degree regardless of whether or not the internal combustion engine is in low idle operation when the adsorption amount estimated by the adsorption amount estimation unit is equal to or larger than a predetermined amount. to correct.

  The amount of adsorption of unburned hydrocarbons varies depending on the state of the oxidation catalyst, the operating conditions, and the like. In this respect, in the above configuration, when the estimated amount of adsorption of unburned hydrocarbon is equal to or greater than a predetermined value, the rapid change of the accelerator opening degree regardless of whether the internal combustion engine is currently in low idle operation or not. Can be suppressed. As a result, excessive temperature rise of the oxidation catalyst can be avoided more reliably.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows typically the flow of the air intake of the internal combustion engine which concerns on one Embodiment of this invention, exhaust, and fuel supply. The functional block diagram which shows the structure of ECU. The flowchart used by low idle driving | running continuation time count-up process. 10 is a flowchart used in accelerator smoothing control. FIG. The figure which shows the calculation map of the accelerator moderation rate alpha based on low idle continuation time and the accelerator opening degree. The figure which shows the base map of the acceleration moderation rate (beta), and a low idle continuation time correction coefficient map. The graph which shows the change rate limitation of the accelerator in the accelerator annealing control of 2nd Embodiment. The figure which shows the state transition time base map of 2nd Embodiment.

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

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

  The engine body 10 includes an intake unit 2 for drawing air from the outside, a cylinder (not shown) having a combustion chamber 3, and an exhaust unit 4 for discharging the exhaust gas generated in the combustion chamber 3 by the combustion of fuel to the outside. As the main configuration.

  The intake unit 2 includes an intake pipe 21 that is an intake passage. Further, the intake unit 2 includes a supercharger 22, a throttle valve 27, and an intake manifold 28 which are disposed in order from the upstream side in the direction in which intake 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. The air drawn from the outside can flow into 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 coupled to the turbine 23 via the shaft 24 rotates as the turbine 23 rotates. Due to the rotation of the compressor 25, the air purified by the air cleaner (not shown) can be compressed and forcibly sucked.

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

  The intake manifold 28 is configured to distribute the air supplied from the intake pipe 21 according to the number of cylinders of the engine body 10 and supply the air to the combustion chambers 3 of the respective cylinders.

  An intercooler (not shown) is installed downstream of the compressor 25 of the supercharger 22 for cooling the compressed air sucked by the supercharger 22 by heat exchange with cooling water or flowing air (ie, wind). You may.

  In the combustion chamber 3, the air supplied from the intake manifold 28 is compressed, and fuel is injected into the high-temperature compressed air to spontaneously burn the fuel and push the piston to move. The power thus obtained is transmitted to an appropriate device downstream of the power via a crankshaft or the like.

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

  Subsequently, a configuration for performing fuel supply and injection 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, thereby removing dust and dirt mixed in the fuel. Thereafter, the fuel is supplied to the common rail 84. The common rail 84 stores fuel at high pressure and distributes and supplies the fuel to the 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 the 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 combustion of fuel in the combustion chamber 3 is discharged from the combustion chamber 3 to the outside of the engine main body 10 through 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 and a DPF (Diesel Particulate Filter) 60, which is an exhaust gas purification device, which are disposed in order from the upstream side in the flow direction of the exhaust gas in the exhaust pipe 41.

  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 into the exhaust pipe 41.

  The exhaust manifold 42 guides the exhaust gas generated in each combustion chamber 3 to the exhaust pipe 41 so as to supply the exhaust gas to the turbine 23 of the turbocharger 22. The exhaust manifold 42 is provided with an exhaust gas temperature sensor 71 for detecting the temperature of the exhaust gas. The exhaust gas 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 disposed 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 as shown in FIG. 1, a part of the exhaust gas can be recirculated to the intake side via the EGR device 50. As a result, for example, the maximum combustion temperature at the time of high load operation of the internal combustion engine 100 can be lowered, so the amount of NOx (nitrogen oxide) generation can be reduced.

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

  The oxidation catalyst 61 and the soot filter 62 are disposed inside the casing. The soot filter 62 is disposed downstream of the oxidation catalyst 61 in the direction in which the exhaust gas flows inside the casing. Exhaust gas introduced into the DPF 60 from the exhaust pipe 41 is purified by the soot filter 62 and then discharged out 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 soot filter 62 collects particulate matter (PM: Particulate Matter) contained in the exhaust gas treated with the oxidation catalyst 61.

  When the deposition amount of PM in the soot filter 62 becomes a predetermined amount or more, the opening degree of the throttle valve 27 is adjusted, and the exhaust gas temperature is raised by the after injection of the fuel from the injector 85 or the like. 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, nitrogen monoxide or the like contained in the exhaust gas. By the action of the oxidation catalyst 61, nitrogen monoxide in the exhaust gas is oxidized to unstable nitrogen dioxide. Then, the oxygen released as nitrogen dioxide returns to nitric oxide is supplied for the oxidation of PM trapped by the downstream soot filter 62. 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 oxidation catalyst 61 does not reach the activation temperature because the temperature of the exhaust gas is low. Therefore, when the low idle operation continues, the oxidation reaction of the unburned hydrocarbon HC and the like in the exhaust gas is not promoted, and the unburned hydrocarbon HC is adsorbed and accumulated in the oxidation catalyst 61.

  After the low idle operation continues for a considerable period of time and the unburned hydrocarbon HC is adsorbed to some extent, if the exhaust gas rapidly increases due to rapid acceleration etc., a large amount of unburned hydrocarbon HC adsorbed by the oxidation catalyst 61 is released at once. As a result, there is a possibility that the oxidation catalyst 61 may be excessively heated and melted.

  In consideration of this situation, the ECU 90 according to the present embodiment operates the operator against the rapid acceleration during the low idle operation or when the adsorption amount of the unburned hydrocarbon HC is equal to or more than the predetermined value when the engine body 10 is operated. The accelerator opening is corrected so as to reduce the responsiveness to the accelerator opening operated by the.

  The ECU 90 shown in FIGS. 1 and 2 is disposed at or near the engine body 10. The ECU 90 is configured as a known computer, and mainly includes a CPU that executes various arithmetic processing and control, and a ROM and a RAM as the storage unit 91.

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

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

  The storage unit 91 stores various information set in advance regarding control of the operation of the internal combustion engine 100. As information stored in the storage unit 91, for example, a calculation map of the acceleration moderating rate α and the like can be mentioned.

  The HC adsorption amount estimation unit 92 estimates the adsorption amount of unburned hydrocarbon HC adsorbed to the oxidation catalyst 61. It is conceivable that this estimation is performed, for example, by the following method. That is, the HC adsorption amount estimation unit 92 detects the load of the internal combustion engine 100 based on the required accelerator opening detected by the required accelerator opening detection 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 rotational speed and the like, and the HC discharge amount of the internal combustion engine 100 is calculated based on this operating state. Then, the HC adsorption amount estimation unit 92 obtains the adsorption amount of HC based on the above-described HC discharge amount, the temperature of the oxidation catalyst 61, the exhaust gas temperature detected by the exhaust gas temperature sensor 71, and the like. However, the above-mentioned HC discharge amount can also be determined by a map based on the load and rotational speed of the internal combustion engine 100. Also, the exhaust temperature can be obtained by a map based on the load and the number of revolutions of the internal combustion engine 100 instead of acquiring from the exhaust gas temperature sensor 71.

  The required accelerator opening degree detection unit 93 is formed 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 instruction of the operator or the like may be called 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 detection unit 93 using the map or the calculation formula stored in the storage unit 91 according to the operation state of the engine body 10 To obtain a correction value so as to reduce the responsiveness to.

  The accelerator opening degree control unit 95 acquires the control accelerator opening degree from the required 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 to match the corrected required accelerator opening degree. Control. On the other hand, when the accelerator opening degree correction unit 94 does not correct the required accelerator opening degree, the actual accelerator opening degree is controlled to match the required accelerator opening degree.

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

  First, 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 continuation time count-up process. FIG. 4 is a flowchart used in accelerator smoothing control that is executed when acceleration is performed during low idle operation.

  The flow shown in FIG. 3 is always executed when the engine body 10 is in operation. When this flow starts, the ECU 90 first determines whether the number of revolutions of the engine body 10 is less than or equal to a predetermined value (step S101).

  If it is determined in step S101 that the rotational speed is greater than the predetermined value, the ECU 90 determines that the internal combustion engine 100 is not in low idle operation, and resets the count value for the duration of low idle operation to zero (step S102). , And return to step S101. On the other hand, if the rotational speed is less than or equal to the predetermined value, the ECU 90 determines whether the fuel injection amount instruction value is less than or equal to the predetermined value (step S103).

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

  The flow shown in FIG. 4 is always performed at the time of operation of the engine body 10 in parallel with the flow of FIG. 3. When this flow starts, the ECU 90 first determines whether the HC adsorption amount estimated by the HC adsorption amount estimation unit 92 is equal to or greater than a predetermined threshold (step S201).

  If it is determined in step S201 that the HC adsorption amount is equal to or greater than the predetermined threshold value, it means that the accelerator smoothing control needs to be performed. Therefore, in this case, the ECU 90 stores, for internal processing, that the accelerator smoothing control is to be performed (step S202). However, the process of step S202 may be omitted. Thereafter, the ECU 90 determines the presence or absence of the accelerator operation based on whether or not the required accelerator opening detected by the required accelerator opening detection unit 93 is other than zero (step S203).

  If it is determined in step S203 that the accelerator operation is performed, the accelerator opening correction unit 94 corrects the required accelerator opening based on the low idle operation continuation time, the required accelerator opening, and the like (step S204). Thereafter, the accelerator opening control unit 95 acquires the required accelerator opening corrected by the accelerator opening correction unit 94 as the control accelerator opening (step S205), and based on the acquired control accelerator opening, The accelerator opening degree is controlled (step S206). Thereafter, the process returns to step S201.

  If it is determined in step S203 that the accelerator operation is not performed, the accelerator opening degree is set to 0% (step S207), and the process proceeds to step S206.

  On the other hand, if it is determined in step S201 that the HC adsorption amount is less than the predetermined threshold value, the ECU 90 determines whether the duration of the low idle operation of the engine body 10 is counted up (that is, the low idle operation is in progress). (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 it is determined in step S208 that the duration of the low idle operation is zero, 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 performed (step S209). However, the process of step S209 may be omitted. Thereafter, the ECU 90 determines the presence or absence of the accelerator operation (step S210).

  If it is determined in step S210 that the accelerator operation is performed, the accelerator opening control unit 95 acquires the required accelerator opening detected by the required accelerator opening detection unit 93 as it is as the control accelerator opening (step S211). Then, the accelerator opening control unit 95 controls the actual accelerator opening based on the acquired control accelerator opening (step S206). Thereafter, the process returns to step S201.

  If it is determined in step S210 that there is no accelerator operation, the ECU 90 determines that the accelerator opening is 0% (step S207), and proceeds to step S206.

  On the other hand, if it is determined in step S208 that the low idle operation is being performed, it is necessary to execute the accelerator smoothing control, so the above-described processing of steps S202 to S207 is performed.

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

  FIG. 5 shows that the operator sharply accelerates the accelerator from 0% to 100% at time t1 which is a timing after a long low idle operation and at time t2 which is a timing after a short low idle operation. The graph shows the change in each value when the operation of opening is performed. The horizontal axes of the five graphs are all time, and the time is corresponded by the upper and lower graphs.

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

  In the rapid acceleration operation at time t1, the above-described accelerator smoothing control is performed. Until that time, the low idle operation was performed for a long time, so the increase in accelerator opening (control accelerator opening) after correction is sluggish with respect to the increase in required accelerator opening. The rise is also moderate.

  Therefore, the amount of HC adsorbed to the oxidation catalyst 61 decreases more slowly in some cases than in the absence of accelerator annealing control, which indicates that the release of HC is gradual. 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 to 100% again at time t2, which is the timing when a little time has passed.

  Although the acceleration mode control is performed also for this rapid acceleration operation, since the low idle operation until time t2 is a short time, the correction of the accelerator opening degree is substantially not performed. Therefore, the control accelerator opening changes almost in the same manner as the required accelerator opening. However, since the amount of HC adsorbed to the oxidation catalyst 61 is small at time t2, an excessive temperature rise of the oxidation catalyst 61 does not occur.

  As described above, the ECU 90 according to the present embodiment can avoid a rapid change of the control accelerator opening by correcting the accelerator opening input by the operation of the operator. As a result, the rapid increase of the exhaust gas can be avoided, so the unburned hydrocarbon HC adsorbed by the oxidation catalyst 61 is gradually released without being rapidly released in a large amount. Therefore, the excessive temperature rise of the oxidation catalyst 61 can be avoided.

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

  An example of the first correction is to use the accelerator smoothing rate α shown in FIG. The accelerator smoothing rate α corresponds to how much the increase in the control accelerator opening in the second graph from the top is slowed with respect to the increase in the required accelerator opening shown in the top graph of FIG. 5 It is a thing. As the accelerator easing rate α increases, the inclination of the increase in the control accelerator opening becomes closer to horizontal (in other words, the increase becomes gentle).

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

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

  That is, when the low idle operation continuation time is short, there is a high possibility that the amount of unburned hydrocarbon HC adsorbed to the oxidation catalyst 61 is still small, and a large amount of unburned hydrocarbon HC is released by the change of the accelerator opening. Risk of Further, when the accelerator opening operated by the operator is small, the amount of increase in the exhaust gas is limited, so the possibility that a large amount of unburned hydrocarbon HC is released is low. In such a case, by setting the moderation rate α to the accelerator opening to a small value or zero, it is possible to promptly respond to the accelerator opening operated by the operator.

  On the other hand, when the low idle operation continuation time is long and the detected accelerator opening degree is large, the gradient for changing the control accelerator opening degree should be reduced by setting the moderation rate α to the accelerator opening degree large. Can. As a result, a large amount of unburned hydrocarbon HC can be avoided from being released at once.

  An example of the second correction is to use the acceleration smoothing rate β and the low idle duration correction coefficient shown in FIG.

  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 number of revolutions of the engine body 10 and the target load rate of the engine body 10. This base map can be expressed as a two-dimensional table in which the moderating rate β is associated with the combination of the target rotational speed and the target load factor, as shown in FIG. The target rotational speed and the target load factor can be calculated based on the required accelerator opening degree.

  As shown in FIG. 7, the accelerator smoothing rate β is set to increase as the target rotational speed increases and to increase as the target load rate increases.

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

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

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

  Thus, appropriate correction can be realized by performing correction of the accelerator opening based on the target rotation speed and the target load factor that better reflects the increase amount of the exhaust gas.

  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 required accelerator opening degree detecting unit 93, an accelerator opening degree correcting unit 94, and an accelerator opening degree control unit 95. The required accelerator opening degree detecting unit 93 detects the required accelerator opening degree. The accelerator opening correction unit 94 sets the required accelerator opening to lower the responsiveness to the increase in the required accelerator opening detected by the required accelerator opening detection unit 93 after the internal combustion engine 100 is in low idle operation. to correct. The accelerator opening control unit 95 controls the accelerator opening based on the required accelerator opening corrected by the accelerator opening correction unit 94.

  Thereby, after the low idle operation continues, the responsiveness to the required increase in the accelerator opening can be reduced, so that the sudden increase in the actual accelerator opening prevents the exhaust gas from rapidly increasing. it can. As a result, it is possible to avoid the excessive temperature rise of the oxidation catalyst 61 due to the unburned hydrocarbon HC adsorbed to the oxidation catalyst 61 being rapidly released in a large amount.

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

  Thereby, it is possible to effectively prevent the excessive temperature rise of the oxidation catalyst 61 while suppressing the decrease in the operation feeling related to the accelerator by the simple process of measuring the time.

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

  As a result, the amount of adsorption of unburned hydrocarbon HC on the oxidation catalyst 61 can be taken into consideration, so that the excessive temperature rise of the oxidation catalyst 61 can be reliably avoided while maintaining the operation 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 the predetermined value, the accelerator opening correction unit 94 performs low idle operation of the internal combustion engine 100, The required accelerator opening degree is corrected (steps S201, S208, and S202 in FIG. 4). The accelerator opening degree correction unit 94 corrects the required accelerator opening degree regardless of whether or not the internal combustion engine 100 is in low idle operation when the adsorption amount estimated by the HC adsorption amount estimation unit 92 is equal to or greater than a predetermined amount. (Steps S201 and S202 in FIG. 4).

  That is, the amount of adsorption of unburned hydrocarbon HC fluctuates depending on the state of the oxidation catalyst 61, the operating condition, and the like. In this respect, in the above configuration, when the estimated amount of adsorption of unburned hydrocarbon HC is equal to or greater than a predetermined value, the accelerator opening rapidly decreases regardless of whether or not the internal combustion engine 100 is currently in low idle operation. Change can be suppressed. As a result, the excessive temperature rise of the oxidation catalyst 61 can be avoided more reliably.

  Moreover, in the example of the above-mentioned 1st correction | amendment, the memory | storage part 91 with which ECU90 is equipped memorize | stores the map of the moderation rate (alpha) which the accelerator opening degree correction | amendment part 94 uses. The smoothing rate α is set to increase as the duration of the low idle operation increases, and to increase as the accelerator opening degree detected by the required accelerator opening degree detection unit 93 increases.

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

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

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

  Next, a second embodiment will be described. FIG. 8 is a graph showing the change rate limitation 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 the present embodiment, members that are the same as or similar to the above-described embodiment may be assigned the same reference numerals in the drawings, and descriptions thereof may be omitted.

  In the ECU 90 according to the present embodiment, when the estimated amount of unburned hydrocarbon HC adsorbed to the oxidation catalyst 61 is equal to or greater than a predetermined value, or when the accelerator is operated during low idle operation, In order to limit the rate of change, accelerator smoothing control is performed for the required accelerator opening. That is, the time when the control accelerator opening reaches the required accelerator opening input by the operation of the operator is delayed.

  Specifically, as shown by a in the graph of FIG. 8, the accelerator opening correction unit 94 applies a predetermined state transition time with the required accelerator opening detected by the required accelerator opening detection unit 93 as a target. Thus, the accelerator opening degree is corrected so as to obtain a control accelerator opening degree which 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 number of revolutions of the engine body 10 and the target load factor. 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 rotational speed and the target load factor, as shown in FIG.

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

  That is, when the target rotational speed and the target load factor are small, the amount of increase in the exhaust gas is limited, so the possibility that a large amount of unburned hydrocarbon HC is released is low. 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 rotational speed and the target load factor are large, the increase amount of the exhaust gas is also considered to be large, so the state transition time with respect to the accelerator opening degree is set large. As a result, since the change gradient of the control accelerator opening becomes smaller, it is possible to avoid a large amount of unburned hydrocarbon HC being released at once.

  The low idle duration correction coefficient can be set in association with the low idle duration as shown in FIG. 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 continuation time is 5 hours, the map of FIG. 9 is referred to. 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.

  As described above, by limiting the change rate of the control accelerator opening degree of the engine main body 10 with respect to the required accelerator opening degree input by the operation of the operator, it is possible to avoid the rapid increase of the exhaust gas. As a result, it is possible to prevent the excessive temperature rise of the oxidation catalyst 61 due to the large amount of unburned hydrocarbon HC being released at a stretch.

  It is optional how to make a correction to the required accelerator opening, for example, it can be corrected to show a curvilinear change like b or c instead of a in the graph of FIG. . The correction shown by b or c in FIG. 8 is obtained by dividing the difference between the required accelerator opening degree and the current accelerator opening degree by a predetermined value (moderate value) and adding the current accelerator opening degree to the control accelerator opening degree It can be realized by This smoothing value is determined according to the state transition time. In this case, the rapid increase of the exhaust gas can be mitigated without significantly reducing the response to the required accelerator opening.

  Further, the correction for the required accelerator opening degree can also be performed as indicated by d in the graph of FIG. The correction shown by d in FIG. 8 is obtained by multiplying the difference between the required accelerator opening and the current accelerator opening by the function of the change amount set to increase with time and adding the current accelerator opening This can be realized by setting the value to the control accelerator opening degree. The function of the 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 has elapsed.

  In addition, the formula shown by the part of d of the lower part of FIG. 8 can implement | achieve not only d but all the ac opening degree curves of ac by defining the function of change amount suitably.

  As described above, the ECU 90 of the present embodiment includes the storage unit 91 that stores the state transition time until the accelerator opening detected by the required accelerator opening detection unit 93 is reached and the time correction coefficient. . The state transition time is set based on the target rotational speed and the target load factor of 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 so as to realize a rate of change based on the state transition time and the time correction coefficient with respect to the accelerator opening detected by the required accelerator opening detection unit 93. .

  Thus, by limiting the rate of change of the control accelerator opening, it is possible to prevent the unburned hydrocarbon HC adsorbed by the oxidation catalyst 61 from being rapidly released in a large amount.

  Although the preferred embodiment and modification of the present invention have been described above, the above configuration can be modified as follows, for example.

  In FIG. 2, the HC adsorption amount estimation unit 92 can be omitted. In other words, in the flow of FIG. 4, the determination in step S201 can be omitted, and it can be changed to determine whether to perform the accelerator smoothing control only by the determination in step S208.

  The degree of correction of the required accelerator opening degree can also be changed according to the magnitude of the HC adsorption amount estimated by the HC adsorption amount estimation unit 92. For example, in place 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 a combination of the required accelerator opening and the HC adsorption amount.

  The ECU 90 executes the above-mentioned accelerator smoothing control when the estimated adsorption amount of unburned hydrocarbon HC is a predetermined amount or more, or when the change amount of the accelerator opening degree is a predetermined amount or more during low idle operation, If not, it may be configured not to execute.

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

  Instead of the target load factor for determining the smoothing rate β and the state transition time, it is possible to use a fuel injection amount, an intake amount, or the like.

  Information on the correction of the required accelerator opening (for example, moderation rates α, β, state transition time, low idle duration correction coefficient, etc.) is changed to be obtained by, for example, a predetermined calculation formula instead of a map etc. It can also be done.

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

90 ECU (control device)
93 request accelerator opening detection unit 94 accelerator opening correction unit 95 accelerator opening control unit 100 internal combustion engine

Claims (4)

A control device for an internal combustion engine provided with an oxidation catalyst, comprising:
A required accelerator opening degree detecting unit for detecting a required accelerator opening degree which is a required accelerator opening degree;
The accelerator opening correction for correcting 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 at low idle Department,
An accelerator opening control unit that controls an accelerator opening based on the required accelerator opening corrected by the accelerator opening correction unit;
A control device for an internal combustion engine, comprising: The control device for an internal combustion engine according to claim 1,
The control device for an internal combustion engine according to claim 1, wherein the accelerator opening degree correction unit makes at least one of the presence or absence of the correction of the required accelerator opening degree and the degree of the correction different according to a continuation time of the low idle operation. The control device for an internal combustion engine according to claim 1 or 2, wherein
An adsorption amount estimation unit configured to estimate an adsorption amount of unburned hydrocarbons adsorbed to the oxidation catalyst;
The internal combustion engine is characterized in that the accelerator opening correction unit varies at least one of the presence or absence of the correction of the required accelerator opening and the degree of the correction 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 3,
The accelerator opening correction unit
If the adsorption amount estimated by the adsorption amount estimation unit is less than a predetermined amount, the required accelerator opening degree is corrected when the internal combustion engine is in a low idle operation,
When the adsorption amount estimated by the adsorption amount estimation unit is equal to or more than a predetermined value, the required accelerator opening degree is corrected regardless of whether the internal combustion engine is in low idle operation or not. Engine control device.

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