JP4807335B2 - Control device for internal combustion engine system - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine system, and in particular, an internal combustion engine for performing control in an internal combustion engine system configured to include a pre-catalyst, a post-catalyst, and a catalyst bypass system that bypasses exhaust gas flowing into the pre-catalyst. The present invention relates to a control device for an engine system.

Conventionally, an internal combustion engine having a catalyst in an exhaust system for purifying exhaust gas is generally known. Further, in an internal combustion engine, fuel cut control (hereinafter also simply referred to as deceleration F / C) is generally performed during deceleration operation for the purpose of reducing fuel consumption, etc. When the deceleration F / C is performed, fresh air is introduced into the catalyst. Therefore, the inside of the catalyst becomes a lean atmosphere. In this regard, it is known that if deceleration F / C is performed while the bed temperature of the catalyst is high, sintering occurs and the catalyst deteriorates. Here, sintering is a phenomenon in which metal powder grows at a high temperature. In the catalyst, small Pt (platinum) is bonded to each other by atomic movement activated at a high temperature to become large Pt. It is considered that the sintering occurs due to the oxidation reaction caused by ₂ excess, and as a result, the grain growth of Pt is promoted. In this regard, when Pt grows, the total area of Pt that comes into contact with the exhaust gas becomes small, so the exhaust purification performance deteriorates.

  On the other hand, for example, Patent Document 1 proposes a technique for prohibiting fuel cut control during deceleration operation in order to suppress catalyst deterioration due to sintering. In addition, in order to suppress deterioration of the catalyst due to sintering, instead of performing fuel cut control during deceleration operation, the amount of fuel that does not cause misfire is injected, so that the catalyst temperature is reliably lowered to a low temperature range. A technique for starting the fuel cut control above is disclosed in Patent Document 2, for example.

JP-A-8-144814 JP 2003-278583 A

  Incidentally, as an internal combustion engine provided with a catalyst in the exhaust system, specifically, an internal combustion engine provided with a front catalyst and a rear catalyst in series in the exhaust system is known. In such an internal combustion engine, even when cold starting, the bed temperature of the pre-catalyst disposed immediately after the internal combustion engine rises quickly and the pre-catalyst is activated early, so that the exhaust gas is suitably purified. be able to. Also known is an internal combustion engine further comprising a catalyst bypass system configured to include a bypass passage that bypasses the pre-catalyst and a passage opening / closing means that communicates and shields the bypass passage. Yes. This catalyst bypass system is configured to bypass the exhaust that is about to flow into the pre-catalyst by opening the passage opening and closing means according to the operating state of the internal combustion engine, for example, the internal combustion engine is operated at high load and high rotation speed. When the passage opening / closing means is opened during the operation, it is possible to reduce the thermal deterioration due to the rise in the bed temperature of the pre-catalyst and to improve the output performance due to the pressure loss reduction.

  However, in the internal combustion engine system configured to have a pre-catalyst, a post-catalyst, and a catalyst bypass system that bypasses exhaust gas flowing into the pre-catalyst as described above, there are the following problems during deceleration operation. Here, when the bed temperature of the pre-catalyst is high enough to deteriorate the catalyst in the lean atmosphere, the pre-catalyst is brought into the lean atmosphere by performing deceleration F / C and bypassing fresh air. Therefore, sintering can be prevented from occurring in the pre-catalyst.

  However, since the temperature difference between the pre-catalyst and the post-catalyst becomes small when the mounting interval between the pre-catalyst and the post-catalyst is short, the bed temperature of the pre-catalyst is so high that the catalyst deteriorates in a lean atmosphere. In this case, the bed temperature of the post catalyst may be similarly high. Even when the mounting distance between the front catalyst and the rear catalyst is relatively long, the reaction with the front catalyst is insufficient due to the oxygen storage amount, while the reaction with the rear catalyst is active. In some cases, the pre-catalyst and the post-catalyst may become so hot that the catalyst deteriorates in a lean atmosphere. In such a case, when fresh air is bypassed, instead of preventing the sintering of the pre-catalyst, sintering occurs in the post-catalyst, resulting in deterioration of the post-catalyst. Things can happen.

  On the other hand, if the post-catalyst bed temperature is not so high that the catalyst deteriorates in a lean atmosphere, the post-catalyst does not generate sintering even if fresh air is bypassed. If the operation is continued for a long time, the bed temperature of the post-catalyst becomes lower than the activation temperature, and as a result, there is a possibility that the purification performance cannot be secured when the acceleration operation is performed later. In this regard, for example, it may be possible to purify the exhaust gas with the pre-catalyst by closing the bypass passage with the passage opening and closing means when the operation state changes from the deceleration operation to the acceleration operation, but after the acceleration operation is started Exhaust gas that passes through the bypass passage before the passage opening / closing means is closed cannot be purified by both the front catalyst and the rear catalyst.

  Accordingly, the present invention has been made in view of the above problems, and is an internal combustion engine system configured to include a front catalyst, a rear catalyst, and a catalyst bypass system that bypasses exhaust gas flowing into the front catalyst. An object of the present invention is to provide a control device for an internal combustion engine system capable of ensuring the purification performance of the post catalyst while preventing sintering of the post catalyst.

In order to solve the above problems, the present invention provides an internal combustion engine, a pre-catalyst disposed in an exhaust system of the internal combustion engine, a post-catalyst disposed downstream of the pre-catalyst, and the front catalyst. A control device for an internal combustion engine system for performing control with an internal combustion engine system configured to include a bypass passage that bypasses the catalyst and passage opening / closing means that communicates and shields the bypass passage, the front depending on the bed temperature of the-catalyst and the post-catalyst, communicating the bypass passage with said passage opening and closing means, a certain opening and closing control means for controlling for shielding, the pre-catalyst and the at the deceleration Specific injection control means for performing fuel injection control in the internal combustion engine according to the bed temperature of the post catalyst, and the catalyst deteriorates when the bed temperature of the pre catalyst and the bed temperature of the post catalyst are lean. The specific opening / closing system Means together performs control for communicating the bypass passage with said passage opening and closing means, the specific injection control means and performing control for injecting ignitable minimum fuel.

Here, when the bed temperature of the pre-catalyst is high enough to cause the catalyst to deteriorate in a lean atmosphere, the pre-catalyst is sintered by performing deceleration F / C and bypassing fresh air. Although it can be prevented from occurring, sintering of the post-catalyst also occurs when the post-catalyst is also at a high temperature. On the other hand, according to the present invention in which the smallest ignitable fuel is injected instead of performing the deceleration F / C and the generated combustion gas is bypassed, sintering is prevented from occurring in the pre-catalyst. Meanwhile, the purification performance of the post catalyst can be secured.

  According to the present invention, in an internal combustion engine system configured to include a pre-catalyst, a post-catalyst, and a catalyst bypass system that bypasses exhaust gas flowing into the pre-catalyst, the occurrence of sintering in the pre-catalyst is prevented. However, it is possible to provide a control device for an internal combustion engine system that can ensure the purification performance of the rear catalyst.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram schematically showing a control device for an internal combustion engine system realized by an ECU (Electronic Control Unit) 1 together with the internal combustion engine system 100. The internal combustion engine system 100 includes an exhaust system 10 and an internal combustion engine 50. The exhaust system 10 includes a pre-catalyst 11, a post-catalyst 12 disposed on the downstream side of the pre-catalyst 11, a bypass passage 13 that bypasses the pre-catalyst 11, and an on-off valve that communicates and shields the bypass passage 13. (Corresponding to the passage opening / closing means described in the claims) 14. Both the pre-catalyst 11 and the post-catalyst 12 are configured to purify exhaust gas, and the pre-catalyst 11 and the post-catalyst 12 are arranged in series with the exhaust system 10. The front catalyst 11 is provided with a first bed temperature detection sensor 31 for detecting the bed temperature, and the rear catalyst 12 is provided with a second bed temperature detection sensor 32 for detecting the bed temperature. Yes. An A / F sensor 33 is disposed upstream of the pre-catalyst 11, and an oxygen sensor 34 is disposed downstream of the pre-catalyst 11.

  The on-off valve 14 includes a valve body and a valve shaft, and the valve shaft that supports the valve body is connected to an actuator 15 via a link mechanism. The actuator 15 is configured to open and close the on-off valve 14 and incorporates a diaphragm valve that operates in accordance with air pressure. The actuator 15 is configured to open the on-off valve 14 via a link mechanism when a negative pressure is introduced, and to close the on-off valve 14 via a link mechanism when a positive pressure (atmospheric pressure) is introduced. The actuator 15 is connected to a VSV (vacuum switching valve) 16 by a conduit 17a. The VSV 16 is a solenoid valve configured as a three-way valve, and a negative pressure conduit 17b and a positive pressure conduit 17c are connected to the VSV 16 in addition to a conduit 17a. The negative pressure conduit 17b connects the VSV 16 and the negative pressure tank 18, and the positive pressure conduit 17c communicates with the atmosphere via an air cleaner (not shown). The negative pressure tank 18 is connected to the intake system (not shown) of the internal combustion engine 50 via the check valve 19, and the negative pressure generated in the intake system is accumulated in the negative pressure tank 18.

  When the VSV 16 communicates the conduit 17a and the negative pressure conduit 17b, negative pressure is introduced from the negative pressure tank 18 to the actuator 15. As a result, the on-off valve 14 communicates with the bypass passage 13. When the VSV 16 communicates the conduit 17a and the positive pressure conduit 17c, positive pressure is introduced from the atmosphere to the actuator 15. As a result, the on-off valve 14 shields the bypass passage 14. The catalyst bypass system 20 includes a bypass passage 13 and an on-off valve 14. In this embodiment, the catalyst bypass system 20 further includes an actuator 15, a VSV 16, a conduit 17, and a negative pressure tank 18. The actuator 15 may be realized by other appropriate actuators that can be controlled directly or indirectly by the ECU 1, and the catalyst bypass system 20 has a different configuration in addition to the bypass passage 13 and the on-off valve 14 accordingly. And may be realized. The on-off valve 14 may have another appropriate structure, and may be configured integrally with the actuator 15, for example.

  The ECU 1 is mainly configured to control the internal combustion engine 50, and includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory) (not shown). And an input / output circuit. The ECU 1 is electrically connected to the VSV 16 as a control target. In addition to the first bed temperature detection sensor 31, the second bed temperature detection sensor 32, the A / F sensor 33, the oxygen sensor 34, the ECU 1 includes sensors for detecting the operating state of the internal combustion engine 50. A crank angle sensor (not shown), a water temperature sensor, an air flow meter, a throttle opening sensor, an accelerator opening sensor, and the like are electrically connected. In addition, various control objects, sensors, and switches may be electrically connected to the ECU 1.

  The ROM is configured to store a program describing various processes executed by the CPU, map data, and the like. In this embodiment, in addition to the internal combustion engine control program, the specific opening / closing control program and the specific injection shown below. It also stores control programs. Note that these programs may be configured integrally. The specific opening / closing control program is created so as to perform control for communicating and blocking the bypass passage 13 by the opening / closing valve 14 in accordance with the bed temperatures of the front catalyst 11 and the rear catalyst 12 during deceleration operation. This specific opening / closing control program is created to specifically control the VSV 16 in this embodiment as a control for communicating and blocking the bypass passage 13 by the opening / closing valve 14. The specific injection control program is created so as to perform fuel injection control in the internal combustion engine 50 in accordance with the bed temperatures of the front catalyst 11 and the rear catalyst 12 during deceleration operation.

  Next, before describing the specific passage opening / closing program and the specific injection control program more specifically, the relationship between the catalyst bed temperature and the catalyst state will be described with reference to FIG. As shown in FIG. 2, the state of the catalyst changes according to the bed temperature. When the bed temperature is equal to or higher than T2 (corresponding to the first predetermined value recited in the claims), the catalyst is in a state of being deteriorated in a stoichiometric atmosphere. The temperature range at this time is A. When the bed temperature is lower than T2 and equal to or higher than T1 (corresponding to the second predetermined value in the claims), the catalyst is in a state of deteriorating in a lean atmosphere. The temperature range at this time is B. For example, when the deceleration F / C is performed when the bed temperature of the catalyst is included in the temperature range B, the inside of the catalyst becomes a lean atmosphere, and as a result, sintering occurs and the catalyst deteriorates. When the catalyst bed temperature is included in the temperature range B and the inside of the catalyst is not in a lean atmosphere, the exhaust gas can be purified by the catalyst.

  When the bed temperature is lower than T1 and equal to or higher than T0 (corresponding to a third predetermined value in the claims), the catalyst is activated. The temperature range at this time is C. At this time, the exhaust gas can be purified by the catalyst. At this time, since the sintering does not occur even if the deceleration F / C is performed, the catalyst is not deteriorated by this. If the bed temperature is less than T0, the catalyst becomes inactive. Note that D is a temperature range at this time. At this time, the catalyst cannot exhibit purification performance.

  In consideration of the relationship shown in FIG. 2, the specific passage opening / closing program and the specific injection control program are more specifically created as follows. For example, when the bed temperature of the pre-catalyst 11 is lower than T2 and equal to or higher than T1 during the deceleration operation, and the bed temperature of the post-catalyst 12 is lower than T0, the specific open / close control program uses the open / close valve 14 and the bypass passage 13 The specific injection control program is created to perform control for injecting the minimum ignitable fuel.

  As a result, it is possible to prevent the inside of the pre-catalyst 11 from becoming a lean atmosphere and further to a higher temperature, so that it is possible to prevent sintering from occurring in the pre-catalyst and the pre-catalyst 11 is deteriorated in a stoichiometric atmosphere. Can also be prevented. Further, this allows the combustion gas that has been heated at the pre-catalyst 11 to be heated to the post-catalyst 12, so that the bed temperature of the post-catalyst can be improved more appropriately. The purification performance of the post catalyst 12 can be ensured.

  Further, for example, when the bed temperature of the pre-catalyst 11 is equal to or higher than T1 and the bed temperature of the post-catalyst 12 is equal to or higher than T1 during the deceleration operation, the specific open / close control program communicates the bypass passage 13 with the open / close valve 14. The specific injection control program is created so as to perform control for injecting the minimum ignitable fuel. Thereby, since it is possible to prevent the interior of both the pre-catalyst 11 and the post-catalyst 12 from becoming a lean atmosphere, it is possible to prevent sintering of the pre-catalyst 11 and the post-catalyst 12. In addition, since the post-catalyst 12 can be prevented from becoming higher in temperature, the post-catalyst 12 can be prevented from being deteriorated in a stoichiometric atmosphere.

  Further, for example, when the bed temperature of the pre-catalyst 11 is equal to or higher than T1 and the bed temperature of the post-catalyst is lower than T1 and equal to or higher than T0 during the deceleration operation, the specific open / close control program uses the open / close valve 14 and the bypass passage 13. The specific injection control program is created so as to perform fuel cut control. Thereby, since the inside of the pre-catalyst 11 can be prevented from becoming a lean atmosphere, it is possible to prevent the sintering of the pre-catalyst 11. Further, since the bed temperature of the post-catalyst 12 is at an activation temperature below the temperature at which the catalyst deteriorates in a lean atmosphere, even if the inside of the post-catalyst 12 becomes a lean atmosphere due to execution of fuel cut control, it deteriorates due to sintering. Therefore, the purification performance of the post catalyst 12 can be secured. Further, the fuel consumption can be further reduced by executing the fuel cut control.

  For example, when the bed temperature of the pre-catalyst 11 is lower than T1 and the bed temperature of the post-catalyst 12 is lower than T1 and equal to or higher than T0 during the deceleration operation, the specific open / close control program uses the open / close valve 14 and the bypass passage. 13 is created to perform control for shielding 13, and the specific injection control program is created to perform fuel cut control. In this case, since both the pre-catalyst 11 and the post-catalyst 12 are not deteriorated by sintering even if the inside becomes a lean atmosphere, this prevents the pre-catalyst 11 from causing sintering, The purification performance of the post catalyst 12 can be secured. Further, the fuel consumption can be further reduced by executing the fuel cut control.

  For example, when the bed temperature of the pre-catalyst 11 is lower than T1 and the bed temperature of the post-catalyst 12 is lower than T0 during the deceleration operation, the specific open / close control program blocks the bypass passage 13 with the open / close valve 14. The specific injection control program is created to perform control for injecting fuel. In this case, since both the pre-catalyst 11 and the post-catalyst 12 do not deteriorate due to sintering even if the inside becomes a lean atmosphere, this causes the pre-catalyst 11 and the post-catalyst 12 to sinter. Can be prevented. Further, since the combustion gas reacted in the front catalyst 11 is supplied to the rear catalyst 12, the bed temperature of the rear catalyst 12 can be suitably improved, and thus the purification performance of the rear catalyst 12 can be ensured.

  FIG. 3 is a diagram showing a table in which the on-off valve 14 and the injection control state during the deceleration operation are classified according to the bed temperatures of the front catalyst 11 and the rear catalyst 12. As a result of the control being performed during the deceleration operation based on the specific opening / closing control program and the specific injection control program described above, the state of the on / off valve 14 and the injection control is specifically the bed temperatures of the front catalyst 11 and the rear catalyst 12. As shown in FIG. As an example, a case where the bed temperature of the pre-catalyst 11 is lower than T2 and T1 or higher and the bed temperature of the post-catalyst 12 is lower than T0 will be described with reference to FIG.

  In this case, the bed temperature of the pre-catalyst 11 is included in the temperature range B, and the bed temperature of the post-catalyst 12 is included in the temperature range D. This case is shown in the fourth column from the bottom in the table shown in FIG. At this time, the ECU 1 performs control for shielding the bypass passage 13 by the on-off valve 14 based on the specific opening / closing control program, and performs control for injecting the minimum ignitable fuel based on the specific injection control program. Is called. On the other hand, when the fourth column from the bottom of the table shown in FIG. 3 is viewed, it can be seen that the state of the on-off valve 14 is closed and the state of the injection control is “Yes”. The table shown in FIG. 3 also shows the corresponding on-off valve 14 and the state of injection control when the bed temperatures of the front catalyst 11 and the rear catalyst 12 are otherwise.

  In the present embodiment, various control means, determination means, detection means, calculation means, etc. are realized by the program and microcomputer stored in the ROM, and in particular, the specific opening / closing control means by the specific opening / closing control program and the microcomputer, Specific injection control means is realized by the specific injection control program and the microcomputer.

  Next, the process performed by the ECU 1 will be described in detail with reference to the flowchart shown in FIG. Note that although this flowchart includes processing that is performed based on a program that is not particularly specified in the above description because it is a well-known technique, all of the processing shown in this flowchart is stored in a program stored in the ROM. Based on. CPU performs the process which determines whether it became deceleration driving | operation (step S11). Whether or not the vehicle is decelerated is determined based on, for example, the output of the crank angle sensor, and whether or not the rotational speed NE is equal to or higher than a predetermined rotational speed, and the accelerator is turned off based on the output of the accelerator opening sensor. It can be determined by determining whether or not the vehicle is decelerating if it is both affirmative and by determining that the vehicle is not decelerating otherwise.

  If a negative determination is made, no special processing is required in this flowchart, and the process returns and returns to step S11. On the other hand, if the determination is affirmative, the CPU executes a process of detecting the bed temperature of the pre-catalyst 11 based on the output of the first bed temperature detection sensor 31 and outputs to the output of the second bed temperature detection sensor 32. Based on this, a process for detecting the bed temperature of the post-catalyst 12 is executed (step S12). Subsequently, the CPU executes processing for performing control (bypass control) for communicating and shielding the bypass passage 13 with the on-off valve 14 in accordance with the detected bed temperatures of the front catalyst 11 and the rear catalyst 12. Then, a process for performing fuel injection control in the internal combustion engine 50 is executed (step S13). At this time, the state of the on-off valve 14 and the injection control is specifically one of the states shown in FIG. 3 according to the bed temperatures of the front catalyst 11 and the rear catalyst 12. Thereby, the purification performance of the post catalyst 12 can be ensured while preventing the sintering of the pre catalyst 11.

  After executing the process shown in step S13, the process returns to step S11. If the determination in step S11 is affirmative, the process proceeds to step S12. That is, the process shown in this flowchart is repeatedly executed during the deceleration operation. As a result, even when the bed temperature of the pre-catalyst 11 or the post-catalyst 12 is included in a different temperature range during the deceleration operation, the post-catalyst 11 is prevented from being sintered while the post-catalyst is prevented. The purification performance of the catalyst 12 can be ensured. As described above, in the internal combustion engine system 100 including the pre-catalyst 11, the post-catalyst 12, and the catalyst bypass system 20 that bypasses the exhaust gas flowing into the pre-catalyst 11, sintering of the pre-catalyst 11 is prevented. Thus, the ECU 1 capable of ensuring the purification performance of the post catalyst 12 can be realized.

  The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. For example, the specific passage opening / closing means and the specific injection control means may perform control according to the bed temperatures of the pre-catalyst and the post-catalyst detected by the sensor as the bed temperatures of the pre-catalyst and the post-catalyst. Although suitable, it is also possible to perform control according to the bed temperature as an estimated value calculated by calculation. Further, in the above-described embodiment, the combination of the bypass control and the injection control which are considered to be optimal according to the bed temperatures of the pre-catalyst 11 and the post-catalyst 12 is shown, but the invention according to claim 1 is not limited thereto, By performing bypass control and injection control in other different combinations according to the bed temperature of the front catalyst and the rear catalyst, purification performance of the rear catalyst can be improved while preventing sintering from occurring in the front catalyst. It is also possible to ensure.

1 is a diagram schematically showing an ECU 1 together with an internal combustion engine system 100. FIG. It is a figure which shows typically the relationship between the bed temperature of a catalyst, and the state of a catalyst. It is a figure which shows the table | surface which classified the state of the on-off valve 14 and the injection control at the time of deceleration driving | operation according to the bed temperature of the front catalyst 11 and the rear catalyst 12. FIG. It is a figure which shows the process performed by ECU1 with a flowchart.

Explanation of symbols

1 ECU
DESCRIPTION OF SYMBOLS 10 Exhaust system 11 Pre-catalyst 12 Post-catalyst 13 Bypass passage 14 On-off valve 15 Actuator 16 VSV
17 conduit 20 catalyst bypass system 31 first bed temperature detection sensor 32 second bed temperature detection sensor 50 internal combustion engine 100 internal combustion engine system

Claims (1)

An internal combustion engine, a pre-catalyst disposed in an exhaust system of the internal combustion engine, a post-catalyst disposed downstream of the pre-catalyst, a bypass passage bypassing the pre-catalyst, and the bypass A control device for an internal combustion engine system for performing control with an internal combustion engine system configured to include a passage opening / closing means that communicates and shields the passage,
The front depending on the bed temperature of the-catalyst and the post-catalyst during deceleration operation, communicating the bypass passage with said passage opening and closing means, a certain opening and closing control means for controlling for shielding,
In response to said bed temperature of the pre-catalyst and the post-catalyst during the reduction operation, and a specific injection control means for performing injection control of fuel in the internal combustion engine,
When the bed temperature of the pre-catalyst and the bed temperature of the post-catalyst are temperatures at which the catalyst deteriorates in a lean atmosphere, the specific opening / closing control means performs control for communicating the bypass passage with the passage opening / closing means. And performing control for injecting the minimum ignitable fuel by the specific injection control means .

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