JP5040702B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine having an EGR catalyst in an EGR passage for, for example, an external EGR (Exhaust Gas Recirculation: EGR).

  In this type of internal combustion engine, for example, Patent Document 1 proposes a configuration in which an EGR catalyst is disposed in an EGR passage that communicates an upstream portion of the exhaust passage with respect to the turbine and the intake passage. In this configuration, the EGR passage and the downstream portion of the turbine communicate with each other so that the exhaust can bypass the turbine, and an adjustment valve that adjusts the exhaust flow rate of each passage is provided, and the exhaust gas is exhausted according to the temperature of the EGR catalyst. Techniques for controlling the flow have been proposed.

Japanese Unexamined Patent Publication No. 7-91232 JP 2005-264821 A

  However, for example, Patent Document 1 described above does not consider the temperature retention of the EGR catalyst. Specifically, when the exhaust gas is not recirculated by the external EGR, the temperature of the EGR catalyst is lowered, so that it is difficult to maintain the EGR catalyst in an active state.

  The present invention has been made in view of, for example, the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine for keeping the EGR catalyst warm even when exhaust gas recirculation is not performed.

  The control apparatus for an internal combustion engine according to the present invention is a first passage that communicates an upstream portion of the exhaust passage of the internal combustion engine with respect to a turbine driven by exhaust and an intake passage provided with a compressor driven by the turbine. A first passage provided with an EGR catalyst for purifying exhaust gas and a first control valve for adjusting the flow rate of exhaust gas flowing through the first passage in this order from the upstream side of the exhaust passage, and the first passage among the first passage A second passage that communicates a downstream portion from the EGR catalyst and a downstream portion from the turbine in the exhaust passage, and includes a second control valve that adjusts a flow rate of the exhaust gas flowing through the second passage. A control device for an internal combustion engine that controls an internal combustion engine including a passage, wherein a required recirculation amount of exhaust gas recirculated to the intake passage through the first passage is specified based on operating conditions of the internal combustion engine Required recirculation amount specifying means, temperature specifying means for specifying the temperature of the EGR catalyst, the specified required recirculation amount being lower than a predetermined recirculation amount, and the temperature of the specified EGR catalyst being lower than a predetermined temperature Comprises a control means for controlling the temperature of the EGR catalyst by controlling the second control valve to open intermittently.

  According to the control apparatus for an internal combustion engine according to the present invention, the first passage communicates the upstream portion of the exhaust passage of the internal combustion engine with the intake passage provided with the compressor. The first passage is provided with an EGR catalyst and a first control valve in this order from the upstream side of the exhaust passage. As the first control valve is opened, the flow rate of the exhaust gas flowing through the first passage and returning to the intake passage increases. Thereby, so-called external EGR processing is performed. Note that an EGR cooler for exhaust cooling and exhaust heat recovery may be provided at the subsequent stage of the EGR catalyst. The “exhaust passage” and the “intake passage” are not limited to literal meanings, but may have a comprehensive meaning including an exhaust manifold and a surge tank, and may be synonymous with an exhaust system and an intake system, respectively.

  The second passage is branched from the first passage, and communicates the downstream portion of the first passage with respect to the EGR catalyst and the downstream portion of the exhaust passage with respect to the turbine. The second passage is provided with a second control valve. As the second control valve is opened, the flow rate of the exhaust gas flowing through the second passage increases.

  The required recirculation amount specifying means includes, for example, an internal combustion engine clan angle sensor and an electronic control unit, and specifies the required recirculation amount of exhaust required according to the operating condition of the internal combustion engine based on the operating condition of the internal combustion engine. To do. The operating condition of the internal combustion engine is, for example, the rotational speed or torque of the internal combustion engine. The required recirculation amount is defined in association with the operating condition of the internal combustion engine in a predetermined map, for example, and is about 15% at the maximum, and is substantially zero at idling and at a high required output.

  The temperature specifying means specifies the temperature of the EGR catalyst. The temperature specifying means is, for example, an EGR catalyst, a cooling water for an internal combustion engine, or a temperature sensor installed in a pipe line of an exhaust passage. The temperature specifying means is not particularly limited as long as the temperature of the EGR catalyst can be specified within a range of errors allowed in determination processing by the control means described later. For example, instead of the temperature sensor, when the internal combustion engine is cold started, it may be estimated that the temperature of the EGR catalyst does not exceed a predetermined temperature described later.

  Here, in order to reduce the exhaust gas recirculation amount when the recirculation amount of the exhaust gas specified as described above is lower than a predetermined recirculation amount (for example, the exhaust gas recirculation amount necessary to keep the EGR catalyst in an activated state). The first control valve is almost or completely closed. Further, when the second control valve is almost or completely closed, the flow of the exhaust gas from the exhaust passage to the first passage side is almost or completely eliminated, and the temperature rise of the EGR catalyst due to the exhaust cannot be expected. The temperature of the EGR catalyst is lower than a predetermined temperature (for example, an activation temperature of the EGR catalyst or a temperature slightly higher than that), and the purification ability of the EGR catalyst may be reduced. In this situation, when the exhaust gas recirculation is instructed again, until the EGR catalyst becomes active, the aged fuel and particulate matter in the exhaust gas are not sufficiently removed, so that they accumulate in the intake passage, There is a risk of contaminating the EGR cooler.

  Therefore, when the recirculation amount of the exhaust gas specified as described above is lower than the predetermined recirculation amount and the temperature of the specified EGR catalyst is lower than the predetermined temperature, the control means composed of, for example, the electronic control device, performs the second control. The valve is controlled to open intermittently, that is, the EGR catalyst is kept warm. Note that “intermittently opening the second control valve” is sufficient to bring the EGR catalyst to an active state or a state close to it as a result, but a reduction in supercharging pressure due to exhaust bypassing the turbine. Means that the second control valve is opened at a predetermined low frequency for a short time so as not to cause a practical problem. When the second control valve is opened, it may be simply opened fully, but the opening may be in accordance with other parameters such as operating conditions of the internal combustion engine. In addition, when the EGR cooler is further provided, the fact that there is no waste heat recovery request may be further added as an execution condition of the above EGR catalyst heat retention control.

  As described above, according to the control apparatus for an internal combustion engine according to the present invention, even if the recirculation amount of the specified exhaust gas is lower than the predetermined recirculation amount, and the temperature of the specified EGR catalyst is lower than the predetermined temperature, However, since the second control valve is intermittently opened, the exhaust gas flows intermittently through the second passage via the EGR catalyst. Thereby, the EGR catalyst can be suitably kept warm by the exhaust energy. Meanwhile, if the first control valve is closed, it is possible to suppress the recirculation of excess exhaust gas to the intake passage, while the second control valve is also closed for most of the period, so that the reduction of the supercharging pressure can be suppressed as much as possible. .

  In one aspect of the control apparatus for an internal combustion engine according to the present invention, the control device further includes an intake air amount adjusting means for adjusting a flow rate of the intake air sucked from the intake passage, and the control means performs the heat retention control of the EGR catalyst. In addition, the intake air amount adjusting means is further controlled so as to relatively increase the flow rate of the intake air in accordance with the opening period of the second control valve that opens intermittently.

  According to this configuration, the intake air amount adjusting means adjusts the flow rate of the intake air drawn from the intake passage. The flow rate of the intake air can be adjusted by changing the opening of the intake throttle valve, the valve timing, and the valve lift amount. The control means further includes an intake air amount adjusting means so as to relatively increase the intake air flow rate in accordance with the opening period of the second control valve that is intermittently opened when executing the EGR catalyst heat retention control. Control. As a result, the intake passage pressure also rises relatively, so that the supercharging pressure that can be reduced as a result of the second control valve being opened intermittently is compensated for, so that a reduction in the output of the internal combustion engine can be avoided. The period for relatively increasing the flow rate of the intake air does not have to be completely coincident with the valve opening period of the second control valve, and the period may be changed in consideration of a response delay or the like.

  In the aspect in which the intake air amount adjusting unit is further controlled, when the intake air flow rate is adjusted to the maximum flow rate by the intake air amount adjusting unit, the control unit stops or inhibits the heat retention control of the EGR catalyst. Good.

  According to this configuration, if the intake throttle valve is already fully opened or in the vicinity thereof, the intake flow rate cannot be increased even if the intake throttle valve is further opened. Stop or disable the heat insulation control. Thereby, the fluctuation | variation of the torque which the said internal combustion engine outputs can be avoided in advance. Note that the second control valve may be fixed in an open state or a closed state.

  In the aspect of stopping or prohibiting the temperature control of the EGR catalyst, the fluctuation of the output torque of the internal combustion engine even though the temperature control of the EGR catalyst is stopped or prohibited and the internal combustion engine is in an idle state. When the amount exceeds the predetermined fluctuation amount, it is preferable to further include a failure determination means for determining that the first control valve is broken.

  According to this configuration, it can be determined that at least the first control valve of the first control valve and the second control valve has failed (specifically, the closing failure). The accompanying misfire or engine stall can be avoided. The fluctuation amount of the output torque of the internal combustion engine can be specified by a clan angle sensor of the internal combustion engine, a torque sensor, or a torque reaction force calculation device based on the rotation speed and power generation amount of the motor generator.

  In another aspect of the control device for an internal combustion engine according to the present invention, the control means keeps the temperature of the EGR catalyst at the time of an acceleration request when the difference between the target boost pressure by the compressor and the actual boost pressure exceeds a predetermined boost pressure difference. Stop or prohibit control.

  According to this configuration, at the time of an acceleration request, in order to meet the acceleration request, priority can be given to avoiding a decrease in the output of the internal combustion engine over the heat retention control of the EGR catalyst. The “predetermined supercharging pressure difference” is a value determined in advance by experiments or the like as a pressure difference that allows the driver to recognize a deterioration in acceleration feeling because the response time for filling the supercharging pressure difference is relatively long. The feedback may be corrected.

  In this aspect, even when the acceleration is requested, if the flow rate of exhaust gas surplus for the turbine exceeds the maximum flow rate of exhaust gas that can pass through the second passage, the control means controls the heat retention of the EGR catalyst. It is advisable to allow execution.

  According to this configuration, the EGR catalyst can be kept warm and the waste heat can be recovered by the EGR cooler without reducing the supercharging pressure, that is, responding to the acceleration request. More specifically, when the flow rate of exhaust gas surplus for the turbine exceeds the maximum flow rate of exhaust gas that can pass through the second passage, the flow rate of exhaust gas for driving the turbine decreases even when the second control valve is fully opened. Therefore, even when the acceleration is requested, execution of the EGR catalyst heat retention control is permitted. The “excessive exhaust gas in the turbine” is exhaust gas having a flow rate exceeding the capacity of the turbine, for example, exhaust gas that passes through a waste gate valve. The "maximum exhaust flow rate that can pass through the second passage" is the flow rate of exhaust gas that passes through the second passage when the second control valve is fully opened. It is good also as the flow volume which did.

  In another aspect of the control apparatus for an internal combustion engine according to the present invention, the second control valve is disposed within a predetermined distance from a branch point of the second passage where the second passage branches from the first passage. ing.

  According to this configuration, the exhaust passage capacity upstream of the turbine (including the capacity of the first passage to the closed first control valve and the second passage to the closed second control valve) is minimized. Control responsiveness is improved.

  The operation and other advantages of the present invention will become apparent from the best mode for carrying out the invention described below.

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

<Configuration of Control Device for Internal Combustion Engine According to Embodiment>
First, the configuration of the control apparatus for an internal combustion engine according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic plan view showing a part of a vehicle 1 provided with a control device for an internal combustion engine according to an embodiment of the present invention.

  The vehicle 1 includes an intake passage 21, an internal combustion engine 200, an exhaust passage 31, a supercharger 40, and an external EGR device 7.

  The intake passage 21 is a passage for sending intake air from the outside to the internal combustion engine 200. In addition to an air cleaner and an intake flow meter (not shown), the intake passage 21 includes a compressor 41, which is a part of the supercharger 40, and an intake throttle valve 22. In preparation for the pipe line, the internal combustion engine 200 is connected via a surge tank 23. The compressor 41 increases the intake pressure using the rotation of the turbine 42 described later. The intake throttle valve 22 adjusts the intake air amount according to the opening degree. The opening degree of the intake throttle valve 22 is variable by a driving motor (not shown) under the control of the electronic control unit 100, and is detected by an opening sensor (not shown).

  The internal combustion engine 200 is an internal combustion engine that can output power by using a hydrocarbon-based fuel such as gasoline or light oil. For example, intake air used for combustion is taken in from the intake passage 21 and exhaust gas generated by the combustion is passed through the exhaust passage 31. To discharge. The communication state between the internal combustion engine 200 and the intake passage 21 changes according to opening / closing of an unillustrated intake valve, and the communication state between the internal combustion engine 200 and the exhaust passage 31 changes according to opening / closing of an unillustrated exhaust valve. To do. In addition, the internal combustion engine 200 includes a fuel injection valve and an ignition device. In general, the intake stroke, the compression stroke, the combustion / expansion stroke, and the exhaust stroke are repeated for each cylinder. The output of the internal combustion engine 200 is taken out by converting the vertical movement of a piston (not shown) in the cylinder into the rotational movement of a crankshaft (not shown).

  The exhaust passage 31 is a passage for exhausting the exhaust discharged along with the combustion of the internal combustion engine 200 to the outside, and includes an air-fuel ratio sensor, an exhaust temperature sensor, and a catalyst device 32 (not shown) in its pipeline. The catalyst device 32 is, for example, a three-way catalyst, which is activated when the activation temperature is reached, and purifies harmful components such as carbon monoxide, hydrocarbons, and nitrogen oxides contained in the exhaust gas. In addition, the exhaust passage 31 includes a turbine 42 which is a part of the supercharger 40 in its pipeline.

  The supercharger 40 includes a turbine 42 that is rotated by exhaust energy, a compressor 41 that performs supercharging that compresses intake air as the turbine 42 rotates, a turbine bypass passage 43 that bypasses the upstream and downstream of the turbine 42, and the turbine 42. And a waste gate (W / G) valve 44 for adjusting the flow rate of the exhaust gas flowing through the turbine bypass passage 43. The opening degree of the waste gate valve 44 is adjusted according to the required supercharging pressure under the control of the electronic control unit 100.

  The external EGR device 7 includes a first passage 70 and a second passage 80. The first passage 70 communicates the upstream portion of the exhaust passage 31 with respect to the turbine 42 and the intake passage 21 (for example, the surge tank 23 which is a part thereof), and in order from the upstream portion, the EGR catalyst 71 and the EGR cooler. 73 and a first control valve 74. The EGR catalyst 71 is a catalyst that purifies unburned fuel and particulate matter contained in the exhaust gas flowing through the first passage 70 and returning to the intake passage 21 during external EGR, thereby reducing deposits accumulated in the intake passage 21. it can. The EGR catalyst 71 includes an EGR catalyst temperature sensor 72 that detects the temperature, and the detection result is transmitted to the electronic control unit 100. The EGR cooler 73 functions not only as a cooling function but also as a waste heat recovery device. The first control valve 74 opens and closes under the control of the electronic control device 100, and adjusts the flow rate of exhaust gas flowing through the first passage 70 and returning to the intake passage 21 according to the opening degree. The second passage 80 branches from the first passage 70 at the branch point 78 and communicates with the downstream portion of the exhaust passage 31 relative to the turbine 42. The second control valve 81 opens and closes under the control of the electronic control device 100, and adjusts the flow rate of the exhaust gas flowing through the second passage 80 according to the opening degree. The second control valve 81 may be controlled only in two stages of fully open / fully closed. However, in this embodiment, “fully open” and “fully closed” do not mean only the literal states of “fully open” and “fully closed”, but an expected effect is obtained. The purpose is to allow some margin as much as possible. The second control valve 81 is preferably provided at or near the branch point 78. This is because when the capacity upstream of the turbine 42 in the exhaust passage 31 is large, the supercharging response is deteriorated. The two thick arrows in FIG. 1 indicate the first route and the second route. The first path is a path through which the exhaust flows through the first passage 70 when the first control valve 74 is fully open and the second control valve 81 is fully closed. The second path is a path through which exhaust flows through the second passage 80 when the first control valve 74 is fully closed and the second control valve 81 is fully open. Incidentally, in the case of the first path, the above-described EGR cooler 73 functions as a literal cooling device, and in the second path, the EGR cooler 73 functions as a waste heat recovery device.

  The electronic control device 100 is a digital computer in which a ROM (Read Only Memory: ROM), a RAM (Random Access Memory: RAM), a CPU (Central Processing Unit: CPU), an input port and an output port are connected to each other via a bidirectional bus. Consists of. The input port of the electronic control unit 100 includes an EGR catalyst temperature sensor 72, an accelerator opening sensor 101 that receives an acceleration request from a driver by detecting the depression amount of an unillustrated accelerator pedal, and a crank angle sensor 62. Various sensors are connected. The electronic control device 100 performs basic control such as fuel injection control and ignition timing control of the internal combustion engine 200 via the output port, and also performs heat retention control of the EGR catalyst 71 described later. In the heat retention control of the EGR catalyst 71, the opening control of the first control valve 74, the second control valve 81, the intake throttle valve 22, and the waste gate valve 44 is appropriately performed.

<Operation of Control Device for Internal Combustion Engine According to Embodiment>
By the way, the above-described external EGR and waste heat recovery are not used under all operating conditions of the internal combustion engine 200. Temporarily, under the operating conditions in which external EGR and waste heat recovery are not performed, the purification performance of the EGR catalyst 71 is lowered, which causes deposits in the intake passage 21. Therefore, the temperature control of the EGR catalyst 71 is performed under the control of the electronic control device 100. This control will be described with reference to FIGS.

  FIG. 2 is a flowchart showing a main routine by the control device for an internal combustion engine according to the embodiment.

  As shown in FIG. 2, prior to the heat retention control of the EGR catalyst 71, it is determined whether or not there is a request for external EGR (step S1). For example, it is determined whether the required recirculation amount specified based on the operating condition of the internal combustion engine 200 is smaller than a predetermined recirculation amount. The required recirculation amount is specified by, for example, the crank angle sensor 62 and the electronic control device 100 with reference to a map in which the correspondence relationship between the rotational speed of the internal combustion engine 200 and the required recirculation amount is described.

  When there is no request for external EGR (step S1: Yes), the first control valve 74 is fully closed, so that the exhaust does not flow through the first path. Next, it is determined whether or not there is a waste heat recovery request (step S2). The presence / absence of the waste heat recovery request is determined based on the operating condition of the internal combustion engine 200 and the opening control signal for the second control valve 81. Here, when there is no waste heat recovery request (step S2: Yes), the second control valve 81 is fully closed, so that the exhaust does not flow through the second path. Then, since the exhaust does not flow to the EGR catalyst 71, the exhaust energy is insufficient and the temperature of the EGR catalyst 71 decreases. Therefore, the temperature of the EGR catalyst 71 is specified by the EGR catalyst temperature sensor 72, and it is determined whether or not the temperature is lower than a predetermined temperature (for example, a value close to the catalyst activation temperature) (step S3). Here, when the temperature of the EGR catalyst 71 is lower than the predetermined temperature (step S3: Yes), the purification performance of the EGR catalyst 71 is deteriorated. If the first control valve 74 is opened again in this state, immediately after that, the unburned fuel and the particulate matter are not sufficiently reduced, which causes deposits in the intake passage 21. Therefore, the temperature control of the EGR catalyst 71 is performed under the control of the electronic control unit 100 (step S4). Specifically, as will be described later with reference to FIG. 3, the second control valve 81 is intermittently opened, and the exhaust gas is caused to flow through the second path for exhaust heat recovery. Further, the intake throttle valve 22 is also synchronously controlled in order to prevent a torque drop at that time. Thereby, even when the first control valve 74 is opened again, the EGR catalyst 71 can suitably purify the exhaust gas flowing through the first path.

  When there is a request for external EGR (step S1: Yes), there is a request for waste heat recovery (step S2: No), or when the temperature of the EGR catalyst 71 exceeds a predetermined temperature (step S3: No). Since the exhaust gas flows through the EGR catalyst 71 or is kept at a sufficiently high temperature even if it does not flow, the temperature control of the EGR catalyst 71 can be omitted.

  By the way, in the heat retention control of the EGR catalyst 71, if the second control valve 81 is intermittently opened, the following problem may occur. This problem and its solution will be described with reference to FIG.

  FIG. 3 is a timing chart showing a change with time such as torque output from the internal combustion engine 200 when the second control valve is intermittently opened in comparison with (a) the comparative example and (b) the embodiment. .

  As shown in the two timing charts from the top of FIG. 3, when the second control valve 81 is intermittently opened, the differential pressure across the turbine 42 decreases in synchronization therewith. At this time, as shown in the comparative example of FIG. 3A, the surge tank 23 pressure is also intermittently lowered unless any measures are taken with respect to the opening degree of the intake throttle valve 22. As a result, the output torque from the internal combustion engine 200 also decreases intermittently, and the amount of fluctuation in the output torque increases. Therefore, in the present embodiment shown in FIG. 3B, the opening degree of the intake throttle valve 22 is relatively increased in accordance with the opening period of the second control valve 81 so as to keep the surge tank 23 pressure constant. As a result, the EGR catalyst 71 can be kept warm while suppressing the fluctuation amount of the output torque by the internal combustion engine 200. The temperature control of the EGR catalyst 71 is shown in FIG.

  FIG. 4 is a flowchart showing a subroutine for the heat retention control of the EGR catalyst 71 by the control device for an internal combustion engine according to the embodiment.

  As shown in FIG. 4, in the heat retention control of the EGR catalyst 71, first, it is determined whether or not the opening degree of the intake throttle valve 22 is less than a predetermined opening degree near the fully open position (step S41). When the opening degree of the intake throttle valve 22 is equal to or larger than the predetermined opening degree near the full opening (step S41: No), the opening degree of the intake throttle valve 22 is set to be larger than the opening period of the second control valve 81. It is almost impossible to raise. Therefore, intermittent opening of the second control valve 81 is prohibited, and the first control valve 74 and the second control valve 81 are fully closed and fixed (step S45).

  On the other hand, when the opening degree of the intake throttle valve 22 is less than the predetermined opening degree near the full opening (step S41: Yes), it is then determined whether or not the predetermined acceleration request is being made (step S42). For example, when the predetermined acceleration is requested, the difference between the target supercharging pressure and the actual supercharging pressure related to the supercharger 40 exceeds the predetermined supercharging pressure difference. Here, at the time of a predetermined acceleration request (step S42: No), in order to respond to the acceleration request, it is prohibited to open the second control valve 81 intermittently, and the first control valve 74 and the second control valve 81 are turned off. Fully closed and fixed (step S45).

On the other hand, if it is not at the time of a predetermined acceleration request (step S42: Yes), it is permitted to open the second control valve 81 intermittently. Specifically, over the second control valve 81 for a predetermined period _{T 1} is fully closed (step S43), then the fully opened for a predetermined time period _{T 2} (step S44). This is repeated. As a result, the EGR catalyst 71 can be kept warm while suppressing the fluctuation amount of the output torque by the internal combustion engine 200. The predetermined time period T ₂ are, it is preferable to minimize a short period in a range through which the exhaust as needed warmth of the EGR catalyst 71.

  By the way, at the time of the above-mentioned acceleration request | requirement (step S42: No), both the 1st 1st control valve 74 and the 2nd control valve 81 are closed (step S45), and a boost pressure boost has priority. Then, the rotation speed increases while the acceleration request continues. Along with this, the back pressure increases and the waste gate valve 44 of the supercharger 40 opens. Therefore, when the W / G flow rate, which is the exhaust flow rate flowing through the waste gate valve 44, exceeds a predetermined flow rate (for example, the maximum flow rate that can flow through the second passage 80, or a flow rate that adds a slight margin to the flow rate). (Step S46: Yes), the second control valve 81 is opened intermittently (Steps S43 and S44). Then, the EGR catalyst 71 can be kept warm without reducing the supercharging pressure. This will be described in detail with reference to FIG.

  FIG. 5 is a characteristic diagram showing (a) the relationship between the rotational speed and the supercharging pressure in the fully opened state and the fully closed state of the second control valve, and (b) the relationship between the rotational speed and the W / G flow rate, respectively. is there.

  As shown in FIG. 5A, as the rotational speed of the internal combustion engine 200 increases, the boost pressure also increases due to the increase in exhaust gas. Further, as shown in FIG. 5 (b), as the rotational speed of the internal combustion engine 200 increases, surplus exhaust gas increases due to an increase in exhaust gas, so the W / G flow rate also increases. However, when the second control valve 81 is fully opened, the increase in the supercharging pressure is delayed compared to when the second control valve 81 is fully closed. This is because part of the exhaust escapes to the second passage 80. The same applies to the W / G flow rate.

Here, as shown in FIG. 5B, when the rotational speed of the internal combustion engine 200 exceeds Ne ₂ , the exhaust gas increases excessively, and the exhaust gas is excessive even though the second control valve 81 is fully opened. , W / G flow rate exceeds 0. In other words, the surplus exhaust gas flow rate for the turbine 42 exceeds the maximum exhaust gas flow rate that can pass through the second passage 80. In this case (step S46: Yes), even if the second control valve 81 is fully opened, the flow rate of the exhaust gas for driving the turbine 42 does not decrease. The second control valve 81 is intermittently opened (steps S43 and S44).

  As described above, according to the control device for an internal combustion engine according to the present embodiment, the EGR catalyst 71 can be suitably kept warm even when external EGR or waste heat recovery is not performed.

<Operation of Control Device for Internal Combustion Engine According to Modification>
Next, an operation process according to the above modification will be described with reference to FIG. This modification is particularly for determining whether the first control valve 74 has failed. The basic configuration may be the same as in FIG. 1, and the same components are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

  FIG. 6 is a flowchart showing a routine by the control device for the internal combustion engine according to the modified embodiment.

  As shown in FIG. 6, in the control according to the modification, first, the catalyst warm-up control for the EGR catalyst 71 is performed (step S101: Yes), but the temperature of the EGR catalyst 71 is lower than the predetermined temperature. In that case (step S102: Yes), the first control valve 74 is fully closed and the second control valve 80 is fully opened (step S103). On the other hand, if the temperature of the EGR catalyst 71 is equal to or higher than the predetermined temperature (step S102: No), the first control valve 74 is fully closed and the second control valve 80 is fully closed (step S104).

  When the catalyst warm-up control for the EGR catalyst 71 is not performed (step S101: No) and there is a request for external EGR (step S105: Yes), the first control valve 74 is opened to a predetermined opening. Then, the second control valve 80 is fully closed (step S106).

  On the other hand, if there is no request for external EGR (step S105: No), the first control valve 74 is basically fully closed. Here, when it is a light load region (step S107: Yes), since the required supercharging pressure is low, the second control valve 80 is fully opened (step S108). On the other hand, if it is not in the light load region (step S107: No), the second control valve 80 is fully closed to avoid a decrease in supercharging pressure (step S109). As a result, if the supercharging pressure becomes equal to or higher than the predetermined pressure (step S110: No), it is considered that the first control valve 74 and the like are closed as controlled.

  On the other hand, if the supercharging pressure does not become equal to or higher than the predetermined pressure (step S110: Yes), it is temporarily determined that the first control valve 74 is closed poorly (step S111). If the variation amount of the output torque is equal to or greater than the predetermined variation amount (step S113: Yes) even though the idling is on (step S112: Yes), it is determined that the first control valve 74 is poorly closed. Then, the diagnosis is turned on (step S115).

  On the other hand, even if it is temporarily determined that the first control valve 74 is poorly closed, if the idle is not on (step S112: No) or the variation amount of the output torque is not equal to or greater than the predetermined variation amount (step S113: No), the provisional determination is canceled (return).

  According to the above-described modification, since a part of the exhaust gas passes through the EGR catalyst 71 even in the non-EGR region on the light load side, the EGR catalyst 71 can be kept warm, and deposits in the intake system are deposited. Can be suppressed. In addition, since the closing failure of the first control valve 74 can be specified, the diagnostic lighting can be performed only when it is really necessary.

In the above embodiment and modified embodiments,
The “exhaust passage 31” is an example of the “exhaust passage” according to the present invention,
"Turbine 42" is an example of the "turbine" according to the present invention,
“Compressor 41” is an example of the “compressor” according to the present invention.
The “intake passage 21” is an example of the “intake passage” according to the present invention,
The “first passage 70” is an example of the “first passage” according to the present invention,
“EGR catalyst 71” is an example of “EGR catalyst” according to the present invention,
The “first control valve 74” is an example of the “first control valve” according to the present invention,
The “second passage 80” is an example of the “second passage” according to the present invention,
The “second control valve 81” is an example of the “second control valve” according to the present invention,
“The rotational speed of the internal combustion engine 200” is an example of the “operating condition of the internal combustion engine” according to the present invention,
"Electronic control device 100" is an example of "required reflux amount specifying means" according to the present invention,
"EGR catalyst temperature sensor 72" is an example of "temperature specifying means" according to the present invention,
"Electronic control device 100" is an example of "control means" according to the present invention,
The “intake throttle valve 22” is an example of the “intake amount adjusting means” according to the present invention,
The “branch point 78” is an example of the “branch point” according to the present invention.
In addition, known components necessary for the internal combustion engine are omitted as appropriate.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. The control device is also included in the technical scope of the present invention.

1 is a schematic plan view showing a part of a vehicle 1 including a control device for an internal combustion engine according to an embodiment of the present invention. It is a flowchart which shows the main routine by the control apparatus of the internal combustion engine which concerns on embodiment. FIG. 6 is a timing chart showing a temporal change in torque and the like output from the internal combustion engine 200 when the second control valve is intermittently opened, comparing (a) a comparative example and (b) an embodiment. 7 is a flowchart showing a subroutine for heat retention control of the EGR catalyst 71 by the control device for an internal combustion engine according to the embodiment. It is a characteristic view which shows the relationship between (a) rotation speed and supercharging pressure in the fully open state of a 2nd control valve, and a fully closed state, respectively, and (b) the relationship between rotation speed and W / G flow volume. It is a flowchart which shows the routine by the control apparatus of the internal combustion engine which concerns on a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vehicle, 1 ... Vehicle, 21 ... Intake passage, 22 ... Intake throttle valve, 23 ... Surge tank, 200 ... Internal combustion engine, 31 ... Exhaust passage, 32 ... Catalyst device, 40 ... Supercharger, 41 ... Compressor, 42 ... Turbine, 43 ... Turbine bypass passage, 44 ... Waste gate valve, 7 ... External EGR device, 70 ... First passage, 71 ... EGR catalyst, 72 ... EGR catalyst temperature sensor, 73 ... EGR cooler, 74 ... First control valve 80 ... second passage, 81 ... second control valve, 100 ... control device,

Claims (7)

An exhaust passage of an internal combustion engine, which is a first passage that communicates an upstream portion of a turbine driven by exhaust with an intake passage provided with a compressor driven by the turbine, the exhaust gas purifying EGR catalyst, and A first passage provided with a first control valve for adjusting the flow rate of the exhaust gas flowing through the first passage in this order from the upstream side of the exhaust passage;
A second passage that communicates the downstream portion of the first passage with respect to the EGR catalyst and the downstream portion of the exhaust passage with respect to the turbine, and adjusts the flow rate of the exhaust gas flowing through the second passage. A control device for an internal combustion engine that controls an internal combustion engine including a second passage including two control valves,
A required recirculation amount specifying means for specifying a required recirculation amount of exhaust gas recirculated to the intake passage via the first passage based on operating conditions of the internal combustion engine;
Temperature specifying means for specifying the temperature of the EGR catalyst;
By controlling the second control valve to open intermittently when the specified required reflux amount is below a predetermined reflux amount and the temperature of the specified EGR catalyst is below a predetermined temperature, An internal combustion engine control apparatus comprising: control means for executing heat retention control of the EGR catalyst. Further comprising an intake air amount adjusting means for adjusting the flow rate of the intake air drawn from the intake passage,
The control means adjusts the intake air amount so as to relatively increase the flow rate of the intake air in accordance with a valve opening period of the second control valve that is intermittently opened when performing the heat retention control of the EGR catalyst. The control device for an internal combustion engine according to claim 1, further comprising controlling the means. 3. The internal combustion engine according to claim 2, wherein when the flow rate of the intake air is adjusted to a maximum flow rate by the intake air amount adjusting unit, the control unit stops or prohibits the heat retention control of the EGR catalyst. Control device. When the temperature control of the EGR catalyst is stopped or prohibited, and the amount of torque fluctuation output from the internal combustion engine exceeds a predetermined amount of fluctuation even though the internal combustion engine is idle, the first The control device for an internal combustion engine according to claim 3, further comprising a failure determination unit that determines that one control valve has failed. 3. The control device according to claim 1, wherein the control means stops or prohibits the heat retention control of the EGR catalyst when an acceleration request is made such that a difference between a target boost pressure by the compressor and an actual boost pressure exceeds a predetermined deviation. The internal combustion engine control device described. When the flow rate of exhaust gas surplus for the turbine exceeds the maximum flow rate of exhaust gas that can pass through the second passage, the control means permits the EGR catalyst to perform heat retention control even when the acceleration is requested. The control device for an internal combustion engine according to claim 5, wherein: The said 2nd control valve is arrange | positioned within the predetermined distance from the branching point where the said 2nd passage branches from the said 1st passage among the said 2nd passages. The control device for an internal combustion engine according to one item.

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