JP2011196290A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device which sufficiently exhibits adsorption capacity by increasing the amount adsorbed by an adsorbent immediately after starting of an internal combustion engine.SOLUTION: This exhaust emission control device includes: the adsorbent adsorbing HC in exhaust gas when the temperature of the adsorbent is below emission temperature and discharging the adsorbed HC when the temperature of the adsorbent reaches temperatures higher than the emission temperature T1; a heat recovery device arranged upstream of the adsorbent and recovering heat from exhaust gas by performing heat exchange with exhaust gas; and an adsorption state determination means S13 determining that an adsorbable state is established on condition that the temperature of the adsorbent is below the emission temperature. When it is determined by the adsorption state determination means S13 that the adsorbable state is established (S11:YES, S13:YES), heat recovery increase control S14 is performed so that the amount of heat recovered by the heat recovery device is increased in comparison with a period when it is determined that the adsorbable state is not established, and also engine output reduction control S16 is performed so that the engine output is reduced in comparison with the period when it is determined that the adsorbable state is not established.

Description

  The present invention relates to an exhaust gas purification apparatus that adsorbs a specific component in exhaust gas of an internal combustion engine with an adsorbent.

  The adsorbent that adsorbs a specific component (for example, HC) in the exhaust gas of the internal combustion engine adsorbs HC when the adsorbent temperature is lower than the release temperature T1, and releases adsorbed HC when the adsorbent temperature is equal to or higher than the release temperature T1. The oxidation catalyst that oxidizes HC released from the adsorbent is activated and becomes oxidizable when the catalyst temperature is equal to or higher than the activation temperature T2. The activation temperature T2 is generally higher than the discharge temperature T1 (T2> T1). In short, HC is adsorbed by the adsorbent until the temperature of the oxidation catalyst reaches the activation temperature T2.

  By the way, at the time of cold start of the internal combustion engine, control for retarding the ignition timing (ignition retarding control) so as to raise the catalyst temperature to the activation temperature T2 at an early stage is disclosed in Patent Documents 1 and 2 and the like. Yes. However, if ignition retard control is performed immediately after the start of the internal combustion engine, the adsorbent temperature becomes equal to or higher than the release temperature T1 in a state where the adsorbed HC has not reached the saturation amount, and the adsorbing capacity by the adsorbent is sufficiently exhibited. Disappear. Therefore, in this type of exhaust gas purifying apparatus, ignition retard control is started from the time when the adsorbent temperature reaches the discharge temperature T1. Thereby, the catalyst warm-up is completed early while sufficiently increasing the amount of adsorption by the adsorbent.

JP 2004-116370 A JP 2001-164930 A

  However, if the exhaust gas temperature rises immediately after the start of the internal combustion engine, the adsorbent temperature may be equal to or higher than the discharge temperature T1 in a state where the adsorbed HC has not reached the saturation amount. In this case, since HC can be adsorbed only in an amount smaller than the saturation amount, it cannot be said that the adsorption capacity is sufficiently exhibited. This problem is not limited to the case where HC in the exhaust gas is adsorbed and oxidized, but can also occur in the same manner when NOx is adsorbed and reduced, for example.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to increase the amount of the adsorbent that is adsorbed immediately after the internal combustion engine is started so that the adsorption capacity can be sufficiently exerted. Is to provide.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  In the first aspect of the invention, the adsorbent that adsorbs the specific component in the exhaust gas of the internal combustion engine when its own temperature is lower than the release temperature, and releases the adsorbed specific component when its temperature is equal to or higher than the release temperature; A heat recovery unit that is arranged upstream of the adsorbent and exchanges heat with exhaust gas to recover heat from the exhaust gas, and is determined to be in an adsorbable state on condition that the temperature of the adsorbent is lower than the discharge temperature. An adsorption state determination unit, and when the adsorption state determination unit determines that the adsorption is possible, the amount of heat recovered by the heat recovery device is increased compared to when the adsorption state determination unit determines that the adsorption state is not possible The heat recovery increase control is performed, and the output decrease control is performed to decrease the output of the internal combustion engine as compared to when it is determined that the adsorption is not possible.

  According to this, the heat recovery device for recovering heat from the exhaust gas is arranged on the upstream side of the adsorbent, and the heat recovery amount is increased when the adsorption is possible (heat recovery increase control). Temperature rise can be suppressed. Furthermore, since the output of the internal combustion engine is reduced (output reduction control) when the adsorption is possible, the exhaust gas temperature rise immediately after the start of the internal combustion engine can be further suppressed. Therefore, it is possible to ensure a long time until the adsorbent temperature reaches the discharge temperature immediately after the start of the internal combustion engine. As a result, it is possible to increase the amount of adsorption by the adsorbent and to fully exhibit the adsorption capacity.

  According to a second aspect of the present invention, the adsorbable state can be maintained for a predetermined time or longer by performing the heat recovery increase control without performing the output reduction control when it is determined that the adsorbable state is achieved. Output reduction necessity determination means for determining whether or not the output reduction necessity determination means performs the output reduction control on the condition that the suction possible state cannot be maintained for a predetermined time or more by the output reduction necessity determination means. It is characterized by.

  Here, when the output reduction control is performed, there is a concern that the output of the internal combustion engine is reduced against the driver's output request, and the driver feels uncomfortable. In response to this concern, according to the above-described invention, if the adsorbable state can be maintained for a predetermined time or more only by performing the heat recovery increase control without performing the output decrease control, the heat recovery increase without performing the output decrease control. Since the control is performed, the adsorption capability of the adsorbent can be sufficiently exhibited while eliminating the above-mentioned concerns.

  The invention according to claim 3 is applied to a vehicle that uses the output of the electric motor in addition to the output of the internal combustion engine as a travel drive source. When the output reduction control is being executed, the output reduction control is being executed. Motor output increase control for increasing the output of the electric motor as compared to when there is not is performed.

  According to this, since the output of the electric motor is increased when the output reduction control is performed (motor output increase control), the actual output of the internal combustion engine in response to the driver's output request performs the output decrease control. It is possible to suppress the decrease with the increase. Therefore, it is possible to suppress the above-mentioned concern of “giving the driver a sense of incongruity”.

  According to a fourth aspect of the present invention, there is provided motor output increase enable / disable determining means for determining whether or not the output decrease by the output decrease control can be supplemented by the output increase of the electric motor, and the output decrease is The output reduction control is performed on the condition that it is determined that the output increase can be compensated.

  According to this, when the decrease in the output of the internal combustion engine cannot be compensated by the increase in the output of the electric motor, the execution of the output decrease control is not permitted. The output can be reduced and the driver can feel uncomfortable.

1 is a diagram showing a schematic configuration of an entire engine control system in a first embodiment of the present invention. The figure which shows the purification apparatus single-piece | unit of FIG. The flowchart which shows the process sequence of heat recovery increase control and engine output decrease control in 1st Embodiment. The time chart which shows the one aspect | mode by having implemented the process of FIG. The figure which shows schematic structure of the whole engine control system in 2nd Embodiment of this invention. The flowchart which shows the process sequence of heat recovery increase control and engine output decrease control in 2nd Embodiment. The time chart which shows the one aspect | mode by having implemented the process of FIG.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the same reference numerals is used.

(First embodiment)
The exhaust gas purifying apparatus according to this embodiment is applied to an ignition type gasoline engine (internal combustion engine). First, a schematic configuration of the entire engine control system will be described with reference to FIG.

  An intake pipe 12 of an engine 11 that is an internal combustion engine is provided with a throttle valve 13 that adjusts the throttle opening, and fuel is injected into each branch pipe portion of each cylinder of the intake manifold 14 that introduces air into each cylinder. A fuel injection valve 15 is attached.

  On the other hand, in the exhaust pipe 16 of the engine 11, a purification device 30 that reduces harmful components in the exhaust gas is installed in a downstream portion of the exhaust manifold 17. FIG. 2A is a view of the purification device 30 as viewed from the exhaust gas flow direction, and FIG. 2B is an enlarged view of FIG. As shown in FIG. 2, the purification device 30 includes a three-way catalyst that purifies HC, CO, and NOx or an oxidation catalyst that purifies HC and CO (hereinafter simply referred to as “catalyst 33”), and an adsorption that adsorbs HC. And a material 32.

  More specifically, the purifying device 30 coats an adsorbent 32 such as zeolite on the inner wall surface of a carrier 31 formed in a honeycomb shape with a ceramic such as cordierite, and the surface of the adsorbent 32 is a three-way catalyst. Alternatively, a catalyst 33 such as an oxidation catalyst is supported by a coating or the like. The catalyst 33 is formed in a porous shape having innumerable fine holes, and HC in the exhaust gas passes through the fine holes of the catalyst 33 and is adsorbed by the adsorbent 32.

  The carrying amount of the catalyst 33 of the purification device 30 is formed so that the downstream portion is larger than the upstream portion of the purification device 30, and the HC purification reaction amount in the downstream portion of the purification device 30 is increased. . Further, the zeolite forming the adsorbent 32 has a characteristic that the heat resistance improves as the ratio of silica / alumina as the raw material increases, but the HC adsorption rate decreases. The adsorbent 32 (zeolite) increases the ratio of silica / alumina in the upstream part exposed to high heat to ensure heat resistance, and decreases the ratio of silica / alumina in the downstream part where the temperature is lower than the upstream part. The HC adsorption rate is increased.

  The adsorbent 32 adsorbs HC in the exhaust gas at a low temperature when the temperature of the adsorbent 32 is lower than the discharge temperature T1. On the other hand, when its own temperature becomes equal to or higher than the release temperature T1, the adsorbed HC is released and released. Further, the catalyst 33 is activated when its own temperature becomes equal to or higher than the activation temperature T2 (for example, about 250 ° C.), and functions to oxidize and reduce HC, CO, and NOx are exhibited. The activation temperature T2 is higher than the discharge temperature T1.

  At the time of cold start of the engine 11 whose exhaust gas temperature is low, the catalyst 33 is inactive because the catalyst temperature Tc is lower than the activation temperature T2, and the HC discharged from the engine 11 is purified. Can not do it. Therefore, during a period in which the catalyst 33 is inactive and HC cannot be purified, HC in the exhaust gas flowing into the purification device 30 passes through the fine holes of the catalyst 33 and is once adsorbed by the adsorbent 32. Thereafter, when the temperature of the purifier 30 rises, the adsorbent temperature Ta rises to the discharge temperature T1, and the catalyst temperature Tc rises to the activation temperature T2, HC released from the adsorbent 32 is oxidized by the catalyst 33. It will be purified.

  Since the catalyst 33 is carried on the upper layer side of the adsorbent 32, the catalyst 33 is directly exposed to the exhaust gas. Therefore, the catalyst temperature Tc is always higher than the adsorbent temperature Ta. Therefore, the time from the time when the adsorbent temperature Ta reaches the release temperature T1 and the release of HC to the time when the catalyst temperature Tc reaches the activation temperature T2 and can be purified can be shortened. Therefore, it is possible to prevent HC released from the adsorbent 32 from being discharged from the purification device 30 without being purified by the catalyst 33.

  An engine control circuit (hereinafter referred to as “ECU18”) is configured mainly by a microcomputer, and executes an engine operation by executing a fuel injection control program (not shown) stored in a built-in ROM (storage medium). The fuel injection amount of the fuel injection valve 15 is controlled according to the state (for example, engine speed and engine load). Specifically, the relationship between the engine speed and the engine load and the optimum injection amount is obtained by testing in advance, and the relationship between the engine speed and the engine load and the optimum injection amount created based on the test is shown. With reference to the injection amount map, the optimum injection amount (target injection amount) is calculated based on the engine rotation speed and the engine load.

  The ECU 18 controls the ignition timing of the spark plug 19 by executing an ignition control program (not shown) stored in the ROM. Specifically, the relationship between the engine speed and the engine load and the optimum injection amount is obtained by testing in advance, and the relationship between the engine speed and the engine load and the optimum ignition timing created based on the test is shown. Referring to the ignition timing map, the optimal ignition timing (target ignition timing) is calculated based on the engine speed and the engine load.

  When the engine 11 is cold started, the exhaust gas temperature is controlled by performing catalyst warm-up control (ignition delay control) such as an increase correction for increasing the fuel injection amount or a delay angle correction for retarding the ignition timing. The catalyst 33 can be activated early by promoting the increase.

  The engine 11 shown in FIG. 1 is a water-cooled type that is cooled by cooling water (heat medium), and the cooling water that exchanges heat with the engine 11 is cooled by heat exchange with the outside air by the radiator 20. A bypass pipe 22 that bypasses the radiator 20 and circulates the cooling water is connected to the circulation pipe 21 that circulates the cooling water between the engine 11 and the radiator 20. At the time of cold start when the cooling water temperature is equal to or lower than a predetermined temperature, the thermostat 23 (switching valve) is operated so that the cooling water is circulated through the bypass pipe 22 by bypassing the radiator 20. Thereby, warming-up promotion of the engine 11 is achieved. On the other hand, if the cooling water temperature is equal to or higher than the predetermined temperature, the thermostat 23 is operated so that the cooling water circulates through the radiator 20.

  The cooling water is circulated by a water pump 24 that operates using the engine output as a drive source. Therefore, the higher the engine rotation speed, the higher the rotation speed of the water pump 24, the circulation flow rate also increases, and the amount of cooling water heat exchanged with the outside air by the radiator 20 (the amount to be cooled) also increases. The cooling water is also used as a heat source for an air conditioner that air-conditions the interior of the vehicle. The air blown toward the interior of the vehicle is heated by heat exchange with the cooling water to become warm air. It is blown into the room.

  A heat recovery unit 40 that recovers heat from the exhaust gas by circulating a heat medium that exchanges heat with the exhaust gas is installed in the exhaust pipe 16 at a downstream portion of the exhaust manifold 17 and an upstream portion of the purification device 30. . In the present embodiment, cooling water circulated by the water pump 24 is used as a heat medium circulated in the heat recovery unit 40.

  The heat recovery pipe 25 for circulating the cooling water between the engine 11 and the heat recovery unit 40 is provided with a flow rate adjusting valve 41 (heat recovery amount adjusting means) for adjusting the flow rate of the cooling water. The flow rate adjustment valve 41 is an electromagnetic valve, and the opening degree of the electromagnetic valve is controlled by the ECU 18. Then, by controlling the valve opening degree, the circulation flow rate through which the cooling water circulates through the heat recovery device 40 is adjusted (controlled).

  Therefore, if the valve opening degree of the flow rate adjustment valve 41 is fully closed and the circulation flow rate to the heat recovery device 40 is made zero, the entire amount of cooling water discharged from the water pump 24 circulates in the circulation pipe 21. On the other hand, if the flow rate adjustment valve 41 is opened, a part of the cooling water discharged from the water pump 24 circulates to the heat recovery unit 40, and the cooling water recovers heat by exchanging heat with the exhaust gas. By recovering heat from the exhaust gas in this manner, warm-up of the engine 11 can be promoted during cold start of the engine 11, and early heating of the conditioned air blown into the passenger compartment can be achieved.

  An exhaust gas temperature sensor 42 that detects the exhaust gas temperature is provided in an upstream portion of the heat recovery unit 40 in the exhaust pipe 16. The temperature detected by the exhaust gas temperature sensor 42 is the exhaust gas flowing into the heat recovery device 40 and is the temperature of the exhaust gas before heat exchange (hereinafter referred to as “exhaust gas inlet temperature Tex”). Based on the detected exhaust gas inlet temperature Tex, the ECU 18 controls the operation of the flow rate adjustment valve 41 to adjust the circulation flow rate to the heat recovery unit 40, thereby adjusting the exhaust heat recovery amount.

  By the way, when the engine warm-up control (ignition retarding control) such as the fuel injection amount increase correction and the ignition timing retardation correction described above is performed immediately after the engine is started, In a state where the amount of HC adsorbed at 32 has not reached the saturation amount, the adsorbent temperature Ta becomes equal to or higher than the release temperature T1, and the adsorbing ability by the adsorbent 32 is not fully exhibited.

  Therefore, in the present embodiment, “heat recovery increase control” and “engine output decrease control” described below are performed until the adsorbent temperature Ta reaches the discharge temperature T1. In the “heat recovery increase control”, the flow rate (circulation flow rate) of the cooling water circulating through the heat recovery unit 40 is set so as to delay the temperature increase of the adsorbent temperature Ta and delay the adsorbent temperature Ta from reaching the discharge temperature T1. Maximize heat recovery at maximum capacity. As a result, the temperature of the exhaust gas flowing into the purification device 30 is reduced. In “engine output reduction control”, the engine output is decreased by correcting the target injection amount (normal target injection amount) calculated based on the above-described injection amount map. As a result, the temperature of the exhaust gas flowing into the purification device 30 is reduced.

  On the other hand, after the adsorbent temperature Ta reaches the discharge temperature T1, the above-mentioned “heat recovery increase control” is performed so as to accelerate the temperature rise of the catalyst temperature Tc and accelerate the catalyst temperature Tc to reach the activation temperature T2. After completing the flow rate to the heat recovery unit 40 to zero (minimum) and ending the “engine output reduction control”, based on the normal target injection amount (or the amount obtained by correcting the injection amount by warming up) Inject fuel. Thereby, the catalyst warm-up is completed early while increasing the amount of adsorption by the adsorbent 32 sufficiently. The adsorbent temperature Ta and the catalyst temperature Tc are estimated based on the detected value of the exhaust gas temperature sensor 42 (exhaust gas inlet temperature Tex), the amount of heat recovery, and the like.

  FIG. 3 is a flowchart showing a processing procedure of heat recovery increase control and engine output decrease control by the microcomputer of the ECU 18. The processing is repeatedly executed at a predetermined cycle (for example, every calculation cycle performed by the above-described CPU or every predetermined crank angle) after being activated with the ignition switch being turned on as a trigger.

  First, in step S10 shown in FIG. 3, the exhaust gas inlet temperature Tex detected by the exhaust gas temperature sensor 42 is acquired. Further, the catalyst temperature Tc is estimated based on the acquired exhaust gas inlet temperature Tex and the amount of heat recovered by the heat recovery unit 40. The heat recovery amount may be calculated based on the opening degree of the flow rate adjustment valve 41 and the engine coolant temperature. Then, a temperature decrease due to heat exchange in the heat recovery unit 40 is calculated based on the calculated heat recovery amount, and the catalyst temperature Tc is calculated by subtracting the temperature decrease from the exhaust gas inlet temperature Tex. In the process of FIG. 3, the adsorbent temperature Ta is considered to be the same as the catalyst temperature Tc.

  In subsequent step S11 (adsorption state determination means), it is determined whether or not the adsorbent temperature Ta is lower than the discharge temperature T1. If it is determined that Ta <T1 (S11: YES), the amount of HC adsorbed by the adsorbent 32 is estimated in the subsequent step S12. For example, it is adsorbed by the adsorbent 32 based on at least one of the operating state of the engine 11 (for example, engine rotation speed, engine load, engine coolant temperature, etc.), the elapsed time from the start of engine start, and the adsorbent temperature Ta. What is necessary is just to estimate the adsorption amount of HC.

  Specifically, the amount of HC discharged from the engine 11 (HC discharge amount) is calculated based on the engine operating state described above, and the adsorption rate of the adsorbent 32 is calculated based on the adsorbent temperature Ta. Then, the HC adsorption amount is calculated by multiplying the calculated HC discharge amount by the adsorption rate.

  Strictly speaking, the adsorbent 32 starts to be released at a temperature lower than the release temperature T1 (release start temperature), but if it is lower than the release temperature T1, the adsorption function is also exhibited. That is, when the adsorbent temperature Ta is in a temperature range that is equal to or higher than the discharge start temperature (for example, 100 ° C.) and lower than the discharge temperature T1 (for example, 150 ° C.), the adsorption and the discharge are simultaneously performed and the temperature rises to the discharge temperature T1 At that time, the adsorption function is not exhibited. In the temperature range (100 ° C. ≦ Ta <150 ° C.), the adsorption rate gradually decreases as the adsorbent temperature Ta increases. Therefore, in the calculation of the adsorption rate described above, the adsorption rate is calculated to be lower as the adsorbent temperature Ta is higher.

  In subsequent step S13 (adsorption state determination means), it is determined whether or not the HC adsorption amount calculated in step S12 is less than the saturation amount. If it is determined that the HC adsorption amount is less than the saturation amount (S13: YES), in the subsequent step S14 (heat recovery increase control means), the flow rate adjustment valve 41 is controlled to be fully opened, and heat recovery increase control is performed. In short, if the adsorbent temperature Ta <the release temperature T1 and the HC adsorption amount <saturation amount, it can be said that the adsorbent 32 can adsorb HC. That is, if the adsorbent temperature Ta has reached the discharge temperature T1 even if it is not saturated, the adsorption is impossible, and if the adsorbent temperature Ta has not reached the discharge temperature T1, it is adsorbed. It is impossible. And heat recovery increase control is implemented on condition that it is an adsorption | suction possible state. As a result, the temperature of the exhaust gas flowing into the purification device 30 can be lowered, and hence the catalyst temperature Tc and the adsorbent temperature Ta can be lowered, so that the adsorbent temperature Ta can be delayed from reaching the discharge temperature T1, and the adsorption is possible. Can be a long time.

  In the subsequent step S15 (output reduction necessity determination means), is it possible to maintain the adsorbable state time for a predetermined time or more only by performing the heat recovery increase control in step S14 without performing the engine output decrease control? Determine whether or not. For example, if the adsorbent temperature Ta at that time is equal to or lower than a predetermined threshold temperature, it is determined that the maintenance is possible. The threshold temperature may be variably set according to the engine coolant temperature at that time. That is, the lower the engine coolant temperature, the greater the amount of heat exchange, and the temperature of the exhaust gas flowing into the purification device 30 can be greatly reduced. Therefore, the lower the engine coolant temperature, the higher the threshold temperature is set.

  If it is determined that the maintenance is not possible only by the heat recovery increase control (S15: NO), in the subsequent step S16 (output decrease control means), the engine output is corrected by correcting the normal target injection amount to decrease. Implement engine output reduction control to decrease. As a result, the temperature decrease of the exhaust gas flowing into the purifying device 30 and the decrease in the catalyst temperature Tc and the adsorbent temperature Ta are promoted, so that it is possible to delay the adsorbent temperature Ta from reaching the discharge temperature T1, and the adsorbable state. This time can be maintained for a predetermined time or more.

  If it is not in the adsorbable state (S11: NO, S13: NO), the process of FIG. 3 is terminated without performing any of the heat recovery increase control and the step S16 engine output decrease control in step S14. Although it is in an adsorbable state (S11: YES, S13: YES), if the above-described maintenance is possible only by heat recovery increase control (S15: YES), engine output decrease control is not performed although heat recovery increase control is performed. .

  FIG. 4 is a time chart showing an embodiment by performing the process of FIG. 4 (a) is the driving power of the vehicle, (b) is the engine output, (c) is the exhaust heat quantity directly under the engine, (d) is the exhaust heat recovery quantity by the heat recovery device 40, (e) is the catalyst temperature Tc, The solid line in (f) indicates the flow rate of HC flowing into the catalyst 33, and the alternate long and short dash line in (f) indicates the flow rate of HC flowing out from the catalyst 33.

  In the example of FIG. 4, at time t1 when the engine is started, heat recovery increase control and engine output decrease control are started. Thereafter, both the above-described controls are terminated at the time t2 when the exhaust temperature immediately below the engine (exhaust gas inlet temperature Tex) reaches the discharge temperature T1 or when the estimated catalyst temperature Tc (that is, the adsorbent temperature Ta) reaches the discharge temperature T1. Let

  By performing the engine output reduction control in the period up to the time point t2, the engine output and the traveling power are reduced from the values shown by the dotted line to the values shown by the solid line as shown in (a) and (b), and as a result, (c ), The exhaust heat quantity directly under the engine (exhaust gas inlet temperature Tex) decreases from the value shown by the dotted line to the value shown by the solid line. Further, by performing heat recovery increase control during the period up to time t2, the amount of exhaust heat recovery increases as shown in (d).

  As described above, as shown in (e), the time during which the catalyst temperature Tc is lower than the discharge temperature T1 (the time from t1 to t2) can be lengthened, and the amount adsorbed by the adsorbent 32 can be increased. That is, the HC flow rate flowing out from the purification device 30 (see the one-dot chain line in (f)) can be sufficiently reduced with respect to the HC flow rate flowing into the purification device 30 (see the solid line in (f)).

  According to the embodiment described in detail above, the following effects are exhibited.

  (1) The temperature of the exhaust gas flowing into the purification device 30 (by adjusting the heat recovery amount by arranging the heat recovery device 40 upstream of the purification device 30 and adjusting the cooling water circulation flow rate to the heat recovery device 40 ( The exhaust gas outlet temperature Tout) can be adjusted.

  (2) When the adsorbent temperature Ta is lower than the discharge temperature T1, the circulation flow rate is maximized and the engine output is reduced, so that an increase in the exhaust gas temperature flowing into the purification device 30 is suppressed. Therefore, it is possible to secure a long time until the adsorbent temperature Ta reaches the discharge temperature T1, and as a result, the amount of adsorption by the adsorbent 32 can be increased to sufficiently exhibit the adsorption capacity. When the catalyst temperature Tc is equal to or higher than the activation temperature T2, the circulation flow rate may be set to zero to promote the increase in the exhaust gas temperature flowing into the purification device 30. According to this, it is possible to shorten the time from when the adsorbent 32 is no longer in an adsorbable state to when the catalyst temperature Tc reaches the activation temperature T2, thereby achieving early completion of catalyst warm-up.

  (3) Even if the adsorbent temperature Ta is lower than the heat dissipation temperature T1, if the adsorbent temperature Ta is not adsorbable due to saturation or the like, the circulation flow rate is reduced to zero to promote the increase of the catalyst temperature Tc. The catalyst temperature Tc can be immediately increased without waiting for the catalyst to rise to the discharge temperature T1, and the wasteful time during which neither adsorption nor oxidation is performed can be shortened, and the catalyst warm-up can be completed early. be able to.

  (4) Here, when the output reduction control is performed, there is a concern that the engine output is reduced against the driver's output request and the driver feels uncomfortable. In response to this concern, according to the present embodiment, the output reduction control is performed when the adsorbable state can be maintained for a predetermined time or longer only by performing the heat recovery increase control without performing the output reduction control (S15: YES). Therefore, the heat recovery increase control is performed without causing the adsorption capability of the adsorbent 32 to be sufficiently exhibited while eliminating the above-described concerns.

  (5) Since the circulation flow rate is maximized until the adsorbent temperature Ta reaches the discharge temperature T1, the heat recovery amount in the heat recovery device 40 can be increased sufficiently, and in turn, the heat source of the air conditioner can be used. Can be implemented at an early stage, and the time required for the vehicle interior temperature to reach the target temperature by heating from the engine start time t1 can be shortened.

(Second Embodiment)
In the present embodiment shown in FIG. 5, a schematic configuration of the entire engine control system will be described. The vehicle shown in FIG. 5 is a so-called hybrid vehicle. In addition to the output of the engine 11, the output of a motor generator 27 (electric motor) that is driven by being supplied with electric power from the battery 26 is used as a travel drive source. It is also possible to charge the battery 26 with electric power generated by driving the motor generator 27 with engine output. In the example of FIG. 5, the crankshaft that is rotationally driven by the engine 11 is assisted and driven by the motor generator 27. Then, the outputs of the engine 11 and the motor generator 27 are transmitted to the transmission 28 to drive the drive wheels 29. Incidentally, in FIG. 1, the exhaust gas temperature sensor 42 is disposed on the upstream side of the heat recovery device 40, whereas in the present embodiment illustrated in FIG. 5, the exhaust gas temperature sensor 42 is disposed on the downstream side of the heat recovery device 40. ing.

  The ECU 18 performs charge / discharge control so that the state of charge (SOC) of the battery 26 is within a predetermined range. In particular, when the SOC indicating the charging rate is lower than the lower limit value, the motor generator 27 generates electric power with the engine output to charge the battery 26. Therefore, in this case, the assist by the motor generator 27 is not possible.

  In the present embodiment, when the engine output reduction control is performed, the assist by the motor generator 27 is performed on the condition that the SOC does not fall below the lower limit value. In particular, it is desirable to assist the motor generator 27 by the amount that the output is reduced by the engine output reduction control.

  FIG. 6 is a flowchart showing a processing procedure of heat recovery increase control and engine output decrease control by the microcomputer of the ECU 18. Step S17 is added to the flowchart of FIG. 3, and step S16 of FIG. 3 is changed to step S18. is doing. In FIG. 3 and FIG. 6, the same reference numerals are assigned to the steps for performing the same processes, and the description of the same reference numerals is used.

  First, if it is determined that the adsorption is possible based on steps S10 to S13, heat recovery increase control is performed in step S14. If it is determined in the subsequent step S15 that the adsorbable time cannot be maintained for a predetermined time or more only by the heat recovery increase control (S15: NO), the process proceeds to the next step S17.

  In the subsequent step S17 (motor output increase enable / disable determining means), it is determined whether or not the motor generator 27 can assist the output decrease by the engine output decrease control. In other words, it is determined whether or not the amount of charge (SOC) of the battery 26 is sufficient to assist the motor with the output decrease by the engine output decrease control. For example, an output decrease by the engine output decrease control (injection amount decrease) is fixed, and if the SOC is equal to or greater than a predetermined value, it may be determined that the output decrease can be supplemented by the output of the motor generator 27. .

  If it is determined that the motor assist possible output is equal to or greater than the engine output decrease (S17: YES), the engine output decrease control is performed in the subsequent step S18 (output decrease control means, motor output increase control means). Then, the control for increasing the power supply amount to the motor generator 27 (motor output increase control) is performed, and the output decrease due to the engine output decrease control is compensated by the output of the motor generator 27.

  On the other hand, if it is determined that the motor assist possible output is not equal to or greater than the engine output decrease (that is, the SOC is less than the predetermined value) (S17: NO), both the engine output decrease control and the motor output increase control in step S18 are controlled. Do not allow implementation.

  FIG. 7 is a time chart showing an aspect of the execution of the process of FIG. 7 (a) is the driving power of the vehicle, (b) is the engine output, (c) is the charge / discharge amount of the battery 26, (d) is the exhaust heat quantity directly under the engine, and (e) is the exhaust heat by the heat recovery unit 40. The recovered amount, (f) indicates the catalyst temperature Tc, the solid line in (g) indicates the flow rate of HC flowing into the catalyst 33, and the alternate long and short dash line in (g) indicates the flow rate of HC flowing out from the catalyst 33.

  In the example of FIG. 7, at time t1 when the engine is started, heat recovery increase control, engine output decrease control, and motor output increase control are started. Thereafter, both the above-described controls are terminated at the time t2 when the exhaust temperature immediately below the engine (exhaust gas inlet temperature Tex) reaches the discharge temperature T1, or at the time t2 when the catalyst temperature Tc (that is, the adsorbent temperature Ta) reaches the discharge temperature T1. .

  By performing heat recovery increase control during the period up to time t2, the amount of exhaust heat recovery increases as shown in (e). Further, during the period up to the time t2, even if the engine output decrease control shown in (b) is performed by performing the motor output increase control for increasing the battery discharge amount as shown in (c), A decrease in travel power as shown by the dotted line can be avoided, and the travel power can be maintained at the travel power required by the driver as shown by the solid line in FIG.

  As described above, by performing the heat recovery increase control and the engine output decrease control, the time during which the catalyst temperature Tc is lower than the discharge temperature T1 (time from t1 to t2) can be lengthened as shown in (f). The amount to be adsorbed by the adsorbent 32 can be increased. That is, the HC flow rate flowing out from the purification device 30 (see the one-dot chain line in (g)) can be sufficiently reduced with respect to the HC flow rate flowing into the purification device 30 (see the solid line in (g)). Moreover, the driving power required by the driver can be maintained.

  Further, since the motor output increase control is performed, it is possible to avoid the actual traveling power from being reduced with respect to the traveling power requested by the driver. In addition, when the motor-assistable output is not equal to or greater than the engine output decrease (S17: NO), the engine output decrease control is not permitted, and thus the actual travel power is reduced with respect to the travel power requested by the driver. Can be avoided reliably.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows. Moreover, you may make it combine the characteristic structure of each embodiment arbitrarily, respectively.

  In each of the above embodiments, in the heat recovery unit 40, the engine cooling water flowing through the radiator 20 and the exhaust gas are heat exchanged. However, the engine cooling water is heat exchanged with another heat medium, and the other heat You may make it heat-exchange a medium and waste gas. In the heat recovery increase control in this case, the circulating flow rate of the engine cooling water may be increased, the circulating flow rate by the electric pump for circulating the other heat medium may be increased, or both the circulating flow rates may be increased. You may let them.

  In the embodiment shown in FIG. 1, the heat recovery increase control is performed by controlling the opening degree of the flow rate adjustment valve 41. For example, the exhaust gas bypasses the heat recovery device 40 and exhausts the bypass passage. You may make it provide the switching valve which forms in the pipe | tube 16 and switches the distribution route of waste gas to either a bypass passage or the heat recovery device 40. In this case, the heat recovery increase control may be performed by controlling the operation of the switching valve to switch from the state in which the exhaust gas is circulated to the bypass passage to the state in which the exhaust gas is circulated to the heat recovery unit 40.

  In each of the above embodiments, the flow rate adjusting valve 41 is provided as the heat recovery amount adjusting means. However, in an engine in which the water pump 24 is driven by an electric motor, it is circulated by variably controlling the rotational speed of the water pump 24. Since the flow rate can be adjusted, the flow rate adjustment valve 41 may be eliminated in this case, and the circulation flow rate to the heat recovery unit 40 may be adjusted by controlling the operation of the water pump 24.

  In the embodiment shown in FIG. 1, an exhaust gas temperature sensor 42 is provided in the exhaust pipe 16 upstream of the heat recovery device 40, and the catalyst temperature Tc and the adsorbent temperature Ta are estimated and controlled from the exhaust gas inlet temperature Tex. However, such a temperature sensor may be provided in the purification device 30 to directly detect the temperature of the catalyst 33. Alternatively, the exhaust gas temperature sensor 42 is arranged on the downstream side of the heat recovery unit 40, and the catalyst temperature Tc and the adsorbent temperature Ta are set based on the detection value by the exhaust gas temperature sensor 42, the circulating flow rate of the cooling water, and the operating state of the engine 11. You may make it estimate.

  In step S17 of FIG. 6, if it is determined that the motor assist possible output is not equal to or less than the engine output decrease (S17: NO), the ignition delay that retards the ignition timing compared to the case where the determination is affirmative. You may make it implement control. Further, when it is determined in steps S11 to S13 in FIGS. 3 and 6 that adsorption is not possible (S11: NO, S13: NO), the ignition retard control may be performed.

  Whether or not the adsorbent 32 is saturated may be determined to be saturated when the elapsed time after starting the internal combustion engine reaches a predetermined time set in advance. Alternatively, the determination may be made based on the history of the driver's accelerator operation amount during the warm-up operation period of the engine 11. For example, the saturation value may be determined when the integral value of the manipulated variable exceeds a preset threshold value. Or what is necessary is just to determine with it being saturated when the integrated value of the calorie | heat amount supplied to the adsorbent 32 reaches a predetermined value. For example, based on the fuel injection amount command value correlated with the engine load, the intake air amount, the accelerator operation amount, etc., the engine rotation speed, and the circulation flow rate (for example, the command signal output from the ECU 18 to the flow rate adjustment valve 41). What is necessary is just to calculate the said calorie | heat amount. Alternatively, when the engine rotation speed during the warm-up operation period of the engine 11 reaches a predetermined value, it may be determined that the engine is saturated.

  In each of the above embodiments, the purification device 30 in which the adsorbent 32 and the catalyst 33 are integrally formed is employed. However, in the implementation of the present invention, the adsorbent 32 and the catalyst 33 may be configured separately. Good. In this case, it is desirable to arrange the adsorbent upstream of the catalyst so that the ambient temperature of the adsorbent is higher than the ambient temperature of the catalyst. According to this, the time from when the adsorbent temperature reaches the discharge temperature T1 to the time when the catalyst reaches the activation temperature T2 (the time during which neither adsorption nor oxidation is performed) can be shortened.

  In the second embodiment, the motor generator 27 having a motor function and a power generation function is adopted as an electric motor. However, an electric motor not having a power generation function may be adopted.

  In each of the above embodiments, the specific component in the exhaust gas to be purified is HC, and the present invention is applied to the adsorbent / catalyst that adsorbs / oxidizes this HC, but the present invention is limited to this. It is not a thing. For example, in the case of a lean burn gasoline engine or diesel engine, the present invention may be applied to an adsorbent that adsorbs NOx in exhaust gas as a specific component and a catalyst that reduces the NOx.

  32 ... Adsorbent, 40 ... Heat recovery device, S11 ... Adsorption state determination means, S14 ... Heat recovery increase control means, S15 ... Output decrease necessity determination means, S16 ... Output decrease control means, S17 ... Motor output increase possibility determination means , S18 ... output decrease control means, motor output increase control means, T1 ... release temperature, T2 ... activation temperature.

Claims (4)

An adsorbent that adsorbs a specific component in the exhaust gas of an internal combustion engine when its temperature is lower than the release temperature, and releases the adsorbed specific component when its temperature is equal to or higher than the release temperature;
A heat recovery device that is disposed upstream of the adsorbent and heat-exchanges with the exhaust gas to recover heat from the exhaust gas;
Adsorption state determination means for determining that the adsorbent is in an adsorbable state on condition that the temperature of the adsorbent is lower than the release temperature;
With
When it is determined by the adsorption state determination means that the adsorption is possible, the heat recovery increase control is performed to increase the amount of heat recovered by the heat recovery device compared to when it is determined that the adsorption is not possible. An exhaust gas purification apparatus that performs output reduction control for reducing the output of the internal combustion engine as compared to when it is determined that the adsorption is not possible. Output reduction that determines whether or not the adsorbable state can be maintained for a predetermined time or more by performing the heat recovery increase control without performing the output decrease control when it is determined that the adsorption is possible With necessity determination means,
2. The exhaust gas purification apparatus according to claim 1, wherein the output reduction control is performed on the condition that the adsorbable state cannot be maintained for a predetermined time or longer by the output reduction necessity determination unit. Applied to a vehicle using the output of the electric motor in addition to the output of the internal combustion engine as a travel drive source;
The motor output increase control for increasing the output of the electric motor is performed when the output decrease control is being performed, compared to when the output decrease control is not being performed. Exhaust gas purification equipment. A motor output increase enable / disable determining unit that determines whether or not the output decrease by the output decrease control can be supplemented by the output increase of the electric motor;
The exhaust gas purification device according to claim 3, wherein the output reduction control is performed on the condition that it is determined that the output decrease can be supplemented with the output increase.

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