JP5229181B2 - Exhaust gas purification device - Google Patents

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 and oxidizes or reduces the specific component released from the adsorbent with a catalyst.

  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).

  Incidentally, at the time of cold start of the internal combustion engine, control (catalyst warm-up control) for retarding the ignition timing 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 the catalyst warm-up control is performed immediately after the start of the internal combustion engine, the adsorbent temperature becomes equal to or higher than the discharge 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, catalyst warm-up control is started from the time when the adsorbent temperature reaches the discharge temperature T1 (see Patent Document 1). 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, in the control described in Patent Document 1 described above, since the catalyst is warmed up by retarding the ignition timing, fuel consumption is deteriorated by retarding the ignition. 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 its purpose is to achieve early completion of catalyst warm-up while sufficiently increasing the amount of adsorption by the adsorbent and to suppress deterioration in fuel consumption. The object is to provide an exhaust gas purification device that has been realized.

  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 below the release temperature and releases the adsorbed specific component when the temperature is higher than the release temperature, and the temperature of the adsorbent is higher than the release temperature. When the temperature becomes higher than the high activation temperature, a catalyst that oxidizes or reduces the specific component released from the adsorbent and a heat medium that is disposed upstream of the adsorbent and exchanges heat with the exhaust gas are circulated from the exhaust gas. A heat exchanger for recovering heat, a flow rate adjusting means for adjusting the circulation flow rate of the heat medium, a control means for controlling the operation of the flow rate adjusting means, and an exhaust gas temperature upstream of the heat exchanger is activated. An exhaust gas state determination unit that determines whether the temperature is higher than a temperature or a low temperature state lower than the activation temperature, and the control unit determines the exhaust gas state determination When being judged that the a high-temperature state by stage, which comprises carrying out the flow reduction control to reduce the circulation flow rate as compared to when it is determined that the low-temperature state.

  According to this, the temperature of the exhaust gas flowing into the adsorbent and the catalyst is adjusted by arranging a heat exchanger for recovering heat from the exhaust gas on the upstream side of the adsorbent and adjusting the circulation flow rate of the heat medium by the flow rate adjusting means. it can. Then, when the exhaust gas temperature on the upstream side of the heat exchanger is in a high temperature state where the activation temperature is equal to or higher than the activation temperature, the circulation flow rate is reduced compared to when it is determined as the low temperature state.

  Therefore, in the low temperature state immediately after starting the internal combustion engine, the circulation flow rate is increased and the amount of heat recovered by the heat exchanger is increased compared to the high temperature state, so that the exhaust gas temperature flowing into the adsorbent is lowered. Therefore, it is possible to ensure a long time until the adsorbent temperature reaches the discharge temperature, and as a result, the amount of adsorption with the adsorbent can be increased and the adsorption capability can be sufficiently exhibited. On the other hand, when the exhaust gas temperature rises to a high temperature after starting the internal combustion engine, the circulation flow rate is reduced and the amount of heat recovered by the heat exchanger is reduced compared to the low temperature state. To rise. Therefore, it is possible to shorten the time from when the adsorbent reaches the release temperature to start the release until the catalyst temperature reaches the activation temperature, thereby achieving early completion of catalyst warm-up.

  As described above, according to the present invention, the catalyst warm-up can be completed early without increasing the ignition timing (or suppressing the ignition delay amount) and sufficiently increasing the adsorption amount of the adsorbent. it can. Therefore, it is possible to achieve both the suppression of fuel consumption deterioration due to the ignition timing retardation and the early completion of catalyst warm-up while sufficiently increasing the adsorption amount.

  Incidentally, in the apparatus described in Japanese Patent Laid-Open No. 11-218202, a bypass passage that bypasses the heat exchanger is formed in the exhaust pipe, and a switching valve that switches the exhaust gas flow path between the heat exchanger and the bypass passage is provided. Yes. Then, the temperature of the exhaust gas flowing into the catalyst is adjusted by controlling the operation of the switching valve. However, this conventional device has a structure in which the bypass passage and the switching valve are provided in the exhaust pipe, so that the exhaust passage is greatly complicated.

  On the other hand, according to the present invention, the temperature of the exhaust gas flowing into the adsorbent and the catalyst can be adjusted by adjusting the circulation flow rate of the heat medium, so that the bypass passage and the switching valve can be made unnecessary, and the above problem can be solved.

  According to a second aspect of the present invention, there is provided an adsorption state determination means for determining whether or not the adsorption material can be adsorbed, and the control means can be adsorbed by the adsorption state determination means. When it is determined that it is not in a state, the flow rate reduction control is performed regardless of the determination result by the exhaust gas state determination means.

  Here, for example, when idling of the internal combustion engine continues for a long time, the adsorption amount exceeds the allowable amount of the adsorbent by adsorbing a specific component for a long time, and the exhaust gas temperature is in a low temperature state. In spite of this, there is a concern that a specific component cannot be adsorbed (saturated state). In this case, it is desirable to start the catalyst warm-up immediately without waiting for the exhaust gas temperature to rise to a high temperature state, and to achieve early completion of the catalyst warm-up.

  In addition, if the upstream exhaust gas temperature is higher than the discharge temperature and lower than the activation temperature for a long time, the flow rate decreases due to the fact that it is determined as a low temperature state even though it cannot be adsorbed by the adsorbent. There is a concern that the state where the control is not performed continues for a long time. In this case, it is desirable to start the catalyst warm-up immediately without waiting for the exhaust gas temperature to rise to a high temperature state, and to achieve early completion of the catalyst warm-up.

  In the above invention in view of these points, when it is determined that the adsorption state is not possible, the flow rate reduction control is performed regardless of the determination result by the exhaust gas state determination means. The time until the catalyst temperature reaches the activation temperature, that is, the time during which “release temperature T1 <exhaust gas temperature <activation temperature T2” is shortened, the catalyst warm-up can be completed early.

  According to a third aspect of the present invention, the exhaust gas temperature sensor for detecting the exhaust gas temperature on the upstream side is provided, and the exhaust gas state determination means is configured to detect either the high temperature state or the low temperature state based on a detection value of the exhaust gas temperature sensor. It is characterized by determining whether it is.

  According to this, if the detected value is equal to or greater than a predetermined value, it is determined that the temperature is high, and if it is less than the predetermined value, it can be determined that the temperature is low. And since the said determination is performed based on the upstream exhaust gas temperature detected directly by the exhaust gas temperature sensor, the determination by the exhaust gas state determination means can be performed with high accuracy.

  According to a fourth aspect of the present invention, the apparatus includes a heat medium temperature sensor that detects a temperature of the heat medium, and the exhaust gas state determination unit is configured to detect either the high temperature state or the low temperature state based on a detection value of the heat medium temperature sensor. It is characterized by determining whether it is.

  Here, the higher the temperature of the upstream exhaust gas temperature, the higher the temperature of the heat medium, and the upstream exhaust gas temperature and the heat medium temperature are highly correlated. According to the above invention in view of this point, the temperature of the heat medium temperature having a high correlation with the upstream side exhaust gas temperature is detected, and if the detected value is equal to or higher than a predetermined value, it is determined that the temperature is high, and is less than the predetermined value. If it is, it can be determined that the temperature is low.

  In the invention according to claim 5, the adsorbent that adsorbs the specific component in the exhaust gas of the internal combustion engine below the release temperature and releases the adsorbed specific component when the temperature is equal to or higher than the release temperature, and the temperature of the adsorbent is higher than the release temperature. When the temperature becomes higher than the high activation temperature, a catalyst that oxidizes or reduces the specific component released from the adsorbent and a heat medium that is disposed upstream of the adsorbent and exchanges heat with the exhaust gas are circulated from the exhaust gas. A heat exchanger that recovers heat, a flow rate adjusting unit that adjusts the circulation flow rate of the heat medium, a control unit that controls the operation of the flow rate adjusting unit, and an adsorbable state in which adsorption by the adsorbent is possible. An adsorbing state determining means for determining whether the adsorbing state is determined to be the adsorbable state when the adsorbing state determining means determines that the adsorbing state is not possible. Which comprises carrying out the flow reduction control to reduce the circulation flow rate than when there.

  According to this, the temperature of the exhaust gas flowing into the adsorbent and the catalyst is adjusted by arranging a heat exchanger for recovering heat from the exhaust gas on the upstream side of the adsorbent and adjusting the circulation flow rate of the heat medium by the flow rate adjusting means. it can. Then, when it is determined that the suction is not possible, the circulation flow rate is reduced compared to when it is determined that the suction is possible.

  Therefore, when the internal combustion engine is in an adsorbable state immediately after starting, the circulation flow rate is increased and the amount of heat recovered by the heat exchanger is increased compared to when the internal combustion engine is in an unadsorbable state. Therefore, it is possible to ensure a long time until the adsorbent temperature reaches the discharge temperature, and as a result, the amount of adsorption with the adsorbent can be increased and the adsorption capability can be sufficiently exhibited. On the other hand, when the internal combustion engine is started, if the adsorption amount exceeds the allowable amount of the adsorbent and becomes saturated or the adsorbent temperature becomes higher than the discharge temperature, the circulation flow rate is higher than in the adsorbable state. Is reduced to reduce the amount of heat recovered by the heat exchanger, so that the temperature of the exhaust gas flowing into the catalyst rises. Therefore, it is possible to shorten the time from when the adsorbent starts to be released until the catalyst temperature reaches the activation temperature, thereby achieving early completion of catalyst warm-up.

  As described above, according to the present invention, the catalyst warm-up can be completed early without increasing the ignition timing (or suppressing the ignition delay amount) and sufficiently increasing the adsorption amount of the adsorbent. it can. Therefore, it is possible to achieve both the suppression of fuel consumption deterioration due to the ignition timing retardation and the early completion of catalyst warm-up while sufficiently increasing the adsorption amount.

  Incidentally, in the apparatus described in Japanese Patent Laid-Open No. 11-218202, a bypass passage that bypasses the heat exchanger is formed in the exhaust pipe, and a switching valve that switches the exhaust gas flow path between the heat exchanger and the bypass passage is provided. Yes. Then, the temperature of the exhaust gas flowing into the catalyst is adjusted by controlling the operation of the switching valve. However, this conventional device has a structure in which the bypass passage and the switching valve are provided in the exhaust pipe, so that the exhaust passage is greatly complicated.

  On the other hand, according to the present invention, the temperature of the exhaust gas flowing into the adsorbent and the catalyst can be adjusted by adjusting the circulation flow rate of the heat medium, so that the bypass passage and the switching valve can be made unnecessary, and the above problem can be solved.

  The invention according to claim 6 is characterized in that the adsorption state determination means determines whether or not the adsorption state is possible based on an elapsed time since the start of the internal combustion engine.

  According to this, when the elapsed time reaches a predetermined time, it can be determined that the adsorbent is in an incapable adsorption state by assuming that the adsorbent is in the saturated state. Therefore, it is possible to determine whether or not the suction is possible without using a dedicated sensor for detecting the suction amount.

  The invention according to claim 7 is characterized in that the adsorption state determination means determines whether or not the adsorption is possible based on an accelerator operation amount of a driver during a warm-up operation period of the internal combustion engine. .

  According to this, when the driver depresses the accelerator pedal during the warm-up period, it is considered that the adsorbent is saturated due to an increase in the specific component in the exhaust gas, and the adsorption is disabled. It can be determined that it has become. Therefore, it is possible to determine whether or not the suction is possible without using a dedicated sensor for detecting the suction amount.

  In the invention according to claim 8, the adsorption state determination means determines whether or not the adsorption state is possible based on an integrated value of the amount of heat supplied to the adsorbent after starting the internal combustion engine. It is characterized by that.

  According to this, when the integrated value of the amount of heat supplied to the adsorbent reaches a predetermined value, it can be determined that the adsorbent is in an adsorbable state by assuming that the adsorbent is in the saturated state. Therefore, it is possible to determine whether or not the suction is possible without using a dedicated sensor for detecting the suction amount.

  The invention according to claim 9 is characterized in that the determination means determines whether or not the adsorption is possible based on an engine speed during a warm-up operation period of the internal combustion engine.

  According to this, when the engine rotational speed reaches a predetermined value, it can be determined that the adsorbent is in an incapable adsorption state by assuming that the adsorbent is in the saturated state. Therefore, it is possible to determine whether or not the suction is possible without using a dedicated sensor for detecting the suction amount.

  The invention according to claim 10 is characterized in that the adsorption state determination means determines whether or not the adsorption state is possible based on the temperature of the adsorbent.

  According to this, when the temperature of the adsorbent reaches the discharge temperature, it can be determined that the adsorbent is in an incapable adsorption state by assuming that the adsorbent is in the saturated state. Therefore, it can be reliably determined that the adsorbent is in a non-adsorbable state due to the temperature of the adsorbent reaching the discharge temperature.

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 flow volume fall control in 1st Embodiment. The time chart which shows the one aspect | mode by having implemented the process of FIG. The flowchart which shows the process sequence of flow volume fall control in 2nd Embodiment of this invention. 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, although the activation temperature T2 is higher than the release temperature T1, the catalyst temperature Tc reaches the activation temperature T2 and can be purified when the adsorbent temperature Ta reaches the release temperature T1 and HC is released. Can be later than (or both can be almost the same). Therefore, it is possible to avoid that HC released from the adsorbent 32 is 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 ignition timing of the spark plug 19 is controlled by controlling the fuel injection amount of the fuel injection valve 15 according to the state and executing an ignition control program (not shown). When the engine 11 is cold-started, the exhaust gas temperature is increased by performing control (catalyst warm-up control) such as an increase correction for increasing the fuel injection amount and a delay angle correction for retarding the ignition timing. Thus, early activation of the catalyst 33 can be achieved.

  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 exchanger 40 that recovers heat from the exhaust gas by circulating a heat medium that exchanges heat with the exhaust gas is installed in a portion of the exhaust pipe 16 downstream of the exhaust manifold 17 and upstream 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 exchanger 40.

  The heat recovery pipe 25 for circulating the cooling water between the engine 11 and the heat exchanger 40 is provided with a flow rate adjusting valve 41 (flow rate 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 (control means). Then, by controlling the valve opening, the circulation flow rate at which the cooling water circulates through the heat exchanger 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 exchanger 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 regulating valve 41 is opened, a part of the cooling water discharged from the water pump 24 circulates to the heat exchanger 40, and the cooling water exchanges heat with the exhaust gas to recover heat. By recovering heat from the exhaust gas in this way, warm-up of the engine 11 can be promoted at the time of cold start of the engine 11, and early heating of the conditioned air can be achieved.

  An exhaust gas temperature sensor 42 for detecting the exhaust gas temperature is provided in the exhaust pipe 16 upstream of the heat exchanger 40. The temperature detected by the exhaust gas temperature sensor 42 is the exhaust gas flowing into the heat exchanger 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 exchanger 40, thereby adjusting the amount of recovered waste heat.

  By the way, when the engine warm-up control such as the fuel injection amount increase correction and the ignition timing retardation correction described above is performed immediately after the engine start when the engine 11 is cold started, the HC adsorbed by the adsorbent 32. The adsorbent temperature Ta becomes equal to or higher than the discharge temperature T1 in a state where the amount of the adsorbent does not reach the saturation amount, and the adsorption capability by the adsorbent 32 is not sufficiently exhibited. Therefore, in the present embodiment, until the exhaust gas inlet temperature Tex reaches the activation temperature T2, the heat exchanger 40 is configured to suppress the temperature rise of the adsorbent temperature Ta and delay the adsorbent temperature Ta from reaching the discharge temperature T1. The flow rate (circulation flow rate) of the cooling water circulating through is maximized to recover heat with the maximum capacity.

  On the other hand, after the exhaust gas inlet temperature Tex reaches the activation temperature T2, circulation to the heat exchanger 40 is performed so as to accelerate the temperature increase of the catalyst temperature Tc and accelerate the catalyst temperature Tc to reach the activation temperature T2. The flow rate is set to zero (minimum) to minimize heat recovery. Thereby, the catalyst warm-up is completed early while increasing the amount of adsorption by the adsorbent 32 sufficiently.

  Next, the procedure when the ECU 18 controls the flow rate adjustment valve 41 to reduce the flow rate so as to reduce the circulation flow rate from the maximum to zero as the exhaust gas inlet temperature Tex increases as described above. This will be described with reference to FIG. FIG. 3 is a flowchart showing a processing procedure of the flow rate lowering control by the microcomputer of the ECU 18, and this processing is started with a trigger as the ignition switch is turned on, and then a predetermined cycle (for example, the CPU described above) It is repeatedly executed at every calculation cycle or every predetermined crank angle.

  First, in step S10 shown in FIG. 3, whether the exhaust gas inlet temperature Tex detected by the exhaust gas temperature sensor 42 is in a high temperature state higher than the activation temperature T2 or a low temperature state lower than the activation temperature T2. judge. Specifically, a temperature slightly higher than the activation temperature T2 is set as the threshold value TH1, and when the exhaust gas inlet temperature Tex> the threshold value TH1, it is determined that the temperature is high.

  By setting the threshold value TH1 to a temperature slightly higher than the activation temperature T2, it is determined that the exhaust gas inlet temperature Tex is in a high temperature state in a situation where the exhaust gas inlet temperature Tex is reliably equal to or higher than the activation temperature T2. However, if the threshold value TH1 is set to a temperature much higher than the activation temperature T2, it is possible to increase the certainty that the exhaust gas inlet temperature Tex is equal to or higher than the activation temperature T2 when it is determined that the temperature is high. However, in the state where the exhaust gas outlet temperature Tout is excessively high, the circulation flow rate is made zero to promote the increase of the catalyst temperature Tc, as will be described later. Therefore, the catalyst temperature Tc exceeds the heat resistance temperature of the catalyst 33. There is a concern that Therefore, in this embodiment, the threshold value TH1 is set to a temperature sufficiently lower than the heat resistant temperature of the catalyst 33.

  When it is determined that the temperature is high (exhaust gas inlet temperature Tex> threshold value TH1) (S10: YES), in step S20, the flow rate adjustment valve 41 is actuated so that the circulation flow rate to the heat exchanger 40 becomes zero. To control. As a result, the amount of heat recovered in the heat exchanger 40 is minimized, and the temperature of the exhaust gas flowing into the purification device 30 (hereinafter referred to as “exhaust gas outlet temperature Tout”) increases. Therefore, early activation of the catalyst 33 is achieved.

  On the other hand, when it is determined that the temperature is low (exhaust gas inlet temperature Tex ≦ threshold TH1) (S10: NO), it is determined in subsequent step S30 whether the adsorbent 32 is in an adsorbable state. The “adsorbable state” is a state that satisfies the following two conditions. The first is that the temperature of the adsorbent 32 has not reached the discharge temperature T1. Second, the amount of adsorption of HC by the adsorbent 32 is maximized and is not saturated. That is, if the temperature of the adsorbent 32 has reached the discharge temperature T1 even if it is not saturated, it cannot be adsorbed, and even if the temperature of the adsorbent 32 has not reached the discharge temperature T1, it cannot be saturated. Adsorption is impossible.

  Whether or not the temperature of the adsorbent 32 has reached the discharge temperature T1 is determined based on the detected value of the exhaust gas temperature sensor 42 and the circulation flow rate (for example, a command signal output from the ECU 18 to the flow rate adjustment valve 41). The temperature may be estimated and determined based on the estimated temperature. Alternatively, a sensor that detects the temperature of the adsorbent 32 may be provided, and determination may be made based on the detection value of the sensor.

  Whether or not the adsorbent 32 is saturated may be determined to be saturated when the elapsed time since the start of 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, it may be determined that the engine 11 is saturated when the engine speed during the warm-up period of the engine 11 reaches a predetermined value.

  When it is determined in steps S10 and S30 described above that the temperature is low and the adsorption is possible (S10: NO, S30: YES), in the subsequent step S40, the circulation flow rate to the heat exchanger 40 is maximized. The operation of the flow rate adjustment valve 41 is controlled. As a result, the heat recovery amount in the heat exchanger 40 is maximized, and an increase in the exhaust gas outlet temperature Tout is suppressed. Therefore, since the time until the temperature of the adsorbent 32 reaches the discharge temperature T1 can be increased in the adsorbable state, the amount of adsorption on the adsorbent 32 can be sufficiently increased.

  On the other hand, when it is determined that it is in a low temperature state but not in an adsorbable state (S10: NO, S30: NO), the process proceeds to step S20 described above and the circulation flow rate is controlled to zero. Thus, the exhaust gas outlet temperature Tout is increased in preference to the HC adsorption, and the catalyst 33 is activated early.

  Next, one aspect by performing the process of FIG. 3 will be described with reference to the time chart of FIG. FIG. 4A shows a change in the cooling water circulation flow rate to the heat exchanger 40. 4B, the broken line indicates the exhaust gas inlet temperature Tex, the solid line indicates the exhaust gas outlet temperature Tout, and the alternate long and short dash line indicates the change in the temperature Tc of the catalyst 33.

  As shown in the drawing, at the time point t1 when the engine is started, the circulation flow rate is controlled to the maximum by step S40 because it is in a low temperature state and in an adsorbable state. Thereafter, the exhaust gas inlet temperature Tex gradually increases as the engine temperature gradually increases. However, since the circulation flow rate is maximized and the heat recovery amount is maximized, an increase in the exhaust gas outlet temperature Tout is suppressed, and thus an increase in the catalyst temperature Tc is also suppressed. Note that the temperature of the adsorbent 32 is substantially the same as the catalyst temperature Tc, and the temperature rise of the adsorbent 32 is also suppressed.

  Thereafter, when the exhaust gas inlet temperature Tex rises to the threshold value TH1 (TH1> activation temperature T2) without the adsorbent 32 becoming saturated and without the temperature of the adsorbent 32 reaching the discharge temperature T1, the exhaust gas At time t2 when the inlet temperature Tex reaches the threshold value TH1, it is determined that the high temperature state has been reached, and the circulation flow rate is controlled to the minimum (zero) by step S20. Therefore, the amount of heat recovered by the heat exchanger 40 is minimized, so that the rise of the exhaust gas outlet temperature Tout is promoted, and consequently, the rise of the catalyst temperature Tc is also promoted.

  The oxidation reaction in the catalyst 33 is started at time t4 when the catalyst temperature Tc reaches the activation temperature T2, and the catalyst temperature Tc is higher than the exhaust gas inlet temperature Tex due to the heat of oxidation reaction.

  In the present embodiment, the catalyst warm-up control described above is performed at time t2 when the exhaust gas inlet temperature Tex reaches the threshold value TH1. However, the catalyst warm-up control may be performed at the engine start time t1, or the catalyst warm-up control may be abolished.

  As described above, according to the present embodiment, the heat exchanger 40 is arranged on the upstream side of the purification device 30, and the heat recovery amount is adjusted by adjusting the cooling water circulation flow rate to the heat exchanger 40. It is possible to adjust the temperature of the exhaust gas flowing into the exhaust gas (exhaust gas outlet temperature Tout).

  And since the circulation flow rate is maximized in the low temperature state where the exhaust gas inlet temperature Tex is lower than the activation temperature T2, the rise of the exhaust gas outlet temperature Tout flowing into the purification device 30 is suppressed. Therefore, it is possible to secure a long time until the adsorbent temperature 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.

  On the other hand, since the circulation flow rate is made zero in a high temperature state where the exhaust gas inlet temperature Tex is equal to or higher than the activation temperature T2, an increase in the exhaust gas outlet temperature Tout flowing into the purification device 30 is promoted. Therefore, the catalyst warm-up can be completed early by shortening the time from time t3 when the adsorbent 32 is no longer in an adsorbable state to time t4 when the catalyst temperature Tc reaches the activation temperature T2.

  Further, even in a low temperature state (exhaust gas inlet temperature Tex <activation temperature T2), if the adsorption is not possible, the circulation flow rate is set to zero and the catalyst temperature Tc is promoted. The catalyst temperature Tc can be immediately increased without waiting for the temperature to rise, and the catalyst warm-up can be completed early. In particular, if the adsorbent temperature exceeds the discharge temperature T1, the flow rate reduction control is performed even in a low temperature state, so that a useless time (time from t3 to t4) during which neither adsorption nor oxidation is performed can be shortened.

  Further, the catalyst warm-up control is performed at the time point t2 when the temperature is changed from the low temperature state to the high temperature state. However, since the increase in the catalyst temperature Tc is promoted by reducing the circulation flow rate as described above, the catalyst warm-up control is performed. Such a control amount (for example, a fuel injection amount increase correction amount or an ignition timing retardation correction amount) can be reduced. Alternatively, the time for performing the catalyst warm-up control can be shortened. Therefore, fuel consumption deterioration due to the catalyst warm-up control can be suppressed.

  Further, since the circulation flow rate is maximized in the low temperature state, the heat recovery amount in the heat exchanger 40 can be increased sufficiently, and the heat source of the air conditioner can be used at an early stage. As a result, the time required for the vehicle interior temperature to reach the target temperature can be shortened.

(Second Embodiment)
In the first embodiment, whether it is a high temperature state or a low temperature state is determined based on the detection value (exhaust gas inlet temperature Tex) of the exhaust gas temperature sensor 42, whereas in the present embodiment shown in FIG. A water temperature sensor 43 (see FIG. 1) that detects the temperature Tw of the cooling water that is the heat medium of the heat exchanger 40 is provided, and the temperature is high based on the detected value (cooling water temperature Tw) of the water temperature sensor 43 (heat medium temperature sensor). Whether the state is a low temperature state or not is determined.

  More specifically, the water temperature sensor 43 is disposed in the vicinity of the cooling water outlet of the heat exchanger 40 in the heat recovery pipe 25. With this arrangement, the water temperature sensor 43 detects the temperature of the cooling water whose flow rate has been adjusted by the flow rate adjusting valve 41 and just after the heat exchange in the heat exchanger 40.

  Here, the higher the exhaust gas inlet temperature Tex, the higher the cooling water temperature Tw. In particular, if the circulation flow rate of the heat exchanger 40 is not zero, the tendency becomes remarkable. Therefore, in step S15 in FIG. 5, when the cooling water temperature Tw detected by the water temperature sensor 43 is higher than a preset threshold value TH2, a high temperature state (exhaust gas inlet temperature Tex ≧ activation temperature T2). It is determined that On the other hand, when the cooling water temperature Tw is equal to or lower than the threshold value TH2, it is determined that the temperature is low (exhaust gas inlet temperature Tex <activation temperature T2).

  With respect to the threshold value TH2 used in the determination in step S15, a correlation between the cooling water temperature Tw and the exhaust gas inlet temperature Tex is acquired in advance by a test, and from the correlation, the exhaust gas inlet temperature Tex becomes the threshold value TH1 used in step S10 in FIG. The coolant temperature Tw when the temperature is reached is calculated, and the temperature is set as the threshold value TH2. Since the correlation changes according to the engine speed, the engine load, etc., the threshold value TH2 may be variably set according to the engine speed, the engine load, etc. In addition, about process S20, S30, S40 after step S15, since it is the same as step S20, S30, S40 of FIG. 3, description of these processes is omitted.

  FIG. 6 is a time chart showing an embodiment by performing the processing of FIG. FIG. 6A shows a change in the cooling water circulation flow rate to the heat exchanger 40. Further, the broken line in FIG. 6B indicates the change in the exhaust gas inlet temperature Tex, the solid line indicates the exhaust gas outlet temperature Tout, and the alternate long and short dash line indicates the change in the temperature Tc of the catalyst 33. FIG. 6C shows a change in the cooling water temperature Tw.

  As shown in the drawing, at the time point t1 when the engine is started, the circulation flow rate is controlled to the maximum by step S40 because it is in a low temperature state and in an adsorbable state. Thereafter, as the engine temperature gradually increases, the exhaust gas outlet temperature Tout and the coolant temperature Tw gradually increase. However, since the circulation flow rate is maximized and the heat recovery amount is maximized, an increase in the exhaust gas outlet temperature Tout is suppressed, and thus an increase in the catalyst temperature Tc is also suppressed. Note that the temperature of the adsorbent 32 is substantially the same as the catalyst temperature Tc, and the temperature rise of the adsorbent 32 is also suppressed.

  Thereafter, it is determined that the adsorbent 32 has reached a high temperature state at time t20 when the coolant temperature Tw reaches the threshold value TH2 without the adsorbent 32 becoming saturated and without the temperature of the adsorbent 32 reaching the discharge temperature T1. In step S20, the circulation flow rate is controlled to the minimum (zero). Therefore, the amount of heat recovered by the heat exchanger 40 is minimized, so that the rise of the exhaust gas outlet temperature Tout is promoted, and consequently, the rise of the catalyst temperature Tc is also promoted.

  As described above, the same effects as those of the first embodiment are also exhibited by this embodiment. That is, when the temperature is low, the circulation flow rate is maximized to suppress the increase in the exhaust gas outlet temperature Tout. Therefore, it is possible to secure a long time until the adsorbent temperature 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. In addition, since the circulation flow rate is set to zero and the exhaust gas outlet temperature Tout is increased in a high temperature state, the time from the time t3 when the adsorbent 32 is no longer in an adsorbable state to the time t4 when the catalyst temperature Tc reaches the activation temperature T2 is reached. It is possible to shorten the time and achieve early completion of catalyst warm-up.

  Even in a low temperature state, if the adsorption is not possible, the circulation flow rate is made zero to promote the increase in the catalyst temperature Tc, so that the catalyst can be immediately used without waiting for the exhaust gas inlet temperature Tex to rise to a high temperature state. An increase in temperature Tc can be promoted, and catalyst warm-up can be completed early. In particular, if the adsorbent temperature exceeds the discharge temperature T1, the flow rate reduction control is performed even in a low temperature state, so that a useless time (time from t3 to t4) during which neither adsorption nor oxidation is performed can be shortened.

  Further, since the increase in the catalyst temperature Tc is promoted by setting the circulation flow rate to zero in the low temperature state, the control amount (for example, the fuel injection amount increase correction amount or the ignition timing retardation correction amount) required for the catalyst warm-up control is reduced. Can be small. Alternatively, the time for performing the catalyst warm-up control can be shortened. Therefore, fuel consumption deterioration due to the catalyst warm-up control can be suppressed.

  Further, since the circulation flow rate is maximized in the low temperature state, the heat recovery amount in the heat exchanger 40 can be increased sufficiently, and the heat source of the air conditioner can be used at an early stage. As a result, the time required for the vehicle interior temperature to reach the target temperature can be shortened.

(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, the circulation flow rate to the heat exchanger 40 is switched in steps from the maximum to zero, but the circulation flow rate may be varied according to the exhaust gas inlet temperature Tex and the cooling water temperature Tw. . According to this, the catalyst temperature Tc at the time points t2 and t20 at which it is determined that the low temperature state is changed to the high temperature state is set higher than the temperature shown in FIGS. 4 and 6 while being lower than the discharge temperature T1. be able to. Thereby, the time required from the high temperature state determination time points t2 and t20 to completion of catalyst warm-up can be shortened, and early completion of catalyst warm-up can be promoted.

  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 each of the above embodiments, the flow rate adjusting valve 41 is provided as a flow rate adjusting means. However, in an engine in which the water pump 24 is driven by an electric motor, the circulating flow rate is controlled by variably controlling the rotational speed of the water pump 24. In this case, the flow rate adjustment valve 41 may be eliminated and the operation of the water pump 24 may be controlled to adjust the circulation flow rate to the heat exchanger 40.

  In each of the above embodiments, both the exhaust gas state determination means S10 and S15 and the adsorption state determination means S30 are provided. However, the exhaust gas state determination means S10 and S15 may be eliminated and only the adsorption state determination means S30 may be used.

  According to this, in the adsorbable state immediately after the engine is started, the circulation flow rate is maximized to prevent the exhaust gas outlet temperature Tout from rising. Therefore, it is possible to secure a long time until the adsorbent temperature 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. On the other hand, when the engine 11 is started and the adsorption amount exceeds the allowable amount of the adsorbent 32 and becomes saturated or the adsorbent temperature becomes higher than the discharge temperature, the adsorbing state becomes impossible. Since the rise in the outlet temperature Tout is promoted, it is possible to shorten the time until the catalyst temperature Tc reaches the activation temperature T2 after the adsorbent 32 is no longer in an adsorbable state, thereby achieving early completion of catalyst warm-up. it can.

  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.

DESCRIPTION OF SYMBOLS 18 ... ECU (control means), 32 ... Adsorbent, 33 ... Catalyst, 40 ... Heat exchanger, 41 ... Flow rate adjustment valve (flow rate adjustment means), 42 ... Exhaust gas temperature sensor, 43 ... Water temperature sensor (heat medium temperature sensor) , S10, S15 ... exhaust gas state determination means, S30 ... adsorption state determination means, T1 ... discharge temperature, T2 ... activation temperature, Tex ... exhaust gas inlet temperature (exhaust gas temperature upstream of the heat exchanger).

Claims (10)

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 catalyst that oxidizes or reduces the specific component released from the adsorbent when its temperature is higher than an activation temperature higher than the release temperature;
A heat exchanger that is disposed upstream of the adsorbent and that recovers heat from the exhaust gas by circulating a heat medium that exchanges heat with the exhaust gas;
A flow rate adjusting means for adjusting a circulating flow rate of the heat medium;
Control means for controlling the operation of the flow rate adjusting means;
Exhaust gas state determination means for determining whether the exhaust gas temperature on the upstream side of the heat exchanger is a high temperature state where the activation temperature is equal to or higher than the activation temperature and a low temperature state where the exhaust gas temperature is less than the activation temperature;
With
The control means performs flow rate reduction control for reducing the circulation flow rate when it is determined by the exhaust gas state determination means that the high temperature state is present, compared to when the low temperature state is determined. Exhaust gas purification device. Comprising an adsorption state determination means for determining whether or not the adsorbent is capable of being adsorbed,
2. The control unit according to claim 1, wherein when the adsorption state determination unit determines that the adsorption state is not possible, the control unit performs the flow rate reduction control regardless of a determination result by the exhaust gas state determination unit. The exhaust gas purification apparatus according to 1. An exhaust gas temperature sensor for detecting the exhaust gas temperature on the upstream side,
The exhaust gas purification device according to claim 1 or 2, wherein the exhaust gas state determination means determines whether the high temperature state or the low temperature state based on a detection value of the exhaust gas temperature sensor. A heat medium temperature sensor for detecting the temperature of the heat medium;
The exhaust gas state determination unit determines whether the high-temperature state or the low-temperature state is based on a detection value of the heat medium temperature sensor. Exhaust gas purification equipment. 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 catalyst that oxidizes or reduces the specific component released from the adsorbent when its temperature is higher than an activation temperature higher than the release temperature;
A heat exchanger that is disposed upstream of the adsorbent and that recovers heat from the exhaust gas by circulating a heat medium that exchanges heat with the exhaust gas;
A flow rate adjusting means for adjusting a circulating flow rate of the heat medium;
Control means for controlling the operation of the flow rate adjusting means;
Adsorption state determination means for determining whether or not the adsorbent is capable of being adsorbed; and
With
The control means performs flow rate reduction control for reducing the circulating flow rate when the adsorption state determination unit determines that the adsorption state is not possible, compared to when the adsorption state determination unit determines that the adsorption state is possible. Exhaust gas purification device.   The exhaust gas purification apparatus according to claim 2 or 5, wherein the adsorption state determination means determines whether or not the adsorption is possible based on an elapsed time since the internal combustion engine was started.   The said adsorption | suction state determination means determines whether it is the said adsorption | suction possible state based on the driver | operator's accelerator operation amount in the warming-up period of the said internal combustion engine. The exhaust gas purification apparatus as described in any one.   The adsorption state determination means determines whether or not the adsorption state is possible based on an integrated value of the amount of heat supplied to the adsorbent after the internal combustion engine is started. , 5-7 The exhaust gas purification apparatus as described in any one of 5-7.   The determination unit determines whether or not the adsorption is possible based on an engine speed during a warm-up operation period of the internal combustion engine. The exhaust gas purification apparatus as described.   The exhaust gas purifying apparatus according to any one of claims 2 to 5, wherein the adsorption state determination unit determines whether or not the adsorption state is possible based on a temperature of the adsorbent.

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