JP2008274760A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely purify a purge gas separating from an adsorption material by a catalyst, and also to improve its purification rate, in an internal combustion engine. <P>SOLUTION: In this internal combustion engine 10 having two cylinder groups 12A and 12B, between an exhaust passage 20A of the one-side cylinder group 12A and an intake passage 18B of the other-side cylinder group 12B, a purge passage 34 and a purging passage changeover valve 36 connecting these passages to each other through an absorbing material 30 are arranged. When fuel cut control is being made only to the one-side cylinder group 12A, air exhausted from the cylinder group 12A is supplied to the absorbing material 30 through the purge passage 34 to separate an un-purified constituent in the absorbing material 30. A purge gas having flowed out from the absorbing material 30 is circulated back to the other-side cylinder group 12B in a normal combustion state, and purified by catalysts 24B and 26. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a multi-cylinder internal combustion engine, and more particularly, to an internal combustion engine provided with an adsorbent that adsorbs components in exhaust gas.

  Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 11-148343, an apparatus in which an adsorbent is arranged in an exhaust passage of an engine is known. This adsorbent adsorbs unpurified components such as HC contained in the exhaust gas when the catalyst is in an inactive state, such as when the engine is cold started. Such an adsorbent needs to desorb the unpurified components once adsorbed at an appropriate timing so that the adsorption capacity is not saturated.

  For this reason, in a conventional apparatus, for example, when performing fuel cut control of an engine, exhaust gas (air or residual exhaust gas) discharged from a cylinder is used to desorb unpurified components from the adsorbent. Yes. Specifically, exhaust gas from the cylinder is supplied to the adsorbent when the fuel is cut, and unpurified components are desorbed from the adsorbent by the exhaust. Then, the mixed gas (purge gas) of the exhaust gas and the desorbed component is recirculated to the intake passage of the cylinder.

Japanese Patent Laid-Open No. 11-148343

  In the prior art, unpurified components are desorbed from the adsorbent using exhaust during fuel cut, and the purge gas is recirculated to the intake passage. For this reason, the recirculated purge gas is discharged as it is from the cylinder during fuel cut and purified by the catalyst.

  However, the catalyst is generally designed to exhibit sufficient purification performance in a specific air-fuel ratio region (region called a purification window) including the theoretical air-fuel ratio. On the other hand, in the cylinder under fuel cut, an operation that maintains the stoichiometric air-fuel ratio (so-called stoichiometric operation) is not performed. As a result, the characteristics of the air (gas) discharged from the cylinder during fuel cut often deviate from the purification window.

  For this reason, in the conventional apparatus, even if air containing purge gas is circulated through the catalyst, unpurified components contained therein may not be sufficiently purified by the catalyst, which may cause deterioration of exhaust emission. .

  The present invention has been made to solve the above-described problems, and provides an internal combustion engine capable of reliably purging purge gas desorbed from an adsorbent with a catalyst and improving its purification rate. With the goal.

The first invention comprises two cylinder groups each having a fuel injection valve, an intake passage and an exhaust passage,
A catalyst connected to the exhaust passages of the two cylinder groups and purifying exhaust gas flowing through the exhaust passage;
An adsorbent connected to the exhaust passages of the two cylinder groups and adsorbing components in the exhaust gas;
A purge passage branched from the exhaust passage of one of the two cylinder groups and connected to the intake passage of the other cylinder group via the adsorbent;
Purge passage opening / closing means for opening and closing the purge passage upstream of the adsorbent with respect to the flow of exhaust gas;
A fuel injection control means for reducing the fuel injection amount for the one cylinder group of the two cylinder groups, and injecting an amount of fuel that the catalyst can exhibit purification performance into the other cylinder;
Purge control means for causing the air discharged from the one cylinder group to flow to the purge passage by the purge passage opening and closing means when the fuel injection amount to the one cylinder group is reduced by the fuel injection control means; ,
It is characterized by providing.

  According to a second aspect of the invention, the fuel injection control means is configured to stop fuel injection to the one cylinder group.

  In a third aspect of the present invention, a pre-stage catalyst is provided in a position upstream of the purge passage in the exhaust passage of the one cylinder group, and the fuel injection control means is configured to provide a fuel injection amount to the one cylinder group. Is reduced to an amount combustible by the preceding catalyst.

  In a fourth aspect of the invention, the exhaust passages of the two cylinder groups are provided with a common exhaust passage that joins these exhaust passages downstream, and the common exhaust passage is formed as a passage that branches from the common exhaust passage. A bypass passage in which the adsorbent is disposed, and a bypass passage opening / closing means for opening and closing the bypass passage on the upstream side of the adsorbent, and a passage connected to the downstream side of the adsorbent And a passage switching means for switching between the common exhaust passage and the purge passage.

  According to the first invention, the fuel injection control means can reduce the fuel injection amount for one of the cylinder groups (or stop the fuel injection) and stop the combustion of this cylinder group. Further, the purge control means can introduce the air discharged from the cylinder group in the deactivated state into the purge passage and desorb the unpurified components from the adsorbent by the air.

  Here, the air discharged from the cylinder group in the idle state contains almost no exhaust gas or moisture generated during combustion, and therefore maintains an oxygen concentration close to that of the intake air and has low humidity. In addition, this air is heated in a high-temperature cylinder or exhaust passage, and has a high temperature. On the other hand, in general, an adsorbent that is more suitable for desorption treatment in air than exhaust gas can obtain high desorption efficiency in high-temperature and low-humidity air containing sufficient oxygen.

  Therefore, in the present invention, unpurified components in such an adsorbent can be efficiently desorbed using the air discharged from the cylinder group in the idle state. Moreover, the purge passage can recirculate the air (purge gas) containing this unpurified component to the intake passage of the other cylinder group. At this time, the fuel injection control means can inject an amount of fuel (in other words, an amount of fuel for which the stoichiometric operation is performed) with which the catalyst can exhibit purification performance with respect to the other cylinder group. . Therefore, when exhaust gas containing purge gas is discharged from the other cylinder group, the catalyst can efficiently purify these gases in an air-fuel ratio region where the purification ability is high, and unpurified components contained in the purge gas. Can be stably decomposed and removed.

  According to the second invention, the fuel injection control means can stop the fuel injection to one of the cylinder groups in accordance with, for example, the operating state of the internal combustion engine. For this reason, for example, the adsorbent desorption process can be performed smoothly using fuel cut control during deceleration.

  According to the third aspect of the invention, the fuel injection control means can inject an amount of fuel combustible by the pre-stage catalyst into the cylinder group in the idle state. As a result, a lean air-fuel mixture is discharged from the cylinder group in the idle state. However, the air-fuel mixture is almost completely combusted and purified by passing through the front catalyst, and the temperature of the air and the front catalyst rises due to this combustion. For this reason, when desorbing the adsorbent, it is possible to supply the adsorbent with air sufficiently heated by the pre-catalyst, and to desorb the unpurified components in the adsorbent more efficiently with high-temperature air. Can do.

  According to the fourth invention, when the catalyst is in an inactive state, the bypass passage can be opened by the bypass passage opening / closing means while the purge passage is closed by the purge passage opening / closing means. As a result, the exhaust gas discharged from the two cylinder groups can be introduced to the position of the adsorbent. The exhaust gas after passing through the adsorbent can be returned to the common exhaust passage by the passage switching means.

  On the other hand, when the adsorbent desorption process is performed, the purge passage can be opened by the purge passage opening / closing means and the bypass passage can be closed by the bypass passage opening / closing means. Thereby, when air is discharged from one cylinder group, this air can be introduced into the position of the adsorbent through the purge passage. The purge gas that has passed through the adsorbent can be held in the purge passage by the passage switching means and can be circulated toward the intake passage of the other cylinder group.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. An internal combustion engine 10 shown in FIG. 1 is, for example, a multi-cylinder engine having two banks, and includes cylinder groups 12A and 12B divided into left and right banks. In the present embodiment, a six-cylinder internal combustion engine 10 in which two cylinder groups 12A and 12B are each constituted by three cylinders 14 is illustrated.

  The internal combustion engine 10 is configured as a variable cylinder type engine that performs fuel cut control of one or both of the cylinder groups 12A and 12B in accordance with, for example, a deceleration operation of the operator.

  The cylinder groups 12A and 12B are provided with a fuel injection valve 16, intake passages 18A and 18B, and exhaust passages 20A and 20B. Here, the fuel injection valve 16 is driven by the ECU 40 to inject fuel toward the individual cylinders 14. Further, the intake passages 18A and 18B allow air (intake air) sucked into the individual cylinders 14 to be circulated, and are connected to the intake sides of the cylinder groups 12A and 12B, respectively.

  Further, the exhaust passages 20A and 20B discharge exhaust gas from each cylinder 14, and the base end side (upstream side in the exhaust gas flow direction) is connected to the exhaust side of the cylinder groups 12A and 12B, respectively. Further, a common exhaust passage 22 that joins these passages is connected to the front end side (downstream side in the exhaust gas flow direction) of the exhaust passages 20A and 20B. A silencer (muffler) (not shown) is provided on the downstream side of the common exhaust passage 22.

  The exhaust passages 20A and 20B are provided with front-stage catalysts (SC) 24A and 24B, respectively, and the common exhaust passage 22 is provided with a rear-stage catalyst (UF) 26. Of these catalysts 24A, 24B, and 26, the upstream catalyst 24A of the exhaust passage 20A is disposed upstream of the purge passage 34 described later. The catalysts 24A, 24B, and 26 purify components such as HC, NOx, and CO contained in the exhaust gas when activated by the exhaust heat of the internal combustion engine 10 or the like.

  On the other hand, the common exhaust passage 22 is provided with a bypass passage 28 connected in parallel with the main passage portion 22a which is a part thereof. The bypass passage 28 branches from the common exhaust passage 22 on the upstream side of the main passage portion 22a. Further, the bypass passage 28 merges with the common exhaust passage 22 on the downstream side of the main passage portion 22a.

  An adsorbent 30 is provided in the middle of the bypass passage 28. The adsorbent 30 adsorbs unpurified components such as HC, NOx, and CO contained in the exhaust gas when the catalysts 24 and 26 are in an inactive state.

The adsorbent 30 is made of, for example, a zeolite-based or ceria-based material. In this case, as an example of the zeolitic material, a material (Fe / ZSM5) in which iron (Fe) is ion-exchanged with one kind of zeolite (ZSM5) is used. Moreover, Pd / CeO ₂ is used as an example of the ceria-based material.

  Further, an adsorption passage switching valve 32 is provided at a branch portion between the common exhaust passage 22 and the bypass passage 28. The adsorption passage switching valve 32 is constituted by, for example, a three-port two-position switching electromagnetic valve, and is disposed on the upstream side of the main passage portion 22a. Further, the adsorption passage switching valve 32 is driven by an ECU 40 which will be described later, and is switched to one of the positions x and y shown in FIG.

  The adsorption passage switching valve 32 is held at the position x when the catalysts 24A, 24B, and 26 are activated. At this position x, the adsorption passage switching valve 32 opens the main passage portion 22 a of the common exhaust passage 22 and closes the bypass passage 28. Further, when the catalysts 24A, 24B, and 26 are in an inactive state, for example, at the time of cold start of the internal combustion engine 10, the adsorption passage switching valve 32 is switched to the position y. At this position y, the adsorption passage switching valve 32 is configured to close the main passage portion 22 a and open the bypass passage 28.

  On the other hand, the system configuration of the present embodiment includes a purge passage 34, a purge passage switching valve 36, and a passage switching valve 38 in order to perform the desorption processing of the adsorbent 30. First, the purge passage 34 will be described. The upstream side of the purge passage 34 is an exhaust passage 20A of one cylinder group (illustrated as the cylinder group 12A) of the two cylinder groups 12A and 12B provided in the internal combustion engine 10. Branch from. Further, the downstream side of the purge passage 34 is connected to the intake passage 18B of the other cylinder group 12B via the adsorbent 30. For example, a surge tank that becomes a part of the intake passage 18B may be selected as the connection portion.

  The purge passage 34 includes an introduction passage portion 34a and a reflux passage portion 34b that are disposed with the adsorbent 30 interposed therebetween. Here, the introduction passage portion 34a introduces air for desorption treatment from the exhaust passage 20A of the cylinder group 12A toward the adsorbent 30. The introduction passage portion 34a branches from the exhaust passage 20A on the downstream side of the upstream catalyst 24A, and is connected between the exhaust passage 20A and the upstream side of the adsorbent 30.

  The recirculation passage 34b recirculates the purge gas containing the decontaminated unpurified component to the intake passage 18B. The reflux passage 34b branches from the bypass passage 28 on the downstream side of the adsorbent 30, and is connected between the bypass passage 28 and the intake passage 18B. Therefore, if attention is paid to the arrangement of the adsorbent 30, the adsorbent 30 is arranged in the middle of the bypass passage 28 and in the middle of the purge passage 34.

  Next, the purge passage switching valve 36 will be described. The purge passage switching valve 36 is constituted by, for example, a three-port two-position switching type electromagnetic valve, and is provided at a branch portion between the exhaust passage 20A of the cylinder group 12A and the introduction passage portion 34a of the purge passage 34. The purge passage switching valve 36 is driven by an ECU 40 described later, and is switched to one of the positions x and y shown in FIG.

  Here, the purge passage switching valve 36 is held at the position x when the internal combustion engine 10 is in a normal operation state. At this position x, the purge passage switching valve 36 closes the purge passage 34 and opens the common exhaust passage 22 with respect to the exhaust passage 20A. The purge passage switching valve 36 is switched to the position y when the adsorbent 30 is desorbed. At this position y, the purge passage switching valve 36 is configured to open the purge passage 34 with respect to the exhaust passage 20A and close the common exhaust passage 22.

  Further, the passage switching valve 38 will be described. The passage switching valve 38 is configured by an electromagnetic valve similar to the other switching valve 36 and the like, and is driven by the ECU 40. The passage switching valve 38 is located on the downstream side of the adsorbent 30 and is provided at a branch portion between the bypass passage 28 and the reflux passage portion 34 b of the purge passage 34.

  The passage switching valve 38 is normally held at the position x, and in this state, the downstream side of the adsorbent 30 is connected to the bypass passage 28 (that is, the common exhaust passage 22). The passage switching valve 38 is switched to the position y together with the purge passage switching valve 36 when the adsorbent 30 is desorbed. At this position y, the passage switching valve 38 connects the downstream side of the adsorbent 30 to the reflux passage portion 34 b of the purge passage 34.

  In addition, the system configuration of the present embodiment includes an ECU (Electronic Control Unit) 40 that controls the operating state of the internal combustion engine 10. Sensors for detecting various physical quantities necessary for driving are connected to the input side of the ECU 40. This physical quantity is, for example, the amount of intake air of the internal combustion engine 10, the rotational speed, the opening degree of the throttle valve, the oxygen concentration in the exhaust gas, the temperature of the engine cooling water, the temperature of the catalyst, and the like. The ECU 40 is connected to the fuel injection valve 16 and the three types of switching valves 32, 36, and 38 as well as other actuators (not shown) (for example, an ignition system of the cylinder 14). ing.

  Then, the ECU 40 detects the operation state of the internal combustion engine 10 and the operation of the operator by various sensors, and injects an appropriate amount of fuel from the fuel injection valve 16 to each of the cylinder groups 12A and 12B according to the detection result. Further, the ECU 40 appropriately controls the operating state of the internal combustion engine 10 by operating other actuators in the same manner.

  Further, the ECU 40 also performs fuel cut control for both the cylinder groups 12A and 12B as necessary when a condition such as the operator performing a deceleration operation is established. In this fuel cut control, for example, fuel injection to one cylinder group 12A is stopped, and fuel injection in an amount that allows the catalysts 24B and 26 to exhibit purification performance may be continued to the other cylinder group 12B. (Fuel cut control for only one bank). During the fuel cut control for only one bank, the purge control described later is performed.

[Operation of Embodiment 1]
Next, the system operation according to the first embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, and FIG.
(Operation during normal operation)
First, in the normal operation state in which the catalysts 24A, 24B, and 26 are activated, the switching valves 32, 36, and 38 are held at the position x by the ECU 40 as shown in FIG. In this state, the cylinder groups 12A and 12B burn the air sucked from the intake passages 18A and 18B and the fuel injected from the fuel injection valve 16 in the cylinder 14. Exhaust gas generated after combustion is discharged to the outside through the exhaust passages 20A and 20B and the common exhaust passage 22, as indicated by arrows.

(Suction operation)
Next, the adsorption operation of the adsorbent 30 performed when the internal combustion engine 10 is cold started will be described with reference to FIG.
This adsorption operation is started when the ECU 40 switches the adsorption passage switching valve 32 to the position y and holds the purge passage switching valve 36 and the passage switching valve 38 at the position x. As a result, the exhaust gas discharged from the cylinder groups 12A and 12B flows through the bypass passage 28 in the middle of the common exhaust passage 22 as indicated by an arrow. Unpurified components contained in the exhaust gas are adsorbed when passing through the adsorbent 30. Further, when the catalyst 24A, 24B, 26 is activated while continuing such an adsorption operation, the adsorption passage switching valve 32 is switched to the position x, and the adsorption operation is completed.

(Purge operation)
Next, the purge operation (desorption process) of the adsorbent 30 performed in synchronization with the fuel cut control will be described with reference to FIG.
First, the purge operation is started as necessary when fuel cut control for only one bank is performed on one cylinder group 12A. When the purge operation is started, the ECU 40 switches the purge passage switching valve 36 and the passage switching valve 38 to the position y, and the adsorption passage switching valve 32 is held at the position x.

  At this time, the cylinder group 12A is a non-combustion cylinder that does not perform the combustion stroke, but the piston, the intake valve, and the exhaust valve perform normal operations in the cylinder. For this reason, the cylinder group 12A performs a pumping operation in accordance with the reciprocation of the piston, and discharges the air sucked from the intake passage 18A to the exhaust passage 20A.

  Here, each cylinder 14 of the cylinder group 12A, the exhaust passage 20A, the pre-stage catalyst 24A, and the like are at a high temperature because the exhaust gas generated in the normal combustion stroke flows. As a result, the air discharged from the cylinder group 12A reaches a high temperature by circulating through these high-temperature parts. The high-temperature air reaches the adsorbent 30 through the introduction passage portion 34a of the purge passage 34 and passes through the adsorbent 30 as indicated by an arrow.

  As described above, in the purge operation according to the present embodiment, it is possible to supply the adsorbent 30 with high-temperature and low-humidity air containing sufficient oxygen by using the cylinder group 12A in the idle state. Thereby, the unpurified component in the adsorbent 30 can be efficiently desorbed during the purge operation. In particular, for an adsorbent that is suitable for desorption treatment in air rather than exhaust gas, such as adsorbent 30 formed of zeolite-based or ceria-based material, the desorption efficiency is higher. It can be further enhanced.

  On the other hand, the air that has passed through the adsorbent 30 serves as a purge gas containing the desorbed unpurified components. As indicated by the arrow Q, the purge gas passes through the recirculation passage 34b of the purge passage 34 and is recirculated to the intake passage 18B of the cylinder group 12B, and is sucked into the cylinder group 12B where fuel cut control is not performed. The purge gas is discharged from the cylinder group 12B to the exhaust passage 20B together with the exhaust gas generated by the normal combustion stroke. Further, the mixed gas of the exhaust gas and the purge gas is purified by passing through the catalysts 24B and 26, and thereafter discharged from the common exhaust pipe 22 to the outside.

  At this time, the cylinder group 12B is performing a normal fuel stroke (stoichiometric operation) with substantially the stoichiometric air-fuel ratio maintained, so that the combustion gas has an air-fuel ratio suitable for purification by the catalysts 24B and 26 ( The air / fuel ratio is maintained so as to enter the catalyst purification window. For this reason, when exhaust gas containing purge gas is discharged from the cylinder group 12B, the catalysts 24B and 26 can efficiently purify these gases in an air-fuel ratio region where the purification ability is high, and unpurified in the purge gas. The components can be stably decomposed and removed.

[Specific Control Processing for Realizing Embodiment 1]
FIG. 4 is a flowchart of a routine executed by the ECU 40 in order to realize the adsorption operation and the purge operation in the present embodiment. 4 is started immediately after the internal combustion engine 10 is started.

  First, in step 100, the ECU 40 detects, for example, the engine coolant temperature, the temperatures of the catalysts 24A, 24B, and 26, the oxygen concentration (or A / F) of the exhaust gas, and the like by a sensor (not shown), and according to the detection result. To determine whether to start the suction control. In step 102, for example, whether or not the adsorption control is completed is determined according to the same conditions as in step 100, the duration of the adsorption control, the flow rate of the exhaust gas, and the like. In this case, basically, for example, when the detected temperature is lower than the set temperature corresponding to the activation of the catalyst, the adsorption control is performed.

  If it is determined in step 100 that the suction control is to be started and it is determined in step 102 that the suction control is not completed, the suction control is executed in step 104. Specifically, the purge passage switching valve 36 and the passage switching valve 38 are held at the position x, and the adsorption passage switching valve 32 is switched to the position y. Thereby, the adsorption operation shown in FIG. 2 described above is realized, and the unpurified components in the exhaust gas are adsorbed by the adsorbent 30.

  Further, for example, when it is determined that the temperature of the engine cooling water or the catalyst has risen and the catalyst has been activated, in step 106, all the switching valves 32, 36, 38 are switched to the position x. As a result, the adsorption control is terminated, and the adsorbent 30 is sealed in the bypass passage 28 until the purge control is started.

  Then, the internal combustion engine 10 ends the warm-up operation and shifts to a normal operation state. Further, the ECU 40 executes fuel cut control in step 110 when a predetermined fuel cut condition is satisfied in step 108 in a normal operation state. In this fuel cut control, for example, when a predetermined fuel cut condition is established according to an operator's deceleration operation or the like, the fuel injection of only one bank (cylinder group 12A) is stopped, or all cylinders ( The fuel injection of the cylinder groups 12A, 12B) is stopped.

  Next, in steps 112 to 120, purge control of the adsorbent 30 is performed. In this purge control, first, in step 112, it is determined whether or not a fuel cut is performed on one cylinder group 12A. In step 114, it is determined whether or not a fuel cut has been performed on the other cylinder group 12B.

  Then, when the fuel injection for only the cylinder group 12A is stopped and the normal fuel injection is performed for the cylinder group 12B, the routine proceeds to step 116 described later. In other cases, the process returns to step 108 to continue the normal operation state.

  Next, in step 116, the temperature of the catalysts 24B, 26 is detected by a temperature sensor or the like (not shown), and warm-up determination (activation determination) of the catalysts 24B, 26 involved in purging purge gas is performed. If it is determined that these catalysts are activated, it is determined in step 118 whether it is time to complete the purge control. When it is determined in steps 116 and 118 that the purge control execution timing is reached, the purge control is started in step 120.

  In this purge control, the purge passage switching valve 36 and the passage switching valve 38 are switched to the position y, and the adsorption passage switching valve 32 is held at the position x. As a result, the purge operation shown in FIG. 3 described above is realized. That is, the air discharged from the cylinder group 12 </ b> A in the deactivated state performs a desorption process of the adsorbent 30 in the purge passage 34 and becomes purge gas. The purge gas is sucked into the cylinder group 12B that performs a normal operation (stoichiometric operation) while maintaining the stoichiometric air-fuel ratio, and is purified by the catalysts 24B and 26 together with the exhaust gas.

  On the other hand, when it is determined in step 118 that the purge control is completed, in step 122, all the switching valves 32, 36, 38 are switched to the position x, and the process returns to step 100 to repeat the process.

  Thus, in the present embodiment, unpurified components can be efficiently desorbed from the adsorbent 30 by using the air discharged from the cylinder group 12A in the deactivated state. The depurified unpurified components can be reliably purified by the catalysts 24B and 26 together with the exhaust gas discharged from the cylinder group 12B during the stoichiometric operation.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. Note that the system according to the present embodiment uses the system configuration shown in FIG. However, the present embodiment is different from the first embodiment in that it is realized by using the routine shown in FIG. 5 instead of the routine shown in FIG.

[Features of Embodiment 2]
The system of the present embodiment is characterized by injecting a moderately reduced amount of fuel into the cylinder group 12A in a state where the fuel cut control for only one bank with respect to the one cylinder group 12A is performed. Here, the moderately reduced injection amount is defined as a minute amount that can be completely combusted by the pre-stage catalyst 24A and does not adversely affect the exhaust emission.

  That is, when a moderately reduced amount of fuel is injected into the cylinder group 12A in the idle state, this fuel becomes a lean air-fuel mixture together with air and is discharged from the cylinder group 12A and reaches the front catalyst 24A. The lean air-fuel mixture is almost completely combusted and purified in the high temperature front catalyst 24A, and the temperature of the air and the front catalyst 24A is further increased by the combustion at this time.

  For this reason, according to the present embodiment, when performing the purge control, air sufficiently heated by the pre-stage catalyst 24A can be supplied to the adsorbent 30, and the unpurified components in the adsorbent 30 can be supplied by this high-temperature air. Can be more efficiently desorbed.

[Specific Control Processing for Realizing Embodiment 2]
FIG. 5 is a flowchart of a routine executed by the ECU 40 in order to realize the adsorption operation and the purge operation in the present embodiment. In the description of this routine, the same steps as those in the first embodiment (FIG. 4) are denoted by the same reference numerals, and the description thereof is omitted.

  Here, the routine of the present embodiment has a configuration in which steps 200 and 202 are added after step 120 is performed. That is, in the present embodiment, after the purge control is started in step 120, it is first determined in step 200 whether or not the temperature of the pre-stage catalyst 24A is lower than a predetermined temperature.

  The predetermined temperature is defined as a temperature at which the air passing through the pre-stage catalyst 24A can be maintained at a high temperature suitable for the desorption treatment of the adsorbent 30. In other words, if the pre-stage catalyst 24A is hotter than the predetermined temperature, the air warmed therein is maintained at a high temperature that promotes the desorption of unpurified components from the adsorbent 30. .

  When it is determined in step 200 that the temperature of the pre-stage catalyst 24A is too low, in step 202, the appropriate amount of fuel described above is injected into the deactivated cylinder group 12A. As a result, a lean air-fuel mixture is discharged from the cylinder group 12A, and this air-fuel mixture burns in the front catalyst 24A to raise the temperature of the air and the front catalyst 24A.

  When it is determined in step 200 that the pre-stage catalyst 24A is higher than the predetermined temperature, and at the timing after execution of step 202, the process returns to step 108 and the process is repeated as in the first embodiment.

  As described above, according to the present embodiment, even when the cylinder group 12A is stopped, it is possible to raise the air temperature for the desorption process by injecting the fuel that is moderately reduced, and to achieve high desorption efficiency. Can be realized.

  In each of the above-described embodiments, the purge passage switching valve 36 is a specific example of the “purge passage opening / closing means” in the first invention. The adsorption passage switching valve 32 represents the “bypass passage opening / closing means” in the fourth aspect of the invention, and the passage switching valve 38 represents a specific example of the “passage switching means”. Steps 108 and 110 in FIG. 4 show a specific example of “fuel injection control means” in the second invention, and steps 108, 110 and 202 in FIG. 5 show “fuel injection control” in the third invention. Specific examples of “means” are shown. Further, steps 112 to 120 in FIGS. 4 and 5 show specific examples of the “purge control means” in the first invention.

  In each embodiment, as the internal combustion engine 10, a 6-cylinder engine in which each of the cylinder groups 12 </ b> A and 12 </ b> B is configured by three cylinders 14 is illustrated. However, the present invention is not limited to this, and each cylinder group may be composed of one, two, or four or more cylinders. Further, it is sufficient that there are at least two cylinder groups, and a configuration including three or more cylinder groups may be employed.

  In each embodiment, when fuel cut control for variable cylinders is performed, the fuel injection of one bank (cylinder group 12A) of the cylinder groups 12A and 12B constituting the left and right banks is reduced. It was supposed to be. However, the present invention is not limited to the configuration in which the two cylinder groups are divided for each bang, and the two cylinder groups may be configured by arbitrary sections as long as the intake system and the exhaust system are independent. is there.

  Further, in each embodiment, the general fuel cut control performed during the operation of the internal combustion engine 10 has been described as an example of the fuel injection control means. However, the present invention is not limited to this. For example, the purge control may be performed by temporarily creating a deactivated cylinder regardless of the fuel cut control performed during the deceleration operation or the like.

  In each embodiment, the exhaust passage 20A is closed by the purge passage switching valve 36 when the purge passage switching valve 36 is switched to the position y. However, the present invention is not limited to this, and the purge passage opening / closing means only needs to be able to open and close the purge passage 34 with respect to at least the exhaust passage 20A. That is, at the time of purge control, only a part of the air flowing through the exhaust passage 20A may be circulated through the purge passage 34.

  In each embodiment, the adsorbent 30 is arranged in the bypass passage 28 branched from the common exhaust passage 22. However, the present invention is not limited to this. For example, the present invention may be applied to an internal combustion engine having a configuration in which the adsorbent 30 is disposed in the common exhaust passage 22 without the bypass passage 28.

  Furthermore, in each embodiment, the adsorbent 30 has been described using a zeolite-based or ceria-based material as an example. However, the adsorbent of the present invention is not limited to these materials, and any other adsorbent material may be used.

It is a figure for demonstrating the system configuration | structure of the internal combustion engine in Embodiment 1 of this invention. It is a figure which shows system operation | movement when the internal combustion engine is performing adsorption | suction control during cold operation. It is a figure which shows system operation | movement when the internal combustion engine is performing purge control during fuel cut. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12A, 12B Cylinder group 14 Cylinder 16 Fuel injection valve 18A, 18B Intake passage 20A, 20B Exhaust passage 22 Common exhaust passage 22a Main passage part 24A, 24B Pre-stage catalyst 26 Rear-stage catalyst 28 Bypass passage 30 Adsorbent 32 Adsorption passage Switching valve (Bypass passage opening / closing means)
34 purge passage 34a introduction passage 34b recirculation passage 36 purge passage switching valve (purge passage opening / closing means)
38 Passage switching valve (passage switching means)
40 ECU

Claims (4)

Two cylinder groups each having a fuel injection valve, an intake passage, and an exhaust passage;
A catalyst connected to the exhaust passages of the two cylinder groups and purifying exhaust gas flowing through the exhaust passage;
An adsorbent connected to the exhaust passages of the two cylinder groups and adsorbing components in the exhaust gas;
A purge passage branched from the exhaust passage of one of the two cylinder groups and connected to the intake passage of the other cylinder group via the adsorbent;
Purge passage opening / closing means for opening and closing the purge passage upstream of the adsorbent with respect to the flow of exhaust gas;
A fuel injection control means for reducing the fuel injection amount for the one cylinder group of the two cylinder groups, and injecting an amount of fuel that the catalyst can exhibit purification performance into the other cylinder;
Purge control means for causing the air discharged from the one cylinder group to flow to the purge passage by the purge passage opening and closing means when the fuel injection amount to the one cylinder group is reduced by the fuel injection control means; ,
An internal combustion engine comprising:   The internal combustion engine according to claim 1, wherein the fuel injection control unit is configured to stop fuel injection to the one cylinder group.   A pre-stage catalyst is provided in the exhaust passage of the one cylinder group at a position upstream of the purge passage, and the fuel injection control means burns the fuel injection amount to the one cylinder group by the pre-stage catalyst. The internal combustion engine according to claim 1, wherein the internal combustion engine is configured to be reduced to a possible amount.   The exhaust passages of the two cylinder groups are provided with a common exhaust passage that joins these exhaust passages on the downstream side. The common exhaust passage is formed as a passage branched from the common exhaust passage, and the adsorbent is disposed therein. A bypass passage opening and closing means for opening and closing the bypass passage on the upstream side of the adsorbent, and a passage connected to the downstream side of the adsorbent on the common exhaust passage. The internal combustion engine according to claim 1, 2 or 3, further comprising passage switching means for switching to any one of the purge passages.

Images