JP4591238B2 - Exhaust gas purification system failure diagnosis device and exhaust gas purification system with failure diagnosis function - Google Patents

Description

  The present invention relates to a technical field of an exhaust gas purification system failure diagnosis device for diagnosing a failure of an exhaust gas purification system in an internal combustion engine and an exhaust gas purification system with a failure diagnosis function including such a failure diagnosis device.

  As this type of exhaust gas purification system, a system using a temperature sensor has been proposed (see, for example, Patent Document 1). According to the exhaust purification device for a diesel engine disclosed in Patent Document 1 (hereinafter referred to as “conventional technology”), the exhaust gas passages are branched into first and second passages each provided with a filter. The exhaust gas switching valve is selectively switched. Each flow path is provided with a temperature sensor, and at this time, an abnormality of the exhaust gas switching valve can be detected based on the temperature of the unselected filter.

It has been proposed that an inner cylinder has a switching valve and an HC adsorbent is provided between the inner cylinder and the outer cylinder covering the inner cylinder (see, for example, Patent Document 2).
In addition, a technique has been proposed in which a thermometer is provided downstream of the catalyst, and the exhaust gas has passed through the catalyst if the temperature rises when the switching valve is operated (see, for example, Patent Document 3).

JP-A-8-210120 JP 2000-345829 A JP 2004-92432 A

  When a flow path is selected by a switching valve, if no exhaust gas flows through the unselected flow path, it is determined that the switching valve has failed due to a temperature rise in the non-selected flow path. Is possible to some extent. However, in practice, a part of the exhaust gas also flows into the flow path that is not selected regardless of the failure of the switching valve. Therefore, even when the switching valve is operating normally, the temperature of the unselected channel may rise. Such a temperature rise in the normal range and a temperature rise caused by a failure of the switching valve may be indistinguishable depending on the traveling conditions of the vehicle, and are erroneously diagnosed as a failure of the switching valve. The occurrence of diagnosis cannot be avoided. That is, the conventional technique has a technical problem that it is difficult to accurately diagnose a failure of a switching means such as a switching valve.

  The present invention has been made in view of the circumstances described above, and includes a failure diagnosis device for an exhaust gas purification system capable of accurately diagnosing a failure of a switching means in the exhaust gas purification system, and such a failure diagnosis device. Another object of the present invention is to provide an exhaust gas purification system with a fault diagnosis function.

In order to solve the above-described problem, a failure diagnosis device for an exhaust gas purification system according to the present invention (hereinafter referred to as a “failure diagnosis device” as appropriate) is provided in a main exhaust passage of an internal combustion engine and purifies exhaust gas. A bypass flow path that bypasses a bypassed flow path that is a part of the main exhaust flow path on the upstream side of the first catalyst that is defined as a side of the first catalyst that approaches the engine portion of the internal combustion engine; A second catalyst that is provided in the bypass flow path and purifies the exhaust gas; and by selectively closing the bypass flow path, the exhaust gas discharge path is changed to a discharge path including the bypass flow path. to diagnose a failure of the switching means in the exhaust gas purification system comprising a switching means for selectively switching between the discharge path that does not include and the target bypass flow path includes said bypass passage A failure diagnosis apparatus for an exhaust gas purification system, wherein: (i) a downstream side of a start point of the bypassed part defined as a side away from an engine part of the internal combustion engine in the main exhaust flow path; ii) a first temperature detecting means that is installed in the upstream section of the first catalyst and detects the temperature of the section; and a second temperature sensor that is installed in the bypass flow path and detects the temperature of the bypass flow path. The temperature detecting means comprises diagnostic means for diagnosing a failure of the switching means based on the relative relationship between the temperature of the section and the temperature of the bypass flow path.

  In the present invention, the “internal combustion engine” is a concept that encompasses an engine that converts combustion of fuel into motive power, and preferably refers to an engine for a vehicle that uses gasoline, light oil, LPG, or the like as fuel.

  The “main exhaust passage” in the present invention is a concept including a passage through which exhaust gas exhausted in the exhaust stroke of the internal combustion engine is mainly guided, and preferably, at least one of exhaust pipes including an exhaust manifold and the like. Refers to the part.

  The “first catalyst” provided in such a main exhaust passage is a concept that includes means for purifying exhaust gas, and as long as such a concept is secured, it is a filter that provides the same effect as the catalyst. It may be anything. Such a filter mainly adsorbs and desorbs HC among components to be removed such as HC (hydrocarbon), CO (carbon monoxide) and NOx (nitrogen oxide) contained in exhaust gas. It may be a zeolite or a similar crystalline inorganic porous material. Further, it may be a three-way catalyst capable of purifying all of these components to be removed, or may be a NOx occlusion reduction catalyst that stores and reduces NOx among these components to be removed.

The main exhaust passage portion serving as the bypass flow path on the upstream side of the first catalyst is bypassed by the bypass flow path under a predetermined condition. The form of this bypass flow path is not limited as long as it is a flow path that can bypass the bypass flow path and return the exhaust gas to the main exhaust path again. For example, it may be a cylindrical channel (for example, an outer cylinder) that covers the outside of the bypass channel. In this case, the bypassed flow path may be a cylindrical flow path (for example, an inner cylinder) formed inside the cylindrical bypass flow path.

  The “upstream side” in the present invention is a concept including a direction and a position defined as a side approaching the engine part of the internal combustion engine. That is, it refers to the source side of the exhaust gas when the exhaust gas is flowing normally. More specifically, for example, in each of the main exhaust passage and the bypass passage, it indicates a position in the direction of the cylinder (cylinder) of the internal combustion engine.

  A second catalyst is provided in the bypass channel. The “second catalyst” provided in the bypass channel is a concept that includes means for purifying the exhaust gas, like the first catalyst, and may take various aspects as described above. Further, the combination of the first catalyst and the second catalyst may be freely determined according to the purification function required for the exhaust gas purification system. For example, an exhaust gas purification system in which the first catalyst is a three-way catalyst (underfloor catalyst) installed under the floor of a vehicle and the second catalyst is an HC adsorbent that adsorbs HC in the exhaust gas may be configured. Good.

Discharge path of the exhaust gas by selectively closable switching means to be bypass passage, between the discharge path that does not include a discharge path including the bypass passage, a and the bypass passage comprises a bypass passage Can be switched selectively. The switching means according to the present invention may be any means as long as such switching is possible, but preferably the bypassed flow path is shielded or opened according to the open / closed state. It takes the form of possible valves. In this case, for example, the open / close valve is installed so that the exhaust gas flows into the bypass channel when the valve is open, and the exhaust gas flows into the bypass channel when the valve is closed. Such an on-off valve may be linked to a diaphragm that opens and closes according to the negative pressure of the internal combustion engine in accordance with opening and closing of an electromagnetic valve such as a VSV (Vacuum Switching Valve) and a link mechanism such as a rod. Good. In addition, regardless of the negative pressure, the link mechanism may be operated by electrically driving an actuator or the like.

  How to switch the switching means is variously determined according to the type of catalyst (that is, the first and second catalysts) provided in the exhaust gas purification system, the required purification performance, or the driving situation of the vehicle. For example, when the first catalyst is an underfloor catalyst and the second catalyst is an HC adsorbent, the underfloor catalyst does not reach the activation temperature when the internal combustion engine is cold, such as when the vehicle is started. The switching means may switch the flow path so that the exhaust gas is purified by the HC adsorbent during the period. Note that the switching unit may be controlled higher by some control device (controller). In this case, such a control device may be an electronic control unit such as an ECU (Electronic Controlling Unit) that controls the operation of the internal combustion engine.

  According to the failure diagnosis apparatus of the present invention, during the operation, the first temperature detection means is a section (in the main exhaust flow path that is downstream from the start point of the bypass flow path and upstream of the first catalyst) ( Hereinafter, the temperature of the “normal flow path” is detected as appropriate, and the temperature of the bypass flow path is detected by the second temperature detection means.

  The “downstream side” in the present invention is a concept including a direction and a position defined as a side away from the engine part of the internal combustion engine. That is, it is a concept opposite to the upstream side.

  Here, the “first temperature detecting means” and the “second temperature detecting means” according to the present invention are not limited in any way as long as the temperatures of the normal flow path and the bypass flow path can be detected. Note that “detecting temperature” is not necessarily limited to detecting the temperature itself, and has a corresponding relationship with a temperature change, and a physical quantity that can indirectly specify the temperature based on the corresponding relationship. This is a concept that includes detecting. For example, when the temperature detection means is made of a material such as a thermistor that changes its electrical resistance in response to a temperature change, a voltage that changes in accordance with the temperature change may be output as a detection value. The “normal channel temperature” means that the temperature of any part on the normal channel may be used. For example, it may be the temperature of a part on the bypassed flow path, or may be a part close to the first catalyst. Further, “the temperature of the bypass channel” means that the temperature of any part of the bypass channel may be used.

  Here, in particular, whether or not the switching means is operating normally, that is, whether or not the flow of exhaust gas is normal, is important from the viewpoint of reducing vehicle emissions. It must be detectable in the actual use state of the vehicle. In other words, in the exhaust gas purification system, it is necessary that the switching means has an OBD (On Board Diagnosis).

  Ideally, the temperature of the bypass channel and the bypass channel that is not selected by the switching means does not change, but actually, the driving pattern of the vehicle varies and is not necessarily selected. The temperature of the flow path does not always change. In addition, when the bypassed flow path and the bypass flow path are structurally close to each other, they are selected transiently as the temperature of the selected flow path rises regardless of the driving pattern of the vehicle. In many cases, the temperature of the flow path that has not been increased also increases. Therefore, if it is attempted to diagnose the failure of the switching means only by the temperature of the unselected flow path, the occurrence of misdiagnosis cannot be avoided.

  Therefore, the failure diagnosis apparatus according to the present invention solves the problem by including a diagnosis unit that diagnoses the failure of the switching unit based on the temperature of the normal flow path and the temperature of the bypass flow path.

  The temperature of the flow path selected by the switching means rises as hot exhaust gas passes. On the other hand, the temperature range of the unselected channel tends to be relatively low with respect to the temperature of the selected channel. Here, when the flow path is switched (control is performed to switch), the temperature of each of the normal flow path and the bypass flow path changes when the switching means is operating normally. The mode of change is lowered for the selected flow path and increased for the newly selected flow path. This tendency is particularly remarkable when the internal combustion engine is started (when cold). On the other hand, when the switching means is not operating normally, the temperature magnitude relationship in each of the normal flow path and the bypass flow path behaves differently from the normal time.

  The failure of the switching means is diagnosed based on the temperature of the bypass flow path and the temperature of the normal flow path, and at this time, one of the temperatures fluctuates for some reason not caused by the failure of the switching means. However, the relative relationship with the other temperature is not greatly affected. Furthermore, as described above, both temperatures change in different directions (lowering with respect to rising) according to the operation of the switching means, so that such a relative relationship is more likely to appear more clearly and a misdiagnosis occurs. The possibility of doing is significantly reduced. That is, it is possible to diagnose the failure of the switching means with high accuracy.

  Since the normal flow path is a section downstream of the start point of the bypass flow path and upstream of the first catalyst, conceptually, between the bypass flow path and the bypass flow path and the first catalyst. Including a flow path. Accordingly, the temperature of the normal flow path may be the temperature of the bypassed flow path or the temperature of the exhaust gas immediately before flowing into the first catalyst. In any case, if the switching means selects the bypass flow path, the temperature of the bypass flow path rises first, and if the bypass flow path is selected, the temperature of the normal flow path Because it rises first, there is no problem.

  In the present invention, “diagnosis” means that the degree of failure is specified in multiple stages according to a predetermined standard or some algorithm in addition to binary detection of the presence or absence of a failure of the switching means. It is a concept that includes.

  The timing at which the diagnosis means performs the diagnosis is preferably when the internal combustion engine is cold, but may be a period in which the internal combustion engine is in a transient operating condition (sufficiently warmed). At this time, an index or standard for diagnosing a failure may be given in advance based on the relative relationship between the temperature of the bypass flow path and the temperature of the normal flow path, and the diagnosis is performed according to some algorithm each time. May be. The failure diagnosis may be performed based on the temperature of the normal flow path and the temperature of the bypass flow path at a certain time (timing), or based on a profile of these temperature changes acquired over a certain period. It may be done.

  Note that “diagnosis based on the temperature of the normal flow path and bypass flow path” means that diagnosis is performed based on the value of some diagnostic index that can be derived from the value of both, such as the difference between them or the ratio of both. It is a concept that includes things. At this time, the criterion based on the diagnostic index may be given in advance experimentally, empirically, or by simulation.

In one aspect of the failure diagnosis apparatus for an exhaust gas purification system according to the present invention, the bypass flow path is formed in a cylindrical shape that covers the bypass flow path , and regardless of the state of the switching means on the downstream side. the communication with the bypass passage, if the discharge path of the exhaust gas is switched to the discharge path including the object to be bypass passage by the switching means, wherein the exhaust gas passing through the object to be bypass channel one The part is formed so as to return from the downstream side to the upstream side of the bypass flow path, and the second temperature detecting means is installed on the upstream side of the second catalyst.

  In this case, the exhaust gas purification system adopts a configuration in which the bypass passage is covered with the bypass passage. At this time, the exhaust gas purification system is configured such that a part of the exhaust gas that has passed through the inner cylinder (inner cylinder, i.e., bypassed flow path) flows from the downstream side of the outer cylinder (outer cylinder, i.e., bypass flow path). It is configured to flow in and to reversely flow in the bypass channel toward the upstream side. Since the exhaust gas flows in the main exhaust passage, the exhaust gas that flows backward eventually returns to the bypass passage again through the start point of the bypass passage on the upstream side of the second catalyst. Such a reflux phenomenon is caused by the cross-sectional area ratio between the bypassed flow path and the bypass flow path, or the flow path in the vicinity of the merging position on the downstream side of the bypassed flow path and the bypass flow path (that is, the end point of the bypass flow path). This is a phenomenon caused by the pressure difference between the bypassed flow path and the bypass flow path, which is caused by the shape (curvature) of the gas. At this time, the bypass channel may be formed in advance in a structure in which such a reflux phenomenon is likely to occur based on experiments, experience, or simulation.

  According to this aspect, the second temperature detection means is installed on the upstream side of the second catalyst. This installation position is a position where the exhaust gas that recirculates (reverses) reaches after being further cooled by the second catalyst, and when the bypass passage is selected by the switching means, the exhaust gas is cooled by the second catalyst. Therefore, the temperature difference between the temperature of the normal flow path and the temperature of the bypass flow path tends to appear clearly. The temperature difference clearly appears at least when the bypassed flow path is selected. Therefore, the failure of the switching means can be diagnosed with higher accuracy.

In this aspect, the exhaust gas purification system may further include a heat insulating layer formed between the bypass passage and the bypassed passage .

  In this case, since the exhaust gas purification system includes a heat insulating layer formed between the bypassed flow path and the bypass flow path, heat exchange between the bypassed flow path and the bypass flow path is suppressed, and the normal flow A temperature difference between the temperature of the passage and the temperature of the bypass passage clearly appears. Therefore, the failure of the switching valve can be diagnosed with high accuracy.

In order to solve the above-described problem, another failure diagnosis apparatus for an exhaust gas purification system according to the present invention is provided in a main exhaust flow path of an internal combustion engine, and includes a first catalyst for purifying exhaust gas, and the first catalyst. A bypass passage that bypasses a bypass passage that is a part of the main exhaust passage on the upstream side that is defined as a side approaching the engine portion of the internal combustion engine, and the exhaust gas that is provided in the bypass passage. a second catalyst for purifying the by selectively closing the bypass flow path, a discharge path of the exhaust gas, and the object to be bypass comprises the bypass flow passage and the discharge path including the object to be bypass channel the switching in a plurality of exhaust gas purification system, provided in an exhaust gas purification system wherein each of the plurality of selective respectively and a switching means for switching the between the discharge path that does not include the channel A failure diagnosis apparatus for an exhaust gas purification system for diagnosing a failure of stages, said in one of the plurality of exhaust gas purification system, the starting point of the main exhaust passage in (i) the object to be bypass flow path, said (Ii) a first temperature detection means that is installed in a section that is defined as a side away from the engine portion of the internal combustion engine and that is on the upstream side of the first catalyst, and that detects the temperature of the section; A second temperature detection means for detecting the temperature of the bypass flow path in each of the plurality of exhaust gas purification systems, and the relative temperature between the temperature of the section and the temperature of the bypass flow path in each of the sections; And diagnosing means for diagnosing a failure of the switching means in each of the plurality of exhaust gas purification systems based on the relationship.

  For example, when the internal combustion engine is a V-type engine with cylinders arranged in a V-type, an exhaust purification system may be assigned to each bank. In the case of an in-line engine, a plurality of exhaust purification systems may be used. That is, a plurality of exhaust gas purification systems described above may be installed in a vehicle or the like.

  According to another failure diagnosis apparatus for an exhaust gas purification system according to the present invention, the second temperature detection means is provided in each exhaust gas purification system, while the first temperature detection means is provided in one exhaust gas purification system. Shared among multiple exhaust gas purification systems. Therefore, the number of temperature detecting means is reduced and it is economical.

  The temperature of the normal flow path detected by the first temperature detection means is used as the reference temperature. That is, an exhaust gas purification system having temperature detection means in both the normal flow path and the bypass flow path is used as a reference system. In the reference system, the failure of the switching means is diagnosed as already described.

  On the other hand, in an exhaust gas purification system that is not a reference system (that is, does not include the first temperature detection means), the temperature detection value of each flow path in the reference system or a diagnosis result based thereon is used as a reference. Thus, failure diagnosis can be performed. For example, the exhaust gas from the internal combustion engine is treated in the same manner, so that it is unlikely that each of the plurality of exhaust gas purification systems behaves completely differently, and a failure occurs in the switching means in one exhaust gas purification system. If so, the temperature of the bypass flow path in the system deviates from the behavior in other exhaust gas purification systems. A failure can be diagnosed from the degree of deviation from the reference. The diagnostic criteria at this time may be determined in advance experimentally, empirically, or based on simulations.

In order to solve the above-described problems, an exhaust gas purification system with a failure diagnosis function according to the present invention is an exhaust gas purification system for purifying exhaust gas in an internal combustion engine, and is provided in a main exhaust flow path of the internal combustion engine. And bypassing the bypassed flow path that is a part of the main exhaust flow path on the upstream side of the first catalyst that is defined as the side of the first catalyst that approaches the engine portion of the internal combustion engine. A bypass flow path, a second catalyst provided in the bypass flow path for purifying the exhaust gas, a discharge path for the exhaust gas, a discharge path including the bypassed flow path, and the bypass flow path; and switching means for selectively switching between the discharge path that does not include the bypass flow path, in the main exhaust passage (i) of the starting point of the object to be Paibasu passage, far from the engine unit of the internal combustion engine (Ii) a first temperature detection means for detecting the temperature of the first catalyst, and a second temperature sensor for detecting the temperature of the first catalyst; A second temperature detecting means for detecting the temperature of the bypass flow path; and a diagnostic means for diagnosing a failure of the switching means based on a relative relationship between the temperature of the section and the temperature of the bypass flow path. It is characterized by.

  The exhaust gas purification system with a failure diagnosis function according to the present invention has a failure diagnosis function equivalent to the above-described failure diagnosis device of the exhaust gas purification system according to the present invention, so that the failure of the switching means is diagnosed with high accuracy. It is possible.

In one aspect of the exhaust gas purification system with a failure diagnosis function according to the present invention, the bypass flow path is formed in a cylindrical shape covering the bypassed flow path , and regardless of the state of the switching means on the downstream side. the communication with the bypass passage, if the discharge path of the exhaust gas is switched to the discharge path including the object to be bypass passage by the switching means, wherein the exhaust gas passing through the object to be bypass channel one The part is formed so as to return from the downstream side to the upstream side of the bypass flow path, and the second temperature detecting means is installed on the upstream side of the second catalyst.

  According to this aspect, since it has a failure diagnosis function equivalent to the above-described failure diagnosis device for the exhaust gas purification system according to the present invention, it is possible to diagnose the failure of the switching means with high accuracy.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

<Embodiment>
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
<Configuration of Embodiment>
First, the configuration of the engine system according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a half sectional system configuration diagram of the engine system 10.

  In FIG. 1, the engine system 10 includes an ECU 100, an engine 200, and a catalyst device 300.

  The ECU 100 is an electronic control unit that includes a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown) and can control the operation of the engine 200. The ECU 100 is configured to be able to execute a failure diagnosis process, which will be described later, by executing a program stored in the ROM, and the “exhaust gas purification with a failure diagnosis function” according to the present invention together with the catalyst device 300. It is configured to function as an example of a “system”. Further, it is configured to function as an example of an “exhaust gas purification system failure diagnosis device” together with a part of the catalyst device 300.

  The engine 200 can cause the air-fuel mixture to explode in the cylinder 201 by the spark plug 202, and can convert the reciprocating motion of the piston 203 generated according to the explosive force into the rotational motion of the crankshaft 205 via the connection rod 204. It is an example of the internal combustion engine which concerns on this invention comprised. Below, the principal part structure of the engine 200 is demonstrated.

  When the fuel is burned in the cylinder 201, the air sucked from the outside passes through the intake pipe 206 and is mixed with the fuel injected from the injector 207 to become the above-mentioned air-fuel mixture. The injector 207 is supplied with fuel (gasoline) from a fuel tank (not shown), and the injector 207 is configured to be able to inject the supplied fuel into the intake pipe 206 in accordance with the control of the ECU 100. Yes.

  The communication state between the inside of the cylinder 201 and the intake pipe 206 is controlled by opening and closing the intake valve 208. The air-fuel mixture burned in the cylinder 201 becomes exhaust gas, passes through the exhaust valve 209 that opens and closes in conjunction with opening and closing of the intake valve 208, and is exhausted through the exhaust pipe 210.

  A cleaner 211 is disposed on the intake pipe 206 to purify air sucked from the outside. An air flow meter 212 is disposed on the cylinder side of the cleaner 211. The air flow meter 212 has a form called a hot wire type, and is configured to be able to directly measure the mass flow rate of the inhaled air. The intake pipe 206 is further provided with an intake air temperature sensor 213 for detecting the temperature of the intake air.

  A throttle valve 214 that adjusts the amount of intake air into the cylinder 201 is disposed on the cylinder side of the air flow meter 212 in the intake pipe 206. The throttle valve 214 is provided with a throttle valve motor 217 and a throttle position sensor 215. On the other hand, the depression amount of the accelerator pedal 223 is input to the ECU 100 via the accelerator position sensor 216, and a signal indicating the throttle valve opening corresponding to the output of the accelerator position sensor 216 is output from the ECU 100 to the throttle valve motor 217. The intake air volume is controlled.

  A crank position sensor 218 that detects the rotational position of the crankshaft 205 is provided in the vicinity of the crankshaft 205. The crank position sensor 218 is a sensor configured to be able to detect the position of the crankshaft 205, and the control unit 100 determines the position of the piston 203 and the rotational speed of the engine 200 based on the output signal of the crank position sensor 218. Etc. are configured to be able to obtain. The position of the piston 203 is used for controlling the ignition timing in the spark plug 202 described above. The ignition timing in the spark plug 202 is, for example, retarded or advanced with respect to a preset basic value associated with the position of the piston 203.

  Further, a knock sensor 219 capable of measuring the knock strength of the engine 200 is disposed in the cylinder block that accommodates the cylinder 201, and the cooling water of the engine 200 is placed in the water jacket in the cylinder block. A water temperature sensor 220 for detecting the temperature is provided.

  A three-way catalyst 222 is installed in the exhaust pipe 210. The three-way catalyst 222 is a catalyst capable of purifying CO (carbon monoxide), HC (hydrocarbon), and NOx (nitrogen oxide) discharged from the engine 200, respectively. An air-fuel ratio sensor 221 is disposed upstream of the three-way catalyst 222 in the exhaust pipe 210. The air-fuel ratio sensor 221 is configured to be able to detect the air-fuel ratio of the engine 200 from the exhaust gas discharged from the exhaust pipe 210.

  The catalyst device 300 is a catalyst device installed downstream of the three-way catalyst 222 in the exhaust pipe 210, and functions as an example of the “exhaust gas purification system with a failure diagnosis function” according to the present invention together with the ECU 100. It is configured to be possible. The catalyst device 300 and the ECU 100 are electrically connected via a control bus line.

  Next, a detailed configuration of the catalyst device 300 will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view of the catalyst device 300. In the figure, the same reference numerals are assigned to the same portions as those in FIG. 1, and the description thereof is omitted.

  In FIG. 2, the catalyst device 300 includes an underfloor catalyst 310, a bypass flow path 320, an HC adsorbent 330, a switching control valve 340, a first temperature sensor 350, a second temperature sensor 360, and a heat insulating layer 370.

  The underfloor catalyst 310 is a three-way catalyst installed under the floor of the vehicle, and purifies exhaust gas that passes through the preceding three-way catalyst 222 (not shown in FIG. 2) and flows in the direction A in the drawing. It is an example of a “first catalyst”.

  The bypass channel 320 is an example of a “bypass channel” according to the present invention, and is an example of a part of the exhaust pipe 210 (that is, “a part of the main exhaust channel (bypassed channel)” according to the present invention. ) To guide the exhaust gas to the underfloor catalyst 310.

  The HC adsorbent 330 is a filter formed of zeolite, and is an example of the “second catalyst” according to the present invention. The HC adsorbent 330 is a mesh filter that adsorbs (or traps) HC molecules at a low temperature (approximately less than 100 ° C.). The trapped HC molecules have a kinetic energy due to heat at a high temperature (approximately 100 ° C. or more). Desorption begins spontaneously with increasing numbers.

  The switching control valve 340 is configured to selectively switch an exhaust gas passage that has passed through the three-way catalyst 222 between the bypass passage 210a and the bypass passage 320 according to the present invention. It is an example of “switching means”. The switching control valve 340 can switch the flow path of the exhaust gas by rotating the shaft portion supported rotatably so as to rotate in the B direction in the drawing along with the linear motion of the rod 342 in the horizontal direction of the paper surface. It is configured. The operation of the rod 342 is controlled by an actuator 341, and the actuator 341 is electrically connected to the ECU 100 via the control bus line described above. That is, the catalyst device 300 is configured so that the open / close state of the switching control valve 340 changes in accordance with a control signal from the ECU 100.

  The first temperature sensor 350 is formed of a thermistor element, and is located upstream of the underfloor catalyst 310 in the exhaust pipe 210 (that is, downstream of a part of the starting point of the bypass and the first catalyst). It is an example of the “first temperature detecting means” according to the present invention configured to be able to detect a temperature T1 of an example of “upstream section (normal flow path)”. The first temperature sensor 350 detects the temperature T1 as a voltage value corresponding to the temperature and outputs it to the ECU 100, and the temperature T1 is specified by the ECU 100.

  The second temperature sensor 360 is composed of a thermistor element, and is configured to be able to detect the temperature T2 upstream of the HC adsorbent 330 in the bypass flow path 320. Is an example. The second temperature sensor 360 detects the temperature as a voltage value corresponding to the temperature and outputs it to the ECU 100, and the temperature T2 is specified by the ECU 100.

  The heat insulating layer 370 is a heat insulating body formed between the bypass flow path 320 and the bypass flow path 210a, and is an example of the “heat insulating layer” according to the present invention. The heat insulation layer 370 suppresses heat exchange between the bypass flow path 320 and the bypass flow path 210a.

<Operation of Embodiment>
<Details of exhaust gas flow path>
Next, an exhaust gas flow path associated with the operation of the switching control valve 340 will be described with reference to FIGS. 3 is a schematic diagram of the exhaust gas flow when the switching control valve 340 is closed in the catalyst device 300, and FIG. 4 is an exhaust gas when the switching control valve 340 is opened in the catalyst device 300. It is a schematic diagram of a flow. In these drawings, the same parts as those in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 3, the exhaust gas flowing in from the direction of the arrow A does not flow to the bypass flow path 210 a because the switching control valve 340 is closed, but is guided to the bypass flow path 320, and the HC adsorbent 330 absorbs HC. After the adsorption, the gas flows out from the vent formed on the downstream side of the HC adsorbent 330 in the direction of arrow C and flows into the underfloor catalyst 310.

  In FIG. 4, the exhaust gas flowing in from the direction of arrow A is guided to the bypassed flow path 210a from the difference in exhaust resistance because the switching control valve 340 is open. On the other hand, a part of the exhaust gas passing through the bypassed flow path 210a changes its direction in the direction indicated by the arrow D in the vicinity of the terminal end of the bypassed flow path 210a, and the vent hole formed in the bypass flow path 320 And flows into the bypass flow path 320 from the downstream side. Then, the direction of the exhaust gas is changed again in the flow direction of the exhaust gas (in the direction of arrow A) at the upstream end of the bypass flow channel 320 and is guided to the bypass flow channel 210a. That is, part of the exhaust gas recirculates inside the catalyst device 300. In the catalyst device 300, the cross-sectional area ratio between the bypass flow path 210a and the bypass flow path 320, the curvature of the wall surface defining the end portion of the bypass flow path 320, the shape and size of the vent holes, and the like are set in advance. It has been determined to cause a reflux phenomenon.

  Next, with reference to FIG. 5, the behavior of each temperature associated with the operation of the switching control valve 340 will be described. FIG. 5 is a schematic diagram of each temperature according to the opening / closing pattern of the switching control valve 340.

  In FIG. 5, the vertical axis and the horizontal axis represent temperature and time, respectively, FIG. 5A shows the behavior of the temperature T2, and FIG. 5B shows the behavior of the temperature T1.

  In FIG. 5A, three profiles (characteristic lines) Pr1 (solid line), Pr2 (dotted line), and Pr3 (dashed line) are drawn. Profile Pr1 represents characteristics when the switching control valve 340 is closed, profile Pr2 represents characteristics when the switching control valve 340 is open, and profile Pr3 is obtained from a state where the switching control valve 340 is closed. It represents the characteristics when opened at time T.

  As shown in the figure, when the switching control valve 340 is closed, the exhaust gas flows into the bypass flow path 320, so that the profile Pr1 changes at a relatively higher temperature than the profile Pr2. Further, when the switching control valve 340 is switched from the closed state to the open state, the profile Pr3 exhibits the same behavior as the initial profile Pr1, and gradually approaches the profile Pr2 after time T.

  Also in FIG. 5B, three profiles Pr4 (solid line), Pr5 (dotted line), and Pr6 (dashed line) are drawn. Profile Pr4 represents the characteristics when the switching control valve 340 is closed, profile Pr5 represents the characteristics when the switching control valve 340 is open, and profile Pr6 is from the state where the switching control valve 340 is closed. It represents the characteristics when opened at time T.

  As shown in the drawing, when the switching control valve 340 is closed, the exhaust gas flows into the bypass flow path 320, so that the profile Pr5 changes at a relatively higher temperature than the profile Pr4. When the switching control valve 340 is switched from the closed state to the open state, the profile Pr6 shows the same behavior as the initial profile Pr4 and gradually approaches the profile Pr5 after time T.

  Here, obviously, the relative relationship between the temperature T1 and the temperature T2 is reversed according to the open / close state of the switching control valve 340. Such a reversal of temperature occurs remarkably when the engine 200 is started (when cold).

<Details of failure diagnosis processing>
The ECU 100 is configured to be able to diagnose a failure of the switching control valve 340 by executing a failure diagnosis process according to a program stored in the ROM during the operation of the engine system 10.

  Here, the details of the failure diagnosis processing will be described with reference to FIG. FIG. 6 is a flowchart of the failure diagnosis process. 6 is a process performed when the engine 200 is started.

  In FIG. 6, ECU 100 determines whether engine 200 has started (step A10). When the engine 200 has not started (step A10: NO), the ECU 100 repeats step A10 until the engine 200 starts, and when the engine 200 starts to start (step A10: YES), the first The temperatures T1 and T2 are acquired from the output voltages of the temperature sensor 350 and the second temperature sensor 360 (step A11).

  At the time of start-up, since the engine 200 is not warmed as a whole, the three-way catalyst 222 and the underfloor catalyst 310 have not reached the catalyst activation temperature. For this reason, it is difficult to purify the HC contained in the exhaust gas, and the ECU 100 controls the switching control valve 340 to be closed when the engine 200 is started, and guides the exhaust gas to the bypass flow path 320, thereby causing the ECU 100 HC is adsorbed on the HC adsorbent 330. Then, after a predetermined warm-up period that can be considered that the three-way catalyst 222 and the underfloor catalyst 310 have reached the catalyst activation temperature, the switching control valve 340 is opened, and the exhaust gas is led to the bypass flow path 210a to While preventing a decrease in capacity, the HC trapped in the HC adsorbent 330 is purified.

  When the temperature T1 and the temperature T2 are acquired, the ECU 100 calculates a value of a diagnostic index (hereinafter referred to as “diagnostic index value” as appropriate) (step A12). Here, the diagnostic index according to the present embodiment will be described with reference to FIG. FIG. 7 is a schematic diagram of a diagnostic index. In this figure, as in FIG. 5, the horizontal axis represents time, and the time elapsed of the diagnostic index value is represented. The same reference numerals are given to the portions overlapping with FIG. Will be omitted.

  7A shows a temperature difference which is an example of a diagnostic index, and FIG. 7B shows a temperature area ratio which is another example of the diagnostic index.

  The temperature difference represented by FIG. 7A is a difference between the temperature T2 of the bypass flow path 320 and the temperature T1 upstream of the underfloor catalyst 310. In FIG. 7 (a), profiles Pr7 (solid line), Pr8 (dotted line), and Pr9 (dashed line) correspond to the switching control valve 340 in the closed state, open state, and switching from the closed state to the open state, respectively. Is represented.

  The temperature T2 is higher in the valve closed state (the state where the bypass flow path 320 is selected) than in the open state (the state where the bypass flow path 210a is selected), and the temperature T1 is the opposite. Therefore, the value of the diagnostic index becomes relatively larger when the bypass flow path 320 is selected. Furthermore, when the exhaust gas flow path is switched at time T, the value of the diagnostic index gradually decreases, and a gradual switching characteristic is realized.

  The temperature area ratio represented by FIG. 7 (b) means that in the graph shown in FIG. 5, at least a part of the profile, a perpendicular line extending from the start point and end point of the part toward the horizontal axis (time axis), The ratio of the area of the portion surrounded by the shaft is obtained by dividing the temperature area (corresponding to temperature T1) on the upstream side of the underfloor catalyst 310 by the temperature area (corresponding to temperature T2) for the bypass flow path 320. . In FIG. 7 (b), Pr10 (solid line), Pr11 (dotted line), and Pr12 (dashed line) correspond to the closed state, open state, and switching from the closed state to the open state of the switching control valve 340, respectively. expressed.

  The temperature T2 is higher in the valve closed state (the state where the bypass flow path 320 is selected) than in the open state (the state where the bypass flow path 210a is selected), and the temperature T1 is the opposite. Therefore, the value of the diagnostic index becomes relatively smaller when the bypass flow path 320 is selected. Further, when the exhaust gas flow path is switched at time T, the value of the diagnostic index gradually increases, and a gradual switching characteristic is realized.

  When the temperature area ratio is used as a diagnostic index, a minute change amount corresponding to noise or error as shown in FIG. 5 or FIG. This is based only on the relative relationship between the temperature 320 and the temperature upstream of the underfloor catalyst 310. Therefore, the accuracy of diagnosis is easily ensured, and in this embodiment, the temperature area ratio is used as a diagnostic index as shown in FIG. 7B.

  Returning to FIG. 6, when the diagnostic index value is calculated, the ECU 100 compares the threshold value of the diagnostic index value stored in advance in the ROM with the calculated diagnostic index value, and determines whether or not the switching control valve 340 has failed. It discriminate | determines (step A13).

  Here, the presence or absence of a failure of the switching control valve 340 is determined based on the temperature T1 and the temperature T2 at a predetermined timing (time), but the detection of each temperature may be executed over a certain period. At this time, the temperature detection result may be buffered in a predetermined storage unit provided in the ECU 100. For determination in step A13, a profile having a length corresponding to the period may be used. For example, in FIG. 7B, when the profile tends to increase immediately after the engine is started (that is, tends to approach the profile Pr11), it is estimated that the exhaust gas does not flow into the bypass flow path 320. It may be determined that the control valve 340 has failed.

  When it is determined that the switching control valve 340 is broken (step A13: YES), the ECU 100 notifies the vehicle driver or the like of the failure through a predetermined indicator or the like as a result of diagnosis (step A19). Then, the failure diagnosis process is terminated.

  On the other hand, when it is determined that the switching control valve 340 is operating normally (step A13: NO), the ECU 100 determines whether it is time to switch the exhaust gas flow path (step A14). As already described, the ECU 100 switches the flow path at a timing at which the underfloor catalyst 310 can be regarded as being sufficiently warm. This switching timing may be a fixed value stored in advance in a ROM or the like, or may be a variable value determined each time.

  If it is not the switching timing of the switching control valve 340 (step A14: NO), the ECU 100 repeats step A14 until the switching timing comes, and closes the switching control valve 340 when the switching timing comes (step A14: YES). Then, the flow path of the exhaust gas is switched from the bypass flow path 320 to the bypass flow path 210a (step A15).

  When the flow path is switched, the ECU 100 detects the temperature T1 and the temperature T2 again at a predetermined timing (step A16). As described above, the temperature detection may be continued for a predetermined period after the flow path switching is executed.

  When the temperature detection is completed, the ECU 100 calculates the diagnostic index value again (step A17), and compares the calculated diagnostic index value with a preset threshold value to determine whether or not the switching control valve 340 has failed. It discriminate | determines (step A18). Note that the ECU 100 holds a plurality of threshold values of diagnostic index values corresponding to the elapsed time from the start time in a predetermined storage unit, appropriately reads out the one corresponding to the time at which Step A16 is performed, and performs the determination related to Step A18. You may do it. In addition, when the diagnostic index value over a certain period is calculated (that is, when the profile is calculated), the switching control valve 340 fails due to the transition of the diagnostic index value (profile shape) or the like. It may be determined whether or not.

  When it is determined that the switching control valve 340 is malfunctioning (step A18: YES), the ECU 100 notifies the malfunction as already described (step A19), and ends the malfunction diagnosis processing and also the switching control valve. If it is determined that 340 is operating normally (step A18: NO), the failure diagnosis process is terminated.

  As described above, in the engine system 10 according to the present embodiment, the ECU 100 detects the relative relationship between the two points (the bypass flow path and the underfloor catalyst upstream side) where the magnitude relationship of the temperatures is reversed according to the open / close state of the switching control valve 340. Since the failure is diagnosed based on the relationship, it is possible to diagnose the failure of the switching control valve 340 with high accuracy. Further, the heat insulating layer 370 suppresses heat exchange between the bypass flow path 320 and the bypass flow path 210a, and the bypass flow path 320 has a reflux structure, so that the relative relationship between the temperature T1 and the temperature T2 is increased. Since it is clearly defined, a failure of the switching control valve 340 can be diagnosed with higher accuracy.

<Second Embodiment>
A plurality of catalyst devices 300 according to the first embodiment may be provided depending on the configuration of the engine. Here, an engine system according to the second embodiment of the present invention will be described with reference to FIG. FIG. 8 is a schematic diagram of the engine system 11. In the figure, the same reference numerals are assigned to the same parts as those in FIG. 1, and the description thereof is omitted.

  In FIG. 8, the engine system 11 includes an engine 400. The engine 400 is a V-type 8-cylinder engine in which four cylinders 201 are arranged in each bank. From each bank, the exhaust pipe 210 is connected to the three-way catalyst 222 so as to gather from each cylinder 201. The catalyst device 300 described above is connected to the downstream side of one of the three-way catalysts 222, and the catalyst device 500 according to the second embodiment of the present invention is arranged on the downstream side of the other three-way catalyst 222. ing. The operations of the catalyst devices 300 and 500 and the engine 400 are controlled by an ECU 100 (not shown).

  The catalyst device 500 is different from the catalyst device 300 in that the first temperature sensor 350 is not provided. The failure diagnosis of the switching control valve 340 in the catalyst devices 300 and 500 is executed for each catalyst device by the above-described failure diagnosis process executed by the ECU 100. At this time, the temperature upstream of the underfloor catalyst 310 in the catalyst device 500 is replaced by the temperature in the catalyst device 300.

  The temperature on the upstream side of the underfloor catalyst 310 in the catalyst device 300 does not represent the temperature on the upstream side of the underfloor catalyst 310 in the catalyst device 500. However, in the catalyst device 300, if the switching valve 340 is not broken as a result of the failure diagnosis based on the diagnosis index value as described above, if the switching control valve 340 of the catalyst device 500 is in a normal state, The diagnostic index value calculated based on the temperature of the bypass flow path 320 in the catalyst device 500 and the temperature on the upstream side of the underfloor catalyst 310 of the catalyst device 300 should also show a similar value. Therefore, by using the diagnosis result in the catalyst device 300 as a reference value, the sensor corresponding to the first temperature sensor in the catalyst device 500 can be omitted.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification, and an exhaust gas purification system with such changes The failure diagnosis apparatus and the exhaust gas purification system with a failure diagnosis function are also included in the technical scope of the present invention.

It is a half section system configuration figure of the engine system concerning a 1st embodiment of the present invention. It is a schematic cross section of the catalyst device in the engine system of FIG. FIG. 3 is a schematic diagram of an exhaust gas flow when a switching control valve is closed in the catalyst device of FIG. 2. FIG. 3 is a schematic diagram of an exhaust gas flow when a switching control valve is open in the catalyst device of FIG. 2. It is a schematic diagram of the temperature of the bypass flow path according to the opening / closing pattern of the switching control valve and the temperature upstream of the underfloor catalyst. It is a flowchart of the failure diagnosis process which ECU performs in the engine system of FIG. FIG. 7 is a schematic diagram of a diagnosis index in the failure diagnosis process of FIG. 6. It is a schematic diagram of the engine system which concerns on 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine system, 11 ... Engine system, 100 ... ECU, 200 ... Engine, 210 ... Exhaust pipe, 210a ... Bypass flow path, 300 ... Catalyst device, 031 ... Underfloor catalyst, 320 ... Bypass flow path, 330 ... HC adsorption Material: 340: switching control valve, 350: first degree sensor, 360: second temperature sensor, 370: heat insulation layer. 400 ... engine, 500 ... catalyst device.

Claims (6)

A first catalyst that is provided in a main exhaust passage of the internal combustion engine and purifies exhaust gas; and an upstream side of the first catalyst that is defined as a side closer to an engine portion of the internal combustion engine; a bypass flow path for bypassing a portion serving the bypass passage, provided in the bypass passage, and a second catalyst for purifying the exhaust gas, by selectively closing the object to be bypass passage, the exhaust the discharge path of the gas, the exhaust gas purification comprising a switching means for selectively switching between the discharge path that does not include and the target bypass flow path comprises a discharge path said bypass flow path including a target bypass channel An exhaust gas purification system failure diagnosis device for diagnosing a failure of the switching means in a system,
In the main exhaust passage, (i) the downstream side of the starting point of the bypassed part is defined as the side away from the engine part of the internal combustion engine, and (ii) the upstream side of the first catalyst. First temperature detecting means installed in the section and detecting the temperature of the section;
A second temperature detecting means installed in the bypass flow path for detecting the temperature of the bypass flow path;
A failure diagnosis device for an exhaust gas purification system, comprising: diagnosis means for diagnosing a failure of the switching means based on a relative relationship between the temperature of the section and the temperature of the bypass flow path. The bypass flow path, the communication with the target bypass passage irrespective of the state of the switching means at said downstream side is formed in a cylindrical shape covering the target bypass flow path, wherein the switching discharge path of the exhaust gas When the exhaust path including the bypass flow path is switched by means, a part of the exhaust gas that has passed through the bypass flow path is recirculated from the downstream side to the upstream side of the bypass flow path. Is formed to
The failure diagnosis apparatus for an exhaust gas purification system according to claim 1, wherein the second temperature detection means is installed on the upstream side of the second catalyst. The failure diagnosis apparatus for an exhaust gas purification system according to claim 2, wherein the exhaust gas purification system further includes a heat insulating layer formed between the bypass flow path and the bypassed flow path . A first catalyst that is provided in a main exhaust passage of the internal combustion engine and purifies exhaust gas; and an upstream side of the first catalyst that is defined as a side closer to an engine portion of the internal combustion engine. a bypass flow path for bypassing a portion serving the bypass passage, provided in the bypass passage, and a second catalyst for purifying the exhaust gas, by selectively closing the object to be bypass passage, the exhaust the discharge path of the gas, said plurality of respectively and a switching means for switching selectively between a discharge path that does not include and the target bypass flow path comprises a discharge path said bypass flow path including a target bypass channel In the exhaust gas purification system, a failure diagnosis device for an exhaust gas purification system for diagnosing a failure of the switching means provided in each of the plurality of exhaust gas purification systems,
In one of the plurality of exhaust gas purification systems, (i) a downstream side of the start point of the bypassed flow path in the main exhaust flow path that is defined as a side away from the engine portion of the internal combustion engine and ( ii) first temperature detection means installed in the upstream section of the first catalyst and detecting the temperature of the section;
A second temperature detection unit that is installed in the bypass passage in each of the plurality of exhaust gas purification systems and detects the temperature of the bypass passage in each of the plurality of exhaust gas purification systems;
Exhaust gas comprising diagnostic means for diagnosing a failure of the switching means in each of the plurality of exhaust gas purification systems based on the relative relationship between the temperature of the section and the temperature of the bypass flow path in each of the sections Failure diagnosis device for purification system. An exhaust gas purification system for purifying exhaust gas in an internal combustion engine,
A first catalyst provided in a main exhaust passage of the internal combustion engine for purifying exhaust gas;
A bypass flow path that bypasses the bypassed flow path that is a part of the main exhaust flow path on the upstream side of the first catalyst that is defined as the side that approaches the engine portion of the internal combustion engine;
A second catalyst provided in the bypass flow path to purify the exhaust gas;
Switching means for selectively switching between a discharge path for said exhaust path of exhaust gas, wherein a discharge path including the bypass flow path includes said bypass passage and said not including the bypass passage,
In the main exhaust flow path, (i) a section that is defined as a downstream side of the starting point of the pipe bus flow path that is defined as a side away from the engine portion of the internal combustion engine, and (ii) a section that is the upstream side of the first catalyst And a first temperature detecting means for detecting the temperature of the section;
A second temperature detecting means installed in the bypass flow path for detecting the temperature of the bypass flow path;
An exhaust gas purification system with a failure diagnosis function, comprising: a diagnosis unit that diagnoses a failure of the switching unit based on a relative relationship between the temperature of the section and the temperature of the bypass passage. The bypass flow path, the communication with the target bypass passage irrespective of the state of the switching means at said downstream side is formed in a cylindrical shape covering the target bypass flow path, wherein the switching discharge path of the exhaust gas When the exhaust path including the bypass flow path is switched by means, a part of the exhaust gas that has passed through the bypass flow path is recirculated from the downstream side to the upstream side of the bypass flow path. is formed so as to,
The exhaust gas purification system with a fault diagnosis function according to claim 5, wherein the second temperature detection means is installed on the upstream side of the second catalyst.

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