JP2011058375A - Method for controlling exhaust emission control device for internal combustion engine, exhaust emission control device for internal combustion engine, and internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling an exhaust emission control device of an internal combustion engine, the exhaust emission control device being capable of generating exhaust gas purifying ability with a catalyst at start and during operation, an exhaust emission control device for an internal combustion engine, and an internal combustion engine. <P>SOLUTION: The exhaust emission control device 7 includes a heat exchanger 14 on the upstream side of a catalyst device 15 having a catalyst for purifying an exhaust gas Ae. The catalyst temperature of the catalyst device 15 is sensed so that in the case the temperature is lower than a temperature enabling purification of the exhaust gas Ae, the exhaust gas Ae on the downstream side of the catalyst device 15 is not fed to the heat exchanger 14. In the case the catalyst temperature is in a temperature range enabling purification of the exhaust gas Ae, the exhaust gas Ae on the downstream side of the catalyst device 15 is fed to the heat exchanger 14 via a bypass pipe 16. Thereby, the exhaust gas purification ability with a catalyst is performed at the start and during operation. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for controlling an exhaust gas purification apparatus for an internal combustion engine, an exhaust gas purification apparatus for an internal combustion engine, and an internal combustion engine, and more specifically, an internal combustion engine capable of generating an exhaust gas purification capability by a catalyst at the time of start and operation. The present invention relates to an exhaust gas purification device control method, an internal combustion engine exhaust gas purification device, and an internal combustion engine.

  Diesel vehicle exhaust gas regulations are becoming stricter, and it is essential to install an aftertreatment device downstream of the turbocharger. In order for the catalyst of the aftertreatment device to purify the exhaust gas, a catalyst temperature higher than a certain level is required. Therefore, the purification of the exhaust gas largely depends on the catalyst temperature.

  On the other hand, development of an exhaust heat recovery device is being promoted for the purpose of effectively using thermal energy obtained from exhaust gas. FIG. 6 shows a configuration of an exhaust purification device (post-processing device) 51 including the exhaust heat recovery device 50. The exhaust heat recovery device 50 shown here is a device that recovers heat by causing convection of the exhaust gas Ae that has passed through the catalyst device 52 of the exhaust purification device 51 at the inlet of the catalyst device 52. When this exhaust heat recovery device 50 is provided, a relatively stable temperature can be maintained in a state where warm-up is performed, and a temperature range showing a high purification rate in the catalyst can be maintained.

  However, at the time of cold start, the apparent heat capacity increases due to the exhaust heat recovery device, so it takes time to raise the temperature of the catalyst of the aftertreatment device, and NOx is consumed more than a normal DeNOx (NOx reduction) catalyst. There is a problem that a lot is discharged.

  In order to solve this problem, a method of heating the catalyst with an electric heater (for example, see Patent Documents 1 and 2) and a method of injecting fuel into the exhaust pipe (for example, see Patent Document 3) have been developed. As a result, the fuel consumption rate increases.

  As a technology for effectively using the exhaust gas of a diesel engine, a exhaust heat boiler is provided in the exhaust path downstream of the engine, and a catalyst device for purifying the exhaust gas is provided between the engine and the exhaust heat boiler. There is a technique for preventing an adverse effect on exhaust heat boiler caused by exhaust gas (see, for example, Patent Document 4).

JP 2006-105073 A JP-A-5-1512 JP 2005-061249 A JP 2004-218454 A

  An object of the present invention is to provide a method for controlling an exhaust gas purification device for an internal combustion engine, an exhaust gas purification device for an internal combustion engine, and an internal combustion engine capable of producing an exhaust gas purification ability by a catalyst at the time of start and operation. .

  In order to achieve the above object, a method for controlling an exhaust gas purification apparatus for an internal combustion engine according to the present invention comprises a catalyst device having a catalyst for purifying exhaust gas in an exhaust path, and heat of exhaust gas downstream of the catalyst device. An exhaust heat recovery device that recovers the thermal energy of the exhaust gas by transmitting the exhaust gas to the exhaust gas upstream of the catalyst device, in an in-line state with the catalyst device in the exhaust path upstream of the catalyst device In a method for controlling an exhaust emission control device of an engine, when the temperature of the catalyst is detected and the temperature is lower than a temperature at which the exhaust gas can be purified, the exhaust gas downstream of the catalyst device is When the exhaust heat recovery device is stopped and the temperature of the catalyst is a temperature at which the exhaust gas can be purified, the exhaust gas on the downstream side of the catalyst device is passed to the exhaust heat recovery device. Control flow It is intended.

  In order to achieve the above object, an exhaust gas purification apparatus for an internal combustion engine according to the present invention includes a catalyst device having a catalyst for purifying exhaust gas in an exhaust path, and heats the exhaust gas downstream of the catalyst device. Exhaust gas of an internal combustion engine provided with an exhaust heat recovery device that recovers thermal energy of the exhaust gas by transmitting to exhaust gas upstream of the device in a state in series with the catalyst device in the exhaust path upstream of the catalyst device In the purification apparatus, a temperature detecting means for detecting the temperature of the catalyst, a sub exhaust path for flowing the exhaust gas downstream of the catalyst apparatus to the exhaust heat recovery apparatus, and an opening / closing means for opening and closing the sub exhaust path When the temperature of the catalyst detected by the temperature detection means is lower than the temperature at which the exhaust gas can be purified, the opening / closing means is closed to close the downstream of the catalyst device. When the gas is stopped from flowing through the auxiliary exhaust path to the exhaust heat recovery device, and the temperature of the catalyst is a temperature capable of purifying the exhaust gas, by opening the opening and closing means, A control unit that controls the exhaust gas that has passed through the catalyst device to flow through the auxiliary exhaust path to the exhaust heat recovery device.

  In order to achieve the above object, an internal combustion engine of the present invention has the exhaust purification device.

  According to the method for controlling an exhaust gas purification apparatus for an internal combustion engine, the exhaust gas purification apparatus for an internal combustion engine, and the internal combustion engine according to the present invention, the exhaust gas is exhausted until the catalyst temperature reaches a temperature at which the exhaust gas can be purified. In this case, the increase in the heat capacity due to the exhaust heat recovery device can be eliminated, so that the catalyst temperature can reach the temperature range showing a high purification rate in a short time. For this reason, the exhaust gas can be purified by the catalyst at an early stage after starting. On the other hand, after the catalyst temperature reaches a temperature that is sufficiently sufficient to purify the exhaust gas, the exhaust gas is allowed to flow through the exhaust heat recovery device, whereby the catalyst temperature can be maintained in a temperature range that exhibits a high purification rate. Therefore, the exhaust gas purification ability by the catalyst can be generated at the time of start-up and operation. In addition, the fuel consumption rate can be reduced by not heating the catalyst by the electric heater or injecting the fuel into the exhaust pipe.

It is a block diagram of the principal part of the internal combustion engine in embodiment of this invention. It is a block diagram of the principal part of the aftertreatment apparatus of the internal combustion engine of FIG. It is a block diagram of the principal part of the aftertreatment apparatus of the internal combustion engine of FIG. It is a block diagram of the principal part of the aftertreatment apparatus of the internal combustion engine of FIG. It is a graph which shows transition of the temperature value of a nitrogen oxide reduction catalyst. It is a block diagram of the principal part of the post-processing apparatus of the conventional internal combustion engine.

  Hereinafter, an internal combustion engine according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a configuration of a main part of the internal combustion engine of the present embodiment. The internal combustion engine of the present embodiment is configured as an in-line four-cylinder common rail type diesel engine 1 mounted on an automobile such as a truck. In addition, this invention is not limited to a diesel engine, It can also apply to a gasoline engine etc.

  This diesel engine (hereinafter simply referred to as engine) 1 includes an engine body (internal combustion engine body) 2, an intake manifold 3, an exhaust manifold 4, a supercharger 5, an intercooler 6, an exhaust purification device (post-processing). Device) 7. In FIG. 1, reference symbol Ae indicates exhaust gas, reference symbol Ai indicates intake gas, and arrows indicate the flow thereof.

  The engine body 2 includes, for example, four cylinders 8. The fuel is supplied to the air compressed in the combustion chambers of each cylinder 8 and heated to self-ignite, and the expansion gas generated by the combustion by the self-ignition The piston in the cylinder 8 is driven.

  The intake port of each cylinder 8 is connected to the intake manifold 3. The intake manifold 3 is connected to the intercooler 6 through the intake pipe (intake path) 9a, and further connected to the outlet of the compressor 5a of the supercharger 5 through the intake pipe 9b. On the other hand, the exhaust port of each cylinder 8 is connected to the exhaust manifold 4. The exhaust manifold 4 is connected to the inlet of the turbine 5b of the supercharger 5 through the exhaust pipe 10a.

  The supercharger 5 includes a compressor (compressor) 5a and a turbine 5b that are integrally formed with each other. When the turbine 5 b is rotationally driven by the force of the exhaust gas discharged from the exhaust port of each cylinder 8, the intake gas compressed and densified by the compressor 5 a being interlocked with the driving force is supplied to each cylinder through the intake manifold 3. 8 is sent in.

  The inlet of the exhaust gas purification device 7 is connected to the outlet of the turbine 5a of the supercharger 5 through the exhaust pipe 10b. The exhaust purification device 7 is a device that purifies exhaust gas that could not be purified by the engine body 2. Further, the outlet of the exhaust purification device 7 is connected to a muffler (not shown) through the exhaust pipe 10c.

  Next, FIG. 2 shows a configuration of a main part of the exhaust purification device 7 of the present embodiment.

  The exhaust purification device 7 includes, in an exhaust pipe 10d, a heat exchanger 14 that recovers thermal energy of the exhaust gas Ae and a catalyst device 15 that has a catalyst that purifies the exhaust gas Ae in series from upstream to downstream. And a bypass pipe 16 that returns the exhaust gas Ae that has passed through the catalyst device 15 to the heat exchanger 14.

  When the temperature of the catalyst in the catalyst device 15 is detected and the temperature is lower than the temperature at which the exhaust gas Ae can be purified, the exhaust gas Ae on the downstream side of the catalyst device 15 is heated through the bypass pipe 16. When the flow to the exchanger 14 is stopped and the temperature of the catalyst is a temperature at which the exhaust gas Ae can be purified, the exhaust gas Ae on the downstream side of the catalyst device 15 is passed through the bypass pipe 16 through the heat exchanger 14. The control part 20 which performs control to flow through is provided.

  That is, in the exhaust purification device 7 of the engine 1 of the present embodiment, the exhaust gas is exhausted until the catalyst temperature of the catalyst device 15 reaches a temperature at which the exhaust gas Ae can be purified when the engine 1 is cold. The gas Ae is prevented from flowing into the heat exchanger 14. Thereby, since the increase in the heat capacity by the heat exchanger 14 can be eliminated, the catalyst temperature of the catalyst device 15 can be reached in a temperature range showing a high purification rate in a short time. As a result, the exhaust gas Ae can be purified by the catalyst at an early stage after the engine 1 is started.

  On the other hand, after the catalyst temperature of the catalyst device 15 reaches a temperature that is sufficient to purify the exhaust gas Ae, the exhaust gas Ae is allowed to flow through the heat exchanger 14. Thereby, catalyst temperature can be maintained in the temperature range which shows a high purification rate.

  Therefore, in the engine 1 of the present embodiment, the exhaust gas purification ability by the catalyst can be generated at the time of starting and during operation. In addition, the fuel consumption rate can be reduced by not heating the catalyst by the electric heater or injecting the fuel into the exhaust pipe.

  Hereinafter, each structure of the exhaust emission control device 7 will be described. The heat exchanger 14 is a device that recovers heat energy of the exhaust gas Ae by transferring the heat of the exhaust gas Ae on the downstream side of the catalyst device 15 to the exhaust gas Ae on the upstream side of the catalyst device 15. That is, the exhaust gas Ae that has passed through the catalyst device 15 flows through the bypass pipe 16 to the heat exchanger 14 and is convected at the inlet of the catalyst device 15, so that the heat of the exhaust gas Ae is transferred from the turbine 5 b through the exhaust pipe 10 b. It is a device that supplies exhaust gas Ae that has flowed to the heat exchanger 14. The exhaust gas Ae that has flowed to the heat exchanger 14 through the bypass pipe 16 flows through another exhaust pipe to the exhaust pipe 10c downstream of the exhaust purification device 7 (upstream position from the muffler).

  As the heat exchanger 14, for example, a counter flow heat exchanger is used. As a result, high heat exchange efficiency can be stably obtained, and the apparatus can be made compact. The heat exchanger 14 is not limited to the counter flow type and can be variously changed. For example, a heat storage type heat exchanger may be used.

  In the catalyst device 15, for example, an oxidation catalyst part, a DPF (Diesel Particulate Filter), and a nitrogen oxide reduction (DeNOx) catalyst part are arranged in series from upstream to downstream. The oxidation catalyst part of the catalyst device 15 is a purification part having a catalyst for purifying carbon monoxide (CO) and hydrocarbons (HC). The downstream DPF is a purification unit that removes particulate matter (PM) using a filter. Further, the downstream DeNOx catalyst part is a purification part having a catalyst for purifying nitrogen oxide (NOx). Note that the configuration of the catalyst device 15 is not limited to that described above, and can be variously changed. For example, a configuration in which various catalyst layers are formed on the DPF itself may be used.

  A temperature sensor 21 is installed at the purification unit (the oxidation catalyst unit, the DeNOx catalyst unit, or both) having the catalyst of the catalyst device 15 or at the inlet of the catalyst device 15. The temperature sensor 21 is a sensor that detects the catalyst temperature, and is electrically connected to the control unit 20.

  Moreover, you may make it cover the whole catalyst apparatus 15 or the purification | cleaning part which has a catalyst with heat insulation or a heat insulating material (not shown). Thereby, since heat transfer to the heat exchanger 14 can be reduced or eliminated, the structure equivalent to that of the exhaust gas purification apparatus 7 without the heat exchanger 14 can be brought close to the viewpoint of the catalyst temperature when the engine 1 is started. . That is, the rate of temperature increase of the catalyst at the start of the engine 1 can be made comparable to that in the case of the exhaust purification device 7 without the heat exchanger 14. For this reason, the rate of temperature increase of the catalyst temperature when the engine 1 is started can be further improved, so that the exhaust gas Ae can be purified by the catalyst at an earlier stage after the engine 1 is started. The catalyst device 15 is disposed away from the heat exchanger 14 by a space 22.

  The bypass pipe 16 is installed adjacent to the exhaust pipe 10d so as to surround the exhaust pipe 10d (catalyst device 15). Thereby, size reduction of the exhaust gas purification apparatus 7 is attained. Moreover, since the heat retaining property of the catalyst device 15 can be improved, the catalyst temperature can be maintained at a temperature showing a high purification rate.

  On the lower part of the bypass pipe 16 (downstream of the catalyst device 15), an opening / closing valve (opening / closing means) 23 is provided at the boundary with the exhaust pipe 10d. The on-off valve 23 is a valve that opens and closes the bypass pipe 16 (that is, opens and closes the bypass pipe 16 and the exhaust pipe 10d). The opening / closing valve 23 is electrically connected to the control unit 20, and the opening / closing thereof is controlled by the control unit 20.

  On the boundary between the exhaust pipes 10d and 10c, an open / close valve 24 for opening and closing the exhaust pipes 10d and 10c is installed. The opening / closing valve 24 is electrically connected to the control unit 20, and the opening / closing thereof is controlled by the control unit 20.

  Next, a control method of the control unit 20 of the exhaust purification device 7 will be described with reference to FIGS. 3 and 4. 3 shows a state in which the on-off valve 23 is closed, and FIG. 4 shows a state in which the on-off valve 23 is opened.

  When the engine 1 is cold, the temperature of the catalyst of the exhaust purification device 7 is detected by the temperature sensor 21, and the temperature is lower than the temperature at which the exhaust gas Ae can be purified, as shown in FIG. Thus, the on-off valve 23 is closed and the on-off valve 24 is opened. This prevents the exhaust gas Ae that has passed through the catalyst device 15 from flowing into the heat exchanger 14. That is, when the engine 1 is cold, the exhaust gas Ae is passed to the heat exchanger 14 by closing the on-off valve 23 until the catalyst temperature of the catalyst device 15 reaches a temperature at which the exhaust gas Ae can be purified. Do not flush. Thereby, since the negative heat exchange can be prevented when the engine 1 is cold started, the temperature drop in the heat exchanger 14 of the exhaust gas Ae flowing into the heat exchanger 14 from the exhaust pipe 10b can be reduced. it can. For this reason, the delay in the temperature rise of the catalyst of the catalyst device 15 can be shortened, and the catalyst temperature of the catalyst device 15 can reach the temperature range showing a high purification rate in a short time. The exhaust gas Ae can be purified by a catalyst at an early stage later.

  Subsequently, when the catalyst temperature detected by the temperature sensor 21 reaches a temperature at which the exhaust gas can be purified, the on-off valve 23 is opened and the on-off valve 24 is closed as shown in FIG. Thereby, the exhaust gas Ae that has passed through the catalyst device 15 is caused to flow to the heat exchanger 14 through the bypass pipe 16 as indicated by an arrow. As a result, the exhaust gas Ae flowing from the exhaust pipe 10b to the heat exchanger 14 is warmed by the heat exchanger 14 and flows into the catalyst device 15, so that the catalyst temperature of the catalyst device 15 is maintained in a temperature range showing a high purification rate. can do. Immediately after opening of the on-off valve 23, it is expected that negative heat exchange will be performed in the heat exchange portion for raising the temperature of the heat exchanger 14, but the catalyst (oxidation catalyst, DeNOx catalyst) of the catalyst device 15 has already been heated. Since the on-off valve 23 is opened in a state in which the exhaust gas is being used, the adverse effect on the exhaust gas purification rate can be reduced.

  FIG. 5 shows the transition of the temperature value of the DeNOx catalyst. Reference numeral T1 represents the case where the exhaust purification apparatus 7 of the present embodiment is used (expected predicted value), reference numeral T2 represents the case where a conventional post-treatment apparatus having no heat exchanger is used (simulation result), and reference numeral T3 represents The case (simulation result) where the conventional post-processing apparatus having a heat exchanger is used is shown.

  In the case of the exhaust purification device 7 of the present embodiment (T1), the DeNOx catalyst temperature is changed to the conventional rear having a heat exchanger as in the case of using the conventional post-treatment device having no heat exchanger (T2). It can be seen that the temperature can be increased to a temperature range showing a high purification rate in a shorter time than when the processing apparatus is used (T3). For this reason, the exhaust gas Ae can be purified by the catalyst at an early stage after the engine 1 is started. Therefore, in the engine 1 of the present embodiment, the exhaust gas purification ability by the catalyst can be generated at the time of starting and during operation.

  The method for controlling an exhaust gas purification apparatus for an internal combustion engine, the exhaust gas purification apparatus for an internal combustion engine, and the internal combustion engine according to the present invention controls the flow of exhaust gas to the exhaust heat recovery device in accordance with the catalyst temperature, so that it can be started and operated. Since the exhaust gas purification ability by the catalyst can be produced in the engine, it can be used for a method for controlling an exhaust gas purification apparatus for an internal combustion engine such as an automobile, an exhaust gas purification apparatus for an internal combustion engine, and an internal combustion engine.

1 Diesel engine (internal combustion engine)
2 Engine body (Internal combustion engine body)
3 Intake manifold 4 Exhaust manifold 5 Supercharger 7 Exhaust gas purification device (post-treatment device)
8 Cylinders 10a to 10d Exhaust pipe 14 Heat exchanger (exhaust heat recovery device)
15 Catalytic device (Purification body)
16 Bypass pipe (sub exhaust path)
20 control part 21 temperature sensor 23 on-off valve (opening-closing means)
24 On-off valve

Claims (3)

A catalyst device having a catalyst for purifying the exhaust gas is provided in the exhaust path, and the heat of the exhaust gas downstream of the catalyst device is transferred to the exhaust gas upstream of the catalyst device, whereby the thermal energy of the exhaust gas is reduced. In a control method for an exhaust gas purification device for an internal combustion engine, the exhaust heat recovery device to be recovered is provided in a state in series with the catalyst device in the exhaust path upstream of the catalyst device,
When the temperature of the catalyst is detected and the temperature is lower than the temperature at which the exhaust gas can be purified, the flow of the exhaust gas downstream of the catalyst device to the exhaust heat recovery device is stopped. When the temperature of the catalyst is a temperature at which the exhaust gas can be purified, an exhaust purification device for an internal combustion engine that performs control to flow the exhaust gas downstream of the catalyst device to the exhaust heat recovery device Control method. A catalyst device having a catalyst for purifying the exhaust gas is provided in the exhaust path, and the heat of the exhaust gas downstream of the catalyst device is transferred to the exhaust gas upstream of the catalyst device, whereby the thermal energy of the exhaust gas is reduced. In the exhaust gas purification apparatus for an internal combustion engine, the exhaust heat recovery apparatus to be recovered is provided in a state in series with the catalyst apparatus in the exhaust path upstream of the catalyst apparatus.
Temperature detecting means for detecting the temperature of the catalyst;
A sub exhaust path for flowing the exhaust gas downstream of the catalyst device to the exhaust heat recovery device;
Opening and closing means for opening and closing the auxiliary exhaust path;
When the temperature of the catalyst detected by the temperature detection means is lower than the temperature at which the exhaust gas can be purified, the exhaust gas downstream of the catalyst device is reduced by closing the opening / closing means. When the temperature of the catalyst is such that the exhaust gas can be purified, the flow through the catalyst device is opened by opening the opening / closing means. An exhaust gas purification apparatus for an internal combustion engine, comprising: a control unit that controls the exhaust gas to flow through the auxiliary exhaust path to the exhaust heat recovery apparatus.   An internal combustion engine comprising the exhaust gas purification device for an internal combustion engine according to claim 2.

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