Exhaust emission control device for engine and engine

Abstract

To suppress heat radiation from a catalyst carrier.SOLUTION: This exhaust gas purifying device for the engine is provided with a catalytic carrier 331, a carrier vessel 332, holding members 333a and 333b for holding the catalytic carrier 331 at a prescribed position in the carrier vessel 332, and a communicating pipe 334 for connecting the carrier vessel 332 and an exhaust gas pipe 32 of the engine. The holding member has a first member 331a wound on the outer periphery of the exhaust-gas inlet-portion 333a of the catalytic carrier 331 and a second member 331b wound on the outer periphery of the exhaust-gas outlet-portion 333b, and a space S in which the outer peripheral surface of the catalytic carrier 331 is exposed is formed between the inner peripheral surface of the carrier vessel 332 and the outer peripheral surface of the catalytic carrier 331. The space S and the exhaust pipe 32 communicate with each other via a communication pipe 334.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an exhaust gas purification device for an engine and an engine. [Background technology]

[0002] Patent document 1 discloses a catalytic converter in which the catalyst case is formed into a double cylindrical shape with an inner and outer cylindrical portion, and a catalyst carrier carrying catalytic components is housed in the inner cylindrical portion of the catalyst case with a carrier holding mat wrapped around its outer periphery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-083417 Summary of the Invention [Problem to be solved by the invention]

[0004] In the catalytic converter described in the aforementioned document 1, the gap formed between the inner and outer tubular parts acts as a heat insulating layer, which suppresses heat radiation from the catalyst carrier and keeps the catalyst carrier warm. However, because the entire outer periphery of the catalyst carrier is covered with the mat and the catalyst carrier and mat are in contact with each other over the entire outer periphery of the catalyst carrier, heat from the catalyst carrier is easily released to the outside through the mat, and there is still room for improvement in terms of heat insulation.

[0005] In view of the above circumstances, an object of the present invention is to provide an exhaust gas purification device for an engine that can further suppress heat radiation from a catalyst carrier, and an engine equipped with the same. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, an engine exhaust purification device according to one embodiment of the present invention is an exhaust purification device installed in an exhaust pipe of an engine, and includes a catalyst carrier that supports a catalytic component that promotes an exhaust purification reaction, a carrier container that houses the catalyst carrier, a holding member that holds the catalyst carrier in a predetermined position within the carrier container, and a communicating pipe that connects the carrier container to the exhaust pipe. The holding member has a first member that is wrapped around the outer periphery of an exhaust inlet portion of the catalyst carrier, and a second member that is wrapped around the outer periphery of an exhaust outlet portion, and a space is formed between the inner circumferential surface of the carrier container and the outer circumferential surface of the catalyst carrier, the outer circumferential surface of the catalyst carrier is exposed to the space between the first member and the second member, and the space and the exhaust pipe are in communication with each other via the communicating pipe.

[0007] An engine according to another aspect of the present invention includes an engine body having a combustion chamber, an exhaust pipe extending from an exhaust port of the engine body, and the exhaust purification device interposed in the exhaust pipe. [Effects of the Invention]

[0008] According to one aspect of the present invention, heat radiation from the catalyst carrier to the outside is suppressed, catalyst component activity is promoted during cold start of the engine, and a temperature drop in the catalyst carrier during normal operation after warming up is suppressed. Here, by dividing the holding member into a first member and a second member, and wrapping the first member around the outer periphery of the exhaust inlet portion of the catalyst carrier and the second member around the outer periphery of the exhaust outlet portion of the catalyst carrier, respectively, heat transfer through the holding member is suppressed, thereby further suppressing heat radiation from the catalyst carrier. Furthermore, since the space and the exhaust pipe are connected via a connecting pipe, the pressure in the space is maintained close to the pressure inside the exhaust pipe, i.e., the exhaust pressure, and this prevents an excessive increase in the pressure difference between the inside and outside of the catalyst carrier, which could cause the holding member to shift or the catalyst carrier to deform or break. [Brief explanation of the drawings]

[0009] [Figure 1]1 is a schematic diagram showing the overall configuration of an engine to which an exhaust purification device according to a first embodiment of the present invention is applied. [Figure 2] FIG. 2 is a partial cross-sectional view showing the schematic configuration of the exhaust gas purification device according to the embodiment; [Figure 3] FIG. 4 is a partial cross-sectional view schematically showing the configuration of a modified example of the exhaust gas purification device according to the embodiment. [Figure 4] FIG. 4 is a schematic diagram showing the overall configuration of an engine to which an exhaust purification device according to a second embodiment of the present invention is applied. [Figure 5] FIG. 2 is a partial cross-sectional view showing the schematic configuration of the exhaust gas purification device according to the embodiment; [Figure 6] FIG. 4 is a partial cross-sectional view schematically showing the configuration of a modified example of the exhaust gas purification device according to the embodiment. [Figure 7] FIG. 4 is a partial cross-sectional view that schematically shows the configuration of an exhaust gas purification device according to a third embodiment of the present invention. [Figure 8] FIG. 3 is a partial cross-sectional view schematically showing the configuration of a first modified example of the exhaust gas purification device according to the above embodiment. [Figure 9] FIG. 4 is a partial cross-sectional view schematically showing the configuration of a second modified example of the exhaust purification device according to the above embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0011] (Overall engine configuration) FIG. 1 is a schematic diagram showing the overall configuration of an internal combustion engine (hereinafter simply referred to as "engine") E1 to which an exhaust purification device according to a first embodiment of the present invention is applied.

[0012] In the following description, the terms "upstream" and "downstream" are used in relation to the direction of the flow of exhaust gas emitted from engine E1 (E2). For example, the upstream side of the exhaust gas purification device refers to the upstream side of the exhaust gas purification device in the direction of the exhaust gas flow, and the downstream side of the exhaust gas purification device refers to the downstream side of the exhaust gas purification device in the direction of the exhaust gas flow.

[0013] The engine E1 is mounted on a vehicle and constitutes its drive source. In this embodiment, the engine E1 is a gasoline engine that uses gasoline as fuel. However, the engine E1 may be an engine that uses a fuel other than gasoline, for example, a gas engine that uses a gas fuel such as compressed natural gas (CNG) that contains methane gas as a main component, or may be a so-called bi-fuel engine that switches between gas fuel and liquid fuel such as gasoline. The engine E1 may not only constitute a standalone drive source for the vehicle, but may also be used as a power generation engine that drives a generator in a series hybrid vehicle.

[0014] The engine E1 includes an engine body 1 having a combustion chamber, an intake system 2, and an exhaust system 3. In this embodiment, the engine E1 is an in-line four-cylinder engine, but the type of the engine E1, i.e., the number and arrangement of cylinders in the engine E1, is not limited to this. Various types of engines can be applied, such as single-cylinder, two-cylinder, six-cylinder, V-type, and horizontally opposed type.

[0015] The engine body 1 includes a cylinder block, a cylinder head, and a crankcase. A piston is inserted into the cylinder block, and the space formed between the piston crown surface and the inner surface of the cylinder head serves as a combustion chamber.

[0016] The intake system 2 includes an intake pipe 21 and an intake manifold 22, as well as an air cleaner 23 attached to the inlet of the intake pipe 21. Air from which foreign matter such as dust has been removed via the air cleaner 23 is introduced into the intake pipe 21. The intake pipe 21 is connected to a collecting section of the intake manifold 22, and the intake manifold 22 branches off from the collecting section and is connected to a side section of the cylinder head. The air that flows from the intake pipe 21 into the intake manifold 22 is distributed to each cylinder via the branching sections of the intake manifold 22.

[0017] In this embodiment, a port injection fuel supply system is employed. The engine E1 is equipped with a plurality of fuel injectors 41 embedded in the cylinder head, and each of the plurality of fuel injectors 41 injects fuel into a corresponding cylinder. The fuel injectors 41 are installed at branching portions of the intake manifold 22 and inject fuel into the intake ports of the corresponding cylinders. The fuel supply system is not limited to this, and a supply system other than port injection, such as direct injection, can also be employed.

[0018] The fuel injected by the fuel injector 41 is mixed with air that has passed through a branching portion of the intake manifold 22 and is introduced into the corresponding cylinder. In each cylinder, the fuel and air continue to mix, forming an air-fuel mixture. This mixture is then ignited by a spark plug 51, causing the mixture to burn.

[0019] The exhaust system 3 includes an exhaust manifold 31 and an exhaust pipe 32, as well as a catalytic converter 33. After combustion, the exhaust gas remaining in the cylinders is discharged to a branching portion of the exhaust manifold 31. The exhaust gas is collected from the branching portion to a collecting portion in the exhaust manifold 31 and introduced into the exhaust pipe 32. The catalytic converter 33 is installed in the exhaust pipe 32, and the exhaust gas flowing through the exhaust pipe 32 is introduced into the catalytic converter 33, where harmful components in the exhaust are purified by an exhaust purification catalyst 331 housed in the catalytic converter 33, before being released into the atmosphere. In this embodiment, the catalytic converter 33 includes a three-way catalyst as the exhaust purification catalyst 331. The catalytic converter 33 constitutes the "exhaust purification device" according to this embodiment.

[0020] (Outline of control system configuration) In addition to the above, the engine E1 is equipped with an engine controller 101 and various sensors 201 to 206 as a control system for the exhaust purification device.

[0021] The engine controller 101 is an electronic control unit that is configured by a microcomputer equipped with a central processing unit (CPU), storage devices such as ROM and RAM, an input / output interface, and the like.

[0022] The engine E1 is equipped with an accelerator sensor 201 and an engine rotation speed sensor 202, as well as an air flow meter 203, a coolant temperature sensor 204, an air-fuel ratio sensor 205, and a catalyst temperature sensor 206. Detection signals output from these sensors 201 to 206 serve as indicators of the operating state of the engine E1, and are input to the engine controller 101.

[0023] The accelerator sensor 201 detects the amount of depression of the accelerator pedal by the driver as the accelerator opening APO, which is an index of the target load required for the engine E1.

[0024] The engine rotation speed sensor 202 detects the rotation speed Ne of the engine E1. A crank angle sensor can be used as the engine rotation speed sensor 202, and converts the elapsed time per unit crank angle or reference crank angle detected by the crank angle sensor into the rotation speed Ne.

[0025] The air flow meter 203 detects the flow rate of air introduced into the engine E1 as the intake air amount Qa.

[0026] The coolant temperature sensor 204 detects the temperature Tw of the coolant flowing through a coolant passage formed in the cylinder block of the engine body 1 .

[0027] The air-fuel ratio sensor 205 is installed in the exhaust pipe 32 upstream of the catalytic converter 33, in this embodiment upstream of the connection portion of the connecting pipe 334 described later, and detects the air-fuel ratio λf of the exhaust gas before it flows into the catalytic converter 33.

[0028] The catalyst temperature sensor 206 detects the temperature Tcat (hereinafter referred to as "catalyst temperature") of the exhaust purification catalyst 331 provided in the catalytic converter 33. In this embodiment, the temperature of the exhaust gas at the inlet or introduction part of the catalytic converter 33 is detected as the catalyst temperature Tcat.

[0029] The engine controller 101 controls the operating state of the engine E1 while controlling the air-fuel ratio of the mixture used for combustion based on the detection signals output from the sensors 201 to 206 described above.

[0030] (Catalytic converter configuration) FIG. 2 is a partial cross-sectional view that schematically shows the configuration of the catalytic converter 33 according to this embodiment.

[0031] In this embodiment, the catalytic converter 33 includes a catalyst carrier 331 and a carrier container 332 .

[0032] The catalyst carrier 331 is a monolithic ceramic carrier in a cylindrical honeycomb shape, and supports catalytic components that promote the purification reaction of harmful components in the exhaust (i.e., the exhaust purification reaction). The catalytic components include precious metals such as platinum, palladium, and rhodium, and the catalyst carrier 331 constitutes a so-called three-way catalyst. As a result, when the engine E1 is operated at a stoichiometric air-fuel ratio, the oxidation of total hydrocarbons (THC) and carbon monoxide (CO), which are harmful exhaust components, and the reduction of nitrogen oxides (NOx) proceed simultaneously.

[0033] The carrier container 332 is cylindrical overall and houses the catalyst carrier 331. The catalyst carrier 331 is housed in the carrier container 332 with catalyst holding mats 333a and 333b wrapped around its outer periphery. The mats 333a and 333b hold the catalyst carrier 331 at a predetermined position within the carrier container 332, specifically, at a central position in the front and rear of the carrier container 332, concentrically with the carrier container 332. In this embodiment, the mats are wrapped around the outer periphery of the exhaust gas inlet 331a and the outer periphery of the exhaust gas outlet 331b of the catalyst carrier 331. The mats 333a and 333b constitute a "holding member" according to this embodiment. The mat 333a wrapped around the outer periphery of the exhaust gas inlet 331a (hereinafter sometimes referred to as the "inlet mat") corresponds to the "first member," and the mat 333b wrapped around the outer periphery of the exhaust gas outlet 331b (hereinafter sometimes referred to as the "outlet mat") corresponds to the "second member."

[0034] The carrier container 332 has an intermediate bulge portion 332a and an inlet portion 332b and an outlet portion 332c that sandwich the intermediate bulge portion 332a from the front and rear in the exhaust flow direction A. The inlet portion 332b and the outlet portion 332c are both funnel-shaped, narrowing in the direction away from the intermediate bulge portion 332a. An inlet flange portion 332d is provided at the tip of the inlet portion 332b, and an outlet flange portion 332e is provided at the tip of the outlet portion 332c. The catalytic converter 33 is connected to the upstream exhaust pipe 32a via the inlet flange portion 332d and to the downstream exhaust pipe 32b via the outlet flange portion 332e.

[0035] Here, intermediate bulging portion 332a bulges in a direction perpendicular to the front-to-rear center line C of catalyst carrier 331 from the outer peripheral edges of inlet portion 332b and outlet portion 332c, which are closer to catalyst carrier 331, and forms an outer peripheral surface at a position farther from the front-to-rear center line C than the outer peripheral edges of inlet portion 332b and outlet portion 332c. As a result, a space S is formed between inlet mat 333a and outlet mat 333b, sandwiched between the inner peripheral surface of intermediate bulging portion 332a and the outer peripheral surface of catalyst carrier 331, and the outer peripheral surface of catalyst carrier 331 is exposed to space S. The inner peripheral surface of intermediate bulging portion 332a is located farther from the outer peripheral surface of catalyst carrier 331 than the outer peripheral edges of inlet mat 333a and outlet mat 333b.

[0036] In addition to the above, a communication pipe 334 is provided that connects the carrier container 332 and the exhaust pipe 32, and the space S surrounding the catalyst carrier 331 and the exhaust pipe 32 are communicated with each other via the communication pipe 334. In this embodiment, one end of the communication pipe 334 is connected to the intermediate bulge portion 332a, and the other end is connected to the exhaust pipe 32a on the upstream side of the catalytic converter 33, so that the space S is communicated with the upstream side exhaust pipe 32a.

[0037] (Explanation of action and effect) The effects obtained by this embodiment will be described below.

[0038] The carrier holding mat is formed as two separate members, specifically, an inlet mat 333a and an outlet mat 333b. The inlet mat 333a is wrapped around the outer periphery of the exhaust inlet 331a of the catalyst carrier 331, and the outlet mat 333b is wrapped around the outer periphery of the exhaust outlet 331b of the catalyst carrier 331, respectively, so that the outer periphery of the catalyst carrier 331 is exposed to a space S formed between the inner periphery of the carrier container 332 and the outer periphery of the catalyst carrier 331, between the inlet mat 333a and the outlet mat 333b.

[0039] This allows the space S to function as a heat insulating layer, suppressing heat radiation from the catalyst carrier 331 to the outside and maintaining the temperature inside the carrier container 332. Therefore, for example, when the engine E1 is started in a cold state, it is possible to promote the activity of the catalyst components and suppress a drop in the temperature of the catalyst carrier 331 during normal operation after warming up (for example, during idling stop).

[0040] Furthermore, by wrapping the inlet mat 333a around the outer periphery of the exhaust inlet portion 331a of the catalyst carrier 331 and the outlet mat 333b around the outer periphery of the exhaust outlet portion 331b of the catalyst carrier 331, it is possible to suppress heat transfer through the mats 333a and 333b and further suppress heat radiation from the catalyst carrier 331 compared to when the mats are wrapped around the entire outer periphery of the catalyst carrier.

[0041] Furthermore, since the space S and the exhaust pipe 32 are connected via the connecting pipe 334, it is possible to maintain the pressure in the space S at a level close to the pressure inside the exhaust pipe 32, i.e., the exhaust pressure. This makes it possible to prevent situations in which, when high-temperature exhaust gas flows into the catalyst carrier 331 during high-load operation of the engine E1, the pressure in the space S rises, causing the inlet mat 333a or the outlet mat 333b to shift position, or the pressure difference between the inside and outside of the catalyst carrier 331 to increase excessively, causing deformation or damage to the catalyst carrier 331.

[0042] Here, by surrounding the catalyst carrier 331 all over its periphery with the space portion S, it is possible to further suppress heat radiation from the catalyst carrier 331.

[0043] Furthermore, by connecting one end of the communication pipe 334 to the carrier container 332 and the other end to the exhaust pipe 32a upstream of the catalytic converter 33, the air in the space S heated by the exhaust gas flowing through the catalyst carrier 331 can be introduced into the catalytic converter 33 via the upstream exhaust pipe 32a and used as a heat source to heat the catalyst carrier 331.

[0044] (Modification of the first embodiment) FIG. 3 is a partial cross-sectional view that schematically shows the configuration of a modified example of the catalytic converter 33 according to this embodiment.

[0045] 3, a communication pipe 334 is provided that connects the carrier container 332 and the exhaust pipe 32, as in the above-described case, and the space S surrounding the catalyst carrier 331 and the exhaust pipe 32 are communicated with each other via the communication pipe 334. The carrier container 332 (intermediate bulging portion 332a, inlet portion 332b, outlet portion 332c) has the same configuration as in the example shown in FIG. 2. In this embodiment, one end of the communication pipe 334 is connected to the intermediate bulging portion 332a, and the other end is connected to the exhaust pipe 32b downstream of the catalytic converter 33, so that the space S is communicated with the downstream exhaust pipe 32b.

[0046] In this way, by connecting one end of the communicating pipe 334 to the carrier container 332 and the other end to the exhaust pipe 32b downstream of the catalytic converter 33, when the air in the space S is at a relatively low temperature, it is possible to avoid the adverse effects caused by the air being returned to the exhaust pipe 32 and flowing into the catalytic converter 33 (specifically, preventing the temperature of the catalyst carrier 331 from rising).

[0047] (Second embodiment) FIG. 4 is a partial cross-sectional view that schematically shows the configuration of an exhaust purification device (catalytic converter 33) according to a second embodiment of the present invention.

[0048] In this embodiment, engine E2 differs from engine E1 described above only in that it is equipped with an exhaust gas recirculation device 61. The exhaust gas recirculation device 61 lowers the combustion temperature in the cylinders and suppresses the generation of nitrogen oxides by returning a portion of the exhaust gas into the cylinders. Engine E2 is equipped with a recirculation gas flow pipe 611, a recirculation control valve 612, and a recirculation gas cooler (EGR cooler) 613 as main elements that constitute the exhaust gas recirculation device 61.

[0049] The recirculation gas flow pipe 611 connects the exhaust pipe 32 and the intake pipe 21, and forms a flow path for exhaust gas (i.e., recirculation gas) from the exhaust pipe 32 to the intake pipe 21. The recirculation gas flow pipe 611 is connected to the intake pipe 21 downstream of a recirculation control valve 612, which will be described next.

[0050] The recirculation control valve 612 is installed in the intake pipe 21 and adjusts the flow path area in the intake pipe 21. By closing the recirculation control valve 612 and narrowing the flow path, negative pressure is created downstream, promoting the flow of recirculation gas from the recirculation gas flow pipe 611 into the intake pipe 21.

[0051] The recirculation gas cooler 613 is installed in the recirculation gas flow pipe 611 and cools the exhaust gas flowing through the recirculation gas flow pipe 611 before it is introduced into the intake pipe 21 .

[0052] The communication pipe 334 is connected to the recirculation gas flow pipe 611, and connects the space S to the exhaust pipe 32 via the recirculation gas flow pipe 611. Specifically, the communication pipe 334 is connected to the recirculation gas flow pipe 611 on the upstream side of the recirculation gas cooler 613 with respect to the flow of recirculation gas in the recirculation gas flow pipe 611. This prevents the recirculation gas cooled by the recirculation gas cooler 613 from being heated by the air flowing in from the space S, which would reduce the intake air filling efficiency.

[0053] FIG. 5 is a partial cross-sectional view that schematically shows the configuration of a catalytic converter 33 according to this embodiment.

[0054] In this embodiment, the exhaust gas recirculation device 61 has a piping configuration of so-called high-pressure EGR, and the recirculation gas flow pipe 611 is connected between the exhaust pipe 32a on the upstream side of the catalytic converter 33 and the intake pipe 21.

[0055] The communication pipe 334 is connected between the carrier container 332 and the recirculation gas flow pipe 611, and connects the space S surrounding the catalyst carrier 331 to the exhaust pipe 32a on the upstream side of the catalytic converter 33 via the recirculation gas flow pipe 611. The carrier container 332 has the same configuration as the example shown in FIG. 2 and includes an intermediate bulge portion 332a, an inlet portion 332b, and an outlet portion 332c. In this embodiment, one end of the communication pipe 334 is connected to the intermediate bulge portion 332a, and the other end is connected to the recirculation gas flow pipe 611 upstream of the recirculation gas cooler 613.

[0056] According to this embodiment, in addition to the aforementioned effects of suppressing heat radiation from the catalyst carrier 331 and suppressing deformation and damage to the catalyst carrier 331, the following effects are particularly obtained in relation to the exhaust gas recirculation device 61.

[0057] By connecting the communicating pipe 334 to the recirculation gas flow pipe 611 of the exhaust gas recirculation device 61 and connecting the space S to the exhaust pipe 32 via the recirculation gas flow pipe 611, it is possible to use the recirculation gas flow pipe 611 that is already provided as an element of the exhaust gas recirculation device 61, thereby shortening the pipe length of the communicating pipe 334 itself and simplifying the overall configuration of the catalytic converter 33.

[0058] Furthermore, by extending the recirculation gas flow pipe 611 from the exhaust pipe 32a upstream of the catalytic converter 33 and connecting it to the intake pipe 21 of the engine E2, the relatively high-temperature exhaust gas before passing through the catalytic converter 33 can be introduced into the space S via the recirculation gas flow pipe 611 and the connecting pipe 334.

[0059] This allows the temperature of the space S to be increased before the engine E2 is warmed up, thereby facilitating the early activation of the catalyst components. At the same time, it also allows relatively high-temperature exhaust gas to be recirculated into the cylinder, facilitating the warm-up of the engine body 1.

[0060] Furthermore, by introducing the exhaust pressure upstream of the catalytic converter 33 into the space S and increasing the pressure in the space S, it is possible to prevent the pressure inside the catalyst carrier 331 from increasing excessively after warm-up, particularly when operating in a high-load range, resulting in deformation or damage to the catalyst carrier 331.

[0061] (Modification of the second embodiment) FIG. 6 is a partial cross-sectional view that schematically shows the configuration of a modified example of the catalytic converter 33 according to this embodiment.

[0062] In this embodiment, the exhaust gas recirculation device 61 has a piping configuration for so-called low-pressure EGR, and the recirculation gas flow pipe 611 is connected between the exhaust pipe 32b downstream of the catalytic converter 33 and the intake pipe 21.

[0063] The communication pipe 334 is connected between the carrier container 332 and the recirculation gas flow pipe 611, and connects the space S surrounding the catalyst carrier 331 to the exhaust pipe 32b downstream of the catalytic converter 33 via the recirculation gas flow pipe 611. The carrier container 332 has the same configuration as the example shown in FIG. 2 and includes an intermediate bulge portion 332a, an inlet portion 332b, and an outlet portion 332c. In this embodiment, one end of the communication pipe 334 is connected to the intermediate bulge portion 332a, and the other end is connected to the recirculation gas flow pipe 611 upstream of the recirculation gas cooler 613.

[0064] In this way, by extending the recirculation gas flow pipe 611 from the exhaust pipe 32b downstream of the catalytic converter 33 and connecting it to the intake pipe 21 of the engine E2, the air in the space S can be introduced into the cylinder together with the relatively low-temperature exhaust gas that has passed through the catalytic converter 33.

[0065] This makes it possible to suppress the effects of introducing air that has become hot due to heat received from the catalyst carrier 331 into the recirculation gas flow pipe 611, while promoting the enhancement of the effectiveness of the exhaust gas recirculation device 61 itself by recirculating low-temperature exhaust gas.

[0066] During warm-up, the entire amount of exhaust gas flowing through the exhaust pipe 32 is introduced into the catalytic converter 33, which makes it possible to quickly activate the catalytic components and promote warm-up.

[0067] (Third embodiment) FIG. 7 is a partial cross-sectional view that schematically shows the configuration of an exhaust purification device (catalytic converter 33) according to a third embodiment of the present invention.

[0068] In this embodiment, the engine to which the catalytic converter 33 is applied is equipped with an exhaust gas recirculation system, similar to the engine E2 described above. The exhaust gas recirculation system includes, as its main components, a recirculation gas flow pipe, a recirculation control valve, and a recirculation gas cooler.

[0069] In this embodiment, a first recirculation gas circulation pipe 611a on the upstream side and a second recirculation gas circulation pipe 611b on the downstream side with respect to the flow of recirculation gas are provided as the recirculation gas circulation pipe 611. The first recirculation gas circulation pipe 611a is connected between the carrier container 332 and the exhaust pipe 32, and the second recirculation gas circulation pipe 611b is connected between the carrier container 332 and the intake pipe 21.

[0070] FIG. 7 is a partial cross-sectional view that schematically shows the configuration of a catalytic converter 33 according to this embodiment.

[0071] In this embodiment, the recirculation gas flow pipe 611 extends from the exhaust pipe 32a upstream of the catalytic converter 33 and is connected to the intake pipe 21 via the carrier container 332. The recirculation gas flow pipe 611 connects the exhaust pipe 32 and the intake pipe 21 via the space S of the carrier container 332, and recirculates a portion of the exhaust gas flowing through the exhaust pipe 32 into the cylinder via the space S.

[0072] The first recirculation gas circulation pipe 611a is connected between the carrier container 332 and the exhaust pipe 32a upstream of the catalytic converter 33, and connects the space S surrounding the catalyst carrier 331 to the exhaust pipe 32a upstream of the catalytic converter 33. In other words, the first recirculation gas circulation pipe 611a also serves as the communication pipe 334 shown in FIG. 2. The carrier container 332 has the same configuration as the example shown in FIG. 2, and includes an intermediate bulge portion 332a, an inlet portion 332b, and an outlet portion 332c. In this embodiment, one end of the first recirculation gas circulation pipe 611a is connected to the intermediate bulge portion 332a, and the other end is connected to the exhaust pipe 32a.

[0073] According to this embodiment, in addition to the aforementioned effects of suppressing heat radiation from the catalyst carrier 331 and suppressing deformation and damage to the catalyst carrier 331, the following effects can be obtained in particular in relation to the exhaust gas recirculation device.

[0074] By configuring the first reflux gas flow pipe 611a to also function as a connecting pipe, a special configuration for connecting the space portion S and the exhaust pipe 32 is not required, which promotes the standardization of parts and makes it possible to further simplify the overall configuration of the catalytic converter 33.

[0075] Furthermore, by extending the first recirculation gas flow pipe 611a from the exhaust pipe 32a upstream of the catalytic converter 33 and connecting it to the carrier container 332, it is possible to introduce relatively high-temperature exhaust gas before passing through the catalytic converter 33 into the space S via the first recirculation gas flow pipe 611a. This promotes a temperature rise in the space S before warming up the engine, thereby facilitating early activation of the catalyst components, and after warming up, particularly when operating in a high-load range, it is possible to introduce a relatively high exhaust pressure into the space S, thereby preventing deformation or damage to the catalyst carrier 331 due to an increased pressure difference between the inside and outside of the catalyst carrier 331.

[0076] (Modification of the third embodiment) FIG. 8 is a partial cross-sectional view that schematically shows the configuration of a first modified example of the catalytic converter 33 according to this embodiment.

[0077] 8, one end of the first recirculation gas flow pipe 611a is connected to the intermediate bulge portion 332a of the carrier container 332, and the other end is connected to the exhaust pipe 32b downstream of the catalytic converter 33, thereby connecting the space S surrounding the catalyst carrier 331 to the exhaust pipe 32b downstream of the catalytic converter 33. In other words, the first recirculation gas flow pipe 611a also serves as the connecting pipe 334 shown in FIG. 3. This eliminates the need for a special configuration for connecting the space S to the exhaust pipe 32, promotes the use of common parts, and makes it possible to further simplify the overall configuration of the catalytic converter 33.

[0078] Furthermore, by extending the first recirculation gas flow pipe 611a from the exhaust pipe 32b downstream of the catalytic converter 33 and connecting it to the intake pipe 21 via the carrier container 332, the air in the space S can be introduced into the cylinders together with the relatively low-temperature exhaust gas that has passed through the catalytic converter 33. This makes it possible to suppress the effects of introducing air that has become hot due to heat received from the catalyst carrier 331 into the recirculation gas flow pipe 611, while promoting the enhancement of the effectiveness of the exhaust gas recirculation device itself by recirculating the low-temperature exhaust gas. Furthermore, during warm-up, it is possible to introduce the entire amount of exhaust gas flowing through the exhaust pipe 32 into the catalytic converter 33, thereby enabling early activation of the catalyst components and promoting warm-up.

[0079] FIG. 9 is a partial cross-sectional view that schematically shows the configuration of a second modified example of the catalytic converter 33 according to this embodiment.

[0080] 9, similar to the example shown in Fig. 8, the first recirculation gas circulation pipe 611a also serves as a communication pipe, with one end connected to the intermediate bulge 332a of the carrier container 332 and the other end connected to the exhaust pipe 32b downstream of the catalytic converter 33. In contrast, the second recirculation gas circulation pipe 611b is disposed diagonally to the first recirculation gas circulation pipe 611a with respect to the front-rear center line C of the catalyst carrier 331.

[0081] This places the catalyst carrier 331 in the flow path when the exhaust gas that flows into the space S from the first recirculation gas flow pipe 611a flows out to the second recirculation gas flow pipe 611b, promoting contact between the exhaust gas and the catalyst carrier 331, further suppressing heat dissipation from the catalyst carrier 331 and a drop in temperature of the catalyst carrier 331, and also making it possible to promote the enhancement of the effectiveness of the exhaust gas recirculation device itself by cooling the recirculation gas. [Explanation of symbols]

[0082] E1, E2...internal combustion engine, 1...engine body, 2...intake system, 21...intake pipe, 22...intake manifold, 3...exhaust system, 31...exhaust manifold, 32...exhaust pipe, 33...catalytic converter, 331...exhaust purification catalyst, 332...catalyst container, 333...mat (holding member), 333a...inlet mat (first member), 333b...outlet mat (second member), 41...fuel injector, 51...spark plug, 101...engine controller, 201...accelerator opening sensor, 202...engine rotation speed sensor, 203...air flow meter, 204...coolant temperature sensor, 205...air-fuel ratio sensor, 206...catalyst temperature sensor.

Claims

1. An exhaust purification device installed in an exhaust pipe of an engine, a catalyst carrier that supports a catalytic component that promotes an exhaust purification reaction; a carrier container that accommodates the catalyst carrier; a holding member that holds the catalyst carrier at a predetermined position within the carrier container; a communication pipe connecting the carrier container and the exhaust pipe, the holding member has a first member wound around an outer periphery of the exhaust inlet portion of the catalyst carrier and a second member wound around an outer periphery of the exhaust outlet portion of the catalyst carrier, a space is formed between an inner peripheral surface of the carrier container and an outer peripheral surface of the catalyst carrier, and the outer peripheral surface of the catalyst carrier is exposed to the space between the first member and the second member; The space and the exhaust pipe are in communication with each other via the communication pipe.

2. 2. The engine exhaust gas purification device according to claim 1, wherein the space surrounds the catalyst carrier over its entire periphery.

3. 2. The exhaust gas purification device for an engine according to claim 1, wherein one end of the communication pipe is connected to the carrier container, and the other end is connected to an exhaust pipe located upstream of the exhaust gas purification device with respect to the flow of exhaust gas.

4. 2. The engine exhaust purification device according to claim 1, wherein one end of the communication pipe is connected to the catalyst container, and the other end is connected to an exhaust pipe downstream of the exhaust purification catalyst with respect to the flow of the exhaust.

5. 2. An exhaust gas purification device for an engine according to claim 1, which is provided in an engine having an exhaust gas recirculation device that recirculates a portion of the exhaust gas into a cylinder, the exhaust gas recirculation device includes a recirculation gas flow pipe extending from the exhaust pipe and through which exhaust gas to be recirculated into the cylinder flows, The communication pipe is connected to the recirculation gas flow pipe, and the space communicates with the exhaust pipe via the recirculation gas flow pipe.

6. 6. The exhaust gas purification device for an engine according to claim 5, wherein the recirculation gas flow pipe is connected between an exhaust pipe upstream of the exhaust gas purification device and an intake pipe of the engine.

7. 6. The exhaust gas purification device for an engine according to claim 5, wherein the recirculation gas flow pipe is connected between an exhaust pipe downstream of the exhaust gas purification device and an intake pipe of the engine.

8. 2. An exhaust gas purification device for an engine according to claim 1, which is provided in an engine having an exhaust gas recirculation device that recirculates a portion of the exhaust gas into a cylinder, The exhaust gas recirculation device is a first recirculation gas flow pipe connecting the carrier container and the exhaust pipe, and a second recirculation gas flow pipe connecting the carrier container and an intake pipe of the engine, An exhaust gas purification device for an engine, which recirculates a portion of the exhaust gas into the cylinder through the space.

9. 2. An engine exhaust purification device as described in claim 1, wherein the carrier container has an intermediate bulge portion between the first member and the second member that bulges in a direction perpendicular to the front-to-rear center line of the catalyst carrier, and the inner surface of the carrier container that defines the space portion is located farther from the outer surface of the catalyst carrier than the outer edges of the first and second members.

10. 10. The engine exhaust gas purification device according to claim 1, wherein the catalyst carrier is a ceramic carrier.

11. an engine body having a combustion chamber; an exhaust pipe extending from an exhaust port of the engine body; An engine comprising: the exhaust purification device according to claim 10, which is installed in the exhaust pipe.

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