JP2008175125A - Exhaust heat recovery device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable heating of a catalyst and recovery of an exhaust gas at the same time. <P>SOLUTION: The exhaust gas heat recovery device 300 comprises an inner cylinder part 310 communicating with an exhaust conduit 221, and an outer cylinder part 320 covering the inner cylinder part 310. A reflux pipe 330 is branched at a branch position downstream of a S/C catalyst 223 in the inner cylinder part 310 for communicating with the outer cylinder part 320 at a joint position upstream of the S/C catalyst 223 in the outer cylinder part 320. Thereby, a part of the exhaust gas flowing through the inner cylinder part 310 is guided to a reflux space between the inner cylinder part 310 and the outer cylinder part 320 via the reflux pipe 330. An exhaust gas heat recovery machine 340 is installed for collecting the exhaust heat in the reflux pipe 330 so that the exhaust gas heat is collected by providing exhaust gas heat to cooling water. The exhaust gas flowing in the reflux pipe 330 is cooled down by the collection of the exhaust gas heat, but it is heated by heat exchange with the inner cylinder part outer wall and the S/C catalyst outer wall in the process of moving toward a U/F catalyst 225 in the reflux space. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technical field of an exhaust heat recovery device for an internal combustion engine that recovers exhaust heat in the internal combustion engine.

  As this type of apparatus, an apparatus considering catalyst warm-up has been proposed (see, for example, Patent Document 1). According to the Stirling engine disclosed in Patent Document 1 (hereinafter referred to as “prior art”), when the catalyst temperature is equal to or lower than a predetermined value, the Stirling engine is stopped so that heat recovery by the Stirling engine is not performed. By doing so, the temperature rise of the catalyst is promoted.

  In addition, in the configuration including the exhaust heat recovery device and the electric water pump, a technique for preventing local boiling of the cooling water by delaying the timing for stopping the electric water pump when the engine is stopped by a predetermined time has been proposed (for example, Patent Document 2).

JP 2005-337178 A JP-A-2-104952

  When the recovery of exhaust heat is stopped to promote the warming up of the catalyst, the temperature rise of the cooling water or the like that can be warmed by the recovered heat is hindered. In this case, the operation of a heater or the like that heats the interior of the vehicle by heat exchange with the cooling water may be hindered. That is, the conventional technique has a technical problem that it is difficult to achieve both warm-up of the catalyst and operation of the equipment using the recovered exhaust heat. In particular, in a vehicle such as a hybrid vehicle where the operating efficiency of the internal combustion engine is relatively high or the vehicle can travel with the internal combustion engine stopped, the cooling loss tends to be inevitably small, and such a problem is remarkable. Can occur.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an exhaust heat recovery device for an internal combustion engine that can achieve both warming up of the catalyst and recovery of exhaust heat.

  In order to solve the above-described problem, an exhaust heat recovery device for an internal combustion engine according to the present invention is a first exhaust pipe that communicates with the inside of a cylinder and that can purify exhaust gas that is guided through the exhaust pipe. An exhaust heat recovery apparatus for an internal combustion engine that recovers exhaust heat in an internal combustion engine having a catalyst, wherein the cylinder communicates with the exhaust pipe upstream of the first catalyst and guides the exhaust to the first catalyst. A cylindrical inner cylinder part and a cylindrical part formed by covering the inner cylinder part so that a space is interposed therebetween, the upstream end part being closed, and the downstream end part communicating with the first catalyst At least a part of the exhaust gas is branched from the inner cylinder part at a predetermined branching position with the outer cylinder part and communicates with the inside of the outer cylinder part at a predetermined merging position located upstream of the branching position. A reflux pipe for refluxing the liquid into the space, and the reflux pipe Is installed, characterized by comprising an exhaust heat recovery means for performing recovery of the exhaust heat from the exhaust to the return.

  The “internal combustion engine” in the present invention has, for example, a plurality of cylinders, and power as an explosive force generated when various fuels such as gasoline, light oil or alcohol are burned in the combustion chamber of each of the plurality of cylinders. For example, a two-cycle or four-cycle reciprocating engine for automobiles, through a mechanical transmission path such as a piston and a connecting rod, and at least an engine that can output as power via, for example, a crankshaft. Alternatively, for example, an engine system including, for example, an intake system or an exhaust system connected to the front stage or the rear stage of the engine in addition to the engine is employed.

  The internal combustion engine according to the present invention is provided with an exhaust pipe as a concept including, for example, an exhaust port, an exhaust manifold, and a general exhaust pipe that mainly constructs an exhaust path, which communicates with the inside of the cylinder, for example, combustion gas or unburned fuel Exhaust gas including the like is guided. This exhaust is, for example, a three-way catalyst, a NOx occlusion reduction catalyst, an oxidation catalyst, or various forms such as a DPF (Diesel Particulate Filter), or a name derived from the installation location of an S / C (Start Converter) catalyst or U / F. (Under Floor) It is purified by a catalytic reaction related to the first catalyst that can take various forms such as a catalyst.

  The exhaust heat recovery device for an internal combustion engine according to the present invention is provided with a cylindrical inner tube portion that communicates with the exhaust pipe upstream of the first catalyst, and preferably has an annular inner cylinder portion, for example, similar to the exhaust pipe. This cylindrical inner cylinder part has a structure which guides exhaust gas to the first catalyst directly or indirectly through a suitable space, for example, at one end part on the downstream side.

  The inner cylinder part is covered with a cylindrical outer cylinder part concentrically arranged in cross section with the inner cylinder part so that a space is interposed, that is, with an appropriate gap. The outer cylinder is physically closed at the upstream end so that exhaust does not flow directly through at least the exhaust pipe, and communicates with the first catalyst at the downstream end. It has become. Therefore, the first catalyst has at least the inner cylinder part and the above-described space interposed between the inner cylinder part and the outer cylinder part in communication with each other. Preferably, the inner cylinder part and the space are also mutually connected. It is configured to communicate with.

  In the present invention, “upstream” and “downstream” are directional concepts based on the flow of exhaust in a state of normal flow (that is, excluding the case of recirculation described later). The side closer to the cylinder as viewed from the flow is defined as upstream, and the far side is defined as downstream.

  Here, the return pipe branches from the inner cylinder portion at a predetermined branch position, and communicates with the inside of the outer cylinder portion at a merging position located upstream from the branch position. At least a part of the exhaust gas that is guided through the inner cylinder part recirculates so as to reverse the normal flow of the exhaust gas (that is, the exhaust gas flow in the inner cylinder part), for example, in a cross section along the exhaust gas flow. In such a merging position, it is guided to the space described above.

  On the other hand, as described above, this space communicates with the first catalyst together with the inner cylinder portion, and the upstream end portion of the outer cylinder portion is closed. The led exhaust is finally led to the first catalyst. That is, the exhaust gas flowing through the inner cylinder portion without recirculating through the recirculation pipe and the exhaust gas recirculated into the space finally flow into the first catalyst.

  On the other hand, according to the exhaust heat recovery apparatus for an internal combustion engine according to the present invention, at least a part of the reflux pipe is formed of, for example, stainless steel or the like, for example, a material having a large heat storage capacity and relatively good heat transfer performance. The exhaust heat recovery means can be provided, and the exhaust heat related to the recirculated exhaust gas can be recovered.

  In the present invention, “recovering exhaust heat” includes at least taking a part of the exhaust heat from the exhaust gas being recirculated, and at least a part of the exhaust heat is temporarily removed by, for example, a heat storage means. After heat storage or directly, for example, heat exchange as a concept including spatial radiation, physical heat transfer, etc. with cooling water such as LLC (Long Life Coolant), etc. This is a broad concept including, for example, converting exhaust heat to mechanical energy, generating electric energy from exhaust heat by a heat pump, a thermoelectric conversion module, and the like. Note that exhaust heat may be taken from the exhaust by performing heat exchange directly between the exhaust and the cooling water.

  Here, in particular, in order to activate the catalytic reaction related to the first catalyst, a catalyst temperature equal to or higher than a predetermined activation temperature is required. For example, the first catalyst and the exhaust heat recovery means are physically connected in series. In the case where the catalyst is disposed, the heat supply to the catalyst is hindered by recovering the exhaust heat. For example, when the catalyst temperature is relatively low at the time of cold or starting, the catalyst temperature When the temperature is higher than the activation temperature, the emission and power performance may be degraded.

  However, according to the exhaust heat recovery apparatus for an internal combustion engine according to the present invention, the exhaust heat recovery means is installed in the reflux pipe branched from the inner cylinder portion and connected to the upstream side of the outer cylinder portion. Accordingly, the relatively low-temperature exhaust gas from which the exhaust heat has been recovered by the exhaust heat recovery means is caused by heat radiation from the outer wall of the inner cylinder portion in the process of guiding the above-described space toward the first catalyst, or The temperature is raised again by heat transfer due to physical contact with the outer wall of the inner cylinder portion. That is, the high temperature exhaust gas that has passed through the inner cylinder portion without branching to the reflux pipe and the exhaust gas that has been raised in temperature while recovering the exhaust heat by the exhaust heat recovery means flow into the first catalyst. It becomes.

  For this reason, according to the exhaust heat recovery apparatus for an internal combustion engine according to the present invention, the exhaust heat recovery by the exhaust heat recovery means is caused to manifest the trouble due to the impediment to the temperature rise of the first catalyst in practice. It becomes possible to execute without. That is, the catalyst warm-up related to the first catalyst and the exhaust heat recovery can be performed independently of each other, and both are compatible.

  Note that the material, physical shape, and spatial positional relationship of the inner cylinder part and the outer cylinder part are the first in a state where the exhaust gas after exhaust heat recovery led to the above-described space is at least somewhat heated. There is no limitation as long as it can be led to the catalyst. For example, the outer wall of the inner cylinder part may have a shape that can increase the surface area, such as unevenness and fins for heat dissipation, so that heat radiation from the inner cylinder part is performed more efficiently and effectively. .

  In one aspect of the exhaust heat recovery apparatus for an internal combustion engine of the present invention, the internal combustion engine is installed in the inner cylinder portion in a section upstream from the branch position and downstream from the joining position, The 2nd catalyst which can purify is provided.

  According to this aspect, the internal combustion engine includes, for example, a three-way catalyst installed in the inner cylinder portion in a section of the inner cylinder portion that is upstream from the aforementioned branch position and downstream from the aforementioned merging position. In addition, there is provided a second catalyst that can take various forms such as NOx storage reduction catalyst, oxidation catalyst, or DPF, or various forms such as S / C catalyst or U / F catalyst as a name derived from the installation location. Exhaust gas that has flowed into the inner cylinder portion passes through the second catalyst, and after being purified, the exhaust gas is discharged from the inner cylinder portion.

  Here, in view of the fact that the second catalyst is upstream of the first catalyst, as a preferred embodiment, the second catalyst is an S / C catalyst configured as a three-way catalyst, This catalyst is also a U / F catalyst configured as a three-way catalyst. In this case, the exhaust state of the noble metal is used so that the exhaust gas can be sufficiently purified by the second catalyst and the first catalyst can purify, for example, NOx that cannot be completely removed by the second catalyst. It is determined.

  In this configuration, since the exhaust heat is preferentially provided for warming up the second catalyst, the exhaust heat related to the exhaust gas flowing into the first catalyst is attenuated accordingly, and the exhaust heat recovery is performed. The exhaust heat recoverable by means can also be reduced accordingly. On the other hand, since the second catalyst is installed on the upstream side of the branch position, the exhaust led through the exhaust pipe passes through the second catalyst before the exhaust heat is recovered. For this reason, the warm-up of the second catalyst is substantially completely unaffected by the recovery of the exhaust heat more than the warm-up of the first catalyst.

  That is, according to this aspect, as much exhaust heat as possible is recovered from the exhaust while the exhaust is practically sufficiently purified by the second catalyst, and further, the exhaust heat is recovered by the first catalyst. Practical benefits such as reducing the impact on warm-up as much as possible are provided.

  In another aspect of the exhaust heat recovery apparatus for an internal combustion engine according to the present invention, the exhaust heat recovery means performs heat exchange with cooling water of the internal combustion engine as at least part of the recovery of the exhaust heat.

  According to this aspect, the exhaust heat recovery means is configured to be able to exchange heat with cooling water such as LLC that is used for cooling the internal combustion engine. At this time, the exhaust heat imparted to the cooling water is used for heating the passenger compartment, for example, through heat supply to a heater core or the like.

  The internal combustion engine cooling system is a system that is installed regardless of whether or not exhaust heat is recovered, and a part of the cooling system or the like is newly installed so that heat can be exchanged with the exhaust heat recovery means. Regardless of whether or not it is necessary to extend or expand the exhaust heat, when exhaust heat is recovered in the form of using a part of the existing system in this way, the physical and mechanical of the exhaust heat recovery means It becomes possible to make the electrical or chemical configuration relatively small, and more efficient and effective utilization of exhaust heat is promoted.

  In another aspect of the exhaust heat recovery apparatus for an internal combustion engine according to the present invention, flow rate control means capable of controlling the flow rate of the recirculated exhaust gas, and the flow rate changes according to operating conditions of the internal combustion engine. And a control means for controlling the flow rate control means.

  In view of the fact that the reflux pipe needs to return the exhaust gas to the upstream side, the flow resistance of the inner cylinder portion tends to be at least smaller than the flow resistance of the reflux pipe. Therefore, the amount of exhaust gas recirculated through the recirculation pipe branched from the branch position (hereinafter referred to as “recirculation amount” as appropriate) tends to be smaller than the amount of exhaust gas that passes through the inner cylinder portion without flowing into the recirculation pipe. Also, it is difficult to control the desired characteristics relatively.

  Therefore, in this aspect, for example, a flow rate control unit that can take the form of an electromagnetic on-off valve, a butterfly valve, or the like is provided. For example, various processing units such as an ECU (Electronic Control Unit), various controllers, microcomputer devices, and the like. For example, the flow rate of the exhaust gas can be variably controlled by receiving, for example, physical, mechanical, or electrical control via a control unit that can be configured as a computer system or the like.

  At this time, the control means, for example, according to various operating conditions of the internal combustion engine that are associated with the recirculation amount in advance, such as the temperature of the first catalyst, the temperature of the second catalyst, or the temperature of the cooling water. For example, the recirculation amount of the exhaust gas is controlled continuously, stepwise, or in a binary manner according to an index value that defines operating conditions.

  Therefore, according to this aspect, for example, when a relatively large recirculation amount is required, the recirculation amount increases. For example, when the necessity for recirculating exhaust gas is low, the recirculation amount is relatively high. Therefore, it is possible to control the amount of reflux so that it decreases to a minimum.

  In an aspect of the exhaust heat recovery apparatus for an internal combustion engine according to the present invention, comprising the flow rate control means, the flow rate control means is installed in at least one of the return pipe and the inner cylinder portion, and the return according to the open / close state Including a first on-off valve that controls a communication state between the pipe and the inner cylinder portion, and the control means controls the on-off state of the first on-off valve in accordance with the operating condition.

  According to this aspect, for example, depending on whether the first on-off valve is open or closed, which can take the form of an electromagnetic on-off valve, for example, depending on whether the valve is open or closed, the return pipe and the inner cylinder portion The communication state between is controlled. Since the communication state between the reflux pipe and the inner cylinder part greatly affects the exhaust gas recirculation amount, the control of the exhaust gas recirculation amount is compared when the flow control means includes the first on-off valve. It is possible to make it simple and convenient.

  The “communication state” is not limited to the communication area between the reflux pipe and the inner cylinder part, but relates to at least one of the reflux pipe and the inner cylinder part, and defines the exhaust gas recirculation amount in the reflux pipe. It is a concept that includes a wide range of situations. That is, the communication state is intended to include, for example, the opening area of the inner cylinder portion on the downstream side of the branch position in addition to the communication area between the reflux pipe and the inner cylinder portion. For example, in view of the above-described channel resistance and the like, if the opening area is large, the reflux amount can be small even if the communication area is the same.

  In another aspect of the exhaust heat recovery apparatus for an internal combustion engine according to the present invention, comprising the flow rate control means, the flow rate control means is installed in at least one of the return pipe and the outer cylinder part, and the It includes a second on-off valve that controls the communication state between the reflux pipe and the outer cylinder portion, and the control means controls the on-off state of the second on-off valve according to the operating condition.

  According to this aspect, for example, depending on whether the second on-off valve is open or closed, which can take the form of an electromagnetic on-off valve, for example, depending on whether the valve is open or closed, The communication state between is controlled. Since the communication state between the reflux pipe and the outer cylinder part greatly affects the exhaust gas recirculation amount, the control of the exhaust gas recirculation amount is compared when the flow control means includes the second on-off valve. It is possible to make it simple and convenient.

  In addition, since the inner cylinder part, the reflux pipe, and the outer cylinder part are in communication with each other, for example, the function of the first on-off valve described above can be replaced by the second on-off valve. The function of the second on-off valve can be replaced by the first on-off valve described above. However, when both the first and second on-off valves are provided, it is possible to more reliably suppress exhaust gas recirculation, which is preferable.

  When both the first and second on-off valves are provided in this way, the first on-off valve is downstream of the exhaust heat recovery means in the reflux pipe (upstream if the recirculated exhaust is used as a reference). For example, the second on-off valve may be installed in the vicinity of the branch position, and the second on-off valve may be installed upstream of the exhaust heat recovery means in the reflux pipe (on the downstream side when the refluxed exhaust is used as a reference), for example, in the vicinity of the merge position. Good.

  In another aspect of the exhaust heat recovery apparatus for an internal combustion engine according to the present invention, comprising a flow rate control means, it comprises first specifying means for specifying the temperature of the first catalyst, and the control means is specified. When the temperature of the first catalyst is lower than a predetermined value, the flow rate control means is controlled so that the exhaust does not recirculate through the reflux pipe.

  According to this aspect, the temperature of the first catalyst specified by the first specifying means that can be configured as various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device is, for example, the catalyst activation temperature. Alternatively, when the first catalyst is lower than a predetermined value defined as a temperature or the like set in advance so that the first catalyst can operate sufficiently effectively in practice, the control means prevents the exhaust from recirculating through the recirculation pipe. The flow rate control means is controlled. That is, exhaust gas recirculation is prohibited. Accordingly, the exhaust gas guided through the inner cylinder portion predominantly flows into the first catalyst, and warming up of the first catalyst is promoted.

  If priority is given to warming up the first catalyst in this way, exhaust heat cannot be recovered, so the recovered exhaust heat is used secondarily, for example, the operation of a secondary device such as a heater. Can be hindered. However, in this aspect, it is possible to supply heat enough to warm up the first catalyst while recovering exhaust heat to the last. The warming up of the catalyst is only a top priority.

  Therefore, for example, when a relatively urgent exhaust heat recovery request is made, the first catalyst is warmed up, at least the temperature of the first catalyst is lowered, and a practical problem may occur. It is also possible to quickly recover the exhaust heat while continuing without making it manifest. That is, for example, this aspect is clearly advantageous compared to the case where exhaust heat recovery must be stopped to warm up the first catalyst.

  The “specific” according to the present invention means, for example, detecting directly or indirectly as a physical numerical value or an electrical signal corresponding to the physical numerical value through some detecting means, appropriate storage means, etc. Select or estimate the corresponding numerical value from the map etc. stored in the above, and the logic according to the preset algorithm or calculation formula from the detected physical numerical value or electrical signal or the selected or estimated numerical value A broad concept encompassing derivation as a result of computation, numerical computation, or electrical or mechanical control, or simply obtaining a value detected, selected, estimated or derived as an electrical signal, etc. It is. Within the scope of such a concept, the first specifying means obtains the temperature detected by, for example, a temperature sensor provided upstream or downstream of the first catalyst, for example, as an electric signal, etc. The temperature of the catalyst is specified.

  In another aspect of the exhaust heat recovery apparatus for an internal combustion engine according to the present invention, comprising the flow rate control means, the internal combustion engine is located in the section upstream of the branch position and downstream of the junction position. Provided with a second catalyst capable of purifying the exhaust, and the exhaust heat recovery device for the internal combustion engine further includes a second specifying means for specifying the temperature of the second catalyst. The control means controls the flow rate control means so that the exhaust gas recirculates through the reflux pipe when the temperature of the specified second catalyst is equal to or higher than a predetermined value.

  According to this aspect, for example, the temperature of the second catalyst specified by the second specifying unit that can be configured as various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device, The flow rate control means is controlled by the control means so that the exhaust gas recirculates through the recirculation pipe when the temperature is higher than a predetermined value defined as a temperature that is high enough to cause failure, damage or damage of the catalyst due to heat load. .

  At this time, the outer wall portion of the inner cylinder portion where the second catalyst is installed and the outer wall portion of the second catalyst are in contact with the exhaust gas relatively cooled via the reflux pipe, and the outer wall portion is in contact with the outer wall portion. Since the temperature of the exhaust gas flowing into the second catalyst and the temperature of the second catalyst are reduced by heat exchange, the second catalyst can be protected from an excessive heat load. When the internal combustion engine includes the second catalyst, exhaust gas is directly supplied to the second catalyst via the exhaust pipe, and the second catalyst is easily exposed to a relatively high temperature. High profit is provided by being made.

  In another aspect of the exhaust heat recovery apparatus for an internal combustion engine according to the present invention, comprising a flow rate control means, further comprising a third specifying means for specifying the temperature of the cooling water of the internal combustion engine, wherein the exhaust heat recovery means Heat exchange is performed with the cooling water as at least a part of the recovery of the exhaust heat, and the control means is configured such that when the temperature of the specified cooling water is equal to or higher than a predetermined value, the exhaust is recirculated. The flow rate control means is controlled so as not to reflux the pipe.

  According to this aspect, for example, the temperature of the cooling water specified by the third specifying means that can be configured as various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device, The flow rate control means is controlled by the control means so that the exhaust gas does not recirculate through the recirculation pipe when the temperature is equal to or higher than a predetermined value defined as a temperature that is high enough to cover the operation. That is, exhaust gas recirculation is prohibited.

  Exhaust heat directly or indirectly applied to the cooling water by heat exchange is, for example, when the temperature of the cooling water is secured to such an extent that the secondary device can be driven, for example, via a heat radiating means such as a radiator. Therefore, it is difficult to obtain a significant effect. In addition, an increase in the load of the heat radiating means tends to become obvious. Furthermore, if the amount of recovered heat is large, boiling of the cooling water and accompanying overheating of the internal combustion engine may be caused.

  Therefore, by controlling the operation of the flow rate control means based on the temperature of the cooling water in this way, it is possible to recover the exhaust heat more efficiently and effectively while ensuring the safety of the internal combustion engine. It becomes.

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

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

  In FIG. 1, an engine system 10 is mounted on a vehicle (not shown) and includes an ECU 100 and an engine 200.

  The ECU 100 is an electronic control unit that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and is configured to be able to control the entire operation of the engine 200. It is an example of “first specifying means”, “second specifying means”, “third specifying means”, and “control means”. The ECU 100 is configured to be able to execute exhaust heat recovery control described later according to a control program stored in the ROM.

  The engine 200 is a gasoline engine that functions as a power source for a vehicle, and is an example of an “internal combustion engine” according to the present invention. The engine 200 causes the air-fuel mixture to explode by the ignition operation of the ignition device 202 in which a part of the spark plug that is part of the cylinder 201 is exposed, and the reciprocating motion of the piston 203 that occurs according to the explosion force It can be converted into a rotational motion of the crankshaft 205 via the rod 204. A crank position sensor 206 that detects the rotational position of the crankshaft 205 is installed in the vicinity of the crankshaft 205. The crank position sensor 206 is electrically connected to the ECU 100, and the ECU 100 can control the ignition timing of the ignition device 202 based on the rotational position of the crankshaft 205 detected by the crank position sensor 206. It is configured. Further, the ECU 100 is configured to be able to calculate the engine speed Ne of the engine 200 based on the rotational position of the crankshaft 205. Below, the principal part structure of the engine 200 is demonstrated with a part of the operation | movement.

  When the fuel in the cylinder 201 is burned, the air sucked from the outside passes through the intake pipe 207 and is mixed with the fuel injected from the injector 214 at the intake port 213 to become the above-mentioned air-fuel mixture. The fuel is stored in the fuel tank 215 and is pumped and supplied to the injector 214 via the delivery pipe 216 by the action of the feed pump 217. The injector 214 is electrically connected to the ECU 100, and is configured to be able to inject the supplied fuel into the intake port 213 according to the control of the ECU 100.

  The communication state between the inside of the cylinder 201 and the intake pipe 207 is controlled by opening and closing the intake valve 218. The air-fuel mixture combusted in the cylinder 201 becomes exhaust gas and is guided to the exhaust pipe 221 via the exhaust port 220 when the exhaust valve 219 that opens and closes in conjunction with opening and closing of the intake valve 218 is opened.

  A cleaner 208 is disposed on the intake pipe 207 to purify air sucked from the outside. An air flow meter 209 is disposed on the intake pipe 207. The air flow meter 209 has a form called a hot wire type, and is configured to be able to directly detect the mass flow rate of the sucked air (that is, the intake air amount). The air flow meter 209 is electrically connected to the ECU 100, and the detected mass flow rate of the intake air is grasped by the ECU 100 continuously or at a constant or indefinite period.

  The intake pipe 207 is further provided with a throttle valve 210 that can adjust the amount of intake air. The throttle valve 210 is configured to be opened / closed by a throttle valve motor 211, and a throttle opening degree indicating the opened / closed state is detected by a throttle position sensor 212.

  Note that the throttle position sensor 212 is electrically connected to the ECU 100, and the detected throttle opening degree is constantly recognized by the ECU 100 at a constant or indefinite period. Further, the ECU 100 controls the driving state of the throttle valve motor 211 based on an accelerator opening detected by an unillustrated accelerator position sensor.

  The throttle valve 210 is an electronically controlled throttle valve that is driven by the driving force of the throttle valve motor 211 controlled by the ECU 100. The throttle opening is determined by the ECU 100 according to the driver's intention (that is, the accelerator opening). ) Can be controlled independently.

  An S / C catalyst 223 is installed in the exhaust pipe 221. The S / C catalyst 223 is a three-way catalyst configured to be able to purify CO (carbon monoxide), HC (hydrocarbon), and NOx (nitrogen oxide) discharged from the engine 200, It is an example of a “second catalyst” according to the present invention. In the vicinity of the S / C catalyst 223, a temperature sensor 224 configured to detect the catalyst temperature Tsc that is the temperature of the S / C catalyst 223 is installed. The temperature sensor 224 is electrically connected to the ECU 100, and the detected catalyst temperature Tsc is grasped by the ECU 100 constantly or at a constant or indefinite period.

  A U / F catalyst 225 is further installed in the exhaust pipe 221. The U / F catalyst 225 is a three-way catalyst installed under the floor of the vehicle and configured to purify CO, HC and NOx discharged from the engine 200 in the same manner as the S / C catalyst 223. It is an example of a “first catalyst” according to the present invention. Further, in the vicinity of the U / F catalyst 225, a temperature sensor 226 configured to detect the catalyst temperature Tuf, which is the temperature of the U / F catalyst 225, is installed. The temperature sensor 226 is electrically connected to the ECU 100, and the detected catalyst temperature Tuf is grasped by the ECU 100 constantly or at a constant or indefinite period. The detailed configuration of the peripheral portions of the S / C catalyst 223 and the U / F catalyst 225 will be described in detail later with reference to FIG.

  An air-fuel ratio sensor 222 is disposed in the exhaust pipe 221. The air-fuel ratio sensor 222 is configured to detect the air-fuel ratio of the engine 200 from the exhaust gas discharged through the exhaust port 220. The air-fuel ratio sensor 222 is electrically connected to the ECU 100, and the detected air-fuel ratio is grasped by the ECU 100 constantly or at a constant or indefinite period.

  In addition, a water jacket installed in a cylinder block that accommodates the cylinder 201 is used to detect a temperature (hereinafter referred to as “cooling water temperature”) Tw of cooling water (that is, LLC) for cooling the engine 200. Temperature sensor 227 is provided. The temperature sensor 227 is electrically connected to the ECU 100, and the detected cooling water temperature Tw is grasped by the ECU 100 constantly or at a constant or indefinite period.

  The cooling water of the engine 200 is circulated and supplied by, for example, a pumping means such as an electric water pump so that a predetermined cooling target portion of the engine 200 is cooled while including the water jacket as a part of the circulation path. In the circulation process, for example, heat exchange can be performed with an exhaust heat recovery device 300 described later.

  The cooling water is configured to be able to exchange heat with a heater core (not shown). In this heater core, the temperature of the air sucked into the air conditioning duct (not shown) is raised by the heat acquired from the cooling water. The heated air is blown into the passenger compartment from an air-conditioning outlet such as a defroster or a register. That is, in the present embodiment, the cooling water of the engine 200 functions as a heat supply source for a secondary device that uses exhaust heat, such as a heating device that is used for heating the passenger compartment.

  The engine system 10 is further provided with an exhaust heat recovery device 300 so that a part of the exhaust heat can be recovered. Here, the detailed configuration of the exhaust heat recovery apparatus 300 will be described with reference to FIG. FIG. 2 is a schematic configuration diagram conceptually showing the configuration of the exhaust heat recovery apparatus 300. In the figure, the same reference numerals are given to the same portions as those in FIG. 1, and the description thereof will be omitted as appropriate.

  In FIG. 2, the exhaust heat recovery apparatus 300 is provided in the exhaust pipe 221 around the S / C catalyst 223 and the U / F catalyst 225 described above, and stores the exhaust heat of the exhaust led through the exhaust pipe 221. Furthermore, it is possible to recover exhaust heat by applying at least a part of the stored exhaust heat to the cooling water of the engine 200 by heat exchange. It is an example of an “exhaust heat recovery device”.

  The exhaust heat recovery apparatus 300 includes an inner cylinder part 310, an outer cylinder part 320, a reflux pipe 330, a heat exchanger 340, a first control valve 350, and a second control valve 360.

  The inner cylinder part 310 communicates with the exhaust pipe 221 by connecting the upstream end part to the exhaust pipe 221 via a flange (not shown) and the like, and the downstream end part is inside the outer cylinder part 320. It is a metal cylindrical member formed by opening in the. In addition, the S / C catalyst 223 described above is installed in the inner cylinder portion 310, and the exhaust led through the exhaust pipe 221 is purified by the S / C catalyst 223, and then the downstream end. It is the structure discharged | emitted from a part.

  The outer cylindrical portion 320 is concentric with the inner cylindrical portion 310 when viewed in a cross section orthogonal to the paper surface, and the inner cylindrical portion 310 is separated from the inner cylindrical portion 310 by a space (hereinafter referred to as “reflux space” as appropriate). It is a metal cylindrical member which accommodates the whole. The upstream end portion of the outer cylindrical portion 320 is physically closed by, for example, a flange that penetrates the inner cylindrical portion 310 so as to communicate with the exhaust pipe 221, and the U / F at the downstream end portion. The catalyst 225 is in communication. That is, the above-described reflux space communicates with the U / F catalyst 225.

  The reflux pipe 330 is a tubular member that branches off from the inner cylinder portion 310 at a branch position (reference numeral omitted) set on the inner cylinder portion 310 on the downstream side of the S / C catalyst 223. The reflux pipe 330 is connected to the outer cylinder part 320 at the junction position (reference numeral omitted) set on the upstream side of the S / C catalyst 223 in the outer cylinder part 320, starting from the branch position. 320 is configured to communicate with 320.

  The exhaust heat recovery unit 340 is an example of the “exhaust heat recovery means” according to the present invention, which is provided on the reflux pipe 330 and configured to recover the exhaust heat from the exhaust gas flowing through the reflux pipe. The exhaust heat recovery unit 340 has a configuration in which a plurality of stainless steel matrix members (or mesh members) as heat storage materials are stacked, and heat transfer from the exhaust gas when the exhaust gas passes through the matrix member. It is possible to take away at least a part of the exhaust heat through the air. Further, the flow loss and the pressure loss of the exhaust heat recovery unit 340 are determined so that the magnitude of the exhaust resistance does not become practical.

  In the exhaust heat recovery unit 340, a cooling water pipe (not shown) of the engine 200 is stretched around the matrix member. The cooling water pipe is installed so that sufficient heat exchange can be performed between the exhaust heat recovery unit 340 (remarkably the matrix member) and the cooling water, and is deprived by the matrix member to store heat. The exhaust heat is applied to the cooling water as efficiently as possible, and the exhaust heat is collected.

  The cooling water pipe is configured to flow from the cooling water pipe 227A communicating with the above-described cooling water circulation system such as the water jacket and similarly discharged to the cooling water pipe 227B communicating with the cooling water circulation system. Further, as described above, the cooling water of the engine 200 is configured to be used as a heat source of various secondary devices (not shown) such as a heater device for heating the vehicle interior. The configuration of the exhaust heat recovery unit 340 is not limited as long as the exhaust heat can be recovered by applying the exhaust heat to the cooling water.

  The first control valve 350 is an electromagnetic on-off valve installed at the above-described branch position in the inner cylinder portion 310, and is an example of the “flow control means” and the “first on-off valve” according to the present invention.

  The first control valve 350 is configured to be able to take a fully open state and a fully closed state as its open / close state. In the fully open state, the first control valve 350 allows the inner cylinder portion 310 and the reflux pipe 330 to communicate with each other, and the fully closed state. In this state, the communication between the inner cylinder part 310 and the reflux pipe 330 can be blocked. The first control valve 350 is electrically connected to the ECU 100 (not shown in FIG. 2), and receives the electrical control from the ECU 100 to control the above-described binary open / close state. Yes.

  The second control valve 360 is an electromagnetic on-off valve installed at the above-described merging position in the outer cylinder portion 320, is another example of the “flow control means” according to the present invention, and is a “second on-off valve”. It is an example.

  The second control valve 360 is configured to be able to take a fully open state and a fully closed state as its open / closed state. In the fully open state, the second control valve 360 communicates the outer cylinder part 320 and the reflux pipe 330 with each other and is fully closed. In this state, the communication between the outer cylindrical portion 320 and the reflux pipe 330 can be blocked. The second control valve 350 is electrically connected to the ECU 100 (not shown in FIG. 2), and is configured to control the above-described binary open / close state under electrical control by the ECU 100. Yes.

<Operation of Embodiment>
The ECU 100 executes exhaust heat recovery control for controlling the operation of the exhaust heat recovery apparatus 300 having the above configuration in accordance with a control program stored in the ROM. Here, the details of the exhaust heat recovery control will be described with reference to FIG. FIG. 3 is a flowchart for explaining the flow of processing in the exhaust heat recovery control.

  In FIG. 3, the ECU 100 first determines whether or not the catalyst temperature Tsc is equal to or lower than a predetermined upper limit temperature Tscth (step A10). The S / C catalyst 223 is on the upstream side of the U / F catalyst 225 installed under the floor, and the temperature of the inflowing exhaust gas tends to be high. Therefore, depending on the operating conditions, environmental conditions, and the like of the engine 200, a physical, mechanical, or chemical malfunction such as a catalyst carrier erosion due to a thermal load may occur. The upper limit temperature Tscth is previously set experimentally, empirically, theoretically, or based on simulations, for example, as a temperature at which such a problem may become apparent when it continues for a predetermined time or longer.

  When the catalyst temperature Tsc is higher than the upper limit temperature Tscth (step A10: NO), the ECU 100 determines that the S / C catalyst 223 is exposed to an excessive heat load, and executes the exhaust heat recovery mode (step). A13).

  Here, the details of the exhaust heat recovery mode will be described with reference to FIG. FIG. 4 is a schematic configuration diagram conceptually illustrating the exhaust flow in one operation state of the exhaust heat recovery apparatus 300. In the figure, the same reference numerals are given to the same portions as those in FIG. 2, and the description thereof will be omitted as appropriate.

  In FIG. 4, when executing the exhaust heat recovery mode, the ECU 100 controls the first control valve 350 and the second control valve 360 to the fully opened state described above. FIG. 4 shows the state of the exhaust heat recovery apparatus 300 when each control valve is controlled to be fully opened.

  When the exhaust heat recovery mode is executed, the exhaust path guided through the exhaust pipe 221 includes an exhaust path corresponding to the exhaust ExA indicated by the solid line and an exhaust path corresponding to the exhaust ExB indicated by the broken line. The exhaust gas follows each exhaust path and finally flows into the U / F catalyst 225.

  Here, the exhaust paths will be described in detail. Exhaust gas guided from the exhaust pipe 221 passes through the inner cylinder portion 310 and the S / C catalyst 223 on the upstream side of the S / C catalyst 223, and then at a predetermined branch position. The exhaust ExA flows directly into the U / F catalyst 223 without being guided to the reflux pipe 330, and the exhaust ExB is guided to the reflux pipe 330 via the first control valve 350.

  The exhaust ExB led to the reflux pipe 330 is refluxed through the reflux pipe 330 and led to the above-described reflux space inside the outer cylinder part 320 via the second control valve 360, and from this reflux space to the U / F catalyst 225. Inflow. Here, since the exhaust heat recovery unit 340 is installed in the reflux pipe 330, the exhaust ExB is deprived of a part of the exhaust heat by the matrix member in the process of passing through the exhaust heat recovery unit 340. The exhaust heat stored in this matrix member flows into the cooling water by heat exchange with the cooling water flowing into the exhaust heat recovery device 340 from the cooling water tube 227A and discharged from the exhaust heat recovery device 340 via the cooling water tube 227B. Granted and collected. Thus, the cooling water to which the exhaust heat is applied is used as a heat source of a heater device for heating the interior of the vehicle, for example, and efficient use of energy is promoted.

  On the other hand, since the exhaust ExB guided to the reflux space is deprived of heat by the exhaust heat recovery device 340, the exhaust ExB is significantly cooled compared to the exhaust ExA immediately after being guided to the reflux space. Here, since the merging position related to the reflux pipe 330 is set on the upstream side of the S / C catalyst 223, the exhaust ExB in the relatively cooled state is separated from the outer wall portion of the S / C catalyst 223. While the S / C catalyst 223 is cooled by contact, in other words, while the temperature is raised by heat exchange with the S / C catalyst 223, the reflux space proceeds downstream, that is, toward the U / F catalyst 225. .

  Returning to FIG. 3, when the catalyst temperature Tsc is higher than the upper limit temperature Tscth, the exhaust heat recovery mode is executed, whereby the S / C catalyst 223 is relatively cooled, and the S due to a high heat load is generated. / C catalyst 223 can be avoided.

  On the other hand, when the catalyst temperature Tsc is equal to or lower than the upper limit temperature Tscth (step A10: YES), the ECU 100 further determines whether or not the catalyst temperature Tuf is higher than a predetermined lower limit temperature Tufth (step A11).

  Each of the U / F catalyst 225 and the S / C catalyst 223 preferably performs exhaust in a temperature range above a predetermined catalyst activation temperature (a concept that can be easily replaced with “greater” depending on the setting of the catalyst activation temperature). While it can be purified, the exhaust purification efficiency is significantly reduced in a temperature range below the catalyst activation temperature (which is a concept that can be easily replaced with “below” depending on the setting of the catalyst activation temperature). The lower limit temperature Tufth is set, for example, as a value associated with the catalyst activation temperature, and for example, the catalyst activation temperature itself or a margin on the safe side (that is, higher side) than the catalyst activation temperature is provided. The temperature is set.

  Note that since the U / F catalyst 225 is located downstream of the S / C catalyst 223, the catalyst temperature Tuf is basically lower than the catalyst temperature Tsc. Therefore, only the catalyst temperature Tuf, which is the temperature of the U / F catalyst 225, is referred to in the determination processing according to step A11.

  When the catalyst temperature Tuf is higher than the lower limit temperature Tufth (step A11: YES), that is, when it can be considered that the catalytic activity of the U / F catalyst 225 is secured, the ECU 100 further sets the cooling water temperature Tw of the engine 200 to a predetermined value. It is determined whether or not the upper limit temperature Twth is below (step A12).

  A secondary device such as a heater that uses the heat of the cooling water cannot operate effectively unless the cooling water has a certain amount of heat (that is, if the cooling water temperature does not exceed a certain level). On the other hand, in a state where the cooling water has excessive heat (that is, an excessively high temperature), the excessive heat is only radiated by the heat radiating means such as a radiator installed in the cooling water circulation system. Yes, the disadvantage of overloading the radiator can become more obvious than the benefit of supplying a heat source to such a secondary device. In addition, when the exhaust heat that exceeds the heat dissipation capability of the radiator is recovered, the temperature of the cooling water rises excessively and may cause overheating of the engine 200, for example.

  The upper limit temperature Twth according to step A12 is a temperature set from such a viewpoint, and for example, experimentally, empirically, theoretically, or based on simulations in advance, the exhaust heat is practically applied to the cooling water. It is set to a temperature at which it can be determined that it is not necessary to apply, or to a temperature at which the cooling water may boil if, for example, it continues for a predetermined time or longer. For example, the upper limit temperature Twth is set to a value that is slightly lower than a value around 90 ° C., which is a typical steady state temperature of cooling water, for example, around 80 ° C.

  When the cooling water temperature Tw is equal to or lower than the upper limit temperature Twth (step A12: YES), the ECU 100 determines that it is still necessary to provide exhaust heat to the cooling water (or has an advantage), and the exhaust heat described above. The collection mode is executed (step A13).

  Here, returning to FIG. 4 and supplementing the exhaust heat recovery mode, the exhaust ExB subjected to heat exchange with the cooling water is heated by the S / C catalyst 223 and the inner cylinder portion 310 in the process of returning to the return space. The temperature is raised by replacement. Therefore, at the time of flowing into the U / F catalyst 225, the temperature of the exhaust ExB is maintained at least to the extent that the U / F catalyst 225 does not reveal a malfunction due to a decrease in the catalyst temperature. Therefore, according to the exhaust heat recovery mode, the exhaust heat can be recovered without impeding the operation of the U / F catalyst 225, that is, independently from the warm-up of the U / F catalyst 225.

  Returning to FIG. 3, when the catalyst temperature Tuf is lower than the lower limit temperature Tufth (step A11: NO), or when the cooling water temperature Tw is higher than the upper limit temperature Twth even if the catalyst temperature Tuf is higher than the lower limit temperature Tufth (step A12: NO), ECU 100 executes the exhaust heat non-recovery mode (step A14).

  Here, the exhaust heat non-recovery mode will be described with reference to FIG. FIG. 5 is a schematic configuration diagram conceptually illustrating the flow of exhaust gas in another operation state of the exhaust heat recovery apparatus 300. In the figure, the same reference numerals are given to the same portions as those in FIG. 4, and the description thereof will be omitted as appropriate.

  In FIG. 5, when executing the exhaust heat non-recovery mode, the ECU 100 controls the first control valve 350 and the second control valve 360 to the fully closed state described above. FIG. 5 shows the state of the exhaust heat recovery apparatus 300 when each control valve is controlled to be fully closed.

  When the exhaust heat non-recovery mode is executed, the first control valve 350 and the second control valve 360 are fully closed, so that almost all of the exhaust guided through the exhaust pipe 221 passes through the inner cylinder portion 310. The exhaust ExA flows into the U / F catalyst 225. Since the temperature of the exhaust ExA is higher than that of the exhaust ExB, relatively high-temperature exhaust flows into the U / F catalyst 225, and the catalyst warm-up is further promoted. When the exhaust heat non-recovery mode is executed in response to the request for the cooling water temperature Tw, there is no need for such catalyst warm-up. However, if the cooling water temperature Tw is too high as described above, the load on the radiator and the like increases. Therefore, the exhaust heat recovery is prohibited in the exhaust heat non-recovery mode.

  Returning to FIG. 3, when the exhaust heat recovery mode or the exhaust heat non-recovery mode is executed, the ECU 100 returns the process to step A10 and repeats a series of processes.

  As described above, according to the exhaust heat recovery apparatus 300 and the exhaust heat recovery control according to the present embodiment, the exhaust heat recovery mode and the exhaust heat non-recovery mode include the S / C catalyst 223, the U / F catalyst 225, and the cooling water. It can be switched selectively as appropriate in consideration of the temperature state. For this reason, it is possible to optimize these temperature states as much as possible. Further, even if the exhaust heat recovery is performed in the exhaust heat recovery mode, the temperature of the exhaust (that is, the exhaust ExB) is raised in the reflux space, so that the recovery of the exhaust heat causes the temperature of the U / F catalyst 225 to decrease. The possibility is low enough to be ignored in practice. That is, it is possible to achieve both warming up of the catalyst and recovery of exhaust heat.

  In this embodiment, the S / C catalyst 223 and the U / F catalyst 225 are provided as the catalyst device of the engine 200, and the exhaust gas passes through the S / C catalyst 223 before the exhaust heat is recovered. However, the above-described effect relating to the exhaust heat recovery apparatus 300 is ensured even when such a configuration is not adopted. For example, a branch position for branching to the reflux pipe may be set on the upstream side of the S / C catalyst.

  In this embodiment, the exhaust heat non-recovery mode is set as a mode opposite to the exhaust heat recovery mode and is appropriately executed by the ECU 100. However, as described above, the configuration of the present embodiment is used. Therefore, the recovery of the exhaust heat does not significantly inhibit the warming up of the U / F catalyst 225 (that is, the U / F catalyst 225 is not significantly cooled by the exhaust gas recirculated through the reflux space). From the viewpoint of catalyst warm-up, the exhaust heat non-recovery mode may not necessarily be executed.

  In the present embodiment, the first control valve 350 and the second control valve 360 are each configured as an electromagnetic on-off valve that takes a binary state of full open or full close. The control valve 360 may be configured to be able to take an intermediate opening located between the fully open and fully closed positions, respectively. In this case, since the relative ratio between the exhaust gas recirculated through the recirculation pipe 330 and the exhaust gas ExA guided to the U / F catalyst 225 without recirculation through the recirculation pipe 330 can be continuously changed, the S / C catalyst 223, U / It becomes possible to control the temperature states of the F catalyst 225 and the cooling water more precisely.

  In view of the point that the exhaust gas needs to be recirculated (that is, typically reverse to the original flow of the exhaust gas), the flow resistance of the recirculation pipe 330 is compared with the flow resistance of the inner cylinder portion 310. It tends to be expensive. Therefore, it may be difficult to efficiently guide the exhaust gas to the reflux pipe 330 simply by opening and closing the first control valve 350. In such a case, at least the first control valve 350 may be configured as a multi-way valve such as a three-way valve. That is, when exhaust is led to the reflux pipe 330 (for example, when the exhaust heat recovery mode is executed), the multi-way valve is driven to drive the inner cylinder portion 310 and the U / F at the branch position or downstream of the branch position. Communication with the catalyst 225 may be blocked.

  The present invention is not limited to the above-described embodiment, 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. A heat recovery apparatus is also included in the technical scope of the present invention.

1 is a schematic configuration diagram of an engine system according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram conceptually showing a configuration of an exhaust heat recovery device provided in the engine system of FIG. 1. It is a flowchart explaining the flow of the process in the exhaust heat recovery control performed by ECU. It is a schematic block diagram which illustrates notionally the flow of the exhaust in one operation state of the exhaust heat recovery apparatus. It is a schematic block diagram which illustrates notionally the flow of the exhaust in the other operation state of an exhaust heat recovery apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine system, 100 ... ECU, 200 ... Engine, 223 ... S / C catalyst, 225 ... U / F catalyst, 227A, 227B ... Cooling water pipe, 300 ... Exhaust heat recovery device, 310 ... Inner cylinder part, 320 ... Outer A cylinder part, 330 ... recirculation pipe, 340 ... exhaust heat recovery device, 350 ... 1st control valve, 360 ... 2nd control valve.

Claims (9)

An exhaust heat recovery apparatus for an internal combustion engine that recovers exhaust heat in an internal combustion engine that includes an exhaust pipe that communicates with the inside of a cylinder and a first catalyst that can purify exhaust gas that is guided through the exhaust pipe. And
A cylindrical inner tube portion communicating with the exhaust pipe on the upstream side of the first catalyst and guiding the exhaust gas to the first catalyst;
A cylindrical outer cylinder part that covers the inner cylinder part so that a space is interposed, has an upstream end part closed, and communicates with the first catalyst at a downstream end part;
At the predetermined branching position, the air pipe branches from the inner cylinder part, communicates with the inside of the outer cylinder part at a predetermined merging position located upstream from the branching position, and returns at least a part of the exhaust gas to the space. A reflux tube,
An exhaust heat recovery device for an internal combustion engine, comprising: an exhaust heat recovery means that is installed in the return pipe and recovers the exhaust heat related to the exhaust that recirculates. The internal combustion engine includes a second catalyst that is installed in the inner cylinder portion in a section upstream from the branch position and downstream from the joining position and capable of purifying the exhaust gas. The exhaust heat recovery device for an internal combustion engine according to claim 1. The exhaust heat recovery means for an internal combustion engine according to claim 1 or 2, wherein the exhaust heat recovery means performs heat exchange with cooling water of the internal combustion engine as at least part of the recovery of the exhaust heat. apparatus. Flow rate control means capable of controlling the flow rate of the recirculated exhaust gas; and
The internal combustion engine according to any one of claims 1 to 3, further comprising: a control unit that controls the flow rate control unit so that the flow rate changes according to an operating condition of the internal combustion engine. Exhaust heat recovery device. The flow rate control means includes a first on-off valve that is installed in at least one of the reflux pipe and the inner cylinder part and controls a communication state between the reflux pipe and the inner cylinder part according to an open / close state. ,
The exhaust heat recovery apparatus for an internal combustion engine according to claim 4, wherein the control means controls an open / close state of the first on-off valve in accordance with the operating condition. The flow rate control means includes a second on-off valve that is installed in at least one of the reflux pipe and the outer cylinder part and controls a communication state between the reflux pipe and the outer cylinder part according to an open / close state. ,
The exhaust heat recovery apparatus for an internal combustion engine according to claim 4 or 5, wherein the control means controls an open / close state of the second open / close valve in accordance with the operating condition. Comprising first specifying means for specifying the temperature of the first catalyst;
The control means controls the flow rate control means so that the exhaust does not recirculate through the recirculation pipe when the temperature of the identified first catalyst is lower than a predetermined value. The exhaust heat recovery device for an internal combustion engine according to any one of claims 1 to 6. The internal combustion engine includes a second catalyst that is installed in the inner cylinder portion in a section upstream from the branch position and downstream from the merge position, and is capable of purifying the exhaust gas,
The exhaust heat recovery device of the internal combustion engine further includes a second specifying means for specifying the temperature of the second catalyst,
The control means controls the flow rate control means so that the exhaust gas recirculates through the recirculation pipe when the temperature of the specified second catalyst is equal to or higher than a predetermined value. The exhaust heat recovery device for an internal combustion engine according to any one of claims 1 to 7. Further comprising third specifying means for specifying the temperature of the cooling water of the internal combustion engine,
The exhaust heat recovery means performs heat exchange with the cooling water as at least part of the recovery of the exhaust heat,
The control means controls the flow rate control means so that the exhaust does not recirculate through the return pipe when the temperature of the specified cooling water is equal to or higher than a predetermined value. The exhaust heat recovery device for an internal combustion engine according to any one of the above.

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