JP2020056351A - EGR cooler - Google Patents

Abstract

To provide an EGR cooler that has a heat generating body including an organic metal structure and can efficiently and effectively controlling a temperature of EGR gas.SOLUTION: An EGR cooler includes: an EGR gas flow passage for causing EGR gas to flow; a refrigerant flow passage formed to exchange heat between the EGR gas flowing in the EGR gas flow passage and a refrigerant; a heat generating body accommodation part formed to cause at least a part of the heat generating body to come into contact with a wall surface of the EGR gas flow passage; a working gas tank for storing working gas; and a gas transfer device for transferring the working gas stored in the working gas tank from the working gas tank to the heat generating body accommodation part. The EGR cooler further includes an upstream side region and a downstream side region in the EGR gas flowing direction. In the EGR cooler, the heat generating body accommodation part is disposed in the downstream side region of the EGR cooler, and the heat generating body includes an organic metal structure.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an EGR cooler.

  2. Description of the Related Art In recent years, in an EGR (Exhaust Gas Recirculation) device for recirculating a part of exhaust gas discharged from an internal combustion engine to an intake system, an EGR cooler for exchanging heat between an EGR gas and a refrigerant has an EGR flow. Some are arranged in the middle of the road.

In an EGR device equipped with an EGR cooler, when EGR gas flows into the EGR cooler when the ambient temperature inside the EGR cooler is low, such as immediately after a cold start of the internal combustion engine, the flow path wall in the EGR cooler and the EGR When the gas comes into contact with the gas, water in the EGR gas may condense and generate condensed water. Since the condensed water thus generated contains an acidic substance such as sulfuric acid (H ₂ SO ₄ ), sulfuric anhydride (SO ₃ ), or nitric acid (NHO ₃ ), the components of the EGR gas flow path May cause problems such as corrosion of the steel.

  To solve such a problem, as disclosed in Patent Document 1, a method of arranging a heat storage material in an EGR flow path upstream of an EGR cooler and warming the EGR gas flowing into the EGR cooler with heat stored in the heat storage material has been proposed. Conceivable. Further, a method of providing a heat storage material in an EGR cooler as in Patent Document 2 is also conceivable.

JP-A-2006-125215 JP 2011-052919 A

  With respect to the above problem, the present inventors have devised that a heating element accommodating section for accommodating a heating element is disposed in an EGR cooler, and that the heating element adsorbs a working gas to generate heat.

  As such a heating element, the organic metal structure is expected to have a high heat storage density because of its large adsorption capacity. Therefore, the present inventors have considered using an organometallic structure for the heating element of the EGR cooler. In using the organometallic structure for the heating element of the EGR cooler, the present inventors dissolve the organometallic structure under a high-temperature environment because the organometallic structure contains an organic component. Have found that the heat storage function may be reduced or lost.

  That is, an object of the present disclosure is to provide an EGR cooler that includes a heating element containing an organometallic structure and that can efficiently and effectively adjust the temperature of EGR gas.

The present inventors have found that the above object can be achieved by the following means:
An EGR cooler which is disposed in the middle of an EGR flow path connecting the exhaust flow path and the intake flow path of the internal combustion engine and exchanges heat between a refrigerant and an EGR gas which is a gas flowing through the EGR flow path. So,
A flow path formed inside the EGR cooler, and an EGR gas flow path for flowing the EGR gas;
A refrigerant flow path for allowing the refrigerant to flow inside the EGR cooler, wherein a refrigerant flow path is formed such that heat exchange is performed between the EGR gas and the refrigerant flowing through the EGR gas flow path;
A space for accommodating a heating element that generates heat by adsorbing a predetermined working gas inside the EGR cooler, wherein at least a part of the heating element is formed so as to contact a wall surface of the EGR gas flow path. Heating element housing,
A working gas tank that stores the working gas, and a gas moving device that moves the working gas stored in the working gas tank from the working gas tank to the heating element housing unit,
The EGR cooler has an upstream region and a downstream region in the flow direction of the EGR gas,
The heating element housing is disposed in the downstream area of the EGR cooler, and the heating element contains an organic metal structure.
EGR cooler.

  According to the present disclosure, it is possible to provide an EGR cooler that includes a heating element containing an organometallic structure and that can efficiently and effectively adjust the temperature of EGR gas.

FIG. 1 is a schematic diagram illustrating one embodiment of the EGR cooler of the present disclosure. FIG. 2 is a schematic diagram of an internal combustion engine to which the EGR cooler of the present disclosure is applied. FIG. 3 is a schematic diagram illustrating another embodiment of the EGR cooler of the present disclosure. FIG. 4 is a schematic diagram illustrating still another embodiment of the EGR cooler of the present disclosure. FIG. 5 shows the state of the switching valve, the pressure in the working gas tank and the pressure in the heating element housing, the amount of water (steam) in the working gas tank, and the temperature of the heating element when the internal combustion engine is cold started. 5 is a timing chart showing, in a time series, the state of the wall surface temperature of the EGR gas passage, the state of the permission flag, and the state of the EGR valve. FIG. 6 is a diagram showing the behavior of the working gas when the EGR cooler is in a cold state. FIG. 7 is a diagram showing the behavior of the working gas when the EGR cooler is in a warm state. FIG. 8 is a diagram showing a state in which the working gas is stored in the working gas tank. FIG. 9 is a flowchart showing a processing routine executed by the ECU when switching the switching valve from the closed state to the open state. FIG. 10 is a flowchart showing a processing routine executed by the ECU when switching the switching valve from the open state to the closed state.

  Hereinafter, embodiments of the present disclosure will be described in detail. The present disclosure is not limited to the following embodiments, but can be implemented with various modifications within the scope of the present disclosure.

《EGR cooler》
The EGR cooler of the present disclosure is disposed in the middle of an EGR flow path that connects an exhaust flow path and an intake flow path of an internal combustion engine, and exchanges heat between a refrigerant and EGR gas that flows through the EGR flow path. This is an EGR cooler for performing. The EGR cooler of the present disclosure is a flow path formed inside the EGR cooler, an EGR gas flow path for flowing EGR gas, and a flow path for flowing refrigerant inside the EGR cooler. A refrigerant flow path formed so that heat exchange is performed between the EGR gas flowing through the flow path and the refrigerant, and a space for accommodating a heating element that generates heat by adsorbing a predetermined working gas inside the EGR cooler. A heating element housing part formed so that at least a part of the heating element is in contact with a wall surface of the EGR gas flow path, a working gas tank storing working gas, and a working gas stored in the working gas tank. A gas moving device for moving the working gas tank to the heating element housing is provided. Further, the EGR cooler according to the present disclosure has an upstream region and a downstream region in the flow direction of the EGR gas. In the EGR cooler according to the present disclosure, the heating element housing is disposed in a downstream region of the EGR cooler, and the heating element contains an organic metal structure.

  In the EGR cooler configured as described above, when the working gas stored in the working gas tank is moved from the working gas tank to the heating element housing by the gas moving device, the working gas is transferred to the heating element in the heating element housing. Adsorbed. When the working gas is adsorbed on the heating element, the heating element generates heat. Heat generated by the heating element adsorbing the working gas is directly transmitted from the heating element to the wall surface of the EGR gas flow path. Therefore, of the heat generated by the heating element, the ratio of heat transmitted to the wall surface of the EGR gas passage tends to increase. As a result, the wall surface of the EGR gas passage in the EGR cooler can be efficiently warmed. Further, according to the EGR cooler configured as described above, when it is necessary to warm the wall surface of the EGR gas flow path in the EGR cooler, the working gas is moved from the working gas tank to the heating element housing by the gas moving device. Also becomes possible. Thereby, the wall surface of the EGR gas passage in the EGR cooler can be effectively warmed.

  The EGR cooler of the present disclosure further has an upstream area and a downstream area in the flow direction of the EGR gas, and the heating element housing is arranged in a downstream area of the EGR cooler. Therefore, in the upstream region where the temperature of the EGR gas is high, the refrigerant flowing through the cooling flow path lowers the temperature of the EGR gas. Thermal decomposition of the metal structure can be suppressed.

  FIG. 1 is a schematic diagram illustrating one embodiment of the EGR cooler of the present disclosure. In FIG. 1, an EGR cooler 400 includes an EGR cooler main body 401 arranged in the middle of the EGR flow passage 40. Inside the EGR cooler main body 401, a plurality of EGR gas flow paths 405, a plurality of refrigerant flow paths 406, and a plurality of heating element housing portions 407 are formed. The EGR gas flow path 405 is a flow path that communicates with the EGR flow path 40, and is a flow path for flowing the EGR gas. Here, the EGR cooler has an upstream region 400a and a downstream region 400b in the flow direction of the EGR gas, and the heating element housing portion 407 is arranged in the downstream region 400b of the EGR cooler.

  The refrigerant flow path 406 is a flow path through which a refrigerant that exchanges heat with the EGR gas flowing through the EGR gas flow path 405 flows. In FIG. 1, a coolant for the vehicle is used as the coolant flowing through the coolant channel 406, but a liquid or a gas other than the coolant for the vehicle may be used.

  The heating element housing section 407 is a space for housing a heating element described later. Here, the heating element housing section 407 is adjacent to the EGR gas flow path 405 via a partition for defining the EGR gas flow path 405, while being adjacent to the EGR gas flow path 405 via a partition for defining the refrigerant flow path 406. It is also adjacent to the coolant channel 406. At this time, the heating element accommodated in the heating element housing section 407 contacts a partition wall between the EGR gas flow path 405 and the heating element housing section 407 (that is, a partition wall defining the EGR gas flow path 405), and It can be arranged so as to be in contact with the partition wall between the refrigerant flow path 406 and the heating element housing section 407 (that is, the partition wall defining the refrigerant flow path 406). The heating element accommodated in the heating element accommodating portion 407 is a partition that defines at least the EGR gas channel 405 among the partition that defines the EGR gas channel 405 and the partition that defines the refrigerant channel 406. It only needs to be in contact with. The heating element contains an organometallic structure.

  The EGR gas flow path 405 and the coolant flow path 406 are adjacent to each other with a partition wall defining the flow path therebetween, and the EGR gas flowing through the EGR gas flow path 405 and the coolant flowing through the refrigerant flow path 406 The heat exchange is performed directly between the heat exchanger and the heat exchanger. Further, the EGR cooler main body 401 is provided with an inlet 408 for letting coolant flow into the coolant channel 406 and an outlet 409 for letting coolant flow through the coolant channel 406. Although not shown in FIG. 2, the coolant flowing out of the outlet 409 is cooled by a heat exchanger such as a radiator and then flows back into the inlet 408.

  FIG. 2 is a schematic diagram of an internal combustion engine to which the EGR cooler of the present disclosure is applied. In FIG. 2, an internal combustion engine 1 is a spark ignition type internal combustion engine using gasoline as a fuel or a compression ignition type internal combustion engine using gas oil as a fuel. An intake passage 2 and an exhaust passage 3 are connected to the internal combustion engine 1. The intake passage 2 is a passage for guiding fresh air (air) taken from the atmosphere into a cylinder (not shown) of the internal combustion engine 1. The exhaust passage 3 is a passage through which the gas burned in the cylinder of the internal combustion engine 1 flows through an exhaust purification catalyst (not shown) or the like.

  The internal combustion engine 1 is provided with an EGR device 4. The EGR device 4 is a flow passage that branches off from the middle of the exhaust passage 3 and joins in the middle of the intake passage 2, and guides a part of the exhaust flowing through the exhaust passage 3 to the intake passage 2 as EGR gas. And an EGR valve 41 which is provided in the middle of the EGR passage 40 and is a valve device for changing the cross-sectional area of the EGR passage 40. In a configuration in which the internal combustion engine 1 includes an exhaust turbine supercharger (turbocharger) (not shown), the EGR flow path 40 is provided from the exhaust flow path 3 upstream of the turbine to the intake flow path 2 downstream of the compressor. Or may be configured to guide the EGR gas from the exhaust passage 3 downstream of the turbine to the intake passage 2 upstream of the compressor.

In the above-described EGR device 4, when the EGR valve 41 is opened, a part of the exhaust gas (EGR gas) flowing through the exhaust passage 3 is guided to the intake passage 2 via the EGR passage 40. The EGR gas guided to the intake passage 2 is drawn into the cylinder of the internal combustion engine 1 together with fresh air flowing through the intake passage 2 and is provided for combustion. At that time, since the like action of the inert gas component contained in the EGR gas combustion temperature of the mixture is lowered, it is possible to reduce the generation amount of NO _X.

  Since the EGR gas is a part of the gas burned in the cylinder of the internal combustion engine 1, the temperature of the EGR gas becomes higher than the temperature of the fresh air. Therefore, when the EGR gas is mixed into the fresh air, the volume of the fresh air expands due to an increase in the temperature of the fresh air. As a result, the mass of fresh air charged into the cylinders of the internal combustion engine 1 decreases, which may lead to a decrease in charging efficiency. Therefore, the EGR device 4 in this embodiment is provided with an EGR cooler 400 for cooling the EGR gas.

  FIG. 3 is a schematic diagram illustrating another embodiment of the EGR cooler of the present disclosure. As shown in FIG. 3, in another aspect of the EGR cooler of the present disclosure, as the EGR cooler 400 moves from the outer edge to the center, the width of the EGR gas flow path 405 decreases, and the width of the refrigerant flow path 406 decreases. It has increased.

  The outer edge of the EGR cooler 400 is capable of exchanging heat between the EGR cooler 400 and the outside, in addition to cooling by the coolant flow path 406. Therefore, in the EGR cooler 400, it is considered that the outer edge portion of the EGR cooler 400 is particularly easily cooled, and the EGR gas is hardly cooled toward the center portion. Therefore, in the downstream region 400b, it is considered that the organometallic structure in the central portion of the EGR cooler 400 is more likely to deteriorate than the organometallic structure in the extension portion.

  In another embodiment of the EGR cooler of the present disclosure illustrated in FIG. 3, the width of the refrigerant flow path 406 increases from the outer edge to the center of the EGR cooler. The amount of cooling increases. Thereby, the temperature can be further reduced inside the EGR cooler, and the temperature in the direction from the outer edge portion to the center portion inside the EGR cooler can be made more uniform. Therefore, in the downstream region 400b, the deterioration of the organometallic structure can be further suppressed.

  FIG. 4 is a schematic diagram illustrating still another embodiment of the EGR cooler of the present disclosure. As shown in FIG. 4, in still another embodiment of the EGR cooler according to the present disclosure, an inlet 408 and an outlet 409 for flowing the refrigerant through the refrigerant flow path 406 of the EGR cooler include an upstream region 400 a and a downstream side, respectively. They are arranged at two places in the area 400b. This makes it possible to independently control the cooling of the EGR gas by the refrigerant flow path in the upstream region 400a and the downstream region 400b of the EGR cooler.

<Upstream area and downstream area>
The EGR cooler according to the present disclosure has an upstream region and a downstream region in the flow direction of the EGR gas, and the heating element housing is disposed in a downstream region of the EGR cooler.

  Here, it is preferable that the downstream region has a temperature lower than a temperature at which the heat generating function is deteriorated or lost due to thermal decomposition or the like of the organometallic structure as the heat generating element during operation. It is preferable that the upstream region has such a size that the temperature of the EGR gas flowing into the inside of the EGR cooler can be cooled to such a temperature in the downstream region.

  The size of the upstream region can be determined, for example, as follows.

The exchanged heat quantity Q (kcal / hr) of the cooling portion of the entire EGR cooler is determined by the heat transfer area A (m ² ) of the entire EGR cooler, the overall heat transfer coefficient U (kcal / m ² hr ° C.), and the inlet side of the EGR cooler. The following equation (1) can be expressed using the logarithmic average temperature difference ΔT between the exhaust gas and the refrigerant at the outlet and the outlet side.

  Here, the temperature of the exhaust gas at the inlet side of the EGR cooler is T1, the temperature of the refrigerant at the inlet side of the EGR cooler is t1, the temperature of the exhaust gas at the outlet side of the EGR cooler is T2, and the temperature of the refrigerant at the outlet side of the EGR cooler is T1. Assuming that the temperature is t2, the logarithmic average temperature difference ΔT can be expressed by the following equation (2).

Similarly, the exchange heat quantity Q (kcal / hr) of the cooling portion in the upstream region of the EGR cooler is determined by the heat transfer area A ′ (m ² ) in the upstream region of the EGR cooler and the overall heat transfer coefficient U (kcal / m ^2). hr °) and the logarithmic average temperature difference ΔT ′ between the exhaust gas and the refrigerant at the inlet side of the EGR cooler and at the downstream end of the upstream area, and can be expressed by the following equation (3).

  Here, the temperature of the exhaust gas at the inlet side of the EGR cooler is T1, the temperature of the refrigerant at the inlet side of the EGR cooler is t1, the temperature of the exhaust gas at the downstream end of the upstream region of the EGR cooler is T2 ', and EGR. Assuming that the temperature of the refrigerant at the downstream end of the upstream region of the cooler is t2 ′, the logarithmic average temperature difference ΔT ′ can be expressed by the following equation (4).

  Then, the ratio of the upstream region in the EGR cooler can be calculated using the following formula (5) as the area ratio A '/ A in consideration of, for example, the above formulas (1) and (3).

Here, as an example for calculating specific numerical values of the area ratio, MOF801 (Zr ₆ O ₄ (OH) which is an organometallic structure having zirconium oxide as a material and fumaric acid as a ligand is used. ₄ ) (FUM) ₆ ).

  It is considered that MOF801 may be thermally decomposed at a temperature of 340 ° C. or higher. Therefore, it is preferable to design the size of the upstream region so that the temperature of the EGR gas at the downstream end of the upstream region becomes 340 ° C.

  When the EGR cooler inlet temperature of the EGR gas is 450 ° C., the outlet temperature is 120 ° C., the temperature of the refrigerant at the inlet side of the EGR cooler is 25 ° C., and the temperature of the refrigerant at the outlet side of the EGR cooler is 90 ° C. From the above equations (2), (4), and (5), the area ratio A ′ / A is 0.14.

  The ratio of the surface area of the EGR passage in the upstream region to the total surface area of the EGR gas passage in the upstream region and the downstream region of the EGR cooler is, for example, 0.10 or more, 0.14 or more, 0.20 or more, or It may be 0.30 or more, and may be 0.50 or less, 0.45 or less, 0.40 or less, or 0.35 or less.

  If the area ratio of the upstream region of the EGR cooler is too small, the degree of decrease in the temperature of the EGR gas flowing from the upstream region to the downstream region becomes small, and the repetitive use of the EGR cooler causes The organic metal structure may be deteriorated due to thermal decomposition or the like. On the other hand, when the area ratio of the upstream region of the EGR cooler is too large, the area ratio of the downstream region becomes small, so that the portion in which the heating element housing portion can be arranged becomes small, and the organic metal structure as the heating element is formed. The function of adjusting the temperature of the EGR gas may be reduced.

<EGR gas flow path>
The EGR gas passage is a passage formed inside the EGR cooler. EGR gas is circulated through the EGR gas passage.

<Refrigerant flow path>
The refrigerant flow path is a flow path through which the refrigerant flows inside the EGR cooler. The refrigerant flow path is formed so that heat exchange is performed between the EGR gas flowing through the EGR gas flow path and the refrigerant.

  The refrigerant that is allowed to flow in the coolant channel is not particularly limited as long as it can flow in the coolant channel and can cool the EGR gas flowing in the EGR gas channel. As the refrigerant, for example, a vehicle coolant can be used, but a liquid or a gas other than the vehicle coolant may be used.

<Heat element housing section>
The heating element accommodating portion is a space for accommodating a heating element that generates heat by adsorbing a predetermined working gas inside the EGR cooler, so that at least a part of the heating element contacts the wall surface of the EGR gas flow path. Is formed.

  The heating element housing is arranged in a downstream area of the EGR cooler. This can prevent the temperature of the heating element housed in the heating element housing section from becoming too high.

<Heating element>
The heating element contains an organometallic structure. The organometallic structure is not particularly limited as long as it can absorb a working gas and generate heat. Here, the metal organic structure is a structure having a porous structure formed by alternately bonding a metal or metal oxide and an organic compound molecule as a ligand by a coordination bond.
Examples of the metal organic structure include Fe (BTC), Fe ₃ OX (H ₂ O) ₂ (BTC ₂ ), where X = F or OH, Zr ₆ O ₄ (OH) ₄ (BDC) ₆ , Zr ₆ O ₄ (OH) ₄ (PZDC) ₅ (HCOO) ₂ (H ₂ O) ₂ , Zr ₆ O ₄ (OH) ₄ (BTC) ₂ (HCOO) ₆ , Zr ₆ O ₄ (OH) ₄ (DOBDC) ₆ , Zr ₆ O ₄ (OH) ₄ (FUM) ₆ , and Zr ₆ O ₄ (OH) ₄ (TDC) ₄ (HCOO) ₄ can be used, but not limited thereto.

<Working gas tank>
The working gas tank is a working gas tank that stores a working gas.

<Working gas>
The working gas is a gas that releases heat when it is adsorbed on the organometallic structure serving as the heating element. As the working gas, specifically, a gas obtained by vaporizing a substance such as water, ammonia, alcohol (for example, methanol or ethanol), carbon dioxide, and sulfur trioxide, and a combination thereof may be used. .

  The heat generated when the working gas is adsorbed on the organometallic structure may be, for example, heat of adsorption, but is not limited thereto.

  The method for introducing the working gas into the working gas tank is not particularly limited. For example, in a manufacturing process of the EGR cooler, the inside of the working EGR gas flow path including the heating element housing, the communication flow path, and the working gas tank is used. The working gas tank may be filled with the working gas after the switching valve is closed while the chamber is evacuated.

<Gas transfer device>
The gas moving device is a device that can move the working gas stored in the working gas tank from the working gas tank to the heating element housing. The configuration of the gas moving device is not particularly limited as long as the configuration is such that the working gas stored in the working gas tank can be moved from the working gas tank to the heating element housing section.

  As a specific configuration of the gas moving device, for example, as shown in FIG. 1, a configuration including a communication channel, a switching valve, and an ECU (Electronic Control Unit) can be cited.

(Communication channel)
The communication flow path is a flow path that connects a working gas tank disposed outside the EGR cooler main body and a heating element housing section in the EGR cooler main body.

(Switching valve)
The switching valve is provided in the middle of the communication flow path, and is a valve device that switches between conduction and cutoff of the communication flow path.

(ECU)
The ECU is a device that switches a switching valve from an open state to a closed state. The ECU includes, for example, a CPU, a ROM, a RAM, a backup RAM, and the like. The ECU can receive detection signals from various sensors such as an air flow meter and an air-fuel ratio sensor in addition to the temperature sensor. Here, the temperature sensor may be a sensor that detects the temperature of the coolant circulating in the internal combustion engine.

  Note that the ECU of the gas moving device can also serve as an ECU for controlling the operating state and the like of the internal combustion engine to which the EGR cooler of the present disclosure is applied. May be provided separately.

<< Operation of EGR cooler >>
Here, the operation of the above-described EGR cooler 400 will be described with reference to FIGS. In the following, a material that can adsorb water is used as the organometallic structure, and water (steam) is used as the working gas. However, the embodiment of the EGR cooler of the present disclosure is not limited to this. The pore diameter of the pores of the organometallic structure can be formed to be larger than the molecular diameter of water (water vapor). This is because water (steam) can easily enter into the pores of the organometallic structure, thereby more surely adsorbing water (steam) by the organometallic structure. FIG. 5 shows the state of the switching valve 404, the pressure in the working gas tank 402 and the pressure in the heating element housing 407, and the working gas amount (water (steam) in the working gas tank 402 when the internal combustion engine 1 is cold started. 3) is a timing chart showing the temperature of the heating element (organic metal structure), the wall surface temperature of the EGR gas flow path 405, the state of the permission flag, and the state of the EGR valve 41 in a time series. In FIG. 5, when the internal combustion engine 1 is cold started (t0 in FIG. 5), most of the water (steam) is in a liquid phase and / or a gas phase in the working gas tank 402 in a state of liquid phase and / or gas phase. Shall be stored in In addition, the permission flag in FIG. 5 is turned off when it is estimated that condensed water can be generated by the flow of the EGR gas through the EGR gas passage 405 of the EGR cooler main body 401, while the EGR cooler main body is turned off. This flag is turned ON when it is estimated that condensed water cannot be generated due to the flow of the EGR gas in the EGR gas flow path 405 of 401. More specifically, the permission flag indicates that the wall temperature of the EGR gas flow path 405 is lower than a predetermined warm-up completion temperature higher than the dew point Tdp of the EGR gas (that is, a temperature obtained by adding a margin to the dew point Tdp of the EGR gas) Twc. It is turned off when it is estimated that there is, and is turned on when it is estimated that the wall surface temperature of the EGR gas flow path 405 is equal to or higher than the warm-up completion temperature Twc. FIG. 6 is a diagram showing the behavior of the working gas when the EGR cooler main body 401 is in a cold state. FIG. 7 is a diagram showing a behavior of the working gas when the EGR cooler main body 401 is in a warm state. FIG. 8 is a diagram illustrating a state in which the working gas is stored in the working gas tank 402.

  As shown in FIG. 5, at the time when the internal combustion engine 1 is cold started (t0 in FIG. 5), the EGR cooler main body 401 is in a cold state (that is, the wall surface temperature of the EGR gas passage 405 is a warm-up completion temperature). Twc). When the EGR valve 41 is opened while the EGR cooler body 401 is in a cold state, when the EGR gas flows through the EGR gas flow path 405 of the EGR cooler body 401, the EGR gas and the EGR gas flow path There is a possibility that condensed water is generated due to contact with the wall surface of the 405. Therefore, in the present embodiment, when the EGR cooler main body 401 is in a cold state, the permission flag is turned off and the EGR cooler main body 401 is warmed up. The warming-up of the EGR cooler main body 401 here is performed by using heat generated when the heating element of the heating element housing section 407 adsorbs water (steam). In order to realize the warm-up of the EGR cooler main body 401 by such a method, it is necessary to move water (steam) stored in the working gas tank 402 from the working gas tank 402 to the heating element housing 407. Here, when the internal combustion engine 1 is cold started (t0 in FIG. 5), the temperature in the working gas tank 402 and the temperature in the heating element housing 407 are substantially equal (for example, a temperature equivalent to the outside air temperature). become. In such a situation, if most of the water (steam) is stored in the working gas tank 402, the pressure in the working gas tank 402 becomes close to the saturated vapor pressure of the water (steam). As a result, the pressure in the heating element housing 407 of the EGR cooler main body 401 becomes substantially vacuum. As a result, the pressure in the working gas tank 402 becomes higher than the pressure in the heating element housing 407. Therefore, immediately after the internal combustion engine 1 is cold-started (t1 in FIG. 5), the ECU 5 switches the switching valve 404 from the closed state to the open state, so that the communication flow path 403 changes from the cutoff state to the conduction state. When the switching is performed, as shown in FIG. 6, the steam (Gw in FIG. 6) stored in the working gas tank 402 necessarily moves from the working gas tank 402 to the heating element housing section 407 via the communication flow path 403 ( (See the white arrow in FIG. 6). When the pressure in the working gas tank 402 becomes lower than the saturated vapor pressure of water due to the conduction of the communication flow path 403, the water stored in the working gas tank 402 in a liquid phase changes into a gas phase. It is inevitably moved from the working gas tank 402 to the heating element housing 407. As described above, according to the gas moving device according to the present embodiment, when water (steam) stored in the working gas tank 402 is moved from the working gas tank 402 to the heating element housing 407, a pump or the like is used. The transfer of the working gas from the working gas tank 402 to the heating element housing 407 can be realized without depending on a mechanism for forcibly moving the working gas. The movement of water (steam) from the working gas tank 402 to the heating element housing 407 as described above is continued until the pressure in the working gas tank 402 and the pressure in the heating element housing 407 are balanced. At this time, of the water (steam) stored in the working gas tank 402, the water (steam) of a predetermined amount or more is operated during the manufacturing process of the EGR cooler 400 so that the water (steam) moves from the working gas tank 402 to the heating element housing section 407. It is assumed that the amount of water (steam) sealed in the gas tank 402 is adjusted. The “predetermined amount” here is an amount that can raise the wall surface temperature of the EGR gas flow path 405 in the EGR cooler main body 401 to the above-mentioned warm-up completion temperature Twc or more, and is a flow path that communicates with the heating element housing portion 407. This is the amount that occupies most of the working gas filled in the working EGR gas flow path including the working gas tank 403 and the working gas tank 402.

  The water (steam) moved from the working gas tank 402 to the heating element housing 407 is adsorbed by the heating element (Eh in FIG. 6) stored in the heating element housing 407. At this time, as described above, the pore size of the organometallic structure as the heating element is formed so as to be larger than the molecular diameter of water (water vapor), and thus the organic metal structure is moved from the working gas tank 402 to the heating element housing section 407. Since the water (steam) easily enters the pores of the heating element, the adsorption of the water (steam) by the heating element is performed more reliably. When the heating element adsorbs water (steam), heat of adsorption is generated due to the water (steam) being adsorbed by the heating element, and the heating element generates heat by the heat of adsorption. Here, as described in the description of FIG. 1 described above, the heating element is disposed so as to be in contact with the partition wall that defines the EGR gas flow path 405. Therefore, the heat generated by the heating element is directly transmitted to the wall surface of the EGR gas flow path 405 (see the black arrow in FIG. 6). Accordingly, the ratio of heat transmitted to the wall surface of EGR gas flow path 405 out of the heat generated by the heating element increases, so that the wall surface of EGR gas flow path 405 can be efficiently warmed. Therefore, the wall surface temperature of the EGR gas flow path 405 can be quickly increased.

  When the wall surface of the EGR gas passage 405 is estimated to have risen to the warm-up completion temperature Twc or more by warming the wall surface of the EGR gas passage 405 by the heat generated by the heating element (see FIG. 5). t2), the permission flag is switched from OFF to ON. At this time, if the operating state of the internal combustion engine 1 belongs to the EGR execution region, the EGR valve 41 is switched from the closed state to the open state. That is, if the predetermined EGR gas flow conditions including that the operating state of the internal combustion engine 1 belongs to the EGR execution region and that the permission flag is ON are satisfied, the EGR valve 41 is in the closed state. Is switched to the valve open state, and the EGR gas flows through the EGR gas passage 405 in the EGR cooler main body 401. In this case, since the wall surface temperature of the EGR gas passage 405 has risen to the warm-up completion temperature Twc higher than the dew point Tdp of the EGR gas, even if the EGR gas contacts the wall surface of the EGR gas passage 405, Is suppressed, and the generation of condensed water is suppressed. In the example shown in FIG. 5, when the wall temperature of the EGR gas flow path 405 is estimated to have risen to the warm-up completion temperature Twc or more, in other words, when the permission flag is switched from OFF to ON (FIG. At t2), the EGR valve 41 is switched from the closed state to the open state, but the timing at which the EGR valve 41 is switched from the closed state to the open state depends on the wall surface temperature of the EGR gas flow path 405. If the timing is after the time when it is estimated that the temperature has risen to the warm-up completion temperature Twc or more (t2 in FIG. 5), it can be changed appropriately according to the operating state of the internal combustion engine 1.

  When the EGR cooler body 401 is warmed up by the above-described method, a predetermined amount or more of water (steam) among the water (steam) stored in the working gas tank 402 is adsorbed by the heating element. Become. Therefore, even in the next and subsequent operations of the internal combustion engine 1, in order to realize the efficient and effective warm-up of the EGR cooler main body 401 by the above-described method, the water (steam) adsorbed on the heating element is removed. It is necessary to remove water (steam) from the heating element from the heating element housing 407 to the working gas tank 402 while removing the heating element from the heating element.

  Here, in order to desorb water (steam) adsorbed on the heating element from the heating element, it is necessary to raise the temperature of the heating element to a predetermined desorption temperature Tdes or higher. Here, the predetermined desorption temperature Tdes is the lowest temperature at which water (steam) adsorbed on the organometallic structure as the heating element is desorbed from the organometallic structure. After the wall temperature of the EGR gas flow path 405 is estimated to have risen to the warm-up completion temperature Twc or more, the EGR valve is switched after the permission flag is switched from OFF to ON (after t2 in FIG. 5). When the EGR gas flows through the EGR gas passage 405 of the EGR cooler main body 401 by switching the valve 41 from the valve closing state to the valve opening state, the heat of the EGR gas is transmitted through the wall surface of the EGR gas passage 405. The heat is transmitted to the heat generating element of the heat generating element housing 407. At this time, since the temperature of the EGR gas is sufficiently higher than the desorption temperature Tdes, the temperature of the heating element rises to a temperature equal to or higher than the desorption temperature Tdes (t3 in FIG. 5). Here, when the heat of the EGR gas is continuously transmitted to the heating element as described above, the heating element may be overheated. However, as described in the above description of FIG. 1, the heating element of the heating element housing section 407 is arranged so as to be in contact with the partition that defines the coolant flow path 406. Therefore, a part of the heat transmitted from the EGR gas to the heating element is radiated to the coolant flowing through the coolant flow path 406 via the partition that defines the coolant flow path 406. Therefore, even if the heat of the EGR gas is continuously transmitted to the heating element, overheating of the heating element is suppressed.

  Further, in order to move the water (steam) released from the heating element from the heating element housing section 407 to the working gas tank 402, the pressure in the heating element housing section 407 is reduced while the switching valve 404 is opened. It must be higher than the pressure in 402. Here, when the temperature of the heating element becomes higher than the desorption temperature Tdes (that is, the EGR cooler main body 401 is in a warm state), water (steam) adsorbed by the heating element is removed from the heating element. When detached, the amount of water (steam) in the heating element housing 407 becomes larger than the amount of water (steam) in the working gas tank 402, so that the pressure in the heating element housing 407 becomes the pressure in the working gas tank 402. Higher. Therefore, when the warming-up of the EGR cooler body 401 is started (t1 in FIG. 5), the temperature of the heating element reaches the desorption temperature Tdes through the switching valve 404 switched from the closed state to the open state (FIG. 5). If the valve is kept open even after t3), when the temperature of the heating element rises to the desorption temperature Tdes or more, as shown in FIG. The phase water changes into gaseous vapor (Gw in FIG. 7) while being desorbed from the heating element, and the water (steam) released from the heating element passes through the communication channel 403 from the heating element housing 407. After that, it inevitably moves to the working gas tank 402 (see the white arrow in FIG. 7). That is, according to the gas transfer device according to the present disclosure, when water (steam) adsorbed on the heating element is collected in the working gas tank 402, a mechanism for forcibly heating the heating element such as a heater, or a pump. Desorption of water (steam) adsorbed on the heating element and generation of water (steam) desorbed from the heating element without depending on a mechanism for forcibly moving the working gas such as The movement from the storage section 407 to the working gas tank 402 can be realized.

  When the water (steam) adsorbed on the heating element is collected in the working gas tank 402 by the above-described method, the water (steam) collected in the working gas tank 402 is required for the next warm-up of the EGR cooler main body 401. Until (ie, immediately after the next cold start of the internal combustion engine 1), it is necessary to store it in the working gas tank 402. Therefore, in the present embodiment, the switching valve 404 is switched from the open state to the closed state by the ECU 5 at a predetermined shut-off timing (t4 in FIG. 5) after the temperature of the heating element exceeds the desorption temperature Tdes. Shall be. The “predetermined cutoff timing” here means that the desorption of water (steam) adsorbed on the heating element from the heating element is completed and the heating element housing section of the water (steam) detached from the heating element. This is the timing at which it can be estimated that the movement from 407 to the working gas tank 402 has been completed. At this time, "completed desorption of water (steam) adsorbed on the heating element from the heating element" means that the entire amount of water (steam) adsorbed on the heating element is desorbed from the heating element. The present invention is not limited to the embodiment, and it is sufficient that a predetermined amount or more of water (steam) adsorbed on the heating element is separated from the heating element. Similarly, "the movement of the water (steam) detached from the heating element from the heating element storage section 407 to the working gas tank 402 is completed" means that the total amount of water (steam) detached from the heating element is reduced to The embodiment is not limited to the mode of moving from the heating element 407 to the working gas tank 402, and a predetermined amount or more of water (steam) among the water (steam) desorbed from the heating element moves from the heating element housing section 407 to the working gas tank 402. Is enough. In short, immediately after the next cold start of the internal combustion engine 1, when the communication flow path 403 is switched from the cutoff state to the conduction state by the switching valve 404, the heating element can adsorb a predetermined amount or more of the working gas. Amount of working gas may be separated from the heating element and returned to the working gas tank 402. Therefore, the shutoff timing is a timing at which it can be estimated that the water (steam) amount in the working gas tank 402 has returned to substantially the same amount as the water (steam) amount immediately before t1 in FIG. The timing at which the amount can be estimated to have returned to substantially the same amount as the water adsorption amount immediately before t1 in FIG. 5, or the pressure in the working gas tank 402 has returned to substantially the same as the pressure immediately before t1 in FIG. This can be rephrased as timing that can be estimated. The above-described shutoff timing may be set to a timing at which the operation of the internal combustion engine 1 is stopped (that is, a timing at which an unillustrated ignition switch is switched from ON to OFF). This is because, as long as the operation of the internal combustion engine 1 is continued after the temperature of the heating element exceeds the desorption temperature Tdes, a situation in which the temperature of the heating element housing section 407 falls below the temperature of the working gas tank 402 is unlikely to occur. Accordingly, it is considered unlikely that the pressure in the heating element housing section 407 becomes lower than the pressure in the working gas tank 402. Therefore, the water (steam) adsorbed by the heating element is completely collected in the working gas tank 402. After that, even if the switching valve 404 continues to be opened until the timing at which the operation of the internal combustion engine 1 is stopped, the water (steam) collected in the working gas tank 402 moves from the working gas tank 402 to the heating element housing 407. This is because it is considered difficult.

  After opening the switching valve 404 to warm up the EGR cooler main body 401, it is not necessary to continuously open the switching valve 404 until the above-described shutoff timing. When it is estimated that the temperature has risen to the warm-up completion temperature Twc or higher (t2 in FIG. 5), the switching valve 404 is temporarily closed, and then the temperature of the heating element rises to the desorption temperature Tdes. By opening the switching valve 404 again at the estimated time (t3 in FIG. 5), the water (steam) adsorbed by the heating element may be collected in the working gas tank 402.

  When the switching valve 404 is switched from the open state to the closed state at the above-described shutoff timing, as shown in FIG. 8, water (steam) collected from the heating element housing portion 407 to the working gas tank 402 is used as the working gas tank 402. It will be stored inside. As a result, when the next warm-up of the EGR cooler main body 401 becomes necessary, the switching valve 404 is switched from the closed state to the open state to reproduce the above-described operation of FIGS. It becomes possible.

  The above-described ECU 5 is provided in addition to the EGR cooler 400 configured as described above. Note that the ECU 5 in the present embodiment also serves as an ECU for controlling the operation state and the like of the internal combustion engine 1, but may be provided separately from the ECU for controlling the operation state and the like of the internal combustion engine 1. . The ECU 5 includes a CPU, a ROM, a RAM, a backup RAM, and the like. The ECU 5 receives detection signals from various sensors such as an air flow meter and an air-fuel ratio sensor (not shown) in addition to the temperature sensor 6. The temperature sensor 6 is a sensor that detects the temperature of the coolant circulating in the internal combustion engine 1. The ECU 5 is electrically connected to various devices such as a fuel injection valve (not shown) in addition to the EGR valve 41 and the switching valve 404 described above, so that the various devices can be controlled. . For example, the ECU 5 performs warm-up control of the EGR cooler main body 401 in addition to known control such as fuel injection control.

<< Warm-up control flow of EGR cooler body >>
Here, the warm-up control of the EGR cooler main body 401 executed by the ECU 5 will be described with reference to FIGS. FIG. 9 is a flowchart showing a processing routine executed by the ECU 5 when switching the switching valve 404 from the closed state to the open state. The processing routine shown in FIG. 9 is executed with the start of the internal combustion engine 1 as a trigger. FIG. 10 is a flowchart showing a processing routine executed by the ECU 5 when switching the switching valve 404 from the open state to the closed state. The processing routine shown in FIG. 10 is repeatedly executed at a predetermined cycle while the internal combustion engine 1 is operating.

  First, in the processing routine of FIG. 9, the ECU 5 reads the coolant temperature Thw1 detected by the temperature sensor 6 in the processing of S101. Subsequently, in the process of S102, the ECU 5 determines whether the coolant temperature Thw1 read in the process of S101 is lower than a predetermined threshold Thwthr. When the coolant temperature Thw1 is lower than the threshold Thwthr, the “predetermined threshold value Thwthr” is that the wall temperature of the EGR gas passage 405 is lower than the warm-up completion temperature Twc and the temperature of the heating element is the desorption temperature. The temperature is estimated to be less than Tdes. Such a threshold Thwtre is determined in advance based on the results of experiments and simulations.

  It is assumed that immediately after the cold start of the internal combustion engine 1, the wall surface temperature of the EGR gas flow path 405 and the temperature of the heating element are assumed to be substantially equal (for example, equal to the outside air temperature). A temperature sensor for measuring the wall surface temperature or the temperature of the heating element is attached to the EGR cooler main body 401, or a temperature sensor for measuring the outside air temperature is provided in the EGR cooler 400, and the measured temperature of the temperature sensor is a warm-up completion temperature. If it is less than Twc (<Tdes), it may be estimated that the wall surface temperature of the EGR gas passage 405 is less than the warm-up completion temperature Twc and that the temperature of the heating element is less than the desorption temperature Tdes.

  If an affirmative determination is made in the process of S102 (Thw1 <Thwtre), as described above, it is estimated that the wall surface temperature of the EGR gas passage 405 is lower than the warm-up completion temperature Twc. When the EGR gas flows through the EGR gas flow path 405 of the EGR cooler main body 401, the EGR gas comes into contact with the wall surface of the EGR gas flow path 405, and condensed water may be generated. Therefore, when an affirmative determination is made in the processing of S102, the ECU 5 proceeds to the processing of S103, and turns off the permission flag. In this case, the EGR gas flow condition described above is not satisfied, so that the EGR valve 41 is not opened. In a state where the wall surface temperature of the EGR gas flow path 405 is estimated to be lower than the warm-up completion temperature Twc, unless the EGR valve 41 is opened, the exhaust gas flow path 3 passes through the EGR flow path 40 to the intake flow path 2. Since the flow of the flowing EGR gas is interrupted, the EGR gas stops flowing through the EGR gas passage 405 of the EGR cooler main body 401. As a result, generation of condensed water in the EGR cooler main body 401 is suppressed.

  After completing the processing of S103, the ECU 5 proceeds to the processing of S104, and starts warming up the EGR cooler main body 401. Specifically, the ECU 5 switches the communication flow path 403 from the shut-off state to the communication state by switching the switching valve 404 from the valve-closed state to the valve-opened state (corresponding to the processing at t1 in FIG. 5 described above). . Here, when the EGR cooler main body 401 is in a cold state, such as immediately after the internal combustion engine 1 is cold started (that is, it is estimated that the wall surface temperature of the EGR gas passage is lower than the warm-up completion temperature Twc). 5), it is assumed that the temperature in the working gas tank 402 and the temperature in the heating element housing section 407 are substantially equal, as described in the above description of FIG. In such a state, when a predetermined amount or more of water (steam) is stored in the working gas tank 402, the pressure in the working gas tank 402 becomes close to the saturated vapor pressure of water (steam), while the heating element housing The pressure in the section 407 becomes close to a vacuum. As a result, the pressure in the working gas tank 402 becomes higher than the pressure in the heating element housing 407. Therefore, when the switching valve 404 is switched from the closed state to the open state in the process of S104, the water (steam) stored in the working gas tank 402 is released as described in the description of FIG. It will inevitably move from the working gas tank 402 to the heating element housing 407 of the EGR cooler main body 401. Then, the water (water vapor) that has moved from the working gas tank 402 to the heating element housing section 407 undergoes a phase change from a gas phase to a liquid phase by being absorbed by the heating element of the heating element housing section 407. As a result, the heating element generates heat due to latent heat accompanying the phase change of water (water vapor). When the heating element generates heat as described above, the heat is transmitted from the heating element to the wall surface of the EGR gas flow path 405. At this time, since the heating element in the heating element accommodating portion 407 is arranged so as to be in contact with the partition wall defining the EGR gas flow path 405, heat generated in the heating element is transmitted from the heating element to the EGR gas flow path 405. It will be transmitted directly to the wall. As a result, of the heat generated by the heating element, the proportion of the heat transmitted to the wall surface of the EGR gas passage increases. Therefore, it is possible to efficiently warm the wall surface of the EGR gas passage 405.

  After completing the processing of S104, the ECU 5 proceeds to the processing of S105, and determines whether or not the wall surface temperature of the EGR gas flow path 405 has risen to the warm-up completion temperature Twc or more. At this time, the ECU 5 measures, for example, the elapsed time from when the switching valve 404 is opened in the process of S104, and if the elapsed time is equal to or longer than the predetermined temperature increasing time, the ECU 5 While it is determined that the wall surface temperature has risen to the warm-up completion temperature Twc or more, if the elapsed time is less than the predetermined temperature increase time, the wall surface temperature of the EGR gas flow path 405 is less than the warm-up completion temperature Twc. It may be determined that there is. The “predetermined heating time” here means that the wall temperature of the EGR gas flow path 405 rises to the warm-up completion temperature Twc or more after the switching valve 404 is opened to start the warm-up of the EGR cooler main body 401. It is the time it takes to do. The time required from when the switching valve 404 is opened to start warming up the EGR cooler main body 401 to when the wall surface temperature of the EGR gas flow path 405 rises to the warming-up completion temperature Twc or more is determined by the time required for the EGR cooler main body 401 to change. This correlates with the wall surface temperature of the EGR gas flow path 405 at the start of warm-up and the amount of heat generated by the heating element per unit time. Here, it is assumed that the wall surface temperature of the EGR gas passage 405 at the start of warm-up of the EGR cooler main body 401 becomes substantially equal to the outside air temperature. Also, it is assumed that the coolant temperature when the internal combustion engine 1 is cold started is substantially equal to the outside air temperature. Therefore, it can be estimated that the wall surface temperature of the EGR gas passage 405 when the EGR cooler body 401 starts to warm up becomes substantially equal to the coolant temperature Thw1 when the internal combustion engine 1 is cold started. On the other hand, the heat value of the heating element per unit time can be considered to be substantially constant. In consideration of these correlations and trends, the above-mentioned heating time may be determined using the coolant temperature Thw1 read in the process of S101 as a parameter. For example, the above-mentioned heating time may be determined so that it is longer when the coolant temperature Thw1 is lower than when it is higher. Here, the correlation between the above-mentioned heating time and the coolant temperature Thw1 may be stored in advance in a ROM or the like of the ECU 5 in the form of a map or a function using the coolant temperature Thw1 as an argument. As another method for determining whether or not the wall surface temperature of the EGR gas passage 405 has risen to a temperature equal to or higher than the warm-up completion temperature Twc, a temperature sensor for measuring the wall surface temperature of the EGR gas passage 405 is provided by an EGR cooler. It may be attached to the main body 401 to determine whether or not the measured value of the temperature sensor is equal to or higher than the warm-up completion temperature Twc.

  Here, when the EGR gas flows through the EGR gas passage 405 when the wall surface temperature of the EGR gas passage 405 is lower than the warm-up completion temperature Twc, the EGR gas comes into contact with the wall surface of the EGR gas passage 405. Condensed water may be generated. Therefore, when a negative determination is made in the process of S105 (wall surface temperature <Twc), the ECU 5 executes the process of S105 again while maintaining the permission flag OFF. On the other hand, when the wall temperature of the EGR gas flow path 405 is equal to or higher than the warm-up completion temperature Twc, when the EGR gas flows through the EGR gas flow path 405 of the EGR cooler main body 401, the EGR gas contacts the wall surface of the EGR gas flow path 405. It is presumed that condensed water cannot be generated even if contact occurs. Therefore, when an affirmative determination is made in the process of S105 (wall surface temperature ≧ Twc), the ECU 5 proceeds to the process of S106 and turns on the permission flag. After completing the process of S106, the ECU 5 terminates the execution of the present processing routine.

  If a negative determination is made in the above-described processing of S102 (Thw1 ≧ Thwthr), it can be estimated that the wall surface temperature of the EGR gas flow path 405 is equal to or higher than the warm-up completion temperature Twc, and thus the processing of S103 to S105 Is skipped and the process proceeds to S106, and the permission flag is turned ON.

  As described above, when the switching valve 404 of the EGR cooler 400 is controlled in accordance with the processing routine of FIG. 9, when the EGR cooler main body 401 is in a cold state, the wall surface of the EGR gas flow path 405 is efficiently and effectively. Can be warmed. Then, when it becomes possible to efficiently and effectively warm the wall surface of the EGR gas flow path 405, the amount of the heating element stored in the heating element storage section 407 and the water (steam) stored in the working gas tank 402 are reduced. It is possible to increase the wall surface temperature of the EGR gas flow path 405 to a temperature at which condensed water cannot be generated (that is, a temperature equal to or higher than the warm-up completion temperature Twc) while keeping the amount relatively small. As a result, an increase in the size of the EGR cooler main body 401 and an increase in the size of the working gas tank 402 can be suppressed, so that a reduction in the in-vehicle performance of the EGR device 4 including the EGR cooler 400 can also be suppressed.

  Next, in the processing routine of FIG. 10, the ECU 5 first determines whether or not the switching valve 404 is in the open state in the processing of S201. If a negative determination is made in the process of S201, the EGR cooler main body 401 is not warmed up after the internal combustion engine 1 is started (that is, the wall surface of the EGR gas passage 405 at the time when the internal combustion engine 1 is started). Since the temperature was equal to or higher than the warm-up completion temperature Twc, it was not necessary to warm up the EGR cooler main body 401), or the EGR cooler main body 401 was warmed up after the internal combustion engine 1 was started. It can be determined that the valve 404 has already been closed (that is, the recovery of water (steam) to the working gas tank 402 has already been completed after the EGR cooler main body 401 has been warmed up). In this case, since there is no need to perform the process of closing the switching valve 404, the ECU 5 ends the execution of this processing routine. On the other hand, if the determination in step S201 is affirmative, the switching valve 404 is opened to warm up the EGR cooler body 401 after the start of the internal combustion engine 1, and then the switching valve 404 is kept open. Can be determined. That is, the timing at which the process of S201 is executed is the timing after t1 in FIG. 5 described above and before the timing t4. In this case, since it is necessary to perform the process of closing the switching valve 404, the ECU 5 proceeds to the process after S202.

  In the process of S202, the ECU 5 determines whether the EGR valve 41 is in an open state. If a negative determination is made in step S202, the EGR valve 41 has been closed because the warming-up of the EGR cooler main body 401 has not been completed yet (ie, the permission flag has been turned off), or the EGR cooler 401 has been closed. Although the warm-up of the cooler body 401 has been completed (that is, the permission flag has been turned ON), the EGR valve 41 is closed because the operating state of the internal combustion engine 1 is not in the EGR execution region. Become. In this case, the ECU 5 once ends the execution of the present processing routine. On the other hand, if an affirmative determination is made in the process of S202, the warm-up of the EGR cooler main body 401 has already been completed (that is, the permission flag has been turned ON), and the operation state of the internal combustion engine 1 has been shifted to the EGR execution region. For this reason (that is, because the above-mentioned predetermined EGR gas flow condition is satisfied), the EGR valve 41 is opened. That is, the timing at which the process of S202 is executed is the timing after t2 in FIG. 5 described above and before the timing t4. In this case, the ECU 5 proceeds to the process of S203.

  In the process of S203, the ECU 5 updates the integration counter Cint. The integration counter Cint mentioned here is an integrated value of the opening time of the EGR valve 41 after the completion of the warm-up of the EGR cooler main body 401 (after t2 in FIG. 5 described above) (hereinafter, referred to as “integrated valve opening time”). Is counted. After completing the process of S203, the ECU 5 proceeds to the process of S204.

  In the process of S204, the ECU 5 determines whether or not the integrated valve opening time Cint updated in the process of S203 is equal to or longer than a predetermined recovery time Crt. Here, the “predetermined recovery time Crt” is a time required for collecting the water (steam) adsorbed by the heating element into the working gas tank 402 when the EGR cooler main body 401 is warmed up. Here, as described in the description of FIG. 5 above, in order to recover the water (steam) adsorbed by the heating element to the working gas tank 402 when the EGR cooler main body 401 is warmed up, the temperature of the heating element must be reduced. By increasing the temperature above the separation temperature Tdes, it is necessary to desorb water (water vapor) from the heating element and to make the pressure in the heating element housing section 407 higher than the pressure in the working gas tank 402. In order to satisfy such a condition, the EGR valve 41 is opened to allow the high-temperature EGR gas to flow through the EGR gas flow path 405 of the EGR cooler main body 401, and the heat generated by the heat of the EGR gas. Needs to be heated. Therefore, the time required for collecting the water (steam) adsorbed on the heating element into the working gas tank 402 when the EGR cooler main body 401 is warmed up is the accumulated valve opening time of the EGR valve 41 after the EGR cooler main body 401 is completely warmed up. It can be said that it depends on Cint. Therefore, in the present embodiment, substantially all of the water (steam) adsorbed on the heating element when the EGR cooler main body 401 is warmed up is in a state where the EGR valve 41 is opened after the EGR cooler main body 401 is completely warmed up. The time required to be collected in the working gas tank 402 is obtained in advance based on the results of experiments and simulations, and the obtained time is set as the above-mentioned collection time Crt. If the accumulated valve opening time Cint is equal to or longer than the recovery time Crt, it is determined that the recovery of the water (steam) adsorbed by the heating element into the working gas tank 402 when the EGR cooler body 401 is warmed up is completed. On the other hand, if the integrated valve opening time Cint is less than the recovery time Crt, the recovery of the water (steam) adsorbed by the heating element to the working gas tank 402 when the EGR cooler main body 401 is warmed up is completed. It was decided that there was no.

  If a negative determination is made in the process of S204, the ECU 5 once ends the execution of the present processing routine. In this case, since the switching valve 404 is maintained in the open state, the recovery of the water (steam) adsorbed by the heating element into the working gas tank 402 when the EGR cooler body 401 is warmed up is continued. On the other hand, when an affirmative determination is made in the process of S204, as described above, it is estimated that the recovery of the water (steam) adsorbed by the heating element to the working gas tank 402 when the EGR cooler main body 401 is warmed up is completed. Therefore, the ECU 5 proceeds to the process of S205, and switches the switching valve 404 from the open state to the closed state (this timing corresponds to the shutoff timing t4 in FIG. 5 described above). As a result, as described in the description of FIG. 8, the water (steam) collected in the working gas tank 402 is stored in the working gas tank 402. Then, after executing the processing of S205, the ECU 5 proceeds to the processing of S206, and resets the count value of the integrated valve opening time Cint to an initial value (that is, zero).

  As described above, when the switching valve 404 of the EGR cooler 400 is controlled according to the processing routine of FIG. 10, the water (steam) adsorbed on the heating element when the EGR cooler body 401 is warmed up can be collected in the working gas tank 402. At the same time, the water (steam) collected in the working gas tank 402 can be stored in the working gas tank 402. Thereby, when the next warm-up of the EGR cooler main body 401 becomes necessary, it becomes possible to efficiently and effectively warm the wall surface of the EGR gas passage 405 in the EGR cooler main body 401.

  In the processing routine of FIG. 10, the closing timing of the switching valve 404 (that is, the shutoff timing t4 in FIG. 5 described above) is determined using the accumulated valve opening time Cint as a parameter. A sensor for measuring the amount of stored water (water vapor) is attached to the working gas tank 402, and the measured value of the sensor is used to determine the working gas amount (for example, in the working gas tank 402 immediately before the warming-up of the EGR cooler body 401 is started). The switching valve 404 may be closed at the timing when it returns to the amount of water (steam) stored in the switching valve 404. Alternatively, a sensor for measuring the pressure in the working gas tank 402 is attached to the working gas tank 402, and the measured value of the sensor is set to a predetermined pressure (for example, the working gas tank 402 just before the warming-up of the EGR cooler body 401 is started). The switching valve 404 may be closed at the timing when the pressure returns to the internal pressure.

  Here, the “control unit” according to the present disclosure is realized by the ECU 5 executing the processing of S101-S102, the processing of S104-S105 of the processing routine of FIG. 9, and the processing routine of FIG. The “distribution control unit” according to the present disclosure is realized by the ECU 5 executing the processing of S103 and S106 in the processing routine of FIG.

  In the present embodiment, the heating element accommodated in the heating element accommodating section 407 contacts the partition wall separating the heating element accommodating section 407 and the EGR gas flow path 405, and the heating element It is arranged so as to be in contact with the partition wall separating the accommodating portion 407 and the coolant channel 406. However, when a substance having a high heat-resistant temperature is used as the heating element housed in the heating element housing section 407, the heating element contacts a partition wall separating the heating element housing section 407 and the EGR gas flow path 405, while The heating element may be arranged so that the heating element does not come into contact with the partition wall separating the heating element housing portion 407 and the coolant flow path 406. According to such a configuration, when the EGR cooler main body 401 is warmed up, the ratio of the heat transmitted to the wall surface of the EGR gas passage 405 to the heat generated by the heating element can be further increased. Therefore, it is possible to warm up the EGR cooler body 401 more efficiently.

Reference Signs List 1 internal combustion engine 2 intake passage 3 exhaust passage 4 EGR device 5 ECU
6 Temperature sensor 40 EGR flow path 41 EGR valve 400 EGR cooler 400a Upstream area 400b Downstream area 401 EGR cooler main body 402 Working gas tank 403 Communication flow path 404 Switching valve 405 EGR gas flow path 406 Refrigerant flow path 407 Heating element housing

Claims (1)

An EGR cooler which is disposed in the middle of an EGR flow path connecting the exhaust flow path and the intake flow path of the internal combustion engine and exchanges heat between a refrigerant and an EGR gas which is a gas flowing through the EGR flow path. So,
A flow path formed inside the EGR cooler, and an EGR gas flow path for flowing the EGR gas;
A refrigerant flow path for allowing the refrigerant to flow inside the EGR cooler, wherein a refrigerant flow path is formed such that heat exchange is performed between the EGR gas and the refrigerant flowing through the EGR gas flow path;
A space for accommodating a heating element that generates heat by adsorbing a predetermined working gas inside the EGR cooler, wherein at least a part of the heating element is formed to be in contact with a wall surface of the EGR gas passage. Heating element housing,
A working gas tank that stores the working gas, and a gas moving device that moves the working gas stored in the working gas tank from the working gas tank to the heating element housing unit,
The EGR cooler has an upstream region and a downstream region in the flow direction of the EGR gas,
The heating element housing is disposed in the downstream area of the EGR cooler, and the heating element contains an organic metal structure.
EGR cooler.

Images