JP2009036063A - Exhaust gas recirculation device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas recirculation device for an internal combustion engine capable of inhibiting clogging of an EGR cooler, stabilizing temperature of exhaust gas recirculated to an intake air passage better than before and simply adjusting the same. <P>SOLUTION: In the exhaust gas recirculation device for the internal combustion engine provided with an EGR passage 8 recirculating part of exhaust gas to the intake gas passage 4 from an exhaust gas passage 5 of the internal combustion engine 1 as EGR gas, and the EGR cooler 10A provided in the EGR passage 8 and cooling EGR gas, the EGR cooler 10A is provided with a cooling part 18 cooling EGR gas flowing in a channel L formed inside thereof and a slide valve 16 changing cross section area of the channel L by changing the number of cooling pipes 14 blocking an upstream side end part 14a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine that includes an EGR passage that recirculates a part of exhaust gas as EGR gas from an intake passage to an exhaust passage, and an EGR cooler that is provided in the EGR passage and cools the EGR gas.

  The EGR cooler and the bypass pipe are sandwiched between the EGR valve and the bypass valve so that the EGR cooler and the bypass pipe are arranged in parallel, and the EGR valve and the bypass valve are controlled according to the temperature of the exhaust gas discharged from the engine. An exhaust gas recirculation device that adjusts the temperature of the exhaust gas returned to the intake system is known (see Patent Document 1). Further, the cooling unit and the bypass unit are provided in parallel, and the flow rate of the exhaust gas passing through the cooling unit and the bypass unit are adjusted by adjusting the position of the swing valve so that the temperature of the exhaust gas returned to the intake pipe becomes a predetermined temperature. There is known an exhaust gas recirculation control device that adjusts the flow rate of exhaust gas passing through each of them (see Patent Document 2). In addition, Patent Documents 3 to 5 exist as prior art documents related to the present invention.

International Publication No. 03/060314 Pamphlet JP 2006-37765 A JP 2005-273564 A JP 2005-98278 A JP 2003-113742 A

  When adjusting the temperature of the exhaust gas recirculated to the intake passage by changing the mixing ratio of the exhaust gas that has passed through the EGR cooler and the exhaust gas that has bypassed the EGR cooler as in the devices of Patent Documents 1 and 2, the EGR cooler Since the flow resistance differs greatly between the bypass passage and the bypass passage, the flow rate of the exhaust gas flowing through each of them is not stable, and it is difficult to stably adjust the temperature of the exhaust gas recirculated to the intake passage to the target temperature. In addition, when the flow rate of the exhaust gas to be passed through the EGR cooler is small, the flow rate of the exhaust gas in the EGR cooler decreases, and particulate matter such as soot contained in the exhaust gas easily adheres to the EGR cooler. Therefore, the EGR cooler may be easily clogged with particulate matter.

  Accordingly, the present invention provides an exhaust gas recirculation device for an internal combustion engine that can suppress the clogging of the EGR cooler and can stably adjust the temperature of the exhaust gas recirculated to the intake passage to a target temperature more easily than before. For the purpose.

  An exhaust gas recirculation device for an internal combustion engine according to the present invention includes an EGR passage that recirculates a part of exhaust gas from an exhaust passage of the internal combustion engine to an intake passage as EGR gas, an EGR cooler that is provided in the EGR passage and cools the EGR gas, In the exhaust gas recirculation apparatus for an internal combustion engine, the EGR cooler includes at least one of a cooling unit that cools EGR gas flowing through a flow path formed therein, a cross-sectional area of the flow path, and a length of the flow path The above-described problem is solved by providing cooling capacity changing means for changing either one of them (Claim 1).

  According to the exhaust gas recirculation apparatus of the present invention, since at least one of the cross-sectional area of the flow path of the cooling section and the length of the flow path can be changed, for example, EGR according to the temperature and flow rate of EGR gas guided to the cooling section The cooling performance of the EGR gas by the cooler can be changed. In this case, since the temperature of the EGR gas flowing out from the cooling section can be changed, the EGR gas temperature is compared with that in which the temperature of the EGR gas is adjusted by the ratio of the uncooled EGR gas to the cooled EGR gas. The temperature control accuracy can be improved. Therefore, for example, by changing the cooling performance of the EGR cooler by changing the cross-sectional area and length of the flow path according to the temperature of the exhaust gas of the internal combustion engine, the temperature of the exhaust gas that is recirculated to the intake passage, that is, the temperature of the EGR gas. Can be adjusted to the target temperature stably and easily. Further, for example, by changing the cross-sectional area and length of the flow path according to the pressure difference before and after the cooling unit, and changing the flow resistance of the cooling unit, the flow rate of the EGR gas passing through the cooling unit is stable and easy. It can also be adjusted. This also makes it possible to adjust the temperature of the EGR gas to the target temperature stably and easily. Furthermore, according to the exhaust gas recirculation apparatus of the present invention, when the flow rate of the EGR gas to be passed through the cooling unit is small, the flow area of the EGR gas in the cooling unit is increased by decreasing the cross-sectional area of the flow channel, Since the EGR gas can be quickly discharged from the cooling section by shortening the length, it is possible to prevent the particulate matter or the like from adhering to the flow path. Therefore, clogging of the EGR cooler can be suppressed.

  In one form of the exhaust gas recirculation device of the present invention, the cooling unit is disposed so as to penetrate the refrigerant chamber through which the refrigerant flows and the EGR gas passes through the interior of the refrigerant chamber to form the flow path. The cooling capacity changing means may change the cross-sectional area of the flow path by changing the number of the plurality of cooling pipes that allow passage of EGR gas. ). Thus, by forming a flow path with a plurality of cooling pipes and changing the number of cooling pipes that allow passage of EGR gas among the plurality of cooling pipes, the cross-sectional area of the flow path can be easily changed. Can do.

  In this embodiment, the plurality of cooling pipes are arranged in a predetermined direction and arranged so that at least one end thereof is aligned on the same plane, and are aligned on the same plane as the cooling capacity changing means. The cooling tube is disposed so as to face one end portion of the plurality of cooling pipes, and is fully closed to block all one end portions of the plurality of cooling pipes and fully opened to open all one end portions of the plurality of cooling pipes. There may be provided a slide valve means for reciprocating a valve body driven between positions in the predetermined direction to change the number of the cooling pipes that allow passage of EGR gas. 3). In this case, the number of cooling pipes that allow passage of EGR gas among the plurality of cooling pipes can be changed by one slide valve means.

  The slide valve means may be configured such that when one end of two or more cooling pipes is closed by the valve body, the other end of one cooling pipe among the cooling pipes which have closed one end thereof. EGR gas that has flowed into the one cooling pipe from a portion leaks from a gap between one end of the one cooling pipe and the valve body, and then the cooling pipe whose one end is closed by the valve body It may be provided so as to be prevented from flowing into the other cooling pipe from one end of the other cooling pipe and being discharged from the other end of the other cooling pipe. 4). By providing the slide valve means in this way, it is possible to prevent a flow path different from the flow path from being formed by the cooling pipes blocking the opening. Therefore, useless cooling of the EGR gas can be suppressed, and clogging of the cooling pipe that closes the opening can be suppressed.

  In an embodiment of the exhaust gas recirculation apparatus according to the present invention in which a heat exchanger having a plurality of cooling pipes is provided as a cooling unit, the smaller the amount of EGR gas to be cooled in the cooling unit, the more it is included in the EGR gas. A control means for controlling the cooling capacity changing means may be further provided so that the number of the cooling pipes that allow passage of EGR gas among the plurality of cooling pipes decreases as the amount of the particulate matter increases ( Claim 5). By controlling the cooling capacity changing means in this way, it is possible to appropriately suppress adhesion of particulate matter or the like in the cooling pipe.

  In this embodiment, the EGR cooler bypasses the cooling unit and guides EGR gas downstream of the cooling unit, a fully closed position that fully closes the bypass passage, and a fully open position that fully opens the bypass passage. Bypass valve means capable of changing the opening between the control means, the control means, the number of cooling pipes allowed to pass EGR gas among the plurality of cooling pipes by the cooling capacity changing means The opening degree of the bypass valve means may be controlled so that the amount of EGR gas passing through the bypass passage increases as the amount decreases. By providing the bypass passage in this way, the temperature adjustment range by the EGR cooler can be expanded. Further, since the opening degree of the bypass valve means and the number of cooling pipes that are allowed to pass EGR gas are adjusted in association with each other, for example, the sum of the flow rate that passes through the bypass passage and the flow rate that passes through the cooling unit is the same. By adjusting these, the temperature of the EGR gas flowing out from the EGR cooler can be changed while maintaining the flow rate of the EGR gas passing through the EGR cooler at a constant flow rate.

  In one form of the exhaust gas recirculation apparatus of the present invention in which a heat exchanger having a plurality of cooling pipes is provided as a cooling unit, the plurality of cooling pipes are two cooling pipe groups formed by a different number of cooling pipes. The EGR cooler further includes a first bypass passage and a second bypass passage that bypasses the cooling section and guides EGR gas downstream of the cooling section, and the cooling capacity changing means includes the two One end of each of the cooling pipes forming one cooling pipe group of the cooling pipe group is closed and the closed position where the first bypass passage is opened and one end of the cooling pipe forming the one cooling pipe group A first switching valve that can be switched between an open position that opens each part and closes the first bypass passage, and one of the cooling pipes that forms the other cooling pipe group of the two cooling pipe groups A closed position that closes each of the portions and opens the second bypass passage, and an open position that opens one end of the cooling pipe forming the other cooling pipe group and closes the second bypass passage. A second switching valve that can be switched between them may be provided (Claim 7). In this case, the cross-sectional area of the flow path can be switched in four stages depending on the combination of the position of the first switching valve and the position of the second switching valve. By switching both the first switching valve and the second switching valve to the open position, the cross-sectional area of the flow path can be maximized. On the other hand, the cross-sectional area of the flow path can be minimized by switching both the first switching valve and the second switching valve to the closed position. In addition, by switching the switching valve of one cooling pipe group having a large number of cooling pipes of the two cooling pipe groups to the open position and switching the switching valve of the other cooling pipe group to the closed position, the cross-sectional area of the flow path is reduced. It can be adjusted to the second largest value, and the switching valve of one cooling pipe group is switched to the closed position and the switching valve of the other cooling pipe group is switched to the open position so that the cross-sectional area of the flow path is set to the third largest value. Can be adjusted. In this way, the cross-sectional area of the flow path can be easily changed by switching the positions of these switching valves.

  In one form of the exhaust gas recirculation apparatus of the present invention, the flow path is divided into a plurality of sections, and the cooling capacity changing means changes the number of sections through which EGR gas should pass through the plurality of sections. You may change the length of a flow path (Claim 8). By dividing the flow path into a plurality of sections in this manner, the length of the flow path can be easily changed.

  In this embodiment, the flow path is divided into a first section and a second section, and the EGR cooler bypasses the cooling section and guides EGR gas downstream of the second section; and A second bypass passage that guides EGR gas downstream from the flow path between the first section and the second section to the downstream of the second section, and uses EGR gas as the cooling capacity changing means as the first section. A first valve means capable of switching between an introduction position leading to EGR gas and a bypass position leading EGR gas to the first bypass passage, and allowing EGR gas to flow into the second section and EGR into the second bypass passage. Second valve means capable of switching between a permitting position for blocking gas inflow and a blocking position for blocking EGR gas inflow into the second section and permitting inflow of EGR gas into the second bypass passage. , It may also be provided with (claim 9). In this case, the length of the flow path can be changed in three stages by the combination of the position of the first valve means and the position of the second valve means. By switching the first valve means to the introduction position and switching the second valve means to the permission position, the EGR gas can flow in both the first section and the second section. That is, the length of the flow path is maximized. By switching the first valve means to the introduction position and switching the second valve means to the blocking position, EGR gas can flow only in the first section. In this case, the length of the flow path is the second largest value. By switching the first valve means to the bypass position, the entire amount of EGR gas can be guided to the first bypass passage. In this case, introduction of EGR gas into the cooling section is prevented, and the length of the flow path is zero, that is, minimized. Thus, according to this embodiment, the length of the flow path can be easily changed by the two valve means.

  Further, the smaller the amount of EGR gas to be cooled in the cooling section and the larger the amount of particulate matter contained in the EGR gas, the shorter the length of the flow path through which the EGR gas should pass. Control means for controlling the first valve means and the second valve means may be further provided (claim 10). The smaller the amount of EGR gas and the greater the amount of particulate matter, the easier the particulate matter will adhere to the flow path. Therefore, the length of the flow path is changed in this way, and the EGR gas is removed from the flow path. By discharging quickly, adhesion of particulate matter into the flow path can be appropriately suppressed.

  In this embodiment, the control means switches the first valve means to the introduction position and switches the second valve means to the permission position to supply EGR gas to both the first section and the second section. The longest state of guiding, the intermediate state in which the first valve means is switched to the introduction position and the second valve means is switched to the blocking position to guide EGR gas only to the first section, and the first valve means is bypassed The first valve means and the second valve means are switched so that the state of the EGR cooler is switched to the shortest state where the second valve means is switched to the blocking position and the EGR gas is guided to the first bypass passage. The amount of particulate matter contained in the EGR gas increases as the amount of EGR gas to be controlled and cooled by the cooling unit decreases. I, wherein the state of the EGR cooler up state, the intermediate state may be switched in the order of the shortest state (claim 11). By switching the state of the EGR cooler in this order, the length of the flow path can be shortened as the particulate matter easily adheres to the flow path. Therefore, it is possible to appropriately suppress the particulate matter from adhering to the flow path.

  As described above, according to the exhaust gas recirculation device of the present invention, since at least one of the cross-sectional area of the flow path of the cooling unit and the length of the flow path can be changed, the EGR that recirculates to the intake air passage more than before. The gas temperature can be adjusted to the target temperature stably and easily. Further, when the operation state of the internal combustion engine becomes a state where particulate matter or the like is likely to adhere to the flow path, the particulate matter is changed by changing at least one of the cross-sectional area and the length of the flow path of the cooling unit. Can be prevented from adhering to the inside of the flow path. Therefore, clogging of the EGR cooler can be suppressed.

(First form)
FIG. 1 is a diagram schematically illustrating an internal combustion engine in which an exhaust gas recirculation apparatus according to a first embodiment of the present invention is incorporated. An internal combustion engine (hereinafter sometimes referred to as an engine) 1 shown in FIG. 1 is a diesel engine mounted on a vehicle as a driving power source, and a plurality (four in FIG. 1) of cylinders 2 are provided. An engine body 3 and an intake passage 4 and an exhaust passage 5 connected to each cylinder 2 are provided. The intake passage 4 is provided with an air filter 6 for intake air filtration and a throttle valve 7 for adjusting the intake air amount. As shown in FIG. 1, the exhaust passage 5 and the intake passage 4 are connected by an EGR passage 8. The EGR passage 8 is a known one that recirculates a part of the exhaust gas from the exhaust passage 5 to the intake passage 4 as EGR gas. The EGR passage 8 is provided with an EGR valve 9 that adjusts the flow rate of the EGR gas to be recirculated to the intake passage 4 and an EGR cooler 10A that cools the EGR gas by exchanging heat between the EGR gas and the cooling water.

  FIG. 2 is an enlarged view showing the inside of the EGR cooler 10A. The EGR cooler 10A includes a casing 11 into which EGR gas is guided, partition plates 13 and 13 provided so as to form a refrigerant chamber 12 in which cooling water as a refrigerant flows in the casing 11, and the refrigerant chamber 12. And a plurality of cooling pipes 14 arranged so as to pass through and through which the EGR gas passes. As shown in FIG. 2, the plurality of cooling pipes 14 are arranged in one direction in the casing 11. The plurality of cooling pipes 14 are arranged such that the upstream end 14a and the downstream end 14b are aligned on the same plane. Fins 15 are provided in the cooling pipe 14 so as to promote the transfer of heat from the EGR gas to the cooling water. EGR gas is introduced into the casing 11 from an inlet 11a provided on the left side of FIG. Thereafter, the EGR gas passes through the plurality of cooling pipes 14 and is discharged from the discharge port 11b provided on the right side of FIG. Therefore, the EGR gas flow path L is formed by the plurality of cooling pipes 14. On the other hand, cooling water is introduced into the refrigerant chamber 12 from a cooling water inlet 12a provided on the lower side of FIG. Thereafter, the cooling water passes between the plurality of cooling pipes 14 and is discharged from a cooling water discharge port 12b provided on the upper side of FIG. By flowing the cooling water in this way, the EGR gas can be cooled by causing heat exchange between the EGR gas passing through the plurality of cooling pipes 14 and the cooling water. Therefore, the cooling unit 18 of the present invention is formed by the refrigerant chamber 12 and the plurality of cooling pipes 14. As the cooling water, for example, cooling water of a cooling system provided in the engine 1 for cooling the engine body 3 is used.

  As shown in FIG. 2, the EGR cooler 10 </ b> A is provided with a slide valve 16 that can be reciprocated in the direction intersecting the flow of EGR gas along the upstream end portions 14 a of the plurality of cooling pipes 14. . The slide valve 16 is an actuator that drives the valve body 16a between a fully closed position that closes the upstream ends 14a of all the cooling pipes 14 and a fully open position that opens the upstream ends 14a of all the cooling pipes 14. 17 is provided.

  FIG. 3 is an enlarged view of the range A in FIG. As shown in FIG. 3, the slide valve 16 has almost no gap between the valve body 16a and the upstream end portion 14a when the valve body 16a is driven to a position where the upstream end portion 14a of the cooling pipe 14 is closed. It is provided so that it cannot be done. Further, in the slide valve 16, when the upstream end portions 14a of the two or more cooling pipes 14 are closed by the valve body 16a, EGR gas leaked from the upstream end portions 14a of the cooling pipes 14 is the upstream end portion. It is provided so as to be restricted from flowing into the upstream end portion 14a of the other cooling pipe 14 blocking the 14a. That is, EGR gas flows in from the downstream end 14b of the cooling pipe 14 blocking the upstream end 14a, and passes through the upstream end 14a of the cooling pipe 14 and the upstream end 14a of the other cooling pipes 14. Then, the slide valve 16 is provided so that the flow of the EGR gas discharged from the downstream end portion 14b of the other cooling pipe 14 is not formed.

  The operation of the slide valve 16 is controlled by an engine control unit (ECU) 20. The ECU 20 is configured as a computer including a microprocessor and peripheral devices such as a ROM and a RAM necessary for its operation, and refers to output signals from various sensors provided in the engine 1 so as to control the throttle valve 7 and the EGR valve 9. Is a well-known computer unit that controls the operating state of the engine 1. The ECU 20 calculates the amount of EGR gas to be returned to the intake passage 4 based on, for example, the rotational speed and load of the engine 1, and opens the EGR valve 9 so that the calculated amount of EGR gas is returned to the intake passage 4. Control the degree. The control of the EGR gas may be performed by a known control method for increasing the amount of EGR gas to be recirculated as the load and the rotation speed of the engine 1 are increased, for example. The ECU 20 is connected to various sensors such as a crank angle sensor 21 that outputs a signal corresponding to the engine rotational speed (rotation speed) of the engine 1 and an air flow meter 22 that outputs a signal corresponding to the intake air amount.

  An outline of operation control of the slide valve 16 by the ECU 20 will be described. The position of the slide valve 16 is adjusted so that the temperature of the EGR gas returned to the intake passage 4 is stably adjusted to the target temperature. Note that the target temperature of the EGR gas is appropriately set according to the operating state of the engine 1 so that the exhaust emission is improved. The temperature of the EGR gas can be changed by changing the cross-sectional area of the flow path L by adjusting the number of the cooling pipes 14 through which the EGR gas passes. For example, when the valve body 16a of the slide valve 16 is moved to the fully open position side to increase the number of the cooling pipes 14 through which the EGR gas passes and the cross-sectional area of the flow path L is increased, the temperature of the EGR gas is decreased. be able to. On the other hand, when the valve body 16a of the slide valve 16 is moved to the fully closed position side to reduce the number of the cooling pipes 14 through which the EGR gas passes and the cross-sectional area of the flow path L is reduced, the temperature of the EGR gas is increased. Can be made. Therefore, for example, a temperature sensor that outputs a signal corresponding to the temperature of the EGR gas is provided in the EGR passage 8 between the EGR cooler 10A and the EGR valve 9, and the temperature of the EGR gas detected by the temperature sensor is The slide valve 16 is controlled so as to be adjusted to a target temperature suitable for the operating state. Hereinafter, this control may be referred to as normal control.

  Further, the slide valve 16 is controlled based on the operating state of the engine 1 so that clogging of the plurality of cooling pipes 14 is suppressed. Depending on the operating state of the engine 1, particulate matter or the like is likely to adhere to the cooling pipe 14, and the cooling pipe 14 may be easily clogged. For example, when the amount of EGR gas to be recirculated to the intake passage 4 is small, the flow rate of the EGR gas when passing through the cooling pipe 14 is decreased, and particulate matter and the like are easily attached. Therefore, the cooling pipe 14 is easily clogged. In addition, for example, when the amount of hydrocarbon (HC) in the EGR gas, that is, the exhaust gas is large, particulate matter easily adheres in the cooling pipe 14, so that the cooling pipe 14 is easily clogged. Therefore, when the cooling pipe 14 is easily clogged in this way, the position of the slide valve 16 is adjusted so that the flow rate of the EGR gas when passing through the cooling pipe 14 is increased. That is, when the cooling pipe 14 is easily clogged, the valve body 16a of the slide valve 16 is moved to the fully closed position side to reduce the number of cooling pipes 14 through which the EGR gas passes. Thereby, since the cross-sectional area of the flow path L can be reduced, the flow rate of the EGR gas in the cooling pipe 14 can be increased. Hereinafter, this control may be referred to as flow rate increase control.

  FIG. 4 shows a valve control routine that the ECU 20 repeatedly executes at a predetermined cycle during operation of the engine 1 to control the operation of the slide valve 16 as described above. The ECU 20 functions as control means of the present invention by executing this control routine.

  In the control routine of FIG. 4, the ECU 20 first acquires the operating state of the engine 1 in step S11. As the operating state of the engine 1, the rotational speed of the engine 1 and the intake air amount are acquired. In the next step S12, the ECU 20 determines whether or not the operation state of the engine 1 is an operation state in which the cooling pipe 14 is likely to be clogged. That is, it is determined whether or not the engine 1 is operated in an operation state in which the flow rate of EGR gas is low or in an operation state in which HC in the exhaust gas increases. When it is determined that the operation state of the engine 1 is an operation state in which the cooling pipe 14 is likely to be clogged, the process proceeds to step S13, and the ECU 20 controls the slide valve 16 by flow rate increase control. At this time, the valve body 16a of the slide valve 16 is driven by the actuator 17 at a position where only one of the plurality of cooling pipes 14 is opened and the rest is closed. Thereafter, the current control routine is terminated.

  On the other hand, when it is determined that the operation state of the engine 1 is an operation state in which clogging of the cooling pipe 14 is unlikely to occur, the process proceeds to step S14, and the ECU 20 controls the slide valve 16 by normal control. At this time, as described above, the position of the valve body 16a of the slide valve 16 is controlled according to the temperature of the EGR gas discharged from the EGR cooler 10A. Thereafter, the current control routine is terminated.

  According to the EGR cooler 10A, the number of the cooling pipes 14 through which the EGR gas passes can be changed, and thereby the size of the cross-sectional area of the flow path L through which the EGR gas passes can be changed. The cooling performance of the EGR cooler 10A can be appropriately changed according to the flow rate. Therefore, for example, the temperature of the EGR gas discharged from the EGR cooler 10A is conventionally changed by changing the cross-sectional area of the flow path L in accordance with the exhaust temperature of the engine 1 and thereby changing the cooling performance of the EGR cooler 10A. The target temperature can be adjusted more stably and easily. Further, for example, even if the pressure difference between both ends of the EGR passage 8 changes due to the operating state of the engine 1 or the like, the cross-sectional area of the flow path L can be changed and the flow resistance of the flow path L can be changed. The flow rate of EGR gas passing through 10A can be adjusted stably and easily. Therefore, the temperature of the EGR gas can be adjusted to the target temperature more stably.

  Further, when the engine 1 is operated in an operation state in which the cooling pipe 14 is likely to be clogged, the number of the cooling pipes 14 through which the EGR gas passes is decreased and the flow rate of the EGR gas passing through the cooling pipe 14 is increased. Therefore, adhesion of particulate matter or the like in the cooling pipe 14 can be suppressed. Therefore, clogging of the cooling pipe 14 can be suppressed. Note that the slide valve 16 corresponds to the cooling capacity changing means of the present invention by changing the cross-sectional area of the flow path L of the EGR cooler 10A in this way.

  FIG. 5 shows a main part of a modification of the exhaust gas recirculation apparatus according to the first embodiment. FIG. 5 is an enlarged view of the EGR cooler 10B according to the modification. In FIG. 5, the same parts as those in FIG. As shown in FIG. 5, the EGR cooler 10 </ b> A of this modified example bypasses the cooling unit 30 formed by the refrigerant chamber 12 and the plurality of cooling pipes 14 to guide the EGR gas downstream of the cooling unit 30. The EGR cooler 10A shown in FIG. 2 is different from the EGR cooler 10A shown in FIG. The operation of the on-off valve 32 is controlled by the ECU 20. The ECU 20 opens the on-off valve 32 when it is necessary to introduce EGR gas having a high temperature into the intake passage 4, for example, when the engine 1 is warmed up.

  According to the EGR cooler 10B, by guiding the EGR gas to the bypass passage 31, the EGR gas can be discharged from the EGR cooler 10B with almost no cooling. Therefore, EGR gas having a higher temperature than that of the EGR cooler 10 </ b> A in FIG. 2 can be introduced into the intake passage 4.

  The on-off valve 32 and the slide valve 16 may be operated in association with each other. For example, the opening degree of the on-off valve 32 is controlled according to the number of the cooling pipes 14 whose upstream end portions 14a are blocked by the valve body 16a of the slide valve 16, and the valve body 16a is driven to the fully open position side. The on-off valve 32 is controlled to be closed as the number of the cooling pipes 14 with the upstream end 14a blocked is reduced. By controlling the opening degree of the on-off valve 32 in this way, it is possible to suppress a decrease in the flow rate of the EGR gas in the cooling pipe 14, so that clogging of the cooling pipe 14 can be suppressed.

(Second form)
An exhaust gas recirculation apparatus according to the second embodiment of the present invention will be described with reference to FIGS. In this embodiment as well, FIG. 1 is referred to for the engine 1. FIG. 6 shows an enlarged view of the EGR cooler 10C of the exhaust gas recirculation apparatus according to the second embodiment. In FIG. 6, the same parts as those in FIG. As shown in FIG. 6, in the EGR cooler 10 </ b> C, the refrigerant chamber 12 is formed in the center of the casing 11 and the cooling unit 40 is provided. Further, a first bypass passage 41 is provided on one side (upper side in FIG. 6) of the cooling unit 40, and a second bypass passage 42 is provided on the other side (lower side in FIG. 6). That is, in the EGR cooler 10C, the inside of the casing 11 is divided into three stages in a direction intersecting the flow direction of the EGR gas, and the first bypass passage 41, the cooling unit 40, and the second bypass passage 42 are arranged in order from the top in FIG. Provided. The height of the second bypass passage 42 is set higher than the height of the first bypass passage 41. Therefore, the flow passage cross-sectional area of the second bypass passage 42 is set wider than the flow passage cross-sectional area of the first bypass passage 41.

  As shown in FIG. 6, the cooling section 40 is provided with a plurality of cooling pipes 14 penetrating the refrigerant chamber 12, and the cooling pipe 14 forms a flow path L through which the EGR gas flows in the cooling section 40. Further, the cooling unit 40 is provided with a wall 43 arranged along the cooling pipe 14, and the plurality of cooling pipes 14 of the cooling unit 40 by the wall 43 are used for the first cooling pipe group 44 and the second cooling pipe group. 45. The first cooling pipe group 44 and the second cooling pipe group 45 have different numbers of cooling pipes 14, and the second cooling pipe group 45 has more cooling pipes 14 than the first cooling pipe group 44.

  Further, the EGR cooler 10 </ b> C includes a first switching valve 46 and a second switching valve 47. The first switching valve 46 includes a rotating shaft 46a and two valve bodies 46b. As shown in FIG. 6, the two valve bodies 46b are attached to the rotating shaft 46a at a distance of about 90 °. Similarly, the second switching valve 47 includes a rotating shaft 47a and two valve bodies 47b, and the two valve bodies 47b are attached to the rotating shaft 47a at a distance of about 90 °. The first switching valve 46 opens the upstream end 14 a of each cooling pipe 14 of the first cooling pipe group 44 and closes the first bypass passage 41, and each of the first cooling pipe groups 44. It is possible to switch to the closed position P12 (see FIG. 7) where the upstream end portion 14a of the cooling pipe 14 is closed and the first bypass passage 41 is opened. The second switching valve 47 opens the upstream end portion 14a of each cooling pipe 14 of the second cooling pipe group 45 and closes the second bypass passage 42, and each of the second cooling pipe group 45. It is possible to switch to the closed position P22 (see FIG. 8) where the upstream end portion 14a of the cooling pipe 14 is closed and the second bypass passage 42 is opened. The first switching valve 46 is provided such that there is almost no gap between the valve body 46b and the upstream end 14a of the cooling pipe 14 when the position is switched to the closed position P12. Similarly, the second switching valve 47 is also provided so that there is almost no gap between the valve body 47b and the upstream end portion 14a of the cooling pipe 14 when the position is switched to the closed position P22.

  According to this EGR cooler 10C, the cross-sectional area of the flow path L formed in the cooling unit 40 by the plurality of cooling pipes 14 can be adjusted in four stages. As shown in FIG. 6, by switching the first switching valve 46 to the open position P11 and switching the second switching valve 47 to the open position P21, the upstream end portions 14a of all the cooling pipes 14 are opened. Therefore, the cross-sectional area of the flow path L is maximized. In this case, since both the first bypass passage 41 and the second bypass passage 42 are closed, the entire amount of EGR gas is guided to the cooling unit 40. Hereinafter, this state may be referred to as a first state.

  FIG. 7 shows the EGR cooler 10C in a state where the first switching valve 46 is switched to the closed position P12 and the second switching valve 47 is switched to the open position P21. In this case, the EGR gas is guided to the first bypass passage 41 and the second cooling pipe group 45. As described above, the number of cooling pipes 14 arranged in the second cooling pipe group 45 is larger than the number of cooling pipes 14 arranged in the first cooling pipe group 44. Therefore, the cross-sectional area of the flow path L is the second largest value. Hereinafter, this state may be referred to as a second state.

  FIG. 8 shows the EGR cooler 10C in a state where the first switching valve 46 is switched to the open position P11 and the second switching valve 47 is switched to the closed position P22. In this case, the EGR gas is guided to the second bypass passage 42 and the first cooling pipe group 44. Therefore, the cross-sectional area of the flow path L is the third largest value. Hereinafter, this state may be referred to as a third state.

  FIG. 9 shows the EGR cooler 10C in a state where the first switching valve 46 is switched to the closed position P12 and the second switching valve 47 is switched to the closed position P22. In this case, since the upstream end portions 14a of all the cooling pipes 14 are closed, the cross-sectional area of the flow path L is 0, that is, the minimum. On the other hand, since both the first bypass passage 41 and the second bypass passage 42 are opened, the entire amount of EGR gas is guided to the bypass passages 41 and 42. Hereinafter, this state may be referred to as a fourth state.

  The operation of the first switching valve 46 and the operation of the second switching valve 47 are controlled by the ECU 20. The ECU 20 controls the first switching valve 46 and the second switching valve 47 so that the state of the EGR cooler 10C is switched based on, for example, the rotational speed and load of the engine 1. This control may be performed, for example, by storing the relationship between the rotational speed and load of the engine 1 shown in FIG. 10 and each state of the EGR cooler 10C as a map in the ROM of the ECU 20, and referring to this map. . The relationship shown in FIG. 10 as an example is obtained in advance through experiments and stored in the ROM of the ECU 20. As shown in FIG. 10, the state of the EGR cooler 10C is switched in the order of the first state, the second state, the third state, and the fourth state as the rotational speed of the engine 1 increases and the load increases. The first switching valve 46 and the second switching valve 47 are each controlled. Further, when the engine 1 is operated in an operation state in which the cooling pipe 14 is likely to be clogged, the ECU 20 changes the state of the EGR cooler 10C to the first state in order to reduce the number of the cooling pipes 14 through which the EGR gas passes. The second state, the third state, and the fourth state may be sequentially switched. By switching the state of the EGR cooler 10C in this way, the flow rate of the EGR gas when passing through the cooling pipe 14 can be increased, and adhesion of particulate matter or the like in the cooling pipe 14 can be suppressed.

  Also in the exhaust gas recirculation device of the second embodiment, the cross-sectional area of the flow path L of the EGR cooler 10C can be changed according to the temperature and flow rate of the EGR gas, thereby changing the cooling performance of the EGR cooler 10C. Therefore, similarly to the first embodiment, the temperature of the EGR gas can be adjusted to the target temperature more stably and easily than before. Further, when the engine 1 is operated in an operation state in which the cooling pipe 14 is likely to be clogged, the flow rate of the EGR gas passing through the cooling pipe 14 is reduced by reducing the number of cooling pipes 14 through which the EGR gas passes. Since it can raise, clogging of the cooling pipe 14 can be suppressed. Thus, by changing the cross-sectional area of the flow path L of the EGR cooler 10C, the first switching valve 46 and the second switching valve 47 correspond to the cooling capacity changing means of the present invention. In the EGR cooler 10C of the second embodiment, the number of cooling pipe groups provided in the EGR cooler is not limited to two. Three or more cooling pipe groups may be provided, and the number of cooling pipe groups through which EGR gas passes may be appropriately changed. In this case, the cross-sectional area of the channel can be adjusted more finely.

(Third form)
An exhaust gas recirculation apparatus according to a third embodiment of the present invention will be described with reference to FIGS. In this embodiment as well, FIG. 1 is referred to for the engine 1. FIG. 11 is an enlarged view of the EGR cooler 10D of the exhaust gas recirculation apparatus according to the third embodiment. In FIG. 11, the same reference numerals are given to portions common to FIG. 2, and description thereof is omitted. As shown in FIG. 11, the EGR cooler 10 </ b> D includes a main passage 50 connected to the EGR passage 8, one end connected to the main passage 50 and the other end connected to the intermediate chamber 51. A first cooling section 52 and a second cooling section 53 communicated with each other, and a bypass path 54 as a second bypass path that connects the intermediate chamber 51 and the main path 50 downstream from the connection position of the second cooling section 53 are provided. ing.

  The first cooling unit 52 includes a first refrigerant chamber 55 through which cooling water flows and a plurality of cooling pipes 14 provided so as to penetrate the first refrigerant chamber 55. The second cooling unit 53 includes a second refrigerant chamber 56 through which cooling water flows and a plurality of cooling pipes 14 provided so as to penetrate the second refrigerant chamber 56. As shown in FIG. 11, the first cooling part 52 and the second cooling part 53 are such that the connection position between the first cooling part 52 and the main passage 50 is more than the connection position between the second cooling part 53 and the main passage 50. Arranged on the upstream side and adjacent to each other. Further, the number and length of the cooling pipes 14 arranged in the first cooling unit 52 and the number and length of the cooling pipes 14 arranged in the second cooling unit 53 are set to be substantially the same. In this EGR cooler 10D, the EGR gas can be passed through the first cooling part 52 and the second cooling part 53 in this order, so in this embodiment, the cooling pipe 14 of the first cooling part 52 and the cooling pipe 14 of the second cooling part 53 are used. As a result, a flow path L is formed. Therefore, both the 1st cooling part 52 and the 2nd cooling part 53 are equivalent to the cooling part of this invention. And the 1st cooling part 52 is equivalent to the 1st section of the present invention, and the 2nd cooling part 53 is equivalent to the 2nd section.

  The EGR cooler 10 </ b> D is provided in the main passage 50, closes the main passage 50, opens the introduction position P <b> 31 that guides the EGR gas to the first cooling unit 52, and the main passage 50, and EGR gas from the second cooling unit 53. The first switching valve 57 as the first valve means that can be switched between the bypass position P32 (see FIG. 13) for preventing the outflow of the EGR gas, and the second cooling unit while preventing the EGR gas from flowing into the bypass passage 54 A permission position P41 that permits the inflow of EGR gas to 53, and a blocking position P42 that permits the inflow of EGR gas to the bypass passage 54 and blocks the inflow of EGR gas to the second cooling section 53 (see FIG. 12). And a second switching valve 58 as second valve means that can be switched between.

  According to the EGR cooler 10D, the EGR gas cooling performance of the EGR cooler 10D can be changed by switching the positions of the first switching valve 57 and the second switching valve 58. FIG. 11 shows the EGR cooler 10D in a state where the first switching valve 57 is switched to the introduction position P31 and the second switching valve 58 is switched to the permission position P41. In this case, the EGR gas is guided from the main passage 50 to the first cooling section 52 as indicated by an arrow A in FIG. 11, and then returns to the main passage 50 through the first cooling section 52 and the second cooling section 53. It is. Since the EGR gas passes through the cooling pipe 14 of the first cooling section 52 and the cooling pipe 14 of the second cooling section 53, the length of the flow path L in the EGR cooler 10D is equal to the length of the cooling pipe 14 of the first cooling section 52. The total length of the cooling pipes 14 of the second cooling unit 53 is the length, and the length of the flow path L is maximized. Therefore, this state corresponds to the longest state of the present invention. Further, since the entire amount of EGR gas passes through both the cooling units 52 and 53, the cooling performance of the EGR cooler 10D is the highest. Hereinafter, this state may be referred to as an eleventh state.

  FIG. 12 shows the EGR cooler 10D in a state where the first switching valve 57 is switched to the introduction position P31 and the second switching valve 58 is switched to the blocking position P42. In this case, as shown by the arrow B in FIG. 12, the entire amount of EGR gas is led to the first cooling unit 52 and then led to the main passage 50 via the bypass passage 54. Therefore, in this state, the length of the flow path L in the EGR cooler 10D is the length of the cooling pipe 14 of the first cooling unit 52, and is the second longest value. Therefore, this state corresponds to the intermediate state of the present invention. Further, in this state, the entire amount of EGR gas is guided to the first cooling unit 52 and cooled, so that the cooling performance of the EGR cooler 10D has the second highest value. Hereinafter, this state may be referred to as a twelfth state.

  FIG. 13 shows the EGR cooler 10D in a state where the first switching valve 57 is switched to the bypass position P32 and the second switching valve 58 is switched to the blocking position P42. In this case, as indicated by an arrow C in FIG. 13, part of the EGR gas is guided to the first cooling unit 52, and the remaining EGR gas passes through the main passage 50 as it is. The EGR gas guided to the first cooling unit 52 is cooled by the first cooling unit 52 and then guided to the main passage 50 via the bypass passage 54. Therefore, in this state, only a part of the EGR gas guided to the first cooling unit 52 is cooled, so that the cooling performance of the EGR cooler 10D is the third highest value. Hereinafter, this state may be referred to as a thirteenth state.

  FIG. 14 shows the EGR cooler 10D in a state where the first switching valve 57 is switched to the bypass position P32 and the second switching valve 58 is switched to the permission position P41. In this case, discharge of EGR gas from the second cooling unit 53 is blocked by the first switching valve 57 and discharge of EGR gas from the intermediate chamber 51 to the bypass passage 54 is blocked by the second switching valve 58. Therefore, the flow of EGR gas from the main passage 50 to the first cooling section 52 is obstructed, and the entire amount of EGR gas passes through the main passage 50 and is discharged from the EGR cooler 10D as shown by the arrow D in FIG. Can do. In this state, the length of the flow path L in the EGR cooler 10D is 0, that is, the minimum. Therefore, this state corresponds to the shortest state of the present invention. In this state, since the EGR gas is not cooled by the EGR cooler 10D, the cooling performance of the EGR cooler 10D is the lowest. Hereinafter, this state may be referred to as a fourteenth state. The main passage 50 functions as the first bypass passage of the present invention by guiding the EGR gas to the downstream of the cooling portions 52 and 53 by bypassing the first cooling portion 52 and the second cooling portion 53 in this way. .

  The first switching valve 57 and the second switching valve 58 of the EGR cooler 10D are controlled by the ECU 20. ECU20 controls the 1st switching valve 57 and the 2nd switching valve 58 so that the state of EGR cooler 10D may switch according to the rotation speed and load of the engine 1 similarly to the 2nd form mentioned above. In this embodiment, the EGR cooler 10D is switched in the order of the eleventh state, the twelfth state, the thirteenth state, and the fourteenth state as the rotational speed of the engine 1 increases and as the load on the engine 1 increases. The first switching valve 57 and the second switching valve 58 are controlled. Therefore, for example, the first state in the relationship shown in FIG. 10 is changed to the eleventh state, the second state is changed to the twelfth state, the third state is changed to the thirteenth state, and the fourth state is changed to the fourteenth state. The map may be stored in the ROM of the ECU 20, and the first switching valve 57 and the second switching valve 58 may be controlled with reference to this map. Further, the ECU 20 switches the state of the EGR cooler 10D so as to increase the flow rate of the EGR gas when the engine 1 is operating in an operating state in which the cooling pipe 14 is likely to be clogged. . In this case, the ECU 20 switches the state of the EGR cooler 10D in the order of, for example, the eleventh form, the thirteenth form, the twelfth form, and the fourteenth form. By switching the state of the EGR cooler 10D in this manner, the flow rate of the EGR gas when passing through the cooling pipe 14 is increased in order, and in the fourteenth embodiment, the EGR gas to the first cooling unit 52 and the second cooling unit 53 is increased. Can be prevented, so that adhesion of particulate matter or the like into the cooling pipe 14 can be suppressed.

  In the exhaust gas recirculation apparatus of the third embodiment, the length of the flow path L of the EGR cooler 10D can be changed according to the temperature and flow rate of the EGR gas, thereby changing the cooling performance of the EGR cooler 10D. Therefore, similarly to the other embodiments, the temperature of the EGR gas can be adjusted to the target temperature more stably and easily than before. Further, when the engine 1 is operated in an operation state in which the cooling pipe 14 is likely to be clogged, the state of the EGR cooler 10 </ b> D is set so that the flow rate of EGR gas when passing through the cooling pipe 14 is increased. Since switching is performed, clogging of the cooling pipe 14 can be suppressed. The first switching valve 57 and the second switching valve 58 correspond to the cooling capacity changing means of the present invention by changing the length of the flow path L of the EGR cooler 10D in this way.

  In the third embodiment, the number of cooling units provided in the EGR cooler 10D is not limited to two. Three or more cooling units may be provided, and the length of the flow path may be changed by changing the number of cooling units through which the EGR gas passes among these cooling units. In this case, the length of the flow path can be adjusted more finely. Further, the number of cooling pipes arranged in each cooling unit, the length of the cooling pipe, and the inner diameter of the cooling pipe may be different from each other. In this case, since the cooling capacities of the respective cooling units are different from each other, the control accuracy of the temperature of the EGR gas can be further improved by the combination of the cooling units that allow the EGR gas to pass therethrough.

  This invention is not limited to each form mentioned above, It can implement with a various form. For example, the present invention is not limited to a diesel engine, and may be applied to various internal combustion engines that use gasoline or other fuels. In each form mentioned above, either the cross-sectional area of the flow path of the EGR cooler or the length of the flow path was changed to change the cooling capacity of the EGR cooler. The slide valve of the form may be provided, and each of these may be controlled to change both the cross-sectional area of the flow path of the EGR cooler and the length of the flow path. In this case, the control accuracy of the temperature of the EGR gas can be further improved.

The figure which shows the outline of the internal combustion engine in which the exhaust gas recirculation apparatus which concerns on the 1st form of this invention was integrated. The figure which expands and shows the inside of the EGR cooler of FIG. The figure which expands and shows the range A of FIG. The flowchart which shows the valve control routine which ECU performs. The figure which shows the principal part of the modification of the exhaust gas recirculation apparatus which concerns on a 1st form. The figure which expands and shows the inside when the EGR cooler of the exhaust gas recirculation apparatus which concerns on the 2nd form of this invention is a 1st state. The figure which shows the inside when the EGR cooler of a 2nd form is a 2nd state. The figure which shows the inside when the EGR cooler of a 2nd form is a 3rd state. The figure which shows the inside when the EGR cooler of a 2nd form is a 4th state. The figure which shows an example of the correspondence of the rotation speed and load of an engine, and the state of EGR cooler. The figure which expands and shows an inside when the EGR cooler of the exhaust gas recirculation apparatus which concerns on the 3rd form of this invention is an 11th state. The figure which shows the inside when the EGR cooler of a 3rd form is a 12th state. The figure which shows the inside when the EGR cooler of a 3rd form is a 13th state. The figure which shows the inside when the EGR cooler of a 3rd form is a 14th state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 4 Intake passage 5 Exhaust passage 8 EGR passage 10A, 10B, 10C, 10D EGR cooler 12 Refrigerant chamber 14 Cooling pipe 16 Slide valve (slide valve means, cooling capacity change means)
16a Valve body 18 Cooling part 20 Engine control unit (control means)
30 Cooling section 31 Bypass passage 32 On-off valve (bypass valve means)
40 cooling section 41 first bypass passage 42 second bypass passage 44 first cooling pipe group 45 second cooling pipe group 46 first switching valve (cooling capacity changing means)
47 Second switching valve (cooling capacity changing means)
50 Main passage (first bypass passage)
52 1st cooling section (first section)
53 Second cooling section (second section)
54 Bypass passage (second bypass passage)
57 1st switching valve (1st valve means, cooling capacity change means)
58 Second switching valve (second valve means, cooling capacity changing means)
L channel

Claims (11)

In an exhaust gas recirculation apparatus for an internal combustion engine, comprising: an EGR passage that recirculates part of exhaust gas from the exhaust passage of the internal combustion engine to the intake passage as EGR gas; and an EGR cooler that is provided in the EGR passage and cools the EGR gas.
The EGR cooler includes a cooling unit that cools EGR gas that flows through a channel formed therein, a cooling capacity changing unit that changes at least one of the cross-sectional area of the channel and the length of the channel, An exhaust gas recirculation device for an internal combustion engine, comprising: The cooling unit includes a refrigerant chamber for flowing a refrigerant, and a plurality of cooling pipes that are arranged so as to penetrate the refrigerant chamber and through which the EGR gas passes to form the flow path,
2. The exhaust of the internal combustion engine according to claim 1, wherein the cooling capacity changing unit changes a cross-sectional area of the flow path by changing the number of the plurality of cooling pipes that allow passage of EGR gas. Reflux apparatus. The plurality of cooling pipes are arranged so as to be aligned in a predetermined direction, and at least one end thereof is aligned on the same plane,
As the cooling capacity changing means, it is disposed so as to face one end of the plurality of cooling pipes arranged on the same plane, and a fully closed position that covers all one end of the plurality of cooling pipes; A number of valves that allow passage of EGR gas among the plurality of cooling pipes by reciprocating a valve body that is driven between a fully open position that opens all one ends of the plurality of cooling pipes in the predetermined direction. 3. The exhaust gas recirculation device for an internal combustion engine according to claim 2, further comprising a slide valve means for changing.   The slide valve means is configured such that when one end of two or more cooling pipes is closed by the valve body, the other end of one cooling pipe among the cooling pipes that have closed one end thereof. The EGR gas that has flowed into the one cooling pipe leaks from the gap between the one end of the one cooling pipe and the valve body, and then the other of the cooling pipes whose one end is closed by the valve body. The cooling pipe is provided so as to be prevented from flowing into the other cooling pipe from one end of the cooling pipe and being discharged from the other end of the other cooling pipe. 3. An exhaust gas recirculation device for an internal combustion engine according to 3.   The smaller the amount of EGR gas to be cooled in the cooling section and the greater the amount of particulate matter contained in the EGR gas, the more cooling tubes that allow passage of EGR gas among the plurality of cooling tubes. The exhaust gas recirculation device for an internal combustion engine according to any one of claims 2 to 4, further comprising control means for controlling the cooling capacity changing means so as to decrease. The EGR cooler opens between a bypass passage that bypasses the cooling portion and guides EGR gas downstream of the cooling portion, a fully closed position that fully closes the bypass passage, and a fully open position that fully opens the bypass passage. A bypass valve means capable of changing the degree,
The control means increases the amount of EGR gas passing through the bypass passage as the number of cooling pipes allowed to pass EGR gas among the plurality of cooling pipes is reduced by the cooling capacity changing means. 6. The exhaust gas recirculation device for an internal combustion engine according to claim 5, wherein the opening degree of the bypass valve means is controlled. The plurality of cooling pipes are divided into two cooling pipe groups formed by different numbers of cooling pipes,
The EGR cooler further includes a first bypass passage and a second bypass passage that bypass the cooling unit and guide EGR gas downstream of the cooling unit,
As the cooling capacity changing means, one end of each of the cooling pipes forming one cooling pipe group of the two cooling pipe groups is closed, and the closed position where the first bypass passage is opened and the one cooling pipe A first switching valve that can be switched between an open position that opens one end of each of the cooling pipes forming the group and closes the first bypass passage, and the other cooling pipe of the two cooling pipe groups One end of each of the cooling pipes forming the group is closed, the closed position where the second bypass passage is opened, and one end of the cooling pipe forming the other cooling pipe group are opened and the first 2. The exhaust gas recirculation device for an internal combustion engine according to claim 2, wherein a second switching valve that can be switched between an open position that closes the bypass passage is provided. The flow path is divided into a plurality of sections;
The exhaust of the internal combustion engine according to claim 1, wherein the cooling capacity changing means changes the length of the flow path by changing the number of sections through which EGR gas should pass through among the plurality of sections. Reflux apparatus. The flow path is divided into a first section and a second section;
The EGR cooler bypasses the cooling section and guides EGR gas to the downstream of the second section, and from the flow path between the first section and the second section to the downstream of the second section A second bypass passage for guiding EGR gas to
As the cooling capacity changing means, a first valve means capable of switching between an introduction position for guiding EGR gas to the first section and a bypass position for guiding EGR gas to the first bypass passage; and EGR gas for the second section Of the EGR gas to the second bypass passage, and to permit the EGR gas to flow into the second bypass passage and to permit the EGR gas to flow into the second bypass passage. 9. The exhaust gas recirculation device for an internal combustion engine according to claim 8, further comprising second valve means that can be switched to a blocking position.   The first passage is configured such that the smaller the amount of EGR gas to be cooled in the cooling section and the greater the amount of particulate matter contained in the EGR gas, the shorter the length of the flow path through which the EGR gas passes. The exhaust gas recirculation apparatus for an internal combustion engine according to claim 9, further comprising control means for controlling the valve means and the second valve means, respectively. The control means switches the first valve means to the introduction position and switches the second valve means to the permission position to guide the EGR gas to both the first section and the second section, An intermediate state in which the first valve means is switched to the introduction position and the second valve means is switched to the blocking position to guide EGR gas only to the first section, and the first valve means is switched to the bypass position. Controlling the first valve means and the second valve means so that the state of the EGR cooler is switched to the shortest state in which the second valve means is switched to the blocking position and the EGR gas is guided to the first bypass passage;
As the amount of EGR gas to be cooled in the cooling section decreases and as the amount of particulate matter contained in the EGR gas increases, the state of the EGR cooler is changed to the longest state, the intermediate state, and the shortest state. The exhaust gas recirculation device for an internal combustion engine according to claim 10, wherein the exhaust gas recirculation device is switched in the following order.

Images