JP4323333B2 - Exhaust gas recirculation device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas recirculation device that suppresses the emission amount of nitrogen oxides in exhaust gas by returning a part of the exhaust gas of an internal combustion engine to the intake passage side, and particularly has a gas cooling function for cooling the recirculated gas. The present invention relates to an exhaust gas recirculation device for an internal combustion engine.

  An exhaust gas recirculation device for an internal combustion engine recirculates a part of high-temperature exhaust gas taken out from an exhaust system to an intake passage. In order to efficiently introduce thermally expanded exhaust gas into an intake passage, It is known that it is effective to cool the exhaust gas with a gas cooler and introduce the cooled exhaust gas into the intake passage. At present, exhaust gas recirculation devices equipped with various gas coolers have been developed. When cooling of the reflux gas is not preferable depending on the operating conditions of the engine, for example, at the time of low-temperature start-up or low-load operation, problems such as deterioration of emission suppression performance of nitrogen oxides, particulates, etc. are caused. Thus, as an exhaust gas recirculation device capable of coping with this, those described in Patent Document 1 and Patent Document 2 have been devised.

  In the exhaust gas recirculation device described in Patent Document 1, a bypass pipe is provided in parallel with a gas cooler pipe, a switching valve is provided at the junction of both pipes, and the switching valve is turned on / off according to the operating conditions of the internal combustion engine. It is structured to be switched by using an off type or a modulation type.

In addition, the exhaust gas recirculation device described in Patent Document 2 has a heat insulation passage nested in the center of a cooling pipe of a so-called air-cooled gas cooler that cools a peripheral wall with outside air, and has an inner heat insulation passage and an outer gas cooling device. It has a structure in which a flow rate adjusting valve that adjusts the flow rate of gas flowing through both passages is provided at the junction of the passages.
Japanese National Patent Publication No. 9-508691 JP 2003-328864 A

  The apparatus described in Patent Document 1 has a structure in which a gas cooling pipe and a bypass pipe that bypasses the cooling pipe are separately provided and both pipes are connected to the outside. It is not preferable for mounting.

  In the device described in Patent Document 2, since the bypass passage is nested inside the gas cooling passage, the entire device can be made compact, but only the outer surface of the peripheral wall of the cooling pipe is exposed to the outside air and cooled. Therefore, it is difficult to obtain sufficient gas cooling performance.

  Accordingly, the present invention is intended to provide an exhaust gas recirculation device for an internal combustion engine that can adjust the temperature of the recirculation gas in accordance with engine operating conditions without causing an increase in the size of the device or a deterioration in gas cooling performance. .

  As means for solving the above-mentioned problems, the present invention includes a cylindrical housing having a gas inlet and a gas outlet, and a cooling liquid flow passage formed in a peripheral wall, which is disposed inside the cylindrical housing. A heat exchange cylinder member forming a first gas cooling passage on the inner peripheral side, and a second member between the inner peripheral surface and the heat exchange cylinder member interposed between the cylindrical housing and the heat exchange cylinder member. A gas cooling passage is formed, and a partition cylinder that forms a bypass passage between the outer peripheral surface and the cylindrical housing, and is disposed on either the gas inlet side or the gas outlet side in the cylindrical housing, The first and second gas cooling passages and the flow rate adjusting valve for adjusting the gas passage ratio of the bypass passages are provided.

  In the case of the present invention, when the gas passage ratio of the first and second gas cooling passages is increased by operating the flow rate adjusting valve, the heat exchange between the reflux gas and the coolant is efficiently performed on the inner and outer surfaces of the heat exchange cylinder member. It becomes like this. Further, when the gas passage ratio of the first and second gas cooling passages is decreased by operating the flow rate adjusting valve, the heat exchange amount on the inner and outer surfaces of the heat exchange cylinder member is decreased, The gas passage ratio passing through the bypass passage increases. At this time, the second gas cooling passage inside the partition cylinder functions as a heat insulation layer so that the reflux gas passing through the bypass passage is prevented from being cooled by the coolant of the heat exchange cylinder member. Become.

The flow rate adjusting valve includes a pair of valve plates arranged on the gas inlet side and rotatably supported by a shaft portion orthogonal to the axial center of the cylindrical housing. When the gas passage ratio of the first and second gas cooling passages is increased, the pair of valve plates are rotated in a direction substantially parallel to the axial center of the cylindrical housing to reduce the gas passage ratio. In addition, the pair of valve plates may be rotated so as to incline outwardly toward the partition tube.

  In this case, although the structure is very simple, when the gas passage ratio of the first and second gas cooling passages is reduced, the valve body (valve plate) itself of the flow rate adjusting valve can reduce the recirculation gas flowing in from the gas inlet. It functions as a guide for guiding the bypass passage on the outer peripheral side. Therefore, the gas passage flow rate of the bypass passage can be relatively increased without causing turbulence.

  According to a third aspect of the present invention, a guide wall that inclines outwardly from the axial center toward the partition tube is provided on the gas inlet side in the cylindrical housing, and the gas inlet side is provided on the guide wall. In addition, a window communicating with the first and second gas cooling passages may be formed, and a valve body for opening and closing the window may be provided, and the flow rate adjusting valve may be configured by the window and the valve body.

  In this case, since the flow of the reflux gas to the bypass passage is basically guided by the guide wall, for example, the guide wall is formed more smoothly by forming a conical shape continuous from the axial center portion of the cylindrical housing to the partition cylinder. A reflux gas stream can be created.

  The present invention adjusts the ratio of the reflux gas passing through the gas cooling passage and the bypass passage by the flow rate adjustment valve in the cylindrical housing, so that the temperature of the reflux gas can be reliably adjusted according to the engine operating conditions, Moreover, when the reflux gas needs to be cooled, heat exchange with the coolant is basically performed in the first and second gas cooling passages facing the inner and outer surfaces of the heat exchange cylinder member, so that high cooling performance can be obtained. In addition, since all the passages can be arranged almost coaxially inside the cylindrical housing, the entire apparatus can be made compact.

  When the reflux gas does not need to be cooled, a special heat insulating material is added because the second gas cooling passage inside the partition tube functions as a heat insulating layer that blocks heat transfer between the bypass passage and the heat exchange tube member. Therefore, it is possible to prevent a problem that the reflux gas is unnecessarily cooled.

  Next, each embodiment of the present invention will be described with reference to the drawings.

  1 to 3 show a first embodiment of the present invention. FIG. 1 is a longitudinal sectional view of an exhaust gas recirculation apparatus according to the present invention, and FIG. 2 is a view of the apparatus in FIG. FIG. 3 is a side view of the apparatus.

  In FIG. 1, reference numeral 1 denotes a substantially cylindrical tubular housing in which a gas inlet 2 and a gas outlet 3 are provided at both ends in the axial direction. The flanges 4 and 4 are bolted to pipes (not shown) communicating with the exhaust side passage and the intake side passage of the internal combustion engine. The connection with the pipe is not limited to the bolt connection at the flanges 4 and 4 but may be welding or brazing in a fitted state.

  Inside the cylindrical housing 1, a substantially cylindrical heat exchanging cylinder member 5 is provided substantially coaxially. The heat exchanging cylinder member 5 has an inner tube 5a made of a thin metal plate such as stainless steel and both ends of an outer tube 5b joined in a liquid-tight manner, and a substantially cylindrical flow passage 6 between the tubes 5a and 5b. Is formed. This flow passage 6 is a portion through which the coolant flows, and an inflow pipe 7 and a discharge pipe 8 are provided in the vicinity of both ends of the outer tube 5b so as to project radially outward. Passes through the peripheral wall of the cylindrical housing 1 and is connected to a coolant pipe (not shown).

  A partition tube 9 is provided between the tubular housing 1 and the heat exchange tube member 5 so as to be substantially coaxial with them. The partition tube 9 forms a substantially cylindrical bypass passage 10 between the outer peripheral surface thereof and the cylindrical housing 1. Further, the inner peripheral side of the heat exchange cylinder member 5 is a first gas cooling passage 11, and a substantially cylindrical second gas cooling passage 12 is provided between the inner peripheral surface of the partition cylinder 9 and the heat exchange cylinder member 5. It is said that. The first and second gas cooling passages 11 and 12 and the bypass passage 10 are recirculation gas passages that enter from the gas inlet 2 and exit to the gas discharge port 3, but the first and second gas cooling passages 11, Only the gas passing through 12 performs heat exchange with the coolant flowing through the heat exchange cylinder member 5, and the gas passing through the bypass passage 10 does not exchange heat with the coolant. The inflow pipe 7 and the exhaust pipe 8 projecting from the heat exchange cylinder member 5 penetrate the vicinity of both end portions of the partition cylinder 9 in the same manner as the cylindrical housing 1.

  Fins 13 are brazed on the inner peripheral surface of the inner tube 5a of the heat exchange cylinder member 5 in order to improve the heat exchange efficiency in the first gas cooling passage 11, and similarly, the outer tube 5b has In order to improve the heat exchange efficiency in the second gas cooling passage 12, bellows-like irregularities 14 are provided.

  Further, the through portions of the pipes 7 and 8 of the cylindrical housing 1 and the partition tube 9 partially protrude in the axial direction, and the three portions of the cylindrical housing 1, the partition tube 9, and the outer tube 5 b are formed at the protruding portions. A member is connected to each pipe 7, 8 in a polymerized state. Therefore, in this embodiment, the heat exchanging cylinder member 5 and the partition cylinder 9 are supported and fixed to the inner peripheral wall of the cylindrical housing 1 by coupling at the raised portions.

  On the other hand, a flow rate adjusting valve 15 for adjusting the gas passage ratio between the first and second gas cooling passages 11 and 12 and the bypass passage 10 is provided in the vicinity of the gas inlet 2 in the cylindrical housing 1. . The flow rate adjusting valve 15 includes a pair of valve plates (valve bodies) 16 and 16 that are rotatably supported by shaft portions 16 a and 16 a that are orthogonal to the axis of the cylindrical housing 1. The opening area of the inner peripheral portion of the heat exchanging cylinder member 5 can be manipulated by the pivoting operation.

  Specifically, the shaft portions 16a and 16a of the valve plates 16 and 16 are arranged in parallel to positions near the axial center portion of the cylindrical housing 1, and as shown in FIGS. The actuator 17 is rotated by an actuator 17 fixedly installed on the outer wall. As the actuator 17 of this embodiment, a negative pressure actuator that moves the plunger 18 forward / backward using the intake negative pressure of the internal combustion engine is used, and the forward / backward movement of the plunger 18 is performed via the link mechanisms 19, 19 through the valve plates 16, 19. 16 rotation operations are converted. The negative pressure supplied to the actuator 17 is controlled according to the operating state of the internal combustion engine. However, the actuator 17 is not limited to the negative pressure actuator, and may be an electric type, a hydraulic type, or the like.

  Further, the end of the partition tube 9 on the gas inlet 2 side is offset to the gas inlet 2 side with respect to the inner heat exchanging cylinder member 5, and the end side edge of each valve plate 16 is substantially the same. It operates in this offset region. The leading edge of each valve plate 16 is formed in a substantially arc shape, and the valve plate 16 is set at a set angle from a state substantially parallel to the axis of the cylindrical housing 1 (a state indicated by a solid line in FIG. 1). When tilted (the state indicated by the chain line in FIG. 1), the leading edge of the valve body 16 approaches the peripheral wall of the partition tube 9 and substantially closes the inner periphery of the partition tube 9. In addition, the base end of each valve plate 16 is formed in a straight line parallel to the shaft portion 16a, and the base end portions are closed as the inclination angle of both valve bodies 16 and 16 increases. ing.

  When the internal combustion engine is normally operated at a high temperature, the flow rate adjusting valve 15 is maintained in an initial state in which the pair of valve plates 16 and 16 are substantially parallel to the axis of the cylindrical housing 1. In this state, the recirculated gas entering from the gas inlet 2 advances straight along the valve plates 16 and 16, and at this time, the first and second gas cooling passages 11 and 12 partially pass through the bypass passage 10. It is discharged from the gas outlet 3. At this time, since the reflux gas mainly passes through the first and second gas cooling passages 11 and 12 located on the center side of the cylindrical housing 1, the cooling gas and the efficiency pass through the inner and outer surfaces of the heat exchange cylinder member 5. The heat is exchanged well.

  On the other hand, when the internal combustion engine is started at a low temperature, the valve plates 16 and 16 of the flow rate adjusting valve 15 are rotated so as to maximize the inclination angle under the control of the actuator 17, and the valve plates 16 and 16 are partitioned. The inner peripheral portion of the tube 9 is almost closed. As a result, almost no recirculation gas flows through the first and second gas cooling passages 11 and 12, and almost all of the recirculation gas flowing into the cylindrical housing 1 from the gas inlet 2 passes through the bypass passage 10 to form gas. It is discharged from the discharge port 3. At this time, since the gas in the second gas cooling passage 12 is between the bypass passage 10 and the heat exchange cylinder member 5 and functions as a substantially cylindrical heat insulating layer, the reflux gas passing through the bypass passage 10 is the heat exchange cylinder. It is guided to the gas outlet 3 without taking heat away by the coolant of the member 5. Therefore, in this exhaust gas recirculation apparatus, it is possible to reliably prevent the deterioration of the emission suppression performance of nitrogen oxides, particulates, and the like due to the temperature of the recirculation gas being lowered more than necessary.

  The flow rate adjusting valve 15 not only switches the inner peripheral portion of the heat exchanging cylinder member 5 between the fully open state and the fully closed state as described above, but also opens any intermediate valve according to the operating state of the engine. Can be adjusted to the state. Therefore, in this exhaust gas recirculation device, the ratio of the recirculation gas passing through the first and second gas cooling passages 11 and 12 and the bypass passage 10 is arbitrarily adjusted according to the engine operating conditions. The optimum temperature can be maintained. Therefore, according to this device, it is possible to always maintain high emission suppressing performance such as nitrogen oxides and particulates during engine operation.

  As described above, this exhaust gas recirculation device can arbitrarily set the flow rate of the recirculation gas between the first and second gas cooling passages 11 and 12 and the bypass passage 10 by operating the flow rate adjusting valve 15 according to the operating condition of the internal combustion engine. Although it can be operated, the first and second gas cooling passages 11 and 12, the coolant flow passage 6 and the bypass passage 10 are configured by coaxially assembling a plurality of pipe-like members, so that the cylindrical housing There is an advantage that the outer diameter of 1 can be reduced and the entire apparatus can be made compact. Therefore, when this exhaust gas recirculation device is adopted, it is advantageous in terms of in-vehicle layout.

  Furthermore, in this embodiment, the flow rate adjusting valve 15 is arranged in the vicinity of the gas inlet 2 in the cylindrical housing 1, but it can also be arranged in the vicinity of the gas outlet 3 in the cylindrical housing 1. . However, when the flow rate adjusting valve 15 is arranged on the gas inlet 2 side as in this embodiment, smooth gas to the bypass passage 10 side is increased when the ratio of the reflux gas passing through the bypass passage 10 is increased. There is an advantage that it is easy to make the flow.

  In particular, in the flow rate adjusting valve 15 of this embodiment, the pair of valve plates 16, 16 open outwardly from the axial center portion of the cylindrical housing 1 to reduce the passing gas flow rate on the inner peripheral side of the partition tube 9. At this time, the valve plates 16 and 16 themselves function as guide walls for smoothly guiding the reflux gas to the bypass passage 10 on the outermost peripheral side. On the other hand, when the passage flow rate on the inner peripheral side of the partition tube 9 is increased, the valve plates 16 and 16 are rotated so as to be substantially parallel to the axial center of the cylindrical housing 1. Gas flow can be reduced.

  In the above embodiment, the pair of valve plates 16 and 16 are arranged on the gas inlet 2 side of the cylindrical housing 1, but one or three or more valve plates are similarly rotated. It is also possible to provide it.

  Next, a second embodiment shown in FIGS. 4 and 5 will be described. The exhaust gas recirculation apparatus of this embodiment is basically the same as that of the first embodiment except that the inflow pipe 7 is attached in the direction of flow, the flow rate adjusting valve 115 disposed near the gas inlet 2, The peripheral structure is slightly different. In the following, the same reference numerals are given to the same parts as those in the first embodiment, including the third embodiment described later, and duplicate explanations are omitted.

  In this apparatus, a conical guide wall 20 that is inclined outwardly from the axial center of the cylinder 9 is integrally attached to the end of the partition cylinder 9 on the gas inlet 2 side. Since the guide wall 20 extends from the axial center toward the outer peripheral surface of the partition tube 9, the guide wall 20 functions to smoothly guide the reflux gas toward the bypass passage 10. In addition, a plurality of substantially fan-shaped windows 21 are formed in the guide wall 20 at substantially equal intervals in the circumferential direction, and the reflux gas is introduced into the first and second gas cooling passages 11 and 12 through the windows 21. It has come to be.

  Inside the guide wall 20, a substantially conical valve body 22 for opening and closing the windows 21 is disposed. This valve body 22 has windows 23 corresponding to the windows 21 of the guide wall 20. When the positions of the windows 21 and 23 coincide, the windows 21 of the guide wall 20 are fully opened. When they are shifted, the windows 21 are gradually closed. The valve body 22 is connected and supported by an operation rod 24 that penetrates the top of the guide wall 20, and the operation rod 24 is rotated by an actuator (not shown). In this embodiment, a flow rate adjusting valve 115 is configured by the windows 21 of the guide wall 20 and the valve body 22.

  In the exhaust gas recirculation apparatus of this embodiment, the recirculation gas can be always guided smoothly and reliably to the bypass passage side 10 by the conical guide wall 20. Further, since the valve body 22 opens and closes in a sliding state, so that the window 21 of the guide wall 20 is opened, when the entire amount of the reflux gas is to flow to the bypass passage 10 side, the reflux gas flows toward the inside of the partition tube 9. Leakage can be reduced. Further, since the valve body 22 slides open / closes the windows 21..., There is an advantage that the backlash caused by the operation of the valve body 22 can be reduced.

  FIG. 6 shows a third embodiment of the present invention. In the exhaust gas recirculation apparatus of this embodiment, fins 13 are arranged in the mounting direction of the inflow pipe 7 and in the heat exchange cylinder member 5. Instead of this, the point that bellows-like fins are formed in the portions excluding both sides of the inner tube 11 and the configuration of the flow rate adjusting valve 215 are different from those of the first embodiment.

  That is, in the flow rate adjusting valve 215 of this embodiment, the valve body 30 is formed by a heat-sensitive shape variable member (shape memory member) such as a bimetal, and the valve body 30 is controlled according to the gas temperature around the valve body 30. The body 30 itself changes its shape. A pair of valve bodies 30 are provided in the same manner as in the first embodiment, and a base portion of each plate-like valve body 30 is supported by a frame member 31 attached to the cylindrical housing 1 near an axial center portion. Each valve body 30 is formed in an arc shape at the tip side edge portion, and has a straight shape so as to be substantially parallel to the axial center of the cylindrical housing 1 when the surrounding gas temperature is low (indicated by a broken line in the figure). .) When the ambient gas temperature rises from this state, the tip end side is curved and deformed to open outward, and the inner peripheral portion of the partition tube 9 is closed (indicated by the solid line in the figure).

  The device of this embodiment can basically obtain the same effects as those of the first embodiment, but the shape of the valve body 30 itself of the flow regulating valve 215 changes according to the temperature. Since no other special actuator for operating the body 30 is required, the flow rate adjusting valve 215 can be reduced in size and weight, and the manufacturing cost can be reduced.

  Note that what has been described so far is the exhaust gas recirculation apparatus having a substantially cylindrical tubular housing, but the shape of the tubular housing is not limited to a substantially cylindrical shape, and is substantially rectangular or polygonal. Also good. In this case, it goes without saying that the heat exchange cylinder member or the like may have an arbitrary shape according to the shape of the cylindrical housing.

1 is a longitudinal sectional view of an exhaust gas recirculation device showing a first embodiment of the present invention. The A arrow directional view of FIG. 1 which shows the same embodiment. The side view of the exhaust gas recirculation apparatus which shows the embodiment. The longitudinal cross-sectional view of the exhaust gas recirculation apparatus which shows the 2nd Embodiment of this invention. The B arrow directional view of FIG. 4 which shows the same embodiment. The longitudinal cross-sectional view of the exhaust gas recirculation apparatus which shows the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cylindrical housing 2 ... Gas inflow port 3 ... Gas discharge port 5 ... Tube member 6 for heat exchange ... Flow channel 9 ... Partition tube 10 ... Bypass passage 11 ... First gas cooling passage 12 ... Second gas cooling passage 15, 115, 215 ... Flow rate adjusting valve 16 ... Valve plate (valve element)
16a ... Shaft 20 ... Guide wall 21 ... Window 22, 30 ... Valve

Claims (3)

A cylindrical housing having a gas inlet and a gas outlet;
Forming a coolant flow passage in the peripheral wall, and being disposed inside the cylindrical housing, and forming a first gas cooling passage on the inner peripheral side;
The second gas cooling passage is interposed between the inner peripheral surface and the heat exchanging cylinder member and interposed between the outer peripheral surface and the cylindrical housing. A partition tube forming
A flow rate adjusting valve that is disposed on either the gas inlet side or the gas outlet side in the cylindrical housing and adjusts the gas passage ratio of the first and second gas cooling passages and the bypass passage;
An exhaust gas recirculation device for an internal combustion engine. The flow rate adjusting valve includes a pair of valve plates disposed on the gas inlet side and rotatably supported by a shaft portion orthogonal to the axial center of the cylindrical housing,
When increasing the gas passage ratio of the first and second gas cooling passages, when rotating the pair of valve plates in a direction substantially parallel to the axial center of the cylindrical housing to decrease the gas passage ratio 2. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein the pair of valve plates are rotated so as to be inclined outwardly toward the partition tube. A guide wall is provided on the gas inlet side in the cylindrical housing so as to incline outwardly from the axial center toward the partition tube, and the gas inlet side and the first and second gas cooling passage sides are provided on the guide wall. 2. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein a communicating valve is formed and a valve body for opening and closing the window is provided, and the flow rate adjusting valve is configured by the window and the valve body.

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