JP2012140926A - Exhaust heat exchange apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately adjusted a heat exchange amount according to an exhaust gas flow rate in spite of the simple configuration in which a movable part such as a valve member is not used.SOLUTION: An exhaust heat exchange apparatus 10 is configured so that an exhaust gas flows branched into a heat exchange passage 15 and a bypass passage 14. A cooling water passage 16 in which cooling water for heat exchange flows is disposed in the surrounding of the heat exchange passage 15. The bypass passage 14 is disposed inside the heat exchange passage 15 so as not to be adjacent to the cooling water passage 16. In a low and medium output region where the exhaust gas flow rate is low, excessive heat exchange is suppressed since the exhaust gas flows in the bypass passage 14 at a fixed flow rate, and in a high output region where the exhaust gas flow rate is high, the flow rate in the bypass passage 14 is restricted by a throttling section 40, and the exhaust temperature is decreased by the promotion of the heat exchange.

Description

  The present invention relates to an exhaust heat exchange device that is provided, for example, in an exhaust system of an internal combustion engine for a vehicle and performs heat exchange between an exhaust gas and a refrigerant (cooling water).

  Patent Document 1 describes a technique for recovering exhaust heat to shorten heating and warm-up time. In this configuration, the exhaust passage through which the exhaust gas flows is disposed close to the cooling water passage through which the cooling water flows so that heat exchange is performed between the exhaust gas and the cooling water (refrigerant) for heat exchange. A heat exchange passage and a bypass passage arranged to bypass the cooling water passage are provided, and both passages are switched according to the flow rate of the exhaust gas. That is, the first valve member that opens and closes the bypass passage and the second valve member that opens and closes the heat exchange passage are connected so as to rotate integrally, and as the first valve member opens the bypass passage. The second valve member closes the heat exchange passage.

JP 2007-247638 A

  However, in the thing of the said patent document 1, since a valve member is required, a structure is complicated. In addition, since movable parts such as a valve member and a support mechanism that rotatably supports the valve member are always exposed to high-temperature exhaust gas, it is very difficult to ensure the durability and reliability of these movable parts. . Furthermore, in a high output region where the exhaust gas flow rate increases, it is desirable to actively exchange heat to recover the exhaust heat, thereby lowering the exhaust temperature and thus the temperature of the catalyst disposed downstream, In the medium output range where the exhaust gas flow rate is lower than in the high output range, if the heat exchange is excessively performed and the refrigerant is overheated, there is a risk of overheating (overheating) of cooling system components such as a radiator.

  The present invention has been made in view of such circumstances. That is, the heat exchange device according to the present invention is configured such that the exhaust gas flowing in the exhaust passage flows in a branched manner into the heat exchange passage and the bypass passage. The heat exchange passage is arranged close to the refrigerant so that heat exchange is performed with the heat exchange refrigerant, while the bypass passage is arranged so as to bypass the heat exchange passage. Yes. When the exhaust gas flow rate is high, that is, when the exhaust gas flow rate exceeds a certain flow rate, the exhaust gas including the heat exchange passage and the bypass passage so that the flow rate of the exhaust gas flowing into the bypass passage is constant. The passage shape of the passage is set.

  According to the present invention, the exhaust gas is distributed to the heat exchange passage and the bypass passage at a predetermined ratio in the low / medium output range, thereby preventing excessive heat exchange / recovery with the refrigerant. In addition, overheating of cooling system parts such as a radiator can be avoided. At this time, exhaust gas having a constant flow rate ratio with respect to the total flow rate flows on the heat exchange passage side, so that exhaust heat can be recovered within a range that does not become excessive. The recovered thermal energy can be used for a heating device and warming-up promotion, and can also be used for a Rankine cycle as described in, for example, Japanese Patent Application Laid-Open No. 2010-77964.

  Also, in a high output region where the exhaust gas flow rate is large, when the exhaust gas flow rate exceeds a certain flow rate, the flow rate of the exhaust gas flowing into the bypass passage becomes constant, and the flow rate of the heat exchange passage is increased accordingly. Therefore, the heat recovery amount of the exhaust heat by heat exchange increases, and an excessive increase in the exhaust temperature and the catalyst temperature provided in the exhaust passage can be suppressed.

  In other words, in the present invention, when the flow rate of the exhaust gas exceeds a predetermined value, the flow rate on the bypass passage side is restricted, thereby relatively increasing the flow rate of the heat exchange passage to promote heat exchange. In the low / medium output range where the exhaust gas flow rate is relatively low, the exhaust gas is allowed to flow through the bypass passage at a predetermined flow rate ratio without limiting the flow rate on the bypass side. Therefore, excessive heat exchange can be suppressed. Such effects are realized by the shape of the exhaust passage including the heat exchange passage and the bypass passage. For this reason, unlike Patent Document 1, it is not necessary to provide a moving part such as a valve member for opening and closing a heat exchange passage or a bypass passage in an exhaust system that is exposed to high temperatures, and it is excellent in reliability and durability. The number of points and the cost can be reduced.

  As described above, according to the present invention, the flow rate of the bypass passage is reduced when the flow rate of the exhaust gas is relatively small, such as in the low / medium output range, although the configuration does not use a movable part such as a valve member. When exhaust gas flows at a predetermined ratio to the bypass passage without limitation, excessive heat exchange is prevented and overheating of cooling system parts such as a radiator is avoided, while the exhaust gas flow rate increases. By restricting the flow rate of the exhaust gas flowing into the bypass passage to a certain level, the flow rate of the heat exchange passage is relatively increased to promote the heat exchange between the exhaust gas and the refrigerant, and the exhaust temperature is excessively increased. Can be suppressed.

1 is an exploded perspective view showing an example of an exhaust heat exchange device according to the present invention. 1 is a cross-sectional view showing an exhaust heat exchange device according to a first embodiment of the present invention. Sectional drawing which expands and shows the principal part of the exhaust heat exchange apparatus of FIG. The block diagram (a) which shows simply the channel | path structure which concerns on the said 1st Example, and the characteristic view (b) which shows the relationship of the flow volume of each channel | path. Sectional drawing which shows the exhaust heat exchange apparatus which concerns on 2nd Example of this invention. Sectional drawing which expands and shows the principal part of the exhaust heat exchanger of FIG. The block diagram (a) which shows simply the channel | path structure which concerns on the said 2nd Example, and the characteristic view (b) which shows the relationship of the flow volume of each channel | path.

  Hereinafter, an embodiment of an exhaust heat exchanger according to the present invention will be described with reference to the drawings. This exhaust heat exchange device 10 is applied to an exhaust system of an internal combustion engine for a vehicle and constitutes a part of an exhaust passage, and between exhaust gas flowing in the exhaust passage and cooling water as a refrigerant for heat exchange. As shown in FIG. 2, the upstream side is attached to the side wall 2 on the exhaust side of the cylinder head 1 of the internal combustion engine and the exhaust pipe 5 (see FIG. 3) on the downstream side. ) Is attached. The exhaust passage in the exhaust heat exchange device 10 communicates with the three exhaust ports 3 opened in the cylinder head side wall 2 on the upstream side, and joins in the middle and is connected to the exhaust pipe 5 on the downstream side. It is divided into a bypass passage 14 and a heat exchange passage 15 by an inner tubular member 12 described later.

  With reference to FIGS. 1 and 2, the exhaust heat exchanger 10 includes an inner tubular member 11, an intermediate tubular member 12 covering the inner tubular member 11, and a cover-like outer tubular member covering the intermediate tubular member 12. 13 is roughly constituted. Parts constituting these passage forming bodies are formed of a metal material having excellent heat resistance such as iron or aluminum alloy. A bypass passage 14 through which exhaust gas flows is formed inside the inner tubular member 11, and a heat exchange passage 15 through which exhaust gas flows is formed in a gap between the inner tubular member 11 and the intermediate tubular member 12, In the gap between the intermediate tubular member 12 and the outer tubular member 13, a cooling water passage 16 is formed as a water jacket through which cooling water that is a refrigerant for heat exchange flows.

  As shown in FIG. 1, the inner tubular member 11 has a branch pipe structure in which three upstream tubular inner branch parts 17 are integrally connected to one tubular inner merging part 18 on the downstream side. Yes. A ring portion 19 having a diameter larger than the outer periphery of the pipe portion is provided concentrically at the upstream end portion of each inner branch portion 17 via four support rib portions 20. These ring portions 19 are fitted into an annular groove portion 21A formed in an inlet flange portion 21 having a plate shape on the upstream side of the intermediate tubular member 12, and in the assembled state shown in FIG. By being sandwiched between the exhaust-side side wall 2 of the cylinder head 1, the inner tubular member 11 is supported and fixed in a state of being positioned with respect to the intermediate tubular member 12 and the cylinder head 1. In this fixed state, a gap is secured over the entire circumference between the outer circumference of the inner tubular member 11 and the inner circumference of the intermediate tubular member 12, and this gap constitutes a part of the heat exchange passage 15. is doing. The exhaust gas is supplied to the heat exchange passage 15 through a gap 22 between the ring portion 19, the support rib portion 20, and the outer periphery of the pipe portion.

  In this embodiment, only the inlet side end of the inner tubular member 11 is fitted and fixed to the intermediate tubular member 12, but the present invention is not limited to this. For example, the outlet side end of the inner tubular member 11 is used. Alternatively, a fixing structure similar to that at the inlet side end may be applied to fix both the inlet side and the outlet side of the inner tubular member 11.

  The intermediate tubular member 12 has a branch pipe shape in which three intermediate branch portions 23 merge into one intermediate confluence portion 24 on the downstream side, like the inner tubular member 11 included therein, and the intermediate branch portion 23 is upstream. It is integrally connected to the inlet flange portion 21 on the side. The intermediate tubular member 12 has a half structure that is divided into two divided members 25 and 26 along the passage longitudinal direction, including the inlet flange portion 21, the intermediate branch portion 23, and the intermediate junction portion 24. At the time of assembly, the inner tubular member 11 is sandwiched between the pair of divided members 25 and 26, and each of the divided members 25 and 26 is a cylinder by a plurality of fixing bolts 27 (see FIGS. 4 and 5). It is fixed to the head 1 side.

  The outer tubular member 13 has a cover shape that covers the entire intermediate tubular member 12, and the upstream flange portion 28 together with the inlet flange portion 21 of the intermediate tubular member 12, as shown in FIGS. 4 and 5. The fixing bolt 27 is fastened and fixed to the exhaust-side side wall 2 of the cylinder head 1 together. As shown in FIG. 1, a bolt hole 31 into which a bolt (not shown) for connecting the exhaust pipe 5 is inserted is formed in the outlet flange portion 29 on the downstream side of the outer tubular member 13.

  In the exhaust heat exchange device 10 having such a structure, as shown in FIG. 2, the inner tubular member 11 causes the inner exhaust passage to have a heat exchange passage 15 on the outer peripheral side and a bypass on the inner peripheral side over its entire length. It is separated from the passage 14, and is separated by the intermediate tubular member 12 into an outer peripheral cooling water passage 16 and an inner peripheral heat exchange passage 15 over the entire length thereof. That is, the heat exchange passage 15 is disposed concentrically with the bypass passage 14, and the cooling water passage 16 is formed around the heat exchange passage 15. The heat exchange passage 15 is cooled in the cooling water passage 16 (that is, in the cooling water passage 16 so that heat exchange is performed between the exhaust gas flowing in the heat exchange passage 15 and the cooling water flowing in the cooling water passage 16. It is arranged close to water), specifically, it is arranged with only the wall portion of the intermediate tubular member 12 interposed therebetween. On the other hand, the heat exchange passage 15 is interposed between the bypass passage 14 and the cooling water passage 16, that is, the bypass passage 14 is separated from the cooling water passage 16 so as to suppress and avoid heat exchange. It is arranged by detour.

  Exhaust gas discharged from the cylinder 4 to the exhaust port 3 due to combustion of the internal combustion engine branches into a bypass passage 14 and a heat exchange passage 15 at the inlet portion of the exhaust heat exchange device 10, and the inside of each passage 14, 15 is divided. After flowing, it is discharged to the exhaust pipe 5 on the downstream side. The cooling water passage 16 constitutes a part of the cooling water circulation path of the internal combustion engine including cooling system parts such as a radiator, and the cooling water flows through an inlet portion and an outlet portion (not shown). Yes. Exhaust heat recovered in the cooling water as the refrigerant by heat exchange can be used for the above-mentioned Rankine cycle in addition to heating and warming-up promotion.

  In the present embodiment, a throttle part (first throttle part) 40 having a partially reduced diameter is provided in the middle of the bypass passage 14. When the flow rate of the exhaust gas flowing into the bypass passage 14 exceeds a predetermined amount, the throttle unit 40 becomes a so-called choked state, and makes the flow rate of the exhaust gas constant (equal to the speed of sound and the mass flow rate is The shape, dimensions, and the like are set so that they no longer increase. As shown in FIGS. 2 and 3, the throttle portion 40 has a Venturi shape that is smoothly curved or inclined so as to gradually change the cross-sectional area of the passage along the longitudinal direction of the passage. The passage cross-sectional area of the throttle portion 40 that is the minimum cross section in the bypass passage 14 is set to be smaller than the minimum cross-sectional area in the heat exchange passage 15.

  The effect by this aperture part 40 is demonstrated with reference to FIG. In FIG. 4 and FIG. 7 of the second embodiment to be described later, the upper part (a) shows a simplified passage configuration, and (b) shows the flow rate of the exhaust gas with respect to the engine output (engine speed). FIG. The symbol Qe in (b) is the flow rate of the exhaust gas that has passed through the heat exchange passage 15, the symbol Qb is the flow rate of the exhaust gas that has passed through the bypass passage 14, and the symbol Qa is the exhaust gas that combines the flow rate Qe and the flow rate Qb. (Qa = Qe + Qb). Note that the flow rates Qe and Qb shown in this graph are not flow rates that flow into the heat exchange passage 15 or the bypass passage 14, but flow rates that have passed through the heat exchange passage 15 or the bypass passage 14, that is, the outlet portions of the passages 14 and 15. Corresponds to the flow rate. Further, the symbol L0 corresponds to a heat exchange amount allowable line that the radiator can tolerate (does not overheat), and in the region above the allowable line L0, the heat exchange amount becomes excessive and the radiator may overheat. Corresponds to a certain area.

  The energy generated by combustion in an internal combustion engine is distributed to engine output, heat dissipation to the cooling system, heat dissipation to the exhaust system, friction loss, etc., but the distribution ratio is almost constant regardless of the amount of generated energy. . Therefore, as the engine output increases, the temperature of the cooling water increases and the exhaust temperature also increases. For this reason, in the low output region where the engine output is small, the engine rotational speed is low, the flow rate of the exhaust gas is small, and the temperatures of the cooling water and the exhaust gas are also low, so there is no possibility that the heat recovery amount exceeds the allowable line L0.

  However, in the medium power range where the flow rate of the exhaust gas increases to some extent, the cooling water temperature rises as the engine output increases, so the allowable line L0 of the heat exchange amount that the radiator can tolerate becomes low. As the engine output speed and engine load increase as the output increases and the exhaust gas flow rate increases, the amount of heat exchange inevitably increases as the exhaust gas flow rate increases. For example, there is no bypass passage. In the case of the passage configuration, the total flow rate Qa of the exhaust gas is subjected to heat exchange, and there is a possibility that the heat exchange amount exceeds the allowable line L0 as shown in a region α in the figure.

  In contrast, in the present embodiment, since the bypass passage 14 is provided as described above, the exhaust gas is distributed to the bypass passage 14 and the heat exchange passage 15 at a predetermined flow rate ratio, and the flow rate Qb flowing through the bypass passage 14 is reduced. Therefore, the flow rate Qe of the heat exchange passage 15 is suppressed. As a result, compared with the case where no bypass passage is provided, it is possible to suppress the amount of heat exchange and avoid a situation in which the allowable line L0 of the radiator is exceeded. And by making the flow rate ratio between the heat exchange passage 15 and the bypass passage 14 appropriate, heat exchange is performed within a range that does not become excessive, and the cooling water temperature is increased using exhaust heat to promote heating and warm-up. Can be achieved.

  In the high output range (t1 to t2) where the engine output (engine speed and engine load) is larger than the above medium output range, the allowable line L0 of the radiator increases as the vehicle speed and the air volume increase, and the radiator overheats. However, as the engine output increases, the exhaust temperature and the temperature of the catalyst disposed in the exhaust passage may become excessively high. It is desirable to go and reduce the exhaust temperature.

  Therefore, in this embodiment, when the flow rate Qb flowing into the bypass passage 14 reaches a predetermined value sQb, the flow rate Qb of the bypass passage 14 is limited to the predetermined value sQb or less by the throttle portion 40 described above. . For this reason, as shown in FIG. 4B, in a high output region where the allowable line L0 of the radiator increases as the engine output increases, the proportion is proportional to the increase in the total exhaust gas emission amount Qa. The flow rate Qe flowing through the heat exchange passage 15 is increased, and the decrease in the exhaust temperature and the catalyst temperature can be promoted by the increase in the heat exchange amount.

  Thus, in this embodiment, since the flow rate Qb of the bypass passage 14 is not limited in the low / medium output region where the total exhaust gas flow rate Qa is relatively small, excessive heat exchange can be suppressed, and the exhaust temperature In a high output region where excessive rise of the air current is a problem, the flow rate Qb of the bypass passage 14 is limited to a predetermined value sQb or less, thereby relatively increasing the flow rate Qe of the heat exchange passage 15 and increasing the heat exchange amount. As a result, it is possible to promote a decrease in the exhaust temperature, and hence the catalyst temperature. Further, since the heat exchange passage 15 is not blocked by the valve member or the like, the ventilation resistance is not excessively increased.

  In the present embodiment, the above-described effects are realized by setting the shape of the exhaust passage including the heat exchange passage 15 and the bypass passage 14, and specifically, the throttle portion 40 is provided. This eliminates the need for moving parts such as valve members. In this way, since there is no need to provide moving parts in the exhaust passage used at high temperatures, it is excellent in reliability and durability, can reduce the number of parts and reduce costs, and is easy to manufacture. A great effect in practical use can be obtained.

  The heat exchange passage 15 is included inside the cooling water passage 16 and the bypass passage 14 is included inside the heat exchange passage 15, that is, the bypass passage 14 is provided inside and outside the heat exchange passage 15, respectively. The heat exchange passage 15 has a triple pipe structure in which the heat exchange passages 15 are concentrically arranged, and the three passages 14 to 16 can be configured compactly while being appropriately arranged according to the application.

  If the intermediate tubular member 12 is not divided into two divided members 25 and 26 as in the above-described embodiment, but is formed as an integral part, the degree of freedom of the shape of the inner tubular member disposed therein is greatly increased. Damaged. Specifically, since it is necessary to insert the inner tubular member from the upstream or downstream opening end of the intermediate tubular member, the inner tubular member cannot have a complicated branch pipe structure as in the above-described embodiment. . For this reason, for example, it is necessary to shorten the three inner branch parts 17 and insert them from the upstream side as separate members. In this case, the number of parts increases and the exhaust gas flowing in the bypass passage is in the middle. Since the heat exchange is performed by joining with the heat exchange passage, the bypass efficiency is lowered.

  On the other hand, in this embodiment, since the intermediate tubular member 12 is composed of the two divided members 25 and 26 sandwiching the inner tubular member 11, the degree of freedom of the shape of the inner tubular member 11 is high, which is required. An appropriate shape can be obtained. Therefore, as in the above-described embodiment, the inner tubular member 11 is integrally connected from the three branch portions 17 to the single junction portion 18, thereby extending the bypass passage 14 over the entire length of the passage, thereby bypassing the bypass passage 14. Efficiency can be improved.

  Further, as shown in FIG. 3, the heat exchange passage 15 and the bypass passage 14 are joined at the joining portion 5A inside the exhaust pipe 5 on the downstream side, but the cooling water passage 16 is located upstream of the joining portion 5A. Arranged on the side. Thereby, it can suppress and prevent that the exhaust gas which flowed through the bypass channel | path 14 is heat-exchanged by 5 A of merge parts, and can suppress the fall of bypass efficiency.

  Next, a second embodiment of the present invention will be described with reference to FIGS. The same constituent elements as those in the first embodiment are denoted by the same reference numerals, and the description of overlapping configurations and operational effects will be omitted as appropriate, and differences from the first embodiment will be mainly described.

  In the second embodiment, the bypass passage 14 is provided with the first throttle portion 40A for limiting the flow rate of the exhaust gas flowing through the bypass passage 14 to a predetermined value or less, and also in the middle of the heat exchange passage 15, A second throttle 51 is provided that limits the flow rate of the exhaust gas flowing through the heat exchange passage 15 to a predetermined value or less. The second throttle portion 51 is disposed on the downstream side / exhaust pipe 5 side in the exhaust gas flow direction with respect to the first throttle portion 40A. A communication passage 52 that connects the heat exchange passage 15 and the bypass passage 14 is formed between the first throttle portion 40A and the second throttle portion 51 in the longitudinal direction of the passage.

  Similar to the first embodiment, the first throttle portion 40A is provided in the vicinity of the upstream end portion of the inner tubular member 11 and has a Venturi-shaped curved surface whose inner surface is smoothly reduced in diameter. Further, the first throttle portion 40 </ b> A is disposed in the vicinity of the upstream end of the adjacent cooling water passage 16 or upstream of the cooling water passage 16 in the longitudinal direction of the passage. Thereby, heat exchange is not performed carelessly before reaching the first throttle portion 40A, and the heat exchange amount can be adjusted appropriately.

  Similar to the throttle unit 40 of the first embodiment, the first throttle unit 40A and the second throttle unit 51 are equivalent to the speed of sound when the flow rate exceeds a predetermined value by partially reducing the passage cross-sectional area. Therefore, the flow rate is limited to a predetermined value or less so that the mass flow rate does not increase any more. Moreover, the 2nd aperture | diaphragm | squeeze part 51 is formed in the venturi-type shape which changes a channel | path cross-sectional area gradually so that a pressure loss may be reduced.

  Next, the function and effect of the second embodiment will be described with reference to FIG. In the second embodiment, as the total flow rate Qa of the exhaust gas increases, at the time t1 when the flow rate of the exhaust gas flowing into the heat exchange passage 15 becomes equal to or greater than the predetermined value sQb, first, by the first throttle unit 40A, The flow rate flowing into the bypass passage 14 is limited to a predetermined value sQb. However, in the second embodiment, since the heat exchange passage 15 and the bypass passage 14 communicate with each other through the communication passage 52, the flow rate is limited by the first throttle 40A, and the total flow rate Qa increases. When the flow rate Qe of the heat exchange passage 15 increases, a part of the flow rate Qb is supplied to the bypass passage 14 side downstream of the first throttle portion 40A through the communication passage 52. While increasing.

  Further, the total flow rate Qa of the exhaust gas increases, and the flow rate Qe of the exhaust gas flowing through the bypass passage 14 by the second throttle 51 at the time t2 when the flow rate of the exhaust gas flowing into the heat exchange passage 15 reaches the predetermined value sQe. Is limited to a predetermined value sQe. Therefore, after this time t2, as the total flow rate Qa increases, the flow rate flowing through the heat exchange passage 15 is limited to a constant value, while the exhaust gas flowing into the heat exchange passage 15 exceeds the predetermined value sQe. Flows into the bypass passage 14 side through the communication passage 52, and therefore, the flow rate flowing through the bypass passage 14 greatly increases in proportion to the increase in the total flow rate Qa.

  As described above, in the second embodiment, as in the first embodiment, in the low / medium output range (t0 to t1), the flow rate on the bypass passage 14 side is not limited, and one of the total exhaust gas flow rates. Since the portion flows toward the bypass passage 14 at a predetermined flow rate ratio, the flow rate through the heat exchange passage 15 is suppressed, and the heat exchange amount is suppressed. As a result, excessive heat exchange that causes the radiator to overheat can be avoided. Further, in a predetermined high output region (t1 to t2) in which an excessive increase in the exhaust temperature is a problem, the flow rate of the heat exchange passage 15 is relatively limited by limiting the flow rate Qb of the bypass passage 14 to a predetermined value sQb or less. By increasing Qe, it is possible to promote a decrease in the exhaust gas temperature and consequently the catalyst temperature by increasing the heat exchange amount.

  In the maximum output region (t2) on the higher output side than the high load region (t1 to t2), from the viewpoint of protecting parts such as the intermediate tubular member 12 and the outer tubular member 13 formed of an aluminum alloy, It is desirable to suppress excessive heat exchange. Therefore, in the second embodiment, the flow rate Qe of the heat exchange passage 15 is limited to a certain value sQe or less by the second throttle 51 in such a maximum output range (t2). For this reason, after the flow rate Qe of the heat exchange passage 15 reaches the constant value sQe, if the total exhaust gas flow rate Qa further increases as the engine output increases, the heat exchange passage 15 passes through the communication passage 52 to the bypass passage 14. The flow rate of the flowing exhaust gas increases, and the flow rate Qb at the outlet portion of the bypass passage 14 increases in proportion to the increase in the total flow rate Qa. Thus, in the maximum output range (t2), excessive heat exchange can be prevented by limiting the flow rate flowing through the heat exchange passage 15 to the predetermined value sQe.

  Here, as shown in FIG. 7, the allowable line L0 of the radiator is the lowest in the vicinity of the low / medium output range (t0 to t1), and the engine output / engine speed is higher than the low / medium output range. In the high output range (t1 to t2), on the contrary, the allowable line L0 becomes higher because the vehicle speed and the air volume increase as the engine output increases. Therefore, even if the heat exchange amount is increased by increasing the flow rate Qe of the heat exchange passage 15 in accordance with the increase in the total exhaust gas flow rate Qa in the high output range (t2) as in the present embodiment, the radiator can be There will be no overheating.

  That is, in the second embodiment, similarly to the first embodiment, in the predetermined low / medium output range (t1 to t2), the flow rate flowing through the bypass passage 14 is not limited, and the bypass passage 14 is at a predetermined ratio. In the high output range (t2) where the engine output is higher than the intermediate output range, the first throttle 40 reduces the bypass passage 14 while suppressing and preventing excessive heat exchange. By restricting the flow rate Qb to the constant value sQb, the flow rate Qe of the heat exchange passage 15 can be actively increased as the exhaust gas total flow rate Qa increases, and the exhaust temperature can be lowered.

  As in the first embodiment, such an operational effect is realized by setting the passage shape of the exhaust passage including the heat exchange passage 15 and the bypass passage 14, and specifically, the first throttle portion 40A, This is realized by providing the second restrictor 51, the communication passage 52, etc., and does not require moving parts such as a valve member. Therefore, it is excellent in reliability and durability, and reduces the number of parts and costs. be able to.

  The specific passage configuration for realizing such an effect will be described. As described above, the flow rate Qb of the bypass passage 14 is first increased by the first restrictor 40A as the total flow rate Qa of the exhaust gas increases. Is limited to the predetermined value sQb, and when the total flow rate Qa further increases, the first throttle unit 40A and the second throttle unit are configured such that the second throttle unit 51 limits the flow rate Qe of the heat exchange passage 15 to the predetermined value sQe. An aperture diameter of 51 is set. Specifically, the aperture diameter of the first aperture section 40A is set smaller than the aperture diameter of the second aperture section 51, and the flow rate sQb limited by the first aperture section 40A is the second aperture section 51. Is set to be smaller than the flow rate sQe limited by.

  Furthermore, the sum total of the passage sectional area of the communication passage 52 and the passage sectional area of the second throttle portion 51 is set to be larger than at least the passage sectional area of the inlet portion of the heat exchange passage 15. As a result, even when the flow rate Qe of the heat exchange passage 15 is limited to the predetermined value sQe by the second throttle 51, the exhaust gas flows from the heat exchange passage 15 into the bypass passage 14 through the communication passage 52. Loss can be suppressed.

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes without departing from the spirit of the present invention. . For example, the refrigerant for heat exchange is not limited to the cooling water as in the above embodiment, and an appropriate liquid or gas can be used. In the above embodiment, the present invention is applied to an internal combustion engine for a vehicle. However, the present invention is not limited to this, and the present invention can be applied to various combustion apparatuses that generate exhaust gas.

DESCRIPTION OF SYMBOLS 10 ... Exhaust heat exchange apparatus 11 ... Inner tubular member 12 ... Intermediate tubular member 13 ... Outer tubular member 14 ... Bypass passage 15 ... Heat exchange passage 16 ... Cooling water passage 25, 26 ... Dividing member 40 ... Restriction part (1st restriction | contraction) Part)
40A ... 1st aperture (first aperture)
43 ... Deflection part 51 ... 2nd aperture | diaphragm | squeeze part (2nd aperture_diaphragm | restriction part)
52 ... Communication passage

Claims (10)

The exhaust gas flowing in the exhaust passage is configured to branch and flow into a heat exchange passage and a bypass passage, and the heat exchange passage performs heat exchange with the refrigerant for heat exchange. In the heat exchange device arranged close to the refrigerant while the bypass passage is arranged to bypass the heat exchange passage,
The shape of the exhaust passage including the heat exchange passage and the bypass passage is set so that the flow rate of the exhaust gas flowing into the bypass passage is constant when the flow rate of the exhaust gas is large. Exhaust heat exchange device.   The shape of the exhaust passage including the heat exchange passage and the bypass passage is set so that the flow rate ratio of the bypass passage to the heat exchange passage decreases as the exhaust gas flow rate increases. The exhaust heat exchanger according to claim 1.   The exhaust according to claim 1 or 2, wherein a first throttle part is provided in the middle of the heat exchange passage so that the flow rate of the bypass passage is constant when the flow rate of the exhaust gas is large. Heat exchange device.   A refrigerant passage through which the refrigerant flows is disposed around the heat exchange passage, and the refrigerant passage is disposed upstream of a joining portion where the heat exchange passage and the bypass passage merge on the downstream side. The exhaust heat apparatus according to any one of claims 1 to 3, A refrigerant passage through which the refrigerant flows is disposed around the heat exchange passage,
The exhaust heat exchange device according to any one of claims 1 to 4, wherein the bypass passage is disposed concentrically inside the heat exchange passage. An inner tubular member having the bypass passage formed therein;
An intermediate tubular member covering the inner tubular member;
An outer tubular member covering the intermediate tubular member,
The heat exchange passage is formed between the inner tubular member and the intermediate tubular member,
6. The exhaust heat exchanger according to claim 5, wherein the refrigerant passage is formed between the intermediate tubular member and the outer tubular member.   The exhaust heat exchanger according to claim 6, wherein the intermediate tubular member is constituted by a pair of divided members that sandwich the inner tubular member.   A second constriction is provided in the middle of the heat exchange passage, and the second constriction is disposed downstream of the first constriction, and the first constriction and the first constriction in the longitudinal direction of the passage. The exhaust heat exchanger according to claim 3, wherein a communication passage that connects the heat exchange passage and the bypass passage is formed between the second throttle portion.   When the total flow rate of the exhaust gas is increased, the first throttle unit and the second throttle unit are configured such that, of the heat exchange channel and the bypass channel, the flow rate of the bypass channel is limited first by the first throttle unit. The exhaust heat exchanger according to claim 8, wherein a throttle diameter with the throttle part is set.   The sum total of the passage cross-sectional area of the said communicating path and the passage cross-sectional area of a 2nd aperture | diaphragm | squeeze part is larger than the passage cross-sectional area of the inlet part of the said heat exchange passage at least. Exhaust heat exchanger.

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