JP5673229B2 - Exhaust heat exchanger - Google Patents

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. . In addition, it is desirable to recover heat by actively exchanging heat on the low rotation and low output side where the exhaust gas flow rate is small. However, the middle and high rotation, medium and high output increases the exhaust gas flow rate. On the side, 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. The heat exchange passage and the bypass passage are included so that the flow rate of the exhaust gas flowing into the heat exchange passage becomes constant when the flow rate of the exhaust gas is large, that is, when the flow rate exceeds a certain constant flow rate. The passage shape of the exhaust passage is set.
A first constriction is provided in the middle of the heat exchange passage so that the flow rate of the exhaust gas flowing into the heat exchange passage is constant when the flow rate of the exhaust gas is large. The second throttle part is provided on the downstream side of the first throttle part, and is located between the first throttle part and the second throttle part in the longitudinal direction of the passage. A communication passage that connects the heat exchange passage and the bypass passage is formed, and when the total flow rate of the exhaust gas is increased, the heat exchange passage of the heat exchange passage and the bypass passage is the first throttle portion. Therefore, the throttle diameters of the first throttle part and the second throttle part are set so that the flow rate is limited first.

  According to the present invention, when the flow rate of the exhaust gas is small, heat exchange is performed between the exhaust gas flowing through the heat exchange passage and the refrigerant, and the heat energy of the exhaust gas is recovered via the refrigerant. be able to. 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, when the flow rate of exhaust gas is high, that is, when the flow rate exceeds a predetermined flow rate, the flow rate of the heat exchange passage is constant, so that excessive heat exchange and heat recovery with the refrigerant is prevented, and a cooling system such as a radiator Overheating of the parts can be avoided. At this time, since the exhaust gas having a constant flow rate flows to the heat exchange passage side, the exhaust heat can be recovered as long as it does not become excessive.

  In the present invention, the above-described 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, when the flow rate is high while recovering the thermal energy of the exhaust gas by heat exchange between the exhaust gas and the refrigerant, while having a simple configuration without using movable parts such as a valve member. In this case, by keeping the flow rate of the exhaust gas flowing into the heat exchange passage side constant, excessive heat exchange can be prevented and overheating of cooling system components such as a radiator can be avoided.

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. Sectional drawing which shows typically the flow of exhaust gas when the flow volume of exhaust gas is small. Sectional drawing which shows typically the flow of exhaust gas when there is much flow volume of exhaust gas. Explanatory drawing which shows the relationship between the flow volume of the exhaust gas which concerns on the said 1st Example, and the amount of exhaust heat exchange. 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 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. 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. 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 heat exchange passage 15. When the flow rate of the exhaust gas flowing into the heat exchange passage 15 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 becomes The shape and size (gap distance D1 and the like) are set so that they no longer increase. Specifically, as shown in FIG. 3, the tapered portion 40 is formed at the downstream end of the tapered surface 41 by making the heat exchange passage 15 into a tapered surface 41 that gradually decreases in diameter toward the downstream side. Yes. The passage cross-sectional area of the throttle portion 40 that is the minimum cross section in the heat exchange passage 15 is set to be smaller than the minimum cross-sectional area in the bypass passage 14. Further, the gap distance D1 in the throttle portion 40 is set to be smaller than the minimum radius D2 of the bypass passage 14. The position, shape, and dimensions of the throttle portion 40 are not limited to those shown in FIG. 3. For example, the throttle portion is provided in the middle of the heat exchange passage 15 by partially projecting the outer wall of the inner tubular member 11 outward. You may make it provide.

  The effect by this aperture part 40 is demonstrated with reference to FIG. The vertical axis of FIG. 6 represents the amount of heat exchange and heat recovery from the exhaust gas to the cooling water, and this amount of heat exchange is substantially proportional to the flow rate of the exhaust gas flowing through the heat exchange passage 15. The horizontal axis represents the engine output output from the internal combustion engine, and this engine output is substantially proportional to the engine load, the engine speed, or the exhaust gas flow rate. The symbol L0 corresponds to an allowable line of the heat exchange amount 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 be overheated. Corresponds to the area. Symbol L1 represents the characteristics when the above-described exhaust heat exchanger 10 of the present embodiment is used. Symbol L2 does not include the throttle 40, and the flow rate ratio between the heat exchange passage and the bypass passage is the same. The characteristic of the comparative example which becomes constant irrespective of the flow rate is represented.

  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. Therefore, regardless of the embodiment L1 and the comparative example L2, the heat recovery amount Is not likely to exceed the allowable line L0.

  However, in the middle / high output range, 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 decreases, while the engine rotation increases as the engine output increases. Since the exhaust gas flow rate increases as the speed and engine load increase, the amount of heat exchange inevitably increases as the exhaust gas flow rate increases when the flow rate ratio is constant as in Comparative Example L1. However, as shown in the region α in the figure, the heat exchange amount may exceed the upper limit line L0.

  On the other hand, in the present embodiment L1, as described above, the flow rate of the heat exchange passage 15 is limited to be constant in the middle / high output range where the flow rate of the exhaust gas increases as the engine output increases. For this reason, the heat exchange amount is also constant, and the heat exchange amount does not exceed the allowable line L0 of the radiator.

  As described above, in this embodiment, since the flow rate of the exhaust gas is small in the low output range, the flow rate of the heat exchange passage 15 is not limited by the throttle unit 40, and the cooling water temperature is set using the exhaust heat. In the middle and high output ranges where the allowable line L0 of the radiator is lowered, the flow rate of the exhaust gas increases as the engine output increases, but the throttle unit 40 As a result, the flow rate of the heat exchange passage 15 is limited to a constant value, so that excessive heat exchange that causes the radiator to overheat can be avoided. In the present embodiment, the exhaust gas flowing in the heat exchange passage 15 is not shut off even in the middle and high output ranges, but a constant flow rate of exhaust gas flows through the heat exchange passage 15. Therefore, while avoiding excessive heat exchange, a predetermined amount of heat exchange is performed and exhaust heat can be recovered appropriately. Further, since the heat exchange passage 15 is not blocked, the ventilation resistance is not excessively increased.

  Further, in the present embodiment, as shown in FIGS. 3 to 5, as the flow rate increases, the exhaust port 3 of the cylinder head 1, which is the exhaust passage upstream of the heat exchange passage 15 and the bypass passage 14, increases. A deflection unit 43 is provided for deflecting and guiding the flow of exhaust gas toward the bypass passage 14. The deflecting portion 43 projects inward from the inner wall of the exhaust port 3 so as to partially narrow the passage section. The deflecting portion 43 is provided with a tapered surface 44 that is inclined so as to gradually reduce the diameter of the passage from the upstream side toward the downstream side. When the flow velocity is high, the extension line 45 along the taper surface 44 is directed toward the peripheral edge of the inlet of the bypass passage 14 so that the exhaust gas flow along the taper surface 44 is directed to the vicinity of the inlet of the central bypass passage 14. Is set.

  With such a configuration, when the flow rate of the exhaust gas is small, as shown in FIG. 4, the flow rate is slow, so that the exhaust gas sufficiently flows into the heat exchange passage 15 on the outer peripheral side by turning around the deflection unit 43, As shown in FIG. 5, when the flow rate of the exhaust gas is high, the flow rate becomes faster, so that the flow toward the central bypass passage 14 becomes dominant by the deflection unit 43, and the flow rate ratio of the bypass passage 14 increases. The flow rate ratio on the heat exchange passage 15 side decreases. For this reason, in the middle / high output range where the flow rate of exhaust gas increases, the flow rate ratio on the heat exchange passage 15 side, that is, the flow rate can be suppressed to further reliably suppress excessive heat exchange. it can.

  In the present embodiment, the above-described effects are realized by setting the passage shape of the exhaust passage including the heat exchange passage 15 and the bypass passage 14. This is realized by providing the portion 43 and does not require moving parts such as a valve member. 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 heat exchanging passage 15 is provided with the first throttle portion 40A for limiting the flow rate of the exhaust gas flowing through the heat exchanging passage 15 to a predetermined value or less, and in the middle of the bypass passage 14, A second throttle 51 is provided that limits the flow rate of exhaust gas flowing through the bypass passage 14 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.

  In this embodiment, the first throttle portion 40A is provided by using a ring portion 19 for fixing the inner tubular member 11 to the intermediate tubular member 12. Specifically, a ring portion 19 having a diameter larger than the outer periphery of the tube portion is concentrically provided at the upstream end portion of the inner tubular member 11 via four support rib portions 20 as in the first embodiment. ing. These ring portions 19 are fitted into an annular groove portion 21A formed in the inlet flange portion 21 of the intermediate tubular member 12, and in the assembled state shown in FIG. By being sandwiched between the side wall 2 and the inner tubular member 11, 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. A gap 22 between the ring portion 19, the support rib 20, and the outer periphery of the tube portion functions as a first restricting portion 40 </ b> A that restricts the heat exchange passage 15. Thus, the first throttle part 40A can be provided on the upstream side of the passage by using the ring part 19 for fixing the inner tubular member 11 to the intermediate tubular member 12, and there is no need to separately form a throttle part. Thus, the configuration can be simplified.

  Further, the first throttle portion 40A is disposed at a position distant upstream of the adjacent coolant 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.

  Further, the ring portion 19 is provided with a protruding portion 53 that protrudes inward from the wall surface of the heat exchange passage 15 so that the first throttle portion 40A has an appropriate passage cross-sectional area. Further, the upstream end 54 of the tubular portion of the inner tubular member 11 is located upstream of the ring portion 19, that is, the intake port of the cylinder head 1 so that the first throttle portion 40 </ b> A is provided in the middle of the heat exchange passage 15. 3 is projected to the inside.

  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, with reference to FIG. 9 and FIG. 10, the effect of this 2nd Example is demonstrated, comparing with said 1st Example. 9 (b) and 10 (b), Qe represents the flow rate of the exhaust gas that has passed through the heat exchange passage 15, Qb represents the flow rate of the exhaust gas that has passed through the bypass passage 14, and Qa represents the flow rate described above. It represents the total flow rate of exhaust gas that combines Qe and 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. Similarly to FIG. 6, the symbol L0 corresponds to a heat exchange amount allowable line that the radiator can allow (does not overheat), and the region above the allowable line L0 has an excessive heat exchange amount. This corresponds to an area where the radiator may overheat.

  As shown in FIG. 9, in the first embodiment, when the total exhaust gas flow rate Qa increases in proportion to the increase in engine output, first, the flow rate Qe flowing into the heat exchange passage 15 becomes equal to or greater than a predetermined value sQe. At time t1, the flow rate Qe of the heat exchange passage 15 is limited to the predetermined value sQe by the throttle 40, and thereafter, even if the total flow rate Qa increases, the flow rate Qe of the heat exchange passage 15 is maintained at a constant sQe. As the total flow rate Qa increases, the flow rate Qb of the exhaust gas passing through the bypass passage 14 increases. In the first embodiment, since the communication passage 52 as in the second embodiment is not provided, the flow rate flowing into the heat exchange passage 15 and the flow rate Qe after passing through the heat exchange passage 15 are Are the same.

  In contrast, in the second embodiment, as shown in FIG. 10, at the time t1 when the flow rate of the exhaust gas flowing into the heat exchange passage 15 becomes equal to or higher than the predetermined value sQe as the total exhaust gas flow rate Qa increases. First, the flow rate flowing into the heat exchange passage 15 is limited to the predetermined value sQe by the first throttle portion 40A. 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 Qb of the bypass passage 14 is increased, a part of the flow rate Qe passing through the heat exchange passage 15 is slightly increased because a part of the flow rate Qb is supplied to the heat exchange passage 15 side downstream of the first throttle portion 40A through the communication passage 52. While increasing.

  Further, when the total flow rate Qa of the exhaust gas increases and the flow rate of the exhaust gas flowing into the bypass passage 14 reaches the predetermined value sQb, the flow rate Qb of the exhaust gas flowing through the bypass passage 14 by the second throttle 51 is changed. It is limited to a predetermined value sQb. Therefore, after this time point t2, the flow rate flowing through the bypass passage 14 is limited to a constant value as the total flow rate Qa increases, while the exhaust gas flowing into the bypass passage 14 continues to exceed the predetermined value sQb. It flows into the heat exchange passage 15 side through the passage 52, and for this reason, the flow rate flowing through the heat exchange passage 15 increases greatly in proportion to the increase in the total flow rate Qa.

  Thus, in the second embodiment, as in the first embodiment, in the low output range (t0 to t1), the engine rotational speed is low and the total exhaust gas flow rate Qa is small, so the flow rate Qe of the heat exchange passage 15 is low. However, it is not limited by the first restrictor 40A, and the cooling water temperature can be increased using the exhaust heat to promote heating and warm-up. Further, in the middle output region (t1 to t2) where the allowable line L0 of the radiator is particularly low, the total flow rate Qa of the exhaust gas increases as the engine output increases. Since the inflowing flow rate is limited to a predetermined value sQe or less, excessive heat exchange that causes the radiator to overheat can be avoided.

  In the second embodiment, the flow rate Qb of the bypass passage 14 is limited to a predetermined value sQb or less by the second throttle 51 in a high output range (t2) where the engine output is higher than that in the middle load range. The For this reason, after the flow rate Qb of the bypass passage 14 reaches the constant value sQb, if the total exhaust gas flow rate Qa further increases as the engine output increases, it flows from the bypass passage 14 to the heat exchange passage 15 through the communication passage 52. The flow rate of the exhaust gas increases, and the flow rate Qe at the outlet portion of the heat exchange passage 15 increases in proportion to the increase in the total flow rate Qa. Thus, in the high output region (t2), the flow rate Qe of the heat exchange passage 15 increases as the total flow rate Qa of the exhaust gas increases, and the heat exchange amount is increased, thereby reducing the exhaust temperature and the downstream of the exhaust passage. An excessive increase in the temperature of the arranged catalyst can be suppressed.

  Here, as shown in FIG. 9, the allowable line L0 of the radiator is the lowest in the vicinity of the medium output range (t1 to t2), and in the high output range where the engine output and the engine rotational speed are higher than the intermediate output range. 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 as in this embodiment, the radiator is overheated. It will not happen.

  That is, in the second embodiment, there are two choke points where the flow rate is throttled, and the flow rate Qe flowing into the heat exchange passage 15 by the first throttling part 40A is constant in a predetermined medium output range (t1 to t2). By restricting to the value sQe, excessive heat exchange is suppressed / prevented, and in the high output range (t2) where the engine output is higher than the middle output range, the flow rate Qb of the bypass passage 14 is set by the second throttle 51. Is limited to a constant value sQb, the flow rate Qe of the heat exchange passage 15 is actively increased as the total flow rate Qa of the exhaust gas increases, and the reduction of the exhaust temperature can be promoted.

  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, as the total flow rate Qa of the exhaust gas increases, first, the flow rate of the heat exchange passage 15 by the first throttle 40A. When Qe is limited to the predetermined value sQe and the total flow rate Qa further increases, the first throttle unit 40A and the second throttle unit are configured so that the second throttle unit 51 limits the flow rate Qb of the bypass passage 14 to the predetermined value sQb. 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 sQe limited by the first aperture section 40A is the second aperture section 51. Is set to be smaller than the flow rate sQb 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 bypass passage 14. As a result, even when the flow rate Qb of the bypass passage 14 is limited to the predetermined value sQb by the second throttle 51, the exhaust gas flows from the bypass passage 14 to the heat exchange passage 15 through the communication passage 52, thereby causing a pressure 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 part (2nd aperture part)
52 ... Communication passage

Claims (9)

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,
When the flow rate of the exhaust gas is large, a first throttle portion is provided in the middle of the heat exchange passage so that the flow rate of the exhaust gas flowing into the heat exchange passage is constant ,
A second throttle is provided in the middle of the bypass passage;
The second throttle portion is disposed downstream of the first throttle portion,
A communication passage that connects the heat exchange passage and the bypass passage is formed between the first throttle portion and the second throttle portion with respect to the longitudinal direction of the passage,
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 heat exchange channel is limited first by the first throttle unit. An exhaust heat exchanging device characterized in that a throttle diameter with respect to the throttle part is set . 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 claim 1 , A refrigerant passage through which the refrigerant flows is disposed around the heat exchange passage,
The exhaust heat exchanger according to claim 1 or 2 , 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,
The exhaust heat exchanger according to claim 3 , wherein the refrigerant passage is formed between the intermediate tubular member and the outer tubular member. The exhaust heat exchanger according to claim 4 , wherein the intermediate tubular member is constituted by a pair of divided members that sandwich the inner tubular member. In the exhaust passage upstream of the heat exchange passages and the bypass passage, the flow of exhaust gases to any one of claims 1 to 5, characterized in that a deflecting unit for deflecting, guided to the bypass passage side The exhaust heat exchanger described. The sum of the cross-sectional area and the passage sectional area of the second diaphragm portion of the communication path, in any one of claims 1 to 6, wherein greater than the passage cross-sectional area of the inlet portion of at least the bypass passage The exhaust heat exchanger described. A refrigerant passage through which the refrigerant flows is disposed around the heat exchange passage,
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,
The refrigerant passage is formed between the intermediate tubular member and the outer tubular member,
The upstream end portion of the intermediate tubular member is provided with a ring portion having a diameter larger than the outer periphery of the tube portion via a plurality of support rib portions,
A pair of split members constituting the intermediate tubular member sandwich the ring portion, so that the inner tubular member is fixed to the intermediate tubular member,
The exhaust heat according to any one of claims 1 to 7 , wherein a gap between the outer periphery of the tube portion of the inner tubular member, the ring portion, and the support rib constitutes the first throttle portion. Exchange equipment. A refrigerant passage through which the refrigerant flows is disposed around the heat exchange passage,
The exhaust heat exchanger according to any one of claims 1 to 8 , wherein the first throttle portion is disposed upstream of the refrigerant passage.

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