JP2008202450A - Exhaust heat recovery apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust heat recovery apparatus capable of inhibiting recovery of excessive heat with a simple structure. <P>SOLUTION: This apparatus is provided with; an evaporation part 1 arranged in an exhaust gas path in which exhaust gas exhausted from an engine flows, exchanging heat exhaust gas and working fluid filled inside capable of evaporating and condensing; a condensation part 2 arranged in a cooling water path in which cooling water of the engine flows, exchanging heat between working fluid evaporating in the evaporation part 1 and cooling water, and condensing working fluid; an evaporation side connection part 61 leading working fluid evaporating in the evaporation part 1 to the condensation part 2; and a condensation side connection part 62 leading working fluid condensing in the condensation part 2 to the evaporation part 1. A fixed throttle 7a is provided in the condensation side connection part 62. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust heat recovery device used for a vehicle such as an automobile.

  2. Description of the Related Art In recent years, a technology is known in which exhaust heat of exhaust gas is recovered from an exhaust system of a vehicle engine using the principle of a heat pipe, and this exhaust heat is used for promoting warm-up.

  In such an exhaust heat recovery device, a heat pipe evaporating part is arranged in the exhaust pipe of the engine, and a heat pipe condensing part is arranged in the engine cooling water path so that the cooling water is cooled by the exhaust heat of the exhaust gas. Is heated (see, for example, Patent Document 1).

In addition, a loop heat pipe type heat exchanger has been proposed as a heat exchanger using the principle of a heat pipe (see, for example, Patent Document 2). This includes a closed circulation path that forms a closed loop, a working fluid enclosed in the circulation path that can be evaporated and condensed, and an evaporation unit that is disposed in the circulation path and evaporates the working fluid by heat input from the outside. And a condensing part that is disposed at a position higher than the evaporation part of the circulation path and exchanges heat between the working fluid evaporated in the evaporation part and the heat transfer fluid from the outside.
Japanese Patent Laid-Open No. 62-268722 JP-A-4-45393

  An example of the exhaust heat recovery unit as described above is shown in FIG. FIG. 6 is a cross-sectional view of the exhaust heat recovery device. In the exhaust heat recovery device shown in FIG. 6, the evaporation unit J1 and the condensing unit J2 which are heat exchange units are arranged adjacent to each other in the horizontal direction, and both ends in the vertical direction of the heat pipe J3 of the evaporating unit J1 and the condensing unit J2 are respectively arranged. A header (communication portion) J5 for communication is provided.

  By the way, the exhaust heat recovery device can raise the cooling water temperature at an early stage by recovering the exhaust heat at the start of winter, for example, so that the fuel consumption and the heating performance can be improved. On the other hand, when the engine is heavily loaded in summer, it is necessary to stop the recovery of exhaust heat in order to avoid overheating.

  For this reason, it is desirable to provide the exhaust heat recovery device with a valve mechanism that stops the circulation of the working fluid. As the valve mechanism, for example, a diaphragm type valve mechanism in which the valve body is driven by a diaphragm that is displaced according to the pressure of the working fluid can be considered. Thus, by providing a valve mechanism in the exhaust heat recovery device, it is possible to suppress recovery of an excessive amount of heat.

  However, when the above-described valve mechanism is provided in the exhaust heat recovery device, a diaphragm, a valve body, and the like are required, and the configuration becomes complicated, resulting in an increase in manufacturing cost.

  In view of the above points, an object of the present invention is to provide an exhaust heat recovery device that can suppress recovery of an excessive amount of heat with a simple configuration.

  In order to achieve the above object, according to the present invention, heat is generated between an exhaust gas and a working fluid that can be evaporated and condensed, which is disposed in an exhaust gas passage through which exhaust gas discharged from an internal combustion engine flows. An evaporator (1) that exchanges and evaporates the working fluid, and a cooling water path that is disposed in the cooling water path through which the cooling water of the internal combustion engine flows, and heat is generated between the working fluid evaporated in the evaporating unit (1) and the cooling water. Condensation part (2) which performs exchange and condenses working fluid, evaporation side connection part (61) which leads working fluid evaporated in evaporation part (1) to condensation part (2), and condensation in condensation part (2) And a condensing side connecting part (62) for guiding the working fluid to the evaporating part (1), and the condensing side connecting part (62) is provided with throttle mechanisms (7a to 7c).

  According to this, the upper limit of the recovered heat amount can be determined by presetting the opening degree of the throttle mechanism (7a to 7c) and the amount of working fluid enclosed. At this time, since members constituting the valve mechanism such as a diaphragm and a valve body can be eliminated, it is possible to suppress recovery of an excessive amount of heat with a simple configuration.

  In the exhaust heat recovery device having the above characteristics, the throttle mechanism may be a fixed throttle (7a). According to this, collection | recovery of excess heat quantity can be suppressed with a simpler structure.

  In the exhaust heat recovery device having the above characteristics, the throttle mechanism may be a variable throttle (7b, 7c) that changes the throttle opening according to the temperature of the working fluid.

  According to this, when the temperature of the working fluid becomes high, the throttle opening of the throttle mechanism (7b, 7c) can be reduced to limit the amount of recovered heat. For this reason, since the amount of recovered heat can be limited at the time of high engine load in summer when the temperature of the cooling water and the working fluid is high, overheating can be avoided.

  In the exhaust heat recovery device having the above characteristics, the variable throttles (7b, 7c) may be configured to reduce the throttle opening according to the temperature rise of the working fluid.

  According to this, at the time of high engine load in summer when the temperature of the working fluid is high, the throttle opening of the throttle mechanism (7b, 7c) becomes small, so that the amount of recovered heat can be limited. Thereby, overheating can be avoided.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. The exhaust heat recovery device of the present embodiment recovers exhaust heat of exhaust gas from an exhaust system of a vehicle engine (internal combustion engine) and uses this exhaust heat for promoting warm-up.

  FIG. 1 is a cross-sectional view showing an exhaust heat recovery device according to the first embodiment. As shown in FIG. 1, the exhaust heat recovery device of the present embodiment includes an evaporation unit 1 and a condensing unit 2.

  The evaporation unit 1 is provided in a first housing 100 that is disposed in an exhaust gas path (in this embodiment, an exhaust pipe) of an engine (not shown). Further, the evaporating unit 1 performs heat exchange between the exhaust gas and a working fluid described later to evaporate the working fluid.

  The condensing unit 2 is provided outside the exhaust pipe, and is provided in a second casing 200 that is disposed in a cooling water path of an engine (not shown). Further, the condensing unit 2 performs heat exchange between the working fluid evaporated in the evaporating unit 1 and the engine cooling water to condense the working fluid. The second casing 200 is provided with a cooling water inlet 201 connected to the cooling water outlet side of the engine and a cooling water outlet 202 connected to the cooling water inlet side of the engine.

  In the present embodiment, the first casing 100 and the second casing 200 are disposed adjacent to each other. A clearance is provided between the first casing 100 and the second casing 200.

  Next, the configuration of the evaporation unit 1 will be described.

  The evaporation unit 1 includes a plurality of evaporation side heat pipes 3a and evaporation side corrugated fins 4a joined to the outer surface of the evaporation side heat pipe 3a. The evaporation side heat pipes 3a are formed in a flat shape so that the exhaust gas flow direction (perpendicular to the plane of the drawing) coincides with the major axis direction, and a plurality of the evaporative heat pipes 3a are arranged in parallel so that the longitudinal direction thereof coincides with the vertical direction. Has been.

  In the evaporation section 1, evaporation side headers 5a extending in the stacking direction of the evaporation side heat pipe 3a and communicating with all the evaporation side heat pipes 3a are provided at both ends in the longitudinal direction of the evaporation side heat pipe 3a. Of the two evaporation side headers 5a, the evaporation side header 5a disposed on the upper end side of the exhaust heat recovery device is referred to as a first evaporation side header 51a, and the evaporation side header 5a disposed on the lower end side is referred to as a second evaporation. It is called side header 52a.

  Next, the configuration of the condensing unit 2 will be described.

  The condensing unit 2 includes a plurality of condensing side heat pipes 3b and condensing side corrugated fins 4b joined to the outer surface of the condensing side heat pipe 3b. The condensation side heat pipe 3b is formed in a flat shape so that the exhaust gas flow direction (perpendicular to the plane of the drawing) in the evaporation section 1 coincides with the major axis direction, and a plurality of the condensing side heat pipes 3b coincide with the vertical direction. These are arranged in parallel.

  In the condensing unit 2, condensing side heat pipes 3b are provided with condensing side headers 5b that extend in the stacking direction of the condensing side heat pipes 3b and communicate with all the condensing side heat pipes 3b at both ends in the longitudinal direction. Of the two condensing side headers 5b, the condensing side header 5b disposed on the upper end side of the exhaust heat recovery device is referred to as a first condensing side header 51b, and the condensing side header 5b disposed on the lower end side is referred to as a second condensing side header. It is called the side header 52b.

  The evaporating side header 5a and the condensing side header 5b are connected in a communicating state via a cylindrical connecting portion 6. A closed loop is formed by the evaporation side, the condensation side heat pipes 3a and 3b, the evaporation side, the condensation side headers 5a and 5b, and the connecting portion 6, and a working fluid capable of evaporating and condensing water, alcohol, etc. Is enclosed. As a result, the working fluid circulates through the evaporator 1 and the condenser 2.

  Here, it arrange | positions among two connection parts 6 above, connects the 1st evaporation side header 51a and the 1st condensation side header 51b, and the working fluid evaporated in the evaporation part 1 is made into the condensation part 2. What is guided is referred to as an evaporation side connecting portion 61. Moreover, it arrange | positions in the downward side among the two connection parts 6, connects the 2nd evaporation side header 52a and the 2nd condensation side header 52b, and makes the working fluid condensed by the condensation part 2 to the evaporation part 1. What is guided is referred to as a condensing side connecting portion 62.

  A fixed throttle 7 a is provided in the condensing side connecting portion 62. In the present embodiment, the fixed throttle 7 a is formed on the throttle member 70, and the throttle member 70 is inserted into the condensing side connecting portion 62.

  The throttle member 70 is formed in a shape that gradually reduces the cross-sectional area of the flow path through which the working fluid condensed in the condensing unit 2 passes, and then gradually increases. That is, the throttle member 70 is continuously formed on the first tapered surface 701 having a diameter reduced from the upstream side to the downstream side of the working fluid flow, and on the downstream side of the working fluid flow of the first tapered surface 701, and the working fluid And a second tapered surface 702 having an enlarged diameter from the upstream side to the downstream side.

  Next, the operation of the exhaust heat recovery device according to the first embodiment will be described.

FIG. 2 is a conceptual diagram showing the operation of the exhaust heat recovery device, (a) and (b) show a conventional exhaust heat recovery device, and (c) and (d) show the exhaust of the first embodiment. Each heat recovery unit is shown. Further, (a) and (c) are when the exhaust gas heat quantity Q _in is Q ₁ , and (b) and (d) are when the exhaust gas heat quantity Q _in is Q ₂ (where Q ₁ <Q ₂ ). Is shown.

  2A to 2D, the plurality of evaporation side heat pipes 3a are collectively shown as one for convenience of explanation. Similarly, the plurality of condensing side heat pipes 3b are collectively shown as one. 2A to 2D, the corrugated fins 4a and 4b and the first and second housings 100 and 200 are not shown.

  The working fluid evaporated in the evaporation unit 1 flows into the condensing unit 2 through the evaporation side connecting unit 61, and the working fluid condenses into a liquid in the condensing unit 2, and passes through the condensing side connecting unit 62 to the evaporation unit 1. Inflow. Due to the balance between the evaporation of the working fluid in the evaporation unit 1 and the condensation of the working fluid in the condensing unit 2, a water level difference (water head difference h) of the working fluid (liquid) occurs between the evaporation unit 1 and the condensing unit 2. . Due to the water head difference h, the working fluid is recirculated from the condensing unit 2 to the evaporation unit 1, thereby circulating the working fluid.

In the exhaust heat recovery unit, as shown in FIG. 2 (a), the pressure loss of the return of the working fluid as a [Delta] P _1, the density at the liquid phase of the working fluid [rho, the gravitational acceleration g, when the water head difference is is h, The relationship ΔP ₁ = ρgh is satisfied.

Here, since the density ρ and the gravitational acceleration g in the liquid phase of the working fluid are constant, when the exhaust gas heat quantity Q _in is constant, the water head difference h is determined by the pressure loss ΔP ₁ . Q _out is the amount of heat given to the cooling water from the condensing unit 2.

As shown in FIG. 2 (b), the exhaust gas heat quantity Q _in is increased, the recirculation amount of the working fluid is increased. Thus, since the flow rate of the working fluid increases, the pressure loss [Delta] P ₁ of reflux of the working fluid increases, also increases with the water head difference h thereto.

In the present embodiment, as shown in FIG. 2 (c), since the provided fixed throttle 7a to the condenser side connecting portion 62, the pressure loss [Delta] P of the return of the working fluid 'is due to the fixed throttle 7a and [Delta] P ₁ described above a value obtained by adding the pressure loss [Delta] P _2. Thus, the water head difference h 'in this case, the exhaust heat recovery unit and the fixed throttle 7a pressure is loss [Delta] P ₂ minutes large compared illustrated in FIG. 2 (a).

When the exhaust gas heat quantity Q _in as shown in FIG. 2 (d) is increased, the pressure loss [Delta] P of the return of the working fluid _{'(= ΔP 1 + ΔP 2} ) for increases, the water head difference h required reflux' also growing. If the water head difference h ′ necessary for reflux cannot be secured, the amount of reflux of the working fluid is limited, and the amount of recovered heat reaches a peak.

  As described above, the upper limit of the recovered heat amount can be determined by providing the fixed throttle 7a in the condensing side connecting portion 62 and presetting the throttle opening of the fixed throttle 7 and the amount of working fluid enclosed. At this time, since members constituting the valve mechanism such as a diaphragm and a valve body can be eliminated, it is possible to suppress recovery of an excessive amount of heat with a simple configuration.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIGS. 3A and 3B are enlarged cross-sectional views showing the condensing side connecting portion 62 of the exhaust heat recovery apparatus according to the second embodiment, where FIG. 3A shows the working fluid at a low temperature and FIG. 3B shows the working fluid at a high temperature.

  As shown in FIGS. 3A and 3B, a variable throttle 7 b that changes the throttle opening according to the temperature of the working fluid is disposed in the condensing side connecting portion 62. The variable throttle 7b is configured to reduce the throttle opening according to the temperature rise of the working fluid, that is, to reduce the passage sectional area of the passage through which the working fluid flows.

  In the present embodiment, the variable aperture 7b is made of a material that can be deformed by the ambient temperature. As a material of the variable aperture 7b, for example, a bimetal or a shape memory alloy can be used. In the present embodiment, the passage through which the working fluid flows is not completely blocked even when the temperature of the working fluid in the condensing side connecting portion 62 rises.

Next, the operation of the exhaust heat recovery device according to the second embodiment will be described. When the exhaust gas heat quantity Q _in increases, the temperature of the working fluid also rises. Therefore, the variable throttle 7b responds to the increase _in the exhaust gas heat quantity Q _in. The throttle opening is reduced.

And when the variable throttle 7b is provided in the condensing side connection part 62, the collect | recovered calorie | heat amount of an exhaust-heat-heat recovery device increases with the increase _in exhaust-gas calorie | heat amount Qin. On the other hand, exhaust the gas heat quantity Q _in is increased, since the variable throttle pressure loss [Delta] P ₂ and aperture size decreases and 7b is increased, heat collection amount at a certain point does not increase any further. Further the exhaust gas heat Q _in is increased, the pressure loss [Delta] P ₂ decreases variable throttle 7b of aperture size further increases further, recirculation amount of the working fluid is reduced, heat collection amount decreases.

  As described above, by providing the condensing side connecting portion 62 with the variable throttle 7b that reduces the throttle opening according to the temperature rise of the working fluid, the amount of heat recovered by the exhaust heat recovery device can be reduced according to the temperature rise of the working fluid. Can be reduced. For this reason, since the amount of recovered heat can be limited when the temperature of the working fluid is high in the summer when the engine is heavily loaded, overheating can be avoided.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those in the second embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 4 is an enlarged cross-sectional view showing the condensing side connecting portion 62 of the exhaust heat recovery device according to the third embodiment. As shown in FIG. 4, the variable throttle 7 c of the present embodiment has one end on a throttle hole 71, a valve body 72 that opens and closes the throttle hole 71, and a face opposite to the face of the valve body 72 that faces the throttle hole 71. Has a temperature-sensitive deformation member 73 fixed thereto.

  The other end of the temperature-sensitive deformation member 73 is fixed to a support member 74 disposed in the condensing side connecting portion 62. Further, the temperature-sensitive deformation member 73 is made of, for example, a thermometal made of a metal having a higher thermal expansion coefficient than that of the metal constituting the condensation side connection portion 62, thermowax, or the like. When the temperature of the working fluid reaches a predetermined temperature or more, it expands thermally.

  Therefore, when the temperature of the working fluid in the condensing side connecting portion 62 rises, the valve body 72 moves in a direction to reduce the opening degree of the throttle hole 71. On the other hand, when the temperature of the working fluid in the condensing side connecting portion 62 decreases, the valve body 72 moves in the direction of increasing the opening degree of the throttle hole 71. In the present embodiment, the valve body 72 is configured not to completely close the throttle hole 71 even when the temperature of the working fluid in the condensing side connecting portion 62 rises.

  As described above, by providing the condensing side connecting portion 62 with the variable throttle 7c that reduces the throttle opening according to the temperature rise of the working fluid, the amount of heat recovered by the exhaust heat recovery device can be reduced according to the temperature rise of the working fluid. Can be reduced. Thereby, the effect similar to the said 2nd Embodiment can be acquired.

(Other embodiments)
In the first embodiment, an example in which the throttle member 70 is formed in a shape that gradually expands after the cross-sectional area of the flow path through which the working fluid condensed in the condensing unit 2 passes is gradually reduced. Although it demonstrated, it is not restricted to this, You may form the aperture member 70 in a cylindrical shape.

In the first embodiment, an example in which the fixed throttle 7a is formed on the throttle member 70 has been described. However, the present invention is not limited to this, and the inner diameter of the condensing side connecting portion 62 is partially reduced as shown in FIG. May be formed. Thereby, the diaphragm member 70 is unnecessary, and an increase in the number of parts can be suppressed. In this case, it is possible by determining the inner diameter d and the length L of the fixed throttle 7a, to set the pressure loss [Delta] P ₂ of the fixed throttle 7a.

  In the second and third embodiments, the variable throttles 7b and 7c are arranged so as to be in direct contact with the working fluid, and the throttle openings of the variable throttles 7b and 7c are mechanically controlled according to the temperature of the working fluid. However, the present invention is not limited to this, and a temperature sensor for detecting the temperature of the working fluid in the condensing side connecting portion 62 is provided, and the throttle openings of the variable throttles 7b and 7c are based on the detected temperature of the temperature sensor. It may be electrically controlled.

  Moreover, although each said embodiment demonstrated the example which has arrange | positioned the condensing side connection part 62 in the horizontal direction, you may make it incline with respect to a horizontal direction not only this.

It is sectional drawing which shows the exhaust heat recovery device which concerns on 1st Embodiment. It is a conceptual diagram which shows the action | operation of an exhaust heat recovery device, (a), (b) is the conventional exhaust heat recovery device, (c), (d) has shown the exhaust heat recovery device of 1st Embodiment, respectively. . It is an expanded sectional view which shows the steam side connection part 61 of the exhaust heat recovery device which concerns on 2nd Embodiment, (a) is the time of working fluid low temperature, (b) has shown the time of working fluid high temperature. It is an expanded sectional view which shows the condensation side connection part 62 of the exhaust heat recovery device which concerns on 3rd Embodiment. It is an expanded sectional view which shows the condensing side connection part 62 of the exhaust heat recovery device which concerns on other embodiment. It is sectional drawing which shows the conventional exhaust heat recovery device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Evaporation part, 2 ... Condensing part, 7a ... Fixed aperture (throttle mechanism), 7b, 7c ... Variable aperture (throttle mechanism), 61 ... Evaporation side connection part, 62 ... Condensation side connection part.

Claims (4)

The exhaust gas exhausted from the internal combustion engine is disposed in an exhaust gas passage through which heat is exchanged between the exhaust gas and an evaporating and condensable working fluid enclosed therein to evaporate the working fluid. An evaporation section (1);
A condensing unit that is arranged in a cooling water path through which the cooling water of the internal combustion engine flows and that exchanges heat between the working fluid evaporated in the evaporation unit (1) and the cooling water to condense the working fluid. (2) and
An evaporation side connecting part (61) for guiding the working fluid evaporated in the evaporation part (1) to the condensing part (2);
A condensing side connecting part (62) for guiding the working fluid condensed in the condensing part (2) to the evaporating part (1),
An exhaust heat recovery device, wherein the condensing side connecting portion (62) is provided with a throttle mechanism (7a-7c). The exhaust heat recovery device according to claim 1, wherein the throttle mechanism is a fixed throttle (7a). The exhaust heat recovery device according to claim 1, wherein the throttle mechanism is a variable throttle (7b, 7c) that changes a throttle opening according to a temperature of the working fluid. The exhaust heat recovery device according to claim 3, wherein the variable throttle (7b, 7c) is configured to reduce the throttle opening in accordance with a temperature rise of the working fluid.

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