JP2010275975A - Thermoelectric unit - Google Patents

Abstract

To provide a thermoelectric unit capable of obtaining an electromotive force without reducing the flow rate of exhaust gas even in a region where the exhaust gas flow rate is small, such as a region where the engine speed is low or a low load region.
The exhaust passage 2 is divided to form two divided exhaust passages 6a and 6b, the divided exhaust passages 6a and 6b are provided with thermoelectric elements 3 and heat receiving fins 4, and the exhaust passage 2 is divided. A branch pipe 7 that bypasses the exhaust passages 6a and 6b is provided, and the flow path of the exhaust gas G from the engine is exhausted downstream through both the divided exhaust passages 6a and 6b according to the engine speed and load. A flow path switching means 12 is provided for switching between the parallel flow path and the serial flow path that exhausts downstream through one split exhaust path 6a, the other split exhaust path 6b, and the branch pipe 7.
[Selection] Figure 1

Description

  The present invention relates to a thermoelectric unit that recovers energy as electricity from engine exhaust gas using a thermoelectric element, and in particular, the flow path can be switched in accordance with an exhaust gas flow rate that varies depending on engine speed and load. It relates to a thermoelectric unit.

  A thermoelectric unit that collects energy from the hot exhaust gas of the engine as electricity is installed in the exhaust passage (exhaust pipe) of the engine, one side of the thermoelectric element (thermoelectric conversion element) is placed on the back of the heat receiving fin, and the other side In general, a structure in which a cooling device is arranged is used.

  In the thermoelectric unit, when the exhaust gas passes through the thermoelectric unit, the heat receiving fin receives heat from the exhaust gas, and the received heat is transferred from the heat receiving fin to one side (high temperature contact surface) of the thermoelectric element. The other surface (low temperature contact surface) is cooled by a cooling device. In the thermoelectric unit, an electromotive force is obtained by the temperature difference between both surfaces of such a thermoelectric element.

JP 2002-199762 A JP 11-340524 A

  By the way, it is well known that the electromotive force obtained by the thermoelectric unit is due to the temperature difference between both sides of the thermoelectric element, but in order to obtain a sufficient electromotive force, the point is how efficiently heat is received from the high-temperature exhaust gas. Become.

  The amount of heat received is affected by the heat transfer rate from the exhaust gas to the heat receiving fin and the temperature of the exhaust gas, and the heat transfer rate is governed by the flow rate of the exhaust gas. Therefore, in a region where the exhaust gas flow rate is low, that is, a region where the engine speed is low or a low load region, the exhaust gas flow rate becomes slow, so that the heat transfer rate decreases and almost no electromotive force is obtained. There is.

  Therefore, an object of the present invention is to provide a thermoelectric unit capable of obtaining an electromotive force without reducing the exhaust gas flow rate even in a region where the exhaust gas flow rate is low, such as a region where the engine speed is low or a low load region. There is to do.

  The present invention was devised to achieve the above object. In the thermoelectric unit in which a plurality of thermoelectric elements are provided in the exhaust passage of an engine and the heat receiving fins of the thermoelectric elements face the exhaust passage, the exhaust The passage is divided to form two divided exhaust passages, the thermoelectric element and the heat receiving fin are provided in the divided exhaust passage, and a branch pipe that bypasses the divided exhaust passage is provided in the exhaust passage, Depending on the engine speed and load, the exhaust gas flow path from the engine is exhausted downstream through both of the divided exhaust passages, and one of the divided exhaust passages, the divided exhaust passage. On the other hand, it is a thermoelectric unit provided with a flow path switching means for switching between a serial flow path that sequentially passes through the branch pipe and exhausts downstream.

  The flow path switching means opens and closes the upstream side of the branch pipe, shuts off the other of the divided exhaust passages and the exhaust passage on the upstream side when opened, and connects the branch pipe and the divided exhaust passage. A first valve body that communicates with the other, a downstream side of the divided exhaust passage, and an upstream side of the branch pipe and a downstream side of the exhaust passage, the exhaust passage, A second valve body that opens and closes, and when the rotational speed or load of the engine is large, the first valve body is closed and the second valve body is opened to form the parallel flow path, and the engine Control means for opening the first valve body and closing the second valve body to form the series flow path when the rotational speed or the load is small.

  The heat receiving fins may be provided so as to face each other in the exhaust passage, and a partition plate that connects between the heat receiving fins facing each other may be provided to divide the exhaust passage into the divided exhaust passages.

  The partition plate may be provided at a center portion in the width direction of the heat receiving fin.

  The heat-receiving fin may be composed of a large number of circular pins, and the circular pins may be arranged in a staggered structure with an even-numbered row and an odd-numbered row offset.

  The heat receiving fins may be provided to face the exhaust passage so that the even rows and the odd rows of the circular pins face each other.

  The heat receiving fin may be provided to face the exhaust passage so that the circular pins overlap each other.

  According to the present invention, it is possible to provide a thermoelectric unit capable of obtaining an electromotive force without reducing the flow rate of exhaust gas even in a region where the exhaust gas flow rate is low, such as a region where the engine speed is low or a low load region.

It is a figure which shows the thermoelectric unit which concerns on one Embodiment of this invention, (a) is a top view in case an engine speed or load is large, (b) is a top view in case an engine speed or load is small, (C) is a side sectional view. It is a figure which shows the heat receiving fin used with the thermoelectric unit of FIG. 1, (a) is a top view, (b) is the 2B-2B sectional view taken on the line. It is a figure when the heat receiving fin of FIG. 2 is made to oppose, and an exhaust passage is formed, (a) is a front view, (b) is a top view, (c) is a sectional side view, (d) is a bottom view. . It is a figure explaining the flow of the exhaust gas in the thermoelectric unit of FIG. 1, (a) is a top view, (b) is a sectional side view. It is the schematic of the exhaust system of the vehicle by which the thermoelectric unit of this invention is mounted. It is a figure which shows the influence on the exhaust gas flow velocity, the heat transfer rate, the heat transfer rate, the heat transfer rate, the temperature difference of the thermoelectric element, and the theoretical power generation amount by the flow path area of the exhaust gas.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  1A and 1B are plan views of a thermoelectric unit according to the present embodiment, and FIG. 1C is a longitudinal sectional view thereof.

  As shown in FIGS. 1A to 1C, the thermoelectric unit 1 includes a plurality of thermoelectric elements 3 in an engine exhaust passage (exhaust pipe) 2, and the heat receiving fins 4 of the thermoelectric elements 3 are disposed in the exhaust passage 2. The heat is received by the heat receiving fins 4 from the exhaust gas G from the engine passing through the exhaust passage 2, and is transferred to the thermoelectric element 3, thereby generating electricity from the heat of the exhaust gas G. It is to be collected.

  In the present embodiment, the opposing surfaces (upper and lower surfaces in FIG. 1C) of the exhaust passage 2 are formed by the heat receiving fins 4 and both sides of the heat receiving fins 4 are joined by the side plates 8 to form the exhaust passage 2. Like to do. The heat receiving fin 4 is formed by forming a circular pin 10 as a fin on a flat plate 9. Details of the heat receiving fins 4 will be described later.

  On the rear surface of the heat receiving fin 4 (surface opposite to the exhaust passage 2), a plurality of thermoelectric elements 3 (upper and lower eight in FIG. 1) are arranged with the high temperature contact surface as the heat receiving fin 4 side. A cooling device (heat radiation side cooling device) 11 is provided on the low temperature contact surface which is the other surface of the thermoelectric element 3. In FIGS. 1A and 1B, the cooling device 11 is omitted for simplification of the drawing.

  The thermoelectric element 3 generates a voltage due to the Seebeck effect when a temperature difference is given between the low temperature contact surface and the high temperature contact surface, and is generally called a Peltier element or a Seebeck element.

  In the thermoelectric unit 1 according to the present embodiment, the exhaust passage 2 is divided by a partition plate 5 to form two divided exhaust passages 6a and 6b, and the thermoelectric element 3 and the heat receiving fins 4 are provided in the divided exhaust passages 6a and 6b. And a branch pipe 7 that bypasses the divided exhaust passages 6a and 6b is provided in the exhaust passage 2.

  The partition plate 5 is provided along the exhaust direction so as to connect the opposed heat receiving fins 4, and the exhaust passage is divided in the cross-sectional direction by the partition plate 5 to form divided exhaust passages 6 a and 6 b. The partition plate 5 is provided at the center in the width direction of the heat receiving fin 4. The partition plate 5 is fixed to the heat receiving fin 4 (flat plate 9) by brazing or the like.

  Further, the thermoelectric unit 1 includes a parallel flow path for exhausting the flow path of the exhaust gas G from the engine downstream through both the divided exhaust passages 6a and 6b according to the engine speed and the load, There is provided a flow path switching means 12 that switches between the divided exhaust passage 6a, the other divided exhaust passage 6b, and the serial flow path that exhausts downstream through the branch pipe 7 in order.

  The flow path switching means 12 includes a first valve body 13 provided on the upstream side of the branch pipe 7 (the connection portion on the upstream side of the branch pipe 7 and the exhaust passage 2), the downstream side of the divided exhaust passages 6a and 6b, In addition, the second valve body 14 provided in the exhaust passage 2 on the upstream side of the connecting portion on the downstream side of the branch pipe 7 and the exhaust passage 2 and the flow path of the exhaust gas G by opening and closing both the valve bodies 13 and 14. And a control means (not shown) for switching between.

  The first valve body 13 opens and closes the upstream side of the branch pipe 7 and, when opened, shuts off the other divided exhaust passage 6b and the upstream exhaust passage 2 and opens the branch pipe 7 and the other divided exhaust. The passage 6b is communicated. The second valve body 14 opens and closes the exhaust passage 2 on the downstream side of the divided exhaust passages 6a and 6b. Both valve bodies 13 and 14 are realized by the use of an air cylinder or a hydraulic cylinder, a link mechanism, or the like.

  When the engine speed or load is large, that is, in a region where the flow rate of the exhaust gas G is sufficiently large, the control means closes the first valve body 13 as shown in FIG. The body 14 is opened to form a parallel flow path for exhausting the exhaust gas G from the engine downstream through both the divided exhaust passages 6a and 6b. At this time, the exhaust gas G flows in parallel through the divided exhaust passages 6a and 6b.

  In addition, when the engine speed or load is small, that is, in a region where the flow rate of the exhaust gas G is small, the control means opens the first valve body 13 as shown in FIG. The valve body 14 is closed to form a serial flow path for exhausting the exhaust gas G from the engine downstream through the one divided exhaust passage 6a, the other divided exhaust passage 6b, and the branch pipe 7. At this time, the exhaust gas G passes through one of the divided exhaust pipes 6b, then turns back and passes through the other divided exhaust pipe 6b, and further passes through the branch pipe 7 and joins the exhaust pipe 2.

  Thereby, even when the engine speed is low or the load is low, that is, in the region where the flow rate of the exhaust gas G is small, the flow area of the exhaust gas G can be reduced to about half, and the flow rate of the exhaust gas G is kept high. It becomes possible. Therefore, it is possible to maintain a high heat transfer rate and obtain the maximum power generation from the exhaust heat energy. Since the flow rate of the exhaust gas G is small, there is no increase in exhaust resistance due to the reduction of the flow area of the exhaust gas G.

  The control means is mounted on, for example, an electronic control unit (ECU) of the vehicle. For example, the control means monitors the engine speed and the engine load, determines whether these are higher or lower than a preset threshold value, and switches the flow path of the exhaust gas G. The control means calculates the flow rate of the exhaust gas G from the engine speed and the engine load, determines whether the flow rate of the exhaust gas G is higher or lower than a preset threshold value, and The flow path of the gas G may be switched.

  Next, the heat receiving fin 4 used for the thermoelectric unit 1 will be described.

  As shown in FIGS. 2A and 2B, the heat receiving fin 4 includes a flat plate 9 and a large number of cylindrical circular pins (circular tubes) as fins formed so as to protrude from the surface of the flat plate 9. 10 and.

  The circular pins 10 are arranged in alignment with the flat plate 9, and are arranged in a staggered structure with their even and odd columns (or even and odd rows) offset. The odd-numbered circular pins 10 are arranged offset so as to be located in the middle of the even-numbered circular pins 10. Each circular pin 10 is fixed to the flat plate 9 by brazing or the like.

  In the present embodiment, the circular pin 10 is used as the fin, but a polygonal or cylindrical pin can also be used.

  As shown in FIGS. 3A to 3D, the two heat receiving fins 4 are arranged so that the even and odd rows of the circular pins 10 face each other, that is, the phases of the circular pins 10 are alternated. The heat receiving fins 4 facing each other are joined together with side plates 8 to form the exhaust passage 2.

  At this time, the heat receiving fins 4 are configured such that the circular pins 10 overlap. Specifically, the circular pin 10 has an overlap d of several millimeters to several tens of millimeters within a range where the exhaust resistance does not increase. Thereby, the exhaust passage 2 is also formed above and below the circular pin 10.

  Here, the flow of the exhaust gas G in the thermoelectric unit 1 will be described with reference to FIGS.

  As shown in FIG. 4A, the exhaust gas G flowing in from the front surface (the left side in the drawing) of the heat receiving fins 4 collides with the circular pins 10 in the first row and passes through the gaps in the circular pins 10 in the first row. . The exhaust gas G that has passed through the gap between the first-row circular pins 10 collides with the second-row circular pins 10 arranged in a staggered pattern, and is forced to flow further left and right. In addition, as shown in FIG. 4B, the exhaust gas G is forced to flow in the vertical direction due to the overlap of the circular pins 10.

  As a result, the exhaust gas G forms a turbulent flow, and the generated turbulent flow continues to the rear end (right side in the figure) of the thermoelectric unit 1. That is, the heat receiving fin 4 in the present embodiment has a turbulent heat transfer structure that generates turbulent flow in the exhaust gas G. Therefore, the heat receiving fin 4 can actively receive heat from the exhaust gas G, and the heat receiving fin. The heat transfer coefficient of 4 increases significantly.

  Therefore, by arranging the thermoelectric element 3 on the rear surfaces of the heat receiving fins 4 (in FIG. 4B, the upper surface of the upper heat receiving fin 4 and the lower surface of the lower heat receiving fin 4), the heat from the exhaust gas G can be efficiently obtained. It will be possible to recover electricity.

  A thermoelectric unit 1 according to the present embodiment is mounted on a vehicle and disposed in an exhaust passage 2 of an engine. As shown in FIG. 5, a flexible joint 51, a catalyst 52, a silencer (muffler) 53, and the like are arranged in the exhaust passage 2 of the engine E, and the exhaust gas G from the engine E passes through these in the atmosphere. To be discharged. The thermoelectric unit 1 is provided in the part of the silencer 53, for example.

  The operation of the present embodiment will be described.

  In the thermoelectric unit 1 according to the present embodiment, the exhaust passage 2 is divided to form two divided exhaust passages 6a and 6b, the thermoelectric element 3 and the heat receiving fins 4 are provided in the divided exhaust passages 6a and 6b, and A branch pipe 7 that bypasses the divided exhaust passages 6a and 6b is provided in the exhaust passage 2, and the exhaust gas G flow path is provided downstream of the divided exhaust passages 6a and 6b in accordance with the rotational speed and load of the engine E. And a flow path switching means 12 for switching between a parallel flow path for exhausting the exhaust gas and a serial flow path for exhausting downstream through one split exhaust path 6a, the other split exhaust path 6b, and the branch pipe 7.

  Thereby, when the rotation speed or load of the engine E is large (a region where the flow rate of the exhaust gas G is sufficiently large), the parallel flow path is formed to increase the flow passage area of the exhaust gas G, and the rotation speed of the engine E or When the load is small (a region where the flow rate of the exhaust gas G is small), the flow passage area of the exhaust gas G can be reduced by forming a series flow passage.

  As shown in FIG. 6, when the flow passage area of the exhaust gas G is reduced, the flow rate (exhaust gas flow rate) of the exhaust gas G is increased, whereby the heat transfer rate, the heat transfer rate, the heat transfer rate, the thermoelectric element 3 is increased. The temperature difference (element temperature difference) on both sides and the theoretical power generation amount are improved.

  In the present embodiment, the flow area of the exhaust gas G is large when the flow rate of the exhaust gas G is large, and the flow path area of the exhaust gas G is small when the flow rate of the exhaust gas G is small. Regardless of the flow rate of G (or the rotational speed and load of the engine E), the flow rate of the exhaust gas G can be increased and the heat transfer coefficient in the heat receiving fins 4 can be kept high.

  Accordingly, even in a region where the flow rate of the exhaust gas G is low, such as a region where the engine speed is low or a low load region, it is possible to obtain an electromotive force without reducing the flow rate of the exhaust gas G. The amount of power generation can be obtained throughout the entire area. In other words, the maximum generated power can be extracted without reducing the heat transfer rate from the exhaust gas G even in a region where the exhaust gas flow rate is small (slow flow rate condition; low engine speed or low load). Can do.

  Further, in the thermoelectric unit 1, when the flow rate of the exhaust gas G is small, the flow passage area of the exhaust gas G is reduced, so that the exhaust resistance is not increased and the engine performance is not deteriorated.

  Further, in the thermoelectric unit 1, the heat receiving fins 4 that are opposed to each other in the exhaust passage 2 are formed by a large number of circular pins 10, and the circular pins 10 are offset in even rows and odd rows and arranged in a staggered structure.

  As a result, the flow of the exhaust gas G acting on the heat receiving fins 4 is made turbulent and can be maintained up to the rear end of the thermoelectric unit 1, and positively receives heat from the exhaust gas G without increasing the exhaust resistance. And a turbulent heat transfer structure can be realized. Therefore, it is possible to realize the thermoelectric unit 1 that can improve the heat transfer rate and efficiently receive and generate power.

  Further, in the thermoelectric unit 1, since the circular pins 10 are used as the fins of the heat receiving fins 4, the flow path of the exhaust gas G is not narrowed, and the exhaust resistance is not increased. Therefore, engine performance is not degraded.

  Further, in the thermoelectric unit 1, the heat receiving fins 4 are provided facing the exhaust passage 2 so that the even and odd rows of the circular pins 10 face each other and the circular pins 10 overlap. Therefore, the flow path of the exhaust gas G can be forced in the vertical direction and a turbulent flow can be generated, so that the heat transfer rate can be further improved, and heat can be received and generated more efficiently.

DESCRIPTION OF SYMBOLS 1 Thermoelectric unit 2 Exhaust passage 3 Thermoelectric element 4 Heat receiving fin 5 Partition plate 6a, 6b Divided exhaust passage 7 Branch pipe 8 Side plate 9 Flat plate 11 Circular pin 11 Cooling device 12 Flow path switching means 13 First valve body 14 Second valve body

Claims (7)

In the thermoelectric unit in which a plurality of thermoelectric elements are provided in the exhaust passage of the engine, and the heat receiving fins of the thermoelectric elements face the exhaust passage,
The exhaust passage is divided to form two divided exhaust passages, the thermoelectric element and the heat receiving fin are provided in the divided exhaust passage, and a branch pipe that bypasses the divided exhaust passage is provided in the exhaust passage. ,
Depending on the engine speed and load, the exhaust gas flow path from the engine is exhausted downstream through both of the split exhaust passages, and one of the split exhaust passages, the split exhaust. A thermoelectric unit comprising a flow path switching means for switching between the other of the passages and a serial flow path that sequentially passes through the branch pipe and exhausts downstream. The flow path switching means is
A first opening that opens and closes the upstream side of the branch pipe, shuts off the other of the divided exhaust passages and the upstream exhaust passage when the branch pipe is opened, and communicates the branch pipes with the other of the divided exhaust passages. Valve body,
A second valve body provided in the exhaust passage on the downstream side of the divided exhaust passage and on the upstream side of the connecting portion on the downstream side of the branch pipe and the exhaust passage, and opens and closes the exhaust passage;
When the engine speed or load is large, the first valve body is closed and the second valve body is opened to form the parallel flow path. When the engine speed or load is small 2. The thermoelectric unit according to claim 1, further comprising: a control unit that opens the first valve body and closes the second valve body to form the series flow path.   The said heat receiving fin is provided so that it may oppose in the said exhaust passage, and the partition plate which connects between the said heat receiving fins which oppose is provided, The said exhaust passage is divided | segmented into the said division | segmentation exhaust passage. Thermoelectric unit.   The thermoelectric unit according to claim 3, wherein the partition plate is provided at a center portion in the width direction of the heat receiving fin.   5. The thermoelectric unit according to claim 3, wherein the heat receiving fin is composed of a large number of circular pins, and the circular pins are arranged in a staggered structure with an even number and an odd number being offset.   The thermoelectric unit according to claim 5, wherein the heat receiving fin is provided to face the exhaust passage so that the even and odd rows of the circular pins face each other.   The thermoelectric unit according to claim 5 or 6, wherein the heat receiving fin is provided to face the exhaust passage so that the circular pins overlap each other.

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