JP2013092125A - Thermoelectric generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoelectric generator capable of preventing damage due to a harmful effect of the heat of a thermoelectric transformation module and the deterioration of generating efficiency of the thermoelectric transformation module.SOLUTION: A thermoelectric generator 17 includes an inner tube 21 which has an upward side inner tube 25 and a downward side inner tube 26 disposed at a downward side with respect to the upward side inner tube 25, wherein a throttling unit 25a is formed at the downward end of the upward side inner tube 25 and has a flow channel area A smaller than a flow channel area B of the downward side inner tube 26. Furthermore, a communicating passage 36 communicating an exhaust gas passage 38 and a heat receiving passage 22 is formed by a clearance gap formed between the downward end of the upward side inner tube 25 and the upward end of the downward side inner tube 26. In addition, a communicating hole 37 communicating the exhaust gas passage 38 and the heat receiving passage 22 is formed at a portion of the downward side inner tube 26 which is at a downward side with respect to the communicating passage 36.

Description

  The present invention relates to a thermoelectric power generator, and more particularly to a thermoelectric power generator that performs thermoelectric power generation using exhaust gas discharged from an internal combustion engine.

  Conventionally, since exhaust gas or the like discharged from an internal combustion engine of a vehicle such as an automobile contains thermal energy, if the exhaust gas is discarded as it is, the thermal energy is wasted. Therefore, the thermal energy contained in the exhaust gas is recovered by the thermoelectric generator and converted into electrical energy, and for example, the battery is charged.

  As a conventional thermoelectric generator of this type, one side surface of the thermoelectric conversion module is brought into contact with the outer peripheral surface of the exhaust pipe into which the exhaust gas discharged from the internal combustion engine is introduced, and at the low temperature side of the thermoelectric conversion module. One in which the other side is in contact with a cooling water pipe through which cooling water flows is known.

  This thermoelectric conversion module is configured to include a thermoelectric conversion element such as a semiconductor, an electrode, a heat receiving substrate on the high temperature side, a heat radiating substrate on the low temperature side, and the like. The low-temperature cooling water pipe generates power by generating a temperature difference between the high temperature side and the low temperature side of the thermoelectric conversion module.

  By the way, the power generation efficiency of the thermoelectric conversion module increases as the temperature difference between the high temperature side and the low temperature side of the thermoelectric conversion module increases. For example, Bi-Te-based thermoelectric materials that are frequently used as thermoelectric conversion elements are used. The thermoelectric conversion module has a heat resistant temperature of about 200 ° C., and the thermoelectric conversion module using the Mg—Si heat thermoelectric material has a heat resistant temperature of about 500 ° C.

  For this reason, if the heat resistance temperature is exceeded, the thermoelectric conversion elements and cables of the thermoelectric conversion module may be damaged due to heat damage, and the power generation efficiency may be reduced. Therefore, when using a thermoelectric conversion module, it is necessary to obtain the best power generation efficiency by setting the temperature on the high temperature side as high as possible below the heat-resistant temperature.

  Conventionally, as a thermoelectric power generation apparatus that can improve power generation efficiency while preventing heat damage of the thermoelectric conversion module, for example, a thermoelectric power generation apparatus described in Patent Document 1 is known.

  This thermoelectric generator is provided with an exhaust pipe as an inner pipe into which exhaust gas discharged from an internal combustion engine is introduced, and an outer pipe that is provided outside the exhaust pipe and defines a heat shield space as a heat receiving passage together with the exhaust pipe. A thermoelectric conversion module that performs thermoelectric generation according to the temperature difference between the high temperature side and the low temperature side while the pipe and the high temperature side that is one side are in contact with the outer peripheral portion of the outer pipe, and the low temperature side that is the other side is in contact with the cooling water pipe And an open / close valve provided inside the exhaust pipe for opening and closing the exhaust pipe.

  The thermoelectric generator is provided on the upstream side of the exhaust pipe in the exhaust direction, provided on the exhaust gas introduction passage communicating the interior of the exhaust pipe and the heat shield space, and on the downstream side of the exhaust pipe in the exhaust direction. And an exhaust gas discharge passage communicating with the heat shield space.

  When the temperature rises above the upper limit use temperature of the thermoelectric conversion module, the thermoelectric power generator having such a configuration drives the on-off valve in the opening direction and communicates the exhaust pipe and the heat shield space through the exhaust gas introduction passage. By doing so, the flow rate of the exhaust gas flowing in the heat shield space is reduced.

  For this reason, the thermoelectric conversion module is damaged by lowering the surface temperature on the high temperature side of the thermoelectric conversion module and preventing the temperature of the thermoelectric conversion module from further rising by causing the heat shield space to act as a heat insulating layer. Can be prevented.

  Also, when the temperature of the exhaust gas is low, such as immediately after starting the engine or during idling, the on-off valve is closed and the exhaust gas is allowed to flow positively into the heat shield space, so that the temperature on the high temperature side of the thermoelectric conversion module is increased. It can be raised early.

JP 2000-18095 A

  However, in such a conventional thermoelectric power generator, when the temperature rises above the upper limit temperature of use of the thermoelectric conversion module, the on-off valve is driven in the opening direction, and the exhaust pipe is blocked from the exhaust gas introduction passage. Since the heat space communicates, the exhaust gas flowing through the heat receiving passage is deprived of much of the heat of the exhaust gas by the thermoelectric conversion module upstream of the heat shield space, and is exhausted downstream of the heat shield space. The amount of heat of gas will decrease.

  For this reason, the amount of heat of the exhaust gas varies between the upstream side of the heat shield space and the downstream side of the heat shield space, and the power generation efficiency of the downstream thermoelectric conversion module is lower than that of the upstream thermoelectric conversion module. As a result, there arises a problem that the overall power generation efficiency of the thermoelectric conversion module is lowered.

  The present invention has been made to solve the above-described conventional problems, and can prevent power generation efficiency of the thermoelectric conversion module from being lowered while preventing damage due to heat damage of the thermoelectric conversion module. An object is to provide a thermoelectric generator.

  In order to achieve the above object, a thermoelectric power generation device according to the present invention includes: (1) an inner pipe into which exhaust gas discharged from an internal combustion engine is introduced; and an outer pipe provided outside the inner pipe. An outer tube that forms a heat receiving passage between the outer tube, and one side surface is in contact with the outer peripheral portion of the outer tube and the other side surface is in contact with the inner peripheral portion of the cooling member. A thermoelectric conversion module that performs thermoelectric power generation and an on-off valve that opens and closes the inner pipe, wherein the inner pipe is formed upstream of the exhaust gas flowing in the inner pipe in the exhaust direction, An upstream communication portion that communicates the inside of the inner tube and the heat receiving passage; a downstream communication portion that is provided on the downstream side in the exhaust direction and communicates the interior of the inner tube and the heat receiving passage; and the upstream side Provided on the upstream side in the exhaust direction with respect to the communication part, the flow area of the inner pipe is That is constructed from those having a throttle portion.

  In this thermoelectric generator, the inner pipe is formed on the upstream side in the exhaust direction of the exhaust gas flowing in the inner pipe, and is provided on the upstream side communication portion that communicates the inside of the inner pipe and the heat receiving passage, and on the downstream side in the exhaust direction. Since it has a downstream communication part that communicates the inside of the inner pipe and the heat receiving passage, and a throttle part that is provided on the upstream side in the exhaust direction with respect to the upstream communication part and restricts the flow area of the inner pipe. The flow rate of the exhaust gas downstream in the exhaust direction can be increased, and a negative pressure due to the venturi effect can be generated on the downstream side of the throttle portion in the exhaust direction.

  For this reason, since negative pressure is generated in the heat receiving passage through the upstream communication portion, when the inner pipe is closed by the on-off valve, exhaust gas flowing through the inner pipe is introduced into the heat receiving passage through the downstream communication portion, and The exhaust gas flows in the direction opposite to the flow of the exhaust gas and is again introduced into the inner pipe through the upstream communication portion. That is, it is possible to generate a flow of exhaust gas that flows back to the exhaust gas in the inner pipe in the heat receiving passage.

  Also, the new exhaust gas discharged from the internal combustion engine to the inner pipe is mixed with the exhaust gas after heat recovery introduced into the inner pipe through the upstream communication part and introduced from the inner pipe into the heat receiving passage through the downstream communication part. Is done.

  For this reason, it is possible to prevent the hot exhaust gas from coming into direct contact with the thermoelectric conversion module upstream in the exhaust direction. Therefore, it is possible to prevent the thermoelectric conversion elements and cables of the thermoelectric conversion module on the upstream side in the exhaust direction from being damaged by the heat damage of the exhaust gas.

  In addition, the mixed gas of the new exhaust gas introduced into the heat receiving passage through the downstream communication portion and the exhaust gas after heat recovery is deprived of heat by the cooling member as it moves in the heat receiving passage upstream in the exhaust direction. The amount of heat of the mixed gas can be recovered by being warmed by the radiant heat of the new exhaust gas introduced into the inner pipe.

  For this reason, the temperature of the exhaust gas flowing in the heat receiving passage can be made substantially uniform, and the temperature difference between the one side surface of the thermoelectric conversion module and the other side surface of the low temperature side is prevented from varying in the exhaust direction. And it can prevent that the power generation efficiency of a thermoelectric conversion module falls.

  In the thermoelectric generator according to (1) above, (2) the cooling member includes a cooling water pipe through which cooling water flows, and the cooling member passes cooling water from the exhaust direction upstream side to the exhaust direction downstream side. It is comprised so that it may flow toward.

  In this thermoelectric generator, since the cooling water flowing in the cooling water pipe flows from the upstream side in the exhaust direction toward the downstream side in the exhaust direction, the direction in which the cooling water flows is opposite to the direction of the exhaust gas flowing in the heat receiving passage. Can do.

  That is, the direction of the high-temperature exhaust gas flowing through the heat receiving passage and the low-temperature cooling water flowing through the cooling water pipe is the same direction (parallel flow), and the lower temperature flowing through the heat receiving passage and the cooling water pipe The logarithmic average temperature difference can be increased when the direction of the cooling water is opposite (counterflow). As a result, the power generation efficiency of the thermoelectric conversion module can be improved as compared with the case where the directions of the exhaust gas and the cooling water are parallel flow.

  In the thermoelectric generator according to (1) or (2), (3) the inner pipe is a first inner pipe and a second provided on the downstream side in the exhaust direction with respect to the first pipe. And at least the downstream side in the exhaust direction of the first pipe so that the flow area on the downstream side in the exhaust direction of the first pipe is smaller than the flow area of the second pipe. The throttle portion is formed by reducing the diameter, and the upstream communication portion is formed by a gap formed between the exhaust direction downstream end of the first pipe and the exhaust direction upstream end of the second pipe. Is made up of.

  In this thermoelectric generator, the inner pipe is composed of a first inner pipe and a second inner pipe provided on the downstream side in the exhaust direction with respect to the first pipe. From the flow area of the second pipe, In addition, since the throttle part is formed by reducing the diameter of at least the downstream side of the first pipe in the exhaust direction so that the flow passage area downstream of the first pipe in the exhaust direction is reduced, the throttle part can be easily processed. Can do.

  Further, if the first pipe has the same diameter in the exhaust direction so that the flow area on the downstream side in the exhaust direction of the first pipe is smaller than the flow area of the second pipe, The flow area of the second inner pipe can be increased without reducing the flow path cross section on the downstream side of the pipe. As a result, the exhaust gas introduced from the downstream end of the first inner pipe into the second inner pipe while increasing the flow rate of the exhaust gas introduced from the downstream end of the first inner pipe into the second inner pipe. It is possible to prevent a decrease in pressure loss.

  (1) In the thermoelectric generator according to (1) to (3), (4) the inner pipe has a flow passage area of the heat receiving passage that decreases from the upstream side in the exhaust direction toward the downstream side in the exhaust direction. The channel area on the downstream side in the exhaust direction is formed smaller than the channel area on the upstream side in the exhaust direction of the pipe.

In this thermoelectric generator, the flow passage area of the heat receiving passage is formed smaller as it goes from the downstream side in the exhaust direction to the upstream side in the exhaust direction, so the flow rate of the mixed gas that flows backward in the heat receiving passage is changed from the downstream side in the exhaust direction to the upstream side in the exhaust direction. Can be raised towards.
Therefore, when the flow rate of the exhaust gas increases according to Newton's law of cooling, the heat transfer efficiency from the exhaust gas to the thermoelectric conversion module can be improved, and as a result, the power generation efficiency of the thermoelectric conversion module can be improved. .

In the thermoelectric generator described in (1) to (4) above, (5) the on-off valve is configured to be provided on the downstream side in the exhaust direction with respect to the downstream communication portion.
In this thermoelectric generator, since the on-off valve is provided on the downstream side in the exhaust direction with respect to the downstream communication portion, when the on-off valve is closed, the new exhaust gas in the inner pipe and the heat-recovered exhaust gas are After the mixed gas is introduced into the heat receiving passage through the downstream communication portion, it can be caused to flow back to the heat receiving passage by the negative pressure generated in the heat receiving passage through the upstream communication portion.

  ADVANTAGE OF THE INVENTION According to this invention, the thermoelectric power generator which can prevent that the power generation efficiency of a thermoelectric conversion module falls while preventing the damage by the heat damage of a thermoelectric conversion module can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows 1st Embodiment of the thermoelectric power generator which concerns on this invention, and is a schematic block diagram of the exhaust system of an engine provided with a thermoelectric power generator. It is a figure which shows 1st Embodiment of the thermoelectric power generation apparatus which concerns on this invention, and is sectional drawing of a thermoelectric power generation apparatus. It is a figure which shows 1st Embodiment of the thermoelectric power generating apparatus which concerns on this invention, and is a perspective view of a thermoelectric conversion module. It is a figure which shows 2nd Embodiment of the thermoelectric generator which concerns on this invention, and is sectional drawing of a thermoelectric generator. It is a figure which shows 1st Embodiment of the thermoelectric generator which concerns on this invention, and is sectional drawing of the thermoelectric generator which has another structure.

  Hereinafter, embodiments of a thermoelectric generator according to the present invention will be described with reference to the drawings. In the present embodiment, a case where the thermoelectric generator is applied to a water-cooled multi-cylinder internal combustion engine mounted on a vehicle such as an automobile, for example, a four-cycle gasoline engine (hereinafter simply referred to as an engine) will be described. Yes. The engine is not limited to a gasoline engine.

(First embodiment)
1-3 is a figure which shows 1st Embodiment of the thermoelectric power generation apparatus which concerns on this invention.
First, the configuration will be described.
As shown in FIG. 1, an engine 1 as an internal combustion engine mounted on a vehicle such as an automobile is formed by mixing air supplied from an intake system and fuel supplied from a fuel supply system at an appropriate air-fuel ratio. After the air-fuel mixture is supplied to the combustion chamber and combusted, the exhaust gas generated with this combustion is discharged from the exhaust system to the atmosphere.

  The exhaust system includes an exhaust manifold 2 attached to the engine 1 and an exhaust pipe 4 connected to the exhaust manifold 2 via a spherical joint 3. The exhaust manifold 2 and the exhaust pipe 4 An exhaust passage is formed.

  The spherical joint 3 allows moderate swinging of the exhaust manifold 2 and the exhaust pipe 4 and functions so as not to transmit the vibration and movement of the engine 1 to the exhaust pipe 4 or to attenuate and transmit them.

  Two catalysts 5 and 6 are installed in series on the exhaust pipe 4, and the exhaust gas is purified by the catalysts 5 and 6.

  Among the catalysts 5 and 6, the catalyst 5 installed upstream in the exhaust gas exhaust direction in the exhaust pipe 4 is a so-called start catalyst (S / C). The catalyst 6 installed downstream in the exhaust direction is a so-called main catalyst (M / C) or underfloor catalyst (U / F).

  These catalysts 5 and 6 are constituted by, for example, a three-way catalyst. This three-way catalyst exhibits a purifying action in which carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) are collectively changed to harmless components by a chemical reaction.

  A water jacket is formed inside the engine 1, and the water jacket is filled with a coolant called long life coolant (LLC) (hereinafter simply referred to as coolant).

The cooling water is led out from the outlet pipe 8 attached to the engine 1 and then supplied to the radiator 7, and is returned from the radiator 7 to the engine 1 through the cooling water reflux pipe 9.
The radiator 7 cools the cooling water circulated by the water pump 10 by heat exchange with the outside air.

  A bypass pipe 12 is connected to the reflux pipe 9, and a thermostat 11 is interposed between the bypass pipe 12 and the reflux pipe 9, and the amount of cooling water flowing through the radiator 7 and the bypass are bypassed by the thermostat 11. The amount of cooling water flowing through the pipe 12 is adjusted.

For example, during the warm-up operation of the engine 1, the amount of cooling water on the bypass pipe 12 side is increased to promote warm-up.
A heater pipe 13 is connected to the bypass pipe 12, and a heater core 14 is provided in the middle of the heater pipe 13. The heater core 14 is a heat source for heating the passenger compartment using the heat of the cooling water.

  The air heated by the heater core 14 is introduced into the vehicle interior by the blower fan 15. A heater unit 16 is configured by the heater core 14 and the blower fan 15.

  The heater pipe 13 is provided with an upstream pipe 18 a for supplying cooling water to a thermoelectric generator 17 described later, and between the thermoelectric generator 17 and the reflux pipe 9, the thermoelectric generator 17 to the reflux pipe 9 are provided. A downstream pipe 18b for discharging the cooling water is provided.

  For this reason, when the exhaust heat recovery operation (details of this exhaust heat recovery operation will be described later) is performed in the thermoelectric generator 17, the cooling water flowing through the downstream pipe 18b flows through the upstream pipe 18a. It becomes higher than the temperature of the cooling water.

  On the other hand, the exhaust system of the engine 1 is provided with a thermoelectric power generation device 17 that recovers the heat of the exhaust gas discharged from the engine 1 and converts the heat energy of the exhaust gas into electrical energy. It is supposed to convert.

  As shown in FIG. 2, the thermoelectric generator 17 is provided outside the inner tube 21 into which the exhaust gas discharged from the engine 1 is introduced and the heat receiving passage 22 between the inner tube 21 and the inner tube 21. And an outer tube 23 whose downstream end is connected to the tail pipe 19.

  The inner pipe 21 is provided on the upstream side inner pipe 25 as a first inner pipe connected to the upstream side exhaust pipe 4 and on the downstream side in the exhaust direction of the exhaust gas with respect to the upstream side inner pipe 25. And a downstream inner pipe 26 fixed to the outer pipe 23 via a support member 24.

  An exhaust passage 38 through which exhaust gas flows is formed by the inside of the upstream side inner pipe 25 and the downstream side inner pipe 26, and the exhaust gas discharged from the exhaust pipe 4 to the inner pipe 21 passes through the exhaust passage 38 and the tail pipe. After being discharged to 19, it is discharged from the tail pipe 19 to the outside air.

  In the present invention, the exhaust gas exhaust direction defined in the thermoelectric generator 17 refers to the exhaust gas exhaust direction flowing through the inner pipe 21, and upstream and downstream are directions relative to the exhaust direction. It is. That is, the upstream side with respect to the thermoelectric generator 17 is the engine 1 side, and the downstream side is the tail pipe 19 side.

  Therefore, as will be described later, even if the direction of the exhaust gas flowing through the heat receiving passage 22 is opposite to the direction of the exhaust gas flowing through the exhaust passage 38, the exhaust gas flowing through the heat receiving passage 22 is expressed downstream in the exhaust direction. It shall flow from the side to the upstream side.

  The thermoelectric generator 17 includes a thermoelectric conversion module 27 and a cylindrical cooling water pipe 28 as a cooling member.

  As shown in FIG. 3, the thermoelectric conversion module 27 includes an insulating ceramic heat receiving substrate 29 that constitutes a high temperature side heat receiving portion and an insulating ceramic heat dissipation substrate 30 that constitutes a low temperature side heat receiving portion. A plurality of N-type thermoelectric thermoelectric conversion elements 31 and P-type thermoelectric thermoelectric conversion elements 32 that generate thermoelectromotive force according to a temperature difference by the Seebeck effect are installed, and the N-type thermoelectric thermoelectric conversion element 31 and the P-type thermoelectric thermoelectric conversion The elements 32 are alternately connected in series via the electrodes 33a and 33b. Adjacent thermoelectric conversion modules 27 are electrically connected via wiring 35.

  In this thermoelectric conversion module 27, the heat receiving substrate 29 which is one side surface is in contact with the outer peripheral portion 23a of the outer tube 23, and the heat radiating substrate 30 which is the other side surface is in contact with the inner peripheral portion 28c of the cooling water tube 28. It is installed in parallel with the gas exhaust direction. In FIG. 1, the thermoelectric conversion module 27 is simplified by omitting the heat receiving substrate 29 and the heat dissipation substrate 30.

The thermoelectric conversion module 27 supplies electric power to the battery via the cable 34 by performing thermoelectric power generation according to the temperature difference between the heat receiving substrate 29 and the heat dissipation substrate 30.
Since the thermoelectric conversion module 27 has a substantially square plate shape and needs to be in close contact between the outer tube 23 and the cooling water tube 28, the outer tube 23 and the cooling water tube 28 are formed in a polygonal shape. Yes.

Further, the outer tube 23 and the cooling water tube 28 may be circular. In this case, the heat receiving substrate 29 and the heat radiating substrate 30 of the thermoelectric conversion module 27 may be curved.
The cooling water pipe 28 includes a cooling water introduction part 28a connected to the upstream pipe 18a and a cooling water discharge part 28b connected to the downstream pipe 18b.

  The cooling water pipe 28 is exhausted by the cooling water discharge part 28b with respect to the cooling water introduction part 28a so that the cooling water introduced into the cooling water pipe 28 from the cooling water introduction part 28a flows in the same direction as the exhaust gas exhaust direction. It is provided downstream in the direction. For this reason, the cooling water flows in a direction opposite to the flow of the exhaust gas flowing in the heat receiving passage 22 as described later.

  On the other hand, a throttle part 25 a is formed on the downstream side of the upstream inner pipe 25, and the flow path area A of the throttle part 25 a is smaller than the flow path area B of the downstream inner pipe 26. Further, a communication path 36 serving as an upstream communication portion is formed between the downstream end of the upstream inner pipe 25 and the upstream end of the downstream inner pipe 26, and the communication path 36 is connected to the upstream inner pipe 25. Further, the exhaust passage 38 and the heat receiving passage 22 which are inside the downstream side inner pipe 26 are communicated with each other.

  A communication hole 37 as a downstream communication portion is formed downstream of the communication passage 36 in the exhaust direction. The communication holes 37 are formed at equal intervals in the circumferential direction of the downstream side inner pipe 26 and communicate the exhaust passage 38 and the heat receiving passage 22. The communication holes 37 are not limited to those formed at regular intervals.

  The support member 24 has communication holes 24a formed at equal intervals in the circumferential direction of the support member 24. The heat receiving passage 22 communicates with the tail pipe 19 through the communication holes 24a. The communication holes 24a are not limited to those formed at regular intervals.

  The downstream inner pipe 26 is provided with an open / close valve 39. The open / close valve 39 is provided on the downstream side with respect to the communication hole 37, and is provided on the outer pipe 23 so as to open and close the downstream inner pipe 26. It is pivotally attached. The on-off valve 39 automatically opens and closes according to the pressure of the exhaust gas flowing through the exhaust passage 38.

  In other words, the on-off valve 39 closes the downstream inner pipe 26 by closing the downstream inner pipe 26 when idling the engine 1 where the exhaust gas pressure is low or during low load running, as shown by the solid line in FIG. The introduced exhaust gas is introduced into the heat receiving passage 22.

  Further, the open / close valve 39 releases the downstream side inner pipe 26 as shown by a broken line in FIG. For this reason, the thermoelectric power generation device 17 can prevent the exhaust gas from increasing in back pressure and prevent the exhaust performance from deteriorating.

Next, the operation will be described.
When the engine 1 is cold started, the catalysts 5 and 6 and the cooling water of the engine 1 are all at a low temperature (about the outside temperature).

When the engine 1 is started from this state, for example, 300 to 400 ° C. exhaust gas is discharged from the engine 1 to the exhaust pipe 4 through the exhaust manifold 2 as the engine 1 starts. 6 are heated by the exhaust gas.
Further, the cooling water is returned to the engine 1 through the bypass pipe 12 without passing through the radiator 7, so that the warm-up operation is performed.

  When the engine 1 is cold started, for example, the idling of the engine 1 is performed and the pressure of the exhaust gas is low, so that the on-off valve 39 is closed. For this reason, the exhaust gas introduced into the exhaust passage 38 from the exhaust pipe 4 through the upstream inner pipe 25 is introduced into the heat receiving passage 22, and the cooling water flowing through the cooling water pipe 28 is heated by the exhaust gas passing through the heat receiving passage 22. Then, warming up of the engine 1 is urged.

  Further, when the engine 1 after the warm-up of the engine 1 is running at a low load, the on-off valve 39 is closed because the exhaust gas pressure is low even when the exhaust gas temperature is high. Therefore, the exhaust gas introduced into the exhaust passage 38 from the exhaust pipe 4 through the upstream inner pipe 25 is introduced into the heat receiving passage 22. At this time, the thermal energy of the exhaust gas is efficiently converted into pressure energy by the thermoelectric conversion module 27.

  Further, when the engine 1 is traveling at a high load, it is necessary to improve the cooling performance of the engine 1. When the engine 1 travels at a high load, for example, the engine 1 rotates at a high speed and the pressure of the exhaust gas increases, so the pressure of the exhaust gas introduced into the downstream side inner pipe 26 increases and the on-off valve 39 is released. The

  When the on-off valve 39 is released, the exhaust passage 38 and the tail pipe 19 communicate with each other, and the exhaust gas is discharged directly from the exhaust passage 38 to the tail pipe 19 without flowing through the heat receiving passage 22. For this reason, the temperature of the cooling water flowing through the cooling water pipe 28 is not increased by the high-temperature exhaust gas.

  At this time, since the thermostat 11 blocks communication between the bypass pipe 12 and the reflux pipe 9, the cooling water led out from the engine 1 through the lead-out pipe 8 is led out to the reflux pipe 9 through the radiator 7. For this reason, low-temperature cooling water is supplied to the engine 1, and the cooling performance of the engine 1 can be enhanced. Further, since the on-off valve 39 is released when the engine 1 is traveling at a high load, the back pressure of the exhaust gas flowing through the exhaust passage 38 is not increased, and the exhaust performance of the exhaust gas can be prevented from being lowered. .

Next, the operation of the thermoelectric generator 17 during low-load running of the engine 1 after the warm-up will be described.
When the pressure of the exhaust gas is small, the downstream inner pipe 26 is closed by the on-off valve 39, and the communication between the exhaust passage 38 and the tail pipe 19 is blocked.

  In the thermoelectric generator 17 of the present embodiment, the inner pipe 21 includes an upstream inner pipe 25 and a downstream inner pipe 26 provided on the downstream side with respect to the upstream inner pipe 25, and the upstream inner pipe At the downstream end of 25, a narrowed portion 25a that has a flow area A smaller than the flow area B of the downstream inner pipe 26 was formed.

  A communication passage 36 that connects the exhaust passage 38 and the heat receiving passage 22 is formed by a gap formed between the downstream end of the upstream inner tube 25 and the upstream end of the downstream inner tube 26. On the other hand, a communication hole 37 that connects the exhaust passage 38 and the heat receiving passage 22 is formed in the downstream inner pipe 26 on the downstream side.

  Therefore, the flow rate of the exhaust gas introduced from the upstream inner pipe 25 into the downstream inner pipe 26 increases when the exhaust gas passes through the throttle portion 25a formed at the downstream end of the upstream inner pipe 25, and the throttle portion 25a. Negative pressure due to the venturi effect is generated downstream of the exhaust direction.

  A communication passage 36 that connects the exhaust passage 38 and the heat receiving passage 22 is formed between the downstream end of the throttle portion 25a and the upstream end of the downstream inner pipe 26. Pressure is generated.

  For this reason, the exhaust gas flowing through the downstream side inner pipe 26 is introduced into the heat receiving passage 22 through the communication hole 37 provided downstream of the communication path 36, and flows reversely to the flow of the exhaust gas flowing through the downstream side inner pipe 26. It becomes. In FIG. 2, the flow of exhaust gas in the exhaust passage 38 is indicated by G1, and the flow of exhaust gas in the heat receiving passage 22 is indicated by G2.

  Therefore, the high-temperature exhaust gas flowing through the heat receiving passage 22 acts on the heat receiving substrate 29 that is one side surface of the thermoelectric conversion module 27, and the low-temperature cooling water that circulates the cooling water pipe 28 is the heat radiation that is the other side surface of the thermoelectric conversion module 27. By acting on the substrate 30, power generation is performed by the temperature difference between the heat receiving substrate 29 and the heat dissipation substrate 30 of the thermoelectric conversion module 27. Then, the generated power is supplied to the battery via the cable 34 and charged to the battery.

  On the other hand, the exhaust gas flowing through the heat receiving passage 22 is again introduced into the downstream inner pipe 26 through the communication passage 36. The new exhaust gas discharged from the engine 1 through the exhaust pipe 4 to the upstream side inner pipe 25 is mixed with the exhaust gas after heat recovery introduced into the downstream side inner pipe 26 through the communication path 36, and the downstream side inner pipe 26. To the heat receiving passage 22 through the communication hole 37.

  Therefore, it is possible to prevent the high-temperature new exhaust gas from coming into direct contact with the upstream thermoelectric conversion module 27, and the N-type thermoelectric thermoelectric conversion element 31 and the P-type thermoelectric thermoelectric conversion element of the upstream thermoelectric conversion module 27. 32 or the cable 34 can be prevented from being damaged by the heat damage of the exhaust gas.

  Further, since the amount of heat of the exhaust gas transmitted to the upstream cooling water pipe 28 can be reduced, it is possible to suppress the cooling water from becoming high temperature, and the cooling water pipe 28 is damaged or the engine 1 is cooled. It is possible to prevent the performance from deteriorating.

  Moreover, since it can suppress that the temperature of a cooling water rises, the temperature difference of exhaust gas and a cooling water can be enlarged, and it can prevent that the electric power generation efficiency of the thermoelectric conversion module 27 falls. it can.

  Further, the mixed gas of the new exhaust gas introduced into the heat receiving passage 22 through the communication hole 37 and the exhaust gas after heat recovery is caused by the cooling water flowing through the cooling water pipe 28 as it moves upstream in the heat receiving passage 22. Although the heat is taken away, the amount of heat is recovered by being warmed by the radiant heat of the new exhaust gas introduced into the downstream inner pipe 26 through the upstream inner pipe 25.

  For this reason, the temperature of the exhaust gas flowing in the heat receiving passage 22 can be made substantially uniform, and the temperature difference between the high temperature side heat receiving substrate 29 and the low temperature side heat radiating substrate 30 of the thermoelectric conversion module 27 varies in the exhaust direction. It is possible to prevent the power generation efficiency of the thermoelectric conversion module 27 from decreasing.

Moreover, since the cooling water W flowing through the cooling water pipe 28 flows from the upstream side in the exhaust direction toward the downstream side in the exhaust direction, the thermoelectric power generation device 17 of the present embodiment receives the heat in the direction of the cooling water W flowing through the cooling water pipe 28. The direction of the exhaust gas flowing backward through the passage 22 can be set in the opposite direction.
That is, the thermoelectric power generation device 17 according to the present embodiment is compared with the case where the directions of the high-temperature exhaust gas flowing through the heat receiving passage 22 and the low-temperature cooling water flowing through the cooling water pipe 28 are the same direction (parallel flow). 2, the logarithm average temperature difference is increased by making the directions of the high-temperature exhaust gas G2 flowing through the heat receiving passage 22 and the low-temperature cooling water W flowing through the cooling water pipe 28 face each other (counterflow). Can do. As a result, the power generation efficiency of the thermoelectric conversion module 27 can be improved as compared with the case where the directions of the exhaust gas and the cooling water are parallel flow.

  Here, for example, when the temperature of the exhaust gas upstream of the heat receiving passage 22 is higher than the temperature of the exhaust gas downstream of the heat receiving passage 22 as in the prior art, cooling is performed on the upstream side of the heat receiving passage 22. Water may boil. Therefore, the cooling water on the upstream side of the heat receiving passage 22 is configured such that the exhaust direction of the exhaust gas and the flow direction of the cooling water flow in the same direction from the upstream side to the downstream side in the exhaust direction (cocurrent flow). Although it is effective in preventing the temperature from boiling, in this case, the logarithmic average temperature difference becomes small and the power generation efficiency is lowered.

In the present embodiment, since the temperature of the exhaust gas flowing through the heat receiving passage 22 can be made substantially uniform, the direction of the high temperature exhaust gas G2 flowing through the heat receiving passage 22 and the low temperature cooling water W flowing through the cooling water pipe 28 By facing each other (countercurrent), the logarithmic average temperature difference can be increased, and the power generation efficiency of the thermoelectric conversion module 27 can be improved.
In addition, the thermoelectric generator 17 according to the present embodiment generates a negative pressure on the downstream end of the upstream inner pipe 25 so that a narrowed portion 25a can be formed on the downstream side of the upstream inner tube 25 to generate a negative pressure. Therefore, it is possible to easily process the narrowed portion 25a.

  In addition, since the thermoelectric generator 17 of the present embodiment has the on-off valve 39 provided on the downstream side with respect to the communication hole 37, when the on-off valve 39 is closed, a new exhaust gas in the downstream inner pipe 26 is generated. The mixed gas with the exhaust gas recovered by heat is reliably introduced into the heat receiving passage 22 through the communication hole 37, and reliably flows back into the heat receiving passage 22 by the negative pressure generated in the heat receiving passage 22 through the communication passage 36.

  In addition, you may make it the on-off valve 39 of this Embodiment open and close according to cooling water temperature. For example, when the opening / closing valve 39 is connected to a thermostat that operates in response to the temperature of the cooling water flowing through the downstream side pipe 18b, and the temperature of the cooling water flowing through the downstream side pipe 18b exceeds a predetermined value, The on-off valve 39 is configured to be released.

  In this way, before the cooling water boils, the on-off valve 39 is released to allow the exhaust passage 38 and the tail pipe 19 to communicate with each other so that the exhaust gas does not flow into the heat receiving passage 22. Can be prevented from evaporating, and the cooling performance of the engine 1 can be improved.

(Second Embodiment)
4 and 5 are diagrams showing a second embodiment of the thermoelectric generator according to the present invention. The same reference numerals are given to the same components as those in the first embodiment, and the description will be omitted.
In FIG. 4, an inner pipe 41 is provided on an upstream side inner pipe 42 as a first inner pipe connected to the upstream side exhaust pipe 4, and downstream of the upstream side inner pipe 42 in the exhaust gas exhaust direction. And a downstream inner pipe 43 as a second inner pipe connected to the tail pipe 19 while being fixed to the outer pipe 23 via the support member 24.

  Further, an exhaust passage 46 through which exhaust gas flows is formed by the inside of the upstream side inner pipe 42 and the downstream side inner pipe 43, and the exhaust gas discharged from the exhaust pipe 4 to the inner pipe 41 passes through the exhaust passage 46 to the tail pipe. After being discharged to 19, it is discharged from the tail pipe 19 to the outside air.

  The upstream inner pipe 42 is formed to have the same diameter so that the flow passage area A1 of the upstream inner pipe 42 is the same in the exhaust direction, and the downstream inner pipe 43 is the downstream inner pipe. 43 has a larger inner diameter than the upstream inner pipe 42 so that the flow path area B1 of 43 is larger than the flow path area of the upstream inner pipe 42.

  In the inner pipe 41 of the thermoelectric power generation device 17 of the present embodiment, the upstream inner pipe 42 forms a constricted portion, and the exhaust gas is increased in the flow speed of the exhaust gas in the upstream inner pipe 42, and the downstream inner pipe 43. To be introduced. For this reason, a negative pressure is generated on the downstream side of the upstream inner pipe 42.

  Further, a communication path 44 as an upstream communication portion is formed between the downstream end of the upstream inner pipe 42 and the upstream end of the downstream inner pipe 43, and the communication path 44 is connected to the upstream inner pipe 42. In addition, the exhaust passage 46 and the heat receiving passage 22, which are inside the downstream side inner pipe 43, communicate with each other.

  A communication hole 45 as a downstream communication portion is formed downstream of the communication passage 44 in the exhaust direction. The communication holes 45 are formed at equal intervals in the circumferential direction of the downstream side inner pipe 43 and communicate the exhaust passage 46 and the heat receiving passage 22. The communication holes 45 are not limited to those formed at regular intervals.

  Further, a throttle part 43a is formed on the downstream side of the downstream inner pipe 43, and the flow path area of the downstream part of the downstream inner pipe 43 is smaller than that of the upstream part by the throttle part 43a. For this reason, the flow passage area of the heat receiving passage 22 is smaller on the upstream side than the downstream side, and the flow rate of the exhaust gas flowing through the heat receiving passage 22 is from the downstream side toward the upstream side, that is, from the communication hole 45 to the communication passage 44. Get bigger towards.

  In the present embodiment, the flow rate of the exhaust gas introduced from the upstream inner pipe 42 into the downstream inner pipe 43 is increased when passing through the upstream inner pipe 42 constituting the throttle portion, and the upstream inner pipe 42. A negative pressure due to the venturi effect is generated on the downstream side.

  Since a communication passage 44 that connects the exhaust passage 46 and the heat receiving passage 22 is formed between the downstream end of the upstream inner tube 42 and the upstream end of the downstream inner tube 43, the heat receiving passage 22 is communicated through the communication passage 44. Negative pressure is generated.

  For this reason, the exhaust gas flowing through the downstream inner pipe 43 is introduced into the heat receiving passage 22 through the communication hole 45 provided downstream of the communication path 44, and the flow reverses the flow of the exhaust gas flowing through the downstream inner pipe 43. It becomes. In FIG. 4, the flow of exhaust gas in the exhaust passage 38 is indicated by G3, and the flow of exhaust gas in the heat receiving passage 22 is indicated by G4.

  For this reason, the high temperature exhaust gas flowing through the heat receiving passage 22 acts on the heat receiving substrate 29 of the thermoelectric conversion module 27, and the low temperature cooling water flowing through the cooling water pipe 28 acts on the heat dissipation substrate 30 of the thermoelectric conversion module 27. Power generation is performed by the temperature difference between the heat receiving substrate 29 and the heat dissipation substrate 30 of the thermoelectric conversion module 27. Then, the generated power is supplied to the battery via the cable 34 and charged to the battery.

  On the other hand, the exhaust gas flowing through the heat receiving passage 22 is again introduced into the downstream inner pipe 43 through the communication passage 44. The new exhaust gas discharged from the engine 1 through the exhaust pipe 4 to the upstream side inner pipe 42 is mixed with the exhaust gas after heat recovery introduced into the downstream side inner pipe 43 through the communication path 44, and the downstream side inner pipe 26. To the heat receiving passage 22 through the communication hole 37.

  Therefore, it is possible to prevent the high-temperature new exhaust gas from coming into direct contact with the upstream thermoelectric conversion module 27, and the N-type thermoelectric thermoelectric conversion element 31 and the P-type thermoelectric thermoelectric conversion element of the upstream thermoelectric conversion module 27. 32 or the cable 34 can be prevented from being damaged by the heat damage of the exhaust gas.

  Further, since the amount of heat of the exhaust gas transmitted to the cooling water pipe 28 can be reduced, the cooling water can be prevented from becoming high temperature, the cooling water pipe 28 is damaged, or the cooling performance of the engine 1 is lowered. Can be prevented.

  Moreover, since it can suppress that the temperature of a cooling water rises, the temperature difference of exhaust gas and a cooling water can be enlarged, and it can prevent that the electric power generation efficiency of the thermoelectric conversion module 27 falls. it can.

  Further, the mixed gas of the new exhaust gas introduced into the heat receiving passage 22 through the communication hole 45 and the exhaust gas after the heat recovery is caused by the cooling water flowing through the cooling water pipe 28 as it moves upstream in the heat receiving passage 22. Although the heat is taken away, the amount of heat is recovered by being warmed by the radiant heat of the new exhaust gas introduced into the downstream inner pipe 43 through the upstream inner pipe 42.

  For this reason, the temperature of the exhaust gas flowing in the heat receiving passage 22 can be made substantially uniform, and the temperature difference between the high temperature side heat receiving substrate 29 and the low temperature side heat radiating substrate 30 of the thermoelectric conversion module 27 varies in the exhaust direction. It is possible to prevent the power generation efficiency of the thermoelectric conversion module 27 from decreasing.

  Further, since the thermoelectric generator 17 of the present embodiment flows from the upstream side in the exhaust direction of the cooling water flowing through the cooling water pipe 28 toward the downstream side in the exhaust direction, the direction of the cooling water flowing through the cooling water pipe 28 is changed to the heat receiving passage 22. The direction of the exhaust gas flowing backward can be reversed. As a result, the power generation efficiency of the thermoelectric conversion module 27 can be improved as compared with the case where the directions of the exhaust gas and the cooling water are parallel flow.

  Further, since the thermoelectric generator 17 of the first embodiment has the throttle portion 25a formed on the downstream side of the upstream inner pipe 25, there is a possibility that pressure loss of the exhaust gas occurs in the throttle portion 25a. In the present embodiment, the upstream inner tube 42 has the same diameter in the exhaust direction so that the flow channel area A1 of the upstream inner tube 42 is smaller than the flow channel area B2 of the downstream inner tube 43.

  For this reason, the flow area of the downstream inner pipe 43 can be increased without reducing the flow path cross section on the downstream side of the upstream inner pipe 42, and the downstream end of the upstream inner pipe 42 can be changed from the downstream end to the downstream inner pipe 43. While increasing the flow rate of the introduced exhaust gas, it is possible to prevent the pressure loss of the exhaust gas introduced from the downstream end of the upstream inner pipe 42 to the downstream inner pipe 43 from decreasing.

  Further, in the present embodiment, the throttle part 43a is formed on the downstream side of the downstream inner pipe 43, and the flow area of the downstream part of the downstream inner pipe 43 is made smaller than the upstream part by the throttle part 43a. The flow passage area of the heat receiving passage 22 is configured to be smaller on the upstream side than on the downstream side.

  For this reason, the flow velocity of the mixed gas flowing through the heat receiving passage 22 can be increased from the downstream side toward the upstream side. Therefore, if the flow rate of the exhaust gas increases according to Newton's law of cooling, the heat transfer efficiency from the exhaust gas to the thermoelectric conversion module 27 can be improved. As a result, the power generation efficiency of the thermoelectric conversion module 27 is improved. Can do.

  In the present embodiment, the throttle part 43a is formed on the downstream side of the downstream inner pipe 43, and the flow area of the downstream part of the downstream inner pipe 43 is made smaller than the upstream part by the throttle part 43a. Although the flow passage area of the heat receiving passage 22 is configured to be smaller on the upstream side than on the downstream side, it is not limited to this.

  That is, as shown in FIG. 5, the inner pipe 41 is configured together with the upstream inner pipe 42, a downstream inner pipe 51 having a communication hole 52 is provided, and the flow path area B3 of the downstream inner pipe 51 is set in the exhaust direction. By decreasing from the upstream side toward the downstream side, the flow passage area of the heat receiving passage 22 may be configured to be smaller on the upstream side than on the downstream side. Even if it does in this way, the effect of this Embodiment mentioned above can be acquired. The downstream inner pipe 51 constitutes a second inner pipe, and the communication hole 52 constitutes a downstream communication part.

  As described above, the thermoelectric power generation device according to the present invention has an effect that the power generation efficiency of the thermoelectric conversion module can be prevented from being lowered while preventing damage due to heat damage of the thermoelectric conversion module. It is useful as a thermoelectric power generation device that performs thermoelectric power generation using exhaust gas discharged from an engine.

1 engine (internal combustion engine)
4 Exhaust pipe 17 Thermoelectric generator 21, 41 Inner pipe 22 Heat receiving passage 23 Outer pipe 23a Outer peripheral part 25, 42 Upstream inner pipe (first inner pipe)
25a Restriction portion 26, 51 Downstream inner pipe (second inner pipe)
27 Thermoelectric conversion module 28 Cooling water pipe (cooling member)
28c Inner circumference 29 Heat receiving substrate (one side surface of thermoelectric conversion module)
30 Heat dissipation board (other side of thermoelectric conversion module)
36, 44 Communication path (upstream communication part)
37, 45, 52 Communication hole (downstream communication part)
39 On-off valve 42 Inner pipe on the downstream side (second inner pipe, throttle part)

Claims (5)

An inner pipe into which exhaust gas discharged from the internal combustion engine is introduced; an outer pipe provided outside the inner pipe and forming a heat receiving passage with the inner pipe; and one side surface of the outer pipe A thermoelectric conversion module that makes thermoelectric power generation in accordance with a temperature difference between the one side surface and the other side surface, and an on-off valve that opens and closes the inner pipe. A thermoelectric generator with
The inner pipe is formed on the upstream side in the exhaust direction of the exhaust gas flowing through the inner pipe, provided on the downstream side in the exhaust direction, an upstream communication portion that communicates the inside of the inner pipe and the heat receiving passage, A downstream communication part that communicates the inside of the inner pipe and the heat receiving passage, and a throttle part that is provided upstream of the upstream communication part in the exhaust direction and restricts the flow area of the inner pipe. A thermoelectric generator characterized by.   The said cooling member is comprised from the cooling water pipe | tube with which cooling water distribute | circulates, and the said cooling water pipe | tube flows the cooling water from the said exhaust direction upstream toward the said exhaust direction downstream. Thermoelectric generator. The inner pipe includes a first inner pipe and a second inner pipe provided on the downstream side in the exhaust direction with respect to the first pipe,
The diameter of at least the downstream side of the first pipe is reduced so that the flow area on the downstream side in the exhaust direction of the first pipe is smaller than the flow area of the second pipe. Form the
The upstream communication portion is formed by a gap formed between the exhaust pipe downstream end of the first pipe and the exhaust pipe upstream end of the second pipe. The thermoelectric generator according to claim 2.   The inner pipe has the exhaust passage with respect to the flow area on the upstream side in the exhaust direction of the inner pipe so that the flow passage area of the heat receiving passage decreases from the upstream side in the exhaust direction toward the downstream side in the exhaust direction. The thermoelectric generator according to any one of claims 1 to 3, wherein a flow path area on the downstream side in the direction is formed to be small.   The thermoelectric power generator according to any one of claims 1 to 4, wherein the on-off valve is provided on the downstream side in the exhaust direction with respect to the downstream communication portion.

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