JP2005295725A - Thermoelectric generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoelectric generator capable of recovering an appropriate amount of electric power according to operating conditions.
SOLUTION: A first thermoelectric conversion stack 1 and a second thermoelectric change stack 2 having thermoelectric elements arranged on an exhaust pipe 41 of an engine 40 are provided. Cooling water pipes L1 to L6 are connected to the thermoelectric conversion stacks 1 and 2, and a flow rate control valve 72 for changing the ratio of the cooling water supplied to the stacks 1 and 2 is provided on the cooling water pipes. , 74 are provided. The control ECU 60 refers to the detection results of the thermometers 61 and 63 and the flow meter 62 and adjusts the flow control valves 72 and 74 to change the ratio of the cooling water supplied to the stacks 1 and 2.
[Selection] Figure 1

Description

  The present invention relates to a thermoelectric generator that generates power by converting thermal energy into electrical energy.

BACKGROUND ART A thermoelectric generator is known as a device that recovers thermal energy of exhaust gas discharged from an automobile engine, a factory boiler, or the like as electric power (see, for example, Patent Document 1). In the technique of this Patent Document 1, a high temperature thermoelectric conversion module that operates in a high temperature region is disposed upstream of the exhaust gas flow, and a low temperature thermoelectric conversion module that operates in a lower temperature region is disposed on the downstream side. In addition, the power generation efficiency of the entire power generation apparatus is improved by making each operating temperature appropriate.
JP 2000-286469 A

  By the way, in this kind of thermoelectric power generator, cooling water is circulated through each thermoelectric conversion module to cool it. A power source such as an electric pump is used for circulating the cooling water, but depending on the operating conditions, the electric power required for the operation of the electric pump is larger than the electric power obtained by the thermoelectric conversion module, and the electric power actually recovered The amount may be reduced.

  Then, this invention makes it a subject to provide the thermoelectric power generator which can collect | recover appropriate electric energy according to driving | running conditions.

  In order to solve the above problems, the thermoelectric power generation device according to the present invention is disposed upstream of the heat medium flow path, and generates an electromotive force due to a temperature difference between the heat medium flowing through the heat medium flow path and the supplied refrigerant. A first thermoelectric conversion module having a thermoelectric element, and a thermoelectric element that is arranged downstream of the heat medium flow path and generates an electromotive force due to a temperature difference between the heat medium flowing through the heat medium flow path and the supplied refrigerant. A thermoelectric power generation apparatus comprising a second thermoelectric conversion module, characterized by comprising ratio changing means for changing a ratio of refrigerant supplied to the first thermoelectric conversion module and the second thermoelectric conversion module. .

  The electromotive force generated by the thermoelectric element of the thermoelectric conversion module depends on both the high temperature side temperature and the low temperature side temperature. In the present invention, by changing the ratio of the refrigerant supplied to the first thermoelectric conversion module and the second thermoelectric conversion module, and adjusting the flow rate of the refrigerant supplied to each thermoelectric conversion module, each thermoelectric conversion The temperature on the low temperature side is adjusted so that proper power is obtained in the conversion module.

  In addition, the invention which concerns on the above also includes the structure which makes a thermoelectric conversion module multistage structure, and changes the ratio of the refrigerant | coolant supplied to each thermoelectric conversion module. The ratio change includes a case where the refrigerant is supplied only to one thermoelectric conversion module and the other is not supplied with the refrigerant. Examples of the heat medium referred to in the present invention include exhaust gas from combustion equipment including an internal combustion engine and high-temperature waste water. Moreover, as a refrigerant | coolant said to this invention, various liquids other than cooling water, air, other gas, and also the medium which changes a phase may be sufficient.

  The temperature / flow rate of the heat medium and the temperature of the refrigerant may be determined, and the operation of the ratio changing unit may be controlled based on the determination result. Alternatively, the high temperature side or low temperature side temperature of at least one of the first and second thermoelectric conversion modules may be determined, and the operation of the ratio changing unit may be controlled based on the determination result. Moreover, the electromotive force by the 1st and 2nd thermoelectric conversion module may be measured, and operation | movement of a ratio change means may be controlled based on a measurement result.

  Directly measure the electromotive force of the first and second thermoelectric conversion modules, or determine the temperature on the high temperature side, the low temperature side, the temperature / flow rate of the heating medium, or the temperature of the refrigerant, which is a state quantity that determines the electromotive force Thus, the operation of the ratio changing means is controlled so that the electromotive force becomes appropriate.

  The heat medium flow path is an exhaust system for combustion equipment, and includes an exhaust purification catalyst between the first thermoelectric conversion module and the second thermoelectric conversion module, and when the temperature of the catalyst is equal to or lower than a predetermined value. The refrigerant supply to at least the first thermoelectric conversion module may be stopped.

  For example, at the time of cold start where the temperature of the catalyst is low, if the first thermoelectric conversion module existing on the upstream side of the catalyst is operated, the temperature of the exhaust gas flowing into the catalyst decreases, and it takes time to raise the temperature of the catalyst. Since the emission until the temperature rises worsens, the refrigerant supply to the first thermoelectric conversion module is stopped, and the exhaust gas temperature flowing into the catalyst is prevented from decreasing. Similarly, when the exhaust gas temperature is low or when the exhaust gas inflow amount is small (low speed and low load in the case of an automobile engine), the refrigerant supply to the first thermoelectric conversion module is stopped and the exhaust gas temperature flowing into the catalyst is reduced. Prevent decline.

  According to the present invention, by adjusting the flow rate ratio of the refrigerant, each low temperature side temperature is adjusted so that each of the first thermoelectric conversion module and the second thermoelectric conversion module can generate power efficiently. By controlling the cooling conditions in this way, it is possible to improve the actually recovered power (generated power—power necessary for supplying the refrigerant).

  By controlling the cooling condition based on the electromotive force and the state quantity that determines the electromotive force, the control can be performed with high accuracy and the controllability is also improved.

  When the thermoelectric conversion module is placed across the exhaust purification catalyst, the cooling condition control is performed with reference to the catalyst temperature, thereby improving the warm-up property of the catalyst and reducing the catalyst temperature. It is possible to suppress the deterioration of emission.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.

  FIG. 1 is a schematic configuration diagram showing an exhaust system of a vehicle equipped with a first embodiment of a thermoelectric generator according to the present invention, and FIG. 2 shows a first thermoelectric conversion stack 1 portion of the thermoelectric generator. It is sectional drawing (II-II sectional view taken on the line of FIG. 1), and FIG. 3 is an expanded sectional view of the thermoelectric conversion module 10 part.

  This thermoelectric generator is arranged on an exhaust pipe 41 connected to the engine 40, and the first thermoelectric conversion stack 1 and the second thermoelectric conversion stack 2 sandwich the exhaust purification catalyst 3 from the upstream side. Is arranged in. Here, the first thermoelectric conversion stack 1 and the second thermoelectric conversion stack 2 have the same configuration except that the characteristics of the mounted thermoelectric elements are different.

  As shown in FIG. 2, the first thermoelectric conversion stack 1 includes a first thermoelectric conversion module 10 having a first thermoelectric element 100, heat recovery fins (heat collecting fins) 13 disposed in the exhaust pipe, and The four cooling cases 15 having a passage for circulating cooling water therein are combined.

  The heat collecting fins 13 are formed by integrally forming a plate-like base portion with a plurality of plate-like fins extending in parallel at a predetermined interval in the exhaust flow direction from one surface thereof. The heat collection fins 13 are made of a metal having good thermal conductivity such as aluminum, copper, and stainless steel, or ceramics having high thermal conductivity such as AlN and SiC.

  The height of each fin of the heat collecting fins 13, that is, the distance from the tip to the root, is the highest at the fin located at the center, and takes a configuration that becomes lower toward the peripheral edge. The line connecting the tips of the fins has a so-called wedge shape that matches the shape of the two sides that sandwich the vertical angle of the vertical isosceles triangle.

  On the surface side opposite to the fin forming surface of the heat collecting fins 13, the high temperature side end surface of the thermoelectric conversion module 10 is disposed with the insulating material 11 interposed therebetween. And the cooling case 15 is arrange | positioned on the low temperature side end surface of the opposite surface of the thermoelectric conversion module 10 across the insulating material 12.

  A guide plate 14 having a substantially L-shaped cross section is disposed so as to cover the fin tip side of the heat collection fin 13. The first thermoelectric conversion stack 1 is obtained by fixing the guide plate 14 to the cooling case 15 to the exhaust pipe 41 by the fixing member 16 in a combined state. In the assembled state, the cross-sectional shape orthogonal to the exhaust flow direction of the four guide plates 14 is X-shaped as shown in FIG.

  The second thermoelectric conversion stack 2 has the same configuration as described above, and in the following description of this paragraph, each reference number 1x in FIG. 2 is read as 2x. That is, the second thermoelectric conversion stack 2 has a second thermoelectric conversion module 20 having the second thermoelectric element 200, heat collecting fins 23 arranged in the exhaust pipe, and a passage for circulating cooling water therein. Four sets of assemblies, each of which is a combination of the cooling case 25, the insulating materials 21 and 22, and the guide plate 24, are fixed to the exhaust pipe 41 by the fixing member 26. In addition, although the material and shape of each member may be the same structure as the 1st thermoelectric conversion stack 1, the exhaust gas temperature which passes through the inside is lower than the case of the 1st thermoelectric conversion stack 1, and the 1st thermoelectric conversion stack 1 is the same. Since no heat resistance is required, different materials and shapes may be used.

  In the first and second thermoelectric conversion stacks 1 and 2, a plurality of stacks formed in this manner are arranged in the exhaust flow direction, so that the thermoelectric conversion modules 10 or 20 are arranged in multiple stages in the exhaust flow direction. You may arrange in.

  The cooling water passages of the cooling cases 15 and 25 in the first and second thermoelectric conversion stacks 1 and 2 may be connected in series or in parallel, and they are the same orthogonal to the flow direction of the exhaust gas. It is also possible to connect in parallel between the cooling cases 15 and 25 in the cross section and in series between the cooling cases 15 and 25 located at different positions in the flow direction. The type of connection is appropriately set in consideration of the efficiency of heat recovery and the ease of connection of the cooling water pipes connecting the cooling cases 15 and 25.

  FIG. 3 is a diagram illustrating a configuration of the first thermoelectric conversion module 10. The configuration of the second thermoelectric conversion module 20 is also the same. Hereinafter, the reference numbers in parentheses indicate the case of the second thermoelectric conversion module 20, but notation in the figure is omitted. The thermoelectric conversion module 10 (20) prepares a plurality of two types of semiconductors 101 (201) and 102 (202) of p-type and n-type, and these are electrically connected by electrodes 103 (203) and 104 (204). Are arranged alternately in series and thermally in parallel. The pair of semiconductors 101 and 201 constitute the thermoelectric element 100 (200).

  As the thermoelectric material (semiconductors 101 and 102) of the first thermoelectric element 100 used in the first thermoelectric conversion module 10, an Fe—Si type or Si—Ge type that has good power generation characteristics in a high temperature region (800 K˜). These semiconductors are preferably used. On the other hand, as the thermoelectric material (semiconductors 201 and 202) of the second thermoelectric element 200 used in the second thermoelectric conversion module 20, a PbTe-based material having good power generation characteristics in a lower temperature region (up to 800K) and a scuttle. Use of terdite-based, layered cobalt oxide-based, silicide-based (MnSi-based as p-type, MgSi-based as n-type), ZnSb-based (p-type) TAGS (Te-Ag-Ge-Sb) (p-type) preferable.

  4 and 5 are diagrams showing temperature-power generation characteristics of the first thermoelectric element 100 and the second thermoelectric element 200 in the present embodiment, respectively. In the first thermoelectric element 100 used in the high temperature region, the power generation amount increases as the temperature (Th) on the high temperature end side is higher and as the temperature (Tc) on the low temperature end side is lower. And the difference of the electric power generation amount by the temperature change of Tc in case Th is the same tends to become large, so that Th is high temperature. In the second thermoelectric element 200 used in the low temperature region, when Th is the same, the lower the Tc, the same as the first thermoelectric element 100 in that the amount of power generation increases, but when Tc is the same. Has a maximum power generation amount, and when this peak is exceeded, the power generation amount rapidly decreases as Th increases. And Th which becomes this peak transfers to a high temperature side, so that Tc is low. Also in this case, the difference in the amount of power generation due to the temperature change of Tc when Th is the same tends to increase as Th increases.

  By making the characteristics of the first thermoelectric element 100 and the second thermoelectric element 200 appropriate according to the temperature characteristics of the exhaust gas at the arrangement position, the overall power generation characteristics can be improved. Different thermoelectric materials may be combined in each of the thermoelectric conversion stacks 1 and 2.

  Each thermoelectric conversion stack 1, 2 is electrically connected to a DC-DC converter 50 that performs voltage conversion, and the DC-DC converter 50 is electrically connected to a battery 51 that stores electric power. The thermoelectric conversion stacks 1 and 2 are connected to a cooling system for circulating cooling water. In the present embodiment, an electric pump 70 is disposed on a line L <b> 1 extending from the radiator 45, and is connected to a branch type flow control valve 72. From the flow control valve 72, a line L2 returning to the radiator 45 and a line L3 extending to the second thermoelectric conversion stack 2 are branched, and the flow ratio in each direction is adjusted by the flow control valve 72. . Then, the return line L4 from the second thermoelectric conversion stack 2 joins the line L2. A branch-type flow control valve 71 is further arranged downstream of the line L2, and a line L5 extending to the first thermoelectric conversion stack 1 is branched. Then, the return line L6 from the first thermoelectric conversion stack 1 joins the line L2. This cooling system may be connected in series to the cooling system of the engine 40 (not shown), or may be provided in parallel.

  On the upstream side of the first thermoelectric conversion stack 1 in the exhaust pipe 41, a thermometer 61 for measuring the temperature and flow rate of the exhaust gas and a flow meter 62 are arranged. A thermometer 63 for measuring the cooling water temperature is arranged on the line L1. The outputs of the thermometers 61 and 63 and the flow meter 62 are input to the control ECU 60, and the control ECU 60 controls the operation of the electric pump 70, the flow control valves 71 and 72, and the DC-DC converter 50. The control ECU 60 includes a CPU, a RAM, a ROM, and the like, and may be configured independently, or may be configured as a part of another vehicle control system (not shown).

  Next, the operation of the thermoelectric generator according to the present invention will be described together with the control operation of the cooling system. FIG. 6 is a flowchart showing the control operation of the cooling system. This control is repeatedly executed at a predetermined timing from when the engine 40 is started by the control ECU 60 until it is stopped.

First, read in step S1, the output of the flowmeter 62 and the thermometer 61 and 63, the flow rate V of the exhaust gas, the temperature _{T 1,} the cooling water temperature _{T 2.}

Here, if the power consumption of the electric pump 70 is Pp, the power generation amounts of the thermoelectric conversion stacks 1 and 3 are Ps1 and Ps2, and the recovered power amount is Pr, Pr = Ps1 + Ps2−Pp. Here, the power consumption of the electric pump can be expressed as a function of the cooling water amount Vw. On the other hand, the power generation amount of each thermoelectric conversion stack 1, 3 depends on the temperature Th on the high temperature end side and the temperature Tc on the low temperature end side. Th and Tc can be obtained from the temperature, flow rate and cooling water temperature and flow rate of the exhaust gas introduced into each thermoelectric conversion stack 1 and 3, and the thermal resistance value in the stack. Accordingly, the flow rate V of the exhaust gas, the temperature T _1, if the cooling water temperature T ₂ is known, it is possible to obtain the cooling water flow rate to maximize the Pr. In the present embodiment, the actual heat calculation increases the calculation load, so the valve opening degree of each of the flow control valves 71 and 72 corresponding to the exhaust gas temperature, flow rate and cooling water temperature in the most upstream part is set in advance. This is stored in the control ECU 60 in the form of a map, and an appropriate valve opening is set with reference to this map according to the read V, T ₁ , T ₂ (step) S3).

  In step S5, the flow control valves 71 and 72 are instructed to realize the set valve opening. Thereby, the coolant flow rate of each thermoelectric conversion stack 1, 3 is adjusted. At this time, it is preferable that the flow rate itself for circulating the radiator 45 by the electric pump 70 is also adjusted.

  Here, in each thermoelectric conversion stack 1, 3, the exhaust gas is guided between the fins of the heat collection fins 13 (23) by the guide plates 14 (24) and transfers heat to the fins. This heat is transferred from each fin to the high temperature side end face of the thermoelectric conversion module 10 (20) through the base portion and the insulating material 11 (21). Thereby, the temperature of a high temperature side end surface becomes high.

  On the other hand, heat is taken from the low temperature side end face of the thermoelectric conversion module 10 (20) to the cooling water flowing in the passage of the cooling case 15 (25) through the insulating material 12 (22) and the cooling case 15 (25). Yes. For this reason, the temperature of the low-temperature side end surface is lowered. Thus, a temperature difference is generated between the high temperature side end surface and the low temperature side end surface, and electric power is generated in the thermoelectric element 100 (200) in the thermoelectric conversion module 10 (20) by the Seebeck effect according to this temperature difference. Is converted into a predetermined voltage by the DC-DC converter 50 and stored in the battery 51.

  At this time, since the ratio of the cooling water supplied is changed so that the recovered electric power is maximized, the cooling water is not supplied excessively, and energy can be efficiently recovered from the exhaust gas. Here, an example in which the valve opening is set in a map format from the state quantities of exhaust gas and cooling water has been described. However, in addition to the map format, a function format may be used, and when the calculation capacity of the control ECU 60 has a margin. Or by calculation.

  Although the flow rate of the exhaust gas is measured by the flow meter 62 here, a flow rate meter may be arranged to estimate the flow rate. Alternatively, the flow rate can be estimated based on the operating conditions of the engine 40 (engine speed, fuel injection amount, etc.).

  FIG. 7 is a schematic configuration diagram showing a second embodiment of the thermoelectric generator according to the present invention. Unlike the thermoelectric generator of the first embodiment (see FIG. 1), the thermoelectric generator of this embodiment is provided with only one flow rate control valve 73 on the line L1, and this flow rate control valve 73 allows the first The ratio of the flow rate of the cooling water supplied to the thermoelectric conversion stack 1 and the flow rate of the cooling water supplied to the second thermoelectric conversion stack 2 can be adjusted.

  In this embodiment, the operation is the same as that of the first embodiment, except that the valve used for adjusting the flow rate ratio is limited to the flow control valve 73 only. Therefore, description of the operation / control is omitted.

  FIG. 8 is a schematic configuration diagram showing a third embodiment of the thermoelectric generator according to the present invention. The cooling system of the thermoelectric generator of this embodiment is basically the same as that of the second embodiment. However, in this embodiment, unlike the first and second embodiments, the high temperature end side temperature and the low temperature end side temperature of each thermoelectric conversion stack 1, 2 are directly measured by the thermometers 64a, 64b, 65a, 65b. Is different. The outputs of the thermometers 64a to 65b are input to the control ECU 60.

  In this embodiment, the electric power obtained based on the characteristics can be directly obtained from the high temperature end side temperature and the low temperature end side temperature of each thermoelectric conversion stack 1, 2 measured by the thermometers 64a, 64b, 65a, 65b. . By appropriately controlling the cooling water flow rate based on this amount of electric power, control is performed so that the recovered electric power is maximized. In this case, the feedforward control for controlling the electric pump 70 and the flow rate control valve 73 so as to increase the recovered power amount by predicting the recovered power amount when the cooling water amount is changed by the electric pump 70 and the flow rate control valve 73. The electric pump 70 and the flow rate control valve 73 may be feedback adjusted.

  FIG. 9 is a schematic configuration diagram showing a fourth embodiment of a thermoelectric generator according to the present invention. The cooling system of the thermoelectric generator of this embodiment is basically the same as that of the second embodiment. However, in this embodiment, unlike the first to third embodiments, the current values and electromotive voltages taken from the thermoelectric conversion stacks 1 and 2 are measured by the ammeters 66a and 66b and the voltmeters 67a and 67b, respectively. Is different. The outputs of the ammeters 66a and 66b and the voltmeters 67a and 67b are input to the control ECU 60.

  FIG. 10 is a flowchart showing a control example of the cooling control operation in this case. Here, in order to simplify the description, a case where the amount of circulating water by the electric pump 70 is constant will be described as an example. In actual control, it may be controlled including the amount of circulating water of the electric pump 70.

  First, the current values and voltage values output from the ammeters 66a and 66b and the voltmeters 67a and 67b are read (step S11). Next, the recovered power amount Pr is calculated from the read current and voltage values and the operating power of the electric pump 70 (step S12).

  Next, it is determined whether or not the absolute value of the difference between the calculated recovered power amount Pr and the recovered power amount Prold at the previous time step is less than the threshold value Pth (step S13). If the absolute value of the difference is equal to or greater than the threshold value Pth, the process proceeds to step S14, and Pr and Prold are compared.

  If Pr is greater than Prold, the opening A of the flow control valve is changed by i × D (step S17). Here, D is a change step amount for changing the opening, i takes a value of 1 or -1, and is set to be the same as the previous change direction. That is, as a result of increasing the opening degree of the flow control valve 73 in the previous time step, if it is determined that the recovered power amount has increased, the opening degree of the flow control valve 73 is further increased, and the flow rate is determined in the previous time step. As a result of reducing the opening degree of the control valve 73, if it is determined that the amount of recovered power has increased, control is performed to further reduce the opening degree of the flow control valve 73. When the adjustment is completed, the process proceeds to step S17, where the current value of the recovered power Pr is stored in the variable Prold, and the process ends.

  If Pr is smaller than Prold in step S14, the sign of i is changed in reverse, and the opening degree A of the flow control valve is changed by i × D (step S16). That is, as a result of increasing the opening degree of the flow control valve 73 in the previous time step, when it is determined that the recovered power amount has decreased, the opening degree of the flow control valve 73 is reduced and the flow control is performed in the previous time step. As a result of reducing the opening degree of the valve 73, when it is determined that the amount of recovered power has decreased, control is performed to increase the opening degree of the flow control valve 73. In this flow, since the process may not converge, the opening A may be changed by i × D / 2 in step S16. When the adjustment is completed, the process proceeds to step S17, where the current value of the recovered power Pr is stored in the variable Prold, and the process ends.

  If the absolute value of the difference is less than the threshold value Pth in step S13, the process proceeds directly to step S17, where the current value of the recovered power Pr is stored in the variable Prold, and the process ends.

  In this way, by controlling the operation of the flow rate control valve 73 so that the recovered power amount is maximized, the thermal energy of the exhaust gas can be efficiently recovered as electric power.

  FIG. 11: is a schematic block diagram which shows 5th Embodiment of the thermoelectric power generating apparatus which concerns on this invention. In this embodiment, no flow control valve is provided on the cooling water pipe. Instead, the water flow resistance of the cooling case 25 of the second thermoelectric conversion stack 2 is used.

  FIG. 12 is a diagram (cross-sectional view taken along line XII-XII in FIG. 11) of the second thermoelectric conversion stack 2 of the present embodiment, and FIGS. 13 and 14 show cooling accompanying changes in pump discharge pressure. FIG. 6 is a diagram illustrating a change in cross-sectional shape of a passage 255 in the case 25.

  The cooling case 25 is configured by combining the upper case 251 and the lower case 250 having a comb-shaped cross section so that the respective comb teeth are engaged with each other with a predetermined gap therebetween. Are bound by. This gap becomes a passage 255 through which the cooling water flows. Instead of the spring 252, an elastic body such as rubber or resin, an air spring, a liquid spring, or the like may be used.

  In a state where the discharge pressure of the electric pump 70 is low, the force that the resistance adjusting spring 252 acts to bring the upper case 251 and the lower case 250 closer together causes the cooling water flowing in the passage 255 to expand the cross-sectional area of the passage 255. In order to overcome the force to do, the cross section of the passage 255 is kept narrow as shown in FIG. As a result, the ratio of the cooling water supplied to the 2nd thermoelectric conversion stack 2 becomes low.

  When the discharge pressure of the electric pump 70 is increased, the force that the cooling water flowing in the passage 255 tries to expand the cross-sectional area of the passage 255 acts to cause the resistance adjusting spring 252 to bring the upper case 251 and the lower case 250 closer together. The cross-sectional area of the passage 255 is enlarged until both are balanced (see FIG. 14). As a result, the ratio of the cooling water supplied to the second thermoelectric conversion stack 2 is increased.

  That is, the ratio of the cooling water supplied to the first and second thermoelectric conversion stacks 1 and 2 can be changed by changing the discharge pressure of the electric pump 70. In this embodiment, since the flow rate control valve is not required, the structure of the cooling water pipe can be simplified.

  When the spring constant of the resistance adjustment spring 252 is increased, the cross-sectional area of the passage 255 is unlikely to change even when the discharge pressure of the electric pump 70 is increased. The spring constant may be appropriately set according to the flow rate distribution of the cooling water supplied to the first thermoelectric conversion stack 1 and the second thermoelectric conversion stack 2. It is also possible to use an elastic body whose spring constant changes nonlinearly.

  A similar cooling case may be employed for the first thermoelectric conversion stack 1. For example, if the spring constant of the resistance adjustment spring 252 on the thermoelectric conversion stack 2 side is made smaller than the spring constant of the resistance adjustment spring on the thermoelectric conversion stack 1 side, each thermoelectric conversion stack 1 or 2 corresponding to the pump discharge pressure is supplied. The amount of cooling water supplied can be adjusted as shown in FIG. This is because, on the thermoelectric conversion stack 2 side, the cooling water passage 255 is fully opened at a discharge pressure lower than that of the thermoelectric conversion stack 1, and thereafter the cross-sectional area of the passage 255 does not increase even if the discharge pressure is increased. .

  FIG. 16: is a schematic block diagram which shows 6th Embodiment of the thermoelectric power generator which concerns on this invention. In this embodiment, a switching valve 74 is arranged on a line L2 of the cooling water pipe that returns from the second thermoelectric conversion stack 2 to the radiator 45, and a line L5 that introduces the cooling water to the first thermoelectric conversion stack 1. The cooling water return line L6 from the first thermoelectric conversion stack 1 is merged with the line L2. Further, a thermometer 68 for detecting the catalyst temperature of the exhaust purification catalyst 3 is provided, and input to the control ECU 60 together with the outputs of the thermometers 64a and 65a for measuring the temperatures of the thermoelectric conversion modules 10 and 20 of the thermoelectric conversion stacks 1 and 2, respectively. doing.

  FIG. 17 is a flowchart showing the cooling control of this embodiment. This control is also repeatedly executed by the control ECU 60 at a predetermined timing from when the engine 40 is started to when it is stopped.

First, by reading the output of the thermometer 64a, 65a, 68, reads the module temperature _T 1, _{T 3} of the thermoelectric conversion stack 1, the catalyst temperature _{T 2} of the exhaust gas purifying catalyst 3 (step S20).

Next, it is determined second module temperature T ₃ of the thermoelectric conversion stack 2, whether exceeds the threshold temperature T _e-2 capable of ensuring power generation amount exceeds the operating power of the electric pump 70 at the time of islanding (Step S21). When T ₃ is less than T _e-2 can be subjected to cooling water supply of the second to the thermoelectric conversion stack 2, the power obtained by the second thermoelectric conversion stack 2 is below the operating power of the electric pump 70 In fact, it is determined that there is a possibility that the electric power cannot be collected, and the process proceeds to step S27, the operation of the electric pump 70 is stopped, and the process is ended.

In step S21, if _{the T 3} is higher than the _{T e-2} activates the electric pump 70 and proceeds to step S22, the first module temperature _{T 1} of the thermoelectric conversion stack 1, the first It is determined whether or not the temperature exceeds a threshold temperature T _e-1 that can secure a power generation amount that exceeds the operating power of the electric pump 70 during operation of both the thermoelectric conversion stack 1 and the second thermoelectric conversion stack 2 (step S23). . If T ₁ exceeds T _e−1 , it is further determined whether or not the catalyst temperature T ₂ exceeds the activation temperature T _CAT (step S24).

When T ₂ exceeds T _CAT , it is determined that the exhaust purification catalyst 3 is activated and the exhaust purification catalyst 3 operates satisfactorily even when the first thermoelectric conversion stack 1 is operated. The process proceeds to step S25, the switching valve 74 is switched to the first thermoelectric conversion stack 1 side, and the cooling water is supplied to the first thermoelectric conversion stack 1.

On the other hand, in step S23, when T ₁ is is determined that T _e-1 or less, low exhaust gas temperature, when actuated first thermoelectric conversion stack 1, the exhaust gas temperature flowing to the downstream side is reduced The amount of electric power generated in the second thermoelectric conversion stack 2 is also reduced, and the amount of generated electric power is reduced as compared with the case where only the second thermoelectric conversion stack 2 is operated, and the operating power of the electric pump 70 is secured. It determines with it not being possible, it transfers to step S26, the switching valve 74 is switched to the radiator 45 side, and the action | operation of the 1st thermoelectric conversion stack 1 is stopped.
Further, in step S24, if the T ₂ is determined to be less T _CAT, when actuating the first thermoelectric conversion stack 1, since the exhaust gas temperature is lowered to flow into the exhaust gas purifying catalyst 3, in the warm-up In the meantime, it is determined that the emission may be deteriorated. Similarly, the process proceeds to step S26, the switching valve 74 is switched to the radiator 45 side, and the operation of the first thermoelectric conversion stack 1 is stopped. .

  For example, when the first thermoelectric conversion stack 1 is operated at the initial point of time during the cold start, the temperature of the exhaust gas flowing into the exhaust purification catalyst 3 is lowered, and the exhaust purification catalyst 3 is prevented from warming up. become. Further, even if the second thermoelectric conversion stack 2 is operated, the obtained electric power is lower than the operating electric power of the electric pump 70, and the actual recovered electric power becomes negative. In the present embodiment, under such a condition that the module temperature of the second thermoelectric conversion stack 2 is low, the electric pump 70 is stopped and heat recovery from the exhaust gas is not performed. For this reason, it is possible to warm up the exhaust purification catalyst 3 by quickly raising the temperature.

  When time elapses after the start and the temperature of the second thermoelectric conversion stack 2 is increased, the electric power obtained by the operation exceeds the operating power of the electric pump 70, so the operation of the electric pump 70 is started. On the other hand, when the exhaust purification catalyst 3 has not been warmed up and the catalyst temperature is low, operating the first thermoelectric conversion stack 1 results in preventing the exhaust purification catalyst 3 from warming up. By switching the switching valve 74 to the radiator 45 side, the first thermoelectric conversion stack 1 is not operated, and the temperature increase of the exhaust purification catalyst 3 is prioritized.

  After the exhaust purification catalyst 3 is warmed up, the exhaust gas flow rate from the engine 40 is small and the temperature of the first thermoelectric conversion stack 1 is low in the low speed or low load region. Even if the first thermoelectric conversion stack 1 is operated in this state, the power generation efficiency is low, the water flow resistance is increased, the load of the electric pump 70 is increased, and the power generation efficiency of the entire system is lowered. Moreover, when the exhaust gas temperature which flows into the exhaust purification catalyst 3 falls, the exhaust purification catalyst 3 is cooled, and there exists a possibility that the purification performance may fall. Therefore, in such a case, by switching the switching valve 74 to the radiator 45 side, the first thermoelectric conversion stack 1 is not operated, and only the second thermoelectric conversion stack 2 generates power.

  In the middle / high speed or middle / high load region, the exhaust gas flow rate from the engine 40 also increases, the temperature of the first thermoelectric conversion stack 1 is high, sufficient power generation efficiency is obtained, and the exhaust gas temperature flowing into the exhaust purification catalyst 3 is also purified. It can be maintained at a temperature at which performance can be demonstrated. Therefore, by switching the switching valve 74 to the first thermoelectric conversion stack 1 side, both the first and second thermoelectric conversion stacks 1 and 2 are operated to perform heat recovery.

  By performing such control, it is possible to achieve both warm-up and reliable operation of the exhaust purification catalyst and efficient heat recovery, suppress emission deterioration, and reduce the environmental load.

  Each embodiment described above can be used in combination. For example, in the first to fifth embodiments, the amount of cooling water to the first thermoelectric conversion stack 1 may be adjusted with reference to the catalyst temperature. Including this case, the adjustment of the cooling water flow rate or the ratio also includes completely stopping the supply of the cooling water to one stack. In the sixth embodiment, control according to the operation state of each module is performed with reference to the module temperature. However, control is performed with reference to the exhaust gas state quantity as in the first embodiment. As shown in the third embodiment, control may be performed with reference to the power generation amount of each stack.

  In the above description, the embodiment for adjusting the cooling water supply ratio between the first and second thermoelectric conversion stacks 1 and 2 has been described, but the cooling water supply ratio is adjusted between three or more thermoelectric conversion stacks. Are also included within the scope of the present invention. For example, when it has a 3rd thermoelectric conversion stack, this thermoelectric conversion stack may be arrange | positioned in the middle of the 1st, 2nd thermoelectric conversion stack, and is arrange | positioned in parallel with the 1st or 2nd thermoelectric conversion stack. May be.

  In the above description, the form mounted on the exhaust system of the engine 40 of the vehicle has been described. However, the present invention is not limited to this and is connected to the exhaust system of various combustion devices such as an engine and a boiler. In addition to the thermoelectric power generation apparatus, the present invention can also be suitably applied to a thermoelectric power generation apparatus that recovers heat from hot wastewater or the like.

  Furthermore, in the above description, the case where cooling water is used as the refrigerant is illustrated, but an air cooling type, an oil cooling type, or a phase change medium such as Freon gas may be used.

It is a schematic block diagram which shows the exhaust system of the vehicle carrying 1st Embodiment of the thermoelectric generator which concerns on this invention. It is sectional drawing (II-II sectional view taken on the line of FIG. 1) of the 1st thermoelectric conversion stack 1 part of the thermoelectric generator of FIG. It is an expanded sectional view of the thermoelectric conversion module 10 part of FIG. It is a diagram which shows the temperature-power generation characteristic of the 1st thermoelectric element 100 in 1st Embodiment. It is a diagram which shows the temperature-power generation characteristic of the 2nd thermoelectric element 200 in 1st Embodiment. It is a flowchart which shows the control operation of the cooling system of 1st Embodiment. It is a schematic block diagram which shows 2nd Embodiment of the thermoelectric generator which concerns on this invention. It is a schematic block diagram which shows 3rd Embodiment of the thermoelectric power generator which concerns on this invention. It is a schematic block diagram which shows 4th Embodiment of the thermoelectric generator which concerns on this invention. It is a flowchart which shows the control operation of the cooling system of 4th Embodiment. It is a schematic block diagram which shows 5th Embodiment of the thermoelectric power generator which concerns on this invention. It is a figure (XII-XII sectional view taken on the line in FIG. 11) which shows the cross-sectional structure of the 2nd thermoelectric conversion stack 2 of 5th Embodiment. It is a figure showing the cross-sectional shape change of the channel | path 255 in the cooling case 25 of 5th Embodiment accompanying the change of pump discharge pressure. It is another figure showing the cross-sectional shape change of the channel | path 255 in the cooling case 25 of 5th Embodiment accompanying the change of pump discharge pressure. It is a graph showing the amount of cooling water supply to the thermoelectric conversion stacks 1 and 2 with respect to the pump discharge pressure according to the fifth embodiment. It is a schematic block diagram which shows 6th Embodiment of the thermoelectric power generator which concerns on this invention. It is a flowchart which shows the control operation of the cooling system of 6th Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... 1st thermoelectric conversion stack, 2 ... 2nd thermoelectric conversion stack, 3 ... Exhaust purification catalyst, 10 ... 1st thermoelectric conversion module, 11, 12, 21, 22 ... Insulation material, 13, 23 ... Heat collection Fins 14, 24 ... Guide plates 15, 25 ... Cooling case, 16, 26 ... Fixing member, 20 ... Second thermoelectric conversion module, 40 ... Engine, 41 ... Exhaust pipe, 45 ... Radiator, 50 ... DC-DC Converter, 51 ... Battery, 60 ... Control ECU, 61, 63, 64a, 64b, 65a, 65b, 68 ... Thermometer, 62 ... Flow meter, 66a, 66b ... Ammeter, 67a, 67b ... Voltmeter, 70 ... Electric Pump, 71-73 ... Flow control valve, 74 ... Switching valve, 100, 200 ... Thermoelectric element, 101, 102, 201, 202 ... Semiconductor, 103, 104, 203, 204 ... Electrode, 250 ... Bottom Scan, 251 ... upper case, 252 ... resistance adjusting spring, 255 ... passage.

Claims (5)

A first thermoelectric conversion module having a thermoelectric element disposed upstream of the heat medium flow path and generating an electromotive force due to a temperature difference between the heat medium flowing through the heat medium flow path and the supplied refrigerant; and the heat medium flow A thermoelectric generator comprising a second thermoelectric conversion module that is disposed on the downstream side of a path and has a thermoelectric element that generates an electromotive force due to a temperature difference between a heat medium flowing through the heat medium flow path and a supplied refrigerant. ,
A thermoelectric generator comprising a ratio changing means for changing a ratio of refrigerant supplied to the first thermoelectric conversion module and the second thermoelectric conversion module.   The thermoelectric generator according to claim 1, wherein the temperature / flow rate of the heat medium and the temperature of the refrigerant are determined, and the operation of the ratio changing means is controlled based on the determination result.   The high temperature side and low temperature side temperature of at least one of the first and second thermoelectric conversion modules is determined, and the operation of the ratio changing unit is controlled based on the determination result. Thermoelectric generator.   2. The thermoelectric generator according to claim 1, wherein electromotive force is measured by the first and second thermoelectric conversion modules, and operation of the ratio changing unit is controlled based on a measurement result.   The heat medium flow path is an exhaust system for combustion equipment, and includes an exhaust purification catalyst between the first thermoelectric conversion module and the second thermoelectric conversion module, and the temperature of the catalyst is equal to or lower than a predetermined value. In this case, at least the refrigerant supply to the first thermoelectric conversion module is stopped. The thermoelectric power generator according to any one of claims 1 to 4.

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