JP2009281179A - Waste heat recovery device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device in which a rotor composed of a turbine and a compressor is always driven in a wide operating range of an engine. <P>SOLUTION: In this waste heat recovery device, exhaust gas from the engine 1 is introduced to the turbine 2 to be expanded to vacuum and subsequently introduced to a heat exchanger 3 to be cooled, and the cooled exhaust gas is compressed from negative pressure to the atmospheric pressure by the compressor 4 coaxially with the turbine 2 and discharged, thereby taking it out as power. The device is provided with an exhaust gas removal means 16 for removing a part of the exhaust gas from the engine. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a waste heat recovery apparatus, and more particularly to a waste heat recovery apparatus that recovers waste heat from a heat source as a power source of a drive device using an engine such as a gasoline engine or a diesel engine as a heat source.

A waste heat recovery device that includes a turbine, a compressor, and an exhaust cooling device installed between them, and that converts exhaust heat into power, newly installs an absorption chiller that uses the waste heat of engine cooling water to cool the exhaust Some refrigerants dissipate heat by the evaporator of this absorption refrigerator (see Patent Document 1).
JP 2002-188438 A

  By the way, as shown in FIG. 7, the gas from the heat source is led to the turbine and expanded to a negative pressure which is lower than the atmospheric pressure, and then led to the heat exchanger to be cooled. A waste heat recovery device that uses a reverse Brayton cycle that is extracted as power by compressing and discharging from negative pressure to atmospheric pressure with a coaxial compressor is considered.

  In this case, when considering the use of an automobile engine as a heat source, exhaust from the engine is guided to the turbine. In the automobile engine, there are various operations such as low load operation and high load operation. Operation modes are mixed. For this reason, depending on the operation mode, the rotating body composed of the turbine and the compressor may not be driven. For example, a rotating body composed of a turbine and a compressor may not be driven at a low temperature start or when a vehicle is decelerated where the exhaust temperature (exhaust energy) discharged from the engine is low.

  If the rotating body composed of the turbine and the compressor is not driven in this way, the energy recovery efficiency in the entire operation is lowered.

  Therefore, an object of the present invention is to provide an apparatus in which a rotating body composed of a turbine and a compressor is not driven in a wide operating range of an engine.

  The present invention introduces exhaust from the engine to the turbine (2), expands it to a negative pressure that is lower than atmospheric pressure, and then introduces it into the heat exchanger (3) to cool it. A waste heat recovery device that extracts as power by compressing and discharging from negative pressure to atmospheric pressure with a compressor (4) coaxial with (2), and has an exhaust extraction means (16) for extracting a part of exhaust from the engine. .

  According to the present invention, the exhaust from the engine is led to the turbine and expanded to a negative pressure that is lower than the atmospheric pressure, and then led to the heat exchanger to be cooled, and the cooled exhaust is compressed by a compressor coaxial with the turbine. In the waste heat recovery device that takes out as power by compressing and discharging from negative pressure to atmospheric pressure, it has exhaust extraction means for extracting a part of the exhaust from the engine, so the amount of exhaust extracted through the exhaust extraction means Only the compression work of the compressor can be reduced, and the waste heat recovery efficiency is improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of a waste heat recovery apparatus according to a first embodiment of the present invention. An exhaust pipe 11 of the engine 1 includes a turbine 2 for expanding the exhaust from the engine 1 to a negative pressure, a heat exchanger 3 for cooling the exhaust discharged from the turbine 2 under a negative pressure, and a coaxial with the turbine 1. And a compressor 4 for compressing the exhaust gas cooled by the heat exchanger 3 from negative pressure to normal pressure (atmospheric pressure). In this case, the rotary body composed of the turbine 2 and the compressor 4 is driven by optimally setting the specifications of the turbine 2, the heat exchanger 3 and the compressor 4, the expansion ratio of the turbine 2, and the compression ratio of the compressor 4. .

  In order to extract power from the rotating body, a motor generator 8 is provided on the turbine 2 side coaxially with the turbine 1 and the compressor 4. Driving the turbine 2 with the exhaust energy causes the motor generator 8 to function as a generator, whereby the exhaust energy is recovered as electric energy. This is to recover waste heat by obtaining power by a so-called reverse Brayton cycle, and FIG. 7 shows the basic configuration of the waste heat recovery apparatus of the present invention. Here, the “negative pressure” means a pressure lower than the atmospheric pressure.

  The exhaust discharged from the compressor 4 is led to the three-way catalyst 12 and purified, and then discharged. Although not shown, the engine 1 is mounted on a vehicle.

  In the first embodiment, the exhaust pipe 11A and the throttle unit 15 upstream of the heat exchanger 3 and downstream of the turbine 2 and the throttle unit 15 (a gasoline engine is provided with a throttle valve that throttles intake air) with respect to the basic configuration of such a waste heat recovery apparatus. A bypass passage 16 (exhaust air extraction means) that communicates with the downstream intake pipe 14A is provided. Further, a flow control valve 17 for opening and closing the bypass passage 16 is provided. A check valve 18 is provided in the bypass passage 16 so that the intake air in the intake pipe 14A downstream of the throttle portion 15 does not flow toward the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the turbine 2.

  The bypass passage 16 is for extracting a part of the exhaust in the exhaust pipe 11 </ b> A upstream of the heat exchanger 3 and downstream of the turbine 2 using the suction negative pressure of the engine 1. That is, when the throttle valve is closed, such as when the engine is under low load, a large pressure difference is generated before and after the throttle valve. At this time, when the flow control valve 17 is fully opened, the differential pressure between the exhaust pressure in the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the turbine 2 and the suction negative pressure in the intake pipe 14A downstream of the throttle portion 15 is large. Thus, a part of the exhaust gas in the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the turbine 2 is extracted to the intake pipe 14A downstream of the throttle portion 15 by this large differential pressure. Here, the “suction negative pressure” is a pressure lower than the atmospheric pressure generated downstream of the throttle unit 15 by the throttle valve that throttles the intake air.

  On the other hand, when the engine in which the slot valve is largely opened is in a high load operation, the flow control valve 17 is fully closed. This is because only a small pressure difference is generated before and after the throttle valve during high load operation of the engine. Under this influence, the exhaust pressure in the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the turbine 2 and the intake air downstream of the throttle unit 15 are affected. The differential pressure from the suction negative pressure in the pipe 14A becomes smaller than that in the low load operation of the engine, and the exhaust in the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the turbine 2 is extracted as much as during the low load operation of the engine. This is because it disappears.

  Here, the flow control valve 17 is a two-position valve in a fully open state and a fully closed state, but the amount of exhaust extracted from the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the turbine 2 in the engine low load operation region. It can also be set as the structure which can adjust. For this purpose, the opening degree of the flow control valve 17 may be constituted by a valve capable of duty control.

  Next, an intake air compressor 21 (supercharger) for supercharging the intake air is arranged on the compressor side 4 and coaxially with the turbine 1 and the compressor 4, and the driving force regenerated arbitrarily from waste heat is supplied to the intake air. The structure is such that it can be transmitted to the compressor 21. That is, a bypass passage 22 that bypasses the intake pipe 14 is provided upstream of the throttle portion 15, and an intake compressor 21 is provided in the bypass passage 22.

  A three-way valve 24 is provided at a branch portion of the bypass passage 22 from the intake passage 14. The three-way valve 24 is for switching the flow path of the intake air. When the intake air is introduced into the intake compressor 21 in order to operate the intake compressor 21, the intake passage 14B and the branch passage 22 upstream of the valve 24 are connected. The communication between the intake passage 14B upstream of the valve 24 and the intake passage 14C downstream of the valve 24 is blocked. When the intake compressor 21 is not operated, the communication between the intake passage 14B upstream of the valve 24 and the branch passage 22 is blocked, and the intake passage 14B upstream of the valve 24 and the intake passage 14C downstream of the valve 24 are communicated.

  Further, a shaft 25 connecting the intake compressor 21 and the compressor 4 is provided with a first clutch 26 for arbitrarily connecting and disconnecting the intake compressor 21 and the compressor 4, and a shaft connecting the turbine 2 and the motor generator 8. 27 includes a second clutch 28 for allowing the turbine 2 and the motor generator 8 to be arbitrarily connected and disconnected. That is, when the intake compressor 21 is operated, the first clutch 26 is connected and the second clutch 28 is disconnected. When the intake compressor 21 is not operated, the first clutch 26 is disconnected and the second clutch 28 is connected. The provision of the two clutches 26 and 28 in this manner stops the rotation of the intake compressor 21 when the intake compressor 21 is not required, and causes the motor generator 8 to function as a generator to perform waste heat recovery instead. Because. The type of clutch such as electromagnetic type and hydraulic type is not limited.

  When the intake air is guided to the intake compressor 21 by the three-way valve 24 via the bypass passage 22 and the first clutch 26 is connected, the intake compressor 21 is operated by the power of the rotating body composed of the turbine 2 and the compressor 4, and the intake air The intake air supercharged by the compressor 21 is returned to the intake passage 14 upstream of the throttle portion 15.

  A branch passage 29 branched from the bypass passage 22 is provided, and a safety valve 30 is provided in the branch passage 29. The safety valve 30 is opened when the supercharging pressure by the intake compressor 21 exceeds a limit value.

  In this manner, the power regenerated from waste heat can be transmitted to the intake compressor 21 and the intake compressor 21 can be made to work or not work depending on the operating conditions.

  The engine 1 is provided with a cooling device including a water jacket 31, a radiator 32, a water pump 33, a thermostat 34, and a bypass passage 35 formed so as to cover the cylinder block and the cylinder head.

  In this case, in the first embodiment, the heat exchanger 3 for cooling the exhaust from the turbine 2 and the radiator 32 for cooling the engine coolant are integrated. That is, the heat exchanger 3 is a direct heat exchanger that exchanges heat between the high-temperature exhaust gas and the low-temperature cooling water, and the pipe line 3A through which the exhaust gas that enters at high temperature and releases heat flows. And a conduit 3B through which cooling water that enters in a low temperature state and receives heat flows. In the radiator 32, a tube 32 </ b> A for cooling the high-temperature coolant discharged from the engine outlet 31 </ b> A of the water jacket 31 with outside air is provided, so that it branches from the coolant passage 36 downstream of the water pump 33. A branch passage 37 connected to one end 3C (right end) of the conduit 3B in the heat exchanger 3 and a return passage 38 connected to the other end 3D (left end) of the conduit 3B and joined to the inlet 32C of the radiator are provided. ing.

  If comprised in this way, the cold cooling water which came out of the radiator exit 32B will flow into the water jacket 31 in an engine main body. Cooling water in the water jacket 31 heated by heat exchange with the cylinder block and the cylinder head exits the engine body from the engine outlet 31A, flows through the tube 32A in the radiator 32 from the inlet 32C of the radiator 32, and dissipates heat here. . Further, the cold cooling water exiting from the radiator outlet 32 </ b> B flows from the cooling water passage 36 downstream of the water pump 33 through the branch passage 37 through the pipe 3 </ b> B in the heat exchanger 3. Cooling water in the pipe line 3B heated by the exhaust gas flowing through the pipe line 3A in the heat exchanger 3 also flows through the tube 32A in the radiator 32 from the inlet 32C of the radiator 32 via the return path 38 and dissipates heat here. That is, a circulation path 39 for engine cooling water is mainly formed by four of the tube 32A in the radiator 32, the branch passage 37, the pipe 3B in the heat exchanger 3, and the return passage 38.

  The branch passage 37 is provided with a flow path switching valve 40. The flow path switching valve 40 switches whether the cooling water is allowed to flow into the heat exchanger 3 or not, and is opened when the cooling water is introduced into the heat exchanger 3, and when the cooling water is not introduced into the heat exchanger 3. Closed.

  A safety valve 42 is also provided in the passage 41 branched from the exhaust pipe 11 upstream of the turbine 2.

The flow control valve 17, the three-way valve 24, the two clutches 26 and 28, and the flow path switching valve 40 are controlled by an engine controller 45. As shown in FIG. 2, the engine controller 45 includes an air flow meter 46, a crank angle sensor 47, a vehicle speed sensor 48,
Signals from a front air-fuel ratio sensor 49 provided upstream of the three-way catalyst 12 and a rear air-fuel ratio sensor 50 provided downstream of the three-way catalyst 12 are input. The engine controller 45 determines the engine operation mode based on these signals, and performs control according to the determined engine operation mode.

  The engine 1 is a gasoline engine having a throttle unit 15. Therefore, the engine controller 45 performs air-fuel ratio feedback control based on the output of the front air-fuel ratio sensor 49 and the output of the rear air-fuel ratio sensor 50 so that the actual oxygen storage amount of the three-way catalyst 12 becomes the target value. ing. In order to improve fuel efficiency, fuel injection from the fuel injection valve to the engine 1 is cut when the vehicle is decelerated. The engine is not limited to a gasoline engine, and may be a diesel engine as long as the throttle unit 15 is provided.

  Hereinafter, typical engine operation modes (high load operation, low load operation, vehicle deceleration, start time, cold time) will be described individually.

<1> During high-load operation of the engine The heat exchanger 3 cools the exhaust gas emitted from the engine to obtain driving force. That is, the flow path switching valve 40 is switched to allow cooling water to flow through the heat exchanger 3, and the exhaust discharged from the engine is cooled by the heat exchanger 3. By cooling the exhaust gas with the heat exchanger 3, the volume of the exhaust gas input to the compressor 4 is reduced, and the compression work of the compressor 4 is reduced by the reduction of the exhaust volume corresponding to the cooling. 4 increases the driving force of the rotating body. The intake compressor 21 is operated with the increased driving force. That is, the intake air is guided to the intake compressor 21 by the three-way valve 24, the first clutch 26 is connected, and the second clutch 28 is disconnected.

  Further, when the engine is operating at a high load, the differential pressure across the throttle portion 15 does not increase, and the effect of extracting the exhaust from the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the turbine 2 cannot be obtained so much. Is fully closed.

<2> During low-load operation of the engine or when the vehicle decelerates Exhaust gas emitted from the engine from the heat exchanger 3 is cooled to obtain driving force, and one exhaust gas is discharged from the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the turbine 2 Remove the part. That is, the flow path switching valve 40 is switched to allow cooling water to flow through the heat exchanger 3, and the exhaust discharged from the engine is cooled by the heat exchanger 3. By cooling the exhaust gas with the heat exchanger 3, the volume of the exhaust gas input to the compressor 4 is reduced, and the compression work of the compressor 4 is reduced by the reduction of the exhaust volume corresponding to the cooling. 4 increases the driving force of the rotating body. Unlike the high-load operation of the engine during low-load operation of the engine or deceleration of the vehicle, this increased driving force is used to operate the motor generator 8 as a generator. The intake compressor 21 does not work. That is, the first clutch 26 is disconnected and the second clutch 28 is connected without flowing the intake air to the intake compressor 21 by the three-way valve 24.

  On the other hand, unlike the high-load operation of the engine, the flow control valve 17 is opened and the exhaust gas is extracted from the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the turbine 2 into the bypass passage 16 to be cooled by the heat exchanger 3. The exhaust flow rate to be reduced is smaller than the case where the exhaust gas is not extracted from the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the turbine 2, and the heat exchanger 3 can be reduced in size by the decrease. Further, since the exhaust flow rate compressed by the compressor 4 is also reduced as compared with the case where the exhaust gas is not extracted from the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the turbine 2, the compression work performed by the compressor 4 is reduced by that amount. Waste heat recovery efficiency is improved.

  Now, the control may be different between when the engine is under low load and when the vehicle is decelerated. This will be described. FIG. 3 shows an example of driving the vehicle. In FIG. 3, the section from the timing of t2 to the timing of t3, and the section from the timing of t5 to the timing of t6 are at constant speed operation (during low load operation) with a vehicle speed of about 40-60 km / h. The valve 17 is opened to a predetermined opening a.

  On the other hand, in FIG. 3, the section from the timing t3 to the timing t4, and the section from the timing t6 to the timing t8 are when the vehicle is decelerating. The opening degree of the valve 17 is increased from the predetermined opening degree a to the predetermined opening degree b. The reason is as follows. That is, when the vehicle is decelerated, the fuel cut flag = 1 and the fuel injection from the fuel injection valve to the engine 1 is cut, so-called fuel cut is performed. Therefore, the three-way catalyst 12 provided in the exhaust pipe 11 during the fuel cut. If the oxygen storage amount in the inside increases and reaches a maximum value, there is a problem that NOx purification is hindered immediately after so-called fuel recovery, in which fuel injection from the fuel injection valve is resumed. Therefore, when the vehicle is decelerated where fuel cut is performed, the opening degree of the flow control valve 17 is increased from the predetermined opening degree a to the predetermined opening degree b than during low-load operation of the engine. The engine exhaust gas is returned to the intake pipe 14A downstream of the throttle portion 15 through the bypass passage 16 and circulated, thereby reducing the flow rate of the gas flowing through the three-way catalyst 12 and increasing the oxygen storage amount of the three-way catalyst 12. It is for suppressing.

  Here, the reason that the NOx purification is hindered is that the actual oxygen storage amount of the three-way catalyst 12 is the maximum oxygen storage because the engine controller 45 simultaneously performs the oxidation of HC and CO and the reduction of NOx. The air-fuel ratio feedback control is performed based on the output of the front air-fuel ratio sensor 49 upstream of the three-way catalyst 12 and the output of the rear air-fuel ratio sensor 50 downstream of the three-way catalyst 12 so as to be approximately half of the amount (target value). This is because if the oxygen of the three-way catalyst 12 becomes full when the fuel is cut, oxygen cannot be taken from NOx.

  In addition, the rotational speed of the turbine 2 can be further increased by the amount by which the opening degree of the flow control valve 17 is increased from the predetermined value a to the predetermined value b when the vehicle is decelerating than when the engine is under low load operation.

  In FIG. 3, the vehicle is accelerated from the timing t1 when the vehicle is stopped, the vehicle speed is kept constant from the timing t2, decelerated from the timing t3, re-accelerated from the timing t4, and the vehicle speed is kept constant from the timing t5. The model shows how the throttle valve opening and the opening of the flow control valve 17 change when the vehicle is decelerated from the timing of t6 and stops at the timing of t8.

  In principle, the intake compressor 21 is considered not to operate when the engine is under a low load or when the vehicle is decelerating. However, the relationship between drivability during acceleration from a low load operation state or reacceleration from the vehicle deceleration is considered. In consideration, the intake compressor 21 may be operated in advance even in a low load state or a vehicle deceleration state during acceleration from a low load state or reacceleration from vehicle deceleration.

<3> When the engine is started and when it is cold The exhaust gas is extracted from the upstream side of the heat exchanger 3 and the downstream side of the turbine 2. That is, by opening the flow control valve 17 and extracting the exhaust gas from the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the turbine 2, the passage from the turbine 2 to the compressor 4 can be made negative pressure at an early stage. Startability and responsiveness are improved.

  When the engine is cold started, the switching valve 40 is switched so that the cooling water does not flow to the heat exchanger 3. The reason why the cooling water does not flow to the heat exchanger 3 at the time of cold start of the engine is to give priority to warming up of the engine 1 at the time of cold start of the engine. This is because the completion of warm-up of the engine 1 is delayed as compared with the case where no cooling water is supplied to the engine 3.

  It is conceivable that the second clutch 28 is connected when the engine is started or cold. For example, since the exhaust heat is high during the warming up of the engine, the heat can be recovered by using the motor generator 8 as a generator.

  Note that when the engine is started and when it is cold, the intake air does not flow to the intake compressor 21, and the first clutch 26 is disconnected so that the intake compressor 21 does not work.

  This completes the individual description of a typical engine operation mode.

  Here, the effect of this embodiment is demonstrated.

  According to the present embodiment (the invention described in claim 1), the exhaust from the engine 1 is led to the turbine 2 and expanded to a negative pressure that is a value lower than the atmospheric pressure, and then led to the heat exchanger 3. In a waste heat recovery device that cools and discharges the cooled exhaust gas as power by compressing the exhaust gas from a negative pressure to an atmospheric pressure with a compressor 4 coaxial with the turbine 2, a bypass passage for extracting a part of the exhaust gas from the engine 1 Since 16 (exhaust extraction means) is provided, the compression work of the compressor 4 can be reduced by the amount of the extracted exhaust, and the waste heat recovery efficiency is improved.

  According to this embodiment (the invention described in claim 3), the engine 1 includes the throttle portion 15, and the exhaust extraction means is the exhaust pipe 11 </ b> A upstream of the heat exchanger 3 and downstream of the turbine 2 and the intake pipe downstream of the throttle portion 15. Since the bypass passage 16 communicates with 14A, the exhaust flow rate for cooling the heat exchanger 3 is reduced, so that the heat exchanger 3 can be reduced in size by the reduced amount. Moreover, since the flow rate of exhaust gas compressed by the compressor 4 is also reduced, the compression work of the compressor 4 is reduced, and the waste heat recovery efficiency is improved. Furthermore, since the inside of the exhaust pipe between the turbine 2 and the compressor 4 can be made negative pressure at an early stage, the startability and responsiveness of the reverse Brayton cycle are improved.

  According to the present embodiment (the invention described in claim 4), the intake compressor 21 (supercharger) is arranged coaxially with the compressor 4, and therefore the intake compressor using the rotating body including the turbine 2 and the compressor 4 as power. 21 can be driven regardless of the engine load state.

  According to this embodiment (the invention described in claim 5), the motor generator 8 is coaxial with the turbine 2 and on the turbine 2 side, and the intake turbine 21 (supercharger) is coaxial with the compressor 4 and on the compressor 4 side. And the clutches 26 and 28 that can arbitrarily connect and disconnect the motor generator 8 and the turbine 2 and the intake turbine 21 and the compressor 4, respectively, so that the rotating body including the turbine 2 and the compressor 4 is used as power. The intake turbine 21 and the motor generator 8 can be selectively driven.

  According to this embodiment (the invention described in claim 7), the engine 1 is mounted on a vehicle, the three-way catalyst 12 is disposed in the exhaust pipe 11 downstream of the compressor 4, and the flow control valve 17 is disposed in the bypass passage 16. Air-fuel ratio feedback control means for performing air-fuel ratio feedback control based on the output of the front air-fuel ratio sensor 49 and the output of the rear air-fuel ratio sensor 50 so that the actual oxygen storage amount of the three-way catalyst 12 becomes the target value. And a fuel cut means for cutting fuel injection from the fuel injection valve to the engine 1 when the vehicle is decelerating (cutting the fuel supply to the engine). It opens to (predetermined opening a), and the flow control valve 17 is fully closed during high-load operation of the engine, and the flow-control valve 17 is lower than during low-load operation of the engine during vehicle deceleration. Open to a predetermined opening (b) (see the third stage in FIG. 3), so even if the fuel is cut during deceleration of the vehicle, an increase in the oxygen storage amount of the three-way catalyst 12 during the fuel cut is suppressed. It is possible to suppress the generation of NOx immediately after the fuel recovery from the fuel cut.

  4 and 5 are schematic configuration diagrams of the waste heat recovery apparatus according to the second and third embodiments, and the same parts as those in FIG. 1 are denoted by the same reference numerals.

  First, the second embodiment is a simplification of the first embodiment. That is, the flow rate control valve 17 is deleted as shown in FIG. Thus, even when the flow control valve 17 is deleted, the throttle unit is closed during engine operation (when the engine is under low load operation, when the vehicle is decelerated, when the engine is started, and when the engine is cold) even when the throttle valve is closed. As a result, a large pressure difference occurs around 15, and as a result, the difference between the exhaust pressure in the exhaust pipe 11 </ b> A upstream of the heat exchanger 3 and downstream of the turbine 2 and the negative suction pressure in the intake pipe 14 </ b> A downstream of the throttle unit 15. The pressure is increased, and a part of the exhaust in the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the turbine 2 is extracted to the intake pipe 14A downstream of the throttle portion 15 via the bypass passage 16 due to the large differential pressure. Become. In other words, as long as the engine is operated when the throttle valve is closed, the same effect as in the first embodiment can be obtained with respect to extraction of exhaust gas. In other words, the compression work of the compressor 4 can be reduced by the amount of exhaust extracted through the bypass passage 16, and the effect of improving the waste heat recovery efficiency can be obtained.

  Further, in the second embodiment, the intake compressor 21, the bypass passage 22, the three-way valve 24, and the clutches 26 and 28 are omitted. Thus, in the second embodiment, exhaust energy is recovered as electric energy by using the motor generator 8 as a generator.

  Next, the third embodiment differs from the second embodiment in the exhaust extraction part. That is, in the second embodiment, the exhaust extraction part is the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the turbine 2 as shown in FIG. 4, but in the third embodiment, the exhaust pipe is exhausted as shown in FIG. The extraction part is an exhaust pipe 11B downstream of the heat exchanger 3 and upstream of the compressor 4.

  Here, if the engine load and the rotational speed are considered under the same operating conditions, the exhaust temperature in the exhaust pipe 11B downstream of the heat exchanger 3 and upstream of the turbine 4 is in the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the compressor 2. The exhaust pressure in the exhaust pipe 11B downstream of the heat exchanger 3 and upstream of the turbine 4 is considered to be the same as the exhaust pressure in the exhaust pipe 11A upstream of the heat exchanger 3 and downstream of the compressor 2. . That is, it is considered that there is no significant difference between the second embodiment and the third embodiment as the exhaust extraction part. Therefore, according to the third embodiment, the same effect as the second embodiment, that is, the compression work of the compressor 4 can be reduced by the amount of exhaust extracted through the bypass passage 16, and the waste heat recovery efficiency is improved. An effect is obtained.

  So far, the engine 1 has been considered from the side of the waste heat recovery device.

  Next, looking at the waste heat recovery device from the engine side, the bypass passage 16 provided for exhaust extraction in FIGS. 4 and 5 corresponds to a so-called exhaust recirculation (EGR) passage. That is, according to the second and third embodiments, the exhaust gas is recirculated while reducing the compression work of the compressor 4 by the amount of the exhaust extracted through the bypass passage 16 and improving the waste heat recovery efficiency. Is able to. Thus, when exhaust gas recirculation becomes possible, exhaust gas recirculation can be used for pumping loss reduction, combustion control, and the like.

  In this case, according to the second embodiment (the invention described in claim 3), the exhaust after the exhaust energy is recovered by the turbine 2, that is, the exhaust having a lower temperature than the exhaust upstream of the turbine 2 is passed through the bypass passage 16. Therefore, it is possible to recirculate the high-temperature exhaust gas upstream of the turbine 2 to the intake pipe 14A downstream of the throttle unit 15 via the bypass passage 16 as it is. The exhaust gas recirculation amount can be substantially increased.

  Further, according to the third embodiment (the invention described in claim 2), the exhaust gas further cooled by the heat exchanger 3 can be recirculated to the intake pipe 14 </ b> A downstream of the throttle portion 15 via the bypass passage 16. Therefore, the exhaust gas recirculation amount can be substantially increased as compared with the case where the exhaust gas upstream of the heat exchanger 3 and downstream of the turbine 2 is recirculated to the intake pipe 14A downstream of the throttle unit 15 via the bypass passage 16.

  However, since the flow rate control valve is not provided in the bypass passage 16 in FIGS. 4 and 5, the exhaust gas recirculation amount (EGR amount) and the exhaust gas recirculation rate (EGR rate) are not changed depending on the engine operating conditions. You can't control it. However, by using the motor generator 8 as a motor in FIGS. 4 and 5, it becomes possible to control the exhaust gas recirculation amount and the exhaust gas recirculation rate in accordance with the engine operating conditions. That is, even if the engine load and the rotational speed are the same, the exhaust gas recirculation amount (exhaust gas recirculation rate) flowing through the bypass passage 16 increases when the rotational speed of the turbine 2 is increased using the motor generator 8 as a motor. Conversely, if the rotational speed of the turbine 2 is reduced, the exhaust gas recirculation amount (exhaust gas recirculation rate) flowing through the bypass passage 16 can be reduced.

  As described above, in the second and third embodiments, the motor generator 8 is further used as a motor, and the rotational speed of the motor is controlled according to the operating condition of the engine (the invention according to claim 9). ) The exhaust gas recirculation amount and the exhaust gas recirculation rate can be freely controlled without providing an exhaust gas recirculation control valve (EGR valve) in the bypass passage 16.

  In the case of FIG. 1 as well, if the flow rate control valve 17 is kept fully open, the motor generator 8 is used as a motor, and the rotational speed of this motor is controlled according to the operating conditions of the engine. The recirculation amount and the exhaust gas recirculation rate can be freely controlled.

  FIG. 6 is a schematic configuration diagram of the waste heat recovery apparatus of the fourth embodiment, and the same parts as those in FIG. FIG. 6 replaces the second and third embodiments shown in FIGS.

  In the fourth embodiment, the exhaust extraction part is an exhaust pipe 11C downstream of the compressor 4 and the extracted exhaust is returned to the intake pipe 14A downstream of the throttle part 15 via the bypass passage 16.

  Here, comparing the fourth embodiment with the second and third embodiments, when the engine load and the rotational speed are the same operating conditions, the exhaust temperature in the exhaust pipe 11C downstream of the turbine 4 that is the exhaust extraction part, The exhaust pressure is higher than the exhaust pressure and the exhaust temperature in the exhaust pipes 11A and 11B downstream of the turbine 2 and upstream of the compressor 4 which are exhaust extraction portions of the second and third embodiments. This means that the operating range in which exhaust gas recirculation can be performed is expanded as compared with the second and third embodiments.

  Thus, according to the fourth embodiment (the invention described in claim 8), in a wider operation region (operation region in which the engine load and the rotation speed are parameters) than in the second and third embodiments. Exhaust gas recirculation (EGR) can be performed.

  Further, similarly to the second and third embodiments, the motor generator 8 is used as a motor, and the rotational speed of the motor is controlled according to the operating condition of the engine (the invention according to claim 9). The exhaust gas recirculation amount and the exhaust gas recirculation rate can be freely controlled without providing an exhaust gas recirculation control valve (EGR valve) in the bypass passage 16.

  However, in the fourth embodiment, the exhaust is not extracted from the upstream of the compressor 4 as in the second and third embodiments, so the compression work of the compressor 4 can be reduced by the amount of the extracted exhaust, and the waste heat The effect of improving the recovery efficiency cannot be obtained.

  In the embodiment, the case where the turbine 2 having a constant expansion ratio and the compressor 4 having a constant compression ratio are combined has been described. However, the turbine 2 capable of variably adjusting the expansion ratio and the compression ratio variably adjusted. The present invention can also be applied to a combination with a possible compressor.

  In the embodiment, the case where the heat exchanger 3 for cooling the exhaust from the turbine 2 and the radiator 32 for cooling the engine cooling water are integrated has been described. However, the present invention is not limited to this. You may comprise so that the refrigerant | coolant (cooling water) from the cooling device provided separately may be supplied to the heat exchanger 3. FIG.

1 is a schematic configuration diagram of a waste heat recovery apparatus according to a first embodiment of the present invention. The block diagram which shows the input-output to an engine controller. The timing chart which shows the change of the flow control valve opening degree in a certain driving | operation. The schematic block diagram of the waste heat recovery apparatus of 2nd Embodiment. The schematic block diagram of the waste-heat recovery apparatus of 3rd Embodiment. The schematic block diagram of the waste-heat recovery apparatus of 4th Embodiment. The basic block diagram of the waste heat recovery apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Turbine 3 Heat exchanger 4 Compressor 8 Motor generator 11 Exhaust pipe 11A Exhaust pipe 11A upstream of heat exchanger and downstream of turbine 11B Exhaust pipe downstream of heat exchanger and upstream of compressor 14 Intake pipe 14A Intake pipe downstream of throttle section 15 Throttle Part 16 Bypass passage (exhaust extraction means)
17 Flow control valve 21 Compressor for intake (supercharger)

Claims (9)

The exhaust from the engine is led to the turbine and expanded to a negative pressure that is lower than the atmospheric pressure, then led to a heat exchanger to be cooled, and the cooled exhaust is cooled from a negative pressure to an atmospheric pressure by a compressor coaxial with the turbine. In the waste heat recovery device that takes out as power by compressing and discharging to
A waste heat recovery apparatus comprising exhaust extraction means for extracting a part of exhaust from an engine. The engine has a throttle part,
The waste heat recovery apparatus according to claim 1, wherein the exhaust extraction means is a bypass passage that communicates an exhaust pipe upstream of the compressor and downstream of the heat exchanger and an intake pipe downstream of the throttle portion. The engine has a throttle part,
2. The waste heat recovery apparatus according to claim 1, wherein the exhaust extraction unit is a bypass passage that communicates an exhaust pipe upstream of the heat exchanger and downstream of the turbine and an intake pipe downstream of the throttle unit.   The waste heat recovery apparatus according to claim 1, wherein a supercharging device for supercharging intake air is disposed coaxially with the compressor. A motor generator is arranged coaxially with the turbine and on the turbine side, and a supercharging device for supercharging intake air is arranged coaxially with the compressor and on the compressor side, respectively.
The waste heat recovery apparatus according to claim 1, wherein the motor generator and the turbine and the supercharger and the compressor can be arbitrarily connected to each other. A flow path switching valve is provided in the bypass passage,
4. The waste heat recovery apparatus according to claim 2, wherein the flow path switching valve is fully opened during low load operation of the engine, and the flow path switching valve is fully closed during high load operation of the engine. . The engine is mounted on the vehicle,
A three-way catalyst is provided in the exhaust pipe downstream of the compressor, and a flow control valve is provided in the bypass passage.
Air-fuel ratio feedback control means for performing feedback control of the air-fuel ratio based on the output of the front air-fuel ratio sensor and the output of the rear air-fuel ratio sensor so that the actual oxygen storage amount of the three-way catalyst becomes the target value;
Fuel cut means for cutting fuel supply to the engine when the vehicle decelerates,
When the engine is under low load operation, the flow control valve is opened to a predetermined value. When the engine is under high load operation, the flow control valve is fully closed. When the vehicle is decelerating, the flow control valve is opened more than when the engine is under low load operation. The waste heat recovery apparatus according to claim 2 or 3, wherein The engine has a throttle part,
The waste heat recovery apparatus according to claim 1, wherein the exhaust extraction means is a bypass passage that communicates an exhaust pipe downstream of the compressor and an intake pipe downstream of the throttle portion.   The waste heat recovery apparatus according to any one of claims 2, 3, and 8, wherein a motor generator is disposed coaxially with the turbine, and the rotational speed of the motor is controlled using the motor generator as a motor. .

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