JP2013076372A - Waste heat utilization device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste heat utilization device which can drive an ejector by only waster heat from an engine.SOLUTION: The waste heat utilization device includes a rankine cycle (31) having a waste heat collector (22) for collecting heat of exhaust gas of the engine (2) to cooled water discharged from the engine (2). The waste heat utilization device includes: a cooled water flow rate control means (26) for controlling a flow rate of the cooled water to the waste heat collector (22) based on a temperature of the cooled water discharged from the engine (2); and an exhaust gas flow rate control means (7) for controlling the flow rate of the exhaust gas flowing into the waste heat collector (22) based on the temperature of the cooled water discharged from the waste heat collector.

Description

  The present invention relates to a waste heat utilization device, and more particularly to an integrated Rankine cycle and refrigeration cycle.

  A Rankine cycle system that reuses waste heat of engine exhaust gas as energy is known. Cited Document 1 discloses a cycle circulation for cooling an automobile engine, an exhaust gas heat exchanger for use of engine waste heat, an organic Rankine cycle circulation that drives an expansion device and circulates a first heat exchange medium. Is disclosed.

JP 2008-128254 A

  In the technique described in Patent Document 1 described above, the heat of exhaust gas is recovered by the refrigerant passing through the exhaust gas heat exchanger, and the refrigerant temperature is controlled by the amount of refrigerant circulating in the exhaust gas heat exchanger. At this time, if the refrigerant temperature exceeds the allowable temperature, the exhaust gas is passed through the exhaust gas bypass pipe by the valve to prevent the temperature of the exhaust gas heat exchanger from rising.

  In such a configuration, since it is necessary to set the allowable temperature to a temperature that does not affect the engine (for example, 110 ° C.), the exhaust gas waste heat near the allowable temperature can be sufficiently recovered. There wasn't.

  An object of this invention is to provide the waste heat recovery apparatus which can collect | recover the waste heat of an engine more efficiently.

  The present invention uses a waste heat recovery unit that recovers heat of exhaust gas of an engine into cooling water discharged from the engine, a heat exchanger that recovers heat of cooling water into a refrigerant, and a refrigerant discharged from the heat exchanger. An expander that generates power, a condenser that condenses the refrigerant that has exited the expander, a refrigerant pump that is driven by the power regenerated by the expander and that supplies the refrigerant from the condenser to the heat exchanger, The present invention is applied to a waste heat recovery device used for a vehicle including a Rankine cycle. In this waste heat recovery apparatus, cooling water flow rate limiting means for limiting the flow rate of cooling water to the waste heat recovery unit based on the temperature of the cooling water discharged from the engine, and cooling water discharged from the waste heat recovery unit Exhaust gas flow rate limiting means for limiting the flow rate of the exhaust gas flowing into the waste heat recovery unit based on the temperature.

  According to the present invention, the exhaust water flow rate limiting means and the cooling water flow rate limiting means reliably prevent the engine water temperature from exceeding the allowable temperature, and the cooling water temperature in the waste heat recovery device exceeds the engine water temperature limit temperature. As a result, the waste heat recovery efficiency can be increased.

It is a schematic block diagram of the integration cycle of embodiment of this invention. It is a schematic sectional drawing of the expander pump of embodiment of this invention. It is a schematic sectional drawing of the refrigerant | coolant pump of embodiment of this invention. It is a schematic sectional drawing of the expander of embodiment of this invention. It is the schematic which shows the function of the refrigerant | coolant system valve | bulb of embodiment of this invention. 1 is a schematic configuration diagram of a hybrid vehicle according to an embodiment of the present invention. 1 is a schematic perspective view of an engine according to an embodiment of the present invention. It is the schematic which looked at the hybrid vehicle of the embodiment of the present invention from the lower part. It is a characteristic view of the Rankine cycle operation area of the embodiment of the present invention. It is the timing chart which showed a mode when acceleration of a hybrid vehicle was performed in the middle of assisting rotation of an engine output shaft with the expander torque of embodiment of this invention. It is the timing chart which showed the mode of restart from the stop of Rankine cycle operation of the embodiment of the present invention. It is explanatory drawing of the exhaust pipe centering on the waste heat recovery device of embodiment of this invention. It is explanatory drawing which shows the cooling water temperature and flow volume in the waste heat recovery device of embodiment of this invention.

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

  FIG. 1 is a schematic diagram showing the entire system of a Rankine cycle which is a premise of the present invention. The Rankine cycle 31 in FIG. 1 is configured to share the refrigeration cycle 51 and the refrigerant and the condenser 38, and a cycle in which the Rankine cycle 31 and the refrigeration cycle 51 are integrated is hereinafter expressed as an integrated cycle 30. FIG. 4 is a schematic configuration diagram of the hybrid vehicle 1 on which the integrated cycle 30 is mounted. The integrated cycle 30 includes a circuit (passage) through which the refrigerant of the Rankine cycle 31 and the refrigeration cycle 51 circulates and components such as a pump, an expander, and a condenser provided in the middle, and a circuit for cooling water and exhaust. It shall refer to the entire system including (passage).

  In the hybrid vehicle 1, the engine 2, the motor generator 81, and the automatic transmission 82 are connected in series, and the output of the automatic transmission 82 is transmitted to the drive wheels 85 via the propeller shaft 83 and the differential gear 84. A first drive shaft clutch 86 is provided between the engine 2 and the motor generator 81. One of the frictional engagement elements of the automatic transmission 82 is configured as a second drive shaft clutch 87. The first drive shaft clutch 86 and the second drive shaft clutch 87 are connected to the engine controller 71, and their connection / disconnection (connected state) is controlled according to the driving conditions of the hybrid vehicle. In the hybrid vehicle 1, as shown in FIG. 7B, when the vehicle speed is in the EV traveling region where the efficiency of the engine 2 is poor, the engine 2 is stopped, the first drive shaft clutch 86 is disconnected, and the second drive shaft clutch 87 is connected. Thus, the hybrid vehicle 1 is caused to travel only by the driving force of the motor generator 81. On the other hand, when the vehicle speed deviates from the EV travel region and shifts to the Rankine cycle operation region, the engine 2 is operated to operate the Rankine cycle 31 (described later). The engine 2 includes an exhaust passage 3, and the exhaust passage 3 includes an exhaust manifold 4 and an exhaust pipe 5 connected to a collective portion of the exhaust manifold 4. The exhaust pipe 5 branches off from the bypass exhaust pipe 6 on the way, and the exhaust pipe 5 in the section bypassed by the bypass exhaust pipe 6 has a waste heat recovery unit for exchanging heat between the exhaust and the cooling water. 22. As shown in FIG. 6, the waste heat recovery unit 22 and the bypass exhaust pipe 6 are disposed between the underfloor catalyst 88 and the sub muffler 89 downstream thereof as a waste heat recovery unit 23 in which these are integrated.

  First, the engine coolant circuit will be described with reference to FIG. The cooling water of about 80 to 90 ° C. leaving the engine 2 flows separately into a cooling water passage 13 that passes through the radiator 11 and a bypass cooling water passage 14 that bypasses the radiator 11. Thereafter, the two flows are merged again by a thermostat valve 15 that determines the distribution of the flow rate of the cooling water flowing through both passages 13 and 14, and then returns to the engine 2 via the cooling water pump 16. The cooling water pump 16 is driven by the engine 2 and its rotation speed is synchronized with the engine rotation speed. The thermostat valve 15 relatively increases the amount of cooling water passing through the radiator 11 by increasing the valve opening on the cooling water passage 13 side when the cooling water temperature is high, and on the cooling water passage 13 side when the cooling water temperature is low. The amount of cooling water passing through the radiator 11 is relatively reduced by reducing the valve opening. When the coolant temperature is particularly low, such as before the engine 2 is warmed up, the radiator 11 is completely bypassed and the entire amount of coolant flows through the bypass coolant passage 14 side. On the other hand, the valve opening on the bypass cooling water passage 14 side is not fully closed, and when the flow rate of the cooling water flowing through the radiator 11 is increased, the flow rate of the cooling water flowing through the bypass cooling water passage 14 is However, the thermostat valve 15 is configured so that the flow does not stop completely. A bypass cooling water passage 14 that bypasses the radiator 11 is branched from the cooling water passage 13 and directly connected to a heat exchanger 36, which will be described later, and from the cooling water passage 13 to recover waste heat. The second bypass cooling water passage 25 connected to the heat exchanger 36 after passing through the vessel 22.

  The bypass cooling water passage 14 includes a heat exchanger 36 that exchanges heat with the refrigerant of the Rankine cycle 31. This heat exchanger 36 is an integrated evaporator and superheater. That is, two cooling water passages 36a and 36b are arranged in a row in the heat exchanger 36, and a refrigerant passage 36c through which the refrigerant of the Rankine cycle 31 flows is adjacent to the cooling water passage so that heat can be exchanged between the refrigerant and the cooling water. Is provided. Further, the passages 36a, 36b, and 36c are configured so that the refrigerant and the cooling water of the Rankine cycle 31 are in opposite directions when viewed from the whole heat exchanger 36.

  Specifically, one cooling water passage 36 a located on the upstream side (left side in FIG. 1) for the refrigerant of Rankine cycle 31 is interposed in the first bypass cooling water passage 24. The left side portion of the heat exchanger consisting of the cooling water passage 36a and the refrigerant passage portion adjacent to the cooling water passage directly introduces the cooling water from the engine 2 into the cooling water passage 36a, so that the Rankine that flows through the refrigerant passage 36c. It is an evaporator for heating the refrigerant of cycle 31.

  Cooling water that has passed through the waste heat recovery device 22 is introduced into the other cooling water passage 36b located on the downstream (right side in FIG. 1) side of the refrigerant in the Rankine cycle 31 via the second bypass cooling water passage 25. The right side portion of the heat exchanger (downstream side for the refrigerant of Rankine cycle 31) composed of the cooling water passage 36b and the refrigerant passage portion adjacent to the cooling water passage 36b is a cooling water obtained by further heating the cooling water at the outlet of the engine 2 by exhaust gas. Is a superheater that superheats the refrigerant flowing through the refrigerant passage 36c by introducing the refrigerant into the cooling water passage 36b.

  The cooling water passage 22 a of the waste heat recovery unit 22 is provided adjacent to the exhaust pipe 5. By introducing the cooling water at the outlet of the engine 2 into the cooling water passage 22a of the waste heat recovery unit 22, the cooling water can be heated to, for example, about 110 to 115 ° C. by high-temperature exhaust. The cooling water passage 22a is configured so that the exhaust and cooling water flow in opposite directions when the waste heat recovery device 22 is viewed from the top.

  A control valve 26 is interposed in the second bypass cooling water passage 25 provided with the waste heat recovery unit 22. As will be described later, the control valve 26 prevents the engine water temperature indicating the temperature of the cooling water inside the engine 2 from exceeding an allowable temperature (for example, 100 ° C.) for preventing deterioration of the efficiency of the engine 2 and knocking. In addition, when the detected temperature of the coolant temperature sensor 74 at the engine outlet exceeds a predetermined value, the opening degree of the control valve 26 is decreased. When the engine water temperature approaches the permissible temperature, the amount of cooling water passing through the waste heat recovery device 22 is reduced, so that it is possible to reliably prevent the engine water temperature from exceeding the permissible temperature.

  On the other hand, if the flow rate of the second bypass cooling water passage 25 is decreased, the cooling water temperature rising by the waste heat recovery device 22 is excessively increased and the cooling water is evaporated (boiling). There is a risk that the flow of the cooling water will deteriorate and the component temperature will rise excessively. In order to avoid this, a bypass exhaust pipe 6 that bypasses the waste heat recovery unit 22, and a thermostat valve 7 that controls the exhaust passage amount of the waste heat recovery unit 22 and the exhaust passage amount of the bypass exhaust pipe 6 are provided in the bypass exhaust pipe 6. It is provided at the branch. In other words, the thermostat valve 7 is configured such that the valve opening degree of the cooling water exiting the waste heat recovery unit 22 is such that the temperature of the cooling water exiting the waste heat recovery unit 22 does not exceed a predetermined temperature (for example, boiling temperature 120 ° C.). Adjusted based on temperature.

  The heat exchanger 36, the thermostat valve 7, and the waste heat recovery unit 22 are integrated as a waste heat recovery unit 23, and are arranged in the middle of the exhaust pipe under the floor at the approximate center in the vehicle width direction.

  If the temperature of the cooling water from the bypass cooling water passage 14 toward the thermostat valve 15 is sufficiently lowered by exchanging heat with the refrigerant of the Rankine cycle 31 by the heat exchanger 36, for example, the cooling water passage 13 side of the thermostat valve 15 The amount of cooling water passing through the radiator 11 is relatively reduced. Conversely, when the temperature of the cooling water from the bypass cooling water passage 14 toward the thermostat valve 15 becomes high due to the Rankine cycle 31 not being operated, the valve opening of the thermostat valve 15 on the cooling water passage 13 side is increased. The amount of cooling water passing through the radiator 11 is relatively increased. Based on the operation of the thermostat valve 15, the cooling water temperature of the engine 2 is appropriately maintained, and heat is appropriately supplied (recovered) to the Rankine cycle 31.

  Next, Rankine cycle 31 will be described. Here, Rankine cycle 31 is not a simple Rankine cycle, but is configured as a part of integrated cycle 30 integrated with refrigeration cycle 51. Hereinafter, the basic Rankine cycle 31 will be described first, and then the refrigeration cycle will be referred to.

  The Rankine cycle 31 is a system that recovers waste heat of the engine 2 to a refrigerant through cooling water of the engine 2 and regenerates the recovered waste heat as power. The Rankine cycle 31 includes a refrigerant pump 32, a heat exchanger 36 as a superheater, an expander 37, and a condenser (condenser) 38, and each component is connected by refrigerant passages 41 to 44 through which a refrigerant (R134a and the like) circulates. Has been.

  The shaft of the refrigerant pump 32 is connected to the output shaft of the expander 37 on the same shaft, and the refrigerant pump 32 is driven by the output (power) generated by the expander 37 and the generated power is used as the output shaft of the engine 2 ( (Refer to FIG. 2A). That is, the shaft of the refrigerant pump 32 and the output shaft of the expander 37 are arranged in parallel with the output shaft of the engine 2, and the belt 34 is provided between the pump pulley 33 provided at the tip of the shaft of the refrigerant pump 32 and the crank pulley 2a. (See FIG. 1). Note that a gear-type pump is employed as the refrigerant pump 32 of the present embodiment, and a scroll-type expander is employed as the expander 37 (see FIGS. 2B and 2C).

  Further, an electromagnetic clutch (hereinafter referred to as “expander clutch”) 35 (first clutch) is provided between the pump pulley 33 and the refrigerant pump 32, and the refrigerant pump 32 and the expander 37 are connected to the engine. 2 (see FIG. 2A). Therefore, the expander 37 is connected by connecting the expander clutch 35 when the output generated by the expander 37 exceeds the driving force of the refrigerant pump 32 and the friction of the rotating body (when the predicted expander torque is positive). Rotation of the engine output shaft can be assisted (assisted) by the output generated. Thus, fuel efficiency can be improved by assisting rotation of an engine output shaft using energy obtained by waste heat recovery. Further, the energy for driving the refrigerant pump 32 that circulates the refrigerant can also be covered by the recovered waste heat. The expander clutch 35 may be provided anywhere in the power transmission path from the engine 2 to the refrigerant pump 32 and the expansion register 37.

  The refrigerant from the refrigerant pump 32 is supplied to the heat exchanger 36 through the refrigerant passage 41. The heat exchanger 36 is a heat exchanger that causes heat exchange between the coolant of the engine 2 and the refrigerant, vaporizes the refrigerant, and superheats the refrigerant.

  The refrigerant from the heat exchanger 36 is supplied to the expander 37 through the refrigerant passage 42. The expander 37 is a steam turbine that converts heat into rotational energy by expanding the vaporized and superheated refrigerant. The power recovered by the expander 37 drives the refrigerant pump 32 and is transmitted to the engine 2 via the belt transmission mechanism to assist the rotation of the engine 2.

  The refrigerant from the expander 37 is supplied to the condenser 38 via the refrigerant passage 43. The condenser 38 is a heat exchanger that causes heat exchange between the outside air and the refrigerant to cool and liquefy the refrigerant. For this reason, the condenser 38 is arranged in parallel with the radiator 11 and is cooled by the radiator fan 12.

  The refrigerant liquefied by the condenser 38 is returned to the refrigerant pump 32 via the refrigerant passage 44. The refrigerant returned to the refrigerant pump 32 is sent again to the heat exchanger 36 by the refrigerant pump 32 and circulates through each component of the Rankine cycle 31.

  The refrigerant passage 44 extends upward from the inlet of the refrigerant pump 32 as shown in FIG.

  Next, the refrigeration cycle 51 will be described. Since the refrigerating cycle 51 shares the refrigerant circulating through the Rankine cycle 31, it is integrated with the Rankine cycle 31, and the configuration of the refrigerating cycle 51 itself is simplified. That is, the refrigeration cycle 51 includes a compressor (compressor) 52, a condenser 38, and an evaporator (evaporator) 55.

  The compressor 52 is a fluid machine that compresses the refrigerant of the refrigeration cycle 51 to a high temperature and a high pressure, and is driven by the engine 2. That is, as shown in FIG. 4, the compressor pulley 53 is fixed to the drive shaft of the compressor 52, and the belt 34 is wound around the compressor pulley 53 and the crank pulley 2a. The driving force of the engine 2 is transmitted to the compressor pulley 53 via the belt 34, and the compressor 52 is driven. An electromagnetic clutch (hereinafter referred to as “compressor clutch”) 54 (second clutch) is provided between the compressor pulley 53 and the compressor 52 so that the compressor 52 and the compressor pulley 53 can be connected and disconnected. ing.

  Returning to FIG. 1, the refrigerant from the compressor 52 joins the refrigerant passage 43 via the refrigerant passage 56 and is then supplied to the condenser 38. The condenser 38 is a heat exchanger that condenses and liquefies the refrigerant by heat exchange with the outside air. The liquid refrigerant from the condenser 38 is supplied to an evaporator (evaporator) 55 through a refrigerant passage 57 branched from the refrigerant passage 44. The evaporator 55 is disposed in the case of the air conditioner unit in the same manner as a heater core (not shown). The evaporator 55 is a heat exchanger that evaporates the liquid refrigerant from the condenser 38 and cools the conditioned air from the blower fan by the latent heat of evaporation at that time.

  The refrigerant evaporated by the evaporator 55 is returned to the compressor 52 through the refrigerant passage 58. Note that the mixing ratio of the conditioned air cooled by the evaporator 55 and the conditioned air heated by the heater core is adjusted to a temperature set by the occupant according to the opening of the air mix door.

  Note that the evaporator 55, a part of the refrigerant male passage 44 connecting the condenser 38 and the evaporator 55, and the refrigerant passage 57 are arranged at a position higher than the inlet of the refrigerant pump 32. The refrigerant passage 44 branches at the refrigeration cycle branch point 45 and is connected to the refrigerant passage 57 (see FIG. 8).

  In the integrated cycle 30 including the Rankine cycle 31 and the refrigeration cycle 51, various valves are appropriately provided in the middle of the circuit in order to control the refrigerant flowing in the cycle. For example, in order to control the refrigerant circulating in the Rankine cycle 31, the refrigerant passage 44 that connects the pump upstream valve 61, the heat exchanger 36, and the expander 37 to the refrigerant passage 44 that connects the refrigeration cycle branch point 45 and the refrigerant pump 32. 42 is provided with an expander upstream valve 62. The refrigerant passage 41 that connects the refrigerant pump 32 and the heat exchanger 36 is provided with a check valve 63 to prevent the refrigerant from flowing backward from the heat exchanger 36 to the refrigerant pump 32. The refrigerant passage 43 that connects the expander 37 and the refrigeration cycle merge point 46 is also provided with a check valve 64 to prevent the refrigerant from flowing back from the refrigeration cycle merge point 46 to the expander 37. Further, an expander bypass passage 65 that bypasses the expander 37 from the upstream of the expander upstream valve 62 and merges upstream of the check valve 64 is provided, and a bypass valve 66 is provided in the expander bypass passage 65. Further, a pressure regulating valve 68 is provided in a passage 67 that bypasses the bypass valve 66. Also on the refrigeration cycle 51 side, an air conditioner circuit valve 69 is provided in the refrigerant passage 57 that connects the refrigeration cycle branch point 45 and the evaporator 55.

  The four valves 61, 62, 66, and 69 are all electromagnetic on-off valves. An expander upstream pressure signal detected by the pressure sensor 72, a condenser outlet refrigerant pressure Pd signal detected by the pressure sensor 73, a rotation speed signal of the expander 37, and the like are input to the engine controller 71. The engine controller 71 controls the compressor 52 of the refrigeration cycle 51 and the radiator fan 12 based on these input signals in accordance with predetermined operating conditions, and also controls the four electromagnetic on-off valves 61, 62, 66. , 69 is controlled.

  For example, the expander torque (regenerative power) is predicted based on the expander upstream pressure detected by the pressure sensor 72 and the expander rotational speed, and when the predicted expander torque is positive (assist rotation of the engine output shaft). The expander clutch 35 is engaged, and when the predicted expander torque is zero or negative, the expander clutch 35 is released. Based on the sensor detection pressure and expander rotational speed, the expander torque can be predicted with higher accuracy than when the expander torque (regenerative power) is predicted from the exhaust temperature. Accordingly, the expander clutch 35 can be appropriately engaged / released (refer to Japanese Unexamined Patent Application Publication No. 2010-190185 for details).

  The four on-off valves 61, 62, 66, 69 and the two check valves 63, 64 are refrigerant valves. The functions of these refrigerant valves are shown again in FIG.

  In FIG. 3, the pump upstream valve 61 is provided at the inlet of the refrigerant pump 32 (see FIG. 8). The pump upstream valve 61 prevents the refrigerant (including the lubricating component) from being biased to the Rankine cycle 31 by closing the pump upstream valve 61 under a predetermined condition that makes the refrigerant easily biased to the Rankine cycle 31 circuit as compared to the circuit of the refrigeration cycle 51. Therefore, as will be described later, the circuit of the Rankine cycle 31 is closed in cooperation with the check valve 64 downstream of the expander 37. The expander upstream valve 62 blocks the refrigerant passage 42 when the refrigerant pressure from the heat exchanger 36 is relatively low so that the refrigerant from the heat exchanger 36 can be held until the pressure becomes high. is there. Thereby, even when the expander torque cannot be sufficiently obtained, the heating of the refrigerant is promoted, and for example, the time until the Rankine cycle 31 is restarted (regeneration can actually be performed) can be shortened. The bypass valve 66 is opened so that the refrigerant pump can be operated after bypassing the expander 37 when the amount of refrigerant existing on the Rankine cycle 31 side is not sufficient when the Rankine cycle 31 is started. This is to shorten the start-up time of the cycle 31. By operating the refrigerant pump 32 after the expander 37 is bypassed, the refrigerant temperature at the outlet of the condenser 38 or the inlet of the refrigerant pump 32 has a predetermined temperature difference (subcool degree SC) from the boiling point considering the pressure at that portion. ) If the state lowered as described above is realized, the Rankine cycle 31 is ready to supply a sufficient liquid refrigerant.

  The check valve 63 upstream of the heat exchanger 36 is for maintaining the refrigerant supplied to the expander 37 at a high pressure in cooperation with the bypass valve 66, the pressure adjusting valve 68, and the expander upstream valve 62. When the Rankine cycle regenerative efficiency is low, the Rankine cycle operation is stopped, the circuit is closed over the front and rear sections of the heat exchanger, the refrigerant pressure during the stop is increased, and the high-pressure refrigerant is used. Allow the Rankine cycle to restart quickly. The pressure regulating valve 68 functions as a relief valve that opens when the pressure of the refrigerant supplied to the expander 37 becomes too high and releases the refrigerant that has become too high.

  The check valve 64 downstream of the expander 37 is for preventing the bias of the refrigerant to the Rankine cycle 31 in cooperation with the above-described pump upstream valve 61. If the engine 2 is not warmed immediately after the start of the operation of the hybrid vehicle 1, the Rankine cycle 31 becomes cooler than the refrigeration cycle 51, and the refrigerant may be biased toward the Rankine cycle 31 side. Although the probability of being biased toward the Rankine cycle 31 is not so high, for example, immediately after the start of vehicle operation in summer, the cooling capacity is most demanded in the situation where it is desired to cool the interior quickly, so the slight uneven distribution of refrigerant is also eliminated. Therefore, there is a demand for securing the refrigerant for the refrigeration cycle 51. Therefore, a check valve 64 is provided to prevent uneven distribution of refrigerant to the Rankine cycle 31 side.

  The compressor 52 does not have a structure in which the refrigerant can freely pass when driving is stopped, but can prevent the refrigerant from being biased toward the refrigeration cycle 51 in cooperation with the air conditioner circuit valve 69. This will be described. When the operation of the refrigeration cycle 51 stops, the refrigerant may move from the relatively high temperature Rankine cycle 31 side to the refrigeration cycle 51 side during steady operation, and the refrigerant circulating through the Rankine cycle 31 may be insufficient. In the refrigeration cycle 51, the temperature of the evaporator 55 is low immediately after the cooling is stopped, and the refrigerant tends to accumulate in the evaporator 55 having a relatively large volume and a low temperature. In this case, the movement of the refrigerant from the condenser 38 to the evaporator 55 is interrupted by stopping the driving of the compressor 52, and the air conditioner circuit valve 69 is closed to prevent the refrigerant from being biased to the refrigeration cycle 51.

  Next, FIG. 5 is a schematic perspective view of the engine 2 showing a package of the entire engine. 5 is characterized in that the heat exchanger 36 is arranged vertically above the exhaust manifold 4. By placing the heat exchanger 36 in the space vertically above the exhaust manifold 4, the mountability of the Rankine cycle 31 to the engine 2 is improved. The engine 2 is provided with a tensioner pulley 8.

  Next, a basic operation method of the Rankine cycle 31 will be described with reference to FIGS. 7A and 7B.

  First, FIGS. 7A and 7B are operation region diagrams of the Rankine cycle 31. FIG. FIG. 7A shows the Rankine cycle operating range when the horizontal axis is the outside air temperature and the vertical axis is the engine water temperature (cooling water temperature). FIG. 7B is the engine rotational speed and the vertical axis is the engine torque (engine load). The operating range of Rankine cycle 31 is shown.

  7A and 7B, the Rankine cycle 31 is operated when a predetermined condition is satisfied, and the Rankine cycle 31 is operated when both of these conditions are satisfied. In FIG. 7A, the operation of the Rankine cycle 31 is stopped in a region on the low water temperature side where priority is given to warming up the engine 1 and a region on the high outside air temperature side where the load on the compressor 52 increases. During warm-up when the exhaust temperature is low and the recovery efficiency is poor, the Rankine cycle 31 is not operated, so that the coolant temperature is quickly raised. The Rankine cycle 31 is stopped at a high outside air temperature where high cooling capacity is required, and sufficient refrigerant and cooling capacity of the condenser 38 are provided to the refrigeration cycle 51. In FIG. 7B, since the vehicle is a hybrid vehicle, the operation of the Rankine cycle 31 is stopped in the EV traveling region and the region on the high rotational speed side where the friction of the expander 37 increases. Since it is difficult to make the expander 37 have a high-efficiency structure with little friction at all rotation speeds, in the case of FIG. 7, the expansion is performed so that the friction is small and the efficiency is high in the engine rotation speed range where the operation frequency is high. The machine is configured (the dimensions of each part of the expander are set).

  FIG. 8 is a timing chart showing a model when the hybrid vehicle 1 is accelerated while assisting the rotation of the engine output shaft by the expander torque. Note that, on the right side of FIG. 8, a state in which the operating state of the expander 37 changes at this time is shown on the expander torque map. In the range delimited by the contour lines of the expander torque map, the expander torque is the highest in the portion where the expander rotational speed is low and the expander upstream pressure is high (upper left), the expander rotational speed is high, and the expander upstream pressure is low. The expander torque tends to be smaller as it goes (lower right). In particular, the shaded area represents a region where the expander torque becomes negative on the premise of driving the refrigerant pump and becomes a load on the engine.

  Until t1 when the driver steps on the accelerator pedal, constant speed running is continued and the expander 37 generates a positive torque, and rotation assist of the engine output shaft is performed by the expander torque.

  After t1, the rotation speed of the expander 37, that is, the rotation speed of the pump 32 increases in proportion to the engine rotation speed, but the increase in the exhaust gas temperature or the cooling water temperature has a delay with respect to the increase in the engine rotation speed. Therefore, the ratio of the recoverable heat amount to the refrigerant amount increased by the increase in the rotational speed of the pump 32 is reduced.

  Accordingly, as the expander rotational speed increases, the refrigerant pressure upstream of the expander decreases and the expander torque decreases.

  When the expander torque decreases, the expander 37 and the refrigerant pump 32 are rotated by the driving force of the engine, but rather become an engine load. Therefore, when the expander torque falls below a predetermined value, the expander The clutch 35 is disengaged to avoid the drag phenomenon of the expander 37 (turned by the engine and instead becoming a load on the engine).

  In FIG. 8, the expander upstream valve 62 is closed at the timing t2 prior to t3 when the expander clutch 35 is disconnected, and the expander upstream pressure is almost the same as the expander downstream pressure at the timing t3. . Thus, by closing the expander upstream valve 62 before the expander clutch 35 is disconnected, the refrigerant pressure upstream of the expander (of the refrigerant flowing into the expander) is sufficiently reduced, and the expander clutch 35 is disconnected. The over-rotation of the expander 37 at the time of occurrence is prevented.

  After t3, the expander upstream pressure rises again due to the increase in the heat radiation amount of the engine 2, and at the timing t4, the expander upstream valve 62 is switched from the closed state to the open state, so that the refrigerant is supplied to the expander 37. Resumed. Further, the expander clutch 35 is connected again at t4. By reconnecting the expander clutch 35, rotation assist of the engine output shaft by the expander torque is resumed.

  FIG. 9 is a model of restarting the Rankine cycle in a manner different from that in FIG. 8 (control of t4) after the operation of the Rankine cycle is stopped with the expander upstream valve 62 closed and the expander clutch 35 disconnected. It is the timing chart shown by.

  When the driver depresses the accelerator pedal at the timing of t11, the accelerator opening increases. At t11, the Rankine cycle operation is stopped. For this reason, the expander torque is maintained at zero.

  As the engine rotation speed increases from t11, the heat dissipation amount of the engine 2 increases. Due to the increase in the heat dissipation amount, the temperature of the coolant flowing into the heat exchanger 36 increases, and the temperature of the refrigerant in the heat exchanger 36 increases. To rise. Since the expander upstream valve 62 is closed, the refrigerant pressure upstream of the expander upstream valve 62, that is, the expander upstream pressure, rises due to the increase in the refrigerant temperature by the heat exchanger 36 (t11 to t12).

  Switching from the Rankine cycle non-operating range to the Rankine cycle operating range is performed by the change in the operating state. When the expander clutch 35 is switched from the disconnected state to the connected state and the expander 37 is connected to the engine output shaft when the expander upstream valve 62 is not provided and the operation shifts to the Rankine cycle operation region, the expander 37 is connected. Becomes a load on the engine 2 and causes a torque shock.

  On the other hand, in FIG. 9, when switching to the Rankine cycle operation region, the expander upstream valve 62 is not immediately switched from the closed state to the open state. That is, the expander upstream valve 62 remains closed even after the transition to the Rankine cycle operation region.

  Eventually, it is determined that the expander 37 can be operated (driven) at a timing t12 when the differential pressure between the expander upstream pressure and the expander downstream pressure becomes greater than or equal to a predetermined pressure, and the expansion valve upstream valve 62 is changed from the closed state. Switch to the open state. By switching the expansion valve upstream valve 62 to the open state, a predetermined pressure of refrigerant is supplied to the expander 37, and the rotation speed of the expander rapidly increases from zero.

  At the timing t13 when the expander rotation speed reaches the engine rotation speed due to the increase in the expander rotation speed, the expander clutch 35 is switched from disconnection to connection. If the expander clutch 35 is connected before the expander 37 sufficiently increases the rotational speed, the expander 37 becomes an engine load and torque shock may occur. On the other hand, when the expander clutch 35 is connected at t13 at which the rotational speed difference from the engine output shaft disappears, the expander 37 becomes an engine load, and the torque shock associated with the engagement of the expander clutch 35. Can also be prevented.

  Next, control in the waste heat recovery unit 22 will be described.

  FIG. 10 is an explanatory diagram of the exhaust pipe 5 (waste heat recovery unit 23) centering on the waste heat recovery unit 22 of the present embodiment.

  In FIG. 10, the flow of exhaust gas is indicated by solid arrows, and the flow of cooling water is indicated by dotted arrows.

  As described above, the waste heat recovery unit 22 is attached to the exhaust pipe 5. The waste heat recovery unit 22 is configured to allow the exhaust gas and the cooling water to circulate, and raises the temperature of the cooling water by heat exchange by the heat of the high temperature exhaust gas. The cooling water whose temperature has risen heats the refrigerant in the Rankine cycle 31 in the heat exchanger 36.

  The flow rate of the cooling water introduced into the waste heat recovery unit 22 is controlled by the control valve 26. The engine controller 71 controls the flow rate of the control valve based on the coolant temperature at the outlet of the engine 2 detected by the coolant temperature sensor 74. That is, the engine controller 71 controls the opening degree of the control valve 26 based on the cooling water temperature sensor 74 to limit the cooling water flow rate, thereby constituting the cooling water flow rate limiting means.

  When the coolant temperature detected by the coolant temperature sensor 74 is equal to or higher than the first predetermined temperature, the engine controller 71 decreases the opening of the control valve 26 and the amount of coolant passing through the waste heat recovery unit 22. Decrease.

  The first predetermined temperature is a temperature that does not affect the engine 2, for example, a temperature having a predetermined margin than a temperature at which overheating occurs.

  By controlling in this way, the cooling water temperature, in particular, the temperature of the cooling water temperature circulating through the engine 2 (engine water temperature) is prevented from exceeding the allowable temperature. Since the circulation of the cooling water in the waste heat recovery device has been reduced, the amount of heat transferred to the cooling water can be quickly reduced.

  A thermostat valve 7 is provided in front of the waste heat recovery unit of the exhaust pipe 5.

  The thermostat valve 7 is configured to rotate about a shaft 7b, and closes the bypass exhaust pipe 6 to allow exhaust gas to flow through the waste heat recovery unit 22, or closes the exhaust pipe 5 to bypass exhaust. The exhaust gas is circulated through the pipe 6 to control whether the exhaust gas flow to the waste heat recovery unit 22 is restricted.

  The thermostat valve 7 includes a thermostat 7a. The thermostat 7 a is provided on the cooling water outlet side of the waste heat recovery unit 22. The thermostat 7a is configured to be expandable and contractible based on the cooling water outlet temperature of the waste heat recovery unit 22.

  The thermostat 7a is connected to the thermostat valve 7 through a shaft 7b. By expanding and contracting according to the temperature of the cooling water that the thermostat 7a passes through, the thermostat valve 7 rotates about the shaft 7b in response to the thermostat 7a. Thereby, the opening degree of the exhaust pipe 5 is changed.

  The thermostat valve 7 can change its opening according to the coolant temperature at the outlet of the waste heat recovery unit 22, and change the exhaust passage amount of the waste heat recovery unit 22 and the exhaust passage amount of the bypass exhaust pipe 6. It is configured to be able to. That is, the thermostat 7a expands and contracts due to the cooling water temperature, the opening degree of the thermostat valve 7 changes, and the exhaust gas flow rate limiting means is configured by limiting the flow rate of the exhaust gas to the waste heat recovery unit 22.

  Specifically, the thermostat valve 71 closes the bypass exhaust pipe 6 when the cooling water temperature at the outlet of the waste heat recovery unit 22 is lower than the second predetermined temperature, and removes the exhaust gas from the waste heat recovery unit. 22 to distribute. The waste heat recovery unit 22 performs heat exchange between the circulating exhaust gas and the cooling water.

  On the other hand, when the cooling water temperature at the outlet of the waste heat recovery unit 22 becomes equal to or higher than the second predetermined temperature, the thermostat valve 71 closes the flow of the exhaust gas to the waste heat recovery unit 22 in the exhaust pipe 5. The exhaust gas is circulated through the bypass exhaust pipe 6. Thereby, since exhaust gas does not circulate through the waste heat recovery unit 22, the temperature of the cooling water flowing through the waste heat recovery unit 22 does not rise.

  The second predetermined value is a temperature that does not affect the flow of the cooling water, for example, a temperature having a predetermined margin than the temperature at which the cooling water boils. When the cooling water boils, bubbles are generated and the flowed out bubbles not only reduce the amount of heat exchange (the action of cooling the engine with the cooling water) but also grow to the extent that the bubbles cross the entire cross section of the cooling water passage. There is a risk that the flow will stop.

  That is, in this embodiment, in the waste heat recovery unit 22, the flow rate of the cooling water flowing into the waste heat recovery unit 22 is controlled based on the engine outlet (waste heat recovery unit inlet) cooling water temperature, and the outlet cooling water temperature is set. The exhaust gas flow rate is limited based on this, so that exhaust heat can be recovered sufficiently and reliably as long as the boiling temperature does not occur and the engine water temperature permits, and the temperature rise that affects the engine can be quickly and reliably performed. Can be prevented.

  The thermostat valve 7 may be a relatively simple temperature-sensitive valve using bimetal or the like, or a control valve controlled by a controller to which a temperature sensor output is input.

  FIG. 11 is an explanatory diagram showing the cooling water temperature and flow rate in the waste heat recovery unit 22 of the present embodiment.

  The graph shown in FIG. 11 shows an operating state in which the cooling water temperature on the vertical axis increases with the passage of time on the horizontal axis. In addition, the dotted line in a figure shows the cooling water temperature of the inlet_port | entrance of the waste heat recovery device 22, ie, the temperature measured by the cooling water temperature sensor 74. FIG. Moreover, the one-dot chain line in the figure is the cooling water temperature at the outlet of the waste heat recovery unit 22, that is, the temperature related to the operation of the thermostat 7a.

  When the engine 2 is in steady operation, the temperature of the cooling water from the engine 2 is generally around 80 ° C to 90 ° C. Here, a case where the load of the engine 2 rises transiently, such as when the rotational speed of the engine 2 rises, will be described.

  When the load on the engine 2 rises, first, the temperature of the exhaust gas rises, and the engine water temperature rises with a delay.

  At this time, the temperature of the cooling water at the inlet of the waste heat recovery unit 22, that is, the temperature of the cooling water discharged from the engine 2 gradually increases.

  Here, the cooling water temperature at the inlet of the waste heat recovery unit 22 has a first predetermined temperature (for example, a margin α more than the first limit temperature (the upper limit of the temperature at which the engine does not overheat, for example, 110 ° C.)). 105 ° C.) or higher (time ts1), the engine controller 71 controls the opening degree of the control valve 26 to reduce the coolant flow rate to the waste heat recovery unit 22. By reducing the flow rate of the cooling water passing through the waste heat recovery unit 22, heat exchange in the waste heat recovery unit 22 is reduced, and control is performed so that the engine water temperature (cooling water temperature inside the engine) does not rise excessively. .

  On the other hand, the cooling water temperature at the outlet of the waste heat recovery unit 22 has a margin β more than the second limit temperature (the upper limit of the temperature at which the cooling water does not boil in the pipe, for example, 120 ° C.). When the temperature exceeds a predetermined temperature (for example, 115 ° C.) (time ts2), the opening of the thermostat valve 7 is controlled from fully open to fully closed by the expansion of the thermostat 7a, and the exhaust gas flows through the bypass exhaust pipe 6. And restricting the flow of exhaust gas to the waste heat recovery unit 22. By reducing the flow rate of the exhaust gas passing through the waste heat recovery unit 22, heat exchange in the waste heat recovery unit 22 is reduced, and control is performed so that the cooling water temperature in the waste heat recovery unit 22 does not increase excessively.

  As described above, in the embodiment of the present invention, the circulation of the cooling water to the waste heat recovery unit 22 provided in the exhaust pipe 5 is based on the cooling water temperature at the outlet of the engine 2 (inlet of the waste heat recovery unit 22). The flow of exhaust gas to the waste heat recovery unit 22 was controlled based on the coolant temperature at the outlet of the waste heat recovery unit 22.

  In order to improve the waste heat recovery efficiency, when the temperature of the cooling water at the outlet of the waste heat recovery unit 22 is increased to exceed the allowable temperature of the engine water, the heat from the exhaust gas to the cooling water by the thermostat valve 7 Since the adjustment of the exchange amount is accompanied by a relatively large delay, it is difficult to control the engine water temperature so as not to exceed the allowable temperature if the thermostat valve 7 is adjusted alone. However, since the control valve 26 is controlled based on the engine water temperature, when the cooling water temperature rises, the flow rate of the cooling water flowing through the waste heat recovery unit 22 is limited to quickly reduce the heat recovery amount, It is possible to reliably prevent the engine water temperature from exceeding the allowable temperature.

  Further, if the engine water temperature is in a state where there is an allowance to the allowable temperature, the waste heat recovery is performed in a range where the temperature of the cooling water exiting the waste heat recovery device 22 does not boil (for example, 110 to 115 ° C.) by adjusting with the thermostat valve 7. Since this can be done, the amount of waste heat recovered can be increased.

  Even when the control valve 26 is controlled to the closed side to reduce the flow rate of the cooling water passing through the waste heat recovery unit 22 to the minimum, the flow rate of the cooling water passing through the waste heat recovery unit does not become completely zero. It is configured. Even when the circulation of the exhaust gas to the waste heat recovery unit 22 is stopped by the thermostat valve 7, heat is transferred from the exhaust gas flowing through the bypass exhaust pipe 6 to the cooling water in the waste heat recovery unit 22. Thus, the temperature of the cooling water gradually increases. If a predetermined cooling water flow rate is secured, even if heat is transferred from the exhaust gas flowing through the bypass exhaust pipe 6 to the cooling water in the waste heat recovery unit 22, the cooling water in the waste heat recovery unit 22 gradually increases. It is possible to prevent the cooling water temperature in the waste heat recovery unit 22 from becoming excessively high due to the replacement.

  Further, the margin α at the first predetermined temperature and the margin β at the second predetermined temperature are values that can be appropriately determined according to the responsiveness of the control valve 26 and the thermostat valve 7, for example, about several to 10 ° C. Set.

  In the embodiment of the present invention described above, the hybrid vehicle has been described as an example, but the present invention is not limited to this. The present invention is also applicable to a vehicle equipped with only the engine 2. The engine 2 may be a gasoline engine or a diesel engine.

DESCRIPTION OF SYMBOLS 1 Hybrid vehicle 2 Engine 2a Crank pulley 12 Radiator fan 30 Combined cycle 31 Rankine cycle 32 Refrigerant pump 33 Pump pulley 34 Belt 35 Expander clutch 36 Heat exchanger 37 Expander 51 Refrigeration cycle 52 Compressor 54 Compressor clutch 55 Evaporator 71 Engine controller 92 Ejector 98 Flow control valve

Claims (5)

A waste heat recovery unit that recovers heat of the exhaust gas of the engine into cooling water discharged from the engine;
A heat exchanger that recovers heat of the cooling water into a refrigerant; an expander that generates power using the refrigerant that has exited the heat exchanger; a condenser that condenses the refrigerant that has exited the expander; and the expansion In a waste heat recovery apparatus used in a vehicle including a Rankine cycle, which is driven by power regenerated by a machine and supplies a refrigerant pump from the condenser to the heat exchanger.
Cooling water flow rate limiting means for limiting the flow rate of cooling water to the waste heat recovery unit based on the temperature of the cooling water discharged from the engine;
Exhaust gas flow rate limiting means for limiting the flow rate of exhaust gas flowing into the waste heat recovery device based on the temperature of the cooling water discharged from the waste heat recovery device;
A waste heat recovery apparatus comprising: The cooling water flow rate limiting means is configured to control the temperature detection unit based on the temperature of the temperature detection unit that detects the temperature of the cooling water discharged from the engine, a control valve that controls the flow rate of the cooling water, A controller for controlling the opening of the valve,
The exhaust gas flow restriction means includes a thermostat that expands and contracts based on the temperature of the cooling water discharged from the waste heat recovery unit, and a flow rate of exhaust gas that flows into the waste heat recovery unit according to the expansion and contraction amount of the thermostat. The waste heat recovery apparatus according to claim 1, further comprising: a valve that controls The cooling water flow rate control means limits the flow rate of the cooling water to the waste heat recovery device when the temperature of the cooling water is equal to or higher than the first temperature,
The exhaust gas flow rate control means restricts the flow rate of the exhaust gas flowing into the waste heat recovery unit when the temperature of the cooling water is equal to or higher than a second temperature;
The waste heat recovery apparatus according to claim 1 or 2, wherein the second temperature is higher than the first temperature.   The cooling water flow rate limiting means is configured so that the flow rate of cooling water flowing through the waste heat recovery device does not become zero even when the flow rate of cooling water flowing through the waste heat recovery device is minimized. The waste heat recovery apparatus according to any one of claims 1 to 3.   In the case where the exhaust gas flow rate control unit is set so that the flow rate of the exhaust gas flowing into the waste heat recovery unit is zero, the cooling water flow rate limiting unit is configured such that the temperature of the cooling water has a second temperature. The waste heat recovery apparatus according to claim 4, wherein a flow rate of the cooling water flowing through the waste heat recovery unit is ensured so as not to exceed.

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