Exhaust heat recovery device

The present invention relates to an exhaust heat recovery device that raises the temperature of the cooling water for cooling the engine by exhaust heat at least when the temperature of the cooling water for cooling the engine drops.

In recent years, engines such as in-cylinder direct injection engines (gasoline engines, diesel engines) and lean-burn engines that have improved fuel efficiency and improved fuel efficiency have been installed, and the running load has been reduced to improve fuel efficiency. In the vehicle designed in the above, since the cooling loss of the engine is relatively reduced, the cooling water temperature is difficult to rise, and there is a problem that it takes time to shift to the warm-up completed state in which fuel-efficient operation is possible.

Similarly, since the cooling water temperature does not easily rise, in a vehicle heating system that uses the cooling water temperature, even after the warm-up is completed, depending on the operating environment (for example, cruising in an extremely low temperature environment), the cooling water temperature alone may not be sufficient. , It is becoming difficult to secure the amount of heat required to obtain heating.

As a countermeasure against this, for example, as disclosed in Patent Document 1 (Japanese Unexamined Patent Publication No. 2009-255739), an electric heater is arranged as an auxiliary heat source directly downstream of the heater core and at the outlet, or the engine is intentionally used. Also known are technologies such as increasing the amount of heat released to the cooling water by operating the engine in a low-efficiency state.

Further, as disclosed in Patent Document 2 (Japanese Unexamined Patent Publication No. 2010-163899), during warm-up operation, cooling water is guided to the exhaust heat recovery system and the exhaust heat is recovered by the cooling water to warm the system. A technology that realizes early completion of machine operation and secures a heat source for heating is also known.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2009-255739</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2010-163899</text></patcit></p>

<p> However, the technology disclosed in Patent Document 1 and the technology for operating the engine with low efficiency have an inconvenience that energy consumption increases and fuel consumption deteriorates. On the other hand, in the technique disclosed in Patent Document 2, it is necessary to guide the cooling water passage to the exhaust heat recovery system provided in the exhaust pipe, which not only complicates the piping of the cooling water passage but also remarkably increases the product cost. There is a problem that it will be up.</p><p> Further, since the air conditioner mounted on the vehicle is usually assumed to operate in a normal temperature environment, an efficient refrigeration cycle cannot be performed in an extremely low temperature environment, and the vehicle interior cannot be dehumidified. As a result, a cryogenic outside air having a low humidity is introduced into the vehicle interior in order to prevent fogging of the glass in the vehicle interior, which has a disadvantage that the heating capacity is further reduced.</p><p> In view of the above circumstances, the present invention can efficiently recover the exhaust heat of the engine without changing the cooling system of the engine and the refrigeration cycle of the air conditioner, shorten the warm-up time, and improve the fuel efficiency. It is an object of the present invention to provide an exhaust heat recovery device capable of not only realizing the above, but also improving the heating performance in an extremely low temperature environment and ensuring the dehumidifying performance.</p>

<p> The exhaust heat recovery device according to the present invention includes a heat exchanger arranged in front of the engine room to cool at least the cooling water for cooling the engine, a reversely rotatable fan arranged behind the heat exchanger, and the like. It controls the rotation of the fan and the opening and closing of the ventilation limiting means, the shroud covering the fan and the heat exchanger, the openable and closable ventilation limiting means arranged behind the fan and behind the shroud. The shroud includes a control means, the shroud has a wind guide tunnel communicating with the exhaust system of the engine, and the control means compares the temperature of the cooling water for cooling the engine with a preset low water temperature determination value. When it is determined that the temperature of the cooling water for cooling the engine is lower than the low water temperature determination value, the fan is rotated in the reverse direction and the ventilation limiting means is closed.</p>

<p> According to the present invention, when it is determined that the temperature of the cooling water for cooling the engine is lower than the low water temperature determination value, the fan is rotated in the reverse direction and the ventilation limiting means is closed to pass through the exhaust system of the engine. Since the preheated air is blown toward the heat exchanger, the exhaust heat of the engine can be efficiently recovered and the heat exchanger can be used without changing the cooling system of the engine and the refrigeration cycle of the air conditioner. Can be heated. As a result, the warm-up time can be shortened, the fuel efficiency can be improved, and the heating performance in an extremely low temperature environment can be improved. If a heat exchanger of an air conditioner is installed, the heat exchanger can be heated with preheated air to restore the heat exchange capacity of the heat exchanger and ensure dehumidification performance. it can.</p>

<figref num="1">Cross-sectional side view of the front part of the vehicle equipped with the exhaust heat recovery device</figref><figref num="2">Cross-sectional side view corresponding to FIG. 1 in a state where the flap of the shutter unit is closed.</figref><figref num="3">Configuration diagram of the control system of the exhaust heat recovery device</figref><figref num="4">Flowchart showing exhaust heat recovery control routine</figref><figref num="5">Flowchart showing radio fan motor reversal control routine</figref><figref num="6">Explanatory drawing of reverse rotation torque table</figref>

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the front body 1 of a private car, which is an example of a vehicle, is provided with a front bumper 2 at the front, and a front grill 3 is provided above the front bumper 2 and is provided inside. The engine room E is formed. Further, a front hood 4 is provided on the upper part of the front part 1 of the vehicle body, and the upper part of the engine room E is covered with the front hood 4 so as to be openable and closable.

This engine room E is equipped with a power unit such as engine 5. The engine 5 shown in the present embodiment is a horizontally opposed 4-cylinder engine, and exhaust ports (not shown) for each cylinder are opened in the cylinder heads 5a provided in both the left and right banks, and the left and right cylinder heads 5a The exhaust ports opened in are aggregated via the exhaust manifold 5b.

Further, the left and right exhaust manifolds 5b are further integrated on the front lower side of the engine 5 and communicated with the exhaust pipe 5d, and this exhaust pipe 5d extends to the rear part of the vehicle body and communicates with the muffler (not shown). .. Further, a catalyst 7 is interposed on the upstream side of the exhaust pipe 5d, and the catalyst 7 is arranged in the lower front part of the engine 5. In a vehicle equipped with a turbocharger, an exhaust turbine is arranged upstream of the catalyst 7. In the present embodiment, the heat source is used up to the vicinity of the downstream end of the catalyst 7 interposed in the exhaust manifold 5b and the exhaust pipe 5d.

Further, a radiator 8 as a heat exchanger and a condenser 9 are arranged in front of the engine 5. The radiator 8 cools the engine cooling cooling water (hereinafter, simply referred to as cooling water) that circulates in the engine 5, and a condenser 9 is arranged in front of the radiator 8. The condenser 9 constitutes the refrigeration cycle of the vehicle air conditioner. In the refrigeration cycle, a high-temperature and high-pressure vapor-phase refrigerant compressed by a compressor (not shown) flows into the condenser 9, is cooled by the outside air to be a liquid-phase refrigerant, and then depressurized by an expansion valve and arranged on the passenger compartment side. It constitutes a refrigerant circulation circuit that flows into the evaporator, absorbs heat from the air supplied into the room, becomes a gas phase refrigerant, and is sent to the compressor. The air that has passed through the evaporator is dehumidified and cooled before being sent to the passenger compartment. Therefore, when the humidity in the vehicle interior is high, it is dehumidified, which prevents the window glass from fogging.

The radiator 8 and the condenser 9 are fixed to the radiator panel 10 arranged in front of the radiator 8. The radiator panel 10 is formed in a substantially rectangular frame shape, and a pair of front side frames (not shown) are arranged on both sides in the vehicle width direction on the left and right in the vehicle width direction and extend in the front-rear direction of the vehicle body. It is fixed in. Reference numeral 10a is a stay arranged in the center of the radiator panel 10 in the vehicle width direction, and the upper frame and the lower frame of the radiator panel 10 are connected by the stay 10a.

Further, an air intake port 11a formed at the front end of the air duct 11 is fixedly installed on the upper part of the radiator panel 10. The air intake port 11a is elongated on the radiator panel 10 along the vehicle width direction, and is provided at the intake system of the engine 5 and the outside air introduction port of an air conditioning duct (not shown) provided on the vehicle interior side. It is communicated. Further, when the front hood 4 is closed, the front part of the front hood 4 also serves as a part of the air intake port 11a, and the outside air is set so as to be taken in mainly from the front grill 3 side.

Further, a front bumper 2 integrated with the front grill 3 is connected to the front portion of the radiator panel 10. The lower outside air introduction port 2a is opened in the front bumper 2, and the upper outside air introduction port 3a is formed in the front grill 3. Further, a circulation port 2b is opened on the bottom surface of the lower outside air introduction port 2a of the front bumper 2, and the front end of the front under cover 12 is fixed to the bottom rear end 2c of the front bumper 2. Is communicated to the front undercover 12 side.

This front undercover 12 protects the bottom surface of the power unit such as the engine 5 arranged in the engine room E, and has a function of rectifying the running wind passing through the bottom of the engine room E, and has a function of rectifying the running wind passing through the bottom of the engine room E. Both sides in the vehicle width direction are fixed to engine mount cross members (not shown).

On the other hand, a shroud 14 is arranged at the rear of the radiator 8. The front portion of the shroud 14 is formed in a tubular shape covering the outer periphery of the back surface of the radiator 8, and the tip portion thereof is fixed to the radiator panel 10. The rear part of the shroud 14 extends toward the front surface of the engine 5, and the shutter unit 15 is attached to the portion facing the engine 5. Further, a wind guide tunnel 16 is formed below the portion where the shutter unit 15 of the shroud 14 is attached. Further, an electric fan for cooling the radiator (hereinafter referred to as "radiator fan") 17 is arranged between the front portion and the rear portion of the shroud 14. The radio fan motor 17a of the radio fan 17 is a reversible motor, and forward rotation, stop, and reverse rotation are operated by a drive signal from the control unit 21 described later.

Further, the front part of the wind guide tunnel 16 is communicated with the gap portion 13 between the shutter unit 15 and the radio fan 17, and the rear part is close to the catalyst 7 arranged in the front lower part of the engine 5. .. Furthermore, the bottom surface 16a of the wind guide tunnel 16 is branched to the left and right across the oil pan 5c of the engine 5 and faces directly under the exhaust system of the engine 5, and the rear end 16b of the bottom surface 16a and the front under cover. The rear end 12a of the 12 is connected to each other by welding or via bolts or the like. Further, a large number of ventilation holes 16c are bored on the bottom surface 16a of the wind guide tunnel 16 facing the exhaust system described above.

A warm air return passage 19 is formed by the bottom surface 16a of the wind guide tunnel 16 and the front undercover 12. As described above, the tip of the front undercover 12 is fixed to the bottom of the front bumper 2, and the circulation port 2b is opened on the bottom surface of the lower outside air introduction port 2a of the front bumper 2, and further, the bottom surface 16a and the front are opened. Since the rear ends 16b and 12a are joined to the undercover 12, the air introduced into the warm air recirculation passage 19 from the circulation port 2b is guided to the exhaust system of the engine 5 through the ventilation holes 16c. The exhaust system of the engine 5 includes an exhaust manifold 5b extending from the cylinder head and an exhaust pipe 5d communicating with the exhaust manifold 5b. A catalyst 7 is interposed in the exhaust pipe 5d, and in the case of a vehicle equipped with a turbocharger, an exhaust turbine is arranged upstream of the catalyst 7.

Further, the shutter unit 15 attached to the rear portion of the shroud 14 has a plurality of flaps 15a extending in the vehicle width direction, and each of the flaps 15a is arranged in the vertical direction. Each flap 15a is set to be openable and closable in two directions, a substantially horizontal open state (see Fig. 1) and a hanging closed state (see Fig. 2). The air flow between and is cut off.

Each of the flaps 15a is opened and closed by the flap actuator 15b. The flap actuator 15b is operated in synchronization with the radio fan motor 17a by a drive signal from the control unit 21 described later.

As shown in FIG. 3, the control unit 21 has a water temperature sensor 22 that detects the temperature (cooling water temperature) Tw of the cooling water that cools the engine 5 on the input side, an outside air temperature sensor 23 that detects the outside air temperature To, and a vehicle running. A ram pressure sensor 24 or the like that detects the dynamic pressure (ram pressure) Pa generated by the running wind is connected, and a radio fan motor 17a and a flap actuator 15b are connected to the output side via a drive circuit (not shown). Has been done. The ram pressure sensor 24 is arranged immediately before the capacitor 9, and the ram pressure Pa applied to the front surface of the capacitor 9 is detected.

The control unit 21 is composed of a well-known microcomputer equipped with a CPU, ROM, RAM, etc., and the ROM includes a control program for realizing the operation of the radio fan motor 17a and the flap actuator 15b, and a control program described later. Various fixed data such as a reverse rotation torque table are stored.

The control unit 21 controls the forward rotation, stop, and reverse rotation of the radio fan motor 17a based on the input parameters, and is provided in the shutter unit 15 in synchronization with the forward rotation and reverse rotation control of the radio fan motor 17a. The flap actuator 15b is driven to open and close each flap 15a.

Specifically, the operation of the radio fan motor 17a and the flap actuator 15b is performed according to the exhaust heat recovery control routine shown in FIG.

This routine is executed every predetermined calculation cycle after the ignition switch (not shown) is turned on. First, in step S1, the cooling water temperature Tw detected by the water temperature sensor 22 and the preset low water temperature determination value TWL are combined. To compare. This low water temperature determination value TWL is a temperature at which the cooling water temperature Tw is too low to sufficiently heat the vehicle interior, and in the present embodiment, the temperature is higher than the warm-up completion determination temperature (for example, 65 [° C]) (for example). It is set to 75 [° C]).

Then, if it is determined that the cooling water temperature Tw exceeds the low water temperature determination value TWL (Tw&gt; TWL), the process proceeds to step S2. If it is determined that the cooling water temperature Tw is equal to or less than the low water temperature determination value TWL (Tw TWL), the process proceeds to step S3. The state of Tw TWL is likely to occur not only in the warm-up operation after the cold start, but also in the long-time operation in the low load operation.

Proceeding to step S2, the outside air temperature To detected by the outside air temperature sensor 23 is compared with the low outside air temperature determination value TOL. For example, when the cooling water temperature Tw is high but the outside air temperature To is low, such as when traveling in an extremely cold region, the heat exchange capacity of the condenser 9 is reduced, and sufficient dehumidifying performance cannot be obtained. In the present embodiment, the outside air temperature To at which the heat exchange capacity of the capacitor 9 is significantly reduced is obtained from an experiment or the like, and the value is set as the low outside air temperature determination value TOL. Specifically, this low outside air temperature judgment value TOL is set to about -15 to -20 [° C].

Then, when To TOL, it is determined that the heat exchange capacity of the capacitor 9 is reduced, and the process proceeds to step S3. When To&gt; TOL, it is determined that the heat exchange capacity of the capacitor 9 is secured, and the process proceeds to step S4.

When the process proceeds from step S1 or step S2 to step S3, the control for reversing the radio fan motor 17a is executed and the process proceeds to step S5. The reversing operation of the radio fan motor 17a is executed in the radio fan motor reversing control subroutine shown in FIG.

In this subroutine, first, in step S11, the ram pressure Pa applied to the front of the radiator 8 detected by the ram pressure sensor 24 is read, and in step S12, the torque (reverse) when the radiator motor 17a is rotated in the reverse direction based on the ram pressure Pa. Rotational torque) Tm is variably set by referring to the table or by the calculation formula.

Figure 6 shows the relationship between the ram pressure Pa and the reverse rotation torque Tm of the radio fan motor 17a. The reverse rotation torque Tm is the torque required for the radio fan 17 to generate a wind force (wind pressure) that resists the ram pressure Pa generated by the running wind. When the ram pressure Pa = the wind pressure of the radio fan motor 17a, the reverse rotation torque Tm required to generate the ram pressure Pa can be obtained from experiments, etc., and based on this, the ram pressure Pa and the reverse rotation torque Tm Table the relationships or set an approximate curve formula. Then, the reverse rotation torque Tm of the radio fan motor 17a is calculated from the table search or the approximate curve formula. As shown in FIG. 6, when the ram pressure Pa = 0, the reverse rotation torque Tm is set to the initial value α. This initial value α complements the amount that the wind pressure generated by the radiator fan motor 17a is attenuated by the flow path resistance when passing through the radiator 8 and the condenser 9.

Next, the process proceeds to step S13, the motor voltage Va of the radio fan motor 17a corresponding to the reverse rotation torque Tm is obtained and output, the routine is exited, and the process proceeds to step S5 of FIG. Since the reverse rotation torque is almost proportional to the self-power of the motor voltage Va, the motor voltage Va can be obtained relatively easily from the reverse rotation torque Tm.

Then, when the process proceeds to step S5 in FIG. 4, a closing signal is output to the flap actuator 15b that opens and closes the flap 15a of the shutter unit 15, and the routine is exited.

As a result, if the cooling water temperature Tw is equal to or less than the low water temperature determination value TWL during, for example, cold start, subsequent warm-up operation, or running at an extremely low temperature, each flap 15a of the shutter unit 15 is closed and the radio fan is operated. The connection between 17 and engine 5 is cut off. At the same time, the radio fan motor 17a rotates in the reverse direction with the reverse rotation torque Tm corresponding to the ram pressure Pa. Further, even when the cooling water temperature Tw exceeds the low water temperature determination value TWL, each flap 15a of the shutter unit 15 is closed and the shutter unit 15 is closed even when the outside air temperature To is below the low outside air temperature determination value TOL. The radio fan motor 17a operates in reverse rotation with a reverse rotation torque Tm corresponding to the ram pressure Pa.

The radio fan 17 is covered with a shroud 14, and a wind guide tunnel 16 is formed below the shutter unit 15. Further, a large number of ventilation holes 16c are bored in the bottom surface 16a of the ventilation tunnel 16, and the ventilation tunnel 16 and the warm air recirculation passage 19 formed below the ventilation holes 16c are communicated with each other through the ventilation holes 16c. ing. Therefore, when the radio fan 17 rotates in the reverse direction and each flap 15a of the shutter unit 15 closes, the air flows into the warm air recirculation passage 19 from the circulation port 2b formed on the bottom surface of the lower outside air introduction port 2a of the front bumper 2. Air flows into the air guide tunnel 16 side through the ventilation hole 16c. Next, this air flows into the air gap 13 from the air guide tunnel 16 and is guided in the direction of the radiator fan 17, and a circulation path is formed in which the air blown from the radiator fan 17 passes through the radiator 8 and the condenser 9 and flows forward.

An exhaust system such as an exhaust manifold 5b, an exhaust pipe 5d, a catalyst 7, etc., which is heated by exhaust heat and dissipates heat, is arranged above the ventilation hole 16c, and the air discharged from the ventilation hole 16c uses this exhaust system. As it passes, it is preheated by the radiant heat from this exhaust system and sucked into the radiator fan 17. The air sucked into the radiator fan 17 passes through the radiator 8 and the condenser 9 which are opposed to each other in front of the radiator fan 17 and is sent forward. At that time, the radiator 8 and the condenser 9 are heated by the preheated air. To.

Then, the air sent forward from the condenser 9 collides with the running wind (broken line arrow in FIG. 2) blown from the front of the vehicle body at the time of strike. The wind pressure generated by the operation of the radio fan 17 is set based on the ram pressure Pa detected by the ram pressure sensor 24. Since this ram pressure sensor 24 detects the ram pressure Pa applied to the front surface of the condenser 9, the wind pressure of the running wind and the wind pressure sent from the radiator fan 17 to the front of the condenser 9 are almost the same, and the colliding air moves up and down. Distributed in the direction.

As a result, the condenser 9 and the radiator 8 are not cooled more than necessary by the running wind, and the running wind is less likely to flow into the engine room E, so that the inside of the engine room E is not cooled more than necessary. It is possible to prevent overcooling of the engine 5 and its peripheral parts.

Then, a part of the air dispersed upward is sucked into the inside of the duct from the air intake port 11a of the air duct 11 and supplied to the intake system of the engine 5 and the air conditioning duct of the vehicle air conditioner. On the other hand, a part of the air dispersed downward flows into the warm air recirculation passage 19 from the circulation port 2b, is sucked into the radiator fan 17 again, and is circulated. The air sent from the radiator 17 to the front of the vehicle body, passing through the warm air return passage 19 and the wind guide tunnel 16 and circulating to the radiator 17 is preheated by the radiant heat from the exhaust system each time, so the radiator 8 and the condenser 9 are used. It can be heated efficiently.

On the other hand, in step S2, it is determined that the outside air temperature To exceeds the low outside air temperature judgment value TOL (To&gt; TOL), and when the process proceeds to step S4, the cooling water temperature Tw and the high water temperature judgment value TWH are compared. This high water temperature judgment value TWH is for preventing the temperature of the cooling water from becoming high during normal strike, and is set with hysteresis to prevent control hunting, for example, 90 ± 1.5 [° C]. ing.

Then, when it is determined that Tw TWH, the process proceeds to step S6, the radio fan motor 17a is rotated in the normal direction, and the process proceeds to step S8. On the other hand, when it is determined that Tw &lt;TWH, the process branches to step S7, the operation of the radio fan motor 17a is stopped, and the process proceeds to step S8. Then, in step S8, an open signal is output to the flap actuator 15b to exit the routine. When an open signal is output to the flap actuator 15b, each flap 15a of the shutter unit 15 opens. Then, the traveling wind from the front of the vehicle body passes through the condenser 9 and the radiator 8, passes through the shutter unit 15, and flows into the engine room E.

As described above, according to the present embodiment, the cooling system of the engine 5 and the refrigerating cycle of the air conditioner are not changed at all, and when the cooling water temperature Tw is low, the radiator fan 17 is rotated in the reverse direction and the shutter unit 15 is operated. Since each flap 15a is closed to form an air circulation path and air is circulated, the radiant heat from the exhaust system of the engine 5 can be efficiently recovered and the radiator 8 can be heated. As a result, not only the warm-up time can be shortened and the fuel efficiency can be improved, but also the internal air circulation rate of the air conditioner in the extremely low temperature environment can be increased, and the heating efficiency can be improved. Further, when the heat pump type air conditioner is installed, the temperature of the low heat source can be raised, so that efficient heating becomes possible.

In particular, even in the operating state where the cooling water temperature Tw exceeds the low water temperature judgment value TWL, when traveling in an extremely low temperature environment (To TWL), the radiator fan 17 is rotated in the reverse direction and the flaps 15a of the shutter unit 15 are moved. Since the closed operation is performed, the air blown from the radiator fan 17 is heated and warmed when passing through the radiator 8, and the condenser 9 is heated by this warmed air. As a result, the heat exchange capacity of the capacitor 9 at an extremely low temperature is restored, the refrigeration cycle can be operated efficiently, the dehumidifying operation becomes possible, and a good antifogging effect can be obtained.

Further, since the air in front of the radiator 8 is heated by the reverse rotation of the radiator fan 17, the air taken in from the air duct 11 and supplied to the intake system of the engine 5 and the air conditioning duct of the vehicle air conditioner is preheated. It becomes air and can improve the combustion efficiency of the engine 5 and the heating performance of the air conditioner.

The present invention is not limited to the above-described embodiment. For example, the flap actuator 15b may be operated by closing each flap 15a with an ON signal and opening the flap actuator 15b with an OFF signal. In this case, the closed signal becomes an ON signal and the open signal becomes an OFF signal.

Further, the flap actuator 15b that opens and closes each flap 15a may be omitted, and each flap 15a may be opened by the wind pressure of the running wind. As a result, the processing of the flap actuator 15b and steps S5 and S8 for opening / closing the flap actuator 15b becomes unnecessary, and not only the calculation load of the control unit 21 can be reduced, but also the product cost is reduced by reducing the number of parts. can do.

Further, the ram pressure Pa may be estimated from the vehicle speed detected by the vehicle speed sensor. Since the vehicle speed sensor is usually provided in the vehicle, a special sensor is not required, and the number of parts can be reduced and the cost can be reduced.

1 ... front of the car body, 2b ... Circulation port, 2 ... front bumper, 3 ... front grill, 5 ... engine, 5b ... Exhaust manifold, 5d ... exhaust pipe, 7 ... catalyst, 8 ... radiator, 9 ... Capacitor, 11 ... Air duct, 14 ... Shroud, 15 ... Shutter unit, 15a ... flap, 15b ... flap actuator, 16 ... Wind tunnel, 16c ... vents, 17 ... Radifan, 17a ... Radi fan motor, 19 ... Warm air return passage, 21 ... Control unit, 22 ... Water temperature sensor, 23 ... outside temperature sensor, 24 ... Ram pressure sensor 24,