JP2008057340A - Exhaust gas heat recovering device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas heat recovering device of an internal combustion engine enabling a proper measure to be taken if air bubbles occur by detecting the occurrence of air bubbles in a cooling water. <P>SOLUTION: This exhaust gas heat recovering device of the internal combustion engine is suitably used for exchanging heat between the cooling water and the exhaust gas by using an exhaust gas heat recoverer. Specifically, the exhaust gas heat recovering device detects the occurrence of air bubbles in the cooling water, and when detecting the occurrence of air bubbles, performs a control to take a measure against the air bubbles. For example, the occurrence of air bubbles is detected according to the hydraulic pressure of the cooling water or the drive load of an electric pump. When the occurrence of air bubbles is detected, the device performs a control to increase the flow rate of the electric pump. Consequently, while properly detecting the occurrence of air bubbles, the device can effectively prevent the mal-operation of the internal combustion engine and the breakage of the exhaust gas heat recoverer due to the air bubbles in the cooling water. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust heat recovery apparatus for an internal combustion engine that performs heat exchange between exhaust gas and cooling water.

  Conventionally, techniques for exchanging heat between exhaust gas and cooling water to recover exhaust heat have been proposed. For example, in Patent Document 1, in an exhaust heat recovery device that recovers exhaust heat from an internal combustion engine with cooling water, the cooling water is circulated by driving an electric pump immediately after the internal combustion engine is stopped, and an exhaust heat recovery portion A technique for preventing the boiling of cooling water at the factory is described.

JP-A-2-104952

  By the way, when the cooling water boils, when the circulation of the cooling water stops due to the stop of the internal combustion engine, or when the cooling water is insufficient, bubbles may be generated in the cooling water. The generation of such bubbles can be affected by the amount of exhaust heat from the internal combustion engine and the amount of cooling water. However, with the technique described in Patent Document 1 described above, bubbles generated in the cooling water cannot be detected appropriately. Therefore, if the operation is continued in a state where air bubbles are mixed, there is a possibility that the operation failure of the internal combustion engine or the exhaust heat recovery device is destroyed.

  The present invention has been made to solve the above-described problems, and detects the generation of bubbles in cooling water and can take appropriate measures when bubbles are generated. It aims at providing a recovery device.

  In one aspect of the present invention, an exhaust heat recovery unit that performs heat exchange between cooling water passing through the interior and exhaust gas discharged from the internal combustion engine, an electric pump that circulates the cooling water in a cooling water passage, An exhaust heat recovery device for an internal combustion engine having a bubble generation detecting means for detecting the generation of bubbles in the cooling water, and for coping with the bubbles when the bubble generation detection means detects the generation of the bubbles And a bubble countermeasure executing means for executing the above control.

  The exhaust heat recovery apparatus for an internal combustion engine is preferably used for exchanging heat between cooling water and exhaust gas using an exhaust heat recovery device. Specifically, the exhaust heat recovery device of the internal combustion engine detects the generation of bubbles in the cooling water, and executes control for dealing with the bubbles when the generation of bubbles is detected. Accordingly, it is possible to effectively prevent the malfunction of the internal combustion engine and the destruction of the exhaust heat recovery device due to the bubbles in the cooling water while appropriately detecting the generation of bubbles.

  In one aspect of the exhaust heat recovery apparatus for an internal combustion engine, the internal combustion engine includes a water pressure sensor that detects a water pressure of the cooling water, and the bubble generation detection unit includes bubbles in the cooling water based on the water pressure detected by the water pressure sensor. Whether or not has occurred is determined. When bubbles are generated in the cooling water, the water pressure of the cooling water tends to change. Therefore, it is possible to appropriately determine whether or not bubbles are generated in the cooling water based on the cooling water pressure.

  Preferably, in the exhaust heat recovery apparatus for an internal combustion engine, the bubble generation detection unit determines that bubbles are generated in the cooling water when the water pressure increases. When the water pressure of the cooling water rises, it can be said that bubbles are generated due to the boiling of the cooling water. Therefore, it is possible to appropriately detect the generation of bubbles in the cooling water based on whether or not the water pressure has increased.

  Preferably, in the exhaust heat recovery apparatus for an internal combustion engine, the bubble generation detection unit determines that bubbles are generated in the cooling water when the water pressure decreases. The decrease in the water pressure in the cooling water can be considered to have occurred because the cooling water leaked in the cooling water passage and the amount of cooling water was insufficient. In this manner, when cooling water leaks or the like, it can be said that there is a high possibility that bubbles are generated in the cooling water. Therefore, by determining whether or not the cooling water pressure has decreased, it is possible to appropriately determine whether or not bubbles are generated in the cooling water.

  Preferably, the water pressure sensor is provided in a cooling water passage on the downstream side of the exhaust heat recovery device.

  In another aspect of the exhaust heat recovery apparatus for an internal combustion engine, the bubble generation detection unit determines that bubbles are generated in the cooling water when a drive load of the electric pump is a predetermined value or less. To do. When bubbles are generated in the cooling water, the driving load of the electric pump tends to change. Therefore, it is possible to appropriately determine whether or not bubbles are generated in the cooling water based on the driving load of the electric pump.

  Preferably, in the exhaust heat recovery apparatus for an internal combustion engine, the bubble generation detection unit determines that bubbles are generated in the cooling water when a driving load of the electric pump is a predetermined value or less. Can do.

  Preferably, in the exhaust heat recovery apparatus for an internal combustion engine, the bubble generation detection unit is configured to reduce the drive load of the electric pump when the drive load of the electric pump is a predetermined value or less. Moreover, it can be determined that the cooling water leaks in the cooling water passage.

  The continuous decrease in the driving load in the electric pump as described above is considered to have occurred because the amount of bubbles mixed in the cooling water increased. And it can be considered that the increase in the amount of bubbles mixed in occurred because the cooling water leaked in the cooling water passage. Therefore, it is possible to appropriately detect the leakage of the cooling water based on the continuous decrease in the driving load of the electric pump.

  Preferably, the internal combustion engine is mounted on a hybrid vehicle, and the bubble generation detection means generates the bubbles based on a driving load of the electric pump in a state where the internal combustion engine is set to a predetermined operation state. It is determined whether or not.

  In another aspect of the exhaust heat recovery apparatus for an internal combustion engine, the bubble countermeasure execution unit controls the operating condition of the electric pump to a high flow rate side when the bubble generation detection unit detects the bubble. Thus, by controlling the operating condition of the electric pump to the high flow rate side, the generation of bubbles can be suppressed. Therefore, it is possible to effectively prevent malfunction of the internal combustion engine and destruction of the exhaust heat recovery device due to bubbles in the cooling water.

  In another aspect of the exhaust heat recovery apparatus for an internal combustion engine, the apparatus includes an electric control valve provided on the cooling water passage and configured to change a flow rate of the cooling water flowing through the cooling water passage. The detection means determines whether or not bubbles are generated in the cooling water based on at least the opening of the electric control valve. Based on information such as the opening degree of the electric control valve, it is possible to grasp a change in pressure loss in the cooling water passage. Therefore, generation | occurrence | production of the bubble in cooling water is appropriately detectable based on the opening degree etc. of an electric control valve.

  In another aspect of the exhaust heat recovery apparatus for an internal combustion engine, a check valve is provided on a cooling water passage between the internal combustion engine and the exhaust heat recovery device. By providing the check valve in this way, it is possible to prevent the cooling water flow from being hindered by the vapor pressure generated by boiling in the exhaust heat recovery device. Therefore, it is possible to prevent the drive load of the electric pump from increasing in order to realize the target water flow.

  Preferably, there is provided means for controlling the bubble generation state to continue. That is, by actively boiling the cooling water with the exhaust heat recovery device, the vapor pressure due to boiling is used as energy for circulating the cooling water. In this case, since the check valve is provided as described above, the steam due to the boiling flows only downstream of the exhaust heat recovery device, so that the steam pressure generated by the boiling is the energy for circulating the cooling water. It will be used as. As a result, power saving of the electric pump is possible, and exhaust energy can be efficiently recovered.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[Configuration of cooling system]
FIG. 1 is a diagram showing a schematic configuration of a cooling system 100 to which an exhaust heat recovery apparatus according to an embodiment of the present invention is applied. In FIG. 1, solid arrows indicate the flow of cooling water, and broken arrows indicate input / output of signals. A solid line indicated by a bold line indicates a passage (cooling water passage) through which the cooling water flows.

  The cooling system 100 according to the present embodiment cools the engine 1 using cooling water, collects exhaust heat by exchanging heat between the cooling water and the exhaust gas, and warms the engine 1. This system is used as a heat source for machines and heaters. In this case, the cooling water cools and warms up the engine 1 by passing through the cooling water passages 7a, 7b, and 7c. The exhaust heat recovery device 2 is provided on the cooling water passage 7a, the radiator 3 is provided on the cooling water passage 7b, and the electric pump 5 is provided on the cooling water passage 7c. Hereinafter, when the cooling water passages 7a to 7c are not distinguished from each other, they are simply used as the cooling water passage 7.

  The engine (internal combustion engine) 1 is a device that generates power by burning a mixture of supplied fuel and air. For example, the engine 1 is configured by a gasoline engine, a diesel engine, or the like. The engine 1 is mounted on a hybrid vehicle or the like. Further, the engine 1 is provided with a water temperature sensor 6 for detecting the temperature of the cooling water. The water temperature sensor 6 supplies a detection signal S6 corresponding to the detected temperature to the ECU 50.

  The exhaust heat recovery device 2 is provided on an exhaust passage (not shown) through which exhaust gas from the engine 1 passes. The exhaust heat recovery device 2 recovers exhaust heat by allowing cooling water to pass through and exchanging heat between the cooling water and the exhaust gas. Further, the exhaust heat recovery device 2 has a switching valve (not shown) and the like. The switching valve is configured to be able to switch between execution of heat exchange and restriction of heat exchange by opening and closing. The switching valve is controlled by a control signal S2 supplied from the ECU 50.

  In the radiator 3, the cooling water passing through the inside thereof is cooled by outside air. In this case, cooling of the cooling water in the radiator 3 is promoted by the wind introduced by the rotation of the electric fan (not shown). The electric pump (hereinafter referred to as “electric WP”) 5 includes an electric motor, and the cooling water is circulated in the cooling water passage 7 by driving the motor. Specifically, electric WP5 is supplied with electric power from a battery, and the number of rotations and the like are controlled by a control signal S5 supplied from ECU 50.

  The thermostat 4 is configured by a valve that opens and closes according to the temperature of the cooling water. Basically, the thermostat 4 opens when the temperature of the cooling water becomes high. In this case, the cooling water passage 7 b and the cooling water passage 7 c are connected via the thermostat 4, and the cooling water passes through the radiator 3. Thereby, a cooling water is cooled and the overheating of the engine 1 is suppressed. On the other hand, when the temperature of the cooling water is relatively low, the thermostat 4 is closed. In this case, the cooling water does not pass through the radiator 3. Thereby, since the temperature fall of a cooling water is suppressed, the overcool of the engine 1 is suppressed.

  The ECU (Engine Control Unit) 50 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown). The ECU 50 performs various controls based on the output supplied from the various sensors described above. In the present embodiment, the ECU 50 mainly performs processing for detecting the generation of bubbles in the cooling water. In addition, when the generation of bubbles is detected, the ECU 50 executes control for dealing with the bubbles. Thus, the ECU 50 operates as a bubble generation detection unit and a bubble countermeasure execution unit.

[Configuration of exhaust heat recovery unit]
Here, an example of the exhaust heat recovery device 2 will be specifically described with reference to FIG. FIG. 2 is a diagram showing a schematic configuration of the exhaust heat recovery device 2. FIG. 2 mainly shows the exhaust system of the engine 1 and the exhaust heat recovery unit 2 described above. A solid line arrow indicates the flow of exhaust gas and cooling water, and a broken line arrow indicates signal input / output.

  The exhaust heat recovery device 2 is provided on an exhaust passage 10 through which exhaust gas from the engine 1 flows. Specifically, the exhaust heat recovery device 2 is installed on the exhaust passage 10 on the downstream side of the catalyst 11 that purifies the exhaust gas.

  The exhaust heat recovery device 2 has a cooling water passage 12 disposed so as to cover the outer wall surface of the exhaust passage 10. For example, the cooling water passage 12 has a shape in which the exhaust passage 10 is spirally wound around the exhaust passage 10. In the cooling water passage 12, the cooling water flows in from the cooling water passage 7a as shown by an arrow B1, and the cooling water flows out to the cooling water passage 7a as shown by an arrow B2.

  Further, a switching valve 15 is provided in the exhaust passage 10. The switching valve 15 switches the exhaust passage through which the exhaust gas passes by opening and closing. Specifically, the switching valve 15 switches between the first exhaust passage 10a and the second exhaust passage 10b. Thereby, execution of heat exchange in the exhaust heat recovery unit 2 and switching of heat exchange in the exhaust heat recovery unit 2 are switched.

  Specifically, when the switching valve 15 is closed, the exhaust gas flows through the first exhaust passage 10a as indicated by arrows A1 and A3. In this case, the exhaust gas passes through a location on the exhaust passage 10 where the cooling water passage 12 in the exhaust heat recovery device 2 is provided. Thereby, exhaust heat is transmitted to the cooling water in the cooling water passage 12 through the wall surface of the exhaust passage 10, and heat exchange is executed. Basically, the switching valve 15 is set to be closed when it is cold. This is because the engine 1 is warmed up or the heater is heated by the exhaust heat recovered by the exhaust heat recovery unit 2.

  On the other hand, when the switching valve 15 is open, the exhaust gas flows through the second exhaust passage 10b as indicated by the arrow A2. In this case, the exhaust gas passes through a passage that bypasses a location on the exhaust passage 10 where the cooling water passage 12 is provided. Therefore, the heat exchange between the exhaust gas and the cooling water is hardly performed (that is, the heat exchange is limited). Basically, the switching valve 15 is set to open when it is warm. This is because the engine 1 is efficiently cooled by the cooling water by restricting the heat exchange in the exhaust heat recovery device 2 to suppress the temperature rise of the cooling water.

  The switching valve 15 is controlled to open and close by a VSV (Vacuum Switching Valve) 16. The VSV 12 is controlled by a control signal S16 (corresponding to the control signal S2 shown in FIG. 1) supplied from the ECU 50. That is, the ECU 50 controls opening / closing of the switching valve 15 via the VSV 12.

  Hereinafter, a method for detecting the generation of bubbles in the cooling water, control executed when bubbles are generated, and the like according to the embodiment of the present invention will be specifically described.

[First Embodiment]
First, a first embodiment of the present invention will be described. In the first embodiment, the ECU 50 determines whether or not bubbles are generated in the cooling water based on the cooling water pressure. Specifically, the ECU 50 determines whether or not the cooling water is boiling. Furthermore, in the first embodiment, when the ECU 50 detects boiling of the cooling water, the ECU 50 executes control for dealing with this. For example, when the cooling water boils in the exhaust heat recovery unit 2, the water pressure of the cooling water system increases due to the vapor pressure, and the exhaust heat recovery unit 2 may be damaged or the pipe may be disconnected. Therefore, in the first embodiment, control for preventing the occurrence of such a problem is performed. Specifically, the ECU 50 performs control to increase the flow rate of the electric WP 5 when the boiling of the cooling water is detected.

  FIG. 3 is a diagram illustrating a schematic configuration of the cooling system 101 according to the first embodiment. In addition, the same code | symbol is attached | subjected with respect to the same thing as the component shown in FIG. 1, and the description is abbreviate | omitted.

  In the cooling system 101 according to the first embodiment, the water pressure sensor 20 is provided on the cooling water passage 7a. Specifically, the water pressure sensor 20 is provided on the cooling water passage 7 a on the downstream side of the exhaust heat recovery device 2. The water pressure sensor 20 detects the water pressure of the cooling water and outputs a detection signal S20 corresponding to the detected water pressure to the ECU 50.

  In the first embodiment, the ECU 50 determines whether or not the cooling water is boiling based on the water pressure detected by the water pressure sensor 20. Specifically, since the water pressure tends to increase when the cooling water boils, the ECU 50 determines that the cooling water is boiling when the water pressure of the cooling water increases. Further, the ECU 50 controls the electric WP 5 based on the coolant pressure. Specifically, the ECU 50 performs control to increase the flow rate of the electric WP 5 when it is determined from the coolant pressure that the coolant is boiling. This is because boiling in the cooling water is suppressed by increasing the flow rate of the electric WP5. That is, an increase in the water pressure of the cooling water is suppressed.

  Specifically, the ECU 50 switches the control over the electric WP5 by comparing the coolant pressure with a predetermined pressure. Specifically, when the coolant pressure is equal to or lower than a predetermined pressure, ECU 50 determines the flow rate of electric WP 5 (hereinafter also referred to as “engine required flow rate”) required from the operating state of engine 1 or the like. Then, the electric WP 5 is controlled so that the engine required flow rate flows. For example, when it is not necessary to cool the engine 1 such as when it is cold, the engine required flow rate is substantially “0”, so the ECU 50 stops the electric WP 5. On the other hand, when the water pressure of the cooling water is larger than the predetermined pressure, the ECU 50 calls the flow rate of the electric WP 5 (hereinafter referred to as “boiling prevention required flow rate”) required to prevent boiling instead of the engine required flow rate. )) And the electric WP 5 is controlled so that the boiling prevention required flow rate flows. The boiling prevention required flow rate is basically determined to be larger than the engine required flow rate. Therefore, when the coolant pressure is higher than the predetermined pressure, the flow rate of the electric WP 5 is increased.

  The predetermined pressure used for the water pressure of the cooling water described above is set to either a water pressure when boiling occurs or a water pressure at which boiling occurs and damage to the exhaust heat recovery device 2 or disconnection of piping occurs. By controlling the electric WP 5 based on such a predetermined pressure, until boiling occurs, or even if boiling occurs, until the water pressure reaches such a level that the exhaust heat recovery device 2 is broken or disconnected. The flow rate of the electric WP 5 will not be increased (that is, the engine required flow rate is set). Therefore, the flow rate of the electric WP 5 can be increased only when necessary to prevent the cooling water from boiling. For this reason, it is possible to suppress an unnecessary increase in the flow rate of the electric WP5, and it is possible to suppress deterioration of fuel consumption in the vehicle. For example, when cold, the electric WP 5 can be stopped.

  Here, the control method of the electric WP 5 according to the first embodiment will be specifically described with reference to FIG. FIG. 4 is a flowchart showing a control process of the electric WP 5 according to the first embodiment. This process is repeatedly executed by the ECU 50 at a predetermined cycle.

First, in step S101, the ECU 50 determines the engine required flow rate based on the operating state of the engine 1 and the like. Then, the process proceeds to step S102. In step S <b> 102, the ECU 50 acquires the coolant pressure from the water pressure sensor 20. Then, the process proceeds to step S103.

  In step S103, the ECU 50 determines whether or not the coolant pressure is greater than a predetermined pressure. Here, it is determined whether or not the flow rate of the electric WP 5 should be increased. The predetermined pressure used for the determination is set to a water pressure when boiling occurs and a water pressure at which boiling occurs and damage to the exhaust heat recovery device 2 or disconnection of the piping occurs.

  If the coolant pressure is greater than the predetermined pressure (step S103; Yes), the process proceeds to step S104. In step S104, the ECU 50 determines a boiling prevention request flow rate of the electric WP 5 required to prevent boiling. It can be said that the state that has proceeded to the process of step S104 is a state in which the flow rate of the electric WP5 should be increased. That is, it can be said that the cooling water is boiling or the cooling water is boiled and the exhaust heat recovery device 2 is broken or disconnected. Therefore, the ECU 50 determines the boiling prevention required flow rate, and controls the electric WP 5 using the boiling prevention required flow rate instead of the engine required flow rate determined in step S101. In this case, since the flow rate of the electric WP5 increases, boiling in the cooling water is appropriately prevented. That is, an increase in the coolant pressure is suppressed. When the above process ends, the process exits the flow.

  When the water pressure of the cooling water is equal to or lower than the predetermined pressure (step S103; No), the process exits the flow. In this case, it can be said that the flow rate of the electric WP5 should not be increased. That is, it can be said that the cooling water does not boil, or the cooling water boils and the exhaust heat recovery device 2 is broken or disconnected. Therefore, the ECU 50 controls the electric WP 5 using the engine required flow rate determined in step S101. In this case, the flow rate of the electric WP 5 is not increased from the engine required flow rate. For example, when it is not necessary to cool the engine 1 such as when it is cold, the engine required flow rate is substantially “0”, and the electric WP 5 is stopped.

  Thus, according to 1st Embodiment, generation | occurrence | production of a boiling of cooling water can be detected appropriately based on the water pressure of cooling water, and the control for preventing a boiling can be performed appropriately. Therefore, it is possible to effectively prevent the exhaust heat recovery device 2 from being damaged and the pipe from being detached due to boiling. Moreover, since the flow rate of the electric WP5 can be increased only when necessary to prevent boiling of the cooling water, it is possible to suppress an unnecessary increase in the flow rate of the electric WP5. Therefore, it becomes possible to suppress deterioration of fuel consumption.

  In addition, although the example which provided the water pressure sensor 20 on the cooling water channel | path 7a of the downstream of the exhaust heat recovery device 2 was shown above, it is not limited to this. It is preferable to provide the water pressure sensor 20 in the vicinity of a component that may be damaged or damaged due to an increase in water pressure due to boiling in the exhaust heat recovery unit 2. If the water pressure sensor 20 is provided on the downstream side of the exhaust heat recovery unit 2 as in the above example, it can be said that the exhaust heat recovery unit 2 can be effectively prevented from being damaged. In another example, instead of providing the water pressure sensor 20 at a location on the downstream side of the exhaust heat recovery unit 2, or at a location where the water pressure sensor 20 is provided at this location, there is little margin for the allowable pressure at which the pipe can be removed. A water pressure sensor can be provided in the vicinity. In this case, it can be said that the disconnection of the pipe can be effectively suppressed.

  In the above, the embodiment has been described in which it is determined that bubbles are generated in the cooling water when the water pressure of the cooling water is increased. However, the embodiment is not limited thereto. In another example, the ECU 50 can determine that bubbles are generated in the cooling water even when the cooling water pressure decreases. It can be considered that the decrease in the water pressure of the cooling water occurred because the cooling water leaked in the cooling water passage 7 and the amount of cooling water was insufficient. In this manner, when cooling water leaks or the like, it can be said that there is a high possibility that bubbles are generated in the cooling water. Therefore, by determining whether or not the cooling water pressure has decreased, it is possible to appropriately determine whether or not bubbles are generated in the cooling water.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. The second embodiment differs from the first embodiment in that air bubbles are generated in the cooling water based on the driving load of the electric WP 5 instead of the water pressure of the cooling water. That is, in the second embodiment, the ECU 50 determines whether or not bubbles are generated based on the power consumption of the electric WP5. Specifically, the ECU 50 determines that bubbles are generated in the cooling water when the power consumption of the electric WP 5 is equal to or less than a predetermined value.

  Furthermore, in the second embodiment, when it is determined that bubbles are generated in the cooling water, a process for removing bubbles in the cooling water (hereinafter referred to as “bubble removing process”) and a leakage of the cooling water. Is executed (hereinafter referred to as “cooling water leakage determination process”). Specifically, it is determined whether or not bubbles are generated due to the replacement of the cooling water, and one of the bubble removal processing and the cooling water leakage determination processing is executed based on the determination result. Specifically, when it is determined that bubbles are generated due to the replacement of cooling water, a bubble removal process is performed, and when it is determined that bubbles are not generated due to replacement of the cooling water, bubbles are generated. A process of determining whether or not the occurrence is caused by leakage of cooling water is executed.

  Here, a decrease in power consumption of the electric WP 5 that occurs when bubbles are generated will be specifically described with reference to FIG. In FIG. 5, the horizontal axis indicates the rotation speed (corresponding to the flow rate) of the electric WP 5, and the vertical axis indicates the power consumption of the electric WP 5. A straight line 70 shows an example of the relationship between the rotational speed of the electric WP 5 and the power consumption when no bubbles are generated in the cooling water (when no bubbles are mixed in the cooling water). In addition, although there exists a certain range in such a relationship, in FIG. 5, only one straight line 70 is shown for convenience of explanation. On the other hand, the straight line 71 shows an example of the relationship between the rotational speed of the electric WP 5 and the power consumption when bubbles are generated in the cooling water (when bubbles are mixed in the cooling water). From the straight line 70 and the straight line 71, it can be seen that when air bubbles are generated in the cooling water, the power consumption of the electric WP 5 with respect to the designated rotational speed is considerably small. That is, the driving load of the electric WP 5 is considerably reduced. This is because the cooling water in which bubbles are mixed has a lower resistance than the cooling water in which bubbles are not mixed. From the above, it can be said that it can be determined whether or not bubbles are generated in the cooling water based on the power consumption of the electric WP5.

  Next, a case where bubbles are generated due to leakage of cooling water will be described with reference to FIG. In FIG. 6, the horizontal axis indicates the rotation speed (corresponding to the flow rate) of the electric WP 5, and the vertical axis indicates the power consumption of the electric WP 5. Elements denoted by the same reference numerals as those shown in FIG. 5 indicate the same elements, and the description thereof is omitted.

  As described above, when the relationship between the rotational speed of the electric WP 5 and the power consumption as shown by the straight line 71 is obtained, it is determined that bubbles are generated in the cooling water. A straight line 72 indicates the relationship between the number of rotations of the electric WP 5 and the power consumption obtained after a certain amount of time has elapsed from such determination. From this, it can be seen that the power consumption of the electric WP 5 with respect to the designated rotational speed decreases with the passage of time. Such a decrease in power consumption is thought to have occurred because the amount of bubbles mixed in the cooling water increased. It can be considered that the increase in the amount of bubbles mixed in occurs because the cooling water leaks in the cooling water passage 7. That is, during normal operation of the engine 1, since the electric WP 5 is driven at a certain rotational speed, if the cooling water passage 7 is damaged or the pipe is disconnected, the cooling water leaks from here. Therefore, it is considered that the amount of bubbles mixed in increases. From the above, it can be said that the determination of the leakage of the cooling water (cooling water leakage determination process) can be performed based on the decrease in the power consumption of the electric WP5.

  Next, the bubble generation detection process according to the second embodiment will be described with reference to FIG. FIG. 7 is a flowchart showing the bubble generation detection process according to the second embodiment. This process is repeatedly executed by the ECU 50 in the cooling system 100 shown in FIG. 1 at a predetermined cycle.

  First, in step S201, the ECU 50 determines whether or not the engine 1 has been started. If the engine 1 has been started (step S201; Yes), the process proceeds to step S202. If the engine 1 has not been started (step S201; No), the process exits the flow. When the engine 1 is mounted on a hybrid vehicle, the ECU 50 can determine whether the hybrid system is started instead of determining whether the engine 1 is started.

  In step S202, the ECU 50 determines whether or not bubbles are generated in the cooling water. Specifically, the ECU 50 determines whether or not bubbles are generated by determining whether or not the power consumption of the electric WP 5 (corresponding to the driving load) is equal to or less than a predetermined value. For example, the ECU 50 obtains the power consumption corresponding to the current rotational speed of the electric WP5 from the relationship between the rotational speed of the electric WP5 and the power consumption when bubbles are not generated in the cooling water. The determination is made by comparing the power consumption of the electric WP5. In this case, when the actual power consumption of the electric WP 5 is considerably smaller than the calculated power consumption, the ECU 50 determines that bubbles are generated in the cooling water. When it is determined that bubbles are generated in the cooling water (step S202; Yes), the process proceeds to step S203, and when it is determined that bubbles are not generated in the cooling water (step S202; No), the process is performed. Exits the flow.

  In step S203, the ECU 50 determines whether there is a history of removing the battery terminal of the auxiliary battery. The determination in step S203 is performed to determine whether or not the cooling water has been replaced. That is, since it is highly possible to remove the battery terminal when replacing the cooling water, it is possible to determine whether or not the cooling water has been replaced based on the history of removing the battery terminal. The reason for determining whether or not the cooling water has been exchanged in this manner is to determine whether or not the generation of bubbles is caused by the exchange of the cooling water. If there is a history of removing the battery terminal (step S203; Yes), the process proceeds to step S204. If there is no history of removing the battery terminal (step S203; No), the process proceeds to step S205.

  In step S204, the ECU 50 executes a bubble removal process. In the situation where the process proceeds to step S204, it can be considered that bubbles are generated due to the replacement of the cooling water. In other words, it is considered that the possibility that the cause of the bubble generation is the leakage of the cooling water is very low. Therefore, the ECU 50 executes a process for removing bubbles in the cooling water (bubble removal process). Specifically, the ECU 50 executes control for increasing the rotational speed of the electric WP5. By executing such control, bubbles can be extracted from the reserve tank or the like of the radiator 3. Thereby, it is possible to effectively prevent malfunction of the engine 1 and destruction of the exhaust heat recovery device 2 due to bubbles in the cooling water. In addition, since the possibility that the cooling water is leaking is considerably low as described above, it can be said that the possibility of occurrence of a malfunction is very low even when the control for increasing the rotation speed of the electric WP 5 is executed. When the above process ends, the process exits the flow.

  On the other hand, in step S205, the ECU 50 executes a cooling water leakage determination process. In the situation where the processing has proceeded to step S205, it is unlikely that bubbles are generated due to the replacement of the cooling water. In this case, there is a possibility that the cause of the bubble generation is leakage of cooling water. Therefore, the ECU 50 performs a determination (cooling water leakage determination process) as to whether or not a cooling water leak has occurred in the cooling water passage 7 without executing a process (bubble removing process) for removing bubbles in the cooling water. To do. This is because if the control for increasing the rotational speed of the electric WP 5 is executed in a situation where the coolant is supposed to leak, there is a possibility that the coolant will leak further. Because there is sex. As described above, when it is determined that bubbles are not generated due to the replacement of the cooling water, the cooling water leakage determination process is executed instead of the bubble removal process, thereby resulting in the execution of the bubble removal process. It becomes possible to appropriately suppress the occurrence of defects.

  Specifically, in step S205, the ECU 50 determines whether or not the power consumption of the electric WP 5 has decreased after a certain amount of time has elapsed since the occurrence of bubbles was detected in step S202. That is, the ECU 50 determines whether or not the power consumption of the electric WP 5 continues to decrease. ECU50 determines with the leakage of cooling water having arisen, when the continuous fall of the power consumption in electric WP5 is detected. When the above process ends, the process exits the flow. In addition, when it is determined that the coolant is leaking, the coolant may be displayed so that the driver can recognize the coolant leak. Further, when it is determined that there is no leakage of cooling water, bubble removal processing such as control for increasing the number of rotations of the electric WP 5 may be executed.

  According to the second embodiment, it is possible to appropriately detect the generation of bubbles in the cooling water based on the driving load (power consumption) of the electric WP5. Further, by determining the cause of the generation of bubbles, it is possible to appropriately execute any one of processing for removing bubbles in cooling water and processing for determining leakage of cooling water. Thereby, air bubbles can be appropriately removed while suppressing the occurrence of defects. Furthermore, when the generation of bubbles is detected, a comparison between the control for increasing the rotational speed of the electric WP 5 as in the present embodiment and the control for maintaining the engine rotational speed at a high speed is as follows. Therefore, it can be said that workability can be improved appropriately.

  Note that the above-described processing for detecting the generation of bubbles (the processing in steps S202 and S205) is performed in a state where the engine 1 is set to a predetermined operating state when the engine 1 is mounted on a hybrid vehicle. It is preferable to carry out. That is, it is preferable to make a determination based on the driving load of the electric WP 5 detected when the engine 1 is set in a predetermined operating state. By doing so, it is possible to improve the accuracy of detecting the generation of bubbles and the like.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In the third embodiment, an abnormality has occurred in the cooling system based on the opening of an electric control valve that electrically switches the cooling water passage instead of the cooling water pressure or the driving load of the electric WP5. It differs from 1st Embodiment and 2nd Embodiment by the point which determines whether it exists. Specifically, in the third embodiment, bubbles are generated in the cooling water based on the opening degree of the electric control valve, the rotation speed of the electric WP5, the power consumption of the electric WP5, and the temperature of the cooling water (cooling water temperature). It is determined whether or not.

  In this case, the design pressure loss characteristic of the cooling system is found from the opening of the electric control valve, the flow rate of the cooling water is found from the rotation speed of the electric WP5, the pump load (cooling system pressure loss) is found from the power consumption of the electric WP5, and the cooling water temperature From this, the physical quantity related to the flow of cooling water is known. And the pressure loss of the cooling water channel | path 7 can be grasped | ascertained from such information. Therefore, since pressure loss changes when bubbles are generated in the cooling water, based on the information on the opening degree of the electric control valve, the rotation speed of the electric WP5, the power consumption of the electric WP5, and the cooling water temperature, It can be said that the generation of bubbles can be detected appropriately.

  FIG. 8 is a diagram illustrating a schematic configuration of the cooling system 103 according to the third embodiment. In addition, the same code | symbol is attached | subjected with respect to the same thing as the component shown in FIG. 1, and the description is abbreviate | omitted.

  The cooling system 103 according to the third embodiment is different from the cooling system 100 in that it has an electric three-way valve 22 instead of the thermostat 4 (see FIG. 1). The electric three-way valve 22 has three openings connected to the cooling water passages 7a, 7b, and 7c, respectively. The electric three-way valve 22 electrically adjusts the opening so that the flow rate of cooling water passing through the radiator 3 (that is, the flow rate of the cooling water passage 7b) and the flow rate of cooling water passing through the exhaust heat recovery device 2 (That is, the flow rate of the cooling water passage 7a) is changed. Thus, by providing the electric three-way valve 22 instead of the thermostat 4, the flow rate of the cooling water flowing through each of the cooling water passage 7a and the cooling water passage 7b can be accurately grasped from information such as the opening degree of the electric three-way valve 22. It becomes possible to do.

  The opening degree of the electric three-way valve 22 is adjusted by an actuator 23. The actuator 23 is controlled by a control signal S23 supplied from the ECU 50. That is, the ECU 50 controls the opening degree of the electric three-way valve 22 via the actuator 23. Thus, the electric three-way valve 22 corresponds to the electric control valve in the present invention.

  In the third embodiment, the ECU 50 determines whether or not bubbles are generated in the cooling water based on the opening degree of the electric three-way valve 22 or the like. Specifically, the ECU 50 determines whether or not bubbles are generated in the cooling water based on the opening degree of the electric three-way valve 22, the rotational speed of the electric WP5, the power consumption of the electric WP5, and the cooling water temperature.

  Specifically, the relationship between the opening degree of the electric three-way valve 22 when the cooling system 103 is normal, the rotational speed of the electric WP5, the power consumption of the electric WP5, and the cooling water temperature (hereinafter also referred to as “normal data”). ) Is measured in advance and stored in the ECU 50. Then, the ECU 50 compares the stored normal data with the currently obtained opening degree of the electric three-way valve 22, the rotational speed of the electric WP5, the power consumption of the electric WP5, and the coolant temperature. It is determined whether or not bubbles are generated in the cooling water. For example, the ECU 50 determines that bubbles are generated in the cooling water when the obtained value is significantly different from the normal data. When it is determined that bubbles are generated in the cooling water, the ECU 50 displays such that the driver can recognize it.

  Next, the bubble generation detection process according to the third embodiment will be specifically described with reference to FIG. FIG. 9 is a flowchart showing bubble generation detection processing according to the third embodiment. This process is repeatedly executed by the ECU 50 in the cooling system 103 shown in FIG. 8 at a predetermined cycle.

  First, in step S301, the ECU 50 acquires the opening degree of the electric three-way valve 22, the rotational speed of the electric WP5, the power consumption of the electric WP5, and the coolant temperature during the electric WP5 operation. The opening degree of the electric three-way valve 22 corresponds to the control signal S23 supplied to the actuator 23 by the ECU 50. In addition, when the opening degree sensor etc. are provided in the electric three-way valve 22, ECU50 can acquire the opening degree of the electric three-way valve 22 from this sensor. The rotation speed of the electric WP5 and the power consumption of the electric WP5 correspond to the control signal S5 supplied to the electric WP5, the control signal supplied to the battery, and the like. Further, the cooling water temperature corresponds to the detection signal S6 supplied from the water temperature sensor 6 to the ECU 50. When the above process ends, the process proceeds to step S302.

  In step S302, the ECU 50 determines that the difference between the opening degree of the electric three-way valve 22, the rotation speed of the electric WP5, the power consumption of the electric WP5, the cooling water temperature, and the normal temperature data obtained in step S301 is greater than or equal to a predetermined value. It is determined whether or not. By making such a determination, the ECU 50 detects a change in pressure loss in the cooling water passage 7 and determines whether or not bubbles are generated in the cooling water. If the difference is greater than or equal to the predetermined value (step S302; Yes), the process proceeds to step S303. In this case, it is considered that bubbles are generated in the cooling water. On the other hand, when the difference is less than the predetermined value (step S302; No), the process exits the flow. In this case, it is considered that no bubbles are generated in the cooling water.

  In step S303, the ECU 50 performs a display (abnormal display) so that a driver or the like can recognize that bubbles are generated in the cooling water. Then, the process exits the flow.

  According to the third embodiment described above, it is possible to appropriately detect the generation of bubbles in the cooling water based on the opening degree of the electric three-way valve 22 and the like. As a result, it is possible to prevent malfunction of the engine 1 and destruction of the exhaust heat recovery device 2 due to bubbles in the cooling water.

  In addition, although the example which determines whether the bubble has generate | occur | produced in cooling water based on the opening degree etc. of the electric three-way valve 22 was shown above, it is not limited to this. In another example, breakage of the exhaust heat recovery device 2 can be detected based on the opening degree of the electric three-way valve 22 or the like. When the exhaust heat recovery device 2 is damaged, the pressure loss in the cooling water passage 7 changes. Therefore, the opening degree of the electric control valve, the rotation speed of the electric WP5, the power consumption of the electric WP5, and the cooling water temperature. However, it tends to change from normal data. Therefore, it can be said that breakage of the exhaust heat recovery device 2 can be detected based on these values.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. The fourth embodiment is different from the first to third embodiments described above in that the cooling system is configured so as to prevent the occurrence of problems due to boiling of cooling water. Specifically, in the fourth embodiment, the cooling system is configured so as to prevent the flow of the cooling water from being hindered by steam due to boiling. Specifically, a check valve is provided on the cooling water passage 7 on the upstream side of the exhaust heat recovery device 2.

  FIG. 10 is a diagram illustrating a schematic configuration of a cooling system 104 according to the fourth embodiment. In addition, the same code | symbol is attached | subjected with respect to the same thing as the component shown in FIG. 1, and the description is abbreviate | omitted.

  In the cooling system 104 according to the fourth embodiment, a check valve 24 is provided on the cooling water passage 7 a between the engine 1 and the exhaust heat recovery device 2. The check valve 24 is configured to allow the flow of cooling water from the engine 1 to the exhaust heat recovery device 2 and to block the flow of cooling water from the exhaust heat recovery device 2 to the engine 1. By providing the check valve 24 in this way, it is possible to prevent the water flow of the cooling water from being hindered by the vapor pressure generated by boiling in the exhaust heat recovery device 2. Therefore, it is possible to prevent the drive load of the electric WP 5 from increasing in order to achieve the target flow rate. In other words, it is possible to prevent the actual flow rate from becoming smaller than the target flow rate.

  Moreover, in 4th Embodiment, the steam pressure by boiling is utilized as energy for circulating a cooling water by boiling a cooling water positively with the exhaust heat recovery device 2. FIG. That is, since the check valve 24 is provided as described above, the steam due to the boiling flows only downstream of the exhaust heat recovery device 2, so that the steam pressure generated by the boiling is used for circulating the cooling water. It will be used as energy. In this case, in the situation where the boiling of the cooling water has occurred, the ECU 50 does not perform such boiling when the water pressure of the cooling water does not reach such a water pressure that the exhaust heat recovery device 2 is damaged or the pipe is disconnected. Execution of control for suppression is prohibited. For example, the ECU 50 prohibits execution of control or the like that increases the flow rate of the electric WP 5 as shown in the first embodiment. Thus, by using the vapor pressure as energy for circulating the cooling water, it is possible to save electric power of the electric WP5. That is, exhaust energy can be efficiently recovered.

1 is a diagram illustrating a schematic configuration of a cooling system to which an exhaust heat recovery device is applied. It is a figure which shows schematic structure of an exhaust heat recovery device. It is a figure which shows schematic structure of the cooling system which concerns on 1st Embodiment. It is a flowchart which shows the control processing of the electric WP which concerns on 1st Embodiment. It is a figure for demonstrating the fall of the power consumption of electric WP resulting from generation | occurrence | production of a bubble. It is a figure for demonstrating the case where the bubble has arisen due to the leakage of a cooling water. It is a flowchart which shows the bubble generation detection process which concerns on 2nd Embodiment. It is a figure which shows schematic structure of the cooling system which concerns on 3rd Embodiment. It is a flowchart which shows the bubble generation detection process which concerns on 3rd Embodiment. It is a figure which shows schematic structure of the cooling system which concerns on 4th Embodiment.

Explanation of symbols

1 engine (internal combustion engine)
2 Exhaust heat recovery device 3 Radiator 4 Thermostat 5 Electric pump (Electric WP)
6 Water temperature sensor 7 Cooling water passage 20 Water pressure sensor 22 Electric three-way valve 24 Check valve 50 ECU
100 Cooling system

Claims (13)

Exhaust heat recovery of an internal combustion engine having an exhaust heat recovery device that performs heat exchange between cooling water passing through the interior and exhaust gas discharged from the internal combustion engine, and an electric pump that circulates the cooling water in the cooling water passage A device,
Bubble generation detection means for detecting the generation of bubbles in the cooling water;
An exhaust heat recovery apparatus for an internal combustion engine, comprising: bubble countermeasure execution means for executing control to cope with the bubbles when the bubble generation detection means detects the occurrence of the bubbles. A water pressure sensor for detecting the water pressure of the cooling water;
2. The exhaust heat recovery of the internal combustion engine according to claim 1, wherein the bubble generation detection unit determines whether or not bubbles are generated in the cooling water based on a water pressure detected by the water pressure sensor. apparatus.   The exhaust heat recovery device for an internal combustion engine according to claim 2, wherein the bubble generation detection means determines that bubbles are generated in the cooling water when the water pressure increases.   The exhaust heat recovery device for an internal combustion engine according to claim 2, wherein the bubble generation detection means determines that bubbles are generated in the cooling water when the water pressure is lowered.   The exhaust heat recovery device for an internal combustion engine according to any one of claims 2 to 4, wherein the water pressure sensor is provided in a cooling water passage on a downstream side of the exhaust heat recovery unit.   2. The exhaust heat recovery apparatus for an internal combustion engine according to claim 1, wherein the bubble generation detection means determines whether or not bubbles are generated in the cooling water based on a driving load of the electric pump. .   The exhaust of the internal combustion engine according to claim 6, wherein the bubble generation detection means determines that bubbles are generated in the cooling water when a driving load of the electric pump is a predetermined value or less. Heat recovery device.   The bubble generation detection means has a leakage of the cooling water in the cooling water passage when the driving load of the electric pump is below a predetermined value and the driving load of the electric pump continues to decrease. The exhaust heat recovery apparatus for an internal combustion engine according to claim 6 or 7, characterized in that The internal combustion engine is mounted on a hybrid vehicle,
The bubble generation detection means determines whether or not the bubbles are generated based on a driving load of the electric pump in a state where the internal combustion engine is set in a predetermined operation state. 6. An exhaust heat recovery apparatus for an internal combustion engine according to claim 6.   The said bubble countermeasure execution means controls the operating condition of the said electric pump to the high flow rate side, when the said bubble generation | occurrence | production detection means detects the said bubble, The high flow volume side is controlled. Exhaust heat recovery device for internal combustion engine. An electric control valve provided on the cooling water passage for changing a flow rate of the cooling water flowing through the cooling water passage;
The said bubble generation | occurrence | production detection means determines whether the bubble has generate | occur | produced in the said cooling water based on the opening degree of the said electric control valve at least. An exhaust heat recovery apparatus for an internal combustion engine as described.   The exhaust heat recovery device for an internal combustion engine according to claim 1, wherein a check valve is provided on a cooling water passage between the internal combustion engine and the exhaust heat recovery device.   The exhaust heat recovery apparatus for an internal combustion engine according to claim 12, further comprising means for controlling the bubble generation state to continue.

Images