JP2013024070A - Exhaust gas recirculation device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas recirculation device which can raise a temperature of coolant with a high rate of climb, when it is necessary to heat the coolant.SOLUTION: The exhaust gas recirculation device 50 for an internal combustion engine includes: a cooling means 53 having an exhaust recirculation pipe 51 for introducing exhaust gas exhausted from a combustion chamber of the internal combustion engine to an exhaust passage 40, to an intake passage 30; and coolant circulation passages 55, 56 and 57 which circulate the coolant cooling the exhaust gas flowing in the exhaust recirculation pipe by cooling the exhaust recirculation pipe. In the exhaust gas recirculation device, the coolant is circulated through the coolant circulation passages, so that the temperature of the coolant is lowered, and while introduction of the exhaust gas to the intake passage is stopped, circulation of the coolant in the coolant circulation passages is stopped. The exhaust gas recirculation device further includes a heating means 54 heating the exhaust recirculation pipe, and heats the exhaust recirculation pipe with the heating means, while the circulation of the coolant in the coolant circulation passages is stopped.

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine.

  Patent Document 1 describes an exhaust gas recirculation device for an internal combustion engine (hereinafter, this device is referred to as an “EGR device”). This EGR device is a device that introduces exhaust gas discharged from a combustion chamber of an internal combustion engine into an exhaust passage into the intake passage. Further, the EGR device includes an exhaust gas recirculation pipe (hereinafter referred to as “EGR pipe”) for flowing an exhaust gas introduced into the intake passage (hereinafter referred to as “EGR gas”), and the EGR pipe. And a cooling device for cooling. The cooling device has a cooling water circulation passage for circulating the cooling water. When the cooling water is circulated in the cooling water circulation passage, the temperature of the cooling water decreases.

  Incidentally, in Patent Document 1, if the temperature of the cooling water is excessively lower than the temperature of the EGR gas, the exhaust gas is excessively cooled by the cooling water, and condensed water is generated in the EGR pipe in the region of the cooling device. There are indications that the EGR pipe may be corroded by condensed water. And in order to suppress such corrosion of an EGR pipe, in the EGR device of patent documents 1, when the temperature of cooling water is lower than predetermined temperature, cooling water is heated with a heater.

JP-A-11-125151 JP 2004-197634 A JP 2000-87810 A

  Incidentally, as described above in connection with Patent Document 1, in the EGR device, there is a case where it is required to raise the temperature of the cooling water when the temperature of the cooling water is lower than a predetermined temperature. Such a rise in the temperature of the cooling water may be required for purposes other than the purpose of suppressing the corrosion of the EGR pipe described above. And when such a request | requirement arises, it is preferable to raise the temperature of a cooling water with a high temperature increase rate. However, in the EGR device of Patent Document 1, the cooling water is heated in a state where the cooling water is circulated in the cooling water circulation passage. As described above, when the cooling water is circulated in the cooling water circulation passage, the temperature of the cooling water decreases. Therefore, when the cooling water is circulated in the cooling water circulation passage when the cooling water is heated to increase the temperature of the cooling water as in the EGR device of Patent Document 1, the cooling water by heating the cooling water is used. The rate of temperature rise will be low.

  An object of the present invention is to increase the temperature of the cooling water at a high temperature increase rate when it becomes necessary to heat the cooling water in order to increase the temperature of the cooling water.

  The invention of the present application includes an exhaust gas recirculation pipe for introducing exhaust gas discharged from the combustion chamber into the exhaust passage into the intake air passage, and exhaust gas flowing through the exhaust gas recirculation pipe by cooling the exhaust gas recirculation pipe. Cooling means provided with a cooling water circulation passage for circulating cooling water to be cooled. The cooling water is circulated through the cooling water circulation passage, whereby the temperature of the cooling water is lowered, and the exhaust gas to the intake passage is reduced. The present invention relates to an exhaust gas recirculation device for an internal combustion engine in which the circulation of the cooling water in the cooling water circulation passage is stopped while the introduction is stopped. The exhaust gas recirculation apparatus according to the present invention further comprises heating means for heating the exhaust gas recirculation pipe, and the exhaust gas recirculation pipe is moved by the heating means while the cooling water circulation is stopped in the cooling water circulation passage. Heat.

  The present invention has an advantage that the temperature of the cooling water can be increased at a high temperature increase rate while the introduction of the exhaust gas into the intake passage is stopped. That is, since exhaust gas does not flow in the exhaust gas recirculation pipe while the exhaust gas recirculation device stops the introduction of exhaust gas into the intake passage (hereinafter, this introduction is also referred to as “EGR gas introduction”), the exhaust gas recirculation pipe Temperature drops. Here, if the temperature of the exhaust gas recirculation pipe becomes lower than a certain temperature while the introduction of the EGR gas is stopped, for example, condensed water is generated on the inner wall surface of the exhaust gas recirculation pipe, and the exhaust gas is exhausted by this condensed water. Unfavorable situations can arise where the recirculation pipe is corroded. Therefore, in order to suppress corrosion of the exhaust gas recirculation pipe due to condensed water, it is preferable to maintain the temperature of the exhaust gas recirculation pipe at a temperature higher than the generation temperature of the condensed water while the introduction of EGR gas is stopped. . Further, various control systems for an internal combustion engine having an exhaust gas recirculation device are constructed on the assumption that the temperature of the exhaust gas introduced into the intake passage by the exhaust gas recirculation device is higher than a certain temperature. In this case, when the temperature of the exhaust gas recirculation pipe becomes lower than the certain temperature (hereinafter referred to as “assumed temperature”) while the introduction of the EGR gas is stopped, the introduction of the EGR gas is resumed. Sometimes, exhaust gas having a temperature lower than the assumed temperature may be introduced into the intake passage. This is not preferable from the viewpoint of causing various control systems of the internal combustion engine to exhibit desired control characteristics. Therefore, in order to prevent the exhaust gas having a temperature lower than the assumed temperature from being introduced into the intake passage, the temperature of the exhaust gas recirculation pipe is maintained at a temperature higher than the assumed temperature while the introduction of the EGR gas is stopped. It is preferable.

  In order to maintain the temperature of the exhaust gas recirculation pipe at a temperature higher than the generation temperature of the condensed water, or to maintain the temperature of the exhaust gas recirculation pipe at a temperature higher than the assumed temperature while the introduction of the EGR gas is stopped. It is effective to maintain the temperature of the exhaust gas recirculation pipe while the introduction of EGR gas is stopped at a temperature higher than the generation temperature of the condensed water or higher than the assumed temperature. Thus, in order to suppress the occurrence of an unfavorable situation including the above situation, the temperature of the exhaust gas recirculation pipe while the introduction of EGR gas is stopped is maintained at a relatively high temperature. It is effective.

  Considering that the rate of decrease in the temperature of the exhaust gas recirculation pipe while the introduction of EGR gas is stopped is relatively large, the temperature of the exhaust gas recirculation pipe is maintained at a relatively high temperature while the introduction of EGR gas is stopped. In order to achieve this, it is required to raise the temperature of the exhaust gas recirculation pipe at a high temperature rise rate while stopping the introduction of EGR gas. Here, in the present invention, the exhaust gas recirculation pipe is heated in a state where the circulation of the cooling water in the cooling water circulation passage while the introduction of the EGR gas is stopped is stopped. Therefore, the temperature increase rate of the exhaust gas recirculation pipe is higher than when the exhaust gas recirculation pipe is heated in a state where the circulation of the cooling water in the cooling water circulation passage is not stopped. Therefore, there is an advantage that the temperature of the exhaust gas recirculation pipe can be increased at a high temperature increase rate while the introduction of EGR gas is stopped.

  In the above invention, the timing at which the circulation of the cooling water in the cooling water circulation passage is stopped may be a timing during the stop of the introduction of the exhaust gas into the intake passage, and is not limited to a specific timing. The circulation of the cooling water in the cooling water circulation passage may be stopped simultaneously with the stop of the introduction of the exhaust gas into the intake passage, or when a predetermined time has elapsed since the stop of the introduction of the exhaust gas into the intake passage The circulation of the cooling water in the cooling water circulation passage may be stopped.

  Another invention of the present application is that an exhaust gas recirculation pipe for introducing exhaust gas discharged from the combustion chamber into the exhaust passage into the intake passage, and the exhaust gas recirculation pipe are cooled to cool the exhaust gas recirculation pipe. And a cooling means having a cooling water circulation passage for circulating cooling water for cooling the flowing exhaust gas, and the temperature of the cooling water is reduced by circulating the cooling water through the cooling water circulation passage. It relates to a recirculation device. The exhaust gas recirculation apparatus according to the present invention further comprises heating means for heating the exhaust gas recirculation pipe, and when it becomes necessary to heat the exhaust gas recirculation pipe, the cooling water circulation in the cooling water circulation passage is performed. The exhaust gas recirculation pipe is heated by the heating means while the circulation is stopped.

  The present invention has an advantage that the temperature of the exhaust gas recirculation pipe can be increased at a high temperature increase rate when the exhaust gas recirculation pipe needs to be heated. That is, when there is a temperature required for various reasons as the temperature of the exhaust gas recirculation pipe, the temperature of the exhaust gas recirculation pipe is the lowest of these required temperatures (hereinafter, this temperature is referred to as “minimum required temperature”). It is not preferable to be lower. In the present invention, when the exhaust gas recirculation pipe needs to be heated, for example, the temperature of the exhaust gas recirculation pipe becomes lower than the minimum required temperature. Here, the minimum necessary temperature is, for example, the following temperature.

  If the temperature of the exhaust gas recirculation pipe becomes lower than a certain temperature, for example, condensed water is generated on the inner wall surface of the exhaust gas recirculation pipe, and the exhaust gas recirculation pipe is corroded by this condensed water. A situation may arise. Therefore, in order to suppress corrosion of the exhaust gas recirculation pipe due to condensed water, it is preferable to maintain the temperature of the exhaust gas recirculation pipe at a temperature higher than the generation temperature of the condensed water. In this case, the highest temperature among the generation temperatures of the condensed water (in other words, the lowest temperature among the temperatures at which the condensed water is not generated) corresponds to the minimum required temperature.

  Further, various control systems for an internal combustion engine having an exhaust gas recirculation device are constructed on the assumption that the temperature of the exhaust gas introduced into the intake passage by the exhaust gas recirculation device is higher than a certain temperature. In this case, when the temperature of the exhaust gas recirculation pipe becomes equal to or lower than the certain temperature (hereinafter, this temperature is referred to as “assumed temperature”), when the introduction of EGR gas is started, the temperature is equal to or lower than the expected temperature. Exhaust gas may be introduced into the intake passage. This is not preferable from the viewpoint of causing various control systems of the internal combustion engine to exhibit desired control characteristics. Therefore, it is preferable to maintain the temperature of the EGR pipe at a temperature higher than the assumed temperature in order to prevent the exhaust gas having a temperature lower than the assumed temperature from being introduced into the intake passage. In this case, the lowest temperature among the temperatures of the exhaust gas recirculation pipe necessary for maintaining the temperature of the exhaust gas introduced into the intake passage at a temperature higher than the assumed temperature corresponds to the minimum required temperature.

  When the temperature of the exhaust gas recirculation pipe becomes lower than the minimum required temperature, that is, when it becomes necessary to heat the exhaust gas recirculation pipe, the temperature of the exhaust gas recirculation pipe exceeds the minimum required temperature. It is preferable that the temperature of the exhaust gas recirculation pipe is increased at a high temperature increase rate.

  In the present invention, when it becomes necessary to heat the exhaust gas recirculation pipe, the circulation of the cooling water in the cooling water circulation passage (hereinafter also simply referred to as “cooling water circulation”) is stopped. The exhaust recirculation pipe is heated during the stop. Since the cooling water is cooled when the cooling water circulation is executed, if the exhaust gas recirculation pipe is heated while the cooling water circulation is stopped, the exhaust gas recirculation pipe is executed during the cooling water circulation. As compared with the case where is heated, the temperature increase rate of the exhaust gas recirculation pipe is high. Therefore, the present invention has an advantage that the temperature of the exhaust gas recirculation pipe can be increased at a high temperature increase rate when the exhaust gas recirculation pipe needs to be heated.

  In the above invention, the method for determining that it is necessary to heat the exhaust gas recirculation pipe is not particularly limited. For example, as this technique, the target temperature of the exhaust gas recirculation pipe is set as a target. It is necessary to set the exhaust gas recirculation pipe temperature and to heat the exhaust gas recirculation pipe when the temperature of the exhaust gas recirculation pipe becomes lower than the target exhaust gas recirculation pipe temperature while stopping the introduction of the exhaust gas into the intake passage. It is possible to adopt a method of determining that the occurrence of the problem has occurred.

  When this configuration is adopted, there is an advantage that the temperature of the exhaust gas recirculation pipe can be maintained at the target exhaust gas recirculation pipe temperature while the introduction of the EGR gas is stopped. Then, if the temperature of the exhaust gas recirculation pipe during the stoppage of the introduction of EGR gas desirable for achieving the desired performance as the internal combustion engine performance is set to the target exhaust gas recirculation pipe temperature, the desired performance as the internal combustion engine performance is achieved. Can be achieved reliably.

  Further, as a method for determining that it is necessary to heat the cooling water, for example, the target exhaust gas recirculation pipe temperature is set as the target exhaust gas recirculation pipe temperature, and the introduction of exhaust gas into the intake passage is stopped. When the temperature of the exhaust gas recirculation pipe is predicted to be lower than the target exhaust gas recirculation pipe temperature, or when the temperature of the exhaust gas recirculation pipe is estimated to be lower than the target exhaust gas recirculation pipe temperature. A method of determining that the exhaust recirculation pipe needs to be heated may be employed.

  When a configuration is adopted in which it is determined that it is necessary to heat the exhaust gas recirculation pipe when it is predicted that the temperature of the exhaust gas recirculation pipe will be lower than the target exhaust gas recirculation pipe temperature while the introduction of EGR gas is stopped Since it is judged that the exhaust gas recirculation pipe needs to be heated before the exhaust gas recirculation pipe temperature actually becomes lower than the target exhaust gas recirculation pipe temperature, the introduction of EGR gas is more reliably stopped. There is an advantage that the temperature of the inside exhaust gas recirculation pipe can be maintained at a temperature equal to or higher than the target exhaust gas recirculation pipe temperature. On the other hand, when it is estimated that the temperature of the exhaust gas recirculation pipe becomes lower than the target exhaust gas recirculation pipe temperature while the introduction of the EGR gas is stopped, it is determined that the exhaust gas recirculation pipe needs to be heated. In this case, since it is determined by estimation that the temperature of the exhaust gas recirculation pipe has become lower than the target exhaust gas recirculation pipe temperature, the exhaust gas recirculation pipe during the stoppage of the introduction of EGR gas can be more easily There is an advantage that it can be determined that the temperature is lower than the target exhaust gas recirculation pipe temperature.

  In the above invention, a method for predicting that the temperature of the exhaust gas recirculation pipe is lower than the target exhaust gas recirculation pipe temperature is not particularly limited. For example, as an example of this technique, the operation of the internal combustion engine is stopped. A method of predicting that the temperature of the exhaust gas recirculation pipe will be lower than the target exhaust gas recirculation pipe temperature when it is urged can be adopted. In the above invention, a method for estimating that the temperature of the exhaust gas recirculation pipe is lower than the target exhaust gas recirculation pipe temperature is not particularly limited. For example, as an example of this technique, the operation of the internal combustion engine is performed. It is possible to employ a method of estimating that the temperature of the exhaust gas recirculation pipe is lower than the target exhaust gas recirculation pipe temperature when the engine is stopped.

  When the operation of the internal combustion engine is stopped, the exhaust gas does not flow in the exhaust gas recirculation pipe, so that there is a high probability that the temperature of the cooling water is lower than the target cooling water temperature. In this case, it is predicted that the temperature of the cooling water will be lower than the target cooling water temperature because the operation of the internal combustion engine is stopped, or that the temperature of the cooling water is lower than the target cooling water temperature. Is preferable from the viewpoint of easily performing these predictions or estimations.

  In addition, as a method for determining that it is necessary to heat the exhaust gas recirculation pipe, for example, the target cooling water temperature is set as the target cooling water temperature, and the cooling water temperature becomes lower than the target cooling water temperature. It is also possible to adopt a method of determining that it is necessary to heat the exhaust gas recirculation pipe.

  When this configuration is adopted, there is an advantage that the temperature of the cooling water can be maintained at the target cooling water temperature. If the desired cooling water temperature (for example, the above-mentioned EGR gas lower limit temperature) is set to the target cooling water temperature in order to achieve the desired performance as the performance of the internal combustion engine, the desired performance can be ensured as the performance of the internal combustion engine. Can be achieved.

  Further, as a method for determining that it is necessary to heat the exhaust gas recirculation pipe, for example, a target cooling water temperature is set as the target cooling water temperature, and the cooling water temperature is predicted to be lower than the target cooling water temperature. Alternatively, a method may be employed in which it is determined that the exhaust recirculation pipe needs to be heated when the temperature of the cooling water is estimated to be lower than the target cooling water temperature.

  If a configuration is adopted in which it is determined that the exhaust recirculation pipe needs to be heated when the cooling water temperature is predicted to be lower than the target cooling water temperature, the cooling water temperature is actually Since it is judged that the exhaust gas recirculation pipe needs to be heated before the temperature becomes lower than the water temperature, there is an advantage that the temperature of the cooling water can be maintained more reliably than the target cooling water temperature. . On the other hand, when a configuration is adopted in which it is determined that the exhaust recirculation pipe needs to be heated when it is estimated that the temperature of the cooling water has become lower than the target cooling water temperature, the temperature of the cooling water is reduced to the target cooling temperature. Since it is determined by estimation that the temperature is lower than the water temperature, there is an advantage that it is possible to more easily determine that the temperature of the cooling water has become lower than the target cooling water temperature.

  In the above invention, the method for predicting that the temperature of the cooling water is lower than the target cooling water temperature is not particularly limited. For example, as an example of this method, when the operation of the internal combustion engine is stopped In addition, a method for predicting that the temperature of the cooling water is lower than the target cooling water temperature can be employed. In the above invention, the method for estimating that the temperature of the cooling water has become lower than the target cooling water temperature is not particularly limited. For example, as an example of this method, the operation of the internal combustion engine was stopped. A technique of estimating that the temperature of the cooling water is sometimes lower than the target cooling water temperature can be employed.

  When the operation of the internal combustion engine is stopped, the exhaust gas does not flow in the exhaust gas recirculation pipe, so that there is a high probability that the temperature of the cooling water is lower than the target cooling water temperature. In this case, it is predicted that the temperature of the cooling water will be lower than the target cooling water temperature because the operation of the internal combustion engine is stopped, or that the temperature of the cooling water is lower than the target cooling water temperature. Is preferable from the viewpoint of easily performing these predictions or estimations.

  Further, as a method for determining that it is necessary to heat the exhaust gas recirculation pipe, for example, a method for determining that it is necessary to heat the exhaust gas recirculation pipe when it is predicted that the internal combustion engine is started. It can also be adopted.

  When this configuration is adopted, even if the introduction of the exhaust gas into the intake passage by the exhaust gas recirculation device is started immediately after the internal combustion engine is started, it is possible to introduce a relatively high temperature exhaust gas into the intake passage. There are advantages. That is, when the operation of the internal combustion engine is stopped, the exhaust gas does not flow through the exhaust gas recirculation pipe, so the temperature of the exhaust gas recirculation pipe decreases. Here, if the temperature of the exhaust gas recirculation pipe is too low, exhaust gas having a temperature lower than the assumed temperature may be introduced into the intake passage by the exhaust gas recirculation device. However, when the above configuration is adopted, it is determined that it is necessary to heat the exhaust gas recirculation pipe when it is predicted that the internal combustion engine will be started, and the exhaust gas recirculation pipe is heated. Therefore, when the internal combustion engine is started, at least the temperature of the exhaust gas recirculation pipe is raised. For these reasons, when the above configuration is adopted, even if the introduction of the exhaust gas into the intake passage by the exhaust gas recirculation device is started immediately after the internal combustion engine is started, the exhaust gas having a relatively high temperature is introduced into the intake passage. The advantage of being able to do so is obtained.

  Still another invention of the present application includes an internal combustion engine including the exhaust gas recirculation device according to the invention described above, and an electric motor, and at least of power output from the internal combustion engine and power output from the electric motor. The present invention relates to a hybrid system that outputs one as power. In the hybrid system of the present invention, when it is not necessary to output power from the internal combustion engine, the operation of the internal combustion engine is stopped, and it is necessary to output power from the internal combustion engine while the operation of the internal combustion engine is stopped. When it occurs, the internal combustion engine is started.

  In the hybrid system, since the operation of the internal combustion engine is stopped relatively frequently, the introduction of exhaust gas into the intake passage is also stopped relatively frequently. For this reason, the temperature of the exhaust gas recirculation pipe is likely to be lower than the minimum required temperature. In the present invention, when it is necessary to heat the exhaust gas recirculation pipe when the operation of the internal combustion engine is stopped (that is, when the temperature of the exhaust gas recirculation pipe becomes lower than the minimum required temperature), the exhaust gas is exhausted. Since the recirculation pipe is heated, the present invention has the advantage that when the operation of the internal combustion engine is started, the temperature of the exhaust recirculation pipe is maintained at a temperature higher than the minimum required temperature.

  In the above invention, the timing at which heating of the exhaust gas recirculation pipe by the heating means is started is not limited to a specific timing as long as the cooling water circulation is stopped in the cooling water circulation passage. For example, the heating of the exhaust gas recirculation pipe by the heating means may be started simultaneously with the stop of the circulation of the cooling water in the cooling water circulation passage.

  When this configuration is adopted, when the temperature of the exhaust gas recirculation pipe is greatly reduced within a relatively short time after the stoppage of the introduction of the EGR gas, the temperature of the exhaust gas recirculation pipe is set during the stoppage of the introduction of the EGR gas. There is an advantage that it can be reliably maintained at a relatively high temperature. In other words, if the temperature of the exhaust gas recirculation pipe drops significantly within a relatively short time after the introduction of EGR gas is stopped, heating of the exhaust gas recirculation pipe must be started as soon as possible after the introduction of EGR gas is stopped. In this case, there is a possibility that the temperature of the exhaust gas recirculation pipe becomes a temperature that is equal to or lower than the temperature at which the above undesirable situation occurs. Here, when the above configuration is adopted, heating of the exhaust gas recirculation pipe is started simultaneously with the stop of the circulation of the cooling water, so that the exhaust gas recirculation pipe is started within a relatively short time from the stop of the introduction of the EGR gas. Is heated. For this reason, the temperature of the exhaust gas recirculation pipe can be reliably maintained at a relatively high temperature while the introduction of the EGR gas is stopped.

  Alternatively, in the above invention, heating of the exhaust gas recirculation pipe by the heating means may be started when a predetermined time has elapsed from the stop of the circulation of the cooling water in the cooling water circulation passage.

  When this configuration is adopted, when the temperature of the exhaust gas recirculation pipe does not drop significantly within a relatively short time after the stoppage of the introduction of the EGR gas, the temperature of the exhaust gas recirculation pipe is set during the stoppage of the introduction of the EGR gas. There is an advantage that energy can be efficiently maintained at a relatively high temperature. That is, when the temperature of the exhaust gas recirculation pipe does not drop significantly within a relatively short time after the stop of the introduction of the EGR gas, the circulation of the cooling water is stopped within a relatively short time after the stop of the introduction of the EGR gas. Even if heating of the exhaust gas recirculation pipe is not started simultaneously with the stop, the temperature of the exhaust gas recirculation pipe is less likely to be a temperature equal to or lower than the temperature at which the above undesirable situation occurs. Therefore, in such a case, it is disadvantageous from the viewpoint of energy efficiency to heat the exhaust gas recirculation pipe simultaneously with the stop of the cooling water circulation. When the above configuration is adopted, the heating of the exhaust gas recirculation pipe is started when a predetermined time has elapsed since the circulation of the cooling water is stopped. Therefore, the exhaust gas recirculation pipe is stopped while the introduction of the EGR gas is stopped. It is possible to maintain the temperature at a relatively high temperature in an energy efficient manner.

  The internal combustion engine is provided with an exhaust gas recirculation device, and the above advantages can be obtained when the invention is applied to the internal combustion engine. Therefore, the internal combustion engine of the invention is an internal combustion engine provided with an exhaust gas recirculation device. Any internal combustion engine may be used as long as it is an engine. Therefore, the internal combustion engine of the above invention may be, for example, a compression self-ignition internal combustion engine (so-called diesel engine) or a spark ignition internal combustion engine (so-called gasoline engine).

  Further, the heating means of the above invention may be any means as long as it can heat the exhaust gas recirculation pipe. Therefore, the heating means of the above invention may be, for example, a means for heating the exhaust gas recirculation pipe using electric power, or a means for heating the exhaust gas recirculation pipe using thermal power. It may be a means for heating the exhaust gas recirculation pipe using energy other than electric power or thermal power.

It is the figure which showed the internal combustion engine to which the exhaust gas recirculation apparatus of 1st Embodiment was applied. (A) is a diagram showing an engine operation region in which the exhaust gas is introduced into the intake passage by the exhaust gas recirculation device and an engine operation region in which the introduction of the exhaust gas into the intake passage is stopped by the exhaust gas recirculation device. (B) is the figure which showed the map used in order to acquire a target EGR rate. It is a figure for demonstrating control of the exhaust gas recirculation apparatus of 1st Embodiment. It is the figure which showed an example of the routine which performs control of the exhaust gas recirculation control valve (EGR control valve) of 1st Embodiment. It is the figure which showed an example of the routine which performs control of the EGR cooler and EGR heater of 1st Embodiment. It is a figure for demonstrating control of the exhaust gas recirculation apparatus of 2nd Embodiment. It is the figure which showed a part of example of the routine which performs control of the EGR cooler and EGR heater of 2nd Embodiment. It is the figure which showed a part of example of the routine which performs control of the EGR cooler and EGR heater of 2nd Embodiment. It is a figure for demonstrating control of the exhaust gas recirculation apparatus of 3rd Embodiment. It is the figure which showed a part of example of the routine which performs control of the EGR cooler and EGR heater of 3rd Embodiment. It is the figure which showed a part of example of the routine which performs control of the EGR cooler and EGR heater of 3rd Embodiment. It is a figure for demonstrating control of the exhaust gas recirculation apparatus of 4th Embodiment. It is the figure which showed a part of example of the routine which performs control of the EGR cooler and EGR heater of 4th Embodiment. It is the figure which showed a part of example of the routine which performs control of the EGR cooler and EGR heater of 4th Embodiment. It is the figure which showed an example of the routine which performs control of the EGR cooler and EGR heater of 5th Embodiment. It is the figure which showed an example of the routine which performs control of the EGR cooler and EGR heater of 6th Embodiment. It is the figure which showed a part of example of the routine which performs control of the EGR cooler and EGR heater of 7th Embodiment. It is the figure which showed a part of example of the routine which performs control of the EGR cooler and EGR heater of 7th Embodiment. It is the figure which showed the hybrid vehicle provided with the power unit which comprises the internal combustion engine to which the exhaust gas recirculation apparatus of 8th Embodiment was applied.

  Hereinafter, an embodiment of an exhaust gas recirculation device for an internal combustion engine according to the present invention (hereinafter referred to as “first embodiment”) will be described. In the following description, “engine operation” means “operation of the internal combustion engine”, “engine operation state” means “operation state of the internal combustion engine”, and “engine speed” means “internal combustion engine”. "Engine speed" means "load of the internal combustion engine".

  An internal combustion engine to which the exhaust gas recirculation device of the first embodiment is applied is shown in FIG. The internal combustion engine shown in FIG. 1 is a compression self-ignition internal combustion engine (so-called diesel engine). In FIG. 1, 10 is an internal combustion engine, 20 is a main body of the internal combustion engine 10, 21 is a fuel injection valve, 22 is a fuel pump, 23 is a fuel supply passage, 30 is an intake passage, 31 is an intake manifold, 32 is an intake pipe, 33 Is a throttle valve, 36 is an air cleaner, 40 is an exhaust passage, 41 is an exhaust manifold, 42 is an exhaust pipe, 50 is an exhaust gas recirculation device (hereinafter referred to as "EGR device"), and 80 is an electronic control device. Yes. The intake passage 30 includes an intake manifold 31 and an intake pipe 32. The exhaust passage 40 includes an exhaust manifold 41 and an exhaust pipe 42.

  The electronic control unit 80 is composed of a microcomputer. The electronic control unit 80 includes a CPU (ie, a microprocessor) 81, a ROM (ie, a read-only memory) 82, a RAM (ie, a random access memory) 83, a backup RAM 84, and an interface 85. The CPU 81, ROM 82, RAM 83, backup RAM 84, and interface 85 are electrically connected to each other via a bidirectional bus.

  The fuel injection valve 21 is attached to the main body 20 of the internal combustion engine. A fuel pump 22 is connected to the fuel injection valve 21 via a fuel supply passage 23. The fuel pump 22 supplies high-pressure fuel to the fuel injection valve 21 via the fuel supply passage 23. The fuel injection valve 21 is electrically connected to the interface 85 of the electronic control device 80. The electronic control unit 80 supplies a command signal for causing the fuel injection valve 21 to inject fuel to the fuel injection valve 21. When a command signal is supplied from the electronic control unit 80 to the fuel injection valve 21, the fuel injection valve 21 directly injects fuel into the combustion chamber.

  The intake manifold 31 is branched into a plurality of pipes at one end thereof. These branched pipes are connected to intake ports (not shown) formed respectively corresponding to the combustion chambers of the main body 20 of the internal combustion engine. The intake manifold 31 is connected to one end of the intake pipe 32 at the other end.

  The exhaust manifold 41 is branched into a plurality of pipes at one end thereof. These branched pipes are connected to exhaust ports (not shown) formed respectively corresponding to the combustion chambers of the main body 20 of the internal combustion engine. The exhaust manifold 41 is connected to one end of the exhaust pipe 42 at the other end.

  The throttle valve 33 is disposed in the intake pipe 32. When the opening of the throttle valve 33 (hereinafter, this opening is referred to as “throttle valve opening”) is changed, the flow path area in the intake pipe 32 in the region where the throttle valve 33 is disposed changes. As a result, the amount of air passing through the throttle valve 33 changes, and as a result, the amount of air taken into the combustion chamber changes. An actuator (hereinafter referred to as “throttle valve actuator”) 33A for changing the operating state (that is, the throttle valve opening) is connected to the throttle valve 33. The throttle valve actuator 33A is electrically connected to the interface 85 of the electronic control unit 80. The electronic control unit 80 supplies a control signal for driving the throttle valve actuator 33A to operate the throttle valve 33 to the throttle valve actuator 33A.

  The EGR device 50 includes an exhaust gas recirculation pipe (hereinafter referred to as “EGR pipe”) 51, an exhaust gas recirculation control valve (hereinafter referred to as “EGR control valve”) 52, and an exhaust gas recirculation cooler (hereinafter referred to as “EGR control valve”). This cooler is provided with an “EGR cooler” 53 and an exhaust gas recirculation heater (hereinafter referred to as “EGR heater”) 54. The EGR device 50 can introduce the exhaust gas discharged from the combustion chamber into the exhaust passage 40 into the intake passage 30 via the EGR pipe 51. The EGR pipe 51 is connected to the exhaust passage 40 (more specifically, the exhaust manifold 41) at one end, and connected to the intake passage 30 (more specifically, the intake manifold 31) at the other end. Yes. That is, the EGR pipe 51 connects the exhaust passage 40 to the intake passage and 39.

  The EGR control valve 52 is disposed in the EGR pipe 51. When the opening degree of the EGR control valve 52 (hereinafter, this opening degree is referred to as “EGR control valve opening degree”) is changed, the amount of exhaust gas passing through the EGR control valve 52 is changed, and eventually introduced into the intake passage 30. The amount of exhaust gas is changed. The EGR control valve 52 incorporates an actuator (hereinafter, this actuator is referred to as an “EGR control valve actuator”) for changing its operating state (that is, the EGR control valve opening). The EGR control valve actuator is electrically connected to the interface 85 of the electronic control device 80. The electronic control unit 80 supplies a control signal for driving the EGR control valve actuator to operate the EGR control valve 52 to the EGR control valve actuator.

  The EGR cooler 53 includes a cooling unit 55, a cooling water circulation pipe 56, and a cooling water circulation pump 57. One end of the cooling water circulation pipe 56 is connected to the cooling water inlet of the cooling water passage inside the cooling unit 55, and the other end is connected to the cooling water outlet of the cooling water passage inside the cooling unit 55. A cooling water circulation passage is formed by the cooling water circulation pipe 56 and the cooling water passage inside the cooling portion 55. The cooling water circulation pump 57 is disposed in the cooling water circulation pipe 56. The cooling water circulation pump 57 is electrically connected to the interface 85 of the electronic control device 80. The electronic control unit 80 supplies a control signal (hereinafter, this signal is referred to as “pump operation signal”) for operating the cooling water circulation pump 57 to the cooling water circulation pump 57. When a pump operation signal is supplied from the electronic control unit 80 to the cooling water circulation pump 57, the cooling water circulation pump 57 circulates the cooling water in the cooling water circulation passage. On the other hand, when the supply of the pump operation signal from the electronic control unit 80 to the cooling water circulation pump 57 is stopped, the cooling water circulation in the cooling water circulation passage by the cooling water circulation pump 57 is stopped.

  When the cooling water is circulated in the cooling water circulation passage 56 by the cooling water circulation pump 57, the cooling water released from the cooling water circulation pump 57 is cooled in the cooling water passage inside the cooling unit 55 via the cooling water circulation pipe 56. It flows into the cooling water passage from the water inlet. The cooling water that has flowed into the cooling water passage flows through the cooling water passage and flows out from the cooling water outlet of the cooling water passage to the cooling water circulation pipe 56. Then, the cooling water flowing out to the cooling water circulation pipe 56 reaches the cooling water circulation pump 57 through the cooling water circulation pipe 56. The temperature of the cooling water in the cooling water circulation passage decreases as the cooling water is circulated in the cooling water circulation passage. When the temperature of the cooling water flowing through the cooling water passage inside the cooling unit 55 is lower than the temperature of the EGR pipe 51, the cooling water cools the EGR pipe 51 and consequently exhaust gas flowing through the EGR pipe 51. Cooling.

  The EGR heater 54 is disposed in the cooling part 55 of the EGR cooler 53. Further, the EGR heater 54 is caused to generate heat by electric power, and the cooling water in the cooling water passage inside the cooling unit 55 can be heated by the heat. The EGR heater 54 is electrically connected to the interface 85 of the electronic control device 80. The electronic control unit 80 supplies a control signal for operating the EGR heater 54 (hereinafter, this signal is referred to as “heater operation signal”) to the EGR heater 54. When a heater operation signal is supplied from the electronic control unit 80 to the EGR heater 54, the EGR heater 54 generates heat. On the other hand, when the supply of the heater operation signal from the electronic control unit 80 to the EGR heater 54 is stopped, the heat generation of the EGR heater 54 is stopped.

  Next, control of the EGR control valve of the first embodiment will be described. In the first embodiment, the exhaust gas is introduced into the intake passage by the EGR device (hereinafter, this introduction is referred to as “EGR gas introduction”) according to the engine operating state determined by the engine speed and the engine load. Or not is determined. More specifically, when the engine operating state determined by the engine speed NE and the engine load L is in the region X of FIG. 2A, introduction of EGR gas is executed. On the other hand, when the engine operating state determined by the engine speed NE and the engine load L is in the region Y of FIG. 2A, the introduction of EGR gas is not executed. As can be seen from FIG. 2A, the region X is a region where the engine speed NE is relatively small and the engine load L is relatively small, and the region Y is the other region.

  When the introduction of EGR gas is executed, the appropriate EGR rate (that is, the ratio of the amount of EGR gas to the total amount of gas sucked into the combustion chamber) varies depending on the engine operating state. Therefore, in the first embodiment, an appropriate EGR rate corresponding to the engine operating state is obtained in advance by experiments or the like, and the obtained EGR rate is calculated as the engine speed NE as shown in FIG. The target EGR rate TRegr is stored in the electronic control unit in the form of a function map with the engine load L. Then, when the introduction of EGR gas is executed during engine operation, the target EGR rate TRegr corresponding to the engine speed NE and the engine load L at that time is acquired from the map of FIG. And the control signal for controlling an EGR control valve so that the target EGR rate acquired in this way is achieved is supplied to an EGR control valve actuator from an electronic controller. Then, the EGR control valve actuator drives the EGR control valve according to the control signal thus supplied.

  Next, control of the EGR cooler of the first embodiment will be described. In the first embodiment, the operation of the EGR cooler (more specifically, the cooling water circulation pump) is started simultaneously with the introduction of EGR gas. Then, at the same time as the introduction of EGR gas is stopped, the operation of the EGR cooler is also stopped. Therefore, while the EGR gas is being introduced, the EGR cooler is operated, the cooling water is circulated in the cooling water circulation passage, the cooling water cools the EGR pipe, and the temperature of the EGR pipe is lowered. As a result, the exhaust gas flowing in the EGR pipe is cooled, and the temperature of the exhaust gas is lowered. On the other hand, while the introduction of the EGR gas is stopped, the operation of the EGR cooler is stopped, and the cooling water circulation in the cooling water circulation passage by the cooling water circulation pump (hereinafter, this circulation is also simply referred to as “cooling water circulation”). Is not done.

  Next, control of the EGR heater according to the first embodiment will be described. In the first embodiment, the operation of the EGR heater is started at the same time when the operation of the EGR cooler is stopped (that is, when the introduction of EGR gas is stopped). The operation of the EGR heater is stopped when a predetermined time (hereinafter referred to as “predetermined heater operation time”) has elapsed since the operation of the EGR heater was started. Accordingly, the EGR heater is operated until the predetermined heater operating time elapses after the operation of the EGR cooler is stopped, the cooling water is heated by the EGR heater, and the temperature of the cooling water is increased. As a result, the EGR pipe Is heated to raise the temperature of the EGR tube. On the other hand, from the time when the predetermined heater operation time has elapsed until the next operation of the EGR cooler is stopped, the operation of the EGR heater is stopped and heating of the cooling water by the EGR heater (hereinafter, this heating is simply referred to as “cooling water”). (Also referred to as “heating”) is not performed. When the operation of the EGR cooler is started during the predetermined heater operation time, the operation of the EGR heater is stopped when the operation of the EGR cooler starts.

  In the case where the EGR device (that is, the EGR control valve, the EGR cooler, and the EGR heater) is controlled according to the control described above, whether or not the EGR gas is introduced by the EGR device, whether or not the cooling water is circulated by the EGR cooler, and An example of the presence or absence of heating of the cooling water by the EGR heater is shown in FIG.

  In the example of FIG. 3, the engine operating state is in the region X before time T0. Therefore, before the time T0, the EGR gas is introduced and the cooling water is circulated, but the cooling water is not heated. At time T0, the introduction of the EGR gas is stopped at the same time as the engine operating state shifts from the region X to the region Y, and at the same time, the circulation of the cooling water is stopped, and at the same time, the heating of the cooling water is started. Then, at the time T1 when the predetermined heater operation time has elapsed from the time T0, the heating of the cooling water is stopped. At time T2 after time T1, the engine operating state shifts from the region Y to the region X, and at the same time, introduction of EGR gas is started, and at the same time, circulation of the cooling water is started. Is maintained in a stopped state.

  The first embodiment has an advantage that the temperature of the cooling water can be increased at a high temperature increase rate while the introduction of the EGR gas is stopped. That is, since the exhaust gas does not flow through the EGR pipe while the introduction of the EGR gas is stopped, the temperature of the EGR pipe decreases. Here, if the temperature of the EGR pipe becomes lower than a certain temperature while the introduction of the EGR gas is stopped, for example, condensed water is generated on the inner wall surface of the EGR pipe, and the EGR pipe is corroded by the condensed water. An unfavorable situation may occur. Therefore, in order to suppress the corrosion of the EGR pipe due to the condensed water, it is preferable to maintain the temperature of the EGR pipe at a temperature higher than the generation temperature of the condensed water while the introduction of the EGR gas is stopped. In addition, the temperature of exhaust gas introduced into the intake passage by the EGR device by various control systems (for example, a system for controlling an EGR control valve, a system for controlling a throttle valve, a system for controlling a fuel injection valve) of an internal combustion engine Is constructed on the premise that the temperature is higher than a certain temperature, the temperature of the EGR pipe is equal to or lower than the above certain temperature (hereinafter referred to as “assumed temperature”) while the introduction of the EGR gas is stopped. When the temperature of the EGR gas is reduced, when the introduction of the EGR gas is resumed, there is a possibility that exhaust gas having a temperature lower than the assumed temperature is introduced into the intake passage. This means that various control systems for exhaust gas recirculation exhibit desired control characteristics (for example, control characteristics such as suppressing emission in exhaust gas discharged from the combustion chamber to a level lower than a predetermined level) ) Is not preferred. Therefore, in order to prevent the exhaust gas having a temperature lower than the assumed temperature from being introduced into the intake passage, the temperature of the EGR pipe is maintained at a temperature higher than the assumed temperature while the introduction of the EGR gas is stopped. Is preferred.

  In order to maintain the temperature of the EGR pipe at a temperature higher than the generation temperature of the condensed water while stopping the introduction of the EGR gas, or to maintain the temperature of the EGR pipe at a temperature higher than the assumed temperature, the EGR gas The temperature of the cooling water in the cooling water passage inside the cooling unit when the introduction of the cooling water is stopped (hereinafter, this cooling water is referred to as “cooling unit cooling water”) is higher than the generation temperature of the condensed water or higher than the assumed temperature. It is effective to keep the temperature high. That is, in order to suppress the occurrence of an unfavorable situation including the above situation, it is effective to keep the temperature of the cooling section cooling water relatively high while the introduction of the EGR gas is stopped.

  And considering that the rate of decrease in the temperature of the EGR pipe during the stop of the introduction of the EGR gas is relatively large, in order to maintain the temperature of the cooling section cooling water at a relatively high temperature during the stop of the introduction of the EGR gas. Therefore, it is required to increase the temperature of the cooling section cooling water at a high temperature increase rate while the introduction of EGR gas is stopped. Here, in the first embodiment, the cooling section cooling water is heated by the EGR heater in a state where the circulation of the cooling water in the cooling water circulation passage while the introduction of the EGR gas is stopped is stopped. Therefore, the temperature rise rate of the cooling section cooling water is higher than that in the case where the cooling section cooling water is heated by the EGR heater in a state where the circulation of the cooling water in the cooling water circulation passage is not stopped. Therefore, the advantage that the temperature of the cooling section cooling water can be increased at a high temperature increase rate while the introduction of the EGR gas is stopped is obtained.

  In the first embodiment, when the temperature of the cooling water greatly decreases within a relatively short time after the stop of the introduction of the EGR gas, the temperature of the coolant is relatively high during the stop of the introduction of the EGR gas. There is an advantage that the temperature can be reliably maintained. That is, when the temperature of the cooling water greatly decreases within a relatively short time after the stop of the introduction of the EGR gas, the cooling water is not heated unless the heating of the coolant is started as early as possible after the stop of the introduction of the EGR gas. There is a possibility that the temperature of the temperature will be equal to or lower than the temperature at which the above undesirable situation occurs. Here, in the first embodiment, heating of the cooling water is started simultaneously with the stop of the circulation of the cooling water, that is, simultaneously with the stop of the introduction of the EGR gas. The cooling water is heated inside. For this reason, the temperature of the cooling water can be reliably maintained at a relatively high temperature while the introduction of the EGR gas is stopped.

  In the first embodiment, the EGR heater is arranged in the cooling part of the EGR cooler so that the cooling water in the cooling water passage inside the cooling part of the EGR cooler can be heated. However, in order to obtain the above-mentioned advantage, the essential structure is that the cooling water in the cooling water circulation passage is heated by the EGR heater while the cooling water circulation is stopped by the cooling water circulation pump. Therefore, from the viewpoint of obtaining the above advantages, the EGR heater may be arranged so as to heat the cooling water in the cooling water circulation passage.

  Further, the predetermined heater operating time of the first embodiment is set to a temperature sufficient for the temperature of the cooling section cooling water during the stoppage of the introduction of the EGR gas to rise to a temperature considered appropriate from various viewpoints. For example, it may be set according to the time from the start to the stop of the introduction of the EGR gas immediately before the start of the operation of the EGR heater (hereinafter, this time is referred to as “EGR gas introduction time”). It may be set according to the amount of exhaust gas introduced into the intake passage from the start to the stop of the introduction of EGR gas immediately before the start of the heater operation (this amount is hereinafter referred to as “EGR gas introduction amount”). When the operation time of the EGR heater is set according to the EGR gas introduction time, for example, the predetermined heater operation time is set to a longer time as the EGR gas introduction time is longer, and the operation time of the EGR heater is set to the EGR gas introduction amount. When set accordingly, for example, the predetermined heater operating time is set to a longer time as the EGR gas introduction amount is larger.

  Next, an example of a routine for executing control of the EGR control valve of the first embodiment will be described. An example of this routine is shown in FIG. Note that the routine of FIG. 4 is a routine that is executed every time a predetermined time elapses.

  When the routine of FIG. 4 is started, first, at step 10, the current engine speed NE and the current engine load L are acquired. Next, at step 11, it is determined based on the engine speed NE and the engine load L acquired at step 10 whether or not the current engine operating state is in the region X of FIG. Here, when it is determined that the engine operating state is in the region X, the routine proceeds to step 12. On the other hand, when it is determined that the engine operating state is not in the region X (that is, when the current engine operating state is in the region Y), the routine proceeds to step 15.

  When it is determined in step 11 that the engine operating state is in the region X and the routine proceeds to step 12, the EGR gas introduction flag Fegr is set (Fegr ← 1). This EGR gas introduction flag Fegr is a flag that is set when the introduction of EGR gas is being executed, and is reset when the introduction of EGR gas is stopped. Next, at step 13, the target EGR rate TRegr corresponding to the engine speed NE and engine load L acquired at step 10 is acquired from the map of FIG. Next, at step 14, a control signal Sopen for opening the EGR control valve so as to achieve the target EGR rate TRegr obtained at step 13 is supplied to the EGR control valve actuator, and the routine ends.

  On the other hand, when it is determined in step 11 that the engine operating state is not in the region X and the routine proceeds to step 15, the EGR gas introduction flag Fegr is reset (Fegr ← 0). Next, at step 16, a control signal Close for fully closing the EGR control valve is supplied to the EGR control valve actuator, and the routine ends.

  Next, an example of a routine for executing control of the EGR cooler and the EGR heater according to the first embodiment will be described. An example of this routine is shown in FIG. Note that the routine of FIG. 5 is a routine that is executed every time a predetermined time elapses.

  When the routine of FIG. 5 is started, first, in step 100, the EGR gas introduction flag Fegr is acquired. The EGR gas introduction flag Fegr is a flag that is set at step 12 in FIG. 4 or reset at step 15 in FIG. Next, at step 101, it is judged if the EGR gas introduction flag Fegr acquired at step 100 is set (Fegr = 1). Here, when it is determined that Fegr = 1 (that is, when EGR gas is being introduced), the routine proceeds to step 102. On the other hand, when it is determined that it is not Fegr = 1 (that is, Fegr = 0) (that is, when the introduction of EGR gas is stopped), the routine proceeds to step 104.

  When it is determined in step 101 that Fegr = 1, and the routine proceeds to step 102, the pump operation signal SP is supplied from the electronic control unit to the cooling water circulation pump, and the heater operation signal SH from the electronic control unit to the EGR heater is supplied. Is stopped. Therefore, in this case, the cooling water is circulated, but the cooling water is not heated. Next, in step 103, the heating completion flag Fh is reset (Fh ← 0), and the routine ends. The heating completion flag Fh is a flag that is set when the operation of the EGR heater is stopped and reset when the EGR cooler is operated (that is, when EGR gas is being introduced).

  On the other hand, when it is determined in step 101 that Fegr = 1 is not established and the routine proceeds to step 104, it is determined whether or not the heating completion flag Fh is set (Fh = 1). The heating completion flag Fh is a flag that is set in step 111 when heating of the cooling water is completed after stopping the introduction of EGR gas and reset in step 103 when the introduction of EGR gas is resumed. Here, when it is determined that Fh = 1 (that is, when the heating of the cooling water is completed), the routine ends as it is. On the other hand, when it is determined that Fh = 1 is not satisfied (that is, Fh = 0) (that is, when heating of the cooling water is not completed), the routine proceeds to step 105.

  When it is determined in step 104 that Fh = 1 is not satisfied and the routine proceeds to step 105, the supply of the pump operation signal SP from the electronic control device to the cooling water circulation pump is stopped and the heater operation signal SH is sent from the electronic control device. Supplied to the EGR heater. Therefore, in this case, the cooling water is not circulated, but the cooling water is heated. Next, at step 106, the EGR gas introduction flag Fegr is acquired again. Next, at step 107, it is judged if the EGR gas introduction flag Fegr acquired at step 106 has been reset (Fegr = 0). Here, when it is determined that Fegr = 0 (that is, when the introduction of EGR gas is still stopped), the routine proceeds to step 108. On the other hand, when it is determined that Fegr = 0 is not satisfied (that is, Fegr = 1) (that is, when the introduction of EGR gas is resumed), the routine proceeds to step 112.

  In step 107, it is determined that Fegr = 0 is not satisfied, and when the routine proceeds to step 112, the heater operation time counter Ch is cleared. The heater operation time counter Ch is a counter that indicates the time that has elapsed since heating of the cooling water was started in step 105. Next, in step 102 and step 103, the processing described above is executed, and the routine ends.

  On the other hand, when it is determined in step 107 that Fegr = 0 and the routine proceeds to step 108, the heater operating time counter Ch is counted up. The heater operation time counter Ch is a counter indicating the time that has elapsed since the operation of the EGR heater was started in Step 105. Next, at step 109, it is determined whether or not the heater operation time counter Ch counted up at step 108 is equal to or greater than a value Chth corresponding to a predetermined heater operation time (Ch ≧ Chth). Here, when it is determined that Ch ≧ Chth (that is, when a predetermined heater operation time has elapsed since the operation of the EGR heater was started), the routine proceeds to step 110. On the other hand, if it is determined that Ch ≧ Chth is not satisfied, the routine returns to step 106, and step 106 to step 109 are repeatedly executed until it is determined in step 109 that Ch ≧ Chth.

  When it is determined in step 109 that Ch ≧ Chth and the routine proceeds to step 110, the supply of the heater operation signal SH from the electronic control unit to the EGR heater is stopped. Next, in step 111, the heating completion flag Fh is set (Fh ← 1), the heater operation time counter Ch is cleared, and the routine ends.

  Next, a second embodiment will be described. The configuration of the second embodiment not described below is the same as the configuration of the first embodiment, or is naturally derived from the configuration of the first embodiment when considering the configuration of the second embodiment. It is a configuration.

  Since the control of the EGR control valve of the second embodiment is the same as the control of the EGR control valve of the first embodiment, description of this control will be omitted, and control of the EGR cooler of the second embodiment will be described.

  In the second embodiment, the operation of the EGR cooler (more specifically, the cooling water circulation pump) is started simultaneously with the introduction of EGR gas. When the introduction of the EGR gas is stopped, the operation of the EGR cooler is performed when a predetermined time (hereinafter referred to as “predetermined cooler stop standby time”) has elapsed since the introduction of the EGR gas was stopped. Is stopped. Therefore, while the EGR gas is being introduced, the EGR cooler is operated, the cooling water is circulated in the cooling water circulation passage, the cooling water cools the EGR pipe, and the temperature of the EGR pipe is lowered. As a result, the exhaust gas flowing in the EGR pipe is cooled, and the temperature of the exhaust gas is lowered. In addition, the EGR cooler is activated and the cooling water is circulated in the cooling water circulation passage until the predetermined cooler stop standby time elapses after the introduction of the EGR gas is stopped, and the EGR pipe is cooled by the cooling water. As a result, the temperature of the EGR pipe is lowered. On the other hand, the operation of the EGR cooler is stopped and the circulation of the cooling water in the cooling water circulation passage is not performed until the introduction of the EGR gas is started next after the predetermined cooler stop standby time has elapsed. When the introduction of EGR gas is started during the predetermined cooler stop standby time, the operation of the EGR cooler is started at the start of introduction of the EGR gas.

  Next, control of the EGR heater according to the second embodiment will be described. In the second embodiment, the operation of the EGR heater is started simultaneously with the operation of the EGR cooler being stopped. The operation of the EGR heater is stopped when a predetermined time (hereinafter referred to as “predetermined heater operation time”) has elapsed since the operation of the EGR heater was started. Accordingly, the EGR heater is operated until the predetermined heater operating time elapses after the operation of the EGR cooler is stopped, the cooling water is heated by the EGR heater, and the temperature of the cooling water is increased. As a result, the EGR pipe Is heated to raise the temperature of the EGR tube. On the other hand, the operation of the EGR heater is stopped and the cooling water is not heated until the operation of the EGR cooler is stopped next time after the predetermined heater operation time has elapsed. When the operation of the EGR cooler is started during the predetermined heater operation time, the operation of the EGR heater is stopped when the operation of the EGR cooler starts.

  In the case where the EGR device (that is, the EGR control valve, the EGR cooler, and the EGR heater) is controlled according to the control described above, whether or not the EGR gas is introduced by the EGR device, whether or not the cooling water is circulated by the EGR cooler, and An example of the presence or absence of heating of the cooling water by the EGR heater is shown in FIG.

  In the example of FIG. 6, the engine operating state is in the region X before time T0. Therefore, before the time T0, the EGR gas is introduced and the cooling water is circulated, but the cooling water is not heated. At the time T0, the introduction of the EGR gas is stopped at the same time as the engine operating state shifts from the region X to the region Y, and at the time T1 when the predetermined cooler stop waiting time has elapsed from the stop of the introduction of the EGR gas. Circulation is stopped and at the same time heating of the cooling water is started. Then, at time T2 when a predetermined heater operating time has elapsed from time T1, heating of the cooling water is stopped. At time T3 after time T2, the introduction of EGR gas is started at the same time as the engine operating state shifts from the region Y to the region X, and at the same time, circulation of the cooling water is started. Is maintained in a stopped state.

  The second embodiment has an advantage that the temperature of the cooling water can be increased at a high temperature increase rate during the stop of the introduction of the EGR gas for the same reason as described in relation to the first embodiment. is there.

  Further, in the second embodiment, similarly to the first embodiment, when the temperature of the cooling water greatly decreases within a relatively short time after the introduction of the EGR gas, the cooling water is stopped while the introduction of the EGR gas is stopped. There is an advantage that the temperature can be reliably maintained at a relatively high temperature. That is, when the temperature of the cooling water greatly decreases within a relatively short time after the stop of the introduction of the EGR gas, the cooling water is not heated unless the heating of the coolant is started as early as possible after the stop of the introduction of the EGR gas. There is a possibility that the temperature of the temperature will be equal to or lower than the temperature at which the above undesirable situation occurs. Here, in the second embodiment, the cooling water heating is started at the same time as the cooling water circulation is stopped, that is, in a relatively short time after the EGR gas introduction is stopped. The cooling water is heated within a relatively short time after the stop. For this reason, the temperature of the cooling water can be reliably maintained at a relatively high temperature while the introduction of the EGR gas is stopped.

  Next, an example of a routine for executing control of the EGR cooler and the EGR heater according to the second embodiment will be described. An example of this routine is shown in FIGS. Note that the routines shown in FIGS. 7 and 8 are executed every time a predetermined time elapses.

  When the routines of FIGS. 7 and 8 are started, first, in step 200 of FIG. 7, the EGR gas introduction flag Fegr is acquired. The EGR gas introduction flag Fegr is a flag that is set at step 12 in FIG. 4 or reset at step 15 in FIG. Next, in step 201, it is determined whether or not the EGR gas introduction flag Fegr acquired in step 200 is set (Fegr = 1). Here, when it is determined that Fegr = 1 (that is, when EGR gas is being introduced), the routine proceeds to step 202. On the other hand, when it is determined that it is not Fegr = 1 (that is, Fegr = 0) (that is, when the introduction of EGR gas is stopped), the routine proceeds to step 204.

  When it is determined in step 201 that Fegr = 1, and the routine proceeds to step 202, the same processing as step 102 in FIG. 5 is executed, and then in step 203, the same processing as step 103 in FIG. The routine ends.

  On the other hand, when it is determined in step 201 that Fegr = 1 is not established and the routine proceeds to step 204, it is determined whether or not the heating completion flag Fh is set (Fh = 1). This heating completion flag Fh is a flag that is set in step 211 when heating of the cooling water is completed after stopping the introduction of EGR gas, and reset in step 203 when the introduction of EGR gas is resumed. Here, when it is determined that Fh = 1 (that is, when the heating of the cooling water is completed), the routine ends as it is. On the other hand, when it is determined that Fh = 1 is not satisfied (that is, Fh = 0) (that is, when heating of the cooling water is not completed), the routine proceeds to step 204A.

  When it is determined in step 204 that Fh = 1 is not satisfied and the routine proceeds to step 204A, the EGR gas introduction flag Fegr is acquired again. Next, in step 204B, it is determined whether or not the EGR gas introduction flag Fegr acquired in step 204A has been reset (Fegr = 0). Here, when it is determined that Fegr = 0 (that is, when the introduction of EGR gas is still stopped), the routine proceeds to step 204C. On the other hand, when it is determined that it is not Fegr = 0 (that is, Fegr = 1) (that is, when the introduction of EGR gas is resumed), the routine proceeds to step 212.

  If it is determined in step 204B that Fegr = 0 is not satisfied and the routine proceeds to step 212, the same processing as step 112 in FIG. 5 is executed, and then in step 202 and step 203, step 102 and step 103 in FIG. The same processing is executed, and the routine ends.

  On the other hand, when it is determined in step 204B that Fegr = 0, and the routine proceeds to step 204C, the EGR gas introduction stop time counter Cegr is counted up. The EGR gas introduction stop time counter Cegr is a counter that indicates the time that has elapsed since it was first determined in step 204 that Fegr = 1 is not satisfied, that is, the time that has elapsed since the introduction of EGR gas was stopped. Next, in step 204D, it is determined whether or not the EGR gas introduction stop time counter Cegr counted up in step 204C is equal to or greater than a value Cegrth corresponding to a predetermined cooler stop standby time (Cegr ≧ Cegrth). Here, when it is determined that Cegr ≧ Cegrth (that is, when the predetermined cooler stop standby time has elapsed since the introduction of EGR gas was stopped), the routine proceeds to step 205 in FIG. On the other hand, if it is determined that Cegr ≧ Cegrth is not satisfied, the routine returns to step 204A, and step 204A to step 204D are repeatedly executed until it is determined in step 204D that Cegr ≧ Cegrth.

  When it is determined in step 204D that Cegr ≧ Cegrth and the routine proceeds to step 205, the same processing as step 105 in FIG. 5 is executed, and then in steps 206 to 211, steps 106 to 111 in FIG. The same processing is executed, and the routine ends.

  Next, a third embodiment will be described. The configuration of the third embodiment not described below is the same as the configuration of the first embodiment, or is naturally derived from the configuration of the first embodiment when considering the configuration of the third embodiment. It is a configuration.

  The control of the EGR control valve of the third embodiment is the same as the control of the EGR control valve of the first embodiment, and the control of the EGR cooler of the third embodiment is the same as the control of the EGR cooler of the first embodiment. Therefore, description of these controls is omitted, and control of the EGR heater of the third embodiment will be described.

  In the third embodiment, the operation of the EGR heater is started when a predetermined time (hereinafter referred to as “predetermined heater operation standby time”) has elapsed since the operation of the EGR cooler was stopped. Then, the operation of the EGR heater is stopped when a predetermined time (hereinafter, this time is referred to as “predetermined heater operation time”) after the operation of the heater is started. The operation is stopped and the EGR heater is operated from the time when the predetermined heater operation standby time elapses until the predetermined heater operation time elapses, the cooling water is heated by the EGR heater, and the temperature of the cooling water is increased. As a result, the temperature of the EGR pipe is increased by heating the EGR pipe, while the operation of the EGR cooler is stopped after the elapse of the predetermined heater operation time until the predetermined heater operation standby time elapses. The operation of the EGR heater is stopped and the cooling water is not heated, and the operation of the EGR cooler is started during the predetermined heater operation time. Sometimes, the operation of the EGR heater is stopped at the operation starting time of the EGR cooler.

  In the case where the EGR device (that is, the EGR control valve, the EGR cooler, and the EGR heater) is controlled according to the control described above, whether or not the EGR gas is introduced by the EGR device, whether or not the cooling water is circulated by the EGR cooler, and An example of the presence or absence of heating of the cooling water by the EGR heater is shown in FIG.

  In the example of FIG. 9, the engine operating state is in the region X before time T0. Therefore, before the time T0, the EGR gas is introduced and the cooling water is circulated, but the cooling water is not heated. At time T0, the introduction of EGR gas is stopped at the same time as the engine operating state shifts from the region X to the region Y, and at the same time, the circulation of the cooling water is stopped. At the time T1 when elapses, heating of the cooling water is started. Then, at time T2 when a predetermined heater operating time has elapsed from time T1, heating of the cooling water is stopped. At time T3 after time T2, the introduction of EGR gas is started at the same time as the engine operating state shifts from the region Y to the region X, and at the same time, circulation of the cooling water is started. Is maintained in a stopped state.

  The third embodiment has an advantage that the temperature of the cooling water can be increased at a high temperature increase rate while the introduction of EGR gas is stopped for the same reason as in the first embodiment.

  Further, in the third embodiment, when the temperature of the cooling water does not greatly decrease within a relatively short time after the stop of the introduction of the EGR gas, the temperature of the coolant is relatively high during the stop of the introduction of the EGR gas. There is an advantage that energy can be maintained at temperature efficiently. That is, when the temperature of the cooling water does not drop significantly within a relatively short time after the stop of the introduction of the EGR gas, the cooling water is heated simultaneously with the stop of the introduction of the EGR gas, that is, simultaneously with the stop of the circulation of the coolant. Even if it does not start, there is a low possibility that the temperature of the cooling water will be equal to or lower than the temperature at which the above undesirable situation occurs. Therefore, in such a case, it is disadvantageous from the viewpoint of energy efficiency to heat the cooling water at the same time as stopping the circulation of the cooling water. In the second embodiment, since the cooling water starts heating when the predetermined heater operation standby time has elapsed since the cooling water circulation is stopped, the temperature of the cooling water is relatively high while the introduction of the EGR gas is stopped. It is possible to maintain energy efficiently at temperature.

  Next, an example of a routine for executing control of the EGR cooler and the EGR heater according to the third embodiment will be described. An example of this routine is shown in FIGS. Note that the routines shown in FIGS. 10 and 11 are executed every time a predetermined time elapses.

  When the routines of FIGS. 10 and 11 are started, first, in step 300 of FIG. 10, the EGR gas introduction flag Fegr is acquired. The EGR gas introduction flag Fegr is a flag that is set at step 12 in FIG. 4 or reset at step 15 in FIG. Next, at step 301, it is judged if the EGR gas introduction flag Fegr acquired at step 300 is set (Fegr = 1). Here, when it is determined that Fegr = 1 (that is, when EGR gas is being introduced), the routine proceeds to step 302. On the other hand, when it is determined that it is not Fegr = 1 (that is, Fegr = 0) (that is, when the introduction of EGR gas is stopped), the routine proceeds to step 304.

  When it is determined in step 301 that Fegr = 1 and the routine proceeds to step 302, the same processing as step 102 in FIG. 5 is executed, and then in step 303, the same processing as step 103 in FIG. The routine ends.

  On the other hand, when it is determined in step 301 that Fegr = 1 is not established and the routine proceeds to step 304, it is determined whether or not the heating completion flag Fh is set (Fh = 1). The heating completion flag Fh is a flag that is set in step 311 when the heating of the cooling water is completed after stopping the introduction of EGR gas, and reset in step 303 when the introduction of EGR gas is resumed. Here, when it is determined that Fh = 1 (that is, when the heating of the cooling water is completed), the routine ends as it is. On the other hand, when it is determined that Fh = 1 is not satisfied (that is, Fh = 0) (that is, when heating of the cooling water is not completed), the routine proceeds to step 304A.

  If it is determined in step 304 that Fh = 1 is not satisfied and the routine proceeds to step 304A, the supply of the pump operation signal SP from the electronic control unit to the cooling water circulation pump is stopped. Next, in step 304B, the EGR gas introduction flag Fegr is acquired again. Next, in step 304C, it is determined whether or not the EGR gas introduction flag Fegr acquired in step 204B has been reset (Fegr = 0). Here, when it is determined that Fegr = 0 (that is, when the introduction of EGR gas is still stopped), the routine proceeds to step 304D. On the other hand, when it is determined that Fegr = 0 is not satisfied (that is, Fegr = 1) (that is, when the introduction of EGR gas is resumed), the routine proceeds to step 312.

  If it is determined in step 304C that Fegr = 0 is not satisfied and the routine proceeds to step 312, the same processing as step 112 in FIG. 5 is executed, and then in step 302 and step 303, step 102 and step 103 in FIG. The same processing is executed, and the routine ends.

  On the other hand, when it is determined in step 304C that Fegr = 0 and the routine proceeds to step 304D, the pump stop time counter Cp is incremented. This pump stop time counter Cp is a counter indicating the time that has elapsed since the supply of the pump operation signal SP was stopped in step 304A (in other words, the time that has elapsed since the introduction of EGR gas was stopped). is there. Next, at step 304E, it is determined whether or not the pump stop time counter Cp counted up at step 304D is equal to or greater than a value Cpth corresponding to a predetermined heater operation standby time (Cp ≧ Cpth). Here, when it is determined that Cp ≧ Cpth (that is, when a predetermined heater operation standby time has elapsed since the supply of the pump operation signal SP was stopped), the routine proceeds to step 305 in FIG. On the other hand, if it is determined that Cp ≧ Cpth is not satisfied, the routine returns to step 304B, and step 304B to step 304E are repeatedly executed until it is determined in step 304E that Cp ≧ Cpth.

  When it is determined in step 304E that Cp ≧ Cpth and the routine proceeds to step 305, the heater operation signal SH is supplied from the electronic control unit to the EGR heater. Next, in steps 306 to 311, the same processing as that in steps 106 to 111 in FIG. 5 is executed, and the routine ends.

  Next, a fourth embodiment will be described. The configuration of the fourth embodiment not described below is the same as the configuration of the first embodiment, or is naturally derived from the configuration of the first embodiment in view of the configuration of the fourth embodiment. It is a configuration.

  In the fourth embodiment, the EGR control valve is controlled similarly to the control of the EGR control valve of the first embodiment, the EGR cooler is controlled similarly to the control of the EGR cooler of the first embodiment, and the EGR of the third embodiment is controlled. The EGR heater is controlled in the same manner as the heater control.

  When the EGR device (that is, the EGR control valve, the EGR cooler, and the EGR heater) is controlled according to such control, whether the EGR gas is introduced by the EGR device, whether the cooling water is circulated by the EGR cooler, and the EGR heater An example of the state of the presence or absence of heating of the cooling water by is shown in FIG.

  In the example of FIG. 12, the engine operating state is in the region X before time T0. Therefore, before the time T0, the EGR gas is introduced and the cooling water is circulated, but the cooling water is not heated. At the time T0, the introduction of the EGR gas is stopped at the same time as the engine operating state shifts from the region X to the region Y, and at the time T1 when the predetermined cooler stop waiting time has elapsed from the stop of the introduction of the EGR gas. The circulation is stopped, and heating of the cooling water is started at time T2 when the predetermined heater operation standby time has elapsed since the circulation of the cooling water was stopped. Then, at time T3 when the predetermined heater operating time has elapsed from time T2, heating of the cooling water is stopped. At time T4 after time T3, the engine operating state shifts from the region Y to the region X, and at the same time, the introduction of EGR gas is started, and at the same time, the circulation of the cooling water is started. Is maintained in a stopped state.

  Next, an example of a routine for executing control of the EGR cooler and the EGR heater according to the fourth embodiment will be described. An example of this routine is shown in FIGS. Note that the routines of FIGS. 13 and 14 are routines that are executed every time a predetermined time elapses.

  When the routines of FIGS. 13 and 14 are started, first, in step 400 of FIG. 13, the EGR gas introduction flag Fegr is acquired. The EGR gas introduction flag Fegr is a flag that is set at step 12 in FIG. 4 or reset at step 15 in FIG. Next, at step 401, it is judged if the EGR gas introduction flag Fegr acquired at step 400 is set (Fegr = 1). Here, when it is determined that Fegr = 1 (that is, when EGR gas is being introduced), the routine proceeds to step 402. On the other hand, when it is determined that Fegr = 1 is not satisfied (that is, Fegr = 0) (that is, when the introduction of EGR gas is stopped), the routine proceeds to step 404.

  When it is determined in step 401 that Fegr = 1 and the routine proceeds to step 402, the same processing as step 102 in FIG. 5 is executed, and then in step 403, the same processing as step 103 in FIG. The routine ends.

  On the other hand, when it is determined in step 401 that Fegr = 1 is not established and the routine proceeds to step 404, it is determined whether or not the heating completion flag Fh is set (Fh = 1). The heating completion flag Fh is a flag that is set in step 411 when the heating of the cooling water is completed after stopping the introduction of the EGR gas and reset in step 403 when the introduction of the EGR gas is resumed. Here, when it is determined that Fh = 1 (that is, when the heating of the cooling water is completed), the routine ends as it is. On the other hand, when it is determined that Fh = 1 is not satisfied (that is, Fh = 0) (that is, when heating of the cooling water is not completed), the routine proceeds to step 404A.

  When it is determined in step 404 that Fh = 1 is not satisfied and the routine proceeds to step 404A, the EGR gas introduction flag Fegr is acquired again, and then in steps 404B to 404D, the same processing as in steps 204B to 204D in FIG. Is executed.

  When it is determined in step 404D that Cegr ≧ Cegrth and the routine proceeds to step 404E in FIG. 14, the supply of the pump operation signal SP from the electronic control unit to the cooling water circulation pump is stopped. Next, in steps 404F to 04I, the same processing as in steps 304B to 304E in FIG. 10 is executed.

  When it is determined in step 404I that Cp ≧ Cpth and the routine proceeds to step 405, the heater operation signal SH is supplied from the electronic control unit to the EGR heater. Next, in step 406 to step 411, the same processing as step 106 to step 111 in FIG. 5 is executed, and the routine ends.

  Next, a fifth embodiment will be described. The configuration of the fifth embodiment not described below is the same as the configuration of the first embodiment, or is naturally derived from the configuration of the first embodiment when considering the configuration of the fifth embodiment. It is a configuration.

  In the fifth embodiment, the temperature of the cooling water in the cooling water circulation passage (hereinafter, this temperature is simply referred to as “cooling water temperature”) is set to a predetermined temperature (hereinafter, this temperature is referred to as “target cooling water temperature” or simply “target The cooling water circulation is stopped and heating of the cooling water is started at the same time, regardless of whether the EGR gas is being introduced or not. And while the temperature of a cooling water is lower than the target temperature, a cooling water circulation is stopped and heating of a cooling water is continued. And when the temperature of a cooling water becomes more than the target temperature, the circulation of a cooling water is started and the heating of a cooling water is stopped simultaneously with it.

  The target cooling water temperature is set to a cooling water temperature that is considered necessary for causing the internal combustion engine to exhibit desired performance. For example, the target cooling water temperature is set to a cooling water temperature (particularly, the lowest temperature among the cooling water temperatures) that can suppress the generation of condensed water on the inner wall surface of the EGR pipe. Alternatively, it may be set to a cooling water temperature (especially the lowest temperature among the cooling water temperatures) that can eliminate the possibility that condensed water is generated on the inner wall surface of the EGR pipe, The temperature of the cooling water that can maintain the temperature of the EGR gas at a desired temperature may be set (particularly, the lowest temperature among the temperatures of the cooling water), or the temperature of the EGR gas may be maintained at the desired temperature. It may be set to the temperature of the cooling water that can be used (in particular, the lowest temperature among the temperatures of the cooling water).

  Moreover, in 5th Embodiment, when the temperature of a cooling water becomes more than the target temperature, the circulation of a cooling water is started and the heating of a cooling water is stopped simultaneously, However, This invention is not restrict | limited to this. . For example, when a predetermined time has elapsed after the temperature of the cooling water becomes equal to or higher than the target temperature, the circulation of the cooling water may be started, and at the same time, the heating of the cooling water may be stopped. When the temperature of the coolant becomes equal to or higher than the target temperature, circulation of the cooling water is started, and heating of the cooling water may be stopped when a predetermined time has elapsed from the start of circulation of the cooling water. Then, when a predetermined time has elapsed since the temperature of the cooling water became equal to or higher than the target temperature, circulation of the cooling water is started, and a predetermined time has elapsed since the start of circulation of the cooling water. At some point, heating of the cooling water may be stopped. According to this, since the cooling water heating is stopped when the temperature of the cooling water becomes relatively higher than the target temperature, the cooling water is cooled immediately after the temperature of the cooling water exceeds the target temperature. The temperature of the water never falls below its target temperature. For this reason, there is an advantage that the frequency of stopping and starting the circulation of the cooling water and the frequency of starting and stopping the heating of the cooling water are reduced.

  Further, the means for acquiring the temperature of the cooling water in the fifth embodiment is not particularly limited. For example, a temperature sensor that detects the temperature of the cooling water may be disposed in the cooling water circulation passage, and the temperature detected by the temperature sensor may be acquired as the temperature of the cooling water, or by using various parameters related to the internal combustion engine. An estimated value of the temperature of the cooling water may be calculated by calculation, and the calculated estimated value may be acquired as the temperature of the cooling water, or a temperature sensor that detects the temperature of the EGR pipe is disposed in the EGR pipe, and this temperature Even if the temperature of the cooling water estimated from the temperature detected by the sensor is acquired as the temperature of the cooling water, the temperature itself detected by this temperature sensor may be acquired as the temperature of the cooling water.

  In the fifth embodiment, the cooling water circulation is stopped and the cooling water heating is started when the temperature of the cooling water becomes lower than the target temperature. However, the present invention is not limited to this. For example, when the cooling water temperature is predicted to be lower than the target temperature, the cooling water circulation may be stopped and the cooling water heating may be started. When it is estimated that the temperature is lower than the temperature, the cooling water circulation may be stopped and the cooling water heating may be started.

  The fifth embodiment has an advantage that the temperature of the cooling water can be increased at a high temperature increase rate when the cooling water needs to be heated. That is, when there is a temperature required for various reasons as the temperature of the cooling water, that is, when there is a cooling water temperature that should be a target considered to be necessary for the internal combustion engine to exhibit desired performance, It is not preferable that the temperature of the coolant is lower than the temperature of the cooling water to be targeted (that is, the target cooling water temperature). Therefore, when the temperature of the cooling water becomes lower than the target temperature, it becomes necessary to heat the cooling water. When the temperature of the cooling water becomes lower than the target temperature, the temperature of the cooling water can be quickly increased to a temperature equal to or higher than the target temperature, that is, the temperature of the cooling water can be increased at a high rate of temperature increase. preferable.

  In the fifth embodiment, when the temperature of the cooling water becomes lower than the target temperature, the circulation of the cooling water is stopped and the heating of the cooling water is performed. Since the cooling water is cooled when the cooling water is circulated, when the cooling water is heated after the cooling water circulation is stopped, the cooling water is circulated during the cooling water circulation. Compared to the case where heating is performed, the temperature rise rate of the cooling water is high. Therefore, the fifth embodiment has an advantage that the temperature of the cooling water can be increased at a high temperature increase rate when the cooling water needs to be heated.

  Next, an example of a routine for executing control of the EGR cooler and the EGR heater according to the fifth embodiment will be described. An example of this routine is shown in FIG. Note that the routine of FIG. 15 is a routine that is executed every time a predetermined time elapses.

  When the routine of FIG. 15 is started, first, in step 500, the temperature Tc of the cooling water is acquired. Next, in step 501, it is determined whether or not the temperature Tc of the cooling water acquired in step 500 is equal to or higher than the target temperature TTc (Tc ≧ TTc). Here, when it is determined that Tc ≧ TTc, the routine proceeds to step 502. On the other hand, when it is determined that Tc ≧ TTc is not satisfied, the routine proceeds to step 506.

  When it is determined in step 501 that Tc ≧ TTc and the routine proceeds to step 502, an EGR gas introduction flag Fegr is acquired. The EGR gas introduction flag Fegr is a flag that is set at step 12 in FIG. 4 or reset at step 15 in FIG. Next, at step 503, it is judged if the EGR gas introduction flag Fegr acquired at step 502 is set (Fegr = 1). Here, when it is determined that Fegr = 1 (that is, when the introduction of EGR gas is being performed), the routine proceeds to step 504. On the other hand, when it is determined that it is not Fegr = 1 (that is, Fegr = 0) (that is, when the introduction of EGR gas is stopped), the routine proceeds to step 505.

  When it is determined in step 503 that Fegr = 1 and the routine proceeds to step 504, the pump operation signal SP is supplied to the cooling water circulation pump, and the supply of the heater operation signal SH to the EGR heater is stopped. finish.

  On the other hand, when it is determined in step 503 that Fegr = 1 is not satisfied and the routine proceeds to step 505, the supply of the pump operation signal SP to the cooling water circulation pump is stopped and the supply of the heater operation signal SH to the EGR heater is stopped. The routine is terminated.

  If it is determined in step 501 that Tc ≧ TTc is not satisfied and the routine proceeds to step 506, the supply of the pump operation signal SP to the cooling water circulation pump is stopped and the heater operation signal SH is supplied to the EGR heater. The routine ends.

  Next, a sixth embodiment will be described. The configuration of the sixth embodiment not described below is the same as the configuration of the first embodiment, or is naturally derived from the configuration of the first embodiment when considering the configuration of the sixth embodiment. It is a configuration.

  In the sixth embodiment, the EGR gas is introduced when the temperature of the EGR pipe becomes lower than a predetermined temperature (hereinafter, this temperature is referred to as “target EGR pipe temperature” or simply “target temperature”). Regardless of whether or not the cooling water is circulating, the cooling water circulation is stopped and at the same time, the heating of the cooling water is started. Then, while the temperature of the EGR pipe is lower than the target temperature, the circulation of the cooling water is continued and the heating of the cooling water is continued. Then, when the temperature of the EGR pipe becomes equal to or higher than the target temperature, the circulation of the cooling water is started, and at the same time, the heating of the cooling water is stopped.

  The target EGR pipe temperature is set to the temperature of the EGR pipe that is considered necessary for causing the internal combustion engine to exhibit desired performance. For example, the target EGR pipe temperature is set to the temperature of the EGR pipe (particularly, the lowest temperature among the temperatures of the EGR pipe) that can suppress the formation of condensed water on the inner wall surface of the EGR pipe. Alternatively, it may be set to the temperature of the EGR pipe (especially the lowest temperature among the temperatures of the EGR pipe) that can eliminate the possibility that condensed water is generated on the inner wall surface of the EGR pipe, The temperature of the EGR gas that can maintain the temperature of the EGR gas at a desired temperature (particularly, the lowest temperature among the temperatures of the EGR tube) may be set, or the temperature of the EGR gas may be maintained at the desired temperature. It may be set to the temperature of the EGR pipe (in particular, the lowest temperature among the EGR pipe temperatures) that may be able to.

  Further, in the sixth embodiment, when the temperature of the EGR pipe becomes equal to or higher than the target temperature, the circulation of the cooling water is started and at the same time, the heating of the cooling water is stopped. However, the present invention is not limited to this. . For example, when a predetermined time has elapsed after the temperature of the EGR pipe becomes equal to or higher than the target temperature, the circulation of the cooling water may be started, and at the same time, the heating of the cooling water may be stopped, or the EGR pipe When the temperature of the coolant becomes equal to or higher than the target temperature, circulation of the cooling water is started, and heating of the cooling water may be stopped when a predetermined time has elapsed from the start of circulation of the cooling water. Then, when a predetermined time has elapsed since the temperature of the EGR pipe became equal to or higher than the target temperature, circulation of the cooling water is started, and a predetermined time has elapsed since the start of the circulation of the cooling water. At some point, heating of the cooling water may be stopped. According to this, since the heating of the cooling water is stopped when the temperature of the EGR pipe becomes relatively higher than the target temperature, immediately after the temperature of the EGR pipe becomes equal to or higher than the target temperature. The tube temperature never falls below its target temperature. For this reason, there is an advantage that the frequency of stopping and starting the circulation of the cooling water and the frequency of starting and stopping the heating of the cooling water are reduced.

  In the sixth embodiment, the means for acquiring the temperature of the EGR pipe is not particularly limited. For example, a temperature sensor that detects the temperature of the EGR pipe may be disposed in the EGR pipe, and the temperature detected by the temperature sensor may be acquired as the temperature of the EGR pipe, or may be calculated using various parameters relating to the internal combustion engine. The estimated value of the temperature of the EGR pipe may be calculated by the above, and the calculated estimated value may be acquired as the temperature of the EGR pipe, or a temperature sensor that detects the temperature of the cooling water is disposed in the cooling water circulation passage, and this temperature Even if the temperature of the EGR pipe estimated from the temperature detected by the sensor is acquired as the temperature of the EGR pipe, the temperature itself detected by the temperature sensor may be acquired as the temperature of the EGR pipe.

  Further, in the sixth embodiment, when the temperature of the EGR pipe becomes lower than the target temperature, the circulation of the cooling water is stopped and the heating of the cooling water is started, but the present invention is not limited to this. For example, the cooling water circulation may be stopped and the cooling water heating may be started when the temperature of the EGR pipe is predicted to be lower than the target temperature, or the temperature of the EGR pipe may be set to the target temperature. When it is estimated that the temperature is lower than the temperature, the cooling water circulation may be stopped and the cooling water heating may be started.

  In the sixth embodiment, for the same reason as described in relation to the fifth embodiment, when the cooling water needs to be heated, the temperature of the cooling water can be increased at a high temperature increase rate. There is an advantage.

  Next, an example of a routine for performing control of the EGR cooler and the EGR heater according to the sixth embodiment will be described. An example of this routine is shown in FIG. Note that the routine of FIG. 16 is a routine that is executed every time a predetermined time elapses.

  When the routine of FIG. 16 is started, first, in step 600, the temperature Tegr of the EGR pipe is acquired. Next, in step 601, it is determined whether or not the temperature Tegr of the EGR pipe acquired in step 600 is equal to or higher than the target temperature TTegr (Tegr ≧ TTegr). Here, if it is determined that Tegr ≧ TTegr, the routine proceeds to step 602. On the other hand, when it is determined that Tegr ≧ TTegr is not satisfied, the routine proceeds to step 606.

  When it is determined in step 601 that Tegr ≧ TTegr and the routine proceeds to step 602, an EGR gas introduction flag Fegr is acquired. The EGR gas introduction flag Fegr is a flag that is set at step 12 in FIG. 4 or reset at step 15 in FIG. Next, in step 603 to step 605, the same processing as that in step 503 to step 505 in FIG. 15 is executed, and the routine ends.

  When it is determined in step 601 that Tegr ≧ TTegr is not satisfied and the routine proceeds to step 506, the supply of the pump operation signal SP to the cooling water circulation pump is stopped and the heater operation signal SH is supplied to the EGR heater, The routine ends.

  Next, a seventh embodiment will be described. The configuration of the seventh embodiment not described below is the same as the configuration of the first embodiment, or is naturally derived from the configuration of the first embodiment when considering the configuration of the seventh embodiment. It is a configuration.

  In the seventh embodiment, when it is predicted that the engine operation is started while the engine operation is stopped, the circulation of the cooling water is stopped, and at the same time, the heating of the cooling water is started. Then, heating of the cooling water is stopped when a predetermined time (hereinafter, this time is referred to as “predetermined heater operation time”) has elapsed since the start of the heating of the cooling water.

  The seventh embodiment has an advantage that the temperature of the cooling water can be increased at a high temperature increase rate during the stop of the introduction of the EGR gas for the same reason as described in relation to the first embodiment. is there.

  Further, the seventh embodiment has an advantage that exhaust gas having a relatively high temperature can be introduced into the intake passage even if the introduction of EGR gas is started immediately after the start of engine operation. That is, when the engine operation is stopped, the exhaust gas does not flow through the EGR pipe, so the temperature of the EGR pipe decreases. Here, if the temperature of the EGR pipe is too low, exhaust gas having a temperature lower than the assumed temperature may be introduced into the intake passage by the EGR device. However, in the seventh embodiment, it is determined that the cooling water needs to be heated when it is predicted that the engine operation is started, and the cooling water is heated. Therefore, when the engine operation is started, at least the temperature of the cooling water is raised and the temperature of the EGR pipe is raised. For these reasons, the seventh embodiment has an advantage that exhaust gas having a relatively high temperature can be introduced into the intake passage even if the introduction of EGR gas is started immediately after the start of engine operation.

  Next, an example of a routine for executing control of the EGR cooler and the EGR heater according to the seventh embodiment will be described. An example of this routine is shown in FIGS. Note that the routines shown in FIGS. 17 and 18 are executed every time a predetermined time elapses.

  When the routines of FIGS. 17 and 18 are started, first, at step 700 of FIG. 17, it is determined whether or not the engine is operating. If it is determined that the engine is operating, the routine proceeds to step 701. On the other hand, when it is determined that the engine is not operating (that is, the engine operation is stopped), the routine proceeds to step 706 in FIG.

  When it is determined in step 700 that the engine is operating and the routine proceeds to step 701, an EGR gas introduction flag Fegr is acquired. The EGR gas introduction flag Fegr is a flag that is set at step 12 in FIG. 4 or reset at step 15 in FIG. Next, in step 702, it is determined whether or not the EGR gas introduction flag Fegr acquired in step 701 is set (Fegr = 1). Here, when it is determined that Fegr = 1 (that is, when EGR gas is being introduced), the routine proceeds to step 703. On the other hand, when it is determined that it is not Fegr = 1 (that is, Fegr = 0) (that is, when the introduction of EGR gas is stopped), the routine proceeds to step 705.

  When it is determined in step 702 that Fegr = 1 and the routine proceeds to step 703, the pump operation signal SP is supplied from the electronic control unit to the cooling water circulation pump, and the heater operation signal SH from the electronic control unit to the EGR heater is supplied. Is stopped and the routine proceeds to step 704.

  On the other hand, if it is determined in step 702 that Fegr = 1 is not satisfied and the routine proceeds to step 705, the supply of the pump operation signal SP from the electronic control unit to the cooling water circulation pump is stopped and the electronic control unit to the EGR heater. The heater operation signal SH is stopped, and the routine proceeds to step 704.

  In step 704, the heating completion flag Fh is reset (Fh ← 0), and the routine ends. The heating completion flag Fh is a flag that is set when heating of the cooling water is completed and is reset when the engine operation is started.

  If it is determined in step 700 that the engine is not operating and the routine proceeds to step 706 in FIG. 18, it is determined whether or not the engine operation is predicted to be started. Here, when it is determined that the engine operation is predicted to be started, the routine proceeds to step 707. On the other hand, when it is determined that the engine operation is not predicted to be started, the routine ends.

  If it is determined in step 706 that the engine operation is predicted to be started, and the routine proceeds to step 707, it is determined whether or not the heating completion flag Fh is set (Fh = 1). Here, when it is determined that Fh = 1 (that is, when the heating of the cooling water is completed), the routine ends as it is. On the other hand, when it is determined that Fh = 1 is not satisfied (that is, Fh = 0) (that is, when heating of the cooling water is not completed), the routine proceeds to step 708.

  When it is determined in step 707 that Fh is not 1 and the routine proceeds to step 708, the supply of the pump operation signal SP from the electronic control unit to the cooling water circulation pump is stopped and the heater operation signal SH is transmitted from the electronic control unit. Supplied to the EGR heater. Next, at step 709, it is determined again whether the engine is operating. If it is determined that the engine is operating, the routine proceeds to step 714, the heater operating time counter Ch is cleared, and the routine ends. The heater operation time counter Ch is a counter that indicates the time that has elapsed since the operation of the EGR heater was started in Step 708. On the other hand, when it is determined in step 709 that the engine is not operating, the routine proceeds to step 710.

  When it is determined in step 709 that the engine is not operating and the routine proceeds to step L10, the heater operating time counter Ch is incremented. Next, at step L11, it is determined whether or not the heater operation time counter Ch counted up at step L10 is equal to or greater than a value Chth corresponding to a predetermined heater operation time (Ch ≧ Chth). Here, when it is determined that Ch ≧ Chth (that is, when a predetermined heater operation time has elapsed since the operation of the EGR heater started), the routine proceeds to step L12. On the other hand, if it is determined that Ch ≧ Chth is not satisfied, the routine returns to step L09, and step L09 to step L11 are repeatedly executed until it is determined in step L11 that Ch ≧ Chth.

  When it is determined in step L11 that Ch ≧ Chth and the routine proceeds to step L12, the supply of the heater operation signal SH from the electronic control unit to the EGR heater is stopped. Next, in step L13, the heating completion flag Fh is set (Fh ← 1), the heater operation time counter Ch is cleared, and the routine ends.

  An internal combustion engine provided with the EGR device of the above-described embodiment may be employed as a power device of a so-called hybrid vehicle hybrid system. Next, an embodiment (hereinafter referred to as “eighth embodiment”) in which the internal combustion engine including the EGR device of the first embodiment is employed as a power device of a hybrid system of a hybrid vehicle will be described.

  The hybrid vehicle of the eighth embodiment is shown in FIG. In FIG. 19, MG1 and MG2 are generator motors (hereinafter these generator motors are referred to as “first generator motor” and “second generator motor”, respectively), 10 is an internal combustion engine, 60 is a power distribution mechanism, and 80 is an electronic control unit 80. Denotes an inverter, 91 denotes a battery, 100 denotes an accelerator pedal, and 101 denotes an accelerator pedal depression amount sensor. The internal combustion engine 10 is any one of the internal combustion engines of the above-described embodiments (that is, the internal combustion engine 10 shown in FIG. 1), and the electronic control device 80 is any of the electronic control devices of the above-described embodiments. One (ie, the electronic control unit 80 shown in FIG. 1). In FIG. 19, 13 is a piston disposed in the combustion chamber of the internal combustion engine 10, and 15 is a crankshaft of the internal combustion engine 10.

  The power distribution device 60 has a planetary gear device 61. The planetary gear device 61 includes a sun gear 62, a planetary gear 63, and a ring gear 64. The planetary gear 63 is meshed with the sun gear 62 and meshed with the ring gear 64. The sun gear 62 is connected to a shaft (hereinafter referred to as “first shaft”) 71 of the first generator motor MG1. Accordingly, the first generator motor MG1 can be driven to rotate by the torque input from the sun gear 62 to the first generator motor MG1, and can output torque to the sun gear 62. The first generator motor MG1 can generate electric power by being rotationally driven by the torque input from the sun gear 62 to the first generator motor MG1. The ring gear 64 is connected to a shaft (hereinafter referred to as “second shaft”) 72 of the second generator motor MG <b> 2 via a ring gear carrier 66. Therefore, the second generator motor MG2 can output torque to the ring gear 64 and can be driven to rotate by the torque input from the ring gear 64 to the second generator motor MG2. The second generator motor MG2 can generate electric power by being rotationally driven by the torque input from the ring gear 64 to the second generator motor MG2.

  The planetary gear 63 is connected to the crankshaft 15 via the planetary gear carrier 65. Accordingly, the planetary gear 63 is driven to rotate by torque input from the crankshaft 15 to the planetary gear 63. The planetary gear 63 is engaged with the sun gear 62 and the ring gear 64. Therefore, when torque is input from the planetary gear 63 to the sun gear 62, the sun gear 62 is rotationally driven by the torque. When torque is input from the planetary gear 63 to the ring gear 64, the ring gear 64 is driven by the torque. Driven by rotation. Conversely, when torque is input from the sun gear 62 to the planetary gear 63, the planetary gear 63 is rotationally driven by the torque, and when torque is input from the ring gear 64 to the planetary gear 63, the planetary gear is generated by the torque. 63 is rotationally driven.

  The ring gear 64 is connected to the output gear 67 via the ring gear carrier 66. Therefore, the output gear 67 is rotationally driven by the torque input from the ring gear 64 to the output gear 67, and the ring gear 64 is rotationally driven by the torque input from the output gear 67 to the ring gear 64. .

  The first generator motor MG <b> 1 has a resolver 73. The resolver 73 is connected to the interface 85 of the electronic control device 80. The resolver 73 outputs an output value corresponding to the rotation angle of the first generator motor MG1. This output value is input to the electronic control unit 80. The electronic control unit 80 calculates the rotation speed of the first generator motor (hereinafter, this rotation speed is referred to as “first MG rotation speed”) based on the output value. On the other hand, the second generator motor MG <b> 2 has a resolver 74. The resolver 74 is connected to the interface 85 of the electronic control device 80. The resolver 74 outputs an output value corresponding to the rotation angle of the second generator motor. This output value is input to the electronic control unit 80. The electronic control unit 80 calculates the rotation speed of the second generator motor (hereinafter, this rotation speed is referred to as “second MG rotation speed”) based on the output value.

  The first generator motor MG1 is electrically connected to the battery 91 via the inverter 90. Therefore, when the first generator motor MG1 generates power, the power generated by the first generator motor MG1 (hereinafter, this power is referred to as “first generated power”) can be supplied to the battery 91 via the inverter 90. It is. Further, the first generator motor MG1 can be rotationally driven by the electric power supplied from the battery 91, and the control torque applied to the first generator motor MG1 by the electric power supplied from the battery 91 (hereinafter, this control torque is referred to as “ The number of revolutions is controllable by controlling "first control torque").

  The second generator motor MG2 is electrically connected to the battery 91 via the inverter 90. Therefore, the second generator motor MG2 can be rotationally driven by the power supplied from the battery 91, and the control torque (hereinafter referred to as “the control torque” applied to the second generator motor MG2 by the power supplied from the battery 91). The rotation speed can be controlled by controlling the second control torque. In addition, when the second generator motor MG2 generates power, the power generated by the second generator motor MG2 (hereinafter, this power is referred to as “second generated power”) can be supplied to the battery 91 via the inverter 90. is there. The first generated power can be directly supplied to the second generator motor MG2, and the second generated power can be directly supplied to the first generator motor.

  The battery 91 is connected to the interface 85 of the electronic control device 80. Then, information related to the battery storage amount (that is, the amount of power stored in the battery 91) is input to the interface 85 of the electronic control unit 80. The inverter 90 is also connected to the interface 85 of the electronic control unit 80. The amount of power supplied from the inverter 90 to the second generator motor MG2 and the amount of power supplied to the first generator motor MG1 are controlled by a command sent from the electronic control unit 80 via the interface 85.

  The output gear 67 is connected to a differential gear 76 via a gear train 75. The differential gear 76 is attached to the drive shaft 77. Drive wheels 78 are attached to both ends of the drive shaft 77. Therefore, the torque from the output gear 67 is transmitted to the drive wheels 78 via the gear train 75, the differential gear 76, and the drive shaft 77.

  The accelerator pedal depression amount sensor 101 is connected to the accelerator pedal 100. The accelerator pedal depression amount sensor 101 is electrically connected to the interface 85 of the electronic control unit 80. The accelerator pedal depression amount sensor 101 outputs an output value corresponding to the depression amount of the accelerator pedal 100. This output value is input to the electronic control unit 80. Based on this output value, the electronic control unit 80 calculates the depression amount of the accelerator pedal 100, and hence the output required for the power unit. Note that the power plant of the first embodiment generally includes an internal combustion engine 10, a first generator motor MG1, and a second generator motor MG2.

  Next, an example of engine torque, first control torque, and second control torque control by the control device of the first embodiment will be described. In the following description, “engine torque” means “torque output from the crankshaft of the internal combustion engine”, and “engine operating point” means “operation of the internal combustion engine defined by the engine torque and the engine speed”. Point or operating state of the internal combustion engine ”,“ required output ”is“ output required as output output from the crankshaft of the internal combustion engine ”, and“ accelerator depression amount ”is“ accelerator pedal depression amount ” “Vehicle speed” is “traveling speed of the hybrid vehicle”, and “fuel injection amount” is “amount of fuel injected from the fuel injection valve”.

  In the eighth embodiment, the engine operating point at which the fuel consumption becomes highest when the required output is output from the crankshaft is obtained in advance by experiments or the like as the optimal engine operating point for each required output. A line formed by plotting these optimum engine operating points on a graph defined by the engine torque and the engine speed and connecting these optimum engine operating points is obtained as the optimum engine operating line. Data relating to the optimum engine operation line thus obtained is stored in the electronic control unit 80.

  During engine operation, the required output is calculated based on the accelerator depression amount and the vehicle speed. Then, an engine operating point on the optimum engine operating line that can output the calculated required output from the internal combustion engine is selected. The engine torque and engine speed that define the selected engine operating point are set to the target engine torque and target engine speed, respectively. The fuel injection amount, the intake air amount (that is, the amount of air sucked into the combustion chamber), and the engine speed are controlled so that the set target engine torque and target engine speed are achieved. .

  By the way, when the second MG rotational speed is constant, the engine rotational speed also changes if the first MG rotational speed changes. In other words, the engine speed can be controlled by controlling the first MG speed. The first MG rotational speed is represented by “NMG1”, the second MG rotational speed is represented by “NMG2”, the engine rotational speed is represented by “NE”, and the ratio of the number of teeth of the sun gear to the number of teeth of the ring gear (ie, sun gear). The number of teeth of the ring gear / the number of teeth of the ring gear. Hereinafter, this ratio is also referred to as a “planetary gear ratio”). There is a relationship.

  NMG1 = (NE−NMG2) / ρ + NE (1)

  Therefore, when the target first MG speed is represented by “TNMG1” and the target engine speed is represented by “TNE”, there is a relationship of the following equation 2 between the target first MG speed and the target engine speed. become.

  TNMG1 = (TNE−NMG2) / ρ + TNE (2)

  Therefore, in the eighth embodiment, the target first MG speed is obtained from the above equation 2 using the target engine speed TNE set according to the engine operating point selected according to the required output and the current second MG speed NMG2. TNMG1 is calculated. Then, the deviation (= TNMG1-NMG1) of the current first MG rotation speed NMG1 with respect to the target first MG rotation speed TNMG1 calculated in this way is calculated. Then, the first control torque is controlled so that the calculated deviation becomes zero.

  By the way, the engine torque is represented by “TQE”, and the engine torque input to the ring gear (that is, the drive wheel) (hereinafter, this engine torque is referred to as “ring gear input engine torque”) is represented by “TQEr”. When the ratio of the number of teeth of the sun gear to the number of teeth (ie, the number of teeth of the sun gear / the number of teeth of the ring gear) is represented by “ρ”, the relationship of the following equation 3 is established between the ring gear input engine torque and the engine torque: There is.

  TQEr = 1 / (1 + ρ) × TQE (3)

  That is, the ring gear input engine torque TQEr is a part of the engine torque TQE. Therefore, the ring gear input engine torque TQEr is smaller than the required drive torque (that is, the torque to be input to the drive wheels 78). Therefore, in the first embodiment, the second control torque is controlled such that a torque corresponding to the difference between the required drive torque and the ring gear input engine torque TQEr is input from the second generator motor to the ring gear. Thus, torque equal to the required drive torque is input to the ring gear.

  The above description is a case where the first generator motor functions as a generator and the second generator motor functions as an electric motor. However, depending on the conditions required for the hybrid vehicle, the first generator motor functions as a motor, the second generator motor functions as a generator, or the first generator motor does not function as a generator or a motor. Or the second generator motor may not function as a generator or a motor. In the first embodiment, the internal combustion engine is operated. However, the internal combustion engine may not be operated depending on the conditions required for the hybrid vehicle.

  In the hybrid system described above, since the engine operation is stopped relatively frequently, the introduction of EGR gas is also stopped relatively frequently. For this reason, there is a high possibility that the temperature of the cooling water (and thus the temperature of the EGR pipe) will be a temperature equal to or lower than the temperature at which the undesirable situation described in connection with the first embodiment occurs. However, in the eighth embodiment, the cooling water is heated when the engine operation is stopped and the introduction of the EGR gas is stopped. Therefore, in the eighth embodiment, the engine operation is stopped relatively frequently. Accordingly, there is an advantage that the temperature of the cooling water for the cooling section can be kept relatively high even under a situation where the introduction of EGR gas is stopped relatively frequently.

  In the above-described embodiment, the circulation of the cooling water is started simultaneously with the start of the introduction of the EGR gas. However, the circulation of the cooling water may be started when a predetermined time has elapsed from the start of the introduction of the EGR gas, or when the start of the introduction of the EGR gas is predicted (that is, the introduction of the EGR gas). Circulation of the cooling water may be started at a point just before the start).

  Moreover, embodiment mentioned above is embodiment which heats an EGR pipe | tube by heating a cooling water with an EGR heater. However, the present invention can also be applied to a case where a heater that directly heats the EGR pipe is disposed in the EGR pipe, and the EGR pipe is directly heated by the heater.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 30 ... Intake passage, 40 ... Exhaust passage, 50 ... Exhaust gas recirculation device (EGR device), 51 ... Exhaust gas recirculation pipe (EGR pipe), 52 ... Exhaust gas recirculation control valve (EGR control valve), 53 ... Exhaust gas recirculation cooler (EGR cooler), 54 ... EGR heater, 55 ... Cooling section, 56 ... Cooling water circulation passage, 57 ... Cooling water circulation pump

Claims (14)

An exhaust gas recirculation pipe for introducing exhaust gas discharged from the combustion chamber into the exhaust passage to the intake air passage, and cooling water for cooling the exhaust gas flowing through the exhaust gas recirculation pipe by cooling the exhaust gas recirculation pipe Cooling means having a cooling water circulation passage to circulate, the cooling water being circulated through the cooling water circulation passage, the temperature of the cooling water is lowered, and the introduction of the exhaust gas to the intake passage is stopped In the exhaust gas recirculation device for an internal combustion engine in which the circulation of the cooling water in the cooling water circulation passage is stopped,
A heating means for heating the exhaust gas recirculation pipe;
An exhaust gas recirculation device for an internal combustion engine, wherein the exhaust gas recirculation pipe is heated by the heating means while the cooling water circulation is stopped in the cooling water circulation passage.   The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein the circulation of the cooling water in the cooling water circulation passage is stopped simultaneously with the stop of the introduction of the exhaust gas into the intake passage.   2. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein the circulation of the cooling water in the cooling water circulation passage is stopped when a predetermined time has elapsed since the stop of the introduction of the exhaust gas into the intake passage. An exhaust gas recirculation pipe for introducing exhaust gas discharged from the combustion chamber into the exhaust passage into the intake air passage, and cooling water for cooling the exhaust gas flowing through the exhaust gas recirculation pipe by cooling the exhaust gas recirculation pipe An exhaust gas recirculation device for an internal combustion engine, the cooling means having a cooling water circulation passage to circulate, wherein the temperature of the cooling water is lowered by circulating the cooling water through the cooling water circulation passage.
A heating means for heating the exhaust gas recirculation pipe;
When it becomes necessary to heat the exhaust gas recirculation pipe, the circulation of the cooling water in the cooling water circulation passage is stopped, and the exhaust gas recirculation of the internal combustion engine that heats the exhaust gas recirculation pipe by the heating means while the circulation is stopped. Circulation device.   When the target exhaust gas recirculation pipe temperature is set as the target exhaust gas recirculation pipe temperature, and the temperature of the cooling water becomes lower than the target exhaust gas recirculation pipe temperature while the introduction of exhaust gas into the intake passage is stopped 5. The exhaust gas recirculation device for an internal combustion engine according to claim 4, wherein it is determined that the exhaust gas recirculation pipe needs to be heated.   The target exhaust gas recirculation pipe temperature is set as the target exhaust gas recirculation pipe temperature, and the temperature of the exhaust gas recirculation pipe is lower than the target exhaust gas recirculation pipe temperature while the introduction of the exhaust gas into the intake passage is stopped. 5. It is determined that the exhaust gas recirculation pipe needs to be heated when it is predicted or when the temperature of the exhaust gas recirculation pipe is estimated to be lower than a target exhaust gas recirculation pipe temperature. An exhaust gas recirculation device for an internal combustion engine according to claim 5.   When the operation of the internal combustion engine is stopped, the temperature of the exhaust gas recirculation pipe is predicted to be lower than the target exhaust gas recirculation pipe temperature, or the temperature of the exhaust gas recirculation pipe is lower than the target exhaust gas recirculation pipe temperature. The exhaust gas recirculation device for an internal combustion engine according to claim 6, wherein the exhaust gas recirculation device is estimated to be low.   The target coolant temperature is set as the target coolant temperature, and it is determined that the exhaust recirculation pipe needs to be heated when the coolant temperature becomes lower than the target coolant temperature. The exhaust gas recirculation device for an internal combustion engine according to claim 7.   When the target coolant temperature is set as the target coolant temperature and the coolant temperature is predicted to be lower than the target coolant temperature, or when the coolant temperature is lower than the target coolant temperature. The exhaust gas recirculation device for an internal combustion engine according to any one of claims 4 to 8, wherein it is determined that the exhaust gas recirculation pipe needs to be heated when estimated.   The temperature of the cooling water is predicted to be lower than the target cooling water temperature when the operation of the internal combustion engine is stopped, or the temperature of the cooling water is estimated to be lower than the target cooling water temperature. An exhaust gas recirculation device for an internal combustion engine as described.   The exhaust gas recirculation device for an internal combustion engine according to any one of claims 4 to 10, wherein it is determined that the exhaust gas recirculation pipe needs to be heated when the internal combustion engine is predicted to be started. . An internal combustion engine comprising the exhaust gas recirculation device according to any one of claims 1 to 11, and an electric motor, wherein the power output from the internal combustion engine and the power output from the motor are In a hybrid system that outputs at least one of these as power,
When it is not necessary to output power from the internal combustion engine, the operation of the internal combustion engine is stopped, and when it becomes necessary to output power from the internal combustion engine while the operation of the internal combustion engine is stopped, the internal combustion engine is started. Hybrid system.   The exhaust gas recirculation of the internal combustion engine according to any one of claims 1 to 12, wherein heating of the exhaust gas recirculation pipe by the heating means is started simultaneously with the stop of the circulation of the cooling water in the cooling water circulation passage. apparatus.   The heating of the exhaust gas recirculation pipe by the heating means is started when a predetermined time has elapsed from the stop of the circulation of the cooling water in the cooling water circulation passage. 2. An exhaust gas recirculation device for an internal combustion engine according to 1.

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