JP6648610B2 - Engine control device and engine control method - Google Patents

Description

  The present invention relates to an engine control device and an engine control method.

  2. Description of the Related Art Conventionally, there has been known a variable valve timing control device that controls a valve overlap amount according to a gear position when an engine is in a deceleration state (for example, see Patent Document 1). This variable valve timing control device increases the valve overlap amount when the gear position is smaller than the predetermined position and decreases the valve overlap amount when the gear position is larger than the predetermined position when the engine is in a deceleration state. This prevents a phenomenon (oil rising) in which engine oil is sucked into the combustion chamber side from between the cylinder and the piston, regardless of the magnitude of the gear position, and suppresses wasteful oil consumption.

JP-A-10-299518

  However, in the above-described variable valve timing control device, the air taken into the engine and discharged without being burned is supplied to the catalyst for purifying the exhaust gas. Therefore, oxygen in the air is adsorbed by the catalyst. When the combustion of the engine is restarted, there is a problem that the purification efficiency of the exhaust gas by the catalyst decreases.

  On the other hand, it is conceivable to supply exhaust gas (EGR gas) to the engine by an exhaust gas recirculation device (Exhaust Gas Recirculation) device in order to prevent the above-mentioned oil rise while suppressing oxygen adsorption by the catalyst. In this case, EGR gas having a small oxygen content is supplied from the engine to the catalyst. Therefore, it is possible to prevent problems caused by oxygen adsorption in the catalyst.

  However, when the EGR gas is supplied to the engine, moisture contained in the EGR gas may adhere to peripheral components such as a fuel injection device (injector), and the peripheral components may freeze. For example, when the injector freezes, it is not possible to properly inject fuel into the combustion chamber, and problems such as deterioration of combustion performance in the engine occur.

  The present invention has been made in view of such circumstances, and prevents a problem associated with freezing of moisture in recirculated exhaust gas while preventing a reduction in exhaust gas purification efficiency due to oxygen adsorption of a catalyst. It is an object of the present invention to provide an engine control device and an engine control method that can perform the control.

The engine control apparatus of the present invention, the A control apparatus for an engine having an exhaust gas recirculation device that recirculates exhaust gas discharged from the engine to the intake passage, the intake air temperature detecting unit for detecting an intake temperature of the engine, engine An engine temperature detection unit that detects a temperature, and a control unit that controls opening and closing of an exhaust gas recirculation control valve included in the exhaust gas recirculation device, wherein the control unit is configured to control when combustion of the engine is restricted. Opening the exhaust gas recirculation control valve when the engine temperature is equal to or higher than a predetermined temperature; opening the exhaust gas recirculation control valve when the engine temperature is lower than the predetermined temperature; When the temperature is lower than a predetermined temperature, the exhaust gas recirculation control valve is closed.

According to this configuration, when the combustion of the engine is restricted, the exhaust gas is returned to the intake passage when the intake air temperature of the engine is equal to or higher than the predetermined temperature, so that the exhaust gas is included in the exhaust gas discharged from the engine. The oxygen concentration is reduced. For this reason, it is possible to prevent the catalyst disposed on the exhaust passage from excessively adsorbing oxygen, and to prevent the purification efficiency of the catalyst from decreasing when the engine is recombusted. Further, when the combustion of the engine is restricted, since the exhaust gas is supplied to the engine, it is possible to avoid a situation in which the combustion chamber becomes negative pressure, and it is possible to prevent engine oil from being sucked into the combustion chamber. . On the other hand, when the combustion of the engine is restricted, since the recirculation of the exhaust gas to the intake passage is restricted when the intake air temperature of the engine is lower than a predetermined temperature, in a situation where the moisture in the exhaust gas may freeze. A situation in which exhaust gas is recirculated can be prevented. As a result, it is possible to reliably prevent problems caused by freezing of moisture in the exhaust gas. As a result, it is possible to prevent a problem associated with freezing of moisture in the recirculated exhaust gas while preventing a decrease in purification efficiency of the exhaust gas due to the adsorption of oxygen by the catalyst. The control unit opens the exhaust gas recirculation control valve when the engine temperature is equal to or higher than the predetermined temperature, and controls the opening and closing of the exhaust gas recirculation control valve based on the intake air temperature when the engine temperature is lower than the predetermined temperature. Is higher than a predetermined temperature, the exhaust gas is recirculated to the intake passage. For this reason, the situation where the catalyst excessively adsorbs oxygen can be prevented, and the purification efficiency of the catalyst can be prevented from being reduced when the engine is reburned. On the other hand, when the engine temperature is lower than the predetermined temperature, the opening and closing of the exhaust gas recirculation control valve is controlled. Therefore, when the engine temperature is lower than the predetermined temperature and the intake air temperature is lower than the predetermined temperature, the recirculation of the exhaust gas to the intake passage is regulated. Thereby, the case where the recirculation of the exhaust gas to the intake passage is restricted can be limited, and the reduction of the purification efficiency by the catalyst can be effectively prevented.

  Further, in the engine control device, the engine control device further includes an intake adjustment valve disposed in the intake passage and adjusts an intake amount of the engine, wherein the control unit is configured to operate the intake adjustment valve when closing the exhaust recirculation control valve. You may make it open. According to this configuration, when the exhaust gas recirculation control valve is closed, the intake adjustment valve is opened. For this reason, even when the exhaust gas recirculation valve is closed, air can be supplied to the engine through the intake passage, and the combustion chamber is prevented from becoming negative pressure. Thus, it is possible to prevent the engine oil from being sucked into the combustion chamber and to suppress the consumption of the engine oil.

  Further, in the engine control device, the engine control device further includes a rotation speed detection unit that detects a rotation speed of the engine, and the control unit increases an opening amount of the intake adjustment valve with an increase in the rotation speed of the engine. Is preferred. According to this configuration, since the opening amount of the intake adjustment valve is increased with an increase in the engine speed, the intake air amount of the engine is increased in a situation where the combustion chamber is likely to be under negative pressure. For this reason, it is possible to effectively prevent a situation in which the combustion chamber becomes negative pressure.

An engine control method according to the present invention is a control method for an engine having an exhaust gas recirculation device that recirculates exhaust gas discharged from an engine to an intake passage, wherein an intake air temperature detecting step of detecting an intake air temperature of the engine; An engine temperature detecting step of detecting a temperature, and an opening / closing control step of controlling opening / closing of an exhaust gas recirculation control valve of the exhaust gas recirculation device, wherein in the opening / closing control step, the combustion of the engine is restricted. Opening the exhaust gas recirculation control valve when the engine temperature is equal to or higher than a predetermined temperature, and opening the exhaust gas recirculation control valve when the intake air temperature is equal to or higher than a predetermined temperature when the engine temperature is lower than the predetermined temperature; The exhaust gas recirculation control valve is closed when the intake air temperature is lower than a predetermined temperature.

  ADVANTAGE OF THE INVENTION According to this invention, the trouble accompanying freezing of the water | moisture content in the recirculated exhaust gas can be prevented, preventing the fall of the purification efficiency of the exhaust gas accompanying oxygen adsorption of a catalyst.

1 is a schematic diagram illustrating a configuration around an engine of a vehicle to which an engine control device according to the present embodiment is applied. FIG. 4 is a flowchart for explaining an engine control operation in the engine control device according to the present embodiment. FIG. 4 is an explanatory diagram of a relationship among an engine speed, an opening degree of a throttle valve, and an intake pressure in the engine control device according to the present embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, a case will be described in which the engine control device according to the present invention is applied to a vehicle equipped with a gasoline engine, but is not limited thereto. Regarding the target to which the engine control device according to the present invention is applied, any engine such as a diesel engine or a hybrid engine is mounted on condition that an exhaust gas recirculation device (EGR (Exhaust Gas Recirculation) device) is mounted. Applicable to vehicles.

  FIG. 1 is a schematic diagram showing a configuration around an engine of a vehicle to which the engine control device according to the present embodiment is applied. FIG. 1 shows only components related to the present invention for convenience of explanation. However, it is assumed that the vehicle according to the present embodiment includes components (for example, a vehicle speed sensor) necessary for normal engine control.

  As shown in FIG. 1, a vehicle to which the engine control device according to the present embodiment is applied includes a gasoline engine (hereinafter, simply referred to as “engine”) 100. The engine 100 is configured by an engine that operates a piston in a cylinder during low-load operation or idling. In other words, engine 100 is configured with an engine that does not have a cylinder deactivation function that deactivates some or all of the cylinders during low-load operation or idling. In engine 100 of the present embodiment, the piston in the cylinder reciprocates in the cylinder even when combustion is restricted (fuel cut) during deceleration or the like.

  The engine 100 is configured by attaching a crankcase below a cylinder in which a cylinder block, a cylinder head, and the like are combined. A piston is arranged in the cylinder, and a combustion chamber is provided above the piston. At a predetermined position of the engine 101, a fuel injection device (hereinafter, referred to as "injector") 101 for injecting gasoline into a combustion chamber provided in a cylinder is provided.

  Further, the engine 100 is provided with a rotation speed sensor 102 and a coolant temperature sensor 103. The rotation speed sensor 102 is arranged, for example, on a crankshaft housed in a crankcase, and detects the rotation speed of the engine 100 (engine rotation speed). The cooling water temperature sensor 103 functions as an engine temperature sensor, and is arranged, for example, on a radiator hose (not shown) and detects the temperature of cooling water supplied to the engine 100 via the radiator hose. The engine speed and the coolant temperature detected by these sensors 102 and 103 are output to an ECU 112 described later. The coolant temperature detected by coolant temperature sensor 103 is used for detecting the temperature of engine 100 (engine temperature) in ECU 112.

  An intake pipe (not shown) of the engine 100 is connected to an intake pipe 104 that forms an intake passage. The intake pipe 104 is provided with a throttle valve 105 that is opened and closed by operating an accelerator pedal or the like. The throttle valve 105 functions as an intake adjustment valve that adjusts the amount of intake air supplied to the engine 100 under instructions from the ECU 112 described below. As will be described in detail later, the intake pressure of engine 100 can be controlled by adjusting the opening of throttle valve 105.

  An intake temperature sensor 106 and an intake pressure sensor 107 are provided at predetermined positions of the intake pipe 104. These intake air temperature sensor 106 and intake air pressure sensor 107 are arranged at a position downstream of the throttle valve 105. The intake air temperature sensor 106 is disposed at a position downstream of an exhaust gas outlet 110b to the intake pipe 104 in an exhaust gas recirculation pipe 110 described later. Intake air temperature sensor 106 detects an intake air temperature of engine 100. Intake pressure sensor 107 detects an intake pressure of engine 100. The intake air temperature and intake air pressure detected by these sensors 106 and 107 are output to an ECU 112 described later.

  An exhaust pipe (not shown) of the engine 100 is connected to an exhaust pipe 108 that forms an exhaust passage. The exhaust pipe 108 is provided with a catalytic converter 109. The catalytic converter 109 is formed of, for example, a three-way catalytic converter, oxidizes hydrocarbons and carbon monoxide contained in exhaust gas discharged from the engine 100 to harmless carbon dioxide and moisture, and also produces nitrogen oxides. Also reduce.

  An exhaust recirculation pipe 110 is connected to the intake pipe 104 and the exhaust pipe 108. The exhaust gas recirculation pipe 110 has an intake pipe 104 and an exhaust gas inlet 110a arranged between the engine 100 and the catalytic converter 109 and an exhaust gas exhaust port 110b arranged between the engine 100 and the throttle valve 105. It is connected to the exhaust pipe 108. In addition, the exhaust gas outlet 110 b is arranged at a position on the upstream side of the intake air temperature sensor 106 in the intake pipe 104.

  The exhaust gas recirculation pipe 110 is provided with an EGR valve 111. The EGR valve 111 functions as an exhaust gas recirculation control valve that adjusts exhaust gas recirculated to the intake pipe 104 under instructions from the ECU 112 described later. The EGR valve 111 is controlled to open and close under instructions from the ECU 112 described later. As will be described in detail later, the intake pressure of engine 100 can be controlled by adjusting the opening of EGR valve 111. The exhaust gas recirculation pipe 110 and the EGR valve 111 constitute a part of an EGR device.

  A vehicle to which the engine control device according to the present embodiment is applied includes an ECU (Engine Control Unit) 112 that functions as a control unit that controls engine 100. In the ECU 112, a rotation speed sensor 102, a coolant temperature sensor 103, an intake air temperature sensor 106, and an intake pressure sensor 107 are connected to an input open circuit, and a throttle valve 105 and an EGR valve 111 are connected to an output circuit. The ECU 112 controls the opening and closing of the throttle valve 105 and the EGR valve 111 based on the engine speed, the coolant temperature, the intake air temperature, and the intake pressure detected by various sensors.

  Having such a configuration, the ECU 112 controls opening and closing of the throttle valve 105 and supplies optimal air to the engine 100 for combustion. Intake is performed through the intake pipe 104, and when fuel is injected from the injector 101, the fuel is ignited by a spark plug. Thereby, the compressed gas of the air and the fuel contained in the combustion chamber is burned. Further, the ECU 112 performs the exhaust gas recirculation control according to the engine speed and the engine load. As a result, the reduction of nitrogen oxides from the exhaust gas accompanying the combustion of the engine 100 and the improvement of fuel efficiency are realized.

  By the way, there is known an engine which stops fuel injection from an injector and performs control for limiting combustion (fuel cut control) when the vehicle is decelerated. At the time of fuel cut, it is preferable to close the throttle valve in order to secure engine braking. However, when the throttle valve is completely closed, the pressure in the combustion chamber becomes negative due to the shortage of the intake air to the engine. As a result, a phenomenon occurs in which engine oil is sucked from between the cylinder and the piston to the combustion chamber side (hereinafter, appropriately referred to as “oil rising”), and the engine oil is consumed.

  In the above-described conventional variable valve timing control device, when the engine is in a deceleration state, by controlling the valve overlap amount in accordance with the gear position, regardless of the size of the gear position, it is possible to prevent oil rising and to reduce waste. Low oil consumption. However, in this variable valve timing control device, exhaust gas from the engine is supplied to the catalyst. Therefore, there is a problem that oxygen in the air is adsorbed by the catalyst, and when the combustion of the engine is restarted, the efficiency of purifying the exhaust gas by the catalyst is reduced.

  On the other hand, it is conceivable to supply exhaust gas (EGR gas) to the engine by an EGR device in order to prevent the above-mentioned oil rise while suppressing oxygen adsorption by the catalyst. In this case, EGR gas having a small oxygen content is supplied from the engine to the catalyst. Therefore, it is possible to prevent problems caused by oxygen adsorption in the catalyst.

  However, when the EGR gas is supplied to the engine, the moisture contained in the EGR gas may adhere to peripheral parts such as the injectors and freeze the peripheral parts. For example, when the injector freezes, it is not possible to properly inject fuel into the combustion chamber, and problems such as deterioration of combustion performance in the engine occur.

  The present inventor pays attention to such a situation, and when the combustion of the engine is restricted at the time of deceleration or the like, the EGR gas is supplied to the engine only in a situation in which a trouble caused by moisture contained in the EGR gas is unlikely to occur. It has been found out that the recirculation contributes to the reduction of the purification efficiency of the exhaust gas due to the adsorption of oxygen by the catalyst and the prevention of the troubles caused by the freezing of the moisture in the recirculated EGR gas.

  That is, the gist of the present invention is to open the EGR valve 111 and recirculate the EGR gas to the engine 100 when the intake air temperature of the engine 100 is equal to or higher than a predetermined temperature when the combustion of the engine is restricted during deceleration or the like, When the intake air temperature is lower than the predetermined temperature, the EGR valve 111 is closed to restrict the recirculation of the EGR gas.

  According to the present invention, when combustion of engine 100 is restricted, exhaust gas is recirculated to intake pipe 104 when intake air temperature of engine 100 is equal to or higher than a predetermined temperature. The concentration of oxygen contained is reduced. For this reason, the situation where the catalyst 109 excessively adsorbs oxygen can be prevented, and the purification efficiency of the catalyst 109 can be prevented from decreasing when the engine 100 is reburned. Further, when the combustion of the engine is restricted, since the EGR gas is supplied to the engine 100, it is possible to avoid a situation in which the combustion chamber becomes a negative pressure, and it is possible to prevent engine oil from being sucked into the combustion chamber. You. On the other hand, when the combustion of the engine 100 is restricted, when the intake air temperature of the engine 100 is lower than the predetermined temperature, the recirculation of the EGR gas to the intake pipe 104 is restricted, so that the moisture in the EGR gas freezes. In such a situation, the situation in which the EGR gas is recirculated can be prevented. As a result, it is possible to reliably prevent a problem caused by freezing of water in the EGR gas.

  Hereinafter, an engine control operation in the engine control device according to the present embodiment will be described with reference to FIG. FIG. 2 is a flowchart for illustrating an engine control operation in the engine control device according to the present embodiment. The flow shown in FIG. 2 is executed by the ECU 112. Prior to the flow shown in FIG. 2, it is assumed that information detected from the various sensors 102, 103, 106, and 107 is provided to the ECU 112.

  When performing the intake pressure control operation, as shown in FIG. 2, the ECU 112 monitors whether a fuel cut (fuel cut) condition (fuel cut condition) is satisfied (step ST201). For example, the transition to the deceleration state of the vehicle corresponds to the fuel cut condition. When the fuel cut condition is not satisfied, the ECU 112 continues the monitoring operation of step ST201. On the other hand, if the fuel cut condition is satisfied, ECU 112 proceeds to step ST202.

  In step ST202, the ECU 112 determines whether the engine temperature is equal to or higher than the predetermined temperature x ° C. according to the cooling water temperature from the cooling water temperature sensor 103. For example, the predetermined temperature x ° C can be set to 80 ° C, but is not limited to this. The reason for determining whether or not the engine temperature is equal to or higher than the predetermined temperature x ° C. is to determine whether or not a problem due to moisture contained in the EGR gas is unlikely to occur.

  If the engine temperature is equal to or higher than the predetermined temperature x ° C. (step ST202: Yes), the ECU 112 determines that a problem due to moisture contained in the EGR gas is unlikely to occur, and performs intake pressure control using the EGR valve 111 (step ST202). ST203). In this case, the ECU 112 opens the EGR valve 111 and closes the throttle valve 105. Thus, only the EGR gas recirculated through the exhaust recirculation pipe 110 is supplied to the intake pipe 104. For this reason, even when the combustion of the engine 100 is restricted, the EGR gas is discharged from the engine 100. After performing the intake pressure control by the EGR valve 111 in this way, the ECU 112 returns the process to step ST201, and repeats the processes after step ST201.

  On the other hand, if the engine temperature is lower than the predetermined temperature x ° C (step ST202: No), the ECU 112 determines whether the intake air temperature from the intake air temperature sensor 106 is equal to or higher than the predetermined temperature y ° C (step ST204). It is determined whether the intake air temperature is equal to or higher than the predetermined temperature y ° C., as in the case of the engine temperature, in order to determine whether a malfunction due to moisture contained in the EGR gas is unlikely to occur. For example, the predetermined temperature y ° C can be set to 0 ° C, but is not limited to this.

  If the intake air temperature is equal to or higher than the predetermined temperature y ° C. (step ST204: Yes), the ECU 112 determines that a problem due to moisture contained in the EGR gas is unlikely to occur, and performs intake pressure control using the EGR valve 111 (step ST204). ST203). In this case, as described above, the ECU 112 opens the EGR valve 111 and closes the throttle valve 105. Thus, only the EGR gas recirculated through the exhaust recirculation pipe 110 is supplied to the intake pipe 104. For this reason, even when the combustion of the engine 100 is restricted, the EGR gas is discharged from the engine 100. After performing the intake pressure control by the EGR valve 111 in this way, the ECU 112 returns the process to step ST201, and repeats the processes after step ST201.

  As described above, in the engine control device according to the present embodiment, when the combustion of engine 100 is restricted, the EGR gas is recirculated when the intake air temperature of engine 100 is equal to or higher than predetermined temperature y ° C. Therefore, the concentration of oxygen contained in the exhaust gas discharged from engine 100 is reduced. Accordingly, it is possible to prevent the catalyst 109 disposed in the exhaust pipe 108 from excessively adsorbing oxygen, and to prevent the purification efficiency of the catalyst 109 from decreasing when the engine 100 is reburned. Further, when the combustion of the engine 100 is restricted, since the EGR gas is supplied to the engine 100, it is possible to avoid a situation in which the combustion chamber becomes a negative pressure, and to prevent the engine oil from being sucked into the combustion chamber. Is done.

  On the other hand, if the intake air temperature is lower than the predetermined temperature y ° C. (step ST204: No), the ECU 112 determines that a malfunction due to moisture contained in the EGR gas may occur, and performs the intake pressure control by the throttle valve 105. Perform (Step ST205). In this case, the ECU 112 opens the throttle valve 105 and closes the EGR valve 111. As a result, air is supplied to the intake pipe 104 via the intake pipe 104, and EGR gas is not supplied. After performing the intake pressure control by the throttle valve 105 in this way, the ECU 112 returns the process to step ST201, and repeats the processes after step ST201.

  Thus, in the engine control device according to the present embodiment, when the intake air temperature of engine 100 is lower than predetermined temperature y ° C., the recirculation of the EGR gas to intake pipe 104 is restricted. Therefore, it is possible to prevent a situation in which the EGR gas is recirculated in a situation where the moisture in the EGR gas can be frozen. As a result, it is possible to reliably prevent a problem caused by freezing of water in the EGR gas.

  In particular, in the engine control device according to the present embodiment, intake temperature sensor 106 is arranged at a position downstream of exhaust gas outlet 110b with respect to intake pipe 104. For this reason, the temperature of the EGR gas returned to the intake pipe 104 can be directly detected by the intake temperature sensor 106. Accordingly, the intake air temperature of engine 100 due to the recirculation of the EGR gas can be accurately detected, and the accuracy of the opening / closing control of EGR valve 111 can be improved.

  Further, in the engine control device according to the present embodiment, the engine temperature is determined (step ST202) prior to the determination of the intake air temperature of engine 100 (step ST204). When the engine temperature is equal to or higher than the predetermined temperature x ° C., the intake pressure is controlled by the EGR valve 111, and the EGR gas is returned to the intake pipe 104. For this reason, the situation where the catalyst 109 excessively adsorbs oxygen can be prevented, and the purification efficiency of the catalyst 109 can be prevented from decreasing when the engine 100 is reburned.

  On the other hand, when the engine temperature is lower than the predetermined temperature x ° C., the opening and closing of the EGR valve 111 is controlled based on the intake air temperature of the engine 100. Therefore, when the engine temperature is lower than the predetermined temperature x ° C. and the intake air temperature is lower than the predetermined temperature y ° C., the recirculation of the EGR gas to the intake pipe 104 is restricted. As a result, it is possible to limit the case where the recirculation of the EGR gas to the intake pipe 104 is restricted, and it is possible to effectively prevent the purification efficiency of the catalyst 109 from decreasing.

  Further, in the engine control device according to the present embodiment, when performing the intake pressure control by the throttle valve 105, the EGR valve 111 is closed and the throttle valve 105 is opened. For this reason, even when the EGR valve 111 is closed, air can be supplied to the engine 100 through the intake pipe 104, so that a negative pressure in the combustion chamber is prevented. Thus, it is possible to prevent the engine oil from being sucked into the combustion chamber and to suppress the consumption of the engine oil.

  In particular, in the engine valve control device according to the present embodiment, the opening amount of throttle valve 105 is adjusted according to the rotation speed of engine 100. In this case, the ECU 112 can adjust the opening amount of the throttle valve 105 according to the engine speed detected by the speed sensor 102. More specifically, the ECU 112 increases the opening amount of the throttle valve 105 as the engine speed increases. As a result, the intake air amount of the engine is increased in a situation where the pressure in the combustion chamber tends to be negative. For this reason, it is possible to effectively prevent a situation in which the combustion chamber becomes negative pressure.

  Here, transition of the intake pressure when adjusting the opening amount of the throttle valve 105 according to the engine speed will be described with reference to FIG. FIG. 3 is an explanatory diagram of the relationship between the engine speed, the opening of the throttle valve 105, and the intake pressure of the engine 100 in the engine control device according to the present embodiment. FIG. 3A shows the relationship between the engine speed and the opening of the throttle valve 105 (throttle opening). FIG. 3B shows the relationship between the engine speed and the intake pressure of engine 100.

  As shown in FIG. 3A, when the engine speed exceeds a certain value X, the ECU 112 adjusts the opening of the throttle valve 105 to increase as the engine speed increases (see the solid line A1 in FIG. 3A). ). By controlling the throttle opening in this way, the intake pressure of engine 100 changes as shown in FIG. 3B. That is, the intake pressure of the engine 100 maintains the constant value Y without changing in the negative pressure direction when the engine speed exceeds the constant value X (see the solid line A2 shown in FIG. 3B).

  3A and 3B, broken lines B1 and B2 show cases where the opening of the throttle valve 105 is not adjusted regardless of the engine speed. As shown by the broken line B1 in FIG. 3A, when the opening of the throttle valve 105 is not adjusted regardless of the engine speed, the intake pressure of the engine 100 increases as shown in FIG. 3B. It changes in the negative pressure direction accordingly. That is, the intake pressure of engine 100 continuously changes in the negative pressure direction according to the increase in the engine speed (see broken line B2 shown in FIG. 3B).

  As described above, in the engine control device according to the present embodiment, control is performed such that the opening amount of throttle valve 105 increases as the engine speed increases. For this reason, the intake air amount of the engine is increased in a situation where the combustion chamber is likely to be under negative pressure. As a result, it is possible to effectively prevent a situation in which the combustion chamber has a negative pressure.

  In the engine control device according to the present embodiment, the intake pressure of engine 100 may be controlled based on the intake pressure detected by intake pressure sensor 107 provided in intake pipe 104. In this case, the ECU 112 may control the intake pressure of the engine 100 by adjusting the operation timing or amount of the intake valve or the exhaust valve based on the intake pressure output from the intake pressure sensor 107. For example, the ECU 112 can control a variable valve timing control device (not shown) to adjust the variable valve timing and the variable valve lift.

  By controlling the intake pressure of the engine 100 based on the intake pressure detected by the intake pressure sensor 107 in this way, it is possible to effectively prevent a situation where the combustion chamber becomes negative. In particular, in the present embodiment, the intake pressure sensor 107 is provided downstream of the throttle valve 105. Therefore, the intake pressure of the engine 100 can be directly detected by the intake pressure sensor 107. Thus, the intake pressure of engine 100 due to the recirculation of EGR gas can be accurately detected, and the accuracy of intake pressure control of engine 100 can be improved.

  In addition, in the said embodiment, the magnitude | size of each structure shown in an accompanying drawing, a shape, etc. are not limited to this but can be changed suitably within the range in which the effect of this invention is exhibited. In addition, the present invention can be appropriately modified and implemented without departing from the scope of the object.

  For example, in the above embodiment, the case where the intake pressure control by the EGR valve 111 and the throttle valve 105 (see steps ST203 and ST205 shown in FIG. 2) is switched by judging the engine temperature and the intake temperature. However, the switching method of the intake pressure control described above is not limited to this, and can be appropriately changed. For example, only one of the intake air temperature and the engine temperature may be determined, and the intake pressure control may be switched. Even in such a case, the same effects as in the above embodiment can be obtained.

  Further, in the above-described embodiment, in the intake pipe 104, the intake air temperature sensor 106 is disposed downstream of the exhaust gas outlet 110b of the exhaust gas recirculation pipe 110. However, the arrangement of the intake air temperature sensor 106 is not limited to this, and can be appropriately changed. For example, the intake air temperature sensor 106 may be disposed downstream of the throttle valve 105 and upstream of the exhaust gas outlet 110b, or upstream of the throttle valve 105.

  Further, in the above embodiment, in the intake pressure control by the EGR valve 111 (step ST203 shown in FIG. 2), the throttle valve 105 is closed and the EGR valve 111 is opened. In the intake pressure control by the throttle valve 105 (see step ST205 shown in FIG. 2), the EGR valve 111 is closed and the throttle valve 105 is opened. However, the open / close state of the throttle valve 105 and the EGR valve 111 is not limited to this, and can be appropriately changed. For example, by opening both the throttle valve 105 and the EGR valve 111 and adjusting the opening amounts, the purification efficiency of exhaust gas accompanying the adsorption of oxygen by the catalyst 109 is reduced, and the freezing of moisture in the recirculated EGR gas is prevented. The accompanying trouble may be prevented. In this case, for example, a mode in which the throttle valve 105 is widely opened and the EGR valve 111 is slightly opened, and a mode in which the EGR valve 111 is widely opened and the throttle valve 105 is slightly opened are conceivable.

  The present invention has an effect that it is possible to prevent a problem associated with freezing of moisture in recirculated exhaust gas while preventing a decrease in exhaust gas purification efficiency due to oxygen adsorption of a catalyst. And is useful for vehicles equipped with an engine that recirculates EGR gas.

100 engine (gasoline engine)
DESCRIPTION OF SYMBOLS 101 Injector 102 Revolution speed sensor 103 Cooling water temperature sensor 104 Intake pipe 105 Throttle valve 106 Intake temperature sensor 107 Intake pressure sensor 108 Exhaust pipe 109 Catalytic converter 110 Exhaust recirculation pipe 110a Exhaust gas inlet 110b Exhaust gas outlet 111 EGR valve 112 ECU

Claims (4)

An engine control device having an exhaust gas recirculation device that recirculates exhaust gas discharged from the engine to an intake passage,
An intake air temperature detector that detects an intake air temperature of the engine;
An engine temperature detecting section for detecting an engine temperature;
A control unit that controls the opening and closing of an exhaust gas recirculation control valve of the exhaust gas recirculation device,
The control unit opens the exhaust gas recirculation control valve when the engine temperature is equal to or higher than a predetermined temperature when the combustion of the engine is restricted, and when the engine temperature is lower than the predetermined temperature, the intake air temperature is lower. An engine control device, wherein the exhaust gas recirculation control valve is opened when the temperature is equal to or higher than a predetermined temperature, and the exhaust gas recirculation control valve is closed when the intake air temperature is lower than the predetermined temperature. An intake adjustment valve disposed in the intake passage and adjusting an intake amount of the engine is further provided.
The engine control device according to claim 1, wherein the control unit opens the intake adjustment valve when closing the exhaust gas recirculation control valve. A rotation speed detection unit that detects a rotation speed of the engine;
The engine control device according to claim 2, wherein the control unit increases the opening amount of the intake adjustment valve as the number of revolutions of the engine increases. A control method for an engine having an exhaust gas recirculation device that recirculates exhaust gas discharged from an engine to an intake passage,
An intake air temperature detecting step of detecting an intake air temperature of the engine;
An engine temperature detecting step of detecting an engine temperature;
Opening and closing control step of controlling the opening and closing of the exhaust gas recirculation control valve of the exhaust gas recirculation device,
In the opening and closing control step, when combustion of the engine is restricted, the exhaust gas recirculation control valve is opened when the engine temperature is equal to or higher than a predetermined temperature, and when the engine temperature is lower than the predetermined temperature, the intake air temperature is reduced. An engine control method comprising: opening the exhaust gas recirculation control valve when is higher than a predetermined temperature; and closing the exhaust gas recirculation control valve when the intake air temperature is lower than a predetermined temperature.

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