JP2007211710A - Controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for an internal combustion engine for surely supplying a start motor with electric power required for starting the internal combustion engine that can prevent startability of the internal engine from degrading. <P>SOLUTION: The controller is equipped with the start motor 5, a battery 6 connected with the start motor 5 and a turbosupercharger 8 drivable by an electric motor 8c connected with the battery 6 in which a compressor 8a is provided at an air intake passage 3 of the internal combustion engine 1 started by the start motor 5 and a turbine 8b is provided at an exhaust passage 4 of the internal combustion engine 1. An ECU 30 actuates the start motor 5 at the time of starting the internal combustion engine 1 and controls action of the electric motor 8c so that intake air is supercharged by the turbosupercharger 8. In the case that a factor to degrade startability of the internal combustion engine 1 when starting the internal combustion engine is arisen, the ECU 30 controls action of the electric motor 8c so as to limit supercharge of the intake air by the turbosupercharger 8 when starting the internal combustion engine 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine including a supercharger that can be driven by an electric motor.

  2. Description of the Related Art An engine starter that drives a turbocharger with a rotating electric machine (electric motor) to increase the supercharging pressure and increase the compression pressure in the cylinder when starting the engine is known (see Patent Document 1). In addition, Patent Documents 2 and 3 exist as prior art documents related to the present invention.

Japanese Patent No. 2775195 JP 2004-76687 A Japanese Utility Model Publication No. 5-69317

  In general, an internal combustion engine is started by cranking by a starter motor. However, if the turbocharger is driven by an electric motor without considering the power consumed by the starter motor when starting the internal combustion engine, the voltage of the battery decreases. There is a possibility that the electric power necessary for starting the internal combustion engine from the battery to the starting motor cannot be sufficiently supplied. The lower the temperature of the internal combustion engine, the higher the viscosity of the lubricating oil of the internal combustion engine, so the friction of the internal combustion engine increases. Therefore, when the turbocharger is driven by the electric motor as in the case of starting the internal combustion engine having a high temperature when starting the internal combustion engine having a low temperature, the electric power necessary for starting the internal combustion engine is sufficiently supplied to the start motor. May not be able to supply. In these cases, sufficient power is not supplied to the starter motor, and the output of the starter motor is insufficient, which may deteriorate the startability of the internal combustion engine.

  Accordingly, an object of the present invention is to provide a control device for an internal combustion engine that can reliably supply power necessary for starting the internal combustion engine to the starter motor and prevent deterioration of startability of the internal combustion engine.

  An internal combustion engine control apparatus according to the present invention includes a starter motor, a battery electrically connected to the starter motor, a compressor provided in an intake passage of the internal combustion engine started by the starter motor, and the internal combustion engine. A turbocharger that is provided with a turbine in an exhaust passage and can be driven by an electric motor electrically connected to the battery, and operates the starter motor when the internal combustion engine starts, and suctions by the turbocharger An operation control means for controlling the operation of the electric motor so that air is supercharged, wherein the operation control means increases the startability of the internal combustion engine when the internal combustion engine is started. In the case where a deterioration factor occurs, the electric motor is controlled so that supercharging of the intake air by the turbocharger performed at the start of the internal combustion engine is limited. It allows to solve the problems described above which comprises a supercharging limiting means for controlling the operation (Claim 1).

  According to the control device of the present invention, when a factor that deteriorates the startability of the internal combustion engine occurs, the supercharging of the intake air by the turbocharger is limited, so that the electric power consumed by the electric motor is reduced. Can do. Thereby, the electric power which can be supplied to a starting motor can be increased by suppressing the voltage drop of a battery. Therefore, it is possible to reliably supply electric power necessary for starting the internal combustion engine to the starter motor and to prevent deterioration of the startability of the internal combustion engine.

  The control device according to the present invention further comprises voltage acquisition means for acquiring the voltage of the battery, and the supercharging limiting means is configured such that the battery voltage acquired by the voltage acquisition means takes into account the friction of the internal combustion engine. It may be determined that the factor is generated when the determination voltage is lower than the predetermined determination voltage (claim 2). When the voltage of the battery at the time of starting is low, there is a possibility that the power supplied to the starting motor may be insufficient, and thus the startability may be deteriorated. Therefore, in such a case, the supercharging of the intake air by the turbocharger is limited to reduce the power consumed by the electric motor.

  In one aspect of the control device of the present invention, the supercharging limiting means is configured to start the internal combustion engine when the internal combustion engine starts when the voltage of the battery acquired by the voltage acquisition means is less than the determination voltage. The number of revolutions of the electric motor may be reduced when the internal combustion engine is started than when the voltage of the battery is equal to or higher than the determination voltage (Claim 3). Thus, since the electric power consumed by the electric motor can be reduced by lowering the rotation speed of the electric motor, the voltage drop of the battery can be suppressed.

  In one aspect of the control device of the present invention, the supercharging restriction unit is configured to start the internal combustion engine when the internal combustion engine is started when the voltage of the battery acquired by the voltage acquisition unit when the internal combustion engine is started is less than the determination voltage. The turbocharger may be prohibited from being driven by an electric motor (claim 4). In this case, since electric power is not consumed by the electric motor, the voltage drop of the battery can be further suppressed. Therefore, the electric power that can be supplied to the starter motor can be further increased. In addition, since the turbocharger is not driven by the electric motor, the turbine disposed in the exhaust passage serves as an exhaust flow resistance. In this case, exhaust of the exhaust from the cylinder is hindered, so that the amount of exhaust remaining in the cylinder can be increased. Thereby, the exhaust gas remaining in the cylinder can suppress the temperature drop of the cylinder and increase the temperature in the cylinder at the end of the compression stroke, that is, the so-called compression end temperature, so that the startability of the internal combustion engine can be improved.

  In one form of the control device of the present invention, the electric motor can function as a generator that generates electric power using exhaust energy of the internal combustion engine and can charge the generated electric power to the battery. When the battery voltage acquired by the voltage acquisition unit when the internal combustion engine is started is less than the determination voltage, the limiting unit causes the electric motor to function as a generator when starting the internal combustion engine to charge the battery. (Claim 5). In this case, since the electric power generated in the electric motor is charged in the battery, the voltage drop of the battery can be further suppressed. Therefore, it is possible to reliably supply the electric power necessary for starting the internal combustion engine to the starting motor. In addition, since the turbine can be made difficult to rotate by causing the electric motor to function as a generator, the exhaust is further hardly discharged from the cylinder. Therefore, the amount of exhaust gas remaining in the cylinder can be further increased to further increase the compression end temperature, thereby further improving the startability of the internal combustion engine.

  In one form of the control device of the present invention, the control device further includes an EGR means for returning a part of the exhaust discharged from the cylinder of the internal combustion engine into the cylinder again, and the supercharging limiting means is provided when the internal combustion engine is started. When the battery voltage acquired by the voltage acquisition unit is less than the determination voltage, the operation of the EGR unit may be controlled so that a part of the exhaust is returned into the cylinder when the internal combustion engine is started. (Claim 6). Thus, by returning a part of the exhaust gas to the cylinder, it is possible to suppress the temperature drop of the cylinder. Therefore, it is possible to improve the startability of the internal combustion engine by increasing the compression end temperature.

  In this embodiment, the EGR means is disposed in the path of the EGR passage, the EGR passage connecting the intake passage and the exhaust passage, the EGR valve for adjusting the flow rate of the exhaust gas passing through the EGR passage, and the EGR passage. An EGR cooler that cools the exhaust gas, a bypass passage that bypasses the EGR cooler and guides the exhaust gas from the exhaust passage to the intake passage, and an exhaust gas that is returned from the exhaust passage to the intake passage through the EGR cooler. 1 and a flow path switching valve that can be switched from the exhaust passage to a second position at which exhaust is returned to the intake passage through the bypass passage, and the supercharging limiting means includes the internal combustion engine When the voltage of the battery acquired by the voltage acquisition means at the time of starting the engine is less than the determination voltage, the exhaust gas is returned to the intake passage at the time of starting the internal combustion engine. The EGR valve opened as and may be switched to the flow path switching valve to the second position (claim 7). In this case, adhesion of unburned fuel or the like in the exhaust to the EGR cooler can be suppressed. Therefore, the occurrence of clogging of the EGR cooler can be prevented. Moreover, the temperature drop of the exhaust gas returned to the intake passage can be suppressed by bypassing the EGR cooler. Therefore, the startability of the internal combustion engine can be improved by increasing the temperature of the compression end. Further, since exhaust gas is returned to the intake passage, white smoke can be prevented from being discharged.

  In one form of the control apparatus of the present invention, the internal combustion engine includes an exhaust throttle valve provided in an exhaust passage downstream of the turbine and capable of adjusting a flow rate of exhaust flowing through the exhaust passage, and the supercharging limiting means If the battery voltage acquired by the voltage acquisition means at the start of the internal combustion engine is less than the determination voltage, the exhaust throttle valve is set so that the exhaust flow rate in the exhaust passage decreases at the start of the internal combustion engine. You may close (Claim 8). By closing the exhaust throttle valve in this way, it becomes difficult for exhaust to be discharged from the cylinder of the internal combustion engine. Therefore, it is possible to increase the amount of exhaust gas remaining in the cylinder and raise the compression end temperature. Therefore, the startability of the internal combustion engine can be improved.

  In one form of the control device of the present invention, the turbocharger includes a variable nozzle capable of changing a flow path cross-sectional area of an inlet portion of the turbine, and the supercharging limiting means is configured to start the internal combustion engine when starting the internal combustion engine. When the voltage of the battery acquired by the voltage acquisition means is less than the determination voltage, the variable nozzle may be closed to reduce the flow path cross-sectional area of the inlet portion of the turbine when the internal combustion engine is started. 9). In this case as well, it is difficult to exhaust the exhaust gas from the cylinder of the internal combustion engine, as in the exhaust throttle valve described above. Therefore, since the amount of exhaust gas remaining in the cylinder can be increased, the startability of the internal combustion engine can be improved.

  In one embodiment of the control device of the present invention, the control device includes a variable valve mechanism that can change a closing timing of an exhaust valve provided in a cylinder of the internal combustion engine, and the supercharging limiting means is configured to start the internal combustion engine when the internal combustion engine is started. When the voltage of the battery acquired by the voltage acquisition means is less than the determination voltage, the operation of the variable valve mechanism may be controlled so that the closing timing of the exhaust valve is advanced when the internal combustion engine is started. (Claim 10). Thus, the amount of exhaust gas remaining in the cylinder can be increased by advancing the closing timing of the exhaust valve and closing the exhaust valve before exhaust gas is sufficiently exhausted from the cylinder. Therefore, the startability of the internal combustion engine can be improved.

  In one form of the control device of the present invention, the engine temperature acquisition means for acquiring the temperature of the internal combustion engine, the intake air temperature acquisition means for acquiring the temperature of the intake air, and the engine temperature acquisition means at the start of the internal combustion engine The apparatus may further comprise determination voltage correction means for correcting the determination voltage based on the acquired temperature of the internal combustion engine and the intake air temperature acquired by the intake air temperature acquisition means. The output required for the starting motor when starting the internal combustion engine varies depending on the temperature of the intake air and the temperature of the internal combustion engine. For example, since the friction of the internal combustion engine increases as the temperature of the internal combustion engine decreases, the output required for the starting motor increases. Further, the lower the intake air temperature, the more difficult it is for the temperature at the compression end to rise, so the operation time of the starting motor becomes longer. Therefore, the determination voltage is corrected according to the temperature of the intake air and the temperature of the internal combustion engine, and the starter motor is reliably operated at the output necessary for starting the internal combustion engine. Thereby, the startability of the internal combustion engine can be improved.

  In one form of the control device of the present invention, the engine further includes engine temperature acquisition means for acquiring the temperature of the internal combustion engine, and the supercharging restriction means has a predetermined temperature of the internal combustion engine acquired by the engine temperature acquisition means. It may be determined that the factor has occurred when the temperature is lower than the determination temperature (claim 12). When the temperature of the internal combustion engine at the time of starting is low, the friction of the internal combustion engine increases, so that the output required for the starting motor becomes larger than when the internal combustion engine having a high temperature is started. Therefore, the supercharging of the intake air by the turbocharger is limited to reduce the electric power consumed by the electric motor, and the electric power that can be supplied to the starting motor is increased.

  In this embodiment, the supercharging limiting means is configured to control the internal combustion engine at the time of starting the internal combustion engine when the temperature of the internal combustion engine acquired by the engine temperature acquisition means at the time of starting the internal combustion engine is lower than the determination temperature. The rotational speed of the electric motor may be reduced when the internal combustion engine is started than when the temperature is equal to or higher than the determination temperature. When the temperature of the internal combustion engine acquired by the temperature acquisition unit is lower than the determination temperature, the turbocharger may be prohibited from being driven by the electric motor when the internal combustion engine is started (Claim 14). In addition, the electric motor can function as a generator that generates electric power using the exhaust energy of the internal combustion engine and can charge the generated electric power to the battery. When the temperature of the internal combustion engine acquired by the engine temperature acquisition means at the start is lower than the determination temperature, the battery may be charged by causing the electric motor to function as a generator at the start of the internal combustion engine ( Claim 15). By controlling the operation of the electric motor in this way, it is possible to suppress a battery voltage drop. Therefore, it is possible to reliably supply electric power necessary for starting the internal combustion engine to the starter motor and to prevent deterioration of the startability of the internal combustion engine.

  In one form of the control device of the present invention, the control device further includes an EGR means for returning a part of the exhaust discharged from the cylinder of the internal combustion engine into the cylinder again, and the supercharging limiting means is provided when the internal combustion engine is started. When the temperature of the internal combustion engine acquired by the engine temperature acquisition means is lower than the determination temperature, the operation of the EGR means is controlled so that a part of the exhaust is returned into the cylinder when the internal combustion engine is started. (Claim 16). In this embodiment, the EGR means includes an EGR passage connecting the intake passage and the exhaust passage, an EGR valve for adjusting the flow rate of exhaust gas passing through the EGR passage, and a path of the EGR passage. An EGR cooler that cools the exhaust gas, a bypass passage that bypasses the EGR cooler and guides the exhaust gas from the exhaust passage to the intake passage, and the exhaust gas returns from the exhaust passage to the intake passage through the EGR cooler. And a flow path switching valve that can be switched to a second position where exhaust is returned from the exhaust passage through the bypass passage to the intake passage. When the temperature of the internal combustion engine acquired by the engine temperature acquisition means when starting the internal combustion engine is lower than the determination temperature, the intake passage when starting the internal combustion engine The EGR valve opened so that the exhaust is returned, and may be switched to the flow path switching valve to the second position (claim 17). By returning a part of the exhaust gas to the cylinder in this way, the temperature at the compression end can be raised, so that the startability of the internal combustion engine can be improved.

  In one form of the control apparatus of the present invention, the internal combustion engine includes an exhaust throttle valve provided in an exhaust passage downstream of the turbine and capable of adjusting a flow rate of exhaust flowing through the exhaust passage, and the supercharging limiting means If the temperature of the internal combustion engine acquired by the engine temperature acquisition means at the start of the internal combustion engine is lower than the determination temperature, the exhaust throttle is set so that the exhaust flow rate in the exhaust passage decreases at the start of the internal combustion engine. The valve may be closed (Claim 18), and the turbocharger is provided with a variable nozzle capable of changing a flow path cross-sectional area of the inlet portion of the turbine, and the supercharging limiting means includes the internal combustion engine. When the temperature of the internal combustion engine acquired by the engine temperature acquisition means at the start is lower than the determination temperature, the flow passage cross-sectional area of the inlet portion of the turbine is reduced at the start of the internal combustion engine. May be closed nozzle (Claim 19). In addition, a variable valve mechanism capable of changing a closing timing of an exhaust valve provided in a cylinder of the internal combustion engine is provided, and the supercharging restriction means is acquired by the engine temperature acquisition means when the internal combustion engine is started. When the temperature of the internal combustion engine is lower than the determination temperature, the operation of the variable valve mechanism may be controlled so that the closing timing of the exhaust valve is advanced when the internal combustion engine is started (Claim 20). In these forms, the temperature of the compression end can be increased by increasing the amount of exhaust gas remaining in the cylinder. Therefore, the startability of the internal combustion engine can be improved.

  As described above, according to the present invention, when the voltage of the battery at the start of the internal combustion engine is lower than the determination voltage, or when the temperature of the internal combustion engine at the start of the internal combustion engine is lower than the determination temperature, Since it is determined that a factor that deteriorates the startability has occurred and the operation of the electric motor is controlled such that the supercharging of the intake air by the turbocharger is limited, the voltage drop of the battery can be suppressed. Therefore, the electric power that can be supplied to the starting motor can be increased. Therefore, it is possible to reliably supply power necessary for starting the internal combustion engine to the starter motor, and to prevent deterioration of the startability of the internal combustion engine.

  FIG. 1 shows an internal combustion engine in which a control device according to one embodiment of the present invention is incorporated. The internal combustion engine 1 is configured as a four-cylinder in-line diesel engine that is mounted on a vehicle as a driving power source. Hereinafter, the internal combustion engine 1 may be referred to as an engine. An intake passage 3 and an exhaust passage 4 are connected to each cylinder 2 of the engine 1. The engine 1 also includes a starter motor 5 and a battery 6 electrically connected to the starter motor 5. The intake passage 3 is provided with an air cleaner 7 for filtering the intake air, a compressor 8a of the turbocharger 8, an intercooler 9 for cooling the intake air, and an intake throttle valve 10 for adjusting the flow rate of the intake air. Further, as shown in FIG. 1, the intake passage 3 includes a compressor bypass passage 11 that connects an intake passage upstream of the compressor 8a of the turbocharger 8 and an intake passage downstream of the compressor 8a; An intake bypass valve 12 that can switch the flow of intake air to either the compressor 8a or the compressor bypass passage 11 is provided. During normal operation, the position of the intake bypass valve 12 is switched so that intake air is guided to the compressor 8a. The exhaust passage 4 is provided with a turbine 8b of the turbocharger 8, an exhaust throttle valve 13 for adjusting the flow rate of the exhaust gas flowing through the exhaust passage 4, and an exhaust aftertreatment device 14 for purifying the exhaust gas. The opening degree of the exhaust throttle valve 13 is controlled between a fully open state and a fully closed state. Even if the opening degree of the exhaust throttle valve 13 is changed to the fully closed state, the exhaust passage 4 is not completely closed. That is, even if the exhaust throttle valve 13 is fully closed, a part of the exhaust flows downstream from the exhaust throttle valve 13. The engine 1 includes an injector 15 that is provided in each cylinder 2 and injects fuel into each cylinder 2, and a common rail 16 that stores high-pressure fuel injected from each injector 15.

  As shown in FIG. 1, the exhaust passage 4 and the intake passage 3 are connected by an EGR passage 20. The EGR passage 20 has an EGR cooler 21 for cooling the exhaust and exhaust gas returned to the intake passage 3 (hereinafter referred to as EGR). And an EGR valve 22 that adjusts the flow rate of gas). Further, as shown in FIG. 1, the EGR passage 20 has an EGR bypass passage 23 that bypasses the EGR cooler 21 and guides exhaust gas to the intake passage 3, and EGR gas passes through the EGR cooler 21 to the intake passage 3. An EGR cooler bypass valve 24 is provided as a flow path switching valve that can be switched between a first position for returning and a second position for returning EGR gas to the intake passage 3 via the EGR bypass passage 23. During normal operation of the engine 1, the EGR cooler bypass valve 24 is switched to the first position so that EGR gas is returned to the intake passage 3 via the EGR cooler 21. Hereinafter, switching the EGR cooler bypass valve 24 to the first position is referred to as closing the EGR cooler bypass valve 24, and switching the EGR cooler bypass valve 24 to the second position is referred to as opening the EGR cooler bypass valve 24. Sometimes.

  The turbocharger 8 uses a connection shaft (not shown) that coaxially connects the compressor 8a and the turbine 8b, a motor that can rotationally drive the connection shaft, and rotation of a connection shaft that is rotationally driven by the exhaust of the engine 1. And an electric motor 8c functioning as a generator capable of generating electricity. As shown in FIG. 1, the electric motor 8 c is electrically connected to the battery 6. When the electric motor 8 c functions as an electric motor, the electric motor 8 c is driven by electric power supplied from the battery 6. On the other hand, when the electric motor 8c functions as a generator, the battery 6 is charged with electricity generated by the electric motor 8c. Note that, hereinafter, charging the battery 6 with electricity generated using the exhaust energy of the engine 1 by causing the electric motor 8c to function as a generator may be referred to as regeneration. Further, since the operation is assisted by the electric motor 8c, the turbocharger 8 may be referred to as MAT (Motor Assist Turbo).

  The operation of the electric motor 8c of the turbocharger 8 is controlled by an engine control unit (ECU) 30. The ECU 30 is configured as a computer including a microprocessor and peripheral devices such as RAM and ROM necessary for its operation. The ECU 30 refers to an output signal of a predetermined sensor, the injector 15, the intake bypass valve 12, the exhaust throttle valve 13, the EGR. This is a known computer unit that controls the operation state of the engine 1 by controlling the operation of the valve 22 and the EGR cooler bypass valve 24. As sensors referred to by the ECU 30, a voltage sensor 31 as voltage acquisition means for outputting a signal corresponding to the voltage of the battery 6, a cooling water temperature sensor 32 for outputting a signal corresponding to the temperature of the cooling water of the engine 1, and intake air An intake air temperature sensor 33 is provided as intake air temperature acquisition means for outputting a signal corresponding to the temperature.

  The ECU 30 controls the operation of the electric motor 8 c via a motor assist turbo controller (hereinafter abbreviated as MAT controller) 34. That is, the ECU 30 controls the operation of the electric motor 8c by controlling the MAT controller 34. The MAT controller 34 controls whether the electric motor 8 c functions as an electric motor or a generator, and also controls the transmission and reception of electric power between the electric motor 8 c and the battery 6. For example, the MAT controller 34 adjusts the power supplied from the battery 6 to the electric motor 8c when the electric motor 8c functions as an electric motor, and should generate electric power with the electric motor 8c when the electric motor 8c functions as a generator. Adjust the power. Hereinafter, the MAT controller 34 may be omitted, and the ECU 30 may be described as controlling the operation of the electric motor 8c. During the operation of the engine 1, the ECU 30 controls the operation of the electric motor 8 c according to the operation state of the engine 1. For example, the operation of the MAT 8 is assisted by causing the electric motor 8c to function as an electric motor so as to increase the supercharging pressure when the engine 1 is accelerated. Since this control method may be the same as a known control method, a detailed description thereof is omitted here.

  Moreover, the startability of the engine 1 can be improved by operating the electric motor 8c when the engine 1 is started and supercharging the intake air with the MAT 8. FIG. 2 shows a MAT operation control routine executed by the ECU 30 to control the operation of the electric motor 8 c when the engine 1 is started. The control routine of FIG. 2 is repeatedly executed at a predetermined cycle while the ECU 30 is operating regardless of whether the engine 1 is in operation. Further, the control routine of FIG. 2 is executed in parallel with other control routines executed by the ECU 30.

  In the control routine of FIG. 2, the ECU 30 first determines whether or not there has been a request for starting the engine 1 in step S11. It is determined that the engine 1 has been started when the ignition switch is changed to an on state, for example, when the ignition key is turned to a predetermined starting position. In addition, when the engine 1 is a target of so-called idle stop control that stops the operating engine 1 when a predetermined engine stop condition is satisfied, the engine 1 is stopped when the predetermined engine stop condition is satisfied. For example, when the accelerator pedal or the shift gear is operated by the driver, for example, it is determined that the start of the engine 1 is requested. If it is determined that the engine 1 is not required to be started, the current control routine is terminated.

  On the other hand, if it is determined that there is a start request, the process proceeds to step S12, where the ECU 30 refers to the output signals of the voltage sensor 31, the cooling water temperature sensor 32, and the intake air temperature sensor 33, and the cooling water temperature thw of the engine 1 and the intake air The temperature thia and the voltage Vb of the battery 6 are acquired. In the subsequent step S13, the ECU 30 determines whether or not the starter signal is on. The ECU 30 controls the operation of the starter motor 5 by a control routine different from the control routine of FIG. 2, and the starter signal is generated from this control routine when the starter motor 5 is operating. That is, the starter signal is turned on when the starter motor 5 is operated and the engine 1 is cranked, and is turned off when the starter motor 5 is stopped. If it is determined that the starter signal is off, the current control routine is terminated.

  When it is determined that the starter signal is on, the process proceeds to step S14, where the ECU 30 sets the determination voltage α. The determination voltage α is determined by multiplying the reference determination voltage αb by the cooling water temperature correction coefficient A1 and the intake air temperature correction coefficient A2. For the reference determination voltage αb, for example, when the temperature of the engine 1 and the intake air temperature are respectively predetermined temperatures, that is, when the friction of the engine 1 is in a predetermined state, the starter motor 5 is operated with an output capable of starting the engine 1 reliably and quickly. Is set to the lower limit value of the startable voltage range. Since such a startable voltage range changes according to the specifications of the engine 1 (for example, the compression ratio, the number of cylinders, etc.), the reference determination voltage αb may be appropriately changed based on the specifications of the engine 1. Further, the output required for the starting motor 5 when the engine 1 is started is affected by the temperature of the engine 1 and the intake air temperature. For example, the lower the temperature of the engine 1, the higher the viscosity of the lubricating oil of the engine 1, so that the friction of the engine 1 increases. Further, the lower the intake air temperature, the more difficult the temperature at the compression end rises, so the operation time of the starter motor 5 becomes longer. In such a case, since the output required for the starter motor 5 increases, the amount of power supplied from the battery 6 to the starter motor 5 also increases. Therefore, as the temperature of the engine 1 is lower and the intake air temperature is lower, the determination voltage α is set higher and the correction coefficients A1 and A2 are set so as to secure more power that can be supplied to the starter motor 5. Since the coolant temperature of the engine 1 has a correlation with the temperature of the engine 1, the correction coefficient A1 is set based on the coolant temperature of the engine 1 instead of the temperature of the engine 1.

  FIG. 3 shows an example of the relationship between the cooling water temperature thw of the engine 1 and the cooling water temperature correction coefficient A1, and FIG. 4 shows an example of the relationship between the intake air temperature thia and the intake air temperature correction coefficient A2. These relationships are obtained in advance by experiments or the like and stored in the ECU 30 as a map. As shown in FIG. 3, the coolant temperature correction coefficient A1 increases as the coolant temperature thw of the engine 1 decreases. Further, as shown in FIG. 4, the intake air temperature correction coefficient A2 similarly increases as the intake air temperature thia is lower. By setting the correction coefficients A1 and A2 in this way, power to be supplied to the starter motor 5 is ensured, and a decrease in output of the starter motor 5 is suppressed. In FIG. 3, the correction coefficient A1 is set based on the coolant temperature of the engine 1, but the parameter used for setting the correction coefficient A1 is not limited to the coolant temperature. Various parameters having a correlation with the temperature of the engine 1 such as the temperature of the lubricating oil of the engine 1 may be used instead of the cooling water temperature. By correcting the determination voltage in this way, the ECU 30 functions as the determination voltage correction unit of the present invention. Moreover, since the temperature of the cooling water of the engine 1 has a correlation with the temperature of the engine 1 as described above, the cooling water temperature sensor 31 corresponds to the engine temperature acquisition means of the present invention.

  In subsequent step S15, the ECU 30 determines whether or not the voltage Vb of the battery 6 is less than the determination voltage α. When it is determined that the voltage Vb of the battery 6 is less than the determination voltage α, the process proceeds to step S16, and the ECU 30 performs regeneration by causing the electric motor 8c to function as a generator. The battery 6 is charged by this regeneration. In subsequent step S17, the ECU 30 changes the opening of the exhaust throttle valve 13 to a fully closed state. In the next step S18, the ECU 30 opens the EGR valve 22 and opens the EGR cooler bypass valve 24. Thereafter, in step S19, the ECU 30 determines whether or not the starter signal is in an off state. If it is determined that the starter signal is on, the process returns to step S15. On the other hand, if it is determined that the starter signal is off, the current control routine is terminated.

  If it is determined in step S15 that the voltage Vb of the battery 6 is equal to or higher than the determination voltage α, the process proceeds to step S20, where the ECU 30 causes the electric motor 8c to function as an electric motor, and supercharges intake air using the MAT8. In the following step S21, the ECU 30 determines whether or not the supercharging time (MAT supercharging time) in which the intake air is continuously supercharged by the MAT 8 when the engine 1 is started is equal to or longer than a predetermined determination time T, or the voltage Vb of the battery 6 is It is determined whether or not the determination voltage is less than α. When the electric motor 8c is caused to function as an electric motor, the voltage drop of the battery 6 is accelerated by the electric power consumed by the electric motor 8c. Therefore, a time during which the electric motor 8c can be operated is set, and the voltage decrease rate of the battery 6 is suppressed. The determination time T is set to a time during which the electric motor 8c can be operated. In addition, since such time changes with power consumption of the electric motor 8c, the capacity | capacitance of the battery 6, etc., you may change the determination time T suitably based on these parameters. If it is determined that the MAT supercharging time is less than the determination time T and the voltage Vb of the battery 6 is equal to or higher than the determination voltage α, the process returns to step S13. On the other hand, if it is determined that the MAT supercharging time is equal to or greater than the determination time T or the voltage Vb of the battery 6 is less than the determination voltage α, the process proceeds to step S22, where the ECU 30 stops the electric motor 8c and stops supercharging of the intake air by the MAT8. To do. In subsequent step S23, the ECU 30 determines whether or not the starter signal is in an off state. If it is determined that the starter signal is on, the process proceeds to step S16. On the other hand, if it is determined that the starter signal is off, the current control routine is terminated.

  In the control routine of FIG. 2, when the voltage Vb of the battery 6 is less than the determination voltage α, it is determined that the startability of the engine 1 is deteriorated, and supercharging of the intake air by the MAT 8 is limited, and the electric motor 8c is caused to function as a generator. Since the battery 6 is charged by regeneration, a decrease in the output of the starter motor 5 can be suppressed. Therefore, deterioration of the startability of the engine 1 can be prevented and the engine 1 can be started reliably. On the other hand, when the battery 6 is equal to or higher than the determination voltage α, the intake air is supercharged by the MAT 8, so that the temperature at the compression end can be quickly raised. Therefore, the engine 1 can be started reliably and quickly, and the startability of the engine 1 can be improved.

  When regeneration is performed in the MAT 8, the opening of the exhaust throttle valve 13 is changed to the fully closed state (step S17), so that the amount of exhaust remaining in the cylinder 2, that is, the internal EGR gas amount can be increased. Further, at this time, by opening the EGR valve 22 and the EGR cooler bypass valve 24 (step S18), the EGR gas is returned to the intake passage 3 while returning the EGR gas to the intake passage 3 while suppressing the lowering of the gas temperature and maintaining the high temperature. The amount of can be increased. Thus, by increasing the amounts of the internal EGR gas and the external EGR gas, the temperature at the compression end can be quickly raised. Therefore, the startability of the engine 1 can be improved. Moreover, since exhaust gas is returned to the intake passage 3 as EGR gas, the emission of white smoke can be suppressed. Furthermore, by opening the EGR cooler bypass valve 24 and suppressing the inflow of EGR gas to the EGR cooler 21, the inflow of unburned fuel or the like to the EGR cooler 21 can be suppressed. Therefore, adhesion of unburned fuel to the EGR cooler 21 can be suppressed, and clogging of the EGR cooler 21 can be suppressed.

  The ECU 30 functions as the operation control means of the present invention by executing the control routine of FIG. 2 and supercharging the intake air with the turbocharger 8 when the engine 1 is started. Further, by executing the processing of steps S15 to S19 in FIG. 2 and limiting the supercharging of the intake air by the turbocharger when the voltage of the battery 6 is less than the determination voltage, the ECU 30 controls the supercharging limiting means of the present invention. Function as.

  A voltage larger than the lower limit value of the startable voltage range may be set as the reference determination voltage αb. In this case, the electric motor 8c can be driven by the battery 6 even when the voltage Vb of the battery 6 is lower than the determination voltage α set based on the reference determination voltage αb. Therefore, in this case, even if the determination in step S15 in FIG. 2 is affirmative, the regeneration of the MAT 8 is not performed immediately, and the voltage of the battery 6 is determined until the voltage of the battery 6 reaches the lower limit value of the startable voltage range. Operation may be performed at a rotational speed set when the voltage is equal to or higher than the voltage α, that is, a rotational speed lower than the rotational speed set in step S20 of FIG. In other words, even if the voltage of the battery 6 is less than the determination voltage α, the supercharging of intake air performed when the voltage of the battery 6 is equal to or higher than the determination voltage α is limited until the voltage of the battery 6 reaches the lower limit value of the startable voltage range. In this state, the intake air may be supercharged by MAT8. In this case, since the intake air is supercharged even when the voltage of the battery 6 is lower than the determination voltage α, the temperature of the compression end can be quickly raised. Therefore, the startability of the engine 1 can be improved. When the voltage of the battery 6 reaches less than the lower limit value of the startable voltage range, regeneration is performed by the MAT 8 to charge the battery 6.

  Further, when the voltage larger than the lower limit value of the startable voltage range is set as the reference determination voltage αb as described above, and when priority is given to the increase in EGR gas over the supercharging of the intake air, the electric motor 8c is stopped. You may let them. That is, the driving of the MAT 8 by the electric motor 8c is prohibited. In this case, the turbine 8b becomes an exhaust flow resistance, so that the exhaust gas hardly flows. Therefore, the amount of internal EGR gas can be increased, or the amount of external EGR gas returned to the intake passage 3 via the EGR passage 20 can be increased.

  The means for adjusting the internal EGR gas and the external EGR gas is not limited to the above-described means. When the MAT 8 is provided with a variable nozzle capable of changing the flow passage cross-sectional area of the inlet portion of the turbine 8b, the variable nozzle is closed so that the flow passage cross-sectional area of the inlet portion of the turbine 8b is reduced when the engine 1 is started. May be. In this case as well, the amount of internal EGR gas remaining in the cylinder 2 can be increased or the high-temperature EGR gas can be returned to the intake passage 3 via the EGR passage 20 in the same manner as when the exhaust throttle valve 13 is closed. When the engine 1 has a variable valve mechanism that can change the closing timing of the exhaust valve, the exhaust valve is closed so that exhaust emission from the cylinder 2 is suppressed when the engine 1 is started. The amount of internal EGR gas may be increased by advancing the valve timing.

  FIG. 5 shows a modification of the MAT operation control routine. In FIG. 5, the same processes as those in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. Similar to the control routine of FIG. 2, the control routine of FIG. 5 is repeatedly executed at a predetermined cycle during the operation of the ECU 30, regardless of whether or not the engine 1 is in operation. 5 is also executed in parallel with other control routines executed by the ECU 30.

  In the control routine of FIG. 5, the ECU 30 determines whether or not a start request has been made in step S11. If it is determined that there is a start request, the process proceeds to step S31, and the ECU 30 acquires the coolant temperature thw of the engine 1. In the next step S13, the ECU 30 determines whether or not the starter signal is on. When it is determined that the starter signal is on, the process proceeds to step S32, where the ECU 30 determines whether or not the coolant temperature thw is lower than a predetermined determination temperature β. As described above, since the friction increases as the temperature of the engine 1 decreases, the output required for the starter motor 5 increases. Therefore, the determination temperature β is, for example, the temperature range of the engine 1 in which the engine 1 can be reliably and quickly started by the output of the start motor 5 when the start motor 5 is operated while the electric motor 8c is operated. The cooling water temperature corresponding to the lower limit value is set. Such a cooling water temperature is obtained and set by, for example, experiments.

  If it is determined that the cooling water temperature tha is lower than the determination temperature β, the process proceeds to step S16, and the process proceeds in the same manner as in the control routine of FIG. On the other hand, when it is determined that the cooling water temperature tha is equal to or higher than the determination temperature β, the process proceeds to step S20, and the ECU 30 supercharges intake air by the MAT 8. In subsequent step S33, the ECU 30 determines whether or not the MAT supercharging time is equal to or longer than the determination time T. If it is determined that the MAT supercharging time is less than the determination time T, the process returns to step S13. On the other hand, if it is determined that the MAT supercharging time is equal to or greater than the determination time T, the process proceeds to step S22, and the process proceeds in the same manner as the control routine of FIG.

  In the control routine of FIG. 5, when the coolant temperature thw correlated with the temperature of the engine 1 is less than the determination temperature β, it is determined that the startability of the engine 1 is deteriorated and regeneration is performed at the MAT 8, so that it can be supplied to the starter motor 5. Power can be increased. Therefore, it is possible to reliably supply power necessary for starting the engine 1 to the starting motor 5 to prevent the startability of the engine 1 from deteriorating. On the other hand, when the cooling water temperature thw is equal to or higher than the determination temperature β, the electric motor 8c is operated and the intake air is supercharged by the MAT 8, so that the startability of the engine 1 can be improved.

  Even when the cooling water temperature thw is lower than the determination temperature β, that is, when the determination in step S15 is affirmative, if the charging state of the battery 6 is good, the motor is driven at a lower rotational speed than when the cooling water temperature thw is equal to or higher than the determination temperature β. The motor 8c may be operated to supercharge intake air with MAT8. In this case, since the electric power consumed by the electric motor 8c can be reduced by reducing the rotation speed of the electric motor 8c, the electric power that can be supplied to the starter motor 5 can be increased. Therefore, it is possible to reliably supply the electric power necessary for starting the engine 1 to the starting motor 5 while supercharging the intake air with the MAT 8. When starting the engine 1 and prioritizing the increase in EGR gas over the supercharging of the intake air, the driving of the MAT 8 by the electric motor 8c may be prohibited. In this case, the internal EGR gas amount and the external EGR gas amount can be increased by inhibiting the flow of exhaust gas with the MAT 8.

  Also in the control routine of FIG. 5, when the engine 1 has a variable valve mechanism, the closing timing of the exhaust valve may be advanced. When the MAT 8 has a variable nozzle, the variable nozzle may be closed to reduce the flow path cross-sectional area. By performing these controls, the internal EGR gas amount and the external EGR gas amount can be increased.

  The present invention is not limited to the above-described form and can be implemented in various forms. For example, the internal combustion engine to which the control device of the present invention is applied is not limited to a diesel engine, and may be applied to various internal combustion engines using gasoline or other fuels. An engine in which the control device of the present invention is incorporated may include a preheating device that consumes battery power at the time of starting to preheat the engine. Such a preheating device is, for example, a glow plug and an intake heater that heats intake air. In such an engine, the battery power is also consumed by the preheating device. Therefore, the power consumption in the MAT is suppressed according to the present invention, or the engine is started by regenerating in the MAT and suppressing the voltage drop of the battery. Sexual deterioration can be suppressed.

The figure which shows the internal combustion engine in which the control apparatus which concerns on one form of this invention was integrated. The flowchart which shows the MAT operation | movement control routine which ECU performs. The figure which shows an example of the relationship between the cooling water temperature of an engine, and a cooling water temperature correction coefficient. The figure which shows an example of the relationship between intake temperature and an intake temperature correction coefficient. The flowchart which shows the modification of a MAT operation | movement control routine.

Explanation of symbols

1 engine (internal combustion engine)
2 cylinder 3 intake passage 4 exhaust passage 5 start motor 6 battery 8 turbocharger 8a compressor 8b turbine 8c electric motor 13 exhaust throttle valve 20 EGR passage (EGR means)
21 EGR cooler (EGR means)
22 EGR valve (EGR means)
23 EGR bypass passage (EGR means)
24 EGR cooler bypass valve (flow path switching valve, EGR means)
30 Engine control unit (operation control means, supercharging restriction means, determination voltage correction means)
31 Voltage sensor (voltage acquisition means)
32 Cooling water temperature sensor (engine temperature acquisition means)
33 Intake air temperature sensor (intake air temperature acquisition means)

Claims (20)

A starter motor, a battery electrically connected to the starter motor, a compressor provided in an intake passage of the internal combustion engine started by the starter motor, a turbine provided in an exhaust passage of the internal combustion engine, and the A turbocharger that can be driven by an electric motor electrically connected to a battery; and the electric motor so that the starter motor is operated when the internal combustion engine is started, and intake air is supercharged by the turbocharger. In an internal combustion engine control device comprising an operation control means for controlling the operation of a motor,
The operation control means limits supercharging of the intake air by the turbocharger that is performed when the internal combustion engine is started when a factor that deteriorates the startability of the internal combustion engine occurs when the internal combustion engine is started. A control device for an internal combustion engine, comprising supercharging restriction means for controlling the operation of the electric motor as described above. A voltage acquisition means for acquiring the voltage of the battery;
The supercharging restriction unit determines that the factor has occurred when the voltage of the battery acquired by the voltage acquisition unit is less than a determination voltage set in consideration of friction of the internal combustion engine. Item 2. A control device for an internal combustion engine according to Item 1.   The supercharging limiting means is configured such that when the battery voltage acquired by the voltage acquisition means at the start of the internal combustion engine is less than the determination voltage, the battery voltage at the start of the internal combustion engine is equal to or higher than the determination voltage. 3. The control device for an internal combustion engine according to claim 2, wherein the rotational speed of the electric motor is reduced when the internal combustion engine is started.   The supercharge limiting unit is configured to drive the turbocharger by the electric motor when starting the internal combustion engine when the voltage of the battery acquired by the voltage acquisition unit is less than the determination voltage when starting the internal combustion engine. The control device for an internal combustion engine according to claim 2, wherein the control is prohibited. The electric motor can function as a generator that generates power using exhaust energy of the internal combustion engine and can charge the battery with generated power.
The supercharging limiting means causes the electric motor to function as a generator at the start of the internal combustion engine when the voltage of the battery acquired by the voltage acquisition means at the start of the internal combustion engine is less than the determination voltage. The control apparatus for an internal combustion engine according to claim 2, wherein the battery is charged. EGR means for returning a part of the exhaust discharged from the cylinder of the internal combustion engine into the cylinder again,
When the battery voltage acquired by the voltage acquisition unit when the internal combustion engine is started is less than the determination voltage, a part of the exhaust gas is returned to the cylinder when the internal combustion engine is started. 6. The control device for an internal combustion engine according to claim 2, wherein the operation of the EGR means is controlled as described above. As the EGR means, an EGR passage that connects the intake passage and the exhaust passage, an EGR valve that adjusts the flow rate of the exhaust gas that passes through the EGR passage, and an EGR passage that cools the exhaust gas. An EGR cooler, a bypass passage that bypasses the EGR cooler and guides exhaust from the exhaust passage to the intake passage, a first position at which exhaust is returned from the exhaust passage to the intake passage via the EGR cooler, and the A flow path switching valve that can be switched from an exhaust passage to a second position where exhaust is returned to the intake passage via the bypass passage,
The supercharging limiting means is configured to return exhaust to the intake passage when the internal combustion engine is started when the voltage of the battery acquired by the voltage acquisition means when the internal combustion engine is started is less than the determination voltage. The control device for an internal combustion engine according to claim 6, wherein an EGR valve is opened and the flow path switching valve is switched to the second position. The internal combustion engine includes an exhaust throttle valve provided in an exhaust passage downstream of the turbine and capable of adjusting a flow rate of exhaust flowing through the exhaust passage,
The supercharging limiting unit is configured to reduce the exhaust flow rate in the exhaust passage when starting the internal combustion engine when the voltage of the battery acquired by the voltage acquiring unit is less than the determination voltage when starting the internal combustion engine. The control device for an internal combustion engine according to any one of claims 2 to 7, wherein the exhaust throttle valve is closed. The turbocharger includes a variable nozzle capable of changing a flow path cross-sectional area of an inlet portion of the turbine,
When the internal combustion engine is started, when the voltage of the battery acquired by the voltage acquisition unit is less than the determination voltage, the supercharging restriction unit calculates a flow path cross-sectional area of the inlet portion of the turbine when the internal combustion engine is started. The control device for an internal combustion engine according to any one of claims 2 to 8, wherein the variable nozzle is closed so as to be decreased. A variable valve mechanism capable of changing a closing timing of an exhaust valve provided in a cylinder of the internal combustion engine;
The supercharging limiting means may advance the closing timing of the exhaust valve at the start of the internal combustion engine when the battery voltage acquired by the voltage acquisition means at the start of the internal combustion engine is less than the determination voltage. The control device for an internal combustion engine according to any one of claims 2 to 9, wherein operation of the variable valve mechanism is controlled.   Engine temperature acquisition means for acquiring the temperature of the internal combustion engine, intake air temperature acquisition means for acquiring the temperature of intake air, temperature of the internal combustion engine and intake air temperature acquired by the engine temperature acquisition means when the internal combustion engine is started 11. The internal combustion engine according to claim 2, further comprising a determination voltage correction unit that corrects the determination voltage based on each of the intake air temperatures acquired by the acquisition unit. Engine control device. Engine temperature acquisition means for acquiring the temperature of the internal combustion engine,
2. The internal combustion engine according to claim 1, wherein the supercharging restriction unit determines that the factor has occurred when the temperature of the internal combustion engine acquired by the engine temperature acquisition unit is lower than a predetermined determination temperature. Control device.   When the internal combustion engine temperature acquired by the engine temperature acquisition unit at the start of the internal combustion engine is lower than the determination temperature, the supercharging restriction unit determines the temperature of the internal combustion engine at the start of the internal combustion engine. 13. The control device for an internal combustion engine according to claim 12, wherein the number of revolutions of the electric motor is reduced when the internal combustion engine is started than when the temperature is higher than a temperature.   When the internal combustion engine temperature acquired by the engine temperature acquisition unit at the start of the internal combustion engine is lower than the determination temperature, the turbocharger by the electric motor at the start of the internal combustion engine The control apparatus for an internal combustion engine according to claim 12, wherein driving of the internal combustion engine is prohibited. The electric motor can function as a generator that generates power using exhaust energy of the internal combustion engine and can charge the battery with generated power.
The supercharging restriction means causes the electric motor to function as a generator at the start of the internal combustion engine when the temperature of the internal combustion engine acquired by the engine temperature acquisition means at the start of the internal combustion engine is lower than the determination temperature. The internal combustion engine control device according to claim 12, wherein the battery is charged. EGR means for returning a part of the exhaust discharged from the cylinder of the internal combustion engine into the cylinder again,
If the temperature of the internal combustion engine acquired by the engine temperature acquisition unit is less than the determination temperature when the internal combustion engine is started, a part of the exhaust gas is placed in the cylinder when the internal combustion engine is started. The control device for an internal combustion engine according to any one of claims 12 to 15, wherein the operation of the EGR means is controlled so as to be returned. As the EGR means, an EGR passage that connects the intake passage and the exhaust passage, an EGR valve that adjusts the flow rate of the exhaust gas that passes through the EGR passage, and an EGR passage that cools the exhaust gas. An EGR cooler, a bypass passage that bypasses the EGR cooler and guides exhaust from the exhaust passage to the intake passage, a first position at which exhaust is returned from the exhaust passage to the intake passage via the EGR cooler, and the A flow path switching valve that can be switched from an exhaust passage to a second position where exhaust is returned to the intake passage via the bypass passage,
When the internal combustion engine temperature acquired by the engine temperature acquisition unit at the start of the internal combustion engine is lower than the determination temperature, the supercharging restriction unit is configured to return exhaust gas to the intake passage at the start of the internal combustion engine. The control device for an internal combustion engine according to claim 16, wherein the EGR valve is opened and the flow path switching valve is switched to the second position. The internal combustion engine includes an exhaust throttle valve provided in an exhaust passage downstream of the turbine and capable of adjusting a flow rate of exhaust flowing through the exhaust passage,
When the internal combustion engine temperature acquired by the engine temperature acquisition unit is less than the determination temperature when the internal combustion engine is started, the supercharging restriction unit decreases the exhaust flow rate of the exhaust passage when the internal combustion engine is started. The control device for an internal combustion engine according to any one of claims 12 to 17, wherein the exhaust throttle valve is closed as described above. The turbocharger includes a variable nozzle capable of changing a flow path cross-sectional area of an inlet portion of the turbine,
When the internal combustion engine temperature acquired by the engine temperature acquisition unit at the start of the internal combustion engine is lower than the determination temperature, the supercharging limiting unit is configured to cut off a flow path at the inlet portion of the turbine at the start of the internal combustion engine. The control device for an internal combustion engine according to any one of claims 12 to 18, wherein the variable nozzle is closed to reduce an area. A variable valve mechanism capable of changing a closing timing of an exhaust valve provided in a cylinder of the internal combustion engine;
When the internal combustion engine temperature acquired by the engine temperature acquisition unit at the start of the internal combustion engine is lower than the determination temperature, the supercharging restriction unit advances the closing timing of the exhaust valve at the start of the internal combustion engine. The control device for an internal combustion engine according to any one of claims 12 to 19, wherein the operation of the variable valve mechanism is controlled as described above.

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