JP2007077906A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine providing suitable acceleration performance, by drive of an electric motor of a turbo supercharger and supply of accumulated air of a pressure accumulating tank. <P>SOLUTION: The electric motor for rotating a turbo supercharger compressor and its control means are provided, intake air which has passed through a compressor is accumulated in the pressure accumulating tank, and a control is performed to supply the accumulated air to an exhaust passage of the upstream of a turbine of the turbo supercharger. The control device for an internal combustion engine performs an electric motor assist using the electric motor, and performs an acceleration assist by using an air assist by the supply of the accumulated air. Therefore, compared with the acceleration assist only by the electric motor assist or only by the air assist, the acceleration performance of the control device of the present invention is improved. Even if there are continuous acceleration requests, the acceleration assist is performed suitably. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that controls a turbocharger.

  In order to improve the acceleration performance of a vehicle, a technique for assisting driving of a turbocharger (hereinafter also referred to as “acceleration assist”) is known. For example, Patent Literature 1 and Patent Literature 2 describe a turbocharger with an electric motor in which a compressor of a turbocharger (turbo supercharger) can be driven by an electric motor (electric motor). Patent Document 3 describes a technique for assisting driving of a turbine by accumulating compressed gas in an accumulator tank and supplying the accumulated accumulator air to a turbine of a turbocharger.

JP 2004-169629 A Japanese Patent Laid-Open No. 2004-169662 JP 2002-161751 A

  In the techniques described in Patent Document 1 and Patent Document 2 described above, by performing all of the acceleration assist using only the electric motor, the power balance collapses due to significant power consumption, and the battery power is increased. There was a case. In particular, in a vehicle in which the turbocharger is downsized and the displacement is reduced, there is a high possibility that the torque shortage will be remarkable in the non-supercharging region in the early stage of acceleration.

  On the other hand, in the technique described in Patent Document 3, since there is a limit to the capacity of the pressure accumulation tank, there are cases where sufficient acceleration assistance cannot be performed only by supplying the pressure accumulation air. Furthermore, since the pressure accumulation in the pressure accumulating tank is mainly performed when the internal combustion engine is in a decelerating state, there is a case where the pressure accumulating air that can respond to a plurality of acceleration requests cannot be accumulated.

  The present invention has been made to solve such problems, and the object of the present invention is to drive an electric motor provided in a turbocharger and to supply pressure-accumulated air accumulated in a pressure-accumulation tank. It is an object of the present invention to provide a control device for an internal combustion engine capable of obtaining suitable acceleration performance.

  In one aspect of the present invention, an internal combustion engine control device includes: an electric motor that generates a driving force for rotating a compressor of a turbocharger; an electric motor control unit that controls driving of the electric motor; Accumulation control means for performing control for accumulating the intake air that has passed through the compressor in the accumulator tank, and accumulator for performing control for supplying the accumulated air accumulated in the accumulator tank to the exhaust passage upstream of the turbine of the turbocharger. An air supply control means.

  The control device for the internal combustion engine is used for controlling the turbocharger. Specifically, the control device for an internal combustion engine includes an electric motor that generates a driving force for rotating a compressor of the turbocharger, and an electric motor control unit that controls the driving of the electric motor. Further, the control device for the internal combustion engine includes pressure accumulation control means for controlling the intake air that has passed through the compressor to be accumulated in the pressure accumulation tank, and the accumulated air accumulated in the pressure accumulation tank to the exhaust passage on the upstream side of the turbine of the turbocharger. A pressure-accumulated air supply control means for performing supply control is provided. That is, the control device for the internal combustion engine performs acceleration assist by electric motor assist using an electric motor and air assist by supplying accumulated air. Thereby, the acceleration performance can be improved as compared with the acceleration assist only by the electric motor assist or only the air assist. Further, even when there is a request for acceleration continuously, acceleration assistance can be appropriately performed for each acceleration request.

  In one aspect of the control apparatus for an internal combustion engine, the pressure accumulation control unit performs control for accumulating the intake air in the pressure accumulation tank when the internal combustion engine shifts from a high rotation state to a deceleration state.

  In this aspect, the pressure accumulation control means accumulates pressure in the pressure accumulation tank when the internal combustion engine shifts from the high rotation state to the deceleration state. Thereby, the deterioration of the fuel consumption by execution of pressure accumulation can be suppressed.

  In another aspect of the control apparatus for an internal combustion engine, the pressure accumulation control unit performs control for accumulating the intake air in the pressure accumulation tank based on a load condition indicated by a set pressure accumulation mode.

  In this aspect, a pressure accumulation mode indicating a load condition for performing pressure accumulation is selected by a user or the like, and the pressure accumulation control unit is configured such that when the current load of the internal combustion engine satisfies the load condition indicated by the set pressure accumulation mode, Accumulate pressure in the pressure accumulation tank. Thereby, pressure accumulation can be controlled based on the user's recognition.

  In another aspect of the control device for an internal combustion engine, the electric motor control means generates a driving force from the electric motor when the internal combustion engine is in a non-accelerated state, and the pressure accumulation control means When the electric motor is generating driving force in the acceleration state, control is performed to accumulate the intake air in the accumulator tank.

  In this aspect, the pressure accumulation control means performs control for accumulating intake air in the pressure accumulation tank when the electric motor generates driving force in the non-accelerated state. In other words, the electric motor control means generates a driving force from the electric motor in the non-accelerated state in order to effectively accumulate pressure when in the non-accelerated state. Thereby, the accumulation filling degree of an accumulation tank can be raised.

  In another aspect of the control apparatus for an internal combustion engine, the electric motor control means starts control for driving the electric motor after starting the supply of the accumulated air during acceleration.

  In this aspect, the electric motor control means starts driving the electric motor after the supply of the accumulated air is started. Thereby, since the output of an electric motor can be suppressed, an inverter motor part etc. can be reduced in size.

  In another aspect of the control device for an internal combustion engine, the electric motor control means and the pressure accumulation air supply control means are generated by the electric motor based on at least one of an acceleration request and a pressure accumulation level of the pressure accumulation tank. The driving force to be controlled and the supply of the accumulated air from the accumulator tank are controlled.

  In this aspect, the electric motor control means controls the driving force generated by the electric motor based on at least one of the acceleration request and the pressure accumulation level of the pressure accumulation tank, and the pressure accumulation air supply control means is the pressure accumulation air from the pressure accumulation tank. Control the supply of As a result, it is possible to appropriately perform acceleration assist even in cases where acceleration demand is higher.

  Preferably, in the control apparatus for an internal combustion engine, the pressure accumulation control means performs control for accumulating the intake air in the pressure accumulation tank so that the durability of the turbocharger does not decrease. In this case, the pressure accumulation control means controls pressure accumulation taking into account the load on the turbocharger. Thereby, it is possible to appropriately accumulate pressure while suppressing a decrease in the resistance of the turbocharger.

  In a preferred example, the pressure accumulation control means may perform control for setting a variable nozzle provided in the turbocharger to a closed side when performing control for accumulating the intake air in the pressure accumulation tank. it can. Thereby, since the intake air whose pressure has been increased can be supplied to the pressure accumulation tank, it is possible to effectively accumulate pressure.

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

[Vehicle configuration]
FIG. 1 is a schematic diagram showing the overall configuration of a vehicle to which the control device for an internal combustion engine according to the present embodiment is applied. In FIG. 1, a solid line arrow indicates the flow of gas or the like, and a broken line arrow indicates signal input / output.

  The vehicle mainly includes an air cleaner 2, an intake passage 3, a turbocharger 4, a throttle valve 5, an internal combustion engine (engine) 6, an exhaust passage 7, an air assist passage 10, an electromagnetic control valve. 11, a pressure increasing device 12, a pressure accumulating tank 13, an air assist valve 14, a variable nozzle 15, an electric motor 16, a compressor outlet pressure sensor 20, a throttle opening sensor 21, a rotation speed sensor 22, A pressure accumulation tank internal pressure sensor 23, an ECU (Engine Control Unit) 30, an electric motor controller 31, a user pressure accumulation mode switch 32, and a pressure accumulation lamp 33 are provided.

  The air cleaner 2 purifies air (intake air) acquired from the outside and supplies it to the intake passage 3. A compressor 4a of the turbocharger 4 is disposed in the intake passage 3, and the intake air is compressed by the rotation of the compressor 4a. A throttle valve 5 that adjusts the amount of intake air supplied to the internal combustion engine 6 is provided in the intake passage 3.

  The intake air that has passed through the throttle valve 5 is supplied to the internal combustion engine 6. The internal combustion engine 6 generates power by exploding the supplied intake air and fuel. The internal combustion engine 6 is an engine such as a gasoline engine or a diesel engine.

  Exhaust gas generated by combustion in the internal combustion engine 6 is discharged to the exhaust passage 7. The exhaust gas rotates the turbine 4 b of the turbocharger 4 provided in the exhaust passage 7. Such rotational torque of the turbine 4b is transmitted to the compressor wheel in the turbocharger 4 and the compressor 4a rotates, whereby the intake air passing through the turbocharger 4 is compressed.

  The turbocharger 4 is provided with an electric motor 16. The electric motor 16 generates a driving force when supplied with an electric current, and increases the rotation speed of the compressor 4a, that is, assists the rotation of the compressor 4a (hereinafter also referred to as “electric assist”). As described above, by driving the electric motor 16 to perform the electric assist, the supercharging pressure is increased and the acceleration performance of the vehicle is improved. The electric motor 16 is controlled by the ECU 30 via the electric motor controller 31.

  Furthermore, the turbocharger 4 is provided with a variable nozzle 15. The variable nozzle 15 is constituted by a vane and can throttle exhaust gas supplied to the turbocharger 4. Thereby, the flow volume of the exhaust gas supplied to the turbocharger 4 is adjusted, and the supercharging pressure can be changed. Specifically, when the opening degree of the variable nozzle 15 is set to the closed side, the exhaust gas is throttled, so that the supercharging pressure tends to increase. Conversely, when the opening of the variable nozzle 15 is set to the open side, the throttle to exhaust gas is loosened, so that the supercharging pressure tends to decrease. The opening degree of the variable nozzle 15 is controlled by the ECU 30 via an actuator (not shown).

  On the other hand, an air assist passage 10 is connected to the intake passage 3 downstream of the compressor 4a and the exhaust passage 7 upstream of the turbine 4b. In the air assist passage 10, an electromagnetic opening / closing valve 11, a pressure booster 12, a pressure accumulation tank 13, and an air assist valve 14 are provided in order from the upstream side.

  The electromagnetic on-off valve 11 is a valve that controls the supply of intake air to the air assist passage 10. When the electromagnetic on-off valve 11 is open, intake air is supplied to the air assist passage 10, and when the electromagnetic on-off valve 11 is closed, no intake air is supplied to the air assist passage 10. The pressure booster 12 is configured by a so-called pressure boost valve or the like, and boosts the supplied intake air. The intake air whose pressure has been increased by the pressure booster 12 is supplied to the pressure accumulation tank 13. As a result, the intake air is accumulated in the pressure accumulation tank 13.

  The air assist valve 14 is a valve that controls the supply of accumulated air to the exhaust passage 7. Specifically, when the air assist valve 14 is open, the accumulated air is supplied from the accumulator tank 13 to the exhaust passage 7. As a result, the pressure (flow rate) of the gas supplied to the turbine 4b increases and the rotational speed of the turbine 4b increases, that is, the rotation of the compressor 4a is assisted (hereinafter also referred to as “air assist”). In this way, by supplying the accumulated air and performing air assist, the supercharging pressure rises and the acceleration performance of the vehicle improves. On the other hand, when the air assist valve 14 is closed, the accumulated air is not supplied from the accumulation tank 13 to the exhaust passage 7.

  The following sensors are provided in the vehicle. The compressor outlet pressure sensor 20 detects the pressure of intake air in the vicinity of the outlet of the compressor 4a (hereinafter referred to as “compressor outlet pressure”). The throttle opening sensor 21 detects the opening of the throttle valve 5 (hereinafter also referred to as “throttle opening”). The rotation speed sensor 22 detects the rotation speed of the internal combustion engine 6. The pressure accumulation tank internal pressure sensor 23 detects the internal pressure of the pressure accumulation tank (hereinafter referred to as “pressure accumulation tank internal pressure”). These detected values are output to the ECU 30 as detection signals.

  The ECU 30 includes a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like (not shown). The ECU 30 controls the components of the vehicle based on the outputs of the various sensors described above. Specifically, the ECU 30 controls the drive of the electric motor 16 by controlling the electric motor controller 31. Further, the ECU 30 controls the electromagnetic on-off valve 11 to control the pressure accumulation tank 13 to accumulate the intake air, and controls the air assist valve 14 to supply the pressure accumulation air from the pressure accumulation tank 13. Control. Thus, the ECU 30 functions as an electric motor control unit, a pressure accumulation control unit, and a pressure accumulation air supply control unit.

  The user pressure accumulation mode switch 32 is a switch operated by the user to select the pressure accumulation mode. This pressure accumulation mode includes a weak mode, a medium mode, a strong mode, and an off mode. A signal corresponding to the pressure accumulation mode selected by the user is supplied from the user pressure accumulation mode switch 32 to the ECU 30.

  The pressure accumulation lamp 33 is turned on when the pressure accumulation tank 13 is sufficiently filled. Specifically, it is turned on when the internal pressure of the pressure accumulation tank is higher than a predetermined pressure P1. The pressure accumulation lamp 33 is turned on by the ECU 30.

[Accumulation control method]
Next, a pressure accumulation control method for accumulating intake air in the pressure accumulation tank 13 will be described with reference to FIGS. 2 and 3.

  In this embodiment, control for accumulating intake air in the accumulator tank 13 is performed based on the accumulator mode selected by the user. Specifically, the pressure accumulation mode indicates the load condition of the internal combustion engine 6 when executing pressure accumulation, and when the current load of the internal combustion engine 6 satisfies the load condition indicated by the pressure accumulation mode, Accumulate pressure. Specifically, the pressure accumulation in the pressure accumulation tank 13 is performed by introducing intake air into the air assist passage 10 by opening the electromagnetic on-off valve 11.

  FIG. 2 is a diagram showing the pressure accumulation mode on the load map, and a hatched area indicates a load condition corresponding to the pressure accumulation mode. FIG. 2 shows the rotational speed of the internal combustion engine 6 on the horizontal axis and the shaft torque output from the internal combustion engine 6 on the vertical axis, and the load of the internal combustion engine 6 is defined by the rotational speed and the shaft torque. . Specifically, FIG. 2A shows a diagram when the pressure accumulation mode is the weak mode, FIG. 2B shows a diagram when the pressure accumulation mode is the middle mode, and FIG. 2C shows the pressure accumulation. The figure in case a mode is a strong mode is shown. A curve 50 in FIG. 2 indicates the vehicle running resistance characteristic.

  As shown in FIG. 2 (a), in the weak mode, the load condition for accumulating pressure is set from a medium speed light load to a high load (except for the full load). Further, as shown in FIG. 2B, in the middle mode, the load condition is set by adding the entire load region to the load condition set in the weak mode. In this case, for example, pressure accumulation in the pressure accumulation tank 13 is executed even when the vehicle is in full open acceleration. Further, as shown in FIG. 2 (c), in the strong mode, the load condition for accumulating pressure is set substantially in the entire load region. Therefore, when the pressure accumulation mode is the strong mode, pressure accumulation is executed regardless of the load of the internal combustion engine 6. For example, pressure accumulation is performed even when the internal combustion engine 6 is in a non-accelerated state.

  By setting the pressure accumulation mode from the weak mode to the medium mode or the strong mode, or from the medium mode to the strong mode, the pressure inside the pressure accumulation tank can be effectively set to the predetermined pressure P1, that is, to the pressure accumulation tank 13. The pressure filling degree increases, but the fuel consumption tends to deteriorate. When the pressure accumulation mode is the off mode, pressure accumulation is not executed regardless of the load of the internal combustion engine 6.

  Here, the pressure accumulation control process according to the present embodiment will be described with reference to the flowchart shown in FIG. The pressure accumulation control process is repeatedly executed by the ECU 30.

  First, in step S101, the ECU 30 determines whether or not the pressure accumulation lamp 33 is lit. Specifically, the ECU 30 acquires the pressure accumulation tank internal pressure from the pressure accumulation tank internal pressure sensor 23, and determines whether or not the pressure accumulation tank internal pressure is higher than the predetermined pressure P1. When the pressure accumulation lamp 33 is lit (step S101; Yes), the process exits the flow. In this case, since the pressure accumulation tank 13 is sufficiently filled, a process for accumulating pressure in the pressure accumulation tank 13 is not performed. On the other hand, when the pressure accumulation lamp 33 is not lit (step S101; No), the process proceeds to step S102. In this case, since the pressure accumulation tank 13 is in an insufficiently filled state, a process for accumulating pressure in the pressure accumulation tank 13 described later is performed.

  In step S102, the ECU 30 determines whether or not the pressure accumulation mode is an off mode. When the pressure accumulation mode is the off mode (step S102; Yes), the process exits the flow. In this case, control for accumulating pressure in the accumulator tank 13 is not performed. On the other hand, when the pressure accumulation mode is not the off mode (step S102; No), the process proceeds to step S103.

  In step S103, the ECU 30 determines whether or not the pressure accumulation mode is the weak mode. If the pressure accumulation mode is the weak mode (step S103; Yes), the process proceeds to step S104. If the pressure accumulation mode is not the weak mode (step S103; No), the process proceeds to step S105.

  In step S104, the ECU 30 opens (fully opens) the electromagnetic on-off valve 11 and sets the variable nozzle 15 to the closed side. Specifically, the opening degree of the variable nozzle 15 is set to the initial opening degree VN1. By performing the process in step S104, intake air is introduced into the air assist passage 10 by opening the electromagnetic on-off valve 11, and the rotational speed of the turbine 4b is increased by setting the variable nozzle 15 to the closed side. As a result, the compressor outlet pressure rises. Thereby, the intake air supercharged in the pressure accumulation tank 13 is accumulated. When the above process ends, the process proceeds to step S107. If the current load of the internal combustion engine 6 does not satisfy the load condition in the weak mode, the process of step S104 is not performed. In this case, the process exits the flow.

  In step S105, the ECU 30 determines whether or not the pressure accumulation mode is the middle mode. If the pressure accumulation mode is the middle mode (step S105; Yes), the process proceeds to step S106. If the pressure accumulation mode is not the middle mode (step S105; No), the process proceeds to step S109.

  In step S106, the ECU 30 opens (fully opens) the electromagnetic on-off valve 11 and sets the variable nozzle 15 to the closed side. Specifically, the opening degree of the variable nozzle 15 is set to the initial opening degree VN1. By performing the process of step S106, intake air is introduced into the air assist passage 10, and the rotational speed of the turbine 4b is increased to increase the compressor outlet pressure. Thereby, the intake air supercharged in the pressure accumulation tank 13 is accumulated. When the above process ends, the process proceeds to step S107. If the current load of the internal combustion engine 6 does not satisfy the load condition in the middle mode, the process of step S106 is not performed. In this case, the process exits the flow.

  In step S107, the ECU 30 determines whether the compressor outlet pressure detected by the compressor outlet pressure sensor 20 is equal to or lower than a predetermined pressure P3. When the compressor outlet pressure is high, there is a possibility that the rotational strength of the turbocharger 4 (strength against the load caused by the rotation) may decrease. Therefore, in order to protect the turbocharger 4, the determination in step S107 I do. That is, in step S107, it is determined whether or not the compressor outlet pressure needs to be reduced in order to suppress a decrease in the durability of the turbocharger 4. The predetermined pressure P3 corresponds to the compressor outlet pressure that causes the rotational strength of the turbocharger 4 to decrease.

  If the compressor outlet pressure is equal to or lower than the predetermined pressure P3 (step S107; Yes), the process proceeds to step S112. In this case, there is no possibility that the rotational strength of the turbocharger 4 will decrease. On the other hand, when the compressor outlet pressure is higher than the predetermined pressure P3 (step S107; No), the process proceeds to step S108. In this case, since the rotational strength of the turbocharger 4 may be reduced, it is necessary to reduce the compressor outlet pressure.

  In step S108, the ECU 30 sets the variable nozzle 15 to the open side. This is because by performing such processing, the rotational speed of the turbine 4b is reduced and the compressor outlet pressure is reduced. Specifically, the ECU 30 obtains the opening VN of the variable nozzle 15 to be set by adding a predetermined change amount ΔVN to the initial opening VN1 of the variable nozzle 15. When the above process ends, the process returns to step S102, and the process for accumulating pressure in the accumulator tank 13 is performed again.

  On the other hand, when it is determined in step S105 that the pressure accumulation mode is not the middle mode and the process proceeds to step S109, the pressure accumulation mode is set to the strong mode. Therefore, in step S109, the ECU 30 controls the electromagnetic on-off valve 11 to be opened and the output of the electric motor 16 to be increased. Specifically, control is performed so that the initial output MAT1 is obtained from the electric motor 16. In this case, the ECU 30 sets, as the initial output MAT1, an output obtained by driving the electric motor 16 to the maximum, that is, driving it to the maximum within the allowable range of the battery. For example, when the pressure accumulation mode is set to the strong mode, the ECU 30 generates a driving force from the electric motor 16 even when the internal combustion engine 6 is in a non-accelerated state.

  By performing the process of step S109, intake air is introduced into the air assist passage 10 by opening the electromagnetic on-off valve 11, and the rotational speed of the turbine 4b is increased by driving the electric motor 16, thereby increasing the compressor outlet pressure. Rises. Thereby, the intake air supercharged in the pressure accumulation tank 13 is accumulated. When the above process ends, the process proceeds to step S110. Note that the processing in step S109 is executed regardless of the current load of the internal combustion engine 6 because the pressure accumulation mode is the strong mode.

  In step S110, the same processing as in step S107 described above is performed. Specifically, in step S110, the ECU 30 determines whether or not the compressor outlet pressure is equal to or lower than a predetermined pressure P3. That is, in step S110, it is determined whether or not the compressor outlet pressure needs to be reduced. If the compressor outlet pressure is equal to or lower than the predetermined pressure P3 (step S110; Yes), the process proceeds to step S112. In this case, there is no possibility that the rotational strength of the turbocharger 4 will decrease. On the other hand, when the compressor outlet pressure is higher than the predetermined pressure P3 (step S110; No), the process proceeds to step S111. In this case, since the rotational strength of the turbocharger 4 may be reduced, it is necessary to reduce the compressor outlet pressure.

  In step S111, the ECU 30 performs a process of reducing the output of the electric motor 16. This is because by performing such processing, the rotational speed of the turbine 4b is reduced and the compressor outlet pressure is reduced. Specifically, the ECU 30 obtains the output MAT of the electric motor 16 to be set by subtracting a predetermined change amount ΔMAT from the initial output MAT1 of the electric motor 16. When the above process ends, the process returns to step S102, and the process for accumulating pressure in the accumulator tank 13 is performed again.

  In step S112, the ECU 30 determines whether or not the pressure accumulation tank internal pressure is higher than a predetermined pressure P1. That is, the ECU 30 determines whether or not the pressure accumulation tank 13 is sufficiently accumulated. When the pressure accumulation tank internal pressure is higher than the predetermined pressure P1 (step S112; Yes), the process proceeds to step S113. On the other hand, when the pressure in the pressure accumulation tank is equal to or lower than the predetermined pressure P1 (step S112; No), the process returns to step S102, and the process for accumulating pressure in the pressure accumulation tank 13 is performed again.

  In step S113, the ECU 30 closes the electromagnetic opening / closing valve 11. That is, since the pressure accumulating tank 13 is sufficiently filled, the supply of intake air to the pressure accumulating tank 13 is stopped in order to avoid useless pressure accumulation. Then, the process proceeds to step S114. In step S114, the ECU 30 lights the pressure accumulation lamp 33 because the pressure in the pressure accumulation tank is higher than the predetermined pressure P1. Then, the process exits the flow.

  Thus, in the pressure accumulation control method according to the present embodiment, pressure accumulation in the pressure accumulation tank 13 is performed according to the pressure accumulation mode. For example, when it is desired to suppress deterioration in fuel consumption, pressure accumulation can be performed in a situation where deterioration in fuel consumption does not occur. In particular, by accumulating pressure when the internal combustion engine 6 decelerates from a high rotation, it is possible to suppress deterioration of fuel consumption, and setting the variable nozzle 15 to the occupied side increases pumping loss. The working condition can be improved. On the other hand, when it is desired to improve the pressure accumulation filling degree, the pressure accumulation can be forcibly performed. As a result, the acceleration assist frequency can be improved. As described above, according to the pressure accumulation control method described above, pressure accumulation in the pressure accumulation tank 13 can be appropriately performed according to the situation.

  According to the pressure accumulation control method according to the present embodiment, regardless of the pressure accumulation mode, when the variable nozzle 15 is fully closed during the deceleration process from the high rotation state, the compressor outlet pressure rises, thereby increasing the internal combustion engine 6. As the internal pressure of the exhaust manifold increases, the internal pressure of the intake manifold can be kept low by setting the throttle valve 5 to the closed side. In the normal control of the variable nozzle (control not intended for accumulating pressure in the accumulator tank 13), it is not necessary to increase the compressor outlet pressure in the operating state of the internal combustion engine 6 described above. It is lower than the internal pressure of the exhaust manifold when the pressure accumulation control according to the embodiment is performed. Therefore, according to the pressure accumulation control method according to the present embodiment, the pumping loss can be greatly increased, so that it is possible to effectively improve the condition of the engine brake during deceleration.

[Acceleration assist control method]
Hereinafter, an acceleration assist control method using an electric motor assist and an air assist will be described with reference to FIGS. 4 and 5.

  In the present embodiment, the electric motor assist and the air assist are controlled in accordance with the acceleration level (hereinafter referred to as “vehicle acceleration level”). This vehicle acceleration level is a level indicating whether acceleration is good or bad, and is set by the user. Specifically, levels 1 to 5 are prepared as vehicle acceleration levels, and the acceleration performance is set so as to improve as the level increases.

  More specifically, in the present embodiment, based on the vehicle acceleration level and the amount of pressure accumulation air accumulated in the pressure accumulation tank 13, in other words, the magnitude of the pressure accumulation tank internal pressure (hereinafter referred to as "accumulation level"). The output from the electric motor 16 is controlled. In addition, when the pressure accumulation level is large, the pressure of the pressure accumulation air supplied from the pressure accumulation tank 13 is high.

  FIG. 4 is a diagram showing a specific example of the vehicle acceleration level. In FIG. 4, the horizontal axis indicates the output of the electric motor 16, and the vertical axis indicates the pressure accumulation level of the pressure accumulation tank 13. Line segments 51 to 55 indicate the relationship between the output of the electric motor 16 (hereinafter also simply referred to as “motor output”) and the pressure accumulation level when the vehicle acceleration level is set to level 1 to level 5, respectively. . Basically, when the vehicle acceleration level is set to a large level, the motor output increases and the pressure of the accumulated air increases. Therefore, the acceleration performance of the vehicle is improved.

  Here, the acceleration assist control that is specifically performed will be briefly described with reference to FIG. When the vehicle acceleration level is set to level 1 and the pressure accumulation level is “0”, the ECU 30 controls the electric motor 16 so that the motor output corresponding to the point indicated by the symbol A1 in FIG. 4 is obtained. Control. In this case, control is performed so that the motor output decreases as the pressure accumulation level increases. In other words, since the air assist can be performed when the pressure accumulation level increases, the amount of electric motor assist is reduced by the amount of air assist. On the contrary, when the pressure accumulation level is the maximum, the motor output is set to “0” as indicated by the symbol A2 in FIG. In this case, control is performed so that the motor output increases as the pressure accumulation level decreases. That is, the electric motor assist amount is increased by the amount by which the air assist amount is decreased.

  When the vehicle acceleration level is set to level 3 or level 5, ECU 30 sets the motor output according to the pressure accumulation level based on line segment 53 and line segment 55 in FIG. For example, the motor output corresponding to the point indicated by the symbol B or the symbol C is determined. Also in this case, the motor output is changed according to the fluctuation of the pressure accumulation level. When the vehicle acceleration level is level 5, a combination of a substantially maximum pressure accumulation level and a substantially maximum motor output is used.

  Next, the acceleration assist control process according to the present embodiment will be described with reference to the flowchart shown in FIG. The acceleration assist control process is repeatedly executed by the ECU 30.

  First, in step S201, the ECU 30 acquires the vehicle acceleration level (level 1 to level 5) selected by the user. Then, the process proceeds to step S202.

  In step S202, the ECU 30 determines whether or not the vehicle is rapidly accelerating (for example, acceleration when starting or overtaking). That is, in step S202, it is determined whether it is necessary to perform acceleration assist. Specifically, the ECU 30 determines whether the time change Δacc of the throttle opening detected by the throttle opening sensor 21 is greater than a predetermined value Acc. If the time change Δacc is greater than the predetermined value Acc (step S202; Yes), the process proceeds to step S203. In this case, since the vehicle is rapidly accelerating, acceleration assistance described later is performed. On the other hand, when the time change Δacc is equal to or less than the predetermined value Acc (step S202; No), the process exits the flow. In this case, since the rapid acceleration is not performed, the acceleration assist is not performed. The determination of the rapid acceleration based on the throttle opening detected by the throttle opening sensor 21 is not limited, and for example, the determination may be performed based on the accelerator opening detected by the accelerator opening sensor.

  In step S203, the ECU 30 sets the electromagnetic on-off valve 11 to be closed (fully closed) when the pressure accumulation mode is the weak mode, and closes the electromagnetic on-off valve 11 when the pressure accumulation mode is the middle mode or the strong mode. Set to. This is because when the pressure accumulation mode is the weak mode, as described above, pressure accumulation in the pressure accumulation tank 13 is not performed during rapid acceleration. On the other hand, when the pressure accumulation mode is set to the medium mode or the strong mode, pressure accumulation in the pressure accumulation tank 13 is performed even during rapid acceleration. When the above process ends, the process proceeds to step S204. In step S204, the ECU 30 determines whether or not the pressure accumulation tank internal pressure is higher than the lower limit pressure P0. When the pressure in the pressure accumulating tank is low, even if the pressure accumulating air is supplied from the pressure accumulating tank 13, the rotational speed of the turbine 4b cannot be increased. That is, the air assist effect cannot be obtained. Therefore, in step S204, it is determined using the lower limit pressure P0 whether the pressure in the pressure accumulating tank is sufficient to obtain the effect of air assist.

  When the pressure accumulation tank internal pressure is higher than the lower limit pressure P0 (step S204; Yes), the process proceeds to step S205. In this case, in order to execute air assist, the processing after step S205 is performed. On the other hand, when the pressure in the accumulator tank is equal to or lower than the lower limit pressure P0 (step S204; No), the process exits the flow. In this case, since air assist cannot be performed, the processing after step S205 is not performed. That is, it waits for pressure accumulation until the pressure in the pressure accumulation tank becomes higher than the lower limit pressure P0.

  In step S205, the ECU 30 sets the air assist valve 14 to fully open. By opening the air assist valve 14, the air assist passage 10 and the exhaust passage 7 are brought into conduction, and the accumulated air is supplied to the turbine 4b. That is, air assist is executed. When the above process ends, the process proceeds to step S206.

  In step S206, the ECU 30 determines whether or not the time change ΔP of the pressure accumulation tank internal pressure is higher than the predetermined pressure Pr. Specifically, in step S206, it is determined whether or not the exhaust gas in the exhaust passage 7 is flowing backward to the air assist passage 10. Such a backflow occurs when the pressure of the accumulated air is lower than the pressure of the exhaust gas.

  The reason why the reverse flow can be determined using the time change ΔP of the pressure in the accumulator tank is as follows. When pressure accumulation air is supplied from the pressure accumulation tank 13 to the exhaust passage 7, the pressure in the pressure accumulation tank decreases, so the time change ΔP becomes a small value (for example, a negative value). However, when the time change ΔP has a large value (for example, a positive value), there is a high possibility that the exhaust gas flowing backward from the exhaust passage 7 flows into the pressure accumulation tank 13. In this case, the accumulated air hardly flows out from the accumulation tank 13. Therefore, in step S206, it is possible to determine whether or not a reverse flow has occurred by comparing the time change ΔP of the pressure in the accumulator tank with the predetermined pressure Pr. If the time change ΔP is higher than the predetermined pressure Pr (step S206; Yes), the process proceeds to step S210. In this case, backflow has occurred. On the other hand, when the time change ΔP is equal to or less than the predetermined pressure Pr (step S206; No), the process proceeds to step S207. In this case, no backflow has occurred.

  In step S207, the ECU 30 performs control so that a motor output corresponding to the pressure accumulation level of the pressure accumulation tank 13 and the vehicle acceleration level is obtained. Specifically, as illustrated in FIG. 4, the ECU 30 selects a relationship between the pressure accumulation level corresponding to the vehicle acceleration level and the motor output, and obtains a motor output corresponding to the current pressure accumulation level based on this relationship. . Then, the ECU 30 controls the electric motor 16 so that the obtained motor output is output. That is, electric motor assist is executed. Thus, in the acceleration assist control according to the present embodiment, the electric motor assist is started after the air assist valve 14 is opened and the air assist is started. Therefore, since the motor output is suppressed, the inverter / motor unit and the like can be downsized. When the process in step S207 is completed, the process proceeds to step S209.

  In step S209, similarly to the processing in step S206 described above, it is determined whether or not the time change ΔP of the pressure accumulation tank internal pressure is higher than a predetermined pressure Pr. That is, it is determined whether or not the exhaust gas in the exhaust passage 7 is flowing back to the air assist passage 10. If the time change ΔP is higher than the predetermined pressure Pr (step S209; Yes), the process proceeds to step S210 because a back flow has occurred. On the other hand, when the time change ΔP is equal to or lower than the predetermined pressure Pr (step S209; No), the process returns to step S207 because no back flow has occurred. In this case, air assist is continued and a motor output corresponding to the pressure accumulation level is output from the electric motor 16.

  In step S210, the ECU 30 fully closes the air assist valve 14. In this case, since the backflow of the exhaust gas from the exhaust passage 7 to the air assist passage 10 occurs, the air assist valve 14 is fully closed to suppress the backflow. That is, the execution of air assist is terminated. When the above process ends, the process exits the flow.

  Note that the air assist ends when the above process ends, but the electric motor assist by the electric motor 16 may continue. For example, in order to set the target boost pressure according to the rotational speed of the internal combustion engine 6, the boost pressure control using the electric motor assist can be performed.

  Further, when a check valve is provided in the air assist passage 10 on the downstream side of the pressure accumulating tank 13, it is not necessary to perform the determinations in step S206 and step S209. This is because no backflow to the pressure accumulating tank 13 occurs in this case.

  Here, the effect when the acceleration assist control according to the present embodiment is performed will be described with reference to FIG.

  FIG. 6 is a diagram illustrating an example of acceleration performance by the acceleration assist control according to the present embodiment. FIG. 6 shows a specific example of the time change of the supercharging pressure during acceleration. The abscissa indicates the elapsed time after acceleration, and the ordinate indicates the supercharging pressure. A curve 60 indicates acceleration performance when the acceleration assist control according to the present embodiment, that is, two acceleration assists of air assist and electric assist are performed. A curve 61 indicates acceleration performance when neither air assist nor electric assist is performed, a curve 62 indicates acceleration performance when only electric assist is performed, and a curve 63 indicates when only air assist is performed. Acceleration performance is shown. From these, it can be understood that when the acceleration assist control according to the present embodiment is performed, the boost pressure rises faster than when other controls are performed. That is, according to the acceleration assist control according to the present embodiment, it can be seen that the acceleration performance is excellent. Such a difference is considered to be caused by a synergistic effect of air assist and electric assist.

[Modification]
The present invention is not limited to the user setting the pressure accumulation mode. In another example, the pressure accumulation control can be performed based on a fixed load condition in which the pressure accumulation is performed in advance. For example, it is possible to perform control for accumulating intake air in the accumulator tank 13 only when the internal combustion engine 6 shifts from a high rotation state to a deceleration state. Thereby, the deterioration of the fuel consumption by execution of pressure accumulation can be suppressed.

  Further, the present invention is not limited to the user setting the vehicle acceleration level. In another example, acceleration assist control can be performed using a vehicle acceleration level fixed in advance, that is, a relationship between a fixed pressure accumulation level and a motor output.

1 is a schematic diagram showing a schematic configuration of a vehicle to which a control device for an internal combustion engine according to an embodiment of the present invention is applied. It is a figure for demonstrating the pressure accumulation mode. It is a flowchart which shows the pressure accumulation control process which concerns on this embodiment. It is a figure for demonstrating a vehicle acceleration level. It is a flowchart which shows the acceleration assistance control process which concerns on this embodiment. It is a figure which shows an example of the acceleration performance by acceleration assistance control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Intake passage 4 Turbocharger 4a, 9a Compressor 4b, 9b Turbine 6 Internal combustion engine 7 Exhaust passage 10 Air assist passage 11 Electromagnetic control valve 13 Accumulation tank 14 Air assist valve 15 Variable nozzle 16 Electric motor 30 ECU

Claims (8)

An electric motor for generating a driving force for rotating the compressor of the turbocharger;
Electric motor control means for controlling the driving of the electric motor;
Accumulation control means for performing control for accumulating intake air that has passed through the compressor in an accumulator tank;
A control device for an internal combustion engine, comprising: a pressure-accumulated air supply control unit that performs control to supply the pressure-accumulated air accumulated in the pressure-accumulation tank to an exhaust passage upstream of a turbine of the turbocharger.   2. The control device for an internal combustion engine according to claim 1, wherein the pressure accumulation control unit performs control for accumulating the intake air in the pressure accumulation tank when the internal combustion engine shifts from a high rotation state to a deceleration state.   The control apparatus for an internal combustion engine according to claim 1, wherein the pressure accumulation control means performs control for accumulating the intake air in the pressure accumulation tank based on a load condition indicated by a set pressure accumulation mode. The electric motor control means generates a driving force from the electric motor when the internal combustion engine is in a non-accelerated state,
2. The internal combustion engine according to claim 1, wherein the pressure accumulation control unit performs control of accumulating the intake air in the pressure accumulation tank when the electric motor generates driving force in the non-accelerated state. Control device.   5. The internal combustion engine according to claim 1, wherein the electric motor control unit starts control for driving the electric motor after starting the supply of the accumulated air during acceleration. 6. Control device.   The electric motor control means and the pressure accumulation air supply control means are configured to control the driving force generated by the electric motor based on at least one of the acceleration request and the pressure accumulation level of the pressure accumulation tank, and the pressure accumulation air from the pressure accumulation tank. The control device for an internal combustion engine according to any one of claims 1 to 5, wherein supply control of the engine is performed.   The internal combustion engine according to any one of claims 1 to 6, wherein the pressure accumulation control means performs control for accumulating the intake air in the pressure accumulation tank so that durability of the turbocharger does not decrease. Engine control device.   The said pressure accumulation control means performs the control which sets the variable nozzle provided in the said turbocharger to the close side, when performing the control which accumulates the said intake air in the said pressure accumulation tank. The control device for an internal combustion engine according to any one of claims 7 to 9.

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