JP4229038B2 - Internal combustion engine supercharging system - Google Patents

Description

  The present invention relates to a supercharging system having both a supercharger driven by engine exhaust gas and a supercharger driven by an electric motor.

  2. Description of the Related Art Conventionally, a turbocharger that forcibly sends air into an engine using engine exhaust gas is known as a technique for increasing engine output. As a method for controlling the turbocharging pressure of the turbocharger, a bypass passage that bypasses the turbine of the turbocharger and a supercharging pressure actuator that opens and closes the bypass passage are provided, and the supercharging pressure reaches a target value. It is common to open the supercharging pressure actuator and evacuate through the bypass passage. The supercharging pressure actuator is normally closed by a force such as a spring, and the differential pressure between the pressure in the intake passage downstream of the compressor of the turbocharger and the atmospheric pressure exceeds the force of the spring or the like. A structure that opens sometimes is widely used, and is used by setting a force such as a spring so that the pressure in the intake passage downstream of the compressor is opened by a differential pressure from the atmospheric pressure when it reaches a target value. .

  By the way, the turbocharger has a drawback called a so-called turbo lag in which sufficient supercharging cannot be performed until the flow rate of the exhaust gas increases.

As a method for solving this disadvantage, a turbocharger driven by an electric motor is provided in the intake passage upstream of the turbocharger, and the electric turbocharger is used in an area where the turbocharger cannot perform sufficient supercharging. Patent Document 1 discloses a supercharging system that eliminates turbo lag by performing supercharging.
JP 2002-21573

  However, Patent Document 1 has only a description of “supercharging by the electric supercharger is terminated when the turbocharger reaches a required supercharging pressure” regarding the supercharging pressure control of the turbocharger. There is no description about the detailed control method.

  If control is performed using the above-described general supercharging pressure actuator, even if the supercharging pressure of the turbocharger is low, the pressure downstream of the turbocharger is set to the target value by supercharging by the electric supercharger. The supercharging pressure actuator that operates due to the differential pressure from the atmospheric pressure opens, and the electric supercharger stops.

  In other words, the electric turbocharger stops even though the turbocharging pressure of the turbocharger has not reached the target value, so the time until the turbocharging pressure of the turbocharger reaches the target value Becomes longer.

  Therefore, an object of the present invention is to shorten the time until the supercharging pressure of the turbocharger reaches a target value.

A supercharging system for an internal combustion engine of the present invention includes a turbocharger driven by engine exhaust gas, an electric supercharger provided in an intake passage upstream of the turbocharger and driven by an electric motor, First pressure detecting means for detecting the pressure in the intake passage downstream of the electric supercharger and upstream of the turbocharger; and second pressure detecting means for detecting the pressure in the intake passage downstream of the turbocharger;
In response to the differential pressure between the first pressure detected by the first pressure detecting means and the second pressure detected by the second pressure detecting means, the supercharging pressure of the turbocharger exceeds a predetermined pressure. A supercharging pressure control means for controlling so that there is no acceleration, a means for detecting a request for acceleration of the vehicle, and if an acceleration request is detected, activates the electric supercharger and rises while being controlled by the supercharging pressure control means And an electric supercharger driving force reducing means for reducing the driving force of the electric supercharger after the second pressure reaches a predetermined pressure.

  According to the present invention, pressure control means that responds to the differential pressure between the upstream and downstream of the turbocharger, that is, only the turbocharger, for example, the supercharging pressure control actuator is used. By operating the electric supercharger, the turbocharger downstream pressure reaches the target supercharging pressure due to supercharging by the electric supercharger even though the supercharging pressure of the turbocharger is low. The supercharging pressure actuator does not work. At this time, in order to prevent the pressure downstream of the turbocharger from becoming higher than the target supercharging pressure, if the pressure downstream of the turbocharger reaches the target supercharging pressure, for example, the power of the electric supercharger is reduced. Etc. to reduce the supercharging pressure of the electric supercharger.

  Therefore, until the supercharging pressure of the turbocharger reaches the target pressure, all the exhaust gas passes through the turbine of the turbocharger, so that the supercharging pressure of the turbocharger rises quickly. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a system configuration of the present embodiment, in which 13 is an engine, 6 is a turbocharger driven by exhaust gas of the engine 13, 4 is an electric supercharger driven by a motor 15, Reference numeral 1 denotes an air flow meter (hereinafter referred to as AFM) that measures an intake air amount Qa.

  The intake pipe 2 downstream of the AFM 1 is electrically driven by an intake passage (hereinafter referred to as an electric supercharger side passage) 21 in which the electric supercharger 4 is interposed, and a branch portion 22 upstream of the electric supercharger 4. It branches from the feeder side passage 21 and branches to a bypass passage 20 that joins at a junction 23 downstream of the electric supercharger 4.

  A bypass valve 3 that is opened and closed by an actuator and controls the amount of air passing through the bypass passage 20 is interposed between the branch portion 22 and the junction portion 23 in the bypass passage 20.

  A compressor 7 of the turbocharger 6 is interposed in the intake pipe 5 downstream from the junction 23.

  The compressor 7 is connected to the turbine 8 via a shaft, and rotates when the turbine 8 interposed in the exhaust pipe 24 downstream of the exhaust manifold 14 of the engine 13 is rotated by the pressure of the exhaust gas of the engine 13. The air passing through the tube 5 is compressed.

  The air compressed by the compressor 7 is cooled by passing through an intercooler 9 provided downstream of the compressor 7, and the flow rate is restricted by a throttle chamber 11 provided further downstream. Is sucked into each cylinder.

  A bypass exhaust passage 27 that bypasses the turbine 8 and communicates with the exhaust pipe downstream of the turbine branches from the exhaust pipe 24, and an open / close valve 26 is provided in the bypass exhaust passage 27.

  The on-off valve 26 is controlled to open and close by an actuator 25 connected via a shaft 35.

  The actuator 25 is divided into two chambers by a partition plate 32 that can move inside the main body and is connected to a shaft 35, and a spring 31 is stored in one of the chambers. The force of the spring 31 acts in the direction in which the on-off valve 26 is closed.

  The chamber in which the spring 31 of the actuator 25 is housed communicates with the intake passage 5 upstream of the compressor 7 by a pipe 33, and the internal pressure is equal to that upstream of the compressor 7. Further, the other chamber communicates with the intake passage downstream of the intercooler 9 by the pipe 34, and the internal pressure is equal to that of the intake passage downstream of the intercooler 9.

  In other words, when the pressure downstream of the intercooler 9 becomes larger than the pressure upstream of the compressor 7 due to supercharging by the turbocharger 6, a differential pressure is also generated inside the actuator 25. This differential pressure acts on the shaft 35 in the opposite direction to the force of the spring 31. When the pressure becomes larger than the force of the spring 31, the on-off valve 26 opens.

  The differential pressure when the on-off valve 26 opens can be arbitrarily set according to the spring constant of the spring 31 and the like, considering the output required for the engine 13, the durability of the engine 13, and the like. Set.

  ON / OFF of the electric supercharger 4 is controlled by an engine control unit (hereinafter referred to as ECU) 18, and the motor controller 17 supplies power from the power source 16 to the motor 15 based on a signal from the ECU 18.

  The ECU 18 is provided downstream of the pressure sensor 29 and the intercooler 9 provided downstream of the bypass valve 3 and the electric supercharger 4 and upstream of the compressor 7 of the turbocharger 6 (hereinafter referred to as bypass valve 3). The detection signal of the pressure sensor 30 is also read.

  In addition, without providing the pressure sensor 29, the amount of air pumped by the electric supercharger 4 per rotation is obtained in advance, and the bypass valve 3 and the like are calculated from the air amount and the rotational speed of the electric supercharger 4. It is also possible to calculate the downstream pressure.

  Whether or not the electric supercharger 4 is driven is determined by a signal from the accelerator opening sensor 20 that detects the accelerator opening. For example, it is determined that there is an acceleration request when the accelerator opening exceeds a predetermined opening or when the opening change rate of the accelerator opening becomes faster than a predetermined value.

  Next, control executed by the ECU 18 will be described with reference to FIG.

  FIG. 2 is a flowchart showing the control of this embodiment. Although the turbocharger 6 is driven by the exhaust gas of the engine 13 as described above, there is a drawback that the turbocharger 6 cannot be sufficiently charged until the pressure of the exhaust gas increases. On the other hand, since the electric supercharger 4 is driven by the motor 15, the supercharging rises faster than the turbocharger 6.

  Therefore, according to the flowchart of FIG. 2, supercharging by the electric supercharger 4 is performed in a region where the turbocharger 6 cannot be sufficiently supercharged, and control is performed to increase the responsiveness of the supercharging pressure to the acceleration request. The opening / closing of the bypass valve 3 is controlled by the ECU 18 in association with the ON / OFF of the electric supercharger 4.

  Hereinafter, it demonstrates according to a flowchart.

  In step S100, it is determined whether or not the accelerator opening is equal to or greater than a predetermined value set for each engine speed. If it is equal to or greater than the predetermined value, the process proceeds to step S110, where supercharging by the electric supercharger 4 is started and the bypass valve 3 is fully closed.

  In step S120, the pressure Pb downstream of the intercooler 9 is compared with a pressure (set pressure) P2 set in advance as the target supercharging pressure of the turbocharger.

  When the target boost pressure P2 is larger, the process returns to step S100, and when it is smaller, the process proceeds to step S130.

  In step S130, the rotational speed of the electric supercharger 4 is controlled by current value control so that the pressure Pb maintains the set pressure P2. That is, the rotational speed of the electric supercharger 4 is reduced. At this time, since the supercharging pressure Pa downstream of the bypass valve 3 and the like is higher than the atmospheric pressure due to supercharging of the electric supercharger 4, the differential pressure between the downstream of the bypass valve 3 and the downstream of the intercooler 9 is the target supercharging. It is smaller than the supply pressure P2. Therefore, the actuator 25 does not open.

  In step S140, it is determined whether or not the pressure Pa downstream of the bypass valve 3 or the like is equal to or lower than atmospheric pressure. If it is greater than the atmospheric pressure, the process returns to step S100, and if it is lower, the process proceeds to step S150, the electric supercharger 4 is stopped, and the bypass valve 3 is fully opened.

  As described above, in the present embodiment, after the acceleration request is detected and the bypass valve 3 is fully closed and supercharging by the electric supercharger 4 is started, the pressure Pb downstream of the intercooler 9 becomes the target supercharging pressure. Even when P2 is reached, the actuator 25 that operates by the differential pressure between the downstream of the bypass valve 3 and the like and the downstream of the intercooler 9 does not open. At this time, if the pressure Pb downstream of the intercooler 9 is equal to or higher than the set pressure, the rotational speed of the electric supercharger 4 is decreased.

  This is because, when the target supercharging pressure P2 is first reached, the sum of the supercharging pressure by the electric supercharger 4 and the supercharging pressure by the turbocharger 6 is only the set pressure P2. This is because it is considered that the supercharging pressure of the turbocharger 6 has not reached the set pressure P2.

  When the pressure Pa downstream of the bypass valve 3 or the like becomes substantially equal to the atmospheric pressure, that is, when the electric supercharger 4 is almost stopped, the supercharging pressure of the turbocharger 6 reaches the set pressure P2. Therefore, the electric supercharger 4 is completely stopped and the bypass valve 3 is fully opened. Thereafter, when the supercharging pressure of the turbocharger 6 is further increased, the actuator 25 is opened by the differential pressure between the pressure Pa downstream of the bypass valve 3 and the pressure Pb downstream of the intercooler 9, and the set pressure P2 is maintained.

  Next, a case where the above control is executed will be described with reference to FIGS.

  FIG. 3 shows an electric supercharger 4 and a turbocharger when control is executed in the same system as in the present embodiment by using an actuator 25b that opens according to the differential pressure between the atmospheric pressure and the downstream of the compressor as in the prior art. 6 is a diagram showing a change in supercharging pressure due to 6. FIG. The dashed line A is the supercharging pressure Pas of the electric supercharger 4, the dotted line B is the supercharging pressure Ptc of the turbocharger 6, and the solid line C is a combination of the electric supercharger 4 and the turbocharger 6, that is, turbo. The change about the pressure Pb of a supercharger downstream is represented.

  FIG. 4 shows a supercharging pressure Pas in the present embodiment, that is, when an actuator 25 that is driven by a differential pressure between the pressure downstream of the bypass valve 3 and the like and the pressure downstream of the intercooler 9 is used to open the on-off valve 26. FIG. 4 is a diagram showing changes in supercharging pressure Ptc and pressure Pb, changes in the rotational speeds of both superchargers, and changes in the opening of the bypass valve 3.

  In FIG. 3, the acceleration request is detected at t20 and the electric supercharger 4 starts to be driven, and the supercharging pressures Pas and Ptc increase. Accordingly, the pressure Pb also increases.

  At t21, the supercharging pressure Pas of the electric supercharger 4 reaches the upper limit value P1, but the rotational speed of the turbocharger 6 continues to increase and the supercharging pressure Ptc continues to increase.

  At t22, the pressure Pb reaches the set pressure P2. At this time, the actuator 25b that operates when the differential pressure between the atmospheric pressure and the pressure Pb downstream of the compressor (in this case, downstream of the intercooler 9) reaches the set pressure P2 opens the on-off valve 26. Thereby, the pressure Pb downstream of the intercooler 9 maintains the set pressure P2.

  After t22, the rotational speed of the turbocharger 6 continues to increase. When the set pressure P2 is reached at t23, the electric supercharger 4 is stopped.

  As described above, since the on-off valve 26 opens at t22, a part of the engine exhaust gas flows through the bypass exhaust passage 27 after t22. That is, even if the rotational speed of the engine 13 is increased by the supercharging by the electric supercharger 4 and the exhaust gas flow rate is increased, part of the engine 13 is discharged without rotating the turbine 8.

  On the other hand, in the present embodiment shown in FIG. 4, the acceleration request is detected at t10 to start driving the electric supercharger 4, and the supercharging pressure of the electric supercharger 4 reaches the upper limit value P1 at t11. 3 until the pressure Pb reaches the set pressure P2 at t12.

  However, the actuator 25 does not open the on-off valve 26 at t12. This is because the actuator 25 is operated by the differential pressure between the pressure Pa downstream of the bypass valve 3 or the like and the pressure Pb downstream of the intercooler 9, and the pressure Pb downstream of the intercooler 9 reaches the set pressure P2 at t12. However, because the pressure Pa downstream of the bypass valve 3 and the like has increased to P1 by the electric supercharger 4, the differential pressure has not reached the set pressure P2 for opening the on-off valve 26.

  After the pressure Pb reaches the set pressure P2 at t12, the electric supercharger 4 is maintained so that the pressure Pb downstream of the intercooler 9 maintains the set pressure P2 even if the boost pressure of the turbocharger 6 increases. Reduce the number of revolutions.

  When the rotational speed of the electric supercharger 4 decreases and stops rotating at t13, the supercharging pressure Pb of the turbocharger 6 has reached the set pressure P2, and the pressure Pa downstream of the bypass valve 3 etc. The differential pressure of the pressure Pb downstream of the cooler becomes the set pressure P2. Therefore, the on-off valve 26 is opened by the actuator 25, and thereafter, the exhaust pressure is released from the on-off valve 26 to maintain the supercharging pressure at the set pressure P2.

  As described above, in the present embodiment, the on-off valve 26 is not opened at t12 corresponding to t22 in FIG. 3, so that all the exhaust gas of the engine 13 remains after the pressure Pb downstream of the intercooler reaches the set value P2. It will be used to rotate the turbine 8.

  Therefore, comparing FIG. 3 and FIG. 4, it takes the same time from the start of driving of the electric supercharger 4 until the pressure Pb downstream of the intercooler 9 reaches the set pressure P2, but thereafter, the turbocharger 6 The time until the supercharging pressure Ptc reaches the set pressure P2 is shorter in FIG.

  As described above, in the present embodiment, in the supercharging system having both the turbocharger 6 and the electric supercharger 4 that is installed in series upstream of the turbocharger 6 and that is driven when an acceleration request is detected, In order to control the supercharging pressure of the turbocharger 6, an actuator that operates by a differential pressure between the pressure Pa downstream of the bypass valve 3 or the like and the pressure Pb downstream of the intercooler 9 provided downstream of the turbocharger 6. 25, and when the pressure Pb downstream of the intercooler 9 reaches the set pressure P2 after the electric supercharger 4 starts to be driven, the motor is driven in accordance with the rotation increase of the turbocharger 6 so as to maintain the set pressure P2. Since the rotational speed of the supercharger 4 is reduced, the turbocharger 4 is reduced in comparison with the actuator 25b that is operated by the differential pressure between the atmospheric pressure and the pressure Pb downstream of the intercooler 9 as conventionally used. It can be shortened rise time of the supercharging pressure of the supercharger 6.

  Moreover, since the supercharging of the turbocharger 6 rises in a short time and the operation time of the electric supercharger 4 is shortened, the power consumption of the electric motor 15 can be reduced.

  Furthermore, since the operating time of the motor 15 is shortened, the amount of heat generated by the motor 15 can be reduced, and the efficiency and life of the motor 15 can be improved.

  A second embodiment will be described with reference to FIGS.

  FIG. 5 is a control flowchart of the present embodiment, and FIG. 6 is a time chart for the case where the control of the present embodiment is executed as in FIG.

  Steps S200 to S220 in FIG. 5 are the same as steps S100 to S120 in the first embodiment shown in FIG.

  In step S230, the bypass valve 3 is controlled to open in accordance with the rotation increase of the turbocharger 6 so that the pressure Pb downstream of the intercooler maintains the set pressure P2. This is because when the bypass valve 3 is opened, a part of the air pressurized by the electric supercharger 4 flows back through the intake passage 20 upstream of the bypass valve 3 having a low pressure. This is because the pressure Pa is reduced.

  In step S240, it is determined whether or not the bypass valve 3 is fully opened. If not fully open, the process returns to step S200. If it is fully open, the process proceeds to step S250, and the electric supercharger 4 is stopped. This is because the bypass valve 3 is fully open, so it can be estimated that the pressure Pa downstream of the bypass valve 3 and the like is almost atmospheric pressure, and the pressure Pb downstream of the intercooler 9 maintains the set pressure P2. This is because it can be estimated that the supercharging pressure of the turbocharger 6 has reached the set pressure P2.

  The time chart in FIG. 6 is the same as that in FIGS. 3 and 4 from t30 when the electric supercharger 4 is started to t32 when the pressure Pb downstream of the intercooler 9 reaches the set pressure P2.

  Even after the pressure Pb downstream of the intercooler 9 reaches the set pressure P2 at t32, the electric supercharger 4 keeps the rotation speed constant. However, since the opening degree of the bypass valve 3 gradually increases, the amount of air flowing from the bypass valve 3 to the upstream intake passage 20 increases, the pressure Pa downstream of the bypass valve 3 and the like decreases, and the downstream of the intercooler 9 decreases. The pressure Pb is maintained at the set pressure P2.

  Since the bypass valve 3 is fully opened at t33, the electric supercharger 4 is stopped. In the description of the flowchart of FIG. 5 described above, when the bypass valve 3 is fully opened, the differential pressure between the pressure Pa downstream of the bypass valve 3 and the pressure Pb downstream of the intercooler 9 is the set pressure P2. Strictly speaking, as shown in FIG. 6, the differential pressure becomes the set pressure P2 at t34 when the rotation of the electric supercharger 4 is completely stopped.

  Also in this embodiment, as in the first embodiment, the actuator 25 does not open the on-off valve 26 even if the pressure Pb downstream of the intercooler 9 reaches the set pressure P2 after the electric supercharger 4 starts driving. The exhaust gas is used for the rotation of the turbine 8, whereby the supercharging pressure of the turbocharger 6 rises quickly.

  As described above, in the present embodiment, in the same supercharging system as in the first embodiment, the set pressure P2 is maintained when the pressure Pb downstream of the intercooler 9 reaches the set pressure P2 after the electric supercharger 4 starts to be driven. As described above, since the opening degree of the bypass valve 3 is increased in accordance with the rotation increase of the turbocharger 6, the differential pressure between the atmospheric pressure and the pressure Pb downstream of the intercooler 9 as conventionally used is used. The rise time of the supercharging pressure of the turbocharger 6 can be shortened as compared with the case where the actuator 25b operated by the above is used.

  Further, similarly to the first embodiment, the power consumption of the electric motor 15 can be reduced and the efficiency and life can be improved.

  Furthermore, since the opening degree of the bypass valve 3 is gradually increased, the intake air amount of the engine 13 does not change abruptly, and the occurrence of an engine torque step can be prevented.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

  The present invention can be applied to an internal combustion engine having both an electric supercharger driven by an electric motor and a turbocharger driven by engine exhaust gas.

It is a figure showing the structure of the system of 1st Embodiment. It is a control flowchart of a 1st embodiment. It is a time chart at the time of using a conventional actuator. It is a time chart at the time of performing control of a 1st embodiment. It is a control flowchart of a 2nd embodiment. It is a time chart at the time of performing control of a 2nd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air flow meter 3 Bypass valve 4 Electric supercharger 6 Turbo supercharger 7 Compressor 8 Turbine 9 Intercooler 11 Throttle valve 13 Engine 14 Exhaust manifold 15 Electric motor 16 Battery 17 Motor controller 18 Control unit (ECU)
20 Accelerator opening sensor 25 Actuator 26 On-off valve 29 Pressure sensor 30 Pressure sensor

Claims (6)

A turbocharger driven by engine exhaust,
An electric supercharger provided in an intake passage upstream of the turbocharger and driven by an electric motor;
First pressure detection means for detecting the pressure in the intake passage downstream of the electric supercharger and upstream of the turbocharger;
Second pressure detection means for detecting the pressure in the intake passage downstream of the turbocharger;
In response to the differential pressure between the first pressure detected by the first pressure detecting means and the second pressure detected by the second pressure detecting means, the supercharging pressure of the turbocharger exceeds a predetermined pressure. Supercharging pressure control means for controlling so as not to,
Means for detecting a vehicle acceleration request;
When the acceleration request is detected, the electric supercharger is operated, and after the second pressure rising while being controlled by the supercharging pressure control means reaches a predetermined pressure, the driving force of the electric supercharger is reduced. An internal combustion engine supercharging system comprising: an electric supercharger driving force reducing means for reducing the electric supercharger. A bypass passage that bypasses the electric supercharger;
A bypass valve that is provided in the bypass passage and communicates and blocks the bypass passage; and
When the acceleration request is detected, the bypass valve is fully closed to operate the electric supercharger, and after the second pressure rising while being controlled by the supercharging pressure control means reaches a predetermined pressure, 2. The supercharging system for an internal combustion engine according to claim 1, wherein the electric supercharger driving force reduction means controls the bypass valve and the electric supercharger in association with each other to reduce the driving force of the electric supercharger.   When the second pressure reaches a predetermined pressure, the bypass valve is gradually opened while maintaining the driving force of the electric supercharger, and the differential pressure between the first pressure and the second pressure is The supercharging system for an internal combustion engine according to claim 2, wherein the driving force of the electric supercharger is reduced when the pressure becomes equal to a predetermined pressure.   The supercharging system for an internal combustion engine according to claim 3, wherein the electric supercharger is stopped when the bypass valve is fully opened.   The supercharging system for an internal combustion engine according to claim 2, wherein when the second pressure reaches a predetermined pressure, the driving force of the electric supercharger is gradually reduced while the bypass valve is closed.   The supercharging system for an internal combustion engine according to claim 5, wherein when the first pressure becomes substantially equal to atmospheric pressure, the bypass valve is fully opened and the electric supercharger is stopped.

Images