JP2016011632A - Control device for internal combustion engine - Google Patents

Abstract

[PROBLEMS] To promote warm-up of a catalyst.
An internal combustion engine (1) has a turbocharger (7) provided coaxially with a compressor (4) disposed in an intake passage (2) and a turbine (5) disposed in an exhaust passage (3). The turbocharger 7 has an electric motor 6 that can drive the turbine 5. An exhaust purification catalyst 8 is disposed downstream of the turbine 5 in the exhaust passage 3, and a bypass passage 9 that bypasses the turbine 5 and connects the upstream side and the downstream side of the turbine 5 is connected. . When the temperature of the catalyst 8 is equal to or lower than a predetermined temperature when the internal combustion engine 1 is started, the ECM 11 opens the wastegate 10 disposed in the bypass passage 9 and opens the turbine 5 by the electric motor 6 in the reverse direction. Rotate in the direction.
[Selection] Figure 1

Description

  The present invention relates to a control device for an internal combustion engine having an electric motor capable of rotationally driving a turbocharger turbine.

  Patent Document 1 discloses an electric motor that can drive a turbine of a supercharger disposed in an exhaust passage, a bypass passage that is connected to the exhaust passage so as to bypass the turbine, and an exhaust that is disposed in the bypass passage and flows into the turbine. A configuration having a wastegate valve with adjustable flow rate is disclosed.

  In Patent Document 1, when the exhaust gas purification catalyst disposed downstream of the turbine is warmed up, a reverse torque (torque in the direction opposite to the direction in which the intake amount of the turbocharger compressor is increased) is generated in the electric motor. In order to prevent the turbine from rotating, the exhaust gas is retained upstream of the turbine to raise the temperature of the exhaust gas. Therefore, in Patent Document 1, the temperature of the exhaust gas flowing through the exhaust passage rises in a short time, and early activation of the exhaust purification catalyst disposed downstream of the turbine is possible.

Japanese Patent No. 5177401

  However, in Patent Document 1 described above, even if the temperature of the exhaust gas is increased on the upstream side of the turbine, when the exhaust gas whose temperature has increased passes through the turbine and flows to the downstream side of the turbine, heat is generated in the turbine. May be deprived (heat radiation), and warming up of the exhaust purification catalyst may be delayed.

  Therefore, the internal combustion engine control apparatus of the present invention, when starting the internal combustion engine, by opening the wastegate disposed in the bypass passage that bypasses the turbine of the turbocharger, and by using an electric motor that can drive the turbine, The turbine is rotated in the direction opposite to that at the time of supercharging.

  As a result, part of the exhaust on the downstream side of the turbine is pushed back to the upstream side of the turbine by the reverse rotation of the turbine, and the pressure and temperature of the exhaust gas on the upstream side of the turbine rise.

  According to the present invention, as the pressure and temperature of the exhaust gas upstream of the turbine increase, the pressure and temperature of the exhaust gas in the catalyst communicating with the turbine upstream via the bypass passage can also be increased. It is possible to promote warming up of the catalyst disposed in the exhaust passage.

1 is a system diagram showing the overall configuration of an internal combustion engine to which the present invention is applied. The flowchart which shows the flow of control at the time of promoting warming-up of a catalyst.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a system diagram showing an overall configuration of an internal combustion engine 1 to which the present invention is applied.

  The internal combustion engine 1 is mounted on a vehicle such as an automobile as a drive source, and an intake passage 2 and an exhaust passage 3 are connected to the internal combustion engine 1.

  The internal combustion engine 1 has a turbocharger 7 provided coaxially with a compressor 4 disposed in an intake passage 2 and a turbine 5 disposed in an exhaust passage 3. The turbocharger 7 has an electric motor 6 that can drive the turbine 5. The electric motor 6 can rotationally drive the turbine 5 in the direction of increasing the supercharging pressure, or can rotationally drive the turbine 5 in the opposite direction.

  An exhaust purification catalyst 8 is disposed downstream of the turbine 5 in the exhaust passage 3, and a bypass passage 9 that bypasses the turbine 5 and connects the upstream side and the downstream side of the turbine 5 is connected. . A downstream end of the bypass passage 9 connected to the exhaust passage 3 on the downstream side of the turbine 5 is located upstream of the catalyst 8. A wastegate 10 that is opened and closed by an actuator (not shown) is disposed at the upstream end of the bypass passage 9 that branches from the exhaust passage 3. The wastegate opening area when the wastegate 10 is fully opened is set to be larger than the passage cross-sectional area of the inlet portion of the turbine 5 into which the exhaust flows. Therefore, when the wastegate 10 is fully opened, the ventilation resistance on the wastegate 10 side is relatively low. Here, the wastegate opening area is a passage cross-sectional area of a portion opened and closed by the wastegate 10, and is maximized when the wastegate 10 is in the fully open position, and is zero when the wastegate 10 is in the fully closed position. Become.

  The ECM 11 includes an exhaust temperature sensor 12 that detects the exhaust temperature on the outlet side of the turbine 5, a pressure sensor 13 that detects the exhaust pressure on the outlet side of the turbine 5, a catalyst temperature sensor 14 that detects the temperature of the catalyst 8, Detection signals from various sensors, such as a turbine rotation speed sensor 15 that detects the rotation speed and an accelerator opening sensor 16 that detects the amount of depression of the accelerator pedal (accelerator opening) operated by the driver, are input.

  An ECM (engine control module) 11 controls the ignition timing, air-fuel ratio, etc. of the internal combustion engine 1 and controls the rotation of the electric motor 6 and the waste gate opening area based on detection signals from various sensors inputted. doing. More specifically, the ECM 11 controls the waste gate opening area by controlling the actuator.

  When the temperature of the catalyst 8 is equal to or lower than a predetermined temperature when the internal combustion engine 1 is started, the ECM 11 opens the wastegate 10 and rotates the turbine 5 by the electric motor 6 in the direction opposite to that during supercharging. By performing reverse rotation control, warm-up of the catalyst 8 is promoted. In this turbine reverse rotation control, for example, the rotational speed of the turbine 5 is increased so that the exhaust pressure or the exhaust temperature on the outlet side of the turbine 5 becomes a predetermined value.

  When the turbine reverse rotation control is performed with the wastegate 10 fully open, if there is an acceleration request, the wastegate 10 is fully closed and the turbine reverse rotation control is terminated. That is, when there is an acceleration request, the wastegate 10 is fully closed, and the rotation of the turbine 5 is controlled to be in the rotation direction at the time of supercharging. The acceleration request is determined to be an acceleration request when the accelerator pedal is depressed, for example.

  As a result, part of the exhaust gas on the downstream side of the turbine 5 is pushed back to the upstream side of the turbine 5 due to the reverse rotation of the turbine 5, and the pressure and temperature of the exhaust gas on the upstream side of the turbine rise. Therefore, as the pressure and temperature of the exhaust gas upstream of the turbine increase, the pressure and temperature of the exhaust gas in the catalyst 8 communicating with the turbine upstream via the bypass passage 9 can also be increased. It becomes possible to promote the warm-up of the catalyst 8 arranged in the passage 3. In the present embodiment, the temperature of the exhaust gas purification catalyst 8 located on the downstream side of the turbine can be increased (for example, several tens of degrees or more) at the time of start-up as compared with an internal combustion engine with a normal supercharger. .

  Further, if there is an acceleration request, the wastegate 10 is fully closed and the rotation of the turbine 5 is terminated in the direction opposite to that during supercharging. Warm-up can be promoted.

  If the wastegate 10 is fully opened and the turbine reverse rotation control is started before the internal combustion engine 1 is started, the warm-up of the catalyst 8 can be further promoted at the start.

  Further, the wastegate 10 may be fully opened immediately after the internal combustion engine 1 is stopped. Thus, if the wastegate 10 is fully opened in advance, the pressure and temperature of the exhaust gas in the catalyst 8 can be raised with good responsiveness simultaneously with the start of the turbine reverse rotation control at the start.

  When the wastegate 10 is fully opened, the ventilation resistance on the wastegate 10 side can be relatively lowered. Therefore, when the wastegate 10 is fully opened and the turbine reverse rotation control is performed, The amount of exhaust gas flowing into the passage 9 is increased, and warming up of the catalyst 8 can be promoted.

  FIG. 2 is a flowchart showing a control flow when promoting warm-up of the catalyst 8 at the start.

  In S1, it is determined whether or not the catalyst 8 needs to be warmed up. If the temperature of the catalyst 8 is equal to or lower than the predetermined temperature, it is determined that the catalyst 8 needs to be warmed up, and the process proceeds to S2, and if not, the process proceeds to S5. In S2, the wastegate 10 is fully opened. In S3, the electric motor 6 rotates the turbine 5 in the direction opposite to that during supercharging. In S4, it is determined whether or not there is a request for acceleration of the vehicle. If there is an acceleration request, the process proceeds to S5, and if there is no acceleration request, the current routine is terminated. In S5, the wastegate 10 is fully closed, and the routine proceeds to normal mode control in which the turbine 5 is rotated in the rotation direction during supercharging.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 3 ... Exhaust passage 4 ... Compressor 5 ... Turbine 6 ... Electric motor 7 ... Turbocharger 8 ... Catalyst 9 ... Bypass passage 10 ... Wastegate 11 ... ECM

Claims (8)

A turbocharger comprising a turbine disposed in the exhaust passage and a compressor disposed in the intake passage;
A bypass passage that bypasses the turbine;
A wastegate that opens and closes the bypass passage;
An exhaust purification catalyst disposed on the downstream side of the turbine;
An electric motor capable of driving the turbine,
A control apparatus for an internal combustion engine, wherein when the internal combustion engine is started, the waste gate is opened, and turbine reverse rotation control is performed so that the electric motor rotates the turbine in a direction opposite to that during supercharging.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the turbine reverse rotation control increases the rotation speed so that the exhaust pressure or the exhaust temperature on the outlet side of the turbine becomes a predetermined value.   3. The control device for an internal combustion engine according to claim 1, wherein the wastegate is opened before starting the internal combustion engine, and the turbine reverse rotation control is started.   The control device for an internal combustion engine according to claim 3, wherein when the catalyst is at a predetermined temperature or lower, the wastegate is opened and the turbine reverse rotation control is performed.   The control apparatus for an internal combustion engine according to claim 3, wherein the waste gate is opened immediately after the internal combustion engine is stopped.   6. The internal combustion engine according to claim 1, wherein a waste gate opening area when the waste gate is fully opened is set larger than a passage cross-sectional area of an inlet portion of the turbine into which exhaust gas flows. Engine control device.   The control device for an internal combustion engine according to any one of claims 1 to 6, wherein when the vehicle acceleration request is detected, the waste gate is closed and the turbine reverse rotation control is terminated.   8. The control apparatus for an internal combustion engine according to claim 1, wherein the wastegate is fully opened when the internal combustion engine is started.

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