WO2018150565A1 - Method and device for controlling internal combustion engine - Google Patents

Abstract

This device has a turbo supercharger (14) in which a turbine (17) coaxial with a compressor (18) for supercharging intake air is provided to an exhaust passage (13), and an electric supercharger (15) provided to an intake passage at a different position from the compressor (18). A bypass passage (20) connecting the exhaust passage (13) on the upstream side of the turbine (17) and the exhaust passage (13) on the downstream side is provided so as to circumvent the turbine (17). The bypass passage (20) is provided with a wastegate valve (21) for adjusting the flow rate of intake air flowing through the bypass passage (20). During idling, the wastegate valve (21) is opened and the electric supercharger (15) is driven.

Description

Control method and control apparatus for internal combustion engine

The present invention relates to control of an internal combustion engine that uses both a turbocharger and an electric supercharger.

A technology is known in which a supercharger is disposed on an intake passage of an internal combustion engine, and the startability and warm-up performance of the internal combustion engine are improved by using supercharging by the supercharger. For example, in Patent Document 1, a supercharger driven by an electric motor is arranged on the intake passage, and at the time of engine start, the electric motor is driven to perform supercharging, and the intake air amount is limited, whereby supercharging is performed. The intake air temperature is raised by the compression of the intake air to improve startability and warm-up performance.

JP 2004-340122 A

When warming up the catalyst, if possible, increase the amount of exhaust gas flowing through the bypass passage by increasing the opening of the waste gate valve provided in the bypass passage that bypasses the turbine. Want to increase the exhaust gas supplied to the catalyst.

However, in the configuration in which the electric motor is directly attached between the turbine and the compressor as in the prior art described in Patent Document 1, when the electric motor is driven to increase the supercharging pressure for warming up the catalyst, At the same time, the turbine is rotationally driven, and the amount of exhaust gas passing through the bypass passage provided with the waste gate valve is reduced by the amount of exhaust gas drawn in by this turbine, and the exhaust gas passing through the turbine is deprived of heat by the turbine. There is a problem that the amount of heat given to the catalyst by the exhaust gas cannot be increased sufficiently, and the temperature rise of the catalyst becomes slow.

The present invention has been made in view of such circumstances. For example, during idle operation in a cold state, the engine temperature is increased without impairing combustion stability, and engine startability and warm-up performance are improved. It is an object of the present invention to provide a novel control method and control apparatus for an internal combustion engine that can be improved to enable early activation of a catalyst.

A turbocharger in which a turbine coaxial with a compressor for supercharging intake air is provided in the exhaust passage, an electric supercharger provided in the intake passage at a position different from the compressor, and the turbine bypassing And a bypass passage connecting the upstream exhaust passage and the downstream exhaust passage of the turbine, and a waste gate valve provided in the bypass passage for adjusting the flow rate of the exhaust gas flowing through the bypass passage. When idling, the waste gate valve is opened and the electric supercharger is driven.

According to the present invention, the startability and warm-up performance can be improved by raising the temperature of the intake air by compressing the intake air with the electric supercharger during idling. Moreover, it is not necessary to drive a turbo-type supercharger for temperature rising by supercharging with an electric supercharger. Accordingly, the waste gate valve can be controlled in the opening direction to suppress the amount of exhaust gas passing through the turbine. As a result, more exhaust gas that has not been deprived of heat by the turbine can be supplied to the catalyst, and early activation of the catalyst can be achieved.

The block diagram which shows simply the system configuration | structure of the internal combustion engine which concerns on one Example of this invention. The flowchart which shows the flow of control of the said Example. The characteristic view which shows the relationship between the intake air temperature and the fluctuation rate of average effective pressure. The characteristic view which shows the example of a setting of valve timing.

Hereinafter, the present invention will be described with reference to illustrated embodiments. FIG. 1 schematically shows a system configuration of an internal combustion engine to which a control device and a control method according to an embodiment of the present invention are applied.

The internal combustion engine 10 is a multi-cylinder spark ignition gasoline internal combustion engine, and an intake passage 12 and an exhaust passage 13 are connected to the combustion chamber 11 of each cylinder. The internal combustion engine 10 includes a turbocharger 14 that performs supercharging using exhaust energy as a supercharger that supercharges intake air, and an electric supercharger that performs supercharging when driven by an electric motor 16. 15.

In the turbocharger 14, a turbine 17 provided in the exhaust passage 13 and a first compressor 18 provided in the intake passage 12 are provided coaxially back to back on a single rotating shaft 19, and exhaust energy. As a result, the turbine 17 rotates the first compressor 18 to perform supercharging.

The exhaust passage 13 is provided with a bypass passage 20 that connects the exhaust passage 13 on the upstream side of the turbine 17 and the exhaust passage 13 on the downstream side so as to bypass (bypass) the turbine 17. A waste gate valve 21 whose opening degree can be adjusted is provided so as to adjust the flow rate of the exhaust gas flowing through the bypass passage 20.

The electric supercharger 15 is disposed in the intake passage 12 at a position different from the first compressor 18 of the turbocharger 14, and more specifically, is downstream of the first compressor 18. The second compressor 22 is disposed in the intake passage 12, and the second compressor 22 is rotationally driven by the electric motor 16. The exhaust passage 13 is provided with a second bypass passage 23 that bypasses the second compressor 22, and a bypass valve 24 whose opening degree can be adjusted is provided in the second bypass passage 23.

In addition, a recirculation passage 25 connecting the upstream intake passage 12 and the downstream intake passage 12 of the first compressor 18 is provided so as to release the pressure generated in the first compressor 18 during deceleration or the like. The recirculation passage 25 is provided with a recirculation valve 26 for adjusting the flow rate of the intake air passing through the recirculation passage 25.

In the intake passage 12, in order from the upstream side (the side far from the combustion chamber 11), an air cleaner 27 that removes foreign matter in the intake air, an air flow meter 28 that detects the intake air amount (intake air amount), and the above-mentioned first The first compressor 18 and the second compressor 22, an electronically controlled intake control valve 29 (so-called throttle valve) that adjusts the intake air amount, and a water-cooled intercooler 30 that cools the intake air are provided. The intercooler 30 performs heat exchange with the radiator 32 by the cooling water circulating in the cooling water circuit 31. The cooling water circuit 31 is provided with a water cooling pump 33 for circulating the cooling water.

In the exhaust passage 13, the turbine 17, the upstream catalyst 34 and the downstream catalyst 35 such as a three-way catalyst, and a muffler 36 for noise reduction are arranged in order from the upstream side (side closer to the combustion chamber 11). Is provided. In addition, air- fuel ratio sensors 37 and 38 for detecting the air-fuel ratio of the exhaust are provided on the downstream side of the catalysts 34 and 35, respectively.

Further, a valve timing changing mechanism 39A capable of changing the valve timing of the intake valve of the internal combustion engine and a valve timing changing mechanism 39B capable of changing the valve timing of the exhaust valve are provided.

The control unit 40 is capable of storing and executing various types of control, and based on detection signals from various sensors that detect engine operating conditions such as the air flow meter 28 and the air- fuel ratio sensors 37 and 38, the above-described waste gate valve. 21, control signals are output to the bypass valve 24, the recirculation valve 26, the intake control valve 29, the water cooling pump 33, the valve timing changing mechanisms 39A and 39B, and the operation thereof is controlled.

FIG. 2 is a flowchart showing a flow of control that is a main part of the present embodiment. This routine is stored in the control unit 40 and is repeatedly executed every predetermined period (for example, 10 ms).

In step S11, a predetermined idle operation condition that requires early activation of the catalysts 34 and 35, more specifically, a first idle retard operation (FIR) in which the ignition timing is largely retarded to raise the temperature of the catalysts 34 and 35. Determine if you are in a situation.

In step S12, it is determined whether or not the outside air temperature is equal to or lower than a predetermined temperature (for example, about 25 ° C.). In step S13, it is determined whether the ND select lever (shift position) of the automatic transmission is in the N range (or P range), that is, in the non-power transmission state.

If the above steps S11 to S13 are all affirmed, the process proceeds to step S14. If any of steps S11 to S13 is negative, the control of the present embodiment, which will be described later, is not performed, and the routine proceeds to step S18 where normal control is performed.

In step S14, the electric supercharger 15 is operated. That is, during the FIR, the electric supercharger 15 performs supercharging to compress the intake air and raise the intake air temperature.

In step S15, the intake air amount is controlled according to the boost pressure (boost) so that the intake air amount does not become excessive due to supercharging. Specifically, while obtaining a desired intake amount by the electric supercharger 15 and the intake control valve 29, the valve timing changing mechanisms 39A and 39B promote the in-cylinder oxidation state or optimize the in-cylinder residual gas amount. The intake control valve 29 and the valve timing changing mechanisms 39A and 39B are controlled in a coordinated manner.

In step S16, the waste gate valve 21 is fully opened. As a result, the flow rate of the exhaust gas passing through the turbine 17 is suppressed to a minimum, and the decrease in the exhaust gas temperature is suppressed, so that the catalyst 34, 35 can be raised quickly.

In step S17, the water cooling pump 33 is stopped, and the supply of cooling water to the intercooler 30 is stopped. Thus, by stopping the supply of the cooling water to the intercooler 30, it is possible to suppress the intake air that has been heated by supercharging by the electric supercharger 15 from being cooled again by heat exchange in the intercooler 30. .

Next, the function and effect of this embodiment will be described. When the outside air temperature is 25 ° C. or less during FIR such as when starting a cold machine, if low temperature fresh air is supplied to the combustion chamber 11 as it is, combustion becomes unstable. In addition, since the cylinder and the intake valve are also cooled, the fuel vaporization rate is poor regardless of the fuel injection mode (port fuel injection or cylinder fuel injection), and HC (hydrocarbon substances) and PM (particulate matter) tends to increase.

In this embodiment, the startability and warm-up performance can be improved by raising the temperature of the intake air by compressing the intake air by the electric supercharger 15 during FIR. In addition, the turbocharger 14 need not be driven to raise the temperature by performing supercharging by the electric supercharger 15. Therefore, the amount of exhaust gas passing through the turbine 17 can be suppressed by controlling the waste gate valve 21 in the opening direction. Particularly preferably, the waste gate valve 21 is fully opened, so that the amount of exhaust gas passing through the turbine 17 can be minimized. As a result, more exhaust gas that has not been deprived of heat by the turbine can be supplied to the catalysts 34, 35, and the temperature rise of the catalysts 34, 35 can be promoted to achieve early activation.

FIG. 3 shows the relationship between the variation rate Cpi of the average effective pressure Pi, which is a parameter related to the combustion stability, and the intake air temperature. For example, even when the outside air temperature is a low temperature state of about 7 ° C. or lower as shown by the arrow Y1 in FIG. The variation rate Cpi of the average effective pressure Pi can be reduced, and the combustion stability can be improved.

In this embodiment, since the intake air compressed by the electric supercharger 15 is sufficiently supplied to the combustion chamber 11 due to the compression of the intake air, the intake air amount is increased by the electric supercharger 15 and the intake control valve 29. By controlling this, the degree of freedom of setting the valve timing changing mechanisms 39A and 39B is controlled by the conventional intake control valve 29 and the valve timing changing mechanisms 39A and 39B while securing a desired intake amount. It can be increased compared to the method. Therefore, for example, by reducing the exhaust valve opening timing EVO, the in-cylinder oxidation state is promoted to reduce HC, or by optimizing the valve timing, the in-cylinder residual gas amount is optimized and combustion stabilization is given priority. It can be secured. In addition, by controlling the valve timing appropriately, the exhaust performance at start-up (HC, combustion stability (average effective pressure fluctuation rate Cpi)) is greatly improved, and the PM emission amount in a cryogenic environment of -7 ° C or lower, for example, Reduction and the like can be achieved.

FIG. 4 shows an example of setting the valve timing. FIG. 4A shows a typical setting example of valve timing at the time of general FIR, and both the exhaust valve closing timing EVC and the intake valve opening timing IVO are set near the top dead center. In contrast to such a normal setting example, in this embodiment, as shown in FIG. 4B, it is possible to secure the intake amount as a so-called mirror cycle in which the valve timing of the intake valve is greatly advanced. . In the second setting example of the present embodiment shown in FIG. 4C, the exhaust valve opening timing EVO is advanced to near the bottom dead center, and the exhaust valve closing timing EVC is slightly less than the intake valve opening timing IVO. By advancing and applying a slight overlap, scavenging of the in-cylinder residual gas can be promoted. Further, since the fresh air is compressed by the electric supercharger 15 and the compressed air is introduced into the combustion chamber at a high temperature, the combustion itself is stable and stable combustion can be realized with little flow. Furthermore, since the valve and the piston crown are also warmed by the high-temperature air, the unburned fuel can be reduced and the PM emission amount can be greatly reduced even in the region where the wall temperature at the time of starting the engine is low.

Furthermore, in this embodiment, the water cooling pump 33 is stopped and the circulation of the cooling water is stopped as described above, so that the intake air temperature raised by supercharging does not decrease again due to heat exchange. It should be noted that the flow of cooling water flowing through the internal combustion engine such as the cylinder head may be stopped, and the operation of other water temperature control devices may be stopped.

As described above, the present invention has been described based on specific examples. However, the present invention is not limited to the above-described examples, and includes various modifications and changes. For example, the present invention can be applied to an internal combustion engine that does not include a valve timing changing mechanism. In this case, the intake control valve may be controlled according to the supercharging pressure so as to obtain a desired intake amount.

Claims (7)

1. A turbocharger in which a compressor and a coaxial turbine are provided in the exhaust passage for supercharging intake air;
   An electric supercharger provided in the intake passage at a position different from the compressor;
   A bypass passage connecting an upstream exhaust passage and a downstream exhaust passage of the turbine so as to bypass the turbine;
   In the control method of the internal combustion engine, which is provided in the bypass passage and has a waste gate valve that adjusts the flow rate of the exhaust gas flowing through the bypass passage,
   A control method for an internal combustion engine that opens the waste gate valve and drives the electric supercharger when idling.
2. The method for controlling an internal combustion engine according to claim 1, wherein the waste gate valve is fully opened during the idling.
3. 3. The control method for an internal combustion engine according to claim 1, wherein an intake control valve is provided in the intake passage, and the intake air amount is controlled using the intake control valve during the idling.
4. A valve timing changing mechanism capable of changing the valve timing of at least one of the intake valve and the exhaust valve, and at the time of idling, using the valve timing changing mechanism, the intake amount, the in-cylinder oxidation state, or the in-cylinder residual gas amount, The method for controlling an internal combustion engine according to claim 3, wherein:
5. A water-cooled intercooler is provided in the intake passage,
   The method for controlling an internal combustion engine according to any one of claims 1 to 4, wherein supply of cooling water to the intercooler is stopped during the idling.
6. The method for controlling an internal combustion engine according to any one of claims 1 to 5, wherein the flow of cooling water flowing through the internal combustion engine is stopped during the idling.
7. A turbocharger in which a compressor and a coaxial turbine are provided in the exhaust passage for supercharging intake air;
   An electric supercharger provided in the intake passage at a position different from the compressor;
   A bypass passage connecting an upstream exhaust passage and a downstream exhaust passage of the turbine so as to bypass the turbine;
   A waste gate valve that is provided in the bypass passage and adjusts the flow rate of the exhaust gas flowing through the bypass passage;
   When idling, the waste gate valve is opened, and a controller that drives the electric supercharger,
   A control apparatus for an internal combustion engine.

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