JP2011122466A - Method of inhibiting knocking of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a defect that although ignition timing is retarded to avoid the occurrence of knocking when the knocking is detected in an internal combustion engine equipped on a vehicle or the like, retarding of the ignition timing causes the defect that combustion becomes slow and fuel economy is deteriorated. <P>SOLUTION: The internal combustion engine includes: a supercharger including a turbine which includes a waste gate valve controlling an amount of exhaust gas and is driven with the exhaust gas, and a compressor driven by the turbine to compress intake air; an exhaust gas recirculation device refluxing a part of the exhaust gas and mixing it with the intake air; and a throttle valve controlling an intake air amount supercharged. In the internal combustion engine, knocking occurring during performance of exhaust gas recirculation control is detected (S1), the waste gate valve is controlled to a close side and the throttle valve is controlled to a close side. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a knock suppression method in an internal combustion engine including a supercharger that compresses intake air using exhaust gas and an exhaust gas recirculation device that mixes part of the exhaust gas with intake air.

  Conventionally, in an internal combustion engine equipped with an exhaust gas recirculation device, exhaust gas recirculation control is performed by an exhaust gas recirculation device for the purpose of reducing NOx and pumping loss in an operating state in a partial load region, thereby purifying exhaust gas. And improving fuel economy. In such an internal combustion engine, for example, the one disclosed in Patent Document 1 calculates the basic ignition timing according to the operating state, and the basic ignition timing is advanced by a required advance value based on the amount of exhaust gas that is recirculated. Further, there is known an ignition timing control technique in which, when knocking is detected, the ignition timing corrected based on the detected value is retarded to near the knocking generation limit.

JP-A-8-151971

  However, with such a configuration, when knocking is detected, the ignition timing is retarded to avoid the occurrence of knocking. However, in order to retard the ignition timing, combustion is performed. It became sluggish and fuel consumption decreased. Further, if the ignition timing is retarded, ignition is performed in a state where the compression ratio is high, so that the required voltage at the time of ignition becomes high, so that there is a problem that the spark plug is consumed quickly. This can also damage the spark plug if the spark plug is in poor condition, for example when the gap between the electrodes is wide. In addition, the retarded state reduces the combustion state, resulting in a reduction in fuel consumption.

  Therefore, the present invention aims to eliminate such problems.

  That is, the knock suppression method for an internal combustion engine according to the present invention includes a turbine that includes a waste gate valve that controls the amount of exhaust gas and is driven by the exhaust gas, and a compressor that is driven by the turbine and compresses intake air. In an internal combustion engine comprising an exhaust gas recirculation device capable of recirculating a part of exhaust gas and mixing it with intake air, and a throttle valve for controlling the amount of intake air to be supercharged, the exhaust gas recirculation control It is characterized in that knocking occurring during the operation is detected, the waste gate valve is controlled to the closed side, and the throttle valve is controlled to the closed side.

  With such a configuration, when knocking is detected, the back pressure increases by closing the waste gate valve. As a result, the rotation of the turbocharger turbine increases, so that the turbocharging pressure of the compressor increases and the amount of exhaust gas flowing into the exhaust gas recirculation device increases, and the exhaust gas recirculated in the supercharging operation region. It becomes possible to increase the amount of gas. In addition, simultaneously with this, the throttle valve is controlled to the closed side, so that it is possible to suppress an increase in the intake amount of fresh air against an increase in the supercharging pressure. As a result, the ratio of the amount of exhaust gas recirculated with respect to the total amount of intake air increases, making it possible to improve the knocking resistance and eliminating the need to retard the ignition timing.

  Therefore, in order to avoid knocking, it is possible to maintain the original fuel consumption that is reduced by retarding the ignition timing.

  The present invention is configured as described above, and when knocking exceeding a predetermined value is detected, the waste gate valve is controlled to the closed side and the throttle valve is controlled to the closed side, whereby the recirculated exhaust gas is controlled. Increases the amount and increases its ratio to the total intake air volume, improving knocking resistance and preventing the ignition timing from being retarded. can do.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which shows schematic structure of embodiment of this invention. The flowchart which shows the outline of the control procedure of the embodiment.

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

  The embodiment shown in FIG. 1 is an exhaust gas recirculation device for mixing a part of exhaust gas with intake air, for example, a four-cylinder spark ignition type gasoline engine (hereinafter referred to as engine) 1 that is an internal combustion engine. (Hereinafter referred to as an EGR device) 2, an exhaust turbocharger 5 including a compressor 3 that compresses intake air and a turbine 4 that rotates when the exhaust gas is introduced to drive the compressor 3; An intercooler 6 that cools the supercharged air that is provided downstream and is output from the compressor 3 is provided.

  The EGR device 2 includes an exhaust gas recirculation conduit (hereinafter referred to as an EGR conduit) 9 that communicates with an exhaust manifold 7 that is an exhaust system and communicates with an intake conduit 8a that constitutes an intake system 8, and an EGR conduit. 9 is provided with an exhaust gas recirculation valve (hereinafter referred to as EGR valve) 10 that controls the amount of exhaust gas (hereinafter referred to as EGR gas) that is recirculated.

  One end (upstream end) of the EGR pipe 9 is connected to an exhaust manifold 7 connected to the turbine 4, and the other end (downstream end) is connected to a surge tank 8 b of the intake system 8. The EGR pipe 9 is provided with an EGR valve 10 in order to control the amount of EGR gas in accordance with the operating state of the engine 1. The opening and closing of the EGR valve 10 is controlled by an electronic control unit 11 that controls the operation of the engine 1.

  The turbine 4 of the exhaust turbocharger 5 is provided with a waste gate valve 12 for discharging a part of the exhaust gas without passing through the turbine 4. The waste gate valve 12 can be controlled to open and close at a desired timing by the electronic control unit 11. The waste gate valve 12 adjusts the amount of exhaust gas flowing into the turbine 4 by opening and closing the exhaust gate supercharger 5. The rotation speed is controlled.

  A throttle valve 13 for controlling the amount of intake air is provided upstream of the surge tank 8b of the intake system 8. The throttle valve 13 is a so-called electronic throttle, which is driven by an electromagnetic actuator 14 and is opened and closed by operating the actuator 14 in accordance with an operation amount of an accelerator pedal (not shown), that is, a depression degree. A throttle body (not shown) with a built-in throttle valve 13 so that a throttle sensor 15 for detecting the opening degree of the throttle valve 13 corresponding to the opening / closing operation of the throttle valve 13 operates according to the operation of the throttle valve 13. ).

  The electronic control unit 11 includes a microcomputer 11a, a memory 11b, an input interface 11c, and an output interface 11d. The microcomputer 11a controls the operation of the engine 1 by executing various programs described below stored in the memory 11b. Information necessary for operation control of the engine 1 is input to the microcomputer 11a via the input interface 11c, and the microcomputer 11a is connected to the fuel control valve, the EGR valve 10, the waste gate valve 12, the actuator 14, and the like. The control signal is output via the output interface 11d.

Specifically, an intake pressure signal a output from the intake pressure sensor 16 for detecting the pressure in the surge tank 8b and an output speed sensor 17 for detecting the engine speed are output to the input interface 11c. A rotation speed signal b, an opening degree signal c output from the throttle sensor 15, a knock signal d output when knocking occurs from the knock sensor 18 attached to the outer wall of the cylinder, and an O ₂ sensor attached to the exhaust system. An output voltage signal or the like is input. On the other hand, from the output interface 11d, an opening / closing signal e for the actuator 14 that drives opening / closing of the throttle valve 13, an ignition signal for the ignition plug (not shown), and a fuel injection signal for the fuel control valve (not shown). The open / close signal f is output to the EGR valve 10 and the open / close signal g is output to the waste gate valve 12.

  In such a configuration, the electronic control unit 11 sets the intake pressure signal a output from the intake pressure sensor 16 and the rotation speed signal b output from the rotation speed sensor 17 as main information according to the driving state. The fuel injection amount is calculated using the determined coefficient, the fuel injection time corresponding to the fuel injection amount, that is, the energization time for the fuel injection valve, is determined, and the fuel injection valve is controlled based on the determined energization time. Inject into the intake system. Such fuel injection control itself may apply what is known in this field.

  Further, an EGR control program for controlling the opening degree of the EGR valve 10 according to the operating state of the engine 1 to perform EGR control is stored in the electronic control unit. This EGR control program may be widely known in this field.

  Further, the electronic control unit 4 detects knocking that occurs during the exhaust gas recirculation control, and controls the waste gate valve 12 to the closed side when the detected knocking exceeds a predetermined value, and the throttle A knock suppression program for controlling the valve 13 to the closed side is stored. This knock suppression program is executed during execution of EGR control. Therefore, the EGR valve 10 is opened.

  In FIG. 2, first, in step S1, knocking is detected based on the knocking signal d output from the knock sensor 18. In this embodiment, knocking is detected when the strength of knocking exceeds a predetermined value. The predetermined value is for determining that the output signal output from the knock sensor 18 due to various vibrations of the engine 1, for example, vibrations due to opening / closing of the intake / exhaust valve, rotation of the alternator, etc. is not knocking. If knocking has not occurred, this control is terminated.

  In step S2, the waste gate valve 12 is controlled to the closed side, and the throttle valve 13 is also controlled to the closed side. The closing amounts of the waste gate valve 12 and the throttle valve 13 are set according to each operation region. By controlling the waste gate valve 12 to the closed side, the amount of exhaust gas discharged around the turbine 4 is reduced. Therefore, the back pressure in the exhaust manifold 7 increases, and the flow rate of the exhaust gas flowing into the turbine 4 increases. As a result, the rotational speed of the turbine 4 increases, the rotational speed of the compressor 3 increases, the supercharging pressure increases, and the supply amount of fresh air increases.

  While the turbocharger 5 is controlled in this way, even if the supercharging pressure increases and the supply amount of fresh air increases, the fresh air sucked into the cylinder is controlled by controlling the throttle valve 13 to the closed side. The amount of does not increase. Therefore, the amount of EGR gas that flows into the EGR pipe 9 of the EGR device 2 increases as the back pressure increases, but the EGR rate is increased by the amount of EGR gas increased by limiting the amount of fresh air sucked in. Will increase. As a result, the amount of retarding the ignition timing in order to suppress knocking is offset by the amount by which the ignition timing is advanced by the increase in the EGR rate, so that the ignition timing is substantially retarded. Even if not, knocking can be suppressed.

  In this way, when knocking is detected, the waste gate valve 12 and the throttle valve 13 are only controlled to the closed side, and the ignition timing is not retarded, resulting in a reduction in fuel consumption and damage to the spark plug. It is possible to eliminate problems caused by the retarded ignition timing.

  For detecting knocking, an in-cylinder pressure sensor can be used in addition to the knock sensor used in the above-described embodiment. Alternatively, instead of these sensors, an ionic current flowing in the combustion chamber after combustion may be detected by a spark plug, and the occurrence of knocking may be detected based on the characteristics of the detected ionic current.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  As an application example of the present invention, the present invention can be applied to an internal combustion engine including an EGR device and a turbocharger including a waste gate valve, for example, a spark ignition type gasoline engine or a diesel engine.

DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Exhaust gas recirculation device 3 ... Compressor 4 ... Turbine 5 ... Turbocharger 11 ... Electronic control unit 11a ... Microcomputer 11b ... Memory 11c ... Input interface 11d ... Output interface 12 ... Waste gate valve 13 ... Throttle Valve 18 ... Knock sensor

Claims (1)

A turbocharger having a waste gate valve for controlling the amount of exhaust gas and driven by exhaust gas and a compressor driven by the turbine and compressing intake air, and a part of the exhaust gas is recirculated and sucked In an internal combustion engine comprising an exhaust gas recirculation device that can be mixed with air and a throttle valve that controls the amount of supercharged intake air, knocking that occurs during the execution of exhaust gas recirculation control is detected,
A knock suppression method for an internal combustion engine, wherein a waste gate valve is controlled to a closed side and a throttle valve is controlled to a closed side.

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