JP5321147B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device that controls an internal combustion engine, and more particularly to a control device that reduces a start shock of the internal combustion engine.

  Conventionally, when starting an internal combustion engine such as an engine mounted on a vehicle, the torque at the first explosion of the internal combustion engine is increased by closing the throttle valve during cranking and quickly developing a negative pressure downstream of the throttle valve. Some control is performed to suppress the shock at the start.

  As such control, during engine cranking, the negative pressure development in the intake passage downstream of the throttle valve is strengthened more than usual, and then the amount of air filled in the combustion chamber when the first fuel injection is performed and ignition is performed. An engine start control device (refer to Patent Document 1) having an intake valve variable control means for variably controlling an intake valve so as to be reduced than usual is disclosed.

JP 2007-71083 A

  When the air inflow amount is reduced by closing the throttle valve in order to reduce the torque at the time of complete explosion as in Patent Document 1, the timing of the negative pressure peak and the complete explosion do not coincide. In such a case, the continuity of torque is lost and a shock occurs.

  Further, since the startability of the engine is reduced by reducing the air inflow amount, a start failure may occur when the start conditions are bad, such as at high altitude, at a high temperature, or using heavy gasoline.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a control device for an internal combustion engine that can reduce engine start shock while maintaining startability.

According to one embodiment of the present invention, a throttle valve (24) for adjusting the amount of air flowing into the intake passage (20) of the internal combustion engine (10), and a fuel injection for adjusting the amount of fuel injected into the internal combustion engine (10). An internal combustion engine control device (40) for controlling the start of the internal combustion engine (10) by controlling the valve (26) and the cranking means (12) for cranking the internal combustion engine (10), When the start request of the internal combustion engine (10) is detected, the throttle valve (24) is closed, the internal combustion engine (10) is cranked by the cranking means (12), and the fuel is injected from the fuel injection valve (26). before starting the injection, it causes opening the throttle valve (24) to a predetermined opening degree, the peak of the negative pressure internal combustion engine of an intake passage that develops by closing the throttle valve (24) (20) (10) End so that explosion and simultaneous, and controlling the timing of opening of the throttle valve (24) for injection of fuel from the fuel injection valve (26). In addition, although the code | symbol corresponding to embodiment of this invention was attached | subjected, it is not limited to this structure.

According to the present invention, when the internal combustion engine is started, after the throttle valve is closed once, the throttle valve is opened and the throttle valve is closed before the fuel injection is started . The throttle valve opening timing for fuel injection from the fuel injection valve is controlled so that the negative pressure peak coincides with the complete explosion of the internal combustion engine. As well as being able to ensure continuity with the negative pressure development peak in the intake passage, it is possible to suppress a shock when starting the internal combustion engine.

It is explanatory drawing of the intake / exhaust system centering on the engine of embodiment of this invention. It is a timing chart of engine start control of an embodiment of the present invention. 3 is a flowchart of engine start control according to the embodiment of the present invention.

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

  FIG. 1 is an explanatory diagram of an intake / exhaust system centering on an engine 10 of the present invention.

  The engine 10 as an internal combustion engine includes an intake passage 20 that supplies air and an exhaust passage 30 that discharges exhaust gas.

  The intake passage 20 includes a throttle chamber 23 in the middle thereof. The throttle chamber 23 includes a throttle valve 24 inside. The throttle valve 24 adjusts the inflow air amount and supplies it to the engine 10 by changing its opening degree under the control of the ECU 40 described later.

  An intake collector 22 having an enlarged inner diameter of the intake passage 20 is connected to the throttle chamber 23. The intake collector 22 temporarily stores intake air and suppresses intake pulsation. The intake collector 22 is provided with a vacuum sensor 25. The vacuum sensor 25 detects the negative pressure of the intake manifold 21 and detects the intake air amount.

  A fuel injection valve 26 is provided near the connection between the intake passage 20 and the engine 10. The fuel injection valve 26 injects fuel in the form of a mist and mixes it with the intake air introduced from the intake passage 20 to generate an air-fuel mixture, which is supplied to the engine 10.

  The engine 10 is driven by the energy generated by the combustion of the air-fuel mixture, and transmits the output to the outside through the connected crankshaft and flywheel 11.

  A large number of teeth are formed on the outer periphery of the flywheel 11, and a starter motor 12 (cranking means) that cranks the engine 10 by applying a rotational driving force to the engine 10 by a gear engaged with the teeth is provided.

  The exhaust gas after combustion of the engine 10 is exhausted after being purified by the catalyst 31 from the exhaust passage 30.

  The engine control unit (ECU) 40 is a control device that controls the operation of the engine 10 by controlling these various components.

  Next, start control of the engine 10 configured as described above will be described.

  Conventionally, when the engine 10 is started, the throttle valve 24 is closed to reduce the amount of intake air flowing into the engine 10 and the negative pressure on the downstream side of the intake passage 20 is rapidly developed, and then the throttle valve 24 is opened. The engine 10 is started by injecting fuel from the fuel injection valve 26. Such control can suppress a shock when the engine 10 is started.

  FIG. 2A is a timing chart in the starting control of the conventional engine 10 as described above.

  When a request for starting the engine 10 is generated when the engine 10 is stopped, the ECU 40 controls the throttle valve 24 to close the throttle valve 24. Then, the starter motor 12 is controlled to crank the engine 10. Thereby, the negative pressure on the downstream side of the intake passage 20 develops.

  Thereafter, when the rotational speed of the engine 10 is started by cranking, the ECU 40 opens the throttle valve 24 to flow in intake air, and controls the fuel injection valve 26 to start fuel injection. Then, the engine 10 is started.

  Thereby, the engine 10 is started, and the start of the engine 10 is completed at the timing of “complete explosion” shown in the figure. Thereafter, the rotational speed of the engine 10 is controlled by the inflow intake air amount and the fuel injection amount.

  With such control, by reducing the inflow intake air amount when the engine 10 is started, it is possible to prevent the output at the time of complete explosion from becoming excessive and causing a shock.

  However, if the peak of the negative pressure development in the intake passage 20 due to the closing of the throttle valve 24 does not coincide with the timing of the complete explosion of the engine 10, the continuity of torque is lost and a shock occurs in the engine 10. In particular, when a shock occurs at the start of the engine 10 that is not intended by the driver, such as restarting the engine 10 after idling stop or restarting the engine 10 after stopping the running engine 10, the driver feels uncomfortable. , Merchantability is reduced.

  Therefore, in the embodiment of the present invention, control is performed so that the shock of the engine 10 can be suppressed and startability of the engine 10 can be secured by a characteristic configuration as described below.

  FIG. 2B is a timing chart in the start control of the engine 10 according to the embodiment of the present invention.

  As in the case of FIG. 2A described above, when a request for starting the engine 10 is generated when the engine 10 is stopped, the ECU 40 controls the throttle valve 24 to close the throttle valve 24. Then, the starter motor 12 is controlled to rotate the engine 10.

  Here, the ECU 40 opens the throttle valve 24 to a predetermined opening after a predetermined time has elapsed since the throttle valve 24 was closed. When a predetermined time elapses after the throttle valve 24 is opened to a predetermined opening, the fuel injection valve 26 is controlled to start fuel injection, and the engine 10 is started.

  Thus, by opening the throttle valve 24 earlier than the fuel injection timing, it is possible to match the timing of the complete explosion of the engine 10 and the peak of the negative pressure development of the intake passage 20. Thereby, the shock of the engine 10 can be reduced while maintaining the continuity of torque.

  The ECU 40 controls the opening of the throttle valve 24 so that the complete explosion timing of the engine 10 coincides with the peak of negative pressure development.

  Specifically, the development of the negative pressure in the intake passage 20 can be estimated from the closing period of the throttle valve 24, the opening timing, and the valve opening at the time of opening. Therefore, the ECU 40 controls the timing of fuel injection so that the estimated negative pressure peak matches the complete explosion of the engine 10.

  For the estimation of the negative pressure, for example, a map or table is held in advance in the ECU 40, and the ECU 40 refers to the map or table so that the valve is opened during the closing period of the throttle valve 24. And the opening of the valve at the time of opening is controlled.

  Further, the closing period of the throttle valve 24, the valve opening timing, and the valve opening degree at the time of valve opening are set according to the degree of shock suppression in the shock suppression processing, as will be described later with reference to FIG. When giving priority to suppressing the shock of the engine 10, the valve closing period is lengthened. When giving priority to the startability of the engine 10, the valve closing period is shortened.

  FIG. 3 is a flowchart of the start control of the engine 10 according to the embodiment of the present invention.

  The flowchart shown in FIG. 3 is executed when the ECU 40 detects that an engine start request has occurred while the engine 10 is stopped.

  The engine 10 is stopped by another control by the ECU 40. For example, the engine 10 is stopped during a so-called idle stop when the vehicle is stopped or during motor travel in a hybrid vehicle (HEV). Moreover, it stops also when a driver | operator instruct | indicates the stop of the engine 10. FIG.

  From this state, when it is detected that a start request or an acceleration request made by the driver is made by operating the accelerator pedal 27, the depression amount of the accelerator pedal 27, the vehicle speed, the engine rotation speed, etc. Thus, the ECU 40 detects the generation of the engine start request and the required torque. Further, when the start of the engine 10 is instructed by the driver, the generation of the engine start request is detected (start request detection means, request torque detection means).

  First, the ECU 40 determines whether or not the start request for the engine 10 is the first start (S101).

  The first start is the first start after the vehicle on which the engine 10 is mounted is started. On the other hand, an engine start request from an idling stop, an engine start request from an engine stop during traveling in HEV, and the like are determined not to be the first start.

  When it is determined that the engine 10 is started for the first time, the process proceeds to step S102, and it is determined whether or not the water temperature of the engine 10 is equal to or lower than a predetermined water temperature and is extremely low.

  When the water temperature is extremely low (for example, 0 ° C. or lower), the temperature of each component including the engine 10 is low, and it is difficult to start the engine 10 due to an increase in friction or a decrease in ignitability.

  Therefore, in such a case, the ECU 40 controls to give priority to the startability (S103). More specifically, the engine 10 is started immediately without closing the throttle valve 24 in response to the engine start request.

  When it is determined in step S101 that the engine 10 is not started for the first time, the process proceeds to step S104, and the ECU 40 determines whether or not at least one preset difficult-to-start element is established.

  The difficult starting element is a condition that prevents the engine 10 from starting. For example, when the environmental temperature is high (hot area), when the environmental oxygen concentration is low (high altitude), when the fuel is heavy gasoline, If there is a failure in a part, etc.

  Further, when the cumulative travel distance of the engine 10 is less than the predetermined distance, the engine 10 and the transmission are not sufficiently rubbed together and the friction is large, so that it is a difficult start requirement.

  When it is determined that at least one of these difficult-to-start elements is established, the process proceeds to step S105. If no start difficult element is established, the process proceeds to step S108.

  In step S105, it is determined whether only one difficult start requirement is satisfied or two or more.

  When it is determined that two or more difficult start requirements are satisfied, the ECU 40 sets the degree of shock suppression control to a low level in order to improve startability (S106). On the other hand, when it is determined that only one difficult start requirement is satisfied, the ECU 40 sets the degree of shock suppression control to a medium level in order to balance startability and shock suppression (S107).

  In step S108, the ECU 40 determines the magnitude of the required torque for the engine 10 from the driver. The required torque is calculated by the ECU 40 using a map or the like from the rotational speed of the engine 10, the vehicle speed, the opening degree of the accelerator pedal 27, and the like. Then, it is determined whether the calculated required torque level is one of three levels of large, medium, and small.

  If the required torque is large, the process branches to step S109. If the required torque is medium, the process branches to step S110. If the required torque is small, the process branches to step S111.

  In step S109, since the required torque is large, it is required to follow the torque quickly by starting the engine 10. In this case, priority is given to startability, and the degree of shock suppression processing is set to a low level.

  On the other hand, in step S111, since the required torque is small, the degree of shock suppression control is set to a high level in order to give priority to shock suppression over startability of the engine 10.

  In step S110, the degree of shock suppression control is set to a medium level as an intermediate process between steps S109 and S11.

  When these shock suppression processes (S103, S106, S107, S109 to S111) are finished, the process according to this flowchart is finished.

  The shock suppression process of FIG. 3 will be described.

  As described above, in the embodiment of the present invention, the degree of shock suppression is set according to the closing period of the throttle valve 24.

  In step S103 described above, in order to prioritize the startability, the process for suppressing the shock is not performed. Therefore, the engine 10 is started without closing the throttle valve 24 as shown in FIG.

  In this case, a shock is generated as the engine 10 is started. However, the driver is involved in starting the engine, and the starting shock is allowed.

  In steps S106 and S109 described above, the degree of shock suppression is set to a low level, and startability is given priority. Therefore, the period during which the throttle valve 24 is closed is minimized, and control is performed so as to give priority to processing related to startability (fuel injection amount, fuel injection timing).

  Note that step S106 is a case where there is a factor that hinders the startability of the engine 10, and priority is given to the startability. On the other hand, in step S109, the driver's required torque is high, and control is performed so as to start quickly. The shock suppression processing in steps S106 and S109 may be the same or different.

  Further, in step S111 described above, priority is given to shock suppression over engine startability. Therefore, by setting the closing period of the throttle valve 24 to be large, the negative pressure in the intake passage 20 is greatly developed to further enhance the shock suppression effect. In this way, after the closing period of the throttle valve 24 is set, the timing of opening the throttle valve 24 and the timing of fuel injection are set so that the complete explosion of the engine 10 and the peak of the negative pressure coincide with each other. To do. Thereby, the effect of suppressing the shock of the engine 10 is maximized.

  In this case, the period from the start request of the engine 10 to the complete explosion is extended, but the shock of the engine is suppressed, and the driver is not made aware of the stop and start of the engine 10. Further, since there is no factor that hinders the startability of the engine 10, even if the period for closing the throttle valve 24 is extended, the startability is not affected.

  In steps S107 and S110 described above, the degree of shock suppression is set to a medium level. Therefore, the period of the opening degree of the throttle valve 24 is set to an intermediate control between the aforementioned step S106 or S109 and step S111.

  In the process of FIG. 3, the degree of shock suppression is divided into several stages. However, the present invention is not limited to this, and the closing period of the throttle valve 24, the timing of valve opening, and the valve opening at the time of valve opening are not limited thereto. By appropriately changing the timing and amount of fuel injection by the fuel injection valve 26, it is possible to control steplessly between control giving priority to startability and control giving priority to shock suppression.

  As described above, in the embodiment of the present invention, when the engine 10 is started, the throttle valve 24 is closed during cranking in order to suppress the torque at the time of complete explosion, and the negative pressure downstream of the intake passage 20 is developed. Let Further, the throttle valve 24 is opened before the fuel injection timing. By configuring in this way, it is possible to suppress the mismatch between the peak of the negative pressure development and the timing of the complete explosion of the engine 10, maintain the continuity of torque, and reduce the start shock of the engine 10. it can.

  In the embodiment of the present invention, when there is a condition that makes it difficult to start the engine 10, control is performed so that the startability is given priority over the reduction of the start shock. Thereby, suppression of the start shock of the engine 10 and startability can be made compatible.

  In the embodiment of the present invention, the starter motor 12 is provided as the cranking means for cranking the engine 10, but the invention is not limited to this. For example, a motor generator in HEV may be used as the cranking means.

10 Engine 11 Flywheel 12 Starter motor (cranking means)
DESCRIPTION OF SYMBOLS 20 Intake passage 21 Intake manifold 22 Intake collector 23 Throttle chamber 24 Throttle valve 25 Vacuum sensor 30 Exhaust passage 31 Catalyst 40 Engine control unit (control device)

Claims (2)

Controlling a throttle valve for adjusting the amount of air flowing into the intake passage of the internal combustion engine, a fuel injection valve for adjusting the amount of fuel injected into the internal combustion engine, and a cranking means for cranking the internal combustion engine; A control device for an internal combustion engine for controlling start of the internal combustion engine,
When a request to start the internal combustion engine is detected,
Closing the throttle valve;
Cranking the internal combustion engine by the cranking means;
Before starting the fuel injection from the fuel injection valve, the throttle valve is opened to a predetermined opening and the negative pressure peak of the intake passage developed by closing the throttle valve is A control device for an internal combustion engine, wherein the timing of opening the throttle valve with respect to fuel injection from the fuel injection valve is controlled so as to coincide with a complete explosion of the internal combustion engine. 2. The control device for an internal combustion engine according to claim 1 , wherein the timing of complete explosion of the internal combustion engine is controlled by a closing period of the throttle valve, a timing of opening the valve, and a valve opening degree when the valve is opened. .

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