JP2008286044A - Combustion control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent premature ignition of an internal combustion engine by eliminating a high voltage diode without providing any other circuit structure replacing the high voltage diode. <P>SOLUTION: The internal combustion engine provided with a switching transistor 2 controlling turning-on/turning-off of primary current of a spark plug 1 by transition operation based on ignition pulse received from ECU, and a spark plug 3 discharging electricity with receiving secondary induced electromotive force of the ignition coil 1, is provided with a control table storing operation conditions defined based on engine speed and demand load, and the minimum pulse width Ton of ignition pulse SG with which the spark plug 3 can perform ignition under the operation condition with keeping correlation thereof. The ECU outputs ignition pulse of the minimum pulse width Ton corresponding to the operation condition at that time detected by referring to the control table to prevent abnormal ignition operation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a combustion control apparatus for an internal combustion engine that prevents an abnormal discharge of a spark plug without providing a high voltage diode by supplying an optimal ignition pulse according to an operating state.

  In general, in a combustion apparatus for an internal combustion engine, an ignition pulse is generated by electronically controlling a fuel injection amount and ignition timing for each cylinder in real time by an ECU. Here, when the ignition timing is the falling timing of the ignition pulse, it is necessary to take measures to prevent early ignition at the rising timing of the ignition pulse. Therefore, in order to prevent such a malfunction, a high voltage diode is generally arranged between the secondary coil of the ignition coil and the ignition plug in a direction that prevents early ignition (discharge).

  However, since the high voltage diode is disposed on the secondary side of the ignition coil, there is a problem that failure is unavoidable due to aging. In view of this problem, an ignition device that does not use a high-voltage diode has also been proposed (for example, Patent Document 1 and Patent Document 2).

Here, in the invention described in Patent Document 1, a time constant circuit is provided on the input side of the switching transistor, and early ignition is prevented by slowing the rising of the ignition pulse. On the other hand, the invention described in Patent Document 2 employs a configuration that electronically opens and closes the secondary side of the ignition coil.
JP-A-8-277769 Japanese Patent Laid-Open No. 9-088793

  However, the invention described in Patent Document 1 has a drawback in that the time constant circuit also dulls the fall of the ignition pulse in the same manner, and the secondary induced voltage is essential. On the other hand, in the invention described in Patent Document 2, since it is necessary to provide a switching circuit in the high-voltage circuit, it is not easy to select components, and the manufacturing cost increases unnecessarily.

  In addition, any of the above-described inventions simply have a function for preventing the malfunction of the spark plug, and the original ignition operation cannot be optimized. In the first place, in order to maintain stable ignition and combustion operation of an internal combustion engine for a long period of time, a configuration that not only prevents early ignition but also stably realizes an optimal ignition operation according to the operation state is desired.

  The present invention has been made on the basis of the above-mentioned idea. The first object of the present invention is to eliminate the high-voltage diode and to quickly ignite the internal combustion engine without providing any other circuit configuration in place of the high-voltage diode. It is providing the combustion control apparatus which prevents this.

  A second object of the present invention is to provide a combustion control device that can not only prevent early ignition without providing a high-voltage diode but also stably realize an optimal ignition operation according to the operating state.

  In order to achieve the above object, a first invention (Claim 1) includes a switching element that controls ON / OFF of a primary current of an ignition coil by a transition operation based on an ignition pulse received from an ECU, and a transition operation of the switching element. In an internal combustion engine that includes a spark plug that receives a secondary induced voltage of an ignition coil based on the above and performs a discharge operation, and performs an ignition operation on fuel at a timing when the switching element makes a transition operation, an engine speed and a required load A management table for storing the operation state defined on the basis of the above and the minimum pulse width of the ignition pulse that can be ignited by the spark plug in the operation state in association with each other, and the ECU The ignition pulse having the minimum pulse width corresponding to the operation state at that time is detected with reference to Thereby preventing the normal ignition operation.

  In the first invention, since the pulse width as narrow as possible is selected, the start position of the ignition pulse is the most delayed position, and abnormal discharge can be effectively prevented without providing a high voltage diode. That is, the normal ignition timing is before and after TDC (top dead center), and the in-cylinder pressure tends to increase. Therefore, the ignition pulse is generated when the in-cylinder pressure is higher than the conventional ignition pulse start position. Therefore, abnormal ignition (early ignition) is effectively prevented.

  In the management table, the minimum pulse width is not stored for each operating state. The narrower the pulse width, the shorter the primary current of the ignition coil at the end position of the ignition pulse, so the secondary induced voltage is insufficient, and depending on the operating conditions, the original ignition operation is hindered. Because it comes. Therefore, when the minimum pulse width is not detected from the management table, it is preferable to use a preset standard pulse width.

  A second invention (Claim 3) is a switching element that controls ON / OFF of a primary current of an ignition coil by a transition operation based on an ignition pulse received from an ECU, and a secondary induction of the ignition coil based on the transition operation of the switching element. In an internal combustion engine that includes a spark plug that performs a discharge operation upon receiving a voltage, and performs an ignition operation on the fuel at a timing at which the switching element performs a transition operation, a DC output voltage at a level defined by a control signal from the ECU A variable power supply that supplies the primary circuit to the primary circuit of the ignition coil, an operating state that is defined based on the engine speed, a required load, and the like, and the DC output voltage that allows the spark plug to ignite in the operating state. A management table for storing the prescribed optimum pulse width of the ignition pulse in association with each other; An abnormality is detected by outputting the ignition pulse having the optimum pulse width corresponding to the operation state at that time, which is detected with reference to the management table, and the control signal defining the DC output voltage corresponding to the optimum pulse width. Ignition operation is prevented.

  In the second aspect of the invention, the optimum optimum pulse width corresponding to the operating state is supplied to the switching element, and the optimum DC voltage is supplied to the primary circuit of the ignition coil, so that the optimum ignition operation can always be realized. it can.

  According to a third aspect of the present invention, there is provided a switching element that controls ON / OFF of a primary current of an ignition coil by a transition operation based on an ignition pulse received from an ECU, and secondary induction of the ignition coil based on the transition operation of the switching element. In an internal combustion engine that includes a spark plug that performs a discharge operation upon receiving a voltage, and performs an ignition operation on the fuel at a timing at which the switching element performs a transition operation, a DC output voltage at a level defined by a control signal from the ECU A variable power supply unit that supplies the primary circuit to the primary circuit of the ignition coil, an operating state that is defined based on an engine speed, a required load, and the like, and the ignition that defines the DC output voltage that can be output in the operating state A management table for storing the longest pulse width of the pulses in association with each other, and the ECU refers to the management table If the start position precedes the fuel injection timing by comparing the start position of the ignition pulse with the longest pulse width corresponding to the operating state at that time, and the fuel injection timing, it is detected An abnormal ignition operation is prevented by outputting an ignition pulse having the longest pulse width and a control signal that defines the DC output voltage corresponding to the ignition pulse.

  On the other hand, when the start position of the ignition pulse does not precede the fuel injection timing, for example, an ignition pulse having a preset standard pulse width and a control signal that defines a standard DC output voltage corresponding thereto are output. The

  In the third aspect of the invention, an ignition pulse is generated (typically rising) before fuel is injected. That is, there is no possibility of abnormal ignition (early ignition) because there is no air-fuel mixture in the cylinder even if discharge occurs in the spark plug. Note that the secondary induced voltage at the time of extinction of the ignition pulse increases by the longer pulse width. However, in the present invention, since the optimum DC voltage is supplied to the primary circuit of the ignition coil based on the management table, there is an abnormality. Therefore, a high secondary induced voltage is not generated.

  According to the present invention described above, early ignition of the internal combustion engine can be effectively prevented without using a high voltage diode and without providing any other circuit configuration. It is also possible to stably realize the optimal ignition operation according to the operating state.

  Hereinafter, embodiments of the present invention will be further described. FIG. 1 illustrates an example of a combustion control device. In the first embodiment, it is not necessary to use a high voltage diode, and it is possible to prevent early ignition of the internal combustion engine without providing a new circuit.

  As shown in the figure, this combustion control device includes an ECU (Engine Control Unit) which is a computer circuit for controlling the operation of this device, an ignition coil 1 composed of a primary coil 1P and a secondary coil 1S, and an ignition pulse received from the ECU. A switching transistor 2 (IGBT: Insulated Gate Bipolar Transistor) that turns on and off the primary current of the ignition coil 1 by a transition operation based on SG; an ignition plug 3 that receives a secondary induced voltage of the ignition coil 1 and performs a discharge operation; And an ion current detection circuit 4.

  Here, the ECU stores the operation state defined based on the engine speed, the required load, and the like, and the minimum pulse width of the ignition pulse SG that can be ignited by the spark plug 3 in the operation state in association with each other. A management table is provided. The relationship between the operating state and the minimum pulse width of the ignition pulse SG is experimentally specified in advance. However, the minimum pulse width is not stored for each operating state, but the minimum pulse width is stored only in the operating state where the standard pulse width can be reduced. Therefore, when the minimum pulse width is not detected from the management table, a preset standard pulse width is used.

  The ion current detection circuit 4 is charged at the time of ignition discharge of the spark plug 3, and stores a capacitor C1 that stores a bias voltage for detecting the ion current, a Zener diode ZD1 that defines the bias voltage, and at the time of ignition discharge of the spark plug 3. And a voltage conversion circuit 5 for ionic current.

  FIGS. 2A to 2C are diagrams for explaining the operation principle of this combustion control device. Here, the operation content in a certain combustion state is illustrated. At the rising timing and falling timing of the ignition pulse SG, a large positive and negative induced voltage is generated on the secondary side of the ignition coil 1. However, the ECU outputs an ignition pulse SG having a pulse width Ton as narrow as possible based on the data of the built-in management table. Therefore, the rising timing of the ignition pulse is the most delayed position, and abnormal discharge can be effectively prevented without providing a high voltage diode. That is, at the rising timing of the ignition pulse, since the in-cylinder pressure tends to increase before and after TDC (top dead center), the ignition pulse 3 becomes early due to the induced voltage generated on the secondary side of the ignition coil 1. Ignition is effectively prevented.

  However, in the case of operating conditions in which the pulse width is not detected from the management table, a standard pulse width determined in advance is used. Therefore, an optimal driving operation can be realized in real time without the management table occupying the memory area of the ECU unnecessarily, or without requiring a lot of time for the management table search process.

  FIG. 3 illustrates another combustion control device. In the second embodiment, not only can high-pressure diodes be prevented without providing a high-voltage diode, but also an optimal ignition operation according to the operating state can be stably performed. realizable.

  In the illustrated combustion control apparatus, a PWM generation circuit 6 and a chopper circuit 7 are provided between the battery BATT and the ignition coil 1 to output a DC output voltage VB to the ignition coil 1.

  The PWM generation circuit 6 generates a PWM (Pulse width modulation) wave based on a control signal CTL received from the ECU. On the other hand, the chopper circuit 7 includes a choke coil L, a switching transistor Q2, a rectifier diode D3, a smoothing capacitor C2, and a Zener diode ZD2, and outputs a DC output voltage VB having a level corresponding to the control signal CTL. is doing.

  In the ECU according to the second embodiment, the built-in management table defines the operating state specified based on the engine speed, the required load, and the like, and the DC output voltage VB that can be ignited by the spark plug 3 in the operating state. The optimum pulse width of the ignition pulse SG is stored in association with each other. In the operation state that is not detected from the management table, the standard pulse width Ton and the standard DC voltage VB are selected.

  FIG. 4 illustrates an operation example in the third embodiment. In the third embodiment, the ECU controls the ignition pulse SG having the optimum pulse width Ton corresponding to the operation state at that time and the DC output voltage VB corresponding to the optimum pulse width based on the data of the built-in management table. The abnormal ignition operation is prevented by outputting the signal CTL.

  The relationship between the optimum pulse width Ton selected from the management table and the DC output voltage VB has been experimentally specified in advance, and is set to a substantially linear relationship in which the DC output voltage VB increases as the pulse width Ton decreases. ing. Therefore, in this embodiment, since the pulse width is narrow, the secondary induced voltage of the ignition coil 1 will not be insufficient. That is, since the ignition pulse moves backward (a position where the in-cylinder pressure is high), early ignition is prevented, while sufficient secondary induced voltage can be obtained during the original ignition operation.

  FIG. 5 illustrates an operation example of the third embodiment. The third embodiment also has the circuit configuration of FIG. 3, but the ECU management table includes an operation state defined based on the engine speed, a required load, and the like, and a DC output voltage VB that can be output in the operation state. Are stored in association with each other.

  Then, the ECU compares the start position of the ignition pulse SG with the longest pulse width Ton corresponding to the operation state at that time detected with reference to the management table and the fuel injection timing, and the start position is the fuel injection timing. Is preceded by the output of the detected ignition pulse SG having the longest pulse width Ton and the control signal CTL defining the DC output voltage VB corresponding to the detected ignition pulse SG (FIG. 2). 5).

  In this embodiment, at the timing when the ignition pulse SG rises, there is no possibility of early ignition because the fuel has not yet been injected. If the detected start position of the ignition pulse having the longest pulse width does not precede the fuel injection timing, an ignition pulse having a preset standard pulse width and a standard DC output voltage corresponding thereto are defined. A control signal is output. Alternatively, as in the third embodiment, an ignition pulse SG having an optimum pulse width that can be ignited by the spark plug in the current operating state and a control signal that defines the DC output voltage VB corresponding thereto are output.

It is a circuit diagram which shows the combustion control apparatus which concerns on 1st Embodiment. It is a time chart explaining operation | movement of the apparatus of FIG. It is a circuit diagram which shows the combustion control apparatus which concerns on 2nd Embodiment and 3rd Embodiment. It is a time chart explaining operation | movement of the apparatus of FIG. It is a time chart explaining another operation | movement of the apparatus of FIG.

Explanation of symbols

1 Ignition Coil 2 Switching Transistor 3 Spark Plug SG Ignition Pulse Ton Pulse Width

Claims (6)

A switching element that controls ON / OFF of the primary current of the ignition coil by a transition operation based on an ignition pulse received from the ECU, and a spark plug that performs a discharge operation by receiving a secondary induced voltage of the ignition coil based on the transition operation of the switching element An internal combustion engine that performs an ignition operation on the fuel at a timing when the switching element performs a transition operation,
A management table for storing an operation state defined based on an engine speed, a required load, and the like, and a minimum pulse width of the ignition pulse that can be ignited by the spark plug in the operation state;
The ECU is configured to prevent an abnormal ignition operation by outputting an ignition pulse of the minimum pulse width corresponding to the operation state at that time detected with reference to the management table.   The combustion control device according to claim 1, wherein a preset standard pulse width is used when the minimum pulse width is not detected from the management table. A switching element that controls ON / OFF of the primary current of the ignition coil by a transition operation based on an ignition pulse received from the ECU, and a spark plug that performs a discharge operation by receiving a secondary induced voltage of the ignition coil based on the transition operation of the switching element An internal combustion engine that performs an ignition operation on the fuel at a timing when the switching element performs a transition operation,
A variable power supply for supplying a DC output voltage of a level defined in a control signal from the ECU to a primary circuit of the ignition coil;
The operation state defined based on the engine speed, the required load, and the like, and the optimum pulse width of the ignition pulse defining the DC output voltage that can ignite the spark plug in the operation state are related to each other. A management table to be stored,
The ECU outputs an ignition pulse having the optimum pulse width corresponding to the operation state at that time, which is detected with reference to the management table, and a control signal defining the DC output voltage corresponding to the optimum pulse width. A combustion control device that prevents abnormal ignition operation. A switching element that controls ON / OFF of the primary current of the ignition coil by a transition operation based on an ignition pulse received from the ECU, and a spark plug that performs a discharge operation by receiving a secondary induced voltage of the ignition coil based on the transition operation of the switching element An internal combustion engine that performs an ignition operation on the fuel at a timing when the switching element performs a transition operation,
A variable power supply for supplying a DC output voltage of a level defined in a control signal from the ECU to a primary circuit of the ignition coil;
A management table that stores an operation state defined based on the engine speed, a required load, and the like, and a longest pulse width of the ignition pulse that defines the DC output voltage that can be output in the operation state in association with each other. And
The ECU compares the start position of the ignition pulse with the longest pulse width corresponding to the operation state at that time detected with reference to the management table and the fuel injection timing, and the start position is the fuel injection timing. Is a combustion control apparatus that prevents the abnormal ignition operation by outputting the detected ignition pulse having the longest pulse width and a control signal that defines the DC output voltage corresponding to the detected ignition pulse.   If the detected start position of the ignition pulse having the longest pulse width does not precede the fuel injection timing, an ignition pulse having a preset standard pulse width and a control signal that defines a standard DC output voltage corresponding thereto Is output, the combustion control device according to claim 4.   The combustion control device according to claim 3 or 4, wherein the variable power supply unit is configured by a chopper circuit.

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