JP3963889B2 - In-cylinder direct injection internal combustion engine control device - Google Patents

Description

  The present invention generally relates to a method for supplying fuel to an internal combustion engine, and more particularly to a method for supplying fuel to a direct injection type internal combustion engine at the time of starting.

In general, it has been known that when starting an internal combustion engine, it is necessary to supply a larger amount of fuel to each cylinder in order to prevent a misfire from occurring particularly at a low temperature. For this reason, an increased amount of fuel is injected into each cylinder during cranking. However, when the first explosion occurs, the engine speed increases rapidly, and there is a risk that the increased amount of fuel for starting cannot be supplied in one cycle. It was. In order to improve this, in the method of Patent Document 1, fuel for starting is supplied to all the cylinders at least once during a cycle in which ignition of the plug at the time of starting is forcibly stopped. Is going to start. This prevents misfire due to insufficient fuel supply to some of the cylinders after the first explosion and improves startability.
Japanese Patent Laid-Open No. 10-18951

  However, if the fuel is supplied while the ignition of the plug is stopped unconditionally as described above, the proportion of the supplied hydrocarbon component is exhausted as it is, and the emission of the catalyst is not particularly activated at the time of starting in the cold state. Cause it to worsen. Further, in a direct injection engine in which fuel is directly injected into a cylinder, there is a risk of causing plug damage due to fuel adhering to the plug during a cycle in which ignition is stopped. Therefore, even when fuel injection is performed while the ignition of the plug is stopped, it is desirable to minimize this.

  Furthermore, in the prior art, the fuel transportation delay due to the fuel adhering to the wall surface is not taken into consideration with respect to the fuel supply amount. There was concern.

  Accordingly, an object of the present invention is to provide a control device that minimizes the amount of fuel injection during ignition stop according to the state of the internal combustion engine in order to solve the above problem.

  According to one aspect of the present invention (Claim 1), the control device for a direct injection type internal combustion engine of the present invention has detection means for detecting the temperature of the cooling water of the internal combustion engine, and controls ignition stop of the plug. A control device for a direct injection type internal combustion engine capable of performing ignition and determining the number of ignition stop cycles in which the ignition of the plug is stopped and only fuel injection is performed based on the temperature of the cooling water detected by the detecting means at the time of starting Determining means is provided. The number of cycles used here is the number of cycles when the entire stroke of intake, compression, expansion, and exhaust is defined as one cycle. According to this, since it is possible to determine the number of ignition stop cycles suitable for the temperature of the cooling water of the internal combustion engine, that is, the degree of cooling and warming up of the internal combustion engine, and to stop the ignition of the plug, the emission can be improved.

  In the control device for a direct injection type internal combustion engine according to another aspect of the present invention (Claim 2), a predetermined fuel injection amount map is searched based on the temperature of the cooling water, and the number of ignition stop cycles is determined. Determining means for determining the fuel injection amount to be injected within the period. According to this, since the fuel injection amount suitable for the temperature of the cooling water of the internal combustion engine, that is, the degree of cooling and warming of the internal combustion engine can be supplied to the internal combustion engine, the emission can be improved.

  In the control unit for a direct injection type internal combustion engine according to another aspect of the present invention (Claim 3), the number of ignition stop cycles is set larger as the temperature of the cooling water is lower. According to this, when the temperature of the cooling water is high and the fuel injection can be started easily even if the number of fuel injections before the plug ignition is small, the number of fuel injections can be reduced, so that the emission can be improved.

  Further, in the control device for a direct injection type internal combustion engine according to another aspect of the present invention (claim 4), the amount of attached fuel attached to the inside of the cylinder before starting ignition is calculated based on the temperature of the cooling water. An attached fuel amount search means for searching from the map is further provided, and the searched attached fuel amount is reflected in the determination of the fuel injection amount after starting ignition. According to this, since the amount of fuel adhering to the cylinder can be reflected in the fuel injection amount after the ignition of the plug is started, the air-fuel ratio rich immediately after the ignition of the plug can be prevented and the deterioration of the emission can be prevented.

1. Description of Each Function Hereinafter, a control apparatus for a direct injection type internal combustion engine, which is an embodiment of the present invention, will be described with reference to FIG. FIG. 1 shows a configuration of a control device (ECU) and a direct injection engine of the present embodiment using a simple block diagram. The ECU (electronic control unit) 110 constitutes functions of a means for determining an ignition stop cycle, a means for determining a fuel injection amount, and a search means for searching for an attached fuel amount, as will be described later. ECU 110 also performs other controls necessary for the operation of the internal combustion engine, such as torque control, fuel supply control, ignition control, and various calculations.

  The ECU 110 shapes input signal waveforms from various sensors, corrects a voltage level to a predetermined level, and converts an analog signal value into a digital signal value, a central processing circuit (CPU), a CPU And a storage means for storing various calculation programs and calculation results, and an output circuit for supplying a drive signal to a fuel injection valve and a spark plug. The storage means includes a random access memory (RAM) that temporarily stores various data and flag states, a read-only memory (ROM) in which a fuel injection amount map and an attached fuel amount map, which will be described later, are stored in advance, and a calculation by a processor And a rewritable nonvolatile memory for storing data obtained from each part of the engine system to be stored. The nonvolatile memory can be realized by a RAM with a backup function that is always supplied with a voltage even after the system is stopped.

  In the engine 100, the fuel pressure supplied to the fuel injection valve 106 is set higher than the normal injection pressure in order to inject and supply the fuel directly into the high-pressure combustion chamber and to atomize the injected fuel. ing. Here, the structure of a fuel supply device for supplying high-pressure fuel to the engine 100 will be briefly described with reference to FIG.

  As shown in FIG. 1, the fuel supply device of the engine 100 includes a feed pump 104 that sucks and sends fuel from the fuel tank 102, and further pressurizes the fuel sent by the feed pump 104 to the delivery pipe 120. And a high-pressure fuel pump 108 for supply. The fuel supply pressure by the feed pump 104 is, for example, 0.35 MPa in the present embodiment, and the fuel supply pressure by the high-pressure fuel pump 108 is 10 MPa.

  The high-pressure fuel pump 108 includes a plunger 114 that reciprocates when the camshaft 112 connected to the output shaft contacts and rotates, and a pressurizing chamber 116 whose volume changes due to the reciprocating movement of the plunger 114. . The pressurizing chamber 116 is connected to the feed pump 104 via a low-pressure side fuel passage. A pressure regulator 118 is provided in the middle of the low pressure side fuel passage to keep the pressure in the passage constant (that is, 0.35 MPa).

  The pressurizing chamber 116 is connected to the delivery pipe 120 via a high-pressure side fuel passage, and in order to make the pressure in the passage constant (that is, 10 MPa) in the middle of the high-pressure side fuel passage. The pressure regulator 132 is provided. The fuel injection valve 106 is connected to the delivery pipe 120. The fuel injection valve 106 is connected to the ECU 110, and can be injected by a signal pulse from the ECU 110. Therefore, the fuel injection amount can be determined by the fuel injection time based on the pulse width.

  The high-pressure fuel pump 108 is provided with a solenoid valve 122 for communicating and blocking between the low-pressure side fuel passage and the pressurizing chamber 116. This solenoid valve 122. An electromagnetic solenoid 124 is provided, and an opening / closing operation is performed by controlling a voltage applied to the solenoid 124. The electromagnetic solenoid is controlled to open and close by a signal from the ECU 110. Then, when the plunger 114 moves in the direction in which the volume of the pressurizing chamber 116 expands, the solenoid valve 122 is turned off when the electromagnetic solenoid 124 is de-energized. On the other hand, when the plunger 114 moves in the direction in which the volume of the pressurizing chamber 116 contracts, the valve 114 is closed and compressed by the force pushed up from the cam to be pressurized.

  By controlling the opening / closing operation of the solenoid valve 122 as described above, the fuel sent from the feed pump 104 is pressurized to 10 MPa by the high-pressure fuel pump 108. Then, the pressurized fuel is supplied to the fuel injection valve 106 via the high-pressure side fuel passage and the delivery pipe 120.

  Adjustment of the fuel pressure in the high-pressure side fuel passage and the delivery pipe 120, that is, the pressure of the fuel supplied to the fuel injection valve 106 changes the valve closing timing of the solenoid valve 122, and the fuel injection valve 106 is changed from the high-pressure fuel pump 108 to the fuel injection valve 106. It is also possible to adjust the amount of fuel supplied to the side. That is, when the plunger 114 moves in the direction in which the volume of the pressurizing chamber 116 contracts, the amount of fuel supplied from the high-pressure fuel pump 108 to the fuel injection valve 106 side decreases as the closing timing of the solenoid valve 122 is delayed. Thus, the fuel pressure (fuel pressure) supplied to the fuel injection valve 106 can be reduced.

  The delivery pipe 120 is provided with a fuel pressure sensor PF 126 for detecting the fuel pressure to the fuel injection valve 106. In addition, a relief valve 128 is provided in the delivery pipe so that the fuel pressure increased by the high-pressure fuel pump does not exceed a predetermined high-pressure value.

  An engine water temperature (Tw) sensor 130 composed of a thermistor or the like as a water temperature detection means is mounted on the main body of the engine 100, detects the temperature Tw of the engine cooling water, outputs a corresponding temperature signal, and supplies it to the ECU 110 To do.

  The ECU 110 is connected to a TDC sensor 132 that outputs a signal pulse at a predetermined crank angle position in a specific cylinder of the engine. A pulse of the TDC signal is supplied to the ECU 110 every time a predetermined crank angle is passed. In this embodiment, a four-cylinder engine is assumed, and a pulse of a TDC signal is generated every crank angle of 180 degrees. That is, because the engine rotates 720 degrees during the entire stroke (represents the entire stroke of intake, compression, expansion, and exhaust, and this cycle is referred to as one cycle in the present specification), It is transmitted to the ECU 110. These signal pulses are used for various timing controls such as fuel injection timing and ignition timing, engine speed detection, etc., in addition to the increment of a TDC counter described later.

  An ignition plug for igniting gasoline is attached to each cylinder of the engine. These are electrically connected to the ECU 110 to control ignition timing and ignition on / off.

  In addition, this engine can be controlled so that only fuel injection can be performed while stopping ignition of the plug in a predetermined period at the time of starting. For example, when 1 is set as the number of ignition stop cycles described later, at the time of cranking, fuel is injected for one cycle, but the plug is not ignited. This operation will be described in detail in the description of each routine.

2. Description of Ignition Stop Cycle Determination Routine First, the ignition stop cycle determination routine according to the present invention will be described.

  First, ECU 110 determines whether or not the ignition stop cycle determined flag is 1 (S201). The ignition stop cycle determined flag is a flag indicating whether or not the ignition stop cycle determination routine has been executed after the engine is started and the number of cycles to stop ignition has been set. Here, since the ignition stop cycle determined flag has not yet been set to 1, ECU 110 advances the process to S202.

  In S202, ECU 110 determines whether or not the temperature of the engine coolant is higher than the determination water temperature in the predetermined start mode (here, 0 ° C.). When the temperature is higher than 0 ° C., the ECU 110 sets 0 as the number of cycles to stop ignition (S203). Here, the number of cycles to stop ignition represents the number of cycles to stop ignition of the plug while injecting fuel after the start of cranking. For example, when 1 is set as the number of cycles to stop ignition, ignition prohibition control is performed for one cycle, in which fuel is injected at the time of cranking at the start, but the plug is not ignited.

  Next, the ECU 110 sets 0 as the fuel injection time when ignition is stopped (S204). Here, the fuel injection time when ignition is stopped is a fuel injection time when fuel injection is performed while prohibiting ignition of the plug at the time of starting. The ignition stop fuel injection time can be obtained by searching a fuel injection time map stored in the ROM based on the temperature of the cooling water as will be described later.

  Next, the ECU 110 sets 1 to the determined flag of the ignition stop cycle, and ends this process.

  On the other hand, when the cooling water temperature of the engine is 0 ° C. or lower, ECU 110 determines whether or not the cooling water temperature is higher than the determination water temperature (here, −10 ° C.) of the low temperature side ignition stop cycle (S205). ). Here, when the temperature of the cooling water is higher than −10 ° C., 1 is set to the number of cycles to stop ignition (S206). Then, the fuel injection time map 1 (FIG. 5) stored in the ROM is searched to set the fuel injection time when the ignition is stopped (S207). On the other hand, when the coolant temperature is not higher than −10 ° C., the ECU 110 sets 2 as the number of cycles to stop ignition (S208). In this case as well, the fuel injection time map 2 (FIG. 6) in the ROM is similarly searched to set the fuel injection time at the time of ignition stop (S210).

  Then, the ECU 110 sets 1 indicating that the number of cycles for ignition stop has been set in the ignition stop cycle determined flag (S210), and ends this process.

  In S210, since the ignition stop cycle determined flag is set to 1, even if the ignition stop cycle determination routine is called next, the process immediately ends in S201.

  In a direct injection engine, the fuel injection amount is proportional to the fuel injection time. Therefore, the fuel injection amount can be obtained by multiplying the fuel injection time by a predetermined value considering the fuel pressure or the like.

  In the above-described process, the higher the engine coolant temperature, the fewer the number of cycles at which the ignition of the plug stops. That is, when the temperature of the cooling water is high, it can be considered that the engine is in a warm-up state, and fuel injection is not performed during ignition stop of the plug that may cause fuel to adhere to the plug. The fuel injection during the ignition stop of the plug can be performed only when the startability must be improved by the fuel injection during the ignition stop of the plug in the cold state. And, as the temperature of the cooling water is lower, the number of cycles to stop ignition is increased and the startability of the engine is improved.

  In addition, since the fuel injection time during the ignition stop of the plug, that is, the fuel injection amount can be determined in accordance with the temperature of the cooling water of the engine, the fuel injection considering the startability can be performed.

  Next, the ignition of the plug is stopped based on the number of cycles to stop the ignition set above. Here, before the routine responsible for executing plug ignition is called, the ignition stop flag setting routine described below is called.

  When the ignition stop flag setting routine is called, the ECU 110 assigns the following calculation result to the temporary variable tmp2 (S301).

tmp2 = CTINJINHS × NOFCYL + 1
CTINJINHS: number of ignition stop cycles
NODCYL: Number of cylinders (4 cylinders in this embodiment)

Then, ECU 110 determines whether or not the TDC counter stored in the memory is equal to or less than tmp2 (S302). Here, when the TDC counter is less than or equal to tmp2, it indicates that the fuel is injected but the ignition must be cut off. For example, in the above-described ignition stop cycle determination routine, when the number of cycles to stop ignition is set to 2, tmp2 becomes 9, and the TDC counter exceeds 8 (that is, it rotates more than 4 rotations after cranking starts). Until then, it is determined that the fuel must be injected but the ignition must be stopped.

  Therefore, the process proceeds to S303, the ignition stop flag is set to 1, and this process is terminated. On the other hand, when the TDC counter is greater than tmp2, it is determined that the number of cycles to stop ignition has already elapsed, 0 is set to the ignition stop flag (S304), and this process ends.

  When this process ends, the routine responsible for executing plug ignition refers to the ignition stop flag, and when the ignition stop flag is set to 1, the plug is not ignited. On the other hand, when the ignition stop flag is set to 0, ECU 110 controls the ignition of the plug so that the plug is ignited as usual.

3. Calculation of fuel injection amount when considering the amount of attached fuel It is desirable that the fuel injected by the injection is completely used for combustion during the injected cycle. However, in the actual combustion cycle, the injected fuel adheres to the piston and the wall surface in the cylinder and is not used for the combustion immediately after the injection, but is carried over to the combustion in the next and subsequent cycles. Delay occurs.

  If the amount of fuel adhering is not taken into account, if only the amount of fuel required by the engine is supplied, the amount of fuel will be excessive by the amount adhering to the air and the emission will deteriorate due to the rich air-fuel ratio.

  Here, the fuel injection amount when the amount of attached fuel is taken into consideration is considered.

  The relationship between the amount of fuel adhering to the required fuel amount of the engine and the fuel injection amount is defined by the following equation.

Tcyl = A × Tout + B × Twp (3.1)
Tcyl: Required fuel amount
Tout: Fuel injection amount from injection
Twp: Fuel amount adhering to the cylinder
A: Direct rate (0 ≦ A ≦ 1)
B: Carrying rate (0 ≦ B ≦ 1)

The direct rate A is a ratio indicating how much of the fuel amount injected this time is used for combustion in the same cycle. Further, the carry-off rate B is a ratio representing how much of the fuel amount adhering to the wall surface is used for combustion in the current cycle.

  The injection amount Tout can be obtained by the following equation by modifying the above equation.

Tout = (Tcyl-B × Twp) / A (3.2)

Therefore, when the amount of attached fuel is taken into consideration, it is desirable to perform fuel injection by subtracting a predetermined amount of attached fuel according to the above in order to improve emission.

4). Adhesive fuel amount determination routine In order to perform fuel injection in consideration of the above-mentioned in-cylinder attached fuel amount, it is necessary to determine the attached fuel amount Twp. In the present invention, the amount of attached fuel is prepared as a map value (FIG. 7) with respect to the water temperature. Since the fuel amount is proportional to the fuel injection time, the attached fuel amount in FIG. 7 is also given as the fuel injection time. Hereinafter, a routine for determining the amount of attached fuel will be described.

  First, at the time of start-up, ECU 110 acquires the temperature of engine cooling water from engine water temperature sensor 130, and searches the attached fuel amount map stored in ROM based on the acquired temperature of cooling water. Then, the amount of adhered fuel is obtained by multiplying the retrieved value by a coefficient considering the fuel pressure and the like, and this is stored in the memory as a temporary adhered fuel amount (S401).

  Next, ECU 110 determines whether or not the initialization flag is 1 (S402). When the initialization flag is 1, the above-mentioned provisional attached fuel amount is set as the attached fuel amount Twp (S406). Here, the initialization flag is a flag indicating whether or not the amount of attached fuel has already been set. When it is 1, it indicates that it has not been set yet.

On the other hand, when the initialization flag is not 1, the ECU 110 determines whether or not the cooling / warming determination flag is 1 (S403). Here, the cooling / warming determination flag performs a predetermined engine warm-up determination in another routine, and is set to 1 when the engine is in a cold state, and is set to 0 when the engine is in a warm state. Then, when the cooling-heating machine determination flag is not 1, ECU 110 includes a adherent fuel amount value obtained by multiplying a predetermined correction coefficient retrieved provisional adhering fuel amount described above. On the other hand, when the cooling-heating machine determination flag is 1, ECU 110 sets 0 to the adhering fuel amount (S404).

  By setting the amount of adhered fuel Twp as described above, it can be set to 0 assuming that the adhered fuel is evaporated when starting from a cold state. Then, when the engine is in a warm-up state, the amount of adhered fuel multiplied by the correction coefficient can be set on the assumption that the amount of adhered fuel during the previous operation remains while decreasing.

  By considering the amount of attached fuel calculated in this way when calculating the fuel injection amount, fuel injection can be performed in consideration of the amount of attached fuel, and emission can be improved.

The block diagram showing the outline of a direct injection engine and a control apparatus. The flowchart showing an ignition stop cycle determination routine. The flowchart showing an ignition stop flag setting routine. 7 is a flowchart showing a routine for determining the amount of attached fuel. The graph showing the fuel injection time at the time of ignition stop with respect to water temperature. The graph showing the fuel injection time at the time of ignition stop with respect to water temperature. The graph showing the adhesion fuel amount map with respect to water temperature.

Explanation of symbols

100 In-cylinder direct injection engine 110 ECU (electronic control unit)
126 Fuel pressure sensor 130 Water temperature sensor 132 TDC sensor

Claims (3)

A control device for an in-cylinder direct injection internal combustion engine having a detection means for detecting the temperature of cooling water of the internal combustion engine and capable of controlling ignition stop of the plug,
Determining means for determining the number of ignition stop cycles for stopping ignition of the plug and performing only fuel injection based on the temperature of the cooling water detected by the detecting means at the time of starting the internal combustion engine;
An adhering fuel amount search means for searching an adhering fuel amount adhering in the cylinder from an adhering fuel amount map based on the temperature of the cooling water detected by the detecting means at the time of starting the internal combustion engine;
Correction means for correcting the retrieved attached fuel amount with fuel injection pressure;
If it is determined that the internal combustion engine is in a warm-up state, means for reflecting the corrected attached fuel amount in the determination of the fuel injection amount;
An in-cylinder direct injection internal combustion engine control device. Determination of searching a predetermined fuel injection amount map based on the temperature of the cooling water detected by the detecting means at the time of starting the internal combustion engine and determining a fuel injection amount to be injected within the period of the number of ignition stop cycles Further comprising means,
The control apparatus for a direct injection type internal combustion engine according to claim 1. The lower the temperature of the cooling water, the greater the number of ignition stop cycles is set,
The control device for a direct injection type internal combustion engine according to claim 1 or 2.

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