JPH06129296A - Accumulator fuel injection device - Google Patents

Abstract

PURPOSE:To provide an accumulator fuel injection device capable of improving low temperature starting characteristics by way of deciding optimal pre-injection frequency in accordance with a state of an internal combustion engine. CONSTITUTION:To an internal combustion engine 201, fuel is injected from a plural number of fuel injection valves 202a, 202b, 202e, 202f. Fuel is pumped up from a tank 208 by a low pressure pump 209, boosted by a high pressure pump 207 and fed to a common rail 203 with a fuel injection valve installed on it. To an ECU 215, a pressure sensor 211, an engine speed sensor 212, an accelerator opening sensor 213 and a cooling water temperature sensor 214 are connected. At the time of low temperature starting, fuel injection is carried out by separating it into pre-injection and main injection, but by carrying out the pre-injection of the maximum frequency after securing length of time required to certainly practice the main injection, it is possible to improve low temperature startability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-accumulation fuel injection device applied to an internal combustion engine, and more particularly to a pressure-accumulation fuel injection device capable of improving the low temperature startability of the internal combustion engine.

[0002]

As a fuel supply device for an internal combustion engine,
A pressure-accumulation fuel injection device that supplies fuel to a common rail installed along an internal combustion engine and injects fuel from a fuel injection valve is known (see, for example, JP-A-62-258160).
In an internal combustion engine including such a pressure-accumulation fuel injection device, the amount of fuel injected into the cylinder is controlled by the amount of fuel supplied to the common rail, the fuel pressure in the common rail, and the opening period of the fuel injection valve.

When the fuel supply amount to the internal combustion engine is controlled by an electronic control unit (hereinafter referred to as ECU), the fuel amount and the common rail are calculated based on a map having the internal combustion engine speed and the accelerator opening as parameters. The internal fuel pressure, the valve opening timing and the valve opening period of the fuel injection valve are controlled. Of these, the valve opening timing is determined by the elapsed time after the crankshaft reaches a predetermined specific angle.

That is, as shown in the timing chart of the normal fuel injection mode of FIG. 13, the 0th rotation angle pulse (hereinafter referred to as "N _e pulse") is detected in the normal fuel injection mode. After a predetermined time (TTF) has elapsed, a drive pulse for opening the fuel injection valve is output. However, when the internal combustion engine is started, especially when the internal combustion engine is started in a low temperature state, the number of revolutions varies greatly, and therefore, when the fuel injection valve is opened after a predetermined time has elapsed after the detection of the specific N _e pulse. The ignition characteristics deteriorate,
There is a problem that the starting characteristics of the internal combustion engine deteriorate.

As a method of solving this problem, there is a method of controlling the opening timing of the fuel injection valve by the rotation angle of the crankshaft instead of by time, but in order to maintain the control accuracy of the opening timing of the fuel injection valve. Therefore, it is necessary to detect the rotation angle of the crankshaft at a cam angle of about 0.5 °. However, in order to detect the rotation angle of the crankshaft with a cam angle of 0.5 °, 7 rotations per rotation of the crankshaft are required.
Although 20 N _e pulses will be input to the ECU, it is not only difficult to manufacture a pulse generator capable of generating 720 N _e pulses per one revolution of the crankshaft, The interrupt processing for reading the N _e pulse imposes an excessive load on the ECU and is difficult to put into practical use.

[0006]

Therefore, in order to practically solve the low-temperature starting characteristic, so-called pilot fuel injection, which divides the fuel injection into one cylinder into pre-injection and main injection, is adopted, and the cooling water temperature is also adopted. It is conceivable that the pre-injection increases the activity of the air-fuel mixture in the cylinder to increase the number of pre-injections as the number of pre-injections decreases, so that a spark is generated earlier.

In this pilot fuel injection mode, it becomes possible to improve the starting characteristics of the internal combustion engine without increasing the number of N _e pulses per crankshaft revolution. However, in the configuration in which the number of pre-injections is increased as the cooling water temperature is lower, the time interval between the last pre-injection and the main injection becomes too short and the main injection cannot be executed.

FIG. 12 is a timing chart of the pilot injection mode, and FIG. 14 is an example (a) of the drive circuit of the fuel injection valve and a current waveform chart (b). That is, the signal output circuit e1 and the drive circuit e2 included in the output interface 215e of the ECU 215 make the fuel injection valve 202 based on the valve opening command.
The drive current I _P and the holding current I _H (indicates one of 202a to f in FIG. 2) are generated. Since the drive current I _P is obtained by charging the power source + B in the capacitor and then discharging the capacitor in a short time, in order to output the drive current I _P once and then output the drive current I _P again, the drive current I _P It is necessary to secure the charge and discharge time.

Therefore, the pre-injection is not only executed every predetermined time t, but it is necessary to secure the interval t'between the last pre-injection and the main injection to be a predetermined time or more. When this interval t'is short. The main injection cannot be carried out, which may lead to misfire. It is possible to install a plurality of drive circuits for each injection in order to solve the above problems, but this is not realistic because the drive circuits become complicated.

The present invention has been made in view of the above problems, and provides a pressure-accumulation fuel injection device capable of determining the optimum number of pre-injections according to the state of the internal combustion engine and improving the combustion state. With the goal.

[0011]

FIG. 1 is a basic configuration diagram of a pressure-accumulation type fuel injection device according to the present invention, in which an operating state amount detecting means 11 for detecting an operating state amount of an internal combustion engine and an operating state amount detecting means. Fuel injection mode identification means 12 for identifying the fuel injection mode based on the operating state quantity detected by the means 11.
A normal injection mode executing means 13 for executing normal fuel injection at a predetermined injection timing when the fuel injection mode identifying means 12 determines the normal injection mode, and an operating state quantity detected by the operating state quantity detecting means 11. Based on the pre-injection number setting means 14 for setting the number of pre-injections to be performed prior to the main injection that is injected at a predetermined fuel injection timing, and the fuel injection mode identification means 12, the pilot injection mode is determined. Sometimes the pre-injection number setting means 14
The pilot injection mode executing means 15 performs the pre-injection according to the number of injections set in 1. and performs the main injection after a lapse of a predetermined time or more from the completion of the pre-injection.

[0012]

According to the above-described structure of the present invention, in the pilot injection mode, the number of pre-injections is set based on the operating state quantity, and the pre-injection is executed according to the set number of times. Therefore, pre-injection according to the operating state is performed, and it becomes possible to realize appropriate combustion according to each operating state. In the pilot injection mode, after the pre-injection is repeated a plurality of times, the main injection is performed after a lapse of a predetermined time or more from the completion of these pre-injections. Therefore, even if the number of pre-injections changes depending on the operating state, a time longer than the predetermined time is reliably ensured between the pre-injection and the main injection. Therefore, the pre-injection is performed immediately before the main injection, the main injection is affected by the pre-injection, and it is possible to reliably prevent the occurrence of a defect such as not performing the main injection.

[0013]

FIG. 2 is a block diagram of an embodiment of a pressure-accumulation type fuel injection device according to the present invention, in which fuel injection valves 202a to 202f (only four of them are provided corresponding to each cylinder of a six-cylinder internal combustion engine 201). (Shown in the figure) is installed, but the fuel injection valve 202a
202 f are connected to a common rail 203 installed along the internal combustion engine 201, and are connected to the injection control solenoid valve 20.
Fuel is injected while 4a to 204f are excited.

The common rail 203 has a fuel supply pipe 20.
A high-pressure fuel pump 207 is connected via the valve 5 and the check valve 206. The high-pressure fuel pump 207 is supplied with the fuel stored in the fuel tank 208 by the low-pressure fuel pump 209. A discharge amount control device 210 is installed in the high-pressure fuel pump 207, and the common rail 20
Adjust the amount of fuel supplied to No. 3.

The common rail 203 includes the common rail 20.
A pressure sensor 211 for detecting the pressure inside 3 is installed. Further, the internal combustion engine 201 includes a rotation speed sensor 212 for detecting the rotation speed of the internal combustion engine and an accelerator opening degree sensor 21.
3 and a cooling water temperature sensor 214 are installed. The fuel injection timing for each cylinder is controlled by the ECU 215. The ECU 215 includes, for example, the bus 215a and the CPU 21.
5b, memory 215c, input interface 215d
And an output interface 215e.

A pressure sensor 211, a rotation speed sensor 212, an accelerator opening sensor 213 and a cooling water temperature sensor 214 are connected to the input interface 215d. Further, the injection control solenoid valves 204a to 204f and the discharge amount control device 210 are connected to the output interface 215e. FIG. 3 is a flowchart of an injection mode determination routine executed by the ECU 215, which is interrupted every predetermined time.

In step 301, the state of the flag IMODE representing the injection mode is determined. That is, if the flag IMODE is "0", that is, if the current injection mode is the normal injection mode, the process after step 302 is executed. Step 30
If the internal combustion engine starter is turned on in step 2, step 3
In 03, it is determined whether the cooling water temperature THW is less than or equal to a predetermined threshold value θ ₁ or in step 304 whether the internal combustion engine speed N _e is less than or equal to a predetermined threshold value N _e1 (unit is rpm). When a positive determination is made in all steps 303, 304, and 305, the process proceeds to step 305, the flag IMODE is set to "1", and this routine ends. Conversely, steps 303, 304 and 305
If the determination is negative in any of the above cases, this routine is ended while the flag IMODE is maintained at "0".

If an affirmative decision is made in step 301, that is, if the current injection mode is the pilot injection mode, the routine proceeds to step 306, it is decided whether or not the starter is in the on state, and if an affirmative decision is made, step 307. The following processing is executed. That is, whether the cooling water temperature THW is equal to or lower than a predetermined threshold value θ _{1 in} step 307, or step 3
At 08, it is determined whether the internal combustion engine speed N _e is less than or equal to a predetermined threshold N _e1 . And steps 307 and 30
If both steps 8 are affirmative, the flag IMOD
This routine is terminated while E is maintained at "1".

If it is determined in step 306 that the starter is not in the on state, the process proceeds to step 309 to determine whether or not a predetermined time t has passed since the starter was turned off. Proceed to 307. If a positive determination is made in step 309, and step 30
When a negative determination is made in either 7 or 308, the routine proceeds to step 310, the flag IMODE is set to "0", and this routine is ended.

This routine constitutes the fuel injection mode identifying means 12. FIG. 4 is a flowchart of a fuel injection control routine executed by the ECU 215, which is executed at every predetermined crankshaft rotation angle. Step 41
At, the internal combustion engine speed N _e , accelerator opening A _ccp and common rail fuel pressure P _c are read.

In step 42, the target fuel injection amount Q _FIN is calculated as a function of the internal combustion engine speed N _e and the accelerator opening A _ccp.
Ask for. FIG. 5 is a graph for determining the target fuel injection amount Q _FIN , where the horizontal axis represents the internal combustion engine speed N _e and the vertical axis represents the target fuel injection amount Q _FIN . The parameter is the accelerator opening A _ccp . In step 43, the target fuel injection valve opening time TQ is obtained as a function of the target fuel injection amount Q _FIN and the common rail fuel pressure P _c . FIG. 6 is a graph for determining the target fuel injection valve opening time TQ, in which the horizontal axis represents the target fuel injection amount Q _FIN and the vertical axis represents the target fuel injection valve opening time TQ. The parameter is the fuel pressure P _c in the common rail.

In step 44, the flag IMODE indicating the fuel injection mode is determined, and if it is determined that the pilot injection mode is in effect, the routine proceeds to step 45, where pilot injection control is executed and this routine ends. On the contrary, if it is determined that the normal injection mode is set, step 46 is performed.
Then, the routine proceeds to step 1 to execute the normal injection control and terminate this routine.

FIG. 7 is a detailed flowchart of the pilot injection mode executed in step 45 of the fuel injection control routine shown in FIG. In step 71, the valve opening time TQ _p for pre-injection is determined by the following equation. TQ _p = TQ / k Valve opening time TQ for main injection in step 72
Determine _m by the following equation.

TQ _m = (k-1) TQ / k where k is a coefficient for distributing the target fuel injection valve opening time TQ obtained in step 43 of the fuel injection control routine to the pre-injection and the main injection. Therefore, it is determined experimentally based on the following formula. _{TQ = TQ p + TQ m =} (1 + k) · TQ p Therefore, to determine the number n of the pre-injection as a function of the speed N _e of the rotational speed of the internal combustion engine in _{k = (TQ / TQ p)} -1 Step 73. FIG. 8 is a graph for determining the pre-injection number n, where the horizontal axis represents the rotation speed N _e and the vertical axis represents the pre-injection number n.

That is, if the rotation speed N _e is equal to or less than the first predetermined value N _e1 , the pre-injection number n is set to "1" and the first predetermined value N _{e1 is set.}
If the second predetermined value N _e2 or less, the pre-injection number n is set to "2", and the pre-injection number n is similarly determined. In addition, when the main fuel injection is performed at 30 ° CA after the detection of the reference N _e pulse by using the pulser that outputs the N _e pulse every 15 ° CA, the number of pre-injections n is determined by the following procedure. You can also

That is, the time required for 30 ° CA rotation is represented by 30 / (6 · N _e ), so that the following equation is established. (N-1) .t + t '= 30 / ( _6.Ne ) Therefore, the number of pre-injections n is determined by the following equation.

N = INT [(5 / N _e −t ′) / t] +1 where INT [·] is an integer part of the numerical value in [] and the operator t ′ is the last pre-injection and main Time interval required between injections (seconds) t is time interval between pre-injections (seconds) _Ne is internal combustion engine speed (units rpm).

In step 74, the pre-injection time TQ _P and the main injection time TQ _m are output every n times of pre-injection, and this routine is ended. The pilot injection mode routine shown in FIG. 7 constitutes the pre-injection number calculation means 14 and the pilot injection mode execution means 15. FIG. 9 is a detailed flowchart of the normal injection mode executed in step 46 of the fuel injection control routine shown in FIG.

In step 901, the rotation speed (N_e),
Common rail fuel pressure P_cRead. Step 90
At 2, rotation speed N_eAnd found in step 42 of FIG.
Target injection amount Q_FINCalculate injection start timing TFIN from
It FIG. 10 shows a graph for determining the injection start timing TFIN.
It is rough and rolls to N_e, Vertical axis shows injection start timing
Take TFIN. The parameter is the target injection amount Q _FIN
Is. The injection start timing TFIN is shown in FIG.
Similarly, it is based on TDC.

At step 903, the valve opening timing TTF 'based on the 0th N _e pulse is replaced based on the TFIN obtained at step 902. Normally, the valve opening command (drive pulse) should be issued to the fuel injection valve after this TTF 'time, but in reality, after the drive pulse is output, the fuel injection valve opens with a delay of time TD. Moreover, this delay correlates with the common rail pressure.
Therefore, in order to correct this delay, TTF = (TT
It is necessary to issue a driving pulse after F'-TD) time. Therefore, in step 904, the valve opening delay time TD of the fuel injection valve is obtained as a function of the fuel pressure P _c in the common rail.
FIG. 11 is a graph for determining the valve opening delay time TD of the fuel injection valve, where the horizontal axis represents the common rail internal pressure P _C ,
The ordinate represents the valve opening delay time TD.

Then, in step 905, TTF = TT
The TTF is calculated as F'-TD, this TTF and the injection time TQ obtained in step 43 of FIG. 4 described above are output in step 906, and this routine is ended. This routine constitutes the normal injection mode execution means 13. FIG. 12 is a timing chart of the pilot injection mode, in which the horizontal axis represents time, the vertical axis represents _Ne pulse, drive pulse, drive current, and valve lift of the fuel injection valve.

The first pre-injection is executed by the first N _e pulse, the second pre-injection is executed by the second further t time after the time t, and the main pre-injection is executed by the third pulse N _e. Perform injection. The necessary time t'is secured for the time interval between the third pre-injection and the main injection. FIG. 13 is a timing chart of the normal injection mode, and the horizontal axis and the vertical axis are the same as those in FIG.

A drive pulse after TTF time in consideration of the delay time TD of the fuel injection valve is output based on the 0th N _e pulse, and the valve opening time TQ corresponding to the target fuel injection amount is output.
After that, the drive pulse is turned off.

[0034]

According to the pressure-accumulation type fuel injection device of the present invention, the pre-injection can be executed a number of times according to the operating state of the internal combustion engine, combustion according to the operating state can be realized, and the final injection It is also possible to secure the minimum time interval necessary for reliably executing the main injection between the pre-injection and the main injection.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a pressure accumulation type fuel injection device.

FIG. 2 is a configuration diagram of an embodiment.

FIG. 3 is a flowchart of an injection mode determination routine.

FIG. 4 is a flowchart of a fuel injection control routine.

FIG. 5 is a graph for determining a target fuel injection amount.

FIG. 6 is a graph for determining a fuel injection valve opening time.

FIG. 7 is a detailed flowchart of pilot injection mode.

FIG. 8 is a graph for determining the number of pre-injections.

FIG. 9 is a detailed flowchart of a normal injection mode.

FIG. 10 is a graph for determining the injection start timing.

FIG. 11 is a graph for determining a valve opening delay time.

FIG. 12 is a timing diagram of a pilot injection mode.

FIG. 13 is a timing diagram of a normal injection mode.

FIG. 14 is an example (a) of a drive circuit for a fuel injection valve.
It is a current waveform diagram (b).

[Explanation of symbols]

 201 ... Internal combustion engine 202a-f ... Fuel injection valve 203 ... Common rail 204a-f ... Injection control solenoid valve 205 ... Fuel supply pipe 206 ... Check valve 207 ... High pressure fuel pump 208 ... Fuel tank 209 ... Low pressure fuel pump 210 ... Discharge Quantity control device 211 ... Pressure sensor 212 ... Rotation speed sensor 213 ... Accelerator opening sensor 214 ... Cooling water temperature sensor 215 ... Electronic control device (ECU)

Claims (1)

[Claims] 1. An operating state quantity detecting means for detecting an operating state quantity of an internal combustion engine; a fuel injection mode identifying means for identifying a fuel injection mode based on the operating state quantity detected by the operating state quantity detecting means; On the basis of the operating state quantity detected by the operating state quantity detecting means, a normal injection mode executing means for executing normal fuel injection at a predetermined injection timing when it is determined to be the normal injection mode by the fuel injection mode identifying means, Pre-injection number setting means for setting the number of pre-injections to be performed prior to the main injection that is injected at a predetermined fuel injection timing; and the pre-injection number when the fuel injection mode identification means determines that the pilot injection mode is set. The pre-injection is performed according to the number of injections set by the injection number setting means, and the main injection is performed after a predetermined time or more has elapsed from the completion of the pre-injection. Accumulator fuel injection device comprising a pilot injection mode executing means for performing a.