JPH0968081A - Fuel injection timing control device of diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimally control the fuel injection timing of a diesel engine so as to coincide with the target timing by detecting the timing of a characteristic point of a combustion pressure waveform. SOLUTION: Combustion pressure acting on a glow plug or a fuel injection nozzle is detected by a combustion pressure sensor, and the ignition timing θf being a rising point of a combustion pressure waveform is detected (S1) on the basis of this. The target timing X is set (S2) on the basis of an engine operating condition. The fuel injection timing is controlled (S3 to S6) by making a feedback process so that the ignition timing θf coincides with the target timing X. Or the combustion pressure maximum timing being a peak point of a combustion pressure waveform is detected, and the fuel injection timing is controlled by making a feedback process so that this coincides with the target timing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection timing control device for a diesel engine.

[0002]

2. Description of the Related Art A conventional distributed fuel injection pump for a diesel engine includes a timer piston as a fuel injection timing adjusting member, and the fuel injection timing is adjusted according to the moving position of the timer piston. . A high-pressure chamber is formed at one end of the timer piston to guide the high-pressure fuel pumped by the feed pump, and the other end of the timer piston communicates with the suction-side suction chamber of the feed pump. A low pressure chamber is formed.

A communication passage that connects the high pressure chamber and the low pressure chamber is provided, and an electromagnetic control valve is provided in this communication passage. This control valve is opened / closed by duty control, and the pressure of the high pressure chamber is controlled by controlling the amount of fuel flowing from the high pressure chamber to the low pressure chamber by the duty ratio.
In this way, the pressure difference between the high pressure chamber and the low pressure chamber is controlled, and the position of the timer piston is controlled by the balance with the spring that has acted in advance on the timer piston to adjust the fuel injection timing.

By the way, in the case of feedback controlling the fuel injection timing of a diesel engine, conventionally, the injection vibration of the fuel injection nozzle is detected by a piezoelectric sensor (piezo element or the like), and this detection timing becomes a predetermined target time. As described above, the control valve is duty-controlled.

[0005]

However, in feedback control of the fuel injection timing of the diesel engine, it is difficult in terms of layout to mount a sensor for detecting the injection vibration of the fuel injection nozzle at an appropriate position of the fuel injection nozzle. There was a problem. This is because the sensor cannot be installed in the vicinity of the nozzle due to the temperature, and the sensor is located away from the nozzle, making it difficult to pick up the jet vibration.

Further, even if the sensor detects the actual injection timing of the fuel injection nozzle and controls it to the target timing, it does not mean that the actual ignition timing or combustion state is being observed. If ignition deviation or the like occurs due to load conditions (charging efficiency) or the like, an optimal combustion state cannot be obtained, and there is a problem that optimal control is not always achieved.

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and an object thereof is to enable optimum control of fuel injection timing.

[0008]

Therefore, in the invention according to claim 1, as shown in FIG. 1, combustion pressure detecting means for detecting the combustion pressure in the cylinder of the diesel engine,
Combustion pressure waveform characteristic timing detecting means for detecting the timing of the characteristic point of the combustion pressure waveform based on the detected combustion pressure, and fuel injection so that the timing of the characteristic point of the detected combustion pressure waveform matches its target timing. A fuel injection timing feedback control means for feedback controlling the fuel injection timing by the pump is provided to configure a fuel injection timing control device for a diesel engine.

That is, the combustion pressure in the cylinder is detected, and the timing of the characteristic point of the combustion pressure waveform is detected based on this. Then, the fuel injection timing is feedback-controlled so that the timing of the characteristic point of the combustion pressure waveform matches the target timing. In the invention according to claim 2, as the timing of the characteristic point of the combustion pressure waveform, the ignition timing which is the rising point of the combustion pressure waveform is detected.

Therefore, the combustion pressure detecting means for detecting the combustion pressure in the cylinder of the diesel engine, the ignition timing detecting means for detecting the ignition timing which is the rising point of the combustion pressure waveform based on the detected combustion pressure, and the detecting means. And a fuel injection timing feedback control means for feedback controlling the fuel injection timing so that the ignition timing matches the target timing.

That is, the combustion pressure in the cylinder is detected, and based on this, the ignition timing, which is the rising point of the combustion pressure waveform, is detected. Then, the fuel injection timing by the fuel injection pump is feedback-controlled so that the ignition timing coincides with the target timing. In the invention according to claim 3, the combustion pressure maximum timing which is the peak point of the combustion pressure waveform is detected as the timing of the characteristic point of the combustion pressure waveform.

Therefore, the combustion pressure detecting means for detecting the combustion pressure in the cylinder of the diesel engine and the combustion pressure maximum timing detection for detecting the combustion pressure maximum timing which is the peak point of the combustion pressure waveform based on the detected combustion pressure. Means and
The fuel injection timing feedback control means for feedback controlling the fuel injection timing by the fuel injection pump is provided so that the detected maximum combustion pressure timing coincides with the target timing, and the fuel injection timing control device for the diesel engine is configured.

That is, the combustion pressure in the cylinder is detected, and based on this, the maximum combustion pressure timing, which is the peak point of the combustion pressure waveform, is detected. Then, the fuel injection timing is feedback-controlled so that the maximum combustion pressure timing coincides with the target timing. The invention according to claim 4 is characterized by comprising target timing setting means for setting a target timing (target ignition timing, target combustion pressure maximum timing) based on engine operating conditions.

The invention according to claim 5 is characterized in that the combustion pressure detecting means is a piezoelectric sensor provided at a position for receiving the combustion pressure acting on the glow plug. The invention according to claim 6 is characterized in that the combustion pressure detecting means is a piezoelectric sensor provided at a position for receiving combustion pressure acting on the fuel injection nozzle.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. First, a first embodiment will be described. FIG. 2 shows the system configuration. The diesel engine 1 includes a distributed fuel injection pump 2. In this distribution type fuel injection pump 2, the fuel injection timing is adjusted by the duty control of the control valve 3 for adjusting the fuel injection timing, and the high-pressure fuel is delivered to the fuel injection nozzle 4 at the adjusted timing to enter the cylinder. Fuel injection is performed. Then, the fuel is compression ignited in the cylinder and burned. It should be noted that the ignition is assisted by being heated by the glow plug 5 as necessary at the time of starting.

According to the structure of the present invention, as a combustion pressure detecting means, the glow plug 5 has a threaded mounting portion,
A combustion pressure sensor (piezoelectric sensor) 6 composed of a piezoelectric element is provided on the mounting washer so as to detect the combustion pressure P acting on the glow plug 5. As a combustion pressure detecting means, a combustion pressure sensor (piezoelectric sensor) 6'comprising a piezoelectric element is provided in the form of a mounting washer on the screw-in type mounting portion of the fuel injection nozzle 4, and the combustion acting on the fuel injection nozzle 4 The pressure P may be detected.

Further, a crank angle sensor 7 which outputs a pulse signal in synchronization with the crank angle is provided so that the crank angle θ can be detected and the engine speed NE can be calculated. Also, this crank angle sensor 7
A TDC sensor for detecting the TDC position is built in.
Further, a potentiometer-type accelerator sensor 8 is provided to detect the accelerator depression amount AC.

The signals of these sensors 6 to 8 are input to the control unit 9. The control unit 9 controls the duty of the control valve 3 for adjusting the fuel injection timing by executing the fuel injection timing control routine of FIG. 3 every predetermined time or every predetermined crank angle by the built-in microcomputer. Control the fuel injection timing.

The fuel injection timing control routine of FIG. 3 will be described. In step 1 (denoted as S1 in the drawing; the same applies hereinafter), the ignition timing θf, which is the rising point of the combustion pressure waveform, is detected based on the combustion pressure P detected based on the signal from the combustion pressure sensor 6. To do. This portion corresponds to the combustion pressure waveform characteristic timing (ignition timing) detection means.

However, the actual detection is performed by another routine. That is, while monitoring the crank angle based on the signal from the crank angle sensor 7, the signal from the combustion pressure sensor 6 is A / D converted at every predetermined sampling timing to read the combustion pressure P, and at the same time, the previous time. Amount ΔP = P-P from the combustion pressure Pold at the sampling timing of
old is calculated, and this change amount ΔP is compared with a predetermined value. Then, when ΔP ≧ predetermined value, the crank angle at that time is read and used as the ignition timing θf (see FIG. 4).

When the combustion pressure P is detected, the signal from the combustion pressure sensor 6 includes the compression pressure. Therefore, the base pressure based on the compression pressure at each crank angle is calculated in advance, and this is subtracted. It is advisable to detect this as the combustion pressure P. In step 2, the engine operating speed NE calculated based on the signal from the crank angle sensor 7 and the accelerator pedal depression amount AC detected based on the signal from the accelerator sensor 8 are read as engine operating conditions, and from these, , The target time (target ignition time) X is set with reference to the map. This part corresponds to the target time setting means.

In step 3, the actual ignition timing θf is compared with the target timing X. As a result of the comparison, when θf <X, the routine proceeds to step 4, where the duty D for the control valve 3 is advanced to advance the fuel injection timing so that θf = X.
Decrease UTY (%). Note that the duty ratio DUTY decreases, the opening time ratio of the control valve 3 decreases, the differential pressure between the high pressure chamber and the low pressure chamber acting on the timer piston increases, and the timer piston moves to the advance side. The fuel injection timing advances.

On the contrary, when θf> X, the routine proceeds to step 5, where the duty DUTY (%) for the control valve 3 is increased in order to retard the fuel injection timing so that θf = X. The duty ratio DUTY increases, the opening time ratio of the control valve 3 increases, the differential pressure between the high pressure chamber and the low pressure chamber acting on the timer piston decreases, and the timer piston moves to the retard side. The fuel injection timing is delayed.

When θf = X, the duty DUTY
(%) Is maintained at the current value. After that, in step 6, the duty DUTY is output to the control valve 3.
Here, steps 3 to 6 correspond to the fuel injection timing feedback control means.

By controlling the fuel injection timing in this way, the ignition timing can be controlled to the target timing. Next, a second embodiment will be described. The system configuration is the same as that of FIG. 2 except that the microcomputer in the control unit 9 executes the fuel injection timing control routine of FIG.

The fuel injection timing control routine of FIG. 5 will be described. In step 11, the combustion pressure maximum timing θpmax, which is the peak point of the combustion pressure waveform, is detected based on the combustion pressure P detected based on the signal from the combustion pressure sensor 6. This portion corresponds to the combustion pressure waveform characteristic timing (combustion pressure maximum timing) detection means.

However, the actual detection is performed by another routine. That is, while monitoring the crank angle based on the signal from the crank angle sensor 7, the signal from the combustion pressure sensor 6 is A / D converted at every predetermined sampling timing, and the combustion pressure P is read while one combustion is being performed. The maximum value of the combustion pressure P in the stroke is found, the crank angle at that time is stored and held, and this is set as the combustion pressure maximum timing θpmax (Fig. 6).
reference).

In step 12, the target time (maximum target combustion pressure time) Y is set at the MBT point (normal A
TDC 15 degree). In addition to the constant value as described above, the engine speed NE is also the same as in step 2 of FIG.
The target time (target combustion pressure maximum time) Y may be set by reading the accelerator depression amount AC and the accelerator depression amount AC and referring to the map.

In step 13, the actual combustion pressure maximum timing θpmax is compared with the target timing Y. As a result of comparison, θpmax
When <Y, the routine proceeds to step 14, where the duty DUTY (%) for the control valve 3 is decreased in order to advance the fuel injection timing so that θpmax = Y. Conversely, θpmax
When> Y, the routine proceeds to step 15, where the duty DUTY (%) for the control valve 3 is increased in order to retard the fuel injection timing so that θpmax = Y.

When θpmax = Y, the duty DUTY
(%) Is maintained at the current value. After that, in step 16, the duty DUTY is output to the control valve 3.
Here, steps 13 to 16 correspond to the fuel injection timing feedback control means.

By controlling the fuel injection timing as described above, the maximum combustion pressure timing can be controlled to the target timing. In particular, by setting the target time as the MBT point, it is possible to operate at the highest efficiency at all times, and because the MBT point is determined by the engine, there is no need for a map for setting the target time, saving memory, and no further adaptation is required. Therefore, variations in each fuel injection nozzle can be automatically corrected.

[0032]

As described above, according to the first aspect of the invention, since the combustion pressure in the cylinder is detected, the sensor arrangement is different from the conventional case where the injection vibration of the fuel injection nozzle is detected. The effect of increasing the degree of freedom of is obtained. In addition, the timing of the characteristic point of the combustion pressure waveform is detected from the combustion pressure, and the fuel injection timing is feedback-controlled so that this coincides with the target time. The control is performed, and the effect of improving fuel efficiency and the like is obtained.

According to the second aspect of the present invention, the ignition timing, which is the rising point of the combustion pressure waveform, is detected as the characteristic point of the combustion pressure waveform, and the fuel injection timing is set so that it coincides with the target timing. Since the feedback control is performed, even if the ignition deviation occurs, the optimum control is always performed, and the effect of improving the fuel consumption and the like can be obtained. According to the invention of claim 3, the combustion pressure maximum timing, which is the peak point of the combustion pressure waveform, is detected as the timing of the characteristic point of the combustion pressure waveform, and the fuel injection timing is fed back so that this coincides with the target timing. Since the control is performed, the optimum control is always performed, and by setting the target time at the MBT point, it is possible to obtain the effect of operating at the highest efficiency.

According to the fourth aspect of the present invention, the target time is set based on the engine operating conditions, so that there is an effect that the optimum control adapted to the engine operating conditions becomes possible. According to the invention of claim 5, as the combustion pressure detecting means, by using the piezoelectric sensor provided at the position for receiving the combustion pressure acting on the glow plug, there is an effect that the combustion pressure can be detected relatively easily and accurately. can get.

According to the sixth aspect of the present invention, the combustion pressure is detected relatively easily and accurately by using the piezoelectric sensor provided at the position for receiving the combustion pressure acting on the fuel injection nozzle as the combustion pressure detecting means. The effect that it can be obtained.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention.

FIG. 2 is a system configuration diagram showing a first embodiment of the present invention.

FIG. 3 is a flowchart of a fuel injection timing control routine.

FIG. 4 is a diagram showing a method of detecting an ignition timing θf.

FIG. 5 is a flowchart of a fuel injection timing control routine showing a second embodiment.

FIG. 6 is a diagram showing a method for detecting the combustion pressure maximum timing θpmax.

[Explanation of symbols]

 1 Diesel engine 2 Fuel injection pump 3 Control valve for fuel injection timing adjustment 4 Fuel injection nozzle 5 Glow plug 6 Combustion pressure sensor (piezoelectric sensor) 6'Combustion pressure sensor (piezoelectric sensor) 7 Crank angle sensor 8 Accelerator sensor 9 Control unit

Claims (6)

[Claims] 1. A combustion pressure detecting means for detecting a combustion pressure in a cylinder of a diesel engine, and a combustion pressure waveform characteristic time detecting means for detecting a timing of a characteristic point of a combustion pressure waveform based on the detected combustion pressure. Fuel injection timing feedback control means for feedback-controlling the fuel injection timing by the fuel injection pump so that the timing of the characteristic point of the detected combustion pressure waveform matches the target timing, and the fuel injection of the diesel engine including: Timing control device. 2. Combustion pressure detecting means for detecting combustion pressure in a cylinder of a diesel engine; ignition timing detecting means for detecting ignition timing which is a rising point of a combustion pressure waveform based on the detected combustion pressure; A fuel injection timing control device for a diesel engine, comprising: a fuel injection timing feedback control unit that feedback-controls the fuel injection timing of the fuel injection pump so that the ignition timing is matched with the target timing. 3. A combustion pressure detecting means for detecting a combustion pressure in a cylinder of a diesel engine, and a combustion pressure maximum timing detection for detecting a combustion pressure maximum timing which is a peak point of a combustion pressure waveform based on the detected combustion pressure. Fuel injection timing feedback control means for feedback controlling the fuel injection timing by the fuel injection pump so that the detected maximum combustion pressure timing coincides with the target timing. Control device. 4. The fuel injection timing control device for a diesel engine according to claim 1, further comprising target timing setting means for setting a target timing based on engine operating conditions. . 5. The diesel engine according to claim 1, wherein the combustion pressure detecting means is a piezoelectric sensor provided at a position for receiving combustion pressure acting on a glow plug. Engine fuel injection timing control device. 6. The combustion sensor according to claim 1, wherein the combustion pressure detecting means is a piezoelectric sensor provided at a position for receiving combustion pressure acting on a fuel injection nozzle.
And a fuel injection timing control device for the diesel engine.