JPS6318157A - Pilot injection controller - Google Patents

Abstract

PURPOSE:To control a pilot injection quantity of fuel properly, by detecting whether there is ignition of the fuel by pilot injection or not on the basis of a combustion state of the duel sprayed to a combustion chamber, and controlling the pilot injection quantity according to this ignition state. CONSTITUTION:A combustion state detecting device 2 detects a combustion state of the fuel sprayed to a combustion chamber. And, an electric controller 3 controls this combustion state detecting device 2 and a pilot injection device 4 on the basis of each signal out of a crank angle sensor 5, an accelerator sensor 7 and a water temperature sensor 8 or the like, and this controller 3 is constituted of a microcomputer 30 and a waveform shaping circuit 37. In addition, the pilot injection device 4 drives a piezoelectric actuator 40 of a pezoelectric drive circuit 41 according to a control signal out of the microcomputer 3, and controls a pilot injection quantity or an injection stopping period. With this constitution, the pilot injection quantity is controlled so as to be approximated to the irreducible minimum of the injection quantity required for ignition of pilot injection fuel.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides pilot injection prior to main fuel injection (hereinafter referred to as main injection) in order to reduce noise and vibration of a diesel engine, for example, when idling. The present invention relates to a pilot injection control device having a mechanism for controlling.

[Conventional technology]

The main control items for pilot injection to improve the fuel injection rate are the injection amount of pilot injection (hereinafter referred to as pilot injection amount) and the injection stop period between pilot injection and main injection (hereinafter referred to as injection stop period). ), but conventionally, these two items are limited to, for example, idling before the diesel engine warms up, and the values of both at idling are fixed values, and the pilot injection amount is set to the main injection amount. For example, Japanese Unexamined Patent Publication No. 1351/1983 discloses a device that fixes the amount of spark to an appropriate level and determines the injection stop period as a function of diesel engine speed, engine load, engine cooling water temperature, etc. There is.

[Problem that the invention seeks to solve]

However, in the above-mentioned device in which the pilot injection amount and injection stop period are set to fixed values, there is a problem that the pilot injection effect fades after the diesel engine warms up, and also as a function of the diesel engine cooling water temperature etc. Control the injection stop period? Even in IO equipment, the pilot injection amount changes not only due to differences in operating conditions of the diesel engine, such as when it is cold and after it has been warmed up, but also due to engine differences, aging changes in the injection nozzle opening pressure, etc. However, there is a problem in that the variations cannot be corrected in principle.

Therefore, in view of the above points, the present invention provides an appropriate pilot injection amount that reduces engine vibration and noise and exhaust gases such as nitrogen oxides and NOx without being adversely affected by engine differences, aging, etc. The purpose is to provide a pilot injection control device that can control the

[Means for solving problems]

In order to achieve the above object, the pilot injection control 21 device of the present invention includes a pilot injection means for performing pilot injection prior to main fuel injection into the combustion chamber of a diesel engine, and a combustion chamber for the fuel injected into the combustion chamber. combustion state detection means for detecting the combustion state; ignition detection means for detecting whether fuel is ignited by the pilot injection in response to a signal from the combustion state detection means; This configuration includes pilot injection control means for outputting a signal for controlling the injection amount of pilot injection to the pilot injection means.

[Effect]

With the above configuration, the present invention makes it possible to control as the pilot injection amount the minimum injection amount that should become the spark for the main injection that is injected later after the pilot injected fuel ignites. effectively suppress the incidence,
Quiet operation with low NOx emissions is possible.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The pilot injection device according to the present invention will be explained in detail below with reference to embodiments shown in the drawings. FIG. 1 is an overall configuration diagram showing an embodiment of the present invention. 1 is a combustion chamber of a diesel engine. Reference numeral 2 denotes a combustion state B detection means for detecting the combustion state of fuel injected into the combustion chamber of a diesel engine. In this embodiment, for example, a known ignition sensor that converts light into an electrical signal using a phototransistor or the like is used. ing.

Reference numeral 3 denotes an electric control device that receives signals from the combustion state detection means 2 and each sensor described later and controls the pilot injection means 4, which will be described later. It consists of a waveform shaping circuit 37.

The microcomputer 30 includes a CPU 31. R○M32
．． RAM33. A/D converter 34. timer 35, l10
It is composed of 36 etc. Next, the waveform shaping circuit 37
The signal processing in will be explained using FIG. Figure 2 (
al is an electric circuit diagram showing the configuration of the waveform shaping circuit 37, and a resistor R1 is a current detection resistor for converting the phototransistor current outputted from the combustion state detection means 2 into a voltage in this embodiment. The voltage-converted signal is then input to the positive input of the comparator 0P. On the other hand, the negative input has a threshold voltage that becomes the reference voltage, and resistors R2 and R3.
The partial pressure ratio is determined and input.

Figure fb) and fa) show the waveforms of the signals at points A and B in the figure.

■ and ■ indicate when the pilot injection amount is too small, and the ignition of the fuel due to picont injection cannot be observed, and the ignition occurs at the ignition timing t of the main injected fuel. It has only been observed once. ■ and ■ indicate cases where the pilot injection amount is sufficient for pilot injection fuel to ignite. In this case, ignition occurs between the pilot injection fuel ignition timing tiGIF and the main injection fuel ignition timing L. i
It has been observed twice with GM. The signal whose waveform has been shaped in this manner is input to the interrupt port of the microcomputer 30, and by detecting whether ignition has occurred once or twice, it is determined whether or not fuel is ignited by pilot injection. be. Note that it is desirable that the threshold voltage is a value smaller than the minimum value of the voltage level detected when the fuel by pilot injection is ignited.

In FIG. 1, reference numeral 4 denotes a pyro-injection means, in which a piezo drive circuit 41 charges and discharges a piezo actuator 40 in response to a control signal from a microcomputer 30, thereby increasing the amount of pyro-injection or the injection stop period. It controls the Reference numeral 5 denotes a crank angle sensor, which serves both as a rotation speed sensor for detecting the reference angle of the diesel engine and the rotation speed of the diesel engine. or,
This crank angle sensor 5 outputs one pulse for each injection, and serves as a reference for the timing of outputting a control signal to the pilot injection means 4, etc. For example, a known balsa detector using a magnetoresistive element can be used for this purpose.

Other signals input to the electric control device π3 include signals from an accelerator sensor 7 for detecting the amount of accelerator, a water temperature sensor 8 for detecting the cooling water temperature of the diesel engine, and the like. As the accelerator sensor 7, a potentiometer type sensor that detects the opening degree of the accelerator pedal can be used, and as the water temperature sensor 8, a thermistor type sensor can be used.

FIG. 3 shows the configuration of the pilot injection means 4. 6
is, for example, a Bosch type distribution fuel injection pump, and 61
is a plunger that is pushed to the left in the figure by a face cam (not shown) to make the fuel in the high pressure chamber 62 high pressure, and the nozzle 6
3, fuel is injected into the combustion chamber of a diesel engine (not shown).

A piezo actuator 40 is mounted facing the high pressure chamber 62 and utilizes a piezo voltage effect, and has a structure such as that disclosed in, for example, Japanese Patent Laid-Open No. 18249/1983. 41 is a piezo drive circuit, which charges the piezo actuator 40 and discharges the generated charge to expand and contract the piezo element and change the pressure of the high pressure chamber 62 to perform pilot injection. .

This drive circuit 41 receives a signal V B 2 from the microcomputer 30 and includes a transistor 411 for discharging the charge stored in the piezo actuator 40;
a resistor 412 for protecting the transistor 411;
An inductor 413 for storing energy from the battery in the form of current, a diode 414 for preventing current from flowing back from the piezo actuator 40 to the battery via the inductor 413, and the microcomputer 3.
In response to signal Vll from 0, battery inductor 4
13→Piezo actuator 40. The transistor 415 transfers energy along the path of piezo actuator 40 to generate a high voltage between both terminals of piezo actuator 40.

Next, the operation of the pylon injection means 4 will be explained with reference to the time chart shown in FIG. In the figure, (a) is a signal from the crank angle sensor 5, which is set so that one pulse is generated around the time when injection ends and combustion is completed.

tb+ in the figure shows the lifted state of the plunger.

FIG. 4C shows a control signal for the transistor 415, and in this embodiment, the transistor 415 is turned on in synchronization with the signal from the crank angle sensor 5. When the transistor 415 is in the “ON” state,
A current of 1. begins to flow. and time t. Later, the control signal Vll from the microcomputer 30 is cut off, and the transistor 415 is turned off.
When this state is reached, all of the energy stored in the form of current in the inductor 413 is transferred to the piezo actuator 40, so the voltage V between both terminals of the piezo actuator 40 becomes a high voltage VCO as shown in FIG. After that, when the plunger starts to lift, the pressure in the high pressure chamber 62 increases, and the piezo actuator 40 generates its own voltage, so the voltage (2) increases and becomes (2).

By this time, the pressure in the high pressure chamber 62 has reached the nozzle opening pressure or higher, and injection has started (pilot injection) as shown in the figure (gl). At this time, as shown in the figure (d), the transistor 41
1 is the control from the microcomputer 30'<I'll
In response to No. 1s ■8□, it becomes "ON" state, the high voltage v2, 4 stored in the piezo actuator 40 is discharged, the piezo actuator 40 contracts, the pressure in the high pressure chamber 62 decreases, and the injection is stopped once. , a pilot injection is formed. After that, the plunger lifts again and the high pressure chamber 6
2 pressure rises and injection resumes. Then, the injection is stopped by a governor mechanism (not shown), and main injection is formed.

Here, as shown by the dotted line in the figure, the transistor 415 "
When the "ON" state time 1w is increased, the value of the charge voltage VCH becomes larger, and the value of the high voltage ■ becomes thicker.
The larger the values of 1 and 4 are, the larger the amount of contraction of the piezo actuator 40 is, so the injection stop period T becomes longer. That is, the "ON" state time t of the transistor 415. The injection stop period T can be controlled by. Furthermore, by changing the “ON” timing TMG of the transistor 411, the timing at which the injection stop timing starts changes.
The pilot injection amount can be controlled by the N'' timing TMG.

In addition, fhl in the figure shows the combustion waveform output from the combustion state detection means 2. After the pilot injection is started, the pilot injected fuel ignites after an ignition delay period of T, and this ignition phenomenon occurs. It serves as a spark for the main injection fuel that is injected later, and shows how the main injection fuel that is supplied next burns diffusely based on the spark from the pilot injection fuel.

FIG. 1 (1) shows a signal after the combustion waveform has been shaped by the waveform shaping circuit 37. Here, Fig. 4 shows an example in which the injection amount is sufficient for the pilot injection to ignite the fuel, and the signal is converted into a rectangular signal compared with the threshold voltage ① mentioned above. , two ignitions were detected, including fuel ignition due to main injection. In addition, each ignition timing is tiGP+
It is tiGM.

The pilot injection means 4, which can control the pilot injection amount and injection stop period as described above, and the signal from the waveform shaping circuit 37 determine whether or not the fuel is ignited by the pilot injection, and the amount of fuel is set as the pilot injection amount. An example of the algorithm within the microcomputer 30 for controlling the injection to the minimum pilot injection amount that allows ignition will be explained using the flowchart of FIG. 5 and the diagram showing the fuel waveform according to the pilot injection amount of FIG. 6. First, FIG. 5 is a flowchart showing the main program of the microcomputer 30. After confirming the start of the diesel engine in step 100, in step 101 the reference value q of the pilot injection amount and the reference value T of the injection stop period are set to initial values. Put in. This standard value T
For example, it is preferable to set the values of the pyro injection amount and injection stop period that are optimal during idling before warming up the diesel engine in a standard climate. Further, the reference value q is preferably set to a relatively large value as the amount of pilot injection sufficient to ignite the pilot injected fuel in any operating state of the diesel engine.

The reference values q and T are converted to time TMG and time t8 in FIG. 4 according to an experimentally determined conversion formula, and then output to the pilot injection means 4 using the timer interrupt function of the microcomputer 30. It is something that will be done.

Next, in step 102, operating state signals such as the number of rotations of the diesel engine detected by the crank angle sensor 5, the amount of acceleration detected by the accelerator sensor 7, and the cooling water temperature detected by the water temperature sensor 8 are taken in. In step 103, as explained using FIG. 2, the number of times fuel ignition occurs is checked using the interrupt port of the microcomputer 30, and one ignition by main injection (tlGM) is checked. It is detected whether ignition by pilot injection (tiGP) also occurs and the number of ignitions is two.

Next, in steps 104 to 106, the pilot injection amount,
Further, in step 107, the injection stop period is updated. First, in step 104, it is determined whether the pilot injection amount is to be increased or decreased.

This is done by checking the current number of ignitions, which has been taken in at step 103. As shown in FIG. 6(al), if the pilot injected fuel causes an ignition error and the ignition occurs once during the main injection at time t, the process proceeds to step 106 to increase the pilot injection amount.

In addition, as shown in Fig. 6 (C), ignition was performed twice (pilot injection ignition (L 5ap) and main injection ignition (ticM)).
When detected, it is assumed that the pilot injection amount is sufficient, and the process proceeds to step 105 to reduce the pilot injection amount to Nff1.

In step 105, the previous pilot injection amount q(r-
The current pilot injection amount q is reduced by a predetermined amount ΔQD from u, 8. shall be. Incidentally, Δq may be a constant amount or may be arbitrarily determined depending on the operating conditions (for example, rotation speed, accelerator amount, cooling water temperature, etc.).

In step 106, the previous pilot injection amount q<=-
1, is increased by a predetermined amount Δq5 to obtain the current pilot injection amount q. ). Here, Δqu may be the same value as Δq, or may be in the relationship, for example, Δqu>ΔQo, where both Δq, .

By setting Δq to an appropriate amount, the number of pilot injection ignition errors can be reduced.

Next, in step 107, the injection stop period T is controlled according to the operating state. In other words, by referring to predetermined map data according to the rotation speed, accelerator amount, cooling water temperature, etc.
Always control to the optimum injection stop period. After that, step 1
By repeating steps 02 to 107, the sixth
Optimum control of the injection stop period according to the operating state and the minimum pilot injection amount required for ignition as shown in Figure tb+ can be realized.

As described above, according to this embodiment, since the combustion state of the pilot injection to be controlled is directly detected by the combustion state detection means 2, there is no need to worry about engine differences, aging, etc. of the diesel engine in the control. (The pilot injection amount can be stably controlled over a long period of time to the minimum necessary amount that can best reduce the vibration and noise of the diesel engine and exhaust gases such as NOx, and the injection stop period can also be adjusted to the optimum amount according to the operating state.) You can control the period.

It should be noted that the present invention is not limited to the above embodiments, and can be modified in various ways as shown below without departing from the spirit thereof.

(1) In the above embodiment, the base Y$ of the waveform shaping circuit 37
Threshold voltage of lightning voltage ■Yes! [Anti-Rz and R3
The value was determined by the partial pressure ratio of It is also possible to change the value to a value and output the value from the microcomputer 30 to the negative input of the comparator oP.

(2) In the output signal of the waveform shaping circuit 37, for example, detect the interval between the ignition timing j iGP of the pilot injection and the ignition timing t iGM of the main injection, and control the injection stop timing or the pilot injection amount according to the detected value. You may.

(3) In the algorithm in the microcomputer 30, the determination of fuel ignition error due to pilot injection, that is, the number of ignitions is 1, is determined once out of n times (i
Step 1 in Figure 5 only when ≦n) or more is detected.
The control may proceed to 06 and control the pilot injection amount to be increased. By doing this, even when the presence or absence of ignition varies to some extent because the diesel engine uses a self-ignition method,
This can prevent problems such as erroneous judgments.

(4) The microcomputer 30 determines that there is not much variation in the minimum amount of pilot injection necessary for igniting the fuel by pilot injection, such as when the engine speed, load, etc. are approximately constant. In such a case, when an ignition error in pilot injection is detected, control may be performed such that, for example, the previous pilot injection amount is used without being updated for a predetermined period of time.

〔Effect of the invention〕

As described above, according to the pilot injection control device of the present invention, it is possible to control the pilot injection amount so that it approximates the minimum injection amount necessary for the pilot injected fuel to ignite. It is possible to control the large initial heat release rate due to combustion to the minimum initial heat release rate, and it does not depend on engine differences or aging of the diesel engine (also, the optimum pilot It has the excellent effect of being able to control injection and reducing vibration, noise, and exhaust gases such as NOx.

[Brief explanation of the drawing]

Figure 1 is an overall configuration diagram showing one embodiment of the present invention, and Figure 2 (
a) is an electric circuit diagram of the waveform shaping circuit of the embodiment shown in FIG. 4 is a time chart for explaining the operation of the embodiment in FIG. 1; FIG. 5 is a flowchart showing the main program of the microcomputer in the embodiment in FIG. 1; the sixth leap is a pilot It is a diagram showing a combustion waveform according to the injection amount. 1... Combustion chamber, 2... Combustion state detection means, 3...
Electrical control device, 4... Pilot injection means, 5...
- Crank angle sensor, 30... microcomputer, 37... waveform shaping circuit.

Claims (3)

[Claims] (1) Pilot injection means that performs pilot injection prior to main fuel injection into the combustion chamber of a diesel engine; Combustion state detection means that detects the combustion state of the fuel injected into the combustion chamber; and the combustion state detection means ignition detection means for detecting whether or not fuel is ignited by the pilot injection in response to a signal from the ignition detection means; A pilot injection control device comprising a pilot injection control means for outputting an output. (2) The ignition detection means detects the presence or absence of ignition of the fuel by comparing a voltage level serving as a predetermined reference with a voltage level according to a signal from the combustion state detection means. The pilot injection control device according to the range 1 above. (3) The pilot injection control means reduces the injection amount of the pilot injection until the ignition detection means detects that the fuel injected by the pilot injection has not ignited, and the pilot injection control means reduces the injection amount of the pilot injection until the ignition detection means detects that the fuel injected by the pilot injection has not ignited. 3. The pilot injection control device according to claim 1, wherein the pilot injection control device outputs a signal to the pilot injection means to increase the injection amount when it is detected that the injection amount is not increased.