JPH063163B2 - Injection timing control device for diesel engine - Google Patents

Description

The present invention relates to a diesel engine injection timing control device.

In a diesel engine, such as an automobile diesel engine, which is normally used in a wide rotation range, it is necessary to finely control the fuel injection timing in accordance with its operating condition in order to obtain optimum engine performance. In this type of engine, the timing at which the fuel injected into the cylinder ignites and burns is a fundamental factor that determines the engine performance such as output, fuel consumption, exhaust gas components, noise, etc., and good engine performance depending on various operating conditions. It is required for the injection timing control device to realize a combustion timing that obtains

Therefore, various operating conditions such as the engine speed and the injection amount are detected by an electrical operating condition detector, the target injection timing is electrically calculated according to the operating condition, and the injection pump is operated according to the target injection timing. An injection timing control device for electrically controlling the injection timing adjusting mechanism of is required.

It is generally known that there is a strong correlation between the ignition timing of a gasoline engine and the injection timing of a diesel engine and the cylinder pressure, but the crank angle θ (MAX.P) that gives the maximum pressure
Is a tendency to become smaller as the advance / retard factors such as the ignition timing of the gasoline engine and the injection timing of the diesel engine are advanced, but in the best torque state, it does not depend on parameters such as the rotational speed, the intake pipe pressure, and the air-fuel ratio, It has been found that θ (MAX.P) is almost constant. Therefore, it is possible to perform the injection timing control using the crank angle θ (MAX.P) characteristic that gives the maximum pressure.

However, the compression pressure of the diesel engine reaches 50kg / cm ² or more, and the pressure increase P (IGN) due to ignition does not exceed the compression pressure P (COMP) when the load is light as shown in Fig. 1 (A). In some cases. Under such conditions, satisfactory results cannot be obtained by simply controlling θ (MAX.P).

In view of the above problems in the conventional type, the present invention has an idea of controlling the injection timing so that the output of the piezoelectric type pressure detector, that is, the point where the pressure change becomes positive to negative, is detected, and the injection timing is controlled to a predetermined value. Therefore, the injection timing control is performed more appropriately so that the diesel engine can always be operated in the best torque state.

The invention is based on the following facts. First, the pressure waveform of the diesel engine (charge-up output of the piezoelectric type detector) is shown in FIG. 1 (B), and the pressure change waveform (output of the piezoelectric type detector) is shown in FIG. 1 (C). When the fuel is injected at a constant injection amount and the injection timing is changed from the retard side to the advance side, the waveforms of the pressure and the pressure change are from ignition time 1 (IGN-1) to ignition time 3 (IGN-1).
-3) changes.

At ignition time 1 (IGN-1), the injection timing is too late, so the pressure rise due to combustion is not sufficient in the explosion stroke, and no pressure peak due to combustion is seen. The pressure change, which is the output of the pressure detector, does not rise above 0 after TDC. At this time, the torque does not become the best torque.

At ignition time 3 (IGN-3), the injection timing is too early, so the pressure peak during combustion exceeds the compression pressure peak. At this time, knocking generally occurs, vibration and noise are severe, and the torque is smaller than the best torque.

At ignition time 2 (IGN-2), the injection timing is an appropriate value and is near the best torque. The point where the pressure change changes from positive to negative at this time.
The point a in (C) has a substantially constant value depending on the engine, and for example, the crank angle is around 10 ° ATDC.

In the present invention, a piezoelectric pressure detector that detects a change in the combustion pressure of the internal combustion engine, a timing detection circuit that detects that the rotation of the engine is at a predetermined crank angle, and an output signal of the piezoelectric pressure detector. And an output signal of the timing detection circuit for controlling the injection timing, wherein the crank angle counting is started from a predetermined crank angle detected by the timing detection circuit, and the piezoelectric pressure detection is performed. A counter that stops counting the crank angle at a crank angle at which the output of the device becomes more negative than positive, comparison means that compares the output value of this counter with a predetermined value, and the output value of the counter that is compared by this comparison means. There is provided a diesel engine injection timing control device comprising: a control unit that delays the injection timing when the injection timing is smaller than the predetermined value.

FIG. 2 shows a diesel engine injection timing control device as an embodiment of the present invention.

The apparatus shown in FIG. 2 includes a four-cylinder diesel engine E, a pressure detector 1, a timing detection circuit 2, an ignition timing determination circuit 3, a fuel injection timing control circuit 4, a fuel injection pump 5, and fuel injection nozzles 61, 62, 63 ,. 64 are provided.

The timing detection circuit 2 rotates in synchronization with the crankshaft, rotates once every two rotations of the crankshaft, and has a rotor 211 having a protrusion, an angular position detector 22, and a reference position detector 2.
3, and a timing calculation circuit 24. The corrected injection timing calculation circuit 3 includes a zero-cross detection circuit 31, a counter circuit 32, and a comparison circuit 33.

An example of the pressure detector 1 used in the apparatus shown in FIG. 2 is shown in FIG. A pressure receiving plug 103, which is a pressure medium, is inserted between the piezoelectric element 101 and the diaphragm 102. 104
Is an electrode for output, which is the terminal 1 of the connector 105.
06 to the lead wire 107. Reference numeral 108 denotes a grounding electrode, which is grounded to the housing 109 via the pressure receiving plug 103 and the diaphragm 102. 110,111
Is an insulator that insulates the piezoelectric element 101 from the sensor body 112. Similarly, 113 is an insulator that insulates the output electrode 104 from the sensor body 112.

The sensor subassembly is assembled by the following procedure. From the bottom of the sensor body 112, the insulator 110, the electrode 104, the piezoelectric body 101, the pressure receiving body 103, and the insulator 1
11 is inserted, and the metal hollow ring 1 is attached to the outer peripheral portion of the pressure receiving plug 103.
The piezoelectric element 101 and the pressure receiving plug 103 are fixed to the sensor body by caulking the caulking portion 116 of the sensor body via the spacer 14 and the spacer 115. On the other hand, the sensor subassembly is constructed by inserting the insulator 113 from above the sensor body 112 and press-fitting the spacer 117. The piezoelectric element 101 has a metal hollow ring 114.
Preload is applied due to the springiness of the.

The sensor subassembly is press-fitted into the inner wall of the housing 109, and the projection 1031 at the tip of the pressure receiving plug and the housing 1
The diaphragm 102 is welded to the protrusion 1091 at the tip of 09.

The connector 105 is fixed to the housing 109 by caulking the housing 109 with the caulking portion 1092 via the spacer 118 and the O-ring 119.

Since the pressure detector uses a piezoelectric element, it outputs a signal S (1) representing a pressure change per unit time, that is, dp / dt.

The structure of the timing detection circuit 2 is shown in FIG. The angular position detector 22 has a predetermined pulse width, and detects the angle by generating a predetermined number of pulses per rotation.
The reference position detector 23 has a predetermined pulse width and detects the reference position by generating one pulse per one rotation. 212 and 213 are rotation angle sensors, 222 and 232
Is a transistor, and the pulse widths of the resistors 225, 235 are 224, the capacitor 223, and the resistor 234, respectively.
The one-shot multivibrator determined by the capacitor 233 and 226 and 236 are inverters.

241 and 243 are down counters. 242, 24
A piano switch 4 sets a predetermined preset input (JAM input) to the down counters 241 and 243.

The down counter 241 counts down a predetermined JAM input from the output S (23) of the reference position detection circuit 23, and then TDC
At, the pulse S (241) is output to the Z / D terminal.

The down counter 243 outputs the output S of the reference position detection circuit 23.
A pulse S (243) that forcibly stops the counter circuit 32 at the Z / D pin after counting down the predetermined JAM input from (23)
Give out.

The configuration of the correction injection timing calculation circuit 3 is shown in FIG. Three
Reference numeral 11 denotes an operational amplifier having a high input resistance, which constitutes a follower circuit for reducing the impedance of the output S (1) of the piezoelectric pressure detector 1. Reference numeral 312 is an operational amplifier forming a comparator, and 313 and 314 are protection resistors. The operational amplifiers 311 and 312 constitute the zero-crossing detection circuit 31, and when the output S (1) of the pressure detector 1 is positive, that is, when the positive pressure increase rate, a high level signal is output and the pressure detector 1 outputs. When the output S (1) is negative, that is, when the pressure increase rate is negative, a low level signal is output.

A counter circuit 32 resets the contents of the counter 321 at the rising edge of the TDC signal S (241) and starts counting the clock signal S (226) at the falling edge. Reference numeral 322 is an OR gate. The counting of the counter 321 is stopped by the trailing edge of the output S (31) of the zero cross detector 31 or the trailing edge of the output S (243) of the timing calculation circuit 24 after TDC.

The comparison circuit 33 is a latch 331, a one-shot multivibrator 336, and has a resistor 336a and a capacitor 336b. The comparison circuit 33 also includes digital comparators 332 and 333 and a piano switch 33.
4, 335. The piano switches 334 and 335 set the upper limit value and the lower limit value for advancing or retarding the injection timing, respectively.

The one-shot multivibrator 336 generates one pulse at the falling edge of the TRG input. The pulse width is determined by the resistor 336a and the capacitor 336b. Counter 32
The contents of 1 are set by the latch 331 at the fall of the one-shot multivibrator, and the comparators 332, 3
33 is input. When the content of the counter 321 is smaller than the value set by the piano switch 334, the comparator 332 outputs the retard pulse S (332) to the injection timing control device 4. If the content of the counter 321 is larger than the value set by the piano switch 335, the comparator 333 outputs the advance pulse S (333) to the injection timing control device 4.

FIG. 2 shows the signal waveform of each part of the apparatus. Sixth
In the figure, the output S of the down counter 241 as a TDC signal
(241), the output S (1) of the pressure detector 1, the output S (31) of the zero-cross detection circuit 31, and the output S of the down counter 243.
(243), the output S (322) of the OR gate 322, the output S (336) of the multivibrator 336, the output S (333) of the comparator 333 as an advance pulse, and the output S ((S) of the comparator 332 as a retard pulse. 332) waveforms are shown respectively.

Θ shown in relation to the signal S (322) waveform of FIG.
(1) and θ (4) are the contents of the counter, the output of the zero-cross detection circuit 31 after TDC has fallen, and since the value is within the range of the appropriate value, the advance pulse is also delayed. There is no pulse. Since θ (3) is too small, a retard pulse appears. θ (2) is an example in which the output of the zero-cross detection circuit 31 does not fall after TDC, and the counter circuit 32 stops at the fall of the output S (243) of the down counter 243 of the timing calculation circuit 24. In this case, An advance pulse appears at.

According to the present invention, the injection timing control can be more appropriately performed so that the diesel engine can always be operated in the state of the best torque. Moreover, according to the present invention, by counting the crank angle at which the value of the change waveform of the combustion pressure becomes zero, the peak timing of the combustion pressure is determined by a simple circuit configuration, and the peak timing determines the best torque. The injection timing control can be performed so that the predetermined timing is generated.

[Brief description of drawings]

FIG. 1 is a characteristic diagram for explaining a compression pressure characteristic of a diesel engine, FIG. 2 is a diagram showing a diesel engine injection timing control device as one embodiment of the present invention, and FIG. 3 is a pressure detection in the device of FIG. FIG. 4 is a diagram showing a configuration of a fuel injection device, FIG. 4 is a diagram showing a configuration of a timing detection circuit in the device shown in FIG. 2, FIG. 5 is a diagram showing a configuration of a correction injection timing calculation circuit in the device shown in FIG. 2, and FIG. 2 is a diagram showing a signal waveform of each part of the apparatus. (Explanation of Codes) 1 ... Pressure detector, 2 ... Timing detection circuit, 211 ... Rotor, 22 ... Angular position detector, 23 ... Reference position detector,
24 ... Timing arithmetic circuit, 3 ... Corrected injection timing arithmetic circuit, 31 ... Zero cross detection circuit, 32 ... Counter circuit,
33 ... Comparison circuit, 4 ... Fuel injection timing control circuit, 5 ... Fuel injection pump, 61, 62, 63, 64 ... Fuel injection nozzle, E ... Diesel engine.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Minoru Yamamoto Minoru Yamamoto 14 Iwatani, Shimohakaku-cho, Nishio-shi, Aichi Japan Auto Parts Research Institute (72) Inventor Makoto Ozaki 1-1-1, Showa-cho, Kariya city, Aichi Japan Denso Co., Ltd. (56) Reference JP-A-55-46073 (JP, A) JP-A-57-124035 (JP, A)

Claims (1)

[Claims] 1. A piezoelectric pressure detector for detecting a change in combustion pressure of an internal combustion engine, and a timing detection circuit for detecting that a rotation of the engine is at a predetermined crank angle, and an output signal of the piezoelectric pressure detector. And an output signal of the timing detection circuit for controlling the injection timing, wherein the crank angle counting is started from a predetermined crank angle detected by the timing detection circuit, and the piezoelectric pressure detection is performed. A counter that stops counting the crank angle at a crank angle at which the output of the device becomes more negative than positive, comparison means that compares the output value of this counter with a predetermined value, and the output value of the counter that is compared by this comparison means. A diesel engine injection timing control device comprising: a control unit that delays the injection timing when the injection timing is smaller than the predetermined value.