JPS5970936A - Knocking detecting apparatus for diesel engine - Google Patents

Abstract

PURPOSE:To contrive to enhance detection accuracy, by a method wherein pressure change per angle is detected and it is detected that the quotient obtained by dividing the differentiate value of a max. pressure value by the differentiate value directly before ignition reaches a definite value. CONSTITUTION:The change rate of combustion pressure is detected by a pressure detector 1 and engine rotation is detected by an angle detector 2. Measuring timing is calculated in a timing operation circuit 24 by the output of the angle detector 2 and the output value of the pressure detector 1 is taken in a sample hold circuit 33. The max. output value of the pressure detection value is taken in a peak hold circuit 32 and divided by the output of the sample hold circuit in a division circuit 34. This division value and the output value of a reference voltage generating circuit 35 are compared by a comparison circuit 36. By this method, knocking detection can be accurately performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a knocking detection device for a diesel engine.

In a diesel engine, the combustion reaction rapidly progresses from the start of fuel injection to the ignition timing at which the combustion pressure rapidly increases, that is, the ignition delay has a significant effect on subsequent combustion. As the ignition delay increases, the amount of combustible mixture formed before ignition increases, which is then combusted all at once, resulting in a sudden pressure rise, making quiet operation impossible9, and causing vibrations and knocking noise. occurs.

This type of diesel knock is based on the large rate of pressure rise per angle: dP/dθ, and this value is approximately 5.
It is known that when atrrV'deg is exceeded, a significant knocking noise is generated, which adversely affects the engine. In a diesel engine, the compression ratio is originally high, so the pace vibration is large, and the vibration of the engine block is drowned out by the noise caused by the pace vibration. It is Tabata to detect non-king based on the detection of vibrations.

The object of the present invention is to use a differential pressure type pressure detector to detect the pressure change per angle after correcting the rotation speed, and to detect the above value at which knocking occurs, that is, 5 atr.
The idea is to detect a value equivalent to r+7deg, and the idea is to utilize the phenomenon that when knocking occurs, the value exceeds a certain value, regardless of the differential value of pressure P with respect to time t or the rotation speed. The object of the present invention is to more accurately detect knocking in a diesel engine based on the above.

In the present invention, there is provided a pressure detector using a piezoelectric element to detect the rate of change in combustion pressure, an angle detector to detect the rotation of the engine, and a timing calculation circuit that calculates the measurement timing based on the output of the angle detector. , and a sample hold circuit that receives the output value of the pressure detector when the timing calculation circuit outputs the output value at a predetermined crank angle.
It has a peak hold circuit that takes in the maximum output value of the output of the pressure detector, and a division circuit that divides the pressure of the peak hold circuit by the output of the sample hold circuit, and receives the pressure of the pressure detector and the timing calculation circuit. Provided is a knocking detection device for a diesel engine, comprising: a knocking detection circuit that determines that knocking occurs when the output of the division circuit becomes larger than a predetermined value. Ru.

A knocking detection device for a diesel engine as an embodiment of the present invention is shown in FIG.

In FIG. 1, E is an in-line four-cylinder diesel engine.

Reference numeral 1 denotes a pressure detector for detecting the rate of change in combustion pressure, and since a piezoelectric element is used, its output 5(1) represents the rate of change in pressure per hour. 2 is an angle detector, and 3 is a knocking detection circuit.

Step 4 calculates the basic injection timing from the rotational speed n, accelerator pleasure, etc., and if there is a signal from the knocking detection circuit indicating that knocking is present, the injection timing is delayed by a predetermined amount, and if not, it advances to the basic injection timing. This is an injection timing control circuit that has a similar function. 5 is an injection 2 pump, and 61 to 64 are injection ports for injecting fuel into each cylinder.

In the angle detector 2, 21 is a rotation detection section, 22 is an angular position detection circuit, 23 is a reference position detection circuit, and 24 is a timing calculation circuit.

In the knocking detection circuit 3, 32 is a peak hold circuit, 33 is a sample hold circuit, 34 is a division circuit,
35 is a reference voltage generation circuit, and 36 is a comparison circuit.

An example of the pressure detector 1 used in the present invention is shown in FIG.

A pressure receiving plug 103 serving as a pressure medium is inserted between the piezoelectric element lO1 and the diaphragm 102. Reference numeral 104 denotes an electrode for output, which is connected to a terminal 106 of a connector 105 with a lead wire 107. Reference numeral 108 designates a grounding electrode υ, which is grounded to the housing 109 via the pressure receiving plug 103 and the diaphragm 102. Insulators 110 and 11.1 insulate the piezoelectric element 101 from the sensor body 112. The same <113 is an insulator that insulates the output electrode 104 from the sensor body 112.

The sensor subassembly is assembled using the following procedure. From the bottom of the sensor body 112, the insulator 110, the electrode 104, the piezoelectric body 101, the pressure plug 103, and the insulator 1
11 and a metal hollow/glue 1 on the outer periphery of the pressure receiving plug 103.
14 and the spacer 115, 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. On the other hand, an insulator 113 is inserted from the upper part of the sensor body 112, and a spacer 117 is press-fitted to form a sensor subassembly. Note that the piezoelectric element 101 includes a metal hollow ring 11.
A preload is applied by the springiness of 4.

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

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

Since the pressure detector uses a piezoelectric element, the pressure change per time, that is, dP/dt, is detected by a signal 5 (
1) Output.

The configuration of the angle detector 2 is shown in FIG.

22 is an angular position detection circuit.

The rotor 211 is a combination of a rotor having multiple protrusions on the outer periphery and a rotor having one protrusion on the outer periphery.
It is fixed to a distributor shaft (not shown) and rotates together with this distributor shaft.

Reference numerals 212 and 213 denote electromagnetic pickups facing the protrusions of each rotor 211.

221.231 is a transistor, 222.232 is a resistor, 223.233 is a one-shot multivibrator,
224 and 234 are drivers.

Trigger terminals of the one-shot multivibrators 223 and 233 are connected to collectors of transistors 221 and 231, respectively.

The rotor 211 rotates, and each protrusion becomes the electromagnetic pickup 21.
2.When crossing 213, this electromagnetic pickup 212
. .

The one-shot multi-pipe leaks 223 and 233 remain at a low level of 1d for a time determined by the time constant of the resistor and capacitor.
This signal is converted into a high-level inert signal by the reversing drivers 224 and 234.

Based on the above, the output of the angular position detection circuit 22 is a rotation signal 5 (22) having a frequency proportional to the number of rotations and a Noculus width independent of the number of rotations, and the reference position detection circuit 22
Outputs one signal 5 (23) per revolution.

The timing calculation circuit 24 includes down counters 241 to 2
44, flip-flops 245 and 246, and one-shot multivibrators 247 and 248.

Signal 5 (241) based on signals 5 (22) and 5 (23)
), a flip-flop 245 that starts sample hold and a flip-flop 246 that starts peak hold are set. At signal 5 (242), the flip-flop 245 for sampling and holding before TDC is reset and holding is started.

Similarly, in order to hold the peak after detecting the maximum output with signal 5 (243), the flip-flop 246 is reset and hold is started.

5(22) and 5(23), the output of the comparison circuit 36 is output at a predetermined crank angle.

The configuration of the knocking detection circuit is shown in FIG.

The peak hold circuit 32 uses, for example, a BLJRR-BW 4084/25 peak hold module. Hold the maximum output when control input 5 (246) is at a high level, and control input 5 (248)
to reset the hold output.

The sample-and-hold circuit 33 uses, for example, a sample-and-hold module S) 1M series manufactured by D'Till-Intersil. Hold when control human power 5 (245) is at a low level.

The division circuit 34 is manufactured by, for example, Analog Devices: AD.
A 530 series divider circuit module is used. Output 5 (34) is a positive pressure 5 (3) proportional to the ratio of input 5 (32) and input 5 (33), S (32)/S (33).
4) Output.

35 is a reference voltage generation circuit. 36 is a comparison circuit which samples at input 5 (247).

In the non-king detection circuit 3, the output of the peak hold circuit 32 is divided by the output of the sample hold circuit 33, and the comparison operation of the comparison circuit 36 compares the output of the division circuit 34 with a predetermined value. When the output of the division circuit becomes larger than a predetermined value, it is determined that knocking has occurred.

In other words, the reason for performing this division is that if the rotational speed is constant, the value dP just before TDC at which ignition occurs and the pressure rises rapidly regardless of whether or not knocking occurs, and the peak value of the rate of pressure increase - (MAX) (P =P
h).

t dP dP
dP-(MAX) (P=Pt) -aT(t
= Th), -aT (t = Tt) The quotient obtained by dividing t by t is based on the fact that if knocking occurs, the value will be greater than -, regardless of the rotation speed. Knocking is detected by performing division and correcting the output of the pressure change rate detector, which changes depending on the rotational speed.

In the above description, Th and Ph represent the timing and pressure at high rotational speeds, respectively, and Te and Pt represent the timing and pressure at low rotational speeds, respectively.

Signal waveforms at various parts of the device shown in FIG. 1 are shown in FIG.

In FIG. 5, (1) indicates the top dead center timing TDC,
(2) is the output signal 5 (1) of the pressure detector 1, (3) is the sample hold control signal 5 (245), (4) is the output signal 5 (33) of the Zanzor hold circuit 33, ( 5
) is peak hold control 1 i δ 5 (246), (6
) is Peak Hole Birisefu No. 1 5 (248), (7)
is the peak hold circuit: output signal 5 (32) of 32,
(8) represents the sampling timing SMP, and (9) represents the output signal 5 (364) of the knocking detection circuit 3, respectively.

According to the present invention, knocking in a diesel engine can be detected more accurately.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a knocking detection device for a diesel engine as one implementation of the present invention; Fig. 2 (l-i5)E; Figures (a) and (b) are the angles in the device shown in Figure 1;
Figure 4(a) and (b) are diagrams showing the knocking detection circuit in the equipment shown in Figure 1. Figure 5 is a diagram showing the 4ii wave J of each part in the equipment shown in Figure 1. ′
FIG. 1...Pressure detector, 2...Angle detector, 21...
Rotation detection section, 22... Angular position detection circuit, 23...
Reference position detection circuit, 24...timing calculation circuit, 3
Knocking detection circuit, 32... Peak hold circuit, 33... Sample hold circuit, 34... Division circuit, 35... Reference voltage generation circuit, 36... Comparison circuit, 4... Injection timing control circuit, 5... injection pump,
61,62゜63.64...Injection port, E...Diesel engine. Patent applicant Japan Auto Parts Research Institute Co., Ltd. Nippondenso Co., Ltd. Patent application agent Patent attorney Ro Aomizu Patent attorney Kazuyuki Nishidate Patent attorney Masashi Matsushita Akira Yamaguchi Figure 1 Figure 2

Claims (1)

[Claims] 1. A pressure detector that detects the rate of change in combustion pressure using a piezoelectric element; An angle detector that detects the rotation of the engine; A timing calculation circuit that calculates measurement timing based on the output of the angle detector; and a sample hold circuit that takes in the output value of the pressure detector at the time of trigger output at a predetermined crank angle of the timing calculation circuit; a peak hold circuit that takes in the maximum output value of the output of the pressure detector; It has a division circuit that divides by the output of the sample and hold circuit, and receives the outputs of the pressure detector and the timing calculation circuit, and when the output of the division circuit becomes larger than a predetermined value, it is assumed that knocking has occurred. A knocking detection device for a diesel engine, comprising: a knocking detection circuit for determining knocking.