JPS5965238A - Knocking detector for diesel engine - Google Patents

Abstract

PURPOSE:To detect the knocking of a diesel engine accurately, by using a differential output type pressure detector, and detecting the pressure change per angle, to which correction for the number of rotation is applied. CONSTITUTION:The pressure change per time of a four cylinder diesel engine E is detected by a pressure detector 1 and inputted to a dividing circuit 32 in a knocking detecting circuit 3. Meanwhile, output pulses from an angle detecting circuit 2 are converted into a voltage, which is proportional to the number of rotation, by frequency converter circuit 31. The result is inputted to the dividing circuit 32. The output of the pressure detector 1 is divided by the output of the circuit 31 in the dividing circuit 32. The pressure increasing rate per time is converted into the pressure increasing rate per angle. The output is compared with the preset value from a comparing voltage generating circuit 33 in a comparator circuit 34. When the preset value is exceeded, a knocking signal is sent to an injection time controlling circuit 4, and fuel injection of fuel injection nozzles 61-64 are controlled through an injection pump 5. Since the pressure increasing rate per angle is detected, the detection of the knocking is 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 until the ignition time when 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 air-fuel mixture that is formed before ignition increases, and then it burns all at once, causing a sudden pressure rise, making quiet operation impossible, and causing vibrations and knocking noises. Occur.

This type of diesel knock is based on the large rate of pressure rise per angle: dP/dθ, and this value is approximately 5
Exceeding atm/deg will generate a significant knocking sound,
Known to have a negative impact on institutions. In a diesel engine, the compression ratio is originally high, so the vibration of the base is large, and the vibration of the engine block is drowned out by the noise caused by the vibration of the base. It is difficult to detect knocking based on the detection of vibrations.

The purpose of the present invention is to use a differential output type pressure detector to detect the pressure change per angle after adding a correction for the rotation speed, and to detect the above-mentioned value at which knocking occurs, that is, 5 atm/
Based on the concept of detecting the value equivalent to deg,
The object of the present invention is to more accurately detect knocking in a diesel engine.

In the present invention, a pressure detector having a piezoelectric element detects the rate of change in combustion pressure, an angle detector detects the rotation of the engine, and receives the outputs of the pressure detector and the angle detector to prevent knocking. The engine includes a knocking detection circuit that completely determines whether or not knocking has occurred, and the knocking detection circuit includes a rotational speed detection circuit that converts the output of the angle detector into an engine rotational speed, and
It has a division circuit that divides the output of the pressure detector by the output of the rotation speed detection circuit, and the occurrence of knocking is determined when the output of the division circuit becomes larger than a predetermined value. DESCRIPTION OF THE PREFERRED EMBODIMENTS A knocking detection device for a diesel engine is provided, which has the following features: A knocking detection device for a diesel engine as an embodiment of the present invention is shown in FIG.

In FIG. 1, E is a size-type four-cylinder diesel engine.

1 is a pressure detector, and since a piezoelectric element is used, its output 5(1) represents the rate of pressure change per time. 2 is an angle detector, and 3 is a knocking detection circuit. 4 calculates the basic injection timing from the rotational speed n, accelerator amount θ^, etc., and if there is a signal from the knocking detection circuit indicating that there is knob king, the injection timing is advanced by a predetermined amount, and if not, it advances to the basic injection timing. This is an injection timing control circuit with functions such as 5 is an injection pump, and 61 to 64 are injection ports for injecting fuel into each cylinder.

In the knocking detection circuit 3, 31 is a frequency-voltage conversion circuit, and the angle ! 032 is a division circuit that generates an output voltage proportional to the rotation speed by converting the frequency of the output pulse of the detector 2 into a DC voltage. Convert the rate of pressure rise per hour to the rate of pressure rise per angle by dividing by the output.

Reference numeral 33 denotes a comparison voltage generation circuit, which generates a DC voltage corresponding to the above-mentioned pressure increase rate per angle at which knocking occurs: 5 atm/deg. A comparison circuit 34 compares the rate of pressure increase during operation with a set value of 5 atm/deg and generates an output signal 5 (3) if knocking occurs.

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

A pressure receiving frame 103 serving as a pressure medium is inserted between the piezoelectric element 101 and the diaphragm 102. Reference numeral 104 denotes an output electrode, which is connected to the terminal 106 of the connector 1.05 through a lead gland 107. A grounding electrode 108 is grounded to the housing 109 via the pressure receiving frame 103 and the diaphragm 102e. Insulators 110 and 111 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 receiving frame 103, and the insulator 1
11 and caulking the sensor body caulking part 116 to the outer periphery of the pressure receiving frame 103 via the gold J, Y intermediate ring 114 and the spacer 115, the piezoelectric element 101
and fixing the pressure receiving frame 103 to the sensor body. On the other hand, the insulator 113 is inserted from the upper part of the sensor body 112 and press-fitted into the spacer 117-, thereby completing the sensor subassembly ii'J. Note that a preload is applied to the piezoelectric element 101 due to the springiness of the metal ring 114.

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

105 connectors, 118.0 spacers, 119' rings
5, caulk the housing 109 ￥1151092
It is fixed to the housing 109 by caulking.

Since the pressure detector uses a piezoelectric element, the pressure change per time, that is, dP/dt total hail signal 5
(i)'f: Output.

The (1q configuration) of the angle detector 2 is shown in Fig. 3. In the figure, 211 is a rotor having a plurality of protrusions on the outer periphery, and the disc (not shown) is fixed to the IJ beater shaft, Rotate.

212 is a magnetic pickup which faces the protrusion of the rotor 211; o 23=24 is a transistor and a resistor. 25 and 28 are logic circuits, 25 is a one-shot multivibrator, and 28 is a driver. The collector of the transistor 23 is connected to the trigger terminal of the one-shot multivibrator 25 .

When the rotor 211 rotates in the direction of the arrow and each protrusion crosses the electromagnetic pickup 212, this electromagnetic pickup 21
2 sometimes drops to a negative voltage, at this moment the transistor 23 becomes conductive, and the one-shot multivibrator 25 is triggered by the rise 9 of the transistor 23. The one-shot multivibrator 25 outputs a low level signal for a time determined by the time constants of the resistor 27 and capacitor 26, and is converted into a high level signal υ by the inverting driver.

The angle detector 2 outputs a rotation signal 5(2) having a frequency proportional to the rotation speed and a pulse width t independent of the rotation speed.

A detailed circuit diagram of the knocking detection circuit 3 is shown in FIG.

31 is a frequency electrostatic voltage conversion circuit, and the above-mentioned angle detector 2
connected to the output signal of Diode 311 allows only high level pulse width, resistor 313 and capacitor 314
It is integrated with a time constant of , and converted to a DC voltage. Furthermore, it is amplified to a predetermined voltage level by an inverting amplifier 317,
It is converted into a negative DC voltage proportional to the rotation speed.

32 is a dividing circuit, and the rate of pressure increase per time: dP/d
By dividing t by a voltage proportional to the rotational speed, it is converted into a pressure increase rate per angle. Reference numeral 321 denotes a division module, for example, the AD530 series manufactured by Analog Devices. That is, the output of pressure detector 1 is connected to the Z (IN) terminal, a negative DC voltage proportional to the rotation speed is connected to the X (IN) terminal, and the Y (IN) terminal is connected to the resistor 323 and the gain. Grounded through all of the adjustment resistors 322, the ground and the output cover, Z (IN) /X (
The value of the rate of pressure rise per angle is amplified to a predetermined voltage level by a 0321-j non-inverting amplifier that outputs a voltage proportional to IN).

33 is a comparison voltage generation circuit, which includes a Zener diode 331
And the pressure increase rate described above for resistors 332 and 333:
Generates a DC voltage relative to 5 atm/deg.

Reference numeral 34 denotes a comparison circuit which determines whether or not knocking has occurred by comparing the rate of pressure increase per angle with a predetermined voltage level.The operation will now be described. Since the output of the pressure detector l is a differential output, it generates a pressure increase rate per time: dP/dt. The value required to determine whether or not knocking has occurred is the rate of increase in pressure per angle: dP/dθ,
The relationship with the pressure increase rate per hour: (IP/dt) is expressed by the following formula.

That is, by dividing the pressure increase rate by the total angular velocity, that is, the number of rotations, the pressure increase rate per angle can be obtained. Therefore, in Figure 1, the output pulse of the angle detector 2 is converted into a voltage proportional to the rotation speed in the frequency/voltage conversion circuit 31, and then the pressure per angle is calculated by dividing the output of the pressure detector 1. Convert to rate of increase. After this, the presence or absence of knocking is completely determined by comparing with the set value.

The diesel engine is controlled by controlling, for example, a timer groove of a fuel injection pump of the diesel engine in accordance with the knocking determination result and delaying the injection timing.

In carrying out the present invention, various modifications may be made in addition to the above-mentioned specific embodiments. For example, the above embodiment
Although the case where the division is performed using an analog circuit is shown, as another example, as shown in Figure d35, the division is performed digitally>y
You can also do H.

In FIG. 5, 2 is a negative detector, but as shown in FIG. 6, the rotor 211 has only one protrusion. Therefore, the output 5(2) of the angle detector 2 becomes 1 pulse per rotation.

35 is an oscillator that oscillates pulses at a predetermined frequency. 3
Reference numeral 6 denotes a counter that detects the entire rotational speed by measuring the pulses of the oscillator 35.

37 is an A/D converter that performs digital conversion using an internal clock. 38 is a microprocessor which removes the A/D converted value by the number of rotations, converts it into a pressure rise-rise rate of p per angle, and performs a comparison operation with a set value.

Next, the operation will be explained. The counter 36 starts counting the pulses of the oscillator 35 at the rising edge of the angle detector 2, and stops counting at the falling edge at 9. The value of the counter 36 is as follows.
It takes a value that is inversely proportional to the rotation speed. On the other hand, the A/D converter 37
converts the differential output of the pressure sensor into digital data using an internal clock. The microprocessor 38 calculates the maximum value after A/D conversion, and calculates the total number of revolutions of the cycle 36.
By reading and dividing, calculate the rate of pressure increase per square fart.

As mentioned above, in the device shown in Fig. 1, a pressure detector is used, and by correcting the rotation speed to the differential output, it is converted to a pressure increase rate of 1 angle plus 9, and knocking is prevented. By comparing the value to 5 atm/deg, it becomes possible to detect knocking, which could not be detected in conventional diesel engines, and control of injection timing, etc. becomes possible.

According to the present invention, knocking in the diesel engine 4a can be detected more accurately.

[Brief explanation of drawings]

FIG. 1 shows a knocking detection device i! for a diesel engine as an embodiment of the invention. ? 2 is a diagram showing the configuration of the pressure detector in the device d in FIG. 1, FIG. 3 is a diagram showing the 14 configurations of the angle detector in the device 1 in FIG. FIG. 5 is a diagram showing another embodiment of the present invention, and FIG.
It is a diagram showing the configuration of the angle detector in the device.
11... Rotor, 212... Electromagnetic pickup, 3... Knocking detection circuit, 31...
Old... Frequency Lk-voltage conversion circuit, 32... Division circuit, 33... Comparison voltage generation circuit, 34...
... Comparison circuit, 4 ... Injection 8, r timing control circuit, 5 ... Injection pump, 61.62.63. (
54゜65...Injection port, E...Diesel engine.

Claims (1)

[Claims] l A pressure detector that has a piezoelectric element and detects the rate of change in combustion pressure, an angle detector that detects the rotation of the engine, and a knocking device that receives the outputs of the pressure detector and the angle detector. The knocking detection circuit includes a rotation speed detection circuit that converts the output of the angle detector into the rotation speed of the engine, and Knocking for a diesel engine, characterized in that it has a division circuit that divides by the output of a number detection circuit, and when the output of the division circuit becomes larger than a predetermined value, it is determined that knocking has occurred. Detection device. 2 The rotation speed detection circuit detects the pulse output t of the angle detector.
The device according to claim 1, which outputs an analog output after -11 minutes. 2. The apparatus according to claim 1, wherein the output of the pressure detector is digitally converted, and digital division is performed by the output of the counter circuit.