JPH0348742A - Knocking detector for internal combustion engine - Google Patents

Abstract

PURPOSE:To make an easy and accurate detection for a knocking by providing a temperature detecting sensor in a combustion chamber and a knocking detection circuit wherein an amplitude, changing portion for the time, generation timing, etc., of the sensor output pulse are compared with the limit values. CONSTITUTION:The sensor provided with a black body radiation substance 13 at the tip of a heat resistant light transmitting body 12 in rod shape is al lowed to pierce through a wall part 10 of cylinder head to protrude the tip into the combustion chamber 11. An optical connector 16 is attached with screw to a holding component 14 of the transmitting body 12 and optically connected to an optical fiber 17. Then, an optical energy generated by the radiation body 13 in accordance with a combustion gas temperature is propagated to the trans mitting body 12 and fiber 17, and detected by a photodetector 21. The amplitude, changing portion of the unit time and generation timing, of output pulse from the detector 21 are made larger and faster at the time when the knocking is generated, than those at the normal working time; thereby, the easy and accurate detection for the knocking can be made by means of comparing these outputs with the reference limit values.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a Noah-King detection device for an internal combustion engine.

(Prior art) In internal combustion engines installed in automobiles, the ignition timing is advanced to the ignition timing (M, B, T,) that can generate the maximum torque to achieve the best fuel efficiency and output performance. It is necessary to control it as follows. However, the optimal ignition timing differs depending on the driving conditions of the vehicle and the operating state of the internal combustion engine. For example, in a relatively low speed range, the ignition timing limit at which knocking occurs is higher than M, B, and T. Since the ignition timing is on the delayed side, if the ignition timing is set to M, B, or T, knocking will occur, resulting in a significant drop in fuel efficiency and output performance. Therefore, there is a strong demand for the development of a knocking detection device that can accurately detect the occurrence of knocking.

Conventionally, as a sensor for detecting knocking, the
A sensor using a piezoelectric element disclosed in Japanese Patent No. 5154 is known. In this sensor, a washer-shaped piezoelectric element is installed in the spark plug, and pressure changes occurring within the combustion chamber are converted into electrical signals.The pressure changes occurring within the combustion chamber are detected from the detected electrical signals.

Furthermore, as another knocking detection device, a knocking detection device using a vibration sensor composed of a piezoelectric element is known, and the electrical signal from the vibration sensor is passed through various filter circuits and a signal with a frequency component corresponding to knocking is detected. The occurrence of knocking is detected through the knocking determination circuit.

(Problem to be Solved by the Invention) The knocking detection device using the pressure sensor or vibration sensor described above detects the pressure change occurring in the combustion chamber by fixing the sensor to the cylinder head. This has the drawback that vibrations other than combustion are also detected at the same time, resulting in an extremely poor S/N ratio. Moreover,
The detection output of vibration sensors and pressure horn sensors is generated as an electrical signal, and this electrical signal is generated at the position of the cylinder head. Therefore, noise is likely to occur while the electrical signal, which is the output signal, is sent to the signal processing circuit, and the S A problem occurred in that the /N ratio decreased. Therefore, complicated signal processing is required to extract the pressure and vibration components corresponding to knocking, which has the disadvantage of making the processing circuit complicated and expensive. Furthermore, since complex signal processing is required, the signal processing takes a long time, resulting in an inconvenience of poor responsiveness.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks, and to provide a knocking detection device for an internal combustion engine that does not require complicated signal processing, has a simple configuration, and can detect the occurrence of knocking with high accuracy.

(Means for Solving the Problems) A knocking detection device for an internal combustion engine according to the present invention includes a temperature detection sensor that detects the temperature inside a combustion chamber of an internal combustion engine, an amplitude of an output pulse from the temperature detection sensor, a change over time, The present invention is characterized by comprising a knocking detection circuit that detects the occurrence of knocking by comparing at least one of the occurrence timings with a limit value.

(Function) FIG. 1 is a graph showing the relationship between crank angle and combustion chamber temperature in a four-stroke engine.

The horizontal axis shows the crank angle, and the vertical axis shows the combustion chamber temperature (relative value)
shows. First, in the intake cycle, the temperature of the combustion chamber begins to decrease, then shifts to the compression cycle, where the temperature starts to rise rapidly immediately after ignition, reaches a peak temperature after a crank angle of 360°, and then immediately decreases. As is clear from this temperature curve, the operating state of the internal combustion engine can be determined by detecting the combustion chamber temperature. In particular, when knocking occurs, it is predicted that combustion will start earlier than the normal combustion timing due to the principle of knocking, and that the detected combustion temperature will be even higher.

On the other hand, if we measure the temperature inside the combustion chamber continuously over time,
Output pulses corresponding to each combustion cycle are periodically generated from the temperature detection sensor. Based on this recognition, the present invention continuously detects the temperature of the combustion chamber over time, and detects the occurrence of knocking based on the amplitude, generation timing, or change over time of the pulse output from the temperature detection sensor. do. As a method for detecting the temperature inside the combustion chamber, for example, by optically detecting light energy emitted from a black body radiator, the temperature can be detected with a simple configuration and with high precision. A blackbody radiator that emits light energy with an intensity corresponding to the temperature is formed at one end of the heat-resistant light transmitter, and the light transmitter is arranged so that the blackbody radiator is located within the combustion chamber. When the spark plug is activated, combustion occurs, producing high-temperature combustion gas and instantly raising the temperature of the blackbody radiator. This temperature rise causes the blackbody radiator to emit light energy with an intensity corresponding to the temperature of the combustion gas, and this light energy propagates inside the light transmission body. Therefore, by receiving the propagating light from the optical transmitter with a photodetector, the occurrence and timing of combustion occurring within the combustion chamber can be detected, and thereby the situation of an explosion occurring within the combustion chamber can be detected. . Then, the occurrence of knocking can be detected by comparing the amplitude of the pulse output from the photodetector, the change over time, or the occurrence time ζ puffer with a limit value. When using a temperature detection sensor that uses a black body radiator, the light energy emitted from the horse body radiator is completely unaffected by external factors such as vibrations generated in the cylinder, so it can be easily detected using a simple signal processing circuit. The occurrence of knocking can be detected with high accuracy.

Moreover, the advantage of being able to propagate the optical energy emitted from the blackbody radiator to any desired position by using an optical fiber is achieved, and at the same time, there is the disadvantage of being affected by external noise during transmission. will also be resolved. Moreover, the optical temperature detection device using a black body radiator is
Since it has a frequency response of 0 kHz and a high resolution of 0.01°C, highly accurate detection can be performed even when the internal combustion engine rotates at high speed.

(Embodiment) FIG. 2 is a diagram showing the configuration of an example of a four-stroke engine equipped with a knocking detection device according to the present invention. Attach the intake valve 1, exhaust valve 2, and spark plug 3 to the cylinder head. Further, the sensor 4 of the detection device according to the present invention is mounted on the wall of the cylinder head so that the black body radiator 5 at the tip is located inside the combustion chamber.

FIG. 3 is a diagram showing the overall configuration of the knocking detection device according to the present invention. A sensor is mounted so as to penetrate through 1° of the wall of the cylinder head, and the tip of the sensor is made to protrude into the combustion chamber 11. This sensor has a heat-resistant rod-shaped light transmitting body 12 made of a sapphire rod, and a black body radiator 13 is formed at the tip thereof.

The black body radiator 13 is formed by sputtering an optically opaque high melting point material such as platinum or rhodium. The optical transmission body 12 is supported by a support member 14 made of a metal material such as stainless steel.

A thread is formed on the outer periphery of the support member 14 and a thread groove is formed on the wall 1 of the cylinder head, and the support member 14 is screwed into the wall 10 via a washer 15. Further, the optical connector 16 is screwed onto the support part 114 to optically couple the optical transmission body 12 to the optical fiber 17. When the spark plug operates and combustion occurs, the temperature of the black body radiator 13 increases due to the combustion gas.

Since the black body radiator 13 is formed of a vapor-deposited film of a noble metal with an extremely small heat capacity, it responds extremely quickly to changes in the temperature of the combustion gas. When the temperature of the black body radiator 13 increases, light energy with an intensity corresponding to the temperature of the combustion gas is generated from the black body radiator, and the generated light energy is transmitted to the rod-shaped light transmitting body 1.
2 and propagates through optical fiber 17. A lens 18, a filter 19, and a lens 20 are arranged on the output side of the optical fiber 17, and a photodetector 21 detects light of a specific wavelength among the propagating light.
Inject it into the

As mentioned above, since the black body radiator 13 emits light energy with an intensity corresponding to the temperature of the combustion gas, the photodetector 21
generates an electrical signal representing the generation of combustion gases due to ignition and the temperature of the combustion gases. This electrical signal is amplified by an amplifier 22 and then supplied to a signal processing circuit.

Next, actual measurement results of temperature changes within the combustion chamber measured using the detection device configured as described above will be shown. The experimental conditions are as follows.

(1) Internal combustion engine used: Single-cylinder engine with a displacement of 500cc 2) Number of revolutions: 1500 r, p, m.

3) Excess air ratio = 1.0 4) Fuel: Gasoline 5) Ignition timing: O' TDC 6) In parallel with temperature measurement, pressure changes in the combustion chamber were measured with a pressure sensor and matched.

FIG. 4 is a graph showing temperature changes in the black body radiator and pressure changes in the combustion chamber during continuous operation.

The upper row shows the detected temperature change, and the lower row shows the pressure change.

Examining the detected temperature changes, the temperature changes in each cycle correspond to the temperatures shown in Figure 1, and the large temperature peak that occurs at the time of explosion can be clearly observed. Furthermore, the timing of the temperature peak clearly corresponds to the timing of the pressure peak within the combustion chamber. Therefore, by detecting the temperature inside the combustion chamber, it is possible to detect the explosion occurring within the combustion chamber and the timing of the explosion. Furthermore, in FIG. 4, extremely large peak pressure and peak temperature are detected in the fourth cycle. Knocking is a phenomenon that occurs when combustion occurs faster than the normal combustion speed, and it is known that when knocking occurs, the pressure within the combustion chamber becomes extremely high. Therefore, it can be considered that knocking occurs in the fourth cycle. On the other hand, the peak temperature in this cycle is significantly higher than the peak temperatures in other normal cycles. When knocking occurs, high-speed pressure waves are generated within the cylinder and the gas flow rate rapidly increases, which further increases the heat transfer coefficient around the blackbody radiator.

As a result, the amount of heat received by the black body radiator increases, and it is understood that a temperature higher than that detected during normal operation is detected.

FIG. 5 is a graph showing the temperature change during normal operation and the temperature change when knocking detected using the detection device according to the present invention on the same time axis.

The horizontal axis shows time, and the vertical axis shows detected temperature (relative value). The solid line shows the temperature change during normal operation, and the dashed-dotted line shows the temperature change when knocking occurs. The detected peak temperature when knocking occurs is approximately twice or more than the detected peak temperature during normal operation. Furthermore, when knocking occurs, the timing of the temperature peak occurs as much as time Δ earlier than the timing of the temperature peak in normal operation, and the temperature rise characteristic (temperature change with respect to time) also exhibits a sharp characteristic. As described above, when knocking occurs, a high-speed gas flow is generated within the cylinder, so it is understood that a higher peak temperature is detected and a rapid temperature increase characteristic is detected. Based on these experimental results, the detected peak temperature inside the combustion chamber is compared with the reference limit value determined from the peak temperature during normal operation, and if the peak temperature exceeds the reference limit value, it is detected that knocking has occurred. I can do it. Furthermore, by detecting the timing at which the peak temperature occurs and comparing this timing with a reference limit value determined based on the timing at which the peak temperature occurs during normal operation, the change in temperature rise characteristics over time is determined as the reference limit value. The occurrence of knocking can be detected by comparison.

FIG. 6 is a graph showing the relationship between the detected temperature change and its differential output. The upper row shows the detected temperature, and the lower row shows the differential output of the detected temperature. Knocking occurred in the fourth t-th cycle, and the differential output value at this time was detected to be more than four times the differential output value during normal operation. Therefore, by comparing the differential output value of the temperature change within the combustion chamber with the reference value during normal operation, knocking can be detected with high accuracy.

FIG. 7 shows an example of the output signal of the photodetector when knocking occurs. The horizontal axis shows time and the vertical axis shows output value.

A pulse with a large amplitude and a pulse with a small amplitude are output in succession. Among the output pulses, a pulse with a large amplitude corresponds to the occurrence of knocking, and a pulse with a small amplitude corresponds to normal operation.

Further, a signal in which a high frequency component is superimposed on a low frequency component of about 0.01 Hz is output. This low-frequency component is a phenomenon that corresponds to the slow temperature rise in the combustion chamber that occurs during warm-up operation, for example, and by removing this low-frequency component, a pulse signal with an amplitude that corresponds to the combustion cycle of the internal combustion engine can be generated. can be generated.

FIG. 8 is a circuit diagram showing the configuration of an example of a knocking detection circuit according to the present invention. The output signal from the photodetector 21 is
High pass filter 30 consisting of capacitor C and resistor R
is passed through, and low frequency components of about 0.01 Hz are canted. As a result, fluctuations in the base level are canted, and an output pulse signal with a constant base level can be obtained. After amplifying the signal with the low frequency component cut off by an amplifier 31, it is supplied to a differentiating circuit 32, a comparator 33, and a peak detection circuit 34, respectively.

First, the amplitude of each output pulse is compared with a reference limit value in the comparator 33, and when the amplitude of the output pulse exceeds the reference limit value, occurrence of knocking is detected and supplied to the OR gate 35 as a knocking detection signal.

In addition, the differentiation circuit 32 detects the change in the output pulse with respect to time, and the comparator 36 compares it with a reference limit value. If the differential output exceeds the reference limit value, the occurrence of knocking is detected, and the OR gate is used to detect knocking. Output to 35. Furthermore, using the crank angle detection sensor 37,
A signal indicating the detected crank angle is supplied to a peak detection circuit 34 via an amplifier 38 . This peak detection circuit detects the peak generation timing of each pulse.

Then, the timing comparison circuit 39 compares the generation timing of each pulse with a reference limit value, and generates a knocking detection signal if the pulse is generated earlier than the reference timing. In this case, the top dead center position or bottom dead center position detected by the crank angle detection sensor is used as the reference point, a predetermined limit time is determined from this reference point, and if a pulse is generated earlier than this limit time, a non-kinking detection signal is generated. can be done. With this configuration, it is possible to detect the occurrence of knocking when at least one of the amplitude, change over time, and generation timing of the output pulse from the photodetector exceeds the reference limit value. Of course, it is also possible to adopt a configuration in which the occurrence of knocking is detected by comparing only one of the output pulse amplitude, differential output, or generation timing with a reference limit value. Furthermore, although the embodiment described above uses the OR gate 35 at the final stage, an AND gate may be used instead of the OR gate 35. in this case,
It is determined that knocking has occurred only when the amplitude, differential output, and peak occurrence timing all exceed reference limit values. Furthermore, as shown in FIG. 9, an AND gate 40 may be provided after the comparators 33 and 36, and it may be determined that knocking has occurred only when both the amplitude and the differential output exceed the reference limit value. can. By making a knocking determination based on two knocking detection signals in this manner, it is possible to prevent malfunctions caused by sudden noises.

FIG. 10 is a circuit diagram showing the configuration of a modified example of the knocking detection device according to the present invention. In this example, an A, G, C circuit (automatic gain control circuit) 4 is connected between the amplifier 31 and the comparator 33.
1 will be provided. This A, G, C circuit 41 functions to control the gain so that the output signal is maintained substantially constant even if the human input signal strength changes. This A.

By placing the G and C circuits before the comparator 33 or 36, when the output pulse amplitude from the photodetector 21 is smaller than a predetermined setting range, it is automatically amplified so that it falls within the setting range, - acts to reduce the gain if the amplitude of the force output pulse is greater than the set value; Furthermore, by setting the response time constant and response frequency, it is possible to avoid responding to sudden large output pulses.

As a result, the output pulse from the photodetector can be stabilized at a desired level, and the configuration of the knocking detection circuit and knocking judgment circuit can be simplified, and the central processing unit (C, P, U,) can be used to control the output pulse. In this case, the control circuit can be configured as an hour wheel.

Next, a system for controlling the ignition timing of a spark plug using a knocking detection signal according to the present invention will be described. Figures 11a and 11b show the waveform of the output signal output from the photodetector when the engine is operating. Since one peak output signal is generated for each combustion operation of the engine, a pulse train with a period corresponding to the engine rotational speed is generated. In this case, when the ignition timing is at its best, pulses with small amplitudes occur periodically as shown in FIG. 11a. On the other hand, when the knocking condition occurs, the 11th
As shown in the figure, pulses with abnormally large amplitudes begin to occur in the pulse train. The intensity of knocking approximately corresponds to the number of pulses with large amplitude per unit time. Therefore,
The knocking intensity is detected by detecting the number of abnormal amplitude pulses that occur per unit time, and the ignition timing of the spark plug can be maintained in the best condition by delaying the ignition timing according to the detected knocking intensity. . FIG. 12 shows an example of a control circuit that controls ignition timing. The output signal from the photodetector 21 is sent to the amplifier 31.
After being amplified by , it is supplied to a comparator 33 and compared with a reference limit value. When the output signal from the photodetector exceeds the reference value, a detection signal is generated from the comparator 33, and this detection signal is supplied to the pulse generation circuit 50. A reference pulse is generated in the pulse generation circuit 50 based on the input detection signal. The output signal of this pulse generating circuit is shown in FIG. 11C. The output signal from the pulse generation circuit 50 is supplied to a pulse counting circuit 51 to count the number of pulses per unit time. and,
The counting result is supplied to a knocking intensity determination circuit 52 to determine the knocking intensity. In this case, since the period of the output signal of the photodetector differs depending on the engine speed, it can also be corrected using the engine speed. Then, the output signal of the knocking intensity determination circuit 52 is transmitted to the spark plug drive circuit 5.
3 to generate a drive control signal for the spark plug.

The present invention is not limited to the embodiments described above, and various changes and modifications are possible. For example, in the above-described embodiment, the light transmitting body in which the black body radiator is formed is attached to the cylinder head via the support member, but the heat-resistant light transmitting body is inserted inside the spark plug and the light transmitting body is attached to the cylinder head via the support member. It can be made into a monolithic structure. In this case, since the detection signal is an optical signal, it will not be affected in any way even if a high voltage pulse occurs in a lead wire passing near the optical transmission body.

In addition, in the above embodiment, the temperature inside the combustion chamber is detected using an optical sensor that uses a black body radiator, and knocking is detected based on the detected temperature. temperature detection sensor can be used,
For example, a thermocouple for detecting high temperature can be used as the temperature detection sensor.

(Effects of the Invention) The effects of the present invention explained above are summarized as follows.

(1) The output pulse from the temperature detection sensor when knocking occurs has a larger amplitude than the output pulse during normal operation.
The amount of change over time is also large, and the timing of occurrence is early. As a result, the occurrence of knocking can be detected by comparing at least one of the amplitude, temporal change, and generation timing of the output pulse from the temperature detection sensor with the reference limit value. As a result, the knocking detection circuit and determination circuit can be further simplified. Furthermore, since the temperature within the combustion chamber is hardly affected by mechanical vibrations occurring in the cylinder head, knocking detection based on temperature changes within the combustion chamber makes it possible to perform knocking detection that is less susceptible to noise.

(2) Unlike pressure sensors and vibration sensors, the temperature detection sensor does not have any moving parts, so it is possible to achieve knocking detection with excellent reliability and durability.

(3) If a temperature sensor is used using a black body radiator, it will be completely unaffected not only by mechanical vibrations generated in the engine but also by electric and magnetic fields, allowing for highly accurate knocking detection with less layer noise. be able to. Furthermore, since a temperature sensor using a black body radiator has a frequency response of several tens of kHz, it can clearly detect temperature changes within the combustion chamber and perform knocking detection with high accuracy.

(4) Since the black body radiator can be composed of an optically opaque high-melting point material coating, it is hardly affected by the adhesion of soot generated by combustion, making it possible to realize a knocking detection device with excellent durability. can.

(5) If an optical temperature sensor is used, the detection signal is the energy radiated from the black body radiator, so the detection signal can be transmitted to any position using an optical fiber, and moreover, during the transmission Since it is not affected by external factors, knocking detection with a high -layer 3/N ratio can be achieved.

(6) Since the output pulse corresponding to the combustion cycle is constantly output from the temperature detection sensor, if the AGC circuit is placed after the QW detection sensor, the output pulse at the desired set level can be stably output from the temperature detection sensor at all times. It can be output. As a result, the configurations of the signal processing circuit and control circuit can be further simplified.

(7) Since the intensity of knocking approximately corresponds to the number of abnormal amplitude pulses generated per unit time, the intensity of knocking can be detected simply by detecting the number of abnormal amplitude pulses per unit time.

[Brief explanation of drawings]

Fig. 1 is a graph showing the temperature change in the combustion chamber with respect to the crank angle, Fig. 2 is a diagram showing the configuration of an example of a four-cycle engine equipped with the knocking detection device according to the present invention, and Fig. 3 is a graph showing the knocking detection according to the present invention. A diagram showing the configuration of the device, Figure 4 is a graph showing temperature changes and pressure changes in the combustion chamber, Figure 5 is a graph showing the occurrence of temperature peaks during normal operation and when knocking occurs, and Figure 6 is a graph showing the occurrence of temperature peaks during normal operation and when knocking occurs. Fig. 7 is a graph showing an example of an output signal from a photodetector; Fig. 8 is a circuit showing the configuration of an example of a knocking detection circuit; Fig. 9 and FIG. 10 is a circuit diagram showing a modified example of the knocking detection circuit according to the present invention, FIG. Fig. 12 is a circuit diagram showing the configuration of an example of a spark plug control circuit according to the present invention. 12... Optical transmission body 13... Black body radiator 1
4... Support member 17... Optical fiber 21
...Photodetector 22...Amplifier 24...
Crank angle detection sensor 33, 36... Comparator 32... Differentiator circuit 3
4...Peak detection circuit 34...Timing comparison circuit. Fig. 1 --- 7 U / negative (CA>- Fig. 2 Fig. 4

Claims (1)

[Claims] 1. A temperature detection sensor that detects the temperature inside a combustion chamber of an internal combustion engine, and at least one of the amplitude, change over time, and generation timing of an output pulse from the temperature detection sensor is compared with a limit value. A knocking detection device for an internal combustion engine, comprising a knocking detection circuit that detects the occurrence of knocking. 2. The temperature detection sensor is formed by a heat-resistant optical transmission body having one end formed with a black body radiator that emits light energy corresponding to the temperature within the combustion chamber, and this light transmission body is formed by a black body radiator. a support member that supports the tip of the black body radiator so as to be located within the combustion chamber, and a pulse signal that receives light energy emitted from the black body radiator and propagates through the light transmitter, and has an amplitude corresponding to the peak temperature of the combustion chamber. 2. The knocking detection device for an internal combustion engine according to claim 1, further comprising an optical temperature detection sensor having a photodetector that generates the temperature. 3. The internal combustion engine according to claim 1 or 2, wherein the knocking detection circuit has a high-pass filter that cuts low frequency signal components and is configured to constantly generate output pulses at a reference base level. Knocking detection device. 4. The knocking detection device for an internal combustion engine according to claim 1, 2 or 3, wherein the knocking detection circuit has an automatic gain control circuit and is configured to generate an output pulse at a predetermined set level. . 5. A heat-resistant optical transmission body having one end formed with a blackbody radiator that emits light energy corresponding to the temperature inside the combustion chamber;
a support member that supports the light transmission body such that the tip on which the black body radiator is located within the combustion chamber; and a support member that receives light energy emitted from the black body radiator and propagated through the light transmission body; A photodetector generates a pulse signal with an amplitude corresponding to the peak temperature of the combustion chamber, and the amplitude of the output pulse from the photodetector is compared with a limit value, and knocking is detected when the amplitude of the output pulse exceeds the limit value. An ignition control device for an internal combustion engine, comprising a knocking detection pulse generation circuit that generates a detection pulse, and a control circuit that controls the ignition timing of a spark plug according to the number of knocking detection pulses per unit time.