JPH03188344A - Detecting device for operating-state of internal combustion engine - Google Patents

Abstract

PURPOSE:To detect the operating state of an internal combustion engine accurately by arranging a black body radiator in a combustion chamber, receiving the optical energy emitted from the black body radiator, and detecting the burning state through an optical transmission body. CONSTITUTION:A black body radiator 2 is formed at the tip of a heat resisting optical transmission body 1. The optical transmission body 1 is loaded in a wall part 4 of a combustion chamber. In the combustion chamber 5, fuel gas is burned, and heat flux is generated by the heat generation. The heat flux reaches the surface of the black body radiator 2. The heat energy of the heat flux is transferred to the black body radiator 2, and the temperature of the black body radiator 2 rises up. Optical energy corresponding to the temperature of the black body radiator 2 itself is emitted. The emitted optical energy is propagated in the optical transmission body 1 and taken out to the outside. Therefore, the optical energy which is propagated through the optical transmission body 1 is received, and the changing state of the temperature of the black body radiator 2 is obtained based on the optical energy. Thus the change in heat flux generated in each combustion cycle can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an operating state 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 car 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 an internal combustion engine operating state detection device that can accurately detect abnormal operation of the internal combustion engine, particularly the occurrence of non-king.

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, in which an electrical signal from the vibration sensor is passed through various filter circuits to obtain a signal with a frequency component corresponding to non-king. The occurrence of knocking is detected through a knocking determination circuit.

(Problem to be Solved by the Invention) The non-king 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 sensors is generated as an electrical signal, and this electrical signal is generated at the position of the cylinder head, so noise is likely to occur while the electrical signal, which is the output signal, is sent to the signal processing circuit. A problem occurred in that the S/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 Accordingly, an object of the present invention is to solve the above-mentioned drawbacks and to provide an internal combustion engine which can detect the occurrence of abnormal operating conditions in an internal combustion engine, particularly the occurrence of knocking, with a simple configuration without requiring complicated signal processing, and with high precision. The present invention provides an operating state detection device.

(Means for Solving the Problems) An operating state detection device for an internal combustion engine according to the present invention includes a black body radiator that emits light energy according to a heat flux in a combustion chamber of an internal combustion engine, and a black body radiator that emits light energy in accordance with a heat flux in a combustion chamber of an internal combustion engine. a support member that supports the light transmitter so that the black body radiator is located within the combustion chamber; and a support member that supports the light transmitter so that the black body radiator is located within the combustion chamber; It is characterized by comprising a photodetector that receives energy, and a signal processing circuit that detects the operating state of the internal combustion engine based on the output signal from the photodetector.

(Effect) There are various factors that can cause knocking, which is abnormal combustion in ignition type internal combustion engines, such as self-ignition occurring near the wall in front of the fire propagation surface and rapid increase in fire propagation speed. All of these phenomena can be thought of as rapid combustion that ends in a shorter time than normal combustion.
These factors cause a rapid increase in heat flux or an increase in local heat flux. In other words, when the flame propagation velocity rapidly increases and the heat flux increases rapidly, or when the local heat flux increases near the combustion chamber wall, an abnormal pressure wave is generated within the combustion chamber, and this pressure wave causes the combustion chamber wall to Pressure vibration occurs in the
This pressure vibration is detected as knocking. Incidentally, the total amount of heat generated by combustion can be considered to be constant regardless of whether knocking occurs or not. and,
Under normal combustion conditions without knocking, the flame generated near the spark plug propagates relatively slowly toward the opposing wall, resulting in stable combustion over a relatively long period of time.
When knocking occurs, it can be considered that rapid combustion is occurring that ends in a short time.

Therefore, considering that the generated heat is radiated to the wall of the combustion chamber, it can be considered that a relatively large heat flux is generated in normal combustion.

Therefore, by detecting changes in heat flux generated by combustion, the operating state of the internal combustion engine can be accurately detected.

A sensor using a black body radiator shown in FIG. 1 can be considered as a sensor for detecting the heat flux generated within the combustion chamber. A black body radiator 2 is formed at the tip of a heat-resistant main light transmitter 1, and this light transmitter is attached to a combustion chamber wall 4 via a support member 3. It is assumed that fuel gas is combusted in the combustion chamber 5 and a heat amount of Qgas is generated. This heat generation generates a heat flux of Qgas/A, and this heat flux reaches the surface of the blackbody radiator. Then, the thermal energy of the heat flux is transferred to the black body radiator 2, and the temperature of the black body radiator increases according to the inflowing heat flux.
A black body radiator emits light energy according to its own temperature. Therefore, a heat flux pulse of a predetermined frequency is applied to the black body radiator 2.
It can be considered that light energy of the same frequency is radiated from the blackbody radiator. Then, the radiated light energy propagates through the optical transmission body 1 and is taken out to the outside. Therefore, by receiving the light energy propagating through the light transmission body 1 and determining the state of temperature change of the black body radiator 2 based on this light energy, changes in heat flux occurring in each combustion cycle are detected. can do.

FIG. 2 is a graph schematically showing the temperature change of the black body radiator when a high-density heat flux pulse and a low-density heat flux pulse are incident on the black body radiator. The horizontal axis shows time and the vertical axis shows the temperature of the blackbody radiator.

Furthermore, the solid line indicates the characteristics when a high-density heat flux pulse is incident, and the broken line indicates the characteristics when a low-density heat flux pulse is incident. When the heat flux pulse reaches the blackbody radiator surface, the amount of heat transferred to the blackbody radiator is defined by the product of the temperature difference between the combustion gas temperature and the sensor temperature and the heat transfer function: Since the heat transfer function can be thought of as a function of the velocity and pressure of the combustion gas, the amount of heat transferred to the blackbody radiator is
Depends on heat flux. Therefore, when a high-density heat flux pulse is incident, the blackbody radiator rapidly heats up and reaches a high peak temperature in a short time. On the other hand, when a low-density heat flux pulse is incident, the temperature of the blackbody radiator increases relatively slowly,
Generates lower peak temperatures. Therefore, by detecting the time differential of the temperature change of the blackbody radiator, the peak temperature, or the time of peak temperature occurrence, the heat flux density generated by combustion and, therefore, the operating state of the internal combustion engine such as the occurrence of non-king can be detected. be able to. The present invention is based on this recognition; a black body radiator is placed inside the combustion chamber, the light energy emitted from the black body radiator is optically detected, and the output signal from the photodetector is converted into an output signal. The operating state of the internal combustion engine is detected based on the

When using a detection sensor that uses a black body radiator, the light energy emitted from the black body radiator is completely unaffected by external factors such as vibrations generated in the cylinder.
The occurrence of knocking can be detected with high accuracy using a simple signal processing circuit.

Furthermore, by using an optical fiber, the light energy emitted from the black body radiator can be propagated to any desired position, and the disadvantage of being affected by external noise during transmission is also eliminated. be done. Moreover, the optical detection device using a blackbody radiator has a power of several tens of kilohertz.
Since it has a frequency response of z 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. 3 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. Intake valve 10, exhaust valve 11 and spark plug 12 in the cylinder head
Attach. Further, the sensor 13 of the detection device according to the present invention is mounted on the wall of the cylinder head at the black body radiator 14 at the tip.
Install it so that it is located inside the combustion chamber. The device position of this sensor is set so that the black body radiator 14 is located near the top dead center of the piston 15 and further away from the spark plug 12.

By arranging the black body radiator far away from the spark plug in this manner, the state of the generated heat flux can be accurately detected.

FIG. 4 is a diagram showing the overall configuration of the operating state detection device for an internal combustion engine according to the present invention. The sensor is mounted so as to penetrate the wall 20 of the cylinder head, and the tip of the sensor is made to protrude into the combustion chamber 21. This sensor has a heat-resistant rod-shaped light transmitting body 22 made of a sapphire rod, and a black body radiator 23 is formed at the tip thereof. This black body radiator 23
is formed by sputtering an optically opaque high melting point material such as platinum or rhodium to a thickness of several μm. Note that the black body radiator 23 is 5
Place it so that it protrudes beyond the mark. By protruding 5 mm or more, the heat flux density can be accurately detected without being affected by the boundary layer existing near the wall surface. The optical transmission body 22 is supported by a support member 24 made of a metal material such as stainless steel. A thread is formed on the outer periphery of the support member 24 and a thread groove is formed on the wall 20 of the cylinder head, and the support member 24 is screwed into the wall 20 with a washer 25 interposed therebetween. In addition, optical connector 2
6 is screwed onto the support member 24 to optically couple the light transmission body 22 to the optical fiber 27. When the spark plug 12 is activated, a flame is generated near the spark plug, and the flame propagates toward the opposing wall. Therefore, the flame reaches the black body radiator 23 with a delay in the amount of time after ignition (see FIG. 3).

As the flame propagates, combustion gas, that is, heat flux, reaches the surface of the black body radiator 23, and the temperature of the black body radiator increases depending on the state of the generated heat flux. Since the black body radiator 23 is formed of a vapor-deposited film of a noble metal having an extremely small heat capacity, it responds extremely quickly to heat flux. When the temperature of the black body radiator 23 increases, optical energy with an intensity corresponding to the heat flux is generated from the black body radiator, and the generated optical energy propagates through the rod-shaped optical transmission body 22 and the optical fiber 27. optical fiber 2
A lens 28, a filter 29, and a lens 3 are installed on the output side of 7.
0 is placed, and light of a specific wavelength among the propagating light is made to enter the photodetector 31. As mentioned above, the black body radiator 2
3 emits light energy with an intensity corresponding to the generated heat flux, so the photodetector 31 generates an electrical signal representing the generated heat flux, that is, the combustion state in the combustion chamber. This electrical signal is amplified by an amplifier 23 and then supplied to a signal processing circuit.

Next, the results of an experiment in which the dynamic state of an internal combustion engine was measured using the above-mentioned detection device will be explained.

The experimental conditions are as follows.

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

3) The engine was operated in three different operating states by changing the octane number of gasoline and the ignition angle: normal operating state, mild non-knocking state, and severe knocking state.

(i) Normal operating state octane number: 100 Ignition angle knee 8° Compression cost = 7.6 (ii) Slight knocking state octane number: 100 Ignition angle knee 15° Compression cost near, 0 (ji) Severe knocking state octane number :80 Ignition angle knee 15° Compression cost near, 0 4) Process the output signal from the amplified photodetector to output a temperature signal corresponding to the temperature of the black body radiator, and convert this temperature signal into a time signal. Differentiate to generate a differential output signal,
At the same time, a pressure sensor was attached to the engine block to measure the pressure vibrations generated in the engine block. Data from the crank angle detection sensor was also measured.

Figure 5a shows the measurement results during normal operation, Figure 5S shows the measurement results when mild knocking occurs where no knocking sound can be heard, and Figure 5C shows the measurement results when knocking is severe enough that the knocking sound can be heard. The measurement results at the time of occurrence are shown. In Figures 5a-c, the top row shows the detected pressure (relative value), the middle row shows the detected temperature (relative value), the bottom row shows the differential output value (relative value) of the temperature signal, and the horizontal axis is the Indicates crank angle. In the normal operating state shown in FIG. 5a, the measured pressure gradually increases from around 15 degrees of crank angle after ignition, reaches a peak pressure, and then gradually decreases. Furthermore, like the pressure, the temperature of the blackbody radiator rises slowly until it reaches a peak temperature, and then gradually decreases. In addition, the time derivative of temperature also increases slowly, reaches a peak, and then gradually decreases. Fifth
In the mild knocking state shown in the figure, high-frequency pressure vibrations characteristic of knocking occur near the peak pressure of the pressure curve. The temperature of the black body radiator tends to rise slightly, with the peak temperature reaching 2.4 times the normal operating state. Furthermore, a peak appears in the time differential of temperature. In the operating state in which severe knocking is occurring as shown in FIG. 5C, strong high-frequency pressure vibrations characteristic of non-king were detected near the peak pressure. In addition, 1. The black body temperature also exhibits rapid temperature rise characteristics, with the peak temperature reaching 4.5 times that during normal operation. Furthermore, a strong peak occurred in the time derivative of temperature. The results of these experiments are shown in Table 1. Note that since the measured value is a relative intensity, the measured value during normal operation is assumed to be 1 and the relative intensity is displayed.

Table 1 As is clear from the experimental results shown in Table 1, as the non-king intensity increases, the peak temperature also increases, and the time differential of temperature also increases rapidly as the knocking intensity increases.

Therefore, by detecting either the peak temperature or the time differential of the temperature of the black body radiator placed in the combustion chamber, it is possible to detect the occurrence of knocking and the intensity of the knocking that has occurred. Furthermore, as described above, since the operating state of the engine also appears as a change in the timing of the peak occurrence of the time differential of the temperature, the occurrence of knocking can also be detected from the timing of the peak occurrence of this differential. Note that the peak value of the output signal from the photodetector is correlated with the maximum temperature of the blackbody radiator, so the peak value of the output signal from the photodetector represents the knocking intensity, and therefore the output peak is directly used as the detection signal. It can be used as Similarly, since the differential signal obtained by time-differentiating the output signal from the photodetector also has a correlation with the non-king intensity, the peak value of the differential signal can be used as it is as the detection signal.

FIG. 6 is a circuit diagram showing the configuration of an example of the processing circuit of the knocking detection device according to the present invention. The output signal from the photodetector 31 is amplified by an amplifier 32, and a capacitor C and a resistor R
Passed through a bypass filter 40 consisting of 0.01
Cuts low frequency components of around fiz. As a result, a signal indicative of the peak temperature of the blackbody radiator is obtained, with the fluctuations in the base level removed. This signal is A, G, C
, a circuit (automatic gain control circuit), and its output is supplied to a comparator 42.

The signals A, G, and C to be input to the circuit 41 are supplied to the other input terminal of the comparator 42, and these signals are compared.

Since the output signals of the A, G, C, circuit 41 are the reference outputs, the output signals from the bypass filter 40 are A, G, C,
If it is larger than the output signal of the circuit, the occurrence of knocking can be detected. Further, the output of the amplifier 32 is supplied to a differentiating circuit 43 to generate a time-differentiated signal, and this differentiated signal is supplied to a comparator 44 to be compared with a reference limit value. If the differential signal exceeds the limit value, the occurrence of knocking is detected. Furthermore, the differential signal outputted from the differentiating circuit 43 is supplied to the peak detection circuit 45, the timing at which the peak of the differential signal occurs is detected based on the angle signal from the crank angle detection sensor 46, and this output signal is compared with the timing. circuit 47
The ignition timing is compared with the ignition timing detected by the ignition angle detection sensor 48. This comparison result is supplied to a comparator 49 and compared with a limit value, and if the differential peak occurs faster than a predetermined limit value, occurrence of knocking is detected. With this configuration, the occurrence of knocking can be easily detected with a simple circuit configuration.

The present invention is not limited to the embodiments described above, and various modifications and changes are possible. For example, in the above-described embodiment, knocking was cited as an abnormal operation state during the internal combustion period, but it is not limited to non-knocking, and abnormal operation of ignition timing, etc. can also be detected.

In particular, if the ignition timing is too early, the temperature peak and temperature differential peak of the black body radiator will increase as well as knocking, so it can be easily detected with the same circuit configuration.

Furthermore, in the above-mentioned embodiment, the occurrence of knocking was detected by comparing it with a limit value, but it is also possible to detect the occurrence of knocking by using the peak value of the output signal from the photodetector or the peak value of the time differential of the output signal from the photodetector. It is also possible to control the timing of generation of the ignition signal that drives the ignition plug.

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

(1) A black body radiator is placed inside the combustion chamber, and the combustion state is detected by observing the light energy emitted from the black body radiator from the outside via an optical transmitter, so it is not affected by external factors. The operating state of the internal combustion engine can be accurately detected with almost no interference. In particular, when knocking occurs, which is an abnormal operation, the heat flux rapidly increases and the optical energy emitted from the black body radiator increases rapidly. can be detected.

(2) Degree of abnormal operation of the internal combustion engine For example, the intensity of knocking corresponds to the output intensity from the photodetector and the peak value of the time differential of the output signal from the photodetector, so it can be determined based on these output signals. ignition timing can be controlled automatically.

(3) Unlike a detection sensor, a pressure sensor, or a vibration sensor, it does not have a moving part, so it is possible to realize operating state detection that is less susceptible to noise and has excellent reliability and durability.

(4) Since a detection sensor using a black body radiator is used, it is 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 low layer noise. It can be carried out. Further, since the detection sensor using a black body radiator has a frequency response of several tens of kilohertz, it is possible to detect knocking with high precision.

(5) Since the black body radiator can be composed of an optically opaque high-melting point material coating, it is possible to realize an operating state detection device that is hardly affected by the adhesion of soot generated by combustion and has excellent durability. I can do it.

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

[Brief explanation of drawings]

Figure 1 is a diagram schematically showing a configuration for detecting the state of heat flux generated in the combustion chamber by a detection sensor using a blackbody radiator, and Figure 2 is a diagram showing a configuration in which the heat flux reaches the surface of the blackbody radiator. FIG. 3 is a diagram showing the configuration of an example of a four-cycle engine equipped with a detection sensor according to the present invention, and FIG. Figures 5a-c are graphs showing pressure characteristics, temperature characteristics, and time differential characteristics in various operating states, and Figure 6 shows the configuration of an example of an abnormal operation detection circuit. It is a circuit diagram. 20... Cylinder wall 21... Combustion chamber 22.
・・Optical transmission body 24 ・・Support member 27 ・・Optical fiber 23 ・・Black body radiator 26 ・・Optical connector 31 ・・Photodetector

Claims (1)

[Scope of Claims] 1. A blackbody radiator that emits light energy according to the heat flux in a combustion chamber of an internal combustion engine; a heat-resistant optical transmission body that supports the blackbody radiator at its tip; a support member that supports the black body radiator so that the black body radiator is located within the combustion chamber; a photodetector that receives light energy generated from the blackbody radiator and propagated through the light transmission body; and the photodetector. 1. An operating state detection device for an internal combustion engine, comprising: a signal processing circuit that detects an operating state of the internal combustion engine based on an output signal from the internal combustion engine. 2. The operating state detection device for an internal combustion engine according to claim 1, wherein the black body radiator is arranged to protrude toward the internal space by 5 mm or more from the wall surface of the combustion chamber. 3. The signal processing circuit according to claim 1 or 2, wherein the signal processing circuit obtains a peak value of the output signal of the photodetector and detects a state of heat flux generated within the combustion chamber based on the obtained peak value. The operating state detection device for the internal combustion engine described above. 4. Claim 1 or 2, wherein the signal processing circuit obtains a time differential of the output signal of the photodetector and detects a state of heat flux generated within the combustion chamber based on the time differential output.
An operating state detection device for an internal combustion engine according to. 5. Operation of the internal combustion engine according to claim 4, wherein the signal processing circuit detects a peak occurrence timing of the time differential, and detects a state of heat flux in the combustion chamber based on this peak occurrence timing. Condition detection device. 6. The internal combustion engine according to any one of claims 1 to 5, wherein the black body radiator is disposed near the top dead center of the piston of the internal combustion engine and further away from the spark plug. operating state detection device.