JPS6148649B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an ignition timing control for an internal combustion engine that has a function of detecting knocking by vibrations generated outside the cylinder due to internal cylinder pressure of the internal combustion engine and adjusting the ignition timing to a predetermined knocking level. This relates to knocking detectors used in devices and the like.

By the way, it is generally known that there is a strong correlation between ignition timing and cylinder pressure;
When the air-fuel mixture is exploded, the cylinder internal pressure, when no knocking occurs, is a harmonic (a component in a frequency band determined by the bore diameter of the engine cylinder and the sound speed during combustion, which is caused by intermittent rapid combustion). However, when knocking begins to occur, this high frequency wave increases near the maximum value of the internal pressure, and due to its influence, vibrations or noise are generated outside the cylinder. If we look closely at the internal pressure signal generated within the cylinder or the vibration or noise generated outside the cylinder, we can see that knocking (trace knock) begins at the engine crank angle where the internal pressure reaches its maximum value, and gradually increases. When knocking occurs (light knock, heavy knock), the harmonics on the side before the maximum internal pressure (that is, on the ignition side) become large. Therefore, if the vibrations and sounds generated outside the cylinder due to this knocking are accurately detected and feedback is used to control the ignition timing, engine efficiency can be greatly improved. At present, there is no detector that can detect this and operate stably under the harsh environmental conditions required for vehicles.

Furthermore, the frequency components of the harmonics mentioned above vary slightly not only due to engine conditions such as rotational speed load, but also due to combustion fluctuations in each cycle, and do not occur only at a certain frequency. Occurs distributed over frequency bands.

Conventionally, this type of detector has used a vibration system that resonates within the knocking frequency band to detect the presence or absence of knocking. As a result, detection sensitivity is greatly improved for specific frequencies near the resonance point.
It has the advantage that vibration noise of other frequencies is difficult to detect, and both the S/N ratio and sensitivity to knocking are greatly improved. However, resonance also has the disadvantage that the higher the degree of resonance (resonance sharpness Q), the narrower the detection frequency width will inevitably be. A slight deviation makes it difficult to detect knocking.

In other words, an ideal knocking detector is required to have a good S/N ratio within the entire frequency band where knocking occurs, and also to have flat frequency characteristics.

Therefore, in view of the above points, the present invention makes the length of the vibrating body equivalently variable by elastically fixing at least a part of the fixed end of the vibrating body constituting the vibration system with an elastic body, thereby preventing knocking. The purpose of this invention is to provide a knocking detector that has flat frequency characteristics near the generation frequency.

The present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 is a block diagram of a knock feedback ignition system using a knocking detector according to the present invention. In the figure, 1 is a four-cylinder in-line internal combustion engine, and a knocking detector 2 is installed in the cylinder block of the engine 1.
is attached by means such as screws. 3 is a knocking detection circuit that detects engine knocking from the output signal of the knocking detector 2; and 4 is an ignition timing control device that advances or retards the ignition timing in accordance with the output of the detection circuit 3 to control it to an optimum position. The output signal of the control device 4 is passed through a known ignition device 5 to ignite the air-fuel mixture by a spark plug attached to the engine 1. The knocking detection circuit 3 used in this system detects an ignition signal (not shown), and detects noise components due to engine vibration using the output of the detector 2 at a predetermined time period immediately after ignition at which knocking does not occur or at a predetermined crank angle. The ratio of this to the output of the sensor at a predetermined time or at a predetermined angle after top dead center TDC (after the peak of shiatsu pressure) where knocking is likely to occur (an integral value, that is, an averaged value may be used) is calculated. The presence or absence of knocking is detected by Alternatively, the presence or absence of knocking may be processed stochastically, rather than simply based on a single signal. for example
The presence or absence of knocking is determined based on what percentage of knocking occurs in 100 ignitions. The ignition timing control device 4 advances or retards the ignition timing depending on the presence or absence of this knocking. The detailed configurations of the knocking detection circuit 3 and the ignition timing control device 4 are well known and will not be described here, but the present detector can be used with any system that detects knocking and controls the ignition timing. It is clear that it can be used.

Next, the knocking detector will be explained in detail. Second
The figure shows the principle of the invention. The conventional method is shown in Fig. 2a, where the vibrating body 2
The effective vibration length of the vibrating body 21 is fixed, and its frequency characteristics are schematically expressed as a shown by the solid line c in the same figure. become that way. On the other hand, as shown in FIG.
According to the method of elastically fixing the vibration body 21 across the vibration body 21, the effective vibration length of the vibrating body 21 is equivalently variable, and combined with the damper action of the elastic body, its frequency characteristics are shown by the broken line b in the figure c. As such, the half-width of resonance is significantly increased compared to the conventional method.

FIG. 3 shows a first embodiment in which the present invention is applied to a magnetic detection type knocking detector. In the same figure, 21a is a knocking frequency of 5 to 10KHz or 10 to 10KHz.
This is a vibrating body (hereinafter referred to as a reed) made of a magnetic material such as iron or iron-nickel alloy that resonates within 13 KHz. The lead 21a is formed by cutting out or punching a flat plate, and its resonance characteristics are determined by its shape, thickness h, length (equivalent length from the fulcrum) and material. The frequency is the resonance frequency ₀ ∝
It is approximately determined by h/ ² . 22 is a magnet having magnetic force, and 23 is a lead 21a and magnet 2.
2. Iron, iron-nickel alloy, which forms a magnetic path from
It is an L-shaped core made of ferrite or other material.
A gap G is provided between the lead 21a and the core 23 in this magnetic path. Therefore, when the lead 21a vibrates, the gap G changes and the magnetic resistance of the magnetic path changes. 24 is a coil that detects changes in this magnetic flux. The coil bobbin 24a has a hole through which the core 23 passes through the center, and the coil conductor is wound around the outer periphery of the bobbin. Also, the coil 24
In order to prevent changes in the number of interlinked magnetic fluxes due to changes in their relative positions, a bobbin 24a is fixed to the core 23 by adhesive or other means. Reference numeral 25 is a housing made of iron, steel, or the like, which has a threaded portion 25a at the bottom for attaching the detector to the cylinder block of the engine, and support portions 25b and 25c for attaching the core 23 to the upper portion. Reference numeral 26 denotes a holding rod for each component forming the above-mentioned magnetic path.

A part of the vibrating body 21a is firmly fixed at its fixed end by a magnet 22 and a presser bar 26, which constitute a fixed part, and a part thereof is elastically fixed by elastic bodies 220a and 220b, such as rubber. Fixed. Holding rod 26, insulating plates 27, 29,
Along with the lug plate 28 and washer 210 to which the coil output terminals 24a and 24b are attached, one end of the lead 21, the magnet 22, and the core 23 are attached to the screw 21.
1 is firmly fixed to the support portion 25b of the housing 25. After the coil output terminals 24a and 24b are fixed to the lug plate 28 by soldering or caulking, they are outputted to the outside via a lead wire 212. In addition,
The elastic bodies 220a and 220b are compressed and stored in notches provided in the magnet 22 and the presser bar 26.

213 is a sealing material 2 such as rubber on the housing 25.
213a is a hole through which the lead wire 212 is taken out. 215 is a rubber bush through which the lead wire 212 is passed. This detector 2 is firmly attached to the cylinder block by a threaded portion 25a so that it vibrates together with the cylinder block.

Next, the operation of the detector will be explained. As mentioned above, the detector 2 has a threaded portion 25a on the cylinder block.
Tighten and install. The knocking vibration generated in the cylinder block is transmitted to the reed 21a via the housing 25, and since one end of the reed 21a is fixed, it vibrates according to the frequency strength of this vibration. It responds strongly to excitation forces with frequency components near the natural frequency. The natural frequency of the reed 21a is set in advance within the frequency band in which knocking occurs.

At this time, core 23, coil 24, magnet 2
2 is firmly fixed to the housing 25 so as to vibrate, so only the reed 21a relatively vibrates in response to the knock vibration, and the gap G
The distance changes depending on the knot king. here,
The core 23 and the leads 21a are designed in advance so that a predetermined magnetic flux passes through them using the magnet 22, and a change in the gap G results in a change in the number of magnetic fluxes in the magnetic path. The coil 24 detects this change in magnetic flux, that is, the vibration caused by knocking, as a voltage. The detected voltage signal is output to the knocking detection circuit 3 via the lead wire 212.

By the way, the fixed end of the lead 21a is connected to the elastic body 22.
Since a part of the lead 21a is elastically fixed by 0a and 220b, the length of the lead 21a is equivalently variable depending on the vibration intensity, and together with the damper effect, the vibration is generated smoothly. In other words, the half-width of resonance increases significantly compared to when it is simply fixed firmly,
Therefore, the frequency bandwidth in which knocking can be detected also increases significantly. All of the materials shown in this example have sufficient strength and durability for use in automobiles, and the entire detector has excellent earthquake resistance and durability.

FIG. 4 shows a second embodiment in which the frequency band in which knocking can be detected is further expanded. lead 21
In this example, there are three vibrating reed pieces 21b and 2.
It is branched into 1c and 21d, each having a slightly different length, and therefore each having a slightly different natural frequency, that is, a resonant frequency, and can resonate independently. Therefore, which lead pieces 21b to 21d
Even if the magnetic flux resonates, changes in the magnetic flux within one magnetic path can be detected as voltage changes by the coil 24, and the output characteristics are shown by the solid line in Figure 4c, where the horizontal axis represents the frequency and the vertical axis represents the output voltage ratio. Indicated by By using elastic bodies 220a and 220b in this detector, the frequency bandwidth in which knocking can be detected is further increased as shown by the broken line in FIG.

In the above embodiments, only one end of the vibrator was fixed elastically, but as in the third embodiment shown in FIG.
A, 220a', 220b, and 220b' may be elastically fixed, and changes in magnetic flux may be detected at the center of the lead 21. In this case, lead 21
Since both ends of the lead 21 are fixed with the holding rods 26a and 26b, it becomes a vibration mode with both ends fixed.
Changes in magnetic flux are detected at the center of the In this case, two detection coils 24a, 24 are installed in the core 23a.
The coils 24a and 24b are connected in series to increase sensitivity. In other words, even when applied to a vibrating body with multiple fulcrums, there is no difference in principle in its effectiveness.

In each of the above embodiments, it is also possible to use an excitation coil that becomes an electromagnet by being energized by a DC power source instead of the magnet, and a magnetically sensitive element such as a magnetoresistive element can be used instead of the detection coil. You can also do that.

Further, in each of the above embodiments, a lead made of magnetic material was used as the vibrating body, but the material of the vibrating body is not particularly limited as long as the resonant frequency can be realized within the frequency band where knocking occurs.
FIG. 6 shows a fourth embodiment in which a piezoelectric element is used. Reference numerals 21e and 21f are two piezoelectric vibrating bodies called a bimorph type in which a center electrode 21f is sandwiched between two piezoelectric elements 21g and 21h having slightly different lengths from their fixed ends. Each vibrating body 21e, 21f has an outer electrode 21 connected to the upper and lower piezoelectric elements 21g, 21h between two insulators 26c, 26d made of ceramic, baked, etc., each having a concave portion.
The vibrating bodies 21e and 21f are sandwiched together with the elastic bodies 220c and 220d, and are firmly screwed to the metal housing 25 using screws 210a. In this example, the entire surface of the fixed end is covered with elastic bodies 220c, 2
20d, it is elastically fixed.

The center electrode 21i and the outer electrode 21j of one vibrating body 21e are connected as output terminals through a lead wire 212a to each electrode of a sealing terminal 230 (usually called a hermetics seal), which is constructed by insulating two electrodes with glass. and output. Bimorph type vibrating body 21 due to the vibration of notsking
Electric charges are generated at both ends of electrodes e and 21f, specifically, the center electrode 21i and the outer electrode 21j, and a voltage is generated between the two electrodes. The terminal 230 has its metal housing 23
It is soldered to the metal cover 213 by 0a.

In this example, the high side and low side of the resonance frequency are output independently, so they can be summarily combined on the detection circuit side. Alternatively, if the electrodes are harmonically connected in advance or a common electrode is used, a combined output can be obtained with two or one terminal. Of course, it is also possible to use it independently.

In each of the embodiments described above, the elastic bodies were provided on both the upper and lower sides of the vibrating body, but the elastic bodies may only be provided on one side.

Moreover, as the elastic body, in addition to rubber, a synthetic resin having elasticity such as nylon can also be used.

Further, the shape of the vibrating body is not limited to a plate shape, but may be a rod shape.

As described above, in the present invention, the natural frequency of the vibrating body is set approximately near the center of the frequency band in which knocking occurs, and at least a portion of the fixed end of the vibrating body is made elastic so that the effective vibration length of the vibrating body changes. Because it is fixed elastically by the body, it is possible to create a knocking detector that has frequency characteristics with a wide half-width centered around the natural frequency of the vibrating body, and the frequency range in which knocking can be detected increases significantly. Another advantageous effect is that it is possible to detect changes in the knocking occurrence frequency due to combustion fluctuations in each cycle.

Furthermore, the present invention can be realized simply by combining an elastic body with a vibrating body, and it does not matter the material of the vibrating body or the detection principle of knocking, specifically whether it is a magnetic detection method or an electric charge detection method, so it can be widely used. It has an excellent effect of being applicable.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a nok feedback ignition system to which the detector of the present invention is applied, Fig. 2 a, b,
c is a diagram of the principle configuration of a conventional detector and a detector of the present invention and their output characteristic diagrams; FIGS. 3a and b are a cross-sectional view and a vertical cross-sectional view showing the first embodiment of the detector of the present invention; FIG. a, b, and c show a schematic plan view, a schematic front view, and an output characteristic diagram showing the second embodiment of the detector of the present invention, and Fig. 5 a, b show the main part configuration of the third embodiment of the detector of the present invention. Plan view and longitudinal section, Figure 6a,
b, c, and d are a cross-sectional view, a vertical cross-sectional view, a vertical cross-sectional view of a main part, and an enlarged vertical cross-sectional view of a main part, showing a fourth embodiment of the detector of the present invention. 1... Internal combustion engine, 21, 21a, 21e, 21
f... vibrating body included in the vibration-electric conversion means, 2
4... Coil forming magnetic detection means, 26, 26
a, 26b, 26c, 26d, 210a, 211
...The holding rod, insulator, which constitutes the main part of the fixed part,
Screws, 220a, 220a', 220b, 220
b', 220c, 220d...Elastic body.

Claims (1)

[Scope of Claims] 1. A vibration-to-electric conversion means that includes a plate-shaped or rod-shaped vibrating body that vibrates in response to vibrations caused by knocking of an internal combustion engine, and generates an electrical output in accordance with the vibration of the vibrating body; a fixing part for fixing a part of the body from the side; and a fixing part inserted between the fixing part and the vibrating body to elastically fix the vibrating body to the fixing part so that its effective vibration length can be changed. A knocking detector for an internal combustion engine, comprising an elastic body. 2. The knocking detector for an internal combustion engine according to claim 1, wherein the vibrating body is made of a piezoelectric element. 3. The first aspect of the present invention is characterized in that the vibrating body is made of a magnetic material, and the vibration-to-electrical conversion means includes magnetic detection means for detecting a change in magnetic resistance caused by the vibration of the vibrating body. Knocking detector for internal combustion engines as described in . 4. The knocking detector for an internal combustion engine according to claim 3, wherein the magnetic detection means comprises a coil. 5. The knocking detector for an internal combustion engine according to any one of claims 1 to 4, wherein the elastic body is provided on both side surfaces of the vibrating body. 6. Claim 1, wherein the elastic body is provided only on one side of the vibrating body.
A knocking detector for an internal combustion engine according to any one of items 1 to 4. 7. The knocking detector for an internal combustion engine according to any one of claims 1 to 6, wherein the elastic body is made of rubber. 8. Claims 1 to 6, characterized in that the elastic body is made of elastic synthetic resin.
A knocking detector for an internal combustion engine according to any one of the items. 9. Knocking detection for an internal combustion engine according to any one of claims 1 to 8, wherein the vibrating body has a plurality of resonance characteristics at mutually different frequencies in a knocking frequency band. vessel.