JPS647328B2 - - 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 degree. This relates to knocking detectors used in devices and the like.

It is generally known that there is a strong correlation between ignition timing and cylinder pressure, but when the air-fuel mixture is exploded, the cylinder pressure will be harmonic (usually 5KHz to 10KHz or 11KHz) when no knocking occurs.
This is a frequency component of ~13KHz, which is caused by the bore diameter of the engine cylinder and intermittent rapid combustion. Vibration or noise is 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 become large in front of the maximum internal pressure (that is, on the ignition side). 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.

Conventionally, piezoelectric acceleration detectors commonly used for vibration detection have been used for this type of detection, and the frequency characteristics of this detector are higher than the knocking frequency.
There are two types: one in which the characteristics become flat below the resonance point (hereinafter referred to as a non-resonant type), and the other in the resonant type, which is a combination of knocking frequency and resonance characteristics, which is currently under consideration by the present inventors.
In the non-resonant type, the resonance point is higher than the knocking frequency, so the sensitivity in the low frequency band including the knocking frequency below this resonance point is almost constant. Therefore, in principle, knocking can be detected over the entire knocking frequency range. However, during engine operation, a lot of vibration noise such as valve seating vibration occurs, and the S/N ratio between vibration noise and knocking deteriorates, so it is practically impossible to detect knocking at high speeds with the non-resonant type. be. In addition, the overall detection sensitivity is low, making it difficult to detect slight knocking even at low rotation speeds.

In the resonance type, detection sensitivity is greatly improved for a specific frequency near the resonance point, vibration noise at other frequencies is difficult to detect, and both the S/N ratio and sensitivity against 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.The higher the Q, the more the resonance frequency will shift and change depending on combustion. A slight deviation in the knocking frequency makes detection difficult. In other words, it is desirable for an ideal detector to have a wide and almost uniform sensitivity characteristic over the entire knocking frequency range.

Therefore, in view of the above points, the present invention has devised a good detector that has multiple resonance points within the knocking frequency band to expand the frequency detection width, has a good S/N ratio, and has good sensitivity. , a multi-resonant knocking detector that prevents differences in vibration detection output signals for each vibrating element for each resonance frequency due to the characteristics of the vibrating body, and has almost uniform detection ability over the entire knocking frequency range. The purpose is to provide

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. 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; however, this detector can be used in any system that detects knocking and controls the ignition timing. It is clear that it is possible.

Next, the knocking detector of the present invention will be explained in detail. In the first embodiment shown in FIG. 2, 21 is a magnetic material (for example, a magnetic material such as iron, iron-nickel alloy, etc.) having a plurality of resonance points that resonate at knocking frequencies of either 5 to 10 KHz or 11 to 13 KHz. This is a vibrating body (hereinafter referred to as a reed) manufactured by The lead 21 is formed by cutting or stamping a flat plate, and its resonance characteristics are determined by its shape, thickness h, length l (equivalent length from the fulcrum), and material. The resonance frequency is approximately determined by f∝h/l ₂ ,
The width of the lead 21 contributes relatively little to frequency. The lead 21 is provided with a recess 21a, which allows the lead 21 to have two resonant lead pieces 2.
It is branched into 1A and 21B. Lead piece 21A, 2
1B is constructed with slightly different equivalent lengths, and their resonance points are at lead piece 21A = 7.5KHz,
Lead piece 21B is set to 8.5KHz. 22
23 is a magnet having magnetic force, and 23 is an L-shaped core made of a material such as iron, iron-nickel, or ferrite, which forms a magnetic path from the lead 21 and the magnet 22. In this magnetic path, each lead piece 21A, 2
A gap G is provided between 1B and the core 23, respectively. Therefore, when the reed pieces 21A and 21B vibrate, the gap G changes and the magnetic resistance of the magnetic path changes. 24 is a coil that detects changes in magnetic flux due to changes in magnetic resistance. coil bobbin 2
A hole 4c is provided so that the core 23 passes through the center thereof, and the conductor for the coil is wound around the outer periphery of this bobbin. Further, in order to prevent changes in the number of interlinked magnetic fluxes due to changes in the relative positions of the coil 24 and the core 23, a bobbin 24c is fixed to the core 23 by adhesive or other means. Reference numeral 25 is a housing made of iron, steel, etc., 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. 26
is a holding rod for each component forming the above-mentioned magnetic path, and together with the washer 210, one end of the lead 21, the magnet 22, and the core 23 are held down by the screw 21.
1 is firmly fixed to the support portion 25b of the housing 25. The coil output terminals 24a, 24b are outputted to the outside by a lead wire 212 via the coil bobbin 24c. 213 is a cover that is attached to the housing 25 by sandwiching and caulking a sealing material 214 such as rubber;
This is the hole to take out. 215 is a rubber bush through which the lead wire 212 is passed. This detector 2 is mounted on a threaded portion 2 so as to vibrate together with the cylinder block.
5a to firmly attach it to 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. Therefore, the knocking vibration generated in the cylinder block is transmitted to the housing 2.
5 to the lead 21, and each lead piece 2
Since one end of 1A and 21B is fixed, each lead piece 21A,
The natural vibration of 21B itself is also added to the vibration. At this time, since the core 23, coil 24, and magnet 22 are strongly made to vibrate together with the housing 25, only the lead pieces 21A and 21B vibrate relative to each other in the magnetic path in response to the knock vibration. , the gap G distance changes depending on the knocking. Here, the core 23, each lead piece 21A, 2
1B is designed in advance by a magnet 22 so that a predetermined magnetic flux passes through it, and a change in the air 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, since the vibrations of each lead piece 21A, 21B are almost independent, the voltage generated in the coil 24 is output as a composite value of the vibrations. That is, one coil 24 can detect two resonance characteristics, and the detector has particularly good detection sensitivity at frequencies near the two resonance points. That is, in this example, by providing a recess 21a in the magnetic plate, the ends are branched so as to resonate separately, and the individual lead pieces 21A and 21B are detected by the coil 24 as a magnetic flux change in one magnetic path. Therefore,
Even if a plurality of resonating lead pieces are provided, there is no need to attach a plurality of detection coils, and the structure can be simple and inexpensive. Incidentally, the vibration characteristics of each lead piece 21A, 21B are affected by its structure or resonance frequency, and the combined output voltage obtained from the coil 24 also differs at each resonance point depending on the resonance frequency. Normally, this difference is small and there are few problems, but to further improve accuracy, more uniform output is required. in general,
The vibrating body (reed pieces 21A, 21B) tends to have a smaller vibration amplitude as the vibration frequency becomes higher. Therefore, if the vibrating bodies are made of the same material, the higher the frequency, the lower the output voltage tends to be. In this example, in order to reduce this difference in output as much as possible, the lead piece 2
The widths of 1A and 21B are made wider on the side 21B where the resonance frequency is higher. In this way, as the width of the lead piece increases, the magnetic resistance decreases even with the same gap G, so the number of interlinked magnetic fluxes increases and the output voltage increases. By arbitrarily changing this width, a substantially uniform output voltage can be obtained, resulting in ideal characteristics. 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.

FIGS. 3a and 3b show two recesses 2 in this lead 21.
1a and 21b are provided and branched into three lead pieces 21A, 21B, and 21c having different lengths. FIG.

A specific configuration can be easily realized by incorporating this in place of the lead 21 in FIG. 2. In this example as well, the lead piece having a higher resonant frequency has a wider width. That is, the widths are in the relationship 21A>21B>21C. Figure 3c is the lead 21 shown in Figures 3a and b.
A detector was constructed using the above, this detector was attached to an exciter, and the coil output voltage was measured using a frequency analyzer.The results are shown below. The excitation force is 2G (converted to 1G), and the vertical axis in the figure is the coil output voltage ratio E, which is the coil output voltage per unit acceleration, and the horizontal axis is the frequency f. . The lengths l ₁ to _{l 3} of each lead piece 21A, 21B, and 21C are set to 10 mm, 11 mm, and 12 mm, respectively. As is clear from the figure, if a recess is provided and the leads 21 are branched (by processing a flat iron plate and making it uneven),
It can be seen that a plurality of sharp resonance characteristics with a good S/N ratio can be obtained even with one magnetic path and one coil. It is also seen that the output voltage can be uniformly adjusted by changing the width of each lead piece 21A, 21B, 21C. The number of resonance characteristics is simply determined by the number of recesses (number of branches), and there is no limit to the number. Therefore, an appropriate frequency band (1KHz, 500KHz,
By providing branches (such as providing five resonance characteristics at a pitch), knocking can be easily detected over the entire frequency band. If the material, thickness, and shape of the lead 21 are specified, the resonance point is determined simply by the length of each lead piece, so it is easy to set the resonance frequency, and furthermore, the width of each lead piece is specified. In this case, the output voltage can also be controlled. In addition, the resonance characteristics are sharp, and the knocking detection sensitivity is improved, while the sensitivity to vibration noise components at other frequencies is reduced. Therefore, weak knocking can be detected sufficiently, and the frequency width to be detected can be widened in total.
Flat and sufficient sensitivity and S/N ratio can be obtained over the entire knocking frequency band, and knocking detection accuracy is greatly improved. Further, even if the knocking frequency changes depending on the combustion process, it can be sufficiently detected.

In each of the above-mentioned detectors, the magnetic force of the magnet 22 acts between the air gaps G, and the reed piece 21 is pulled in one direction by this attraction force, so that it has vibration characteristics having damper characteristics. This means that as soon as the knotting ends (as mentioned above, knotting occurs at a specific crank angle),
There is also the effect that the reed piece acts in a direction to stop vibration, and that the detector 2 generates an output only in the area where knocking occurs. The effect of this damper characteristic becomes greater as the magnetic force of the magnet 22 is strengthened.

FIG. 4 shows a third embodiment in which a plurality of lead pieces 21B, 21B' having the same length and the same resonance frequency are provided to equivalently expand the width of the lead piece at a specific resonance frequency. . In this example, a specific resonance frequency is detected using two lead pieces 21B and 21B' having the same length (in some cases three or more), and one lead piece having a longer length than these lead pieces 21B and 21B' ( Other resonant frequencies are detected by the reed pieces 21A (in some cases 2 or more), and the vibration detection output at different resonant frequencies is adjusted uniformly by the difference in the number of reed pieces at each resonant frequency. It is.

When adjusting the output uniformly in a detector with multiple resonant frequencies, the easiest design method is to change the width of the lead pieces as in the first to third embodiments, but this poses methodological limitations. In some cases, adjustment can be made using other methods as well. Next, an example will be shown in which the output is adjusted by changing the gap G and changing the number of interlinking magnetic fluxes in a detector using a magnetic vibrating body. FIGS. 5 and 6 show fourth and fifth embodiments in which the size of each gap G is made smaller as the resonance frequency increases. If the vibrator is made of the same material and has the same width, the smaller the gap G, the larger the output voltage will be. In the fourth embodiment shown in FIG. 5, the lead pieces 21A, 21B are slightly bent in the direction opposite to the core 23 from the root portion, and each lead piece 21A, 21B, 2
The width of each gap G between 1C and core 23 is 2
The vibration detection outputs at mutually different resonance frequencies are adjusted uniformly with the relationship 1A>21B>21C. Further, in the fifth embodiment shown in FIG. 6, each lead piece 21A, 21B, 21C
The end face of the core 23 facing the core 23 is formed in a stepwise manner so that the width of each gap G between each lead piece 21A, 21B, 21C and the core 23 is set to the relationship 21A>21B>21C as in the fourth embodiment. It has been adjusted to

FIG. 7 shows a sixth embodiment of the present invention, in which the width of each gap G between each lead piece 21A, 21B, 21C and the core 23 is made the same, and each lead piece 2
The thicknesses of 1A, 21B, and 21C are set in the relationship that the higher the resonance frequency is, the thicker it is (21A<21B<21C), and by taking advantage of the fact that the larger the thickness, that is, the larger the cross-sectional area, the smaller the magnetic resistance, The vibration detection output at the resonant frequency is adjusted uniformly.

FIG. 8 shows a seventh embodiment of the present invention, in which a cup-shaped housing 125 made of a magnetic material is shown.
A coil 24 wound around a bobbin 24c is placed inside, and a cylindrical magnet 12 is placed in the center of the bobbin 24c.
2 and the cylindrical core 123, and the collar 123a provided at the upper end of the core 123 is press-fitted into the center of a ring-shaped spacer 29 made of a non-magnetic material.
and the housing 125 are magnetically separated,
A ring-shaped holding part 121b of the lead 121 made of a magnetic material is placed on the spacer 29, and a plurality of lead pieces 121a having mutually different resonance frequencies (lengths) are arranged from the inner end of the ring-shaped holding part 121b toward the center. is extended to form a gap G between each lead piece 121a and the core 123, and a sealing plate 28 is placed over the gap G to close the housing 1.
25 is fixed by caulking the caulking portion 125a at the open end. 125b
125c is a hexagonal wrench for tightening the housing 125 to the engine block using the threaded portion 125b. Also in the lead 121 of the detector configured as shown in FIG.
Each lead piece 121 has a structure similar to that of the lead 21 shown in FIGS. 2 to 7, but has a different resonance frequency.
By varying the shapes of the portions a, it is possible to uniformly adjust the vibration detection outputs at different resonance frequencies.

Further, the material of the resonant leads is not particularly limited either. FIG. 9 shows a recess 201a formed by molding or punching a thin plate of a piezoelectric element and then firing it.
This shows an eighth embodiment in which a plurality of resonant characteristics are constructed by creating a filter 201b. In this Figure 9, 2
01 is a lead of a piezoelectric element (generally called a bimorph) that vibrates in response to engine vibration, and has three lead pieces 201A to 201C of different lengths. 204a, 204b are each lead piece 201A~
An electrode for synthesizing and extracting multiple resonance characteristics made of 201C, 205 is a housing to which the lead 201 is screwed together with a screw 211, a spring washer 208, and a spacer 207 made of an insulator, and although not shown, it is used for engine mounting. A screw is provided.

According to the eighth embodiment, when the engine knocks, the reed pieces 201A to 201C of the reed 201 made of piezoelectric elements each have a resonant frequency, so they vibrate with each other, and the electrodes 204a and 204b have a plurality of combined resonances. A voltage with a frequency is generated and knocking is detected. When the lead 201 is composed of one piezoelectric element in this way, by changing the cross-sectional area of each lead piece 201A, 201B, and 201C, the output generated between the electrodes 204a and 204b at each resonance frequency can be adjusted. Voltage can be adjusted. In the figure, each lead piece 201A, 20
The width of 1B and 201C is 201A<201B<2
01C, the vibration detection outputs at mutually different resonance frequencies are adjusted uniformly.
By changing the thickness of 1C, its cross-sectional area also changes, and vibration detection outputs at mutually different resonance frequencies can be adjusted uniformly.

As described above, in the present invention, the configuration has a plurality of resonant frequencies within the frequency band in which knocking occurs, and knocking is detected by combining the respective resonance outputs, so that a non-resonant detector without resonance characteristics is used. The disadvantage of not being able to detect weak knocking due to vibration noise during vehicle operation (for example, valve seating vibration) has been greatly improved, and when the resonance Q becomes large, the sensitivity increases only at frequencies near the resonance point. On the other hand, the detection frequency range becomes narrower, and if the target knocking frequency deviates due to a shift in the resonance point or a change in the knocking frequency according to the combustion process, the Q will increase and the frequency width will increase. Although the disadvantage is that it is sometimes difficult to detect knocking due to the narrow band, multiple resonance points are provided within the frequency band where knocking occurs, and the range of sensitive frequency detection is expanded. The higher the resonant frequency, the greater the width and/or thickness of each reed piece, or the smaller the width of the gap for vibration detection. The vibration detection output of the vibrating element for each resonance frequency can be uniformly adjusted, and as a result, there is an excellent effect that the knocking detection performance can be greatly improved. For example, as shown in one embodiment of the configuration, this configuration for creating a plurality of resonance points is such that a recess is provided in the vibrating body and a plurality of vibrating pieces are integrally provided by branching, and the resonance characteristics of each vibrating piece are utilized. The number of resonant frequencies is simply determined by the number of branches, and the shape of the vibrating body can be determined by simply creating concave portions to make the branches. Therefore, cheap and simple manufacturing methods such as punching, shaving, and cutting of plates can be used. It is possible to obtain excellent effects in terms of performance, manufacturing method, price, etc.

[Brief explanation of drawings]

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 and b are cross-sectional views and vertical sectional views showing the first embodiment of the detector of the present invention, and Fig. 3 a, b, and c are 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. 4 is a front view of the vibrating body showing the third embodiment of the detector of the present invention. , FIGS. 5a and 5b are a schematic front view and a schematic side view showing a fourth embodiment of the detector of the present invention, and FIGS. 6a and b are a schematic front view and a schematic diagram showing a fifth embodiment of the detector of the present invention. 7a and 7b are a schematic plan view and a schematic side view showing the sixth embodiment of the detector of the present invention, and FIG. 8 is a vertical cross-sectional view showing the seventh embodiment of the detector of the present invention, and FIG. Figures a and b are a plan view and a longitudinal cross-sectional view of the main parts showing an eighth embodiment of the detector of the present invention. 1... Internal combustion engine, 21, 121, 22, 12
2, 23, 123, 24... Vibrating body, magnet, core (common magnetic path), coil (magnetic detection means), 21A, 21B, constituting vibration-electric conversion means,
21B', 21C, 121a...Magnetic lead piece forming a vibrating piece, 21a, 21b, 201a, 2
01b... recess, 201... vibrating body made of a piezoelectric element, G... gap.

Claims (1)

[Scope of Claims] 1. The vibrating body includes a plate-shaped vibrating body that vibrates in response to vibrations caused by knocking of an internal combustion engine, and includes vibration-to-electrical conversion means that generates an electrical output in accordance with the vibration of the vibrating body. has a plurality of vibrating pieces having resonance points at mutually different frequencies within the knocking frequency band, and in order to uniformly adjust the vibration detection output of the vibrating pieces for each mutually different resonance frequency,
A knocking detector for an internal combustion engine, characterized in that the higher the resonance frequency, the larger at least one of the width and thickness of each vibrating element, or the smaller the width of a gap for vibration detection. 2. The vibrating body is made of a magnetic material, and the vibration-to-electrical conversion means includes a common magnetic path that includes the vibrating body and forms the gap adjacent to each of the vibrating pieces, and a common magnetic path that includes the vibrating body and forming the gap adjacent to each of the vibrating pieces, and 2. The knocking detector for an internal combustion engine according to claim 1, further comprising magnetic detection means for detecting a change in magnetic resistance of the common magnetic path due to a change in the gap. 3. The knocking detector for an internal combustion engine according to claim 1, wherein the vibrating body is made of a piezoelectric element. 4. The vibrating body has a plurality of vibrating pieces having the same resonant frequency, and by varying the number of the vibrating pieces at different resonant frequencies, the equivalent width of the vibrating pieces is changed to obtain vibration detection outputs at different resonant frequencies. A knocking detector for an internal combustion engine according to any one of claims 1 to 3, characterized in that the knocking detector is uniformly adjusted. 5. The internal combustion engine according to any one of claims 1 to 4, wherein each of the vibrating pieces is integrally formed by branching by providing a recess in the vibrating body. Notking detector.