JPS59162459A - Engine revolution detector - Google Patents

Abstract

PURPOSE:To simplify the measurement by measuring revolutions from an electromagnetic wave from the ignition system of the engine. CONSTITUTION:An antenna 1 is set at the bottom or the like of an engine room and a metal plate 2 is arranged parallel with the antenna 1 and grounded. When an electromagnetic wave is emitted from the ignition system and received with the antenna 1, a resonance circuit 3 is excited to obtain a continual vibration according to the attenuation characteristic thereof. The repetition frequency in the generation of this electromagnetic wave is proportional to the revolutions of the engine and the generation cycle of the vibration voltage thereof is computed 13 to determine the revolutions of the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a tt! The present invention relates to a device for contactlessly detecting the rotational speed of an engine having a % ignition device, that is, a Regiglo type or rotary type gasoline engine.

In the past, various configurations have been proposed for increasing this kind of engine speed. For example, one of them focuses on the fact that the voltage on the primary side of the ignition coil fluctuates at a frequency proportional to the engine speed. There is one in which the period of the voltage described above is measured with a measuring device and determined as the rotational speed. However, in recent ignition systems, there is a tendency to integrate the ignition coil, power distributor, breaker transistor, etc.
7-, the terminal to 1 of the ignition coil is hidden and closed, and it is becoming impossible to detect the voltage on the primary side from here. The same can be said of other rotational speed detection configurations.

The object of the present invention is to detect the rotational speed without contacting the engine, regardless of the configuration of the ignition device.

The present invention is characterized in that an antenna detects electromagnetic waves generated from the secondary system of the ignition coil during ignition, and the rotation speed is measured from the voltage generated thereby.

In this type of engine, at the time of ignition, a stream of discharge flows to the ignition plug in the secondary system of the ignition coil, but at the moment the discharge occurs, the conductor from the ignition coil in the secondary system to the ignition plug via the distributor An impulse-like electromagnetic wave is generated from the line segment, and is generated repeatedly with the force of each ignition, that is, the ignition period.

This impulse-like electromagnetic wave has a wide range of frequency components from a low frequency band to a VHF band.

In particular, it is known that strong radiation exists in the 20-20-5O band due to factors such as the inductance and stray capacitance of the line segment. The emitted electromagnetic waves are re-radiated in a complex manner by being reflected from the surfaces of metal structures or by the ground surface within the engineering room. Therefore, electric field polarization of electromagnetic waves.

It is thought that the magnetic field polarization will be diverse. Therefore, in this invention, an antenna is installed near the engine in any direction, excited by the electric field or magnetic field component vector of the electromagnetic wave, and the rotation speed is detected from the electromotive force generated based on this. That is.

Embodiments of the invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes an antenna made of metal wire, the length of which is defined as i. A planar metal plate 2 is arranged at a distance from the antenna 1. The antenna 1 is arranged substantially parallel to and opposite to the metal plate 2. A parallel resonant circuit 6 is connected between the antenna 1 and the metal plate 2. The parallel resonant circuit 3 is composed of a coil 4 and a capacitor 5 in parallel. 6
゜7#,? This is an output terminal for outputting the voltage generated in the parallel resonant circuit 3. Note that the width of the metal plate 20 is appropriately selected so that the distributed capacitance 8 between the antenna 1 and the metal plate 2 is hardly affected by this width.

Specifically, the antenna 1 is installed below the engine, for example, in the lower part of the engine room, and the metal plate 2 is installed in contact with the ground. When the engine is rotated, the above-mentioned N magnetic waves are emitted from the ignition system, particularly from the conductor on the secondary side of the ignition system. When antenna 1 receives this electromagnetic wave,
The resonant circuit 6 is excited in an impulse manner by the electric field energy of the electric field polarization of the impulse electromagnetic wave flowing into the antenna 1, and the resonant circuit 6 is excited at the characteristic frequency of the circuit 3 (or when the capacitance 8 of the antenna is connected in parallel to the circuit 3). Even after the incoming electric field energy disappears,
This becomes a sustained vibration that is attenuated by the damping characteristics unique to this resonant circuit.

If the resonant frequency is set to a low frequency in the range of 20 to 5 Q MHz where radiation is strong, the inflow energy will be relatively maximized, and the oscillating voltage generated at terminals 6 and 7 of the circuit 6 will also be maximized. Can be done.

As described above, the repetition frequency of electromagnetic wave generation is proportional to the engine rotational speed, so the engine rotational speed can be determined by calculating the generation period of the oscillating voltage.

This calculation configuration is not particularly different from the configuration used to calculate the generation period of the secondary voltage of the ignition coil as in the past. An example of this is shown in FIG. 2, where the oscillating voltage from the antenna circuit 11 consisting of the antenna 1 and the resonant circuit 3 is amplified by the amplifier 12 and then sent to the period calculation circuit 13. The period is measured. The measured period is then converted into a rotational speed by the measuring device 14. That is, the measuring device 14 outputs or displays a signal corresponding to the rotational speed.

In the configuration shown in Figure 1, if antenna 1 is placed in the space between the lower part of the engine room and the ground surface, antenna 1
The distance A between the metal plate and the gold nugget plate 2 cannot be set too large. Therefore, the effective height of the antenna has to be small. Furthermore, since the intensity of the Fi electromagnetic waves is weak in the space, the oscillating voltage from the resonant circuit 6 is low, which may cause difficulty in amplification. To solve this problem, a large oscillating voltage can be obtained. FIG. 3 shows the configuration for this purpose. This is two (or more than three) antennas I.
This is a configuration in which A and IB are arranged at arbitrary angles, for example, along directions orthogonal to each other, substantially in a single plane. In this case, the metal plate 2 is L-shaped so as to face each antenna jJ, 1B. Further, parallel resonant circuits 5A, 3B similar to those shown in FIG. 1 are connected between each antenna 1A, 1B and the metal plate 2. i resonant circuit 3A.

If the oscillating voltages from 3B are added together, a larger oscillating voltage can be obtained than when there is only one resonant circuit. Each resonant circuit has a resonant frequency of the same or a different frequency.

FIG. 4 shows an example of the antenna 1 having a ring shape with one end open. Although the shape of the moat is rectangular in the figure, it may be a circle or any other shape.

By doing this, even when installing in a limited space,
A long antenna 1 can be used, and the deafening energy can be increased.

FIG. 5 shows a case where annular antennas IA and IJ (two in the figure, but more may be used) similar to the annular antenna in FIG. 4 are used. f3A.

This is the distributed capacity of each 8Bu antenna IA and 1B. Even in this case, the oscillating voltages of the respective resonant circuits 5A and 3B may be added in the same way as in FIG. 3, and thereby an even larger oscillating voltage can be obtained.

The configurations of each of the antennas described above are based on electric field type antennas, but since electromagnetic waves include magnetic field polarization in addition to electric field polarization, magnetic field type antennas can also be used. An example will be explained below. Figure 6 shows what is normally called a loop antenna, with three axes X, Y, and Z that are orthogonal to each other.
Annular antenna 212.2131 extended in the direction of
．． From 212. A primary coil 22 is connected between both ends of each antenna to form a closed circuit. A resonant circuit 25 is configured by an electromagnetic coupling coil 23 and a capacitor 24 for each primary coil. Each resonant circuit has a different frequency or the same frequency as a resonant frequency. The configuration shown in FIG. 7, in which the oscillating voltages from each resonant circuit 25 are added together, omits the coils 22 and 23 in FIG.
1. Compared to the configuration shown in Fig. 6, in which each inductance of f, 21yt, and 21g is designed to be large, and a resonant circuit is formed directly with the capacitor 24, the coil 2
Since there is no loss due to 2.25, the Q can be designed to be higher, and a larger resonant voltage can be obtained for the same incoming magnetic field polarization energy.

Note that when this antenna is placed directly under the engine room and close to the ground surface, the antenna 21Z, which extends in a direction parallel to the ground surface, receives incoming radio waves from the engine room and at the same time receives reflected radio waves from the ground surface. Therefore, the induced voltages of the antenna 24Z may cancel each other out due to the phase relationship between the two, so the antenna 21Z may be omitted.

It should be noted that whether to use the above-mentioned electric field type or magnetic field type antenna can be arbitrarily selected depending on the surroundings of the vehicle, the strength of electromagnetic waves at the location where the antenna is installed, the compatibility conditions for use of the antenna, etc. It goes without saying that the metal plate 2 in use includes anything that can be used as a virtual ground, such as a wire mesh, a measuring instrument case, etc.

FIG. 8 shows an example of the amplifier shown in FIG. 2, with two antenna circuits as shown in FIGS. 3, 5, and 6. Output voltage g1 of each antenna circuit 51.52. g2 is input to high frequency amplifiers 33 and 34.

This input impedance is matched with the output impedance of the output terminal of the antenna circuit.
1.32 has a particularly high Q, it is naturally designed to have a high input impedance. This amplifier 35.34 has an input voltage g1. Current output i1. proportional to g2. i2, but it has a constant current characteristic that is not affected by the load, and therefore exhibits high output invinidance.

35.36 is a diode, 37 is a capacitor, 68° coil 39. A parallel resonant circuit consisting of a resistor 40, 41 a high input impedance amplifier, 42 a variable gain amplifier that changes the gain in response to a control voltage gc, and a 45Fi variable gain amplifier 42 that holds the output voltage at its peak and has a time constant of several seconds. This is a pseudo peak hold circuit that self-discharges. The difference between the output voltage -f of the peak hold circuit 43 and the reference voltage Er is determined by the comparator 44, and the difference voltage is integrated by the integrator 45. This integrated voltage is used as the control voltage #C. These constitute an automatic gain adjustment circuit 46 that stabilizes the pseudo peak. The output of the variable gain amplifier 42 is compared with a threshold value Et by a comparator 47, and when it is greater than Et, an output is produced to trigger the monostable circuit 48. The resulting regular shaped rectangular pulse is output from terminal 49.

Assuming that the antenna circuits 31 and 32 are set in advance to resonate at different frequencies, with the arrival of electromagnetic waves, the resonant circuit of each antenna changes to its resonant frequency, e.g.
It is excited according to a tuning characteristic centered on MH2, 40 MHz, and minute voltages with a duration of 0.1 to 0.2 μs are input to amplifiers 33 and 34 as gl and g2.

The output currents of amplifiers 33 and 34 '1. i2 is half-wave rectified by the diodes 35 and 36, and becomes a summed current on the line A, which excites the resonant circuit 67. Resonant circuit 37
The resonance frequency is, for example, approximately 1 MHI, and an oscillating voltage Cα having a peak value proportional to 11+1L21, that is, 1e11+hzl, appears on the line A.

The oscillating voltage 6α is amplified by the amplifier 441C without amplification distortion, and is input to the variable gain amplifier 42. The voltage ta is generated every time the ignition coil ignites, and the voltage ta is generated by the amplifier 42.
The output voltage 1d has a similar waveform proportional to the voltage eα. The output voltage = f of the peak hold circuit 46 is the voltage ad
The maximum amplitude value of the vibration waveform is maintained at the time of occurrence, but since the self-discharge function also exists, the retained value decreases over time.

Since the time constant of this discharge is a sufficiently large value compared to the ignition period, the voltage -f can be regarded as almost direct current,
The value indicates the peak value in the relevant time period.

The voltage difference between the voltage 6f and the reference voltage Er is integrated by an integrator 45, and the gain of the variable gain amplifier 42 is controlled based on the result of the integration. Therefore the voltage gf.

Er is equal to the output voltage 6d of the variable 21I gain amplifier 42
The maximum peak value of is compensated for the change in the maximum peak value of the input, and is controlled to a constant value given by the voltage Er.

The output voltage ad also appears due to electromagnetic noise other than the regular ignition pulse, but since this is at a lower level than the ignition pulse, the comparator 47 uses the voltage 6 due to the ignition pulse.
A threshold value Et is provided between the highest level of voltage gd caused by noise and the highest level of voltage gd due to noise, and a logic output is output when the voltage cd is larger than this. The monostable circuit 48 is triggered by the output of , and a square pulse is output from terminal 49. Since this output pulse is always generated with an ignition period, if this is processed as shown in FIG. 2, the number of revolutions per minute can be measured.

FIG. 9 is waveform 1 for explaining the operation in the circuit diagram of FIG. 8. 1i in the figure, I + Hi2117)
In the waveform, the average value is indicated by dots. Let τ be the time when the amplitude of this average value becomes /10 of the peak value,
When the resonant frequency of the resonant circuit 67 is fa and the period is Tα, if the resonant frequency f- is set to be τξ)47a, it is possible to sufficiently excite the resonant circuit 37 within the time τ. Moreover, since the output characteristics of the amplifiers 33 and 34 are constant current characteristics, that is, high impedance, the oscillating voltage ga can be maintained without impairing the Q of the resonant circuit 67.
can be generated to the maximum extent, and as a result, a high gain can be easily obtained. Also, each antenna circuit 31.32
When the resonant frequencies are fl and f2, the resonant frequency f- can be set to a sufficiently low frequency (about 1 MH2 as mentioned), so Since it does not have a complicated circuit configuration and has a similar frequency conversion function, it can avoid oscillation due to feedback in the amplification path or unstable amplification, and can easily obtain a high gain.

As detailed above, according to the present invention, the rotation speed is measured from the electromagnetic waves emitted from the ignition system of the engine, so unlike conventional methods, the terminals, conductors, etc. for taking out the output for measurement from the ignition system are connected. There is no need to draw it out, so it is easy to measure.

[Brief explanation of drawings]

FIG. 1 is a layout diagram showing an embodiment of the present invention, FIG. 2 is a front view of the measuring device, FIGS. 6 to 7 are layout diagrams showing other embodiments of the invention, and FIG. A circuit diagram of an amplifying device suitable for use in the present invention, and FIG. 9 is a waveform diagram for explaining the operation. 1, M+ 1B121xr 21y, 2iz...
, antenna, 6.3A, 3B, 31 , 32 , ,
,, Resonant circuit, 46 ++++ Automatic gain adjustment device (1 0゛゛゜O)

Claims (1)

[Claims] an antenna that receives electromagnetic waves emitted from the ignition system when the engine is ignited; a resonant circuit excited by a high-frequency voltage induced when the antenna receives the electromagnetic waves; and an oscillating voltage extracted from the resonant circuit. An engine rotation speed detection device comprising an automatic gain control circuit that maintains a constant average value of pseudo-peak values for each peak value generated.