JPS6321741Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an engine ignition timing detection device using a magnetic circuit.

Generally, this type of engine ignition timing detection device is
As shown in the plan cross-sectional view of the figure, a rotor 1 that rotates in a constant relationship with the rotation of the engine, a stator 2 that faces the rotor 1 with a predetermined gap A in between,
The rotor 1 and stator 2 and the gap A between them
The magnet includes a magnet such as a permanent magnet M inserted into a magnetic path shown by a broken line, and a detection coil D that detects a change in magnetic flux passing through the magnetic path. In conventional devices of this type, the rotor 1
As shown in the partially enlarged front view of FIG. 2, the stator 2 and the stator 2 have sawtooth-shaped protrusions arranged at equal intervals formed on the outer circumferential surface of the rotor 1 and the inner circumferential surface of the stator 2, respectively. It had a similar shape.
As shown in the figure, when the rotor 1 is at a certain rotation angle position, the tops of the convex portions 1a, 1a', 1a'', . . . and the convex portions 2a, 2a', 2a'', . ……
The top of the head is the closest to the other. At this time, the air gap A between the rotor 1 and the stator 2 becomes the narrowest, and the magnetic resistance of the magnetic path including the rotor 1 → air gap A → stator 2 becomes the minimum. When the rotor 1 rotates from the above position, the air gap A changes, so the magnetic resistance described above also changes following the rotation of the rotor 1. Such a change in magnetic resistance causes a change in the magnetic flux passing through the above-mentioned magnetic path, so it is converted into an electromotive force by the detection coil D described with reference to FIG. 1 and outputted to the outside as a voltage signal. Therefore, as the rotor 1 rotates, a voltage signal as shown in the waveform diagram of FIG. 3 is obtained. The amount of rotational displacement of the rotor 1 (that is, the amount of rotational displacement of the engine) can be detected by counting the wavefront of the voltage signal shown in FIG. 3 using a counter or the like. However, the rotational position of the engine required for detecting the ignition timing cannot be known unless the amount of rotational displacement and the reference position from which this displacement is based are detected. For this reason, conventional devices of this type have a displacement detecting section having a combination of a rotor and a stator having sawtooth protrusions as described above, and a reference position detecting section having a similar structure. They had a parallel configuration. In such conventional devices, time is calculated from the point in time when a signal corresponding to the reference position is emitted from the reference position detection section, and by counting the number of wavefronts of the output signal from the displacement detection section after that point. The rotation angle position of the engine was detected and the required ignition timing was detected.

In a single-cylinder engine, for example, a position where the piston is at the bottom dead center (or top dead center) is selected as the above-mentioned reference position, and the configuration is such that the reference signal is generated once at this position. Then, the amount of displacement from this reference position (i.e., bottom dead center or top dead center position) is detected by counting the number of wave crests of the output signal of the displacement signal generating section described above, and an appropriate rotational angular position (for example, 10゜) so that the ignition operation is performed. Recently, an electronic advance device has appeared which inputs the output signals (reference position signal and displacement signal) of such an ignition timing detection device into a microcomputer to optimally advance the engine according to the rotational speed of the engine. Of course, even in a multi-cylinder engine, ignition timing detection can be performed for each cylinder in exactly the same manner as in the case of a single-cylinder engine. However, in the conventional ignition timing detection device as described above, a reference position detection section and a displacement detection section having similar structures are separately arranged side by side.
The structure is complicated and the device is large, and the manufacturing cost is extremely high because the rotor and stator of both the reference position detection section and displacement detection section described above require high mechanical precision. It's expensive. In recent years, the prices of electronic components used in various electronic engine control devices have been rapidly decreasing due to mass production, but on the other hand, sensors with mechanical structures such as the rotor and stator mentioned above generally have a low structure. Simplification,
Lower prices are lagging behind. The present invention has been developed in view of the above points, and it is an object of the present invention to provide an ignition timing detection device for engines of this type that is simple in structure, easy to downsize, and inexpensive.

FIG. 4 is a front view of essential parts of the engine ignition timing detection device of the present invention. In the figure, reference numeral 10 denotes a rotor substantially similar to that in the conventional device described above. However, in the device of the present invention, the rotor 10 has relatively high protrusions 10b, 10b', . . . at a predetermined first interval on its outer peripheral surface.
(10b' and the following not shown) are provided, and relatively low protrusions 10a, 10a', 10a'', .
... are formed into respective shapes. The stator 20 is also substantially the same as in the conventional device described above. However, in the case of the present invention, the stator 20 has relatively high protrusions 2 on its inner peripheral surface at a predetermined third interval.
0b, 20b', ... are provided, and each of these convex portions 2
0b, 20b', . . . relatively low convex portions 20a, 20a, 20a'', . A detection coil D is provided which is exactly the same as described with reference to the figures.

In the device of the present invention having the above-described structure, when the rotor 10 is in the position shown in FIG.
The top of the head of b″, ... and the high convex part 20 of the stator 20
b, 20b', 20b'', ... are closest to each other and face each other.At this time, the rotor 10 and stator 2
The gap with 0 becomes the narrowest. As the rotor 10 rotates from the position shown, the air gap changes. The state of this change is as follows: The air gap becomes narrowest each time the high convex parts of the rotor 10 and stator 20 come to a position where they exactly face each other, and at each other position, using FIGS. 2 and 3, This is substantially the same as the conventional case described above. Therefore, as the rotor 10 rotates, a voltage signal as shown in the waveform diagram of FIG. 5 is obtained from both ends of the detection coil D. In FIG. 5, the point where the change in the peak value of the signal voltage becomes steeper than other parts corresponds to the time t ₀ when the rotor reaches the position shown in FIG. 4 described above. As is clear from the figure,
Immediately after this t ₀ , the level of the signal wave becomes higher than the others.

Therefore, by separating and extracting such a high-level waveform and other low-level waveforms using a discrimination circuit or the like, a reference position signal (that is, a signal corresponding to a waveform with a high peak value) and a displacement signal ( In other words, a signal corresponding to a waveform with a low peak value is obtained. In order to distinguish and extract the reference position signal and displacement signal from the signals shown in the waveform diagram of FIG.
A discriminator circuit as shown in the figure is used.

In the figure, 30 and 31 are input terminals to which both ends of the detection coil D are connected. The positive input terminal 30 is connected to each negative terminal of a high level discrimination comparator 40 and a low level discrimination comparator 50. A reference level generation circuit 6 that generates a reference level signal at a level approximately proportional to the engine speed.
0 is connected to each of the negative terminals of the high level discrimination and low level discrimination comparators 40 and 50. The other terminal of the reference level circuit 60 is directly connected to the positive terminal (reference input terminal) of the high level discrimination comparator 40, and is also connected to the low level discrimination comparator via a voltage dividing circuit consisting of resistors _R1 and _R2 . It is connected to the positive terminal of 50. The signal level from the detection coil D increases overall in approximately proportion to the engine speed,
Even in that case, the level difference between the high-level reference position signal and the low-level displacement signal does not decrease. Therefore, both the comparators 40
By appropriately changing the voltages applied to the respective reference input terminals of the comparators 40 and 50, the desired reference pulse signals S1 can be obtained from the output terminals of the comparators 40 and 50, respectively.
and displacement pulse signal S2 are obtained.
In the above-described discrimination circuit, the reference level generation circuit 6
The purpose of signal level discrimination is achieved by supplying each comparator 40, 50 with a reference level signal that changes as described above. The reference pulse signal S1 and displacement pulse signal S2 obtained from each comparator 40 and 50 are, for example, FIG. 7a and FIG. 7b.
as shown in the waveform diagram. these signals
Input S1 and S2 into the microcomputer. The microcomputer simply counts the displacement pulse signal S2 from the time when the reference pulse signal S1 is generated (e.g., the time corresponding to the position where the piston is at the bottom dead center) and corresponds to the predetermined ignition position (e.g., 10 degrees before the top dead center). A signal to drive the ignition coil is generated when the displacement pulse signal S2 is counted. The microcomputer has the optimum ignition timing depending on the engine speed (for example, 10 degrees before top dead center when idling;
15 degrees at 4000 rpm; 20 degrees at 6000 rpm, etc.), the ignition timing can be automatically advanced with high precision based on this memory.

As described above, according to the engine ignition timing detection device of the present invention, both the reference position signal and the displacement signal can be obtained by the pair of rotor 10 and stator 20. Therefore, compared to conventional devices of this type, the manufacturing cost can be reduced to approximately half due to the reduction in the number of parts and required man-hours. Furthermore, it has various advantages such as being smaller and lighter and having improved reliability.

[Brief explanation of the drawing]

1 is a plan sectional view showing a conventional engine ignition timing detection device, FIG. 2 is a partially enlarged front view of the device in FIG. 1, and FIG. 3 is a waveform diagram of the output signal of the device in FIG. 4 is a front view of the main parts of the device of the present invention, FIG. 5 is a waveform diagram of the output signal of the device of FIG. 4, FIG. 6 is a circuit diagram of a discrimination circuit used in combination with the device of FIG. 4, and FIG. 7a and 7b are waveform diagrams of output signals of the discrimination circuit of FIG. 6, respectively. 1, 10... Rotor, 2, 20... Stator, A
...air gap, D...detection coil, M...permanent magnet.

Claims (1)

[Claims for Utility Model Registration] A motor that rotates at a speed that has a certain relationship with the rotational speed of the engine, and that has a plurality of triangular protrusions provided at equal intervals on its outer periphery, at least one of which has a higher tooth height than the others. and a stator that faces the rotor with a predetermined gap therebetween and has a plurality of triangular convex portions provided at equal intervals on the inner periphery of the stator, at least one of which has a higher tooth height than the others. , a magnet provided in a magnetic path including the rotor and the stator, a detection coil that detects a change in magnetic flux passing through the magnetic path, and a frequency of a pulse signal output from the detection coil. and a discriminating means for discriminating a pulse peak having a higher voltage than others caused by the triangular convex portions of the rotor and stator with high tooth height. Time detection device.