JPS5935151A - Apparatus for detecting rotation of engine - Google Patents

Abstract

PURPOSE:To obtain an engine rotation detecting apparatus excellent in noise resistance and high in reliability, by constituting so as to detect the primary side signal of an ignition coil by light. CONSTITUTION:The primary current of an ignition coil 2, that is, the primary current of current transformer 7 is intermittently flowed every when a point is subjected to opening and closing operation and a current 1/N times of the primary current is flowed through the secondary winding of the current transformer 7. A light emitting element 8 emits light by the aforementioned secondary current and comes to light emitting operation synchronous to the opening and closing operation of the point 3. A resistor 9 is inserted in order to prevent the generation of overvoltage when the secondary side of the current transformer is opened. In the next step, a light receiving element 10 receives the light signal of the light emitting element 8 to convert the same to an electric signal and an electric signal synchronous to the rotation of an engine is obtained at the output terminal of a wave form shaping circuit 11. By the above mentioned constitution, the noise signal of the primary side of the ignition coil 2 does not directly entire the circuit 11 and an engine rotation detecting apparatus high in reliability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an engine rotation detection device that detects a primary side signal of an ignition coil using light.

Conventionally, there has been a device for applying this glue as shown in FIG. In the figure, ) is the batch '), +21 is the ignition coil, which has a negative winding (Ll) and a secondary winding (L2), (3) is the point), +41 is the ignition glove,
(5) is a waveform shaping circuit, and (6) is a signal line, which are connected as shown in the figure.

Next, the operation will be explained. When point (3) closes the contact, the battery (ll to ignition coil (2)
A current flows to point (3) through the second winding (Ll) of. Next, point (3) opens the contact (and the above current is cut off, the magnetic flux in the iron core of the ignition coil (2) changes rapidly, inducing a high voltage in the secondary winding (L2),
A discharge spark is generated at the spark plug (4).

Point (3) opens and closes in synchronization with engine rotation, so point (3) and ignition coil (
The engine rotation can be detected by detecting the voltage waveform at the connection point (a) with the second winding (Ll) of 2) via the signal line (6) with the waveform shaping circuit (5). However, the voltage waveform at the connection point (a) is a very disordered waveform, and moreover, a high voltage of several hundred square meters may be generated immediately after the negative current is cut off. Therefore, the waveform shaping circuit (5) must take certain measures to prevent malfunction and to protect against overvoltage. Further, if the waveform shaping circuit (5) is placed apart from the ignition coil (2), the distance of the signal line (6) becomes long, and noise countermeasures are also required.

Since the conventional engine rotation detection device is configured as described above, the waveform shaping circuit (5) has the disadvantage that the circuit is complicated due to various protection and noise countermeasures.

This invention was made to eliminate the drawbacks of the conventional devices as described above. By detecting the primary side signal of the ignition coil with light, engine rotation can be achieved with sufficient reliability with a simple circuit configuration. The purpose is to provide a detection device.

An embodiment of the present invention will be described below with reference to the drawings. Second
In the figure, (1) to (4) are completely similar to the conventional device described above. (7) is a current transformer, which is composed of an annular magnetic core (71) made of ferrite or the like and a secondary winding (72) with N turns, and the -order current flows through the annular magnetic core (71).

Next, (8) is a light emitting element such as a light emitting diode, which is connected in series with the secondary winding (72) of the current transformer (7). Further, (9) is a resistor as an overvoltage prevention element, and is read in parallel with the light emitting element (8). (20) is a light-emitting device consisting of the above-mentioned light-emitting element (8) and resistor (9).

00) is a light receiving element such as a phototransistor that receives the original signal of the light emitting element (8), and +Ill is a waveform shaping circuit including a signal amplification circuit and the like.

Next, the operation will be explained. Every time point (3) performs an opening/closing operation, the negative current of the ignition coil (2), that is, the negative current of the current transformer (7), is intermittent, and as is well known, the secondary current of the current transformer (7) The wire (72) has a negative current of 17' within the range where the magnetic flux of the annular magnetic core (71) is saturated.
N times the current flows. The light emitting element (8) emits light due to the secondary current, and its light emitting operation is synchronized with the opening/closing operation of the point (3). As is well known, the resistor (9) is inserted to prevent overvoltage from occurring when the secondary side of the current transformer (7) is opened. Next, the light receiving element GO) receives the original signal from the light emitting element (8) and converts it into an electrical signal, and an electrical signal synchronized with engine rotation is obtained at the output terminal of the waveform shaping circuit 0D.

With this configuration, the noise signal on the primary side of the ignition coil will not directly enter the waveform shaping circuit, and a highly reliable engine rotation detection device can be configured. Furthermore, as is well known, the current transformer (7) has almost no influence on the negative side, so the original electrical characteristics of the ignition device do not change.

FIG. 3 is a diagram showing an engine rotation detection device according to another embodiment of the present invention. In the figure, σ is a light emitting diode, (13) is a diode connected in antiparallel to the light emitting diode (12) as an overvoltage prevention element, and (20) is composed of the light emitting diode +I21 and the diode (13). It is a light emitting device. The rest of the structure is the same as that of the embodiment shown in FIG. In the case of the configuration shown in Figure 13, since no resistor is connected in parallel with the light emitting diode α4, all the current induced in the secondary winding (72) of the current transformer (7) flows through the light emitting diode a:fJ. flow, improving luminous efficiency. Also, the current component in the reverse direction is the diode 0.
3), there is no risk of overvoltage occurring due to an open circuit on the secondary side.

In addition, in the embodiments shown in FIGS. 2 and 3 above, a configuration is shown in which the light from the light emitting element is directly received by a transponder, but the original fiber may be used as the original transmission line, and the original fiber may be used as the original transmission line. By using this, the light-emitting element and the light-receiving element can be separated in distance, and the degree of freedom in positioning them increases.

Further, the magnetic core of the current transformer (7) does not necessarily have to be annular, but may be rectangular, and furthermore, the number of turns of the primary current is 1.
Even if it is a plurality of turns instead of a turn, the gist of the present invention is not impaired.

Furthermore, the current transformer (7) does not have the characteristics required in commonly used instruments, that is, the physical property that the current waveform on the secondary side is proportional to the current waveform on the primary side over the entire time range. A pulse waveform of the secondary current is sufficient. Therefore, even a small magnetic core with low saturation magnetic flux can be used.

As described above, the present invention uses the primary current of the ignition coil as the primary current of a current transformer, connects a light emitting element between the secondary winding ends of the current transformer, and extracts an optical signal from the light emitting element. Since the configuration is configured to detect the primary side signal of the ignition coil, there is an effect that a highly reliable engine rotation detection device with excellent noise resistance can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a conventional engine rotation detection device.
FIG. 2 is a diagram showing the configuration of an engine rotation detection device according to one embodiment of the present invention, and FIG. 3 is a diagram showing the configuration of an engine rotation detection device according to another embodiment of the invention. In the diagram, (1) is batch! j s (21 is the ignition coil, (Ll) the primary winding of the ignition coil, (7) is the current transformer, (72) is the secondary winding of the current transformer, (20) is the light emitting device, +81 +13 is Light emitting element%
(9) is a resistor (overvoltage prevention element), +13) is a diode (overvoltage prevention element), and +10+ is a light receiving element. Note that the same reference numerals in the figures indicate the same or opposite parts. Agent Shin Kuzuno - Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] An engine rotation detection device that detects engine rotation using a primary current of a +1144 injection coil, comprising: -
A current transformer to which the primary side current of the ignition coil is passed, a light emitting device connected between the ends of the secondary winding of the current transformer, and a light receiving element that photoelectrically converts light from the light emitting device. An engine rotation detection device characterized by comprising: (2) A patent characterized in that the light emitting device is comprised of a light emitting element and an overvoltage generation prevention element connected to the light emitting element to prevent overvoltage generation when the secondary side of the current transformer is opened. An engine rotation detection device according to claim 1. (3) The engine rotation detection device according to claim 2, wherein the overvoltage prevention element is a resistor connected in parallel with the light emitting element. +41 The engine rotation detection device according to claim 2, wherein the light emitting element is a light emitting diode, and the overvoltage generation prevention element is a diode connected in antiparallel to the light emitting diode.