JPH0719003Y2 - Engine speed detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an improved technique of a detection device for detecting an engine speed.

(Prior Art) Conventionally, as an engine speed detecting device of this type, an ignition timing control device of an engine is used as shown in, for example, JP-A-58-22962, and its ignition coil (ignition coil) is used. ), In which the engine speed is detected by calculation based on the cycle of the primary current is well known and widely used.

(Problems to be Solved by the Invention) By the way, the ignition timing control device is usually provided with a circuit closing rate control circuit for controlling the energization time (circuit closing rate) to the ignition coil. That is, the closed-circuit rate control circuit calculates the ignition timing by applying the constant ignition energy to the ignition coil in consideration of the rising characteristic of the primary current when the ignition timing is given. This is to obtain the timing of starting energization (closing angle) of the coil, that is, the energization time.

Then, in the circuit closing rate control circuit, for example, the circuit closing rate is determined based on the battery voltage. Therefore, for example, as the battery voltage decreases, the closing angle is advanced in order to secure the ignition energy. It has the function of energizing the ignition coil at an early stage.

However, even if the battery voltage is temporarily reduced by another electric load such as a winker device or a hazard device, the closing angle is advanced and the ignition coil is energized early, and as a result, the ignition coil There is a problem that the cycle of the primary current fluctuates, and although the ignition timing, that is, the engine speed is actually constant, the detected engine speed fluctuates, resulting in an erroneous detection state.

The present invention has been made in view of such a point, and an object thereof is to suppress voltage fluctuations in the above-mentioned closed circuit rate control circuit,
It is to prevent erroneous detection of the engine speed due to a change in the energization time to the ignition coil based on the function.

(Means for Solving the Problem) In order to achieve this object, the solution means of the present invention is to make the battery voltage applied to the closed circuit control circuit constant.

Specifically, in the present invention, an ignition coil connected to a battery and a closed circuit for controlling the energization time for the ignition coil based on the crank angle of the engine and for adjusting the energization time according to the voltage applied to the battery. A rotation speed detection device comprising a rate control means and a rotation speed detection means for detecting an engine speed based on a cycle of a primary current of an ignition coil whose energization time is controlled by the closed circuit rate control means,
Connected in series between the closed circuit rate control means and the battery,
It is characterized in that a diode for allowing a current from the battery to the closed circuit rate control means and a capacitor connected between the diode and the circuit between the closed circuit rate control means and the ground are provided.

(Operation) With this configuration, in the present invention, the diode is connected in series between the closed circuit rate control means and the battery, and the capacitor is connected between the diode and the closed circuit rate control means. Is stored,
In addition, the diode can prevent the stored charge from being discharged to the battery side. Therefore, the battery voltage supplied to the circuit closing rate control means can be smoothed, and even if the battery voltage is temporarily reduced by another electric load such as a winker device or a hazard device, the circuit is closed by the operation of the capacitor and the diode. A stable and substantially constant voltage is always applied to the rate control means. Therefore, the closing angle determined by the closed-circuit rate control means is kept constant and the ignition coil is energized.
The cycle of the next current does not fluctuate, so that the engine speed can be accurately detected and the erroneous detection state can be prevented.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall configuration of an engine speed detecting device according to an embodiment of the present invention, in which 1 is a high voltage secondary voltage for igniting an air-fuel mixture of an engine (not shown) mounted on a vehicle. An ignition coil for generating the
Secondary coil 1a and secondary coil 1b for generating a high voltage induced voltage when the current applied to the primary coil 1a is cut off
And one terminal of the secondary coil 1b is a primary coil 1a.
The other terminal is connected to the positive terminal of the battery B via the ignition key switch 2, and the other terminal of the secondary coil 1b is connected to a spark plug (not shown).

On the other hand, 3 is an igniter for controlling the energization of the ignition coil 1, and the igniter 3 is energized to the ignition coil 1 based on an output signal from a crank angle sensor 6 for detecting the crank angle of the engine ( A circuit closing rate control circuit 4 (circuit closing rate control means) for controlling the circuit closing rate), and a drive circuit 5 for turning ON / OFF the switching transistor Tr based on the output signal of the circuit closing rate control circuit 4.
The collector of the switching transistor Tr is connected to the other terminal of the primary coil 1a of the ignition coil 1,
According to the closing angle determined by the circuit closing rate control circuit 4, the second
Turn ON / O the switching transistor Tr as shown in the figure (b).
The FF is operated to energize the ignition coil 1.

Further, the closure rate control circuit 4 is connected to the battery B via the ignition key switch 2, and determines the closing rate based on the battery voltage V _o, with the variation of the battery voltage V _o , Has a function of energizing the ignition coil 1 by adjusting the closing angle to secure the ignition energy.

The collector of the switching transistor Tr in the igniter 3 (the primary coil 1a of the ignition coil 1) is connected to the period measuring type tachometer 7. The period measuring type tachometer 7 constitutes a rotational speed detecting means, and is composed of the switching transistor Tr and the ignition coil 1.
The ignition primary voltage V output to the secondary coil 1a is used as a trigger signal to measure the cycle of the ignition primary voltage V, and thus the end of the primary current i, to calculate and display the engine speed based on the measured value. To do.

Further, as a feature of the present invention, in the circuit 8 between the ignition key switch 2 and the closing ratio control circuit 4 of the igniter 3, a battery is provided on the closing ratio control circuit 4 side with respect to the connection portion with the ignition coil 1. A diode D that allows a current from B to the closed circuit rate control circuit 4 is inserted.
Further, a capacitor C whose end is grounded is connected to a circuit 8 closer to the circuit closing ratio control circuit 4 than the diode D, and a battery voltage applied to the circuit closing ratio control circuit 4 by the diode D and the capacitor C. The smoothing means 9 is configured to smooth. In the figure, reference numeral 10 denotes other vehicle-mounted electric components such as a winker device and a hazard device.

Therefore, in the above-described embodiment, the closing ratio control circuit 4 of the igniter 3 determines the closing angle of the ignition coil 1 based on the crank angle detected by the crank angle sensor 6 during operation of the engine. The switching transistor Tr is turned on / off by the output signal of 4 as shown in FIG. 2 (b). With the operation of this transistor Tr, the primary coil 1a of the ignition coil 1 is turned on as shown in FIG. 2 (c). The current from the battery B, that is, the primary current i flows,
When the primary current i is cut off, a high voltage secondary voltage is generated in the secondary coil 1b, and this secondary voltage is applied to the spark plug to ignite the air-fuel mixture of the engine.

Further, the tachometer 7 is operated by using the ignition primary voltage V output from the switching transistor Tr to the primary coil 1a of the ignition coil 1 as a trigger signal, and the tachometer 7 causes the ignition primary voltage V (primary current i) to be generated. Is measured, and the engine speed is detected and displayed based on the measured cycle.

In that case, since the circuit 8 between the closed circuit rate control circuit 4 and the ignition key switch 2 in the igniter 3 is provided with the smoothing means 9 including the diode D and the capacitor C, the capacitor C is connected to the battery. The charge from B is stored and the stored charge is discharged to the battery B side by the diode D. Therefore, for example, the other electrical component 10 such as a winker device or a hazard device is turned on, and the electrical load thereof temporarily changes the battery voltage from the standard voltage (several + μsec) as shown in FIG. 2 (a). Even if the voltage drops by several volts, regardless of that, a substantially constant voltage is always stably applied to the closed circuit rate control circuit 4 by the charges accumulated in the capacitor C. For this reason,
As shown by the solid lines in FIGS. 2B to 2C, the closing angle determined by the closed circuit rate control circuit 4 is kept constant and the ignition coil 1 is energized, and the primary current to the ignition coil 1 is increased. The cycle of i does not fluctuate as shown by the broken line, and therefore, the engine speed can be accurately detected and the fluctuation of the display of the tachometer 7 of the speed can be prevented.

The capacitor C may be replaced by a radio noise capacitor of about 0.5 Fμ for preventing noise from entering the in-vehicle radio. In that case, the number of parts can be reduced, which is preferable.

(Effect of the Invention) As described above, according to the present invention, the ignition coil 1
In a rotation speed detection device for detecting the engine rotation speed by the cycle of the next current, a closed circuit rate control means for controlling the energization time to the ignition coil is connected to the battery through a diode, and the diode and the closed circuit are connected. A capacitor is connected between the rate control means and the ground, and an electric charge is stored in this capacitor by a diode so as not to be discharged to the battery side, so that the battery voltage applied to the closed circuit rate control means is made constant. By
Even when the battery voltage temporarily drops due to another electric load or the like, it is possible to constantly stably apply a substantially constant voltage to the closed circuit rate control means to keep the cycle of the primary current to the ignition coil constant. Therefore, the engine speed can always be detected stably and accurately.

[Brief description of drawings]

The drawings show an embodiment of the present invention, FIG. 1 is an electric circuit diagram showing the overall configuration thereof, and FIG. 2 is a timing chart diagram showing characteristics such as voltage in each circuit portion. 1 ... Ignition coil, B ... Battery, 4 ... Closed circuit rate control circuit (closed circuit rate control means), 7 ... Tachometer (rotation speed detection means), 8 ... Circuit, D ... Diode, C ... Capacitor , 9 ... Smoothing means.

Claims (1)

[Scope of utility model registration request] 1. An ignition coil connected to a battery, and a circuit closing rate control means for controlling the energization time for the ignition coil based on the crank angle of the engine and for adjusting the energization time according to the voltage applied to the battery. A rotation speed detection device comprising: a rotation speed detection means for detecting an engine rotation speed based on a cycle of a primary current of an ignition coil whose energization time is controlled by the closure ratio control means; A diode connected in series between the battery and allowing a current from the battery to the closed circuit rate control means, and a capacitor connected between the diode and the closed circuit rate control means and the ground are provided. And engine speed detection device.