JPS6235894Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a contactless engine ignition system that generates an ignition voltage by intermittent feeding current to an ignition coil using a transistor that responds to an ignition signal from a magnetic pickup or the like.

In this type of device, a magnetic pickup that generates the ignition signal is installed in a power distributor that distributes the ignition voltage, and also amplifies and shapes the ignition signal to supply power to the ignition coil with a desired closed circuit ratio. In recent years, the ignition circuit unit that controls the intermittent current has been miniaturized by integrated circuits, and attempts have been made to integrate it into the power distributor.

By the way, in such a case, at least a part of the lead wire for connection between the ignition coil and the ignition circuit unit through which the intermittent current of the ignition coil flows will be wired close to the magnetic pickup, and therefore the lead wire will be wired close to the magnetic pickup. Changes in magnetic flux caused by intermittent current flowing through the line act on the magnetic pickup, generating a signal (noise signal) in addition to the normal ignition signal, which can cause the device to malfunction.

This invention prevents malfunctions caused by noise signals especially when the primary current is cut off by adding a means to regulate the input level of the ignition signal waveform shaping circuit to a specified value in synchronization with the opening of the output transistor. By controlling the level regulation period according to the engine speed, malfunctions caused by other noise signals can be effectively prevented.

An embodiment of this invention shown in the figure will be described below.

First, in Fig. 1, numeral 1 is a magnetic pickup that generates an ignition signal that is synchronized with the engine rotation and has a magnitude corresponding to the engine rotation speed, and 2 is a magnetic pick-up that rectifies and smoothes the ignition signal to generate the engine rotation speed. A bias circuit 3 generates a direct current bias voltage _V1 of a corresponding magnitude and superimposes it on the ignition signal, and 3 receives the superimposed output of the ignition signal and bias voltage through a resistor 4, and has a magnitude relationship with respect to the switching operation level _V2. A waveform shaping circuit that performs a switching operation to generate a pulse output in response to, for example, a differential amplifier that receives the above-mentioned superimposed output at one input terminal and receives a set voltage that determines the switching operation level _V2 at the other input terminal. It consists of 5 is a Darlington output transistor connected in series with a current detection resistor 8 to the power supply circuit of the ignition coil 7 by the battery 6; It is a drive circuit that operates in the saturation region when the current rises and controls the current in the active region after the current reaches a certain value, for example 6A, and the output of the current detection resistor 8 is the bias circuit of the bias circuit 2. Control the value of voltage V ₁ . A transistor 10 is connected to the input terminal of the waveform shaping circuit 3 and regulates the input level of the input terminal to below the switching operation level _V2 . Reference numeral 11 denotes a time limit circuit which receives the output of the waveform shaping circuit 3 and closes the transistor 10 for a desired period of time from the opening of the output transistor 5 in synchronization with the opening of the output transistor 5. It is composed of a well-known monostable circuit or the like that generates an output pulse corresponding to the period until the potential of the capacitor that starts the process reaches a predetermined level. 12 is a rotation speed detection circuit that generates a rotation speed detection output in response to whether the ignition signal voltage of the magnetic pickup 1 reaches a predetermined value and controls the output pulse width of the time limit circuit 11; Therefore, for example, the time constant pulse width is controlled by changing the charging/discharging time constant of the capacitor of the time limit circuit or the detection level of the capacitor voltage.

Next, the operation of the embodiment configured in this manner will be explained.

When an alternating current ignition signal is generated in the magnetic pickup 1 due to engine rotation, this ignition signal is superimposed on the bias voltage V ₁ of the bias circuit 2 as shown by the solid line in FIG. When the switching operating voltage V ₂ is reached, the waveform shaping circuit 3 generates an "H" level output as shown in FIG. Start power supply. Next, when the superimposed output becomes lower than the switching operation level _V2 , the operation is the opposite of the above, and the output of the waveform shaping circuit 3 is inverted to the "0" level, the output transistor 5 is opened, and the ignition coil 7 is ignited. Generates voltage and ignites the engine.
Incidentally, in practice, the switching operation level _V2 of the waveform shaping circuit 3 is provided with a difference so as to have a predetermined hysteresis width between opening and closing.

Here, when the primary current of the ignition coil 7 reaches a specified value based on the output of the current detection resistor 8, the drive circuit 9 suppresses the base current of the output transistor 5 and performs constant current control in the active region to prevent excessive current. is prevented from flowing to the output transistor 5.
Further, the bias circuit 2 superimposes a bias voltage V ₁ of a magnitude corresponding to the ignition signal voltage on the ignition signal, thereby determining the angular timing (of the output transistor 5) at which the superimposed output reaches the switching operation level V ₂ of the waveform shaping circuit 3. The circuit closing timing) is advanced in accordance with the increase in the engine speed, and the closing angle width of the output transistor 5 is increased to maintain a constant closing period (primary current conduction period) for the output transistor 5 regardless of engine speed fluctuations. The closed circuit rate is controlled to give the following. Furthermore, the bias circuit 2 has the magnitude of the bias voltage V ₁ corrected by the output of the current detection resistor 8, so that
The minimum value of 1 required for the primary current to reach the specified value.
The closing rate is controlled to an optimum value in order to provide the next current energization period.

Now, these ignition circuit units that control the power supply to the ignition coil 7 intermittently in response to the ignition signal are integrated circuits, etc., and are attached to a power distributor, and the lead wires of the power supply circuit of the ignition coil 7 are connected to the magnetic pickup 1.
When the lead wire is wired close to the lead wire, the magnetic flux generated by the primary coil current flowing through the lead wire changes rapidly when the output transistor 5 is opened, and this magnetic flux generates a noise signal in the interlinked magnetic pickup 1. However, this noise signal is blocked by the transistor 10, so that the waveform shaping circuit 3 does not malfunction, and the output transistor 5 is kept open. That is, the timer circuit 11 is triggered by the output of the waveform shaping circuit 3 as shown in FIG. Therefore, since the input level of the waveform shaping circuit 3 is forcibly regulated below its switching operation level _V2 , the ignition signal and bias voltage
Even if a noise signal is generated after the superimposed output of V ₁ reaches the switching operation level V ₂ or lower and the waveform shaping circuit 3 switches in one direction, this noise signal will not cause the switching operation level V ₂ to be exceeded. Therefore, the waveform shaping circuit 3 does not perform any inversion operation and can keep the output transistor 5 open. Further, the output pulse width T of the time limit circuit 12, which determines the closing period of the transistor 10, is controlled by the output of the rotation speed detection circuit 12 (see FIG. 3).
When the rotation speed is N ₁ or less, it is about 5 ms corresponding to the long open period of the output transistor 5, and when the rotation speed is N ₁ or more, it is 1 ms.
By setting the output transistor 5 to a certain level, it is possible to prevent noise signals from being generated over a wide range during a long open circuit period of the output transistor 5 at low speeds, without affecting the switching operation of the waveform shaping circuit 3 when the output transistor 5 is closed. Malfunctions can be prevented.

Note that the output pulse width of the timer circuit 11 is not limited to being controlled in two stages as in this embodiment, but can also be controlled in multiple stages or continuously in accordance with the number of revolutions.

As described above, according to this invention, by providing means for regulating the input level of the ignition signal waveform shaping circuit to a specified value in synchronization with the opening timing of the output transistor, malfunctions caused by noise signals when the primary current is cut off are prevented. In addition to completely preventing the above-mentioned input level regulation period, since the above-mentioned input level regulation period is controlled by the engine speed, not only the above-mentioned noise signal but also other noises can be detected over a wide range, especially during the long open-circuit period of the output transistor at low speeds. This has the effect of preventing malfunctions caused by signals.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of this invention, and FIGS. 2 and 3 are explanatory diagrams of the operation of FIG. 1. In the figure, 1 is a magnetic pickup, 2 is a bias circuit, 3 is a waveform shaping circuit, 4 is a resistor, 5 is an output transistor, 6 is a battery, 7 is an ignition coil, 8 is a current detection resistor, 9 is a transistor circuit, and 10 is a A transistor, 11 is a timer circuit, and 12 is a rotation speed detection circuit.

Claims (1)

[Scope of utility model registration request] A pickup that generates an ignition signal in synchronization with the rotation of the engine, a waveform shaping circuit that responds to the ignition signal and shapes the waveform of the ignition signal, and is controlled to open and close by the output of this waveform shaping circuit, thereby intermittent power supply to the ignition coil. an output transistor that responds to the output of the waveform shaping circuit, and generates a timed output that continues for a predetermined period from the opening of the output transistor in synchronization with the opening of the output transistor; an input level regulating means for regulating the input level to a specified value; and a means for controlling the duration of the timed output according to the rotation speed of the engine to control the input level regulating period by the input level regulating means; An engine ignition system in which a level regulation circuit maintains the output transistor open circuit at least during an input level regulation period regardless of the occurrence of a noise signal.