JPS6146459Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a voltage control circuit that prevents tachometer needle deflection caused by oscillation of a transistor igniter due to inertial rotation of a motor load such as an electric fan for engine cooling.

In recent years, contactless ignition devices using switching transistors that cut off the current to the engine's ignition coil have replaced the conventional mechanical contact-type interrupters used as ignition systems in large motorcycles, etc. Equipped with a type switch,
This enables extremely stable ignition control with no ignition errors due to mechanical wear or point misalignment.

In addition, the engine cooling fan is now driven from the conventional belt-driven engine-linked type to a thermally-responsive type in which the fan is fixed to a thermostatically controlled electric motor, which can be expected to provide a more reliable cooling effect. It's starting to look like this. By the way, non-contact type switches using switching transistors require reliable current control to obtain ignition timing or appropriate spark potential.
The circuit is composed of many control transistors, resistors, and capacitors, which are densely packed together, so when the power supply voltage drops below the operation compensation voltage, mutual interference between each component and connection pattern may cause oscillation. The resulting oscillating current may be superimposed on the signal path or voltage line to an electrical load, such as a tachometer circuit, causing malfunction. Under normal operating conditions, this abnormal drop in power supply voltage does not occur and is hardly a problem. Due to the power generation effect caused by the inertial rotation, a low voltage continues to be applied to the electrical load through the voltage line, which tends to induce oscillation of the non-contact switch and cause, for example, a tachometer needle deflection phenomenon.

That is, in the conventional configuration, as shown in FIG. 1, a primary coil 3 of an ignition device and a contactless switch 4 are connected in series from an on-vehicle power source 1 through a key switch 2, and a voltage pulse generated at this voltage terminal is transmitted to a tachometer circuit 5. The engine rotation speed is detected by applying the voltage to the input of the tachometer circuit 5, and an electric engine cooling fan 6 is connected in parallel with the tachometer circuit 5 to control the rotation according to the amount of heat generated by the engine.

In this case, if the electric fan 6 is rotating while the key switch 2 is closed and the engine is running, the voltage supplied to the tachometer circuit 5 or the ignition device will remain at the normal level, and the tachometer will also not operate. It is being done normally. If the key switch 2 is opened now, the voltage from the on-board power supply 1 will be cut off, but the electric fan 6 will continue to rotate for a while due to inertia, and the ignition system will be activated by the electric power generation action of the fan motor. Application of low voltage to etc. will continue. In other words, the voltage applied to the electrical load will exhibit a drop phenomenon as shown in FIG. 2, but as mentioned above, the component circuit in the non-contact type switch 4 may exhibit an oscillation phenomenon below the compensation voltage. This oscillating current will be applied to the voltage line or the signal line to the tachometer circuit 5, and will induce malfunction of the electrical load as voltage noise as seen in the oscillating waveform of FIG. 2a, for example.

Conventionally, in order to prevent such an effect on the electrical load, a configuration has been proposed in which a switch that opens and closes in conjunction with the key switch 2 is connected in series with the electric fan, and when the key switch 2 is opened, the line of the electric fan is simultaneously opened. However, the above-mentioned open/close switch requires a large one with a relatively large current capacity, which not only increases costs, but also has problems with durability due to the mechanical opening/closing operation, and furthermore, the timing of opening and closing with the key switch 2 is not perfect. The disadvantage is that voltage cut-off cannot be guaranteed.

This invention was proposed in view of the above points,
By connecting a transistor circuit that opens and closes the voltage supply path to the tachometer circuit, and connecting this control terminal to the voltage terminal of a series circuit of a Zener diode and a current limiting resistor, the power supply voltage can be lowered to a predetermined level or below. The purpose of this is to open the voltage supply path to the tachometer circuit when the voltage decreases to 100,000,000 yen, to prevent the needle from wobbling due to noise from the signal line.

Hereinafter, one embodiment of the present invention will be described in detail based on the accompanying drawings. In FIG. 3, 10 is a voltage terminal connected to the negative terminal of the key switch 4 (not shown);
11 indicates a tachometer circuit, and a signal input terminal 12
For example, a moving coil type indicating instrument is actuated by pulse input from a moving coil type indicator. Reference numeral 13 denotes a voltage detection circuit, which is composed of a Zener diode 14 and current limiting resistors 15, 16, and 17 in series. A transistor circuit 18 controls the supply of power supply voltage from the voltage terminal 10 to the tachometer circuit 11, and is composed of transistors 19 and 20 and resistors 21 and 22. Here, the base of the transistor 19 is the arbitrary voltage terminal of the voltage detection circuit 13, and in this case, the resistor 1
Zener diode 14 is connected between 6 and 17.
Its emitter is grounded so that it is biased when it is conductive. The capacitor 23 is connected to supply voltage to the tachometer circuit 11 with a slight delay when the key switch is closed, and during the initial charging time the base of the transistor 19 is grounded to prevent the voltage supply from the transistor circuit 18. This prevents erroneous instructions due to noise from the non-contact switch when energizing.

In the above configuration, if a power supply voltage of 12 V is currently being supplied, the Zener diode 14 in the voltage detection circuit 13 becomes conductive to apply an appropriate bias to the control terminal of the transistor circuit 18. Here, since the capacitor 23 is already in a charged state, the terminal voltage of the resistor 17 is applied to the base of the transistor 19, and as a result of making it conductive, the transistor circuit 18 closes the voltage supply path to the tachometer circuit 11, and the signal input terminal 12 The engine speed is instructed according to the amount of input pulses from the engine. At this time, if the engine is heated, a thermally responsive electric fan rotates to cool the engine body or the radiator.

Here, when the key switch is released, the voltage supply from the on-vehicle power supply is cut off, but the power generation output is continuously supplied to the voltage terminal 10 due to the power generation effect due to the inertial rotation of the electric fan. The inertial rotation of the electric fan gradually attenuates, and the voltage supplied to the voltage terminal 10 due to the power generation action also decreases, but since the Zener diode 14 in the voltage detection circuit 13 is cut off below a predetermined level, the transistor circuit 18 also stops voltage supply operation, and tachometer circuit 1
The drive voltage to 1 is cut off. That is, as shown in Fig. 4, the drive voltage to the tachometer circuit 11 maintains the normal level of 12V until the key switch is turned off, and immediately after the key switch is turned off, the voltage continues to gradually decrease due to the power generation action of the electric fan. However, before the voltage drops to a voltage level that induces oscillation of the non-contact switch, the Zener diode 14 of the voltage detection circuit 13 shuts off at about 10V, opening the voltage supply path by the transistor circuit 18. become.

Therefore, the drive voltage to the tachometer circuit 11 is cut off, and even if an oscillating current accompanying oscillation of the contactless switch is applied to the signal input terminal 12, no needle deflection will occur.

As detailed above, according to the voltage control circuit of the present invention, by connecting a transistor circuit that cuts off below a predetermined voltage level to the voltage supply path from the on-vehicle power supply to the tachometer circuit, Even if an oscillation phenomenon occurs in the non-contact switch due to the low voltage applied due to the power generation effect due to the inertial rotation of the fan, it is possible to prevent the tachometer needle from swinging due to this and ensure accurate measurement instructions. This makes it possible to increase the reliability of the indicating instrument to the user.

[Brief explanation of the drawing]

Figure 1 is an electrical wiring diagram showing the connection state of a conventional tachometer circuit in a vehicle equipped with a non-contact switch and an electric fan for engine cooling, and Figure 2 is an electrical wiring diagram showing the tachometer circuit associated with key switch off in the same connection state. FIG. 3 is an electrical wiring diagram showing an embodiment of the voltage control circuit according to the present invention, and FIG. 4 is a voltage waveform diagram of a tachometer circuit when the key switch is turned off to which the same circuit is added. 11... Tachometer circuit, 13... Voltage detection circuit, 14... Zener diode, 15, 16,
17... Current limiting resistor, 18... Transistor circuit, 4... Non-contact type switch, 6... Electric fan for engine cooling, 2... Key switch.

Claims (1)

[Scope of utility model registration request] This is installed on vehicles equipped with a non-contact switch using a switching transistor that continues current to the engine's ignition coil, and with a motor load such as an electric engine cooling fan connected to the negative terminal of the key switch. This is a voltage supply circuit to a tachometer, in which a Zener diode and a current limiting resistor are connected in series to the negative terminal of a key switch, and a transistor circuit is connected to open and close a voltage supply path to the tachometer circuit, and includes the Zener diode. A tachometer voltage control circuit that connects the control terminal of a transistor circuit to the arbitrary voltage terminal of a resistor series circuit.