JPS6015173Y2 - Rotation speed detection circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a rotation speed detection circuit that detects the rotation speed of an alternating current generator driven by an engine in machines without batteries such as agricultural machinery, construction machinery, and motorcycles.

The conventional rotation speed detection circuit has a configuration in which resistors R1 and R2 are not connected in the figure.

That is, output terminals A and B of the alternating current generator G are connected to two input terminals of a bridge type rectifier circuit consisting of diodes D1 to D4.

The other output terminal of the rectifier circuit, one output terminal of which is grounded, is connected to a smoothing circuit S consisting of a capacitor C2.

The collector of a transistor Tr serving as a switch means whose emitter is grounded is connected to the output terminal (2) of the smoothing circuit S via a resistor R6.

Diode D connected to one input terminal of the rectifier circuit
, is grounded via resistors R4 and R5, and the resistance H4
．． The connection point of R5 is connected to the base of the transistor Tr.

The alternating current voltage generated at the output terminals A and B of the alternator G driven by the engine (not shown) is rectified by the rectifier circuit and charged to the capacitor C□, and is then transferred from the parallel circuit of the Zener diode ZD and the capacitor C2. Supplied to terminal ■ as a constant DC voltage.

On the other hand, when the output terminal B of the alternating current generator G becomes a high potential (or low potential) with respect to the output terminal A, the diode D5 becomes conductive (or non-conductive), and the transistor Tr is turned on (or off).

Therefore, the potential of the collector of the transistor Tr is the output terminal B.
When output terminal B becomes a high potential with respect to output terminal A, it becomes a low potential, and when output terminal B becomes a low potential with respect to output terminal A, it becomes a high potential.

By counting the lanopulse signal from this collector, the rotational speed of the alternator G (therefore, the engine) can be determined.

However, in such a conventional rotation speed detection circuit, a malfunction occurs if the waveform of the output voltage of the alternator G is steep at the peak portion.

For example, if the output voltage of the alternator G has a steep fall, the diode D1. D. Due to its frequency characteristics, a situation may occur in which backflow cannot be prevented.

In this state, the potential of the output terminal A of the alternator G is
When the potential becomes lower than the charging potential of capacitor C□, capacitor C1, diode D□, alternator G, and diode D
1. A discharge current flows to the ground, a positive pulse is applied to the diode D5, and the transistor Tr is turned on.

As a result, more pulse signals than the actual number of rotations are output.

An object of the present invention is to eliminate such drawbacks, stabilize the waveform of the output voltage from the alternator, and provide a rotation speed detection circuit that is resistant to noise and less likely to malfunction.

As shown in the figure, the present invention has a configuration in which the output terminals A and B of the alternator G of the conventional rotation speed detection circuit are grounded via resistors R1 and R2, and the rest has the same configuration as the conventional one. ing.

When output terminal A of alternator G is at a higher potential than output terminal B and lower potential than capacitor C1, the output of alternator G is connected to output terminal A1 through resistor R3, ground, diode D4, and output terminal B. Flows in the path.

Therefore, the output terminal A has a potential higher than the ground by at least the output voltage of the alternator G, and the output terminal B has a potential lower than the ground by the forward voltage drop of the diode D4.

As a result, diode D is non-conductive and transistor Tr is turned off.

When the output terminal A has a higher potential than the capacitor C1, in addition to the above-mentioned operation, the output terminal A
1, the capacitor C1 is charged through the path of diode D1, capacitor C1, ground, diode D4, and output terminal B.

The charging voltage of capacitor C□ is 1. The voltage is supplied to a parallel circuit consisting of a Zener diode and a capacitor C2 through a DC voltage, and is taken out from a terminal V as a constant DC voltage.

When output terminal B has a higher potential than output terminal A, capacitor C1 is charged through the path of output terminal B1 diode D2, capacitor C1, ground, diode D3, and output terminal A, while diode D becomes conductive. Therefore, the transistor Tr is turned on.

Therefore, the transistor Tr is turned on and off in response to the rotation of the alternator G, and the number of rotations of the alternator G can be determined by counting the pulse signals obtained from the collector.

Note that resistor B2 does not directly contribute to preventing malfunctions, but when charging capacitor C1 when output terminal B has a higher potential than output terminal A, it changes the potential of output terminal B with respect to the ground by When charging capacitor C1 when the potential is higher than output terminal B, make it the same as the potential of output terminal A with respect to ground, and charge capacitor C□ with the same voltage.
It has the function of charging.

Therefore, it is desirable to set the paper stack B□ and R2 to the same value.

As described above, in this invention, two diode bridges are used.
Since the two input terminals are each connected to one output terminal via a resistor, the transistor can be controlled in accordance with the actual rotational speed of the alternator without being affected by noise.

[Brief explanation of the drawing]

The figure represents a circuit diagram of a rotation speed detection circuit according to the present invention. G: AC generator, D: Rectifier circuit,
D□ to D5...Diode, ZD...
・Zener diode, Tr...transistor, C1, C2...capacitor, R□ to R6・
·····resistance.

Claims (1)

[Scope of utility model registration request] An alternating current generator, four diodes arranged in a bridge, a rectifier circuit that rectifies the output of the alternator, a smoothing circuit that smoothes the output of the rectifier circuit, and a circuit that is controlled by the output of the alternator. What is claimed is: 1. A rotational speed detection circuit comprising: a switch means, and two resistors each connected between two input terminals and one output terminal of the rectifier circuit.