JPS6375566A - Engine revolution detecting circuit - Google Patents

Abstract

PURPOSE:To easily set and vary plural engine revolutions by setting a comparison voltage by a variable resistance element connected to a constant current circuit. CONSTITUTION:A constant voltage circuit is connected to a constant voltage power source 1 and outputs a constant voltage VCC. Then plural variable resistors 10 and 12 connected to the constant voltage circuit in series generate plural comparison voltage Vc and VB across the variable resistors 10 and 12. The voltage comparators 9 and 11 compare the comparison voltages Vc and VB generated by the variable resistors 10 and 12 with the signal of a frequency- voltage converting circuit which generates a voltage corresponding to an engine revolution and generates an output based upon the comparison results. A revolution detecting circuit is controlled with the outputs of the comparators 9 and 11 and is provided with an FF which uses one of their output terminals as the output terminal of the whole circuit. Consequently, the resistance values of the variable resistors are varied to set and vary the comparison voltage, thereby easily setting and varying the plural revolution of an engine.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an engine control circuit for detecting whether the engine rotation speed is a preset rotation speed and performing optimal engine control. This relates to a rotation speed detection circuit.

[Conventional technology]

Generally, this type of circuit has two preset engine speeds, one of which is the operating point speed and the other is the hysteresis speed. It is well known that by providing two set rotational speed points in this way, it is possible to eliminate hunting in the output of this type of detection circuit due to fluctuations in the engine rotational speed near the operating point.

Conventionally, the engine rotation speed detection circuit has been constructed using, for example, one voltage comparator and three resistors. This connects the output of the SiV conversion circuit to the inverting input terminal of the voltage comparator, divides the constant voltage power supply using two resistors, and uses this voltage as the comparison voltage of the voltage comparator at its non-inverting input terminal. and one resistor is connected between the output of the voltage comparator and the non-inverting input terminal to apply positive feedback, and the engine speed is set by the voltage hysteresis effect caused by this positive feedback. This circuit can be installed at two points and detects the engine rotation speed with such a configuration.

[Problem that the invention seeks to solve]

However, the conventional engine rotation speed detection circuit described above uses three resistance values to set the engine rotation speed based on a complicated calculation formula, so one of the three resistances is changed completely to determine the engine rotation speed. If one point is set at the target engine speed, it becomes impossible to set the other set speed, and in order to set both points to the target engine speed, three resistance values must be changed at the same time. When a plurality of set rotational speeds exist, there are problems in that it is very difficult to adjust them.

The present invention has been made to solve the above-mentioned conventional problems, and it is an object of the present invention to provide an engine rotation speed detection circuit that can easily set and change a plurality of engine rotation speeds.

[Means for Solving the Problems] The engine rotation speed detection circuit according to the present invention includes a comparison voltage generating means that generates different comparison voltages by means of variable resistance elements connected in series with a constant current converter circuit; The circuit includes a comparator that compares a comparison voltage with a signal voltage, and a free-lag flop that is controlled by the output of the comparator and uses the output as the output terminal of the entire circuit.

[Effect]

In this invention, the comparison voltage of the comparator is set or changed by completely changing the resistance value of each variable resistance element. For example, the operating point rotation speed is set as the engine rotation speed,
Hysteresis rotation speed setting.

Make changes. It also has an output holding function to control the free-lag frog using the output of the comparator.

〔Example〕

FIG. 1 is a diagram showing the configuration of an engine rotation speed detection circuit according to an embodiment of the present invention. In FIG. 1, l is a power supply terminal connected to a constant voltage power supply of an engine rotation speed detection circuit or an engine control circuit incorporating this circuit. 2 is a frequency-voltage conversion circuit (the previous stage circuit) that converts the engine speed into a voltage corresponding to the engine speed.
3 is an output terminal of this engine rotational speed detection circuit. 4 is power supply terminal 1 and P for taking out constant current
A resistor was connected between the emitter of the NP transistor 5, 6 and 7 were resistors and diodes connected in series between the pace of the transistor 50 and the power supply terminal l, and 8 was connected between the pace of the transistor 5 and GND. It is resistance. The collector of the transistor 5 is connected to the non-inverting input terminal of the operational amplifier used as the voltage comparator 9 and one end of the variable resistor 1°, and the other end of the variable resistor IO is connected to the non-inverting input terminal of the operational amplifier used as the voltage comparator 9. It is connected to an input terminal and is grounded via a variable resistor 12.

The inverting input terminals of the voltage comparators 9 and 11 are both connected to the Luya input terminal 3, and their respective outputs are input to the NOR circuit 13 and also to the NOR circuit 16 via the inverters 14 and 15. . Reference numerals 17 and 18 are NOR circuits that constitute the R-S free lag frog, and the outputs of the NOR circuits 13 and 16 are connected to the first input terminals of each, and the second input terminals are connected to the output terminals of the other side. and the output terminal of the NOR circuit 17 is connected to the output terminal 3.

Next, the operation of the engine rotation speed detection circuit having the above configuration will be explained. When the power is turned on and a constant voltage power supply is applied to the power supply terminal 1, the resistor 6. Power supply voltage VCC is divided by diode 7 and resistor 8, and this voltage is applied to connection point A. Assuming that the voltage applied to this connection point A is kVA, the difference between this VA and the constant voltage power supply Vcc is Vcc -V
A becomes a reference voltage, and a value subtracted from the transistor 5 pace-emitter voltage VBK k reference voltage vcc - VA is applied to both ends of the resistor 4. At this time, the collector current IC of the transistor 5 continues to flow as a constant current regardless of the load connected to the collector of the transistor 5.

Further, the diode 7 has a negative voltage-temperature characteristic, and the pace-emitter voltage VBE of the transistor 5 (this V
BE also has a negative voltage-temperature characteristic) for the purpose of canceling out the temperature drift.

The collector current IC as the above constant current is connected to the variable resistor t.
o, 12, variable resistor 1 according to Ohm's law
A voltage of VB = Ic-VRI (VRI is the resistance value of the variable resistor 12) is applied to both ends of the variable resistor IO, and a voltage of Vc = Ic-VB2 (VB2 is the resistance value of the variable resistor 10) is applied to both ends of the variable resistor IO. Voltage is generated. The voltage vn generated here is applied to the connection point B of the non-inverting input terminal of the voltage comparator 11, and becomes a comparison voltage of the voltage comparator 11 that detects the operating point rotation speed. Further, Vc+Vn is similarly applied to the connection point C, and serves as a comparison voltage for the voltage comparator 9 that detects the hysteresis rotation speed.

By the way, the output voltage after linear conversion is generally generated as a linear function as shown in FIG.

In other words, the characteristics shown in Figure 2 mean that regardless of the magnitude of the difference in engine speed between the two points you want to set, it is always possible to extract the signal voltage that corresponds only to the difference in engine speed. . In Figure 2, a certain rotational speed is set to Na
, Nb, a voltage of te vB is generated for Na, and a voltage of VBa + vcb is generated for Nb. This voltage is applied to signal input terminal 2 shown in FIG. It will be compared with the comparison voltages at connection points B and C.

Now, assuming that the engine speed is gradually increasing, the signal voltage also increases in the same manner as shown in FIG. At this time, if the signal voltage is lower than the comparison voltage vB of the voltage comparator 11 (CF/V signal voltage<VB), the outputs of the voltage comparators 9 and 11 are both at vkH' level (approximately VCC level). ), therefore the output of the NOR circuit 13 is at %Ll level (approximately GND level), and the output of the NOR circuit 16 is
Since the phase of the input is inverted by the inverter 14.15, the output is %H level.

The outputs of these NOR circuits 13 and 16 are R-
It becomes the input of the S free lag frog, and 1Hl is input to the output terminal 3.
The level will be output.

Next, the signal voltage is equal to or higher than the comparison voltage Vn, and VB
Condition lower than VC (VB ≦ signal voltage (VB
c), the output of the voltage comparator 11 is inverted and becomes 1.
Since this output is inverted by the inverter 15, the output of the NOR circuit 16 is also 'H' v
From Bell to 1Ll level! = f = f. Since the NOR circuit 18 which receives the output of the NOR circuit 16 as an input constitutes an R-8 flip-flop with the NOR circuit 17, the output of the output terminal 3 is changed to the value before the input of the NOR circuit 18 changes, that is, a whisper. It operates to maintain the Hl level.

Furthermore, the engine speed increases, and the signal voltage becomes equal to or higher than the comparison voltage CVn + Vc of the voltage comparator 9 (Vn+V
c≦Luya signal voltage), the voltage comparison i90 output changes from the 'H' level to the whisper Ll level, and as a result, the output of the NOR circuit 13 also inverts from the %LI level to the %Hl level, and the output terminal 3 outputs the %L level of the R-S free lag frog. From this state, the engine speed decreases, and VB < F/y signal voltage ≦ VB +
When it enters the VC state, it performs the same operation as described above,
The output terminal 3 maintains the value before the input signal of the R-S free lag frog changes, that is, the signal at the %Ll level. In this way, hysteresis can be provided by the R-S flip-flop, which is located at the final stage of the engine speed detection circuit and has a holding function. Thereafter, the output terminal 3 repeats the above-described operation in each of the states of b to signal voltage.

Therefore, the comparison voltage that sets the operating point rotation speed and hysteresis rotation speed at which the signal output to the output terminal 3 is inverted is the GND (OV) reference for vn, and VB is the reference for VC. , this VC determines the hysteresis rotation speed. That is, the operating point rotational speed is set by vn, and the hysteresis rotational speed is set by VC, and each of the two set rotational speeds has a separate comparison voltage. With this, each can be set or changed independently without mutual interference.

In the above embodiment, the output terminal 3 is connected to the output of the NOR circuit 17.
However, if the output needs to be inverted, it can be easily achieved by connecting the output of the NOR circuit 18 to the output terminal 3. Moreover, if the input of the NOR circuit 13 side is connected to the inverter 14.15, and the output terminal 3 is connected to the output of the NOR circuit I8, the NOR circuits 13, 16, 17, and 18 can be replaced with NAND circuits. You can perform the same operation as . Furthermore, a variable resistor 10. is used as a variable resistance element.
Automatic control can be easily achieved by replacing 12 with an element having a variable resistance element such as a transistor, and adding a control circuit for controlling this transistor and the like. Contrary to the above embodiment, if it is necessary to set an operating point when the engine speed increases, the variable resistor for setting the comparison voltage is connected to the output of the constant current circuit as shown in Figure 3. The variable resistors 19 and 20 are all connected in series to the collector of the transistor 5, and the comparison voltage for the operating point rotation speed is taken from one end of the variable resistor 19 (collector side of the transistor 5), and the comparison voltage for the hysteresis rotation speed is If the variable resistor 20 is taken out from any point, the same operation as in the above embodiment is performed, and the voltage comparator 9 can detect the operating point rotation speed, and the voltage comparator 11 can detect the entire hysteresis rotation speed.

Further, in the above embodiment, the comparison voltage and the signal are compared, but the present invention is similarly applicable to any signal having a linear relationship as shown in FIG.

〔Effect of the invention〕

As described above, according to the present invention, a constant current circuit is provided.

A comparison voltage is set using a connected variable resistance element, this comparison voltage is compared with a voltage corresponding to the engine speed using a comparator, and the output of this comparator is used to control a flip-flop. It is possible to very easily set and change a plurality of engine rotational speeds, such as a point rotational speed and a hysteresis rotational speed, and there is an effect that an engine control device that is inexpensive, highly accurate, and has a wide range of applications can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an engine speed detection circuit according to one embodiment of the present invention, FIG. 2 is a diagram showing the relationship between signal voltage and engine speed, and FIG. 3 is a diagram according to another embodiment of the present invention. FIG. 2 is a circuit diagram of a main part of an engine rotation speed detection circuit. 1...Power terminal, 2...L~signal input terminal, 3...
- Output terminal, 4, 6.8... Resistor, 5... Transistor, 9.11... Voltage comparator, 10, 12, 19.
20... Variable resistor, 13, 16, 17, 18...
NOR circuit, 14.15...inverter.

Claims (1)

[Claims] A constant current circuit that is connected to a constant voltage power supply and outputs a constant current, and a comparison voltage generator that uses multiple variable resistance elements connected in series to this constant current circuit to generate multiple different voltages across each of these variable resistance elements. means, a comparator that compares the plurality of comparison voltages generated by the comparison voltage generation means and a signal of a frequency-voltage conversion circuit that generates a voltage corresponding to the engine rotation speed, and generates an output based on the comparison result; An engine rotation speed detection circuit comprising a flip-flop controlled by the output of this comparator and having one of its output terminals as the output terminal of the entire circuit.