JPS6347906B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an ignition timing control device for a spark-ignited internal combustion engine, and in particular to a method of determining ignition timing using an electronic circuit. This invention relates to an improvement of an electronic ignition timing control device that controls ignition timing by electric discharge.

[Prior art and its problems]

FIG. 1 shows a general circuit configuration for determining ignition timing using an electronic circuit. This circuit consists of a rotor 1 that rotates in synchronization with the engine speed, an electromagnetic pickup coil 2 that outputs an output signal according to the rotation of the rotor,
An input circuit 3 that shapes the waveform of the output signal of this pickup coil, a lead angle calculation circuit 4 that calculates the lead angle time, a closing angle control circuit 5 that controls the primary current conduction time of the ignition coil, and a lead angle and closing angle calculation result. It is comprised of an amplifier circuit 6 for combining and amplifying, a power transistor 7 for controlling the ignition coil primary current, an ignition coil 8, and the like.

FIG. 2 shows a diagram of the advance principle of a conventional electronic ignition timing control device that controls ignition timing by charging and discharging a single capacitor. In Figure 2, A is the output waveform of the pickup coil, B is the output waveform of the input circuit,
C is the charging/discharging voltage waveform of the lead angle calculation capacitor, D
is the constant current waveform that charges and discharges the lead angle calculation capacitor, I _P1 is the constant current discharge waveform _{, I Q is} the constant current charging waveform,
E is the advance angle signal output waveform. Also, θ ₁ of the B waveform,
θ ₂ is a constant angle signal determined by the rotor shape, pickup coil, and input circuit, regardless of engine speed. FIG. 3 shows an example of advance angle characteristics.

Now, in FIG. 2, during a period of a constant angle θ ₂ , the advance angle calculation capacitor is charged with constant currents having different values I _P1 and I _P2 . Next, during a period of a constant angle θ ₁ , the battery is discharged with a constant current _IQ , and the ignition position is set at the time when the discharge ends, that is, when the amount of charge due to the constant current charging becomes zero. The E waveform t ^a becomes the advance time.
As a result, as shown in Fig. 3, the engine speed N ₁ −
The advance angle for the period N ₂ is determined by the charging current (I _P1 , I _P2 ) for the period t ₁ + tx ₂ , and for the period N ₂ - N ₃ ,
Charging current (I _P1 ) during t ₁ (actually tx ₁ described later)
determined by

In the advance angle calculation method that operates in this manner, the theoretical advance angle during the period of engine rotational speed N ₂ -N ₃ becomes a constant value θ _a as shown in FIG. 3B.

In Figure 3, find the advance angle when the engine speed is N _X1 .

θ ₁ + θ ₂ = 360゜ ...(1) t〓 ₁ +t〓 ₂ = 60/Nx ₁ ...(2) If t ₁ at Nx ₁ is tx ₁ , the amount of charged charge and the amount of discharged charge are the same Therefore, I _P1 tx ₁ = I _Q tx ₃ ...(3) The advance time ta is ta=t〓 ₁ −tx ₃ =t〓 ₁ −tx ₁・I _P1 /I _Q ...(4) Converting equation (4) to an advance angle, the advance angle θa is: θa=6Nx ₁・t〓 ₁ (1+I _P1 /I _Q )−360° ・I _P1 /I _Q ……(5) 6Nx ₁・t〓 ₁ is the value θ ₁ obtained by converting t〓 ₁ into an angle at engine speed Nx, and formula (5) is θa = θ ₁ (1 + I _P1 /I _Q ) - 360°・I _P1 /I _Q ...( 6) becomes.

In equation (6), θ ₁ is a constant angle signal that is unrelated to the engine speed, and both I _P1 and I _Q are constant currents and have constant values. Therefore, θa is a constant value regardless of the engine speed.

Similarly, when θb is calculated for Nx ₂ , θb=θ ₁ −6Nx ₂ (t ₁・I _P1 /I _Q +tx ₂ ) ...(7), and t ₁ , θ ₁ , I _P1 , I Since _Q is a constant value, it becomes an advance angle that changes depending on tx ₂ .

Now, as described above, the advance angle during the period of engine speed _N2 - _N3 is theoretically a constant value θa, but when the ignition position is actually measured, it has the characteristics as shown in FIG. 3C. This is thought to be caused by an electrical delay between the input circuit and the power transistor, since the circuit configuration of the electronic ignition timing control device is as shown in FIG.

If the advance angle characteristic becomes as shown in (c), it is undesirable because it may cause a decrease in engine output in the high-speed region of engine rotation, contamination of exhaust gas, etc.

[Purpose of the invention]

An object of the present invention is to correct the advance angle characteristics shown in FIG. 3C and to obtain advance angle characteristics shown in FIGS. 3B and 3D depending on the type of engine.

[Key points of the invention]

The present invention provides a circuit that calculates the ignition timing based on the fact that the amount of charged charge and the amount of discharged charge of the capacitor become equal, and outputs the ignition signal a certain period of time earlier than the amount of discharged charge becomes zero. It is characterized by

[Embodiments of the invention]

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

FIG. 4 shows an embodiment of the present invention. In FIG. 4, terminal ○D of the charging/discharging capacitor 9 is connected to a transistor 10 and a constant current source 11, and the other terminal ○H is connected to a transistor 12 and a constant current source 13, and the constant current source 11, 13, switches S ₁ and S ₂ and a transistor 12 are turned on and off at respective timings to charge and discharge the capacitor 9 with a constant current.

A resistor 14 is connected to the transistor 10 from the power supply Vcc, and another resistor 15 is connected to the contact point between the resistor 14 and the transistor 10 to connect the transistor 1 to the transistor 10.
6 is connected, and the transistor 16 turns on and off, so that the potential to the contact point changes between the resistor 14 and the resistor 1.
It is designed to fluctuate by a ratio of 5.

Further, a discharge end detection circuit 17 is connected to the collector of the transistor 10, and is configured to detect the presence or absence of a collector current of the transistor 10.

The output of the discharge end detection circuit 17 is input to the flip-flop circuit 18,
The output of 8 is input to logic circuit 19, and logic circuit 1
9 outputs the advance angle advance sign.

On the other hand, the output of the flip-flop circuit 18 is also connected to the transistor 16, and the transistor
Turn it on and off.

The output of the discharge end detection circuit 17 is the NOR circuit 20
Also, the output of the flip-flop circuit 18 is inputted to the other terminal of the NOR circuit 20 through a delay circuit 21.

The output of the NOR circuit 20 is input to the logic circuit 22, and the output of the logic circuit 22 controls the switches S ₁ and S ₂ and the transistor 12 according to their respective timings.
Turn it on and off.

The flip-flop circuit 18 is provided with a reset input and is reset by a reset signal.

Further, the constant current source 13 is adapted to change the amount of constant current according to a signal from a timer 23.

The operation of the embodiment shown in FIG. 4 will be explained below based on the operation waveform diagram shown in FIG. 5. Furthermore, Figure 5 shows the third
FIG. 3 is an operation waveform diagram during the N ₂ -N ₃ period in the figure.

The signal shown in FIG. 5F, which is a constant angle signal generated in synchronization with the rotation of the engine, is used as a reference timing signal, and the capacitor 9 is charged on the charging path _IP for a period of θ ₂ .

Charging path I _P : Power supply Vcc → Resistor 14 → Transistor 10 → Capacitor 9 → Constant current source 13 → Switch
S ₂ → Ground At this time, transistor 16 is ON, transistor 12 is OFF, switch S ₂ is ON, and switch S ₁ is
It's turned off. Further, the waveform at the contact point E between the capacitor 9 and the constant current source 13 is as shown in FIG. 5H.

Next, in the period θ ₁ , the reset signal (Fig. 5G) is activated.
is input to the reset input of the flip-flop circuit, thereby resetting the flip-flop and turning off transistor 16. On the other hand, the logic circuit 22 connects the switch _S1 and the transistor 12.
ON, switch _S2 is turned OFF, and the capacitor 9 is discharged.

Discharge path I _Q : Power supply Vcc → Transistor 12 → Capacitor 9 → Constant current 11 → Switch S ₁ → Earth At this time, the waveform at contact point ○2 between capacitor 9 and constant current source 11 is as shown in Figure 5 J. As shown by the J waveform, the potential of the contact ○2 is raised simultaneously with the reset signal, so that the transistor 10 is automatically turned off.

Now, the discharge progresses and the potential of contact ○2 becomes the power supply voltage.
When the voltage becomes smaller than VCC by about _VBE , a small base current flows through the transistor 10, and therefore a collector current Ic flows.The discharge end detection circuit 17 detects this Ic and operates the flip-flop circuit 18. The output of the flip-flop circuit 18 first operates the logic circuit 19 to output the advance angle signal K in FIG. 5, and turns on the transistor 16. When the transistor 16 turns on, the potential at the emitter side connection point ○ of the transistor 10 changes to the resistor 14.
becomes lower by the ratio of resistor 15 and transistor 10
becomes OFF again. The transistor 10
When turned OFF, collector current Ic stops flowing. However, transistor 16 maintains the ON state due to the flip-flop output.

Note that when the collector current Ic of the transistor 10 flows as described above, the discharge end detection circuit operates and operates the flip-flop circuit 18, and at the same time, the output of the discharge end detection circuit is output to the NOR circuit 20.
is also entered. However, while the output of the flip-flop circuit is delayed by the delay circuit 21,
Since the transistor 10 is turned off as described above, the NOR circuit 20 does not operate at this stage.

Capacitor 9 continues to be discharged, and when the potential of contact ○2 becomes lower than the potential of contact ○ by V _BE ,
In other words, when time tb has elapsed with the waveform shown in FIG. do. At this time, the output of the flip-flop circuit has already reached the other input of the NOR circuit 20, and the NOR circuit immediately operates to operate the logic circuit 22, which in turn operates the transistor 1.
Turn 2 off. In this way, the discharge state ends.
However, regarding the switches _S1 and _S2 , during the period _θ1 , the switch _S1 remains ON and the switch _S2 remains OFF. Therefore, the base current of the transistor 10 continues to flow through the constant current source 11 switch _S1 .

Furthermore, as shown in FIG.
tb is the voltage at contact ○2 (power supply voltage) at which transistor 10 conducts when transistor 16 is OFF.
Vcc is lower than the base-emitter voltage of transistor 10 ( _VBE ) and transistor 16 is
The voltage Va that is the difference between the voltage of the contact ○2 at which the transistor 10 conducts when it is ON (a voltage lower by V _BE than the voltage obtained by dividing the power supply voltage Vcc by the resistors 14 and 15)
If Va is constant, tb is also constant, and Va is determined by the ratio of resistors 14 and 15.

Now, in the next period θ ₂ , the logic circuit 19 operates to turn off the switch S ₁ and turn on the switch S ₂ to enter the charging state again, and the above-described operation is repeated.

Note that the timer 23 can change the constant current amount of the constant current source 13 according to a certain set time. The period t ₁ in FIG. 2C is the period N ₂ -N ₃ in FIG. 3, and the period t ₁ +t ₂ is the period N ₁ -N ₂ in FIG.

As described above, if the advance angle signal is outputted tb earlier than the time when the capacitor 9 is completely discharged, the advance angle signal as shown in FIG. 3A can be obtained.

In Fig. 5, the advance angle time tc is tc=t〓 ₁ −tx ₃ +tb ……(8) When formula (8) is converted to the advance angle (however, the engine speed is Nx ₁ ), the advance angle θc is becomes.

In equation (9), θ ₁ is a constant angle signal that is unrelated to the engine speed, and I _P0 and I _Q0 are constant currents and constant values.
Furthermore, if Va and I _Q0 are kept constant, tb becomes a constant value regardless of the engine speed. Therefore, the term Y is
The term X, which is a constant angle unrelated to the engine speed, will vary depending on the engine speed. Therefore, the advance angle θc changes depending on the engine speed, and the advance angle characteristic shown in FIG. 3A is obtained. Further, the upward right angle α of A can be freely changed by changing tb.

In this way, the theoretical advance angle characteristic is set as shown in A, and the rising angle α can be changed freely, so the optimum advance angle characteristic is set by taking into account the type of engine, internal electrical circuit delay, etc. It became possible.

〔Effect of the invention〕

As explained above, according to the present invention, a circuit is provided which calculates the ignition timing based on the fact that the amount of charged charge and the amount of discharged charge of one capacitor 9 become equal, and the ignition timing is set to be equal to the amount of discharged charge. Since the ignition signal is issued a certain fixed time tb earlier than the amount of electric charge becomes zero, the advance angle characteristic in the high speed rotation region of the engine, that is, the region N ₂ - _{N 3} in Figure 3, is This prevents the engine from sloping downward and prevents engine output from decreasing and exhaust gas from being contaminated.

According to a particularly advantageous embodiment of the present invention, a dividing ratio of resistors 14 and 15 is used to set the predetermined time tb, and the amount of charged charge and the amount of discharged charge of the capacitor 9 are ultimately the same. Since the delay circuit 21 is used in order to achieve this, there is an effect that the advance angle characteristic can be freely set according to the type of engine without impairing the advance angle calculation characteristic by the capacitor 9.

[Brief explanation of the drawing]

Figure 1 is a circuit configuration diagram of a general electronic advance ignition device that determines ignition timing using an electronic circuit, Figure 2 is a waveform diagram of the conventional advance principle operation, and Figure 3 is a characteristic diagram of an example of advance angle characteristics. FIG. 4 is a circuit diagram of an embodiment of the present invention, and FIG.
The figure is an operational waveform diagram for explaining the operation of the embodiment of FIG. 4. DESCRIPTION OF SYMBOLS 1... Rotor, 2... Electromagnetic pick-up coil, 3... Input circuit, 4... Advance angle calculation circuit, 5...
... Closed angle control circuit, 6 ... Amplification circuit, 7 ... Power transistor, 8 ... Ignition coil, 9 ... Capacitor, 10, 12, 16, 24 ... Transistor, 11, 13 ... Constant current source, 14 , 15...Resistor, 17...Discharge end detection circuit, 18...Flip-flop circuit, 19, 22...Logic circuit, 20
...NOR circuit, 21 ... delay circuit, 23 ... timer circuit.

Claims (1)

[Claims] 1. A constant angle signal generating means that generates a constant angle signal that takes a first value during a constant angle in the first half of each cycle and takes a second value in the second half in synchronization with the rotation of the engine; a charging/discharging capacitor 9; A first constant current source 13 connected between one end of the capacitor and a reference potential point
a second constant current source 11 connected between the other end of the capacitor and a reference potential point; a first transistor 12 connected between one end of the capacitor and a power supply potential point; A second transistor 10 whose base is connected to the other end of the capacitor and whose emitter is connected to the power supply potential point via the first resistor 14;
a third transistor 1 connected via a second resistor 15 between the connection point with the resistor and the reference potential point;
6, a discharge end detection circuit 17 that detects the presence or absence of the collector current of the third transistor, and is reset at the start of the second value of the constant angle signal, and is reset by the discharge end detection circuit detecting the presence of current. flip-flop circuit 18 which is set and makes the third transistor conductive by the set output.
, a delay circuit 21 that delays the set output of the flip-flop circuit for a predetermined period of time, and a gate circuit 2 that detects and outputs the occurrence of both the output of the delay circuit and the set output of the flip-flop circuit.
0, the first constant current source and the second constant current source are operated by the first value and the second value of the constant angle signal, respectively, and the second value of the constant angle signal is operated.
charge/discharge control means 22 that conducts the first transistor from the start of the value until generation of the output of the gate circuit; and lead angle signal generation means 19 that generates the lead angle signal in response to the set output of the flip-flop circuit. An electronic advance ignition device for an internal combustion engine, comprising: an electronic advance ignition device for an internal combustion engine.