JPS5817351B2 - Engine ignition control device - Google Patents

Description

Detailed Description of the Invention The present invention controls the ignition coil-next side closing time (hereinafter simply referred to as closing time) in an ignition device that interrupts the primary current of the ignition coil and generates an ignition voltage on the secondary side of the ignition coil. This invention relates to an engine ignition control device.

Generally, in this type of ignition system, the ignition energy increases as the primary breaking current of the ignition coil increases;
The transistor that switches the ignition coil-next-side current (hereinafter simply referred to as primary flow) has a current capacity limit, and its cutoff current cannot be increased unnecessarily.

Therefore, an appropriate breaking current value T is naturally determined based on the balance between the current capacity of the transistor and the ignition energy.

After the circuit is closed, the primary current increases exponentially with time,
The time Te until the predetermined current value (■) is reached is determined by the battery voltage, the inductance of the ignition coil, the resistance next to the ignition coil, etc.

Therefore, if the battery voltage or the specified force of the ignition coil changes, the closing time must also change.

This invention was made in view of these points, and it is possible to automatically control the energization time even when the primary current rise speed of the ignition coil changes due to changes in battery voltage or when the ignition coil is changed. The present invention aims to provide an ignition control device that provides an appropriate energization time that corresponds to a desired cut-off current.

Embodiments of the invention shown in the figures will be described below.

First, in FIG. 1, 1 is an ignition coil whose primary side is supplied with power from a DC power source (not shown) and an ignition plug is connected to its secondary side, 2 is a switch circuit that connects the primary power supply current to this ignition coil, and 3 is a switch circuit that connects the primary power supply current to the ignition coil. A primary current limiting circuit 4 detects the primary current of the ignition coil 1 and generates a primary current limiting signal when it reaches a predetermined value to reduce the degree of conductivity of the switch circuit 2 and limit an increase in the primary current; This is an ignition timing signal generator that generates an ignition timing signal at the ignition timing of the engine, and consists of a signal generator built into the distributor, a waveform shaping circuit, etc.

5 is an oscillator that generates a clock pulse of a predetermined frequency f; 6 is a frequency divider for the clock pulse;
A divider r whose counting direction is controlled by the level of the next current limit signal is controlled to switch between n and 1 according to the level of the next current limit signal, and a pulse of frequency (f/n) from the divider 6. an up/down counter that counts down the pulses of frequency f and counts up the pulses of frequency f;
8 is a down counter that receives the ignition timing signal, reads the count contents of the up/down counter γ at this generation timing, and counts down the Norita pulse of the oscillator 5 to a set value of zero, and corresponds to whether or not it is the counting operation period. The switching circuit 2 generates an opening/closing signal with an inverted level to control opening/closing of the switch circuit 2.

Next, the operation of the device constructed as described above will be explained with reference to FIG.

When the ignition timing signal generator 4 generates an ignition timing signal at time t1 as shown in FIG. 2A due to engine rotation, the down counter 8 outputs //H/ as shown in FIG. 2C.
/ to // I, //, the switch circuit 2 cuts off the primary current of the ignition coil 1, and the engine is ignited by the ignition voltage on the secondary side.

The down counter 8 simultaneously reads the contents of the up/down counter γ at that time and counts down the clock pulse of frequency f generated from the oscillator 5 as shown by the dashed line in FIG.

When the content of this count becomes zero at time t2, the output is u
I, tt is reversed to //H//, the switch circuit 2 is closed, and power supply to the ignition coil 1 is started.

On the other hand, at time t1, the frequency divider 6 divides the clock pulse using the outputs of tt I and tt from the primary current limiting circuit 3, as shown in FIG. 2d, to generate a pulse of frequency (f/n). , the up/down counter γ counts down the pulses as shown by the solid line in FIG. 2, and the count gradually decreases.

When the ignition coil 1 is supplied with power from time t2 and its primary current increases as shown in Fig. 2 e and reaches a predetermined value ■ at time t3, the primary current limit signal (Fig. 2 d) becomes //H// and the switch is turned on. The degree of conductivity of the circuit 2 is reduced to limit the increase in the primary current, and the division ratio of the frequency divider circuit 5 is changed from n to 1, and the up/down counter γ is adjusted to its frequency f.
The pulses are counted up until the next ignition timing signal generation time t4.

(See the solid line in Figure 2) In a steady state, the maximum value A and the minimum value B of the count contents of the up/down counter γ are constant for each ignition cycle, and the time T shown in Figure 2, , T2 is as follows.

A-B'A-B T = --, T -- 1f 2 f Therefore, the time T2 during which the primary current is limited to a constant value ■
The ratio α to the ignition interval (T1+T2) is a constant value shown below.

,,-1・8□.

. -nee,. 0 (correspondence) T1+T2n+1 n is the division ratio of the branching device 6, and for example, if it is n-19, it is α-5 (correspondence).

Therefore, in a steady state, the ratio α of the time T2 during which the primary current is maintained at a constant value ■ to the ignition interval is a constant value determined by the frequency division ratio n.

Note that this division ratio is assumed to be n and 1, but when the division ratios are n and m (m key), α becomes a constant value determined by the ratio of n and m.

Next, an unsteady state when the power supply voltage, ignition coil, and ignition interval change will be explained.

When the power supply voltage or the ignition coil changes, the rise time Te during which the current after closing reaches the predetermined value ■ changes.

In FIG. 2, if the rise time Te increases by ΔTe, the limit time T2 decreases by ΔTe.

When the time limit T2 decreases by ΔTe, the maximum value A of the up-down counter decreases by f·ΔTe.

When the maximum value A decreases f・ΔTe, the open circuit time Tff・Δ
Te decreases by □-ΔTe.

When the opening time Tf decreases by ΔTe, the closing time Tn decreases by ΔT.
e, and the decrease in time limit T2 is canceled out.

Conversely, when the rising time Te becomes smaller, the operation opposite to the above is performed, and the time limit T2 remains constant.

When the engine speed changes and the ignition interval (T1+T2) changes, the rise time Te does not change.

That is, in FIG. 2, if the ignition interval increases by ΔT, the time limit T2 increases by ΔT.

When the time limit T2 increases by ΔT, the maximum value A becomes f・
It increases by ΔT.

When the maximum value A increases by f・ΔT, the open circuit time Tff・Δ
T increases by □-ΔT.

When the opening time Tf increases by ΔT, the closing time Tn decreases by ΔT, canceling out the increase in the limit time T2.

The time limit T2 at this time is the same as before the ignition interval was increased, and since the ignition interval has increased by ΔT, the ratio of the time limit T2 to the ignition interval is smaller than the constant value α.

Therefore, the next maximum value A decreases, the closing time Tf decreases, the closing time Tn increases, the time limit T2 increases, and eventually the ratio of the time limit T2 to the ignition interval becomes equal to the constant value α. It becomes a steady state.

Conversely, when the ignition interval becomes smaller, the operation opposite to the above is performed, and the ratio of the time limit T2 to the ignition interval becomes equal to the constant value α, resulting in a steady state.

Note that when the rise time Te is large and the ignition interval is small,
If the opening time Tf becomes too small, the closing time Tf
The switch circuit 2 may be driven using the logical product of a constant closing rate signal whose ratio of n to the ignition interval is constant and the switching circuit control signal of the present device (FIG. 2C).

As described above, although the present invention has a simple configuration, even if the power supply voltage, ignition coil, and ignition interval change, the period during which the ignition coil's primary current reaches a predetermined value is equal to the ignition interval. The circuit closing timing can be automatically controlled to maintain a constant ratio, and the power loss in the primary circuit can be reduced by providing an appropriate primary current energization time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the operation of the embodiment shown in FIG. In the figure, 1 is an ignition coil, 2 is a switch circuit, 3 is a primary current limiting circuit, 4 is an ignition timing signal generator, 5 is an oscillator, 6 is a branching unit, γ is an up/down counter, and 8 is a down counter. .

Claims (1)

[Claims] 1. In an engine ignition system that supplies power to the primary side of an ignition coil, cuts off the supplied current at the ignition timing of the engine, and generates an ignition voltage on the secondary side of the ignition coil, the primary current of the ignition coil reaches a predetermined value. A means for detecting the timing, the ignition timing and the timing when the primary current reaches a predetermined value are set as the reversal operation timing.
, an up/down counter that alternately counts up and down the second clock signal, and a third clock signal is counted from the ignition timing by a value corresponding to the count value of this up/down counter at the ignition timing, and the counting operation time is An engine ignition control device comprising: a counter that generates a switching output whose level changes depending on the switching output and the non-operation time; and a switch means that switches the primary current of the ignition coil on and off based on the switching output.