JPS6156419B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Application of the Invention) The present invention relates to an ignition device for an internal combustion engine, and in particular to an ignition device for an internal combustion engine.
This invention relates to technology for improving fuel efficiency and durability of an ignition system that uses a DC-DC converter to increase ignition energy.

(Prior Art) An example of an ignition device that uses a conventional DC-DC converter to increase ignition energy is shown in FIG. (For example, Published Patent Publication No. 14242/1983) In Figure 1, 1 is a battery that serves as a power source, 2
is the key switch, 3 is the primary winding 3A and the secondary winding 3
It is a four-terminal type ignition coil separated from B. 4
is an ignition timing sensor that detects ignition timing, such as an electromagnetic pickup. 5 is a transistor ignition device, 6 is a transistor for primary current cutoff,
7 is a DC-DC converter that generates a high voltage of about -2kV. 8 is a power distributor, and 9A to 9D are spark plugs provided for each cylinder.

During operation when the key switch 2 is turned on, when the ignition timing sensor 4 outputs an ignition signal at the ignition timing, the transistor ignition device 5 outputs a signal to turn off the transistor 6. Therefore, the primary current of the ignition coil 3 is cut off, and the secondary winding 3
A high voltage of -several 10 kV is generated at A, which is applied to the corresponding spark plug via the power distributor 8, and a spark discharge is generated at the spark plug.

On the other hand, the output from the DC-DC converter 7 is -
A high voltage of about 2 kV is constantly applied to the power distributor 8 via the secondary winding 3B. When the discharge occurs as described above, the discharge continues due to the high voltage from the DC-DC converter 7. Therefore, the discharge duration is 10 to 4 ms, which is 2 to 4 ms with normal igniters.
Since the time is increased several times to 20ms, the ignition energy is significantly increased and even a lean mixture can be ignited reliably.

Therefore, the engine can be operated with a leaner mixture than before, improving fuel efficiency, and stable operation can be achieved even if the EGR (exhaust gas recirculation) rate is increased. It is also possible to improve exhaust purification performance.

However, in the conventional device as described above, when the key switch 2 is turned on, the DC
-Since the DC converter is configured to operate at all times regardless of the operating state of the engine, the power consumption of the DC-DC converter reduces the fuel saving effect and accelerates the deterioration of the power distributor and spark plug electrodes. There are problems such as a shortened lifespan.

In other words, increasing ignition energy has a large effect on improving fuel efficiency during idling, acceleration, and when combustion tends to become unstable.
This is the operating range where EGR is performed, and in other operating states, there is no significant effect.

Therefore, if the DC-DC converter is constantly operated as described above, the resulting fuel saving effect will be canceled out by the power consumption of the DC-DC converter, and the overall fuel saving effect will decline. There's a problem.

Also, if high energy injection is carried out constantly,
There are also problems in that the rotor electrodes of the power distributor overheat, reducing the durability of the rotor, and the spark plugs become severely worn out, shortening their lifespan.

(Objective of the Invention) The present invention has been made to solve the above problems, and it is possible to stably and reliably ignite a lean mixture, further improve fuel efficiency, and further improve the layout. The purpose is to provide an ignition device that can also improve the durability of electric appliances and spark plugs.

(Summary of the invention) In order to achieve the above object, the present invention includes:
It detects specific operating conditions where combustion in the engine tends to become unstable, operates the DC-DC converter only during the above-mentioned specific operating conditions, and controls the injection time of high energy by the DC-DC converter, that is, each ignition timing. By controlling the duration of each operation (hereinafter referred to as operation time) according to the above-mentioned operation state, the required amount of ignition energy is injected when necessary.

(Examples of the Invention) The present invention will be described in detail below based on Examples.

FIG. 2 is a circuit diagram of an embodiment of the present invention, and the same reference numerals as in FIG. 1 indicate the same components.

In FIG. 2, the DC-DC converter 7 includes transistors 7A and 7B, a step-up transformer 7C, a rectifying diode 7D, a capacitor 7E, and an amplifier 7.
F and an oscillator 7G. Then, by alternately turning on transistors 7A and 7B with a signal obtained by amplifying the output of oscillator 7G with amplifier 7F, the voltage of 12V given from battery 1 is reduced to -
It boosts the voltage to about 2kV, rectifies it, and outputs it.

Note that the oscillator 7G performs an oscillating operation only when a control signal _S5 given from a control device 10, which will be described later, is "1", and stops when _S5 is "0". Therefore, the DC-DC converter 7 performs the step-up operation only when the control signal _S5 is "1".

The control device 10 includes, for example, an input/output device 10A, a central processing unit (CPU) 10B, a RAM 10C, and a ROM.
It is composed of a microcomputer such as 10D.

Reference numeral 11 is a crank angle sensor, which outputs a reference pulse S ₁ every time the crankshaft rotates by a reference angle (180° for a 4-cylinder engine),
゜) Outputs unit pulse S ₂ every time it rotates.

Further, 12 is an intake pressure sensor, which outputs an intake pressure signal _S3 corresponding to the intake negative pressure of the engine.

13 is an idle switch, which is an idle signal that becomes "1" when the engine is idling.
Output S ₄ .

Next, the action will be explained.

Unit pulse S ₂ output by crank angle sensor 11
The engine rotational speed calculated by counting the intake pressure signal S3 and the value obtained by AD converting the intake pressure signal _S3 output according to the intake negative pressure are stored in the RAM 10C of the control device 10. In addition, the ROM10D stores in advance a two-dimensional advance angle value data map with engine speed and suction negative pressure as parameters, and a primary current conduction angle data map of the ignition coil with battery voltage as a parameter, depending on the characteristics of the engine. I'll let you. And the reference pulse S ₁ of the crank angle sensor 11
The ignition timing is determined by referring to the data map based on the detected engine speed, suction negative pressure, and battery voltage, and the predetermined timing is determined by counting the unit pulse _S2 of the crank angle sensor 11. By detecting the ignition timing of the spark plug and setting the ignition signal _S4 to "0", thereby turning off the transistor 6, the primary current is cut off and the spark plug starts discharging.

Injecting the high energy of the DC-DC converter 7 during operating conditions with poor combustion conditions such as idling, EGR region, and acceleration is very effective in terms of power saving and fuel efficiency. be. Therefore, the idle signal to detect the idle state
When S ₄ is "1" and when it is detected from the engine speed and suction negative pressure that the engine is accelerating, the input/output device 10A that receives the signal from the CPU 10B outputs the control signal S ₅ set to “1”
Operate the DC-DC converter 7. In this case, the operating time of the DC-DC converter 7 may be set to a constant value, or a separate water temperature sensor may be provided to measure the water temperature A.
The −D conversion value may be corrected and made variable as a parameter. In addition, the operation in the EGR region is controlled by the DC-
The operating time of the DC converter 7 is controlled. That is, the higher the EGR rate, the longer the high energy injection time of the DC-DC converter 7 becomes. In this case, a function related to the EGR rate may be set to calculate the energy injection time.

Furthermore, since the ignition interval varies greatly depending on the engine speed, it may be determined by referring to a two-dimensional data map using the engine speed and EGR rate as parameters, as shown in FIG. 7, for example. Data outside the grid points of the map are obtained by performing interpolation calculations. The timing of high energy injection into the DC-DC converter 7, that is, the timing of starting operation, can be set arbitrarily, but it is appropriate to start the injection delayed by about 1° to 2° in crank angle from the ignition timing.

Figure 3 is an example of the signal waveform in the above operation, with an engine speed of 1200 rpm and an EGR rate of 20.
%, when the ignition timing is BTDC40°.

Next, FIGS. 4 to 6 are flowcharts of a control program stored in the ROM 10D.

FIG. 4 shows the main routine. First, at _P1 , after the key switch 2 is turned on and the power is turned on, the RAM 10C is initialized, and necessary constants in the memory are set and cleared. Next, at _P2 , the engine rotation speed is measured by counting unit pulses _S2 of the crank angle sensor 11 and stored in the RAM 10C. Then in P ₃ ,
The optimum advance angle value is calculated from the engine rotational speed and the suction negative pressure obtained by A-D conversion performed in the interrupt processing routine described later.

Next, at P ₄ , select the optimum value based on engine speed and suction negative pressure.
The EGR rate is calculated, and finally, in _P5 , the operating time of the DC-DC converter is calculated (see Figure 6 below).

Next, FIG. 5 is a diagram showing an example of an interrupt processing routine. When an interrupt having priorities in the order of timer and reference pulse _S1 occurs during execution of the main routine of FIG. 4, the routine jumps to this routine. First, the _P6 timer interrupt is generated using the internal timer of CPU10B.
An interrupt is generated every ms, and _P7 converts analog values such as battery voltage and suction negative pressure into digital values.
Store in memory (RAM10C). At this time, a count is also performed at _P8 to detect engine stalling. Next, at _P9 , an interrupt is also generated when the reference pulse _S1 of the crank angle sensor 11 is input, and at _P10 ,
The lead angle value, primary current conduction time, and DC-DC converter operating time calculated in the main routine are set in a register to be compared with the contents of the counter of the input/output device 10A. Note that the operation start timing of the DC-DC converter is set in the initial value setting section _P1 of the main routine.

Next, FIG. 6 shows a routine for calculating the operating time of the DC-DC converter (P ₅ in FIG. 4).

First, at _P11 , idle signal _S4 is “1” or “0”
If the idling state is detected, and it is determined that the idling state is idling, the DC-DC converter operating time is set to 20 ms in _P12 . On the other hand, if it is determined that it is not idling, then P ₁₃
to determine whether EGR is being performed,
If EGR is being performed, on P ₁₄ ,
The optimum operating time of the DC-DC converter is determined by referring to a data map (Fig. 7) that uses the EGR rate and engine speed as parameters.
In FIG. 7, the unit of operation time is ms.

If it is not idling and EGR is not being performed, go to _P15 and set the operating time of the DC-DC converter to zero.

As described above, the operation of the DC-DC converter is controlled, and immediately after the primary current of the ignition coil is cut off and the spark plug starts discharging, high energy of the DC-DC converter is injected to increase the duration of the discharge. Extend. The high energy of the DC-DC converter allows stable combustion even with a lean mixture, improving fuel efficiency and increasing the EGR rate (see Figure 8), making it possible to further reduce _NOx , etc. Moreover, since the operation of the DC-DC converter, which generates high energy, is controlled to the minimum necessary, current consumption can be reduced, reducing the load on the alternator and further improving fuel efficiency.

Figure 8 is a characteristic diagram showing the limits of the EGR rate,
It shows the limit value of the EGR rate at an engine speed of 1400 rpm. Note that the solid line X shows the characteristics of the present invention, and the broken line Y shows the characteristics of a normal ignition device without a DC-DC converter.

By controlling the operating time of the DC-DC converter according to the EGR rate as described above, the limit of the EGR rate can be increased as shown in FIG.

The microcomputer used in this example includes a CPU, ROM, RAM, and AD on the same chip.
By using a single-chip microcomputer with a built-in converter, etc., the system can be significantly downsized, and the microcomputer system can also be built into a DC-DC converter or a power distribution device.

(Effects of the Invention) As explained above, in the present invention, the operation of the DC-DC converter is controlled according to engine operating conditions such as idling, acceleration, and EGR rate. Even under bad operating conditions, high energy injection from the DC-DC converter allows for stable and reliable combustion, improving fuel efficiency. Also EGR
When applied occasionally, stable operation can be achieved even if the EGR rate is increased, and exhaust purification performance can also be improved. In addition, since the operating time of the DC-DC converter can be precisely controlled and the required amount of energy can be injected when needed, unnecessary power consumption is eliminated and power consumption can be significantly reduced. It is possible to further improve fuel efficiency, suppress deterioration of the power distributor and spark plug, and improve durability.

[Brief explanation of the drawing]

Fig. 1 is a diagram of an example of a conventional ignition system, Fig. 2 is a diagram of an embodiment of the present invention, Fig. 3 is a signal waveform diagram of the circuit of Fig. 2, and Figs. 4 to 6 are flowcharts of a control program. FIG. 7 is a diagram showing an example of operating time characteristics of a DC-DC converter, and FIG. 8 is a diagram showing a limit characteristic of an EGR rate. Explanation of symbols, 1...Battery, 2...Key switch, 3...Ignition coil, 3A...Primary winding, 3
B... Secondary winding, 4... Ignition timing sensor, 5...
Transistor ignition device, 6...Transistor, 7
...DC-DC converter, 7A, 7B...transistor, 7C...step-up transformer, 7D...diode, 7E...capacitor, 7F...amplifier, 7
G...Oscillator, 8...Distributor, 9A to 9D...Spark plug, 10...Control device, 10A...Input/output device, 10B...CPU, 10C...RAM, 10
D...ROM, 11...Crank angle sensor, 12
...Intake pressure sensor, 13...Idle switch.

Claims (1)

[Claims] 1. A high voltage generated by the DC-DC converter is applied to the ignition plug via the secondary winding of the ignition coil, and a discharge is generated in the ignition plug by the high voltage generated in the ignition coil at the ignition timing. Subsequently, the above DC-DC
In an ignition system that increases ignition energy by extending the duration of discharge by causing discharge using high voltage from a converter, there is a method for detecting specific operating conditions that tend to cause combustion in an internal combustion engine to become unstable. and a second means for operating the DC-DC converter only in the specific operating state and controlling the duration of operation for each ignition timing in accordance with the detected operating state. An ignition device for an internal combustion engine characterized by: 2 The first means detects that the internal combustion engine is in at least one operating state of an idling state, an acceleration state, and an EGR operating region, and the second means detects that the internal combustion engine is in at least one operating state of an idling state, an acceleration state, and an EGR operating region. A patent claim characterized in that the DC-DC converter is operated for a predetermined operating duration at each ignition timing only when in any of the operating states described above. The ignition device for an internal combustion engine according to item 1.