JPH0321749B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an ignition control device for a diesel engine. For example, an ignition device as shown in FIG. 1 is sometimes provided in the pre-combustion chamber of a pre-chamber type diesel engine in order to improve the engine's low-temperature startability.
This is done by boosting the 12V DC power supply voltage provided by the battery 1 to a high voltage of, for example, 1500V by the DC-DC converter 2, and charging the main capacitor 7 with this high voltage as ignition energy. 8
is a diode. Also, every time the crankshaft of the engine (not shown) rotates 180 degrees, the ignition timing signal output from the crank angle sensor 4 is supplied to the monostable multivibrator 5, and the output of the monostable multivibrator 5 ignites the thyristor 6. This is triggered at the appropriate time to turn it on, and a part of the charge accumulated in the main capacitor 7 is discharged and supplied to the auxiliary capacitor 10 via the primary coil 9 of the step-up transformer, and the discharge current at this time is A high voltage is induced in the secondary coil 11 of the step-up transformer. This high voltage is then transferred from the secondary coil 11 to the distributor 1.
2 and between the electrodes of the ignition plug 13 installed in the combustion chamber (pre-combustion chamber), and at the same time as discharge starts between the electrodes, the remaining charge accumulated in the main capacitor 7 is transferred to the ignition plug 13. It was injected between the electrodes to ignite high-energy plasma. In addition, 3 is the thyristor 6
This is a monostable multivibrator for stopping the operation of the DC-DC converter 2 for a certain period of time after ignition in order to return from the ON state to the OFF state. In this way, when a spark plug is installed in the combustion chamber of a diesel engine to ignite the engine, the low temperature startability of the engine is greatly improved compared to the conventionally well-known glow plug, etc. This has the effect of improving stability during idling and reducing idle knock. However, in such conventional ignition systems, the ignition is performed at the same average timing when the engine is started and when the engine is idling, and the ignition is always performed during these operations. Since the timing is not necessarily optimal, diesel noise cannot be sufficiently reduced.
In addition, since the configuration was such that ignition was always performed, there were problems in that power consumption increased and at the same time, the distributor, spark plug, etc. were rapidly worn out. The present invention has been made in view of these conventional problems, and includes a means for setting the ignition timing to the optimal timing for starting and idling, respectively, based on the starting operation and engine speed of the engine. , a means for setting the ignition duration after startup according to the engine cooling water temperature or intake air temperature, and ignition to high revolutions when the revolutions are rising during idling operation, and restarting at low revolutions when the revolutions are falling. By providing means for controlling the DC-DC converter or switch circuit,
The purpose is to improve both engine startability and idling performance, and to reduce power consumption and spark plug wear by eliminating unnecessary ignition. The present invention will be explained in detail below based on an embodiment shown in FIG. In the drawings, the same reference numerals are given to the parts having the same functions as in the prior art, and detailed explanation thereof will be omitted. In the figure, the anode of a thyristor 6 and one end of a main capacitor 7 for storing ignition energy are connected to the output terminal of a DC-DC converter 2 that boosts the voltage 12V of a battery 1 to a high voltage of 1500V. is grounded. The other end of the main capacitor 7 is connected to the anode of the diode 8 and the primary coil 9 and secondary coil 1 of the step-up transformer.
One terminal (input terminal) of 1 is connected. The other terminal of the step-up transformer primary coil 11 is connected to an auxiliary capacitor 10 having a smaller capacity than the main capacitor 7.
The spark plugs 13 corresponding to the number of cylinders are connected to the other terminal (output terminal) of the secondary coil 11 via a distributor 12. The spark plug 13 is installed, for example, in a pre-combustion chamber of a pre-chamber diesel engine. Further, a first crank angle sensor 16 that detects the optimum timing at startup and outputs an ignition timing signal, and a second crank angle sensor 17 that outputs an ignition timing signal at the optimum timing during idling are each equipped with a single unit. The input ends of stable multivibrators 19 and 20 are connected. Then, the starting signal output from the starter 15 and the starting signal are transferred to an inverter 28, which will be described later.
The signal obtained through
Take AND with 4 and 25, and both AND circuits 24 and 25
The output is supplied to the monostable multivibrator 3 and the gate of the thyristor 6 via the OR circuit 26. Note that the output signal of the starter 15 is transmitted to the inverter 2.
8, and the output of this inverter 28 and F/
After supplying the idle operation signal from the V converter 21 and the comparator 22 and the output of the timer 23 whose continuation time is set based on the outputs of the starter 15 and the engine cooling water temperature sensor 18 to the AND circuit 27, The output of the circuit 27 and the output of the monostable multivibrator 3 are connected through the OR circuit 14.
By supplying it to the DC-DC converter 2, for example, after the set time of the timer 23, the converter 2
I am trying to stop the function of. The F/V converter 21 outputs a voltage responsive to the engine speed (outputs the engine speed),
A predetermined hysteresis function is added to the comparator 22. In the above configuration, the 12V power supply voltage provided by battery 1 is applied to DC-DC converter 2.
The voltage is boosted to a high voltage of 1500V and stored in the main capacitor 7 via the diode 8. In this way, a predetermined charge (approximately 1 J) is stored in the main capacitor 7, and when a pulse of the ignition signal is supplied to the gate of the thyristor 6 at the ignition timing, the thyristor 6 becomes conductive. Then, a part of the charge accumulated in the main capacitor 7 flows into the auxiliary capacitor 10 through the primary coil 9 of the step-up transformer, and this inflow (current)
As a result, a high voltage is generated in the secondary coil 11 of the step-up transformer. Then, this high voltage is supplied to the spark plug 13 via the distributor 12, and discharge is started between the electrodes of the plug 13. Then, since the electrodes become electrically conductive, the electric charge remaining in the main capacitor 7 is injected between the electrodes of the spark plug 13, and so-called plasma ignition is performed. In a diesel engine, the fuel pumped from the fuel injection pump is injected from the injection valve into each cylinder during the explosion stroke, but the timing of this injection is
If BTDC is 10°, the first crank angle sensor 1
6 is BTDC3°, and the second crank angle sensor 17 is
An output (ignition timing signal) is generated at BTDC9°, and each of these signals is a monostable multivibrator 1.
9 and 20 result in a pulse with a width of 100 μS. On the other hand, when the engine is started, the signal from the starter 15 becomes "H", so the output of the AND circuit 24 becomes "H" at the time of BTDC3°, and this "H" signal is sent to the thyristor 6 via the OR circuit 26. Since it is applied to the gate, ignition is performed at BTDC3° when starting the engine. Note that the other AND circuit 25 is connected to the inverter 2.
Since the start signal which became "L" at 8 is being supplied, this AND circuit 25 continues to hold the "L" state,
Further, since the output of the AND circuit 27 is also held at "L", the DC-DC converter 2 also continues to operate. In addition, in order to maintain engine speed and combustion stability even after the starter has stopped, it is necessary to continue ignition for a while after the starter has stopped, even after starting has been completed. Particularly at extremely low temperatures, stopping ignition may stop combustion, so the lower the engine cooling water temperature, the longer the ignition continuation time needs to be. To deal with this situation, water temperature sensor 1
The timer 23 whose output time (setting time) is determined according to the output of
Since it is supplied to the AND circuit 27, the DC-DC converter 2 continues to operate for the time set by the timer 23 even after the starter stops (after completion of starting) and continues ignition. Furthermore, even after warm-up, the engine speed is set even after the timer 23 stops and its output becomes "H" in order to reduce diesel knock during idling operation including light loads. If it is lower than the value
By guiding the output “H” of the AND circuit 25 to the gate of the thyristor 6 via the OR circuit 26.
Ignition is performed at BTDC9°. Then, a stop signal is supplied to the DC-DC converter 2.
By providing hysteresis to the comparator 22 that provides the remaining one signal to the AND circuit 27, it continues to output "L" until the rotation speed reaches higher than the reference value when the rotation is rising, and when the rotation is falling, it is lower than the reference value. Since "L" is output at a low rotation speed, there is a difference between the ignition stop and turn speed when the rotation increases and the ignition restart rotation speed when the rotation decreases. For this,
Even if the engine speed changes, there is no risk of hunting occurring in the ignition operation, and the rotation is stable.
In addition, in the region where the engine speed is higher than the set value and the effect of ignition is not manifested, the output of the comparator 22 becomes "H" and the output (stop signal) of the AND circuit 27 becomes "H", so the DC- The DC converter 2 is stopped to prevent power wastage, and a stop signal is instantaneously supplied from the monostable multivibrator 3 to the DC-DC converter 2 via the OR circuit 14 every time ignition occurs, so the thyristor 6 is reliably activated. Of course, it can return to the OFF state at any time.
The above operation is shown in the table below, but the ignition timing may be set as appropriate depending on the model characteristics of the engine, etc.

[Table] As explained above, according to the present invention, the ignition timing at the time of engine startup, which is performed to improve engine startability, and the ignition timing at idling, which is performed to stabilize combustion, are independently set. The ignition duration at startup is automatically controlled according to the temperature of the cooling water or intake air, and hysteresis is provided between the ignition stop speed and restart speed for combustion stabilization, so that the ignition duration during startup and idle operation is controlled automatically. It is possible to maximize the effect of ignition by setting the ignition timing at the optimum timing, and also to avoid engine rotation hunting caused by stopping and restarting ignition while suppressing power wastage by omitting unnecessary ignitions. .

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the circuit configuration of a conventional example.
FIG. 2 is a block diagram showing the circuit configuration of one embodiment of the present invention. 1...Battery, 2...DC-DC converter,
6...Thyristor, 7...Main capacitor, 8...
Diode, 9... Primary coil, 10... Auxiliary capacitor, 11... Secondary coil, 12... Distributor, 13... Spark plug, 14, 26
...OR circuit, 15...Starter, 16,17...
... Crank angle sensor, 18 ... Engine cooling water temperature sensor, 19,20 ... Monostable multivibrator,
21... F/V converter, 22... Comparator,
23...Timer, 24, 25, 27...AND circuit, 28...Inverter.

Claims (1)

[Claims] 1 A main capacitor for charging ignition energy inserted between the output terminal of a DC-DC converter that boosts the DC power supply voltage to a high voltage and the input terminal of a step-up transformer, and one terminal connected to the DC-DC of the main capacitor. a switch circuit for ignition timing control connected to a terminal on the converter side and the other terminal grounded; a diode whose anode is connected to the step-up transformer side terminal of the main capacitor and whose cathode is grounded; and a diode whose cathode is grounded; An auxiliary capacitor with a smaller capacity than the main capacitor is interposed between the output terminal of the coil and the ground, and a distributor is connected to the output terminal of the secondary coil of the step-up transformer, and the ignition energy is transmitted through the distributor. By providing a distributed spark plug, when the switch circuit is conductive, a high voltage is induced in the secondary coil by the discharge flowing from the main capacitor via the primary coil of the step-up transformer to the auxiliary capacitor, and the After applying a high voltage between the electrodes of the spark plug to generate a discharge spark, the main capacitor is connected to the step-up transformer.
In an ignition system for a diesel engine that supplies large energy between the electrodes of a spark plug via a secondary coil and a distributor to cause plasma ignition, means for detecting the start of the engine and detecting idling operation of the engine are provided. means for detecting the engine cooling water temperature or intake air temperature; means for detecting the engine speed; means for setting the ignition duration according to the temperature when starting the engine; and when the engine speed increases during idling. means with hysteresis to control the DC-DC converter or switch circuit so that ignition continues until high engine speeds and resumes ignition at low engine speeds when engine speeds drop, and ignition timings are set separately for when the engine starts and when the engine is idling. An ignition control device for a diesel engine, comprising means for individually setting.