JPH034745B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma ignition device for starting a diesel engine, and more specifically, the present invention relates to a plasma ignition device for starting a diesel engine. The present invention relates to a plasma ignition device that starts using a plasma ignition plug that discharges large electrical energy in the form of plasma instead of a red-hot glow plug.

As a starting device for a conventional pre-chamber type diesel engine, for example, a swirl chamber type diesel engine, a resistance glow plug as shown in FIG. 1 is generally used. That is, in FIG. 1, 1 is a cylinder block, 2 is a piston, and 3 is a cylinder block.
4 is the main combustion chamber, 4 is the cylinder head, 5 is the intake valve, 6 is the swirl chamber formed in the cylinder head 4,
7 is a fuel injection valve, and 8a is a glow plug of a resistance red-hot type that becomes red-hot when an electric current is passed through it, and the vortex chamber 6
will be installed on the

This glow plug 8a is activated by an ignition device shown in FIG. 2, in which 9 is a battery and 10 is a starter switch for stopping, preheating,
It is switched between the operation and start terminals. 11
is a pilot lamp 8a that lights up and indicates this when the starter switch 10 is in the preheating position.
8d is a glow plug attached to the swirl chamber 6 of each cylinder, and is connected to the starting terminal of the starter switch 10 and the preheating terminal via the pilot lamp 11.

To start this swirl chamber type diesel engine, first, the starter switch 10 is set to the preheating position and current is passed through the glow plugs 8a to 8d. When the current is passed for several to several tens of seconds, glow plugs 8a to 8
d is red hot, so these glow plugs 8a to 8d
When the engine becomes red hot, the starter switch 10 is set to the starting position, and while the glow plugs 8a to 8d are kept red hot, the starter motor (not shown) is rotated to rotate the engine, and fuel is injected into the high temperature compressed chamber. Combustion is started by being injected from the injection valve 7, and the engine is started in this way.

However, in the case of such a conventional diesel engine starting device, before turning the starter motor and starting engine cranking, it takes several to several tens of seconds until the glow plugs 8a to 8d become red hot.
Since you have to wait for a few seconds, it takes time to start, and furthermore, the glow plug 8a is heated due to the preheating operation.
It is difficult to judge whether glow plugs 8a to 8d have been heated to a temperature suitable for starting.
Even if the starter motor is rotated after preheating the engine, there are problems such as failure to start the engine due to insufficient preheating or fuel fog.

In recent years, progress has been made in the development and practical use of plasma ignition plugs that apply high electrical energy and discharge into plasma, mainly for use in gasoline engine ignition systems, and of plasma ignition devices to operate them. It is an object of the present invention to solve the above problems by applying a plasma ignition device using a plasma ignition plug for starting an engine instead of a conventional resistance glow plug.

Embodiments of the present invention will be described below with reference to the drawings. The swirl chamber 6 of the swirl chamber type diesel engine shown in FIG. 3 is equipped with a plasma ignition plug 12a that applies high electrical energy to generate a plasma-like discharge in place of the conventional resistance glow plug.

FIG. 4 shows these plasma ignition plugs 12a to 1.
FIG. 2 is a circuit diagram of a plasma ignition device that operates 2d.

In Fig. 4, 13 is the voltage V _B of battery 9
This is a DC-DC converter that boosts the voltage (=12V) to a high DC voltage V ₀ (for example, 1500V). Reference numeral 14 denotes a crank angle sensor, which is attached to the engine crankshaft and emits a crank angle reference signal. For example, in the case of a 4-cylinder engine, the crank angle sensor
When the engine rotates by a predetermined angle after fuel injection from the fuel injection valve 7 (that is, every 180 degrees of crank angle), a pulse is output as a reference signal. 15 is a first monostable multivibrator, which uses the reference pulse signal from the crank angle sensor 14 as a trigger pulse to output a pulse that is ON for a certain period of time, and only while this pulse is output, the DC-DC converter is activated. Turn off 13. Reference numeral 16 denotes a second monostable multivibrator, which simultaneously uses the reference pulse signal from the crank angle sensor 14 as a trigger pulse for a certain period of time (approximately
The number of pulses a, b, c, and d that are on for 100 μs) equal to the number of cylinders is output.

The output side of the DC-DC converter 13 is connected in parallel to the same number of diodes _D1 as the number of cylinders, and a capacitor _C1 for charging ignition energy (capacity about 1 μF) is connected to the cathode side of each diode _D1 . The connection between the diode D ₁ and the capacitor C ₁ is preferably grounded via a high voltage semiconductor switch such as a thyristor 17, and the gates a, b,
c and d are connected to the output of the second monostable multivibrator 16 described above, and therefore, when the output of the second monostable multivibrator 16 turns on (that is, "1" level), the thyristor 17 becomes conductive. .

T is a step-up transformer, which has a primary coil L _P and a secondary coil L _S. The connection between the ignition energy charging capacitor C ₁ and the step-up transformer T is connected to the anode layer of a diode D ₂ which is used to prevent current from flowing to the step-up transformer T when charging the capacitor C ₁ . The cathode side of ₂ is grounded. The primary coil L _P of the step-up transformer T is grounded via an auxiliary capacitor C ₂ with a smaller capacity (approximately 0.2 μF) than the ignition energy charging capacitor C ₁ mentioned above, and the secondary coil L _S is connected to each cylinder. are connected to the center electrodes of the plasma ignition plugs 12a to 12d.

Next, the operation will be explained with reference to FIG. 4 and FIGS. 5a to 5k showing the fuel injection timing of each cylinder and the output waveforms of the main components of FIG. 4.

The battery power supply V _B (12V) is boosted to a high voltage V ₀ (for example, 1500V) by the DC-DC converter 13. On the other hand, as the engine rotates, fuel is injected from the fuel injection valve 7 for each cylinder at a predetermined time (Fig. 5 a to d), and the crank angle is predetermined in relation to the fuel injection timing. At this point, the crank angle sensor 14 outputs a reference pulse signal (see e in FIG. 5). The first monostable multivibrator 15 uses this reference pulse as a trigger pulse to output a pulse (Fig. 5g) that is turned on for a predetermined period of time, and this output pulse causes the DC-DC converter 13 to be activated for a predetermined period of time. Turn it off. The second monostable multivibrator 16 also uses the reference pulse from the crank angle sensor 14 as a trigger pulse.
Pulses a, b, c, and d (FIG. 5f) of 100 μs are outputted, and these output pulses a, b, c, and d serve as gate pulses for the thyristor 17 as described later.

While the DC-DC converter 13 is on, the DC-
The high voltage V ₀ output from the DC converter 13 is applied to the capacitor C ₁ via the diodes D ₁ and D ₂ , and the capacitor C ₁ is charged with high ignition energy (approximately 1 joule).

The reference pulse from the crank angle sensor 14 is the second
When input to the monostable multivibrator 16,
The second monostable multivibrator 16 outputs a pulse of about 100 μs, and using this pulse as a gate pulse, all the thyristors 17 become conductive at the same time. As a result, the terminal A of the capacitor _C1 is connected, and the potential of the terminal B suddenly drops from _V0 to 0V, so that the electric charge of the capacitor _C1 is increased to 1V of the step-up transformer T.
flows into the capacitor C ₂ through the next coil L _P ,
Therefore, a high voltage is induced in the secondary coil _LS , and the plasma ignition plugs 12a to 12d are brought into conduction. Next, the remaining charge in the capacitor C ₁ passes through the secondary coil L _S to the plasma spark plugs 12 a to 1.
2d, the plasma spark plug 12
Steps a to 12d generate a plasma-like discharge to ignite and burn the fuel injected into the swirl chamber 6, thereby starting the diesel engine.

When the output of the first monostable multivibrator 16 is turned off after the ignition by the plasma ignition plugs 12a to 12d is completed, the DC-DC converter 13 is operated, and at this time the thyristor 17 is turned off, and the capacitor C ₁ Charging is performed.

In the above embodiment, all the plasma spark plugs are caused to discharge plasma at the same time. (Figure 5h-k)
Normally, in a diesel engine, fuel is sequentially injected by a fuel injection pump only into the cylinders that are in the explosion stroke, so the cylinders into which fuel is injected are ignited and burned. In addition, cylinders that are not in the explosion stroke have no fuel spray and ignition takes place, but even if ignition occurs in a cylinder without fuel spray, it does not have any particular negative effect on the engine, and instead the spark plugs are ignited. It has the effect of becoming more resistant to fog.

As explained above, according to the present invention, by using a plasma ignition plug and its ignition device in the pre-chamber of a diesel engine, the diesel engine can be started instantaneously, and the fuel sprayed into the pre-chamber can be started instantly. Even when the atomization condition is poor, the fuel can be reliably ignited and the engine can be started instantly. Furthermore, since the control circuit of the ignition device is simple, the cost is low and there are fewer failures and malfunctions. Furthermore, since the plasma ignition plugs of all cylinders are ignited at the same time, and even the cylinders that are not in the explosion stroke are ignited, effects such as preventing the plasma ignition plugs from causing fuel fog can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing how a glow plug is installed in a conventional diesel engine, Fig. 2 is a circuit diagram of an ignition device that operates the glow plug shown in Fig. 1, and Fig. 3 is a plasma ignition in a diesel engine according to the present invention. 4 is a circuit diagram of the ignition device that operates the plasma ignition plug shown in FIG. 3, and FIGS. 5 a to 5 k are fuel injection timings and output waveforms of the main components shown in FIG. 4. FIG. 1...Cylinder block, 4...Cylinder head, 6...Swirl chamber, 9...Battery, 12a-1
2d...Plasma spark plug, 13...DC-DC
Converter, 14... Crank angle sensor, 15...
...first monostable multivibrator, 16...second
Monostable multivibrator, 17... Thyristor, C ₁ ... Capacitor for ignition energy charging, C ₂
... Auxiliary capacitor, D ₁ , D ₂ ... Diode,
L _P ...Primary coil, L _S ...Secondary coil, T
...Step-up transformer.

Claims (1)

[Claims] 1 DC- boosting DC power supply voltage to DC high voltage
a DC converter, an ignition energy charging capacitor for storing ignition energy with one terminal connected to the output terminal of the DC-DC converter, and one terminal connected to the DC-DC converter side terminal of the ignition energy charging capacitor; When the terminal is connected, the other terminal is grounded, and the input terminal is connected to the switch circuit for the number of cylinders that becomes conductive after the engine rotates by a predetermined crank angle after fuel injection, and the other terminal of the ignition energy charging capacitor. Step-up transformers for the number of cylinders connected to each other and each having a primary coil and a secondary coil, and diodes for the number of cylinders having an anode connected to a terminal on the step-up transformer side of the ignition energy charging capacitor and a cathode grounded. auxiliary capacitors for the number of cylinders each having one end connected to the output end of the primary coil of the step-up transformer and the other end grounded; and a negative electrode connected to the output end of the secondary coil of the step-up transformer. and plasma ignition plugs for the number of cylinders installed in the combustion chamber of a diesel engine, and when the switch circuit is turned on, the ignition energy is transferred from the ignition energy charging capacitor to the primary coil of the step-up transformer. A high voltage is induced in the secondary coil by the discharge current flowing through the capacitor, and the high voltage brings conduction between the electrodes of the plasma ignition plug.
A plasma ignition device for starting a diesel engine, characterized in that a large amount of energy is supplied between electrodes of the plasma ignition plug through a next-side coil to generate plasma discharge between the electrodes. 2. After the engine rotates by a predetermined crank angle after fuel injection, switch circuits for all cylinders are brought into conduction simultaneously, and plasma spark plugs for all cylinders are simultaneously discharged with plasma. The device according to item 1.