JPS606628Y2 - Glow plug energization control device in diesel engine - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a glow plug energization control device for a diesel engine.

Generally, in a diesel engine, the air in the combustion chamber is preheated by a glow plug to start the engine.

In addition, if the outside air is relatively low, even if the engine completely explodes when starting, it may not be able to reach a good combustion state immediately and misfire may occur, so the glow plug is energized even after starting. It has been proposed and put into practical use to provide an after-blow circuit that continues the process.

However, when using an energization control device having this after-blow circuit, the glow plug is operated under high voltage for a long time, so its durability becomes a problem.

In order to solve this problem, it has been proposed to lower the voltage applied to the glow plug after the engine has completely exploded, and at the same time to cut off the power to the glow plug when the voltage applied to the glow plug exceeds a predetermined value.

Such control allows the operating voltage of the glow plug to be kept relatively low, which is advantageous from the viewpoint of durability of the glow plug.

In order to lower the voltage applied to the glow plug after the engine has completely exploded, a resistor may be inserted in series with the glow plug, but there is a problem in setting the applied voltage.

In other words, this applied voltage is determined by the resistance value of the glow plug and the resistor inserted in series with it.
Immediately after the engine has completely exploded, the resistance value of the glow plug is relatively high due to the effects of preheating during startup.

Therefore, the voltage applied to the glow plug after the engine completely explodes is
It is relatively high at first, then gradually decreases, and changes to a stable value after a certain amount of time has passed.

Therefore, if the voltage is set so that the initial value of the applied voltage has sufficient margin with respect to the cut-off voltage at which power is cut off to the glow plug, the stable voltage will be relatively low and the after-blow effect will be reduced. will not be able to achieve its full potential.

The present invention aims to solve the above-mentioned problem in controlling the energization of glow plugs in diesel engines, and is characterized by delaying the start of energizing the glow plugs by a predetermined period of time after the engine has completely exploded. .

The delay time is set to a relatively short time.

During this time delay period, the glow plug will not operate, but
Since the time is short, there are almost no negative effects, and since the set voltage for after-blow can be increased to a value that is effective for that purpose, it is possible to make the glow plug work effectively as a whole. .

Below, an embodiment of the present invention will be explained with reference to the drawings. First, in Fig. 1, a starter switch 2 and an ignition switch 3 are connected in parallel to a power source 1, and the ignition switch 3 is connected to the emitter of a transistor TR. ing.

The base of the transistor TR1 is connected to the output of a timer circuit 5, which receives power from the power source 1 via the switch 3 and is controlled by the engine coolant temperature sensor 4.

The collector of the transistor TR1 is connected to the first relay lane nod R.

The time limit circuit 5 controls the time during which the transistor TR1 is turned on, depending on the temperature of the engine cooling water detected by the water temperature sensor 4.

The starter switch 2 is further connected to a solenoid R□ via a diode D.

The contact S1 of the first relay is connected to the switch 3, and the contact S is connected to the solenoid R2 of the second relay.

An indicator light 6 is placed in parallel with the solenoid R2 to indicate the excitation state of the solenoid R2.

A cylinder 7 of a diesel engine is provided with a pre-combustion chamber 7a and an intake passage 7b, and a glow plug CP is arranged in the pre-combustion chamber 7a.

The contacts S2 of the second relay are connected on the one hand to the power supply 1 and on the other hand to this glow plug CP, which is energized when the contact S2 is closed.

This second relay contact S2 constitutes a first switch.

A contact S3 of a third relay is arranged in parallel with the second relay contact S2, and the contact S3 is connected to the power supply 1 on the one hand and to the glow plug GP via a resistor 13 arranged in the intake passage 7b on the other hand. has been done.

The contact S3 constitutes a second switch, and when this contact S3 is closed, the glow plug GP is connected to the resistor 1.
It is energized via 3.

The solenoid R3 of the third relay is connected to the ignition switch 3, and the operation of the solenoid R3 is controlled by the control circuit 8.
controlled by

FIG. 2 shows details of the control circuit 8, which includes a second relay solenoid R3 that controls the operation of the third relay solenoid R3.
It has a transistor TR2.

The transistor TR2 has a collector connected to the solenoid R3 and an emitter grounded.

The base of the transistor TR2 is connected to the switch 3 through voltage dividing resistors 9 and 10, and is grounded through a resistor 11.

Therefore, when the ignition switch 3 is closed, the base voltage of the transistor TR2 is increased by the resistor 11, the transistor TR2 becomes conductive, and the solenoid R3 is energized.

The output of a comparator 12 for comparing the glow plug applied voltage with a reference voltage is applied between the resistors 9 and 10.

The comparator 12 has an input 12a supplied with the voltage applied to the glow plug GP, and an input 12b supplied with a reference voltage, for example 7.
When 5V is applied and the applied voltage increases due to a defect such as breakage of the glow plug GP, the output of the comparator 12 becomes zero, the base voltage of the transistor TR2 decreases, and the transistor becomes non-conductive.

Therefore, solenoid R3 becomes de-energized and contact S
3 will be opened.

Further, an engine complete explosion switch 14 that responds to the output of the voltage regulator is connected between the resistors 9 and 10, and this switch 14 opens when the engine is fully exploded and works to increase the base voltage of the transistor TR2. .

Furthermore, the output of the vehicle speed sensor 15 is applied between the resistors 9 and 10 via the third transistor TR3.

The speed sensor 15 detects the vehicle speed at a predetermined value, for example, 8 b/h.
When the above is the case, an output is generated, and the output is
TR3 is applied to the base of TR3 to make the transistor TR3 conductive.

Therefore, the base voltage of the transistor TR2 is lowered, and the conduction of the transistor TR2 is cut off.

In addition to the above-described circuit that controls the transistor TR2, the potential at the connection between the resistors 9 and 10 is configured to be controlled by the starter switch 2.

That is, the starter switch 2 is connected to the base of the fourth transistor (2) via the diode D1 and the resistor 16, and the collector of the transistor TR is connected to the resistors 9, 10.
and the emitter is grounded.

A connection portion between the diode D1 and the resistor 16 is grounded via a resistor 17 and a capacitor 18 to form a delay circuit.

In operation, first, when the ignition switch 3 is closed, the transistor TR1 becomes conductive for a time determined by the time limit circuit 5 according to the temperature of the engine coolant, energizing the solenoid R1 and closing the contact S1. The solenoid R2 is energized, which closes the contact S2, energizes the glow plug CP, and preheats the pre-combustion chamber 7a.

During this time, the indicator light 6 indicates that the glow plug is energized.

When a predetermined period of time has elapsed, the timer circuit 5 disconnects the transistor TR1, opens the contacts S and S2, and at the same time the indicator light 6 turns off.

With this light off, when the switch 3 remains closed and the starter switch 2 is closed, the solenoid R1 is energized at the same time as cranking by the operation of the engine starter.
In the same manner as described above, contact S2 closes and glow plug GP
is energized.

At this time, the voltage from the power supply 1 is applied to the base of the transistor TR4 of the delay circuit 8 with a slight delay due to charging of the capacitor 18, so the transistor TR1 becomes conductive and the base voltage of the transistor TR2 is increased. lower.

Transistor TR2 is therefore non-conducting, solenoid R3 is deenergized, and contact S3 is open.

When the engine reaches a complete explosion state, the complete explosion switch 14 is opened and the starter switch 2 is also opened at the same time, but since the discharge of the capacitor 18 of the delay circuit continues for a set time, for example, several seconds, the transistor TR4 is maintained in a conductive state. Transistor TR2 is non-conductive and contact S3 remains open.

Simultaneously with the opening of the starter switch 2, the excitation of the solenoid R1 is cut off, and as a result, the contact S2 is opened, so that the power to the glow plug GP is cut off.

When the base voltage of the transistor m falls below a predetermined value due to the discharge of the condenser 18, the transistor TR,
becomes non-conductive, the base voltage of the transistor TR2 rises, and the transistor 9TR becomes conductive.

Therefore, the solenoid R3 is energized, the contact S3 is closed, and the glow plug GP is energized via the resistor 13.

After the starter switch 2 is opened, there is a time delay of several seconds before power is restarted to the glow plug GP, so the glow plug CP is cooled down during this time.
When electricity is restarted, a stable voltage will be applied to the glow plug CP.

Note that the delay circuit for providing this time delay is not limited to the illustrated example, and may have any configuration.

When the applied voltage becomes higher than the reference voltage while the glow plug CP is energized, the output of the comparator 12 becomes zero, the transistor TR2 becomes non-conductive, the relay contact S3 is opened, and the energization to the glow plug GP is stopped. Cut off.

Further, when the car starts and the vehicle speed reaches a predetermined value or more, the transistor TR3 is turned on by a signal from the vehicle speed sensor 15, and the base voltage of the transistor TR2 decreases.

Therefore, the transistor TR2 becomes non-conductive, the solenoid R3 is demagnetized, the contact S3 is opened, and the current to the glow plug GP is cut off.

As described above, according to the present invention, in a device that energizes the glow plug before the complete explosion of the engine during preheating and cracking, when the glow plug is energized after the engine complete explosion, the second switch is activated by the delay circuit. Since the application of the voltage through the electrode is delayed for an appropriate period of time, a relatively stable voltage with no peak voltage can be applied from the beginning.

Therefore, the voltage applied through the second switch can be set relatively high, and effective afterglow can be achieved by a long shot.

[Brief explanation of the drawing]

FIG. 1 is a schematic wiring diagram of a glow plug energization control device showing one embodiment of the present invention, and FIG. 2 is a wiring diagram showing details of the control circuit. 2... Starter switch, 3... Ignition switch, 5... Time limit circuit, S□, S
2. S3...Relay contact, Control circuit, TR□, TR2, TR3゜TR4...Transistor, 17...Resistor, 18...・Capacitor, GP...Glow plug.

Claims (1)

[Scope of utility model registration request] A first switch and a second switch are connected in parallel to each other between a power source and a glow plug provided in the combustion chamber, and the first switch
The switch is combined with a first control device for closing the first switch during engine preheating and cranking for starting, and the second switch includes a complete explosion switch for detecting complete explosion of the engine and a glow plug. and a voltage detection switch that detects when the applied voltage of the glow plug exceeds the set value, and closes the second switch after a complete explosion is detected, and closes the second switch when the glow plug applied voltage exceeds the set value. In the glow plug energization control device for a diesel engine combined with a second control device that opens, the second control device is provided with a delay device that delays the closing operation of the second switch by a set time after the engine complete explosion. A glow plug energization control device for a diesel engine, characterized by: