JPS5996483A - Control method for electrification of glow plug - Google Patents

Abstract

PURPOSE:To uniformize the effective applying voltage of a glow plug without depending on a source voltage, by a method wherein, in the case of intermittent electrical connection, intermittent electrical connection is effected in response to a pulse signal, the duty ratio of which varies according to the voltage of the glow plug. CONSTITUTION:A waveform generated from a waveform generating circuit 16 is added to the non-inversion input terminal of a comparator 27. A voltage, being a source voltage divided by resistors 28 and 29, is applied to the inversion input terminal of the comparator 27. When the source voltage is high, a reference voltage increases, and when the source voltage is low, the reference voltage decreases. Thus, a time, for which the output of the comparator 27 generates a logic 1 signal, decreases when the source voltage is high, and increases when the source voltage is low. This causes uniformizing of the effective applying voltage of a glow plug without depending on the source voltage.

Description

[Detailed description of the invention] The present invention applies a voltage higher than the rated voltage to rapidly heat the
The present invention relates to a method for controlling energization of a glow plug in which stable heating is performed by switching the voltage to intermittent energization after reaching a predetermined upper limit temperature.

The present invention relates to an improvement (1) of the glow plug energization control device of the above type as exemplified in Japanese Patent Application Laid-Open No. 57-2471. The purpose is to maintain the glow plug temperature.

That is, the present invention provides a pulse signal whose duty ratio changes depending on the glow plug power supply voltage during intermittent energization, that is, a pulse signal whose duty ratio is small when the power supply voltage is high, and large when the power supply voltage is low. By generating a signal and performing intermittent energization based on this pulse signal, the effective voltage applied to the glow plug due to intermittent energization is made constant (not dependent on the power supply voltage).

In FIG. 1 showing one embodiment of the present invention, ■ is a battery;
2 is a key switch, 3 is a rapid heating timer circuit whose output becomes a logic level for a predetermined time depending on the power supply voltage after the key switch is closed, 4 is a comparator that compares the capacitor charging voltage with the reference voltage, and 5 is a voltage regulator. , 6.7
is a resistor for dividing the regulated voltage, 8 is a capacitor, 9 is a pull amplifier resistor, 10 is a driver circuit, 11
12a, 12b, 12c, and 12d are plug energizing circuits that open and close battery voltage application to the glow plugs (2), and are installed near the glow plugs;
13 is a glow plug non-ground terminal.

14 is a nonlinear time constant circuit for charging the capacitor, and 15 is a diode that maintains the logic θ level of the output of the comparator 4. 16 is a capacitor discharge waveform generation circuit, 17
is a comparator, 18 is a capacitor, 19 is a resistor, 20
．． 21 is a resistor for dividing the regulated voltage, 22
2 is a transistor for raising the reference level of the comparator, 23 is a resistor, 24 is a transistor for forced discharge of the capacitor, and 25 is a resistor.

26 is a pulse generation circuit that generates pulses with a duty ratio according to the power supply voltage, 27 is a comparator that compares the output waveform from the waveform generation circuit with a reference level, 28 and 29 are resistors for dividing the power supply voltage, and 30 is a It is a pull-up resistor. 31 is a diode, 32 is an afterglow timer circuit, 33 is a transistor for deactivating the driver circuit 10(3) after one hour of afterglow, and 34 is a diode.

In FIG. 1, when the key switch 2 is closed, the rapid heating timer circuit 3 connects the non-inverting input terminal of the comparator 4 with the output voltage (for example, 5V) of the voltage regulator 5 through the resistor 6. While the voltage is divided by the resistor 7, the voltage at the inverting input terminal is initially Ov at the capacitor 8, so that a logic level signal is generated from the output of the comparator 4.
The driver circuit 10 is energized via the pull amplifier resistor 9.

The output of the driver circuit 10 makes the plug energizing circuit 11 conductive, and the battery voltage is applied to the glow plugs 128 to 12d to start rapid heating.

Due to this energization, the voltage at the glow plug ungrounded terminal 13 is
The capacitor 8 is charged via the charging time constant circuit 14. This charging time constant circuit 14 has nonlinear characteristics. The time it takes for the voltage of the capacitor 8 to reach the non-inverting input terminal voltage of the comparator 4 is
This is to coincide with the time for the temperature (4) degrees of 8 to 12 days to reach the required upper limit temperature (for example, 900 degrees Celsius).

When the voltage of the capacitor 8 reaches the non-inverting input terminal voltage of the comparator 4, the output of the comparator 4 generates a logic 0 signal, the driver circuit 10 becomes de-energized, and the plug energizing circuit 11 also becomes non-conducting, causing the glow plug to become non-conducting. 12a-12
The direct current supply to d is terminated.

It should be noted that when the output of the comparator 4 reaches the logic 0 level, the non-inverting input terminal voltage of the comparator 4 becomes approximately Ov via the diode 15, so the output of the comparator 4 maintains the logic 0 level.

After the rapid heating by the rapid heating timer circuit 3, the rated effective voltage is applied to the glow plug.
The battery voltage is applied intermittently at a frequency of about 0 Hz, that is, the waveform generating circuit 16 continuously generates a capacitor discharge waveform as shown in FIG. In detail, when the key switch 2 is closed, the non-inverting input (5) input terminal of the comparator 17 receives the second voltage generated by the capacitor 18 and the resistor 19.
The waveform shown in the figure is applied, and the regulator voltage is applied to the inverting input terminal through the resistor 20. Reference voltage VLS divided by resistor 21
(for example, 0.5V), the comparator 17
The output of generates a logic I signal.

When the capacitor 18 is charged and the voltage at the non-inverting input terminal of the comparator 17 drops to the reference voltage Vs and the output of the comparator 17 is inverted to the logic 0 level, the transistor 22 becomes conductive and the regulated voltage is passed through the resistor 23. It is applied to the inverting input terminal of the comparator 17, and the reference voltage rises from VL5 to Vss (4V, for example). Furthermore, at the same time as transistor 22 becomes conductive, transistor 24 also becomes conductive.

Transistor 24 becomes conductive and the regulated voltage is applied to resistor 2.
When it reaches the reference voltage VH5, the output of the comparator 17 is again inverted to a logic level, transistors 23 and 24 become non-conducting, and the reference voltage (6) becomes V+. -Go down to S. At this time, the capacitor 18 is forcibly discharged and returns to its initial state.

The waveform shown in FIG. 2 generated by the waveform generating circuit I6 is applied to the non-inverting input terminal of the comparator 27. The power supply voltage is connected to the inverting input terminal of the comparator 27 through the resistor 28. The voltage divided by the resistor 29 is applied, and as shown in FIG. 2, when the power supply voltage is high, the reference voltage becomes high, and when the power supply voltage is low, the reference voltage becomes low. Therefore, the time during which the output of the comparator 27 generates a logic 1 signal becomes shorter when the power supply voltage is high (duty ratio is small), and becomes longer when the power supply voltage is low (duty ratio is low).

When the output of the comparator 27 is a logic level, the driver circuit 10 is energized via the pull-up resistor 30, and the plug energization circuit 11 is made conductive by the output, causing the glow plugs 12a to 12a to
Battery voltage is applied to 12d.

As a result, intermittent energization is performed as shown in FIG. In other words, when the power supply voltage is high (e.g. 12V), the duty ratio becomes small, and when the power supply voltage is low (e.g. 8V), the duty ratio becomes large (7). Therefore, the effective voltage applied to the glow plug is to be constant regardless of the power supply voltage.For this purpose, the waveform generated by the waveform generation circuit 16 must be a waveform that can be applied within the range where the power supply voltage fluctuates. In this embodiment, in order to obtain the above waveform, a diode 3 is connected between the capacitor 18 and the resistor 19.
Enter 1. From the above, by applying a nearly constant rated effective voltage to the glow plug over a wide range of power supply voltages as shown in Figure 3, the glow plug temperature can be maintained at a nearly constant temperature independent of the power supply voltage. dripping

The time during which the glow plug maintains the darkening temperature is, for example, as long as the output of the afterglow timer circuit 32, which is activated from the moment the key switch is turned on, is at logic 0 level, and after one hour of afterglow has elapsed, the afterglow is maintained. The output of the timer circuit 32 becomes a logic level and the transistor 3
3 conducts, forcibly deenergizing the driver circuit 10 and ending the intermittent energization to the glove (8) lug. Note that the time of the afterglow timer circuit can be controlled by a signal such as engine water temperature. Although pulses are generated from the pulse generating circuit 26 from the time when the key switch 2 is closed, the engine whose output from the rapid heating timer 3 is a logic level is not intermittently energized by the diode 34.

Although the above embodiment uses the rapid preheating timer 3 as a rapid preheating method, other timer methods may be used, or the predetermined upper limit temperature can be reached by a change in the resistance value of a plug with a large resistance temperature coefficient, which is well known in the art. It is also possible to use a device with a method of detecting the arrival.

In the waveform generating circuit 16 of this embodiment, a diode is inserted between the capacitor 18 and the resistor 19 in order to obtain a waveform that can be applied over a wide range of power supply voltages, but this can also be achieved by other methods such as using a Zener diode. Furthermore, although a divided voltage of the power supply voltage is used as the reference voltage of the comparator 27 in the pulse generating circuit 26, a voltage obtained by smoothing the non-grounded terminal pre-voltage (9) of the glow plug may also be used.

Further, although a transistor current amplification circuit is used as the plug energization circuit in this embodiment, other switching devices such as a thyristor, a gate turn-off thyristor, or an electromagnetic relay may be used depending on the case.

In addition, in this embodiment, a waveform generation circuit 16,
Although the pulse generation circuit 26 is used, these circuit functions may be realized using a microcomputer or the like.

As described above, according to the present invention, by making the duty ratio of intermittent application to the glow plug correspond to the power supply voltage,
The applied effective voltage can be kept constant using a glow plug.

[Brief explanation of the drawing]

Fig. 1 is an electrical wiring diagram showing an embodiment of the present invention, Fig. 2 is a timer chart for explaining the operation of the duty pulse generation circuit,
FIG. 3 is a time chart showing changes in the operation of the embodiment device with respect to changes in the plug applied voltage. (10) 11...Plug energizing circuit, 12a, 12b, 12c
, 12d... Glow plug, 16... Capacitor discharge waveform generation circuit, 26... Pulse generation circuit. Representative Patent Attorney Takashi Okabe (11)

Claims (1)

[Claims] In a glow plug energization control method in which a voltage higher than the rated voltage is applied to the glow plug to rapidly heat it, and after reaching a predetermined upper limit temperature, the voltage is switched to intermittent energization to perform dark heating, the duty ratio is adjusted according to the power supply voltage. A glow plug energization control method that generates a pulse signal in which the power supply voltage changes, that is, the duty ratio is small when the power supply voltage is high and the duty ratio is large when the power supply voltage is low, and performs intermittent energization based on this pulse signal. .