JPS5996484A - Controller for electrification of glow plug - Google Patents

Abstract

PURPOSE:To uniformize an applied effective voltage without depending on variation in a source voltage, by a method wherein intermittent control is effected through comparision of the time mean value of a voltage, intermittently applied on a glow plug, with a reference value which varies proportionally to a source voltage. CONSTITUTION:The output voltage of a reference voltage generating circuit 20 is automatically rectilinearly varied. The motion is produced by applying an amplifying degree decided by an input resistor 26 and a return resistor 27, in relation to a constant voltage independent on a source voltage in which the output volage of a 3-terminal regulator 7 is divided as the plus side input voltage of an operational amplifier 23 by means of resistors 24 and 25. This causes applying of an approximately constant effective voltage over a wide range of a source voltage, and causes a rated voltage to be applied on the temperature of a glow plug independently on a source voltage, resulting in maintenance of the temperature at an approximately constant value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method (1) of applying a voltage higher than the rated voltage to perform rapid heating, and after reaching a predetermined upper limit temperature, switching the voltage to intermittent energization to perform stable heating. ) Regarding a glow plug energization control device.

The present invention relates to an improvement of the glow plug energization control device of the above-mentioned type as exemplified in Japanese Unexamined Patent Publication No. 5'l-2471, and the glow plug temperature is controlled in consideration of the battery voltage applied to the glow plug. The purpose is to maintain.

That is, the present invention continuously changes the temporal average value of the voltage that is intermittently applied to the glow plug during intermittent energization so that it becomes small when the power supply voltage is high and becomes extra large when the power supply voltage is low. When the intermittent voltage average value is smaller than the reference value, the glow plug is energized, and when it is larger, the energization is stopped. The feature is that the effective voltage is maintained constant regardless of changes in the power supply voltage.

To explain the illustrated embodiment, in Fig. 1 which is a block diagram and an electrical wiring diagram showing its details, ■ is a battery, 2 is a key switch of an automobile, and 3 is an output for a time corresponding to the power supply voltage after the key switch is opened. 11 is a driver circuit, 13 is a plug energization circuit that opens and closes the battery voltage application to the glow plug 16, and is installed near the glow plug (Fig. 2). )1
4.15 are transistors 16a and 16b forming a glow plug energizing circuit;

16c and 16d are four glow plugs connected in parallel,
19 is an average voltage generation circuit that generates an average DC voltage of the voltage that is intermittently applied to the glow plug; 20 is a reference voltage generation circuit that outputs a low voltage when the power supply voltage is high and a high voltage when the power supply voltage is low as a continuous change. , 21 is a comparator, 22 is a delay circuit for delaying and transmitting the high level inversion of the output of the comparator 21 to the driver circuit 11, 28 is a timer circuit for determining the afterglow period, and 30 is a circuit package.

In FIG. 2, when the key switch 2 is opened, the rapid heating timer circuit 3 changes the + side input of the comparator 4 to (
The voltage (for example, 4V) obtained by dividing the voltage (for example, 5V) of the output line 7a of the three-terminal regulator tough (shown in Fig. 2) by the resistor 8.9 (3) Since the voltage is O■ initially, the output of the comparator 4 is at a high level. Therefore, through the pull amplifier resistor 10, the driver circuit ff
611 is energized, and the output line of this driver circuit acts to make the transistor 14.15 of the plug energizing circuit 13 conductive, and the battery voltage is applied to the glow plugs 16a to 16d to start rapid heating.

At the same time, the voltage at the positive terminal 17 of the glow plug charges the capacitor 5 via the charging time constant circuit 6. This charging time constant circuit 6 has nonlinear characteristics depending on the power supply voltage. The time it takes for the voltage of the capacitor 5 to reach the + side input voltage of the comparator 4 is such that the temperature of the glow plugs 16a to 16d reaches the required upper limit temperature (for example, 900℃).
℃), the output of the comparator 4 becomes low level when the voltage of the capacitor 5 reaches the reference voltage (4■) of the comparator 4. As a result, the driver circuit 11 becomes deenergized, and the plug energizing circuits 11 & 13 also become non-conductive, causing a glow (4).
becomes. Note that when the output of the comparator 4 becomes low level, the + side input voltage of the comparator 4 becomes almost low level through the diode 18, so the output of the comparator 4 keeps the low level from then on until the key switch is released. .

Now, once the glow plug voltage becomes Ov, after that, the average voltage generation circuit 19, the reference voltage generation circuit 20, the comparator 21, and the delay circuit 22 control the glow plug voltage, for example, from 10Hz to 10Hz.
The battery voltage is energized intermittently at a frequency of about 0 Hz so that the rated effective voltage is applied to the glow plug. Its operation occurs when the rapid heating timer circuit is activated.
In other words, when the battery voltage is being applied to the glow plugs 16a to 16d in direct current, the capacitor 23 (for example, 10.uF) in the average voltage generation circuit 19 has a resistance of 24°2.
The time constant (10IJFxl It is discharged at OKΩ(5) -100ms).

Therefore, the voltage at the + side input of the comparator 21 is equal to the output voltage of the reference voltage generating circuit 2o having the characteristics shown in FIG.
When the voltage is 12V, it is 1.5V, so when the capacitor voltage drops to 1.5V, the output of the comparator 21, which was previously at a low level, is reversed to a completely high level. This high level signal passes through the delay circuit 22 and energizes the driver circuit 11 after about 10 m5, and the plug energizing circuit 13 is brought into conduction and the battery voltage is again applied to the glow plugs 16a-16d.

However, by applying this voltage, the voltage of the capacitor 23 returns to the output voltage of the reference voltage generating circuit 20 of 1.5■ in a very short time (less than 1 m s) via the resistor 25.
The output of the comparator 21 becomes low level again, and the voltage application to the glow plug is stopped. This is 10011
By repeating at a frequency of about z, the capacitor 23
The plug energizing circuit 13 repeats opening and closing (6) at a duty ratio such that the voltage becomes equal to the output voltage of the reference voltage generating circuit 20. At this time, since the resistors 24 and 25 are both IOKΩ, the capacitor voltage is 1.5V, whereas the average voltage of the glow plug is twice as high as 3V.

The following explanation is based on an intermittent duty cycle in which the power supply voltage is 12V, which is intermittently applied to the glow plug, and the average voltage is always 3cm, which is twice the output voltage of the reference voltage generation circuit 20, which is 1.5cm. As mentioned above, the ratio is constant, but here the output voltage of the reference voltage generation circuit 20 is 2
In this embodiment, as shown in FIG. 3, it automatically changes linearly so that it becomes 2■ when the power supply voltage is 8V and becomes IV when the power supply voltage is 16V.

This movement is performed by using the input resistor 26 and the feedback resistor 27 to increase the amplification of the power supply voltage for a constant voltage that does not depend on the power supply voltage, which is obtained by dividing the output voltage of the three-terminal regulator tough by the resistor 24°25 as the positive input voltage of the operational amplifier 23. It is obtained by applying the determined one-side input. The fact that the output voltage of the reference voltage generator 20 changes with respect to the power supply voltage in this way means that the average voltage applied to the glow plug (7) as shown in Fig. 4 (bl) is 4 cm when the power supply voltage is 8 cm. , voltage [voltage 16V
It also changes linearly so that it becomes 2V at .

The relationship between these voltages and time is as shown in Figure 4. When the power supply voltage is 8V, the average voltage is 4V, and the duty ratio is 50%. 1
At 6V, the average voltage is 2■ and the duty ratio is 12.
．． It will be 5%. At an intermediate power supply voltage of 12V, the average voltage is 3■
The duty ratio is preferably 25%. The effective value of the intermittent applied voltage at each of these power supply voltages is 8V power supply voltage and 5.66Vtsia pressure 1
11 at 2v Ama0.2 = 6.00V electricity 11 voltage 16
16' x O, 125 = 5.66V, and as shown in Figure 5(b), a nearly constant effective voltage is applied over a wide range of power supply voltages, and the temperature of the glow plug changes with the power supply voltage. Regardless of the temperature, the rated voltage is applied and the temperature is maintained at a nearly constant temperature.

The time period (8) for which the glow plug maintains a stable temperature is, for example, the output 29 of the afterglow timer 28, which operates from the time the key switch is closed, continues while the glow plug is in the ossine state, and after the predetermined afterglow period of one hour has elapsed. The output 29 of the afterglow timer circuit 28 becomes low level, the driver circuit is forcibly turned off, and the glow plug energization is ended. Nano's afterglow timer circuit 28 receives a signal from a water temperature sensor (not shown) indicating the engine water temperature, etc.
Time can be controlled.

In the embodiments described above, the rapid heating timer circuit 3 is used as the rapid heating means, but other timer means may also be used. It can also be used in a device for a method of detecting that a predetermined upper limit temperature has been reached. Further, in this embodiment, a current amplifying circuit of transistors 14 and 15 is used as the plug energizing circuit, but a thyristor, a gate turn-off thyristor, or an electromagnetic relay equiaxial switching device may be used as the case may be. Furthermore, in this example, the average value of the voltage applied intermittently to the glow plug (9) is compared.As a reference voltage generation circuit, an inverting amplification method with linear characteristics is used using an operational amplifier, but this characteristic has a curved characteristic. You can make it into something.

Furthermore, as a method for detecting the average voltage, a smoothing circuit method using resistors and capacitors is used, but when this device is configured using a microcomputer, the average voltage is calculated based on the energization period of the glow plug. The reference voltage generation circuit can also use a digital signal that changes depending on the power supply voltage.

As described above, according to the present invention, the effective voltage applied to the glow plug can be maintained even when the power supply voltage fluctuates, and the heating effect is exerted even during cranking, and the plug is prevented from overpowering. Never.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is an electrical wiring diagram showing details of Fig. 1, Fig. 3 is a characteristic diagram of the reference voltage generation circuit (2o), and Fig. 4 is FIG. 5 is an explanatory diagram showing a change in the intermittent duty ratio of the glow plug applied voltage (10), and FIG. 5 is an explanatory diagram of the effective voltage of the glow plug applied voltage. 3... Rapid preheating timer circuit, 11... Driver circuit, 13-... Energizing circuit, 16 a, 16 b
, 16 c. 16d... Glow plug, 19... Average voltage generation circuit. 20... Reference voltage generation circuit, 21... Comparator for comparison. Representative Patent Attorney Takashi Okabe (11) Figure 1 Figure 3

Claims (1)

[Claims] In a glow plug energization control device that applies a voltage higher than the rated voltage to perform rapid heating, and after reaching a predetermined upper limit temperature, switches the voltage to intermittent energization to perform stable heating, for the intermittent energization. means for comparing the temporal average value of the voltage that is intermittently applied to the glow plug with a reference value that continuously changes such that it becomes small when the power supply voltage is high and becomes extra large when the power supply voltage is low; A glow plug energization control device that energizes the glow plug intermittently so that when the intermittent voltage average value is smaller than the reference value, the glow plug is energized, and when it is larger, the energization is stopped.