JPS6128834B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling the preheating time of a glow plug installed in a diesel engine, and in particular to a device for controlling the preheating time of a glow plug installed in a diesel engine, and in particular to a device for controlling the preheating time of a glow plug installed in a diesel engine. The present invention relates to a glow plug preheating time control device that prevents this.

Conventional glow plug type preheating devices, as shown in Japanese Patent Application Laid-Open No. 113441/1984, connect a resistor in series between the glow plug and the battery, and apply the heat generation temperature of the resistor to the bimetal. let me,
It controlled the preheating time of the glow plug. According to this configuration, when the voltage applied to the glow plug, that is, the current flowing through the resistor changes, the heat generation temperature of the resistor changes, so the temperature reached by the glow plug changes due to the change in the voltage applied to the glow plug. will be corrected. However,
Inserting a series resistor in the glow plug as described above has the disadvantage that the resistor wastes power, which is uneconomical, and that the current and voltage applied to the glow plug are reduced, resulting in a longer preheating time.

Another conventional glow plug preheating device is
For example, as shown in Japanese Utility Model Publication No. 49-46347, the voltage applied to a glow plug is applied to a capacitor via a constant current source made up of a transistor and a resistor, and the glow plug is preheated by the charging time of the capacitor. Setting the time. According to this configuration, when the voltage applied to the glow plug changes, the charging current of the capacitor changes, and the habit of the temperature reached by the glow plug due to the change in the voltage applied to the glow plug is corrected. As described above, since the charging current of the capacitor flows through a constant current source, even if the voltage changes, the charging current cannot change enough to completely compensate for the temperature change of the glow plug.

The present invention has been made to eliminate such drawbacks, and improves preheating efficiency by eliminating power wastage and prolonged preheating time due to series resistance, and also reduces the voltage applied to the glow plug. The present invention provides a preheating time control device that prevents the attained temperature of a glow plug from changing even if the temperature changes, and will be explained below based on the drawings.

In FIG. 1 showing an example of a circuit diagram of a control device according to the present invention, a wiring 2 connected to an anode of a battery 1 is connected to an input end of a key switch 3 and an input end of a switching contact 4; Glow plugs 6, 7, 8, and 9, which are provided for each combustion chamber of the engine (not shown), are connected in parallel between the output end of 4 and a wiring (ground) 5 connected to the cathode of the battery 1.

A common contact point between the ON contact ON and the start contact ST in the key switch 3 is connected to one of comparators 13a and 13b as comparators in the preheating voltage detection circuit A and the warming voltage detection circuit B through Zener diodes 12a and 12b. side input terminal is connected, and this input terminal and wiring 5 are connected to resistors 14a and 1.
4b. The Zener diode 12a and the resistor 14a constitute a constant voltage circuit. Resistors 15a, 15b and one end of capacitors 16a, 16b are connected to the + side input terminals of comparators 13a, 13b, respectively, and capacitor 1
The other ends of 6a and 16b are connected to the wiring 5, the other end of the resistor 15a is connected to the off contact OFF of the key switch 3 via a resistor 17a, and the other end of the resistor 15b and the common contact are connected via a resistor 17b. are doing. Diodes 18a and 18b are connected in parallel to the resistors 15a and 15b, respectively, and further, the anode sides of the diodes 18a and 18b and the wiring 5 are connected by transistors 19a and 19b,
Furthermore, transistor 1 of preheating voltage detection circuit A
The base of the transistor 9a is connected to the common contact of the key switch 3 via a resistor 20a, and the base of the transistor 19b of the heat-retaining voltage detection circuit B is connected to the start contact ST of the key switch 3 via a resistor 20b. The resistors 15a, 17a, 20
a, a capacitor 16a, a diode 18a, and a transistor 19a constitute a time constant circuit.
The output terminals of both the comparators 13a and 13b are connected to the base of the transistor 22 of the drive circuit C via resistors 21a and 21b, respectively, and the switching contact 4 is connected between the common contact of the key switch 3 and the wiring 5. The relay coil 10 and the transistor 22 are connected in series, and the output terminal of the comparator 13a of the voltage detection circuit A for preheating is connected to the common contact of the key switch 3 via a resistor 23a, and the output terminal of the comparator 13a of the voltage detection circuit B for keeping warm is connected in series. 13
Connect the output end of b to the start contact ST of key switch 3.
is connected to the relay coil 10 via a resistor 23b, and a diode 24 is connected in parallel to the relay coil 10. Further, an indicator lamp 11 is connected to the output terminal of the preheating voltage detection circuit A.

In the control circuit having such a configuration, when the key switch 3 is connected to the off contact (OFF), the battery voltage is charged to the capacitor 16a via the resistor 17a and the diode 18a, and the voltage is applied to the + side input terminal of the comparator 13a. Battery voltage is applied. Now turn off key switch 3
When the ON contact is switched from OFF to ON, the base voltage is applied to the transistor 19a, so the transistor 19a is turned on, and the capacitor 16 starts discharging via the resistor 15a, and the comparator 13
Gradually lower the voltage at the + side input terminal of a. On the other hand, when the key switch 3 is turned on, the reference voltage regulated by the Zener voltage of the Zener diode 12a becomes - of the comparator 13a.
It is applied to the side input terminal, and the resistors 23a, 21
Since the base voltage is applied to the transistor 22 through a, the transistor 22 is turned on, energizing the relay coil 10 and turning on the switching contact 4.
Power is supplied to the glow plugs 6, 7, 8, and 9 to start preheating, and the indicator lamp 11 is turned on to indicate that preheating is in progress. As the discharge of the capacitor 16a progresses and the voltage applied to the + side input terminal of the comparator 13a becomes lower than the voltage applied to the - side input terminal, the output of the comparator 13a, which had been held at the "H" level, becomes "L". " level, the transistor 22 is turned off, the relay coil 10 is demagnetized, the contact 4 is opened to stop the power supply, and the indicator lamp 11 is turned off to indicate that preheating has been completed.

In this way, the time during which the glow plug is energized is determined by the discharge characteristics of the capacitor 16a when the battery voltage is constant;
By appropriately setting the time constant determined by the temperature and the capacitor 16a, it is possible to energize the glow plug and preheat it to an optimal temperature. Further, the voltage to be compared with the voltage at the connection point between the capacitor 16a and the resistor 15a is set to be a constant voltage by the Zener diode 12a, and when the key switch 3 is connected to the male contact, the charging voltage of the capacitor 16a is Since it depends on the battery voltage, the temperature rise characteristic of the glow plug changes depending on the battery voltage as shown in FIG. 2, and the glow plug can always be preheated to a temperature suitable for starting. Note that the temperature increase characteristics of the glow plug are not affected much by the ambient temperature.

On the other hand, the insulation voltage detection circuit B and the drive circuit C
Since both use the common contact in the key switch 3 as a power source, the reference voltage regulated by the Zener diode 12b and the battery voltage charged in the capacitor 16b are applied to the comparator 13b of the insulation voltage detection circuit B from the preheating stage. has been done. Therefore, in this state, the output of the comparator 13b is at "H" level, but since no voltage is applied to the resistor 23b, the output of the comparator 13b is at "H" level.
No current flows through b, and does not affect the operation of the preheating voltage detection circuit A. Turn key switch 3 on contact
When switching from ON to start contact ST, transistor 19b is turned on, and the charge stored in capacitor 16b begins to be discharged via resistor 15b, and the voltage at the connection point between capacitor 16b and resistor 15b gradually drops. Immediately after the above switching, the voltage at the + side input terminal of the comparator 13b is higher than the voltage at the - side input terminal, so the output of the comparator 13b becomes "H" level. On the other hand, the resistor 22b is turned on, and as in the case of the preheating voltage circuit A described above, the switching contact 4 is closed until the voltage applied to the + side input terminal of the comparator 13b becomes lower than the voltage at the - side input terminal, and the glow This prevents the plugs 6, 7, 8, 9 from being cooled. In this case as well, by appropriately setting the time constant determined by the resistor 15b and the capacitor 16b, as in the case of preheating described above,
The heat retention time of the glow plug can be set optimally. Further, as described above, the heat retention time changes depending on the magnitude of the battery voltage.

As explained above, the preheating time control device according to the present invention includes a switching contact interposed between the battery and the glow plug, a capacitor, and a resistor, and switches the key switch from the OFF position to the ON position. starts operating when the glow plug is turned on, and generates an output voltage whose change characteristic depends on a time constant determined by the capacitor and the resistor, and whose magnitude depends on the magnitude of the power supply voltage applied to the glow plug. a constant voltage circuit that generates a predetermined constant voltage; a comparator that compares the output voltage of the time constant circuit with the constant voltage of the constant voltage circuit;
Since the glow plug is configured with a drive circuit that controls opening and closing of the opening/closing contact in response to the comparison result of the comparator, the glow plug can be heated to a desired temperature even if the power supply voltage applied to the glow plug changes. This improves starting performance. Furthermore, there is no need to provide a series resistor etc. as in the past, simplifying the configuration and eliminating power waste.
By reducing the resistance of the preheating circuit, the preheating time can be shortened, which is advantageous in terms of cost.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a control device according to the present invention, and FIG. 2 is a temperature characteristic diagram of a glow plug. 1... Battery, 3... Key switch, 4... Opening/closing contact, 6, 7, 8, 9... Glow plug, A... Voltage detection circuit for preheating, B... Voltage detection circuit for keeping warm, C... Drive circuit, ON... On contact, ST…Start contact.

Claims (1)

[Claims] 1 It consists of a switching contact interposed between the battery and the glow plug, a capacitor, and a resistor, and starts operating when the key switch is switched from the OFF position to the ON position, and its change characteristics are the same as those of the capacitor. depending on said resistance and a more determined time constant;
a time constant circuit that generates an output voltage whose magnitude depends on the magnitude of the power supply voltage applied to the glow plug, and a constant voltage circuit that generates a predetermined constant voltage;
It is characterized by comprising a comparator that compares the output voltage of the time constant circuit and a constant voltage of the constant voltage circuit, and a drive circuit that controls opening and closing of the switching contact in response to the comparison result of the comparator. Glow plug preheating time control device.