JPH0627831Y2 - Glow plug energization time control circuit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a glow plug energization time control circuit used when starting a diesel engine.

BACKGROUND ART Generally, a glow plug is required to smoothly start a diesel engine. The glow plug is provided in a sub chamber called a pre-combustion chamber above the main combustion chamber. A part of the injected fuel is ignited in the sub chamber, and the pressure generated thereby causes the remaining fuel to be ejected into the main combustion chamber and mixed with air to be completely combusted. However, in an engine having a sub-chamber combustion chamber with a large surface area of the combustion chamber, the compression heat of air is absorbed by the cylinder and the cylinder head,
The high temperature required to ignite the fuel cannot be obtained. Therefore, a glow plug is provided to raise the temperature in the combustion chamber.

FIG. 3 is an electric circuit diagram of a conventional glow plug energization time control circuit. When the ignition switch IG is turned on, power is supplied to the energization time control circuit 41 from the battery 42, and the potential of the output terminal 43 becomes high level.
When the output terminal 43 becomes high level, the relay 4
A coil current flows through the coil 45 of No. 4 and the contact 46 is made conductive. When the contact 46 is conducted, the glow plug 47
Power is supplied from the battery 42 to the a, 47b, 47c, and 47d, and the glow plug 47 rapidly generates heat.

Since the glow plugs 47 are provided in the pre-combustion chamber of each cylinder, four glow plugs are required in the case of a 4-cylinder engine. The switch 48 is provided to heat the pre-combustion chamber even during engine operation, and the switch 48 is turned on at the same time when the ignition switch IG is turned on.

The resistor 49 is a resistor for limiting the current flowing through the glow plug 47, and limits the amount of heat generated by the glow plug 47.
The supply voltage to the glow plug 47 is input to the input terminal 51 of the energization time control circuit 41 via the fuse 50.
The voltage applied to the input terminal 51 is divided by the resistor 52 and the resistor 53, and the divided voltage is applied to the electricity storage means constituted by the resistor 54 and the capacitor 55.

The positive electrode of the capacitor 55 is connected to the positive input terminal of the comparator 56. A reference voltage obtained by dividing the power supply voltage 57 of the conduction time control circuit 41 by the resistors 58 and 59 is applied to the negative input terminal of the comparator 56. The power supply voltage 57 is a stabilized voltage generated by the conduction time control circuit 41,
It is lower than the voltage of battery 42.

The output of the comparator 56 is input to the relay control circuit 61 via the line 60. The relay control circuit 61 is line 6
It outputs a high level while 0 is a low level, and when the line 60 changes from a low level to a high level, it outputs a low level.

When the ignition switch IG is turned on, the voltage applied to the glow plug 47 is applied to the input terminal 51 of the energization time control circuit 41 via the fuse 50. Input terminal 5
The voltage applied to 1 is applied to the capacitor 55 via the resistors 52 and 54, and the potential of the positive input terminal of the comparator 56 rises. When the potential of the positive input terminal of the comparator 56 becomes higher than the reference voltage of the negative input terminal, the output of the comparator 56 becomes high level, and the relay control circuit 61 outputs the low level potential.

When the electric potential to the coil 45 of the relay 44 becomes low level, the contact 46 is opened and the glow plug 47 is not supplied with electric power.

Problems to be Solved by the Invention In such a prior art, when the input terminal 51 is grounded, for example, when it contacts the body of an automobile, an excessive current flows from the battery 42 to the fuse 50 and the fuse 50 is disconnected. It At this time, if the portion in contact with the vehicle body is separated, the terminal 51 is opened and the resistors 62, 52, 5
Since no power is supplied to the capacitor 55 via No. 4, no problem occurs. However, if the portion in contact with the vehicle body is left as it is, the terminal 51 is grounded and the electric charge of the capacitor 55 is discharged through the resistors 54, 53 and 52. When the capacitor 55 is discharged, the potential of the positive input terminal of the comparator 56 drops and the comparator 56 outputs a low level. As a result, the contact 46 of the relay remains conductive, and the glow plug 47 is continuously supplied with electric power from the battery 42. If power is continuously supplied to the glow plug 47, the glow plug 47 may be burned.

FIG. 4 is a diagram showing the relationship between the voltage of the input terminal 51 and the conduction time of the relay 44. When the voltage of the input terminal 51 becomes higher, the time for the output voltage of the capacitor 55 to reach the negative input terminal voltage of the comparator 56 becomes shorter, so that the conduction time of the relay 44 becomes shorter as shown in FIG. Conversely, input terminal 5
The lower the voltage of 1, the longer the conduction time of the relay 44, especially when the input terminal 51 is grounded.
Since the conduction time becomes infinite and the relay 44 is not cut off, the glow plug 47 is burned.

An object of the present invention is to provide a glow plug energization time control circuit that solves the above problems.

Means for Solving the Problems The present invention relates to a glow plug 7, a switching means 4 for supplying / disconnecting electric power to the glow plug, and a control means 2 for switching the operating state of the switching means.
1; a first power supply line to which a voltage applied to the glow plug is supplied; a second power supply line to which a battery voltage is supplied via an ignition switch IG and a first resistor 23; Both voltages supplied from the first and second power supply lines are applied through a common second resistor 12, and the power storage means 15 is charged / discharged based on the both voltages, and an output level of the power storage means. One end is connected between the second resistance and the electricity storage means, and a comparison means 16 that outputs a control signal for comparing with a predetermined reference level and outputs a control signal for switching the operation state of the switching means to the control means. Third means for supplying electric power to the means through the rectifying means 22
Is a glow plug energization time control circuit.

Operation According to the present invention, the voltage applied to the glow plug 7 is applied to the power storage means 15 from the first power supply line through the second resistor 12, and the output level of the power storage means 15 is determined by the comparison means 16 as a predetermined reference. The control means 21 controls the switching means 4 in response to the comparison result with the level, thereby supplying / interrupting the power to the glow plug 7 and controlling the energization time to the glow plug 7. In addition, the battery voltage from the ignition switch IG is applied to the power storage means 15 via the second power supply line formed of the first resistor 23 and the second resistor 12. , Power is supplied through a third power supply line provided with the rectifying means 22.

When the first power supply line for detecting the voltage applied to the glow plug 7 is opened due to, for example, melting of fuse which is interposed in the first power supply line or disconnection of the connector, the rectifying means 22 becomes conductive, When the first power supply line is normal, the power is supplied to the power storage unit 15 via the third power supply line and the power storage unit 15 is charged with the battery voltage via the second power supply line. Charging can be performed with almost the same characteristics as described above, and the switching means 4 can be quickly shut off without burning the glow plug 7.

Embodiment FIG. 1 is an electric circuit diagram of a conduction time control circuit according to an embodiment of the present invention. When the ignition switch IG is turned on, the electric power from the battery 2 is supplied to the conduction time control circuit 1, and the electric power is supplied to the second switch composed of the ignition switch IG and the first resistor 23. It is supplied to the capacitor 15 via the power supply line, the second resistor 12 and the resistor 14. The terminal voltage of the capacitor 15 is applied to the positive input terminal of the comparator 16, and the negative input terminal of the comparator 16 is divided into the reference voltage by dividing the voltage of the high-level power supply 17 by the resistors 18 and 19. It is input as the voltage Vth. The output of the comparator 16 is given to the relay control circuit 21 via the line 20, and the relay control circuit 21 responds to the output from the comparator 16 via the output terminal 3 of the coil 5 of the relay 4. An exciting current is supplied to the contact 6, so that the contact 6 is turned on / off and the glow plug 7 is energized.

At the time when the ignition switch IG is turned on,
The input voltage of the positive input terminal of the comparator 16 is lower than the input voltage of the negative input terminal. Therefore, the output of the comparator 16 becomes low level, and the relay control circuit 21 outputs the high level output to the output terminal 3. Derive.

The potential of the output terminal 3 becomes high level. When the output terminal 3 becomes high level, an exciting current flows through the coil 5 of the relay 4 and the contact 6 becomes conductive. By making the contact 6 conductive,
Electric power from the battery 2 is supplied to the glow plugs 7a, 7b, 7c, 7d. When electric power is supplied to the glow plug 7, the glow plug 7 rapidly generates heat and the temperature in the pre-combustion chamber is rapidly raised. The glow plug 7 is provided in each pre-combustion chamber of each cylinder.

The switch 8 is provided to heat the pre-combustion chamber even during engine operation.
At the same time that G is turned on, the switch 8 is also turned on. As a result, the power from the battery 2 is also supplied to the glow plug 7 via the resistor 9. The resistor 9 is a resistor for limiting the current flowing through the glow plug 7, and is for limiting the amount of heat generated by the glow plug 7.

The supply voltage to the glow plug 7 is given to the input terminal 11 via the fuse 10 which is the first power supply line. The voltage applied to the input terminal 11 is the resistance 12 and the resistance 1
The voltage is divided by 3 and the divided voltage is given to the storage means constituted by the resistor 14 and the capacitor 15. The power supply 17 stabilizes the voltage of the battery 2 supplied to the energization time control circuit by reducing the voltage by a stabilization circuit (not shown). When the supply voltage of the glow plug 7 is applied to the input terminal 11, the voltage at the point P divided by the resistors 12 and 13 is set to be higher than the voltage of the power supply 17 by the resistors 12 and 13. Since it is set, the diode 22 interposed in the third power supply line connecting the power source 17 and the point P has a reverse polarity, and no current flows through the diode 22.

FIG. 2 is a timing chart for explaining the circuit operation of the energization time control circuit 1. FIG. 2 (1) shows a voltage waveform at the positive input terminal of the comparator 16. When the ignition switch IG is turned on at time t ₀ , charges are accumulated in the capacitor 15 via the resistors 12 and 14, and the potential rises as shown in FIG. 2 (1). When the input terminal 11 is grounded at time t ₁ , the fuse 10 is melted,
Without the diode 22, the potential at the positive input terminal of the comparator 16 drops, as indicated by the virtual curve in FIG.

However, when the diode 22 is connected to the power supply line as in the embodiment of the present invention, electric charge is accumulated in the capacitor 15 via the diode 22 and the resistor 14, so that the fuse 10 is grounded to the input terminal 11. Therefore, the potential of the positive input terminal of the comparator 16 rises even in the state of being fused and grounded. At time t ₂ , the comparator 1
When the voltage at the positive input terminal of 6 becomes higher than the reference voltage at the negative input terminal, the output of the comparator 16 becomes high level, as shown in FIG. Given to. When a high level signal is applied to the relay control circuit 21, the output of the relay control circuit 21 becomes low level as shown in FIG. 2 (3), and the contact 6 of the relay 4 is opened.

In addition, when the input terminal 11 is changed from the ground fault state to the open state after the fuse 10 is melted,
Even when the first power supply line to the capacitor 1 is disconnected, the power from the battery 2 is supplied to the capacitor 1 via the second power supply line including the ignition switch IG and the resistor 23.
5, the potential of the positive input terminal of the comparator 16 rises and the contact of the relay 4 can be opened. Moreover, at that time, since the capacitor 15 is charged with the voltage of the battery 2, it can be charged with almost the same characteristics as in the normal case where the fuse 10 is not melted and the contact 6 of the relay 4 is charged.
Can be quickly opened to prevent the glow plug 7 from burning.

As described above, even if the fuse 10 is blown for some reason and the input terminal 11 is opened thereafter, the contact 6 of the relay 4 is opened after a predetermined time has elapsed.

Effect As described above, according to the present invention, when the input terminal of the voltage applied to the glow plug 7, that is, the connection point between the first power supply line and the second power supply line is grounded, the power supply line is rectified. Since electric charge is supplied to the storage means via the means,
The glow plug 7 does not remain energized. Further, when the first power supply line is disconnected and the ignition switch IG is turned on, electric charge is supplied from the battery to the power storage means via the second power supply line, so that the storage device can be quickly and easily configured. The power supply to the glow plug 7 can be cut off.

Therefore, it is possible to reliably prevent the glow plug 7 from being burned due to the glow plug 7 remaining energized.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a timing chart for explaining the operation of the circuit diagram of FIG. 1, and FIG. 3 is an electric circuit diagram of a conventional glow plug energization time control circuit. 4 is a diagram showing the relationship between the voltage of the input terminal 51 and the conduction time of the relay 44 in FIG. 1 ... energization time control circuit, 4 ... relay, 7 ... glow plug, 10 ... fuse, 11 ... input terminal, 14,
18, 19 ... Resistance, 15 ... Capacitor, 16 ... Comparator, 17 ... Power supply, 21 ... Relay control circuit, 22 ...
…diode

Claims (1)

[Scope of utility model registration request] 1. A glow plug 7, a switching means 4 for supplying / disconnecting electric power to the glow plug, and a control means 2 for switching the operating state of the switching means.
1; a first power supply line to which a voltage applied to the glow plug is supplied; a second power supply line to which a battery voltage is supplied via an ignition switch IG and a first resistor 23; Both voltages supplied from the first and second power supply lines are applied through a common second resistor 12, and the power storage means 15 is charged / discharged based on the both voltages, and an output level of the power storage means. One end is connected between the second resistance and the storage means, and a comparison means 16 that outputs a control signal for comparing the control level with a predetermined reference level and switches the operating state of the switching means to the control means. Third means for supplying electric power to the means through the rectifying means 22
And a power supply line for the glow plug energization time control circuit.