JPS626296Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for appropriately controlling the preheating temperature of a glow plug by controlling the energization time to a glow plug installed in a diesel engine in accordance with changes in the applied voltage at the glow plug terminal.

Glow plugs are required to be preheated in a short time and to maintain the temperature necessary for starting the engine even after the temperature has been raised. The energization time required to raise the temperature of the glow plug is largely influenced by the voltage applied to the glow plug terminals, and if the temperature is not properly controlled, the heating element may melt due to overheating or the engine may fail to start due to insufficient preheating. In addition, if the electric wire for detecting the voltage applied to the glow plug terminal or its terminal has an abnormality such as disconnection, poor contact, or grounding, the glow plug voltage will be in the same state as low.
This will induce melting damage due to overheating of the glow plug.

The present invention solves these problems with a simple circuit configuration, and provides a glow plug temperature control device that can raise the temperature of the glow plug to an appropriate temperature in any condition and smoothly start the engine. purpose.

The present invention includes a capacitor, a glow plug terminal voltage input terminal connected to the terminal part of the glow plug by an electric wire, and a glow plug terminal connected to the capacitor via a resistor or transistor to provide a glow to the capacitor. A charging circuit that performs plug terminal voltage-dependent charging, and a comparator that receives as input the input voltage of the capacitor and the resistance division point voltage of the output voltage of the constant voltage circuit,
The output of the above comparator determines the temperature of the glow plug, which regulates the closing time of the normally open relay contact, which is interposed between the glow plug and the power supply and closes when the preheating start switch is turned on, and conducts a large current for preheating. In the control device, a diode is interposed in the charging circuit, an auxiliary charging circuit is provided separately from the charging circuit for charging based on the output voltage of the constant voltage circuit, and a resistor dividing point, which is one input point of the comparator, is provided. It is connected to the above terminal or the voltage application point of the terminal via a diode, and an input resistance is provided to the above terminal, so that it can be used to preheat the glow plug even if voltage is no longer applied to the above terminal due to an accident. The structure is such that the energization time can be maintained appropriately.

Next, the present invention will be explained based on the embodiment shown in the drawings.

FIG. 1 shows a circuit diagram of a temperature control device for a glow plug according to the present invention.

A is the engine's key switch, which has a GL terminal for energizing the glow plug, and an ST terminal for energizing the starter motor while continuing to energize the glow plug, B is for the battery, and G is for the auxiliary combustion chamber. This is a rapid heating temperature rise type glow plug. A preheating control circuit 1 for a glow plug G has a normally open contact a, and a battery B and a glow plug G are connected to each other for the purpose of rapidly raising the temperature of the glow plug G for preheating.
A relay for rapid temperature rise that supplies a large current by short-circuiting the relay, and a temperature maintenance relay that has a contact point a and that conducts a limited current through a current limiting resistor 2 for the purpose of maintaining the glow plug temperature after preheating. A timer T 1 that turns on the relay and a timer T _{1 that is set appropriately after the driver turns on switch A to the GL terminal and a timer T 1 that} is set longer than the time t ₁ when the operator turns on switch A to the GL terminal. time t ₂ relays
The set time is updated (reset) while the switch A is connected to the ST terminal and the starter motor is energized, and the high level output is output again for ₂ hours after the starter motor is no longer energized. The glow plug G has a timer _T2 that turns on a relay, and the terminal g of the glow plug G and the energization control circuit 1 are connected via a wire harness 3. Timer T ₁ inputs voltage V ₁ of the charge charged in capacitor C ₁ and reference voltage V ₂ obtained by dividing the output constant voltage V _Z of constant voltage circuit 4 by voltage dividing resistors R ₅ and R ₆ . The relay 6 includes a comparator 5 and a relay 6 that closes an energizing circuit to the relay using the output of the comparator. Capacitor C ₁ receives current i ₂ supplied by terminal voltage Vg of glow plug G via resistor R ₁ and diode D ₂ and current supplied from the constant voltage circuit 4 via resistor R ₄ and diode D ₁ . The intermediate point a between the voltage dividing resistors _R5 and _R6 is connected to the terminal g of the glow plug G through a resistor _R7 and a diode _{D3 ,} and the point g is grounded through a resistor _R8 . A terminal voltage Vg of the glow plug G is inputted between the diode D ₃ and the resistor R ₈ via a wire harness. R ₂ , R ₃ , R ₉ are resistors, D ₄ is a diode, 7,
8 is an inverter, and 9 is a relay that has the same configuration as the relay 6 and closes the energizing circuit to the relay with the output of the timer _T2 .

Next, along with the time chart shown in Figure 2,
The operation of the glow plug temperature control device shown in the figure will be explained.

As shown in Figure 2A, when key switch A is connected to the GL terminal, comparator 5 indicates that capacitor _C1 is in a discharged state, and the input voltage becomes _V1 < _V2 , producing a high level output and turning on relay I to glow. Start energizing the plug. Capacitor C ₁ has resistance R ₄ and diode D ₁ due to voltage V _Z of constant voltage power supply.
At the same time, it is charged with a current i ₁ through a resistor R ₁ and _a diode D ₂ due to the glow plug terminal voltage Vg.

The comparator 5 generates a high level output until the charging voltage of the capacitor _C1 reaches the reference voltage _V2 of the comparator 5, turns on the relay, and rapidly raises the temperature of the glow plug G as shown in FIG. 2D.

The wire harness 3 that detects the voltage of the terminal g of the glow plug is connected to the glow plug terminal at a connection point 32
If a disconnection or poor contact occurs between the control circuit connection point 31 and the control circuit connection point 31, the charging current of the capacitor C ₁ will be only i ₁ , and the normal state will be shown as V ₁₁ shown in Figure 2 B.
V The battery charges noticeably more slowly from ₁₀ o'clock. At this time, the reference voltage V ₂ of comparator 5 is
Since _D3 electrically connects the grounding resistor _R8 of the terminal in parallel with the resistor _R6 , the reference voltage _V21 shown in FIG. 2B is lower than the normal state. As a result, the output reversal time of comparator 5 is also shortened by the set amount, and the time required for energizing the glow plug by the relay is shown in Figure 2 C.
t ₁₁ to be shorter than or equal to normal t ₁₀ ,
Prevents melting of glow plugs due to excessive temperature rise. In addition, if this reference voltage V ₂₁ is determined to an appropriate value using resistors R ₇ and R ₈ , the time t ₁₁ for energizing the glow plug can be set to a temperature that is sufficient for starting the engine and within a range where the glow plug is not expected to melt. can be reliably set.

Although R ₂ is not essential, it is added here to regulate the maximum input voltage to the comparator 5 and to adjust the charging characteristics. Also with R _3
D1 is for discharging the capacitor with an appropriate time constant when the switch is turned off.

In this example, _C1 is directly charged via the resistor _R1 with the terminal voltage of the glow plug, but the third
As shown in the figure, a charging circuit that depends on the glow plug terminal voltage may be configured using a transistor T. In FIG. 3, R ₁₁ to _{R 13} are resistors, and D ₅ is a diode.

FIG. 4 shows another embodiment, in which a NAND (or AND) circuit 12 is connected to the detection output of the terminal voltage detection section of the terminal g of the glow plug G and the output of the drive circuit 11 of the lamp 10 for indicating the starting time of the starter motor ST. The lamp 10 is turned off when the glow plug G cannot be energized.

As described above, the present invention uses a small number of parts, appropriately controls the energization time according to the glow plug terminal voltage, and even when an abnormality occurs in the wire harness that detects the glow plug voltage. The effect is that the glow plug can be heated to an appropriate temperature and the engine can be started without causing melting.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of a glow plug temperature control device according to the present invention, FIG. 2 is a timing chart for explaining its operation, FIG. 3 is a circuit diagram of another embodiment, and FIG. The figure is a block diagram of yet another embodiment. 1... Control circuit, 2... Current limiting resistor, 3...
...Wire harness, 4... Constant voltage circuit, 5...
Comparator, C ₁ ... Capacitor, ...
Relay, G...Glow plug, _T1 , _T2 ...Timer.

Claims (1)

[Claims for Utility Model Registration] A capacitor, a glow plug terminal voltage input terminal connected to the terminal portion of the glow plug by an electric wire, and a voltage input terminal connected from the terminal to the capacitor via a resistor or transistor. a charging circuit that performs charging depending on the glow plug terminal voltage, and a comparator that receives as input the input voltage of the capacitor and the voltage at the resistance division point of the output voltage of the constant voltage circuit, and the comparator In a glow plug temperature control device that uses the output of A diode is inserted in the charging circuit, and an auxiliary charging circuit is provided separately from the charging circuit to perform charging based on the output voltage of the constant voltage circuit. The terminal is connected to the above terminal or the voltage application point of the terminal, and an input resistance is provided to the above terminal, so that even if voltage is not applied to the above terminal due to an accident, the preheating time of the glow plug can be maintained. A glow plug temperature control device characterized by being able to maintain the temperature appropriately.