JPH0232476B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a glow plug energization control device used to assist in starting a diesel engine.

[Conventional technology] A conventional glow plug energization control device is
A key switch with OFF, ON, and ST terminals,
A rapid heating type glow plug, a rapid temperature increase relay for supplying a large current to the glow plug, a relay for energizing the glow plug via a current limiting resistor, and energization for controlling each of the relays. It is equipped with a control circuit. Further, this energization control circuit detects the terminal voltage of the glow plug using a detection line.

[Problems to be Solved by the Invention] However, the conventional energization control device has the following drawbacks.

If the terminal voltage of the glow plug is not detected due to a break in the detection line or the like, the energization control circuit determines that the battery voltage has decreased and abnormally raises the temperature of the glow plug.

SUMMARY OF THE INVENTION An object of the present invention is to provide a glow plug energization control device that can quickly stop energizing the glow plug when the terminal voltage of the glow plug is not detected due to disconnection of a detection line or the like.

[Means for solving the problem] In order to solve the above object, the present invention provides an OFF/
A key switch S having an ON/ST terminal, a rapid heating type glow plug G, a rapid temperature rising relay 1 for supplying a large current to the glow plug G, and a current limiting resistor 3 connected to the glow plug G. a relay 2 for energizing the glow plug G, and an energization control circuit that controls the relays 1 and 2, detects the terminal voltage of the glow plug G using a detection line, and limits the energization of the glow plug G when the terminal voltage is not detected. 4, the energization control circuit 4 includes: (a) a capacitor C3 for determining a time constant; and one comparator OP1 inputting the charging voltage of the capacitor C3; a timer T1 that controls the relay 1; (b) a capacitor C9 connected to the current side terminal A of the glow plug G for determining a time constant; and the capacitor C
9, and (c) a charging circuit for a capacitor C9 that stops energization to the glow plug G via relay 2 in a short time, and when the terminal voltage is not detected. , a configuration is adopted in which the relay 2 is de-energized in a short period of time.

[Operation and Effects of the Invention] When input of the terminal voltage of the glow plug to the voltage detection circuit stops, capacitor C9 is charged and energization to the glow plug via relay 2 is stopped, so that the terminal voltage of the glow plug is reduced. If this is not detected due to a disconnection of the detection wire, etc., the energization by the relay 2 is stopped in a short period of time, so that it is possible to prevent the glow plug from being excessively heated due to the simultaneous reception of engine combustion heat and joule heat.

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

Figure 1 shows a glow plug energization control device for assisting the starting of a diesel engine, and S is:
OFF terminal and ON for energizing the glow plug
An engine key switch that has a terminal and an ST terminal for energizing the starter motor while intermittent energizing the glow plug, BAT is the battery that is the power source, and G is the rapid heating riser installed in the sub-combustion chamber of the engine. Warm type glow plug, 1 is a relay for rapid temperature rise that supplies a large current to the required temperature sufficient for starting the engine to rapidly raise the temperature of the glow plug G, 2 is a current for maintaining the glow plug G at the required temperature. Temperature maintenance energizing relay for passing a limited small current through limiting resistor 3 (both are installed in a location close to the glow plug attached to the engine); 4 controls relay 1 and relay 2; It is an energization control circuit for
It is located in a location relatively isolated from other institutions.

The energization control circuit 4 includes a capacitor C1 for determining a time constant, a comparator OP1 inputting the charging voltage of the capacitor C1, and a comparator OP1 for synchronizing the charging voltage of the capacitor C1 with the temperature of the glow plug G. A discharging circuit has a constant voltage characteristic to prevent the charging voltage of C1 from increasing to a value somewhat higher than the input voltage value at which the output of the capacitor C1 is inverted. After being switched to
A timer T1 that turns on the relay 1 for an output time t1 set according to the voltage at the power supply terminal A point of the glow plug G (hereinafter referred to as the terminal voltage of the glow plug) and a switch S are connected to the ST terminal. and while the timer T1 is not producing an output to turn on the relay 1 (or while the starter motor is simply energized), a pulse set according to the terminal voltage of the glow plug is output to turn the relay 1 on as specified. Input the terminal voltage of the glow plug and pulse generator T2, which controls opening and closing at the cycle of , and turn on relay 1.
When the input voltage is set to approximately the ground potential, the terminal voltage of the glow plug is output only when the relay 2 is turned on by reversing the relay 1 to OFF, and
A glow plug terminal voltage detection circuit 10 raises the terminal voltage to a relatively high voltage when both relays 1 and 2 are OFF, and generates an output when the output from the detection circuit 10 exceeds a set value, and once outputs it. A comparator 30 is provided with a self-holding function so as to maintain the state even if the input disappears when the output of the NOR circuit 5 is inputted with the output of the timer T1 and the output of the pulse generator T2. Inverter 6 that energizes (ON) relay 1 with its output
By connecting the key switch S to the ST terminal, a logic circuit 40 that holds high-level and low-level outputs, a water temperature switch 13 that detects the temperature of the engine cooling water, and a key switch S
Relay 2 is activated by the energization signal to the starter motor accompanying the connection to the ST terminal of , and the output of the logic circuit 40.
The operating condition of the relay 2 is determined by the output of the inverter 12 provided in the output circuit of the comparator 30, the output of the vehicle speed switch 14, and the output of the OR circuit 11. The AND circuit 16 and the energization signal to the starter motor are input to the inverter 8, and this output and
An AND circuit 9 forms a complete explosion signal indicating a stable combustion state with one output of the logic circuit 40, and the output of the AND circuit 9 and the output of the comparator 30 are input, and the output of the timer T1 is inverted to a low level. OR circuit 24 outputs a signal to turn off relay 1 and stop rapid heating of glow plug G.
When the terminal voltage of the glow plug becomes an excessive voltage (15V to 20V) due to the use of two batteries connected in series, the generation of electricity by a generator installed in the engine, the use of an overcharged battery, etc., a high level output occurs. A high voltage detection circuit 18 that outputs a signal voltage to the comparator 30, and a logic circuit (AND circuit) 7 provided to stably operate the timer T2 down to a low voltage using the energization signal to the starter motor and the output of the NOR circuit 5. and a timer T3 that turns on the glow lamp 21 via the inverter 6 for a set time after the key switch S is connected to the ON terminal.

Next, the operation of the glow plug energization control device of the above embodiment will be explained with reference to the waveform diagram in FIG.

When the driver switches the key switch S from the OFF terminal to the ON terminal as shown in Figure 2A to start the engine, the timer T1 changes according to the terminal voltage of the glow plug G, as shown in Figure 2E. The output time period t1 produces a high level output. While the timer T1 is outputting a high level, the relay 1 is turned ON as shown in FIG. 2S by the output of the NOR circuit 5 shown in FIG. 2F. As a result, relay 1 closes its contacts, a large current is supplied to glow plug G, and glow plug G rapidly rises in temperature to over 600°C, which is sufficient to start the engine, in a short period of time, as shown in Figure 2.
Reach the required temperature below 1100℃. First output time limit
When t1 ends, the output of timer T1 is inverted to low level, and relay 1 is temporarily turned off. Further, when the ON terminal of the key switch S is connected, the timer T3 generates the output shown in FIG. 2A and lights up the indicator lamp 21 as shown in FIG. 2C.

Display of indicator lamp 21 indicating completion of preheating (lights off)
When the driver connects the key switch S to the ST terminal as shown in Figure 2A, the pulse generator T2
outputs the pulse shown in Fig. 2 O and connects relay 1.
The ON time opens and closes (ON/OFF) at a cycle that changes according to the terminal voltage of the glow plug, and the power supply voltage (mainly battery voltage) decreases due to energization of the starter motor and vaporizes the injected fuel. This compensates for the temperature drop in the glow plug G due to the above-mentioned operation, and maintains the glow plug G within the temperature range necessary for the above-mentioned startup, as shown in FIG.

The NOR circuit 5 receives the output of the timer T1 and the output of the pulse generator T2, and produces an output shown by the solid line in FIG. The output of the NOR circuit 5 shown in FIG. 2F is input to an inverter 6, and a drive signal for the relay 1 shown in FIG. 2G is generated. The voltage detection circuit 10 that increases the terminal voltage of the glow plug, when the output of the NOR circuit 5 is at a high level as shown in FIG.
That is, when the output of the timer T1 is at low level and the output of the pulse generator T2 is also at low level, so that the relay 1 is open, the voltage at the terminal A of the glow plug G is connected to the energization control circuit 4. The signal is transmitted to the comparator 30 via the terminal B, and the comparator ₃₀ outputs a signal as shown in FIG. A high level output is produced as shown by the broken line.

When the output of the logic circuit 40 shown in FIGS. 2C and 2 goes to a low level as shown in FIG. As shown in FIG. 2, the terminal voltage E of the glow plug shown in FIG. When E is less than ₀ as shown by the solid line in FIG. 2, and the water temperature switch 13 is closed as shown in FIG. Since a high-level output is generated as shown in Figure 2, even after the starter motor is energized, the voltage applied to the glow plug G remains higher than the set voltage E ₀ as shown by the broken line in Figure 2. As shown by the solid line in FIG. 2D, the relay 2 is kept closed via the inverter 12 and the AND circuit 16 to perform afterglow. In the operation of the relay 2, the detection circuit 1 uses the output of the NOR circuit 5 shown in FIG.
0 and the comparator 30 measures the glow plug terminal voltage (voltage at point A) when relay 1 is OFF.
The glow plug terminal voltage when the glow plug is turned on is normally higher than the set voltage E ₀ and is almost the battery voltage, which prevents the comparator 30 from operating with an input other than the glow plug terminal voltage during afterglow. Afterglow occurs after the key switch S is switched from the ON terminal side to the ST terminal side and returned to the ON terminal side, and the water temperature switch 13 is closed when the engine coolant temperature is at the set value (for example, 50°C or less), and then a power outage occurs. Vehicle speed switch 1 inside
4 is open as a necessary condition for performing afterglow, and when all these conditions are met, the AND circuit 16 produces a high level output. The value of the set voltage E ₀ is set to about 6 volts, for example, for a rapid heating type glow plug with a rated voltage of 12 volts and a heating temperature of 900° C. in 6 seconds. By providing the detection circuit 10 that detects the voltage at point A, the glow plug is reliably protected from burnout accidents. FIG. 2 H shows the output of the inverter 8, FIG. 2 C shows the output of the AND circuit 9, FIG. 2 shows the output of the inverter 12, FIG. 2 C shows the output of the OR circuit 24, FIG. 2H shows the output of the OR circuit 11.

If voltage is no longer applied to terminal B for some reason (for example, insufficient connection of the electric wire 17 that connects the power supply side terminal A of the glow plug and the connection terminal B of the energization control circuit 4), the detection circuit The output of 10 is
Since E is a value larger than ₀ , for example, the broken line V6 in FIG. It becomes zero as shown by the broken line in FIG. 2H, and the relay 2 becomes OFF as shown in the broken line in FIG. 2D. Note that a delay circuit may be added between the detection circuit 10 and the AND circuit 16 so that the zero output is applied to the AND circuit 16 after a predetermined relatively short time has elapsed.

If you use the Battery BAT in an overcharged state,
If another battery is added in series to the rated voltage battery, it is necessary to also turn off relays 1 and 2 to prevent the heating element of glow plug G from melting. In this case, the high voltage detection circuit 18 applies the input high voltage to the capacitor C3 of the timer T1, quickly charges the capacitor C3, and brings the output of the comparator OP1 to a low level in a short time, turning on the relay 1. Turn it off. Furthermore, the high voltage detection circuit 18 outputs a high level to the comparator 30 as shown by the dashed-dotted line in FIG. The output is set to a low level as shown in the dashed-dotted line in Figure 2 T, the output of the AND circuit 16 is set to be low level as shown in the dashed-dotted line in Figure 2N, and the relay 2 is turned off as shown in the dashed-dotted line in Figure 2D. , acts to stop energizing the glow plug G to prevent melting due to overvoltage.

FIG. 3 shows an example of a more detailed circuit of the glow plug energization control device in the embodiment shown in FIG.

OP1 to OP3 are comparators such as operational amplifiers or comparators, R1 to 43 are resistors, D1 to D25
is a diode, D25 and D11 are constant voltage diodes and Zener diodes, C1 to C11 are capacitors, Q1 to Q5 are transistors, and Amp is an amplifier circuit.

When key switch S is connected to the ON terminal, capacitor C3, which determines the time constant of timer T1, is connected to
From the ON terminal, charging with a low voltage via the large resistor R5 and charging via the resistor R3 and diode D3 with the voltage at the power supply side terminal A of the glow plug are started. Comparator OP1 of timer T1
is the reference voltage V2 determined by resistor R7 and resistor R8.
and charging voltage V1 of capacitor C3 are input.
Comparator OP1 outputs a high level until the relationship between V1 and V2 becomes V1>V2, and the high level output turns on relay 1 via NOR circuit 15 and inverter 6, and glow plug Supply large current to G. As a result, the glow plug G is rapidly heated.

Power supply side terminal of capacitor C3 and comparator OP1
is connected to the input terminal of the reference voltage by a discharge circuit L4 formed by connecting a resistor R6 and a diode D4 in series, and the charge in the capacitor C3 is connected to the reference voltage.
When the voltage E1, which is set slightly higher than V2, is exceeded, the discharge circuit L4 discharges, as shown by the solid line in FIG. This will energize the starter motor once,
If you try to start the engine but it fails and you return the key switch S to the ON terminal and then preheat and start it again, the charging voltage V1 of capacitor C3
becomes V1<V2 in a short time, the output of the comparator OP1 is reversed to high level in a short time, and a large current is quickly supplied to the glow plug G via the relay 1. On the other hand, if there is no discharge circuit L4, the charging voltage of capacitor C3 is as shown by the broken line in FIG.
Since V1 is significantly higher than the reference voltage V2, even if the key switch S is returned to the ON terminal, it takes a long time for the charging voltage V2 of the capacitor C3 to drop below the reference voltage V1, making it troublesome to try to start the engine again. It takes.

The pulse generator T2 has a comparator OP2 and a capacitor C6 for determining the time constant. Comparator OP2
inputs the reference voltage V4 determined by the resistor R13 and resistor R14 and the charging voltage V3 of the capacitor C6, and when the key switch S is connected to the ON terminal, there is a relationship of V3 < V4, and a high level is output. are doing. By connecting the key switch S to the ON terminal, the capacitor C6 is charged with the output voltage of the comparator OP2 through the resistor R15 and the diode D7, and the voltage at the terminal A of the glow plug G and the ON terminal is charged through the resistor R2. When the charging voltage V3 of the capacitor C6 becomes V3>V4, the comparator OP2 changes its output to a low level.

When the key switch S is switched to the ST terminal in this state, the voltage at the ST terminal is changed to the resistors R25, R26, and R
A base current is supplied to the transistor Q1 through R27 and R28, the transistor Q1 is turned on, and the charge in the capacitor C6 is discharged through the resistor R12. When the charging voltage V3 of the capacitor C6 decreases to V4 and V3<V4, the output of the comparator OP2 changes to high level again, turning on the relay 1 via the NOR circuit 5 and the inverter 6, and turning on the resistor R.
15 and diode D7 with a low voltage, and the terminal voltage of glow plug G also charges capacitor C6 via resistor R10 and diode D6. At this time, the output of the NOR circuit 5 is at a low level, and the base current to the transistor Q1 is absorbed by the NOR circuit 5 through the diode D19, so the transistor Q1 is turned off and the capacitor C6 is charged as described above.

Diode D19 prevents transistor Q1 from being in a conductive state at all times while the key switch is connected to the ST terminal if the power supply voltage becomes low for some reason, and capacitor C6 is discharged through resistor R12 to charge capacitor C6. voltage is the reference voltage
This is provided to eliminate the situation in which charging to V4 is not possible and to prevent comparator OP2 from operating while timer T1 is ON. When capacitor C6 is charged and V3<V4, the comparator
The output of OP2 changes to low level and relay 1 is activated.
Turn it OFF. At this time, the NOR circuit 5 becomes high level and the diode D19 is biased and turned off.
Therefore, the base current of the transistor Q1 is supplied, and the transistor Q1 is turned on. As a result, capacitor C6 is discharged through resistor R12, and when V3<V4, comparator OP2 changes its output to high level again, and NOR circuit 5 and inverter 6
Turn on relay 1 via .

This operation is repeated while the key switch S is set to the ST terminal. Relay 1 OFF
The time is determined by capacitor C6 and resistor R12, and the ON time of relay 1 is determined by resistor R15 and resistor R12.
10 and capacitor C6, and is determined according to the glow plug voltage.

Also, if you change the key switch S to the ST terminal,
In the logic circuit 40, the base current is supplied to the transistor Q2 via the resistor R29, and the transistor Q2 becomes conductive. Therefore, the base current is not supplied to the transistor Q3, and the transistor Q3 is turned off.
becomes. Therefore, the base current is supplied to the transistor Q2 by the resistors R34 and R30, and the logic circuit 4
0, the transistor Q3 always produces a high level output which is the collector terminal voltage.

However, while the starter motor is energized, the resistor R2
A base current is supplied to the AND circuit 9 and the transistor Q5 of the inverter 8 through the transistor Q5 and the resistor R40, and the output from the transistor Q3 is grounded through the resistor R42. When the engine reaches a complete combustion state and the key switch S is returned to the ON terminal side, the base current to the transistor Q5 is no longer supplied from the ST terminal, and the transistor Q5 is turned OFF.
However, the output of transistor Q3 is connected to resistor R30.
The comparator maintains a high level due to the positive feedback effect of the comparator, and charges capacitors C3 and C6 via resistor R42 and diode D21, and further via diode D23 or D24, respectively.
In OP1 and OP2, the relationship between the reference voltages V2, V4 and the charging voltages V1, V3 of capacitors C3 and C6 is V1>V2 and V3>V4, and the comparator
OP1 and OP2 each output a low level, and while relay 1 maintains the OFF state, relay 2 operates as follows.

When key switch S is set to the ON terminal side, transistor Q2 has no base current and is turned off, so resistor R32, diode D15, and resistor R3
7 and amplifier circuit Amp, turn on relay 2.

While the key switch S is connected to the ST terminal, relay 2 is turned on via diode D8, resistor R37, and amplifier circuit Amp.

The voltage detection circuit 10 and comparator 30 that protect the glow plug G from melting due to overvoltage operate as follows.

Terminal (point A) voltage E of glow plug G is divided by resistor R17 and resistor R18 to form input voltage V5 to comparator OP3, and this input voltage is input to comparator OP3 via resistor R19. The time constant of V5 is determined by capacitor C9. comparator
OP3 receives as input the reference voltage V6 determined by resistors R20 and R21 and the charging voltage V5 of the capacitor C9.

Furthermore, the input voltage to the comparator OP3 is passed through a diode D9 so that the comparator 30 does not detect the terminal voltage E of the glow plug G while the relay 1 is operating.
It is connected to the output of the NOR circuit 5 for driving the relay 1.
By doing this, when the relay 1 is turned ON and the glow plug terminal voltage E becomes high, the charging voltage of the capacitor C9 is transferred to the diode D9 and the NOR circuit 5.
Since the input of the terminal voltage is prohibited by immediately grounding through A comparator 30 measures the terminal voltage E of the glow plug G and constitutes a circuit for comparison.

If the terminal voltage of the glow plug G is not input due to poor contact of the connection potential (coupler) 17 or disconnection of the wire harness, the key switch S
A high voltage is applied from the ON terminal to the input terminal of the comparator OP3 via the resistor R2.

This resistance R2 is set as follows.

Resistance value of current control resistor 3 R<<R2......(1) R2<<R17, R2<<R18, R2<<R19......(2) By doing this, R and R2 are connected in parallel. In this case, from equation (1), the terminal voltage E of the glow plug G is controlled by the resistance R of the resistor 3, and the resistance R2 has no effect. However, if the glow plug voltage is not input in the above situation, V5>V6 from equation (2), and the comparator OP3 changes its output to high level.

The output of the comparator OP3 supplies the base current to the transistor Q4 via the resistor R23, making the transistor Q4 conductive and setting the input of the amplifier circuit 22 to a low level, so the relay 2 is turned off and the glow plug G is energized. stop.

If the key switch S is turned off in an overvoltage state such as an overcharge state,
When connected to the ON terminal, diode D1
1, resistor R22, and diode D12, a high voltage detection circuit 18 applies a high voltage to the input terminal of comparator OP3, instantaneously inverts the output of comparator OP3 to high level, and then
The output of the comparator OP1 rapidly charges the capacitor C3 through the resistor R39, the diode D20, and the diode D25, and quickly inverts the output of the comparator OP1 to a low level.

The diode D11 is a constant voltage diode for determining the protection voltage, and the conduction voltage of the high voltage detection circuit 18 is set to approximately 15V in a 12V power supply. This high voltage detection circuit 18 is isolated by resistor R19 even when relay 1 is ON, and comparator OP3
Activate. On the other hand, this comparator OP3 has a feedback circuit that provides positive feedback to the input via a diode D13 where the output changes to high level when the input voltage becomes V5>V6, and the charging voltage V5 of the capacitor C6 is changed to the resistor R19. becomes almost the power supply voltage due to the action of
This state is maintained even if the input voltage is removed.

As described above, in the glow plug energization control device of the present invention, the energization control circuit 4 includes a capacitor C3 for determining a time constant and one comparator OP1 which receives the charging voltage of the capacitor C3 as input,
A timer T1 for controlling the relay 1, a capacitor C9 connected to the power supply side terminal of the glow plug for determining a time constant, and a comparator OP3 for inputting the charging voltage of the capacitor C9. A voltage detection circuit detects the voltage of the power supply side terminal and controls the relay 2, and when input of the terminal voltage of the glow plug to the voltage detection circuit stops, the capacitor C9 is charged and the voltage is transmitted via the relay 2. Since it has a charging circuit for capacitor C9 that stops energizing the glow plug,
If the glow plug voltage measurement is not input to the control circuit due to a disconnection in the wire harness, etc., the relay 2 can stop the energization in a short time, preventing excessive temperature rise of the glow plug due to the simultaneous reception of engine combustion heat and joule heat. can.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a glow plug energization control device of the present invention, Fig. 2 is a time chart for explaining its operation, Fig. 3 is a circuit diagram showing one embodiment, and Fig. 4 is a diagram of a capacitor C3. It is a graph showing charging characteristics. In the figure, 1, 2... Relay, 3... Current limiting resistor, 4... Energization control circuit, 5... NOR circuit,
6, 8, 12, 15... Inverter, 7, 9, 1
6...AND circuit, 10...Voltage detection circuit, T
1, T2, T3...Timer, OP1, OP2, OP
3...Comparator, G...Glow plug, S...Key switch, C1-C11...Capacitor, 11,
24...OR circuit, 30...Comparator, 40
...Logic circuit.

Claims (1)

[Claims] 1. A key switch S having OFF, ON, and ST terminals, a rapid heating type glow plug G, a rapid temperature increase relay 1 for supplying a large current to the glow plug G, and a current limiting device. The glow plug G via the resistor 3
a relay 2 for energizing the glow plug G; and an energization control circuit that controls the relays 1 and 2, detects the terminal voltage of the glow plug G using a detection line, and limits the energization of the glow plug G when the terminal voltage is not detected. 4, the energization control circuit 4 includes: (a) a capacitor C3 for determining a time constant; and one comparator OP1 inputting the charging voltage of the capacitor C3; a timer T1 that controls the relay 1; (b) a capacitor C9 connected to the power supply side terminal A of the glow plug G for determining a time constant; and the capacitor C9.
(c) a charging circuit for a capacitor C9 that stops energizing the glow plug G via the relay 2 in a short period of time, and when the terminal voltage is not detected, A glow plug energization control device characterized by stopping energization of the relay 2 in a short time.