JPH0121349B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device for a glow plug used to assist in starting a diesel engine.

In a starting aid device using a rapid heating type glow plug, there is a rapid temperature increase energizing relay that supplies a large current to the glow plug for preheating, and a temperature control device that supplies current to the glow plug after preheating via a current limiting resistor. A maintenance energizing relay, a timer _T1 that controls the relay, and a starter relay that controls the relay.
Equipped with a control circuit that includes a timer _T2 that prevents the temperature of the glow plug from falling due to a drop in the power supply voltage and the cooling effect of the injected fuel when the motor is energized, and a relay that supplies a large current to the glow plug for a certain period of time after energization starts. However, after the predetermined period of time has elapsed, the temperature of the glow plug can be controlled so that the engine can be started most smoothly by a glow plug temperature control device that maintains the glow plug at a predetermined temperature for a predetermined period of time by energizing the glow plug via a relay. However, the inventor proposed that when performing so-called afterglow, which involves keeping the glow plug at a high temperature for a certain period of time immediately after engine startup to ensure smooth engine rotation immediately after engine startup, the generator generates less power as the engine speed increases. It was discovered that an excessive current flows through the glow plug due to an increase in the power supply voltage caused by this, and that the glow plug heating element is likely to melt due to excessive temperature rise.

The present invention provides a glow plug that can prevent malfunctions of the glow plug by measuring the voltage applied to the glow plug during afterglow and stopping energization to the glow plug when the applied voltage rises above a set value. The purpose is to provide a plug temperature control device.

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

Figure 1 shows a starting aid for a diesel engine. The key switch, B is the battery, and G is the rapid heating temperature rise type glow plug installed in the auxiliary combustion chamber. The temperature control device 1 of the glow plug G is
A relay for rapid temperature increase to supply a large current to rapidly raise the temperature of the glow plug G for preheating, and a current limiter to maintain the temperature after the glow plug G reaches a predetermined temperature after preheating. A temperature maintenance energizing relay for passing a limited current through resistor 2, and a temperature maintenance energizing relay for passing a limited current through resistor 2, and turning on the relay for a set t ₁ hour after switch A is turned on to the GL terminal.
When timer T ₁ and switch A are connected to the GL terminal, the relay is turned on for t ₂ hours, which was set longer than t ₁ hour, and switch A is connected to the ST terminal and the starter motor is energized. The set time has been updated and the power supply to the starter motor has been stopped, and then the timer _T2 , which generates a high level output _{for 2} hours, and the power supply side terminal D of the glow plug G are set again.
This is an applied voltage detection circuit for a glow plug that inputs the voltage at a point, and produces a high level output when the applied voltage E to the glow plug G exceeds a set value, and an input that once produced a high level output. a comparator 3 that maintains its state even if the relay is turned off; a gate circuit 4 that inputs the applied voltage E to the comparator 3 only when the relay is OFF; and an output terminal of the timer _T1 via an inverter 5. A relay 6 that is connected and closes the contact 6a with the output of timer T ₁ to energize the relay, a logic circuit 7 that determines the operating conditions of the relay, and an AND circuit that receives the output of the logic circuit 7 and the output of the timer T ₂ as inputs. circuit 9;
NOR circuit (or OR circuit) that inputs the output of the above AND circuit and the energization signal to the starter motor.
10, and a relay 11 that closes a contact 11a with the output of the NOR circuit 10 and turns on the relay. Reference numeral 12 is a charge/discharge indicator lamp terminal (hereinafter referred to as L terminal) of the regulator, which generates a low level output and lights up the lamp while the battery is discharging.
During charging, a high level output is generated and the lamp is turned off. 13 is a water temperature sensor switch that is turned off when the temperature is below a predetermined temperature, and 14 is a vehicle speed sensor switch that is turned off when the vehicle is stopped.
Together with the terminals, the output conditions of the logic circuit 7 are determined. 8
is an inverter provided in the output circuit of the comparator and forms part of the logic circuit described above.

Next, the operation of the glow plug temperature control device will be explained with reference to the waveform diagram in FIG. 2. To start the engine, turn key switch A as shown in Figure 2a.
When the OFF terminal is turned on to the GL terminal, timers _T1 and _T2 produce high level outputs for the set times _t1 and _t2 shown in FIG. 2c and d. While timer _T1 is outputting a high level, relay 6 closes contact 6a and operates the relay as shown in Figure 2g.
ON is activated, the relay closes contact a, large current is supplied to glow plug G, and glow plug G
As shown in Figure 2i, the temperature increases rapidly and reaches a temperature of 600°C or more and 1100°C or less, which is necessary for starting the engine. Even after the _time t has elapsed, the relay remains ON (closed) as shown in Figure _2h due to the action of timer T2.
The glow plug G maintains a high temperature after being heated by a current passed through the resistor 2. When the driver connects the key switch A to the ST terminal before or after the preheating completion indicator lamp (not shown) indicates that ₂ hours have elapsed, the time limit _t2 set by the timer _T2 starts at the second time limit.
The timer T2 is updated as shown in Figure d, and the timer _T2 outputs an output to turn on the relay again, and the glow plug is caused by the drop in power supply voltage (battery voltage) due to the energization of the starter motor and the vaporization of the injected fuel. The update of the output time limit of timer _T2 determines the time constant of timer _T2.The capacitor charge of the RC charging circuit is transferred to the starter/motor energization signal. This is done by discharging electricity. Gate circuit 4 uses inverter 5 to ground the input terminal of comparator 3 while the output of timer T ₁ is at high level to block the input of the voltage at point D, and when the output of timer T ₁ is at low level, the relay is open. Only when the voltage at the power supply side terminal D point of the glow plug G is input to the comparator 3, the comparator 3 inputs the second A high level output is produced as shown in Figure e. The logic circuit 7 receives the output of the terminal 18 of the vehicle speed sensor 14, the output of the timer _T2 , the output of the comparator 3 via the inverter 8, the output of the regulator L terminal 12 as shown in FIG. 2b, and the water temperature sensor 13. Input the output of terminal 16 of
Output as follows. The NOR circuit 10 inputs the energization signal to the starter motor and the output of the logic circuit 7, and determines when the starter motor is energized and the voltage applied to the glow plug G is the set voltage as shown in FIG. 2j.
Close the relay and perform afterglow until E becomes higher than ₀ .

FIG. 3 shows an example of a more detailed circuit of the glow plug temperature control device 1, in which R ₁ to R ₁₉ are resistors;
_D1 to _D8 are diodes, _C1 to _C3 are capacitors, _Q1
~ _Q4 is a transistor.

When the driver turns key switch A into the GL terminal, timer _T1 outputs a high level for _t1 hour, and resistor
Transistor Q ₁ is made conductive through R ₁ , thereby turning on relay 6 and the relay as described above, causing glow plug G to rapidly rise in temperature. Timer _T2 is
The charging voltage V ₁ of capacitor C ₁ is determined by the time constant of resistor R ₂ and capacitor C ₁ that make up the RC charging circuit.
increases over time and outputs a high level for t ₂ hours until V ₁ > V ₂ with respect to the reference voltage V ₂ determined by resistor R ₃ and resistor R ₄ , and then outputs a high level through resistor R ₇ to transistor Q _4. conducts. As a result, relay 11 and the relay are turned on and glow plug G is connected via resistor 2.
The glow plug temperature required for starting the engine is maintained.

Here, the output of timer _T2 is controlled by transistor _Q3 , the base of which is connected to terminal 16 of water temperature sensor switch ₁₃ , and water temperature sensor switch 13 is turned on when the engine coolant temperature is high. , which makes transistor _Q3 conductive and cuts off the base current to transistor _Q4 .

On the other hand, the circuit that makes the transistor _Q3 conductive from the resistor _R19 is connected to the regulator L by the diode _D7 .
Since the terminal 12 is grounded, no base current is supplied to the transistor _Q3 until the engine starts. As a result, the relay is controlled by the water temperature sensor switch 13 and the regulator L terminal, and in a high temperature range where afterglow is not required, the switch 13 is closed and the relay is operated only by the energization signal (cranking signal) to the starter motor.

When the key switch A is connected to the ST terminal, the charging voltage V ₁ of the capacitor C ₁ is transferred to the transistor Q ₂ via R ₁₀ .
The output time limit _t2 of timer _T2 is reset, and the energizing signal to the starter motor conducts transistor _Q4 through resistor _R11 , so the relay turns ON again and the resistor Continue energizing the glow plug G via 2.

When the engine starts, key switch A is returned from the ST terminal to the GL terminal by the driver, and the timer starts.
T ₂ starts charging again with the time constant of R ₂・C ₁ , and V ₁ > V ₂
Outputs high level for ₂ hours until t.

Around this time, the regulator L terminal 12 changes to high level, so the glow plug G terminal voltage E
Power is supplied to comparator 3 through resistor R ₁₇ and resistor R ₁₈ to detect afterglow. The water temperature sensor switch 13 and vehicle speed sensor switch 14 also control afterglow in the same way.

When the water temperature sensor switch 13 and the vehicle speed sensor switch 14 are in the afterglow state, the power supply voltage increases due to power generation by the generator as the engine speed increases, and the terminal voltage E of the glow plug G increases accordingly. The capacitor charging voltage of the RC charging circuit consisting of capacitor C ₂ and resistor R ₁₂ is
When the relationship between V ₃ and the reference voltage V ₄ determined by the resistor R ₁₆ becomes V ₃ > V ₄ , the comparator 3 produces a high level output, and the transistor Q ₃ is output via the resistor R ₁₉ .
The base current of transistor _Q4 is grounded by transistor _Q3 , and the relay is connected.
Turn it OFF and stop energizing glow plug G.
At this time, comparator 3 is provided with positive feedback by diode _D6 , and once the output turns to high level, the capacitor charging voltage _V3 becomes almost the power supply voltage, so _V3 > _V4 is maintained and the input voltage is This state persists even if removed. On the other hand, glow plug G
When the terminal voltage E of is high (approximately the power supply voltage) when the relay is ON, the input terminal of comparator 3 is grounded by diode D ₅ and transistor Q ₁ , so V ₃ < V ₄ and the relay is ON. This prevents false detections at times. The voltage detection circuit of the glow plug G may be configured as shown in FIGS. 4 and 5. In this way, by grounding the input terminal of the comparator 3 for detecting the voltage of the glow plug G while the relay is energized (ON), the terminal voltage E of the glow plug G can be increased only when the relay is operating.
can be detected.

In addition, by configuring an AND circuit with a signal such as the regulator L terminal 12, water temperature sensor switch 13, vehicle speed sensor switch 14, etc. and the output of the comparator 3 to control the afterglow, the relays can be controlled only during the afterglow after the engine starts. You can do it like this.

As described above, the glow plug temperature control device of the invention includes a timer T1 that outputs an output for ₁ hour after the start of energization to the glow plug and turns on the relay, a timer _T2 that turns on the relay for a predetermined period of time, and a timer _T2 that turns on the relay for a predetermined time. A detection circuit that detects the voltage applied to the glow plug, generates an output when the applied voltage becomes a set value, and holds that output thereafter; and a detection circuit that detects that the voltage applied to the glow plug is input to the detection circuit while the relay is operating. The relay is equipped with a gate circuit to prevent the relay from energizing when the voltage applied to the glow plug during afterglow exceeds a set value, so the voltage applied to the glow plug during afterglow can be measured. By stopping energization to the glow plug when the applied voltage rises above a set value, failure of the glow plug can be prevented.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a diesel engine starting assist device using the glow plug temperature control device of the present invention, Fig. 2 is a waveform diagram for explaining its operation, and Fig. 3 is the temperature control device of the glow plug of the present invention. The circuit diagrams of the control device, FIG. 4 and FIG. 5 are partial diagrams of the circuit diagrams of other embodiments, respectively. In the figure, 1...Glow plug temperature control device, 2
... Current limiting resistor, 3... Comparator for glow plug terminal voltage detection, 4... Gate circuit, 7
...Logic circuit, 9...AND circuit, 10...NOR circuit, 6, 11,,...Relay, 12...Regulator L terminal, 13...Water temperature sensor switch, 14...Vehicle speed sensor switch, A... Key switch, G...Rapid heating type glow plug.

Claims (1)

[Claims] 1. A plurality of glow plugs for rapid temperature increase connected in parallel, a first timer that operates for a first set time by operating a key switch, and starts operating together with the first timer, a second timer that operates for a second set time longer than the first set time, and whose operation start is updated by operating the key switch to the starter motor energization position; a first relay circuit that directly energizes the glow plug during operation; and a first relay circuit that energizes the glow plug directly through a current limiting resistor when the key switch is in the starter motor energization position or when the second timer is activated. a second relay circuit that energizes the plug; a logic circuit that sets conditions for afterglow by the second relay circuit; and a logic circuit that detects the voltage applied to the glow plug when the first timer is not operating. Afterglow is performed based on the applied voltage detection circuit and the logic circuit,
and a glow plug temperature control device comprising: an energization stop circuit that stops energization of the glow plug by the second relay circuit when the applied voltage detected by the applied voltage detection circuit exceeds a predetermined voltage. .