JPH0160675B2 - - 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.

A starting aid device using a rapid heating type glow plug includes a rapid temperature increase energizing relay that supplies a large current to the glow plug, and a temperature maintenance energizing relay that energizes the glow plug via a current limiting resistor. , a timer _T1 that controls the relay, a circuit that controls the relay, and a circuit that prevents the temperature of the glow plug from decreasing due to a drop in power supply voltage and the cooling effect of the injected fuel when the starter motor is energized by the driver. After the start of energization, a relay supplies a large current to the glow plug for preheating, and after the lapse of the certain period of time, the glow plug is energized via the relay for a predetermined period of time sufficient to start the engine. The temperature of the glow plug is controlled by a temperature control device for maintaining the glow plug at a predetermined temperature so that the engine can be started most smoothly. However, the inventor found that when performing so-called actor glow, in which the glow plug is kept at a high temperature for a certain period of time immediately after starting the engine to ensure smooth engine rotation immediately after starting, the generator generates electricity as the engine speed increases. It has been 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 rapid temperature increase relay for supplying a large current for the purpose of rapidly increasing the temperature of the glow plug G for preheating, and a current limiting resistor 2 for the purpose of substantially maintaining the glow plug G at a predetermined temperature after preheating. A temperature maintenance energizing relay for passing a limited current through the GL terminal, and a timer T1 that turns on the relay for ₁ hour, which is set in advance after switch A is turned on to the GL terminal by the _driver . , while switch A is connected to the ST terminal by the driver and the starter motor is energized, and timer T ₁ is not outputting an ON output (or while the starter motor is simply energized). A pulse generator that outputs pulses and controls the opening and closing of the relay at regular intervals.
T ₂ is an applied voltage detection circuit of the glow plug G that inputs the voltage at the power supply side terminal D point of the glow plug G, and produces an output when the applied voltage E to the glow plug G exceeds a set value. Furthermore, a comparator 3 has a self-holding function so that once an output is generated, the state is maintained even if the input disappears, and a relay is provided to input the applied voltage E to the comparator 3 only when the relay is OFF. Gate circuit 4 that uses the ON signal as a prohibition signal
, a NOR circuit (or OR circuit) 5 that inputs the output of the timer _T1 and the output of the pulse generator _T2 , a relay 6 that closes the contact 6a with the output of the NOR circuit 5, and energizes the relay; A logic circuit 7 that determines afterglow conditions after starting, an inverter 8 provided in the output circuit of the comparator 3, and a NOR circuit (or OR circuit) that inputs the output of the inverter 8 and an energization signal to the starter motor. 10
and closes the contact 11a with the output of the NOR circuit 10,
A relay 11 that turns on the relay, and an AND circuit (or the NOR circuit 10 and The NOR circuit 10 is interposed between the relays 11 and
and the output of the inverter 8 as inputs. Reference numeral 12 denotes a charging/discharging indicator lamp terminal (hereinafter referred to as L terminal) of the regulator, which generates a high level output to turn off the lamp while charging the battery, and generates a low level output to turn on the lamp while discharging. Switches 13 and 14 are opened and closed by a water temperature sensor and a vehicle speed sensor, and serve as output condition factors for the logic circuit 7 together with the regulator L terminal.

Next, the operation of the glow plug temperature control device of the above embodiment will be explained with reference to the waveform diagram of FIG. 2. When the driver turns the key switch A from the OFF terminal to the GL terminal to start the engine as shown in FIG. 2a, the timer _T1 produces a high level output for the set time t1 shown in FIG. _2b . While the timer T ₁ is outputting a high level, the output of the NOR circuit 5 (Fig. 2 e) causes the relay 6 to close the contact 6 a and turn on the relay as shown in Fig. 2 i. A large current is supplied to the plug G, and the glow plug G rapidly rises in temperature as shown in FIG. When the driver connects key switch A to the ST terminal (usually after ₁ hour has elapsed) as indicated by the preheating completion indicator lamp (not shown),
The pulse generator _T2 outputs the pulses shown in Fig. 2c to open and close the relay 6 at regular intervals, thereby starting the starter.
The temperature of the glow plug G is maintained within the temperature range required for starting by preventing a drop in power supply voltage (mainly battery voltage) due to energization of the motor and a drop in temperature of the glow plug due to vaporization of the injected fuel. NOR circuit 5 inputs the output of timer _T1 and the output of timer _T2 , and
produces the output shown in Figure e. The gate circuit 4 operates when the output of the NOR circuit 5 is at high level, that is, when the timer
When the output of T ₁ is low level and the output of pulse generator T ₂ is also low level, and the relay is open, the voltage at point D of the power supply side terminal of the glow plug is transmitted to the comparator 3, and the comparator 3 When the voltage E (voltage at point D) applied to the glow plug is greater than the set value E ₀ as shown in FIG. 2l, a high level output is produced as shown in FIG. 2f. When the logic circuit 7 generates a high level output as shown in FIG. 2g when the L terminal is open as shown in FIG. 2d and the afterglow condition (described later) is satisfied, and the inverter 8 When the output of the comparator 8 is at a high level (normal), the AND circuit 9 outputs a high level as shown in FIG. is input, even after the starter motor is energized, the voltage applied to the glow plug G remains at the set voltage as shown in Figure 2 l.
Until E becomes higher than ₀ , the relay is kept closed as shown in Fig. 2j to produce afterglow. The relay is operated by providing a gate circuit 4 that uses the output of the NOR circuit 5 (Fig. 2 e) as a gate signal.
The reason why comparator 3 measures the voltage at point D when the relay is OFF is because the voltage at point D when the relay is ON is usually higher than the set voltage _E0 , as shown in Figure 2j. This is to prevent the comparator from operating with an input other than the voltage at point D during afterglow, and the logic circuit 7
When the regulator L terminal is open and the engine cooling water temperature is at the set value (for example, below 50°C), the water temperature switch 13 is closed, and when the vehicle is stationary, the vehicle speed switch 13 is closed.
4 is open as a necessary condition for performing afterglow, and when all these conditions are met, a high level output is generated. The value of the set voltage E ₀ is, for example, rated voltage 12V, up to 900℃ 6
For quick heating type glow plugs, set the voltage to about 6V.

FIG. 3 shows an example of a more detailed circuit of the temperature control device 1 of the embodiment shown in FIG. 1, and P is a comparator;
_R1 to _R18 are resistors, _D1 to _D8 are diodes, _C1 to _C3
is a capacitor, and Q ₁ to Q ₄ are transistors.
When the key switch is connected to the GL terminal, the timer _T1 generates a high-level output as described above, conducts the transistor _Q1 of the NOR circuit 5 through the resistor R1, activates the relay ₆ , turns on the relay, and closes the glow plug. A large current is supplied to G to perform preheating.
The output of the timer _T1 is input to the comparator P of the pulse generator _T2 via the resistor _R7 , and while the timer _T1 is producing a high level output, the input voltage _V2 and the capacitor _C1 are connected to the comparator P of the pulse generator T2. The relationship with the voltage V ₁ determined according to the charging load is V ₁ <V ₂ , and the output of the comparator P is charged to the charging capacitor C ₁ via the diode D ₃ and the resistor R ₈ . After time _t1 has elapsed, the resistor _R7 is grounded in the output circuit of the timer _T1 , so _V1 > _V2 , and the pulse generator _T2 produces a low level output. When the key switch A is connected to the ST terminal in this state, the base voltage supplied through the resistor _R3 makes the transistor _Q2 conductive, and the charge in the capacitor _C1 is discharged through the resistor _R5 . The voltage V ₁ determined corresponding to the charge load of the capacitor C ₁ is
When the input voltage is lower than V ₂ , the pulse generator
T ₂ inverts the output to high level, diode D ₃
The capacitor C ₁ is charged by the resistor R ₈ through the capacitor C 1 and the voltage V ₁ is gradually increased. When V ₁ > V ₂ , the output of the pulse generator T ₂ is inverted to low level again, and the charged load of the capacitor C ₁ is Discharge occurs via transistor Q ₂ and resistor R ₅ until V ₁ <V ₂ . This operation is repeated while the energization signal to the starter motor is input from terminal A. Therefore, the OFF time of the relay is determined by the capacitor _C1 and the resistor _R5 , and the ON time of the relay is determined by the resistor _R8 and the capacitor _C1 . When the engine reaches a complete explosion state and normal deflagration begins, key switch A is turned on again.
The signal is returned to the GL terminal, and since the pulse generator _T2 loses the energizing signal to the starter motor, its low level output is maintained, and the relay continues to be in the OFF state. Further, the energization signal to the starter motor is supplied to the base of the transistor _Q4 of the NOR circuit 10 through the resistor _R18 , and the transistor _Q4 is made conductive and operates the relay 11, so the relay is turned on.
The glow plug G is energized via a contact a and a resistor 2. The comparator 3 that detects the terminal voltage E of the glow plug G is divided by the resistors _R1 and _R12 from the glow plug terminal, and receives the input voltage of the terminal voltage E via _R13 , and connects the connection point of the above two resistors. Ground with capacitor C ₃ . Furthermore, the above input voltage is passed through a diode _D6 so that the comparator 3 does not detect the terminal voltage E while the relay is operating.
Connected to the output of relay driving transistor _Q1 . By doing this, when the relay is turned on and the glow plug terminal voltage E increases,
The charging voltage of the capacitor C ₃ is immediately grounded through the diode D ₆ and the transistor Q ₁ to inhibit the terminal voltage, so that the input voltage V ₃ and the reference voltage V ₄ are
When _{the relationship} with
Configure a circuit to compare. In addition, the driving power source for the relay is the regulator L terminal 12 and the switch 13.
Since the switch 14 constitutes and supplies the AND circuit, the relay is driven by the regulator L terminal 12.
is at a high level, the water temperature switch 13 is ON, the vehicle speed switch 14 is OFF, and the comparator ₃ is at a low level.
Conducts Q ₄ .

For example, when the regulator L terminal is at a low level, power cannot be supplied to the transistor Q ₃ , so the transistor Q ₄ cannot be driven through the resistor R ₁₇ regardless of the output of the comparator 3.
Therefore, when the regulator L terminal 12 is at a high level, the switch 13 is ON, and the switch 14 is OFF, power is supplied to the output of the transistor _Q3 , so the relay is controlled by the output of the comparator 3. However, if either switch 13 or switch 14 reverses its state, power will no longer be supplied to transistor Q ₃ and transistor Q ₄ will no longer be able to be driven, so the relay will be turned off and power to glow plug G will be stopped. do. When V ₃ > V ₄ and the output changes to high level, this comparator 3 provides positive feedback to the input of the comparator 3 via the diode D ₇ , and V ₃ becomes almost the power supply voltage due to the action of the resistor R ₁₃ . This state is maintained even if the input voltage is removed. In this way, glow plug G
While the relay is ON, the glow plug terminal voltage E can be detected and accurately determined only when the voltage detection terminal D is grounded and the relay is operating.
In addition, by configuring an AND circuit with the regulator L terminal 12, switch 13, switch 11, etc., and the signal to control the afterglow and the output of the comparator 3, the relay can be controlled only during the afterglow after the engine has started. can.

As described above, the glow plug temperature control device of the present invention includes a detection circuit that detects the voltage applied to the glow plug, generates an output when the applied voltage reaches a set value, and holds the output after the output is generated. and a gate circuit provided between the detection circuit and the glow plug terminal to prevent the voltage applied to the glow plug from inputting to the detection circuit while the relay is in operation, the output of the detection circuit being low. In both cases, the energization by the relay during afterglow is forcibly turned off, so the voltage applied to the glow plug during afterglow is measured, and when the applied voltage rises above the set value, the energization to the glow plug is stopped. This can prevent the above glow plug from malfunctioning.

[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 a diagram of the glow plug temperature control device of the present invention. It is a circuit diagram of a temperature control device. In the figure, 2... Resistor for current limiting, 3... Comparator for detecting terminal voltage of glow plug, 4... Gate circuit, 5... NOR circuit, 7... Logic circuit, 9...
AND circuit, 10...NOR circuit, 12...Regulator L terminal, 13...Water temperature switch, 14...
Vehicle speed switch, , 6, 11...Relay, A
...Key switch, G...Rapid heating type glow plug.

Claims (1)

[Claims] 1. A rapid heating type glow plug, a relay for supplying a large current to the glow plug, a relay for supplying current to the glow plug via a current limiting resistor, a relay, and a relay. In a glow plug temperature control device, the control circuit detects a voltage applied to the glow plug, generates an output when the applied voltage reaches a set value, and generates an output after the output is generated. comprising a detection circuit that holds the output, and a gate circuit that is provided between the detection circuit and the glow plug terminal and prevents the voltage applied to the glow plug from inputting to the detection circuit while the relay is in operation; A temperature control device for a glow plug, characterized in that the output of the detection circuit forcibly turns off energization via a relay at least during afterglow. 2. A rapid heating type glow plug, a relay for supplying a large current to the glow plug, a relay for energizing the glow plug via a current limiting resistor, and a control circuit for controlling the relay and the relay. In the glow plug temperature control device, the control circuit includes a timer T1 that outputs an output for t ₁ hour set after the start of energization to the glow plug and turns on the relay, and a timer T ₁ that outputs an output for a set t ₁ hour after the start of energization to the glow plug and turns on the relay. The pulse generator T ₂ outputs a constant pulse to open and close the relay at a constant cycle while the motor is energized or simply the starter motor is energized, and the voltage applied to the glow plug is detected. When the applied voltage reaches the set value, the relay is activated.
A detection circuit that generates an output to turn OFF and holds the output after the output is generated, and a relay provided between the detection circuit and the glow plug terminal that applies power supply voltage to the glow plug to the detection circuit while the relay is operating. It includes a gate circuit that prevents the input from being input, and a logic circuit that sets an afterglow condition, and the output of the afterglow implementation of the logic circuit and the output of the detection circuit are input to an AND circuit, and the The relay is turned ON by the output of an OR circuit or NOR circuit which inputs the output of the circuit and the energization signal to the starter motor, and the afterglow is stopped when the voltage applied to the glow plug exceeds the set value. Features a glow plug temperature control device. 3. The logic circuit inputs the output of the regulator L terminal, and when the output of the regulator L terminal is at a high level, one of the output generation conditions for performing afterglow is set.
A temperature control device for a glow plug according to claim 2, characterized in that: 4 The logic circuit inputs the engine coolant temperature,
4. The temperature control device for a glow plug according to claim 2, wherein when the temperature is equal to or lower than a set value, one of the conditions for generating an output for performing afterglow is the temperature control device for a glow plug according to claim 2 or 3.