JPS6324153B2 - - Google Patents

Description

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

A energizing relay for rapid temperature increase that supplies a large current to the glow plug, a energizing relay for temperature maintenance that energizes the glow plug via a current limiting resistor, a timer _T1 that controls the relay, and a timer T1 that controls the relay. The glow plug is equipped with a timer T ₂ , and after the start of energization, a relay supplies a large current to the glow plug for a certain period of time, and after the specified period of time, electricity is applied via the relay to maintain the glow plug at a specified temperature for a certain period of time. As a starting aid for diesel engines, a system has been proposed that simulates and controls the temperature rise characteristics of a glow plug, the charging characteristics, cooling characteristics, and discharge characteristics of a timer by controlling the charging and discharging currents (in particular, 16361),
In addition to complicating the circuit, the cooling characteristics of the glow plug may differ between immediately after the engine starts and when it has been sufficiently warmed up, so the former condition is assumed to simulate the cooling characteristics and discharge characteristics. If the glow plug is sufficiently warmed up, the temperature of the glow plug will drop slowly and there is a risk of burning out the glow when the power is turned on again.In the latter case, if these are synchronized,
When I tried to restart the engine after making a startup error, the temperature of the glow plug was low, impairing starting performance.

In view of the above problems, an object of the present invention is to substantially synchronize the heating characteristics and the cooling characteristics using a simple method, thereby making it possible to start the engine reliably and improve the reliability of the glow plug. An object of the present invention is to provide a method for controlling energization of a glow plug.

In order to achieve the above object, the present invention includes a rapid temperature increase current relay that supplies a large current to the glow plug, a temperature maintenance current relay that conducts current to the glow plug via a current limiting resistor, and a key switch. The relay is charged when the key switch is ON and discharged when the key switch is _OFF . The RC charging/discharging circuit starts operating together with the timer _T1 so that the charging voltage of the RC charging/discharging circuit reaches _a predetermined voltage for a period longer than the set time limit of the timer _T1 . A timer _T2 operates for a set time period _t2 to control the relay, and during the operation time period of the timer _T2 , the charging voltage of the RC charging/discharging circuit of the timer _T1 is controlled by the timer T2.
a clamp circuit that limits the voltage to a constant voltage that is higher than the reference voltage of T ₁ and sufficiently lower than the voltage applied to the timer T ₁ ; and a clamp circuit that limits the voltage applied to the timer T ₂ while the starter motor is energized.
The timer discharges the charging voltage of the RC charging/discharging circuit.
T ₂ is configured to consist of a discharge circuit that operates when the starter motor is energized and for a set time period t ₂ after energization, and the clamp circuit is connected to the timer
By limiting the charging voltage _of the RC charging/discharging circuit of the timer _T1 to a constant voltage during the operation of the timer _T2 , the glow The set time limit t ₁ of the timer T ₁ when the plug is reenergized is
It is characterized in that it is set according to the time until the power is re-energized.

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

Fig. 1 shows the starting assist device for a diesel engine, where A is the engine key switch, B is the battery, and G is a rapid heating temperature rise type glow plug installed in the auxiliary combustion chamber. is a rapid temperature increase relay for supplying a large current in order to rapidly increase the temperature of the glow plug G, and a current limiting resistor 2 for the purpose of maintaining the temperature after the glow plug G has risen to a predetermined temperature. It consists of a temperature maintenance energizing relay for passing a limited current through the RC charging/discharging circuit for determining the time constant, a voltage dividing circuit for setting the reference voltage, and a comparator, and controls the relay. timer T ₁ and
a timer T ₂ that controls the relay; a clamp circuit 3 that limits the charge of the charging circuit of the timer T ₁ to a predetermined value during the output time t ₂ of the timer T ₂ ; and a clamp circuit 3 that controls the timer T ₂ ; A relay 31 connects the relay and battery B when the timer _T1 generates a high-level output in order to control the relay, and a relay ₃₁ connects the relay and battery B when the timer _T1 outputs a high-level output. The relay 33 connects the relay and the battery B when the output is generated.

As shown in Fig. 3 A (solid line), the driver turns the engine key switch A from OFF to ON to start energizing the glow plugs and the energization control device, and after a while, turns on ST and starts the starter motor. When the drive operation is performed, the temperature T of the glow plug G changes rapidly, as shown in Figure 3, as the relay closes the contact Ia and a large current flows during the set time _t1 of the timer _T1 . The temperature rises to T ₀ , and after that,
The output of timer _T2 causes the relay to close contact a and conduct electricity through current limiting resistor 2, thereby maintaining the temperature at approximately _T0 . The clamp circuit 3 is
While timer T ₂ is outputting, the charge of the RC charging circuit of timer T ₁ is set to a value slightly higher than the reference voltage, but sufficiently lower than the applied voltage, for example, approximately 1/2 of the applied voltage. Restrict.

If you are unable to start the engine by driving the starter motor and you turn the key switch OFF and then turn it ON again after a short period of time, the glow plug temperature will increase as the key switch turns OFF. The temperature decreases according to the cooling characteristics that depend on the degree of warm-up of the engine, but usually the temperature decreases quickly because the degree of warm-up is poor. On the other hand, when the key switch is turned off, the capacitor C discharges at an appropriately selected fixed time constant, but since the charging voltage is clamped to a voltage sufficiently lower than the applied voltage by the clamp circuit, the capacitor discharges quickly. When the key switch is turned on again for restarting, timer _T1 generates an ON output for a sufficient period of time to continue supplying a large current to the glow plug, covering the possibility that starting performance will be impaired. do. Once the engine has started, timer T ₂ will generate an OFF output after a sufficient period of time, turning off the relay and no longer energizing the glow plug. Since it is released, the charging voltage is charged up to the applied voltage V _Z as shown in FIG. 3B, in preparation for the next key switch OFF. After the engine has been operated and warmed up sufficiently, the key switch is turned off, but when the engine happens to be started again a short time later, a sufficiently high voltage has already been applied to capacitor C. Even with discharge, it takes time for the voltage to drop below the set voltage of timer T ₁ , and when the engine has been sufficiently warmed up, the supply of large current to the glow plug becomes excessive, causing the glow plug to close. Adjustments should be made to prevent overheating accidents or loss of durability.

FIG. 2 shows another embodiment of the glow plug energization control device.

The timer T ₁ includes a comparator 4, a charging resistor R ₁ or a discharging resistor R ₁ + R ₁₄ , and a capacitor C ₁ connected in series, and an RC charging/discharging circuit 5 that determines the time constant of the timer, and a reference voltage setting. It consists of a voltage dividing circuit 6 in which a resistor R ₂ and a resistor R ₃ are connected in series. _D1 is a diode that performs a switching action between a charging resistor and a discharging resistor. The timer _T2 consists of a comparator 14, a resistor R11, and a capacitor _C11 connected in series, and an RC charging circuit 15 that determines the time constant of the timer, and a resistor _R12 and a resistor _R13 for setting a reference voltage connected in series. It consists of a connected voltage dividing circuit 16. Clamp circuit 3
is a diode D ₄ in parallel with the capacitor C ₁ ,
A transistor Q ₁ and a resistor R ₄ are connected in series, and a reference voltage or a voltage slightly higher than the reference voltage is applied to the base of the transistor Q ₁ via a diode D ₃ , and the base and the output terminal of the timer T ₂ are connected through a diode. Become connected via _D2 . 10 is an AND circuit that inputs the timer T ₂ and a water temperature detection signal; 11 is a NOR circuit that inputs the output of the AND circuit 10 and an energization signal to the starter motor; 12 is an energization signal for the starter motor This is a discharging circuit that instantly discharges the charging capacitor _C11 of the timer _T2 while the timer T2 is occurring. 13 is a water temperature sensor for detecting the engine cooling water temperature, and 17 is a starter motor operation timing display device such as an indicator lamp controlled by the state of charge of the capacitor _C1 .

Next, the operation of the diesel engine starting assist device shown in FIG. 2 will be explained in more detail with reference to the graph shown in FIG. 3.

As shown in Figure 3A, when the driver turns on the key switch A to start the engine, the capacitor C ₁ begins to be charged via the diode D ₁ and the resistor R ₁ , and the terminal voltage V ₁ of the capacitor C ₁ increases. , 3rd
As shown in Figure B, the timer T ₁ is activated during the set time period t ₁ until the reference voltage V ₄ determined by the resistors R ₂ and R ₃ is reached.
As shown in FIG. 3C, the relay is energized to close contact a and rapidly heat the glow plug G. As a result, the temperature T of the glow plug G rapidly rises as shown in Figure 3, and after ₁ hour, which is the output time limit of the timer _T1 , the temperature T of the glow plug G reaches T ₀ ℃ (600℃), which is sufficient for a smooth engine start.
~900℃). As shown in FIG. 3D, the timer _T2 starts charging the capacitor _C11 via the resistor _R11 at the same time as the key switch A is turned ON, and at least the terminal voltage _V2 of the capacitor _C11 is set to the reference voltage. During the time period t ₂ until V ₅ is reached, the relay is energized and the glow plug G is energized via the resistor 2. This set time limit _t2 is the set time limit of timer _T1 .
_t1 , and after the relay is turned off, the glow plug temperature T is raised as shown in FIG. 3, and then maintained at approximately the temperature _T0 . In addition, if the starter motor is energized before or after the set time _t2 has elapsed, the energization signal continues to turn on the relay as shown in Figure 3 E, and the ST signal continues to turn on the discharge circuit. Capacitor C ₁₁ through 12
The charge is discharged, and charging starts at the same time as the energization signal to the starter motor stops, and from that point on, timer T ₂ turns on the relay for a predetermined time t ₂ and energizes glow plug G via resistor 2. will be done.

The clamp circuit 3 increases the base potential of the transistor Q ₁ to make the transistor Q ₁ conductive during the output time period when the output of the timer T ₂ is at a high level;
Limit the charge on capacitor _C1 to a constant value.

After seeing the indicator lamp on the display device 17 go out, the driver turns on power to the starter motor using key switch A.
I performed ST ₁ and tried to start the engine, but it failed, and when I returned key switch A to the OFF position,
The glow plug G is cooled and its temperature begins to drop, and correspondingly, the charge in the capacitor C ₁ is also discharged via R ₁ and R ₁₄ . The driver presses key switch A again.
When turned ON, the timer _T1 produces a high level output, but its output time limit _t1 is extended in response to the discharge of the capacitor _C1 , and the glow plug G becomes ToC again.
Since the temperature is reliably raised to 100, and the time for supplying large current by the relay is appropriately adjusted, insufficient temperature rise is prevented. The engine is then started by reenergizing the starter motor ST ₂ . However, timer T ₂
After the output time period has elapsed, the output of timer _T2 is at a low level, the base potential of transistor _Q1 is low, and conduction of transistor _Q1 is stopped, and clamp circuit 3 limits the terminal voltage _V1 of capacitor _C1 . Therefore, the charge on capacitor C ₁ approaches saturation, and V ₁ approaches V _X. In other words, if the time when the driver turns off the key switch A is after the time limit set by the timer _T2 has elapsed, the relay energization time by the timer _T1 when the key switch is turned on again after a short period of time is due to the high charging of the capacitor _C1 . It is adjusted according to the pressure. This is because the engine is often sufficiently warmed up when the output of timer T ₂ is turned off, and the glow plug cooling characteristics after the key switch is turned off are different.
This limits the relay activation time when the power is reenergized a short time after being turned off, thereby preventing damage from overheating of the glow plug. Note that here the applied voltage V _Z
was about 1/2 volt of the nominal power supply voltage, and the discharge time constant was about 20 seconds.

FIG. 4 shows yet another embodiment of the invention.

In this embodiment, the reference voltage setting circuit 6 of timer _T1
A conversion circuit 30 is provided to switch the value of the reference voltage when a predetermined input is received, so that the set time limit of the timer _T1 can be extended.

The conversion circuit 30 includes an energization signal to the starter motor, an output signal from the water temperature sensor 13, and a timer _T1.
AND circuit 9 whose input is the output signal of
A series circuit of a diode _{D 30 and} a resistor R ₄ is connected in parallel with R 3 , and the AND circuit 9 is connected to the intermediate point a between the diode D ₃₀ and the resistor R ₄ via a diode D ₅ .
and a resistance value switching circuit 30 to apply an output voltage of _V8 to the reference voltage.
Switch V ₄ .

In this embodiment, when the cooling water temperature is below a predetermined temperature, within the set time period _t1 of the timer _T1 ,
As shown by the dashed line in Figure 3A, the driver operates key switch A as the energizing contact for the starter motor.
When connected to ST, AND circuit 9 produces a high level output. As a result, the voltage V ₈ at point a increases, the reference voltage V ₄ is disconnected from the resistor R ₄ , and V ₄ ≒ as shown by the dashed line in FIG.
From R ₃・R ₄・V _Z +R ₂・R ₃・V ₃ /R ₂・R ₃ +R ₃・R ₄ +R ₂・R ₄
V _4S ≒R ₃ · V _Z /R ₂ +R ₃ increases, and timer T ₁ energizes the relay for a set time period t _{' 1} which is longer than the set time period t ₁ as shown by the dashed line in FIG. , the glow plug G is supplied with a large current for t' ₁ hour. This compensates for the drop in battery voltage due to the operation of the starter motor and the drop in glow plug temperature due to the injection of firing material, and adjusts the glow plug temperature to rise approximately to the expected value T ₀ °C. Note that when the cooling water temperature is higher than the predetermined temperature or when energization to the starter motor is started after the time limit _t1 set by timer _T1 has elapsed, it is generally not necessary to extend the time limit set by timer _T1 . Therefore, the conversion circuit 30 does not extend the set time limit of the timer _T1 . However, depending on the characteristics of the engine, the change in the reference voltage of the timer _T1 , that is, the switching in the resistance value switching circuit 30, may always be performed by the activation signal of the starter motor even after the time limit of the timer _T1 has elapsed. Specifically, in the embodiment shown in FIG. 4, the inputs of the AND circuit 9 of the resistance switching circuit 30 are the starter motor operation signal, the water temperature signal, and the output signal of the timer _T1 . It may also be useful to have only the motor actuation signal, which is a scheme within the scope of the present invention.

As described above, the present invention uses a clamp circuit to clamp the charging voltage in the RC charging/discharging circuit of timer _T1 to a constant voltage that is higher than the reference voltage and sufficiently lower than the applied voltage only for an appropriate time. A simple method that prevents the glow plug from overheating when restarting immediately after a failed start or when restarting the engine after it has stopped, improving the reliability of the glow plug and improving engine startability. It has a great practical effect of improving the

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a starting assist device for a diesel engine according to the present invention, and FIG. 2 is a circuit diagram of another embodiment.
3A to 3F are graphs for explaining the operation of the circuit diagram, and FIG. 4 is a circuit diagram of still another embodiment. T ₁ , T ₂ ...Timer, ...Relay, 3...
...clamp circuit.

Claims (1)

[Scope of Claims] 1. A energizing relay for rapid temperature rise that supplies a large current to the glow plug, a energizing relay for temperature maintenance that energizes the glow plug via a current limiting resistor, and a energizing relay that is charged when the key switch is turned on. a timer T that is equipped with an RC charging/discharging circuit for discharging when the key switch is OFF and determining a time constant, and operating for a set time period _t1 until the charging voltage of the RC charging/discharging circuit reaches the reference voltage to control the relay; ₁ , the timer is equipped with an RC charging/discharging circuit to determine the time constant.
a timer T ₂ that starts operating at the same time as timer T ₁ and operates for a set time t ₂ longer than the set time of the timer T 1 until the charging voltage of the RC charging/discharging circuit reaches a predetermined voltage, and controls the _relay ; During the operation time of timer _T2 , the charging voltage of the RC charging/discharging circuit of the timer _T1 is set higher than the reference voltage of the timer _T1 .
A clamp circuit that limits the voltage applied to T ₁ to a constant voltage sufficiently lower than the voltage applied to T 1 and a clamp circuit that discharges the charging voltage of the RC charging/discharging circuit of the timer T ₂ while the starter motor is energized, and the timer T ₂ is connected to the starter motor. It consists of a discharging circuit that operates for a set time period _t2 during energization and after energization ends, and the clamp circuit limits the charging voltage of the RC charging/discharging circuit of the timer _T1 to a constant voltage while the timer _T2 is operating. By doing so, the set time limit _t1 of the timer _T1 when the glow plug is re-energized after the operation of the timer _T2 is completed and the power supply to the glow plug is stopped is changed to A diesel engine starting assist device characterized by setting according to the time until energization. 2. The timer _T1 is provided with a set time limit converting circuit that changes and lengthens the set time limit _t1 , and the set time limit converting circuit is activated when an energization signal to the starter motor is input. Range 1
Diesel engine starting aid as described in Section 1.