JPS5870061A - Device for controlling preheating of glow plug - Google Patents

Abstract

PURPOSE:To obtain a device for controlling the preheating of the glow plug with low cost and has a high reliability by carrying out prevention of overheating of the glow plug which occurs when the engine is restarted after the engine stops until the glow plug is sufficiently cooled. CONSTITUTION:The device 1 for controlling the preheating of the glow plug carries out control of supply of a heating current supplied from the battery 3 to glow plugs 41, 42...4n, and controls the glow plugs 41...4n so that these plugs are preheated to a desired temperature. That is, in a case where the key switch 2 is in an ON position, and a switch 6 which carries out the control of the supply of a current flowing to the glow plugs 41...4n is in an OFF state, a predetermined constant voltage is applied to a capacitor 37 of a circuit supplying a charging voltage corresponding to the temperature variation characteristic, thereby the preheating control is carried out and a complicated preheating inhibiting circuit becomes unnecessary.

Description

[Detailed description of the invention] It is.

As a preheating control device for glow plugs, the temperature of the glow plug is obtained by applying the voltage of the heating power source to a charging/discharging circuit consisting of a constant base voltage, a resistor, and a capacitor made by a Zener diode, etc. Compare it with the detected voltage using a comparator.

Conventionally, devices have been used that are configured to control the energization of the glow plug in accordance with the results of this comparison.

In this conventional device, the key switch is turned on. If left unattended, the glow plug will overheat, shorten the life of the glow plug, and waste electricity.
To prevent this, a preheating prevention circuit is provided that cuts off the power to the glow plug after a predetermined time has elapsed after the key switch is turned on, regardless of the output of the comparator, but a timer etc. is required. It also has the problems of increasing the number of parts, increasing the price, and decreasing reliability.Furthermore, conventional ATs have problems such as glow plugs due to the engine's sintering heat while the engine is operating. Since the temperature of the engine is rising, the power source is taken from the charge lamp terminal of the generator attached to the engine, and a predetermined voltage is applied to the capacitor to temporarily stop the engine while it is running and restart it immediately. This prevents the glow plug from overheating when the power source is used.However, since the power source is connected to the charge lamp terminal of the generator, a conductor is required for each water, which leads to another problem: a decrease in reliability. It also has

Therefore, an object of the present invention is to prevent overheating of the glow plug using a simple circuit when restarting the engine after stopping the engine until the glow plug has sufficiently cooled down, without using the conventional complicated preheating prevention circuit. I/C's objective is to provide an inexpensive and highly reliable glove preheating control device.

The present invention will now be described in detail in accordance with the illustrated embodiments.

, A1 shows the glow plug preheating side (2
) A circuit diagram of an embodiment of the device is shown. This glow plug preheating control device 1 is configured such that when a key switch 2 is switched to the ON position or the ST position, the glow plug 4. This is a device for controlling the heating current supplied to the glow/lags 41, . . . 4n so that these glow/lags 41, . One end of each glow plug 43.4n is commonly connected to the negative electrode of the battery 3 and grounded, and each other end is connected to the positive electrode of the battery 3 via a switch 6 that is opened and closed by a relay coil 5. The contact point 2a of the key switch 2 in the ON position is connected to the 1st conductor #9 via the positive conductor 8, and Sumire Otani's capacitor lO is connected between this positive conductor 9 and the °γ-s. has been done.

Reference numeral 11 indicates the reference voltage generation circuit.
)% resistor 12 connected between contact 2a and ground.
A divided voltage V is applied to one input terminal of the operational amplifier 15 via the resistor 14i. A voltage that is not affected by fluctuations in the three terminal voltages created by the Zener diode 16, the diode 17, and the resistor 18 is applied to the input terminal of the operational amplifier 15 via the resistor 19. has been done. The output terminal of the operational amplifier 15 is connected to one input terminal of the operational amplifier 15 through the feedback resistor 20t. Therefore, when the terminal voltage of the battery 3 changes, only the level of the voltage V1 changes, and the terminal voltage of the battery 3 changes. The operational amplifier 15 outputs an output voltage whose level changes as the voltage level changes. The output voltage from the operational amplifier 15 is applied via a circuit St consisting of a diode 21 and a resistor 'a22 to the base of a transistor 24 whose collector is connected to the positive 4 line 9. The emitter circuit of the transistor 24 includes resistors 25, 26°27
are inserted in series with the resistor 27, and a thermistor 28 whose resistance value changes in response to changes in engine cooling water temperature is connected in parallel with the resistor 27.

As a result, from the emitter circuit of the transistor 24, a reference voltage 41 whose level changes in response to fluctuations in the terminal voltage of the battery 3 and a level that changes in response to fluctuations in the terminal voltage of the battery 3 and changes in engine cooling water temperature are generated. The changing second reference voltage vb and third base thread voltage Vc are output, respectively. In the illustrated implementation, the reference voltages Va, Vb,
The level of Vc increases as the terminal voltage of batch I73 decreases, and the reference voltages vb and Vc further decrease as the cooling water temperature increases.

The second standard mm pressure vb is stored in a control circuit 31 for controlling energization of the relay coil 5.

The second reference voltage vb is applied via a resistor 35 to the input terminal of the operational amplifier 34 to which feedback from the output is applied by a diode 32 and a resistor 33, and is connected between the - human power terminal and the ground. A capacitor 37 having a relatively large capacitance is provided between the two through a diode 36. Glow plug 4 that changes according to the opening and closing of switch 6.
[L] In order to simulate the charging/discharging voltage characteristics of the capacitor 37, resistors 38, 39, 40 . A charge/discharge characteristic setting circuit 44 consisting of a variable resistor 41 and diodes 42 and 43 is provided. This charging/discharging characteristic setting circuit 44 is charged by a resistor 40 and a variable resistor 41 via a forward biased diode 43 when the switch 6 is closed, and the charging curve at this time is similar to that of a glow plug. It is adjusted to match a temperature rise curve of 1 to 4n. On the other hand, when the switch 6t is opened, the diode 42 becomes in the vL bias state, and the charge in the capacitor 37 is discharged through the resistor 39 and the glow plug, but the discharge curve at this time is the temperature drop curve of 1 glow lag. It is set to 04 to match.

In addition, in order to apply a trigger to ensure that the output level of the operational amplifier 34.0 reaches the cylinder level when the key switch 2t is switched from the OFF position to the ON position, one input terminal of the operational amplifier 34 is connected to the A trigger circuit 47 consisting of a flexible, small capacitance capacitor 45 and a diode 46 is provided. A capacitor 45 is connected between one input terminal and the ground, and a diode 46 is connected between the single input terminal and the positive conductor 9 with the polarity shown. When switched to the ONN position, the output level of the operational amplifier 34 will definitely become high level. The electric charge charged in this capacitor 45 is
When the key switch 2 is switched to the 0FII' position, a discharge occurs through the diode 46. This allows reliable triggering with an extremely simple circuit.

The output terminal of the operational amplifier 34 is connected to the positive conductor 9 through a resistor 48, and also connected to a resistor 49.50 and a diode 51. It is grounded via '52Th. The voltage generated across the resistor 5o is applied between the base and emitter of the transistor 54, which has a relay 53 in its collector circuit, and the output of the operational amplifier 34 becomes high level. In response, the transistor 54 is turned on to energize the coils 53a-f of the relay 53, and the normally open switch 55 is closed. One end of the switch 55 is the contact 2a
fc connection, and the other end of the switch 55 is grounded via the relay coil 5. Therefore, when the key switch 2 is ON or the 87th position 11Jc is on, when the tow/raster 54 is turned on, the relay coil 5 is energized, the switch 6 is closed, and the glow plugs 4m to dnK are energized. Become. Here, diodes 56 and 57 are storage diodes for the transistor 54, and diode 58 is a surge voltage absorbing diode.

When the key switch 2 is in the ON position and the switch 6 is OFF, the resistor 59.6
A constant voltage applying circuit 62 consisting of a diode 61 and a diode 61 is provided. The constant voltage application circuit 62 includes a resistor 59.6.
0 are connected in series, and this series connection circuit is connected between the collector of the transistor 54 and ground, and the anode of the diode 61 is connected to the connection point of the resistors 59 and 60, and the cathode is connected to the capacitor. It is connected to the high voltage side terminal of No. 37.

Therefore, when the transistor 54 is in the on state, the anode side of the diode 61 is at approximately ground potential and does not contribute to the charging/discharging operation of the capacitor 37; however, when the transistor 54 is in the off state, 37
The charging voltage will not be lower than the potential of the anode of the diode 61 if the voltage drop across the diode 6 is ignored. In this way, by providing the constant voltage application circuit 62, when the output level of the operational amplifier 34 changes to a low level after the glow plug is heated to a predetermined temperature, the capacitor 37 is connected to the diode 42° resistor 639 and Discharge occurs through glow plugs 4m to 4nf, but since constant voltage application 0 times M!62 is provided, capacitor 3
The photoelectric voltage No. 7 never becomes lower than a predetermined constant voltage given by this constant voltage applying circuit 62. On the other hand, the potential at the input terminal of the operational amplifier 34 is controlled by the above-mentioned constant voltage application [! l! Since the voltage AID applied to capacitor 37 on path 62 is pulled down to a low level, the output of operational amplifier 34 is eventually held at a low level.

As a result, even if the glow plug drops below a predetermined temperature,
The glow plug is no longer preheated again by the control circuit. That is, this constant voltage mark 7J! One circuit 62 functions as a preheating prevention circuit (also referred to as K).

Furthermore, by applying the above-mentioned voltage by the constant voltage application circuit 62, the potential of the capacitor 37 will be maintained even in the MII case where the key switch is turned on again immediately after the engine is started and the key switch is turned off. Since the capacitor 37 has a predetermined high potential charged by the constant voltage application circuit 62, charging of the capacitor 37 starts from this predetermined high potential. Excessive preheating of the glow plug can be effectively prevented.

A lamp control circuit 64 is further provided for controlling the lighting of a preheating operation indicator lamp in connection with the preheating operation by the control circuit 31. The lamp control circuit 64 includes an operational amplifier 65 whose -input terminal is connected to one input terminal of the operational amplifier 34, and whose tenth input terminal is connected to a third reference voltage V.
c ((Vb)) is input through a resistor 66. The output terminal of the operational amplifier 65 is connected to its input terminal through a resistor 67 and a diode 68, and is and is connected to the positive conductor 9.

The output terminal of the operational amplifier 65 is grounded via a resistor 70.71 and a diode 72, and the voltage developed across the resistor 71 is connected to the driving IQ! A lamp 63 is connected to the collector circuits of transistors 73 and 74. Therefore, if the level of one input terminal of the operational amplifier 65 is below VC, its output is at a high level, transistors 73 and 74 are both turned on, and the lamp 63 is lit. As the glow plug's sensitivity increases, the level at its one input terminal increases, and V
c (then the lamp 63 goes out. In this case, the reference voltage Vc applied to the input terminal is vb
Since the temperature of the glow plug increases, the lamp 63 first goes out, and then, when the voltage at one input terminal of the operational amplifier 34 rises to be greater than vb, the glow plug's I11! The electricity will be cut off.

The glow plug preheating control device 1 further includes a water temperature detection circuit 76tl which is used to prevent the glow plug from being preheated when the engine cooling water temperature is higher than a predetermined temperature of 9q. Water wet detection [oIM 76 c,
1st Mmll, pressure V B 75g resistor 77.78
, and a voltage is applied to one input terminal of the comparator 79, and a third reference voltage Vc is applied to the ten input terminals of the comparator 79. The value of resistor 77°78 is
e! so that the level of one input terminal becomes higher than the voltage and voltage Vc when the cooling water temperature exceeds a predetermined value. , and when the cooling water temperature reaches a predetermined temperature or higher, the output level of the comparator 79 becomes a low level, and the operational amplifier 34
The level of the output terminal of Vζ1 is forcibly set to approximately the ground level through the diode 80i, and the transistor 54 is forcibly turned off regardless of the operating state of the operational amplifier 34, thereby controlling the group lag preheating operation to not be performed. do. The collector of the transistor 54 is connected to one input terminal of the comparator 79 via a diode 81 and a resistor 82, and when the potential of the collector of the transistor 54 rises, the output level of the comparator 79 becomes low level. locked in state. Both the input voltages of the water and the comparison 579 change in level due to changes in the battery pressure, so the influence of changes in battery voltage is eliminated and the water temperature operates only in response to changes in water temperature.

Next, the operation of the circuit shown in FIG. 1 will be explained with reference to FIG.

Time 1 == 1. When the key switch 2 = i is switched from OFF level W to ON level, the output of the amplifier 34.65 is surely high due to the movement of the trigger circuit 47, and the output of the amplifier 34. is closed and the glow plug 4. ...Heating starts for 4 tons of 4n. In this case, cold I! , II is equal to or higher than a predetermined field temperature, the preheating operation of the glow plug is forcibly stopped by the action of the water temperature detection circuit 76 described above. At this time, the lamp control circuit 64 turns on the rash light 63t to notify the operator that the glow plug is currently being preheated. When the switch 6 is closed, a charging current flows into the capacitor 37 via the diode 43, and from this tLVc, the charging current substantially coincides with the change in the glow plug temperature T shown in FIG. 2(d). The pressure Vo changes (see FIG. 2(e)).

When the value of the charging voltage of the capacitor 37 becomes larger than VC (1==1.), the lamp 63 is turned off, but the preheating operation of the glow plug continues.

At t=ls, the value of the charging voltage of the capacitor 37 is vb
When t becomes larger, temperature T reaches a predetermined forging suitable preheating wetness TO
The charge/discharge characteristic control 1 (b) path 44 is adjusted so that the temperature reaches 100. At this time, the transistor 54 is turned off, the switch 6 is opened, and the preheating is completed.

Therefore, 1=1. After that, the temperature T starts to gradually decrease. At this time, the capacitor 370 yuan vK load is diode 4
2, and its voltage decreases according to a characteristic curve that substantially matches this temperature drop % characteristic curve. As already explained, when the transistor 54 is turned off after being turned on by -H, the constant voltage application circuit 62 is activated, and the voltage of the capacitor 37 does not fall below a predetermined voltage. And resistor 3
3 and the diode 32, the potential at the input terminal of the operational amplifier 34 is kept lower than the constant potential given by the constant voltage application circuit 62, so even if the key switch 2 is left in the ON position, Preheating operations are not repeated.

In the above-described operation, the reference voltages Vb and Vc applied to each operational amplifier 34- and 65 are designed to change in level according to battery voltage fluctuations.
If the water temperature is constant, even if the battery voltage fluctuates and the state of charge of the capacitor 37 is affected, the reference voltage W
b, the level of Vc changes to compensate for this, thus
The temperature of the glow plug at the time of turning off the U/Pro 3 and at the end of preheating is kept constant even if the battery voltage fluctuates.

1 = 1. Turn key switch 2 to -HOFF at
After returning to position, 1=1. Then press key switch 2 again.
When restarting is performed by turning on the capacitor 37, the capacitor 37 will not be charged from zero (predetermined charge + Ji
1 [Since the capacitor 37 is charged from the ratio value, the charging curve of the capacitor 37 almost matches the curve shown in FIG. 2(d), and therefore,
Even at the time of restart, the temperature T when the lamp is turned off (1=1%) and when the preheating is completed (f=!y) remains approximately at a predetermined value as long as the water temperature is constant.

Note that when the key switch 2 is switched to the ST position at 1=18, the base of the transistor 54 is connected to the positive electrode of the battery 3 via the resistor 83, so the diode 5
1, 5.2 are in a reverse bias state, and the transistor 54
This deionizes and heats the glow plug.

Next, 1=1. After the engine starts at , 1
At ==t, turn the key switch to -HOFF, and then 1 = 1. . Next, we will further explain the operation of the aI meeting when the key switch is turned on. 1 = 1°C, the operation of the constant voltage application circuit 62 causes a photoelectric voltage ■.

The voltage Vb of the cage is lower than the value of VbO, and the temperature T of the glow plug is a certain value lower than To because the engine was in operation. t・<
When t<tre, the photoelectric voltage V. and the temperature T of the glow plug tend to gradually decrease. When the key switch 2 is turned ON again in this state, the capacitor 37 is already charged in the predetermined flIi vehicle as described above, so the heating time of the glow plug is short, and the glow plug is already in a high temperature state due to engine operation. Excessive heating of the plug can be effectively prevented.

Furthermore, each reference voltage is configured to change its level in response to the cooling water temperature, so as shown in Figure 3,
As the cooling water iTw rises, the preheating time Tr decreases. Further, as the battery voltage VB decreases, the time Tr increases. As a result, water temperature 1
When 'w is high, the energy key supply amount for preheating decreases, and when the water temperature Tw is low, the energy key supply amount for preheating increases, so even if the water temperature TW changes, the glow plug f: It is possible to preheat to a constant Vζ temperature.

Also, in Figure 3, water 4Tw and lamp fishing 11, F
The relationship with lij T p is shown by a dotted line using the value of battery voltage VB as a parameter.

According to the present invention, when the key switch is in the ON position and the switch for controlling the current flowing to the glow plug is OFF, the capacitor of the circuit outputs a charging/discharging voltage sound corresponding to the temperature change characteristics. Since a predetermined constant potential is applied to the engine, there is no need for the conventional and complicated pre-start stop circuit, and the glow plug can be used when stopping the engine once and restarting it immediately while the engine is running. It is no longer necessary to take power from the charge lamp terminal of the generator attached to the engine to prevent overheating, and it can perform the same functions as before with an extremely simple configuration, and improves shaft reliability. Excellent effect of Qin.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2(a)
2(e) to 2(e) are time charts for explaining the operation of the circuit shown in FIG. 1, and FIG. 3 is a time chart for explaining the operation of the circuit shown in FIG.
It is a graph showing a preheating characteristic curve of a circuit and a lamp lighting characteristic surface Wt. DESCRIPTION OF SYMBOLS 1...Glow plug preheating control device, 2...Key switch, 3...Battery, 41 s""・Glow plug, 6...Switch, 11...Reference voltage generation circuit, 28... Thermistor, 31... control circuit, 34...
...Operation amplifier, 37... Capacitor, 44... Photodischarge characteristics, 47... Trigger circuit, 53... Relay,
54...transistor, 62...constant voltage mark7. I [
11 circuits, 64... lamp control circuit, 76... water temperature detection circuit, Va... first reference voltage, vb-... second
Reference voltage, Vc...Third reference voltage. Patent applicant: Diesel Equipment Co., Ltd.

Claims (1)

[Claims] 1. A glow plug preheating control device for preheating a glow plug for an internal combustion engine in response to the operation of a key switch, which includes a capacitor and controls charging and discharging voltage according to the temperature of the glow plug. A first circuit that outputs an output, and a second circuit that performs a level comparison between a predetermined reference voltage and the charging/discharging voltage.
a circuit, a switch means for controlling the flow of current from the preheating power source to the glow plug according to an output from the second circuit; Glow plug preheating control f! characterized by comprising a third circuit for applying a charging voltage of a predetermined level to the first circuit. pupil. 2. The first circuit is connected in series to the capacitor and supplies a charging current to the capacitor by the glow plug applied voltage; 1. The capacitor is connected in series to the discharge basket flow path of the capacitor; 2. The glow plug preheating control device according to claim 1, further comprising a separate discharge path for providing a discharge path.