JPS6287670A - Control device for glow plug - Google Patents

Abstract

PURPOSE:To control a glow plug to be stably heated to a target preheat temperature and prevented from deteriorating, by providing the glow plug of heat generation self control type, which has the first heating unit rapidly heated and the second heating unit limiting an electric current of the first heating unit, while an after glow electrifying means. CONSTITUTION:A device provides a glow plug 5 of heat generation self control type, having the first heating unit 5a rapidly heated and the second heating unit 5b limiting an electric current of the first heating unit 5a, while an after glow electrifying means 7 which limits an electric current to the first and second heating units 5a, 5b after the glow plug 5 is stably heated to its target preheat temperature. Then the device, after the glow plug 5 is electrified, enables its surface to be promptly heated to the target preheat temperature. And after the surface once reaches the target preheat temperature, the surface temperature can be stably controlled to a region of the target preheat temperature preventing the center temperature from becoming an abnormally high temperature by the action of the after glow electrifying means 7 limiting the electrification current. Accordingly, a long life of the glow plug 5 can be obtained by preventing its deterioration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a glow plug control device that controls the current flowing through a self-heating control type glow plug, and is suitable for, for example, a preheating device for a diesel engine vehicle.

[Conventional technology]

In a diesel engine vehicle, before starting the engine, it is necessary to energize the glow plug provided in the combustion chamber of the engine and heat the glow plug to a predetermined temperature (for example, 800° C.). In this case, it goes without saying that it is desirable to reach the predetermined temperature as quickly as possible. However, if the current applied to the glow plug is made very large in order to perform rapid heating, the glow plug may be abnormally heated even after reaching a predetermined temperature, and in the worst case, may melt.

Therefore, conventionally, a self-heating type glow plug is used as shown in Japanese Utility Model Application Publication No. 60-30373. This glow plug consists of a first heating element for rapid heating made of an iron-nickel alloy with a very small temperature coefficient of resistance, and a second heating element for preventing abnormal heating made of a nickel alloy with a large temperature coefficient of resistance. are electrically connected in series.

For this reason, when using a self-heating type glow plug, the first
As shown in Figure 1, the surface temperature of the glow plug reaches 800"C within a few seconds after the start of energization, and as the temperature rises, the resistance of the second heating element increases rapidly, causing the flow to flow to the first heating element. Since the current is suppressed, the surface temperature of the glow plug is then stabilized between 800'C and 1000C depending on the magnitude of the power supply voltage (9 to 14 in FIG. 11).

However, as described in detail by the present inventors, the first
As shown in Figure 2, the temperature of the center of the glow plug is higher than that of the surface, and the power supply voltage is 14. For V, the center is 1
A high temperature state of 400°C is reached.

For this reason, the conventional self-heating control type 1 glow plug suffers from severe deterioration due to high temperatures, resulting in a shortened service life.

[Problem that the invention seeks to solve]

The present invention was made to solve the above problems, and
It is an object of the present invention to allow the surface temperature of a glow plug to quickly reach a required predetermined temperature, and to prevent abnormal heating of the center of the glow plug.

[Means for solving problems]

Therefore, in order to achieve the above object, the present invention provides a self-heating control type glow plug that has a first heating element that rapidly heats up when energized, and a second heating element that limits the current flowing through the first heating element. , afterglow energization means for limiting the energization current to the first and second heating elements after the temperature of the glow plug stabilizes at the target preheating temperature, the glow plug control device comprising: energization to the glow plug; After the start, before the temperature stabilizes at the target preheating temperature, determining means determines whether the internal temperature of the glow plug reaches an abnormal heating temperature, and generates a determination signal when determining that the internal temperature of the glow plug reaches the abnormal heating temperature; A technical means is adopted which includes a switching means for switching the energization state of the glow plug to the energization state of the afterglow energization means in response to a discrimination signal from the discrimination means.

[Action of the invention]

By employing the above technical means, immediately after the glow plug starts to be energized, the temperatures of the first and second heating elements are low, so a large current flows through both heating elements, causing them to heat up rapidly. When the surface temperature of the glow plug approaches the target preheating temperature, the second heating element works to suppress the current flowing through the first and second heating elements, putting a brake on rapid heating and bringing it to a stable state. Head towards.

In addition, as the surface of the glow plug approaches the target preheating temperature, the temperature at the center of the glow plug approaches the abnormal heating temperature. , Afterglow (;=- By the energizing means, in addition to the heating brake of the second heating element, the iJ1!electricity?Rr''' to the glow plug is limited in size and normal heating of the central part of the stomach. 9 (Effect of the invention) According to Akira, the surface temperature of the I-plug can be reduced to the target preheating temperature somewhat. At the same time, once the target temperature is reached, the surface temperature can be stabilized within the target preheating temperature range without causing the center temperature to reach abnormally high temperatures, making it easier to use glow plugs than conventional glow plugs. Deterioration is prevented and the life of the glow plug is extended.

Further, according to the present invention, in order to prevent an abnormal temperature rise in the center of the glow plug, the afterglow energizing means is used without using a special current limiting device, so abnormal heating can be prevented with a simple configuration. I can do it.

[Example] The present invention will be described in detail below based on an example shown in the drawings.

In Figure 1, 1 is a vehicle battery with a rated voltage of 12V, 2
3 is a key switch with on contacts 2, 1 and a start contact 2h, 3 is a control circuit that controls the energization state of the glow plug according to the engine water temperature and energization time, 3A is a power terminal of the control device 3, and the key Battery voltage is applied when the switch 2 is in the on or starting state. 5 is a glow plug that is connected in parallel as many cylinders as the engine breathes. 1
This glow plug has two heating elements, the first heating element 5a is made of iron-Ninkel alloy wire with a small resistance temperature coefficient and placed near the tip of the glow plug, and the second heating element 5b uses a nickel wire having a large resistance temperature coefficient and connected in series to the first heating element 5a. A main relay contact 6 linearly applies battery voltage to the claw lug 5, and is closed when the coil 6a is energized. This coil 6a is connected to the main relay drive circuit 1 via the terminal 3B.
6. Reference numeral 7 denotes a voltage drop resistor which is normally connected in series between the glow plug and the battery during afterglow, and has a resistance value such that the voltage drop is 20 to 30% of the battery voltage.

Reference numeral 8 denotes a contact point of a sub-relay that opens and closes the current in the path of the voltage drop resistor 7, and is closed by energization of the relay coil 8a. Coil 8a is connected to sub-relay drive circuit 29 via terminal 3C.

The glow plug 5 is connected to the timer circuit 20 via the terminal 3D.
It is connected to the. This timer circuit 20 provides an optimum energization time for the glow plug \ according to the voltage applied to the glow plug 5, and the input voltage of the terminal 3D is applied to the glow plug by a combination of a Zener diode 21 and a resistor 22.23. The lower the voltage, the lower the wedge edge, and the higher the voltage, the more extreme the voltage changes nonlinearly. 24 is a charging resistor that charges the capacitor 15 from the voltage at the connection point of resistors 22 and 23, and 25 is a backflow prevention diode. The output signal of the time limit circuit 20 having the above configuration is input to the plus input terminal of the comparator 10, which is an example of the determining means of the present invention. On the other hand, the negative input terminal has a resistor 11 and a Zener diode 1.
A constant voltage obtained by dividing the voltage of 5.1■ stabilized by 2 and 5.1■ by a resistor 13.14 is manually applied. Further, a transistor 26 that provides hysteresis operation to the comparator 10 is connected to the negative input terminal, and when the transistor 26 is turned on, a resistor 27 is connected in parallel to the resistor 14, and the negative input voltage of the comparator 10 changes to a low value. Has hysteresis.

The output side of the comparator 10 is connected to a main relay drive circuit 16 and a sub relay drive circuit 2 via a resistor 45.
9 is connected. In the main relay drive circuit 16, when the output of the comparator 10 is at a low level, the base current does not flow to the transistor 17 through the resistor 45, so the transistor 17 is off, the transistor 18 is on, the transistor 19 is on, and the main relay coil is turned on. 6a is energized, main relay contact 6 is closed, and battery voltage is applied to glow plug 5.

In FIG. 1, 9 is an engine cooling water temperature sensor composed of a thermistor, and the control circuit 3 is connected to the terminal 3E.
The afterglow timer 28 is connected to the afterglow timer 28. The afterglow timer 28 causes its output 28b to go to high level for a predetermined time period 7& (10 seconds to 2 minutes) from the time the key switch 2 is turned on or the key switch 2 returns to the on position after being set to the start position. Invert. This predetermined timer time is determined by the water temperature sensor 9 and -. By taking in the voltage at the connection point with the resistor 4b connected to the constant voltage of IV to the input 28a of the afterglow timer, the lower the cooling water temperature, the shorter the time. The output 281) of the afterglow timer 28 is input to the sub-relay drive circuit 29, and while the output 28b of the afterglow timer 28 is at a low level, no base current flows to the transistor 30 through the resistor 45, so the transistor 30 is turned off and the transistor 31 is turned off. On, the transistor 32 is turned on, energizing the sub-relay coil 8a, and the sub-relay contact 8 is closed. , 33 is a starter, 34.35 is a resistor that divides the voltage at the input terminal 20 when the source 38 is on, and when the transistor 30 is on, that is, the output of the comparator 10 is at a high level and the transistor 26 is on, and the comparator 10 When the negative input of the resistor 34.35 is low by the hysteresis and the voltage of the input terminal 20, that is, the applied voltage of the glow plug is the optimum voltage for the glow plug 5 (applied voltage that maintains the glow plug sheath surface temperature of about 900°C), the voltage of the resistor 34.35 The connection point voltage is low due to hysteresis -1. 36 is a backflow prevention diode, and 37 is a reverse current prevention diode, and 37 is a reverse current prevention diode, and 37 is a resistor 34 and 35, so that when the transistor 38 is on, the electric charge of the conductor 2/tensor 15 is A discharge resistor that discharges with a certain time constant toward the voltage at the connection point of
[is. 39, when the key switch 2 is turned off, the charge of the condenser 15 is reduced to <I/Jti! ! It has a high resistance for electric current.

40 is because the key switch 2 is turned on and the water temperature is ↓ near, 111';
It is a tie 7 circuit that creates a timer time of 1 second to several seconds at u, and after this predetermined period from the time when key switch 2 is turned on, its output 40b is inverted to 1 line L-her, turning off transistor 41. 4 (C is a preheating table; p knee is a 7 button, 1 is driven by transistor 4N, lights up for the timer period, and turns off to indicate the optimum period for the driver C1 to start cranking. 43 and 44 respectively). The main relay coil 63 is a diode for absorbing the voltage of the main relay filter 8a.

Next, a) 121 of this embodiment having the configuration L. Explain about the imperial order. When the key switch 2 is turned on, that is, the contact 2a is in the contact state, the negative input terminal of the comparator 1o receives the battery voltage applied from the power supply terminal 3A of the control device through the resistor 11. (1,00Ω) and is stabilized by a Zener diode (5,1V), and is further stabilized by a resistor 13 (
A voltage of about 3.4V divided by a resistor 14 (10Ω) is input to 5 and 6. On the other hand, a capacitor 15 (47 .mu.F) is connected between the positive input of the comparator 10 and the ground, and since the voltage of the capacitor 15 is initially 0.times., the output of the comparator 10 is at a low level. Therefore, the transistor I7 of the main relay drive circuit 16 is turned off, the transistor 18 is turned on, and the transistor 19 is turned on, so that 1I11 current is applied to the main relay coil 6a, and the mail/relay contact 6 is closed.

Therefore, the battery voltage (approximately 12V) is applied to the glow plug B'/glow plug B'/glow plug B'/
L is started. In this case, when battery voltage is applied to the low plug 5Q, the resistance value of the second heating element 5b is low at the beginning of application, so the application type r= to the first heating element 5a at the tip is excessive (if applied continuously The voltage at which the first heating element 5] melts is reached, and the tip/end surface portion 5c of the hoop lug 5 reaches the target Ut! in a few seconds, as shown in FIG. ! !
: 800" Ct is reached. During that few seconds, the temperature of the rear end heating part by the second heating element 5b also rises, so the resistance of the second heating element 5b decreases by 1 and the self The heat generation time increases L7, and the voltage applied to the j-th heating element 5a made of iron and cotton is at an optimum value (10
The voltage is stabilized at 00°C to 1200°C).

On the other hand, when voltage application starts to the globe lug 5, the voltage applied to the glow plug is transferred from the plug voltage input terminal 3D to the Zener diode 21 (7,5V), the resistor 22 (1ooΩ),
Instead of the series circuit of resistor 23 (Ω for 1 and 5), resistor 2
Connection of 2 and 23, l) - to resistor 24 (56, Q
), 9E dimension - t'25 ifil, lever 7 capacitor 15 (conducted 1°) Here, the potential at the connection point of resistors 22 and 23 is G rJ - plug mark; Since the applied voltage is proportional to 1:l, the lower the applied voltage, the lower the voltage. Negative input terminal (hereinafter referred to as reference voltage) (3,4V)
The time required for the temperature of the tip heating coil inside the glow plug 5 to reach 1200'C can be made according to the voltage applied to the glow plug 5 so that the time required for the temperature to reach 1200'C is equal to the time taken for the temperature of the tip heating coil inside the glow plug 5 to reach 1200'C. In this circuit, the battery voltage is 11.5■
In the above case, the voltage of the capacitor 15 will be at time 1 in FIG.
When the reference voltage reaches the reference voltage, the output of the comparator 1o is inverted to high level, and after the inversion, the output of the transistor 26
is in the on state, a resistor 27 (13
Ω) is connected to the reference voltage, and the reference voltage has hysteresis and drops from 4.3■ to 2.3■.

Note that at this time, the transistor 38 is also turned on. As described above, when the output of the comparator 1o is inverted to a high level, the transistor 17 is turned on, the transistor 18 is turned off, and the transistor 19 is turned off, and the main relay coil 5 is no longer energized, so the main relay contact 6 is opened.

On the other hand, from the time when the key switch 2 is in the ON state, that is, when it is connected to the 2a, the output 28 of the evening/immediate circuit 28 for afterglow
Since b is in the low level state, the sub relay drive circuit 29
Transistors 30 are on, transistors 31 are off, and transistors 32 are on, and the sub-relay coil 8a is energized and the sub-relay contact 8 is closed, so the output of the comparator 10 becomes high level and the main relay 6 is turned on. Even after being turned off, a voltage 2 to 3 cm lower than the battery voltage is applied to the glow plaque 8 via the sub-relay contact 8 and the voltage drop resistor 7.

This causes the first heating element 5 inside the tip of the glow plug 5 to
The temperature of a is up to <1200''C as shown in Figure 4 A2.
After the voltage rises to 2, due to the braking action of the second heating element inside the glow plug 5 and the voltage drop caused by the voltage drop resistor 7,
After reaching 200° C., the temperature decreases or becomes flat in the range of 1000 to 1200° C., and it is possible to prevent the life of the first and second heating elements 5a and 5b from decreasing.

Note that the broken lines A and Aff in FIG. 4 indicate the case of the conventional control device, and in the broken line A, the temperature of the tip heating element significantly exceeds 1200° C., which is sufficient to ensure the life of the heating element.

On the other hand, according to the method of the present invention shown in the solid line part A2,
Since the main relay 6 is turned off at an effective timing to lower the voltage, the temperature of the first heating element 5a is 120°C.
The temperature is kept below 0℃. Glow plug 5 at this time
The surface of the 8 is lower than the conventional A3 like A4.
It never goes below 00°C.

The reason is explained below. As shown in FIG. 5, the higher the battery voltage, the higher the temperature of the heating element 5a at the tip 2 becomes 1200°C.
Needless to say, it takes a short time to reach
When the tip heating coil reaches 1200°C, that is, when the main relay 5 is turned off, the surface temperature of the sheath tip reaches 800°C, which is too low when the voltage is high. (Figure 6) The reason for this is that the higher the voltage, the more the glow plug 5
The heating rate of the tip heating element 5a is fast and the heat is transferred to the glow plug 5.
This is because the time for conduction to the surface of

Therefore, in the control device of this example, when viewed from the surface temperature of the tip of the glow plug 5, the higher the applied voltage, the higher the target temperature 8.
The voltage drop resistor 7 is connected when the voltage is too low with respect to 00°C. However, the slope of the temperature rise until the main relay contact 6 turns off is steeper as the voltage increases, and heat continues to be conducted from the first heating element 5a inside the glow plug toward the surface. Even when turned off, the surface temperature of the claw plug quickly reaches 800°C.

In addition, according to this example, as shown in Figure 7, in the conventional method, the temperature rise time is shorter than required when the power supply voltage is 12V or higher, compared to when the power supply voltage is 12V or higher, but in this method, the temperature rise time is shorter than required when the power supply voltage is 80V or higher.
By suppressing the time required to reach 0° C. to about 12 V, as shown in FIG. 8, the tip heating coil is prevented from overheating when the power supply voltage is high.

Now, when the main relay 6 is turned off, the normal power supply voltage range when not cranking is 11.5 to 14V.
Now, leave the main light -6 off and turn on the glow plug 5.
The voltage is applied to the glow plug 5 with a voltage drop of 1 degree b'c 7 is connected in series, and a voltage 2 to 3 V lower than the power supply voltage is applied to the glow plug 5 depending on the power supply voltage, but when electricity starts flowing. After time t2, when the key switch 2 is turned to the 2b position and the starter 33 is energized and cranking is performed, the power supply voltage becomes 10 V or less, and depending on the cranking state, battery discharge state, ambient temperature, etc. During ranking, the voltage will be as low as 6 to IOV. If the voltage drop resistor 7 remains connected in series to the glow plug 8 in this state, the glow plug temperature will drop to 800° C. or lower. In order to prevent this, in this example, when the battery voltage drops and the plug applied voltage becomes 7V or less, the voltage applied to the glow plug 5 is divided by the resistor 34.35, and the voltage at the point is divided by the transistor 26.
The resistor 34.35 is selected so that the voltage is 2.4 V or less, which is the comparator reference voltage in the on state. As a result, the charge in the capacitor 15 begins to be discharged through the discharge resistor 37 and the diode 36, and when the voltage of the capacitor 15 becomes lower than the reference voltage 2.4V with hysteresis, the output of the comparator 10 is reversed to low level. Therefore, after time L3 in Fig. 2, the main relay drive circuit 16 turns on the main relay 5 again, and the battery voltage is directly applied to the glow plug 5, and the glow plug voltage, which was about 7 ㎜ with the voltage drop resistor, decreases. The temperature rises to about 9■, ensuring a surface temperature of about 850°C. Note 9■
When the plug voltage is about 9 V (11.5 V), the capacitor voltage cannot reach the comparator reference voltage 3°4 without hysteresis due to the blocking voltage of the Zener diode 21 of 7.5 V. As long as the low voltage (below) continues, the output of the comparator IO will not be inverted to a high level, and the glow plug 8 will be connected to the battery voltage directly applied. In addition, sub relay 8
The more the voltage applied to the glow plug 5 is too low when the voltage is applied through the voltage drop resistor 7, that is, when the voltage is applied through the voltage drop resistor 7, the more
Once the temperature at the tip of the glow plug 5 rises to 800°C or more, the temperature decreases quickly, but the discharge speed of the capacitor 15 via the resistor 37 also becomes faster as the glow plug applied voltage is lower, so the main relay is turned on. The return glow plug temperature can be maintained at a substantially constant value, for example, 700° C., regardless of the degree of undervoltage applied. Note that when the output of the comparator 10 is at a low level, that is, when the main relay is passing, the transistor 38 is off, so the voltage applied to the glow plug is no longer divided by the resistors 34' and 35, so it is passed through the resistor 37 to the capacitor 15. The voltage is not discharged and the only charging route is through the resistor 24. When the cranking is finished and the engine is started, the battery voltage increases, so the capacitor 15 starts charging again, and after a time t from the start of energization, the main relay 6 is turned off and the state shifts to afterglow. Note that resistance 39
has a high resistance of approximately 200Ω, and even after the glow plug 5 is energized many times, the key switch 2 remains in the on position 2.
As long as it is connected to a, the voltage of capacitor 15 is 5.1V
This is the discharge resistance of the capacitor 15 after the pull amplifier resistance and key switch 2 is turned off to maintain the voltage.

The meaning of the pull-up resistor is that even after the glow plug 5 is energized, the glow plug continues to receive heat due to combustion within the engine, so when the glow plug temperature has not cooled down completely after the engine has stopped, the key switch 2 is turned on again. When this occurs, there is a residual voltage in capacitor 15, so main relay 6
The first time to turn on the electricity! It is shorter than when tIN is energized, and it is possible to prevent the glow plug from passing through. The role of the resistor 39 as a discharge resistance depends on the cooling rate of the glow plug when the key switch 2 is turned off after heating the glow plug.
This is to match the heat dissipation speed of 5. The operation up to this point is performed until the output 28b of the afterglow timer 28 is at a low level, that is, the time when the timer ends. When the afterglow timer ends, the output 28b is at a high level, causing the main relay drive circuit 16 and the sub relay drive circuit 29. Since the drive of both relays is stopped, the glow plug 5 is no longer energized at all.

As described above, according to this embodiment, the ninth. As shown in Figure 10, the glow plug surface temperature reached 800 seconds after the start of energization.
℃ or above, and then 800℃ depending on the magnitude of the applied voltage.
It can be stabilized at a temperature of ~1000℃, and
The temperature of the first heating element 5a inside the glow plug 5 is set to 120.
Can be kept below 0°C.

Note that the present invention is not limited to the above-mentioned embodiments, and can be implemented in various embodiments as shown below.

In the embodiment shown in Fig. 1 above, the method of determining the main relay energization time determined by the voltage applied to the glow plug is based on the capacitor charging timer remaining by the capacitor 15, resistor 24, etc. Any other method may be used as long as it generates the time equivalent to reaching 1200 DEG C. of the tip heating coil using voltage, for example, the time may be generated by converting the voltage applied to the glow plug from analog to digital and inputting the converted voltage to the microprocessor. Alternatively, the temperature at the center of the glow plug 5 may be directly detected and controlled.

Further, in the embodiment shown in FIG. 1, the temperature of the tip heating element 5a is 12
When the temperature reaches 00°C, the main relay is turned off, and after that, if the voltage applied to the glow plug is too small with the voltage drop resistor 7 connected in series, the charge on the capacitor 15 will change depending on the degree of the applied voltage. The main relay is turned on again when the voltage of the capacitor 15 is discharged and the voltage of the capacitor 15 is below the hysteresis/threshold level. In some cases, the main relay may be turned off once the temperature of the tip heating element 5a reaches 1200°C, and then it may be turned off for a certain period of time (for example, 1
0 seconds), the main relay may be turned on again. Considering that the battery voltage during cranking is not high (12 to 14 ■) during cranking, when the key switch is in the start state, the main relay will not be turned off regardless of other conditions. It may be configured.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing one embodiment of the device of the present invention, and FIG.
The figure is a waveform diagram showing the operating state of the device shown in FIG. 1, and FIGS. 3 and 4 are the changes in the applied voltage of the glow plug and the temperature change of the glow plug with respect to changes in the energization time of the device shown in FIG. 1, respectively. 5, 6, 7, and 8 are the changes in the time taken for the heating element 5a to reach 1200°C with respect to changes in the power supply voltage, and the glow plug at time t1 shown in FIG. 2, respectively. Characteristic diagrams showing the temperature change of , the time until the glow plug surface reaches 800°C, and the peak temperature change of the heating element 5a, FIGS. 9 and 1
Figure 0 is a characteristic diagram showing the left side temperature of the glow plaque and the temperature change of the first heating element over time after the start of energization of the device shown in Figure 1, respectively. FIG. 7 is a characteristic diagram showing changes in the surface temperature of the glow plug and changes in the temperature of the first heating element over time. ■... Battery, 2... Key switch, 5... Glow plug, 5a... First heating element, 5b... Second
heating element, 6... main relay (switching means), 7...
・Resistor (afterglow energizing means), 8...Sub relay. 9... Water temperature sensor, 1G... Main relay drive circuit. 20... Time limit circuit, 10... Comparator, 29.
・・Zaburi relay drive circuit. Representative Patent Attorney Takashi Okabe Figure 7 Figure 8 Tsutsuden Haruma (Su) Cause 9 Figure 10

Claims (2)

[Claims] (1) A self-heating control type glow plug that has a first heating element that rapidly heats up when energized and a second heating element that limits the current flowing through the first heating element, and the temperature of this glow plug is set to the target preheating temperature. and afterglow energization means for limiting the current flowing to the first and second heating elements after the temperature has stabilized, the glow plug control device comprising: afterglow energizing means that limits the current flowing to the first and second heating elements after the temperature stabilizes at the target preheating temperature after starting energizing the glow plug. determining whether or not the internal temperature of the glow plug reaches an abnormal heating temperature, and generating a determination signal when it is determined that the internal temperature of the glow plug reaches the abnormal heating temperature, and responding to the determination signal from the determining means. and switching means for switching the energization state to the glow plug to the energization state by the afterglow energization means. (2) The determination means includes a detection means for detecting fluctuations in the voltage applied to the glow plug, and determines the necessary energization time to the glow plug according to the magnitude of the detected voltage from the detection means, The glow plug according to claim 1, further comprising a timer means for outputting the discrimination signal when the necessary energization time has elapsed after the start of energization of the glow plug. Control device.