JP2602677B2 - Glow plug energization control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a glow plug energization control device for a diesel engine.

[Conventional technology]

2. Description of the Related Art Conventionally, in a diesel engine, a glow plug is arranged in a combustion chamber in a cylinder head of the diesel engine in order to facilitate starting in cold weather. That is, when the operation of the engine is started, the glow plug is energized and heated to increase the temperature of the compressed air in the cylinder head, thereby ensuring the start thereof. In recent years, in particular, a glow plug has been required to make the preheating time before starting the engine as close to 0 seconds as possible in order to improve the operability of the diesel engine to the level of a gasoline engine. Generally, in such a glow plug, the amount of supplied electric power is controlled through an energization control device that operates simultaneously with the connection of the key switch to the on-mode position. Supply and rapid heating. After the rapid heating, a small amount of power is supplied to the glow plug for a while, thereby stably heating the glow plug.
Generally, the stable heating of the glow plug after the engine is started is called afterglow, and this afterglow promotes warming up of the combustion chamber, prevents the generation of diesel knock, generates noise, white smoke, and reduces HC components. Emissions are being controlled.

The supply of power to the glow plug using such a power supply control device is generally performed by directly applying a battery voltage to the glow plug at the initial stage of power supply (normally, 8 to 10 V is applied).
By doing so, a large electric power at the time of rapid heating is obtained. After the glow plug reaches a predetermined temperature due to the rapid heating, a voltage drop resistor (dropping resistor) is connected in series with the glow plug to reduce the applied voltage, thereby reducing the after-glow. Power is to be obtained. FIG. 8 is a graph showing energization control characteristics when a small power is obtained during afterglow using this dropping resistor.
At this point, the voltage applied to the glow plug is reduced by connecting a dropping resistor.

Also, as a method of obtaining low power during afterglow,
In addition to the above-described direct drop method of the applied voltage by the dropping resistor, the applied voltage at the time of rapid heating is intermittently applied, and the duty value of this applied voltage is duty-controlled to reduce its effective value. An indirect method of lowering the applied voltage has also been considered. FIG. 9 is a graph showing the energization control characteristic. At a point P2 in FIG. 2 after 2 seconds from the start of energization, the duty cycle of the applied voltage is performed so that the effective value of the applied voltage to the glow plug is changed. It is descending.

[Problems to be solved by the invention]

However, according to such a glow plug energization control device, for example, in a severe winter season (a severe cold environment) where the outside air temperature is −10 ° C. or less, the key switch is connected to the start mode position simultaneously with the connection to the on mode position. If the engine is to be cranked (so-called 0 second start of the engine), excessive cranking power is required, and the battery voltage drops significantly (usually from 6 to 7V). And the voltage applied to the glow plug required for rapid heating cannot be sufficiently secured. That is,
Since the glow plug is not rapidly heated when the engine is started, the startability of the glow plug is significantly reduced, and it is difficult to start the engine for 0 seconds.

[Means for solving the problem]

The present invention has been made in view of such problems,
Prepare a high performance glow plug whose applied voltage that enables its rapid heating is lower than the voltage value V _Bs defined as the battery voltage drop value that will decrease when starting the diesel engine in a cold environment A first timer means for starting a timing operation when the key switch is set to the ON mode position; a start signal sending means for sending a start signal when the key switch is set to the start mode position; And a second timer means for restarting the timekeeping operation when the key switch is returned from the start mode position to the on-mode position while starting the timekeeping operation when the switch is set to the on-mode position. None to monitor battery voltage V _B to the glow plug, while the first timer means is performing the counting operation, the first buffer Terry Voltage - seeking the duty ratio corresponding to the battery voltage V _B at that time from the duty ratio characteristic,
By intermittently energizing the high performance glow plug at this duty ratio, the effective value of the voltage applied to the high performance glow plug is decreased and adjusted and maintained to be substantially equal to the voltage value _VBs. means completes its counting operation, if the start signal sending means is sending a start signal, a second battery voltage - calculated the duty ratio corresponding to the battery voltage V _B at that time from the duty ratio characteristic,
By intermittently energizing the high performance glow plug at this duty ratio, the effective value of the voltage applied to the high performance glow plug is lowered and adjusted and maintained to be a predetermined value V1 lower than the voltage value _VBs , If the first timer means completes its timekeeping operation and the start signal sending means does not send out the start signal, the third battery voltage-duty ratio is maintained while the second timer means performs the timekeeping operation. obtains the duty ratio corresponding to the battery voltage V _B at that time from the characteristic, by intermittent energization of the high performance glow plug in the duty ratio, the predetermined value lowers the effective value of the voltage applied to the high-performance glow plug Predetermined value V2 lower than V1
The adjustment is maintained so that

[Action]

Therefore, according to the present invention, at the start of the diesel engine in arctic environments battery voltage V _B even significantly reduced, thereby enabling rapid heating of the glow plugs. That is, in the extremely cold environment, when attempting to start 0 seconds, because the excessive cranking power is required, the battery voltage V _B is remarkably lowered. In this case, when the key switch is set to the ON mode position, the first timer means starts its timekeeping operation, and while the first timer means performs the timekeeping operation, the first battery voltage-duty ratio characteristic duty ratio corresponding to the battery voltage V _B at that time from the (characteristic I) is obtained by energizing the high glow plug is interrupted by this duty ratio, the effective of the voltage applied to the high-performance glow plug The value is decreased (V _B > V _Bs
), _Is adjusted and maintained to be substantially equal to V _Bs (for example, 6 V). By performing such adjustment and maintenance,
High performance glow plug at 0 seconds start in warm season
Ensure that no voltage above V _Bs is applied directly,
That is, in addition to preventing overheating of the high performance glow plug at the start of 0 seconds in a warm season, rapid heating at the start of 0 seconds in a severely cold environment becomes possible.

Further, according to the present invention, when the first timer means has completed its timekeeping operation and the start signal sending means has sent a start signal, that is, after the first timer means has completed its timekeeping operation, during cranking, the second battery voltage - the duty ratio corresponding to the battery voltage V _B at that time from the duty ratio characteristic (characteristic II) is obtained, power supply to the high-performance glow plug is interrupted at this duty ratio it allows the effective value drop of the voltage applied to the high-performance glow plugs, lower than V _Bs predetermined value V1 (e.g., 4.5
V) is adjusted and maintained.

Further, according to the present invention, when the first timer means completes the time counting operation and the start signal sending means does not send out the start signal, that is, the first timer means completes the time counting operation and Once cranking is complete,
While the second timer means is performing its timing operation, the third timer means
Battery Voltage - duty ratio corresponding to the battery voltage V _B at that time from the duty ratio characteristic (characteristic III) is obtained by energizing the high glow plug is interrupted by this duty ratio, high-performance glow plug The effective value of the applied voltage is lowered, and the predetermined value V2 is lower than the predetermined value V1.
(For example, 3 V).

[Embodiment] Hereinafter, a glow plug energization control device according to the present invention will be described in detail.

FIG. 1 is a block circuit diagram showing one embodiment of the glow plug energization control device.

In the figure, 1 is a battery, 2 is a key switch, 3
Is a glow plug disposed in a combustion chamber (not shown) in a cylinder head of a diesel engine, 4 is a water temperature sensor for detecting a cooling water temperature of the engine, and 5 is a cooling water temperature for determining a cooling water temperature detected by the water temperature sensor 4. The determination circuit 6 is a constant voltage circuit connected to the ON terminal 2a of the key switch 2.

The constant voltage circuit 6 receives the supply of the battery voltage via the ON terminal 2a of the key switch 2, and receives a 1.5 second timer circuit 7, an afterglow timer 8, an engine signal detection circuit 9, a reference voltage circuit.
10, duty control circuit 11, drive circuit 12, triangular wave generation circuit 13, battery voltage detection circuit 14, and water temperature determination circuit 5
The 1.5-second timer circuit 7 and the after-glow timer 8 start their timing operation simultaneously with the connection of the movable contact 2d of the key switch 2 to the ON terminal 2a. I have. The 1.5 second timer circuit 7 starts counting the time T1
Until the time (T1 = 1.5 seconds in this embodiment) elapses, an "H" level timer signal is sent to the reference voltage circuit 10, and the afterglow timer 8 performs the time counting operation. At the same time as the start, until the time T2 (T2> T1) elapses, "H" is applied to the duty control circuit 11.
A level timer signal is transmitted. The value of the time 2 measured by the afterglow timer 8 varies according to the cooling water temperature detected by the water temperature sensor 4 input through the water temperature determination circuit 5. The timing operation of the afterglow timer 8 is reset when the movable contact 2d of the key switch 2 is separated from the starter terminal 2b, and restarted.

On the other hand, to the reference voltage circuit 10, a starter signal of "H" level is inputted by connecting the movable contact 2d of the key switch 2 to the starter terminal 2b. When the timer signal transmitted from the 1.5 second timer circuit 7 is at the “L” level, the reference voltage Vb is set to the duty control circuit 11 via the reference voltage circuit 10. When the timer signal transmitted from the 1.5-second timer circuit 7 is at the “H” level, the reference voltage that becomes Va via the reference voltage circuit 10 is set in the duty control circuit 11, and When both the timer signal and the starter signal transmitted from the timer circuit 7 are at the “L” level, the reference voltage Vc is set to the duty control circuit 11 via the reference voltage circuit 10. Further, the potential generated at the ON terminal 2a of the key switch 2, that is, the battery voltage value fluctuating in the battery 1 is input to the duty control circuit 11 via the battery voltage detection circuit 14 every moment. The control circuit 11 includes the battery detection circuit 14
An appropriate duty ratio is selected from the characteristics I to III shown in FIG. 2 on the basis of the battery voltage value input via the reference voltage circuit and the reference voltage value set via the reference voltage circuit 10. Triangular wave generation circuit for duty ratio pulse signal
The pulse signal is generated by using a triangular wave input through the controller 13, and the generated pulse signal is transmitted to the drive circuit 12. The power transistor Tr in the power control unit 15 is turned on and off based on a pulse signal input to the drive circuit 12, and the emitter of the transistor Tr is connected to the positive side of the battery 1. Connected to the transistor
A glow plug 3 is connected between the collector of the Tr and the ground. Here, a specific method of selecting the duty ratio in the duty control circuit 11 will be described. In the case where a reference voltage of Va is set via the reference voltage circuit 10, a rapid heating mode is set based on the characteristic I at that time. The duty ratio according to the battery voltage value is derived, and when the reference voltage Vb is set, the characteristic is set as the cranking mode.
When the reference voltage Vc is set from II, the duty ratio according to the battery voltage value at that time is derived from the characteristic III as the afterglow mode in the afterglow mode.

FIG. 3 shows the rapid heating characteristic of the glow plug 3 employed in the glow plug energization control device. For example, when the applied heating is set to 6 V, the rapid heating characteristic IV shown by the solid line in the drawing can be obtained. . That is, the applied voltage is
At 6V, a high performance glow plug that can reach 800 ° C in 1.5 seconds after the start of energization is adopted. That is, the glow plug conventionally used requires an applied voltage of, for example, 9 V in order to obtain the rapid heating characteristic IV. However, when the glow plug 3 shown in the present embodiment is used, When a voltage of 9 V is applied, a rapid heating characteristic V is obtained as shown by a dashed line in the figure. In the glow plug energization control device shown in FIG. 1, reference numeral 16 denotes a charge relay whose movable contact 16a is connected to the earth side when the engine is stopped, and "L" and "L" through the movable contact 16a of this charge relay. The “H” level signal is taken into the engine signal detection circuit 9 as an engine signal. The engine signal detection circuit 9 uses this charge relay
Based on the engine signal taken in via the switch 16, this engine signal is turned on by the ON terminal 2 a
If the "H" level is not attained even after 10 seconds have passed since the connection to the afterglow timer 8, the compulsion signal for forcibly stopping the time counting operation is sent to the afterglow timer 8. As a result, the pulse signal generation operation in the duty control circuit 11 is interrupted by the completion of the timekeeping operation or the forced stop, and the transistor Tr in the power control unit 15 driven via the drive circuit 12 maintains the off state. I have.

Next, the operation of the glow plug energization control device thus configured will be described. That is, the key switch 2 is now operated to start the engine for 0 seconds, and the movable contact
When 2d is connected to the starter terminal 2b while being connected to the ON terminal 2a (point a shown in FIG. 4 (a)), when the movable contact 2d is connected to the ON terminal 2a, the 1.5 second timer circuit 7, the after The drive power is supplied to each block of the glow timer 8, the engine signal detection circuit 9, the reference voltage circuit 10, the duty control circuit 11, the drive circuit 12, the triangular wave generation circuit 13, the battery voltage detection circuit 14, and the water temperature determination circuit 5. Become so. 1.5 second timer circuit 7 and afterglow timer 8
Starts the timing operation at the same time when the movable contact 2d of the key switch 2 is connected to the ON terminal 2a, and an "H" level timer signal is transmitted to the reference voltage circuit 10 via the 1.5 second timer circuit 7 ( 4 (b), and an "H" level timer signal is transmitted to the duty control circuit 11 via the afterglow timer 8 (a shown in FIG. 4 (c)). point). The reference voltage circuit 10 receiving the "H" level timer signal from the 1.5 second timer circuit 7
Sets a reference voltage of Va to the duty control circuit 11 (point a shown in FIG. 4D). Duty control circuit
11, corresponding to the selected characteristic I from the characteristics I~III shown in FIG. 2 on the basis of the reference voltage value at which Va is the set, then the battery voltage value based on the characteristics I (V _B) The duty ratio to be obtained. Then, the derived pulse signal of the duty ratio is transmitted to the drive circuit 12.

Here, assuming that the above-described 0-second start of the engine is performed in a severe winter season, the voltage value of the battery 1 is significantly reduced because the cranking power is excessively required. For example, assuming that the voltage drop of the battery detected by the battery voltage detection circuit 14 reaches 6 V, the duty ratio of the pulse signal generated in the duty control circuit 11 based on the characteristic I becomes 100%, and the drive circuit The transistor Tr driven via 12 maintains the ON state. That is, the transistor Tr
A voltage value V _Bs = 6 V, which is determined as a reduced battery voltage value that will be reduced at the time of starting in a severe winter environment, is directly applied to the glow plug 3 via the glow plug 3, and the glow plug 3 is connected to the glow plug 3 in FIG. Initiate its rapid heating according to the indicated property IV. When the time T1 (1.5 seconds) elapses in the 1.5 second timer circuit 7, the timer signal to the reference voltage circuit 10 becomes "L" level (b shown in FIG. 4 (b)).
Point), the reference voltage value set in the duty control circuit 11 via the reference voltage circuit 10 becomes Vb (point b shown in FIG. 4 (d)). After the reference voltage value set in the duty control circuit 11 becomes Vb, a duty ratio corresponding to the battery voltage value (V _B ) at that time is derived based on the characteristic II shown in FIG. The pulse signal of the duty ratio is sent to the drive circuit 12,
The effective value of the voltage applied to the glow plug 3 becomes 4.5 V (V1 = 4.5 V) by the transistor Tr that is turned on and off by the output of the drive circuit 12. Therefore, after the temperature of the glow plug 3 reaches 800 ° C. according to its rapid heating characteristic IV, an effective voltage of 4.5 V is applied during cranking,
For example, a high temperature such as 1000 ° C. is maintained. For this reason, even if the battery voltage value is significantly reduced when the engine is started in a severe winter, the 0-second start is reliably performed with good startability.

When the movable contact 2d of the key switch 2 is separated from the starter terminal 2b (point c shown in FIG. 4A),
The starter signal to the reference voltage circuit 10 becomes “L” level, and the reference voltage value set in the duty control circuit 11 via the reference voltage circuit 10 becomes Vc (c shown in FIG. 4D).
point). After the reference voltage value set in the duty control circuit 11 becomes Vc, a duty ratio corresponding to the battery voltage value (V _B ) at that time is derived based on the characteristic III shown in FIG. By the derived pulse signal of the duty ratio, the effective value of the voltage applied to the glow plug 3 becomes 3V (V2 = 3V). By reducing the effective voltage in this way, the glow plug temperature during afterglow is substantially reduced.
Maintain at 800 ° C to ensure the life of the glow plug. On the other hand, the timekeeping operation of the afterglow timer 8 is reset at the time point c shown in FIG. 4 (c) and restarted, and at the time point d shown in FIG. Level. That is,
Upon receiving the "L" level timer signal via the after-glow timer 8, the pulse signal generation operation in the duty control circuit 11 is interrupted, and the interruption of the pulse signal generation operation keeps the transistor Tr in the off state. The power supply to the power supply is cut off. That is, the effective value of the voltage applied to the glow plug 3 is maintained at 3 V during the time T2 from the time point c to the time point d shown in FIG. 4, and the stable heating following the rapid heating is achieved.

In addition, from the time point b to the time point c shown in FIG.
The reason why the effective value of the voltage applied to the glow plug 3 is set to 4.5 V is that consideration is given to compensating for the temperature decrease of the glow plug 3 due to the light oil as fuel and the compressed air flow during the cranking operation. Needless to say, if the "H" level engine signal is not detected even after 10 seconds in the engine signal detection circuit 9, that is, after the movable contact 2d of the key switch 2 is connected to the ON terminal 2a, it is left ON. If the connection to the start terminal 2b is not made after 10 seconds, the timing operation of the afterglow timer 8 is forcibly stopped, the pulse generation operation of the duty control circuit 11 is interrupted, and the power control unit The transistor Tr at 15 is forcibly maintained in the off state, and the subsequent power supply to the glow plug 3 is immediately cut off.

In the above description of the operation, the case where the key switch 2 is kept connected to the start mode position and the engine is cranked even after the time T1 has elapsed in the 1.5 second timer circuit 7 has been described. If the cranking of the engine is completed during the time T1 in the second timer circuit 7, the key switch 2 is returned to the ON mode position from the time point a to the time point b shown in FIG. 7, the reference voltage value to the duty control circuit 11 via the reference voltage circuit 10 immediately becomes Vc, and the effective value of the voltage applied to the glow plug 3 becomes the boost voltage value at the time of cranking. Can be dropped to 3V without going through 4.5V. FIG. 5 shows the change characteristics of the voltage applied to the glow plug 3 in this case.
After P3 point 1.5 seconds after the start of energization, the glow plug 3
The voltage applied to is controlled intermittently, and its effective value is adjusted to 3V. FIG. 6 is a characteristic diagram in which the change characteristic of the applied voltage shown in FIG. 5 is written in an effective voltage value level, and after 1.5 seconds from the start of energization, the effective voltage value changes from 6V to 3V.
The effective voltage value of 3V is continuously applied to the glow plug 3 until the measured time T2 (T2 = 600 seconds in the characteristic shown in the figure) of the afterglow timer 8 elapses. Become so. Note that the characteristic shown by the broken line in the drawing indicates a change in the effective value when a 4.5 V boost voltage is applied to the glow plug. The characteristic shown by the dashed line in the figure indicates the forced shutoff characteristic when the key switch 2 is left on.

By the way, the above description of the operation has been made by taking the engine start at 0 seconds in the severe winter season as an example.
The seconds start is performed as follows. That is, during cranking of the engine during the warm season, the amount of voltage drop in the battery 1 is small, and the voltage value is higher than 6V. In other words, while the reference voltage circuit 10 sets a reference voltage of Va for the duty control circuit 11 (1.5
(During the second), the duty signal is controlled by the pulse signal of the duty ratio derived based on the characteristic I even if the applied voltage to the glow plug 3 is within 1.5 seconds from the start of energization, and the effective value of the applied voltage becomes It will be maintained at 6V. FIG. 7 shows the change characteristics of the voltage applied to the glow plug 3 in this case. When this is shown in the effective value level, the same characteristics as those shown in FIG. 5 can be obtained. it can. That is, when a voltage exceeding 6 V is to be directly applied to the glow plug 3 during cranking of the engine during the warm season, the voltage applied to the glow plug 3 is adjusted so that the effective voltage value becomes 6 V. Since the duty control is performed, overheating due to supply of excessive power to the glow plug 3 can be prevented, and cracks due to rapid temperature rise can be prevented. Also,
Since the effective voltage to the glow plug 3 is always kept constant, the requirement for the temperature variation of the glow plug to be employed does not become severe, and the effect of reducing the cost can be expected.

In this embodiment, the glow plug 3 is
A high-performance glow plug with a 1.5 second energization time to reach 800 ° C when the applied voltage is 6 V is adopted, but as a characteristic limit of the glow plug that enables a true 0-second start with excellent startability It is desired that the energization time until reaching 800 ° C. at an applied voltage of 6 V is within 3 seconds.

〔The invention's effect〕

As described above, according to the glow plug energization control device of the present invention, the minimum value of the applied voltage that enables rapid heating of the glow plug is determined as the reduced voltage value of the battery that will decrease when the diesel engine is started in a severe cold environment. A first timer means for preparing a high performance glow plug having a voltage value lower than a predetermined voltage value V _Bs and starting a timekeeping operation when the key switch is set to the ON mode position; A start signal sending means for sending a start signal when the key switch is turned on, and a timing operation when the key switch is set to the ON mode position;
A second timer means to restart its counting operation when the key switch is returned from the start mode position to the on mode position provided, without to monitor the battery voltage V _B to the high-performance glow plug, first while the timer means is performing the counting operation, the first battery voltage - calculated the duty ratio corresponding to the battery voltage V _B at that time from the duty ratio characteristic (characteristic I), high performance glow plug in this duty ratio By intermittently energizing the high-performance glow plug, the effective value of the voltage applied to the high-performance glow plug is reduced and adjusted to be substantially equal to the voltage value _VBs. after the voltage of more than V _Bs to the performance of the glow plug is to prevent it from being applied directly, that is, the overheating of the high-performance glow plug at the time of 0 seconds start in the warm season After having assumed that the stop (prevent occurrence of cracks due to rapid Atsushi Nobori), 0 in arctic environment
Rapid heating at the start of seconds can be performed, and the engine can be reliably started at 0 seconds with good startability.

Further, according to the present invention, when the first timer means has completed its timekeeping operation and the start signal sending means has sent a start signal, that is, after the first timer means has completed its timekeeping operation, during cranking, the second battery voltage - the duty ratio corresponding to the battery voltage V _B at that time from the duty ratio characteristic (characteristic II) is obtained, power supply to the high-performance glow plug is interrupted at this duty ratio it allows the effective value drop of the voltage applied to the high-performance glow plugs, lower than V _Bs predetermined value V1 (e.g., 4.5
V) is adjusted and maintained so that the temperature of the glow plug is reduced by the flow of fuel and compressed air during the cranking operation, and the startability can be improved.

Further, according to the present invention, when the first timer means completes the time counting operation and the start signal sending means does not send out the start signal, that is, the first timer means completes the time counting operation and Once cranking is complete,
While the second timer means is performing its timing operation, the third timer means
Battery Voltage - duty ratio corresponding to the battery voltage V _B at that time from the duty ratio characteristic (characteristic III) is obtained by energizing the high glow plug is interrupted by this duty ratio, high-performance glow plug The effective value of the applied voltage is lowered, and the predetermined value V2 is lower than the predetermined value V1.
(For example, 3 V), so that the glow plug temperature during the afterglow is kept constant (for example, 800 ° C.) and the life of the glow plug can be ensured. That is, afterglow can be performed for a long time while considering the durability of the glow plug, and warming up of the combustion chamber can be promoted.

Further, according to the present invention, in the rapid heating mode, the cranking mode, and the after-glow mode, the effective voltage value to the glow plug is always kept constant (V _Bs V1, V2). The requirement for temperature variation does not become severe, and the cost reduction effect can be expected.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing an embodiment of a glow plug energization control device according to the present invention, and FIG. 2 is a duty ratio for a battery voltage value selected by a duty control circuit in the glow plug energization control device. FIG. 3 is a diagram showing characteristics, FIG. 3 is a diagram showing a rapid heating characteristic of a glow plug used in this glow plug energization control device, FIG. 4 is a time chart for explaining the operation of this energization control device, and FIG. The figure showing an example of the applied voltage characteristic applied to the glow plug at the start of 0 second of the engine in the severe winter season,
FIG. 6 is a diagram illustrating the applied voltage characteristics in terms of an effective value level, FIG. 7 is a diagram illustrating an example of the applied voltage characteristics applied to the glow plug at the start of 0 second of the engine in a warm season,
FIG. 8 and FIG. 9 are diagrams showing the current control characteristics for a conventional glow plug. 1 ... battery, 2 ... key switch, 3 ... glow plug, 7 ... 1.5 second timer circuit, 10 ... reference voltage circuit, 1
1… Duty control circuit, 14… Battery voltage detection circuit, 15… Power control unit, Tr… Transistor.

Claims (1)

(57) [Claims] 1. A voltage value V defined as a battery voltage drop value at which a minimum value of an applied voltage enabling rapid heating is reduced when a diesel engine is started in a severe cold environment.
_A high performance glow plug lower than _Bs, first timer means for starting a timekeeping operation when the key switch is set to the on mode position, and sending a start signal when the key switch is set to the start mode position. A start signal sending means for starting the timing operation when the key switch is set to the ON mode position, and restarting the timing operation when the key switch is returned to the ON mode position from the start mode position. and second timer means, the battery voltage V _B to the high-performance glow plug monitoring,
While the first timer means is performing its timing operation,
The first battery voltage - by seeking the duty ratio corresponding to the battery voltage V _B at that time from the duty ratio characteristic, intermittently the energization of the high performance glow plug in this duty ratio applied to the high-performance glow plug When the effective value of the voltage is lowered and adjusted so as to be substantially equal to the voltage value _VBs , the first timer means completes its timekeeping operation, and the start signal sending means sends a start signal. , the second battery voltage - calculated the duty ratio corresponding to the battery voltage V _B at that time from the duty ratio characteristic by intermittent energization to the high performance glow plug in the duty ratio, to the high-performance glow plug lower than the voltage value V _Bs lowering the effective value of the applied voltage a predetermined value V1
When the first timer means completes its timekeeping operation and the start signal sending means does not send a start signal, the second timer means performs its timekeeping operation. during the third battery voltage are - by seeking the duty ratio corresponding to the battery voltage V _B at that time from the duty ratio characteristic, intermittently the energization of the high performance glow plug in the duty ratio, the high performance glow plug And an energization control means for adjusting and maintaining the effective value of the applied voltage to the predetermined value V2 lower than the predetermined value V1.