JPH0441255Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> The present invention relates to an improvement of a glow plug energization control device for a compression ignition engine, and particularly to an improvement of a device for detecting disconnection of a glow plug.

<Background Art> For example, in a compression ignition engine such as a diesel engine, a glow plug is used to heat a combustion chamber in advance in order to promote ignition of fuel spray when starting the engine. This glow plug is provided for each cylinder in a multi-cylinder engine, and each glow plug is connected in parallel.Battery voltage is applied to the parallel connection circuit of this glow plug, causing each glow plug to become red hot, and each glow plug is connected in parallel. The room is being heated.

However, if some of the plurality of glow plugs connected in parallel are disconnected during this glow plug energization period, the load on the battery is reduced and the battery terminal voltage increases. Since this increased battery voltage is applied to the remaining normal glow plugs, these glow plugs are heated and their durability deteriorates. That is, if some of the plurality of glow plugs disposed in each cylinder were disconnected, there was a risk that the other glow plugs would be disconnected one after another.

In order to avoid such inconveniences, conventional glow plug energization control devices compare the glow plug terminal voltage V _IN when the glow plug is energized with the voltage V _REF set to a predetermined value, and determine the glow plug terminal voltage. It was determined that the glow plug was disconnected when V _IN became larger than the predetermined voltage V _REF . Here, the predetermined voltage V _REF is obtained by dividing a voltage obtained by stabilizing the battery voltage by, for example, two resistors, and the value thereof is larger than the glow plug terminal voltage when all the glow plugs are normal, and when only one glow plug is connected. It is set to be lower than the glow plug terminal voltage in the event of a disconnection.

A flowchart of the operating process of such a conventional control device is shown in FIG. That is, glow plug energization time t ₀ is set in S1, and energization of the glow plug is started in S2. And in S3 V _IN is
If it is determined that it is larger than V _REF , the glow plug disconnection indicator lamp is lit in S4, and the power supply to the glow plug is stopped in S5. On the other hand, if S3 determines that V _IN is smaller than V _REF , energization continues until S6 determines that the predetermined time t ₀ has elapsed, and _S7 stops energizing the glow plug. will be stopped.

In such a conventional glow plug energization control device, when an engine starting operation is performed while the glow plug is energized and the starter motor rotates, the load on the battery increases, and the battery terminal voltage drops to obtain the predetermined voltage V _REF . In some cases, the stabilizing voltage for this purpose became unable to maintain stability, resulting in a drop in V _REF . For this reason, even though the glow plug is not disconnected, the glow plug terminal voltage V _IN becomes relatively larger than V _REF , and there is a risk that a normal glow plug may be mistakenly determined to be disconnected. Therefore, there was a risk that the current supply would be stopped and the desired preheating effect could not be obtained. In addition, during the engine starting operation period when such a misjudgment of disconnection occurs, the battery voltage decreases as mentioned above, so even if some glow plugs are disconnected, continuing to energize will restore normal operation. In order to ensure startability, it is desirable to continue energizing even if some of the glow plugs are broken during the engine starting operation.

<Purpose> The present invention has been developed with attention to these conventional problems, and it is possible to prevent a normal glow plug from being mistaken for a disconnection by not detecting a disconnection of the glow plug while the engine is being started. The purpose is to avoid judgment.

<Summary of the invention> Therefore, in the present invention, as shown in FIG. 2, the glow plug terminal voltage V _IN of the glow plug energizing circuit 20 is
The stabilized voltage supply means 21 compares _{the glow plug terminal voltage V IN and} the reference voltage V _REF to obtain a predetermined reference voltage V REF for comparison with the voltage V _IN .
Glow plug disconnection detection means 22 determines that the glow plug is disconnected and issues a glow plug disconnection detection signal when V REF becomes larger than V _REF , and when the glow plug disconnection detection signal is input, the glow plug energizing circuit 20 opens and closes. In a glow plug energization control device having a switch driving means 23 for releasing a switch, the engine starting operation period detecting means 24 and the detecting means 24 are provided.
An operation stopping means 25 is provided which suspends the operation of the glow plug disconnection detection means 22 and prohibits the output of the glow plug disconnection detection signal and the opening of the switch based on the signal during the engine starting operation period detected by the glow plug disconnection detection means 22. To achieve the above objectives.

<Example> The present invention will be described below based on an example shown in FIG.

Configuration: In the figure, a circuit in which glow plugs 1 provided for each cylinder are connected in parallel is connected to a battery 5 via a dropping resistor 2, a glow plug relay 3, and an engine key switch 4, and is connected to a glow plug energizing circuit. Configure. The terminal voltage V _IN of the glow plug 1 is input to the control device 6.

On the other hand, the voltage of the battery 5 is also applied to a regulator 7 as a stabilizing voltage supply means, and the regulator 7 outputs a constant voltage, for example, 8V, within a certain battery voltage fluctuation range. The output voltage of the regulator 7 is divided by two resistors 8 and 9 connected in series and input to the control device 6 as a reference voltage V _REF .

Here, the value of these two resistors 8 and 9 is the value of the voltage V _REF divided by these resistors 8 and 9, which is the glow plug 1 terminal voltage when all of the glow plugs 1 connected in parallel are normal. It is selected to be larger than V _IN and smaller than the glow plug 1 terminal voltage V _IN when one of the plurality of glow plugs 1 is disconnected.

As shown in FIG. 4, the control device 6 compares the glow plug terminal voltage V _IN with the reference voltage V _REF and determines that V _IN is
Glow plug disconnection detection means 6a that issues a glow plug disconnection detection signal when it becomes larger than V _REF
When the glow plug disconnection detection signal is input, the switch driving means 6b generates a signal to open the glow plug relay 3, and while the engine starting switch is on, the engine starting operation is performed. During the engine starting operation period detected by the engine starting operation period detecting means 6c, the operation of the glow plug disconnection detecting means 6a is stopped and the glow plug disconnection detection signal is output. The glow plug relay 3 is configured to include an operation stop means 6d for prohibiting the opening of the glow plug relay 3 as a switch.

The control device 6 also includes a glow plug energization control means 6e that issues a signal for controlling the energization of the glow plug 1 to the switch drive means 6b, and a glow lamp lighting that lights the glow lamp 10 when a glow plug disconnection signal is input. Means 6f are also provided.

Specifically, this control device 6 is constituted by, for example, a microcomputer.

Effect Next, the effect will be explained. Note that the symbols in parentheses indicate the steps in the flowchart of FIG. 5 showing the operating process of this embodiment.

When the engine key switch 4 is turned on, the control device 6 becomes operable and the regulator 7
The voltage of the battery 5 is applied to the regulator 7.
The reference voltage V _REF obtained by dividing the output voltage of the control device 6
is input to the glow plug disconnection detection means 6a.

Next, when a preheating switch (not shown) is turned on, the glow plug energization control means 6e of the control device 6 starts operating, and sets the energization time t ₀ of the glow plug 1 based on, for example, the engine cooling water temperature (S11).
A signal for energizing the glow plug 1 for that time is output to the switch driving means 6b. Upon receiving this signal, the switch driving means 6b issues a signal to close the glow plug relay 3, and the glow plug relay 3 is closed, the glow plug 1 becomes red hot, and the combustion chamber is heated ( S12).

Here, when a part of the glow plug 1 is disconnected, the burden on the battery 5 is reduced, the value of the glow plug 1 terminal voltage V _IN becomes larger than the value of the reference voltage V _REF , and the glow plug disconnection detection means 6a detects the disconnection. Emit a signal (S14). This signal is input to the switch driving means 6b and the glow lamp lighting means 6f, and the glow plug relay 3 is opened to protect the remaining glow plugs 1 that are not disconnected, and the glow lamp 10 is turned on. The driver is then notified of the glow plug 1 disconnection (S15, S16).

On the other hand, if there is no abnormality in the glow plug 1 and an engine starting operation is performed during the energization period of the glow plug 1 and an engine starting switch (not shown) is turned on, the engine starting operation period detection means 6c issues a signal and the operation stopping means 6d stops the operation of the glow plug disconnection detection means 6a while the engine starting switch is on. Here, during the period when the engine start switch is on and the starter motor is rotating, the load on the battery 5 increases and the battery 5 terminal voltage decreases, and the output voltage of the regulator 7 cannot maintain stability. Terminal voltage V _IN of glow plug 1 when the value of reference voltage V _REF is relatively normal.
This is a period during which there is a risk that a normal glow plug 1 may be mistakenly determined to be disconnected. The operation stop means 6d is the glow plug 1 during this period.
Since the disconnection detection work is suspended, it is possible to prevent a normal glow plug 1 from being mistakenly determined as a disconnection, and the power supply to the glow plug 1 is stopped due to an erroneous detection due to a drop in battery terminal 5 voltage during the engine starting operation period. Never (S13).

In this device, while the engine start switch is on, the glow plug 1 disconnection detection work is stopped, and the glow plug disconnection detection means 6a outputs a glow plug disconnection detection signal, and the glow plug relay 3 outputs the glow plug disconnection detection signal based on the signal. is prohibited from opening, so even if glow plug 1 breaks during this period,
No disconnection is detected during this period. Therefore,
The power supply to the glow plug 1 following the detection of disconnection is not stopped, but during this period, the terminal voltage of the battery 5 has decreased, so even if the power supply to the glow plug 1 is not stopped, the remaining normal glow plugs 1 does not overheat. Also, especially glow plug 1
Even if some of the glow plugs 1 are disconnected during the start-up period when the machine is cold and requires preheating, the disconnection detection is suspended as described above, so energization can be continued, and the glow plugs 1 It is possible to obtain a preheating effect and enable starting.

Then, when the engine starting operation is completed, the operation stopping means 6d restarts the operation of the glow plug disconnection detection means 6a, so if the glow plug 1 is disconnected, the disconnection is detected as before, and the glow plug 1 protection and lighting of the glow lamp 10 are performed (S15, S16).

Then, when it is determined that there is no abnormality in the glow plug 1 and a predetermined time t ₀ has passed after the start of energization (S17), the energization to the glow plug 1 is stopped (S18).

In this example, the period during which the engine starting operation is performed is from when the engine starting switch is turned on to when it is turned off, but in reality there is a time delay in the activation of the relay that energizes the starter motor. Therefore, it is better to consider that a predetermined period of time after the engine starting switch is turned off is during the engine starting operation.

In this embodiment, the control device 6 is configured by a microcomputer, but it goes without saying that the control device 6 may be configured by an electric circuit that executes the flowchart shown in FIG.

<Effects> As explained above, in the present invention, the glow plug disconnection detection work during the engine starting operation is stopped and the output of the disconnection detection means and energization stop based on this signal are prohibited, so that battery damage due to rotation of the starter motor is prevented. Misjudgment of glow plug disconnection detection due to a drop in terminal voltage and stoppage of energization based on the erroneous determination are prevented, and energization is continued even if some of the glow plugs are disconnected during the engine starting operation period. As a result, reliable heating of the combustion chamber can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing the conventional glow plug energization control process, Fig. 2 is an overall configuration diagram of the present invention, Fig. 3 is a circuit diagram showing an embodiment of the present invention, and Fig. 4 is a diagram of the same control device. The functional block diagram, FIG. 5, is a flowchart showing the glow plug energization control process according to the embodiment shown in FIG. 1...Glow plug, 2...Dropping resistance, 3...Glow plug relay (switch), 4
...Engine key switch, 5...Battery, 6
...control device, 6a...glow plug disconnection detection means, 6b...switch drive means, 6c...engine starting operation period detection means, 6d...operation halting means, 7...
...regulator (stabilized voltage supply means).

Claims (1)

[Claims for Utility Model Registration] A glow plug energizing circuit, a stabilizing voltage supply means for obtaining a predetermined reference voltage V _REF for comparison with the glow plug terminal voltage V _IN of the glow plug energizing circuit, and the glow plug energizing circuit, glow plug disconnection detection means that compares the plug terminal voltage V _IN with the reference voltage V _REF , determines that the glow plug is disconnected when V _IN becomes greater than V _REF , and issues a glow plug disconnection detection signal; In a glow plug energization control device having a switch driving means for opening a switch of the glow plug energization circuit when a plug disconnection detection signal is input, an engine starting operation period for detecting a period during which an engine starting operation is being performed. a detection means; and an operation suspension for suspending the operation of the glow plug disconnection detection means and prohibiting output of a glow plug disconnection detection signal and opening of the switch based on the signal during an engine starting operation period detected by the detection means. 1. A glow plug energization control device for a compression ignition engine, characterized by comprising: means.