JPH1030491A - Abnormal combustion judging device of diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abnormal combustion judging device that is able to judge a combustion defective state that is advantageous in terms of cost and not yet reached to a misfire. SOLUTION: Four ammeters A1, A2, A3 and A4 are interposed on a conductive cable lying between a glow controller C and four self-controlled type glow plugs P1, P2, P3, and P4. These ammeters A1 to A4 transmit information on the detected current value to the glow controller C. When an engine speed detector Ne detects an idling speed, the glow controller C performs its current- carrying to these four glow plugs P1 to P4. The glow controller C performs a magnitudious comparison between the current value being securable from these ammeters A1 to A4 and the preset judged current value. In the case where the current value Jn is larger than the judged current value As, the grow controller C judges whether there is something wrong with combustion or not.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for determining abnormal combustion in a diesel engine.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Application Publication No. Hei 1-210840 and Japanese Unexamined Patent Application Publication No.
-91300. JP 1
In the conventional apparatus disclosed in JP-A-210840, means for detecting pressure in a cylinder is provided in each cylinder, and based on a comparison between an in-cylinder pressure waveform detected by these detecting means and a normal standard pressure waveform. A misfire determination is made. In the device disclosed in Japanese Patent Application Laid-Open No. 7-91300, a change in the engine speed is detected to determine the presence or absence of an abnormality.

[0003]

However, Japanese Patent Laid-Open No. 1-2
In the configuration in which a new pressure detecting means is provided in a cylinder in Japanese Patent Publication No. 10840, the pressure detecting means itself causes an increase in cost. In addition, a new design for mounting the pressure detecting means in the cylinder is required, and it is not limited to an increase in cost of the pressure detecting means itself.

In the system disclosed in Japanese Patent Application Laid-Open No. Hei 7-91300, in which the presence / absence of an abnormality is determined based on a change in rotation speed that is easily affected by various disturbances, it is possible to determine a misfire when the change in rotation speed becomes large. However, it is difficult to accurately determine a poor combustion state that has not caused a misfire.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a combustion abnormality judging device capable of accurately judging a poor combustion state which is advantageous in cost and has not caused misfire.

[0006]

According to the present invention, there is provided:
For diesel engines with cylinders with self-control glow plugs, which reduce the amount of electricity as the ambient temperature rises and increase the amount of electricity as the ambient temperature decreases,
According to the first aspect of the present invention, the self-controlled glow plug is energized in an engine operating state, and a current value by the energization is compared with a predetermined determination current value. A combustion abnormality judging device for judging the combustion in the cylinder to be a combustion failure state when the value exceeds the value is constituted.

When current is supplied to the glow plug and the combustion state in the cylinder is normal, the detected current value does not exceed the determination current value. If the combustion state in the cylinder is poor, the detected current value exceeds the determination current value. The current value flowing through the glow plug directly reflects the combustion state in the cylinder, and the accuracy of the combustion abnormality determination using the existing glow plug is high.

In the invention of claim 2, a current value obtained after a lapse of a predetermined time after the energization is used as a comparison target of the predetermined judgment current value. It takes time for the current value after current supply to the glow plug to reach an equilibrium state. The predetermined time is set in consideration of the time for shifting to the equilibrium state, and the accuracy of the combustion abnormality determination is further improved by setting such a time.

According to the third aspect of the present invention, the energization is performed during idling. The idling state is suitable for setting the determination current value.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, glow plugs P1, P2, P3, and P4 are provided in a plurality of cylinders S1, S2, S3, and S4 of a diesel engine. When electricity is supplied to the glow plug Pn (n = 1, 2, 3, 4), the heater coils H1, H2, H3, H4 of the glow plug Pn generate heat. Due to this heat, the cylinder Sn (n = 1, 2, 3, 4)
The inside heats up. Control coils K1, K of glow plug Pn
2, K3 and K4 control the amount of energization according to the temperature in the cylinder Sn. The control coil Kn decreases the energization amount when the temperature in the cylinder Sn increases, and increases the energization amount when the temperature in the cylinder Sn increases. That is, the glow plug Pn is a self-control type glow plug that reduces the amount of electricity as the ambient temperature increases and increases the amount of electricity as the ambient temperature decreases.

The glow plug Pn is controlled by a glow controller C serving as a power supply means. Ammeters A1, A2, A3, and A4 are interposed on the conductive lines between the glow controller C and each glow plug Pn. Ammeter An
(N = 1, 2, 3, 4) is the detected current value J1, J2,
The information of J3 and J4 is sent to the glow controller C. The glow controller C is provided with an engine speed detector Ne, and the display G is provided with combustion abnormality display sections G1, G2, G3, G4 and disconnection display sections g1, g2, g3, g4.

The glow controller C executes a combustion abnormality determination program shown in a flowchart of FIG. When the engine speed detector Ne as the operating state detecting means detects the idling speed, the glow controller C energizes each glow plug Pn by applying a predetermined voltage. After a predetermined time t has elapsed after the start of energization, the glow controller C sets the current value Jn (n =
Based on (1, 2, 3, 4), it is determined whether there is a disconnection.
When the current value in the glow plug Pn is zero, the glow controller C outputs a disconnection detection signal indicating disconnection of the glow plug Pn. The display G displays a disconnection display portion gn (n = n = n) corresponding to the glow plug Pn based on the disconnection detection signal.
1, 2, 3, 4) are turned on.

If the current value in the glow plug Pn is larger than zero, the glow controller C serving as a judgment means
Performs a magnitude comparison between a preset determination current value As and a detection current value Jn. The detection current value Jn is equal to the determination current value As.
In the following cases, the glow controller C determines the normal combustion. When the detected current value Jn is larger than the determination current value As, the glow controller C determines a combustion abnormality, and outputs a combustion abnormality determination signal indicating a combustion abnormality of the cylinder Sn. The indicator G displays a combustion abnormality display section Gn (n =
1, 2, 3, 4) are turned on.

A curve E in the graph of FIG. 2 shows the relationship between the temperature in the cylinder Sn and the amount of electricity supplied to the glow plug Pn. The temperature range in the cylinder Sn exceeding 200 ° C. is a temperature range that can be regarded as a normal combustion state. 200 ° C to T °
The temperature range in the cylinder Sn of C is a temperature range that can be regarded as a combustion abnormal state that has not led to misfire, and the temperature range in the cylinder Sn below the temperature T ° C is a temperature range that can be regarded as misfire. The energization amount in the glow plug Pn is 200 ° C.
In the temperature range of up to T ° C., the temperature decreases as the temperature in the cylinder Sn increases. A straight line L represents the determination current value As corresponding to the idling state. The relationship between the temperature and the amount of current shown by the curve E has some variation for each glow plug Pn. The determination current value As is set in consideration of this variation.

In the first embodiment, the following effects can be obtained. (1-1) When the glow plug Pn is energized in the engine operating state, the detected current value Jn does not exceed the determination current value As if the combustion state in the cylinder Sn is normal. If the combustion state in the cylinder Sn is poor, the detected current value Jn exceeds the determination current value As. FIG.
As shown by the curve E, the current value flowing through the glow plug Pn directly reflects the combustion state in the cylinder Sn, and the accuracy of the combustion abnormality determination using the existing glow plug Pn is high. (1-2) The value of the current flowing through the glow plug Pn varies within a range from a misfire state to a normal state. A change in the current value in such a range can quickly detect an abnormal combustion state before a misfire, such as a combustion failure due to a time-dependent deterioration such as a pressure drop in the cylinder due to abrasion of a sliding contact portion and a clogged injection of a fuel injection nozzle. become. (1-3) Since the glow plug Pn and the ammeter An serving as current value detecting means are in one-to-one correspondence, the plurality of cylinders S
The cylinder in the abnormal combustion state can be specified from n. (1-4) It takes time for the temperature in the cylinder Pn to reach an equilibrium state after energization of the glow plug Pn. That is,
It takes time for the current value after energizing the glow plug Pn to reach an equilibrium state. The predetermined time t is set in consideration of the time for shifting to the equilibrium state. The determination method in which a current value obtained after a lapse of a predetermined time after energization is used as a comparison target of the determination current value As contributes to an improvement in the accuracy of combustion abnormality determination. (1-5) The idling state is a stable state as an operating state, and the temperature in the cylinder is stable in a normal state. Therefore, the idling state is suitable as a state in which the determination current value is set. (1-6) The combustion abnormality judging device using the existing glow plug is advantageous in terms of cost because it does not increase the cost of newly installed parts and does not require a design change of the diesel engine.

Next, a second embodiment shown in FIGS. 4 and 5 will be described. The same components as those in the first embodiment are denoted by the same reference numerals. In this embodiment, as shown in FIG. 4, one ammeter Ao corresponds to a plurality of glow plugs Pn, and the ammeter Ao detects the total amount of current flowing through all the glow plugs Pn. An indicator Go and a water temperature detector W are connected to the glow controller C by signals. Display G
The o is provided with a combustion abnormality display part G5 and a disconnection display part g5. The water temperature detector W detects the temperature of the cooling water for cooling the diesel engine. The glow controller C performs the combustion abnormality determination shown in the flowchart of FIG. 5 based on the detected current value obtained from the ammeter Ao.

In this embodiment, the power supply timing is the normal power supply timing of the glow plug Pn at the time of starting the engine, and every predetermined time interval thereafter. After a lapse of a predetermined time t from the start of energization to the glow plug Pn, the glow controller C is represented by an engine speed obtained from the engine speed detector Ne and a water temperature obtained from a water temperature detector W serving as operating state detecting means. The determination current values Bs and Cs are read based on the operation state detection information.
The determination current values Bs and Cs (Bs> Cs) are selected from a map of operating state-determination current value stored in the memory.

The current value Jo detected by the ammeter Ao
Is larger than the determination current value Bs, the glow controller C outputs a combustion abnormality determination signal. The display Go lights the combustion abnormality display section G5 based on the output of the combustion abnormality determination signal. When the current value Jo is lower than the determination current value Cs, the glow controller C outputs a disconnection detection signal.
The display Go lights the disconnection display section g5 based on the output of the disconnection detection signal.

The judgment current value Bs is determined by the four glow plugs P
The setting is made on the assumption that one of n is abnormal combustion. The determination current value Cs is determined by the four glow plugs P
The setting is made on the assumption that one of n is in a disconnected state.

Also in this embodiment, it is possible to accurately determine a combustion abnormality that has not caused a misfire without causing high cost.

[0022]

As described above in detail, according to the present invention, in the engine operating state, the self-control type glow plug is energized, and a current value by the energization is compared with a predetermined judgment current value to determine the energized state. If the current value exceeds the predetermined determination current value, the combustion in the cylinder is determined to be a combustion failure state, so that the combustion failure state that is advantageous in terms of cost and has not led to misfire is accurately determined. obtain.

[Brief description of the drawings]

FIG. 1 is a control block diagram showing a first embodiment.

FIG. 2 is a graph showing self-control characteristics of a glow plug.

FIG. 3 is a flowchart showing a combustion abnormality determination program.

FIG. 4 is a control block diagram showing a second embodiment.

FIG. 5 is a flowchart showing a combustion abnormality determination program. S1, S2, S3, S4 ... cylinders, P1, P2, P3, P
4 glow plugs, A1, A2, A3, A4 ... ammeters serving as current value detection means, C ... glow controllers serving as power supply control means and determination means.

Claims (3)

[Claims] A diesel engine having a self-controllable glow plug having a self-controllable glow plug that reduces the amount of electricity as the ambient temperature increases and increases the amount of electricity as the ambient temperature decreases. The control type glow plug is energized, and a current value by the energization is compared with a predetermined determination current value. If the current value by the energization exceeds a predetermined determination current value, combustion in the cylinder is burned. A combustion abnormality determination device for a diesel engine that determines a defective state. 2. The diesel engine combustion abnormality judging device according to claim 1, wherein the current value to be compared with the predetermined judgment current value is a current value obtained after a lapse of a predetermined time after the energization. 3. The diesel engine combustion abnormality judging device according to claim 1, wherein the energization is performed during idling.