JPH0569992B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for detecting burnout of a glow plug in an internal combustion engine, and is particularly suitable for use in electronically controlled diesel engines for automobiles, in which a glow plug is activated at least during startup or fast idle to ensure smooth ignition of fuel. The present invention relates to a method for detecting burnout of a glow plug in an internal combustion engine.

[Prior art]

In general, in internal combustion engines such as diesel engines, which operate glow plugs during startup or fast idle to ensure smooth fuel ignition, the glow plugs may become disconnected due to engine vibration or changes over time. , causing problems such as poor starting. Therefore, it is very important to quickly and reliably detect a break in a glow plug, but in the past, it was not possible to detect a break in a glow plug while it was still attached to the engine. It is not possible to identify starting failures due to glow plug breakage, and it is not possible to quickly take appropriate measures against starting failures, such as:
This has the problem that other parts such as the fuel injection pump, electronic control unit, glow plug relay, etc. must be replaced first, and it takes a lot of time and man-hours to detect a disconnection of the glow plug. Also, even if it is assumed that the cause of the starting failure is a broken glow plug, the resistance of each glow plug installed in each cylinder must be measured to find the broken glow plug. It was necessary and therefore required a great deal of effort and time.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned conventional problems, and it is possible to easily and reliably detect a disconnection of a glow plug while it is still attached to the engine, and therefore to quickly and reliably detect the disconnection of a glow plug. It is an object of the present invention to provide a method for detecting burnout of a glow plug in an internal combustion engine, which enables accurate repair.

[Structure of the invention]

The present invention provides a glow plug disconnection detection method for an internal combustion engine in which the glow plug is activated at least during startup or fast idling to ensure smooth ignition of fuel, as summarized in FIG. A procedure for detecting that the glow plug is in a state where it should be operated, a procedure for determining the engine rotational speed or rotational variation for each cylinder when the glow plug is in a state where it should be operated, and a procedure for determining the engine rotational speed or rotational variation for each cylinder. The above objective is achieved by including the step of determining that the glow plug of the relevant cylinder is disconnected when the glow plug is smaller than the set value. Further, in an embodiment of the present invention, the disconnection determination is not performed when the engine cooling water temperature is extremely low, thereby preventing an erroneous determination at extremely low temperatures when the fuel becomes waxy and normal injection or ignition cannot be expected. It is designed to prevent this. Further, in another embodiment of the present invention, the disconnection determination is not performed at the beginning of startup when the engine speed is very low, thereby preventing an erroneous determination at the beginning of startup when the fuel is not sufficiently ignited. This is how it was done.

[Action of the invention]

In the present invention, the engine rotational speed or rotational fluctuation for each cylinder is determined when the glow plug is in a state in which it should operate, and when the engine rotational speed or rotational fluctuation is smaller than a set value, the glow plug of the relevant cylinder is Since it is determined that the glow plug is disconnected, disconnection of the glow plug can be easily and reliably detected while the glow plug remains attached to the engine. That is, for example, the engine rotational speed when the glow plug is not disconnected, and the state of change in the engine rotational speed of 45°CA calculated every 465°CA, for example, are as follows:
As shown by solid line A in Fig. 2, for example, if the glow plug of the No. 2 cylinder is disconnected, the ignition of the No. 2 cylinder will not occur at all or will not occur smoothly, resulting in an explosion. The increase in rotation due to this will disappear or become very small. Therefore, as shown by the broken line B in FIG. 2, the engine speed of the corresponding No. 2 cylinder decreases, and the
Maximum value of engine rotation speed per 45°CA Minimum value of Nhi
The difference in Nli (hereinafter referred to as rotational fluctuation) ΔNi becomes extremely small. Therefore, since the engine rotational speed or rotational fluctuation has become smaller than the set value, it can be determined that the glow plug of the relevant cylinder has been disconnected.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an electronically controlled diesel engine for automobiles, in which the method for detecting disconnection of a glow plug for an internal combustion engine according to the present invention is adopted, will be described in detail with reference to the drawings. As shown in FIG. 3, the embodiment includes a drive shaft 14 that rotates in conjunction with the rotation of the crankshaft of the diesel engine 10, and a feed pump 16 (third pump) fixed to the drive shaft 14 for pumping fuel. (The figure shows the state unfolded at 90 degrees), a fuel pressure adjustment valve 18 for adjusting the fuel supply pressure, and a system for detecting the rotational state of the diesel engine 10 from the rotational displacement of the gear 20 fixed to the drive shaft 14. For example, an engine rotation sensor 22 consisting of an electromagnetic pickup, a roller ring 25 for driving a pump plunger 24 in cooperation with a face cam 23, and a timer piston 26 for controlling the rotational position of the roller ring 25 (see FIG. 3). a timing control valve 28 for controlling the fuel injection timing by controlling the position of the timer piston 26; a variable inductance, for example, for detecting the position of the timer piston 26; A timer position sensor 30 consisting of a sensor,
A spill ring 32 for controlling the timing of fuel release from the pump plunger 24, a spill actuator 34 for controlling the fuel injection amount by controlling the position of the spill ring 32, and the spill actuator. A spill position sensor 36 consisting of, for example, a variable inductance sensor for detecting the position Vsp of the spill ring 32 from the displacement of the plunger 34A of 34, and a fuel cut solenoid (hereinafter referred to as FCV) for cutting off fuel when the engine is stopped. a distribution type fuel injection pump 12 having a delivery valve 42 for preventing backflow or sag of fuel; an intake pressure sensor 48 for detecting the pressure of air taken in through the intake pipe 46; an intake temperature sensor 50 for similarly detecting the temperature of the intake air; A water temperature sensor 52 disposed on the cylinder block 10 for detecting the engine cooling water temperature, and an accelerator sensor 52 for detecting the depression angle (hereinafter referred to as accelerator opening degree) of the accelerator pedal 54 operated by the driver. a sensor 55; a glow plug 56 disposed such that its tip protrudes into the engine combustion chamber; a warning light 57 for indicating a disconnection of the glow plug 56; and an accelerator sensor detected from the output of the accelerator sensor 55. Opening degree Accp, the engine rotation sensor 2
The control injection timing and control injection amount are determined from the engine rotational speed NE obtained from the output of step 2, the engine cooling water temperature detected from the output of the water temperature sensor 52, etc., and the control injection amount is determined from the fuel injection pump 12 at the control injection timing. The timing control valve 28, spill actuator 34 so that fuel is injected.
An electronic control unit (hereinafter referred to as ECU) controls the above, and also energizes the glow plug 56 during startup or fast idling to operate it, and also lights up the warning etc. 57 when a disconnection of the glow plug 56 is detected. )58. The ECU 58, as shown in detail in FIG.
A central processing unit (hereinafter referred to as CPU) consisting of, for example, a microprocessor, performs various arithmetic processing.
58A, a clock 58B that generates various clock signals, and a random access memory (hereinafter referred to as RAM) 58C for temporarily storing calculation data etc. in the CPU 58A.
, a read-only memory (hereinafter referred to as ROM) 58D for storing control programs and various data, the output of the water temperature sensor 52 inputted via a buffer 58E, and the suction inputted via a buffer 58F. The output of the air temperature sensor 50, the output of the intake pressure sensor 48 inputted via the buffer 58G, the output of the accelerator sensor 55 inputted via the buffer 58H, and the sensor drive circuit 58.
The spill position sensor 36 output Vsp is driven by the sensor driving frequency signal of J output and is input via the sensor signal detection circuit 58K, and is also driven by the sensor driving frequency signal of the sensor driving circuit 58L output. , sensor signal detection circuit 58M
A multiplexer (hereinafter referred to as
MPX) 58N, an analog-to-digital converter (hereinafter referred to as A/D converter) 58P for converting the analog signal output from the MPX 58N into a digital signal, and an output from the A/D converter 58P. An input/output port (hereinafter referred to as I/O port) 58Q for inputting data into the CPU 58A and the output of the engine rotation sensor 22 are waveform-shaped and
Waveform shaping circuit 5 for direct input to CPU58A
8R, and a drive circuit 5 for energizing the glow plug 56 according to the calculation result of the CPU 58A.
8S, a drive circuit 58T for driving the timing control valve 28 in accordance with the calculation result of the CPU 58A, and a digital-to-analog converter (hereinafter referred to as a D/A converter) 58U. The spill position signal of the CPU 58A output and the spill position sensor 36 output
It is comprised of a servo amplifier 58V and a drive circuit 58W for driving the spill actuator 34 according to the deviation from Vsp, and a common bus 58X for connecting each of the constituent devices. The effects of the embodiment will be explained below. The glow plug disconnection determination in this example is as follows:
The process is executed according to the flowchart shown in FIG.
That is, first, in step 110, it is determined whether the glow plug 56 is in a state where it should be operated, for example, during startup or fast idle. This determination is made because the CPU 58A calculates the operating time of the glow plug 56, so for example, if the operating signal is not zero, it can be determined that the glow plug 56 is in a state where it should be operated. If the judgment result in step 110 is positive, the process proceeds to step 112, where the engine coolant temperature THW determined from the output of the water temperature sensor 52 is determined as follows.
It is determined whether the temperature is higher than the set value, for example, -25°C. In this step 112, the fuel is turned into wax,
This is provided to prevent erroneous judgments at extremely low temperatures when normal injection or ignition cannot be expected. If the judgment result in step 112 is positive, the process proceeds to step 114, where the engine rotational speed is
It is determined whether it is larger than the set value, for example 400 RPM. This step 114 is intended to prevent erroneous determination at the initial stage of startup when the fuel is not sufficiently ignited. If the judgment result in step 114 is positive, the process proceeds to step 116, and as shown in the following equation,
Maximum value Nhi and minimum value of engine rotation speed per 45°CA
The difference in Nli, that is, the rotational fluctuation ΔNi is calculated. ΔNi=Nhi−Nli (1) where i is the cylinder number. Next, the process proceeds to step 118, where the calculated rotational fluctuation ΔNi for each cylinder is set to a set value, e.g.
Determine whether it is greater than 50 RPM. If the determination result is positive, that is, if it is determined that the rotation has increased sufficiently due to the explosion and the glow plug 56 is operating normally, this routine is immediately terminated. On the other hand, if the determination result in step 118 is negative, that is, if it is determined that the glow plug 56 of the i-th cylinder is disconnected, step 120 is performed.
Then, the warning light 57 is turned on to notify the driver of the abnormal condition, and this routine ends. On the other hand, if the determination result in step 110, 112 or 114 is negative and it is determined that the glow plug disconnection determination is not suitable, this routine is immediately terminated. In this embodiment, burnout of the glow plug is determined when the rotational fluctuation ΔNi for each cylinder becomes smaller than the set value. It is possible to accurately determine the disconnection of the wire.
The method for determining whether a glow plug is disconnected is not limited to this, and for example, it is also possible to directly determine from a decrease in rotational speed when the average rotational speed is stable, such as in an idling state. In the above embodiment, the present invention was applied to an electronically controlled diesel engine in which the glow plug was activated during startup and fast idle, but the scope of application of the present invention is not limited to this, and the It is clear that the present invention can be similarly applied to an electronically controlled diesel engine, a general diesel engine, and even a gasoline engine, in which a glow plug is operated at all times during engine operation in order to improve the ignitability of the engine.

【Effect of the invention】

As described above, according to the present invention, disconnection of a glow plug can be easily and accurately detected while the glow plug remains installed in the engine. Therefore, it has the excellent effect of allowing quick and accurate repairs.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the gist of the glow plug disconnection detection method for an internal combustion engine according to the present invention, and FIG.
In order to explain the principle of the present invention, FIG. 3 is a graph showing a comparison of changes in the engine rotation speed and rotation fluctuation when the glow plug is normal and when the glow plug is disconnected. Therefore, FIG. 4 is a sectional view including a partial block diagram showing the configuration of an electronically controlled diesel engine according to an embodiment, and FIG. 5 is a block diagram showing the configuration of an electronic control unit used in the above embodiment. 1 is a flowchart showing a routine for determining whether a glow plug is disconnected. 10...Engine, 12...Fuel injection pump,
22...Engine rotation sensor, 44...Injection nozzle, 52...Water temperature sensor, THW...
...Cooling water temperature, 56...Glow plug, 57...Warning light, 58...Electronic control unit (ECU), Nhi
...Maximum value of engine rotation speed per 45° CA, Nli...
...Minimum value of engine speed per 45°CA, ΔNi...
Rotation fluctuation.

Claims (1)

[Scope of Claims] 1. A glow plug disconnection detection method for an internal combustion engine in which the glow plug is operated at least during startup or fast idle to ensure smooth ignition of fuel, wherein the glow plug is in a state in which it should be operated. means for detecting that the glow plug is in a state in which it should be operated; a procedure for determining the engine rotation speed or rotation variation for each cylinder when the glow plug is in a state where it should be operated; A method for detecting a disconnection of a glow plug in an internal combustion engine, comprising: a procedure for determining that a glow plug in a cylinder is disconnected; 2. A glow plug disconnection detection method for an internal combustion engine according to claim 1, wherein the disconnection determination is not performed when the engine cooling water temperature is extremely low. 3. A glow plug disconnection detection method for an internal combustion engine according to claim 1, wherein the disconnection determination is not performed at the initial stage of startup when the engine rotational speed is very low.