JP3312917B2 - Misfire determination device for spark ignition type internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire judging device for judging misfire in a spark ignition type internal combustion engine for each cylinder.

[0002]

2. Description of the Related Art As a misfire determination apparatus of this type, it is most common to determine a misfire when an exhaust temperature of each cylinder falls below the threshold value by setting a constant threshold value for the exhaust gas temperature. However, in such a system, when the difference between the exhaust temperatures of the cylinders is large, such as a relatively small engine, it may be difficult to determine an appropriate misfire. Further, in a lean combustion gas engine, the exhaust gas temperature is low because the mixture is thin, and it is difficult to detect misfire by the above-described determination method. Furthermore, it is often impossible to detect a decrease in exhaust gas temperature only after several misfires, and it is difficult to accurately detect a misfire even if it happens only once. Can not grasp.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to pay attention to these points and accurately determine misfire in a spark ignition type internal combustion engine.

[0004]

In order to solve the above-mentioned problems, according to the present invention, an exhaust gas temperature detecting means for detecting exhaust gas temperature for each cylinder, and an exhaust gas temperature detecting means corresponding to a load and an engine speed during normal operation. Storage means for storing the exhaust temperature of the cylinder; and comparing the detected exhaust temperature with the respective exhaust temperature stored in the storage means for each cylinder. Determination means for determining that a misfire has occurred. FIG. 1 is a diagram showing the configuration of the present invention, wherein A1 is an exhaust gas temperature detecting means, B is a storage means, C1
Denotes a determination unit, D denotes a load detection unit, and E1 denotes a rotation speed detection unit.

[0005]

[Action] The exhaust temperature of each cylinder according to the operation state is stored,
Since this is compared with the detected exhaust temperature for each cylinder, misfiring of individual cylinders is more accurately determined than when comparing with a common threshold value, and measures can be taken only for misfiring cylinders. Become.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below with reference to FIGS.

In FIG. 2, 1 is a spark ignition type internal combustion engine, 2 is a control unit using a microcomputer, 3 is a load sensor for detecting a load based on the intake negative pressure of the engine 1, and 4 is a load sensor for each cylinder of the engine 1. A temperature sensor 5 provided in the exhaust pipe and detecting the exhaust gas temperature is a rotation speed sensor for detecting the rotation speed of the engine 1. The detection signal of each sensor is input to the control unit 2. The control unit 2 performs a misfire determination according to the procedure shown in FIG. 4 and outputs a determination output signal 6, for example, to issue an alarm or stop the engine. Or to be configured.

In FIG. 3, in step S1, the outputs of the load sensor 3 and the rotation speed sensor 5 are read to detect the load and the rotation speed at that time, and the normal exhaust temperature T1 to Tn of each cylinder in this operating state. Is read in step S2.
The exhaust temperature of the engine increases as the load and the rotation speed increase. However, there is considerable variation between the exhaust temperatures of the cylinders, and the tendency of the change depends on the operating state at that time, that is, the load and the rotation speed. FIG. 4 shows an example thereof, where a is a low load, b is a medium load, and c is a high load. As described above, the exhaust temperatures T1 to Tn are different for each operation state, and thus this data is stored in the form of a map in the memory of the control unit 2 before shipping, for example, or the actual The output of each sensor sequentially input at the time of driving is stored and used, and if there is no corresponding data, it can be obtained by interpolation using close data.

Next, in step S3, the current exhaust temperatures t1 to tn of the respective cylinders are input, and in step S4, the difference ΔTi = Ti−ti from the normal exhaust temperature for each cylinder is calculated. In step S5, the value is compared with the misfire determination value H1. If the difference is small and H1> △ Ti, it is determined that the engine is normal. If the difference is large and H1> △ Ti, the i-th cylinder is determined to be misfired. Then, the judgment output signal 6 is output (step S6). The misfire determination value H1 is selected in advance by a test operation or the like.

As described above, in this embodiment, the normal exhaust temperature in the operating state at that time and the detected exhaust temperature are compared for each cylinder, so that there is a difference in exhaust temperature between the cylinders and the operating state Even if it changes, misfiring of each cylinder can be accurately and promptly determined. Therefore, for example, it is possible to appropriately perform individual countermeasures for a misfired cylinder, such as replacing only a deteriorated spark plug. If the learning function of sequentially inputting and storing the exhaust gas temperature during normal operation as described above is used, it is possible to determine the state of deterioration from the change.

[0011]

As is apparent from the above description, the present invention stores the exhaust temperature of each cylinder according to the change of the operating state, and stores the stored exhaust temperature and the detected exhaust temperature in each cylinder. Each is compared. Therefore,
Even when the exhaust temperatures of the cylinders vary, and even if the difference is large, misfires of the individual cylinders can be accurately and promptly determined. The reliability is greatly improved. Further, since it is possible to grasp the state of deterioration of each cylinder, it is not necessary to replace the spark plugs all at once, and only the deteriorated plugs need to be replaced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of the present invention.

FIG. 2 is a schematic configuration diagram of one embodiment of the present invention.

FIG. 3 is a flowchart illustrating a control procedure of the embodiment.

FIG. 4 is a graph illustrating variations in the exhaust gas temperature of the cylinder in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Control part 3 Load sensor 4 Temperature sensor 5 Speed sensor

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hiroki Nishizawa 1-32 Chaya-cho, Kita-ku, Osaka Inside Yanmar Diesel Co., Ltd. (56) References JP-A-62-54138 (JP, A) JP-A-62 -118031 (JP, A) JP-A-61-201135 (JP, A) JP-B-53-4568 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 45/00

Claims (1)

(57) [Claims] An exhaust temperature detecting means for detecting an exhaust temperature for each cylinder, a storing means for storing an exhaust temperature of each cylinder according to a load and an engine speed during a normal operation, and a means for storing the detected exhaust temperature. Comparing with each exhaust gas temperature stored in the storage means for each cylinder, and determining a misfire of the corresponding cylinder when there is a difference equal to or more than a predetermined determination value,
And a misfire determination device for a spark ignition type internal combustion engine.