JPH04246243A - Abnormal combustion detecting device for engine - Google Patents

Abstract

PURPOSE:To prevent engine damage due to the abnormal combustion by previously estimating the abnormal combustion from the stress variation on the outer wall of the combustion chamber of an engine. CONSTITUTION:A strain sensor 2 is attached on the outer wall 1a of a combustion chamber 1b, and the strain sensor 2, i.e., a stress variation detecting means detects the variation of the stress of the outer wall 1a. An abnormal combustion judging means judges the abnormal combustion when the output of the stress variation detecting means is received and the stress variation is over a prescribed value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormal combustion detection device for an engine.

0002

[Prior Art] As a method for detecting abnormal combustion in an engine,
For example, as shown in Japanese Patent Application Laid-Open No. 64-63652, there is a method of detecting with a knock sensor, that is, a method of measuring vibrations during engine operation and picking up the vibration frequency at the time of abnormal combustion, and a method of detecting with a finger pressure sensor, that is, a method of detecting combustion. There are methods such as measuring pressure and picking out characteristics when abnormal combustion occurs.

0003

[Problems to be Solved by the Invention] As in the prior art described above, if the occurrence of abnormal combustion is detected using a knock sensor, a finger pressure sensor, etc., and control such as ignition timing control is implemented, it is difficult to perform controls such as ignition timing control after abnormal combustion has already occurred. In particular, the higher the rotation speed and the higher the output type of engine, the more likely it is that the engine will suffer engine damage such as cracks in the piston etc. due to the above-mentioned control delay. In addition, even in the case of a medium-low speed engine, control after occurrence of abnormal combustion will similarly have an adverse effect on drivability or cause engine damage.

In other words, in the conventional technology, control is performed to suppress abnormal combustion using a signal that captures the phenomenon that occurs after abnormal combustion occurs in the engine, and the problem lies in the fact that control is not based on so-called predictive signals. be.

The present invention has been made in view of the above circumstances, and provides an engine that is capable of predicting abnormal combustion based on the pattern of increase in stress on the outer wall of the combustion chamber of the engine and performing control to suppress it. The purpose of the present invention is to provide an abnormal combustion detection device.

[0006]

[Means for Solving the Problems] The present invention is based on FIG.
- As shown in FIG. 5, a stress change detection means 2 for detecting stress changes in the outer wall 1a of the engine;
The present invention is characterized by comprising an abnormal combustion determining means which determines abnormal combustion when the stress change is equal to or greater than a predetermined value in response to the output.

[0007]

[Operation] In response to the output of the stress change detection means 2, the abnormal combustion determination means can predict the occurrence of abnormal combustion in advance. As a result, it becomes possible to perform control to prevent abnormal combustion before it occurs.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the accompanying drawings. A strain sensor 2 is attached to an outer wall 1a of a housing 1 of a rotary engine shown in FIG. The strain sensor 2 is a stress change detection means that detects stress changes occurring in the outer wall 1a due to the influence of combustion heat in the combustion chamber 1b within the housing 1.

The output signal from the strain sensor 2 is inputted to a control unit (ECU), not shown, via a conductor 3. Note that the above can also be applied to the case of a reciprocating engine.

A graph showing changes in stress σε with the passage of time Δt as shown in FIG. 2 is drawn by the output signal of the strain sensor 2, and when this stress change exceeds a predetermined value, Abnormal combustion is determined by the abnormal combustion determining means.

The basic matters regarding the abnormal combustion determining means will be explained below. Figure 4 shows the experimental data of the sensor outputs and the outputs of the strain sensor 2 according to each conventional abnormal combustion occurrence signal. According to this, in the case of conventional sensors such as knock sensors, the sensor outputs when abnormal combustion occurs, as indicated by the ☆ mark. is obtained.

On the other hand, in the case of using the strain sensor 2 that detects the displacement of the stress on the outer wall of the combustion chamber, the stress on the outer wall (σε) may rise approximately along a straight line l having a predetermined slope immediately before the occurrence of abnormal combustion. It's been found. Therefore, if the stress change near point A before the occurrence of abnormal combustion is equal to or greater than a predetermined value, it is possible to predict abnormal combustion at that point. Note that point B is when abnormal combustion occurs.

Furthermore, FIG. 5 is a graph showing changes in outer wall stress obtained by the strain sensor 2 and changes in engine output, and the outer wall stress sharply increases at a time Δt before abnormal combustion occurs. The stress change at this point is more than a predetermined value, for example 50 to 10
When the speed is 0 mm/sec, occurrence of abnormal combustion can be predicted Δt time in advance. Naturally, when abnormal combustion occurs, engine output drops rapidly.

Next, the control flowchart of the present invention shown in FIG. 3 will be explained. In stage 1 (S1), the displacement map of the outer wall stress obtained by the stress change detection means of the strain sensor 2, ie, σε from FIG. 2, is input, and A/D conversion, that is, the displacement map is read and graph processing is performed . In stage 2 (S2), abnormality determination processing is performed according to the abnormality determination program. That is, here, in response to the output of the stress change detection means, the abnormal combustion determination means determines whether the stress change is greater than or equal to a predetermined value.

[0015] At stage 3 (S3), as a result of the above determination,
It is determined whether the conditions are met, and if the stress change is greater than or equal to a predetermined value (Yes), the process proceeds to stage 4 (S4), where the control unit (ECU) sets the IGt retard or Output is performed so as to retard the ignition timing, and output is performed so as to make Qf rich, that is, to make the supplied fuel rich.

On the other hand, in stage 3 (S3), if the result of the above judgment is that the stress change is less than the predetermined value (No), the process returns to stage 2 (S2) again and judgment is made by the abnormal combustion judgment means.

[0017]

According to the present invention, the abnormal combustion determining means can predict abnormal combustion in advance by receiving the output of the stress change detecting means for detecting stress changes on the outer wall of the engine, thereby preventing engine damage caused by abnormal combustion. It can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an abnormal combustion detection device for an engine showing an embodiment of the present invention.

FIG. 2 is a graph of signal output by stress change detection means.

FIG. 3 is a flowchart of control for preventing occurrence of abnormal combustion.

FIG. 4 is experimental data (graphic data) obtained by various sensors that detect combustion conditions.

FIG. 5 is a graph of stress displacement of the outer wall of the combustion chamber and engine output.

[Explanation of symbols]

1 Engine housing 1a External wall

Claims (1)

[Claims] 1. Stress change detection means for detecting stress changes in the outer wall of the engine; and abnormal combustion determination means for receiving the output of the stress change detection means and determining abnormal combustion when the stress change is equal to or greater than a predetermined value. An abnormal combustion detection device for an engine, characterized by comprising: