JPH04143444A - Engine trouble detector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Industrial Application Field) This invention relates to an abnormality detection device for detecting an abnormality in an engine.

(Prior Art) In general, abnormalities in various engine parts, such as uneven wear of piston rings, intake and exhaust valves, or loosening of cylinder head bolts, are often determined by sensory evaluation. On the other hand, knocking occurs when the ignition timing is accelerated too much as an abnormality that occurs during engine combustion. There is a device. This is done by installing a cylinder pressure sensor (knock sensor) that detects the pressure inside the cylinder, detecting a knocking signal and an intake valve seating signal from the detection output of this cylinder pressure sensor, calculating the knocking judgment output, and also calculating the knocking judgment output. A correction output for the knocking judgment output is calculated based on the signal, and this correction output corrects errors caused by engine vibration caused by intake valve seating vibration included in the knocking judgment output, thereby improving the detection accuracy of knocking that actually occurs. is increasing.

(Problem to be solved by the invention) In this way, since a special sensor is installed to detect knocking, this abnormality detection is performed with high accuracy, and based on this, the ignition timing can be delayed, etc. Desired control is possible, and abnormalities can be promptly dealt with.

On the other hand, abnormalities in various parts of the engine, such as uneven wear of piston rings, intake and exhaust valves, or loosening of cylinder head bolts, are often determined through sensory evaluation during inspection, as described above. In some cases, abnormalities may not be detected.

Therefore, the purpose of this invention is to make abnormality detection easier by automatically determining abnormalities in various parts of the engine, such as uneven wear of piston rings, intake and exhaust valves, or loosening of cylinder head bolts, in the same way as knocking detection. It is said that

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention, as shown in FIG. a frequency analysis means 9 for frequency-analyzing the detected vibration signal to obtain a plurality of vibration modes;
A knock determination means 11 determines engine knocking based on an output signal from the frequency analysis means 9, and a predetermined frequency band analyzed by the frequency analysis means 9 when the knock determination means 11 determines that there is no knocking is focused on. and an abnormality determining means 13 for determining whether or not the engine is abnormal.

(Function) Engine vibration is detected by the vibration detection means 5, this vibration signal is analyzed into a plurality of vibration modes by the frequency analysis means 9, and knocking of the engine is determined by the knock determination means 11 based on the frequency-analyzed vibration modes. Ru.

In this knock determination, when it is determined that there is no knock, the abnormality determination means 13 determines whether there is an abnormality in the engine by focusing on a predetermined frequency band analyzed by the frequency analysis means 9.

(Example) Embodiments of the present invention will be described below based on the drawings.

The vehicle engine 1 shown in FIG. 2 is equipped with a crank angle sensor 3 for detecting engine rotational speed and a knock sensor 5 as vibration detection means for detecting engine vibration. The knock sensor 5 converts engine vibration into an electrical signal using a piezoelectric element, for example, and the engine vibration signal detected thereby is input to the control circuit 7.

A detection signal from the crank angle sensor 3 is also input to the control circuit 7. The control circuit 7 includes a band-pass filter 9 as a frequency analysis means, a knock determination circuit 11 as a knock determination means for determining the occurrence of knock based on the output signal from the band-pass filter 9, and a knock determination circuit 11 that determines whether there is a knock or not. An abnormality determination circuit 13 is provided as an abnormality determination means that determines whether the engine is abnormal when the determination is made.

The bandpass filter 9 analyzes the frequency of the vibration signal detected by the knock sensor 5, as shown in FIG. 3, for example, and processes it as a knock signal. The knock determination circuit 11 determines the occurrence of knock by comparing this knock signal with a reference value corresponding to the time when knock occurs, and based on this determination result, a signal is sent to a spark plug (not shown) of the engine 1 via the ignition timing control circuit 15. Performs ignition timing control. When the knock determination circuit 11 determines that there is no knock, the abnormality determination circuit 13 detects a vibration signal frequency-analyzed by the band-pass filter 9 into a predetermined frequency band that shows a remarkable tendency when a predetermined part of the engine becomes abnormal. Focus on this to determine if there is an abnormality in the engine.

When determining whether there is an abnormality in the piston, the A frequency band on the low frequency side in FIG. 3 is used. This A frequency band is
This is an area that is greatly affected by piston slap, which indicates an abnormality in the engine, and this is well known from papers and the like. If the offset of the piston pin is abnormal, the piston will tilt and the impact force on the liner will increase, liner vibration will increase, and the output in the A frequency band will increase. Also,
The same goes for uneven wear of the piston ring; due to uneven wear, the number of parts that come into contact with the liner decreases, and the vibration input when the piston ring hits the liner becomes larger, and as above, the output in the frequency band becomes larger.

Next, the operation of the engine abnormality detection device having the above configuration will be explained based on the flowchart of FIG. 4. First, engine vibration is detected by the knock sensor 5 and the sensor output S is read (step 401), and this output signal S is frequency-analyzed by the bandpass filter 9 as shown in FIG. 3 (step 403). Next, the engine rotation speed Ne is read by the crank angle sensor 3 (step 405).

The frequency-analyzed engine vibration signal may be frequency-analyzed by using, for example, a plurality of band-pass filters 9 having frequency pass bands that do not overlap with each other and passing through each of the band-pass filters 9 for each of the plurality of frequency bands. Knocking is determined by determining the total sum of knock vibration modes in multiple frequency bands obtained by this, and determining the difference between this total sum and a reference signal generated by the force of the knock sensor 8 in the non-knocking state (step 407). . Then, when a knock occurs where the determined value is greater than or equal to the reference value, the ignition timing control circuit 15 retards the ignition timing of the spark plug (step 409);
Suppresses knocking.

If it is determined in step 407 that there is no knock, the frequency band in FIG. 3 is integrated by an integrator (not shown), and the intensity of the output signal is measured (step 411).

Next, the average value S ava is calculated by dividing the above-calculated integral value Sa by the predetermined number of cycles Nc in the A frequency band (step 413). Then, it is determined whether this average value S ava is larger than a predetermined value Sao (step 415). As shown in FIG. 5, the predetermined value Sao gradually increases as the engine speed Ne increases, and the next input overlaps before the liner vibration is attenuated. Here, if the average value S ava is larger than the predetermined value Sao, it is determined that uneven wear of the piston ring or abnormal offset of the piston pin has occurred (step 417). When such an abnormality occurs in the engine, the driver can be warned by, for example, displaying a message in the vehicle interior or outputting a sound. When the average value S ava is less than or equal to the predetermined value Sao, it means that no engine abnormality such as uneven wear of the piston ring has occurred (step 419).

In this way, engine abnormalities such as uneven piston ring wear or piston pin offset abnormalities are automatically detected using the knock sensor 5, so it is possible to accurately grasp the occurrence of an abnormality, and take measures to prevent this abnormality. It can be dealt with promptly.

FIG. 6 is a flowchart showing a second embodiment of the invention.

This embodiment utilizes eight frequency bands on the high frequency side in FIG. 3 when determining whether the cylinder head bolts are loosened or abnormalities such as intake and exhaust valves and valve guides are worn.

These eight frequency bands are areas that are greatly affected by the seating noise of the intake and exhaust valves, and like the A frequency band, this is also known from papers and the like. here,
Steps 401 to 409 are the same as the flowchart in FIG. 4, and in step 611, the 8 frequency bands in FIG. 3 are integrated by an integrator (not shown) to measure the intensity of the output signal, and then the above-mentioned The average value S av is obtained by dividing the integral value sb by the predetermined number of cycles NC in 8 frequency bands.
b is calculated (step 613).

Then, using this average value S avb, it is determined whether the engine is abnormal based on the following equation (step 615).

1- (Savb /5bo) l≦εHere, Sb
As shown in Fig. 7, o is a predetermined value that gradually increases as the engine speed Ne increases, and the next input overlaps before the seating vibration of the intake and exhaust valves is attenuated, and ε is also This is a predetermined value.

When 1-(Savb/5bo)l>t, it is determined in step 617 that 5avb/Sbo<1-5. Here, when 5avb/Sbo≧1−ε, suck.

This means that uneven wear of the exhaust valve or the valve guide has occurred, causing the valve to hit unevenly (step 619). On the other hand, in step 617 S avb / S
When bo < 1-ε, this indicates that the normal seating noise is caused by the tightening force of the cylinder head bolt becoming smaller and vibration transmission being reduced (step 621).

In step 615, l1-(Sxvb/Sbo
)≦ε, it means that no engine abnormality such as uneven wear of the intake and exhaust valves or valve guides or loosening of cylinder head bolts has occurred (step 623).

In this way, in this embodiment as well, engine abnormalities such as uneven wear of intake and exhaust valves or valve guides and loosening of cylinder head bolts are automatically detected using the knock sensor 5, so that abnormalities can be detected easily. It is possible to accurately grasp the occurrence of such an abnormality in the engine, and to warn the driver of the occurrence of such an abnormality by, for example, displaying a message in the vehicle interior or outputting a voice, as in the above embodiment.
Abnormalities can be dealt with promptly.

FIG. 8 is a flowchart showing a third embodiment of the invention.

In this embodiment, the lift characteristics of the intake valve or exhaust valve are varied depending on the operating condition, and the timing of the intake and exhaust valves is thereby improved in order to achieve both torque during low- and medium-speed operation of the engine and improved output during high-speed operation. Alternatively, it is for detecting an abnormality in the variable valve mechanism that controls the intake and exhaust amount. An example of this variable valve mechanism is a main rocker arm that swings around the main rocker shaft according to a low-speed cam to open and close intake (exhaust) valves during low- to medium-speed engine operation, and Some are equipped with a sub-rocker arm that is relatively swingable via a shaft. In this case, the sub-rocker arm is mechanically coupled and integrated with the main rocker arm during high-speed operation of the engine, and swings together with the main rocker arm according to the high-speed cam to open and close the four (exhaust) valves. Therefore, in this case, the mechanical vibration in the variable valve mechanism differs between low-speed operation and high-speed operation, and a switching abnormality in the variable valve mechanism is detected based on this.

In this embodiment, steps 401 to 409 are similar to the flowchart shown in FIG. The output amplitude Si is obtained as shown in FIG.

Then, in the next step 713, it is determined whether a command signal for switching the variable valve mechanism is on or off. When the switching signal is on, the output amplitude S i-1 from the previous bandpass filter is read (steps 715 and 717), and S
Absolute value of the difference between t and 51-1 $= l S 1-8i-
11 (step 719).

Next, this absolute value $ is compared with a predetermined value $0 (step 721), and if $>$0, it is determined that the variable valve mechanism has been switched (step 723), and it is determined that it has operated normally (step 725). If $≦$0, it is determined that the variable valve mechanism has not been switched even though the switching signal is on (step 727), and an abnormality in the switching operation of the variable valve mechanism is detected (step 729). , a warning is generated in the same way as in each of the above embodiments. Thereby, the occurrence of an abnormality can be accurately grasped, and the abnormality can be promptly dealt with.

In the next steps 731 and 733, the output amplitude Si is stored in preparation for the next determination.

Note that in each of the above embodiments, the use of signals in a plurality of frequency bands when determining the occurrence of knock provides the following advantages.

(1) Although there are multiple knock frequency modes, knock signals are not always generated in all modes. Therefore, if knock determination is performed using only one mode, even if a knock occurs, it may not be detected. Therefore, accurate detection is possible by performing knock determination using signals of a plurality of modes.

(2) The knock frequency mode in which signals are likely to occur changes with the engine speed. Also, it is easy to get noise (
The knock frequency mode also changes, and the noise increases as the engine speed increases for all modes. Therefore, accurate knock detection is possible by making a knock determination using signals of a plurality of knock frequency modes.

(3) As shown in Fig. 2, when one knock sensor 5 is provided in an engine, the knock frequency mode in which a signal is likely to occur changes for each cylinder depending on the distance from the knock sensor 5, and individual differences between engines also occur. Therefore, it is possible to improve the knock detection accuracy by focusing on a plurality of knock frequency modes.

For the above reasons, using signals in multiple frequency bands enables highly accurate knock detection, and by using the knock sensor 5 for such knock detection, it is possible to detect loosening of pistons and cylinder head bolts. It is possible to detect engine abnormalities such as the following without installing new parts for this abnormality detection.

[Effects of the Invention] As explained above, according to the present invention, the output signal of the vibration detection means for detecting engine vibration is frequency-analyzed in order to determine knocking, and this frequency analysis is performed when knocking is not occurring. Since engine abnormalities are determined by focusing on a predetermined frequency band of vibration signals, engine abnormalities can be accurately determined without relying on sensory evaluation.
This abnormality can be promptly dealt with.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to claims of this invention, Fig. 2 is a block diagram showing an embodiment of this invention, Fig. 3 is an explanatory diagram showing an example of frequency analysis, and Fig. 4 shows control operation of this invention. 5 is a characteristic diagram of the predetermined value Sao, FIG. 6 is a flow chart showing the second embodiment, FIG. 7 is a characteristic diagram of the predetermined value Sbo, and FIG. 8 is a flow chart showing the third embodiment. FIG. 9 is a filter output characteristic diagram around the time of switching of the variable valve mechanism. 5... Vibration detection means 9... Frequency analysis means 11... Knock determination means 13... Abnormality determination means

Claims (1)

[Claims] A vibration detection means for detecting engine vibration; a frequency analysis means for frequency-analyzing the vibration signal detected by the vibration detection means to obtain a plurality of vibration modes; and a frequency analysis means for detecting engine knocking based on the output signal from the frequency analysis means. The engine is characterized by comprising: a knock determination means for determining an abnormality in the engine; and an abnormality determination means for determining an abnormality of the engine by focusing on a predetermined frequency band analyzed by the frequency analysis means when the knock determination means determines that there is no knocking. Engine abnormality detection device.