JP2018048576A - Electronic apparatus for detecting loosened fixing of knock sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a low-cost electronic apparatus provided with functionality for detecting loosened fixing of knock sensor.SOLUTION: An electronic apparatus (100), connected to a knock sensor (110) that is fixed, with a fastening member (110a), to an internal combustion engine (130), includes at least: an A-D conversion process circuit (104) for converting a signal output from the knock sensor into a digital value in a sampling cycle; and a digital process circuit (106) for sequentially obtaining digital values output from the A-D conversion process circuit. Further, in the case of determining that the sequentially obtained digital values include a value outside an input range of the A-D conversion process circuit, the digital process circuit determines that there is loosening of the fastening member.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electronic device, and more particularly to an electronic device having a function of detecting looseness of fixing of a knock sensor.

  In general, an internal combustion engine of a vehicle is provided with a knock sensor for detecting knocking caused by abnormal combustion, and the detected vibration intensity of the knocking is an electronic control unit (ECU: ECU) that controls the driving of the internal combustion engine. Analyzed by Electronic Control Unit). The electronic control unit optimizes the ignition timing of the ignition device provided in the internal combustion engine so that desired combustion efficiency and output performance can be achieved while suppressing the knocking from the analysis result of the vibration intensity of the knocking. .

  Since the knock sensor is usually fixed using a fastening member such as a bolt so as to be in direct contact with the outer wall surface of a cylinder block or the like constituting the internal combustion engine, the knocking vibration transmitted through the outer wall surface is highly sensitive. Can be detected. However, on the other hand, the internal combustion engine is likely to be damaged by vibration and heat. For example, a short circuit or disconnection may occur in the internal wiring of the knock sensor, and the knock sensor may break down. Even if the failure does not occur, the fastening member for fixing the knock sensor is loosened by vibration and heat generated by the internal combustion engine, and the fastening state between the internal combustion engine and the knock sensor becomes unstable, causing knock vibration. It may not be detected accurately.

  In order to detect such an abnormality of the knock sensor, the electronic control device mounted on the vehicle is provided with an abnormality detection device for detecting the abnormality of the knock sensor. For example, Patent Document 1 discloses a circuit for detecting a short circuit and a disconnection based on a sensor signal output from the knock sensor to which a bias is applied in order to detect a short circuit or a disconnection of an internal wiring of the knock sensor. An electronic control device comprising: According to the electronic control device of the cited document 1, it is possible to detect an abnormality such as a short circuit or disconnection that occurs inside the knock sensor, and also to determine the type of the short circuit (a power fault or a ground fault).

  However, although the electronic control device of the cited document 1 can determine the failure of the knock sensor due to a short circuit or disconnection of the wiring, it cannot detect the looseness of the fastening member that fixes the knock sensor as described above. In order to detect a defect related to the looseness of the fastening member, a dedicated detection circuit is separately required. However, the electronic control unit is increased in size according to the size of the newly provided detection circuit, and the manufacturing cost is increased.

JP 2006-29158 A

  From such a background, it is desired to realize an electronic device having a function capable of detecting looseness of a fastening member for fixing a knock sensor at a low cost.

One aspect of the present invention is an electronic device connected to a knock sensor fixed to an internal combustion engine by a fastening member. The electronic apparatus includes an A / D conversion processing circuit that converts a signal output from the knock sensor into a digital value at a predetermined sampling period, and a digital processing that sequentially acquires the digital value output from the A / D conversion processing circuit. And the digital processing circuit loosens the fastening member when it is determined that the digital value acquired sequentially includes a value outside the input range of the A / D conversion processing circuit. It is determined that there is.
According to another aspect of the present invention, the digital processing circuit performs the A / D conversion when the sequentially acquired digital value includes a numerical value not less than the maximum value or not more than the minimum value of the input range continuously. It is determined that a value outside the input range of the processing circuit is included.
According to another aspect of the present invention, in the digital processing circuit, the sequentially acquired digital value includes a numerical value that is 98% or more of the maximum value of the input range or 2% or less of the maximum value continuously. Are determined to include values outside the input range of the A / D conversion processing circuit.
According to another aspect of the present invention, the digital processing circuit determines the degree of looseness of the fastening member according to the frequency with which the numerical value continues.
According to another aspect of the invention, the digital processing circuit is connected to at least one of a display device that displays the determination result and a storage device that records the determination result.
Another aspect of the present invention is a vehicle including the electronic device.
Another aspect of the present invention is a slack detection method for detecting slack of a knock sensor fixed to an internal combustion engine. In this looseness detection method, in the A / D conversion processing circuit, the signal output from the knock sensor is converted into a digital value at a predetermined sampling period, and in the digital processing circuit, the A / D conversion processing circuit outputs the signal. Step of sequentially acquiring the digital value and determining that the fixing is loose when it is determined that the digital value acquired sequentially includes a value outside the input range of the A / D conversion processing circuit. And at least.

It is a block diagram which shows the structure of the electronic device which concerns on one Embodiment of this invention. It is a figure which shows the signal waveform output from the knock sensor connected to the electronic device which concerns on this embodiment. It is a flowchart which shows the procedure of the process in the electronic device which concerns on this embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an electronic device according to an embodiment of the present invention. The electronic apparatus 100 is an electronic control unit (ECU) that is mounted on, for example, the vehicle 160 and controls the engine 130 of the vehicle.

  The electronic device 100 is connected to a knock sensor 110 fixed to the outer wall surface of the engine 130 by a fastening member 110a such as a bolt, and an ignition device 120 that ignites fuel at a predetermined timing in the internal combustion engine 130. . The electronic device 100 is connected not only to the knock sensor 110 and the ignition device 120 but also to a plurality of sensors (for example, a cooling water temperature sensor) provided in the engine 130 and a control device (for example, a fuel injection device). Although the engine 130 is comprehensively controlled, for easy understanding, FIG. 1 shows only the connection relationship between the knock sensor 110 and the ignition device 120, and the following explanation is given. However, only control related to knock sensor 110 and ignition device 120 will be described.

  The knock sensor 110 is, for example, a non-resonant type knock sensor, and has a through hole for inserting a fastening member 110a such as a bolt in the center, and the fastening member 110a allows the cylinder block of the engine 130 to be inserted. Directly fixed. The fixing of the knock sensor 110 is not limited to a fastening member such as a bolt or a screw. For example, if the knock sensor such as a clip, a belt-type fixing device, or an adhesive can be fixed, Anything can be used. The knock sensor 110 detects knocking vibration that occurs when abnormal combustion occurs in the engine 130, and outputs the detected knock sensor signal to the input circuit 102 of the electronic device 100.

  The input circuit 102 includes, for example, an electric circuit constituting a band-pass filter, and a low frequency band that is not included in a frequency component of knocking generated inside the engine 130 among knock sensor signals detected by the knock sensor 110. In addition, the high frequency band noise is removed, and for example, only a knock sensor signal of 5 kHz or more and 25 kHz or less passes.

  Further, the input circuit 102 has, for example, a center of 2.5 V so that all of the amplitude of vibration related to the knocking is within the input range (for example, 0 to 5 V) of the A / D conversion processing circuit 104 in the next stage. A gain adjustment circuit for adjusting the output of the knock sensor signal so as to obtain a signal waveform of

The knock sensor signal V _N processed by the input circuit 102 is input to the A / D conversion processing circuit 104, and is converted into a digital value V _CAD for every sampling period of about 10 to 20 μs, for example.

The digital value V _CAD output from the A / D conversion processing circuit 104 is input to the digital processing circuit 106. The digital processing circuit 106 is configured by a digital circuit such as a CPU (Central Processing Unit), a PLD (Programmable Logic Device), or an ASIC (Application Specific Integrated Circuit), for example, and is digitally converted by the A / D conversion processing circuit 104, for example. The knock sensor signal is subjected to computation such as discrete Fourier transform to detect the vibration intensity in the natural frequency band of the engine 130, thereby detecting knocking of the engine 130.

  The digital processing circuit 106 controls the ignition device 120 so that the ignition timing is retarded when knocking is detected, and the ignition timing is set to the advance side when knocking is not detected. By controlling the ignition device 120 as described above, knocking and torque reduction are suppressed.

  Further, the digital processing circuit 106 is also connected to a display device 140 and a failure diagnosis device 150 that display the details of the abnormality detected by the electronic device 100, and the detected abnormality is displayed on the display device 140 and the failure diagnosis device as necessary. 150. The display device 140 notifies the driver of the content of the abnormality by, for example, text or video, and the failure diagnosis device 150 analyzes the abnormality event, for example, and the analysis result is provided in the failure diagnosis device 150. Save it to a storage device.

Next, with reference to FIGS. 2A and 2B, signal waveforms 200 and 210 of the knock sensor immediately before being input to the A / D conversion processing circuit 104 will be described. A signal waveform 200 shown in FIG. 2A is a knock sensor signal output from the knock sensor 110 in a normal mounting state in which the fastening member 110a for fixing the knock sensor 110 is not loosened, and the knock sensor signal it is a signal waveform indicating a temporal change of the voltage value V _N. On the other hand, the signal waveform 210 shown in FIG. 2B is a sensor signal output from the knock sensor 110 that is loose with respect to the fastening member and is movable with respect to the cylinder block, and is a voltage value V of the knock sensor signal. _It is a typical signal waveform which shows the time change of _N. 2A and 2B are signal waveforms output from the input circuit 102 with the same gain.

If there is no looseness in the fastening member 110a of the knock sensor 110, as the signal waveform 200, the maximum value and the minimum value of the peak-shaped waveforms constituting the knock sensor voltage V _N is the A / D conversion circuit 104 It is within the range of 0-5V which is the input range. On the other hand, when the fastening member 110a of the knock sensor 110 is loose, like the signal waveform 210, the input range of the A / D conversion processing circuit 104 among the plurality of peak-shaped waveforms constituting the signal waveform is shown. Peaks (peaks P ₁ and P ₃ ) exceeding 5 V that is the maximum value and peaks (peaks P ₂ and P ₄ ) that are below 0 V that is the minimum value of the input range are observed.

For example, if a dedicated circuit for detecting a peak (P _{1 to} P ₄ ) including a value outside the input range is added on the input side of the A / D conversion processing circuit 104, the fastening member 110a is loosened. Can be constantly monitored, and the fastening member 110a can be appropriately dealt with looseness. However, when such a dedicated detection circuit is provided, there is a problem that the electronic device 100 is increased in size according to the size of the added detection circuit, and the manufacturing cost of the electronic device 100 is increased.

In the electronic apparatus 100 according to the present embodiment, the fastening member 110a is loosened based on the digital value V _CAD output from the A / D conversion processing circuit 104 without providing the dedicated detection circuit as described above. judge. Specifically, the digital processing circuit 106 sequentially acquires the digital value V _CAD converted at a constant sampling period output from the A / D conversion processing circuit 104, and the sequentially acquired digital value V _CAD is When the input range of the A / D conversion processing circuit 104 is continuously near the upper limit (˜5 V) or when the input range is continuously below the lower limit (˜0 V) of the input range, the fastening member 110a. It is determined that there is looseness.

  Thus, only when the numerical value near the upper limit of the input range or the numerical value near the lower limit of the input range is “continuous”, by determining that the fastening member 110a is loose, it comes from the looseness of the fastening member 110a. An erroneous determination due to a signal that is not performed (for example, spike noise that exceeds the range of the input range only once) can be avoided, and the looseness of the fastening member 110a can be accurately determined.

Hereinafter, as an example, in the electronic apparatus 100, the digital data V _CAD sequentially acquired by the digital processing circuit 106 is equal to or higher than the upper limit (˜5 V) of the input range of the A / D conversion processing circuit 104 twice in succession. Or a processing flow for determining that the fastening member 110a is loose when the input range of the A / D conversion processing circuit 104 is not more than the lower limit (˜0V) or less in succession twice. Show about.

  The procedure of the process will be described with reference to the process flow shown in FIG. This processing is composed of a computer having a processor such as a CPU (Central Processing Unit), a ROM (Read Only Memory) in which a program for this processing is written, a RAM (Random Access Memory) for temporary storage of data, and the like. The digital processing circuit 106 is realized by executing the program. In addition, this process starts when the power of the electronic device 100 is turned on and ends when it is turned off.

First, when the power of the electronic apparatus 100 is turned on, a flag for counting the frequency of V _CAD that falls outside the input range is set to an initial value (flag = 0) (S402). The voltage V _N of the knock sensor signal output from the input circuit 102 is converted into a digital value V _CAD at a sampling period of, for example, 20 μs in the A / D conversion processing circuit 104 and input to the digital processing circuit 106.

The digital processing circuit 106 sequentially acquires the V _CAD (S404), and the acquired V _CAD is near the upper limit (˜5V) of the input range of the A / D conversion processing circuit 104 or near the lower limit (˜ 0V) or less is determined (S406).

Here, depending on the specifications of the A / D conversion processing circuit, for example, a voltage value V _N that is not less than the maximum value and / or not more than the minimum value of the input range of the A / D conversion processing circuit may not be converted into the digital value V _CAD. is there. For this reason, it is preferable to provide a certain margin for the maximum value and the minimum value so that a part of the values in the input range are included in the setting of the upper limit and the lower limit, which are the criteria for the determination in S406 of this processing flow. In this processing flow, for example, the upper limit of V _{CAD used} as a reference for determination is set to 2% (0.1 V) of the maximum value of the input range, and the lower limit of V _{CAD used} as a reference for determination is set to the maximum value of the input range. By setting to 98% (4.9 V), it is configured to prevent malfunction based on the specifications of the A / D conversion processing circuit. In the case of an A / D conversion processing circuit that can obtain a digital value V _{CAD that} is greater than or equal to the maximum value and / or less than the minimum value of the input range, the determination criterion in the process of S406 is, for example, V _CAD ≧ 5 V or V _CAD ≦ 0 V As described above, the maximum value and the minimum value of the input range can be used as the boundary of the determination criterion.

In S406 of this processing flow, when V _CAD ≧ 4.9 or V _CAD ≦ 0.1 is not satisfied (S406: No), that is, when it is within the input range, the process is returned to S402 and processed. Is repeated. On the other hand, when V _CAD ≧ 4.9 or V _CAD ≦ 0.1 is satisfied (S406: Yes), after determining as V _CAD exceeding the input range, in S408, the value stored in the flag is 0 or It is determined which is one. If the flag is 0 (S408: No), the flag is set to 1 (S410), and the process returns to S404. If the V _CAD sampled immediately after the processing is returned satisfies the condition shown in S406 again (S406: Yes), the A / D conversion processing circuit continuously converts the digital data V _CAD twice. Thus, the digital processing circuit 106 determines that the fastening member 110a that fixes the knock sensor 110 is loose.

  Then, the digital processing circuit 106 outputs information indicating that the fastening member 110a is loose in the display device 140 and / or the failure diagnosis device 150, for example. The display device 140 notifies the driver that there is a slack in the fastening member 110a by means of characters or images, and stores the slack information in a storage device or the like in the failure diagnosis device 150.

In the electronic apparatus 100 according to the present embodiment, when the digital data V _{CAD that} is outside the input range of the A / D conversion processing circuit 104 is sequentially acquired twice in succession, the fastening for fixing the knock sensor 110 is performed. Although it has been determined that the member 110a is loose, the present invention is not limited to this, and the frequency at which the digital data _VCAD continues can be set to three or more times. In S406 of this processing flow, two conditional expressions of V _CAD ≧ 4.9 and V _CAD ≦ 0.1 are used, but not limited to this, only one of the conditional expressions is used. The processing flow may be configured as described above.

Further, the length of the period exceeding the input range of the A / D conversion processing circuit 104 (for example, the period ab of the peak P1 or the period cd of the peak P2 shown in FIG. 2B) is the degree of looseness of the fastening member 110a. There is a certain correlation, and for example, it is recognized that when the period becomes longer, the degree of looseness of the fastening member 110a also increases. Therefore, the degree of looseness of the fastening member 110a can be evaluated by calculating the number of times that the A / D converted digital data V _CAD continuously appears outside the input range. For example, if the relationship between the number of times described above and the gap between the fastening member 110a and the knock sensor 110 caused by loosening is calculated in advance, the degree of loosening of the fastening member 110a can be evaluated based on the number of times.

  3 is not limited to the detection of the looseness of the fastening member 110a that fixes the knock sensor 110. For example, the signal output of the knock sensor 110 when an abnormality has occurred is represented by A / If the abnormal state includes an output that falls outside the input range of the D conversion processing circuit 104, the present processing flow can be applied to the detection of the abnormality.

  As described above, the electronic device according to the present embodiment is an electronic device connected to a knock sensor fixed to the internal combustion engine by a fastening member, and the electronic device outputs a signal output from the knock sensor. An A / D conversion processing circuit that converts the digital value into a digital value at a predetermined sampling period, and a digital processing circuit that sequentially acquires the digital value output from the A / D conversion processing circuit, the digital processing circuit comprising: When it is determined that the sequentially acquired digital value includes a value outside the input range of the A / D conversion processing circuit, it is determined that the fastening member is loose.

  With this configuration, it is possible to fasten only with an A / D conversion processing circuit and a digital processing circuit normally provided in an electronic device mounted on a vehicle without providing a dedicated detection circuit for detecting looseness of a fastening member for fixing the knock sensor. Since the looseness of the member can be detected, an electronic device that can detect the looseness of the fastening member without increasing the manufacturing cost can be realized.

  Note that the present invention is not limited to the above-described embodiment, and can be modified and used without departing from the spirit of the present invention.

  DESCRIPTION OF SYMBOLS 100 ... Electronic device, 102 ... Input circuit, 104 ... A / D conversion processing circuit, 106 ... Digital processing circuit, 110 ... Knock sensor, 110a ... Fastening member, 120 ... -Ignition device, 130 ... engine, 140 ... display device, 150 ... failure diagnosis device, 160 ... vehicle.

Claims (7)

An electronic device connected to a knock sensor fixed to the internal combustion engine,
The electronic device
An A / D conversion processing circuit for converting a signal output from the knock sensor into a digital value at a predetermined sampling period;
A digital processing circuit for sequentially acquiring the digital values output by the A / D conversion processing circuit;
Comprising at least
The digital processing circuit includes:
When it is determined that the digital value acquired sequentially includes a value outside the input range of the A / D conversion processing circuit, it is determined that the fixation is loose.
Electronic equipment. The electronic device according to claim 1,
The digital processing circuit includes:
Judgment that the digital value obtained sequentially includes a value outside the input range of the A / D conversion processing circuit when a numerical value not less than the maximum value or not more than the minimum value of the input range is continuously included. To
Electronic equipment. The electronic device according to claim 1,
The digital processing circuit includes:
When the digital value obtained sequentially contains a numerical value of 98% or more of the maximum value of the input range or 2% or less of the maximum value, it is out of the input range of the A / D conversion processing circuit. Is determined to contain the value of
Electronic equipment. The electronic device according to claim 2 or 3,
The digital processing circuit includes:
The degree of loosening of the fixing is determined according to the frequency with which the numerical value continues.
Electronic equipment. The electronic device according to any one of claims 1 to 4,
The digital processing circuit includes:
Connected to at least one of a display device for displaying the determination result and a storage device for recording the determination result;
Electronic equipment. Comprising the electronic device according to any one of claims 1 to 5,
vehicle. A looseness detection method for detecting looseness of a knock sensor fixed to an internal combustion engine,
In the A / D conversion processing circuit, converting the signal output from the knock sensor into a digital value at a predetermined sampling period;
In the digital processing circuit, when the digital value output from the A / D conversion processing circuit is sequentially acquired, and the digital value acquired sequentially includes a value outside the input range of the A / D conversion processing circuit. A step of determining that there is a looseness in the fixing when determined,
At least,
Looseness detection method.

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