JP5409061B2 - Spark plug inspection device - Google Patents

Description

  The present invention relates to a spark plug inspection device that inspects a spark plug that is mounted on an internal combustion engine and ignites an air-fuel mixture.

  Conventionally, for ignition of an internal combustion engine such as an automobile engine, a center electrode formed in a long axis, a substantially cylindrical insulator covering the outer periphery thereof, a substantially cylindrical housing covering the insulator, A grounding electrode that extends and provides a predetermined discharge gap with respect to the center electrode and is opposed to the center electrode, and generates a spark discharge between the center electrode and the ground electrode by applying a high voltage to ignite. Spark plugs to perform are widely used. In addition, various technologies have been proposed for use in combustion control by detecting ion misfire, knocking, etc. by detecting ion current that flows through each ignition through an ignition plug during ignition in an internal combustion engine. (For example, see Patent Document 1, Patent Document 2, etc.).

In an actual internal combustion engine, as shown in FIG. 8 (b), ignition is performed as shown in FIG. 8 (b) in accordance with an ignition signal IGt transmitted according to the operating state of the engine from an electronic control device that controls the engine as shown in FIG. 8 (a). is interrupted primary current I _PR of the coil, as shown in FIG. 8 (c), 2 primary voltage V _SC is generated higher by electromagnetic induction, a high voltage is applied to the spark plug, facing the center electrode and the ground electrode When the withstand voltage between the two is exceeded, a spark discharge is generated, and the mixture in the combustion chamber is ignited and flame combustion spreads explosively, and normal combustion occurs as shown in FIG. The combustion chamber pressure P _CYL varies greatly. At this time, ions are generated in the combustion chamber by the combustion explosion of the air-fuel mixture. By using the secondary coil of the ignition coil as the ion current detection coil, as shown in FIG. _8E , the ion current I _ION resulting from the ions generated in the combustion chamber can be detected. Further, as shown in FIG. 8 (f), when misfire occurs due to some abnormality and the combustion chamber pressure _PCYL does not increase, an ionic current associated with combustion is not generated, so that it can be used for misfire detection. However, in practice, as shown in FIGS. 8 (f) and 8 (g), noise generated by disturbance is detected by being superimposed on the ion current I _ION .

  Therefore, in a conventional apparatus that detects ion current and uses it for combustion control as disclosed in Patent Document 2, a correction means such as a comparison with a knock signal period specified in advance is provided to reduce the influence of noise. .

However, in an actual combustion engine, not only knock noise specified in advance, but also noise caused by various disturbances such as external vibration and spark noise from the spark plug is generated in a superimposed manner. Since the noise generated due to the inherent characteristics may vary depending on the individual spark plugs, the correction is not always sufficient, and there is a risk of causing malfunction of the combustion control.
Also, in cases other than misfire detection, for example, when it is intended to have a function of detecting the magnitude of ion current output to perform air-fuel ratio detection, it is more likely to be affected by noise, and it is necessary to reliably remove noise There is.
Furthermore, in the control using a normal ion current, the misfire is not determined by comparing the output detected as in Patent Document 1 or Patent Document 2 with a predetermined threshold value, instead of judging based on the waveform of the ion current. And the presence or absence of knocking is detected.
For this reason, unless the noise is reliably eliminated, it is difficult to distinguish the noise from the normal output in the control device provided with the conventional ion current detection means.
Further, at present, the noise characteristics unique to the spark plug are not necessarily clear.

  Therefore, in view of such a situation, the present invention is a noise characteristic peculiar to a spark plug that can be applied to development of a spark plug that is unlikely to generate noise, removal of a defective product at an actual production site, correction of combustion control of an internal combustion engine, and the like. It is an object of the present invention to provide a spark plug inspection device that detects the above.

The present invention is an ignition plug inspection device, a pressure vessel that divides a pressure chamber simulating a combustion chamber to which a spark plug as a measurement object is attached, a pressure increasing / decreasing means that changes the pressure in the pressure chamber, Pressure detecting means for detecting the pressure in the pressure chamber, high voltage applying means for applying a high voltage to the spark plug, ion current detecting means for detecting an ion current generated from the spark plug, and pressure increasing / decreasing means, The pressure detection means, the high voltage application means, and the input / output control means for controlling the input / output of the ion current detection means, and the pressure increase / decrease means maintains the pressure before decompression for a predetermined time, A high voltage is applied to the spark plug by the high voltage applying means to perform a spark discharge, and then a pressure reducing operation is caused (claim 1).
With this configuration, the input / output control unit can control the pressure increase / decrease unit and the high voltage application unit at an arbitrary timing, and change the pressure in the pressure chamber under a certain condition. In addition, it is possible to apply a high voltage to the spark plug at an arbitrary timing with respect to a pressure change in the pressure chamber, and it is generated from the spark plug under a certain condition that excludes disturbance. The intrinsic ion current can be detected by the ion current detecting means.
Further, by observing the waveform of the generated ion current, it is possible to visually grasp the noise characteristics unique to the spark plug.
The obtained noise characteristics unique to the spark plug can be used for developing a new spark plug, determining the quality of a product actually produced, and correcting combustion control when mounted on a combustion engine. Further, it is much simpler than the case where an ignition plug is attached to an actual internal combustion engine or an experimental combustion engine to cause a combustion explosion and detect an ionic current.
In addition, the inventors' diligent tests have obtained knowledge about the optimum conditions for detecting the noise characteristics specific to the spark plug, depending on the control timing of the pressure increasing / decreasing means and the high voltage applying means.

The second invention is characterized in that the pressure reducing speed of the pressure increasing / decreasing means is set faster than the pressure increasing speed (Claim 2).
As a condition for detecting the noise characteristics specific to the spark plug, it has been found that it is desirable to set the pressure reduction speed faster than the pressure increase speed as a result of the inventors' diligent tests.

According to a third aspect of the invention, there is provided image information detecting means for observing a space between a surface of the insulator of the spark plug in the pressure chamber and a housing forming a side electrode .
By the image information detecting means, it is possible to directly and visually observe how noise is generated from the spark plug.
According to the spark plug detection device of the present invention, the noise inherent to the spark plug is applied to the center of the spark plug when the high voltage is applied to the spark plug by the high voltage applying means and then reduced by the pressure increasing / decreasing means. Generated by corona discharge generated when the electric field accumulated in the stray capacitance formed by the electrode and the side electrode exceeds the dielectric strength of the gas in the pressure chamber when the withstand voltage in the pressure chamber is reduced due to decompression. Furthermore, it was confirmed that the corona discharge was actually generated by the image information detecting means.
Therefore, it is possible to identify a position where corona discharge that causes noise is likely to occur, and to help develop a spark plug that generates less noise.

In a fourth aspect of the invention, the spark discharge that is performed while maintaining the pressure before depressurization for a predetermined time is performed 40 times or more (claim 4).
As a result, the continuous ignition state in the actual engine can be more reliably approached, and the optimum condition for detecting the noise characteristics unique to the spark plug can be obtained.

In a fifth aspect of the present invention, the pressure reducing speed of the pressure increasing / decreasing means is such that the time for the pressure decreasing from 90% of the pressure at the time of completion of pressure increase to 10% is within 0.05 s. 5).
It has been found that by setting such a pressure reduction speed, it is possible to reproduce a noise generation state similar to that of an actual machine, and the quality of the spark plug can be determined more reliably.

  According to the spark plug inspection device of the present invention, it is possible to eliminate a disturbance and detect a noise characteristic unique to the spark plug.

The spark plug test | inspection apparatus in the 1st Embodiment of this invention. The time chart which shows the test | inspection method of the spark plug test | inspection apparatus in the 1st Embodiment of this invention. The control flowchart used for the spark plug test | inspection apparatus in the 1st Embodiment of this invention. The time chart which shows the other test | inspection method of the spark plug test | inspection apparatus in the 1st Embodiment of this invention. The spark plug test | inspection apparatus in the 2nd Embodiment of this invention. (A) Main part sectional drawing of the spark plug used as the test object of this invention, (b) The schematic diagram which shows the mode of a corona discharge. The schematic diagram which shows the mode of the corona discharge observed with the spark plug test | inspection apparatus in the 2nd Embodiment of this invention. The time chart of the ignition timing in an internal combustion engine is shown, (a) is an ignition signal, (b) is a primary current, (c) is a change in secondary voltage, (d) is a change in in-cylinder pressure. (E) shows the state of the ion current detected at the time of ignition, (f) shows the change in the in-cylinder pressure at the time of misfire, and (g) shows the problems of the conventional ion current detection device. The characteristic figure which shows the ion current detected at the time of a misfire shown.

  The spark plug inspection device of the present invention will be described below with reference to the drawings. The spark plug inspection device of the present invention detects noise generated when a high voltage is applied to a spark plug used for ignition of an internal combustion engine to be measured under a predetermined condition, and a noise characteristic specific to the spark plug is obtained. It is to be inspected.

In FIG. 1, the structure outline | summary of the spark plug test | inspection apparatus 100 in the 1st Embodiment of this invention is shown. The spark plug inspection device 100 includes a pressure vessel 3 that _divides a pressure chamber 30 simulating a combustion chamber in which a spark plug 7 that is an object to be measured is mounted, and a pressure increase / decrease means (1) that changes the pressure P _CYL in the pressure chamber 30. -5), pressure detecting means 6 for detecting the pressure P _CYL in the pressure chamber 30, high voltage applying means 8 for applying a high voltage to the spark plug 7, and ion current IION generated from the spark plug 7 are detected. It comprises an ion current detection means 9 and an input / output control means 11 for controlling the input / output of these means (1-6, 8, 9).

The pressure increasing / decreasing means (1-5) includes a high pressure source 1 that generates high pressure, a pressure increasing valve 2 that opens and closes the supply of high pressure from the high pressure source 1 to the pressure vessel 3 and adjusts the pressure increasing speed in the pressure chamber 30; The pressure reducing valve 4 is configured to open and close the discharge of pressure from the pressure vessel 3 to the open end 5 and adjust the pressure reducing speed in the pressure chamber 30.
The pressure P _CYL in the pressure chamber 30 is detected by the pressure detection means 6 and transmitted to the input / output control means 11.
As the high pressure source 1, for example, a compressor capable of supplying compressed air, a nitrogen cylinder capable of supplying high pressure nitrogen, a membrane separation type nitrogen generator, a PSA type nitrogen generator, or the like can be used.
The pressure vessel 3 is a model of a combustion chamber of an internal combustion engine. However, it is not necessary to assume a high pressure as in the case of normal combustion, and it is sufficient if the pressure in the combustion chamber at the time of misfire can be reproduced. The pressure P _CYL in the chamber 30 may be set to at least 0.8 MPa. By setting the pressure P _CYL in the pressure chamber 30 to such a value, it is possible to reproduce a noise generation state similar to that of an actual machine.

A pressure increasing valve opening / closing signal MV ₁ is transmitted from the input / output means 11 to the pressure increasing valve opening / closing circuit 20, and the pressure P _CYL and the pressure increasing speed in the pressure chamber 30 are in a predetermined range according to the pressure increasing valve opening / closing signal MV _1. The opening / closing of the pressure increasing valve 2 is controlled so that
A pressure reducing valve opening / closing signal MV ₂ is transmitted from the input / output means 11 to the pressure reducing valve opening / closing circuit 40 so that the pressure P _CYL and the pressure reducing speed in the pressure chamber 30 are in a predetermined range according to the pressure reducing valve opening / closing signal MV _2. Opening and closing of the pressure reducing valve 4 is controlled.

  The spark plug 7 includes a substantially long axis center electrode 71, a substantially cylindrical insulator 72 covering the center electrode 71, and a substantially cylindrical housing 73 covering the insulator 72. The center electrode discharge part 711 provided at the tip and the ground electrode discharge part 731 provided continuously with the housing 73 are opposed to each other.

The high voltage application means 8 has an ignition coil 80 that boosts the power supply voltage + B in accordance with an ignition signal IGt transmitted from the input / output control means 11 and an ignition circuit drive circuit 81 that includes a switching element that opens and closes the ignition coil 80. .
One end of the primary side coil of the ignition coil 80 is connected to a power supply end provided in the input / output control means 11, and the other end is grounded via an ignition coil drive circuit 81.
The secondary coil of the ignition coil 80 has one end connected to the center electrode terminal of the spark plug 7 and the other end connected to the ion current detection means 9.

  The ion current detecting means 9 includes two Zener diodes 90 and 91 connected in series in opposite directions, a capacitor 92 connected in parallel to one diode 90, and an ion current detecting resistor connected in parallel to the other Zener diode 91. The comparator 96 is connected in parallel between the inverting (-) terminal and the output terminal of the comparator 96, and the potential between the capacitor 93, the capacitor 92, and the ion current detection resistor 93 is inverted (-) input through the resistor 94. And a gain setting resistor 95.

The input / output control device 11 includes a start signal STR for starting the operation of the spark plug inspection device 100, a pressure increasing signal MV ₁ for controlling the driving of the pressure increasing valve 2, a pressure reducing signal MV ₂ for controlling the driving of the pressure reducing valve 4, The ignition signal IGt for controlling the voltage application means 8 is used as an output signal, the output means 14, the pressure monitor 13 using the pressure P _CYL in the pressure chamber 30 detected by the pressure detection means 6 as an input signal, and the ion current detection means 9. And an ion current monitor 12 using the ion current I _ION detected by the above as an input signal.
Based on the data input to the pressure monitor 13 and the ion current monitor 12, the driving of the high pressure source 1, the pressure increasing valve 2, the pressure reducing valve 3, and the high voltage applying means 8 is controlled by the output signal transmitted from the output means 14. Thus, the ion current I _ION resulting from the inherent noise generated from the spark plug 7 under desired conditions can be detected.
It is also possible to determine whether the spark plug 7 is good or bad from the detected ion current _IION . Further, the detected ion current I _ION can be encoded and printed on the spark plug 7 to be used for noise correction for actual misfire detection or knock detection.

With reference to FIG. 2, the operation of the spark plug 100 in this embodiment will be described. When starting of the spark plug inspection device 100 is started and a start signal STR is transmitted, supply of high-pressure gas from the high-pressure source 1 is started. At the same time or subsequently, the pressure increase signal MV ₁ is transmitted and the pressure increase valve 2 is opened. When the pressure P _CYL in the pressure chamber 30 increases and reaches a predetermined pressure, the pressure increasing valve 2 is closed, and the pressure P _CYL in the pressure chamber 30 is kept constant. Next, a high voltage is applied to the spark plug 7 according to the ignition signal IGt to generate a spark discharge. At this time, an ion current I _ION is instantaneously generated as ignition noise.
Next, when the pressure reducing valve 4 is opened at a predetermined pressure reducing speed in accordance with the pressure reducing signal MV ₂ , the withstand voltage in the high pressure chamber 30 is lowered, and the corona discharge is generated by the discharge of the charge accumulated in the spark plug 7. . At this time, discharge noise due to corona discharge is detected as the ion current _IION . FIG. 2 is a time chart showing the operation of the spark plug inspection device 100 of the present invention.

FIG. 3 is an embodiment showing the operation of the spark plug inspection device 100 of the present invention in a flowchart. As shown in FIG. 3, it is activated ignition plug inspection apparatus 100 in S1, when the start signal STR is ON, is turned ON pressure increase signal MV ₁ in S2, the pressure increasing valve 2 is opened, the high pressure source 1 Supply of the high-pressure gas is started, and in S3, it is determined whether or not the pressure P _CYL in the pressure chamber 30 is within a predetermined range (for example, 0.8 MPa or less). is supplied in maintenance, it moves to step S4 reaches the predetermined pressure, the pressure increase signal MV ₁ is turned OFF, the pressure P _CYL in the pressure chamber 30 is maintained at a constant value. In S5, monitoring of the ion current IION is started, in S6, the ignition signal IGt is turned on and off at a predetermined timing, and in S7, a high voltage is applied to the spark plug 7 in accordance with the ignition signal IGt. Vacuum signal MV ₂ is turned ON at S8, pressure reducing valve 4 is opened, the pressure _{P CYL} in the pressure chamber 30 decreases. At this time, the depressurization speed is monitored in S9, and the depressurization signal MV ₂ is set so that the depressurization is performed at a predetermined depressurization speed (for example, the depressurization speed at which the time until the pressure decreases from 90% to 10% of the initial pressure is 0.05 s). When the pressure is reduced to a predetermined pressure (for example, 0.1 MPa) or less, the pressure reduction signal is turned off in S10, the pressure reduction valve 4 is closed, and the measurement of the ion current _IION is completed in S10.

In addition, as a condition for detecting the noise characteristic unique to the spark plug by the inventors' extensive test, it is desirable to set the pressure reduction speed faster than the pressure increase speed. More specifically, the pressure reduction speed is equal to the initial pressure. It is possible to judge whether or not the spark plug is good if the time to decrease from 90% pressure to 10% pressure is within 0.3 s, and it is more preferable that the time is within 0.05 s, as a result of diligent tests by the present inventors. confirmed.
If the pressure is reduced within such a speed range, a noise generation state similar to that of the actual machine can be reproduced, and the quality determination of the spark plug 7 can be reliably performed.
In addition, 0.05 s is a value substantially equal to the pressure decrease speed during engine idling.

In addition, as shown in FIG. 4, the ion current I _ION generated by reducing the pressure after the high voltage is periodically applied to the spark plug 7 while the pressure P _CYL in the pressure chamber 30 is kept constant is detected. To do. When the application of a periodic high voltage is repeated about 40 times by the present inventors' earnest test, the ion current I _ION detected when the pressure is reduced gradually approaches a constant value, and the high voltage application is 125 times. It was found that the noise characteristic unique to the spark plug can be detected by detecting the ionic current I _ION generated when the pressure is reduced after repeating the process.
This is a simulation of the continuous ignition state in an actual engine, and it is tested that it is possible to approach the noise generation state of the actual machine more reliably if spark discharge is performed by applying a high voltage periodically at least 40 times or more. Confirmed.

  With reference to FIG. 5, the spark plug test | inspection apparatus 100a in the 2nd Embodiment of this invention is demonstrated. In the present embodiment, in addition to the same configuration as that of the above-described embodiment, a pressure-resistant observation window 31 is provided in the pressure vessel 3a, and image information detection means 32 such as a high sensitivity camera is provided. Note that the observation window 31 used in the present embodiment needs to have pressure resistance, but combustion does not occur in the high-pressure chamber 30, so the observation window 31 and the image information detection means 32 do not need heat resistance. Compared with the case where the ignition test is performed using the conventional internal combustion engine for the combustion test, it is much simpler and more accurate observation can be realized at a low cost.

In the present embodiment, in addition to the same configuration as that of the above embodiment, the output unit 14a transmits a photographing signal SHT that drives the image information detecting unit 32 at a predetermined timing and also serves as an input unit to the input / output control unit 11a. An image monitor 15 that captures the image information Img output from the image information detection means 32 is provided.
By adopting such a configuration, it is possible to directly observe the phenomenon actually occurring in the spark plug 7a, capture it as image information Img, save it, and analyze it, which can be used to further improve the quality of the spark plug. Become.

By observing the actual state of corona discharge generation using the spark plug inspection device 100a in the present embodiment, the corona discharge noise inherent to the spark plug is caused by the center electrode 71 and the side electrode as shown in FIG. As shown in FIGS. 6B and 7, when the electric charge accumulated in the stray capacitance Cs formed between the housing 73 forming the 732 and the dielectric withstand voltage of the gap 740 is reduced due to the reduced pressure, as shown in FIGS. It was confirmed that corona discharge was discharged between the surface of the insulator 72 and the side electrode 732. In the present embodiment, a part of the housing 73 of the spark plug 7a to be measured is cut out to facilitate observation.
Further, it has been found that corona discharge frequently occurs in a portion where the distance between the insulator 72 and the housing 73 is narrow. In addition, it was confirmed that the insulator 72 acts as a dielectric as well as an insulator, and the charge remains between the center electrode 71 and the housing 73 even after the spark discharge is completed.

The spark plug inspection device of the present invention is not only used for testing and research to develop a new spark plug, but also inspects all actual products to determine whether noise characteristics are good, eliminates defective products, and improves quality. And the obtained noise characteristic data is coded or chipped and printed on or attached to individual spark plugs. When mounted on an actual internal combustion engine, misfire detection device and knock detection It is also possible to provide individual correction data to the apparatus to perform highly reliable combustion control, and the industrial applicability is extremely high.
In the above embodiment, the method of attaching the ignition plug to be measured to the high-pressure vessel is illustrated as being fixed by screwing, but this is not a limitation, and the pressure in the high-pressure chamber at the time of measurement is compared. Therefore, by making the spark plug attachable to the high-pressure vessel with a structure that is easier to attach and detach, it can be diverted to mass production equipment.

100 Spark plug inspection device 1 High pressure source (1-5 Pressure increase / decrease means)
10 High pressure source operation circuit 2 Booster valve 20 Booster valve opening / closing circuit 3 Pressure vessel 30 Pressure chamber (simulated combustion chamber)
4 Pressure reducing valve 40 Pressure reducing valve opening / closing circuit 5 Atmospheric open end 6 Pressure detecting means 7 Spark plug (measuring object)
71 Center electrode 711 Center electrode discharge part 712 Center electrode center shaft 713 Center electrode terminal part 72 Insulator 73 Housing 731 Ground electrode discharge part 732 Side electrode part 734 Screw part 8 High voltage applying means 80 Ignition coil (boost means)
81 Igniter (ignition coil drive means)
9 Ion current detection means 11 Controller 12 Ion current detection result 13 Pressure chamber pressure detection result 14 Control signal + B Power supply voltage STR Start signal MV ₁ Booster valve opening / closing signal MV ₂ Pressure reducing valve opening / closing signal IGt Ignition signal P _CYL Pressure chamber pressure

Japanese Patent Laid-Open No. 10-318885 JP 2007-270830 A

Claims (5)

A spark plug inspection device, a pressure vessel defining a pressure chamber simulating a combustion chamber to which a spark plug as a measurement object is attached, pressure increasing / decreasing means for changing the pressure in the pressure chamber, Pressure detecting means for detecting pressure, high voltage applying means for applying a high voltage to the spark plug, ion current detecting means for detecting an ionic current generated from the spark plug,
The pressure increase / decrease means, the pressure detection means, the high voltage application means, and an input / output control means for controlling the input / output of the ion current detection means ,
A pressure before pressure reduction is maintained for a predetermined time by the pressure increase / decrease means, and a high voltage is applied to the spark plug by the high voltage application means during that time to perform a spark discharge, and then a pressure reduction operation is caused. Spark plug inspection device. 2. The spark plug inspection device according to claim 1, wherein a pressure reducing speed of the pressure increasing / decreasing means is set faster than a pressure increasing speed . 3. The spark plug inspection device according to claim 1 , further comprising image information detecting means for observing a space between a surface of the insulator of the spark plug in the pressure chamber and a housing forming a side electrode . The spark plug inspection device according to any one of claims 1 to 3, wherein the spark discharge performed while maintaining the pressure before the depressurization for a predetermined time is performed 40 times or more. Decompression rate of the pressure adjusting unit is in any of the four claims 1, wherein the time to decrease to 90% of the pressure of the pressure during the pressure increase completed up to 10% of the pressure is within 0.05s The spark plug inspection device described.

Images