JPS5860234A - Knocking sensor - Google Patents

Abstract

PURPOSE:To obtain a knocking sensor having a flat characteristic with respect to frequency and an excellent linearity, by a method wherein a weight constituting a sensing unit is made to face a cooling water directly, and the axial length of the sensing unit is set so that the resonance frequency of the axial vibration will be much larger than the frequency of a knocking to be detected. CONSTITUTION:A metal disc 6 has a flat surface having an area larger than that of a piezoelectric ceramic element 1 and receives the pressure vibration of a knocking by the flat surface. The length L of a sensing unit constituted by the metal disc 6,the piezoelectric ceramic element 1 and a metal column 2 is set so as to be larger than the diameters of the metal disc and the metal cylinder. In addition, the resonance frequency 1 accompanying the lengthwise vaibration obtained from the formulaIwhere V represents the velocity of sound in the metal is determined so as to be much larger than the frequency 6-8KHz of a knocking to be detected. The sensing unit is disposed at a predetermined position of a water chamber in an engine block through a fixing member 15.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a knocking sensor c that detects knocking vibration pressure in engine cooling water.

Nodding in a gasoline engine not only deteriorates the engine's output, fuel consumption rate, thermal efficiency, etc., but in extreme cases, it can even damage the engine.In a normal engine, nodding occurs at low speeds and under full load. In gasoline engines that have a high compression ratio to improve the thermal efficiency of the engine, and in gasoline engines that are supercharged, it tends to occur over a wide operating range. Its strength also increases.

Therefore, it is necessary to detect this knocking and control the ignition timing or air-fuel ratio of the engine to suppress the bumping.

Conventionally, in order to detect knocking, an acceleration sensor that resonates in response to the knocking frequency was attached to the wall of the engine block, and the vibration caused by knocking propagated through the engine block.
This propagating knocking vibration on the wall surface is detected by a resonant acceleration sensor.

In addition to the above elements, external fuel supply equipment, fans,
Consists of many components such as alternators.

Tei It has many resonant frequencies close to the knob king frequency.

Therefore, in the conventional resonant acceleration sensor, the S/N is
There is a problem that the ratio is poor and the detection accuracy of the king is not sufficient.

In order to solve the problem of knocking sensors using resonant acceleration sensors that detect vibrations in the engine block, the present inventors discovered that the knocking vibrations generated in the combustion chamber of a water-cooled gasoline engine It has been proposed to use a picking sensor that detects underwater vibrations that are propagated directly through the cylinder fin into the cooling water in the ice chamber or cooling passage that surrounds the combustion chamber. The water chamber or cooling passage has the advantage of being less susceptible to harmful vibrations propagated to the f/IJ duplex block or vibrations caused by pulp, bearings, etc.

The above-mentioned underwater knocking sensor has the above-mentioned advantages, but in the case of a resonance type knocking sensor.

The resonance point may shift due to changes in the temperature of the cooling water during use or other factors, and '9! There was a problem with usage.

A non-resonant knocking sensor has also been proposed, but in this case, a diaphragm facing the cooling water is arranged at the tip of the support member, and a piezoelectric element is placed between two weights on the back side of the diaphtum [11i]. This is a structure in which a sandwiched sensing unit is fixed. This sensor has a natural frequency for the end arm, so depending on the engine size and model, there may be a resonant frequency around K that is close to the knocking frequency.

As a non-resonant sensor, there was a problem in practical use.In addition, near the resonance frequency, there was a problem that linearity could not be obtained between the knocking intensity, that is, the vibration pressure of knocking, and the electrical output of the sensor. Furthermore, due to the strange difference in the adhesion between the diaphragm and the supporting part, the natural frequency of the diaphragm changes, and I have heard that it is not possible to obtain a reliable sensor, resulting in a poor yield.

The present inventors have repeatedly conducted systematic experiments and theoretical analyzes in order to develop a non-resonant knocking sensor that eliminates the spin point between the two conventional underwater ν king sensors. It has been reached.

An object of the present invention is to provide a novel non-resonant knocking sensor.

The present invention has 7-rat characteristics for 9 frequencies.

The purpose of the present invention is to provide a knocking sensor with good ff1M performance.

The knocking sensor of the present invention includes a sensing unit in which a piezoelectric element is sandwiched between the flat surfaces of eight weights formed between flat surfaces on both sides, and an outer wall of the engine block of a water-cooled internal combustion engine. It has a fixing part for fixing, and supports the sensing unit in a watertight manner so as to be located in the cooling water in the engine block, so that the flat surface of the 11 spindles is substantially parallel to the outer wall of the engine block. and a supporting member disposed so that the flat surface of one weight sandwiched between the piezoelectric elements and the flat surface of the opposite side directly face the cooling water, and the sensing unit The axial length of

The resonant frequency of the axial vibration of the sensing unit and the frequency of knocking to be detected are set to be sufficiently large.

The knocking sensor of the present invention having the above-mentioned configuration has the sensing unit facing the direct cooling water which is a weight, and the axial length of the sensing unit is set so that the resonant frequency of the axial vibration of the sensing unit is Since it is configured to be large enough for the knocking frequency to be detected, it has flat frequency characteristics over a wide frequency band, and the linearity of the electrical output of the sensor with respect to the knocking intensity to be detected. It has the advantage of being a non-resonant knocking sensor.

In other words, the knocking sensor of the present invention eliminates the diameter 7 mm that faced the engine cooling water.
It eliminates the negative effects of the resonance frequency based on the diaphragm's natural perturbation number and ensures flat frequency characteristics over a wide frequency band, so it can be used effectively even if the knocking frequency changes due to changes in engine size and model. This has the advantage that it can be applied to a wide range of engines, and tC has no resonance point in the used frequency band, so it is difficult to detect the strong jamming JflC[
This has the advantage that the electrical output of the sensor has good linearity.

Further, the knocking sensor of the present invention has the advantage that a uniform sensor can be obtained and the yield is high because it eliminates the adverse effects caused by subtle differences in the state of adhesion between the diaphragm and the support of the conventional sensor.

Furthermore, since the knocking sensor of the present invention has a very simple configuration as described above, it is easy to make 11 designs.
It also has the practical advantages of high durability and dependence (and low cost).

Next, the present invention will be described as a typical IJ! The explanation will be based on the embodiment.

A first aspect of the present invention is that the weight of one weight facing the cooling water of the sensing unit is greater than the weight of the other weight.

The first mechanism with the above-mentioned configuration has an ideal configuration as an acceleration mound detection type non-component sensor by increasing the weight of the weight on the back side that does not face the cooling water.
The piezoelectric element effectively detects the knocking intensity to be detected, that is, the force corresponding to the knocking vibration pressure acting on the sensing surface, and sensitively detects the force based on the knocking vibration pressure acting on the sensing surface. It has the advantage of being able to

An eighth aspect of the present invention is that the area of the flat surface of one of the weights facing the cooling water of the sensing unit () is made larger than the area of the flat surface of the piezoelectric element sandwiched between them. be.

In the eighth aspect having the above-mentioned configuration, the vibration pressure based on the knocking vibration is sensed by the flat surface having a large area of the sensing portion, and the vibration pressure based on the knocking vibration is applied intensively to the sensing element, so that the vibration pressure is based on the knocking slow pressure. It has the advantage of being able to detect force with high sensitivity.

In an eighth aspect of the present invention, the spring constant of the portion of the support member that supports the sensing unit is configured to be small, so that the sensing unit is elastically supported.

In the eighteenth aspect having the above-mentioned configuration, the sensing unit is elastically supported by a support member.

Since the resonant frequency of the supporting part of the sensing unit is made sufficiently lower than the knocking frequency, it has the advantage of eliminating the negative influence of the supporting part and ensuring a flatter frequency characteristic over a wide frequency band.

A fourth aspect of the present invention is that the portion between the fixed portion of the support member and the portion that supports the sensing unit has a small spring constant or is made of a wooden material with a vibration damping coefficient. . Therefore, the fourth aspect has the advantage of preventing mechanical vibration propagating from the wall surface of the engine block from being transmitted to the sensing unit, and improving the resistance to external noise and the 8/N ratio. .

In a fifth aspect of the present invention, the fixing portion of the support member is constructed as a separate member, and an elastic body made of a rubber-like substance is interposed between the fixing portion and the support member.

The sixth aspect having the above configuration is strong against external noise because the elastic body attenuates mechanical vibrations propagating from the wall surface of the engine block and prevents them from being transmitted to the sensing unit.

This has the advantage of improving the 8/N ratio.

Next, the present invention will be explained in detail based on a knocking sensor according to an embodiment using one drawing.

The knocking sensor of the first embodiment belongs to the first to fifth aspects of the present invention, and will be explained using FIGS. 1 to 4.

FIG. 1 is a sectional view of the knocking sensor of the first embodiment. In the figure, ■ is a piezoelectric cefmic disk element constituting the sensing unit I, and as shown in a perspective view in FIG. and 0, and no polarization treatment is performed between the opposing electrodes. Fig. wg1 (■) has a concave portion corresponding to the piezoelectric ceramic element, and is a metal as a weight constituting the sensing unit (I) which is bonded to the piezoelectric ceramic element with an adhesive such as epoxy V resin. It is a cylinder. This adhesion is applied sufficiently thinly so that electrical continuity between the piezoelectric cellar element electrode and the metal cylinder can be achieved. Furthermore, the electrical terminal is taken out by soldering or other means (2) and connected to the electrical output terminal (2) via the lead (2).

(2) is a metal disk serving as a weight, which is attached to the piezoelectric ceramic element (2) with a recess corresponding to the piezoelectric ceramic element (2) by the same means as described above, and the electrical terminal (2) Cm
The connected lead wire (■) and soldering have a take-out part (2) by means of such means. As shown in the figure, the metal cylinder (2) and the metal disk (2) are bonded together via the piezoelectric ceramic element (D) so that electrical insulation is maintained when the sum of the depths of their recesses is The metal disk 0 is set to be smaller than the thickness of the element 1.Furthermore, the metal disk 0 has a flat surface with an area larger than the area of the piezoelectric ceramic element 1)! The pressure vibration of the king is received by the flat surface, and it has a fitting part that fits with the holding cylinder [phase] as the support member l, and the fitting part is configured to maintain watertightness. Ru. The holding cylinder ■ is made of resin that can withstand the operating temperature range and operating pressure.
Or, it is made of a material with a large elastic loss, such as a vibration-proof alloy, so that the vibrations from the mounting bracket 0, which is a fixed part of a support member made of a separate member, are not propagated to the metal disc ■ that makes up the sensing unit. At the same time, the sensing unit is supported elastically. Furthermore, the missing cylindrical EV mounting bracket■
The back is elastically fixed through a vibration-proofing material O such as rubber so as to have watertight properties. The plate fitting [phase] is screwed onto the engine block and holds the sensing unit at a predetermined position in the ice chamber in the engine block via the holding cylinder.

Book number 1! i! The 7γ equiangular sensor of the example has a metal disk 6
．． The length of the sensing unit composed of the piezoelectric ceramic element L and the metal cylinder B is set to be larger than the diameters of the metal disk and metal cylinder, and C and V are the sound speeds of the metal, and the length is 2L / + 2L. It was determined that the resonance frequency f associated with the length vibration obtained in the above is sufficiently larger than the knocking frequency of 6 to 8 KHz to be detected.

That is, in the first embodiment, when L = 15 stomachs, the wave number characteristics of Atoden matansu waste are ! As shown in Fig. 8, a flat sensitivity characteristic was obtained below the resonance frequency/+100 KHz.

FIG. 4 is a block diagram of a processing circuit when the above knocking sensor is used, and the input terminal O is connected to the electrical terminal of the knocking sensor. [Phase] is an impedance switching section, and [Phase] is an amplifier circuit. (2) is a bandpass filter that filters the required frequency band of 6 to 15 KHg for detecting the signal band associated with knocking as described above. [
This is a circuit for generating a control processing signal for performing predetermined control based on this output signal, and a control signal corresponding to knocking is obtained at the output terminal @.

As described above, the knocking sensor according to the nine-pronged embodiment has flat characteristics in the frequency band of slow motion associated with wheel knocking.

Also book No. 1 'Ji! In addition to the above-mentioned examples, the embodiment has the effects of the present invention and the first to sixth aspects of the present invention.

Furthermore, conventionally, it has been known to use knocking tubes on multiple sides that correspond to the knocking natural frequencies of multiple sides so that the respective natural frequencies are the same as the resonant frequency ζ. The knock sensor also has the advantages of a single knock sensor.

Next, the present invention will be explained based on the knocking sensor of the eighth embodiment using Figure 6.

*g* The knocking sensor of Example 9 belongs to the first to wg6 aspects of the present invention, and will be explained focusing on the differences from the first example.

1. The sensing unit 1 is composed of a piezoelectric safety sensor, a metal disc 4B as a weight, and a metal cylinder 48, which sandwich the piezoelectric ceramic element 41 from both sides.

The metal cylinder 48 has the same circular shape as the piezoelectric ceramic element 41, and its length is sufficiently long. The metal disc 48 is
It has a circular flat surface with an area larger than that of the piezoelectric ceramic element 41, and an annular leg portion is erected from the periphery of the circular flat surface, and the vertical cross section is formed in a U-shape. A threaded portion is formed on the inner shoulder of the open end of the leg.

Authentic Bs1ll! Compared to the first embodiment, the metal disk corresponding to the weight facing the cooling water is thinner, and the metal cylinder 48 corresponding to the weight facing the cooling water is made thinner. was formed thickly. The length of the total sensing unit was determined so that the resonant frequency of the sensing unit would be 100 KHz or more, which is two orders of magnitude higher than the knocking frequency. The metal disk 49 and the metal cylinder 48 connect the lead wires.

The support member l consists of a first holding cylinder 44, a second holding cylinder 46, and a mounting fitting 46 as a fixed part. The holding cylinder 44 of the tank 1 is made of the same resin as the holding cylinder of the first embodiment, and is a hollow cylinder having two parts with different diameters. Outer circumference Jl of the tip of the large diameter part! A threaded portion is formed in and the metal disc 48 of the sensing knee 1 is screwed and locked. An annular groove with a rectangular cross section is formed on the outer periphery # of the axially intermediate portion of the large diameter portion.

The small diameter portion is integrally formed with the large diameter portion via the bent portion, and forms an annular groove with a rectangular cross section on the outer wall near the bent portion, and forms a threaded portion with the inner circumferential wall of the open end. . 8th
The holding cylinder 46 is made of 0 synthetic resin and is a hollow cylinder having an outer diameter close to the diameter of the small diameter portion of the first holding cylinder, and the outer circumferential wall at the tip forms a threaded portion. The holding cylinder 441C is screwed and locked, and a Kuraray V portion is formed at the other end. The plate fitting 46 is made of an annular member, has a threaded part for mounting the engine block Ic on the outer periphery of the annular member, has an inner diameter larger than the outer diameter part of the small diameter part of the first holding cylinder 44, and has a base part. forms a thick inner part. A protrusion is formed at the boundary between the inner shoulder wall of the mounting bracket 46 and the V section of the 7th flange.

Groove portion 44B formed in the small diameter portion of the first holding cylinder 44
When the knocking sensor of the second embodiment is mounted on the engine block with nine K-rubber O-rings 47 installed, the tip of the mounting bracket 46 and the first holding cylinder are tightly connected to each other, making it watertight. keep it. Attach the 0-ring 48 of car 5 between the jλ part of the 7th flange upper mounting bracket 46 of the second holding cylinder 111145, rotate the φ8th holding cylinder 46, and attach the 0-ring 48 to the 41st part of the mounting bracket 46. bring it into contact with. Therefore, the holding cylinders of the first and sugar 2 constituting the support member l are locked with the mounting bracket 46#c by the O-rings 47 and 48, and the sensing unit I is placed at an appropriate position in the engine water chamber. do. The g! In the knocking sensor of Example J, the metal disc 42 as a weight constituting the sensing unit 12 is directly faced to the cooling water in the water chamber, and the axial length of the sensing unit (2) is Since the resonant frequency of the axial vibration of the sensor is configured to be sufficiently large compared to the knocking frequency to be detected, it has smooth frequency characteristics over a wide frequency band, and the electrical output of the sensor has a straight line with respect to the knocking intensity to be detected. It has the advantage of being a non-resonant knocking sensor with good performance.

The knock sensor of this TSM* example removes the negative effect of the resonant frequency based on the natural vibration frequency of the engine cooling water by eliminating the 7-diaphragm that faces the conventional engine cooling water, and has a wide frequency band. The Luno ensures flat frequency characteristics throughout the engine, and can be put to practical use even if the frequency of the /F King changes depending on the engine size and model. Therefore, the first S
*The knocking sensor of this example has the advantage of being applicable to a wide range of engines, and has the advantage of good output linearity because it does not have a resonance point in the frequency band used. In addition, the no king sensor of the eighth embodiment eliminates the adverse effects caused by subtle differences in the state of adhesion between the foot of the diaphragm and the supporting portion.

This method has the advantage that a simple sensor can be obtained and the yield is good.

Furthermore, the knocking sensor of the second embodiment is as follows.

A metal cylinder as a weight that does not face the cooling water weighs 480 square meters, and the weight is 4 metal discs! Since it is made sufficiently large with respect to Ic, it has an ideal configuration as an acceleration detection type non-resonant sensor, and has the advantage of being able to detect knocking with high sensitivity.

In the knocking sensor of the full-scale G embodiment, the area of one metal disk serving as a weight facing the cooling water is made larger than the area of the piezoelectric ceramic element 41, so that knocking can be detected with high sensitivity. It has the advantage of

In the knocking sensor of this SGS* example, the metal disc 4g of the sensing unit 22 and 1 is elastically supported by the first holding cylinder 44 made of resin, so that the resonance frequency of the support part of the sensing unit can be adjusted. By lowering the frequency, there is an advantage that the single frequency characteristic can be made even softer.

The 7-tracking sensor of the eighth embodiment has t of the support member 1.
Since the holding cylinder of the Igl is made of resin, it effectively damps and prevents mechanical vibrations propagating from the wall surface of the engine block, so it has the advantage of being resistant to external noise.

The knocking sensor of the eighth embodiment has first and eighth holding cylinders 44 and 45 of the support member.

Since the engine block N: is attached via the mounting bracket using only 8 O"h Q blowfish 4?, 48, it effectively damps the mechanical vibration propagating from the wall surface of the engine block, and also reduces the transmission passage area. Since the engine block is compressed by the engine block, it reduces the transmission efficiency of mechanical vibrations propagated from the engine block, which has the advantage of being more resistant to external noise than the first embodiment, and also facilitates assembly and manufacturing. It also has advantages.

The no king sensor of the 11th embodiment has the first holding cylinder 441C of the support member ring formed with the annular grooves 44A and 44B and a bent part between the large diameter part and the small diameter part, so that one mechanical vibration can be avoided. Since the area of the transmission passage is internalized and the thickness of the zero passage is suddenly reduced by Ic, an impedance gap is formed, which has the advantage of effectively blocking the transmission of mechanical vibrations from the engine block.

As is clear from the above, the knocking sensor of the second embodiment has a very simple configuration, so it is easy to manufacture, has high durability and reliability, and is low in price. has advantages.

Further, in the knocking sensor of the g*th embodiment, FIG. 6 shows a sectional view of another embodiment of the holding cylinder in FIG. 1. The holding cylinder 1B' has a notch 81 or 82 on the inner periphery or outer layer. These can further reduce the propagation of vibrations from the mounting bracket (I) in Figure vg1.

Even with such commercial processing, there is an advantage that the S/N ratio can be further improved.

Others 0 The present invention is capable of numerous design changes and additional changes within the spirit set forth in the claims.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 shows the nineteenth aspect of the present invention! A vertical cross-sectional view showing the knocking sensor of the embodiment, Figure @2 is a perspective view of the piezoelectric ceramic element of the knocking sensor of the @1 embodiment, and Figure 8 is a perspective view of the
FIG. 3 is a diagram showing frequency-admittance characteristics of a knocking sensor according to an example. FIG. 4 is a block circuit diagram of a signal processing circuit when using the knocking sensor of the first embodiment, FIG. 15 is a longitudinal sectional view showing the knocking sensor of the second embodiment of the present invention, and FIG. 6 is a holding A vertical cross-sectional view showing another example of a cylinder. In the figure, 1 is the sensing unit, I is the support member, ■ is the pressure patent consultant, Toyota Central Research Institute, Matsushita Electric Industrial Co., Ltd., agent, patent attorney, Shoken Takahashi, patent attorney, Katsutoshi Takahashi, Masaru Hiko, attorney, Katsuda Sugimoto. Bifurcated Figure 3 0 20 40 60 80 100 120 laps 15
r (ni HX) 41 Kyou 52 Chi 6

Claims (1)

[Scope of Claims] (1) A sensing unimad in which a piezoelectric element is sandwiched between the opposing flat surfaces of eight weights each having flat surfaces on both sides. It has a fixing part for fixing to the outer side of the engine plotter of a water-cooled internal engine, and supports the sensing unit in a watertight manner so as to be submerged in the cooling water in the engine block. is arranged so that it is substantially parallel to the outer side 11C of the engine pump, and the flat surface on the opposite side faces the cooling water directly to the flat surface sandwiched between the heavy piezoelectric elements. and a support member arranged so as to Knocking characterized in that the axial length of the sensing unitad is configured such that the resonance frequency of the axial vibration of the sensing unitad is sufficiently larger than the frequency of the knocking to be detected. sensor. (2) Knocking according to claim (1), characterized in that the weight of the other weight facing the cooling water of the sensitive knee W) is greater than the weight of the other weight. sensor. (8) The area of the flat surface of one of the weights facing the cooling water of the sensing unit () is made larger than the area of the flat surface of the sandwiched piezoelectric element. The knocking sensor according to item (11) and item (g). The knocking sensor-0 according to claim 11 and claim 8 is characterized in that the reduction in electrical output due to the restraint 1 of the support portion of sensing n = νF is prevented. (5) Reduce the spring constant of the part between the fixed part of the support member and the part that supports the sensing sensation D=y, or make it made of a material with a large vibration damping coefficient, and A picking sensor according to claims 11 and 4, characterized in that the mechanical vibration is transmitted to the sensing unit. Claims characterized in that an elastic body made of a rubber-like substance is interposed between the fixing part and the supporting member.