JP2006291969A - Non-resonant type knock sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-resonant type knock sensor capable of flattening detection sensitivity in a vibration frequency detection band. <P>SOLUTION: An insulating sleeve 3 is fitted to a cylindrical body 2b of a main fitting 2 integrally formed of SKD-11 (Vickers hardness: 306HV) which is an iron-based material, and an insulating plate 4, a piezoelectric transducer 6, an insulating plate 5 and a characteristic adjusting weight 7 are fitted in this order to the insulating sleeve 3. A nut 9 is screwed with a thread 2d of the cylindrical body 2b through a washer 8, and respective members 4-8 are clamp-fixed between the upper face of a seat face portion 2c of the main fitting 2 and the nut 9. A housing 10 is formed to cover the respective members 4-8. To use the non-resonant type knock sensor 1, the flat seat face portion 2c of the main fitting 2 is allowed to abut on an optimum part (a cylinder block or the like) of an engine. When knocking occurs, its vibration reaches the piezoelectric transducer 6 through the seat face portion 2c, and detection signals are outputted from respective electrodes 6a, 6b of the piezoelectric transducer 6. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a non-resonant knock sensor.

  Conventionally, a technique for performing ignition timing control by using a knock sensor that detects a knocking state of an engine is known. This knock sensor is a kind of vibration pickup that is mainly attached to the cylinder block of the engine. When knocking occurs in the combustion chamber, the vibration reaches the knock sensor via the cylinder block. Such detection is made using vibration detection means such as.

  The knock sensor includes a resonance type knock sensor and a non-resonance type knock sensor. The resonance type knock sensor is tuned so that the detection sensitivity becomes maximum at the resonance point (resonance frequency) at which the frequency (generally 6 to 8 kHz) generated by knocking matches the natural frequency of the vibration detection means. Has frequency characteristics. A non-resonant knock sensor does not have a resonant frequency like a resonant knock sensor, has the same characteristics as a vibration pickup for general measurement, and has a frequency characteristic with almost flat detection sensitivity within the frequency detection band. Have.

  Since the resonance type knock sensor can detect the knock state only at the resonance frequency, it is necessary to match the resonance frequency to the knock frequency of the engine, and it can be used only for a predetermined engine. is there.

  On the other hand, the non-resonant knock sensor can detect a knock state at any frequency within the frequency detection band, and thus can be used for various engines, and has an advantage of excellent versatility. Therefore, the non-resonant knock sensor is required to make the detection sensitivity in the frequency detection band as flat as possible in order to improve versatility.

  The present invention has been made to satisfy the above requirements, and an object thereof is to provide a non-resonant knock sensor capable of flattening the detection sensitivity within the frequency detection band.

  The invention according to claim 1, which has been made to achieve such an object, is a non-resonant knock sensor constructed by attaching a vibration detecting means to a metal shell, and is brought into contact with an engine to be detected for knocking. The main point is that the Vickers hardness of the material of at least the seating surface portion of the metal shell is 95 HV or more.

  According to the present invention, since the strength is increased by hardening at least the seating surface portion of the metal shell, the detection sensitivity in the frequency detection band can be flattened. By the way, as in the invention described in claim 2, in the invention described in claim 1, the material of the seat surface portion may be mainly iron. If it does in this way, it will become difficult to change a detection sensitivity ratio with respect to a temperature change, and the effect of the invention of Claim 1 can be acquired more reliably.

  As in the invention described in claim 3, in the invention described in claim 1 or 2, the entire metal shell including the seat surface portion may be formed of the same material. In this way, the metal shell can be integrally formed, the strength of the metal shell can be increased, and the effect of the invention according to claim 1 or claim 2 can be obtained more reliably. Since the number of parts of the non-resonant knock sensor is reduced and the labor for assembly is reduced and the manufacture becomes easy, the cost can be reduced.

  Further, as in the invention according to claim 4, in the invention according to any one of claims 1 to 3, the detection sensitivity ratio of the frequency detection band at the operating temperature of the engine is 0.5 or more and 1 You may make it contain below .5. If it does in this way, the effect of the invention given in any 1 paragraph of Claims 1-3 can be acquired more certainly.

  Hereinafter, a non-resonant type knock sensor embodying the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a main part of a non-resonant knock sensor 1 of the present embodiment. FIG. 2 is an exploded perspective view of the non-resonant knock sensor 1.

  The non-resonant knock sensor 1 includes a metal shell 2, an insulating sleeve 3, insulating plates 4 and 5, a piezoelectric transducer 6, a characteristic adjusting weight 7, a washer 8, a nut 9, and a housing 10. The metal shell 2 is composed of a cylindrical tube 2b through which a through hole 2a is provided, and a donut-shaped disk-shaped seat surface portion 2c protruding in a flange shape from the periphery of the lower end of the tube 2b. ing. Further, a thread 2d is engraved on the upper portion of the cylindrical body 2b, and a groove 2e for enhancing adhesion to the housing 10 surrounds the outer periphery of the upper end portion of the cylindrical body 2b and the peripheral portion of the seat surface portion 2c. It is carved in. In addition, each part 2a-2d of the metal shell 2 is integrally formed using an appropriate manufacturing method (casting, forging, machining, etc.). Further, the surface of the metal shell 2 is subjected to a plating process (such as zinc chromate plating) in order to improve the corrosion resistance.

  The insulating sleeve 3 has a thin cylindrical shape and is formed of an insulating material (various plastic materials such as PET and PBT, rubber materials, etc.). Each of the insulating plates 4 and 5 has a thin donut-like disk shape and is formed of an insulating material (various plastic materials such as PET and PBT, rubber materials, etc.).

  The piezoelectric transducer 6 as the vibration detecting means is composed of a material layer having a piezoelectric effect between the two thin plate electrodes 6a and 6b (various crystals such as quartz, various ceramics such as barium titanate, zircon and lead titanate, polyfluoride, etc. Various organic materials such as vinylidene, etc.) 6c are laminated to form a donut disk shape as a whole.

  The characteristic adjusting weight 7 has a donut-like disk shape, and is formed of a material having a predetermined density (various metal materials such as brass). An insulating sleeve 3 is fitted to the cylindrical body 2b of the metal shell 2, and an insulating plate 4, a piezoelectric transducer 6, an insulating plate 5, and a characteristic adjusting weight 7 are fitted to the insulating sleeve 3 in this order. Further, a nut 9 is screwed into a thread 2 d of the cylindrical body 2 b of the metal shell 2 via a washer 8. Between the upper surface of the seat surface portion 2c of the metal shell 2 and the nut 9, the insulating plate 4, the piezoelectric transducer 6, the insulating plate 5, the characteristic adjusting weight 7 and the washer 8 are sandwiched and fixed, respectively, and these members 4 The housing 10 is formed of an insulating material (various plastic materials such as PA) injection-molded so as to cover .about.8. Therefore, only the lower surface of the seating surface portion 2 c of the metal shell 2 is exposed from the lower end portion of the housing 10, and only the upper end of the cylindrical body 2 b of the metal shell 2 is exposed from the upper end portion of the housing 10. The periphery of the piezoelectric transducer 6 is surrounded by the insulating sleeve 3, the respective insulating plates 4, 5 and the housing 10, and the metal shell 2, the characteristic adjusting weight 7 and the piezoelectric transducer 6 are insulated. A lead wire (not shown) is connected to each electrode 6a, 6b of the piezoelectric transducer 6, and the lead wire is led out from the housing 10.

  Incidentally, the diameter of the through hole 2a of the metal shell 2 is about 9 mm, the height of the cylindrical body 2b is about 20 mm, the outer diameter of the cylindrical body 2b is about 14 mm, the outer diameter of the seat surface portion 2c is about 20 mm, and the seat surface portion 2c. The wall thickness is set to about 3 mm. In order to use the non-resonant type knock sensor 1 configured as described above, the flat seating surface portion 2c of the metal shell 2 is disposed so as to abut on an optimal location (generally a cylinder block) of the engine, The non-resonant knock sensor 1 is attached to the engine by fitting a bolt into the two through holes 2a and screwing the bolt and the engine. When knocking occurs in the combustion chamber of the engine, the vibration reaches the piezoelectric transducer 6 via the seat surface portion 2c, and detection signals (sensor outputs) corresponding to the vibration are transmitted from the electrodes 6a and 6b of the piezoelectric transducer 6. Is output.

  FIG. 3 shows that when the material of the metal shell 2 is changed, the detected vibration frequency is 20 kHz with respect to the Vickers hardness (HV) of the material and the detection sensitivity when the detection frequency is 7 kHz (sensor output: mV / G). It is a graph which shows the measurement result in normal temperature and the temperature at the time of engine use (125 degreeC) about ratio of the detection sensitivity of. FIG. 4 is a graph showing the measurement results of FIG.

  In addition, the measurement result shown in FIG. 3 is measured in a state where the plating on the surface of the metal shell 2 is peeled off. The frequency detection band of the non-resonant knock sensor 1 is about 1 kHz to about 20 kHz. As shown in FIGS. 3 and 4, although there are some exceptions, as the Vickers hardness of the material of the metal shell 2 increases, the detection sensitivity ratio between 7 kHz and 20 kHz decreases and approaches 1 (that is, the frequency detection band). It can be seen that the detection sensitivity is flattened. It can also be seen that the copper-based material (C3602) has a large detection sensitivity ratio between room temperature and 125 ° C., whereas the iron-based material has a small detection sensitivity ratio between room temperature and 125 ° C. 3 that SKD-11 has the largest Vickers hardness, and the detection sensitivity ratio hardly changes with temperature.

  To summarize the above results, in the non-resonant knock sensor 1, the strength of the metal shell 2 (especially, the seat surface portion 2c in contact with the engine) is increased by using a hard material for the metal shell 2, so that the frequency detection is performed. In-band detection sensitivity can be flattened. Further, if the metal shell 2 is integrally formed, the strength of the metal shell 2 as a whole can be increased, and the number of parts of the non-resonant knock sensor 1 can be reduced and the assembly work can be reduced, thereby facilitating manufacture. Therefore, the cost can be reduced.

  The material of the metal shell 2 is preferably composed mainly of iron, and the range of Vickers hardness is suitably 95 HV or more, preferably 200 to 310 HV, and particularly preferably 225 to 305 HV. If the Vickers hardness is higher than this range, the workability is deteriorated and the seat surface portion 2c is likely to be distorted, so that it is difficult to flatten the detection sensitivity within the frequency detection band. There is a tendency that the detection sensitivity in a high band tends to increase rapidly.

  Further, the detection sensitivity ratio of the non-resonant knock sensor 1 at the engine operating temperature in the frequency detection band (about 1 kHz to about 20 kHz) is set within a range of 1 ± 0.5 (0.5 to 1.5). It is desirable. In addition, this invention is not limited to the said embodiment, You may actualize as follows, Even in that case, the effect | action and effect similar to the said embodiment can be acquired.

  (1) In the above embodiment, the cylindrical body 2b and the seat surface portion 2c of the metal shell 2 are integrally formed of the same material. However, after the cylindrical body 2b and the seat surface portion 2c are formed of different materials, both are assembled and fixed. You may do it. In this case, at least the seat surface portion 2c of the metal shell 2 attached in contact with the engine to be detected for knocking needs to be formed of a material that satisfies the above conditions.

  (2) In the above embodiment, the piezoelectric transducer 6 is used as the vibration detecting means, but other types (electromagnetic induction type (moving coil type, moving iron piece type, moving magnet type, etc.), strain gauge type, electrostatic capacity, etc. Type) vibration detection sensor may be used.

The principal part longitudinal cross-sectional view of the non-resonance type knock sensor of one Embodiment which actualized this invention. The disassembled perspective view of the non-resonant type knock sensor of one embodiment. The chart showing the measurement result at the time of changing the material of the metal shell of one embodiment. The graph showing the measurement result of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Non-resonance type knock sensor 2 ... Main metal fitting 2c ... Seating surface part 6 ... Piezoelectric transducer

Claims (4)

A non-resonant knock sensor constructed by attaching vibration detection means to a metal shell, wherein the Vickers hardness of the material of at least the seat surface portion of the metal shell abutting against the engine to be detected for knocking is 95 HV or more There is a non-resonant knock sensor. The non-resonant knock sensor according to claim 1, wherein the material of the seating surface portion is mainly iron. 3. The non-resonant knock sensor according to claim 1, wherein the entire metal shell including the seat portion is formed of the same material. The non-resonant knock sensor according to any one of claims 1 to 3, wherein a detection sensitivity ratio of a frequency detection band at a temperature during use of the engine is set to 0.5 or more and 1.5 or less. .

Images