CN101443644A - Apparatus and method for detecting drive belt wear and monitoring belt drive system performance - Google Patents

Abstract

An apparatus and method that enables monitoring of wear and abnormal functioning of an endless belt and associated belt drive system via non-contact sensors, determining the status of the belt drive system and detecting early stages of belt and system failure. A sensing unit having one or several individual sensor elements is arranged adjacent or close to the belt, thereby monitoring several simultaneous normal modes of operation of the belt. The sensor can continuously determine the stability of the entire timing drive by processing the collected signals and detecting structural damage. Processing the collected data by a microcontroller integrated with the sensor. The apparatus and method for monitoring wear or abnormal function of an endless belt uses a non-contact capacitor array consisting of one or several detection elements arranged adjacent or close to the belt and connected to an electric circuit adapted to detect dynamic capacitance changes related to the capacitance and piezoelectric effect exhibited by the belt. The apparatus can further monitor a drive component associated with the belt by detecting whether the belt is affected by an abnormal function of the associated component. The sensor continuously monitors the belt during normal operation of the belt drive. The sensor is particularly useful for detecting belts currently used in workshop, industrial and automotive applications and characterized by a polymer matrix with a fiber-wire carrier core.

Description

Apparatus and method for detecting drive belt wear and monitoring belt drive system performance

Background of the invention

In the field of power transmission, belt drives are the preferred components for connecting rotating elements. Traditionally they are generally divided into two categories: non-synchronous and synchronous belt drives. In vehicles, these two types are widely used. Non-synchronous transmissions are the preferred components for driving components such as water pumps, air conditioner compressors, power steering pumps and alternator units. A synchronous drive, commonly referred to as a timing drive, is the preferred component for driving an overhead camshaft system and is widely used in internal combustion engines where the driven components need to be synchronized. An example of such a transmission mechanism is shown in Figure 1.

Timing belts are typically composites of fiberglass, woven fabric, rubber, and various other polymers. All of these materials exhibit piezoelectric properties: they generate electrical charges as they deform. Under normal operating conditions, the belt deforms through tension and bending forces as it runs over sprocket teeth and pulleys. These deformations create electrical charges. Due to the relatively high electrical resistance of the strip material, the charge exists long enough to be detected. The charge generated by the piezoelectric effect is proportional to the tension. This property has been successfully used in force sensors and accelerometers.

The invention described here is applicable to both types of transmissions, but is particularly applicable to timing transmissions. Belts are more economical, less complicated and more efficient than other components used (ie, chains or gear trains). The main disadvantage of belts is that it is difficult to determine their lifespan or the point in the vehicle's life at which belts may potentially fail. Until now, visual inspection was the only way to verify the condition of belt drives and their associated components. However, this is a very cumbersome and impractical process. Timing drives typically operate closed due to their vulnerability to contamination, and removing the housing prior to visual inspection is often a very laborious procedure. Furthermore, damage to ribbons and other components is often invisible to the human eye, and visual inspection proves to be inefficient. Furthermore, failure of the belt can cause the vehicle or transmission to become inoperable, and due to the high compression ratio nature of modern internal combustion engines, a failed belt often result in significant damage to the internal combustion engine.

While timing belts have evolved considerably with improved materials and enhanced tooth geometries, structural developments have not addressed life expectancy issues for timing drive systems as a whole. Uncertainty in life expectancy of belt drives coupled with high repair costs and consequent customer dissatisfaction forces engine manufacturers to make calculations with considerable safety margins when designing and operating such drives. As a result, the belt is made much wider than necessary, and the recommended number of miles at which the belt changes is set prudently lower. The uncertainty of belt life has forced engine manufacturers and timing drive designers to consider going back to using chains instead of belts. This consideration has been particularly reinforced by the market trend towards maintenance-free engines. Still, engine builders have been reluctant to switch to chains, and have spent years trying to solve the conundrum by any means possible.

The prior art shows active activity with some inventions that claim to deal with this problem. Many existing ideas cannot solve this problem and are largely impractical for industrialization. A large number of proposals have not caught the attention of investors because they do not sufficiently justify the additional costs or design challenges involved. This is the type of program that requires a change in design of the band. US Pat. No. 6,181,239 and US Pat. No. 6,523,400 propose a solution in which belt wear is detected by breakage or changing inductance or capacitance of wires or metal structures embedded in the belt. Such a solution would be impractical for those skilled in the art of fabricating the belt. Embedding a metal structure in the belt would mean a significant deviation from the manufacturing method and introduce great uncertainty as to the effect of such a metal structure on the overall durability of the belt. Belt manufacturers tend to have a very conservative approach to any design changes, making implementation of this type of approach very unreliable. Also, the costs associated with such a scheme would make the product very expensive. Another disadvantage is that this solution is only used for OEM installed belts. In the automotive industry aftermarket, belts for use with a particular engine transmission are typically made by several manufacturers. The belts used for service are usually from a different manufacturer than the belts installed by the OEM.

It is also recognized that inventions based on mechanical, photoelectric or on/off switching sensing devices (of which US Pat. This switch detects a faulty tooth or cog, all of which fall short of the target. These devices are prone to contamination and are liable to give false alarms or become unreliable since they remain stationary and are only triggered after damage to the band being protected. Furthermore, it is not possible to check the functionality of such devices because the required inputs cannot be simulated. Because of the possibility of false alarms, they must be calibrated in response to severe disturbances in the system such as occur when the belt has failed significantly. This gives little or no warning to the driver.

Contents of the invention

The present invention of detecting breakage and damage to drive belts in a non-contact manner provides a significant improvement over those described in the prior art, as it provides or structural damage to monitor the performance of the drive mechanism. It will be apparent to anyone skilled in the art that the belt used in the timing system shown in Figure 1 is as durable as the chain provided it is operated under optimum conditions with no abnormal input values. Most of the cases where belts fail prematurely are due to abnormalities such as after the belt has been subjected to faulty behavior of components connected to it, or has been contaminated by fluids like oils, coolants and other fluids commonly used in engines and industrial machines , or exposure to external dirt such as dust, ice, water, and stone flakes that have penetrated the leaking enclosure. Essentially, the invention can be used to monitor the drive belt for any such anomalous effects. Another advantage obtained from the prior implementation of the invention is that no design changes are required for the belt drive mechanism, contrary to the invention described in the prior art. The present invention provides a reliable system for determining the life of a belt drive and enables the designer to adopt multiple strategies for how to improve the quality of the overall system.

In the new strips with uniform intensity, the piezoelectric charge is evenly distributed. The new sensor is sensitive to changes in charge density and therefore does not have large changes in the output signal. As the band wears from use, portions of the band become weaker and exhibit greater deformation strain when loads are applied during engine operation, which in turn results in greater piezoelectricity in the band region effect and higher local charge density. The new sensor detects this higher local charge, resulting in an increased signal amplitude. Thus, the greater the signal amplitude, the weaker the band. The sensor also detects changes in capacitive properties caused by dynamic changes in the dielectric properties of the strip.

The present invention features a non-contact sensor coupled to an MPU (Micro Processing Unit). The sensor operates with one or several capacitive sensing elements coupled into a circuit and designed to detect a change in permittivity or a change in capacitance. The sensor also detects electrostatic capacitance caused by the piezoelectric effect induced by the belt as the belt-tensioned structural material passes a capacitive sensing element during normal operation of the system. During operation of the belt drive, the piezoelectric properties of the belt generate an electrical charge or similar static that accumulates in the belt proportional to the deformation experienced by the belt. This effect can be used as an indication of belt wear since a worn belt portion will have greater deformation and thus generate a higher charge from the sensor which translates to a higher signal level. The sensing elements are positioned in such a way that they produce signal responses corresponding to key characteristics of the belt and specific key modes exhibited by the belt and the belt drive mechanism during operation. Typical detected modes are: basic belt character, span vibration at natural and mesh frequencies, belt tooth induced instantaneous RPM and signal events per revolution. Belt wear leading to damage typically starts at a location on the belt that the sensor will detect and generate a rotation signal event (hereafter referred to as OPRSE) one per belt.

Contamination will cause changes in the dielectric constant and/or electrostatic capacitance and permanent or semi-permanent piezoelectric behavior of the strip recorded by any detection element and lead to an overall change in the signal threshold. Initial failure of any coupling component will result in a change in belt tension. Variations in tension will result in a shift in the vibrational signature reproduced by the span of the belt during normal operation. In addition, the torsional behavior of the belt drive also changes. A change in characteristics can be directly linked to a quantitative increase or decrease in belt tension, as will be apparent to anyone skilled in the belt drive art. The signal obtained by the detection circuit can be processed by any number of signal processing methods. The analog based signal can be further conditioned and coupled to any device capable of data collection and signal analysis. However, the invention is optimally realized as a stand-alone device in which the analog signal is analyzed by a DSP (Digital Signal Processing) algorithm implemented by an MPU (Micro Processing Unit) embedded within the sensor structure. The resulting data is stored on board of the sensor structure and depending on the end user's strategy, this data can be further analyzed by algorithms in an external PLC (Programmable Logic Controller) or vehicle controller, or stored for transmission to central database.

[11] This feature will provide several advantages to the user (OEM), such as: Allowing a non-linear scheme of service intervals, i.e. when a belt or other timing drive Especially beneficial for vehicles with strict duty cycles such as rescue, legal enforcement or rental vehicles). Especially if a failure occurs during the warranty period, detecting early signs of a drive failure before serious damage or loss of function occurs can result in significant cost savings. Based on the collected data, the user can generate a proactive response by issuing a maintenance report. From the collected data, the user can develop a know-how of what constitutes the service life of the timing drive and how best to design the drive. The belt can be made narrower, thereby saving a few millimeters of space where space saving is a concern. When used as a commercially available tool, the present invention can reduce or eliminate the perception that current belt drives are unreliable, providing peace of mind to the end user of the vehicle. The advantages mentioned above are also directly applicable to industrial belt drive systems.

Detailed Description and Preferred Embodiments

[12] The present invention can be better understood from the following detailed description and preferred embodiments in conjunction with the following drawings.

Description of drawings

[13] Figure 1 shows a front view of the belt drive mechanism with the detection device in place;

[14] Figure 2 shows a cross-sectional view of the detection device and the adjacent belt structure;

[15] Figure 3 shows a cross-sectional view of a typical ribbon structure;

[16] Figure 4 shows a side view of a typical ribbon structure;

[17] Figure 5 shows a front view of the ribbon depicting the failure mode when a typical ribbon shows an exposed core and typical structural defects;

[18] Figure 6 shows a side view of the belt depicting the failure of a single belt tooth structure;

Figure 7 shows a front view of the belt drive depicting typical modes of vibration in the belt span between two components;

Figure 8 shows a cross-sectional view of a typical ribbon structure, which depicts the preferred vertical placement of the detection elements;

Figure 9 shows a side view of the belt depicting the preferred vertical placement of the detection elements;

Figure 10 shows a cross-sectional view of a typical ribbon structure, which depicts the preferred parallel placement of the detection elements;

Figure 11 shows a side view of the strip depicting the preferred parallel placement of the detection elements;

Figure 12 shows a cross-sectional view of a typical ribbon structure, which depicts the preferred horizontal placement of the detection elements;

Figure 13 shows a side view of the belt depicting the preferred horizontal placement of the detection elements;

Figure 14 is a front view showing a preferred method of construction of the detection element;

Figure 15 is a front view showing a preferred method of construction of the detection element;

Figure 16 is a front view showing a preferred method of construction of the detection element;

Figure 17 is a front view showing a preferred method of construction of the detection element;

Figure 18 is a front view showing a preferred detection element;

Figure 19 shows a front view of a portion of a typical timing drive with a complete detection device of an exemplary preferred embodiment;

Figure 20 shows an auxiliary diagram of the same detection setup as in Figure 19;

Figure 21 shows a cross-sectional view of the strip depicting the preferred location of the detection element/pickup device and how the element is connected to the circuit;

Figure 22 shows a block diagram depicting the signal pathways through the main components of the detection device and the communication with devices external to the sensor;

Figure 23 shows the signal generated when the span is vibrated at 55 Hz;

Figure 24 shows the spectrum of the signal in Figure 23;

Figure 25 shows the signal generated when the span is vibrated at 30 Hz;

Figure 26 shows the spectrum of the signal in Figure 25;

Figure 27 shows the signals used to pick up an event per rotation;

Figure 28 shows the signal with tooth pulse;

Figure 29 shows a side view of the strip, which depicts a cross-section of the detection element;

Figure 30 shows a side view of the strip depicting the preferred vertical placement of the two detection elements with signal cancellation;

Figure 31 shows the signal with toothed pulses and the effect of band contamination.

Description of the preferred embodiment

A feature of the invention is a detection device and signal analysis method that are particularly suitable for describing the operating conditions of a belt drive and predicting when the belt and/or its associated components should be replaced in order to avoid drive failure. Furthermore, the present invention features the electronic circuit 51 and detection element 36 shown in FIG. 22 , which operate through capacitive components coupled with electrocapacitive and piezoelectric properties to collect signal data without contact strips. The detection element 36 is capable of detecting the tape through a stationary structure, ie the casing of the tape. The nature of this detection makes it especially useful for detecting dynamic harmonic and transient events from passing strips. Anyone skilled in the art of capacitive, capacitive, and piezoelectric detection circuits can implement the circuit in a number of ways. The open literature Capacitive Sensors Design and Applications, Larry K Baxter, IEEE, Piscataway, NJ is a good source for examples of such circuits. The novel approach described in this publication using MOS (Metal Oxide Semiconductor) transistors is preferred because its elements can be easily integrated into mixed signal circuits, but for the purposes of the present invention any capacitive sensing with suitable characteristics can be used circuit. This part of the circuit is called an analog circuit 51 . Detection elements coupled into the analog circuitry are positioned around the target strip structure to best produce the desired signal input. The detection element 51 consists of two adjacently arranged electrodes that generate a specific capacitance and project a capacitive field. The electrodes are oriented towards the strip target such that the changing dielectric properties of the strip will affect the capacitive field in such a way that the capacitance of the electrodes detected by the coupled analog circuit 51 changes. The detection element also detects, by means of inductive coupling, the capacitive charge accumulated on the strip as a result of the piezoelectric material properties of the strip material composite.

As shown in Figures 8 and 9, a detection element 36 positioned across the belt structure will result in a signal response to the passing tooth structure 21 . The signal response of said element is shown in FIG. 28 , where the distance 80 corresponds to the tooth pitch of the belt 17 .

In the context of the present invention, two or more detection elements 36, 38 spaced apart by a plurality of tooth spacings 16 as shown in Figs. 8, 9 and 13 will have the effect of increasing said signal response through the teeth.

A detection element 37 oriented longitudinally in the main direction of belt movement as shown in Figures 19 and 20 will primarily result in a signal response (to lateral movement 27 as shown in Figure 7 of the belt span 14). Lateral movement is generally the result of natural or induced span vibrations. FIG. 23 shows a typical signal response for the natural span vibration 27 shown in FIG. 7 with vibration period 84 and amplitude 73 . FIG. 24 shows the frequency spectrum of the signal, where 74 represents the natural frequency 71 with a span of 14. FIG. A detection element 37 having a length equal to three or more tooth pitches 16 is not affected by the passing tooth and will therefore act as a filter for the meshing signal generated by the tooth. The detection element will only detect an engagement-related frequency 70 if it is present during the lateral movement 26 of the belt span 14 .

As shown in FIG. 21 , a sensor consisting of several detection elements 36 , 37 and 38 is connected to an analog circuit 51 using a multiplex switch 50 . The multiplexing switch is controlled by the MPU 53 shown in Figure 22 and can sample signals from each detection element 36, 37 and 38 individually, collectively or in any combination as required by the DSP strategy used.

As shown in FIG. 30, the two detection elements 36 are located on opposite or the same side of the belt in a special arrangement that they are spaced apart by an increment of half the belt pitch 45 so that one faces the tooth tip and the other to the roots. As shown in FIG. 30 , the properties of the pass signals 46 , 47 cancel each other out 81 , and this detection element configuration results in a significant reduction in the signal response caused by the pass belt tooth 20 , wherein the cancellation is illustrated in a graph 81 . This is especially beneficial when the sensor is looking at OPRSE (signal events per revolution) or looking at internal structural damage (ie belt wear). OPRSE occurs when damage due to structural defects or wear of the belt 17 is detected. In most cases, ribbon damage starts at one point and during further operation the ribbon damage will spread, causing the entire ribbon to fail. OPRSE is the signal that band 17 has failed and should be replaced quickly. Figure 5 shows two types of belt damage commonly represented by OPRSE: initial cord damage 22 and polymer defects 23 . FIG. 6 shows damage to the belt 17 due to missing tooth formations 24 or cracked teeth 25 . These types of lesions appear as clearly identifiable signal events on signal traces. An example of the signal trace is shown in Figure 27, where signal peak 79 represents the OPRSE at a particular point on the tape, and distance 78 represents a complete tape revolution past the detection element. Signal peaks 79 over multiple cycles may be summed before or after comparison to the threshold level to avoid spurious signals and false alarms.

If the belt 17 used in the transmission shown in FIG. 1 is contaminated by a fluid such as oil, engine coolant, or any fluid contamination that leaves residue on the belt, causing its dielectric and/or capacitive properties to develop sufficiently , the sensor assembly will detect the presence of said fluid and register the shift in overall signal threshold as shown in Figure 31, where 82 represents the signal level measured before contamination and 83 represents the signal level measured after contamination. flat.

Figure 1 shows one main application of the invention as a monitoring device for a belt drive commonly used to maintain the synchronization of cams in internal combustion engines and commonly referred to as a timing drive. In the belt drive, a new sensor 30 is arranged close to the camshaft sprocket 7 . In this position, the sensor 30 is optimally fitted to monitor the drive mechanism and detect any abnormal input to the belt 17 as well as detect damage to the belt. Because the sensors 30 operate in a non-contact manner, they are spaced apart by sufficient gaps 34 and 35 as shown in FIG. 2 so as not to interfere with the moving belt structure 17 . As shown in the dotted box in Fig. 22, the sensor 30 has all the detection elements 36, 37, 38 and electronics embedded in its structure, which enable said sensor to operate automatically. The sensor 30 is connected to the vehicle engine controller and typically acts as a slave to a master vehicle engine controller 58 and communicates with the controller via wire 31 or wireless antenna 32 . The signal path is as follows: The detection element 36 detects the strip 17 by means of the electric field 72 . Element 36 is coupled to analog circuitry 51 through multiplexing means 50 shown in FIG. 21 . Said circuit generates an analog signal 61 which is converted by an A/D converter 52 into a digital data stream and stored in a microprocessing unit MPU53. MPU53 performs digital signal processing DSP through the embedded algorithm. Suitable DSPs are known to anyone skilled in the art of digital signal analysis.

The sensor assembly 30 is operable as a self-contained unit with built-in battery power, which enables operation independent of the vehicle power supply. This option is especially suitable for after-sales service applications.

The electronics incorporated in the sensor assembly 30 communicate via wire or wirelessly using a range of automotive communication protocols such as LIN (Local Interconnect Network) or CAN (Controller Area Network) 57, or derivatives of such protocols (FIG. 22). communicate with the vehicle.

The electronics incorporated in the sensor assembly 30 has a built-in microcontroller 53 pre-programmed with algorithms that can make independent decisions based on the detected signals if a belt or drive mechanism failure is imminent.

The sensor assembly 30 can be used as a system monitoring tool, where the sensors can periodically, or on demand, transmit stored timed transmission performance parameters, such as belt tension or camshaft twist characteristics, to the vehicle controller ECU 58 . The performance parameters may be wirelessly transmitted to the vehicle manufacturer if the vehicle is equipped with a communication uplink, or the performance parameters may be downloaded to the vehicle OEM59 database at a typically scheduled service location.

In addition to tuning the surface area of the element, the detection element is manufactured in several ways under conditions that achieve the desired detection length and capacitance value, which determine the sensitivity of the detection element to capacitive effects. The basic detection element consists of two metal structures spaced apart from each other by a predetermined distance by a dielectric component. Figure 14 shows a detection element consisting of two parallel copper traces 40 and 41 etched on a PCB (Printed Circuit Board) 39 using standard electronics industry circuit board fabrication methods. Figure 15 shows how a copper trace 40 surrounded by a U-shaped copper trace 41 increases the sensing element capacitance while maintaining a small footprint. Figure 16 shows two copper traces 40 and 41 shaped as a horseshoe. Figure 17 shows another way of forming the detection element by twisting together two wires 40 and 41 each covered with a dielectric. The thickness of the wiring sheath defines the distance between the two wirings that make up the electrodes. Figure 29 shows two metal plates or strips 42 welded to opposite sides of a dielectric material with a distance between them equal to half or all of the distance 16 of the target belt 17 tooth pitch. The detection element structure is adapted to detect a passing toothed structure.

Preferred Method Embodiment

The detection elements 36, 37 and 38 connected to the analog circuit 51 output continuously modulated analog AC signals as shown in FIG. The signal is converted into a binary signal and transmitted to a memory and calculation unit MPU 53 coupled to the analog circuit 51 . From said signal, an integrated DSP algorithm calculates the instantaneous belt drive speed.

The detection element 37 connected to the analog circuit 51 outputs a continuously modulated analog AC signal as shown in FIGS. 23 and 25 . The signal is converted into a binary signal and transmitted to a memory and calculation unit MPU 53 coupled to the analog circuit 51 . From said signal, the MPU 53 incorporating a DSP algorithm calculates the natural frequency 74 of a particular band span near the detection element. For anyone skilled in the belt drive art, the calculated frequency 74 is related to the tension level in the belt span. Thus, a change in frequency 76 in FIG. 26 represents a shift in belt tension. Monitoring the frequency provides a means for detecting if the tension level in the belt has drifted outside a predetermined operating threshold. Furthermore, if the signal shown in FIG. 25 exhibits additional frequency content, as shown in the enclosed portion 77, the signal is indicative of an additionally induced band span shift. The frequency content is generally associated with the belt and sprocket tooth engagement 26 and is the same as the frequency signal measured through the belt teeth 20 . This phenomenon will be exacerbated by misalignment in the engagement portion 26 due to wrong tension applied to the belt structure. Another part of the MPU 53 incorporating DSP algorithms is designed to monitor the frequency occurrence and magnitude and compare the signal to predetermined operating limits. If the signal threshold exceeds the operating limit, the algorithm-embedded MPU 53 generates a faulty belt drive alarm.

The signal generated by the passing tooth 20 is used in the calculation (DSP) of the torsional phase angle of the camshaft. The data is compiled into a transmission torsional signature and used to diagnose changes in the operating conditions of the belt drive.

The MPU 53 embedded in the sensor 30 has an incorporated DSP algorithm that monitors the signals from the sensing elements 36, 37, 38 and 42 and determines whether the target belt 17 or belt drive exhibits behavior that would cause the belt 17 or belt drive to Faulty operational behavior. If a fault is imminent, the algorithm generates a fault code to notify the driver/operator that the vehicle should be repaired immediately, or communicates the fault code to the vehicle OEM or repair provider for further action.

The sensor 30 is connected to the vehicle harness through a connector 33 . The embedded algorithm uses the digital network communication protocol LIN/CAN57 to communicate with the vehicle ECU (engine control unit) through the harness.

Claims (19)

1. determine composition polymer and the physics of fabric strip and the method for structural condition mobile under normal operating condition for one kind, comprising:

When moving, band portion detects the transient behavior dielectric and the capacitance characteristic of described band portion by capacitance detecting device, with generation transient behavior capacitance signal,

From the described transient behavior capacitance signal of simultaneous any electrostatic capacitance Signal Separation by at least one detecting element generation of described pick-up unit,

The threshold level of described transient behavior capacitance signal and dynamic capacity signal is compared, and

Periodically break through the described threshold level of dynamic capacity signal in response to described transient behavior capacitance signal, excite output signal.

2. method according to claim 1, wherein before exciting described output signal, preset time on the cycle the described transient behavior capacitance signal to the described threshold level of breaking through the dynamic capacity signal sum up.

3. method according to claim 1, wherein said output signal is an alerting signal.

4. capacitance detecting device, it comprises and being suitable for and the normal composition polymer that moves and at least one detecting element of the adjacent setting of fabric strip,

When described band moves past described pick-up unit, described detecting element be suitable for producing in response to the dynamic change of the dielectric property of described band periodically variable electric signal and

Electricity calculating unit, this electricity calculating unit comprise at least one analogue-to-digital converters, microprocessor and the parts that output signal is provided in response to the threshold level of the dynamic change that periodically breaks through described band dielectric property.

5. capacitance detecting device according to claim 4 wherein has a plurality of detecting elements with at least one side gathering on described band.

6. capacitance detecting device according to claim 4 wherein along the position on the moving direction of described band, is adjacent to be provided with at interval a plurality of detecting elements with described band.

7. capacitance detecting device according to claim 4, wherein said output signal is an alerting signal.

8. method of determining under normal operating condition the physical condition of the composition polymer that moves and fabric strip comprises:

When moving, band portion detects the transient behavior electrostatic field of described band portion by pick-up unit, with generation transient behavior signal,

From the described transient behavior signal of simultaneous any electrostatic signal separation by at least one detecting element generation of described pick-up unit,

The threshold level of described transient behavior signal and Dynamic Signal is compared, and

Described threshold level in response to described transient behavior signal period property ground breakthrough Dynamic Signal excites output signal.

9. method according to claim 8, wherein before exciting described output signal, preset time on the cycle the described transient behavior signal to the described threshold level of breaking through Dynamic Signal sum up.

10. method according to claim 8, wherein said output signal is an alerting signal.

11. a pick-up unit comprises being suitable for and the normal composition polymer that moves and at least one detecting element of the adjacent setting of fabric strip,

When described band moves past described pick-up unit, described detecting element be suitable for producing in response to the dynamic change of the electrostatic field of described band periodically variable electric signal and

The electricity calculating unit comprises at least one analogue-to-digital converters, microprocessor and the parts that output signal is provided in response to the threshold level of the dynamic change that periodically breaks through described belts electrical conductivity characteristic.

12. pick-up unit according to claim 11 wherein has a plurality of detecting elements with at least one side gathering on described band.

13. pick-up unit according to claim 11 wherein along the position on the moving direction of described band, is adjacent to be provided with at interval a plurality of detecting elements with described band.

14. pick-up unit according to claim 11, wherein said output signal is an alerting signal.

15. determine composition polymer and the physical condition of fabric strip and the method for wearing and tearing mobile under normal operating condition, comprising for one kind:

When band portion moves, detect the electric charge that produces by the piezoelectricity coupling that exists in the described band portion, thereby produce signal in response to the instantaneous electric density of band portion by the noncontact charge sensor.

16. method according to claim 15, wherein said signal and described electric density are proportional.

17. method according to claim 15 wherein before exciting output signal, sums up the signal of the breakthrough certain threshold level level that produces on the selected time cycle.

18. method according to claim 17, wherein said output signal is an alerting signal.

19. pick-up unit, comprise with at least one conductivity detection element of aliging of moving direction, with vertical at least one the conductivity detection element of the moving direction of described band and at least one the conductivity detection element that is positioned at the plane parallel with the moving direction of described band

Described pick-up unit is configured to surround at least in part a part that moves past described band therebetween.

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