JP5447936B2 - Belt tension measuring device - Google Patents

Description

  The present invention relates to a belt tension measuring device, and more particularly to a belt tension measuring device that vibrates a belt and measures the belt tension based on the vibration frequency or vibration cycle.

  Generally, in order to operate the belt transmission device in a predetermined state, it is necessary to measure and confirm whether or not the belt tension between the pulleys is an appropriate belt tension. Conventionally, various belt tension measuring devices and measuring methods have been proposed. For example, the tension measuring device described in Patent Document 1 includes a reference plate having a contact and a pressure sensor provided at the center and reference portions provided at both ends. The reference plate is pressed against the belt to bend the belt, and the belt is bent until the reference portion provided at the center of the reference plate contacts the belt. The output of the pressure sensor at that time causes a predetermined bend to the belt. Represent the load. Then, based on the value of the load, the predetermined amount of deflection, and the distance between the reference portions, the belt tension is calculated using a known tension calculation formula.

  Further, in Patent Document 2, as a device for detecting natural frequency data representing belt tension, a period measuring means for measuring the vibration period of the belt detected by an optical microphone, and the measured period in time series are disclosed. And a representative value calculating means for calculating representative values for the number of planned end of vibrations among the cycles stored in the storage means as natural frequency data.

  Patent Document 3 proposes an apparatus that measures the natural frequency of the belt based on the vibration waveform of the belt detected by a microphone and measures the tension based on the measured natural frequency.

JP 2003-057136 A JP 2001-304993 A Japanese Patent Application Laid-Open No. 11-241961

  The apparatus described in Patent Document 1 requires an operation of pressing the reference plate against the central portion of the belt, and the pressing operation of the reference plate may be difficult depending on the belt installation location.

  On the other hand, the non-contact type apparatus described in Patent Documents 2 and 3 is not limited as the contact type described in Patent Document 1. However, in the case of detecting vibration sound with a microphone, there is a problem that an error may occur in the measurement sound due to the influence of the ambient sound, which requires a complicated calculation. Further, in the case of using an optical microphone, the measured value may be influenced by ambient light, particularly fluorescent light, and further improvement is required.

  The object of the present invention is to solve the above-mentioned problems by measuring the natural frequency or period of the belt without being affected by ambient sound and light, and calculating the belt tension based on the natural frequency or period. It is an object of the present invention to provide a belt tension measuring device that can be used.

  In order to achieve the above object, the present invention provides a belt tension measuring device for calculating a belt tension using a predetermined tension calculation formula based on a natural vibration period of the belt. A contact having an end as a contact portion, a permanent magnet having a magnetic pole disposed opposite to the intermediate portion between the support portion and the contact portion of the contact at a predetermined interval, and a coil wound around the permanent magnet, A current detector for detecting a current flowing in the coil; a natural period detector for detecting a natural vibration period of the belt from a fluctuation period of a current detected by the current detector; and calculating a tension for the detected natural vibration period A first feature is that it includes a tension calculation unit that inputs the equation into the equation and calculates the belt tension.

  In addition, the present invention has a second feature in that the contact is a piano wire having one end fixed to a sensor housing.

  In addition, the present invention has a third feature in that the contact has a magnetic body at a portion facing the magnetic pole of the permanent magnet.

Further, the present invention provides a belt tension measuring device that calculates a belt tension using a predetermined tension calculation formula based on a natural vibration period of the belt, a permanent magnet, a coil wound around the permanent magnet, and the permanent magnet A cushion portion adhered to the magnetic pole of the magnetic material, a magnetic plate adhered to the opposite side of the adhesive surface of the magnetic pole to the cushion portion, a current detector for detecting a current flowing in the coil, and the current detection A natural period detecting unit for detecting the natural vibration period of the belt from the fluctuation period of the detected current by the detector, and a tension calculating unit for calculating the belt tension by inputting the detected natural vibration period into a tension calculation formula . The point has the fourth feature.

According to a fifth aspect of the present invention, there is provided a belt tension measuring device that calculates a belt tension using a predetermined tension calculation formula based on a natural vibration period of the belt, wherein the cushion portion is formed of urethane. .

  When the present invention having the first feature is used, the tip of the contact (opposite to the support portion) is applied to the belt to be measured for tension by flipping the belt with a fingertip or the like to vibrate the belt. Side contact part) is brought into contact with the belt. As a result, the contact vibrates following the vibration of the belt. Due to this vibration, the facing distance between the intermediate portion of the contact and the magnetic pole fluctuates, and a current flows through the coil by electromagnetic induction. Since this current changes according to the facing distance between the contact and the magnetic pole, the detection signal output from the current detector changes corresponding to the vibration period of the belt. The vibration period of the belt becomes the natural vibration period of the belt after a while from the start of vibration. Therefore, the natural vibration period can be detected based on the detection signal of the current detector. The natural vibration period can be introduced into the tension calculation formula to obtain the tension.

  According to the present invention having the second feature, since the contact is formed of a thin piano wire, the vibration of the belt can be transmitted as the vibration of the contact without accompanying a large contact pressure that hinders the vibration of the belt.

  According to the present invention having the third feature, by providing the contact with a magnetic body, the magnetic efficiency of the magnetic circuit formed by the permanent magnet and the contact increases, so that the detection accuracy can be increased.

According to the present invention having the fourth feature, a permanent magnet around which a coil is wound in a state where the belt is vibrating is given a vibration by flipping the belt with a fingertip or the like. The magnetic plate is positioned so as to contact the belt. As a result, the magnetic plate vibrates following the vibration of the belt. Due to this vibration, the facing distance between the magnetic poles of the permanent magnet and the magnetic plate changes, and current flows through the coil by electromagnetic induction. Since this current changes according to the facing distance between the contact and the magnetic pole, the detection signal output from the current detector changes corresponding to the vibration period of the belt. The vibration period of the belt becomes the natural vibration period of the belt after a while from the start of vibration. This natural vibration period can be introduced into the tension calculation formula to determine the tension.

According to this invention which has a 5th characteristic, it can be set as the structure which can be compressively deformed by a solid shape by using urethane for a cushion part.

  In this way, according to the present invention, unlike the device that bends the belt and obtains the belt tension from the amount of bending, it is only necessary to lightly apply the contactor or the magnetic plate to one of the vibrating portions of the belt. Unlike tension measurement by pressing the device or jig from the front of the belt, there are few restrictions on the tension measurement position, so measurement is easy.

  In addition, a measurement value that is not affected by ambient sound or ambient light can be obtained, and measurement can be performed at any timing without worrying about ambient sound or ambient light.

It is a system block diagram of the tension measurement position which concerns on one Embodiment of this invention. It is a principal part functional block diagram of the controller of the tension | tensile_strength measuring apparatus which concerns on one Embodiment of this invention. It is a 1st figure which shows the example of the natural frequency measured value of a belt. It is a 2nd figure which shows the example of the natural frequency measured value of a belt. It is a front view of the detection part of the tension | tensile_strength measurement position which concerns on one Embodiment of this invention. It is a top view of the detection part of the tension measurement position concerning one embodiment of the present invention. It is a figure which shows the measurement aspect by the tension | tensile_strength measurement position which concerns on one Embodiment of this invention. It is a principal part side view of the belt transmission device to which the tension measuring device which concerns on 2nd Embodiment of this invention was applied.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a system configuration diagram of a belt tension measuring apparatus according to an embodiment of the present invention. In the figure, a belt transmission device 1 is a belt transmission device used for an automobile engine, for example, and has a belt 4 spanned between pulleys 2 and 3. The belt tension measuring device 5 includes a linear contactor 6, a permanent magnet 8 having magnetic poles 7 and 7 disposed so as to face the contactor 6, and a coil 9 wound around the permanent magnet 8. The current detector 10 measures the current flowing through the coil 9. The controller 11 has a calculation unit (microcomputer) that calculates the frequency of the contact 6 based on the current value detected by the current detector 10.

  The detection part D including the permanent magnet 8, the coil 9, and the current detector 10 is housed and fixed in the sensor housing 12, and one end (support part) 6 a of the contact 6 is between the magnetic poles 7 and 7. The gap is maintained and fixed to the outer surface of the sensor housing 12 in a cantilevered manner. The sensor housing 12 is formed of a resin material, and the facing portion between the magnetic poles 7 and 7 and the contact 6 is thinned or opened in accordance with the end surfaces of the magnetic poles 7 and 7.

  The contact 6 is a member that extracts the vibration of the belt 4 by the front end (contact portion) 6b coming into contact with the belt 4 as a measurement object. Therefore, it is preferable to employ a lightweight member, for example, a piano wire having a diameter of about 0.5 mm to 1.0 mm so as to prevent free vibration of the belt 4 as much as possible.

  In the above configuration, for example, in a state where the contact 6 is in contact with the upper surface of the belt 4, the belt 4 is repelled by a finger or the like to vibrate. The vibration of the belt 4 is transmitted to the contact 6 to vibrate the contact 6. The distance between the contact 6 and the magnetic poles 7 and 7 varies due to the vibration of the contact 6. An electromotive force is generated by the variation in the distance, and a current flows through the coil 9. The fluctuation cycle of the current corresponds to the vibration cycle of the contact 6. The current detector 10 outputs a current value that fluctuates in this cycle as a detection signal.

  The belt 4 vibrates at a specific frequency or period according to the shape and material of the belt 4 and the distance between the centers of the pulleys 2 and 3 (span). Therefore, the fluctuation period of the detection signal output from the current detector 10 represents the natural vibration period of the belt 4.

  FIG. 2 is a functional block diagram of the main part of the controller 11. In FIG. 2, the controller 11 includes a natural period detection unit 13, a tension calculation unit 14, a parameter input unit 15, and a tension display unit 16. The tension display unit 16 is a device that displays the value of the tension calculated by the tension calculation unit 14, and can be configured by a known liquid crystal display device. The natural period detection unit 13 includes a waveform shaper 17, a latch 18, a period storage unit 19, a period comparison unit 20, a stable period storage unit 21, and a maximum group detection unit 22.

  The natural period detection unit 13 takes the detection signal input from the current detector 10 into the waveform shaper 17 and shapes it into a rectangular wave. The period of this rectangular wave is held in the latch 18 for each period and stored in the period storage unit 19 in the order of input. The belt 4 initially vibrates at an irregular cycle including impact sound and harmonics, but eventually vibrates at the natural frequency of the belt. Therefore, the period of the rectangular wave stored in the period storage unit 19 also fluctuates initially, but eventually becomes a regular period (t) according to the natural frequency.

  Data indicating the period stored in the period storage unit 19 is compared with a preset reference period by the period comparison unit 20. The period comparison unit 20 detects a rectangular wave within a predetermined range from the reference period. Continuous rectangular waves (stable waveforms) within a predetermined range from the reference period are stored in the stable period storage unit 21 as one group. Since a plurality of such stable waveforms are detected, the maximum group detecting unit 22 detects a group of stable waveforms having the largest number of consecutive among the plurality of stable waveforms. The detected period of the group of stable waveforms is regarded as the natural period of the belt 4 and is input to the tension calculator 14.

  The parameter input unit 15 is an operation unit that inputs the belt vibration unit length (L) and the linear density (A). Here, the belt vibration part length (L) is equal to the distance between the central axes of the pulleys 2 and 3 when the diameters of the pulleys 2 and 3 are the same. The linear density (A) is the mass per unit length of the belt 4.

  The tension calculation unit 14 calculates the following equation from the natural period (t) detected by the natural period detection unit 13, the belt vibration unit length (L) and the linear density (A) input from the parameter input unit 15. The belt tension (T) is calculated based on Equation (1).

T = 4 × L ² × A × (1 / t) ² (Formula 1).

  Here, the unit of belt tension (T) is (N), the unit of belt vibration part length (L) is (m), the unit of belt linear density (A) is (kg / m), and the period (t). The unit of is (s).

  The calculated belt tension (T) value is input to the tension display unit 16 and used for tension display.

  Since the tension measuring device 5 of the present embodiment detects the vibration of the belt 4 by bringing the contact 6 into contact with the belt 4, the contact pressure of the contact 6 affects the natural vibration period of the belt 4. It is assumed that Therefore, the inventors investigated the influence of the contact mode of the contact 6 with the belt 4 on the measured natural frequency.

  3 and 4 are diagrams showing the measurement results of the belt frequency. FIG. 3 shows an example of a piano wire in which the contact 6 has a diameter of 0.55 mm, and FIG. 4 shows an example of a piano wire in which the contact 6 has a diameter of 0.9 mm. The length of the contact 6 (the distance between the support portion 6a and the contact portion 6b) is 40 mm, 60 mm, and 80 mm, respectively. 3 and 4, the horizontal axis indicates the measurement position, that is, the tip position of the contact 6 on the belt 4, as a distance (mm) from the end of the belt vibration section. The vertical axis represents the frequency (Hz), and the belt vibration part length (L) of the average value for the number of measurements 20 times is 150 mm. There are two types of pressure (contact load) for bringing the contact 6 into contact with the belt 4, 10 grams and 20 grams. For comparison, the frequency measured by a method of detecting the natural frequency based on the belt vibration sound detected by the microphone (for example, the method described in Patent Document 3) is shown.

  In FIG. 3, the deviation between the average value of the frequency and the measured value by the microphone is the largest when the belt measurement position is the central part (75 mm) of the vibration part length (L), and the belt measurement position is the vibration part length (L It can be seen that the value decreases as it approaches the end of) until it is not significantly different from the measured value by the microphone. In an example in which the contact load is 10 grams and the length of the contact 6 is 40 mm or 60 mm, the deviation from the measurement value by the microphone is smaller than the others at all measurement positions.

  In the example in which the diameter of the piano wire shown in FIG. 4 is 0.9 mm, the contact 6 having a length of 40 mm is located closer to the center from the end of the belt vibration portion in both cases where the contact load is 10 grams or 20 grams. When separated, the measured value suddenly deviates from the measured value by the microphone. In other examples, the closer the measurement position is to the center of the belt vibration portion, the farther away from the measurement value by the microphone. Among these, in the example in which the length of the contact 6 is as long as 80 mm and the contact load is 20 grams, a result that is not significantly different from the measurement value by the microphone is obtained in a wide range of measurement positions.

  In short, it can be seen that vibration frequency (or period) with high reproducibility can be measured by selecting and measuring the length of contact 6 and the contact load. It can also be seen that if the measurement position is closer to the end of the belt vibration portion, that is, closer to the pulleys 2 and 3, the contact length and the contact load can be widened.

  FIG. 5 is a front view showing a specific example of the detection unit D of the tension measuring device, and FIG. 6 is a plan view of the same. In the system configuration diagram shown in FIG. 1, the detector D has a U-shaped or U-shaped magnetic pole, but in the example of FIG. 5, the permanent magnet 8 is a rod-shaped (I-shaped) magnet. The sensor housing 12 has a cylindrical shape made of resin, and the permanent magnet 8 is disposed on the cylindrical central axis of the sensor housing 12, that is, at the center of the sensor housing 12. The contact 6 is joined to the side surface of the sensor housing 12 at one end 6a by an adhesive or the like, and a bent portion 6c formed in the middle, and a straight line that passes over the magnetic pole 8a of the permanent magnet 8 and extends to the contact portion 6b. Part 8e.

  FIG. 7 is a diagram showing an aspect during measurement in which the contact 6 of the detection unit D of the tension measuring device shown in FIG. 5 is in contact with the belt. As shown in FIG. 6, the contact 6 is brought into contact so that the linear portion 6 e of the contact 6 has a contact angle θ of 15 degrees with respect to the lower surface (which may be the upper surface) 4 </ b> S of the belt 4. The contact angle θ is preferably 15 degrees, but is not limited to this angle.

  The contact 6 may be only a wire such as a piano wire, but a magnetic body may be attached to a portion facing the magnetic pole, for example, the linear portion 6e, to improve the efficiency of the magnetic circuit.

  Next, a second embodiment of the present invention will be described. FIG. 8 is a side view of a main part of a belt transmission device to which the tension measuring device according to the second embodiment is applied. In FIG. 8, a cushion portion 24 made of urethane is bonded to the tip surface (magnetic pole surface) of the rod-shaped permanent magnet 23, and further, the end surface of the cushion portion 24 (opposite to the surface bonded to the permanent magnet 23). A magnetic plate 25 is bonded to the side surface. The plate 25 is preferably arranged at the bottom of a resin cap 26 that protects the tip of the permanent magnet 23 and the cushion portion 24. A coil 27 is wound around the permanent magnet 23, and a current detector 28 for detecting a current flowing through the coil 27 is provided.

  When the tension measuring device shown in FIG. 8 is used, the belt 4 is flipped by a finger or the like to vibrate, and the tension measuring device is positioned so that the cap 26 contacts the upper surface of the belt 4 in this state. The contact load at this time varies according to the vibration frequency of the belt 4, and the cushion portion 24 is deformed (compressed) by a compression amount corresponding to the variation, and the distance between the plate 25 and the magnetic pole surface varies. As a result, an electromotive force is generated in the coil 27 and a current flows. Based on the current fluctuation period, the natural frequency or natural frequency is calculated from the vibration frequency or vibration period of the belt 4 based on the current fluctuation period, and the tension can be obtained using Equation (1). The plate 25 of the second embodiment corresponds to the contact 6 of the first embodiment.

  As described above, in the first and second embodiments, the contact 6 or the metal plate 25 that is brought into contact with the belt 4 is provided, and the current value varies according to the variation in the distance between the permanent magnet 8 or 23 and the contact. Based on this, the natural frequency or period was calculated. This method is called an electromagnetic method. The present invention is not limited to the electromagnetic detection unit D, and can be modified into a capacitance type, a piezoelectric type, an optical type, and the like.

  For example, in the capacitance type, the contact 6 is provided with a flat surface portion (first electrode plate), and a second electrode plate is provided so as to face the first electrode plate. The second electrode plate is preferably attached in the sensor housing 12 in place of a coil or a permanent magnet. In this configuration, a capacitor is formed by the first electrode plate and the second electrode plate. In this capacitor, the distance between the first electrode plate and the second electrode plate varies in accordance with the vibration of the contact 6 and the capacitance changes. Therefore, the contact changes based on the change period of the capacitance. A frequency of 6 can be calculated.

  In the piezoelectric type, a piezoelectric element is disposed on the sensor housing 12 side instead of a coil or a permanent magnet. Unlike the electromagnetic type, the piezoelectric element is brought into contact with the contact 6 at a predetermined pressure. Thus, when the contact 6 is brought into contact with the upper surface of the belt 4 that has been vibrated, the contact 6 vibrates following the vibration of the belt 4. Due to the vibration of the contact 6, the contact pressure between the piezoelectric element and the contact 6 changes from a predetermined pressure, and the output of the piezoelectric element also varies according to the change. Therefore, the vibration period of the belt 4 can be obtained from the output fluctuation period of the piezoelectric element.

  Further, in the optical type, an optical sensor having a light receiving element and a light emitting element is provided in place of the coil and the permanent magnet in the sensor housing 12. On the other hand, a light reflecting surface is formed on the contactor 6, and an optical sensor is disposed so as to face the light reflecting surface. The light emitting element emits light to the light reflecting surface, and the light receiving element receives the reflected light from the light reflecting surface and outputs a detection signal corresponding to the amount of light received. According to this configuration, the distance between the optical sensor and the light reflecting surface changes according to the vibration of the contact 6, so that the amount of light received by the light receiving element changes according to this change, and as a result, the detection of the light receiving element The signal fluctuates with the vibration period of the contact 6. Therefore, if the contact 6 is brought into contact with the upper surface of the belt 4 and the contact 6 is vibrated, the vibration period can be extracted as a fluctuation period of the output of the light receiving element.

  As described above, the present invention can be configured by the detection unit D to which various displacement detection means such as an electrostatic type, a capacitance type, a piezoelectric type, and an optical type are applied.

  As another example of the piezoelectric type, a piezoelectric element may be attached to the tip of the contact 6 so that the piezoelectric element is brought into contact with the upper surface of the belt 4 that has been vibrated. According to this example, the pressure applied from the belt 4 to the piezoelectric element changes with the vibration period of the belt 4, and the vibration period of the belt 4 can be obtained based on the output fluctuation period of the piezoelectric element.

  According to the above-described embodiment, an accurate measurement value that is not affected by ambient sound or ambient light can be obtained. When the detection unit D is optical, it is not affected by ambient light at all. However, unlike the direct detection of the reflected light from the belt, the contactor and the detection unit D are separated from the belt. Since the optical sensor can be arranged between the facing portions, the light shielding device can be easily provided.

  Further, since the contact 6 can contact the surface of the belt 4 with a small area, the tension of a limited region on the belt 4 can be detected. Therefore, the belt tension can be accurately measured in a limited region with an apparatus in which the tension may be different at the position in the width direction in the vicinity of the pulley of the wide belt.

  In the first embodiment, the contact 6 is formed in a needle shape with a piano wire. However, the contact 6 is not limited to this, and is a long plate formed of a lightweight material (for example, resin) that does not easily affect the vibration of the belt 4. It may be.

DESCRIPTION OF SYMBOLS 1 ... Belt transmission device, 2, 3 ... Pulley, 4 ... Belt, 5 ... Belt tension measuring device, 6 ... Contact, 7 ... Magnetic pole, 8, 23 ... Permanent magnet, 9, 27 ... Coil, 10 ... Current detector 11 ... Controller, 12 ... Sensor housing, 13 ... Natural period detection unit, 14 ... Tension calculation unit, 15 ... Parameter input unit, 16 ... Tension display unit, 24 ... Cushion part, 25 ... Plate

Claims (5)

In the belt tension measuring device that calculates the belt tension using a predetermined tension calculation formula based on the natural vibration period of the belt,
A contact portion having one end fixed to the sensor housing and the other end being a contact portion;
A permanent magnet having magnetic poles arranged opposite to each other at a predetermined interval in an intermediate portion between the support portion and the contact portion of the contact;
A coil wound around the permanent magnet;
A current detector for detecting a current flowing in the coil;
A natural period detector that detects a natural vibration period of the belt from a fluctuation period of a current detected by the current detector;
A belt tension measuring apparatus comprising: a tension calculating unit that inputs the detected natural vibration period into a tension calculation formula and calculates belt tension.   2. The belt tension measuring device according to claim 1, wherein the contact is a piano wire having one end fixed to a sensor housing.   The belt tension measuring device according to claim 1, wherein the contact has a magnetic body at a portion facing the magnetic pole of the permanent magnet. In the belt tension measuring device that calculates the belt tension using a predetermined tension calculation formula based on the natural vibration period of the belt,
With permanent magnets,
A coil wound around a permanent magnet;
A cushion part that is bonded to the magnetic pole of the permanent magnet and is three-dimensionally compressible and deformable ;
A magnetic plate bonded to the opposite side of the bonding surface to the magnetic pole with respect to the cushion portion;
A current detector for detecting a current flowing in the coil;
A natural period detector that detects a natural vibration period of the belt from a fluctuation period of a current detected by the current detector;
A belt tension measuring apparatus comprising: a tension calculating unit that inputs the detected natural vibration period into a tension calculation formula and calculates belt tension. The belt tension measuring device according to claim 4, wherein the cushion portion is made of urethane.

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