AU2012276745A1

AU2012276745A1 - Conveyor device bearing unit with malfunction detection function, conveyor equipment and bearing unit monitoring system

Info

Publication number: AU2012276745A1
Application number: AU2012276745A
Authority: AU
Inventors: Hiromitsu Kondou; Mitsuo Sasabe; Takehiko Umemoto
Original assignee: NTN Corp; NTN Toyo Bearing Co Ltd
Current assignee: NTN Corp
Priority date: 2011-06-29
Filing date: 2012-06-26
Publication date: 2013-12-19
Also published as: BR112013032220A2; WO2013002199A1

Abstract

The invention is obtained by setting a rolling bearing (6) inside a housing (8) and is used as a conveyor device bearing unit (10) that is provided in conveying devices such as conveyors (1). The invention is provided with: a power source (12) having a power-generating element (14) that generates electricity using environmental energy and an accumulating means (16) for accumulating the power generated by the power-generating element (14); and a transmitter (13) that wirelessly transmits a signal every time the amount of electricity accumulated by the accumulating means (16) reaches an established value. For the power-generating element (14), a vibrational power-generating element or a thermal power-generating element is used. The invention is used in conveyor rollers (4), plummer blocks, etc. in conveyors (1).

Description

CONVEYOR DEVICE BEARING UNIT WITH MALFUNCTION DETECTION FUNCTION, CONVEYOR EQUIPMENT AND BEARING UNIT MONITORING SYSTEM 5 CROSS REFERENCE TO THE RELATED APPLICATION This application is based on and claims Convention priority to Japanese patent application No. 2011-144588, filed June 29, 2011, and Japanese patent application No. 2011-169783, filed August 3, 2011, the entire disclosures of which are herein incorporated by reference as a part of this application. 10 BACKGROUND OF THE INVENTION (Field of the Invention) The present invention relates to a conveyor device bearing unit with a malfunction detection function to be applied to conveyor devices such as a belt conveyor (for example, a conveyer for conveyance in a mining field of iron ore. 15 coal, or the like), and conveyor system and a bearing unit monitoring system each including the bearing unit. (Description of Related Art) A belt conveyor for conveyance of iron ore, coal, or the like in practical use extends for a relatively long distance from a mining field to a truck 20 loading station, for example, and thus a large number of conveyor bearings are used therein. Examples of the conveyor bearings include bearings incorporated in opposite ends of each of conveyor rollers located in the intermediate portion of a conveyor, and bearings of plummer blocks for supporting rotation shafts of conveyor rollers at the opposite ends of the conveyor. The bearings, which are 25 used in such an environment as described above are desirably replaced as early as possible once a defect that may prevent the rotation occurs. However, since a large number of bearings are installed over a long distance, a check by maintenance workers requires significant time. According to circumstances, it may be necessary to shut down the whole belt conveyor. <DK >- As a measure thereagainst, it has been proposed to provide bearings that are used for each conveyor roller with a temperature switch and an alarm to detect abnormal stop due to bearing damage or the like and issue an alarm (for example, Patent Document 1). In this patent document, the electromotive force 5 of an electric generator composed of a rotor and a stator provided in each conveyor roller is used as means for activating the abnormal rotation alarm. [Prior Art Document] [Patent Document I] Japanese Patent No. 3798494 SUMMARY OF THE INVENTION 10 According to the configuration of Patent Document 1, the structure is complicated and needs to be exclusively designed in order to install the rotor-stator generator in each conveyor roller, and therefore has less design freedom and less applicability. As examples of the abnormality alarm, the patent document mentions illumination of a lamp and sound generation with a 15 buzzer each of which is provided in the vicinity of each conveyor roller. In the case of a conveyor having a longer conveyance distance, however, such a lamp or a buzzer provided in the vicinity of each conveyor roller may not allow an abnormality alarm to be reliably recognized. The reliable recognition of the abnormality alarm can be achieved by central control of abnormality detection 20 signals from the respective conveyor rollers by guiding the signals to a central control room with wiring. However, installation of the signal wiring along such a long course as a belt conveyor for conveyance of iron ore or coal extending from a mining field to a truck loading station is not practicable as it needs not only wires but also means for supporting and connecting the wires, making the 25 system large-scale and involving the possibility of wiring disconnection. The present invention is therefore made to overcome such problems and provide a conveyor device bearing unit with a malfunction detection function, conveyor system, and a bearing unit monitoring system that allow simple -- <2'configuration of a sensor, a power source, and a wiring system; easy central control; and contribution to precise detection of a malfunction in a bearing. A conveyor device bearing unit with a malfunction detection function according to a configuration of the present invention is to be provided to a 5 conveyor device and includes a rolling bearing and a housing accommodating the rolling bearing, the housing including a transmitter and a power source for supplying electric power to the transmitter, the transmitter having a transmission circuit unit for transmitting signals and a transmission control unit for causing the transmission circuit unit to wirelessly transmit the signals, the power source 10 having an electric generating element for generating electric power with environmental energy and electric energy storage element for storing the electric power generated by the electric generating element, wherein the transmission control unit causes the transmission circuit unit to transmit the signals every time the amount of the electric power stored in the electric energy storage element 15 reaches a predetermined value. The transmitter is typified by a transmitter using radio waves; however any transmitter capable of wireless transmission using light or other media than radio waves may be employed. According to the configuration, the electric power generated by the electric generating element is stored in the electric energy storage element, and 20 the transmission circuit unit, controlled by the transmission control unit, performs the transmission every time the amount of the electric power stored reaches a predetermined value. The electric generating element generates electric power using environmental energy, for example, heat and vibration generated with the operation of the bearing. In case of a defect such as poor 25 lubrication and abrasion, the amount of the electric power generation will increase and the vibration will be larger in the bearing. A defect in the bearing therefore accelerates the heat generation by the electric generating element, and thus the amount of the electric power stored will reach the predetermined value faster, shortening the interval of the transmission by the transmission circuit unit. 3>- The receiver side can therefore determine a malfunction of the bearing by monitoring the interval of the transmission from the bearing unit. In case of a malfunction that stops the bearing, the transmission will be stopped. If no signal is received while the conveyor device equipped with the bearing units is in 5 a driven state, it can be determined that a malfunction that stops the bearing 6 has occurred. Using the electric generating element serving as a power source for the transmission as described above, the malfunction detection can be performed with a simple structure. Wireless transmission is employed for the signal transmission, and 10 the power for the transmission is obtained from the power source having the electric generating element in the bearing unit. Thus, the malfunction detection, the information transmission, and the securing of the power source can be completed in each bearing unit, eliminating the need for wiring among the bearing units and from the bearing units to the central control room, and 15 simplifying the wiring system. If wired, the structure will be complicated due to the need to build the infrastructure including wiring, leading to less design freedom, whereas the structure relying on the wireless transmission is free of such a problem. Thus, such a structure can be readily applied also to conveyor system having a long conveyance course such as a conveyor for conveyance of 20 iron ore, coal, or the like, for example. In addition, the use of the electric generating element that generates electric power with environmental energy provides a simplified and compactified structure compared to the case of a rotor-stator generator requiring components on both the rotating and static sides. Thus, the bearing unit is easily applicable, as it can eliminate the need for 25 exclusive design and provide greater design freedom. The bearing unit can be easily replaced with a bearing unit having an existing design. For self-powering in the bearing unit, an ordinary idea is to use a rotor-stator generator using the rotary mechanism of the bearing. However, the bearing unit generates not a little vibration and heat with the rotation of the -<4>rolling bearing. Focusing on such characteristics of the bearing unit, the present invention uses the electric generating element that generates electric power with environmental energy. Such electric power generated with the vibration and the heat is usable enough to cover the electric power that is used for the signal 5 transmission. The electric power thus generated, which may be small, can be used in practice by taking some measures in the detection and the transmission. The electric energy storage element may include a capacitor or a secondary battery. The electric energy storage element allows the transmission even when the electric power generated is too small to be used as is for the 10 wireless transmission by storing the electric power in the electric energy storage element. Furthermore, while constant transmission consumes more electric power, the transmission for the malfunction detection needs only detection and transmission every couple of minutes, for example, and the electric power generated by the electric generating element using environmental energy is 15 enough for such a small amount of electric power. Taking into consideration the vibration and heat generation characteristics of the bearing unit and the need for the malfunction detection, it is possible to achieve the use of the electric generating element using environmental energy. In the configuration, the transmission control unit may cause the 20 electric energy storage element to discharge every time the amount of the electric power stored in the electric energy storage element reaches the predetermined value and the transmission circuit unit is caused to perform the transmission. The amount of the electric power stored in the electric energy storage element is reduced as the electric power is used for the transmission, but the electric power 25 to be consumed by the transmission may vary. The further discharge is therefore caused to stabilize the transmission interval. In the configuration, the bearing unit further includes a sensor for detecting the state of the rolling bearing, the transmission control unit causes the transmission circuit unit to wirelesslv transmit information of the state of the rolling bearing detected by the sensor, and the power source supplies electric power to the sensor. The "state of the rolling bearing" herein refers to data representing one or more characteristics of the rolling bearing including vibration, temperature, rotation frequency, and so on of the rolling bearing. 5 With the configuration of the bearing unit being provided with the sensor for detecting the state of the rolling bearing, and the transmission circuit unit of the transmitter for tirelessly transmitting the information of the state detected (hereinafter, referred to as "sensor information"), a malfunction in a large number of bearings can be detected readily and precisely by detecting the 10 sensor information in the central control room or the like without investment of significant time and effort. The sensor information to be transmitted may be information subjected to signal processing such as analog-to-digital conversion and signal determination processing as well as signals detected by the sensor as is and signals merely amplified. The sensor information may be included in the 15 signals to be transmitted by the transmission circuit unit. The electric generating element of the bearing unit generates electric power using environmental energy, which may be generated with the vibration and the heat. Such electric power can be usable enough to cover the electric power that is used for the transmission of the sensor information. In addition, 20 since the bearing unit is provided with the electric energy storage element, the detection by the sensor and the transmission of the sensor signals can be performed even during the shutdown period or the like of the conveyor device while the electric generating element is generating no electric power. In the configuration, the electric generating element that generates 25 electric power with environmental energy may include a thermo electric generating element or a vibratory or seismic electric generating element. The thermo electric generating element may include an electric generating element using the Seebeck effect. The vibratory or seismic electric generating element may include an electret element. These electric generating elements can -<6"generate electric power by utilizing vibration or heat generation in the environment where the bearing of the conveyor device is installed. In case of a defect such as poor lubrication and abrasion, the amount of generated heat and vibration will increase in the bearing, and thus the defect in the bearing appears 5 as the amount of the electric power generated. By causing the transmission every time the amount of the electric power stored reaches the predetermined value as described above, therefore, the electric power generation can be used also as a sensor for the malfunction detection. In the configuration, the sensor may include at least one of a vibration 10 sensor, a temperature sensor and a rotation sensor. A malfunction in the rolling bearing causes generation of vibration, temperature rise, an impact on the rotation, and so on. Provision of at least one of a vibration sensor, a temperature sensor and a rotation sensor therefore allows the detection of a malfunction in each bearing. 15 In the configuration, the signals transmitted by the transmitter may include identification information of the conveyor device bearing unit. The transmission of the identification information allows the receiver side to identify one out of a large number of bearing units provided in the conveyor device or recognize the conveyor device that the bearing unit belongs to. 20 In the configuration, the bearing unit may further include storage means for storing therein the information detected by the sensor. The storage means may be an IC tag. Provision of the storage means allows a plurality of the detected signals to be gathered and then transmitted at once, and also allows malfunction control according to the information stored therein in addition to the 25 control according to the wirelessly transmitted information. Since the storage means includes an IC tag, the information stored can be easily read with a tag reader. In the configuration, the housing may further accommodate a GPS terminal, which is a terminal of a global positioning system. Provision of the GPS terminal allows identification of the position of the bearing unit and thus facilitates identification of the bearing unit having a malfunction without a central control panel having a complicated structure and/or without any means for identifying each bearing unit. Used in combination with the transmission of 5 the identification information, the GPS terminal allows identification of the conveyor device out of a plurality of conveyor devices as well as the bearing unit even when the identification information identifies only the bearing unit in a conveyor device. In the present invention, the conveyor device may include a belt 10 conveyor. The belt conveyor may be a belt conveyor extending from a mining field of iron ore, coal, or the like to a truck loading station, for example. Some belt conveyors extend for a long conveyance distance and have a large number of bearing units. Even in such cases, the conveyor device bearing unit with a malfunction detection function of the present invention can achieve simple 15 configuration of a sensor, a power source, and a wiring system; easy central control; and contribution to precise detection of a malfunction in a bearing. In the case where the bearing unit is applied to a belt conveyor, the housing may be provided at one of ends of a cylindrical body forming a circumferential portion of a conveyor roller supporting a belt of the belt conveyor, 20 and the rolling bearing may be interposed between a fixed shaft and the housing to rotatably support the conveyor roller. In this case, the conveyor device bearing units with a malfunction detection function of the present invention can be applied to each of a plurality of conveyor rollers provided to one conveyor. Preferably, the conveyor roller is provided with a cover made of a 25 synthetic resin for covering one of end faces of the cylindrical body, and the transmitter is disposed at a position in a space enclosed by the cover where no radio shielding material exists between an antenna of the transmitter and the cover. According to this configuration, the transmission can be performed via -<8>the antenna of the transmitter incorporated in the conveyor roller without a problem such as radio shielding, and the end of the conveyor roller can be sealed. In the case where the bearing unit is applied to a conveyor roller, the housing may be a bearing box of a plummer block for supporting a rotation shaft 5 of a conveyor roller supporting a belt of the belt conveyor. The conveyor rollers at the ends of the conveyor are supported by the plummer blocks. Such conveyor rollers give much load to the bearings or have a great impact when damaged, and thus the malfunction detection is important. By applying the bearing unit to such plummer blocks, it is possible to precisely detect a 10 malfunction in the bearings that are in great need for the malfunction detection. The bearing box of the plummer block may include: a housing main body having opposed openings in both end faces thereof and receiving the shaft through one of the openings; and a lid member for closing the other of the openings of the housing main body. The transmitter and the power source may 15 be provided in the lid member. By providing the sensor and so on in the lid member, components other than the lid member can be common between the bearing unit with a malfunction detection function and an ordinary bearing unit without a detection function, and thus the productivity can be improved. An existing bearing unit can be given a malfunction detection function only by 20 replacing its lid member. The sensor, if provided, may be also provided in the lid member. Conveyor system with a malfunction detection function according to a configuration of the present invention includes a plurality of conveyors each provided with one or more conveyor device bearing units with a malfunction 25 detection function according to the above-described configuration. Such conveyor system having a plurality of conveyors also achieves simple configuration of a power source and a wiring system; easy central control; and contribution to precise detection of a malfunction in the bearings.

In this case, a relay device may be provided between the plurality of conveyors and a central control panel for collectively monitoring information transmitted by the transmitter of each bearing unit of the one or more conveyor device bearing units with a malfunction detection function provided to each of 5 the plurality of conveyors, and the relay device may receive, amplify, and wirelessly transmit the information transmitted by the transmitter. The use of the relay device allows the wireless transmission even when the distance between the conveyors and the central control panel in the central control room is long. A bearing unit monitoring system according to a configuration of the 10 present invention includes: a conveyor device bearing unit with a malfunction detection function according to the above-described configuration; and a monitoring device having a receiver for receiving the signals transmitted by the transmission circuit unit and malfunction determination means, wherein the malfunction determination means determines a malfunction based on a change in 15 the interval of the signals transmitted from the transmitter and received by the receiver. The bearing unit monitoring system provides the action and effect described for the conveyor device bearing unit with a malfunction detection function according to the above-described configuration and allows the determination of a malfunction in the bearing based on a change in the interval of 20 the signals. The change in the interval referred to herein includes the case where the signal reception is disrupted. Since no electric power is generated when the bearing is stopped, occurrence of a malfunction so significant that the bearing is stopped can be determined based on the disruption of the signal reception. 25 In the bearing unit monitoring system, the malfunction determination means may determine a malfunction by constantly comparing the signal interval within a given target time period or within given target transmission times at present with the signal interval within a reference time period or within reference transmission times in the past earlier than the present by a predetermined period -10>of time. For example, the moving average of the target time period is compared with the moving average of the comparative, reference time period. In many cases, bearings that have been used for many years and almost new bearings or the like generate heat and vibration differently. In the bearings that have been 5 used for a long term, the amount of heat generation or vibration that is to some extent large does not necessarily represent a malfunction. Simple comparison between the transmission interval and a set interval does not therefore allow accurate malfunction determination. In contrast, constantly comparing the signal interval within a given target time period or within given target 10 transmission times at present with the signal interval within a reference time period or within reference transmission times in the past earlier than the present by a predetermined period of time as in the configuration described above allows reliable malfunction determination. This is because, when the amount of heat generation or vibration abruptly increases compared to that within a certain time 15 period in the past while the bearing is being used, it often represents a malfunction in the bearing. Any combination of at least two configurations, disclosed in the appended claims and/or the specification and/or the accompanying drawings should be construed as included within the scope of the present invention. In 20 particular, any combination of two or more of the appended claims should be equally construed as included within the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS In any event, the present invention will become more clearly understood from the following description of preferred embodiments thereof, 25 when taken in conjunction with the accompanying drawings. However, the embodiments and the drawings are given only for the purpose of illustration and explanation, and are not to be taken as limiting the scope of the present invention in any way whatsoever, which scope is to be determined by the appended claims. -(11>- In the accompanying drawings, like reference numerals are used to denote like parts throughout the several views, and: Fig. I is a vertical section view of a conveyor roller including conveyor device bearing units with a malfunction detection function according to 5 the first embodiment of the present invention; Fig. 2 is a partially expanded sectional view of the conveyor roller shown in Fig. 1; Fig. 3 is a cutaway perspective view of a plummer block which is a conveyor device bearing unit with a malfunction detection function according to 10 the second embodiment of the present invention; Fig. 4 is a front view of the plummer block shown in Fig. 3; Fig. 5 is a cutaway perspective view of a plummer block which is a conveyor device bearing unit with a malfunction detection function according to the third embodiment of the present invention; 15 Fig. 6 is a block diagram illustrating an example of a configuration of a sensor, a power source, a transmitter, and so on in the conveyor device bearing units with a malfunction detection function according to the first to third embodiments of the present invention; Fig. 7 is a block diagram illustrating a modification of the 20 configuration of the sensor, the power source, the transmitter, and so on shown in Fig. 6; Fig. 8 is a graph showing repetition of storage and discharge of electric power by electric energy storage element of the power source in the bearing unit of Fig. 6 in association with an electric generating element; 25 Figs. 9A and 9B are characteristics diagrams showing a change in the period of the repetition of the discharge by the electric energy storage element of the power source in the bearing unit of Fig. 6 during normal operation and during occurrence of a malfunction, respectively; Fig. 10 is a block diagram illustrating a bearing unit monitoring -(12>system according to the fourth embodiment of the present invention; Fig. 11 is a block diagram illustrating a modification of the bearing unit of the bearing unit monitoring system shown in Fig. 10; Fig. 12 is a front view of a conveyor to which the conveyor device 5 bearing unit with a malfunction detection function according to any of the first to third embodiments of the present invention is applied; and Fig. 13 is a diagram schematically illustrating system including a plurality of conveyors shown in Fig. 12. DESCRIPTION OF EMBODIMENTS 10 Embodiments of the present invention will be described with reference to the drawings. Fig. 12 is a front view of a conveyor 1 which is a conveyor device equipped with the inventive conveyor device bearing unit with a malfunction detection function. The conveyor 1 is a belt conveyor in which an endless conveyor belt 2 is provided so as to hang between conveyor rollers 3 and 15 3 at opposite ends, and lower faces of the conveyor belt 2 are supported by a plurality of conveyor rollers 4 arranged in a conveyance direction (direction A) in the intermediate portion. In addition, a tensioning conveyor roller 4A is provided. The conveyor belt 2 is driven by rotating one of the conveyor rollers 3 at the opposite ends with a motor (not shown). Figs. I and 2 illustrate a 20 bearing unit in the conveyor rollers 4 in the intermediate portion, and Figs. 3 to 5 illustrate a bearing unit in a plummer block for supporting the conveyor rollers 3 at the opposite ends. Fig. 1 illustrates a bearing unit according to the first embodiment of the present invention that is provided to the conveyor 1. The bearing unit is 25 applied to the conveyor rollers 4 located in the intermediate portion of the conveyor I (located in an area other than the opposite ends). The conveyor rollers 4 are each formed of a cylindrical body 7 rotatably attached to a fixed shaft 5 via bearings 6. The opposite ends of the fixed shaft 5 are fixed to a conveyor frame la. The opposite ends of the cylindrical body 7 are provided -<13>with respective housings 8, each having a shape of a stepped cylinder and serving as a side plate. Each housing 8 includes a cylindrical portion 8a having a smaller diameter in which a bearing 6 is fitted. As illustrated in Fig. 2, each housing 8 is fitted into the inner circumference of the cylindrical body 7 at a 5 cylindrical portion 8b thereof having a larger diameter. The bearings 6 are rolling bearings such as deep groove ball bearings. Each of the bearings 6 has an inner ring fitted onto the outer circumference of the fixed shaft 5. One of the bearings 6 and one of the housings 8 form a bearing unit 10. The bearing unit 10, together with a sensor, a power source, a transmitter, and so on to be 10 described later, forms a conveyor device bearing unit with a malfunction detection function according to the first embodiment. A cover 9 and a labyrinth seal 29 are attached to the outer side of each bearing 6 in each housing 8 to prevent rain water and dust from entering the inside space of the bearing 6 or the cylindrical body 7. The labyrinth seal 29 is 15 composed of a fixed side sealing member 29a attached to the fixed shaft 5 and a rotation side sealing member 29b attached to the housing 8. The housings 8 at the opposite ends of each conveyor roller 4 each have a sensor 11, a power source 12, and a transmitter 13 disposed between the bearing 6 and the cover 9. The sensor 11, the power source 12, and the 20 transmitter 13 are fixed to the outer circumference of the fixed shaft 5 serving as the fixed side. The sensor 11, the power source 12, and the transmitter 13 may be provided to a part of the outer circumference of the fixed shaft 5 or provided to the entire outer circumference. The cover 9 is made of a synthetic resin. The transmitter 13 is disposed at a position in a space enclosed by the cover 9 25 where no radio shielding material such as a metal exists between an antenna of the transmitter 13 and the cover 9. In Figs. 1 and 2, the rotation side sealing member 29b of the labyrinth seal 29 is interposed between the cover 9 and the transmitter 13, and the interposed portion or the whole area of the rotation side -<14>sealing member 29b is made of a synthetic resin so as not to have radio shielding properties. The sensor 11 is a sensor for detecting the state of the bearing 6 and is preferably disposed in contact with the bearing 6 but does not necessarily have to 5 be in contact with the bearing. The "state of the bearing" herein refers to data representing one or more characteristics of the rolling bearing. The sensor 11 includes any of a vibration sensor, a temperature sensor, and a rotation sensor, for example. Any two types of or all the three types of the vibration sensor, the temperature sensor, and the rotation sensor may be provided as the sensor 11. 10 An acceleration sensor can be used as the vibration sensor, and a thermistor and the like can be used as the temperature sensor. The rotation sensor detects the relative rotation speed between the inner and outer rings of the bearing 6 or the relative rotation speed between the cylindrical body 7 and the fixed shaft 5 of the conveyor roller 4. The rotation sensor includes, for example, a magnetic or 15 optical ring encoder (not shown) provided on the outer circumference of the fixed shaft 5 and a magnetic or optical sensing element for detecting the encoder, of which the sensing element is fixed to the housing 8. Thus, the "state of the bearing" includes any one of or a combination of the vibration, the temperature, and the rotation frequency of the rolling bearing and so on, depending on the type 20 of the sensor 11. The sensor 11 may have only a sensing element or may have a sensing element and a signal-processing circuit (not shown) for processing signals output by the sensing element. The signal-processing circuit may include an amplifier or one further having an analog-to-digital converter, a filter, 25 and other devices. The power source 12 is for driving the sensor 11 and the transmitter 13, and includes an electric generating element 14, a rectify ing/charging circuit 15, and electric energy storage element 16 as shown in the block diagram of Fig. 6. The electric generating element 14 may include a vibratory electric generating element or a thermo electric generating element that generates electric power with environmental energy in the environment surrounding the element. The vibratory electric generating element may include a semiconductor element such as an electret element. The thermo electric generating element may 5 include an electric generating element using the Seebeck effect. By disposing a high temperature side of the element internally and a low temperature side of the thermo electric generating element on a side of the open air (atmospheric air), necessary electric power can be generated. Increased in contact area with the atmospheric air on the side of the open air and given a shape of a comb (fin) in 10 order to facilitate radiation, the thermo electric generating element can have a larger temperature difference and thus generate more electric power. The electric energy storage element 16 is a capacitor or a storage battery such as a lithium secondary battery. The rectifying/charging circuit 15 is a circuit for rectifying the current generated by the electric generating element 15 14 and charging the electric energy storage element 16 therewith. The power source 12 may include only the electric generating element 14 without having the electric energy storage element 16. The transmitter 13 has a transmission antenna 17, a transmission circuit unit 18, and a transmission control unit 19. The transmission circuit unit 20 18 modulates the signals in a predetermined modulation format to cause the signals to be transmitted from the antenna 17 through radio waves. The transmission control unit 19 includes a circuit for transmission of the signals, a microcomputer, and other devices to cause the transmission circuit unit 18 to transmit the signals according to predetermined conditions. The signals may 25 include any information, for example, information output by the sensor 11, that is, information of the state of the bearing 6 (Fig. 1). While the signals are transmitted through radio waves in this example, the signals may be transmitted by wireless or may be transmitted through other media than radio waves. -- <16>- The transmission control unit 19 determines whether or not the amount of charging (for example, the charges stored) in the electric energy storage element 16 has reached a predetermined value and, when the predetermined value has been reached, causes the transmission, for example. 5 The transmission control unit 19 includes an electronic circuit such as a switching circuit for opening and closing the connection of the electric energy storage element 16 to the transmission circuit unit 18, for example. The details of the transmission control by the transmission control unit 19 will be described later with reference to Fig. 8 and Figs. 9A and 9B. The amount of charging in 10 the electric energy storage element 16 is determined based on the terminal voltage of the electric energy storage element 16, for example. The transmission interval depends on the electric power generated by the electric generating element 14 of the power source 12. In the case of the electric generating element 14 capable of generating electric power of approximately 100 15 ptW, for example, the transmission can be performed every five minutes. The transmission control unit 19 may cause the transmission once the predetermined value has been reached, and thereafter cause the electric energy storage element 16 to discharge electric power until the amount of the electric power stored therein is reduced to zero or to a predetermined value or lower. The amount of 20 the electric power stored in the electric energy storage element 16 is reduced as the electric power is used for the transmission, but further discharge is caused, thereby stabilizing the transmission interval. The electric powers consumed by the transmissions are not always the same about, but the time needed for the electric storage is made constant by causing the further discharge. 25 The transmission control unit 19 transmits identification information of the bearing unit 10 (Fig. 1) provided with the sensor 11 together with the information output by the sensor 11. The identification information may be stored in the transmission control unit 19 or may be stored in storage means provided separately from the transmission control unit 19. -- <17>- The bearing unit 10 may be provided with storage means 20. as a part of the transmitter 13 or of the sensor 11, or separately from the transmitter 13 and the sensor 11, for storing therein the information detected by the sensor II (information of the state of the bearing 6 (Fig. 1)). The storage means 20 may 5 be a memory circuit element or an IC tag provided to a circuit board (not shown) of the transmitter 13 and the sensor 11. The transmitter 13 may transmit the information stored in the storage means 20. If the storage means 20 is an IC tag, maintenance workers can recognize the usage state and condition of the bearing unit 10 on the spot in an on-site check using an IC tag reader, which can be 10 combined with the control in such a place as a central control room, achieving more reliable maintenance and management. Alternatively or additionally, the housing 8 (Fig, 1) may be provided with a GPS terminal 21. The GPS terminal 21 is a terminal of a global positioning system (GPS) and outputs a signal for telling its position. The GPS 15 terminal 21 may be adapted to receive positional information corresponding to its signal from the global positioning system. The positional information received may be transmitted together with the information detected by the sensor 11. The identification information to be transmitted by the transmitter 13 may be information for identifying only the location of the bearing unit 10 in one 20 conveyor 1. In that case, details as to which bearing unit 10 and in which conveyor I can be specified by combining such identification information with the positional information of the GPS terminal 21. While the sensor 11, the power source 12, and the transmitter 13 are individually provided to the bearing unit 10 in the above-described example, a 25 sensor module 22 with transmission and electric generation functions which is a component obtained by integrally assembling the sensor 11, the power source 12, and the transmitter 13 as illustrated in Fig. 7 may be provided to the bearing unit 10, for example. Such a sensor module 22 with transmission and electric -- <18)generation functions, for example, having a size of approximately 25 mm square, has been commercialized. A technique to determine a malfunction in the rolling bearing 6 without relying on the information detected by the sensor 11, that is, a technique 5 to determine a malfunction based on a change in the interval of the signals transmitted from the transmitter 13 and received by a receiver (not shown) will be described with reference to Fig. 8 and Figs. 9A and 9B. The electric power generated by the electric generating element 14 of Fig. 6 is stored in the electric energy storage element 16, and the transmission 10 circuit unit 18, controlled by the transmission control unit 19, performs the transmission every time the amount of the electric power stored reaches a predetermined value. The amount of charging in the electric energy storage element 16 is determined based on the terminal voltage of the electric energy storage element 16, for example. Fig. 8 illustrates the determination, in which 15 the vertical axis represents the terminal voltage V of the electric energy storage element 16, and the horizontal axis represents the time t. Hereinafter, the case where the electric generating element 14 is a thermo electric generating element such as an electric generating element using the Seebeck effect will be described. Since the bearing 6 (Fig. 1) generates heat while in operation, the 20 electric generating element 14 of Fig. 6 generates electric power due to the temperature difference between the bearing 6 and the ambient atmosphere such as the atmospheric air. The electric power generated is stored in the electric energy storage element 16. As illustrated in Fig. 8, the terminal voltage V of the electric energy storage element 16 increases as the amount of charging 25 increases, and once the amount of charging reaches a predetermined value, that is, once the terminal voltage V increases up to a predetermined value VA, the transmission circuit unit 18 transmits signals, controlled according to switching or the like by the transmission control unit 19 of Fig. 6. The signal transmission consumes the electric power stored in the electric energy storage element 16 and -(K19>reduces the terminal voltage V In addition, the transmission control unit 19 may cause discharge after the signal transmission until the amount of the electric power in the electric energy storage element 16 is reduced to a predetermined value or lower, that is, until the tenninal voltage V is reduced to a predetermined 5 voltage VB or lower as illustrated in Fig. 8. Thereafter, the amount of the electric power stored is increased again by the generation of electric power performed by the electric generating element 14 (Fig. 6) to increase the terminal voltage V. Once the terminal voltage V increases up to the predetermined value VA., the transmission and the discharge are caused. Such actions are repeated. 10 With the temperature of the bearing 6 (Fig. 1) being constant, the amount of the electric power generated by the electric generating element 14 of Fig. 6 is constant, too, and therefore the period T of the transmission is constant. On the other hand, if the temperature of the bearing 6 (Fig. 1) rises due to any defects, the transmission period T is shortened. In a certain instance, while the 15 electric generating element 14 generates electric power at a rate of I V/h in terms of the terminal voltage V (that is, the terminal voltage increases by 1 V per hour) at a bearing temperature of 40'C, the electric generating element 14 generates electric power at a rate of 1.5 V/h in terms of the terminal voltage V (that is, the terminal voltage increases by 1.5 V per hour) at a bearing temperature of 20 approximately 50'C. The transmission frequency therefore increases by 1.5-fold (the transmission period is 2/3). A monitoring device (not shown) disposed away from the conveyor 1 (Fig. 1) receives and monitors the signals that are transmitted in the described manner. The monitoring device determines it to be normal when the 25 transmission frequency is constant as shown in Fig. 9A and determines that the bearing has a malfunction when the transmission frequency increases (the transmission period T is shortened) as in the section tc of Fig. 9B, for example, and outputs the determination results. -<20>-- Since no signal is transmitted when the bearing 6 (Fig. 1) is stopped due to a malfunction, the case where no signal is received for a predetermined period of time while a drive source is driving the conveyor 1 is determined as occurrence of a malfunction so significant that the bearing 6 (Fig. 1) comes to a 5 stop. In this malfunction determination processing, the extent of the transmission frequency for the bearing to be determined as having a malfunction may be decided as appropriate based on experience, simulation, or the like. Other than the determination of the occurrence of a malfunction by merely 10 comparing the transmission frequency or the transmission period with a predetermined frequency or period, the occurrence of a malfunction may be determined through statistical processing. For example, in the malfunction determination processing, a malfunction may be determined by constantly comparing the signal interval within a given target time period or within given 15 target transmission times at present with the signal interval within a reference time period or within reference transmission times in the past earlier than the present by a predetermined period of time. In the explanation of the specific example illustrated in Fig. 9B, the current time is t 1, and the average signal interval within given target transmission 20 times (for example, three signals) at present (t1) (section tb in Fig. 9B) is compared with the average signal interval within reference transmission times (three times) in the past earlier than the present tl by a predetermined period of time (for example, by three signals) (section ta in Fig. 9B) to determine it as occurrence of a malfunction when the difference therebetween is larger than a 25 predetermined range. In other words, the moving averages are compared with each other. In many cases, bearings that have been used for many years and almost new bearings or the like generate heat and vibration differently. In the bearings that have been used for a long term, the amount of the heat generation -<21>or vibration that is to some extent large does not necessarily represent a malfunction. Simple comparison between the transmission interval and a set interval does not therefore allow accurate malfunction determination. In contrast, constantly comparing the signal interval within a given target time 5 period or within given target transmission times at present with the signal interval within a reference time period or within reference transmission times in the past earlier than the present by a predetermined period of time as in the configuration described above allows reliable malfunction determination. This is because, when the amount of heat generation or vibration abruptly increases compared to 10 that within a certain time period in the past while the bearing is being used, it often represents a malfunction in the bearing. As described above, a malfunction in the bearing 6 (Fig. 1) can be determined by monitoring the interval of the signal transmission from the bearing unit 10. In case of a malfunction that stops the bearing 6 (Fig. 1), no signal is 15 transmitted. The case where no signal is received while the conveyor I equipped with the bearing unit 10 is in a driven state is therefore determined as occurrence of a malfunction that stops the bearing 6 (Fig. 1). Since a malfunction in the bearing can be detected using the electric generating element 14 as described above, the malfunction detection can be achieved without the 20 sensor 11. In case of a malfunction, therefore, the bearing 6 (Fig. 1) can be replaced at an early stage before the bearing 6 becomes unable to rotate. Since a malfunction in the bearing is determined based on the interval of the signal transmission as described above, the signals transmitted by the transmission circuit unit 18 of the transmitter 13 do not need to include any 25 information. However, the signals may include optional information; the signals may include information of the state of the bearing detected by the sensor 11. In that case, a malfunction can be detected based not only on the transmission interval of the signals transmitted by the transmission circuit unit 18 of the transmitter 13 but also on the sensor information included in the signals.

This allows more reliable malfunction detection. Alternatively, the information of the state of the bearing may be transmitted while being included in different signals from the signals whose transmission interval is monitored. Figs. 3 and 4 illustrate a bearing unit according to the second 5 embodiment of the present invention to be provided to the conveyor 1. The bearing unit is formed of a plummer block loP located at each one of opposite ends of the conveyor 1. The plummer block lOP supports a rotation shaft 31 of the conveyor roller 3 at each end of the conveyor 1 of Fig. 12. The plummer block iP has a housing 32 serving as a plummer block bearing box and a 10 bearing 36 for supporting the rotation shaft 31 inside the housing 32. The bearing 36 includes a rolling bearing such as a double row self-aligning roller bearing. The housing 32 is composed of a housing main body 32a and a lid member 32b. The housing main body 32a accommodates the bearing 36 and has opposed openings in both end faces thereof. The rotation axis 31 is inserted 15 through the opening on one end. The lid member 32b closes the opening on the other end. In this second embodiment, the sensor 11, the power source 12, and the transmitter 13 are embedded in an upper surface of the housing main body 32a of the housing 32. For example, the surface of the housing 32 is provided 20 with recesses, and the sensor 11, the power source 12, and the transmitter 13 are disposed therein. As the sensor 11, the power source 12, and the transmitter 13., those having the configuration described in association with the first embodiment illustrated in Figs. 1 and 2 may be employed. In particular, the transmitter 13 is provided so that the antenna 17 (Fig. 6) is exposed to the atmospheric air. As 25 illustrated in Fig. 7, the sensor 11, the power source 12, and the transmitter 13 may be integrated into the sensor module 22 with transmission and electric generation functions. In the second embodiment, as in the case of the bearing unit according to the first embodiment, the storage means 20 and the GPS terminal 21 may be provided to the housing 32. -<23>- In the bearing unit (plummer block 10P) according to the second embodiment illustrated in Figs. 3 and 4, the sensor 11 and so on are provided to the housing main body 32a. Alternatively, the sensor 11, the power source 12, and the transmitter 13 may be embedded in the lid member 32b of the housing 32 5 as in the bearing unit (plummer block 10P) according to the third embodiment illustrated in Fig. 5. In the same manner as the first and second embodiments, the transmitter 13 is provided so that the antenna 17 (Fig. 6) is exposed to the atmospheric air. The sensor 11, the power source 12, and the transmitter 13 in the 10 bearing unit (plummer block 10P) according to the second embodiment illustrated in Figs. 3 and 4, and in the bearing unit (plummer block 10P) according to the third embodiment illustrated in Fig. 5 have similar configurations to those in the bearing unit 10 according to the first embodiment described above with reference to Figs. I and 2. Furthermore, the bearing unit 15 (plummer block 10P) according to the second and third embodiments illustrated in Figs. 3 to 5 may also be provided with the storage means 20 and the GPS terminal 21 in the same manner as the first embodiment. Fig. 13 illustrates conveyor system 100 with a malfunction detection function including a plurality of conveyors 1 of Fig. 12, that is, a plurality of 20 conveyors I equipped with the conveyor device bearing units 10 with a malfunction detection function. The conveyor system 100 is for conveyance of iron ore, coal, or the like, for example, in which a conveyor line of the conveyors I arranged in tandem extends from a mining field to a truck loading station. In this embodiment, a relay device 43 and a central control room 42 25 having a central control panel 41 are provided. The central control panel 41 has an antenna 44, a receiver (not shown), and a display device (not shown) for displaying a diagram or a table showing the conveyors I and the conveyor device bearing units 10 with a malfunction detection function of each conveyor 1. The display device also displays information of malfunction occurrence in each -,,24>bearing unit 10 on the diagram or the table. The diagram or the table showing the bearing units 10 may be displayed as an image on a screen of one display device. The central control panel 41 has malfunction determination means 45 5 for determining a malfunction for each of the bearings 6 (Fig. 1) and 36 (Fig. 3). The display device (not shown) displays results of the malfunction. The malfunction determination means 45 determines it to be a malfunction when no signal is received for a predetermined period of time while the conveyors I equipped with the bearing units 10 are driven. Alternatively, the malfunction 10 determination means 45 may determine a malfunction based on the information in the signals received (information detected by the sensor, that is, information of the state of the bearing). The malfunction determination means 45 may determine a malfunction based on both the information in the signals received and the interval of the signal reception. In the electric generating element 14 15 including a thermo electric generating element or a vibratory electric generating element, the temperature rises and the vibration increases as a malfunction in the bearings 6 (Fig. 1) and 36 (Fig. 3) develops, and accordingly the amount of electricity generated increases and the transmission interval shortens. Thus, the transmission interval shows a sign of a malfunction in the bearings. 20 The relay device 43 is disposed between some conveyors I and the central control panel 41 to receive, amplify, and wirelessly transmit the signals from the transmitters 13 of one or more bearing units 10 (or IOP) provided to the conveyors 1. In the bearing units according to the first to third embodiments, the 25 sensor 11 for detecting the state of the bearing 6 (Fig. 1) or 36 (Fig. 3) and the transmitter 13 for wirelessly transmitting the information of the state detected by the sensor 11 (hereinafter, referred to as "sensor information".) are provided to the bearing unit 10 (or 1OP). A malfunction in the bearing 6 (Fig. 1) or 36 (Fig. 3) can therefore be detected readily and precisely without investment of significant -<25)time and effort by performing the monitoring of the sensor information in the central control room 42 or somewhere in addition to the monitoring of the signal transmission interval. In case of a malfunction that may prevent the rotation, therefore, the bearing 6 (Fig. 1) or 36 (Fig. 3) can be replaced at an early stage 5 before the bearing becomes unable to rotate. Wireless transmission is employed for the signal transmission, and the electric power for the transmission is obtained from the power source 12 (Fig. 6) having the electric generating element 14 (Fig. 6) in each bearing unit 10. Thus, the malfunction detection, the information transmission, and the securing 10 of the power source can be completed in each bearing unit 10, eliminating the need for wiring among the bearing units 10 and from the bearing units 10 to the central control room 42, thereby simplifying the wiring system. If wired, the structure will be complicated due to the need to build the infrastructure including wiring, leading to less design freedom, whereas the structure relying on the 15 wireless transmission is free of such a problem. With the conveyors I extending for a long distance, the wireless transmission to the central control room 42 is enabled by providing the relay device 43 within every coverage along each conveyor 1. Thus, the wireless transmission can be readily applied also to conveyor system having a long conveyance course such as a conveyor for 20 conveyance of iron ore, coal, or the like, for example. The antenna 17 becomes incapable of communication if covered with a metal during the transmission of the sensor information from the bearing unit 10 (or 10P). In the belt conveyor 1 that is used outdoors, good communication situation can be obtained by exposing a surface of the antenna 17 to the 25 atmospheric air in the bearing units according to the first to third embodiments illustrated in Figs. I to 5. In addition, the power source 12 of Fig. 6 can be stand-alone as being adapted to supply electric power for operating the device by "self-powering". The use of the electric generating element 14 that generates electric power with -26>environmental energy provides a simplified and compactified structure compared to the case of a rotor-stator generator requiring components on both the rotating and static sides. Thus, the bearing unit is easily applicable, as it can eliminate the need for exclusive design and provide greater design freedom. The bearing 5 unit can be easily replaced with a bearing unit having an existing design. As the energy harvesting element 14 capable of "self-powering", a vibratory electric generating element that can generate electric power of approximately 100 ptW has been commercialized. The electric power generated by the vibratory electric generating element allows the transmission every five 10 minutes. Furthermore, by previously charging the electric energy storage element 16 such as a lithium secondary battery, the information can be transmitted using the electric energy storage element 16 even when the electric power generation is not performed during the shutdown period of the conveyor. For the self-powering in the bearing unit 10 (Fig. 1) (or 10P (Fig. 3)), 15 a rotor-stator generator using the rotary mechanism of the bearing has been conventionally used. On the other hand, the bearing unit 10 generates not a little vibration and heat with the rotation of the bearing 6. By focusing on such characteristics of the bearing unit and using the electric generating element 14 capable of generating electric power with the environmental energy, which was 20 inconceivable in conventional bearing units, it is possible to achieve the compactification and simplification of the structure. Such electric power generated with the vibration and the heat is usable enough to cover the electric power that is used for the signal transmission and for driving the sensor. The electric power thus generated, which may be 25 small, can be used in practice by taking some measures in the detection and the transmission by, for example, providing the electric energy storage element 16 and performing the transmission once the amount of the electric power stored therein is enough as described above. -<27>- As the electric generating element 14, a thermo electric generating element (Seebeck element) using the heat generated by the rotation of the bearing 6 can be used as well as the vibratory electric generating element (electret element) as described above. In the thenno electric generating element, 5 necessary electric power can be generated by disposing a high temperature side of the element internally and a low temperature side thereof on a side of the open air (atmospheric air). Furthermore, increased in contact area with the atmospheric air on the side of the open air and given a shape of a comb (fin) in order to facilitate radiation, the thermo electric generating element can have a 10 larger temperature difference and thus generate more electric power. As the sensor 11 for the malfunction detection, a temperature sensor can be used as well as the vibration sensor as described above. Additionally or alternatively, a rotation sensor may be employed, which is considered an effective sensing technique in that occurrence of a malfunction can be predicted 15 by sensing a phenomenon where the rotation speed drops. It is possible to identify the bearing 6 or 36 from which the information comes when identification information is transmitted together with the sensor information from the transmitter 13 of each bearing unit 10. In the system using respective devices in combination or including a plurality of 20 conveyors 1, it is possible to identify details as to which conveyor I and which bearing 6 (Fig. 1) or 36 (Fig. 3) the information comes from by linking them with the information from the GPS terminals 21. In the conveyor device bearing unit with a malfunction detection function according to the first to third embodiments of the present invention, the 25 sensor 11 (Fig. 1) may be dispensed with. Without the sensor 11, the conveyor device bearing unit with a malfunction detection function according to the first embodiment illustrated in Figs. 1 to 6 has a spacer 11 instead of the sensor 11 interposed between the bearing 6 and the power source 12 in Fig. 1. The power source 12 may be disposed in contact with the bearing 6 without the spacer 11. -<28>- In the conveyor device bearing unit with a malfunction detection function without the sensor 11, the power source 12 of Fig. 6 functions as a power source for driving the transmitter 13 and also functions as a sensor for detecting a malfunction in the bearing 6 of Fig. 1. That is, the power source 12 functions as 5 a sensor for detecting a malfunction since the signal transmission interval corresponding to the length of time of the electric power generation by the power source 12 is monitored to detect a malfunction. Next, a bearing unit monitoring system 50 according to the fourth embodiment of the present invention will be described with reference to Fig. 10. 10 The bearing unit monitoring system 50 includes the bearing unit 10 (or 10P) according to any of the first to third embodiments. In the description of the present embodiment, parts that are the same as or equivalent to the parts described in association with the first to third embodiments of the bearing unit of the present invention will be given the same reference numerals, and detailed 15 description thereof will be omitted. As illustrated in Fig. 10, the bearing unit monitoring system 50 according to the fourth embodiment includes one or more bearing units 10 (or 10P) and a central control panel 41 including a monitoring device 46. Each bearing unit 10 (or 10P) is a bearing unit according to any of the first to third 20 embodiments. However, the bearing unit 10 (or 10P) is not provided with the sensor 11 (Fig. 6). The bearing unit 10 (or 10P) is to be provided to the conveyor I as described with reference to Fig. 1. The bearing unit 10 (or 1 OP) may be provided with a GPS terminal 21 in association with the transmitter 13 as illustrated in Fig. 11. 25 In Fig. 10, the monitoring device 46 is provided to the central control panel 41 or the like of the central control room and monitors the signals transmitted by the transmitter 13 of each bearing unit 10. The monitoring device 46 and the conveyor device bearing unit 10 (or 1OP) with a malfunction detection function form the bearing unit monitoring system 50. The monitoring device 46 has a receiver 47 for receiving the signals transmitted by the transmitter 13 of the bearing unit 10 (or 10P), malfunction determination means 45A, and bearing unit identification means 49. The receiver 47 has an antenna 52 and a receiving circuit unit 51. The bearing unit identification means 49 5 identifies, based on the signals received by the receiver 47, the bearing unit 10 from which the signals come. The identification is performed based on the identification information out of the information transmitted. With the bearing unit 10 being provided with the GPS terminal 21 (Fig. 11), the bearing unit identification means 49 identifies the bearing unit 10 (or 1OP) using signals 10 indicating the position according to the GPS terminal 21 (Fig. 11) or using both the signals indicating the position according to the GPS terminal 21 (Fig. 11) and the identification information. The malfunction determination means 45A determines a malfunction based on a change in the interval of the signals transmitted from the transmitter 15 13 and received by the receiver 47. The detailed determination processing by the malfunction determination means 45A is as described for the conveyor device bearing unit according to the first embodiment with reference to Fig. 8 and Figs. 9A and 9B. That is, the malfunction determination means 45A of the monitoring 20 device 46 monitors the signals transmitted by the transmitter 13 of the bearing unit 10 to determine it to be normal when the transmission frequency is constant as shown in Fig. 9A and to determine that the bearing has a malfunction when the transmission frequency increases (the transmission period T is shortened) as in the section tc shown in Fig. 9B, and to output the determination results. 25 In the fourth embodiment, the structure in which the bearing unit is not provided with the sensor is described, but the bearing unit may be provided with the sensor. In that case, the detection of a malfunction in the bearing is performed based not only on the signal transmission interval but also on the -<30>sensor information as in the first to third embodiments. Thus, the detection of a malfunction in the bearing can be more reliable. While the cases where the conveyor device is the belt conveyor I are described in the above embodiments, the present invention can be applied to 5 conveyors other than belt-type conveyors, and thus to conveyor devices other than conveyors. Hereinafter, Modes I to 12 will be described, which do not require the configuration, as a component of the present invention, to cause the transmission circuit unit to perform the transmission every time the amount of 10 electric power stored in the electric energy storage element reaches the predetermined value. [Mode 1] A conveyor device bearing unit with a malfunction detection function according to Mode I is to be provided to a conveyor device and includes a rolling 15 bearing and a housing accommodating the rolling bearing, the housing including a sensor for detecting the state of the rolling bearing, a transmitter, and a power source for providing electric power to the sensor and the transmitter, the transmitter having a transmission circuit unit for wirelessly transmitting information of the state of the rolling bearing detected by the sensor, the power 20 source having an electric generating element that generates electric power with environmental energy. [Mode 2] In Mode 1, the power source preferably has electric energy storage element for storing the electric power generated by the electric generating 25 element. The transmitter may wirelessly transmit the information detected by the sensor every time the amount of the electric power stored in the electric energy storage element reaches a predetermined value. The electric energy storage element may include a capacitor or a secondary battery. [Mode 3] -<3D- In Mode 1, the electric generating element that generates electric power with environmental energy may include a vibratory electric generating element or a thermo electric generating element. The vibratory electric generating element may include an electret element or the like. The thermo 5 electric generating element may include an electric generating element using the Seebeck effect. These electric generating elements can generate electric power by utilizing vibration and heat generation in the environment where the bearing of the conveyor device is installed. [Mode 4] 10 In Mode 1, preferably, at least one of a vibration sensor, a temperature sensor, and a rotation sensor is provided as the sensor. A malfunction in the rolling bearing causes generation of vibration, temperature rise, an impact on the rotation, and so on. Provision of at least one of a vibration sensor, a temperature sensor, and a rotation sensor therefore allows the detection of a 15 malfunction in each bearing. [Mode 5] In Mode 1, the bearing unit may include storage means for storing therein the information detected by the sensor. The storage means may be an IC tag. 20 [Mode 6] The housing may accommodate a GPS terminal, which is a terminal of a global positioning system. [Mode 7] In Mode 1, the conveyor device with a malfunction detection function 25 may include a belt conveyor. [Mode 8] In Mode 7, the housing may be provided at one ends of a cylindrical body forming a circumferential portion of a conveyor roller supporting a belt of -(32>the belt conveyor, and the rolling bearing may be interposed between a fixed shaft and the housing to rotatably support the conveyor roller. [Mode 9] In Mode 8, preferably, the conveyor roller is provided with a cover 5 made of a synthetic resin for covering one of end faces of the cylindrical body, and the transmitter is disposed at a position in a space enclosed by the cover where no radio shielding material exists between an antenna of the transmitter and the cover. [Mode 10] 10 In Mode 7, the housing may be a bearing box of a plummer block for supporting a rotation shaft of a conveyor roller supporting a belt of the belt conveyor. [Mode 11] In Mode 10, the bearing box of the plummer block may include a 15 housing main body having opposed openings in both end faces thereof and receiving the shaft through one of the openings; and a lid member for closing the other of the openings of the housing main body. The sensor, the transmitter, and the power source may be provided in the lid member. [Mode 12] 20 Conveyor system with a malfunction detection function according to Mode 12 includes a plurality of conveyors provided with the conveyor device bearing unit with a malfunction detection function according to any of Modes 1 to 11. In this case, a relay device may be provided between the conveyors 25 and a central control panel for collectively monitoring information transmitted by the transmitters provided to the conveyors, and the relay device may receive, amplify, and wirelessly transmit the information transmitted by the transmitters. Since a malfunction in each bearing is not detected based on the interval of the transmission by the transmitter in Modes I to 12, the electric -<33>energy storage element may be charged by another electric storage means taht is separated from the electric generating element. According to this arrangement, the electric energy storage element can be charged in advance, and information such as the sensor information can be transmitted with the electric power stored 5 therein when electric power generation is not performed during a shutdown period of the conveyor 1, for example. Although the preferred embodiments have been described with reference to the drawings, those skilled in the art will readily conceive various changes and modifications within the framework of obviousness upon the 10 reading of the specification herein presented of the present invention. Accordingly, such changes and modifications are to be construed as included in the scope of the present invention as delivered from the claims annexed hereto. [Reference Signs] 1: conveyor (conveyor device) 15 6, 36: bearing 8, 32: housing 10, loP bearing unit loP plummer block 11: sensor 20 12: power source 13: transmitter 14: electric generating element 16: electric energy storage element 18: transmission circuit unit 25 19: transmission control unit -<31>-

Claims

1. A conveyor device bearing unit with a malfunction detection function to be provided to a conveyor device, the conveyor device bearing unit including: a rolling bearing; and a housing accommodating the rolling bearing, the housing including: a transmitter having a transmission circuit unit for transmitting signals and a transmission control unit for causing the transmission circuit unit to wirelessly transmit the signals; and a power source for supplying electric power to the transmitter, the power source having an electric generating element for generating electric power with environmental energy and electric energy storage element for storing the electric power generated by the electric generating element, wherein the transmission control unit causes the transmission circuit unit to transmit the signals every time the amount of the electric power stored in the electric energy storage element reaches a predetermined value.

2. The conveyor device bearing unit with a malfunction detection function according to claim 1, wherein the transmission control unit causes the electric energy storage element to discharge every time the amount of the electric power stored in the electric energy storage element reaches the predetermined value and the transmission circuit unit is caused to perform the transmission.

3. The conveyor device bearing unit with a malfunction detection function according to claim 1, further including a sensor for detecting the state of the rolling bearing, wherein the transmission control unit causes the transmission circuit unit to wirelessly transmit information of the state of the rolling bearing detected by the sensor, and wherein the power source supplies electric power to the sensor.

4. The conveyor device bearing unit with a malfunction detection -<35>- function according to claim 1, wherein the electric generating element includes a vibratory electric generating element.

5. The conveyor device bearing unit with a malfunction detection fumction according to claim 1, wherein the electric generating element includes a thermo electric generating element.

6. The conveyor device bearing unit with a malfunction detection function according to claim 3, wherein the sensor includes at least one of a vibration sensor, a temperature sensor and a rotation sensor.

'7. The conveyor device bearing unit with a malfunction detection function according to claim 1, wherein the signals transmitted by the transmitter include identification information of the conveyor device bearing unit.

8. The conveyor device bearing unit with a malfunction detection function according to claim 3, further including storage means for storing therein the information of the state of the rolling bearing detected by the sensor.

9. The conveyor device bearing unit with a malfunction detection function according to claim 1. wherein the housing further includes a GPS terminal, which is a terminal of a global positioning system.

10. The conveyor device bearing unit with a malfunction detection function according to claim 1, wherein the conveyor device includes a belt conveyor.

11. The conveyor device bearing unit with a malfunction detection function according to claim 10, wherein the housing is a member provided at one of ends of a cylindrical body forming a circumferential portion of a conveyor roller supporting a belt of the belt conveyor, and wherein the rolling bearing is interposed between a fixed shaft and the housing to rotatably support the conveyor roller.

12. The conveyor device bearing unit with a malfunction detection function according to claim 11, wherein the conveyor roller is provided with a cover made of a synthetic resin for covering one of end faces of the cylindrical -<36>-- body, and wherein the transmitter is disposed at a position in a space enclosed by the cover where no radio shielding material exists between an antenna of the transmitter and the cover.

13. The conveyor device bearing unit with a malfunction detection function according to claim 10, wherein the housing includes a bearing box of a plummer block for supporting one end of a rotation shaft of a conveyor roller supporting a belt of the belt conveyor.

14. The conveyor device bearing unit with a malfunction detection function according to claim 13, wherein the bearing box of the plummer block includes: a housing main body having opposed openings in both end faces thereof and receiving the shaft through one of the openings; and a lid member for closing the other of the openings of the housing main body, and wherein the transmitter and the power source are provided in the lid member.

15. Conveyor system with a malfunction detection function, including a plurality of conveyors each provided with one or more conveyor device bearing units with a malfunction detection function according to claim 1.

16. The conveyor system with a malfunction detection function according to claim 15, wherein a relay device is provided between the plurality of conveyors and a central control panel for collectively monitoring information transmitted by the transmitter of each bearing unit of the one or more conveyor device bearing units with a malfunction detection function provided to each of the plurality of conveyors, and the relay device receives, amplifies, and wirelessly transmits the information transmitted by the transmitter.

17. A bearing unit monitoring system including: a conveyor device bearing unit with a malfunction detection function according to claim 1; and a monitoring device having a receiver for receiving the signals transmitted by the transmission circuit unit and malfimetion determination means, wherein the malfunction determination means determines a malfunction based on a change in the interval of the signals transmitted from the transmitter and received by the -<37>- receiver.

18. The bearing unit monitoring system according to claim 17, wherein the malfunction determination means determines a malfunction by constantly comparing the signal interval within a given target time period or within given target transmission times at present with the signal interval within a reference time period or within reference transmission times in the past earlier than the present by a predetermined period of time. -<38>-