Abstract:
A wireless detonator is provided with: a detonation part; a control part for the detonation part, the control part being connected to the detonation part; a tube for accommodating the detonation part and the control part; and a detonation-side antenna used by the control part for wireless communication and capable of being used for sending and receiving without separately having a transmission-only antenna and a reception-only antenna; the detonation-side antenna being a soft magnetic body coil antenna, and the control part receiving, via the detonation-side antenna, a transmission signal at an operating frequency of 100-500 KHz.

Description:
RELATED APPLICATIONS 
       [0001]    The present application is a National Phase entry of PCT Application No. PCT/JP2013/084923, filed Dec. 26, 2013, which claims priority from JP Patent Application No. 2013-000909, filed Jan. 8, 2013, said applications being hereby incorporated by reference herein in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a wireless initiation system, a wireless initiation method, and a detonator and an explosive unit used therein for tunneling. 
         [0003]    In the related art, there is a blasting method used for drilling a plurality of blast holes with a diameter of approximately several centimeters and a depth of approximately several meters in a blasting face (which is a tunnel working face) in a boring direction, charging explosives into the blast holes, the blasting of the explosives being able to be wirelessly initiated, wirelessly transmitting an initiation signal from a remote position apart from the blasting face, and exploding the blasting face at a tunnel boring site or the like. 
         [0004]    For example, in a signal transmission antenna for a remote wireless initiation system disclosed in JP-A-2001-127511 (Patent Literature 1), a loop antenna of an initiation signal transmitter is disposed close to the entire circumference of a tunnel wall face in such a manner that all of wireless initiating detonators charged into blast holes of a blasting face can stably receive energy even if magnetic energy is small. 
         [0005]    In a remote wireless initiation apparatus disclosed in JP-A-2001-153598 (Patent Literature 2), a signal transmitter transmits a control signal requesting a reply signal indicative of a state of charge of electric energy of each wireless detonator, a blast preparation instruction signal is transmitted to each wireless detonator after the completion of the charging of all of the wireless detonators is confirmed, and an initiation signal is transmitted to each wireless detonator after a blast preparation completion signal is received from all of the wireless detonators. 
         [0006]    JP-A-2001-330400 (Patent Literature 3) discloses a technology in the related art regarding an antenna, fixedly installed on the ground in a tunnel, for a remote wireless initiation system. 
         [0007]    In a signal receiving coil of a wireless detonator disclosed in JP-A-8-219700 (Patent Literature 4), the frequency of the coil is less than or equal to 10 kHz, the number of turns of the coil is 100 turns to 100000 turns, the diameter of the coil is φ 35 mm to φ 47 mm, and the length of the coil is 5 mm to 300 mm. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    In the technology disclosed in Patent Literature 1, since an antenna for signal transmission is wound in a coil shape along the entire circumference of the tunnel side wall multiple times, and the frequency of a signal transmitted from the transmitter is less than or equal to 10 kHz, the number of turns of the antenna is set to be less than or equal to 50 turns, and preferably, to be less than or equal to 30 turns. An extending operation for extending the loop antenna disposed close to the entire circumference of the tunnel side wall while the loop antenna being wound in 30 turns, requires a considerable amount of labor efforts, a large amount of time is required to install the signal transmitting antenna in the vicinity of the blasting face, and rocks in the vicinity of the blasting face may fall or collapse, which is not preferable. A complicated signal receiving coil, obtained by winding a conductive wire around a ferrite core with high magnetic permeability multiple times described later, of the wireless initiating detonator is required in order to receive a signal with a frequency less than or equal to 10 kHz, and draw a large energy. In the signal receiving coil disclosed in Patent Literature 4, the number of turns of the coil is 100 turns to 100000 turns, the diameter of the coil is φ 35 mm to φ 47 mm, and the length of the coil is 5 mm to 300 mm. 
         [0009]    Also in the related art disclosed in Patent Literature 2, since the frequency of a transmission signal from the signal transmitter is less than 10 kHz, similar to Patent Literature 1, an antenna for signal transmission is assumed to be required. Accordingly, similar to Patent Literature 1, a large amount of time is required to perform work in the vicinity of the blasting face, which is not preferable. 
         [0010]    A blasting controller and the wireless initiating detonator in the related art disclosed in Patent Literatures 1 to 4 have the following problems. 
         [0011]    In order for the wireless initiating detonator to receive a transmission signal wirelessly transmitted from the blasting controller, and to draw a large energy, the energy of a transmission signal from the blasting controller is required to be increased, and the wireless initiating detonator is required to more efficiently receive the transmission signal. 
         [0012]    In order for the blasting controller to output a transmission signal with a large energy, it is necessary to increase current to a blasting controller antenna, or to increase the number of turns of the antenna wire. However, when current is increased, current loss associated with Joule heat increases, and in the worst case, the antenna may be burnt out. It is necessary to use a thicker antenna wire with less resistance value, and actually, it is possible to supply only approximately several amperes of current to the antenna. The antenna wire can be realistically wound along an inner wall of the tunnel in at the most approximately 40 turns to approximately 500 turns. Accordingly, as in Patent Literature 1, 40 AT to 500 AT (ampere-turn) is a realistic value which is attainable. 
         [0013]    In order for an antenna for signal reception to more efficiently receive a signal, it is necessary to use an antenna with a length close to λ/2 (λ is the wavelength of a transmission signal), to amplify energy drawn by winding the antenna multiple times, and to integrate transmission signals using the core with high magnetic permeability. In the related art disclosed in Patent Literatures 1 to 4, since the frequency of a transmission signal is 10 kHz, λ=v/f=(30*10 7 )m/(10*10 3 )=30 km, λ/2=15 km, and thus the attaching of an antenna with this length to the wireless initiating detonator is not realistic. Therefore, actually, a coil core with substantially the same diameter as that of a cylindrical explosive, obtained by winding a conductive wire around a core with high magnetic permeability and a diameter of approximately 50 mm in several 100 turns to several 100000 turns, is used as an antenna. In this case, the coil core has substantially the same size as that of a baseball, and the weight of the coil core becomes several 100 g, and when the coil core drops out of a blast hole via a lead wire, the lead wire may be cut. Therefore, the dropping of the coil core out of the blast hole is not preferable. Accordingly, as disclosed in Patent Literatures 1 and 4, the core and the signal receiving coil are preferably disposed in a leading portion of the wireless initiating detonator. However, in such case, since the coil core, which is an antenna for signal reception, is disposed at the bottom charge in the blast hole, a transmission signal is unlikely to reach the coil core, and when the frequency is 10 kHz, it is difficult to improve signal receiving efficiency. 
         [0014]    As such, in the blasting controller and the wireless initiating detonator assumed from Patent Literature 1 to 4, it is necessary to wind an antenna in approximately 40 turns to approximately 500 turns so as to transmit a transmission signal from the blasting controller, and it is necessary to dispose the coil core, which is an antenna for the wireless initiating detonator to receive the transmission signal, at a bottom charge in the blast hole, and wind the conductive wire in several 100 to several 100000 turns. 
         [0015]    In the related art disclosed in Patent Literature 1 to 3, the frequency of a response signal, wirelessly transmitted from the wireless initiating detonator to the blasting controller, is 10 MHz to 60 MHz. Here, when the frequency of the response signal is 10 MHz, the length of the blasting controller antenna with the best signal receiving efficiency is λ/2=[(30*10 7 )/(10*10 6 )]/2=15 m. When the antenna with a length longer than λ is used, standing waves are likely to occur, which is not preferable. As described above, the antenna for receiving the transmission signal from the blasting controller is wound along the side wall of the tunnel in 40 turns to 500 turns, and the length of the antenna easily exceeds λ (in this case, 30 m). Accordingly, as disclosed in Patent Literature 3, it is necessary to configure the blasting controller antenna for receiving the response signal as a half-wavelength dipole antenna only for signal reception. When the aforementioned coil core is used to transmit a response signal from the wireless initiating detonator, the response signal is transmitted from the bottom charge in a blast hole, and a considerably small energy reaches the blasting controller. In the wireless initiating detonator disclosed in Patent Literature 3, the wire-like antenna only for transmitting a response signal drops out of a blast hole. 
         [0016]    As such, with regard to the blasting controller and the wireless initiating detonator assumed from the related art disclosed in Patent Literatures 1 to 4, it is necessary to provide a large coil core as an antenna only for signal reception and a wire-like antenna as an antenna only for signal transmission in the wireless initiating detonator. In the blasting controller, an antenna only for signal transmission is required to be wound along the side wall of the tunnel in 40 turns to 500 turns, and a dipole antenna only for signal reception is needed. Accordingly, an amount of time is taken to set up an antenna for the blasting controller, and a large amount of time is taken to perform work in the vicinity of the blasting face, which are not preferable. 
         [0017]    According to an aspect of the present invention, there is provided a wireless initiating detonator including: an initiator; a controller connected to the initiator, and configured to ignite the initiator; a shell configured to accommodate the initiator and the controller; and a detonator antenna used by the controller for wireless communication, and useable for both signal transmission and signal reception without an antenna only for signal transmission and an antenna only for signal reception being separately provided. The detonator antenna is a soft magnetic coil antenna. The controller receives a transmission signal with an operation frequency via the detonator antenna, the operation frequency being a frequency which is greater than or equal to 100 kHz and is less than or equal to 500 kHz. 
         [0018]    Due to this configuration, since the frequency of a signal wirelessly received by the wireless initiating detonator is set to be greater than or equal to 100 kHz, and to be less than or equal to 500 kHz, it is possible to use the soft magnetic coil antenna, obtained by winding a conductive wire around a soft magnetic material in several turns to several tens of turns, as the detonator antenna. 
         [0019]    Accordingly, it is possible to use a small soft magnetic coil antenna with a very simple structure, to reduce the diameter of the detonator antenna to a size smaller than an inner diameter of a blast hole, and to charge the wireless initiating detonator into the blast hole while the detonator antenna is connected to the wireless initiating detonator. Therefore, it is possible to reduce an amount of time required to charge the wireless initiating detonator into the blast hole of a blasting face. As a result, it is possible to further reduce an amount of time required to perform work in the vicinity of the blasting face. 
         [0020]    The soft magnetic material is a material with a high magnetic permeability, the magnetic poles of which are relatively easily eliminated or reversed among magnetic materials. The soft magnetic material includes, for example, iron, silicon steel, permalloy, sendust, permendur, ferrite, an amorphous magnetic alloy, a nanocrystalline magnetic alloy, or the like, and typically, ferrite is used. 
         [0021]    It is possible to easily set the orientation of the detonator antenna along the axial direction of the blast hole by using the soft magnetic coil antenna as the detonator antenna. Accordingly, it is not necessary to adjust the orientation of each detonator antenna, and it is possible to further reduce an amount of time required to perform work in the vicinity of the blasting face. 
         [0022]    In the wireless initiating detonator according to the above aspect, the detonator antenna may be installed on the axis of a shell while being in contact with the shell, or may be installed around the shell while being in contact with the shell. It is possible to install the detonator antenna at an appropriate position. Since the shell is integrated with the detonator antenna, it is possible to further reduce an amount of time required to charge the wireless initiating detonator into the blast hole of the blasting face. 
         [0023]    In the wireless initiating detonator according to the above aspect, the detonator antenna may be located in such a manner as to be oriented in a predetermined direction via a leading wire without being in contact with the shell. It is possible to increase a degree of freedom in the installation of the detonator antenna. For example, even if the wireless initiating detonator is installed at a bottom in a blast hole, it is possible to install the detonator antenna in an entrance portion of the blast hole, which is convenient. In this case, the detonator antenna can be adjusted such that the detonator antenna is oriented in a direction (a predetermined direction) in which the detonator antenna can satisfactorily perform the wireless supply of electric power and wireless communication. 
         [0024]    In the wireless initiating detonator according to the above aspect, a display device is attached to the wireless initiating detonator directly or via a cable, and displays individual pieces of information by which the wireless initiating detonator can be identified. It is possible to confirm the individual pieces of information regarding the wireless initiating detonator via the display device. Accordingly, it is possible to identify a malfunctioned wireless initiating detonator. 
         [0025]    According to another aspect of the present invention, there is provided an explosive unit that includes the wireless initiating detonator according to the above aspect, and a primary charge which is an explosive, wherein the wireless initiating detonator is attached to the primary charge, wherein when the display device is attached to the wireless initiating detonator via the cable, the length of the cable is set to a length such that the display device can reach the outside of the blast hole when the explosive unit is charged into a blast hole. Accordingly, the explosive unit can be appropriately configured. 
         [0026]    When the display device is attached to the wireless initiating detonator via the cable, the display device, displaying the individual information, sticks out of the blast hole. Therefore, when a malfunction occurs with the wireless initiating detonator, an operator can easily identify the malfunctioned wireless initiating detonator without taking it out of the blast hole. 
         [0027]    According to still another aspect of the present invention, there is provided a wireless initiation system including: the explosive unit according to the above aspect; a blasting controller disposed at a remote position away from the blast hole, and configured to be able to wirelessly transmit the transmission signal to the wireless initiating detonator and to wirelessly receive a response signal from the wireless initiating detonator; and a blasting controller antenna used by the blasting controller for wireless communication, and useable for both signal transmission and signal reception without an antenna only for signal transmission and an antenna only for signal reception being separately provided. 
         [0028]    The blasting controller antenna has a substantial loop shape. When the controller receives the transmission signal from the blasting controller, the controller prepares a response signal corresponding to the received transmission signal, and transmits the prepared response signal with a response frequency higher than the operation frequency via the detonator antenna. The response frequency is set to a frequency corresponding to a wavelength longer than the loop length of the blasting controller antenna. 
         [0029]    Due to this configuration, since the frequency of a signal transmitted from the blasting controller to the wireless initiating detonator is set to be greater than or equal to 100 kHz, and to be less than or equal to 500 kHz, it is possible to reduce the number of turns of the blasting controller antenna to less than or equal to 1/10 of that when the frequency is set to be 10 kHz. Accordingly, it is possible to further reduce an amount of time required to extend the blasting controller antenna in the vicinity of the blasting face. Therefore, it is possible to further reduce an amount of time required to perform work in the vicinity of the blasting face. Since the response frequency of a signal from the wireless initiating detonator is set to a frequency corresponding to a wavelength longer than the length of the blasting controller antenna, it is possible to prevent the occurrence of standing waves, and to improve the reliability of signal transmission and signal reception. Here, the loop length of the blasting controller antenna refers to the total extension length of the blasting controller antenna wound in a substantial loop shape. 
         [0030]    In the wireless initiation system according to the above aspect, it is preferred that the response frequency may exceed the operation frequency, and is less than or equal to 10 MHz. Accordingly, it is possible to set an appropriate response frequency such that the occurrence of standing waves can be prevented, and to improve the reliability of signal transmission and signal reception. 
         [0031]    According to still another aspect of the present invention, there is provided a wireless initiation method for blasting using the above-mentioned explosive unit, and the blasting controller configured to wirelessly transmit a transmission signal to the wireless initiating detonator and to wirelessly receive a response signal from the wireless initiating detonator. The method includes: a step of drilling the blast hole in the blasting face; a step of charging the explosive unit into the blast hole; a step of extending the blasting controller antenna in a substantial loop shape at a position away from the blasting face at a predetermined distance, the blasting controller antenna being used by the blasting controller for wireless communication, and the length of the blasting controller antenna being set to a length shorter than a wavelength corresponding to the response frequency of the response signal; a step of transmitting a preparation start signal with an operation frequency, greater than or equal to 100 kHz, and less than or equal to 500 kHz, from the blasting controller via the blasting controller antenna, the preparation start transmission signal causing the wireless initiating detonator to prepare for initiation; a step of starting the preparation of initiation using the controller when the preparation start signal is received via the detonator antenna; a step of transmitting a preparation completion signal with the response frequency, exceeding the operation frequency corresponding to a wavelength longer than the length of the blasting controller antenna, and less than or equal to 10 MHz, from the controller to the blasting controller via the detonator antenna when preparation is completed, the preparation completion signal being a response signal indicative of the completion of preparation; a step of transmitting an initiation execution signal, which is a transmission signal indicative of the execution of initiation, from the blasting controller when the preparation completion signal is received via the blasting controller antenna; and a step of igniting the initiating explosives and initiating the blasting of the primary charge using the controller when the initiation execution signal is received via the detonator antenna. 
         [0032]    Due to this configuration, since the operation frequency of a signal transmitted from the blasting controller to the wireless initiating detonator is set to be greater than or equal to 100 kHz, and to be less than or equal to 500 kHz, and the soft magnetic coil antenna is used as the detonator antenna, it is possible to realize the wireless initiation method by which it is possible to further reduce an amount of time required to perform work in the vicinity of the blasting face, that is, an amount of time for adjusting the directivity of the detonator antenna, for the charging step, and for the blasting controller antenna extending step. 
         [0033]    In the wireless initiation method according to the above aspect, when the display device is attached to the wireless initiating detonator via the cable with a length such that the display device can reach the outside of the blast hole, the primary charge may be charged into the blast hole in such a manner that the display device can reach the outside of the blast hole. Accordingly, when a malfunction occurs with a wireless initiating detonator, an operator can easily identify the malfunctioned wireless initiating detonator by comparing individual pieces of information (for example, an initiation delay time or an identification number) displayed on the blasting controller with individual pieces of information displayed on the display device that drops out of the blast hole. Accordingly, it is possible to further reduce an amount of time required to perform work in the vicinity of the blasting face after the wireless initiating detonators are charged into the blast holes. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0034]      FIG. 1  is a view illustrating a wireless blast initiation system  1  used for exploding a blasting face  41  at a tunnel excavation site. 
           [0035]      FIG. 2  is a view illustrating a state in which an explosive unit  20  is charged into a blast hole  40  drilled into the blasting face  41  illustrated in Part II in  FIG. 1 . 
           [0036]      FIG. 3  is a view illustrating an example of the structure of the explosive unit  20 . 
           [0037]      FIG. 4  is a view illustrating an example of the structure of a wireless initiating detonator  10  illustrating Part IV in  FIG. 3 . 
           [0038]      FIG. 5  is a view illustrating an example of the structure of a controller  10 B illustrated in Part V in  FIG. 4 . 
           [0039]      FIG. 6A  is a flowchart illustrating a part of a process sequence of a wireless initiation method. 
           [0040]      FIG. 6B  is a flowchart illustrating another part of the process sequence of the wireless initiation method. 
           [0041]      FIG. 7  is a view illustrating an example of the disposition of a detonator antenna relative to a shell that accommodates an initiator and the controller. 
           [0042]      FIG. 8  is a view illustrating another example of the disposition of the detonator antenna. 
           [0043]      FIG. 9  is a view illustrating still another example of the disposition of the detonator antenna. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0044]    Hereinafter, various examples of the present invention, used at a tunnel excavation site, will be described with reference to the accompanying drawings. 
       Entire Configuration (FIG.  1 ) of Wireless Initiation System and State (FIG.  2 ) of Charging of Explosive Unit Into Blast Hole 
       [0045]    A wireless initiation system  1  is formed of an explosive unit  20  charged into a blast hole  40  that is drilled into a blasting face  41 ; a blasting controller  50  that is disposed at a remote position away from the blast hole  40 , and can wirelessly transmit and receive signals to and from the explosive unit  20 ; a blasting controller antenna  60  that extends in the vicinity of the blasting face  41 . 
         [0046]    For example, the blast hole  40  is a hole drilled with a diameter D 1  of approximately 5 cm and a depth D 2  of approximately 2 m, and the blast hole  40  is not limited to a specific size. 
         [0047]    As illustrated in  FIGS. 3 and 4 , a wireless initiating detonator  10  is formed of an initiator  10 A; a controller  10 B; a shell  10 X that accommodates the initiator  10 A and the controller  10 B; and an antenna unit  10 C. The antenna unit  10 C is formed of a substantially loop-like detonator antenna  30 , and a leading wire  31 , one end of which is connected to the controller  10 B and the other end is connected to the detonator antenna  30 . The wireless initiating detonator  10  is charged into the blast hole  40  along with a primary charge  13 A which is a foremost explosive  13  charged into the blast hole  40 , and into which the wireless initiating detonator  10  is inserted, and secondary charges  13 B that are explosives  13 , the quantity of which is appropriately increased or decreased unlike the primary charge  13 A. 
         [0048]    As illustrated in  FIG. 3 , the explosive unit  20  is formed of the explosives  13  and the wireless initiating detonator  10 , and the explosive unit  20  may include only the primary charge  13 A, or the secondary charges  13 B in addition to the primary charge  13 A. As illustrated in  FIG. 2 , the explosive unit  20  is charged into the blast hole  40  while a protective cap  21 , made of an elastic material such as rubber, is fitted to a leading end of the explosive unit  20 , and a trailing end of the explosive unit  20  is covered with a tamping material  22  such as clay. The length of the leading wire  31  may be set to a length such that the detonator antenna  30  can reach the outside of the blast hole  40  when the explosive unit  20  is charged into the blast hole  40 , or as illustrated in  FIG. 2 , the length of the leading wire  31  may be set to a length such that the detonator antenna  30  can be disposed in the blast hole  40 . Alternatively, as illustrated in  FIGS. 7 and 8 , without the leading wire  31 , the detonator antenna  30  may be disposed on the axis of the shell  10 X while being in contact with the shell  10 X, or may be wound around the shell  10 X while being in contact with the shell  10 X. The protective cap  21  works to protect the leading wire  31 , and to reduce shocking to the explosive unit  20  when being charged; however, the protective cap  21  may be omitted. 
         [0049]    A display device  72  displays individual pieces of information (for example, a blast initiation delay time or an identification number) by which an operator can identify the wireless initiating detonator  10 , and is attached to the wireless initiating detonator  10  via a cable  71 . The length of the cable  71  is set to a length such that the display device  72  can reach the outside of the blast hole  40  when the primary charge  13 A is charged into the blast hole  40 . Accordingly, as illustrated in  FIG. 2 , when the primary charge  13 A is charged into the blast hole  40 , the display device  72  is disposed outside of the blast hole  40 . The cable  71  and the display device  72  may be omitted. 
         [0050]    The blasting controller antenna  60  is connected to the blasting controller  50  via a firing cable  62  and a connecting cable  61 . A new blasting controller antenna  60  and a new connecting cable  61  are extended with each blasting. The blasting controller antenna  60  extends along a tunnel floor  42 , a tunnel side wall  43 , and a tunnel ceiling  44  at a position apart from the blasting face  41  by a distance L 1  of approximately 1 m or the like. For example, a distance L 2  between a leading end of the firing cable  62  and the blasting face  41  is approximately 30 m. For example, a distance L 3  between the leading end of the firing cable  62  and the blasting controller  50  is approximately 70 m. 
         [0051]    The blasting controller  50  wirelessly transmits a transmission signal via the firing cable  62 , the connecting cable  61 , and the blasting controller antenna  60 , and an operation frequency, which is the frequency of the transmission signal, is greater than or equal to 100 kHz, and is less than or equal to 500 kHz. When the operation frequency is greater than 500 kHz, standing waves are likely to occur in a tunnel, and an operation frequency greater than 500 kHz is not preferable. 
         [0052]    The blasting controller  50  receives a response signal from the controller  10 B of the wireless initiating detonator  10  via the blasting controller antenna  60 , the connecting cable  61 , and the firing cable  62 . A response frequency, which is the frequency of the response signal from the wireless initiating detonator  10 , exceeds the operation frequency, and is 10 MHz. 
         [0053]    As one example, it is possible to limit the number of turns of the blasting controller antenna  60  to one turn or approximately several turns by setting the operation frequency to a frequency which is greater than or equal to 100 kHz and is less than or equal to 500 kHz. Electric power is supplied to the controller  10 B of the wireless initiating detonator  10 , and ignition energy is stored via the transmission signal with the operation frequency. The transmitted electric power for the supply of electric power to the controller  10 B and the storage of electric power can be a relatively small electric power of approximately several tens of W to approximately several hundreds of W. It is possible to configure the detonator antenna  30  as one soft magnetic coil antenna for signal transmission and reception without separately preparing an antenna only for signal transmission and an antenna only for signal reception. It is possible to reduce the diameter of the detonator antenna  30  to a size smaller than equal to that of the blast hole. 
         [0054]    For example, when the operation frequency is 200 kHz, λ/2 is equal to 750 m (λ/2=[v/f]/2=[(30*10 7 )/(200*10 3 )]/2), wherein λ/2 is the length of the detonator antenna such that the wireless initiating detonator can receive a signal most efficiently; however, a very light and small soft magnetic coil antenna can draw sufficient energy, the soft magnetic coil antenna being obtained by winding a conductive wire around a soft magnetic material in approximately several tens of turns. The soft magnetic material is a material with a high magnetic permeability, the magnetic poles of which are relatively easily eliminated or reversed among magnetic materials. The soft magnetic material may be iron, silicon steel, permalloy, sendust, permendur, ferrite, an amorphous magnetic alloy, a nanocrystalline magnetic alloy, or the like, and typically, ferrite is used as the soft magnetic material. 
         [0055]    The soft magnetic coil antenna as one example of the detonator antenna  30  can very efficiently draw energy compared to that in the related art. Since the operation frequency is high, a wavelength λ is short compared to that in the related art, and the detonator antenna  30  easily draws energy. Since the wireless initiating detonator has a good signal receiving efficiency, an output energy of the transmission signal is not required to be as high as that in the related art, and one to approximately several turns of the blasting controller antenna may be used. 
         [0056]    The soft magnetic coil antenna in the blast hole can be used in common as a transmission antenna for transmitting a response signal from the wireless initiating detonator to the blasting controller. When the response frequency is 10 MHz, the length of a signal receiving antenna of the blasting controller is preferably set not to exceed the wavelength λ (in this case, 30 m) of the response frequency, and one to several turns of the blasting controller antenna can be used in common as the signal receiving antenna. 
         [0057]    In a method in the related art in which the operation frequency is less than or equal to 10 kHz, as described above, it is necessary to wind the blasting controller antenna for transmitting a transmission signal in approximately 40 turns to approximately 500 turns, a dipole antenna for receiving a response signal from the wireless initiating detonator is needed, and a considerably large amount of time is required to perform work in the vicinity of the blasting face. In the example of the present invention, since the winding of the blasting controller antenna  60  in one turn to approximately several turns is good enough, and the dipole antenna only for signal reception is not needed, it is possible to end an extending operation for extending the blasting controller antenna  60  in the vicinity of the blasting face in a very short amount of time compared to that in the related art. 
         [0058]    In the method in the related art in which the operation frequency is less than or equal to 10 kHz, as described above, it is necessary to dispose a complicated and heavy element, obtained by winding a conductive wire around a ferrite core with a diameter of approximately 50 mm multiple times, at the bottom in the blast hole, and to drop a wire-like antenna out of the blast hole. In the example of the present invention, it is good enough only to insert the wireless initiating detonator into an explosive which is the primary charge, a very light and small ferrite rod antenna (obtained by winding a conductive wire around a ferrite rod in approximately several tens of turns) as the soft magnetic coil antenna being attached to the wireless initiating detonator, and only to insert the primary charge into the blast hole. In addition, in the example, since it is possible to limit the diameter of the detonator antenna  30  to a diameter smaller than or equal to that of the blast hole, it is possible to set the wireless initiating detonator  10 , to which the detonator antenna is attached, in a charging apparatus without being disturbed. As a result, it is possible to end a charging operation for charging the wireless initiating detonator  10  into the blast hole  40  in a shorter time. 
       Structure (FIGS.  3  to  5 ) of Wireless Initiating Detonator and Process Sequence (FIGS.  6 A and  6 B) of Wireless Initiation Method  
       [0059]    Subsequently, the structure of the wireless initiating detonator  10  will be described in detail with reference to  FIGS. 3 to 5 . The leading explosive  13  from the explosives charged into the blast holes  40  is the primary charge  13 A into which the wireless initiating detonator  10  is inserted, and which is directly exploded by the wireless initiating detonator  10 . The explosive  13 , disposed behind the primary charge  13 A from the explosives charged into the blast holes  40 , is the secondary charge  13 B that is exploded in connection with the explosion of the primary charge  13 A. The number of secondary charges  13 B is appropriately increased or decreased based on a desirable blasting energy. 
         [0060]      FIG. 4  illustrates a sectional view of the wireless initiating detonator  10 , and the wireless initiating detonator  10  is configured such that the shell  10 X accommodates the initiator  10 A and the controller  10 B, and is sealed with a plug  10 Z. The initiator  10 A has an insulating sleeve  11 A, a fuse head  11 B, an inner tube  11 C, a primary explosive  11 D, a base charge  11 E, and the like. The controller  10 B has a signal transmission and reception unit  12 B, a CPU  12 A, an electric power storage unit  12 C, an electric power charging state detector  12 D, a switch  12 E, an igniter  12 F, an ID storage unit  12 G, and the like. 
         [0061]    Hereinafter, an operation of each configuration element of the controller  10 B will be described with reference to the flowchart illustrated in  FIGS. 6A and 6B . A description hereinbelow will be given on the condition that the operation frequency, which is a frequency of a transmission signal from the blasting controller  50 , is set to 200 kHz, and the response frequency, which is a frequency of a response signal from the wireless initiating detonator  10 , is set to 10 MHz. 
         [0062]    As illustrated in  FIGS. 6A and 6B , in a blast hole drilling step illustrated in step S 10 , an operator drills a plurality of the blast holes  40  in the blasting face  41  using a hole drilling machine or the like, and the procedure proceeds to step S 20 . 
         [0063]    In a charging step illustrated in step S 20 , the operator charges the explosive unit  20  into each of the drilled blast holes  40  using a charging apparatus or the like such that the detonator antenna  30  is positioned in an entrance portion of the blast hole  40  while being oriented so as to be able to efficiently transmit and receive signals, and the procedure proceeds to step S 30 . In the description above, the detonator antenna is disposed in the entrance portion of the blast hole; however, the position of the detonator antenna is not limited to the entrance portion of the blast hole, and it is possible to dispose the detonator antenna at an arbitrary position in the blast hole. 
         [0064]    When the cable  71  and the display device  72  are provided, in the charging step, the operator charges the explosive unit  20  including the primary charge into the blast hole  40  such that the display device  72  reaches the outside of the blast hole  40 , and the procedure proceeds to step S 30 . When the operator charges the explosive unit including the primary charge into the blast hole, the length of the cable  71  is set to a length such that the display device can reach the outside of the blast hole. 
         [0065]    In a blasting controller antenna extending step illustrated in step S 30 , the operator extends the blasting controller antenna  60  along the tunnel floor, the tunnel side wall, and the tunnel ceiling at a position apart from the blasting face  41  by the distance L 1 , and connects together the blasting controller antenna  60 , the connecting cable  61 , the firing cable  62 , and the blasting controller  50 , and the procedure proceeds to step S 40 . The length of the blasting controller antenna  60  is set to a length shorter than a wavelength corresponding to the response frequency of the wireless initiating detonator  10 , that is, the response frequency is set to a frequency corresponding to a wavelength longer than a loop length of the blasting controller antenna. The loop length of the blasting controller antenna refers to the total extension length of the blasting controller antenna wound in a loop shape. 
         [0066]    For example, when the response frequency is 10 MHz, a wavelength is 30 m (=300000 (km/s)/10*10 6  (1/s) according to λ=v/f (wavelength=light velocity/response frequency). When the response frequency is 10 MHz, the blasting controller antenna  60  with a length less than 30 m extends in a substantial loop shape. Accordingly, it is possible to prevent the occurrence of standing waves, and to improve the reliability of wireless communication. Since the blasting controller antenna  60  with this length can extend on the entire circumference of the tunnel when being wound along the tunnel floor, the tunnel side wall, and the tunnel ceiling only in one turn or several turns, it is possible to complete the blasting controller antenna extending operation in a very short amount of time. The length of the blasting controller antenna  60  may be determined after the response frequency is determined Alternatively, the response frequency may be determined after the length of the blasting controller antenna  60  is determined 
         [0067]    In step S 40 , the operator starts to operate the blasting controller  50 . Hereinafter, an operation of the blasting controller  50  and an operation of the controller  10 B of the wireless initiating detonator  10  in association with the operation illustrated in step S 40  performed by the operator will be described. 
         [0068]    In step S 110 , the blasting controller  50  determines whether the operator inputs an instruction indicative of transmitting a preparation start signal causing all the wireless initiating detonators  10  to start initiation preparation. When the instruction is input from the operator (Yes), the procedure proceeds to step S 120 , and when the instruction is not input from the operator (No), the procedure returns to step S 110 , and the blasting controller  50  waits for an input. 
         [0069]    When the procedure proceeds to step S 120 , the blasting controller  50  wirelessly transmits a preparation start signal with the response frequency (in this case, 200 kHz) via the firing cable  62 , the connecting cable  61 , and the blasting controller antenna  60 , and the procedure proceeds to step S 130 . 
         [0070]    A preparation start signal transmitting step can include step S 110  and step S 120 . 
         [0071]    In step S 210 , the CPU  12 A of the controller  10 B of the wireless initiating detonator  10  determines whether the wireless initiating detonator  10  has received the preparation start signal from the blasting controller  50 . When the wireless initiating detonator  10  has received the preparation start signal (Yes), the procedure proceeds to step S 220 , and when the wireless initiating detonator  10  has not received the preparation start signal (No), the procedure returns to step S 210 , and the wireless initiating detonator  10  waits for an input. In this case, the signal transmission and reception unit  12 B in  FIG. 5  detects a transmission signal (in this case, the preparation start signal) directly input from the detonator antenna  30 , or input from the blasting controller  50  via the detonator antenna  30  and the leading wire  31 , and outputs the detected transmission signal to the CPU  12 A. The signal transmission and reception unit  12 B converts the received signal with the response frequency (in this case, 200 kHz) into electric power, and supplies electric power for use in the controller  10 B, and electric power charged into the electric power storage unit  12 C. 
         [0072]    When the procedure proceeds to step S 220 , the CPU  12 A causes the electric power storage unit  12 C to start to store electric power for preparation of initiation, based on the received preparation start signal, and the procedure proceeds to step S 230 . The electric power storage unit  12 C is a capacitor or the like, and can store electrical charge based on a control signal from the CPU  12 A. The CPU  12 A can detect a state of charge of electrical power of the electrical power storage unit  12 C via the electrical power charging state detector  12 D. 
         [0073]    In step S 230 , the CPU  12 A determines whether a state of charge of the electrical power storage unit  12 C has reached a pre-set state of charge based on a detection signal from the electrical power charging state detector  12 D. When the state of charge has reached the set state of charge (Yes), the procedure proceeds to step S 240 , and when the state of charge has not reached the set state of charge (No), the procedure proceeds to step S 220 . 
         [0074]    When the procedure proceeds to step S 240 , the CPU  12 A outputs a preparation completion signal to the signal transmission and reception unit  12 B, the preparation completion signal being a response signal including information indicative of the completion of preparation (of charge), and the procedure proceeds to step S 250 . The preparation completion signal includes ID information read from the ID storage unit  12 G. The blasting controller  50  can appropriately recognize a wireless initiating detonator, the preparation (of charge) of which is completed, using the ID information (ID uniquely pre-assigned to each of the controllers  10 B). The signal transmission and reception unit  12 B outputs a response signal with the response frequency (in this case, 10 MHz) from the CPU  12 A to the blasting controller  50  via the leading wire  31  and the detonator antenna  30 . 
         [0075]    A preparation completion response step can include steps S 210  to S 240 . 
         [0076]    In step S 130 , the blasting controller  50  determines whether the blasting controller  50  has received the preparation completion signal from the wireless initiating detonator  10 . A unique ID is pre-assigned to each of the plurality of wireless initiating detonators  10 , and the preparation completion signal includes ID information. The blasting controller  50  determines whether the blasting controller  50  has received the preparation completion signals from all the wireless initiating detonators. When the blasting controller  50  has received the preparation completion signals from all the wireless initiating detonators  10  (Yes), the procedure proceeds to step S 140 , and when the blasting controller  50  has not received the preparation completion signals from all the wireless initiating detonators  10  (No), the procedure returns to step S 130 , and the blasting controller  50  waits until receiving the preparation completion signals from all the wireless initiating detonators  10 . When the blasting controller  50  does not receive the preparation completion signals from all the wireless initiating detonators  10  even after a predetermined amount of time has elapsed, the operator takes an action for interruption or the like which is not illustrated. 
         [0077]    When the procedure proceeds to step S 140 , the blasting controller  50  determines whether the operator inputs an instruction indicative of the execution of initiation. When the operator inputs the instruction indicative of the execution of initiation (Yes), the procedure proceeds to step S 150 , and when the operator does not input the instruction (No), the procedure returns to step S 140 , and the blasting controller  50  waits for an input. 
         [0078]    When the procedure proceeds to step S 150 , the blasting controller  50  transmits an initiation execution signal with the operation frequency via the firing cable  62 , the connecting cable  61 , and the blasting controller antenna  60 , the initiation execution signal being a transmission signal indicative of the execution of initiation. 
         [0079]    An initiation execution signal transmitting step can include steps S 130  to S 150 . 
         [0080]    In step S 250 , the CPU  12 A of each of the wireless initiating detonators  10  determines whether the CPU  12 A has received the initiation execution signal. In this case, the signal transmission and reception unit  12 B detects a transmission signal (in this case, the initiation execution signal) directly input from the detonator antenna  30 , or input from the blasting controller  50  via the detonator antenna  30  and the leading wire  31 , and outputs the detected transmission signal to the CPU  12 A. The CPU  12 A determines whether a signal input from the signal transmission and reception unit is the initiation execution signal. When the CPU  12 A has received the initiation execution signal (Yes), the procedure proceeds to step S 260 , and when the CPU  12 A has not received the initiation execution signal (No), the procedure returns to step S 250 , and the CPU  12 A waits until the initiation execution signal is transmitted. When the initiation execution signal is not transmitted even after a predetermined amount of time has elapsed, the CPU  12 A determines that this event is timed out, causes the electrical power storage unit  12 C to dissipate charged energy, and ends the process. 
         [0081]    When the procedure proceeds to step S 260 , the CPU  12 A ignites the initiator  10 A and initiates the detonator  10 . In this case, the CPU  12 A supplies energy charged into the electrical power storage unit  12 C to the igniter  12 F by operating the switch  12 E, ignites the initiator  10 A, and initiates the primary charge  13 A and the secondary charges  13 B. 
         [0082]    In the example of the wireless initiation system described above with reference to  FIGS. 1 to 5 , the frequency of a signal transmitted from the blasting controller  50  is set to be greater than or equal to 100 kHz, and to be less than and equal to 500 kHz, and thus it is possible to configure the detonator antenna  30  as a light, small, and soft magnetic coil antenna made of a soft magnetic material, and to reduce the diameter of the detonator antenna  30  to a size smaller than or equal to that of the blast hole. Accordingly, it is possible to install the detonator antenna at an arbitrary position in the blast hole, or to drop the detonator antenna out of the blast hole. As illustrated in  FIGS. 7 to 9 , when the wireless initiating detonator  10  is charged into the blast hole while being attached to the explosive  13 , the detonator antenna  30  is disposed on the axis of the shell  10 X while being in contact with the shell  10 X (refer to  FIG. 7 ) that accommodates the initiator  10 A and the controller  10 B of the wireless initiating detonator  10 , is wound around the shell  10 X while being in contact with the shell  10 X (refer to  FIG. 8 ), or is installed in the blast hole at a remote position via the leading wire while not being in contact with the shell  10 X, and being oriented in a predetermined direction (direction in which the detonator antenna  30  can efficiently transmit and receive signals, and can satisfactorily perform the wireless supply of electric power and wireless communication). 
         [0083]    Accordingly, it is possible to easily set the orientation of the detonator antenna  30  along the axial direction of the blast hole. As a result, when the detonator antenna drops out of the blast hole, it is not necessary to adjust the orientation of each detonator antenna. Accordingly, it is possible to further reduce an amount of time required to perform work in the vicinity of the blasting face. The detonator antenna  30  may drop out of the blast hole. 
         [0084]    The soft magnetic coil antenna can receive a transmission signal and transmit a response signal, and as in the related art, an antenna only for transmission signal reception and an antenna only for response signal transmission are not needed. Accordingly, it is possible to further reduce an amount of time required to charge the primary charge  13 A with the wireless initiation detonator  10  into the blast hole  40 . 
         [0085]    It is good enough to set the frequency of a response signal from the wireless initiating detonator  10  to a frequency which is greater than or equal to 1 MHz and is less than or equal to 10 MHz, and it is good enough to set the length of the blasting controller antenna  60  to a length such that the blasting controller antenna  60  can be wound along the tunnel floor, the tunnel side wall, and the tunnel ceiling in one turn or approximately several turns. The blasting controller antenna  60  can transmit a transmission signal and receive a response signal, and as in the related art, an antenna only for transmission signal transmission and a dipole antenna only for response signal reception are not needed. Accordingly, it is also possible to further reduce an amount of time required to extend the blasting controller antenna. 
         [0086]    Since blasting may cause the occurrence of invisible internal damage in the blasting controller antenna  60 , for reasons of safety, the blasting controller antenna  60  re-extends every blasting. For this reason, it is possible to reduce a considerable amount of time required to extend the blasting controller antenna  60 , wound simply in one turn or several turns in this application, from that required to extend 40 turns to 500 turns of the antenna and the dipole antenna in the related art, and it is possible to improve the safety of a blasting operation. 
         [0087]    In the example of the wireless initiation method described with reference to  FIGS. 6A and 6B , it is possible to further reduce an amount of time required to perform work in the vicinity of the blasting face, and it is possible to explode the blasting face more safely. 
         [0088]    When a malfunction occurs with a wireless initiating detonator after being charged into the blast hole, since the display device is attached to the wireless initiating detonator, and sticks out of the blast hole, the operator can easily identify the malfunctioned wireless initiating detonator by comparing individual pieces of information (regarding the malfunctioned wireless initiating detonator) displayed on the blasting controller with individual pieces of information displayed on the display device that drops out of the blast hole. Therefore, the operator can further reduce working hours. 
         [0089]    Various examples of the present invention have be specifically described; however, it is apparent to persons skilled in the art that the appearance, structure, configuration, and process in the wireless initiation system, the wireless initiation method, the wireless initiating detonator, and the explosive unit are not limited to those in the examples described herein, and modifications, additions, and removals can be made to the examples in various forms insofar as the modifications, additions, and removals do not depart from the scope of the present invention. 
         [0090]    The use of the aforementioned wireless blast initiation system and wireless initiation method is not limited to a tunnel excavation site, and the wireless initiation system and the wireless initiation method can be applied to an explosive operation in various blasting sites. 
         [0091]    In the example described above, the display device  72  is attached to the wireless initiating detonator  10  via the cable  71 ; however, the display device  72  may be directly attached to the wireless initiating detonator  10 . When the display device is directly attached to the wireless initiating detonator  10 , the operator cannot check the display device after the wireless initiating detonator  10  is charged into the blast hole; however, the operator can charge the wireless initiating detonator  10  into the blast hole while checking the display device.