JP2019072960A - Core bit, inverter control core drill, and method of dry-drilling concrete - Google Patents

Abstract

To provide a core bit, an inverter control core drill equipped with the core bit, and a method of dry-drilling concrete that enable high-speed rotation when drilling concrete and efficient and quick dry-drilling in which cutting chips are jetted up even without feeding cooling water.SOLUTION: A core bit 2 for drilling concrete of this invention includes: a blade tip 20a sintered with diamond chips or cemented carbide chips and a cylindrical bit body 20b at a tip of which the blade tip 20a is bonded. An outer diameter D1 of the blade tip 20a is larger than an outer diameter D2 of the bit body 20b so that a gap is formed outside the bit body 20b when performing drilling. In the blade tip 20a one or plural notches 20c each including an inclined taper face 20d are formed to reduce drilling resistance and to discharge cutting chips.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a core drill for concrete drilling, which drills a relatively large diameter hole in a concrete structure in construction, civil engineering, road construction, etc. More specifically, an electric motor driven by a three-phase AC power supply, and The present invention relates to an inverter control core drill provided with an inverter for controlling an electric motor.

  Conventionally, a core drill has been known in which a shaft having a core bit attached to its tip is rotationally driven by an electric motor, and a concrete structure is abraded by a blade portion at the tip of the core bit. In a general conventional core drill, a 100 V AC power supply is converted to DC by a converter, and a core bit is rotationally driven by a DC electric motor for drilling. For this reason, although the conventional core drill can rotate at a high speed of 8000 rpm or more, the torque at high speed rotation is weak, and when drilling a concrete structure, it can not be drilled in a short time by high speed rotation. There was a problem.

  Also, in the conventional core drill, while cooling water is supplied to the drilled hole to cool the cutting edge of the core bit, and the cutting water is not washed away by the cooling water, the core bit at the bottom of the drilled hole There is also a problem that cutting chips accumulate between the cutting edge of the steel and the concrete and it becomes impossible to drill holes. For this reason, a device for circulating water is required, and there is a problem that the device becomes large and there is a possibility of electric leakage if water such as a repair work of an underground pit is used, or the water supply is difficult. There is a problem that drilling is difficult when water can not be used in cases such as civil engineering work in remote areas.

  In order to solve such a problem, for example, Patent Document 1 discloses a dry drilling method. In the dry drilling method described in Patent Document 1, the compressed air supplied from the inside of the main body of the core bit toward the tip is circulated to the outer peripheral portion of the main body through the interval portion of the diamond tip which is the cutting edge, and the outer peripheral portion of the main body together with the chips. Perforation is carried out while discharging to the outside along the direction (see claim 1 of the patent document 1, paragraphs [0016] to [0019] of the specification, FIG. 1 etc. of the drawing).

  However, although the dry drilling method described in Patent Document 1 does not require water, it requires a compressor and a dust collector, and as in the case of supplying water, it is possible to solve the problem that the apparatus becomes large. It was not. Also, the core drill used in the dry drilling method described in Patent Document 1 is a core drill of a conventional direct current electric motor, and the torque at high speed rotation is weak, and when drilling a concrete structure, the high speed rotation is performed. There is a problem that it can not be drilled in a short time.

  Further, Patent Document 2 discloses a core bit in which at least one of a cylindrical body and a tube has a groove for swarf discharge formed on the peripheral surface of either or both of the inner and outer peripheral surfaces. (Refer to claim 1 of patent claim 2, paragraphs [0017] to [0020] of the specification, FIG. 7 etc. of the drawing).

  In the core bit described in Patent Document 2, even if the gap between the body or the tube and the work material is small or almost eliminated due to the wear of the side surface of the diamond tip, the groove may be chipped even if chips are clogged. It is said that it can function as a discharge path for cooling medium and continue the drilling process.

  However, the core bit described in Patent Document 2 is also unchanged from being rotationally driven by the core drill of the conventional DC electric motor, and the torque at high speed rotation is weak, and when drilling a concrete structure, the speed is short at high speed. It has not been possible to solve the problem of not being able to drill in time. Also, the core bit described in Patent Document 2 is also premised on circulating water as a cooling medium, and when water can not be used, the problem that drilling is difficult and the problem of upsizing of the device still remain. It was not resolved.

JP 2001-49979 A JP, 2010-82812, A

  Therefore, the present invention has been devised in view of the above-mentioned problems, and the purpose of the present invention is to enable high-speed rotation at the time of concrete drilling and to blow up cutting chips without supplying cooling water. It is an object of the present invention to provide a core bit capable of efficiently performing dry drilling in a short time, an inverter-controlled core drill equipped with the core bit, and a method of dry drilling concrete.

  The core bit according to claim 1 is a core bit for drilling concrete, comprising a cutting edge on which a diamond tip or a cemented carbide tip is sintered, and a cylindrical bit body having the cutting edge joined to the tip, The outer diameter of the cutting edge is larger than the outer diameter of the bit body so that a gap is formed on the outer side of the bit body at the time of drilling, and cutting resistance is reduced and the cutting edge of the cutting edge is reduced. It is characterized in that one or more oblique notches having inclined tapered surfaces are formed for discharging.

  The core bit according to claim 2 is characterized in that in the core bit according to claim 1, the joint between the cutting edge and the bit body is welded by laser welding.

  The inverter control core drill according to claim 3 is a core drill for concrete for drilling concrete, comprising: an electric motor for rotationally driving a core bit with a three-phase AC power supply, and an inverter for controlling the electric motor, the inverter The output frequency and the output current to the electric motor can be set freely, and the rotation speed at the time of drilling of the electric motor can be set freely, and the core bit according to claim 1 or 2 is mounted. It is characterized by

  The inverter control core drill according to claim 4 is characterized in that, in the inverter control core drill according to claim 3, the rotation speed at the time of concrete drilling of the electric motor is set to at least 4500 rpm and less than 8000 rpm by the inverter. Do.

  The dry drilling method of concrete according to claim 5 is a dry drilling method of concrete for dry drilling concrete, wherein the electric control is performed by the inverter using the inverter controlled core drill according to claim 3 or 4 A motor is controlled to drill the core bit at a rotational speed of at least 4500 rpm and less than 8000 rpm at the time of concrete drilling.

  According to the core bit or the inverter control core drill according to claims 1 to 4, high speed rotation at the time of concrete drilling can be made possible, and cutting chips can be blown out without supplying cooling water to efficiently carry out dry drilling in a short time. Is possible.

  In particular, according to the core bit according to claim 2, in addition to the functions and effects described above, since the joining between the cutting edge and the bit body is welded by laser welding, unlike the general core bit, the melting point is higher than that of the base metal. Since it is not brazing joining via a low alloy, there is little possibility that the chip will be worn away by the frictional heat at the time of drilling and the drilling efficiency will be reduced.

  In particular, according to the inverter control core drill according to claim 3, since it is an inverter control core drill (high frequency core drill) provided with an inverter for controlling an electric motor that rotationally drives the core bit by a three-phase AC power supply This enables high-speed rotation during concrete drilling. In addition, since an oblique notch is formed and a core bit with a gap formed between the hole and the bit body is attached, drilling is performed with high-speed rotating wind pressure without supplying cooling water. The chips can be sprayed from the concrete surface in a tornado shape and discharged out of the hole. Therefore, dry drilling can be efficiently performed in a short time even if the drilled hole is deep.

  In particular, according to the inverter control core drill according to claim 4, in addition to the above-mentioned operation and effect, the rotational speed at the time of concrete drilling is set to at least 4500 rpm and less than 8000 rpm. , There is little risk of carbonization (graphitization) exceeding 600 ° C.

  According to the dry drilling method of concrete according to the fifth aspect of the present invention, high torque can be achieved during high speed rotation, and even with dry drilling, high speed rotation can be achieved during concrete drilling. In addition, since an oblique notch is formed and drilling is performed by the core bit in which a gap is formed between the hole and the bit body, the wind pressure of high-speed rotation does not supply cooling water but at the time of drilling Cutting chips can be blown out of the concrete surface in a tornado shape and discharged out of the hole. Therefore, dry drilling can be efficiently performed in a short time even if the drilled hole is deep. In addition, since the electric motor is controlled by the inverter and the rotation speed of the core bit at the time of concrete drilling is drilled at not less than 4500 rpm and less than 8000 rpm, the edge of the core bit carbonizes over 600 ° C due to frictional heat with concrete (graphitization Less likely to

It is a side view showing typically the composition of the inverter control core drill concerning the embodiment of the present invention. It is a look-down perspective view which shows the core bit which concerns on 1st Embodiment of the inverter control core drill same as the above. It is a figure which shows the bit main body of the core bit same as the above, (a) is a front view which shows a core bit main body, (b) is the bottom view. It is a bottom perspective view which shows the blade edge shape of the bit main body same as the above. It is a bottom perspective view which shows the blade-tip shape of the bit main body which concerns on 2nd Embodiment which is another form of the bit main body same as the above.

  Hereinafter, an inverter control core drill and a core bit according to an embodiment of the present invention will be described with reference to the drawings.

<Inverter control core drill>
First, a core drill 1 which is an inverter control core drill according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a side view schematically showing the configuration of the core drill 1. As shown in FIG. 1, the core drill 1 comprises a core bit 2 according to a first embodiment of the present invention, a drilling means 3 for rotating the core bit 2 to drill a concrete structure C, and the drilling means It comprises the guide means 4 for guiding the movement of the No. 3 toward the concrete structure C, the control means 5 for controlling the drilling means 3, and the like. The core bit 2 will be described in detail later.

(Pore drilling means)
The drilling means 3 is a drilling machine provided with a main motor 30 of the core drill 1 and a rotation shaft of the main motor 30, and a shaft 31 to which the core bit 2 is attached at its tip.

  The main motor 30 is an electric motor composed of a squirrel cage induction motor driven by a three-phase alternating current power supply via a control means 5 described later. The main motor 30 according to the present embodiment is a high-speed, high-torque type capable of high-speed rotation at 4500 rpm or more when mounting the core bit 2 and drilling a concrete structure C (high frequency motor, for example, working frequency 280 to 380 Hz: Upper limit value 400 Hz)

(Guide means)
The guide means 4 is configured to be linearly movable (liftable) along a base 41 mounted or fixed on the surface of the concrete structure C, a support 41 erected on the support 40, and the support 41. The guide member 42 and the positioning plate 43 for positioning the drilling position are included. The guide means 4 has a function of guiding so that the rotation of the drilling means 3 does not shake.

  The base 40 is bolted to the concrete structure C with an anchor bolt or the like, or is adsorbed and fixed to the concrete structure C with a vacuum pump or the like (not shown). For this reason, the guide means 4 can be fixed to any of the horizontal surface and the vertical surface of the concrete structure C.

  The support column 41 is erected substantially perpendicularly to the base 40, and a rack 41a, which is a linear gear meshed with a pinion gear described later, is formed on one side surface.

  The guide member 42 has a pinion gear (not shown) rotated by the handle 42a at a position of the support column 41 facing the rack 41a, and the pinion gear is rotated by turning the handle 42a and meshes with the rack 41a. Linear movement is possible along the column 41.

  A feed motor 44 is attached to the guide member 42 for rotating the above-mentioned pinion gear to move the guide member 42 along the rack 41 a of the support column 41. Similarly to the main motor 30, the feed motor 44 is also an electric motor composed of a squirrel cage induction motor driven by a three-phase AC power supply, and the setting of the rotational speed is freely performed by an inverter described later.

  The positioning plate 43 is attached to the side surface of the base 40 to position the drilling position of the core bit 2 and ensure the verticality of the shaft 31 which is the rotation axis of the core bit 2 with respect to the surface of the concrete structure C. It is a plate.

  It is needless to say that the guide means 4 is not an essential component of the present invention, and a worker may drill the core drill 1 without the guide means 4 by hand.

(Control means)
As shown in FIG. 1, the control means 5 is connected to a three-phase AC power supply, and in a control box 50 which is a housing, two inverters 51 and 52 for controlling the main motor 30 and the feed motor 44 described above. It is a control means of the so-called variable voltage variable frequency control (VVVF control) system.

  The control means 5 includes a display panel (not shown), and can set and control the output frequency of each motor, the number of rotations of the motor, the output current, and the like arbitrarily via the display panel. That is, the control means 5 arbitrarily sets the rotational speed, the torque setting, etc. according to the voltage / frequency characteristics of the torque of the main motor 30 and the feed motor 44 by the respective inverters 51 and 52 by inputting by the display panel. be able to.

  In the core drill 1 according to the present embodiment, the rotational speed at the time of concrete drilling of the main motor 30 is set to at least 4500 rpm and less than 8000 rpm by the inverter 51. The rotation speed at drilling is set at 4500 rpm or more because the core bit 2 is rotated at high speed, and the cutting pressure at the time of drilling is blown out from the concrete surface in a tornado-like manner by the wind pressure. It is because it can be discharged out of h1.

  Further, the reason that the rotation speed at the time of drilling is set to less than 8000 rpm is that there is less possibility of carbonization (graphitization) of the cutting edge of the core bit 2 exceeding 600 ° C. by frictional heat with concrete.

  On the other hand, in the conventional core drill which performs dry drilling, cutting waste is pushed up out of the hole along the groove etc. and discharged, but when cutting is always accumulated in the bottom of the drilling hole It had become. For this reason, at the time of drilling, cutting chips mixed with diamond chips dropped from the cutting edge are always present between the cutting edge of the core bit and the concrete, and the drilling efficiency was poor. In addition, when cutting chips are accumulated, heat is difficult to escape, and it is necessary to drill holes at low speed so that the cutting edge of the core bit is not worn away by frictional heat, and the drilling time can not be shortened. That is, in the dry drilling of the conventional core drill, the rotation speed at the time of concrete drilling can not be set to 4500 rpm or more.

  And the control means 5 is also equipped with a main fault electric leakage breaker which judges that it is a short circuit and shuts off the output current when the output current becomes equal to or more than a predetermined value (for example, 30 mA).

  The inverter 51 for the main motor 30 according to the present embodiment is an inverter of model number FRN 3.7E1S-2J manufactured by Fuji Electric Co., Ltd., and the inverter 52 for the feed motor 44 according to the present embodiment is a Fuji Electric Co. The inverter of model number FRN0.1E1S-2J. Since these two inverters 51 and 52 are extremely small, they can be housed in a small control box 50, and the entire core drill 1 can be made compact. For this reason, it can be made smaller than the core drill of the conventional direct current electric motor, and it is easy to carry by one person.

  Furthermore, the inverter 51 for the main motor 30 separates the output current flowing to the main motor 30 from the main motor 30 when the output current flowing to the main motor 30 becomes a constant value or more with respect to the rated current at normal times except startup. It is set to cut off the current. This is to prevent the internal reinforcement bars and the like of the concrete structure C from being cut accidentally. Here, the constant value or more means, for example, the case where the output current reaches a predetermined ratio or more with respect to the rated current at the normal time, such as stopping when the output current reaches 120% of the rated current. pointing.

<Core bit>
First Embodiment
Next, the core bit 2 according to the first embodiment of the present invention will be described in detail with reference to FIGS. FIG. 2 is a looking down perspective view showing the entire core bit 2 according to the first embodiment of the core drill 1 described above. 3 (a) is a front view showing the core bit body 20 of the core bit 2, and FIG. 3 (b) is a bottom view thereof. FIG. 4 is a bottom perspective view showing the shape of the cutting edge of the bit body 20. As shown in FIG.

  As shown in FIG. 2, the core bit 2 according to the present embodiment includes a core bit body 20, a tube 21 extending according to the depth of a hole for drilling the core bit body 20, and a cup connected with the shaft 31 described above It is a three-point core bit composed of a ring 22 and the like. The core bit body 20, the tube 21, and the coupling 22 are screwed together and joined. In addition, the arrow of FIG. 2 is an arrow which shows the normal rotation direction of the core bit 2 at the time of drilling.

  Although a three-point core bit is exemplified as the core bit 2 according to the present embodiment, even a two-point core bit in which the core bit body 20 and the tube 21 are integrated or a single-point core bit in which the whole is integrated. It goes without saying that it is good.

  As shown in FIGS. 3 and 4, the core bit body 20 is a concrete drilling hole provided with a cutting edge 20a in which a diamond tip is sintered and a cylindrical bit body 20b in which the cutting edge 20a is joined to the tip. Core bits. Of course, the cutting edge 20a may not be a diamond tip but may be a sintered hard metal tip. In short, the core bit according to the present invention may be a core bit capable of drilling a concrete structure C.

  The joint between the cutting edge 20a and the bit body 20b is welded by laser welding, and the base materials of the cutting edge 20a and the bit body 20b melt and integrate with each other. For this reason, unlike a general core bit, since it is not brazed joining through an alloy having a melting point lower than that of the base material, there is little possibility that the chip is worn away by frictional heat at the time of drilling and the drilling efficiency is lowered. Note that laser welding refers to a welding method in which laser light is irradiated to a metal as a heat source in a condensed state, and the metal is locally heated to melt and solidify to join.

  Further, as shown in FIG. 3A, the outer diameter D1 of the cutting edge 20a is larger than the outer diameter D2 of the bit body 20b. For this reason, at the time of drilling, a gap for discharging cutting waste is formed between the hole h1 (see FIG. 1) drilled by the cutting edge 20a and the bit body 20b.

  Furthermore, as shown in FIG. 3 and FIG. 4, the cutting edge 20 a is formed with an oblique notch 20 c for discharging cutting chips. The oblique notch 20c is a tapered surface 20d in which the rear end side in the rotational direction shown by the arrows in FIGS. 2 and 4 is inclined. For this reason, the area of the tip surface of the cutting edge 20a in contact with the concrete structure C is smaller than the bonding area of the cutting edge 20a welded by laser welding and the bit body 20b, thereby reducing the contact resistance at the time of drilling. be able to. Further, the impact force with the aggregate or the like at the time of drilling which is transmitted to the cutting edge 20a can be reduced by the tapered surface 20d.

  Moreover, since the tapered surface 20d is gently inclined along the rotational direction, the progress of wear and tear due to the friction of the cutting edge 20a starts from an obtuse corner on the tip side of the tapered surface 20d, and the progress of drilling Acts to gradually reduce the contact resistance. That is, in the core bit 2 according to the present embodiment, the diamond chip which has been chipped off from the cutting edge 20a is discharged from the gap between the hole h1 and the bit body 20b or the notch 20c and is not caught during drilling. For this reason, the contact resistance decreases as the amount of the diamond tip from the cutting edge 20a decreases.

  On the other hand, since the tip of the conventional core bit has a flat end face and the notch is a right angle corner (see FIG. 3 of Patent Document 2 etc.), the progress of wear and tear due to friction is generally It was supposed to progress unambiguously. In other words, the diamond tip that was chipped off from the cutting edge of the core bit was to be further crushed by the cutting edge. As a result, the contact resistance increases, leading to a decrease in the drilling efficiency.

  In addition, as shown to Fig.3 (a), the screw part 20e screwed together with the tube 21 is formed in the upper outer peripheral surface of the bit body 20b.

  According to the core drill 1 according to the embodiment described above and the core bit 2 according to the first embodiment, since it is an inverter control core drill (high frequency core drill), high torque can be achieved at high speed rotation, and concrete drilling High-speed rotation is possible. Further, the core bit 2 is formed with an oblique notch 20c, and the outer diameter D1 of the cutting edge 20a is larger than the outer diameter D2 of the bit body 20b. For this reason, the cutting pressure at the time of drilling is spouted from the concrete surface in a tornado shape by wind pressure of high speed rotation (4500 rpm or more) from the gap between the hole h1 (see FIG. 1) drilled by the cutting edge 20a It can be discharged out of the hole h1. Therefore, dry drilling can be efficiently performed in a short time even if the depth of the hole h1 to be drilled is deep.

  In addition, according to the core drill 1 according to the present embodiment, since the rotation speed at the time of concrete drilling is set to at least 4500 rpm and less than 8000 rpm, not only it is possible to spray and discharge cutting chips from concrete surface in a tornado shape. There is little possibility that the cutting edge 20a of the core bit 2 will carbonize (graphitize) over 600 ° C. by frictional heat with concrete.

Second Embodiment
Next, core bits 2 'according to the second embodiment of the present invention will be described in detail using FIG. The core bit 2 'is different from the core bit 2 described above only in the shape of the cutting edge, and therefore, this point is mainly described, and the same configuration is denoted by the same reference numeral and the description is omitted. FIG. 5 is a bottom perspective view showing a cutting edge shape of a core bit body 20 'of a core bit 2' according to a second embodiment of the present invention.

  The core bit 2 ′ according to the second embodiment includes the core bit body 20 ′, the above-mentioned tube 21 screwed with the core bit body 20 ′, the coupling 22 connected with the shaft 31, etc. Is a three-point core bit (see also FIG. 2).

  As shown in FIG. 5, a cutting edge 20a 'of the core bit body 20' is formed with another oblique notch 20c 'of the same shape at a point-symmetrical position in addition to the aforementioned oblique notch 20c. Like the notch 20c, the notch 20c 'is a tapered surface 20d' in which the rear end side in the rotational direction indicated by the arrow is inclined.

  For this reason, the core bit 2 ′ according to the second embodiment has a cutting resistance smaller than that of the core bit 2 described above, and makes it easy to discharge cutting debris at the time of drilling. Therefore, the discharge of cutting chips by the wind pressure of high speed rotation becomes more efficient from the gap with the bit body 20b, and the dry drilling can be performed in a shorter time.

  As mentioned above, although core drill 1 and core bit 2 and 2 'concerning an embodiment of the present invention were explained in detail, any of the embodiments mentioned above or shown in the drawings showed one embodiment embodied in carrying out the present invention It is only a thing. Therefore, the technical scope of the present invention should not be interpreted limitedly by these.

  In particular, as the core bits 2 and 2 'according to the embodiment, although one or two oblique notches 20c and 20c' have been illustrated as an example, there are a plurality of oblique notches having three or more, or a large number And the cutting edge may be saw-shaped. Theoretically, even if the number of oblique notches increases, the cutting resistance decreases and the drilling efficiency improves, so the durability is not significantly affected.

1: Core drill (inverter control core drill)
2, 2 ': core bit 20, 20': core bit body 20a, 20a ': cutting edge 20b: bit body 20c, 20c': oblique notch 20d, 20d ': tapered surface 20e: threaded portion 21: tube 22: coupling 22: coupling 3: Pore forming means 30: Main motor 31: Shaft 4: Guide means 40: Base 41: Post 41a: Rack 42: Guide member 42a: Handle 43: Positioning plate 44: Feed motor 5: Control means 50: Control box 51 : (For main motor) inverter 52: (for feed motor) inverter C: concrete structure h1: hole

Claims (5)

A core bit for drilling concrete, comprising: a cutting edge on which a diamond tip or a cemented carbide tip is sintered; and a cylindrical bit body having the cutting edge joined to the tip,
The outer diameter of the cutting edge is larger than the outer diameter of the bit body so that a gap is formed outside the bit body at the time of drilling.
A core bit characterized in that one or more oblique notches having inclined tapered surfaces are formed on the cutting edge for reducing cutting resistance and discharging chips. The core bit according to claim 1, wherein the joint between the cutting edge and the bit body is welded by laser welding. A core drill for concrete drilling holes,
An electric motor that rotationally drives the core bit with a three-phase AC power supply, and an inverter that controls the electric motor,
With this inverter, the output frequency and output current to the electric motor can be set freely, and the rotation speed at the time of drilling of the electric motor can be set freely,
An inverter control core drill characterized in that the core bit according to claim 1 or 2 is mounted. The inverter control core drill according to claim 3, wherein a rotation speed at the time of concrete drilling of the electric motor is set to at least 4500 rpm and less than 8000 rpm by the inverter. It is a dry drilling method of concrete for dry drilling concrete,
A concrete in which the electric motor is controlled by the inverter using the inverter control core drill according to claim 3 or 4, and the rotation speed of the core bit at the time of concrete drilling is drilled at 4500 rpm or more and less than 8000 rpm. Dry drilling method.

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