JP6963339B1 - Drilling bit and ground drilling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bit for drilling capable of boring by air digging even when the geology of the ground is soft. SOLUTION: The tip surface is on a tip surface of a bit body having a bit head on the side including the tip surface and a cylindrical tubular body formed on the base end side of the bit head with a diameter smaller than that of the bit head. Three or more cutting blades are arranged radially with respect to the center of the bit, and the outer peripheral side end of each cutting blade is in contact with the hole surface which is the outer peripheral surface of the bit head or is outside the hole surface. Arrange so as to protrude. A concave groove-shaped powder discharge groove is formed in the middle of the two adjacent cutting blades on the hole surface from the tip end side to the base end side of the bit head. Then, when the distance from the outer end of each cutting blade to the central axis of the bit body is taken as the drilling radius of the cutting blade, the drilling radius of each cutting blade is partially or completely different. Form to. [Selection diagram] Fig. 1

Description

The present invention relates to a drilling bit used for excavating the ground and a ground drilling method using the bit.

The drilling bits (JIS M 0103: 2003) are specified in various shapes in the Japanese Industrial Standards JIS M 0103: 2003 (terms for boring machines and appliances). Among them, as a technique relating to a drilling bit classified into a metal crown (JIS M 0103: 2003; 3301), for example, the technique described in Patent Document 1-12 is known. The basic configuration of the metal crown type drilling bit is a bit head a having a metal tip (JIS M 0103: 2003; 3303) on the tip surface from the tip to the base end, a cylindrical body b, and the like. It is composed of three parts of a joint portion c having a joint structure for connecting to a boring rod (JIS M 0103: 2003; 5101) (see Patent Document 3 and FIG. 1). The metal chip is generally composed of a cemented carbide such as a sintered tungsten carbide alloy. In each Patent Document 1-12, the shape of the bit head a directly related to the cutting of the ground is mainly devised.

In Patent Document 1, a cross shape (equal width equal length cross line shape, root taper tip gradually widening equal length cross line shape, spiral ray) formed integrally with the tip surface of the bit head a by being radially connected. A drilling bit (a type of cross-chopping bit (JIS M 0103: 2003; 3502)) equipped with a cemented carbide cutting blade (metal tip) with a (spiral ray) curved, etc. long crosshair is described. (See the literature, Fig. 1-Fig. 3). In Patent Document 2-12, for drilling, a metal chip made of cemented carbide is fixed (bitten) to a concave groove formed radially from the center so that the distances from the center are equal to each other. Bits (a type of cross-chopping bit) are listed. In Patent Document 2, the metal chip having a mountain-shaped cross section has an inclined structure in which the upper end thereof becomes higher toward the center side or the peripheral side (see References, FIGS. 2 to 6).

In Patent Document 3, when soft rock is drilled, the bit head is milled powder (dust) during drilling, and rock debris that is crushed by a bit during boring work and is generated at the tip of the drilled hole. It adheres to the outer periphery of part a, and the jamming transition (granular material) of particles such as flour and sand is crowded and clogged, so that it becomes solid from a fluid-like state. It was devised to solve the problem that the rotational resistance of the bit increases and it becomes impossible to drill due to the occurrence of a transition phenomenon that changes to such a state (see Non-Patent Document 2). See page 1, right column, line 15-2, page 1, upper left, line 4). In the drilling bit of the literature, the shape of the bit head a is relatively short in the axial direction near the embedded bottom of the metal chip (4) arranged in the front cross shape, and each metal chip (4) is used. ), The outer peripheral surface (anaguri surface) is provided with a relatively deep and wide head recess (tobu dent) (5) (powder discharge groove). , Fig. 1-Fig. 3, page 2, upper right row 6 lines-lower right row 16 lines). Further, the head recess (5) is provided with a ejection hole (11) for ejecting a pressure fluid (water, air, a liquid mixed with a foaming agent, etc.). Further, the outer diameter of the body portion b is smaller than the outer diameter of the bit head portion a. Further, the length of the joint portion c in the axial direction is shorter than the length in the axial direction of the bit head a, and the outer diameter thereof is smaller than the outer diameter of the bit head a and the outer diameter of the body portion b. Is larger than. Further, on the outer peripheral surface of the joint portion c, relatively shallow but wide joint portion recesses (9) are formed alternately with the land portion (10). In this drilling bit, a mixed fluid of powder generated by drilling and a pressure fluid for discharging the powder to the outside of the hole is easily taken into the head recess (5), and the bit head a Since it does not wrap around the outer peripheral surface, there is no possibility that the powder will adhere to the outer peripheral surface and increase the rotational resistance. Further, the resistance of the mixed fluid to the flow of the mixed fluid in the direction of the joint portion in the body portion b is small, so that the flow can be smoothly performed. Further, the mixed fluid can be applied to the hole wall by the action of the land portion accompanying the rotation of the bit itself. The concave portion of the joint portion allows the excess mixed fluid that could not be applied to the hole wall to be smoothly flowed and discharged backward (see the literature, page 2, upper right column, lines 2-14).

Similar to Patent Document 3, Patent Document 4-8 also has a cross-shaped tip mounting groove formed on the tip surface of the bit head a, and each portion of the radial four-branch groove of the cross-shaped tip mounting groove. A metal chip is brazed and fixed in the branch groove, and a powder discharge groove is provided between the groove ends of the respective branch grooves opened on the side surface of the bit head a, and the powder discharge groove is provided in the powder discharge groove. , Communicating with the central cavity of the bit body and the hole center axis (hereinafter "spout hole axis") direction is inclined outward by about 40 degrees from the tip direction center axis (hereinafter "bit axis") of the bit body. A drilling bit is described in which a ejection hole is provided and the outer diameter of the body portion b is smaller than the outer diameter of the bit head a (Patent Document 4, FIG. 1-FIG. 5, FIG. 8, FIG. 9). Patent Document 5, FIG. 1; Patent Document 6, FIG. 1, FIG. 2; Patent Document 7, FIG. 2, FIG. 3; Patent Document 8, FIG. 7, FIG. 3-FIG. 6). In this case, since the ejection hole axis is closer to the tip of the bit body, the pressure fluid injected from the ejection hole becomes a front blow (injection flow injected toward the tip of the bit). Further, in the drilling bit of Patent Document 4, each of them is fixedly provided in the radial four-branch groove of the cross-shaped tip mounting groove formed on the tip surface of the bit head a in the axial direction. In the resulting metal chip (16, 16, 17, 17) having a pentagonal cross section, the length of the metal chip (16, 16) in the pair of opposing branch grooves is a pair of portions in the direction orthogonal to it. It is set longer on the central side of the bit body than the length of the metal chips (17, 17) in the branch groove. As a result, the range without the cutting edge in the central portion is reduced to expand the cutting range, and good drilling performance is ensured (see Patent Document 4, page 4, lines 2-5). Further, in the drilling bit of Patent Document 7, a configuration is shown in which the direction of the powder discharge groove is twisted in the bit rotation direction toward the base end direction of the bit body (Patent Document 7). , See Figures 2 and 3). Further, in the drilling bit of Patent Document 8, a configuration is shown in which the shape of the metal chip is a so-called fan shape that becomes wider toward the peripheral edge in the axial direction tip view (Patent Documents 8 and 7). reference). Further, as a conventional technique of the literature, the shape of the cross-shaped tip mounting groove is X-shaped (the angle formed by the branch groove is not 90 degrees) in the axial direction (the literature, FIGS. 5 and 5). 6), a single character shape (no branching) instead of a cross shape, a spherical shape with the tip surface of the bit head a bulging at the center, and a ridgeline of the blade at the tip of the metal tip bulging out from the side. A curved shape (a type of straight chopping bit (JIS M 0103: 2003; 3502)) (see References, Fig. 1 and Fig. 2) is shown.

Further, in the drilling bit of Patent Document 9, the shape of the tip mounting groove on the tip surface of the bit head a is a three-pronged shape (Y-shaped), and each branch of the radial three-branch groove is formed. A metal chip is brazed and fixed in the groove, and a powder discharge groove is provided between the groove ends of the respective branch grooves opened on the side surface of the bit head a, and the powder discharge groove is provided in the powder discharge groove. A drilling bit is described that communicates with the central cavity of the bit body and is provided with an ejection hole in which the axial core direction of the ejection hole is inclined outward by about 105 degrees from the bit axial core direction (Reference, FIG. 1-). (See FIG. 3). In this case, since the ejection hole axis is closer to the tip of the bit body, the pressure fluid injected from the ejection hole becomes a back blow (injection flow injected in the direction opposite to the tip direction of the bit). By this back blow, the powder that enters the powder discharge groove from the tip of the excavation hole is urged backward (toward the outlet of the excavation hole), and the fluid is discharged more smoothly. The powder discharge performance is improved (see the literature, page 4 of the specification). Further, in the drilling bit of Patent Document 10, a wear-resistant side member is provided on the outer peripheral surface (hole surface, reaming surface) of the bit head a slightly protruding, and the bit head is provided. An example of suppressing the wear of the outer peripheral surface of a is shown (see References, Fig. 1, Fig. 2, and pp. 3-4 of the specification).

Further, in the drilling bit (rotary bit) of Patent Document 11, a metal chip is attached to the tip of the bit body (base metal), and the metal chip is extended axially to the side surface side in the longitudinal direction of the side surface of the bit body. In a drilling bit provided with a powder discharge groove (powder groove) and opened in the powder discharge groove to provide a water hole, the bit body behind the exposed end (outer end) of the metal chip to the side surface of the bit body. A drilling bit provided with an auxiliary groove for discharging powder is described on the side surface (see the literature, specification, page 1, line 3-9, page 3, line 4-13, FIG. 4). By providing the auxiliary groove for discharging the powder, the powder collected at the exposed end (outer end) of the metal chip without being completely discharged from the perforated hole is discharged to the outside from the auxiliary groove for discharging the powder. (See References, pp. 3, pp. 14-4, pp. 2, line 2 of the specification). Further, also in the drilling bit of Patent Document 12, an example in which the same auxiliary groove for powder discharge (groove (11)) is provided is described (Reference, Document, p. 4, p. 17, line, p. 5-5, 1). Line, see Figure 1-3).

Japanese Unexamined Patent Publication No. 2007-277957 (perforated bit) JP-A-2002-295166 (Punching Bit) Japanese Unexamined Patent Publication No. 3-122395 (bit for perforating soft rock) Jikkenhei 2-116588 Gazette (Rock Drill Bit) Jitsukaisho 60-027192 (Rotkubit) Jikkai Sho 54-100902 (Bite for rocks) Jikkai Sho 52-030702 (Bite for rock drilling) Jikkai Sho 52-01430 No. 1 (Ultra-hard lock bit) Jikkai Sho 51-106202 (Percution Bit) Jitsukaisho 51-081301 (Bite for rock drilling) Akira Jinkai No. 48-056301 (Rotsukubito) Jikkai Sho 58-094782 (Punching Bit)

Ryohei Seto and 3 others, "Shea Thinking and Contact Friction", Multiphase Flow, Japanese Society for Multiphase Flow, March 2014, Vol.28, No.3, pp.296-303. Michio Otsuki, "Jamming Transition of Powder: Physics of" Flowing Solid "", Ensemble, Molecular Simulation Study Group, April 2014, Vol.16, No.2, pp.88-93.

When the geology of the ground to be dug is soft rock, the rock mass is easily crushed at the incision and the volume fraction (particle density) of the powder in the pores near the incision tends to increase as compared with the normal hard ground. Therefore, the powder that has penetrated between the outer surface (hole surface) of the bit head a and the hole wall causes a jamming transition, which tends to cause difficulty in rotating the drilling bit (Non-Patent Documents 2 and 2). 3). In consideration of this point, in Patent Document 3, the shape of the bit head a is relatively short in the axial direction near the embedded bottom of the metal chip, and the outer peripheral surface (hole surface) of the bit head a is made relatively short. The shape is such that a relatively deep and wide head recess (powder discharge groove) is provided between each of the metal chips.

However, if the geology of the ground to be excavated is softer, the viscosity of the powder generated at the incision in the drilling work of the boring work is high, and the friction between the particles of the powder increases, so that the jamming transition point (jamming transition occurs). The resulting volume fraction) is considered to be low (see Non-Patent Document 1). Therefore, the powder is extremely likely to be clogged in the powder discharge groove or the gap between the outer peripheral surface of the bit head a and the hole wall, and the drilling bit is extremely likely to be in a non-rotatable state. This is actually a problem even at the actual excavation site. Therefore, in the actual digging site, in order to forcibly push out the powder generated at the incision in the drilled hole to the outside, high-pressure water is press-fitted into the central cavity of the bit body as a pressure fluid, and the bit body Used by so-called "water feeding digging", which injects high-pressure water from the center hole on the tip surface and the ejection hole in the powder discharge groove to increase the fluidity of the powder and at the same time forcibly push the powder from the incision to the outside. Has been done.

On the other hand, the milling generated at the incision during the boring work is very important as a geological sample for knowing the rock condition of the incision at each excavation point. However, when the water supply digging is performed, the incised end is discharged from the hole end as a slurry-like bored slime dispersed in the injected water, which makes it difficult to use it as an accurate geological sample. Therefore, from the viewpoint of obtaining an accurate geological sample of the incision, it is preferable to adopt a so-called "air digging" in which compressed air is used as the pressure fluid to be pumped into the central cavity of the bit body. However, when compressed air is used as the pressure fluid, the compressibility of air is extremely higher than that of water (about 10,000 times that of water). Therefore, as described above, in extremely soft ground, the bit head a is affected by jamming transition. The problem arises that it is not possible to extrude the solidified powder around it.

Therefore, an object of the present invention is to provide a drilling bit capable of boring by air digging even when the geology of the ground to be excavated is further soft, and a ground drilling method using the bit. be.

The first configuration of the drilling bit according to the present invention includes a bit body and three or more cutting blades arranged radially on the tip surface of the bit body with respect to the center of the tip surface. It is a bit for drilling
The bit body has a bit head on the side including the tip surface and a cylindrical tubular body formed on the base end side of the bit head with a diameter smaller than that of the bit head.
Each of the cutting blades is arranged so that its outer peripheral end is in contact with a hole surface which is an outer peripheral surface of a bit head or protrudes outward from the hole surface.
A concave groove-shaped powder discharge groove is formed between the two adjacent cutting blades on the hole surface from the tip end side to the base end side of the bit head.
When the distance from the outer peripheral end of each cutting blade to the central axis of the bit body is taken as the drilling radius of the cutting blade, the drilling radius of each cutting blade is part or all. Is different.

According to this configuration, the radius of the drilling hole to be drilled is slightly larger than the largest drilling radius of the drilling radii of each cutting blade (hereinafter referred to as "maximum drilling radius"). Therefore, the smaller powder is discharged from the powder discharge groove having the larger volume fraction of the powder through the gap formed between the hole surface having the drill radius smaller than the maximum drill radius and the inner wall of the drilling hole. Since the powder is moved to the groove, it is possible to prevent the powder in the powder discharge groove from becoming excessively congested and overcrowded. As a result, the powder in the gap between the borehole surface and the inner wall of the excavation hole and the powder in the powder discharge groove are suppressed from jamming transfer, and even if the geology of the ground is very soft, air is suppressed. It is possible to realize boring by moat. In addition, by forming the drilling radius of some cutting blades to be shorter than the maximum drilling radius, the shortest drilling radius of the drilling radii of each cutting blade at the cutting edge during excavation (hereinafter referred to as The rock mass in the area inside the "minimum drilling radius") is finely crushed into powder with a small particle size, while the rock mass in the region near the hole wall outside the minimum drilling radius is coarsely crushed. The powder has a large particle size. In this way, the powder generated near the pore wall becomes coarse particles having a large particle size, so that the increase in the viscosity of the powder is suppressed (particularly in the case of mudstone or the like). This makes it difficult for the powder to adhere to the hole wall, and has the effect of preventing hole clogging.

The "central axis of the bit body" means the cylindrical central axis (rotational axis) of the cylindrical tubular body.

The second configuration of the drilling bit according to the present invention is the first configuration in which three or more of the cutting blades are arranged on the tip surface of the bit head. When one of the cutting blades is the first and each cutting blade is sequentially numbered clockwise or counterclockwise with respect to the center of the tip surface, the odd-th drilling radius and the even-th It is characterized in that the drilling radius of the cutting blade is different from that of the above.

According to this configuration, at the cutting edge during excavation, the rock mass in the area inside the shortest drilling radius of the drilling radii of each cutting blade (hereinafter referred to as "minimum drilling radius") is finely crushed. While the powder has a small particle size, the bedrock in the region near the hole wall outside the minimum drilling radius is coarsely crushed to form a powder with a large particle size. Further, by alternately setting the drilling radii of each cutting blade to be long and short, the particle size distribution of the milled powder at the cutting edge can be made as uniform as possible. This makes it difficult for the powder to adhere to the hole wall, and has the effect of preventing hole clogging.

The configuration of the ground drilling method according to the present invention is to use a boring machine provided with a tubular boring rod and a drilling bit having the first or second configuration connected to the tip of the boring rod. This is a ground drilling method for drilling holes.
In each of the powder discharge grooves of the drilling bit, a ejection hole communicating with a lumen formed in the body portion is formed, and the lumen in the body portion is a lumen in the boring rod. Communicate with
Compressed air is pumped from the base end to the tip of the boring rod through a cavity in the boring rod to inject compressed air from the ejection hole of the drilling bit, and the boring rod is subjected to axial striking vibration. It is characterized in that the ground is drilled by rotating while adding.

As a result, even when the geology of the ground to be excavated is very soft, boring by air digging becomes possible.

As described above, according to the drilling bit and the ground drilling method according to the present invention, it is possible to suppress the jamming transition of the powder in the pore gap and the powder in the powder discharge groove, and on the hole wall. Since it becomes difficult for the powder to adhere and clogging of the holes can be prevented, it is possible to realize boring by air digging even when the ground geology is very soft.

It is a perspective view of the drilling bit which concerns on Example 1 of this invention. (A) Plan view, (b) AA direction arrow side view, (c) BB direction arrow side view, and (d) CC line arrow side sectional view of the drilling bit of FIG. Is. Enlarged photo of the concave part. (A) A view of the recessed portion from the side. (B) The figure which looked at the concave part from the front. It is a schematic diagram which shows the movement of the drilling bit 1 at the time of excavation of the ground. It is a schematic diagram which shows the flow of the milling powder at the time of excavation of the ground. It is a schematic diagram which shows the state of the crushing of the ground at the incision at the time of excavation by the drilling bit of this Example. It is a hexagonal view of the drilling bit which concerns on Example 2 of this invention. (A) is a plan view, (b) is a bottom view, (c) is a front view, (d) is a left side view, (e) is a right side view, and (f) is a rear view. FIG. 7 is a perspective view and a cross-sectional view of the drilling bit of FIG. 7. (A) is a perspective view seen from the front upper right, (b) is a perspective view seen from the front upper left, and (c) is a cross-sectional view taken along the line AA of FIG. 7 (a). It is a top view of the drilling bit which concerns on Example 3 of this invention. 9 is a side view of the drilling bit of FIG. 9 taken along the line AA, a side view taken along the line BB, and a cross-sectional view taken along the line CC. 9 is a perspective view of the drilling bit of FIG. 9 as viewed from diagonally above the line AA, and FIG. 9B is a perspective view viewed from diagonally above the line BB. It is a hexagonal view of the drilling bit which concerns on Example 4 of this invention. (A) is a plan view, (b) is a bottom view, (c) is a front view, (d) is a left side view, (e) is a right side view, and (f) is a rear view. FIG. 12 is a perspective view and a cross-sectional view of the drilling bit of FIG. (A) is a perspective view seen from the front upper right, (b) is a perspective view seen from the rear upper left, and (c) is a cross-sectional view taken along the line AA of FIG. 12 (a). It is a hexagonal view of the drilling bit which concerns on Example 5 of this invention. (A) is a plan view, (b) is a bottom view, (c) is a front view, (d) is a left side view, (e) is a right side view, and (f) is a rear view. FIG. 14 is a perspective view and a cross-sectional view of the drilling bit of FIG. (A) is a perspective view seen from the front upper right, (b) is a perspective view seen from the rear upper left, and (c) is a cross-sectional view taken along the line AA of FIG. 14 (a).

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of a drilling bit according to a first embodiment of the present invention. 2A and 2B are a plan view of the drilling bit of FIG. 1, a side view of the arrow in the AA direction, a side view of the arrow in the BB direction, and a line CC in the BB direction. It is a cross-sectional view taken along the arrow. In the drilling bit 1 according to the first embodiment, the entire bit body is formed of one piece of steel, and the bit body is composed of two parts, a bit head a and a body b. Hereinafter, the side of the bit head a of the drilling bit 1 is referred to as the “tip side”, and the side of the body portion b is referred to as the “base end side”. The bit head a has a shape that is twice symmetrical with respect to the central axis (hereinafter referred to as “rotation axis”) of the drilling bit 1. The body portion b has a cylindrical shape, and the outer diameter of the body portion b is slightly smaller than the outer diameter of the bit head portion a. A lumen 3 is formed inside the bit body of the drilling bit 1 from the body portion b to the base end side of the bit head portion a. A screw groove 3a for screwing the tip end portion of the boring rod is engraved on the inner surface of the lumen 3 on the proximal end side. The innermost portion on the distal end side of the lumen 3 reaches the proximal end side of the bit head a, and a lumen end portion 3b in which the lumen diameter is reduced in a stepped shape is formed in this portion.

The distal end surface of the bit head a includes four elongated pentagonal prism shaped cutting blade 2 (metal chips), two lines L ₁ intersecting the X-shape in the rotational axis position of the drilling bit 1 in a plan view, They are arranged radially on L ₂ (see FIG. 2A) on all four sides of the rotation axis position. In this embodiment, the two straight lines L ₁ and L ₂ are not orthogonal to each other, but in the present invention, the two straight lines L ₁ and L ₂ may be configured to be orthogonal to each other. Each cutting blade 2 is made of a cemented carbide such as a sintered tungsten carbide alloy, and has a cross-sectional shape of a quadrangle (a pentagon in which a triangle is joined to one side of a quadrangle with its base aligned). Then, these cutting blades 2 are tightly attached and fixed with brazing in the concave groove formed on the tip surface with the pointed side thereof facing outward. The outer ends (outer ends with respect to the rotation axis) of the four cutting blades 2 are in contact with the outer peripheral surface (hereinafter referred to as "hole surface") 1a of the bit head a, or are outside the hole surface 1a. It is slightly protruding. Of the four cutting edges 2, the distance between the outer end of one of the lines L ₁ of the two cutting edges 2, 2 disposed on the pair (opposing cutting cutter set) and drilling diameter D _1. The distance between the outer ends of the set of two cutting blades 2 and 2 (opposed cutting blade sets) arranged on the other straight line L _{2 is defined as the drilling diameter D 2} . These two drilling diameters D ₁ and D ₂ are different, and in this embodiment, D ₁ > D ₂ is set.

Further, the distance from the outer end of each cutting blade 2 to the central axis O (rotation center axis) of the bit body is defined as the "drilling radius". As shown in FIGS. 1 and 2 (a), one of the four cutting blades 2 (the cutting blade indicated by reference numeral 2 (1) in FIGS. 1 and 2 (a)) is used. The other cutting blades 2 are numbered as the first, and the other cutting blades 2 are numbered 2, 3, and 4 in order counterclockwise with respect to the central axis O when viewed from the tip side (in FIGS. 1 and 2 (a)). Indicated by reference numerals 2 (2), 2 (3), 2 (4)). Then, the drilling radii of the numbered cutting blades 2 (1), 2 (2), 2 (3), and 2 (4) are set to r ₁ , r ₂ , r ₃ , and r ₄ (FIG. 2 (Fig. 2). a) See). Shikaraba, the odd-numbered cutting blades 2 (1), drilling the radius _r 1 of 2 (3), _{r 3} and the even-numbered cutting blades 2 (2), drilling radius _r 2 of 2 (4), r ₄ is different.

A concave groove-shaped powder discharge groove 4 is provided on the tip side of the bit head a in the middle of the outer ends of the two adjacent cutting blades 2 and 2 on the hole surface 1a on the outer periphery of the bit head a. It is formed from the base end side. In the groove of each powder discharge groove 4, a ejection hole 5 communicating with the lumen 3 in the body portion b is formed. Further, these four powder discharge grooves 4 are numbered 4-1, 4-2, 4-3, 4-4 counterclockwise when viewed from the tip surface side (see FIG. 2A). At this time, the ejection hole 5 in the groove of the even-numbered powder discharge groove (4-2, 4-4) is the hole outward direction of the hole axis of the ejection hole 5 (hereinafter referred to as “the ejection hole axis”). (Hereinafter referred to as "spouting direction") C ₁ is formed so as to be closer to the tip of the bit body (that is, _{the angle formed by the rotation axis direction C 0 in} the tip direction and the spouting direction C ₁ is a sharp angle) (that is, the angle formed by the spouting direction C 1). See FIG. 2 (d)). Further, in the ejection holes 5 in the grooves of the odd-numbered powder discharge grooves (4-1, 4-3), the ejection direction C ₂ of the ejection hole shaft is closer to the base end of the bit body (that is, toward the tip end direction). The angle formed by the rotation axis direction C ₀ and the ejection direction C ₂ is an obtuse angle).

Further, in a set of two adjacent powder discharge grooves 4, 4 (a powder discharge groove set (4-2, 4-3) and a powder discharge groove set (4, 4-1)), they are repeated. A recess on the hole surface 1a located between the powder discharge groove sets, from the bottom surface position of the cutting blade 2 to the base end side from the position, connecting both the powder discharge grooves 4 and 4 of the powder discharge groove set. 6 is formed up to the connection point 7 between the bit head portion a and the body portion b. Here, a supplementary explanation will be given regarding the configuration of the recess. FIG. 3 is an enlarged photograph of the portion of the recess 6. FIG. 3A is an enlarged photograph of the concave portion viewed from the side, and FIG. 3B is an enlarged photograph of the same concave portion viewed from the front. Originally, the hole surface 1a is the dotted line S _{0 in FIG. 3 (a).}
As shown in the above, the cutting blade 2 draws a bulging curved surface from the base end side of the outer end surface of the cutting blade 2 substantially parallel to the rotation axis, and reaches the connection point 7 with the body portion b. In No. 6, this portion is scraped off so as to be scooped out, and has a curved surface that is concave from the base end side of the cutting blade 2 to the rotation axis in the vertical direction (rotation axis direction) when viewed from the side (FIG. 3). (A)). The bottom surface near the outer end of the cutting blade 2 is completely exposed on the recess 6 side. Further, the recess 6 is formed over the region surrounded by the dotted line in FIG. 3 (b). That is, the recess 6 is formed over substantially the entire outer surface region of the bit head portion a straddling between the two adjacent powder discharge grooves 4 and 4.

In the present specification, the term "dent" is an envelope circle (or envelope ellipse) that encloses the outer peripheral surface (hole surface) of the cross section of the bit head when the bit body is viewed in a plane. It is used to mean a clearly recessed area. In addition, the word "anagurimen" is used to mean the surface of the digging hole that is reaming (hollowing out to make a hole or enlarging an existing hole). ing.

The drilling bit 1 according to the first embodiment configured as described above will be described below with reference to a ground drilling method using the bit 1.

FIG. 4 is a schematic view showing the movement of the drilling bit 1 during excavation of the ground. FIG. 4A shows a view of the drilling bit 1 viewed from the direction of FIG. 2C, and FIG. 4B is a view of the drilling bit 1 viewed from the direction of FIG. 2C. Represents. When drilling holes in the ground, the drilling bit 1 is screwed onto the tip of the boring rod 10, and compressed air is pumped through the boring rod 10 into the lumen 3 inside the main body of the drilling bit 1. This compressed air is ejected into the drilling hole 11 from the ejection hole 5 in the powder discharge groove 4 of the drilling bit 1. In this case, ejection holes 5 in the groove of the even-numbered Kukona discharge groove (4-2,4-4), since the ejection direction F ₁ faces the front end side of the bit body, ejected from these jets The compressed air generated becomes a front blow, and while blowing off the powder in the excavation hole 11 near the incision 11a and diffusing, it is transported toward the inlet of the excavation hole 11. On the other hand, ejection holes 5 in the grooves of the odd-numbered Kukona discharge grooves (4-1, 4-3), since the ejection direction F ₂ faces the base end side of the bit body, ejected from these jets The compressed air is back blown, and the powder in the powder discharge groove (4-1, 4-3) is transported while being urged toward the inlet of the drilling hole 11.

Then, as shown by the arrow P in FIG. 4, the boring rod 10 is vibrated in the vertical direction with an amplitude of about 5 to 20 mm, and the cutting edge 2 strikes the incision end 11a at the bottom of the excavation hole 11 to strike the incision end 11a. While crushing the ground G of the above, the boring rod 10 is rotated in the direction of the arrow Q. The ground crushed by the cutting edge 11a becomes powder and accumulates in the excavation hole 11 near the cutting edge 11a, and the accumulated powder is sequentially transported toward the inlet of the excavation hole 11 by the compressed air.

FIG. 5 is a schematic view showing the flow of milling during excavation of the ground. FIG. 5A shows a view of the drilling bit 1 viewed from the direction of FIG. 2C, and FIG. 5B is a view of the drilling bit 1 viewed from the direction of FIG. 2C. Represents. In FIG. 5, the boring rod 10 and the drilling bit 1 are viewed from fixed coordinates, and the ground G is relatively rotated in the direction of arrow −Q. Kukona occurring incisal 11a is by compressed air, is transported to the inlet direction of Kussaku hole 11 through Kukona discharge groove 4 (upward) (arrow _{T 1, T} 2). _{Further, since the gap between the outer ends of the cutting blades 2 and 2 having} the shorter drilling diameter D 2 and the hole wall of the drilling hole 11 is wide, the milling powder is used for the drilling hole by compressed air through this gap. 11 of the inlet direction is transported to (upward) (arrow _{T 3, T} 4). Due to this flow, the volume fraction of the milled powder in the excavation hole near the incision 11a is further lowered. Further, since the powder is moved from the powder discharge groove 4 having the larger volume fraction of the powder to the powder discharge groove 4 having a smaller volume fraction 4 through the recess 6 provided behind the cutting blade 2 (arrow). T _5), Kukona of Kukona discharge groove 4 that is overcrowded overly congested be suppressed. As a result, the powder in the gap between the hole surface 1a and the inner wall of the excavation hole 11 and the powder in the powder discharge groove 4 are suppressed from jamming transfer, and the geology of the ground is very soft. However, it is possible to realize boring by air digging.

FIG. 6 is a schematic view showing a state of crushing of the ground at the incision at the time of excavation by the drilling bit of this embodiment. In FIGS. 6 (a) and 6 (b), reference numeral 2 indicates the cutting blade 2 shown in FIGS. 1 and 2, and the outermost circle C ₀ indicates the cutting hole edge, which is inside FIG. 6 (b). The dotted circle C ₁ represents the locus of the outer end of the cutting blade when the cutting blade having the shorter drilling radius rotates. At the time of excavation, vibration in the hole axis direction is applied to the drilling bit, and the rock at the cut end is struck by the cutting blade 2. At this time, the rock at the incision is crushed, but at that time, cracks occur in the rock at the incision as shown in FIG. 6A, in addition to the portion directly struck by the cutting blade 2. While drilling bit is rotated while oscillating, when the hitting applied during one rotation N times, and FIG. 6 (b) inside bedrock areas S ₁ of the dotted circle C ₁ of the one rotation It will be hit directly by the cutting blade about 4N times. On the other hand, the bedrock in the region S _{2 between the circle C 0} and the dotted circle C ₁ (that is, the region outside the outer end of the cutting blade with the shorter drilling radius) is cut about 2N times per rotation. It will be hit directly by the blade. Thus, while the rock in the region S ₁ which is finely ground becomes small Kukona particle sizes, rock region S ₂ in the vicinity of the hole wall is roughened ground with great Kukona particle size. In this way, the powder generated near the pore wall becomes coarse particles having a large particle size, so that the increase in the viscosity of the powder is suppressed (particularly in the case of mudstone or the like). This makes it difficult for the powder to adhere to the hole wall, and has the effect of preventing hole clogging.

In addition, the present inventor actually carried out a boring test of soft ground by air digging using the drilling bit 1 of Example 1. As a result, even in soft ground where it is difficult for the conventional drilling bit to rotate due to jamming, the drilling bit 1 of the first embodiment rotates the drilling bit 1. It became possible, and it was demonstrated that it is possible to perform drilling by air digging normally.

FIG. 7 is a hexagonal view of the drilling bit according to the second embodiment of the present invention. 7A is a plan view, FIG. 7B is a bottom view, FIG. 7C is a front view, FIG. 7D is a left side view, FIG. 7E is a right side view, and FIG. 7F is a rear view. FIG. 8 is a perspective view and a cross-sectional view of the drilling bit of FIG. 7. 8A is a perspective view seen from the front upper right, FIG. 8B is a perspective view seen from the front upper left, and FIG. 8C is a cross-sectional view taken along the line AA of FIG. 7A. .. In FIGS. 7 and 8, the components corresponding to those in the first embodiment are designated by the same reference numerals. Similar to the first embodiment, the drilling bit 1 of this embodiment has a bit body composed of two parts, a bit head portion a and a body portion b. The body portion b has a cylindrical shape, and the outer diameter of the body portion b is smaller than the outer diameter of the bit head portion a. Although not shown in FIGS. 7 and 8, a screw groove for screwing the tip of the boring rod is engraved on the inner surface of the lumen 3 in the body b on the proximal end side. The innermost portion on the distal end side of the lumen 3 reaches the proximal end side of the bit head a, and a lumen end portion 3b in which the lumen diameter is reduced in a stepped shape is formed in this portion.

In this embodiment, the tip surface of the bit head a is formed in a flat conical shape with the rotation center of the tip surface as an apex, and six cutting blades 2 (metal chips) are radially centered on this apex. Are arranged at equal intervals. As shown in FIG. 7A, these six cutting blades 2 are viewed counterclockwise from the tip surface side, 2-1, 2-2, 2-3, 2-4, 2-5, 2-. Number 6 The outer peripheral surface of the bit head a is a hole surface 1a, and a concave groove-shaped powder discharge groove 4 is formed on the hole surface 1a between the cutting blades 2 from the tip of the bit head a. It is formed over the edges.

其's cutting edge 2-i (i = 1, 2, ..., 6) the distance from the outer end the central axis of the bit body to (rotation axis) of the drilling radius r _i of該切Kezuha 2-i do. At this time, the hole surface 1a located at the outer end of each cutting blade 2-i of the bit head a is an even-numbered cutting than _{the drilling radii r 1} , r ₃ , r _{5 of the odd-numbered cutting blade 2.} drilling blade 2 radius _{r 2, r 4, r 6} is formed to be shorter. That is, in FIG. 7A, the circle shown by the dotted line C indicates an envelope that envelops the hole surface 1a located at the outer end of the odd-numbered cutting blades 2-1, 2-3, 2-5. However, the hole surface 1a located at the outer end of the even-numbered cutting blades 2-2, 2-4, 2-6 is located inside the envelope C.

In the groove of each powder discharge groove 4, a ejection hole 5 communicating with the lumen 3 in the body portion b is formed. As shown in FIG. 7A, these six powder discharge grooves 4 are arranged counterclockwise when viewed from the tip surface side, 4-1 and 4-2, 4-3, 4-4, 4-5. Number 4-6. However, the powder discharge groove 4-1 is a powder discharge groove 4 located between the cutting blades 2-1 and 2. At this time, the ejection hole 5 that opens in the groove of the odd-numbered powder discharge groove 4 (4-1, 4-3, 4-5) is referred to as the hole axis of the ejection hole 5 (hereinafter referred to as "the ejection hole axis"). The outward direction (hereinafter referred to as the "spouting direction") is formed so as to be closer to the tip of the bit body. On the other hand, in the ejection hole 5 opened in the groove of the even-numbered powder discharge groove 4 (4-2, 4-4, 4-6), the ejection direction of the ejection hole shaft of the ejection hole 5 is the bit main body. It is formed so as to be closer to the base end.

In addition, 3 sets of adjacent powder discharge grooves 4, 4 (mill powder discharge groove sets (4-6, 4-1), (4-2, 4-3), (4, 4, 4-5) )), Both the powder discharge grooves 4 of the powder discharge groove set are located on the hole surface 1a located between the powder discharge groove sets, from the bottom surface position of the cutting blade 2 to the base end side from the position. A recess 6 connecting the parts and 4 is formed over the bit head portion a, the body portion b, and the connection portion 7.

Even with such a configuration, the drilling surface 1a having a small drilling radius (the drilling surface 1a located at the outer end of the even-numbered cutting blades 2-2, 2-4, 2-6) and the drilling hole. Through the gap formed between the inner wall and the recess 6 provided behind the odd-numbered cutting blades 2-1, 2, 3 and 2-5, the powder with the larger volume fraction of the powder is discharged. Since the powder moves from the groove 4 to the smaller powder discharge groove 4, it is possible to prevent the powder in the powder discharge groove 4 from becoming excessively congested and overcrowded. As a result, the powder in the gap between the hole surface 1a and the inner wall of the excavation hole and the powder in the powder discharge groove 4 are suppressed from jamming transfer, and even when the geology of the ground is very soft. , It is possible to realize boring by air moat.

Also, as in the case described in FIG. 6 of Example 1, drilling the radius _r 1 of the odd-numbered cutting blades _2-1,2-3,2-5, r _3, than _{r 5,} the even-numbered by drilling radius _{r 2, r 4, r 6} of the cutting blade 2-2,2-4,2-6 was formed so as to be shorter, in the incisal during Kussaku, boring radius _r 2, _{r 4} while a small Kukona grain size bedrock inner region is finely ground than r _6, drilling radius r _2, r _4, bedrock areas near the outer hole wall than r ₆ is coarsely crushed It becomes a powder with a large particle size. In this way, the powder generated near the pore wall becomes coarse particles having a large particle size, so that the increase in the viscosity of the powder is suppressed (particularly in the case of mudstone or the like). This makes it difficult for the powder to adhere to the hole wall, and has the effect of preventing hole clogging.

In this embodiment, an example in which the drilling radius of the odd-numbered cutting blade 2 is configured to be longer than the drilling radius of the even-numbered cutting blade 2 is shown, but the drilling of the odd-numbered cutting blade 2 is shown. The radius can also be configured to be shorter than the drilling radius of the even-numbered cutting blade. Further, the drilling radii of all the cutting blades 2 may be different.

FIG. 9 is a plan view of the drilling bit according to the third embodiment of the present invention. 10A and 10B are a side view of the drilling bit of FIG. 9 taken along the line AA, a side view taken along the line BB, and a cross-sectional view taken along the line CC. .. 11A and 11B are a perspective view of the drilling bit of FIG. 9 as viewed from diagonally above line AA, and FIG. 11B is a perspective view viewed from diagonally above line BB. In FIGS. 9 to 11, the components corresponding to those in the first embodiment are designated by the same reference numerals. Similar to the first embodiment, the drilling bit 1 of this embodiment has a bit body composed of two parts, a bit head portion a and a body portion b. The body portion b has a cylindrical shape, and the outer diameter of the body portion b is smaller than the outer diameter of the bit head portion a. A screw groove 3a (not shown) for screwing the tip end portion of the boring rod is engraved on the inner surface of the lumen 3 on the proximal end side. The innermost portion on the distal end side of the lumen 3 reaches the proximal end side of the bit head a, and a lumen end portion 3b in which the lumen diameter is reduced in a stepped shape is formed in this portion. The drilling bit 1 of this embodiment is calibrated into a shape symmetrical twice with the rotation axis as the axis of symmetry. Therefore, the side view and the perspective view seen from the DD line direction of FIG. 9 are the same as those of FIGS. 10 (a) and 11 (a), and the side view and the perspective view seen from the EE line direction of FIG. 9 are the same. The figure is the same as that of FIGS. 10 (b) and 11 (b).

In this embodiment, six cutting blades 2 (metal chips) are radially arranged at equal angular intervals on the tip surface of the bit head a. As shown in FIG. 9, these six cutting blades 2 are arranged counterclockwise as 2-1,2-2,2-3,2-4,2-5,2-6 when viewed from the tip surface side. Number. Of the six cutting edges 2, drilling radius _r 3 of the two cutting edges 2-3,2-6 along the longitudinal center line of FIG. 9, _{r 6} is relatively short, the other four cutting edges 2 boring radius _r 1 of _{-1,2-2,2-4,2-5, r 2, r 4,} r 5 is configured to be relatively long. The two relatively short cutting blades 2-3, 2-6 are the same length, and the other four cutting blades 2-1, 2, 2-4, 2-5 are all the same length. Is. The two cutting blades arranged on the same straight line facing each other with the rotation axis in between are arranged symmetrically with respect to the rotation axis. The outer peripheral surface of the bit head a is a hole surface 1a, and a concave groove-shaped powder discharge groove 4 is formed on the hole surface 1a between the cutting blades 2 from the tip of the bit head a. It is formed over the edges. In the groove of each powder discharge groove 4, a ejection hole 5 communicating with the lumen 3 in the body portion b is formed. As shown in FIG. 9, these six powder discharge grooves 4 are arranged counterclockwise when viewed from the tip surface side, 4-1, 4-2, 4-3, 4-4, 4-5, 4-6. Numbered. However, the powder discharge groove 4-1 is a powder discharge groove 4 located between the cutting blades 2-1 and 2. At this time, the ejection holes 5 in the grooves of the left and right powder discharge grooves (4-1, 4-4) in FIG. 9 are outside the holes of the hole shafts of the ejection holes 5 (hereinafter referred to as "spout hole shafts"). The orientation direction (hereinafter referred to as “spouting direction”) is formed so as to be closer to the tip of the bit body (see FIGS. 10 and 11). On the other hand, in the ejection holes 5 in the grooves of the four powder discharge grooves (4-2, 4-3, 4-5, 4-6) above and below in FIG. 9, the ejection direction of the ejection hole shaft is the bit body. It is formed so as to be closer to the base end.

Further, in the plan view of FIG. 9, a set of two adjacent powder discharge grooves 4 and 4 located on the upper side and the lower side (powder discharge groove set (4-2, 4-3) and a powder discharge groove set). In (4-5, 4-6)), the powder discharge groove of the hole surface 1a located between the powder discharge groove sets is located from the bottom surface position of the cutting blade 2 to the base end side from the position. A recess 6 connecting the two powder discharge grooves 4 and 4 of the set is formed up to the connection point 7 between the bit head portion a and the body portion b. Here, the bit head a, as shown in FIG. 9, a plan view of the bit head a, an envelope ellipse C _e two vertical cutting lines L _c, the bit head a was cleaved with L _c and accommodated in an envelope such as, rest recess 6, as shown in FIG. 9, with respect to the envelope ellipse C _e bit head a of a plan view of the bit head a, a clearly recessed region It has become.

Even with such a configuration, a gap is formed between the drilling surface 1a having a small drilling radius (the drilling surface 1a located at the outer end of the cutting blades 2-3 and 2-6) and the inner wall of the drilling hole. Because the powder moves from the powder discharge groove 4 having the larger volume fraction of the powder to the powder discharge groove 4 having a smaller volume fraction 4 through and through the recess 6 provided behind the cutting blade 2. It is possible to prevent the powder in the powder discharge groove 4 from becoming excessively congested and overcrowded. As a result, the powder in the gap between the hole surface 1a and the inner wall of the excavation hole 11 and the powder in the powder discharge groove 4 are suppressed from jamming transfer, and the geology of the ground is very soft. However, it is possible to realize boring by air digging. Further, in this embodiment, a set of two powder discharge grooves (4-2, 4-3) and a powder discharge groove set (4-5, 4-6) connected by a recess 6 )), The ejection holes 5 and 5 in the grooves of the powder discharge grooves 4 and 4 of both of these powder discharge groove sets have the hole outward direction of the hole shaft of the ejection hole as the base end of the bit body. It is formed so as to be closer. As a result, all the pressure fluids injected from the ejection holes 5 of the powder discharge groove set (4-2, 4-3) and (4-5, 4-6) are back blown (opposite to the tip direction of the bit). The jet flow is jetted in the direction). As a result, the powder in the powder discharge groove is transported to the body side and acts to reduce the volume fraction of the powder in the powder discharge groove, so that the discharge and transportation of the powder from the incision are further smoothed. Can be done.

Also, as in the case described in FIG. 6 of Example 1, drilling the radius _r 1 of the cutting edge _{2-1,2-2,2-4,2-5,} r _2, than r 4, _{r 5} , by the drilling radius _r 3, _{r 6} of the cutting blade 2-3,2-6 was formed so as to be shorter, in the incisal during Kussaku, the region inside the boring radius _r 3, _{r 6} while bedrock as a finely divided smaller particle size Kukona, rock region near the outer hole wall than boring radius r _3, r ₆ is roughened ground with great Kukona particle size. In this way, the powder generated near the pore wall becomes coarse particles having a large particle size, so that the increase in the viscosity of the powder is suppressed (particularly in the case of mudstone or the like). This makes it difficult for the powder to adhere to the hole wall, and has the effect of preventing hole clogging.

The present inventor also used the drilling bit 1 of Example 3 to carry out a boring test on soft ground by air digging. As a result, even in soft ground where it is difficult to rotate the drilling bit due to jamming with the conventional drilling bit, the drilling bit 1 of the third embodiment can rotate. It became possible, and it was demonstrated that it is possible to perform drilling by air digging normally.

FIG. 12 is a hexagonal view of the drilling bit according to the fourth embodiment of the present invention. 12A is a plan view, FIG. 12B is a bottom view, FIG. 12C is a front view, FIG. 12D is a left side view, FIG. 12E is a right side view, and FIG. 12F is a rear view. FIG. 13 is a perspective view and a cross-sectional view of the drilling bit of FIG. 13 (a) is a perspective view seen from the front upper right, (b) is a perspective view seen from the rear upper left, and (c) is a cross-sectional view taken along the line AA of FIG. 12 (a). .. In FIGS. 12 and 13, the components corresponding to the first and second embodiments are designated by the same reference numerals. Similar to Examples 1 and 2, the drilling bit 1 of this embodiment has a bit body composed of two parts, a bit head portion a and a body portion b. The body portion b has a cylindrical shape, and the outer diameter of the body portion b is smaller than the outer diameter of the bit head portion a. Although not shown in FIG. 13, a screw groove for screwing the tip end portion of the boring rod is engraved on the inner surface of the lumen 3 in the body portion b on the proximal end side. The innermost portion on the distal end side of the lumen 3 reaches the proximal end side of the bit head a, and a lumen end portion 3b in which the lumen diameter is reduced in a stepped shape is formed in this portion.

In this embodiment, the tip surface of the bit head a is formed in a flat conical shape with the rotation center of the tip surface as an apex, and three cutting blades 2 (metal chips) are radially centered on this apex. Are arranged at equal intervals. As shown in FIG. 12A, these three cutting blades 2 are numbered 2-1, 2, 2-3 in a counterclockwise direction when viewed from the tip surface side. The outer peripheral surface of the bit head a is a hole surface 1a, and a concave groove-shaped powder discharge groove 4 is formed on the hole surface 1a between the cutting blades 2 from the tip of the bit head a. It is formed over the edges.

The distance from the outer end of其's cutting edge 2-i (i = 1,2,3) center axis of the bit body to (rotation axis), and drilling the radius _{r i} of該切Kezuha 2-i. At this time, holes Ku surface 1a positioned at the outer end of each cutting blade 2-i of the bit head a is the even-numbered than odd boring radius r ₁ of the cutting blade _2, r ₃ of the cutting blade 2 It is formed so that the drilling radius r _{2 is shortened.} That is, in FIG. 12A, the circle shown by the dotted line C indicates an envelope that encloses the hole surface 1a located at the outer end of the odd-numbered cutting blades 2-1 and 2.3. The hole surface 1a located at the outer end of the even-numbered cutting blade 2-2 is located inside the envelope C.

In the groove of each powder discharge groove 4, a ejection hole 5 communicating with the lumen 3 in the body portion b is formed. As shown in FIG. 12A, these six powder discharge grooves 4 are numbered 4-1, 4-2, 4-3 counterclockwise when viewed from the tip surface side. However, the powder discharge groove 4-1 is a powder discharge groove 4 located between the cutting blades 2-1 and 2. At this time, the ejection hole 5 that opens in the groove of the powder discharge groove 4-1 and 4-2 is in the outward direction (hereinafter, "ejection hole axis") of the hole axis of the ejection hole 5 (hereinafter referred to as "ejection hole axis"). The direction ") is formed so as to be closer to the tip of the bit body. On the other hand, the ejection hole 5 that opens in the groove of the powder discharge groove 4-3 is formed so that the ejection direction of the ejection hole shaft of the ejection hole 5 is closer to the base end of the bit body.

Further, in two sets of adjacent powder discharge grooves 4, 4 (powder discharge groove sets (4-1, 4-2), (4-2, 4-3)), the powder discharge groove sets are used. The recess 6 connecting both the powder discharge grooves 4 and 4 of the powder discharge groove set is a bit from the bottom surface position of the cutting blade 2 to the base end side of the hole surface 1a located between the two. It is formed over the head a, the body b, and the connection point 7.

Even with such a configuration, through the gap formed between the drilling surface 1a having a small drilling radius (the drilling surface 1a located at the outer end of the even-numbered cutting blade 2-2) and the inner wall of the drilling hole. , And through the recesses 6 provided behind the odd-numbered cutting blades 2-1 and 2, from the powder discharge groove 4 having the larger volume fraction of the powder to the powder discharge groove 4 having the smaller volume fraction 4. Since the milling moves, it is possible to prevent the milling in the milling discharge groove 4 from becoming excessively congested and overcrowded. As a result, the powder in the gap between the hole surface 1a and the inner wall of the excavation hole and the powder in the powder discharge groove 4 are suppressed from jamming transfer, and even when the geology of the ground is very soft. , It is possible to realize boring by air moat.

Also, as in the case described in FIG. 6 of Example 1, than boring radius _r 1, _{r 3} of the odd-numbered cutting blades 2-1 and 2-3, cutting of even-numbered cutting blades 2-2 Since the hole radius r ₂ is formed to be short, _{the rock mass in the region inside the drilling radius r 2} is finely crushed into powder with a small particle size at the incision during digging, while drilling. rock region near the outer hole wall than the radius r ₂ is coarsely pulverized by a major Kukona particle size. In this way, the powder generated near the pore wall becomes coarse particles having a large particle size, so that the increase in the viscosity of the powder is suppressed (particularly in the case of mudstone or the like). This makes it difficult for the powder to adhere to the hole wall, and has the effect of preventing hole clogging.

In this embodiment, an example in which the drilling radius of the odd-numbered cutting blade 2 is configured to be longer than the drilling radius of the even-numbered cutting blade 2 is shown, but the drilling of the odd-numbered cutting blade 2 is shown. The radius can also be configured to be shorter than the drilling radius of the even-numbered cutting blade. Further, the drilling radii of all the cutting blades 2 may be different.

FIG. 14 is a six-view view of the drilling bit according to the fifth embodiment of the present invention. 14A is a plan view, FIG. 14B is a bottom view, FIG. 14C is a front view, FIG. 14D is a left side view, FIG. 14E is a right side view, and FIG. 14F is a rear view. FIG. 15 is a perspective view and a cross-sectional view of the drilling bit of FIG. 15 (a) is a perspective view seen from the front upper right, (b) is a perspective view seen from the rear upper left, and (c) is a cross-sectional view taken along the line AA of FIG. 14 (a). .. In FIGS. 14 and 15, the components corresponding to the first and second embodiments are designated by the same reference numerals. Similar to Examples 1 and 2, the drilling bit 1 of this embodiment has a bit body composed of two parts, a bit head portion a and a body portion b. The body portion b has a cylindrical shape, and the outer diameter of the body portion b is smaller than the outer diameter of the bit head portion a. Although not shown in FIG. 15, a screw groove for screwing the tip end portion of the boring rod is engraved on the inner surface of the lumen 3 in the body portion b on the proximal end side. The innermost portion on the distal end side of the lumen 3 reaches the proximal end side of the bit head a, and a lumen end portion 3b in which the lumen diameter is reduced in a stepped shape is formed in this portion.

In this embodiment, the tip surface of the bit head a is formed in a flat conical shape with the rotation center of the tip surface as an apex, and five cutting blades 2 (metal chips) are radially centered on this apex. Are arranged at equal intervals. As shown in FIG. 14A, these five cutting blades 2 are numbered 2-1, 2-2, 2-3, 2-4, 2-5 counterclockwise when viewed from the tip surface side. do. The outer peripheral surface of the bit head a is a hole surface 1a, and a concave groove-shaped powder discharge groove 4 is formed on the hole surface 1a between the cutting blades 2 from the tip of the bit head a. It is formed over the edges.

其's cutting edge 2-i (i = 1, 2, ..., 5) the distance from the outer end to the center axis of the bit body (rotational shaft), and the drilling radius r _i of該切Kezuha 2-i do. At this time, the hole surface 1a located at the outer end of each cutting blade 2-i of the bit head a is an even-numbered cutting than _{the drilling radii r 1} , r ₃ , r _{5 of the odd-numbered cutting blade 2.} The drilling radii r ₂ and r _{4 of the} blade 2 are formed to be short. That is, in FIG. 14A, the circle shown by the dotted line C indicates an envelope that encloses the hole surface 1a located at the outer end of the odd-numbered cutting blades 2-1, 2-3, 2-5. However, the hole surface 1a located at the outer end of the even-numbered cutting blades 2-2, 2-4 is located inside the envelope C.

In the groove of each powder discharge groove 4, a ejection hole 5 communicating with the lumen 3 in the body portion b is formed. As shown in FIG. 12A, these six powder discharge grooves 4 are arranged counterclockwise as 4-1, 4-2, 4-3, 4-4, 4-5 when viewed from the tip surface side. Number. However, the powder discharge groove 4-1 is a powder discharge groove 4 located between the cutting blades 2-1 and 2. At this time, the ejection hole 5 opened in the groove of the powder discharge groove 4-1, 4-2, 4-4 is the outward direction of the hole axis of the ejection hole 5 (hereinafter referred to as "the ejection hole axis"). (Hereinafter referred to as "spouting direction") is formed so as to be closer to the tip of the bit body. On the other hand, the ejection holes 5 that open in the grooves of the powder discharge grooves 4-3 and 4-5 are formed so that the ejection direction of the ejection hole shaft of the ejection holes 5 is closer to the base end of the bit body. There is.

In addition, 3 sets of adjacent powder discharge grooves 4, 4 (mill powder discharge groove sets (4-5, 4-1), (4-2, 4-3), (4, 4, 4-5) )), Both the powder discharge grooves 4 of the powder discharge groove set are located on the hole surface 1a located between the powder discharge groove sets, from the bottom surface position of the cutting blade 2 to the base end side from the position. A recess 6 connecting the parts and 4 is formed over the bit head portion a, the body portion b, and the connection portion 7.

Even with such a configuration, between the hole surface 1a having a small drilling radius (the hole surface 1a located at the outer end of the even-numbered cutting blades 2-2, 2-4) and the inner wall of the drilling hole. Through the gaps that can be formed and through the recesses 6 provided behind the odd-numbered cutting blades 2-1, 2, 3 and 2-5, the volume fraction of the powder is smaller than the powder discharge groove 4 having the larger volume fraction. Since the powder is moved to the powder discharge groove 4 on the other side, it is possible to prevent the powder in the powder discharge groove 4 from becoming excessively congested and overcrowded. As a result, the powder in the gap between the hole surface 1a and the inner wall of the excavation hole and the powder in the powder discharge groove 4 are suppressed from jamming transfer, and even when the geology of the ground is very soft. , It is possible to realize boring by air moat.

Also, as in the case described in FIG. 6 of Example 1, drilling the radius _r 1 of the odd-numbered cutting blades _2-1,2-3,2-5, r _3, than _{r 5,} the even-numbered by drilling radius _r 2, _{r 4} of the cutting edges 2-2 and 2-4 is formed to be shorter, in the incisal during Kussaku, rock a region inside the boring radius _r 2, _{r 4} whereas been finely ground becomes small Kukona particle sizes, rock region near the outer hole wall than boring radius r _2, r ₄ becomes coarsely crushed by a large Kukona particle size. In this way, the powder generated near the pore wall becomes coarse particles having a large particle size, so that the increase in the viscosity of the powder is suppressed (particularly in the case of mudstone or the like). This makes it difficult for the powder to adhere to the hole wall, and has the effect of preventing hole clogging.

In this embodiment, an example in which the drilling radius of the odd-numbered cutting blade 2 is configured to be longer than the drilling radius of the even-numbered cutting blade 2 is shown, but the drilling of the odd-numbered cutting blade 2 is shown. The radius can also be configured to be shorter than the drilling radius of the even-numbered cutting blade. Further, the drilling radii of all the cutting blades 2 may be different.

1 Bit for drilling a Bit Head b Body 1a Hole surface 2 Cutting blade 3 Cavity 3a Thread groove 3b Cavity end 4 Powder discharge groove 5 Ejection hole 6 Concave 7 Connection point 10 Boring rod 11 Drilling hole 11a Cut edge G ground

Claims (3)

A drilling bit provided with a bit body and three or more cutting blades radially arranged on the tip surface of the bit body with respect to the center of the tip surface.
The bit body has a bit head on the side including the tip surface and a cylindrical tubular body formed on the base end side of the bit head with a diameter smaller than that of the bit head.
Each of the cutting blades is arranged so that its outer peripheral end is in contact with a hole surface which is an outer peripheral surface of a bit head or protrudes outward from the hole surface.
A concave groove-shaped powder discharge groove is formed between the two adjacent cutting blades on the hole surface from the tip end side to the base end side of the bit head.
In each of the powder discharge grooves, a ejection hole that communicates with the lumen in the body to which compressed air is pumped is formed.
The cutting blade is formed in a pentagonal shape in which the cross-sectional shape is a pentagon in which a triangle is joined to one side of a quadrangle with the base aligned.
When the distance from the outer peripheral end of each cutting blade to the central axis of the bit body is taken as the drilling radius of the cutting blade, the drilling radius of each cutting blade is part or all. A bit for drilling, which is characterized by being different.


Three or more cutting blades are arranged on the tip surface of the bit head, and one of the cutting blades is set as the first cutting blade, and each cutting blade is set with respect to the center of the tip surface. 1 bit. A ground drilling method for drilling the ground using a boring machine provided with a tubular boring rod and the drilling bit according to claim 1 or 2 connected to the tip of the boring rod.
In each of the powder discharge grooves of the drilling bit, a ejection hole communicating with a lumen formed in the body portion is formed, and the lumen in the body portion is a lumen in the boring rod. Communicate with
Compressed air is pumped from the base end to the tip of the boring rod through a cavity in the boring rod to inject compressed air from the ejection hole of the drilling bit, and the boring rod is subjected to axial striking vibration. A ground drilling method in which the ground is drilled by rotating while adding.

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