JP7440907B2 - Female thread machining method, estimated cutting edge distance determination device, and tool presetter - Google Patents

Description

The present invention relates to a technique for machining a female thread on the inner circumferential surface of a through hole of a workpiece using a tap.

As a method of attaching a spark plug to the cylinder head of an internal combustion engine, a female thread is machined on the inner circumferential surface of a through hole (called a "plug hole") that passes through the outer and inner circumferential surfaces of the cylinder head, and the spark plug is In this method, a method of processing a male thread that can be screwed together with a female thread is used. As a method of machining a female thread on the inner circumferential surface of a through hole of a cylinder head, a method is used in which a female thread is machined using a tap held in a tool holder attached to a main shaft of a machine tool.
When installing the spark plug in the cylinder head, it is necessary to direct the opening of the ground electrode of the spark plug toward the fuel injection port in order to improve combustion efficiency and the like. That is, when machining a female thread on the inner circumferential surface of the through hole of the cylinder head, it is necessary to start thread cutting from a predetermined position (predetermined phase) on the inner circumferential surface.
Conventionally, a technique disclosed in Patent Document 1 (Japanese Unexamined Patent Publication No. 2012-240179) is known as a technique for starting machining of a female screw from a thread cutting start position.

Japanese Patent Application Publication No. 2012-240179

By using the technology disclosed in Patent Document 1, the cutting edge phase of the cutting edge of a tap held in a tool holder attached to the main shaft of a machine tool is set to a predetermined thread cutting start phase. I can do it.
However, the technique disclosed in Patent Document 1 is complicated and time-consuming.
The present invention was devised in view of these points, and an object of the present invention is to provide a technique that can easily process a female thread from a predetermined thread cutting start position.

The first invention is a tap that is held in a tool holder attached to the main shaft of a machine tool, has a cutting edge formed at a thread pitch P, and has a threaded part at its tip consisting of a chamfered part and a fully threaded part. The present invention relates to a female thread machining method for machining a female thread on the inner circumferential surface of a through hole of a workpiece by feeding.
The cutting blade is, for example, formed in a spiral shape. In pitch feeding, the tap moves one screw pitch P in one rotation. The pitch feed start position is preferably set at a position that is an integral multiple of the thread pitch P from the workpiece (thread cutting start position).
The diameter of the cutting edge (tool diameter) of the cutting blade that forms the biting portion is set to increase from the tap tip side toward the fully threaded portion side.
In the present invention, a reference position along the extension direction of the spindle, a machine tool reference phase around the spindle, a tool holder reference phase having a phase difference α with respect to the machine tool reference phase, and a phase difference with respect to the machine tool reference phase are provided. A thread cutting start phase corresponding to the thread cutting start position of the female thread is defined, which has β. The reference position is preferably a position on the tool holder, and is set to a position that can be recognized by the machine tool when the tool holder is attached to the spindle. The expression "extending direction of the spindle" means "extending direction of the spindle rotation center" or "extending direction of the tool holder rotation center line." The expression "around the spindle" means "around the spindle rotation center line" or "around the tool holder rotation center line."
The present invention includes the step of measuring the tap tip distance M1 along the extending direction of the main shaft between the tap tip of the tap and the reference position.
Various methods can be used to measure the tap tip distance M1.
The method also includes a step of measuring a phase difference θ between a cutting edge phase corresponding to a cutting edge of a predetermined cutting edge of the cutting blades forming a fully threaded portion of the threaded portion of the tool and a tool holder reference phase. The cutting edge phase is the phase of the cutting edge around the tool holder rotation center line when the tool is held in the tool holder.
The phase difference θ can be measured, for example, by rotating the tool holder around the spindle while holding the tap and measuring the rotation angle between the tool holder reference phase and the cutting edge phase.
The method also includes a step of measuring a cutting edge distance M3 between the cutting edge of a predetermined cutting blade and a reference position along the extending direction of the main shaft.
Various methods can be used to measure the cutting edge distance M3.
The tap tip distance M1, the phase difference θ, and the cutting edge distance M3 can be measured on a machine tool, but are preferably measured using a tool presetter.
Note that having the step of measuring at least two of the tap tip distance M1, the phase difference θ, and the cutting edge distance M3 is equivalent to having the step of measuring at least two of each.
Also, based on the tap tip distance M1, the cutting edge distance M3, the phase differences α, β, θ, and the thread pitch P, a , a step of determining an estimated cutting edge distance M2 on the thread cutting start phase.
Further, the tap is pitch fed from the pitch feed start position based on the estimated cutting edge distance M2 on the thread cutting start phase. For example, if the estimated blade edge position indicated by the estimated blade edge distance M2 on the thread cutting start phase matches the pitch feed start position, pitch feed of the tap is started as is. On the other hand, if the estimated blade edge position indicated by the estimated blade edge distance M2 on the thread cutting start phase does not match the pitch feed start position, after moving the tap so that the estimated blade edge position matches the pitch feed start position, , start pitch feeding of taps. Specifically, after moving the spindle by a distance between the estimated cutting edge position and the pitch feed start position, pitch feed is started.
According to the present invention, thread cutting of a female thread can be easily started from a predetermined thread cutting start position.
In a different form of the first invention, in the step of determining the estimated cutting edge distance M2 on the thread cutting start phase, the outer edge of the fully threaded portion on the cutting edge phase is determined based on the tap tip distance M1, the cutting edge distance M3, and the thread pitch P. , the distance Δm1 along the direction in which the main shaft extends between the estimated cutting edge of the estimated cutting edge formed by extending from the tap tip toward the opposite side of the tool holder and the tap tip is determined. Then, based on the tap tip distance M1, the phase differences α, β, θ, the thread pitch P, and the distance Δm1, the estimated cutting edge distance M2 at the thread cutting start phase is calculated as [M2=M1+Δm1+(φ/360 degrees)× P] and [φ=θ−(α−β)].
In this embodiment, the estimated cutting edge distance on the thread cutting start phase can be easily determined.
A second invention relates to an estimated cutting edge distance discriminating device for determining an estimated cutting edge distance on a thread cutting start phase, which is used in the female thread machining method of the first invention.
In the present invention, a reference position is set along the extending direction of the spindle, and around the spindle, there is a machine tool reference phase, a tool holder reference phase having a phase difference α with respect to the machine tool reference phase, and a machine tool reference phase. A thread cutting start phase is set that corresponds to the thread cutting start position of the female thread and has a phase difference β with respect to the reference phase.
The present invention includes a measuring device and a processing device.
The measuring device is configured to be able to measure the tap tip distance M1, the phase difference θ, and the cutting edge distance M3.
The tap tip distance M1 is the distance between the tap tip of the tap and the reference position along the extending direction of the main shaft. The phase difference θ is the phase difference between the cutting edge phase corresponding to the cutting edge of a predetermined cutting blade among the cutting blades forming the complete threaded portion of the threaded portion and the tool holder reference phase. The cutting edge distance M3 is the distance between the cutting edge of a predetermined cutting blade and the reference position along the extending direction of the main shaft.
The measurement device is constructed by combining one or more types of measurement devices selected from various measurement devices such as a light transmission type measurement device, a light reflection type measurement device, an imaging type measurement device, and a rotation angle measurement device. .
Based on the tap tip distance M1, the blade edge distance M3, the phase differences α, β, θ, and the screw pitch P, the processing device calculates the distance between the estimated blade edge position on the thread cutting start phase and the reference position in the direction of extension of the main shaft. The estimated cutting edge distance M2 on the thread cutting start phase along the thread cutting start phase is determined.
In the present invention, it is possible to easily determine the estimated cutting edge distance on the thread cutting start phase.
In a different form of the second invention, the processing device extends the outer edge of the fully threaded portion on the cutting edge phase from the tap tip to the opposite side of the tool holder, based on the tap tip distance M1, the cutting edge distance M3, and the thread pitch P. It is configured to determine the distance Δm1 along the extending direction of the main shaft between the estimated cutting edge of the estimated cutting edge to be formed and the tap tip. Further, the processing device calculates the estimated cutting edge distance M2 at the thread cutting start phase based on the tap tip distance M1, the phase differences α, β, θ, the thread pitch P, and the distance Δm1, [M2=M1+Δm1+(φ/ 360 degrees)×P] and [φ=θ−(α−β)].
In this embodiment, the estimated cutting edge distance on the thread cutting start phase can be easily determined.
The third invention relates to a tool presetter used in the female thread machining method of the first invention.
The present invention includes the estimated cutting edge distance classification device of the second invention.
According to the present invention, since the estimated cutting edge distance at the thread cutting start phase can be determined in advance outside the machine tool, the machining time for female threads can be shortened.

According to the present invention, a female thread can be easily machined from a predetermined thread cutting start position.

It is a figure showing an example of a spark plug. FIG. 3 is a diagram showing a state in which a spark plug is attached to a cylinder head. FIG. 2 is a view of FIG. 1 viewed from the direction of arrow III. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows one embodiment of the female thread processing apparatus of this invention. 5 is an enlarged view of the portion indicated by arrow V in FIG. 4. FIG. 6 is a view taken along the line VI-VI in FIG. 5. FIG. It is a figure explaining the method of measuring the phase difference (theta) between a tool holder reference phase and a cutting edge phase, and the cutting edge distance M3. It is a figure explaining operation of one embodiment of a female screw processing device of the present invention.

Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, a case will be described in which a female thread that can be screwed together with a male thread machined into a spark plug is formed on the inner circumferential surface of a communication hole of a cylinder head of an internal combustion engine.

First, an example of a spark plug will be described with reference to FIGS. 1 and 2. FIG. 1 shows a spark plug 100, and FIG. 2 shows a state in which the spark plug 100 is attached to a cylinder head 200.

The spark plug 100 has a cylindrical metal fitting 110.
The mounting fitting 110 has a threaded portion 120. A male thread 121 is machined on the outer periphery of the threaded portion 120 and can be screwed to a female thread 211 machined on the inner peripheral surface of the through hole 210 of the cylinder head 200. The male thread 121 has a thread pitch P (mm).
An insulator 140 is inserted inside the mounting fitting 110.
A center electrode 150 is arranged inside the insulator 140 . The center electrode 150 has a tip portion 151 that protrudes from the threaded portion 120 to one side (tip side) along the direction in which the spark plug center line K extends.
A ground electrode 160 is arranged on one side of the threaded portion 120 along the direction in which the spark plug center line K extends. The ground electrode 160 has a base portion 161 and a tip portion 162, and is formed in an L-shape. A spark gap G is formed between the tip 151 of the center electrode 150 and the tip 162 of the ground electrode 160.
The mounting fitting 110 has a flange portion 130 on the other side (rear end side) of the threaded portion 120 along the direction in which the spark plug center line K extends. The collar portion 130 has a contact surface 131 that contacts the outer peripheral surface 201 of the cylinder head 200 .

The cylinder head 200 has an outer circumferential surface 201 and an inner circumferential surface 202. The inner circumferential surface 202 forms a combustion chamber.
The cylinder head 200 has a through hole 210 that communicates between an outer circumferential surface 201 and an inner circumferential surface 202. The through hole 210 extends along the through hole center line S. A female thread 211 that can be screwed together with the male thread 121 of the spark plug 100 is machined on the inner circumferential surface of the through hole 210 . The female thread 211 has a thread pitch P (mm).

To attach the spark plug 100 to the cylinder head 200, as shown in FIG. 211 with screws. The spark plug 100 is installed in a prescribed installation state. For example, the threaded portion 120 of the spark plug 100 is inserted into the through hole 210 of the cylinder head 200 such that the contact surface 131 of the flange portion 130 contacts the outer peripheral surface 201 of the cylinder head 200.
The cylinder head 200 corresponds to the "workpiece into which a female thread is machined" according to the present invention. Further, the spark plug 100 corresponds to the "coupled object screwed to a workpiece" of the present invention.

In order to improve combustion efficiency, etc., as shown in FIG. 2, when the spark plug 100 is attached to the cylinder head 200, the opening 170 of the ground electrode 160 should be aligned in the direction of the fuel injection port (not shown). It needs to be configured to suit.
Here, the thread pitch P of the male thread 121 of the spark plug 100 and the female thread 211 of the cylinder head 200 is set. Furthermore, the state in which the spark plug 100 is attached to the cylinder head 200 is defined. For example, a state in which the contact surface 131 of the collar portion 130 contacts the outer peripheral surface 201 of the cylinder head 200 is defined as the installed state.
Therefore, the orientation of the opening 170 of the ground electrode 160 of the spark plug 100 when the spark plug 100 is attached to the cylinder head 200 is determined by the thread cutting start position 210a (thread cutting start phase T) of the female thread 211. Ru. That is, by setting the thread cutting start position 210a of the female thread 211 shown in FIG. 3 based on the position of the fuel injection port, the ground electrode The opening 170 of 160 can be directed towards the fuel injection port.
The thread cutting start phase T around the through-hole center line S corresponding to the thread cutting start position 210a is set based on the machine tool reference phase N of the machine tool 500. That is, the phase difference β between the thread cutting start phase T and the machine tool reference phase N is set depending on the position of the fuel injection port and the like.

Next, a method of starting thread cutting of the female thread 211 of the cylinder head 200 from the set thread cutting start position 210a (thread cutting start phase T) will be described with reference to FIGS. 4 to 6.
FIG. 4 is a diagram illustrating an embodiment of a female thread processing device that uses a tap 400 to form a female thread 211 on the inner peripheral surface of the through hole 210 of the cylinder head 200. 5 is an enlarged view of the portion indicated by arrow V in FIG. 4, and FIG. 6 is a view taken along the line VI-VI in FIG.

The female thread machining device of this embodiment includes a machine tool 500, a tool holder 300, and a tap 400.
Note that the machine tool 500 has an xyz coordinate system. In this specification, one side along the z-axis (the tap 400 side) is referred to as the "tip side", and the other side (the machine tool 500 side) along the z-axis is referred to as the "rear end side".
The machine tool 500 is rotatable (the phase on the xy plane is variable) around a spindle rotation center line Q (see FIGS. 5 and 6) that is parallel (including "substantially parallel") to the z-axis, and It has a main shaft 510 whose position along the z-axis can be adjusted. The main shaft 510 has a main shaft distal end surface 511 on the distal end side along the extending direction of the main shaft rotation center line Q.
The main shaft 510 has a tool holder insertion space (not shown) that is open at the main shaft end surface 511 and into which the shank portion 320 of the tool holder 300 can be inserted.
The extending direction of the main shaft rotation center line Q corresponds to the "extending direction of the main shaft" in the present invention, and the area around the main shaft rotation center line Q corresponds to the "around the main shaft" in the present invention.

The tool holder 300 has a tool holder main body portion (hereinafter simply referred to as “main body portion”) 310 and a tightening member 330.
The main body part 310 has a shank part 320 on the rear end side along the extending direction of the main body rotation center line (hereinafter referred to as "tool holder rotation center line"). The shank portion 320 is inserted and held (installed) in the tool holder insertion space of the main shaft 510 of the machine tool 500 .
When the shank portion 320 of the main body portion 310 is attached to the spindle 510, the tool holder 300 rotates around the spindle rotation center line Q in conjunction with the spindle 510, and rotates in the extending direction of the spindle rotation center line Q. move along. In this specification, the expression "extending direction of the tool holder rotation center line" refers to the extending direction of the tool holder 300 when it is attached to the main spindle 510, that is, the extending direction of the main spindle rotation center line Q.
In this embodiment, the tool holder 300 is attached to the spindle 510 with the phase around the spindle rotation center line Q set. That is, as shown in FIG. 6, the phase difference α between the tool holder reference phase R of the tool holder 300 and the machine tool reference phase N of the machine tool 500 is set in advance.

Moreover, the main body part 310 has a tool insertion space (not shown) into which a tool shank part (not shown) of the tap 400 can be inserted, on the distal end side along the extending direction of the tool holder rotation center line. The tool shank portion of the tap 400 is configured to be insertable into the tool insertion space while rotation around the tool holder rotation center line is restricted. For example, by forming the cross-sectional shape of the rear end of the tool shank and the portion of the tool insertion space into which the rear end of the tool shank is inserted into a square or triangular shape, the tap 400 for the tool holder 300 can be A rotation regulating mechanism is configured to regulate the rotation of. Note that the phase of the tap 400 relative to the main body 310 around the tool holder rotation center line when the tap 400 is held in the tool holder 300 is determined by the insertion state of the tap 400 into the tool insertion space of the tool shank. be done. That is, the phase of the tap 400 with respect to the machine tool reference phase N of the machine tool 500 depends on the insertion state of the tool shank portion into the tool insertion space.
When held in the tool holder 300, the tap 400 rotates around the tool holder rotation center line (around the spindle rotation center line Q) in conjunction with the tool holder 300, and rotates around the tool holder rotation center line (the spindle rotation center line Q). move along the extending direction of line Q). In this specification, the expression "extending direction of the tap rotation center line (tool rotation center line)" refers to the extending direction in a state where the tap 400 is held in the tool holder 300, that is, the tool holder rotation center line ( The direction in which the spindle rotation center line Q) extends is shown.

The tightening member 330 is formed in an annular shape. The inner peripheral surface of the tightening member 330 is machined with a female thread that can be screwed into a male thread machined on the outer periphery of the distal end side of the main body part 310.
The tap 400 is held in the tool holder 300 (specifically, the main body 310 of the tool holder 300) by tightening the tightening member 330 with the tool shank inserted into the tool insertion space of the main body 310. Ru.

In this embodiment, a female thread 211 is machined on the inner circumferential surface of the through hole 210 of the cylinder head 200 using the tap 400 shown in FIGS. 5 and 6. 5 is a side view of the threaded portion 410 of the tap 400, and FIG. 6 is a view taken along the line VI-VI in FIG.
The tap 400 has a threaded portion 410 at its tip.
As shown in FIG. 5, the threaded portion 410 has a cutting blade 412 formed in a spiral shape with a thread pitch P (mm).
Furthermore, the threaded portion 410 is divided into a plurality of lands by grooves. In this embodiment, the threaded portion 410 is divided into four lands 411 by four grooves 414, as shown in FIG. That is, the cutting blade 412 is divided into four parts by four grooves 414. Each divided cutting blade 412 has a cutting edge 413 on the rotation direction F side of the tap 400. Note that the shape of the groove 414 can be set to various shapes such as a linear shape and a spiral shape. The cutting blade 412 is provided with relief machining from the cutting edge 413 toward the opposite side of the rotation direction F in order to improve machining accuracy.
Further, the threaded portion 410 has a chamfered portion 420 and a fully threaded portion 430. The diameter (tool diameter) of the cutting edge 413 of the cutting edge 412 forming the biting portion 420 decreases from the fully threaded portion 430 side (front end side) toward the tap tip surface 400a side (rear end side).
The tap tip surface 400a corresponds to the "tap tip" of the present invention.

In the female thread machining device of this embodiment, with the tool holder 300 holding the tap 400 attached to the main spindle 510 of the machine tool 500, the main spindle 510 (tool holder 300, tap 400) is placed in a processing standby position. . An appropriate position can be set as the processing standby position. In FIG. 4, the main shaft 510 is arranged at a processing standby position where the main shaft rotation center line Q and the through-hole center line S of the through-hole 210 of the cylinder head 200 coincide.
Further, in the processing standby position, the rotation angle of the main spindle 510 is adjusted so that the phase of the main spindle 510 becomes the set phase.
Further, in the female thread processing device of this embodiment, the female thread 211 is machined on the inner peripheral surface of the through hole 210 by pitch-feeding the tap 400 from the pitch-feeding start position. In pitch feeding, the tap 400 (main shaft 510) moves one screw pitch P along the extending direction of the main shaft rotation center line Q in one rotation.
In FIG. 4, a position away from the cylinder head 200 (outer peripheral surface 201 of the cylinder head 200) by a pitch feed distance H that is an integral multiple of the screw pitch P is set as the pitch feed start position Ha. Then, pitch feeding of the tap 400 (main shaft 510) is started from a state in which the estimated blade edge position 410a (described in detail later) on the thread cutting start phase T matches the pitch feeding start position Ha.

Next, the operation of the female thread machining device of this embodiment will be explained.
In this embodiment, a reference position J (see FIG. 4) is defined along the direction in which the main shaft 510 extends. The reference position J is set as a position on the tool holder 300 that can be recognized by the machine tool when the tool holder 300 is attached to the spindle 510.
Further, as shown in FIG. 6, around the spindle rotation center line Q of the spindle 510 of the machine tool 500, the machine tool reference phase N, the tool holder reference phase R, and the start of thread cutting corresponding to the thread cutting start position 210a. A phase T and a cutting edge phase W corresponding to the cutting edge 413c of a predetermined cutting edge 412c are defined.
The tool holder reference phase R is set to have a phase difference α (degrees) with respect to the machine tool reference phase N. That is, the tool holder 300 is attached to the main shaft 510 such that the phase difference between the machine tool reference phase N and the tool holder reference phase R is α.
The thread cutting start phase T is set to have a phase difference β (degrees) with respect to the machine tool reference phase N. The phase difference β is set such that when the spark plug 100 is attached to the cylinder head 200, the opening 170 of the ground electrode 160 of the spark plug 100 faces the fuel injection port.
The cutting edge phase W is a phase corresponding to the cutting edge of a predetermined cutting blade among the cutting blades forming the fully threaded portion 430 of the threaded portion 410. The cutting edge phase W has a phase difference θ (degrees) with respect to the tool holder reference phase R. The phase difference θ varies depending on the state in which the tap 400 is held in the tool holder 300. The phase difference θ is measured by a method described later.
The phase difference φ between the thread cutting start phase T and the blade edge phase W is determined by the method described below based on the preset phase differences α and β and the measured phase difference θ.

Further, as shown in FIGS. 4 and 5, a tap tip distance M1, an estimated blade edge distance M2 on the thread cutting start phase T, a blade edge distance M3, a distance Δm1, and a distance Δm2 are defined.
The tap tip distance M1 is the distance (mm) between the tap tip surface 400a and the reference position J along the extending direction of the spindle rotation center line Q. The tap tip distance M1 is measured by a method described later.
The cutting edge distance M3 (mm) is the distance of the spindle rotation center line Q between the cutting edge position corresponding to the cutting edge of a predetermined cutting blade among the cutting blades forming the fully threaded part 430 of the threaded part 410 and the reference position J. This is the distance (mm) along the extending direction. The cutting edge distance M3 is measured by a method described later.
The distance Δm1 is the estimated cutting edge of the estimated cutting edge formed by extending the outer edge of the fully threaded portion 430 of the threaded portion 410 on the cutting edge phase W from the tap tip surface 400a to the side opposite to the tool holder 300 (tip side) and the tap tip surface 400a along the extending direction of the spindle rotation center line Q (mm). The distance Δm1 is determined by a method described below based on the measured tap tip distance M1 and cutting edge distance M3, and a preset screw pitch P.
The distance Δm2 is the distance (mm) between the estimated cutting edge of the estimated cutting blade and the estimated cutting edge position 410a on the thread cutting start phase T along the extending direction of the spindle rotation center line Q. The distance Δm2 is determined based on the determined phase difference φ and the screw pitch P by a method described later.
The estimated blade edge distance M2 on the thread cutting start phase T is the distance between the estimated blade edge position 410a on the thread cutting start phase T and the reference position J along the extending direction of the spindle rotation center line Q. The estimated cutting edge distance M2 on the thread cutting start phase T is determined by the method described below based on the measured tap tip distance M1 and the determined distances Δm1 and Δm2.

Next, the operation of machining the female thread 211 on the inner peripheral surface of the through hole 210 of the cylinder head 200 using the tap 400 will be described.
First, the tap tip distance M1, phase difference θ, and cutting edge distance M3 are measured. Although the tap tip distance M1, the phase difference θ, and the cutting edge distance M3 can be measured on the machine tool 500, in this embodiment, the tap tip distance M1, the phase difference θ, and the cutting edge distance M3 can be measured on the machine tool 500, but in this embodiment, they are measured with the tool holder 300 holding the tap 400 placed in the tool presetter. Measuring.

(Step 1)
A tap tip distance M1 between the tap tip surface 400a of the tap 400 and the reference position J is measured by a tap tip distance measuring device (tap tip distance measuring means) of the tool presetter.
As the tap tip distance measuring device, various known non-contact type or contact type measuring devices (measuring means) can be used. For example, multiple detection devices consisting of a light irradiation device and a light receiving device that receives light emitted from the light irradiation device and not blocked by an object are arranged, and the tap tip distance is determined based on the placement position and light reception state of each detection device. A light transmission type measuring device for measuring M1 can be used. Alternatively, a plurality of detection devices consisting of a light irradiation device and a light receiving device that receives the light emitted from the light irradiation device and reflected by an object are arranged, and the tap tip distance M1 is determined based on the placement position and light reception state of each detection device. A light reflection type measuring device can be used for the measurement. Alternatively, it is possible to use an image processing type measurement device that measures the tap tip distance M1 by processing image information captured by an imaging device.

(Step 2)
The phase difference θ is measured by the phase difference measuring device (phase difference measuring means) of the tool presetter.
The phase difference measuring device includes a rotation angle measuring device (rotation angle measuring means) and a cutting edge distance measuring device (cutting edge distance measuring means).
The rotation angle measuring device is configured to be able to measure the rotation angle from the tool holder reference phase R when the tool holder 300 rotates around the tool holder rotation center line (around the spindle rotation center line Q). As the rotation angle measuring device, various known measuring devices can be used.
The cutting edge distance measuring device measures the distance between a predetermined cutting edge of the cutting blades forming the fully threaded portion 430 of the threaded portion 410 and the tool holder rotation center line (spindle rotation center line Q). For example, a predetermined cutting edge 412c is selected from among the cutting edges 412a to 412c forming the fully threaded portion 430 shown in FIGS. 5 and 6. Then, while rotating the tool holder 300 around the tool holder rotation center line, as shown in FIG. 7, the cutting blade 412c and the tool are Measure the distance D (mm) from the holder rotation center line. As the cutting edge distance measuring device, measuring means having various known configurations can be used.
Here, the longest distance D indicates the distance between the cutting edge 413c of the cutting blade 412c and the tool holder rotation center line. Then, the rotation angle (rotation angle from the tool holder reference phase) when the longest distance D is measured is the phase difference θ between the cutting edge phase W corresponding to the cutting edge 413c of the cutting edge 412c and the tool holder reference phase R. It shows.

(Step 3)
The cutting edge distance M3 is measured by the cutting edge distance measuring device (cutting edge distance measuring means) of the tool presetter.
The cutting edge distance measuring device measures the rotational position of the tool holder 300 when the longest distance D is measured by the cutting edge distance measuring device of the phase difference measuring device in the N direction (Fig. 6), the distance between the cutting edge 413c and the reference position J along the extending direction of the tool holder rotation center line (spindle rotation center line Q) is measured as the cutting edge distance M3. As the cutting edge distance measuring device, measuring means having various known configurations can be used.

Next, the distance Δm1, the distance Δm2, and the estimated cutting edge distance M2 are determined (calculated). The distance △m1, the distance △m2, and the estimated cutting edge distance M2 are calculated using the measured tap tip distance M1, cutting edge distance M3, and phase difference θ, and the preset phase differences α, β, and screw pitch P by the processing device of the machine tool 500. (processing means).
Note that the processing device of the machine tool 500 recognizes the reference position J of the tool holder 300 and the position of the cylinder head 200 (outer peripheral surface 201 of the cylinder head 200) on the machine tool 500.

(Step 4)
The processing device has an estimated cutting edge distance determining device (estimated cutting edge distance determining means) that determines the estimated cutting edge distance M2 on the thread cutting start phase T.
The estimated cutting edge distance discriminating device determines the cutting edge phase W corresponding to the cutting edge (the cutting edge 413c in FIGS. 5 and 6) of a predetermined cutting blade among the cutting blades forming the fully threaded portion 430 of the threaded portion 410 and the start of thread cutting. The phase difference φ between the thread cutting start phase T corresponding to the position 210a is determined.
The phase difference φ is a preset phase difference α between the machine tool reference phase N and the tool holder reference phase R, and a phase difference β between the machine tool reference phase N and the thread cutting start phase T. Based on the measured phase difference θ between the tool holder reference phase R and the cutting edge phase W, it can be determined by [φ=θ−(α−β)].
Also, the distance Δm1 is determined.
The distance Δm1 is the distance between the estimated cutting edge and the tap tip surface of the estimated cutting edge formed by extending the outer edge of the fully threaded portion 430 on the cutting edge phase W from the tap tip surface 400a to the side opposite to the tool holder 300 (tip side) 400a along the extending direction of the main shaft rotation center line Q. As the estimated cutting edge of the estimated cutting blade, the estimated cutting edge of the estimated cutting blade whose distance from the tap tip surface 400a is shorter than the screw pitch P is preferably selected. In FIG. 5, the estimated cutting edge 413f of the estimated cutting edge 412f is selected.
The position of the estimated cutting edge (estimated cutting edge 413f in FIG. 5) is based on the measured tap tip distance M1 between the tap tip surface 400a and the reference position J and the cutting edge forming the fully threaded portion 430. The determination can be made based on the blade edge distance M3 between the blade edge of a predetermined cutting blade (the blade edge 413c in FIGS. 5 and 6) and the reference position J, and the preset screw pitch P.
Also, the distance Δm2 is determined.
The distance Δm2 is the intersection between the estimated cutting edge (estimated cutting edge 412f in FIG. 5) and the thread cutting start phase T (estimated cutting edge position 410a on the thread cutting start phase T) and the estimated cutting edge of the estimated cutting edge (in FIG. 5, the estimated cutting edge position 410a) 5 is the distance along the extending direction of the spindle rotation center line Q between the estimated cutting edge 413f). The distance △m2 is determined based on the measured phase difference φ between the blade edge phase W and the thread cutting start phase T and the preset screw pitch P, [△m2=(φ/360 degrees)×P] It can be determined by
Furthermore, the estimated cutting edge distance M2 on the thread cutting start phase T is determined.
The estimated blade edge distance M2 on the thread cutting start phase T is the distance between the estimated blade edge position 410a on the thread cutting start phase T and the reference position J along the extending direction of the spindle rotation center line Q. The estimated cutting edge position 410a on the thread cutting start phase T is the intersection of the estimated cutting edge (estimated cutting edge 412f in FIG. 5) and the thread cutting start phase T.
The estimated cutting edge distance M2 on the thread cutting start phase T can be determined based on the tap tip distance M1, the distance Δm1, and the distance Δm2, as [M2=M1+Δm1+Δm2].

(Step 5)
The processing device pitch-feeds the tap 400 (main shaft 510) from the pitch-feed start position Ha based on the determined estimated blade edge distance M2 on the thread cutting start phase T. As a result, machining of the female thread 211 on the inner circumferential surface of the through hole 210 of the cylinder head 200 starts from the thread cutting start position 210a.
Specifically, the processing device recognizes the reference position J of the tool holder 300 on the machine tool 500. Thereby, the estimated blade edge position 410a on the thread cutting start phase T on the machine tool 500 can be determined based on the estimated blade edge distance M2 in the thread cutting start phase T.
Further, the processing device recognizes the position of the cylinder head 200 (the outer peripheral surface 201 of the cylinder head 200) on the machine tool 500. Thereby, it is possible to determine a pitch feed start position Ha on the machine tool 500 that is away from the cylinder head 200 by a pitch feed distance H that is an integral multiple of the screw pitch P.
Thereby, the processing device can determine whether the estimated blade edge position 410a on the thread cutting start phase T matches the pitch feed start position Ha.
When the estimated blade edge position 410a on the thread cutting start phase T matches the pitch feed start position Ha, the tap 400 (main shaft 510) is pitch fed as is.
On the other hand, as shown in FIG. 8, when the estimated blade edge position 410a on the thread cutting start phase T does not match the pitch feed start position Ha, the tap 400 (main shaft 510) is After moving the tap 400 (main shaft 510) by the distance between the estimated cutting edge position 410a on T and the pitch feed start position Ha along the extending direction of the main shaft rotation center line Q, the tap 400 (main shaft 510) is pitch fed.

The order in which the processes of (Step 1) to (Step 3) are executed can be changed as appropriate. Further, the processing of at least two steps selected from (Step 1) to (Step 3) can be configured to be processed in a common step.
An aspect in which the processing of at least two steps selected from (Step 1) to (Step 3) is executed in a common step is included in a configuration in which the processing of at least two steps is executed in different steps.
Further, the processes (step 1) to (step 3) can also be performed on a machine tool.

The above describes the female thread machining method or the female thread machining device, but the present invention is an estimated cutting edge distance discrimination method that determines the estimated cutting edge distance at the thread cutting start phase, which is used in the female thread processing method or the female thread processing device. It can also be configured as a device.
for example,
(Aspect 1) A tap that is held in a tool holder attached to the main spindle of a machine tool, has a cutting edge formed at a thread pitch P, and has a threaded part consisting of a chamfered part and a fully threaded part at the tip. An estimated cutting edge distance discriminating device for determining an estimated cutting edge distance at a thread cutting start phase, which is used in a female thread machining method of machining a female thread on the inner circumferential surface of a through hole of a workpiece by feeding,
A reference position is set along the extending direction of the spindle, and around the spindle are a machine tool reference phase, a tool holder reference phase having a phase difference α with respect to the machine tool reference phase, and the machine tool. A thread cutting start phase corresponding to a thread cutting start position of the female thread is set, having a phase difference β with respect to a reference phase,
Equipped with measuring equipment and processing equipment,
The measuring device includes:
a tap tip distance M1 along the extending direction of the main shaft between the tap tip of the tap and the reference position;
a phase difference θ between a cutting edge phase corresponding to a cutting edge of a predetermined cutting blade of the cutting blades forming the fully threaded portion of the threaded portion and the tool holder reference phase;
configured to be able to measure a cutting edge distance M3 along the extending direction of the main shaft between the cutting edge of the predetermined cutting blade and the reference position,
The processing device calculates the estimated blade edge position on the thread cutting start phase and the blade edge position based on the tap tip distance M1, the blade edge distance M3, the phase difference α, the phase difference β, the phase difference θ, and the thread pitch P. An estimated blade edge distance determining device, characterized in that it determines an estimated blade edge distance M2 on a thread cutting start phase along the extending direction of the main shaft between a reference position and a reference position. ”.
Further, “(Aspect 2) The estimated cutting edge distance discriminating device of Aspect 1,
The processing device includes:
Based on the tap tip distance M1, the cutting edge distance M3, and the thread pitch P, an estimated cut is formed by extending the outer edge of the fully threaded portion on the cutting edge phase from the tap tip to the opposite side of the tool holder. Determining the distance Δm1 along the extending direction of the main shaft between the estimated cutting edge of the blade and the tap tip;
Based on the tap tip distance M1, the phase difference α, the phase difference β, the phase difference θ, the thread pitch P, and the distance Δm1, the estimated cutting edge distance M2 on the thread cutting start phase is calculated as [M2=M1+ △m1+(φ/360 degrees)×P] and [φ=θ−(α−β)]. ”.
The measuring device in the estimated cutting edge distance discriminating device of aspect 1 or aspect 2 may be provided in a machine tool, or a measuring device of a tool presetter may be used.

Further, the present invention can also be configured as a tool presetter used in a female thread machining method or a female thread machining device.
For example, "(Aspect 3) A tap that is held in a tool holder attached to the main shaft of a machine tool, has a cutting edge formed with a thread pitch P, and has a threaded part consisting of a chamfered part and a fully threaded part at the tip. A tool presetter used in a female screw machining method for machining a female screw on the inner peripheral surface of a through hole of a workpiece by pitch feeding,
A tool presetter comprising the estimated cutting edge tip distance determining device according to aspect 1 or aspect 2. ”.
As the processing device in the tool presetter of aspect 3, the processing device of the tool presetter is used. Moreover, in this aspect, since the estimated cutting edge tip distance on the thread cutting start phase can be determined in advance outside the machine tool, it is possible to shorten the machining time of the female thread in the machine tool.

The present invention is not limited to the configuration described in the embodiments, and various changes, additions, and deletions are possible.
The method of determining the distance Δm1, the distance Δm2, and the estimated cutting edge distance M2 on the thread cutting start phase is not limited to the method described in the embodiment.
The number of grooves that divide the threaded portion 410 into a plurality of land portions can be set as appropriate.
A tap with a threaded part divided into a plurality of land parts by a groove was used, but a tap with a threaded part without a groove (for example, a rolled tap with a polygonal cross section or a tap without groove) was used. You can also do that.
The processing in each step is not limited to the processing described in the embodiment.
The case where a female thread is machined on the inner circumferential surface of a through hole in a cylinder head has been described, but what about the workpiece on which the female thread is machined? It is not limited to cylinder heads.
In the embodiment, a case has been described in which a female thread is machined on the inner circumferential surface of a through hole extending in the vertical direction, but the present invention is also applicable to the case where a female thread is machined on the inner circumferential surface of a through hole extending in various directions. It can be used when
The configurations described in the embodiments can be used alone, or a plurality of appropriately selected configurations can be used in combination.

100 Spark plug 110 Mounting bracket 120 Threaded portion 121 Male thread 130 Edge 131 Contact surface 140 Insulator 150 Center electrode 151 Tip portion 160 Ground electrode 161 Base portion 162 Tip portion 170 Opening portion 200 Cylinder head 201 Outer circumferential surface 202 Inner circumferential surface 210 Through hole 210a Thread cutting start position 211 Female thread 300 Tool holder 310 Tool holder main body (main body)
320 Shank part 330 Tightening member 400 Tap 400a Tap tip surface (tap tip)
410 Threaded part 410a Estimated cutting edge position on thread cutting start phase 411, 411a to 411f Land 412, 412f Cutting blade 413, 413a to 413f Cutting edge 414 Groove 420 Chamfered part 430 Completely threaded part 500 Machine tool 510 Main spindle 511 Main spindle tip surface G Spark gap H Pitch feed distance Ha Pitch feed start position K Spark plug center line M1 Tap tip distance M2 Estimated cutting edge distance M3 Cutting edge distance on thread cutting start phase N Machine tool reference phase P Thread pitch Q Spindle rotation center line (tool holder rotation center line, tool rotation center line)
α, β, θ, φ Phase difference R Tool holder reference phase S Through hole center line T Thread cutting start phase W Cutting edge phase

Claims (5)

By pitch-feeding a tap that is held in a tool holder attached to the main shaft of a machine tool and has a cutting edge formed at a thread pitch P and a threaded part at the tip consisting of a chamfered part and a fully threaded part, In the female thread machining method of machining a female thread on the inner peripheral surface of the through hole of the workpiece,
A reference position is set along the extending direction of the spindle, and around the spindle are a machine tool reference phase, a tool holder reference phase having a phase difference α with respect to the machine tool reference phase, and the machine tool. A thread cutting start phase corresponding to a thread cutting start position of the female thread and a pitch feeding start position at which pitch feeding of the tap starts, which has a phase difference β with respect to a reference phase,
measuring a tap tip distance M1 along the extending direction of the main shaft between the tap tip of the tap and the reference position;
measuring a phase difference θ between a cutting edge phase corresponding to a cutting edge of a predetermined cutting edge of the cutting blades forming the fully threaded portion of the threaded portion and the tool holder reference phase;
measuring a cutting edge distance M3 along the extending direction of the main shaft between the cutting edge of the predetermined cutting blade and the reference position;
Based on the tap tip distance M1, the blade edge distance M3, the phase difference α, the phase difference β, the phase difference θ, and the thread pitch P, the distance between the estimated blade edge position on the thread cutting start phase and the reference position a step of determining an estimated cutting edge distance M2 on the thread cutting start phase along the extending direction of the spindle;
A female thread machining method characterized in that the tap is pitch fed from the pitch feed start position based on the estimated cutting edge distance M2 on the thread cutting start phase. The female thread processing method according to claim 1,
In the step of determining the estimated cutting edge distance M2 on the thread cutting start phase,
Based on the tap tip distance M1, the cutting edge distance M3, and the thread pitch P, an estimated cut is formed by extending the outer edge of the fully threaded portion on the cutting edge phase from the tap tip to the opposite side of the tool holder. Determining the distance Δm1 along the extending direction of the main shaft between the estimated cutting edge of the blade and the tap tip;
Based on the tap tip distance M1, the phase difference α, the phase difference β, the phase difference θ, the thread pitch P, and the distance Δm1, the estimated cutting edge distance M2 on the thread cutting start phase is calculated as [M2=M1+ △m1+(φ/360 degrees)×P] and [φ=θ−(α−β)]. By pitch-feeding a tap that is held in a tool holder attached to the main shaft of a machine tool and has a cutting edge formed at a thread pitch P and a threaded part at the tip consisting of a chamfered part and a fully threaded part, An estimated cutting edge distance discriminating device for determining an estimated cutting edge distance on a thread cutting start phase used in a female thread machining method for machining a female thread on the inner peripheral surface of a through hole of a workpiece, the device comprising:
A reference position is set along the extending direction of the spindle, and around the spindle are a machine tool reference phase, a tool holder reference phase having a phase difference α with respect to the machine tool reference phase, and the machine tool. A thread cutting start phase corresponding to a thread cutting start position of the female thread is set, having a phase difference β with respect to a reference phase,
Equipped with measuring equipment and processing equipment,
The measuring device includes:
a tap tip distance M1 along the extending direction of the main shaft between the tap tip of the tap and the reference position;
a phase difference θ between a cutting edge phase corresponding to a cutting edge of a predetermined cutting blade of the cutting blades forming the fully threaded portion of the threaded portion and the tool holder reference phase;
configured to be able to measure a cutting edge distance M3 along the extending direction of the main shaft between the cutting edge of the predetermined cutting blade and the reference position,
The processing device calculates the estimated blade edge position on the thread cutting start phase and the blade edge position based on the tap tip distance M1, the blade edge distance M3, the phase difference α, the phase difference β, the phase difference θ, and the thread pitch P. An estimated blade edge distance determining device, characterized in that it determines an estimated blade edge distance M2 on a thread cutting start phase along the extending direction of the main shaft between a reference position and a reference position. The estimated cutting edge distance discriminating device according to claim 3,
The processing device includes:
Based on the tap tip distance M1, the cutting edge distance M3, and the thread pitch P, an estimated cut is formed by extending the outer edge of the fully threaded portion on the cutting edge phase from the tap tip to the opposite side of the tool holder. Determining the distance Δm1 along the extending direction of the main shaft between the estimated cutting edge of the blade and the tap tip;
Based on the tap tip distance M1, the phase difference α, the phase difference β, the phase difference θ, the thread pitch P, and the distance Δm1, the estimated cutting edge distance M2 on the thread cutting start phase is calculated as [M2=M1+ △m1+(φ/360 degrees)×P] and [φ=θ−(α−β)]. By pitch-feeding a tap that is held in a tool holder attached to the main shaft of a machine tool and has a cutting edge formed at a thread pitch P and a threaded part at the tip consisting of a chamfered part and a fully threaded part, A tool presetter used in a female screw machining method for machining a female screw on the inner peripheral surface of a through hole of a workpiece,
A tool presetter comprising the estimated cutting edge distance determining device according to claim 3 or 4.

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