JP2001276948A - Screw thread producing method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw treated producing method and apparatus which enable one to reduce a production cost by shortening processing hours and to select at random an opening position of the threading on the peripheral surface of a workpiece. SOLUTION: Relatively rotating a hardware for threading (a round die for thread rolling) 27 and a workpiece (a shaft like workpiece constituting a main hardware for a spark plug), the rotational angle position of the tool 27 is detected, an opening commencement signal is announced under a predetermined condition, and the tool 27 begins to threading (thread rolling) sticking fast to the workpiece W. The angle position signal which triggers to transmit the opening commencement signal can use the output signal for an encoder 28 which detects the rotational angle position of the tool 27 and the encoder 28 is provided on the motor spindle 21a which rotates synchronously to the rotation shaft 26 of the tool 27.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread forming method and a thread forming apparatus, and more particularly, to a thread rolling method and a thread rolling apparatus for an axial workpiece.

[0002]

2. Description of the Related Art A metal shell of a spark plug can be exemplified as a shaft-shaped work whose outer peripheral surface is subjected to screw processing.

[0003] In recent years, in automobile engines and the like, as the exhaust gas regulations are tightened, air-fuel mixtures in the lean region are often used (so-called lean burn engines). As shown in FIG. 8, in most engines, the gasket seating surface S of the gas seal portion 201b formed on the metal shell 201 of the spark plug 200 and the gasket supporting surface R of the cylinder head SH are provided.
The screw portion 201a formed on the metal shell 201 is screwed into the cylinder head SH while the gasket G is sandwiched between and. As a result, the spark plug 200 is fixed to the cylinder head SH while maintaining gas sealing.
Here, since the lean mixture has a low fuel mixture ratio, the ground electrode 20 in the combustion chamber K of the spark plug 200 is not used.
Depending on the direction of 4, the spark discharge gap g may be shaded by the ground electrode 204 with respect to the swirl flow (mixed air flow) generated during the compression stroke in the combustion chamber K, and an ignition error may occur. Therefore, in such an engine, the ground electrode 204 is required to be located at an optimal position for ignition, and an angular position at which the screwing of the screw portion 201a of the metal shell 201 with respect to the cylinder head SH is completed may be specified. . This means that the start position of the screw processing is specified when the screw part 201a is processed.

On the other hand, as shown in FIG. 9, a gas sensor 300 or the like, which is screwed and fixed to an exhaust pipe E of an engine and has a plate-like detecting element 304 having a detecting surface 304a, also has Since the detection surface has directionality, an angle position at which the screwing of the screw portion 301a of the metal shell 301 is completed may be specified. Again, in this case,
In the same manner as when processing the screw portion 201a, the start position of the screw processing is specified when processing the screw portion 301a.

Therefore, here, a case will be described in which a threaded portion of a shaft-shaped work W to be the metal shell 201 of the spark plug 200 is threaded. Conventionally, a threading start position (also referred to as a biting position) on a work W to which a ground electrode material X to be the ground electrode 204 is welded so that the ground electrode 204 of the spark plug 200 is located at an optimum position for ignition. In order to position the roller in the circumferential direction, for example, thread processing by positioning rolling has been performed. This positioning rolling means, as shown in FIG. 10, a tool (round die 400) in a stopped state is brought closer to a stopped work W set in a predetermined position (see FIG. 10 (a)). When the bite into the work W, the round die 4
This is a rolling method in which the outer peripheral surface of the workpiece W is threaded by driving and rotating 00 (see FIG. 10B). Round die 4
The timing of the biting of the workpiece W at 00 is performed by detecting, for example, a change in the pressing pressure of the round die 400 or the like.

[0006]

As described above, in the thread processing by the positioning rolling, the round die 400 is used.
Is driven and rotated after contacting (biting) the work W. Therefore, in order to position the biting position of the round die 400, the work W is held at a predetermined position with the ground electrode material X joined to the work W as a reference position in the circumferential direction, and a predetermined position with respect to the ground electrode material X is determined. It is necessary to position the round die 400 and the work W such that the screw processing is started from the rotational angle position of the round die 400. Moreover, since these operations are performed visually in each thread machining cycle on the work W, it is difficult to arbitrarily set the start position of the thread machining on the work W, and the machining time becomes long. At the same time, it takes time and effort for processing, which may increase the manufacturing cost.

[0007] In performing the thread cutting process on the outer peripheral surface of the shaft-shaped work using a milling machine, a lathe, or the like, the same problem can be pointed out in the following cases. That is, the stopped tool (thread cutting tool, thread milling cutter, etc.) is relatively approached (closed) to the stopped workpiece W positioned in the circumferential direction, and the tool or the workpiece is driven and rotated when both come into contact. In this case, thread cutting is performed on the outer peripheral surface of the work W. In such a case, as in the case of positioning rolling, it is difficult to arbitrarily set the start position of the threading process on the work W. In addition, the processing time becomes longer and the process is troublesome, and the manufacturing cost is increased. There is a risk of rising.

[0008] An object of the present invention is to set an arbitrary starting position for thread machining on the outer peripheral surface of a work.
It is an object of the present invention to provide a screw processing method and a screw processing apparatus capable of shortening a processing time and reducing a manufacturing cost.

[0009]

Means for Solving the Problems and Actions / Effects In order to solve the above-mentioned problems, a screw machining method according to the present invention holds an axial work rotatably around a center axis of the work, While relatively rotating the work and a tool for threading the outer peripheral surface of the work, a circumferential reference position defined on the work and one or a plurality of tool-side reference positions defined on the tool. The relative rotation angle position relationship is detected, and a lean start signal is output when the circumferential reference position and the tool-side reference position satisfy a predetermined rotation angle position relationship. The method is characterized in that an outer peripheral surface of the work is subjected to a screw process by relatively approaching the work.

[0010] Similarly, a screw machining apparatus according to the present invention provides a support for holding a shaft-shaped work rotatably around a central axis of the work, and a thread for machining the work and the outer peripheral surface of the work. Rotational drive for detecting a relative rotational angular positional relationship between a circumferential reference position defined on the workpiece and one or more tool-side reference positions defined on the tool while relatively rotating the tool. A control unit that outputs a lean start signal when the circumferential reference position and the tool-side reference position satisfy a predetermined rotational angle positional relationship, and the tool and the work are relatively approached by the signal output. And a screw drive on the outer peripheral surface of the work.

In the screw processing method and the screw processing apparatus according to the present invention, while the screw processing tool and the work are relatively rotated, a circumferential reference position defined on the work and one or more reference positions defined on the tool are determined. The relative rotational angle positional relationship with the tool-side reference position is detected. Then, when the circumferential reference position and the tool-side reference position satisfy a predetermined rotational angle positional relationship, a deviation start signal is output, and the tool and the workpiece are relatively approached by this signal output. Thereby, the relative rotation angle positional relationship between the circumferential reference position on the work and the tool-side reference position on the tool can be arbitrarily set in advance in accordance with the start position (biting position) of the thread machining on the outer peripheral surface of the work. It only needs to be set, and screw processing becomes easy. Moreover,
There is no need to visually set the tool and workpiece in each threading cycle so that threading is started from a predetermined rotation angle position with respect to the circumferential reference position, shortening the machining time and reducing manufacturing costs. You can also plan.

In this case, as a specific embodiment, for example, the circumferential reference position on the work is set to the first biting position at which the tool bites the outer peripheral surface of the work and starts threading. It is possible to have a relative rotational angular positional relationship, while the tool-side reference position has a second relative rotational angular positional relationship to the biting expected position.

When the outer peripheral surface of the work is threaded, the tool and the work are first rotated relative to each other, and the circumferential reference position and the tool-side reference position are rotated by a predetermined amount in the rotating state. An angular position signal is detected when the angular position relationship is satisfied, and when a lean start signal is output based on the angular position signal, the load on the tool is reduced, wear of the tool is suppressed, and the life is extended. be able to.

The reference position in the circumferential direction of the work can be determined in advance corresponding to a specific portion in the circumferential direction of the work. Specifically, if the work is an axial work that should be the metal shell of the spark plug, the circumferential reference position should be determined in accordance with the joining position or the expected joining position of the ground electrode material that should be the ground electrode. Can be. Also,
In the case where the workpiece is an axial workpiece that is to be the metal shell of the gas sensor, it can be determined as the circumferential reference position corresponding to the position of the gas detection surface of the gas detection element.

An output signal of an encoder for detecting a rotational angle position of a tool or a work can be used as an angular position signal for triggering the output of a shift start signal. It is installed on one of the rotating shafts or a shaft that rotates synchronously with the rotating shaft and detects the rotational angle position. Therefore, the other of the tool and the work may be stopped at least during the period from the completion of the setting of the work to the start of threading.

After the angular position signal is obtained, the approach start signal may be output with a delay of a predetermined rotation angle (hereinafter referred to as a delay angle) with respect to the rotation direction of the tool or the work. . The delay angle can be set and detected by using an encoder installed on one of the rotation axis of the tool and the work or an axis that rotates synchronously with the rotation axis. Here, if this delay angle is set in advance with a plurality of phase angles with respect to the circumferential reference position, a screw having a plurality of phase angles (delay angles) with respect to the circumferential reference position is set. A processed product is obtained. Specifically, when the workpiece is an axial workpiece that is to be a metal shell of a spark plug, for example, a joining position or a joining position (a circumferential reference position) of a ground electrode material to be a ground electrode is used as a reference. A total of four types of processed products can be obtained in which the positions separated by 90 degrees in the circumferential direction are the biting positions of the tools (start positions of the screw processing). Even when the threading start position of the thread part (female thread) of the cylinder head varies depending on the model and individual of the engine, a spark plug appropriate for the threading start position of the cylinder head is appropriately selected from these four types. This makes it easier to set the ground electrode to an optimal position for ignition. In the case where the workpiece is an axial workpiece that is to be a metal shell of the gas sensor, for example, the position of the gas detection surface of the gas detection element (the circumferential reference position)
With reference to the above, a total of four types of processed products can be obtained in which the positions separated by 90 degrees in the circumferential direction are the biting positions of the tools (start positions of the screw processing).

Furthermore, when the tool of the present invention is a multi-thread thread die for rolling, the candidate biting position which is set as a tool-side reference position and at which screw machining is started is determined in accordance with the number of threads in the circumferential direction of the die. Are set at predetermined angular intervals. Then, the angle position signal is output in association with one or more of the plurality of biting candidate positions (preferably, the angle position signal is output for each of the biting candidate positions. To). This makes it possible to easily utilize the biting candidate position as the tool-side reference position and easily detect the relative rotational angle positional relationship with the circumferential reference position defined on the workpiece.

When the tool of the present invention is a multi-thread thread die for rolling, one of a plurality of angular position signals arriving in a predetermined order along with the relative rotation between the tool and the workpiece is selected at random. By using the signal for starting the shift start signal, it is possible to prevent uneven wear of the multi-thread screw die. For example, if five angular position signals are set for a five-thread screw die having five biting candidate positions in the circumferential direction, screw processing is started at the corresponding biting candidate position for each angular position signal. Therefore, five biting candidate positions are used at random.

In the case where the tool of the present invention is a multi-thread thread for rolling, a plurality of angular position signals corresponding to a plurality of biting candidate positions are obtained when thread rolling is repeatedly performed on a plurality of workpieces. Are determined so that each of them can be used with almost equal probability as the machining cycle is repeated, so that the wear of the multi-threaded die can be made uniform. Specifically, a method of counting the number of appearances of the angle position signal for each different phase, distributing a plurality of angle position signals to each processing cycle so that the count number for each phase is equalized, A method of using a plurality of angular position signals corresponding to the biting candidate positions in a predetermined order along with repetition of a machining cycle can be adopted.

[0020]

Embodiments of the present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 is a block diagram showing a basic configuration of a thread rolling device according to one embodiment of the present invention. The thread rolling device (thread processing device) 100 includes a support portion 1 for supporting a work W, a rotation drive portion 2 for rotating a tool, a drive portion 3 for leaning a tool in a circumferential direction of the work W, and a rotation drive portion 2. And a control unit 4 for issuing a control command for thread rolling to the offset drive unit 3.
In this embodiment, a shaft-shaped work to be used as a metal shell for a spark plug (hereinafter, also simply referred to as a metal shell) is used as the shaft-shaped work W, and a screw portion W0 is formed on the outer peripheral surface thereof. Is shown. A ground electrode material X to be a ground electrode is welded to a specific portion on the tip end surface of the work W. Note that the ground electrode material X is not a final form of the ground electrode bent toward the center electrode side (see FIG. 8), but a straight rod shape before bending.

In the support portion 1, a mandrel type stopper 1 for holding the work W from the inside by an elastic body such as a spring.
1 is inserted from above the work W (the side opposite to the side where the ground electrode material X is joined) to support the work W rotatably around the central axis. A work set detection sensor 12 (for example, a contact type sensor such as a limit switch, a non-contact type sensor such as a photoelectric sensor / proximity switch, or an image) for detecting that the work W is set at a predetermined position shown in FIGS. Imaging means for software processing such as analysis) is provided on the support unit 1. Here, the work W
Is set on the support unit 1 by a work supply device (not shown) such as a parts feeder and the stopper 11 so that the (joining position of) the ground electrode material X is arranged at a predetermined position. It is desirable that the work set detection sensor 12 be provided at a position where it can also detect whether or not the ground electrode material X is set at the circumferential reference position of the work W. The work W
Gasket seat S and thread rolling round dies 27 (described later)
Work W so that the distance h from the upper end surface of the
Is set.

Next, the rotary drive unit 2 has a rotary first actuator 21 (for example, an electric motor, a hydraulic motor, or the like).
The rotation of the drive shaft 21a is provided by three gear shafts 23A and 23A synchronously rotated in the same direction by the gear train 22.
3B and 23C. Gear shafts 23A, 23B, 2
The rotation of 3C is performed by sliding shafts 24A, 24
24B, 24C and worm and worm wheel 25
A, 25B, 25C (however, 25C is not shown) and the like, and a thread rolling round die 27A, 2
Three die rotating shafts 26A, 26 to which 7B, 27C (thread processing tool; 27C is not shown) are fixed.
B, 26C (tool rotation axis; 26C is not shown)
Is transmitted to Three thread rolling round dies 27A, 27
In B and 27C (these are collectively referred to as a dice 27), a plurality of (five in this embodiment) screws 27a are formed on the outer peripheral surface having substantially the same diameter. By pressing against the outer peripheral surface and rotating the work W and the die 27 relative to each other, a screw portion W0 of the work W is formed. The rotation shafts 26A, 26B, 26C of the die 27
An encoder 28 is provided as a rotation angle position detecting means on the drive shaft 21a that rotates synchronously with the drive shaft 21a, and detects a relative rotation angle position of the die 27 with respect to the ground electrode material X (a circumferential reference position). The encoder 28 may be provided on any of the other shafts, for example, any of the die rotation shafts 26A, 26B, and 26C (these are collectively referred to as the die shaft 26).

The drive unit 3 has a die rotating shaft 26
A, 26B, and three shaft cases 3 on which each of 26C is supported.
2A, 32B and 32C are arranged. The shaft case 32A, 32B, 32C is provided with a reciprocating (for example, a fluid pressure cylinder or the like) or rotary (for example, an electric motor, a hydraulic motor or the like) second actuator 31. The second actuator 31 includes shaft cases 32A, 32B,
32C, 32A, 32B, 3
2C is simultaneously moved inward via a cam or the like, and each axis is moved inward. As a result, the outer peripheral surface of the die 27 is
(In this specification, “closed” means that the outer peripheral surface of the die 27 approaches the outer peripheral surface of the work W due to thread rolling, and the screw 27a on the outer peripheral surface of the die 27 Starting screwing in contact with the surface is called "biting".

The control section 4 is constituted by a microprocessor comprising an I / O port 41 and a CPU 42, a ROM 43, a RAM 44 and the like connected thereto.
3 stores a control program 43a. The output side of the I / O port 41 is connected to the first actuator 21 of the rotary drive unit 2 via the servo drive unit 20 for driving the actuator, and the second actuator 31 of the leaning drive unit 3 is connected thereto. It is connected via a servo drive unit 30 for driving the actuator. On the other hand, the input side of the I / O port 41 is connected to the workset detection sensor 12 and the encoder 28.

FIG. 2 showing an arrangement relationship between a die and a work.
, Three 5-thread thread rolling round dies 27A, 27B, and 27C are arranged around the work W at substantially equal intervals in the circumferential direction. As described above, with the reciprocation or rotation of the second actuator 31, the die shaft 26 moves synchronously toward the center of the workpiece W, and the die 27
From the state separated from the work W (solid line) to the state contacted with the work W (broken line).

Here, the rolling round dies 27A, 27B,
Since the diameter of each of 27C is set to five times the diameter of the work W, when the die 27 makes one rotation while in contact with the work W, if there is no slippage between the outer peripheral surfaces, the work W makes five rotations. . That is, when the die 27 rotates 72 °, the work W makes one rotation. On the other hand, the encoder 28 provided on the drive shaft 21 a that rotates in synchronization with the die shaft 26 constantly detects the relative rotation angle position of the die 27. Then, in this embodiment, as shown in FIG. 2A, when the No. 1 position of the rolling round die 27A is opposed to the ground electrode material X as a circumferential reference position defined on the work W. When the predetermined rotational angle position relationship is satisfied, the control unit 4 outputs the pulse (detection signal) No. 1 of the angular position signal using the detection signal of the rotational angle position of the dice 27 obtained by the encoder 28. It is configured to

Next, the rolling round die 27A is used for the work W
When the No. 2 position is rotated by the rotation amount (that is, 72 ° rotation) to face the ground electrode material X of the work W (when a predetermined rotation angle positional relationship is satisfied), the rotation of the die 27 by the encoder 28 again. A pulse (detection signal) No. 2 of the angle position signal is output from the control unit 4 using the detection signal of the angle position. In this way, using the encoder 28 provided on the drive shaft 21a that rotates in synchronization with the die shaft 26, the rolling round die 27A rotates 72 ° (the work W rotates once).
Each time the pulse No. 1 to No. 5 of the angular position signal is output. The pulse Nos. 1 to 5 of the angular position signal are output irrespective of the presence or absence of contact (biting and co-rotation) between the rolling round die 27A and the work W (see FIG. 4).

By the way, the die 27 is a five-start thread, and has five end candidates on the outer peripheral edge of the end face for starting thread rolling by biting the outer peripheral surface of the work W as shown in FIG. 2B. Positions T1 to T5 (points at which the screw 27a starts to be formed) are equally spaced in the circumferential direction. And rolling die 27
In A, these biting candidate positions T1 to T5 are set as the tool-side reference positions, and the above-mentioned transmission positions of the angular position signal pulses No. 1 to No. 5 and these biting candidate positions T1 to T5 are set. Is set to correspond to each.

Here, as shown in FIG. 2A, the sending position of the pulse No. 1 of the angular position signal is set to the ground electrode material X of the work W.
Let us consider a case where the position is set to a position opposite to. When set in this way, the position of the ground electrode material X defined on the workpiece W (circumferential reference position) and the biting candidate position T1 defined on the rolling round die 27A (tool-side reference position).
In order to detect the relative rotation angle position relationship between the workpiece W and the rolling round die 27A, the pulse No. 1 of the angle position signal based on the encoder 28 in the relative rotation state between the work W and the rolling round die 27A.
It is good to use. That is, the pulse N of the angular position signal
When the position of the ground electrode material X and the biting candidate position T1, which is the tool-side reference position, are opposed to each other at the delivery position of o.1 (the circumferential reference position and the tool-side reference position are at predetermined rotation angle positions). When the relationship is satisfied), the pulse number of the angular position signal
1, the approach start signal is output. Due to the approach start signal, the rolling round die 27A immediately approaches the work W and bites into the work W.
Is formed from the position of the ground electrode material X.

In a normal use mode in which the die shaft 26 is driven and rotated at a constant rotation speed, the biting candidate positions T1 to T5, which are five tool-side reference positions, are the work W which is the circumferential reference position. 5 when facing the ground electrode material X
Pulse Nos. 1 to 5 of the angular position signals are sequentially output. By using these angular position signals No. 1 to No. 5 randomly (randomly), the biting candidate positions T1 to T5 of the die 27 contribute to the start of threading at random. Is prevented.

Next, the work W is moved at the position A where the rolling round die 27A is moved 18 ° from the position No. 1 to the lower rotation side.
Begins to bite into the outer peripheral surface of the workpiece W
0 is 90 ° (18) from the position of the ground electrode material X to the lower rotation side.
゜ × 5) It is formed from the moved position. Similarly, B moved further 18 ° from the position A to the lower rotation side.
Starts to bite into the outer peripheral surface of the work W at the position of the screw W0.
形成 It is formed from the moved position. In this way, the biting position of the threaded portion W0 of the workpiece W (starting position of threading).
Phase difference of 90 ° in the circumferential direction between the ground electrode material X and the position of the ground electrode material X (reference position in the circumferential direction).
Four types of metal shells for a spark plug having (phase difference of ゜) A, B, C, D can be obtained. Therefore, it is possible to select a spark plug (a metal shell for a spark plug) having the ground electrode material X at a position where the optimum ignition performance is exhibited from these, and attach it to the cylinder head of the engine. The phase difference A, B, C, D of 18 ° in the rolling round die 27A is not only between No. 1 and No. 2, but also between No. 1 and No. 2.
It is formed similarly between No. 2 and No. 3. In addition, the phase angle difference in the circumferential direction of the work W is not limited to 90 ° and can be set arbitrarily, and the phase differences A, B, C, and D need not be at equal intervals.

Here, the suitability of the threading start position between the spark plug and the cylinder head will be described with reference to FIG. In general, the starting position of threading of the threaded portion (female thread) of the cylinder head varies depending on the model of the engine (in some cases, even with the same model, depending on each engine). Therefore, the screw part (male screw) of the spark plug
Even if the screw processing start position of the spark plug is set to one point, when the spark plug is screwed into the screw portion (female screw) of the cylinder head of the engine and fixed, the ground electrode X of the spark plug is located at a position where the optimum spark performance is exhibited. 'Is not always located. In FIG. 11, when a spark plug W '(axial workpiece W to be a metal shell for a spark plug) is prepared in which the position of the ground electrode X' and the screw processing start position of the screw portion W0 coincide at the position A. Is assumed. Since the threading start position of the thread portion w0 of the cylinder head w varies in the circumferential direction as described above, when the thread portion W0 of the spark plug W 'is screwed into the thread portion w0 of the cylinder head w, the ground electrode X' The position in the circumferential direction is not fixed.

Therefore, in this embodiment, the threading start position of the threaded portion W0 is 9 in the circumferential direction with respect to the position of the ground electrode X '.
Four types of spark plugs W ′ having phase differences A, B, C, and D for every 0 ° are created. Next, the range (entire circumference) of the threading start position of the threaded portion w0 of the cylinder head w into which the threaded portion W0 of the spark plug W 'is screwed is a, b,
c and d are divided into four equal parts, and the screw processing start positions A, B, C, and D of the spark plug W 'correspond to the screw processing start position ranges a, b, c, and d of the cylinder head w. As a result, the threading start positions A, according to the threading start position ranges a, b, c, d of the threaded portion w0 of the cylinder head w,
The spark plug W ′ having B, C, and D can be appropriately selected, and the ground electrode X ′ can be easily set to an optimal position for ignition. The screw portion W of the spark plug W '
0, the threading start positions A, B, C, and D, and the ranges a, b, c, of the threading start positions of the threaded portion w0 of the cylinder head w.
The number of divisions with d can be changed as appropriate.

Further, a method of forming the phase differences A, B, C and D in the rolling round die 27A will be described with reference to the timing chart of FIG. As described above, every time the round die 27A for rolling is rotated by 72 ° (the workpiece W makes one rotation), the ground electrode material X of the workpiece W at the circumferential reference position is set.
Any one of the biting candidate positions T1 to T5 of the round die 27, which is the tool-side reference position, opposes each other and satisfies a predetermined rotational angle positional relationship. Position signal pulse No.
One of No. 1 to No. 5 is output. When the output of the first pulse of the angular position signal is detected after the completion of the work setting (pulse No. 1 is detected in the present embodiment), the set delay angle 90 ° is detected by the encoder 28 as the rotational angle position. Count using the signal. Delay angle 90
As soon as the counting of ゜ is completed (falling of the pulse), the approach start signal is immediately turned ON, and the approach of the dice to the work W is started. As a result, FIG.
In (a), the rolling round die 27A is moved by 18 ° from the position of No. 2 to the lower rotation side at the position A ′ (the phase difference is the same as A), and the rolling round die 27A is moved to the outer periphery of the work W. Since it starts to lean (bite) on the surface, the screw portion W0 of the work W is formed at a position shifted 90 ° to the lower rotation side from the position of the ground electrode material X. If the delay angle is set to 108 °, the approaching (biting) position is B ′ (the phase difference is B
To the same). The approaching (biting) position is C '
And D 'are similarly set. Note that the delay angle in the rotation direction is not limited to 90 °, but can be set arbitrarily according to a desired screw processing start position of the work W. Further, the delay angle may be counted using a second encoder provided on the rotary shaft 26 of the die 27 or the like, which is different from the encoder 28 that detects the rotational angle position of the die 27.

Here, a flow chart showing the flow of the rolling process in FIG. 3 will be described with reference to the timing chart in FIG. First, a delay angle (the delay angle is set to 90 ° in FIG. 4) and a thread rolling time are read as a preparation stage of the rolling process (S1). Mandrel type stopper 1
The work W is set by 1 or the like (S2), and it is checked whether or not the detection sensor 12 detects the completion of the work setting (S3). If the work set has not been completed, the operation is terminated (alarm may be output). If the work set has been completed, when the first actuator 21 is driven to rotate, the die shaft 26 rotates at a constant rotational speed (for example, 410 rpm).
m), the motor rotates synchronously (S4).

Next, after the completion of the work setting, the detection of the first angular position signal is confirmed (pulse No. 1 of the angular position signal is output in FIG. 4) (S5), and the set delay angle 90 ° is encoded by the encoder. It counts using 28 (S6). When the count of the delay angle 90 ° ends (the pulse falls), the approach start signal is turned ON (S
7) The second actuator 31 is driven to
7 starts to lean on the work W (S8). Thread rolling starts from the biting of the die 27 on the outer peripheral surface of the workpiece W (S9), and after a lapse of a set screw rolling time, a die separation signal is output (S10), and the second actuator 31 is turned off. Reverse the operation to move the die 27 to the workpiece W
(S11). Finally, the work W is carried out by the mandrel-type stopper 11 or the like (S12), the one-loop thread rolling for the work W is completed, and the process returns to the step of setting the next work W. The thread rolling time may be measured directly by a timer or the like. However, if the die shaft 26 rotates at a constant speed during thread rolling, the number of rotations (rotation angle) of the die shaft 26 may be counted by the encoder 28. Good.

Next, a modified example of the flowchart of FIG. 3 and the timing chart of FIG. 4 will be described. (1) As a first modification, the number of appearances of an angle position signal is counted for each different phase, and a plurality of angle position signals are used in each machining cycle so as to equalize the count number for each phase. An example of the case is shown in the flowchart of FIG. In this example, five angular position signals No. 1 to No. 5
, A total of five occurrence counters K1 to K5 are provided for each angular position signal, and the maximum value Ki and the minimum value Kj of the counters K1 to K5 (where i and j are 1 to 5 When the difference from i ≠ j) is within a predetermined number of times (5 times in FIG. 5), the same control as in the embodiment of FIG. 3 is performed. When the difference between the maximum value Ki and the minimum value Kj exceeds a predetermined number, the control using the angle position signal No.j related to the minimum value Kj is intensively performed.

Specifically, at the start, the counter K1
Since K5 are all reset (S14), the difference between the maximum value Ki and the minimum value Kj is kept within 5 times for a while after the start (Yes in S21), similar to the embodiment of FIG. Is performed (S3 to S13). However, the number of the angular position signal No. n (n is any one of 1 to 5) that has been used is stored (S51), and 1 is added to the counter Kn corresponding to the angular position signal No. n at the end of threading. Yes (S1
3). Eventually, when the difference between the maximum value Ki and the minimum value Kj exceeds 5 times (No in S21), control using the angle position signal No.j related to the minimum value Kj is intensively performed (S30 to S30).
130). The angular position signal used at this time is No.j instead of the signal (S5) that first appears after the work set.
(S50). By repeating the above, die 2
7, the plurality of biting candidate positions T1 to T5 are almost equally used, and the wear of the dice 27 can be made uniform.

(2) As a second modification, FIG. 6 shows an example in which angular position signals corresponding to a plurality of biting candidate positions are used in a predetermined order with the repetition of a machining cycle. This is shown in the flowchart and the timing chart of FIG. In this example, a cumulative work number counter K is provided (S15), and the angular position signal No. 1 → the angular position signal No. 2 →
Angle position signal No.3 → Angle position signal No.4 → Angle position signal
The angular position signals are sorted and used in the order of No. 5. That is, each time the cumulative work number counter K increases by one, the angular position signal to be used is shifted by one. M is a parameter for such order use, [(K−
1) / 5] represents an integer part of (K-1) / 5 (S22). In this way, by using the angular position signals in a predetermined order, the wear of the dice 27 can be made uniform.

In the first and second modified examples, an absolute type encoder 28 is used to detect the absolute value of the rotational angle position, or the angular position signals No. 1 to No.
It is preferable to use five increment type encoders corresponding to each of the five.

In the present invention, the thread forming method (apparatus) includes not only thread rolling but also thread cutting with a lathe, milling machine or the like. In the thread rolling process, two round dies other than three may be used, and a rolling attachment with a rolling head for a lathe can also be used. Furthermore, although the spark plug and the gas sensor have been described as examples of the workpiece, the scope of the present invention is not limited to these.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a thread rolling device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an arrangement relationship between a die and a work in FIG. 1;

FIG. 3 is a flowchart showing a flow of a rolling process of the thread rolling device in FIG. 1;

FIG. 4 is a timing chart showing the operation of the thread rolling device of FIG. 1;

FIG. 5 is a first modification of the flowchart of FIG. 3;

FIG. 6 is a second modification of the flowchart of FIG. 3;

FIG. 7 is a timing chart of FIG. 6;

FIG. 8 is a sectional view showing a state in which the spark plug is attached to a cylinder head.

FIG. 9 is a sectional view showing a state where the gas sensor is attached to an exhaust pipe.

FIG. 10 is a schematic diagram of positioning rolling.

FIG. 11 is a schematic diagram showing the suitability of the screw processing start position between the spark plug and the cylinder head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 100 Thread rolling device (screw processing device) 1 Support part 2 Rotation drive part 26 Dice rotation axis (tool rotation axis) 27 Dice (thread processing tool) 28 Encoder 3 Leaning drive part 4 Control part W Work X Ground electrode material (circumference) Direction reference position) T1 to T5 biting candidate position (tool-side reference position)

Claims (18)

[Claims] An axial work is rotatably held around a central axis of the work, and the work and a tool for threading an outer peripheral surface of the work are relatively rotated on the work while rotating the work. Detecting a relative rotation angle positional relationship between a determined circumferential reference position and one or more tool-side reference positions defined on the tool, wherein the circumferential reference position and the tool-side reference position are predetermined; A deviation start signal is output when the rotation angle positional relationship is satisfied, and the tool and the work are relatively approached by this signal output to perform threading on the outer peripheral surface of the work. Method. 2. The thread working method according to claim 1, wherein the reference position in the circumferential direction of the work is predetermined corresponding to a specific portion in the circumferential direction of the work. 3. The method according to claim 1, wherein the tool and the workpiece are relatively rotated first, and when the circumferential reference position and the tool-side reference position satisfy a predetermined rotational angle positional relationship in the rotating state. 3. The screw processing method according to claim 1, wherein an angular position signal is detected, and the deviation start signal is output based on the angular position signal. 4. 4. The angular position signal is issued based on an output of an encoder installed on one of the rotating shaft of the tool and the work or a shaft that rotates synchronously with the rotating shaft and detecting a rotating angular position. The screw processing method according to claim 3. 5. The screw working method according to claim 4, wherein the other of the tool and the work is stopped at least until the start of the screw working after the setting of the work is completed. 6. After the angular position signal is obtained, the shift start signal is output with a delay by a predetermined rotation angle (hereinafter referred to as a delay angle) with respect to the rotation direction of the tool or the work. 6. The thread working method according to any one of 3 to 5. 7. The screw processing method according to claim 6, wherein the delay angle is set by selecting from a plurality of predetermined phase angles. 8. The delay angle is detected using an encoder installed on one of the rotation axis of the tool and the work or an axis that rotates synchronously with the rotation axis, and the output of the encoder starts the leaning. 8. The method according to claim 6, wherein the method is used as a signal trigger. 9. The thread working method according to claim 1, wherein the tool is a thread rolling die. 10. The tool is a multi-thread screw die,
A plurality of biting candidate positions that are set as the tool-side reference positions and that start screw machining are set at predetermined angular intervals in the circumferential direction of the die in accordance with the number of threads. 10. The apparatus according to claim 3, wherein the angular position signal is output in correspondence with one or more of the angular position signals.
The thread working method according to any one of the above. 11. The method according to claim 10, wherein the angular position signal is output for each of the biting candidate positions. 12. A plurality of angular position signals arriving in a predetermined order according to a relative rotation between the tool and the workpiece, one of which is randomly selected and used for outputting the lean start signal. Or the screw processing method according to 11. 13. The method according to claim 10, wherein the approach start signal is output when a signal having a predetermined timing relationship from a reference time is detected among the plurality of angular position signals. Screw processing method. 14. The screw working method according to claim 13, wherein the deviation start signal is output based on the angular position signal that arrives first after the setting of the work is completed. 15. When repeatedly performing a thread rolling process on a plurality of workpieces, each of the plurality of angular position signals corresponding to the plurality of biting candidate positions becomes substantially uniform with repetition of a machining cycle. The screw machining method according to claim 10 or 11, wherein a selection sequence of the angular position signals is determined so as to be used with probability. 16. The method according to claim 1, wherein the number of appearances of the angle position signal is counted for each different phase, and the plurality of angle position signals are used in each machining cycle so that the count number for each phase is equalized. 15. The thread working method according to 15. 17. A plurality of angular position signals corresponding to a plurality of biting candidate positions are used in a predetermined order as the machining cycle is repeated.
The thread processing method described. 18. A rotating device comprising: a support for holding a shaft-shaped work rotatably around a center axis of the work; and a tool for threading an outer peripheral surface of the work while rotating the work relatively. A rotation drive unit that detects a relative rotation angle position relationship between a circumferential reference position defined on the workpiece and one or more tool-side reference positions defined on the tool, and the circumferential reference position and the rotation drive unit. A control unit that outputs a lean start signal when the tool-side reference position satisfies a predetermined rotational angle positional relationship, and a lean drive unit that relatively closes the tool and the workpiece by outputting the lean signal, A thread processing device for performing thread processing on an outer peripheral surface of a work.