JP4485008B2 - Screw processing method and screw processing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a screw machining method and a screw machining device, and is particularly preferably applied to a screw rolling method and a screw rolling device for a shaft-like workpiece.
[0002]
[Prior art]
A metal shell of a spark plug can be exemplified as a shaft-shaped workpiece whose outer peripheral surface is threaded.
[0003]
By the way, in recent automobile engines and the like, as the exhaust gas regulations are strengthened, a mixture of lean air-fuel mixture is increasingly used (so-called lean burn engine). As shown in FIG. 8, in most engines, the gasket G is sandwiched between 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 support surface R of the cylinder head SH. A screw part 201a formed on the metal fitting 201 is screwed into the cylinder head SH. Thereby, the spark plug 200 is fixed to the cylinder head SH while maintaining the gas sealing property. Here, since the lean air-fuel mixture has a low fuel mixing ratio, depending on the direction of the ground electrode 204 in the combustion chamber K of the spark plug 200, a swirl flow (mixed air flow) generated in the compression stroke in the combustion chamber K is generated. On the other hand, the spark discharge gap g may be behind the ground electrode 204 and cause an ignition error. Therefore, in such an engine, the ground electrode 204 is required to be in an optimal position for ignition, and the angular position of the screwing end with respect to the cylinder head SH of the threaded portion 201a of the metal shell 201 may be designated. . This means that the start position of the screw processing is specified when the screw portion 201a is processed.
[0004]
On the other hand, as shown in FIG. 9, even in a gas sensor 300 or the like that is screwed and fixed to an exhaust pipe E or the like of an engine and includes a plate-like detection element 304 having a detection surface 304a, the detection surface against the flow of exhaust gas is provided. In order to have directionality, the angular position of the screwing end of the threaded portion 301a of the metal shell 301 may be designated. Also in this case, similarly to the processing of the screw portion 201a, the start position of the screw processing is specified when the screw portion 301a is processed.
[0005]
Therefore, here, a case will be described in which the thread portion of the shaft-shaped workpiece 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 the workpiece W to which the ground electrode material X to be the ground electrode 204 is welded so that the ground electrode 204 of the spark plug 200 is an optimal position for ignition. In order to position in the circumferential direction, for example, threading by positioning rolling has been performed. In this positioning rolling, as shown in FIG. 10, a stopped tool (round die 400) is brought close to a stopped workpiece W set at a predetermined position (see FIG. 10A), and the round die 400 is moved. Is a rolling method in which the round die 400 is driven and rotated when it bites into the workpiece W, and the outer peripheral surface of the workpiece W is threaded (see FIG. 10B). The timing of biting of the round die 400 onto the workpiece W is performed by detecting a change in the pressing pressure of the round die 400, for example.
[0006]
[Problems to be solved by the invention]
As described above, in screw processing by positioning rolling, the round die 400 is driven and rotated after contacting (working on) the workpiece 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 bonded 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 workpiece W so that the threading is started from the rotational angle position. Moreover, since these operations are performed visually for each threading cycle for the workpiece W, it is difficult to arbitrarily set the starting position for threading the workpiece W, and the machining time becomes long. At the same time, labor is required for processing, which may increase manufacturing costs.
[0007]
In addition, when performing threading on the outer peripheral surface of the shaft-like workpiece with a milling machine, a lathe or the like, the same problem can be pointed out in the following cases. That is, a stopped tool (screw cutting tool, threading milling cutter, etc.) is relatively approached (approached) to a stopped workpiece W positioned in the circumferential direction, and the tool or the workpiece is driven to rotate when they come into contact with each other. In this case, the outer peripheral surface of the workpiece W is threaded. In such a case, as in the case of positioning rolling, it is difficult to arbitrarily set the starting position of the threading process on the workpiece W, and the processing time is increased and the processing is troublesome, and the manufacturing cost is increased. May increase.
[0008]
An object of the present invention is to provide a screw machining method and a screw machining apparatus capable of arbitrarily setting a screw machining start position on the outer peripheral surface of a workpiece and reducing machining time by reducing machining time. There is to do.
[0009]
[Means for solving the problems and actions / effects]
In order to solve the above-described problem, a threading method according to the present invention includes:
Axial workpiece is held rotatably around the center axis of the workpiece,
The workpiece and a tool for threading the outer peripheral surface of the workpiece are first rotated relative to each other, and the circumferential reference position determined on the workpiece and the tool are determined in the rotated state. An angular position signal is detected when one or more tool side reference positions satisfy a predetermined rotational angular positional relationship ;
In the screw machining method in which an approach start signal is output based on the angular position signal, the tool and the workpiece are relatively approached by this signal output, and the outer circumferential surface of the workpiece is threaded.
The tool is a multi-thread screw die, and there are a plurality of biting candidate positions that are set as the tool-side reference position and start screw machining at predetermined angular intervals in the circumferential direction of the die corresponding to the number of threads. The angular position signal is output corresponding to one or more of the plurality of biting candidate positions .
[0010]
Similarly, the threading device according to the present invention is:
A support that holds the shaft-shaped workpiece so as to be rotatable about the central axis of the workpiece;
The workpiece and a tool for threading the outer peripheral surface of the workpiece are first rotated relative to each other, and the circumferential reference position determined on the workpiece and the tool are determined in the rotated state. A rotation drive unit that detects an angular position signal when one or more tool side reference positions satisfy a predetermined rotational angular position relationship ;
A control unit that outputs an approach start signal based on the angular position signal ;
With this signal output, it has a leaning drive unit for relatively approaching the tool and the workpiece,
In a screw machining apparatus for threading the outer peripheral surface of the workpiece ,
The tool is a multi-thread screw die, and there are a plurality of biting candidate positions that are set as the tool-side reference position and start screw machining at predetermined angular intervals in the circumferential direction of the die corresponding to the number of threads. The angular position signal is output corresponding to one or more of the plurality of biting candidate positions .
[0011]
In the screw machining method and the screw machining device according to the present invention, the circumferential reference position defined on the workpiece and the one or more tool sides defined on the tool while relatively rotating the screw machining tool and the workpiece. A relative rotational angle positional relationship with the reference position is detected. Then, when the circumferential reference position and the tool side reference position satisfy a predetermined rotational angle positional relationship, an approach start signal is output, and the tool and the workpiece are relatively approached by this signal output. As a result, the relative rotational angular position relationship between the circumferential reference position on the workpiece and the tool side reference position on the tool is arbitrarily set in advance in accordance with the start position (chamfering position) of screw machining on the workpiece outer peripheral surface. It only needs to be set, and threading is easy. In addition, it is not necessary to visually set the tool and the work for each screw machining cycle so that the screw machining is started from a predetermined rotational angle position with respect to the circumferential reference position, thereby shortening the machining time and reducing the manufacturing cost. It can also be reduced.
[0012]
As a concrete embodiment at this time, for example,
The circumferential reference position on the workpiece has a first relative rotation angle positional relationship with a planned biting position where the tool bites the outer peripheral surface of the workpiece and starts screw machining,
On the other hand, the tool-side reference position can be set to have a second relative rotational angle position relationship with respect to the planned biting position.
[0013]
Then, when threading the outer peripheral surface of the workpiece, the tool and the workpiece are first rotated relative to each other, and the circumferential reference position and the tool-side reference position are in a predetermined rotational angular position relationship in the rotated state. When the angle position signal is detected and the approach start signal is output based on the angle position signal, the load applied to the tool can be reduced, and the wear of the tool can be suppressed to extend the life. .
[0014]
The reference position in the circumferential direction of the workpiece can be determined in advance corresponding to a specific part in the circumferential direction of the workpiece. Specifically, when the workpiece is a shaft-shaped workpiece that should be the metal shell of the spark plug, the circumferential reference position should be determined according to the bonding position or planned bonding position of the ground electrode material that should be the ground electrode. Can do. In the case where the workpiece is a shaft-shaped workpiece that is to be the metal shell of the gas sensor, the circumferential reference position can be determined corresponding to the position of the gas detection surface of the gas detection element.
[0015]
Further, the angular position signal that triggers the output of the approach start signal can use the output signal of the encoder that detects the rotational angular position of the tool or workpiece, and this encoder can be either a tool or a workpiece. The rotation angle position is detected by being installed on the rotation shaft or the shaft rotating in synchronization therewith. Therefore, the other of the tool and the workpiece may be stopped at least during the period from the completion of the workpiece setting to the start of threading.
[0016]
Then, after the angular position signal is obtained, the approach start signal may be output after being delayed by a predetermined rotation angle (hereinafter referred to as a delay angle) with respect to the rotation direction of the tool or the workpiece. This delay angle can be set and detected using an encoder installed on one of the rotating shafts of the tool and the workpiece or a shaft that rotates in synchronization therewith. 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 the circumferential reference position as a reference. A processed product is obtained. Specifically, when the workpiece is a shaft-shaped workpiece that should be the metal shell of the spark plug, for example, based on the bonding position or planned bonding position (circumferential reference position) of the ground electrode material to be the ground electrode, A total of four types of processed products can be obtained in which the positions spaced 90 degrees apart in the circumferential direction are used as tool biting positions (starting positions for screw machining). When the threading start position of the cylinder head thread (female thread) varies depending on the engine model or individual, the spark plug corresponding to the cylinder head threading start position is selected appropriately from these four types. This makes it easier to set the ground electrode at the optimum position for ignition. In addition, when the workpiece is a shaft-shaped workpiece that should serve as the metal shell of the gas sensor, for example, the positions separated by 90 degrees in the circumferential direction with reference to the position (circumferential reference position) of the gas detection surface of the gas detection element. A total of four types of workpieces can be obtained as tool biting positions (starting positions for screw machining).
[0017]
Further, when the tool of the present invention is a rolling multi-thread screw die, the biting candidate position that is set as the tool-side reference position and starts threading is a predetermined angle in the circumferential direction of the die corresponding to the number of threads. Multiple items are set at intervals. The angular position signal is output in correspondence with one or more of the plurality of biting candidate positions (preferably, the angular position signal is output for each of the biting candidate positions. Can be associated). Accordingly, the biting candidate position can be effectively used as the tool side reference position, and the relative rotational angle position relationship with the circumferential reference position determined on the workpiece can be easily detected.
[0018]
And when the tool of the present invention is a rolling multi-thread screw die, one of a plurality of angular position signals that arrives in a predetermined order with relative rotation of the tool and the workpiece is selected at random, and an approach start signal By using this output, uneven wear of the multi-thread screw die can be prevented. For example, if five angular position signals are set for a five-thread screw die having five biting candidate positions in the circumferential direction, each angular position signal starts threading at the corresponding biting candidate position. Therefore, the five biting candidate positions are used randomly.
[0019]
Further, when the tool of the present invention is a rolling multi-thread screw die, each of a plurality of angular position signals corresponding to a plurality of biting candidate positions is obtained when the thread rolling process is repeatedly performed on a plurality of workpieces. Since the selection sequence of the angular position signals is determined so as to be used with almost equal probability as the machining cycle is repeated, the wear of the multi-thread screw dies can be made uniform. Specifically, the number of appearances of the angular position signal is counted for each different phase, and a plurality of angular position signals are distributed and used in each machining 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 as the machining cycle is repeated can be employed.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to examples shown in 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. The screw rolling device (screw processing device) 100 includes a support unit 1 that supports a workpiece W, a rotation drive unit 2 that rotates a tool, a close-up drive unit 3 that moves the tool toward the circumferential direction of the workpiece W, and a rotation drive unit 2. And a control unit 4 that issues a control command for thread rolling to the approaching drive unit 3. In this embodiment, a shaft-shaped workpiece to be a cylindrical spark plug metal shell (hereinafter also simply referred to as a metal shell) is used as the shaft-shaped workpiece W, and the threaded portion W0 is formed on the outer peripheral surface thereof. Shows when to do. A ground electrode material X to be a ground electrode is welded to a specific portion of the tip surface of the workpiece W. The ground electrode material X is not a final form of the ground electrode bent toward the center electrode side (see FIG. 8), but is a straight bar shape before bending.
[0021]
In the support portion 1, a mandrel type stopper 11 that holds the workpiece W from the inside with an elastic body such as a spring is inserted from above the workpiece W (opposite to the side where the ground electrode material X is joined). Is supported so as to be rotatable around the central axis. Then, 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) that detects that the work W is set at a predetermined position shown in FIGS. An imaging means for software processing such as analysis is provided on the support unit 1. Here, the workpiece W is set on the support 1 by a workpiece feeder (not shown) such as a parts feeder and the stopper 11 so that the ground electrode material X (joining position) is arranged at a predetermined position. The The work set detection sensor 12 is desirably provided at a position where it can be detected whether or not the ground electrode material X is set at the circumferential reference position of the work W. The workpiece W is set so that the distance h between the gasket seat surface S of the workpiece W and the upper end surface of the round die 27 for thread rolling (described later) is constant.
[0022]
Next, the rotary drive unit 2 is provided with a rotary first actuator 21 (for example, an electric motor, a hydraulic motor, etc.), and the rotation of the drive shaft 21a is synchronously rotated by the gear train 22 in the same direction. Are distributed to the gear shafts 23A, 23B, and 23C. The rotations of the gear shafts 23A, 23B, and 23C are respectively screwed on one end side through sliding shafts 24A, 24B, and 24C such as splines, worms and worm wheels 25A, 25B, and 25C (25C not shown). Three dice rotating shafts 26A, 26B, 26C (tool rotating shaft; 26C not shown) to which the rolling round dies 27A, 27B, 27C (screw processing tool; 27C not shown) are fixed Is transmitted to. The three round dies 27A, 27B, and 27C for thread rolling (collectively referred to as dies 27) are formed with multiple threads (in the embodiment, 5 threads) 27a on the outer peripheral surface having substantially the same diameter. Then, the threaded portion W0 of the workpiece W is formed by pressing the unevenness of the screw 27a against the outer peripheral surface of the workpiece W and rotating the workpiece W and the die 27 relative to each other. The drive shaft 21a that rotates in synchronization with the rotation shafts 26A, 26B, and 26C of the die 27 is provided with an encoder 28 as a rotation angle position detecting means, and the die 27 is relatively relative to the ground electrode material X (circumferential reference position). The rotational angle position is detected. The encoder 28 may be provided on any of other shafts, for example, the die rotation shafts 26A, 26B, and 26C (these are collectively referred to as the die shaft 26).
[0023]
In the approaching drive unit 3, three shaft cases 32A, 32B, and 32C on which the die rotation shafts 26A, 26B, and 26C are respectively supported are disposed. These shaft cases 32A, 32B, 32C are provided with a second actuator 31 of a reciprocating type (for example, a fluid pressure cylinder) or a rotating type (for example, an electric motor, a hydraulic motor, etc.). The second actuator 31 moves each shaft center inward in conjunction with each shaft case 32A, 32B, 32C, or simultaneously through the shaft cases 32A, 32B, 32C via a cam or the like. As a result, the outer peripheral surface of the die 27 approaches the outer peripheral surface of the workpiece W (in this specification, the fact that the outer peripheral surface of the die 27 approaches the outer peripheral surface of the workpiece W due to thread rolling is referred to as “sticking”. That the screw 27a on the outer peripheral surface of the screw contacts the outer peripheral surface of the workpiece W and starts screw processing is referred to as “biting”).
[0024]
The control unit 4 includes a microprocessor including an I / O port 41 and a CPU 42, ROM 43, RAM 44, and the like connected to the I / O port 41. The ROM 43 stores a control program 43a. The first actuator 21 of the rotary drive unit 2 is connected to the output side of the I / O port 41 via a servo drive unit 20 for driving the actuator, and the second actuator 31 of the leaning drive unit 3 is connected. The actuator is connected via a servo drive unit 30 for driving the actuator. On the other hand, the work set detection sensor 12 and the encoder 28 are connected to the input side of the I / O port 41.
[0025]
In FIG. 2 showing the positional relationship between the die and the workpiece, three round dies 27A, 27B, and 27C for rolling five-threaded screws are arranged around the workpiece W so as to surround at almost equal intervals in the circumferential direction. . As described above, as the second actuator 31 reciprocates or rotates, the die shaft 26 moves synchronously toward the center of the workpiece W, and the die 27 moves away from the workpiece W (solid line). Close to the state (broken line) in contact with
[0026]
Here, since the diameters of the rolling dies 27A, 27B, and 27C are all set to 5 times the diameter of the workpiece W, when the die 27 makes one rotation in contact with the workpiece W, the distance between both outer peripheral surfaces If there is no slip, the workpiece W rotates 5 times. That is, when the die 27 rotates 72 °, the work W rotates once. On the other hand, the encoder 28 provided on the drive shaft 21 a that rotates synchronously with the die shaft 26 always detects the relative rotational angle position of the die 27. In this embodiment, when the No. 1 position of the rolling round die 27A is opposed to the ground electrode material X as the circumferential reference position determined on the workpiece W as shown in FIG. When the rotation angle position detection signal of the die 27 obtained by the encoder 28 is satisfied (when a predetermined rotation angle position relationship is satisfied), the control unit 4 outputs a pulse (detection signal) No. 1 of the angle position signal. It is configured as appropriate.
[0027]
Next, when the rolling round die 27A is rotated by one rotation of the workpiece W (that is, by rotation of 72 °) and the No. 2 position is opposed to the ground electrode material X of the workpiece W (a predetermined rotational angle positional relationship is satisfied). When the rotation angle position of the die 27 is detected by the encoder 28 again, the control unit 4 outputs a pulse (detection signal) No. 2 of the angle position signal. In this way, every time the rolling round die 27A rotates 72 ° (the workpiece W rotates once) by using the encoder 28 provided on the drive shaft 21a that rotates synchronously with the die shaft 26, a pulse of the angular position signal is obtained. Outputs No.1 to No.5. The angular position signal pulses No. 1 to No. 5 are output regardless of whether or not the rolling round die 27A and the workpiece W are in contact with each other (biting and accompanying rotation) (see FIG. 4).
[0028]
By the way, the die 27 is a five-thread screw, and as shown in FIG. 2 (b), the die 27 bites the outer peripheral surface of the work W and starts five biting candidate positions T1 to T. T5 (starting point of the screw 27a) is provided at equal intervals in the circumferential direction. Then, in the rolling round die 27A, these biting candidate positions T1 to T5 are set as the tool side reference positions, and the angular position signal pulses No. 1 to No. 5 are sent and their biting positions. The attachment candidate positions T1 to T5 are set so as to correspond to each other.
[0029]
Here, as shown in FIG. 2A, a case is considered where the position where the pulse No. 1 of the angular position signal is sent is set to a position facing the ground electrode material X of the workpiece W. When set in this way, the position (circumferential reference position) of the ground electrode material X determined on the workpiece W and the biting candidate position T1 (tool-side reference position) determined on the rolling round die 27A In order to detect the relative rotational angular position relationship, the angular position signal pulse No. 1 based on the encoder 28 in the relative rotational state of the workpiece W and the rolling round die 27A may be used. That is, 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 sending position of the pulse No. 1 of the angular position signal (circumferential reference position and tool side reference position) , When a predetermined rotational angular position relationship is satisfied), an approach start signal is output based on the pulse No. 1 of the angular position signal. By this approaching start signal, the rolling round die 27A immediately approaches the workpiece W and bites against the workpiece W, and the threaded portion W0 of the workpiece W is formed from the position of the ground electrode material X.
[0030]
In the normal usage mode in which the die shaft 26 is driven to rotate at a constant rotational speed, the biting candidate positions T1 to T5 which are the five tool side reference positions are the ground reference electrodes of the workpiece W which are the circumferential reference positions. When facing the material X, five angular position signal pulses No. 1 to No. 5 are sequentially output. In addition, since these angular position signals No. 1 to No. 5 are used randomly (randomly), the bite candidate positions T1 to T5 of the die 27 randomly contribute to the start of threading, and therefore, uneven wear. Is prevented.
[0031]
Next, when the rolling round die 27A starts to bite to the outer peripheral surface of the workpiece W at the position A where the rotary die 27A has moved 18 ° from the position of No. 1 to the lower side of the rotation, the threaded portion W0 of the workpiece W becomes the ground electrode material. It is formed from a position moved 90 ° (18 ° × 5) from the X position to the lower rotation side. Similarly, when biting on the outer peripheral surface of the work W is started at the position B, which is further moved 18 ° from the position A toward the lower rotation side, the screw portion W0 is moved 180 ° from the position of the ground electrode material X toward the lower rotation side. It is formed from the position. In this way, the phase difference (rolling) by 90 ° in the circumferential direction between the biting position (screwing start position) of the threaded portion W0 of the workpiece W and the position of the ground electrode material X (circumferential reference position). With the round die 27A, four types of spark plug metal shells having A, B, C, and D (18 ° phase difference) are obtained. Therefore, it is possible to select a spark plug (spark plug metal shell) having the ground electrode material X at a position where optimum ignition performance is exhibited, and attach it to the cylinder head of the engine. The phase differences A, B, C and D of 18 ° in the rolling round die 27A are the same not only between No. 1 and No. 2, but also between No. 2 and No. 3, etc. Formed. Moreover, the phase angle difference in the circumferential direction of the workpiece W is not limited to 90 ° and can be arbitrarily set, and the phase differences A, B, C, and D may not be equally spaced.
[0032]
Here, the suitability of the threading start positions of the spark plug and the cylinder head will be described with reference to FIG. In general, the threading start position of the threaded portion (female thread) of the cylinder head varies depending on the engine type (in some cases, the same type depends on the individual engine). Therefore, even if the threading start position of the spark plug thread (male thread) is set to one point, the optimal ignition performance is achieved when this spark plug is screwed into the engine cylinder head thread (female thread) and fixed. The ground electrode X ′ of the spark plug is not always located at the position where In FIG. 11, when a spark plug W ′ (axial work W to be a spark plug metal shell) is prepared in which the position of the ground electrode X ′ and the threading start position of the threaded portion W0 coincide at the A position. Is assumed. Since the threading start position of the threaded portion w0 of the cylinder head w varies in the circumferential direction as described above, when the threaded portion W0 of the spark plug W ′ is screwed into the threaded portion w0 of the cylinder head w, the ground electrode X ′ The position in the circumferential direction is not fixed.
[0033]
Therefore, in this embodiment, four types of spark plugs W ′ having a phase difference A, B, C, D of 90 ° in the circumferential direction with respect to the position of the ground electrode X ′. Create Next, the range (whole 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 divided into four equal parts a, b, c, and d in the circumferential direction. The threading start positions A, B, C, and D of the plug W ′ are made to correspond to the threading start positions ranges a, b, c, and d of the cylinder head w. Accordingly, the spark plug W ′ having the threading start positions A, B, C, and D corresponding to the threading start position ranges a, b, c, and d of the threaded portion w0 of the cylinder head w can be appropriately selected. Thus, it becomes easy to set the ground electrode X ′ to an optimum position for ignition. It should be noted that the number of divisions between the screw machining start positions A, B, C, and D of the thread portion W0 of the spark plug W ′ and the screw machining start position ranges a, b, c, and d of the screw portion w0 of the cylinder head w is appropriately determined. Can change.
[0034]
Further, a method for 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 rolling round die 27A rotates 72 ° (the workpiece W rotates once), the ground electrode material X of the workpiece W that is the circumferential reference position and the round die 27 that is the tool side reference position are bitten. Any one of the attachment candidate positions T1 to T5 is opposed to satisfy a predetermined rotational angle position relationship, and based on the rotation angle position detection signal from the encoder 28, pulses No. 1 to No. 5 of the angular position signal are detected. Either one is output. When the output of the first pulse of the angular position signal is detected after the work set is completed (pulse No. 1 is detected in this embodiment), the rotation angle position is detected by the encoder 28 using the set delay angle of 90 °. Count using the signal. When the count at the delay angle of 90 ° ends (pulse falling), the approach start signal is immediately turned ON, and the approach of the die to the workpiece W (break-in) starts. Thereby, in FIG. 2A, the rolling round die 27A is moved at the position A ′ (the phase difference is the same as A) where the rolling round die 27A has moved 18 ° from the position of No. 2 to the lower side of the rotation. Starts to bite against the outer peripheral surface of the workpiece W, so that the screw portion W0 of the workpiece W is formed from a position moved 90 ° from the position of the ground electrode material X toward the lower rotation side. If the delay angle is set to 108 °, the approaching (creaking) position shifts to B ′ (the phase difference is the same as B). The same is set when the close-up (catch-in) positions are C ′ and D ′. The delay angle in the rotation direction is not limited to 90 °, and can be set arbitrarily according to the desired threading start position of the workpiece W. Further, the delay angle may be counted using a second encoder provided on the rotating shaft 26 of the die 27 and the like other than the encoder 28 for detecting the rotational angle position of the die 27.
[0035]
Here, the flowchart showing the flow of the rolling process in FIG. 3 will be described with reference to the timing chart in FIG. 4. First, as a preparatory stage for the rolling process, a delay angle (the delay angle is set to 90 ° in FIG. 4) and a thread rolling time are read (S1). The workpiece W is set by the mandrel type stopper 11 or the like (S2), and it is checked whether or not the detection sensor 12 detects the completion of the workpiece 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). ) To rotate synchronously (S4).
[0036]
Next, when the detection of the first angular position signal is confirmed after completion of the work setting (the pulse No. 1 of the angular position signal is output in FIG. 4) (S5), the set delay angle of 90 ° is used by the encoder 28. Is counted (S6). When the count of the delay angle of 90 ° ends (pulse falling), the approach start signal is turned ON (S7), the second actuator 31 is driven, and the approach of the die 27 to the workpiece W is started (S8). Screw rolling starts from the biting of the die 27 on the outer peripheral surface of the workpiece W (S9), and after the set screw rolling time has elapsed, a die separation signal is output (S10), and the second actuator 31 is turned on. The die 27 is separated from the work W by reverse operation (S11). Finally, the workpiece W is unloaded by the mandrel type stopper 11 or the like (S12), and the one-roll thread rolling process for the workpiece W is completed, and the process returns to the step of setting the next workpiece W. The screw rolling time may be measured directly with a timer or the like, but if the die shaft 26 is rotating at a constant speed during screw rolling, the number of rotations (rotation angle) of the die shaft 26 may be counted by the encoder 28. Good.
[0037]
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 the angular position signal is counted for each different phase, and a plurality of angular position signals are distributed and used in each machining cycle so that the count number for each phase is equalized. An example of the case is shown in the flowchart of FIG. In this example, corresponding to the five angular position signals No. 1 to No. 5, counters K1 to K5 having a total of five appearances are provided for each angular position signal, and the maximum value among the counters K1 to K5 is provided. When the difference between Ki and the minimum value Kj (where i and j are any one of 1 to 5 and i ≠ j) is within a predetermined number of times (five times in FIG. 5), the same as in the embodiment of FIG. Control. When the difference between the maximum value Ki and the minimum value Kj exceeds a predetermined number of times, control using the angular position signal No. j relating to the minimum value Kj is performed intensively.
[0038]
Specifically, since all the counters K1 to K5 are reset at the start (S14), the difference between the maximum value Ki and the minimum value Kj is maintained within 5 times for a while after the start (Yes in S21). ), The same control as in the embodiment of FIG. 3 is performed (S3 to S13). However, it stores the number of the angular position signal No.n (where n is any one of 1 to 5) (S51), and adds 1 to the counter Kn corresponding to the angular position signal No.n at the end of threading. (S13). Eventually, when the difference between the maximum value Ki and the minimum value Kj exceeds five times (No in S21), control using the angular position signal No. j relating to the minimum value Kj is performed intensively (S30 to S130). The angular position signal used at this time is No. j (S50) instead of the first appearing after the work set (S5). By repeating the above, the plurality of biting candidate positions T1 to T5 of the die 27 are distributed and used almost evenly, and the wear of the die 27 can be made uniform.
[0039]
(2) As a second modification, an example in which angular position signals corresponding to a plurality of biting candidate positions are used in a predetermined order as the machining cycle is repeated is shown in the flowchart and FIG. 7 is a timing chart. In this example, a cumulative work number counter K is provided (S15), and angular position signal No. 1 → angular position signal No. 2 → angular position signal No. 3 → angular position signal No. 4 → angular position signal No. 5 The angular position signals are distributed and used in order. That is, the angular position signal to be used is shifted one by one each time the cumulative work number counter K increases by one. M is a parameter for such order use, and [(K-1) / 5] represents an integer part of (K-1) / 5 (S22). Thus, the wear of the die 27 can be made uniform by using the angular position signals in a predetermined order.
[0040]
In the first and second modified examples, an absolute type encoder 28 is used to detect the absolute value of the rotational angular position, or 5 corresponding to each of the angular position signals No. 1 to No. 5. It is recommended to use an increment encoder.
[0041]
In the present invention, the threading method (apparatus) includes threading by a lathe, a milling machine, etc., in addition to thread rolling. In the thread rolling process, two round dies may be used in addition to three, and a rolling attachment with a rolling head for a lathe may be used. Furthermore, although the example of the spark plug and the gas sensor has been described as the workpiece, the scope of application of the present invention is not limited thereto.
[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 workpiece in FIG.
FIG. 3 is a flowchart showing a flow of a rolling process of the screw rolling device of FIG. 1;
4 is a timing chart showing the operation of the thread rolling device of FIG. 1. FIG.
FIG. 5 is a first modified example of the flowchart of FIG. 3;
6 is a second modification of the flowchart of FIG.
FIG. 7 is a timing chart of FIG.
FIG. 8 is a cross-sectional view showing a state in which a spark plug is attached to a cylinder head.
FIG. 9 is a cross-sectional view showing a state where the gas sensor is attached to the exhaust pipe.
FIG. 10 is a schematic view of positioning rolling.
FIG. 11 is a schematic diagram showing the compatibility of the threading start position between the spark plug and the cylinder head.
[Explanation of symbols]
100 Screw rolling device (screw processing device)
DESCRIPTION OF SYMBOLS 1 Support part 2 Rotation drive part 26 Dice rotation axis (tool rotation axis)
27 Dies (Threading tools)
28 Encoder 3 Drive unit 4 Control unit W Work X Ground electrode material (circumferential reference position)
T1-T5 biting candidate position (tool side reference position)

Claims (15)

Axial workpiece is held rotatably around the center axis of the workpiece,
The workpiece and a tool for threading the outer peripheral surface of the workpiece are first rotated relative to each other, and the circumferential reference position determined on the workpiece and the tool are determined in the rotated state. An angular position signal is detected when one or more tool side reference positions satisfy a predetermined rotational angular position relationship ;
In the screw machining method in which an approach start signal is output based on the angular position signal, the tool and the workpiece are relatively approached by this signal output, and the outer circumferential surface of the workpiece is threaded.
The tool is a multi-thread screw die, and there are a plurality of biting candidate positions that are set as the tool-side reference position and start screw machining at predetermined angular intervals in the circumferential direction of the die corresponding to the number of threads. A screw machining method characterized in that the angular position signal is output in correspondence with one or more of the plurality of biting candidate positions .   The threading method according to claim 1, wherein the circumferential reference position of the workpiece is predetermined corresponding to a specific portion in the circumferential direction of the workpiece. Said angular position signal, the tool and the workpiece and one of the rotary shaft or its synchronization installed rotated an axis by the rotational angular position claim issued on the basis of the output of the encoder 1 for detecting or 2 of The threading method described. The threading method according to claim 3 , wherein the other of the tool and the workpiece is stopped rotating at least after the completion of setting of the workpiece until the start of threading. After obtained the angular position signal, any one of claims 1 to 4 wherein the tool or by a delay angle is a predetermined rotational angle with respect to the direction of rotation of the workpiece and outputs the approaching start signal The thread processing method as described in 2. The threading method according to claim 5 , wherein the delay angle is selected and set from a plurality of predetermined phase angles. The delay angle is detected by using an encoder installed on one of the rotation axis of the tool and the workpiece or an axis that rotates in synchronization therewith, and the output of the encoder is used as a trigger for the approach start signal. claim 5 or 6 threading method according is. Threading method according to any one of claims 1 to 7 wherein the tool is a die for thread rolling. The threading method according to any one of claims 1 to 8, wherein the angular position signal is output for each of the biting candidate positions. 10. The system according to claim 1, wherein one of the plurality of angular position signals arriving in a predetermined order with relative rotation between the tool and the workpiece is randomly selected and used for outputting the approach start signal . The threading method according to item 1 . The indu start signal, among the plurality of angular position signals, threaded according to any one of the angular positions claims 1 is output based on the signal 10 first arriving after completion of setting of the workpiece Method. When repeatedly performing screw machining on a plurality of workpieces, each of the plurality of angular position signals corresponding to the plurality of biting candidate positions is used with a substantially equal probability as the machining cycle is repeated. The threading method according to any one of claims 1 to 9, wherein a selection sequence of the angular position signals is defined. 13. The thread machining according to claim 12 , wherein the number of appearances of the angular position signal is counted for each different phase, and the plurality of angular position signals are distributed and used in each machining cycle so that the count number for each phase is equalized. Method. The screw machining method according to claim 12 , wherein a plurality of the angular position signals corresponding to the plurality of biting candidate positions are used in a predetermined order as the machining cycle is repeated. A support that holds the shaft-shaped workpiece so as to be rotatable about the central axis of the workpiece;
The workpiece and a tool for threading the outer peripheral surface of the workpiece are first rotated relative to each other, and the circumferential reference position determined on the workpiece and the tool are determined in the rotated state. A rotation drive unit that detects an angular position signal when one or more tool side reference positions satisfy a predetermined rotational angular position relationship ;
A control unit that outputs an approach start signal based on the angular position signal ;
With this signal output, it has a leaning drive unit for relatively approaching the tool and the workpiece,
In a screw machining apparatus for threading the outer peripheral surface of the workpiece ,
The tool is a multi-thread screw die, and there are a plurality of biting candidate positions that are set as the tool-side reference position and start screw machining at predetermined angular intervals in the circumferential direction of the die corresponding to the number of threads. A screw machining apparatus , wherein the angular position signal is output in correspondence with one or more of the plurality of biting candidate positions .

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