JP4439666B2 - Spark plug manufacturing method and manufacturing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spark plug manufacturing method and manufacturing apparatus, and particularly to a spark plug manufacturing method and manufacturing apparatus that involve thread rolling.
[0002]
[Prior art]
In general, the metal shell of the spark plug is formed with a thread portion for screwing into the cylinder head on the outer peripheral surface by screw machining.
[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]
Hereinafter, a case where the thread portion of the shaft-like workpiece W to be the metal shell 201 of the spark plug 200 is threaded will be described. 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. 9, a stopped tool (round die 400) is brought close to a stopped workpiece W set at a predetermined position (see FIG. 9A), 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. 9B). 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.
[0005]
[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 thread rolling process is started from the rotational angle position. Moreover, since these operations are performed visually for each thread rolling process cycle on the workpiece W, it is difficult to arbitrarily set the starting position of the thread rolling process on the workpiece W. As time increases, processing is time-consuming and the manufacturing cost may increase.
[0006]
The object of the present invention is to arbitrarily set the starting position of the thread rolling process on the outer peripheral surface of the shaft-shaped workpiece to be the metal shell of the spark plug, and to accurately position it, and to shorten the machining time. Thus, it is an object of the present invention to provide a spark plug manufacturing method and manufacturing apparatus capable of reducing the manufacturing cost.
[0007]
[Means for solving the problems and actions / effects]
  In order to solve the above problems, a method for manufacturing a spark plug according to the present invention includes:
  A shaft-shaped workpiece that is to be the metal shell of the spark plug, and a workpiece in which a gas seal portion protrudes outward in the radial direction on the outer peripheral surface of the base end side of the screw formation scheduled portion is formed around its central axis. While being held rotatably,
  In the axial direction of the workpiece, the end surface of the gas seal portion on the side of the thread formation portionWorkpiece side positioning end faceAnd an end surface corresponding to the workpiece-side positioning end surface in a die for thread rolling the outer peripheral surface of the workpieceDice side positioning end faceA certain amount betweenDistance between positioning end facesThe die and the workpiece are positioned so that
  The work and the dieFirst, let it be in a state of relative rotation.A circumferential reference position determined corresponding to a joining position or a planned joining position of a ground electrode material to be a ground electrode on the workpiece, and one or a plurality of tool side reference positions defined on the die.Is detected when the rotation angle position relationship is satisfied.,
  AboveBased on angular position signalA close-up start signal is output, and by this signal output, the die and the workpiece are relatively approached to perform thread rolling on the outer peripheral surface of the workpiece.In the spark plug manufacturing method,
  After the angular position signal is obtained, the approach start signal is output after being delayed by a predetermined delay angle with respect to the direction of rotation of the die.It is characterized by that.
[0008]
  Similarly, the spark plug manufacturing apparatus according to the present invention includes:
  A shaft-shaped workpiece that is to be the metal shell of the spark plug, and a workpiece in which a gas seal portion is formed to protrude radially outward on the outer peripheral surface of the base end side of the portion where the screw is to be formed, around its central axis While holding it rotatable,
  In the axial direction of the workpiece, between the end surface of the gas seal portion on the side where the thread formation is scheduled and the end surface corresponding to the workpiece-side positioning end surface in the die for thread rolling the outer peripheral surface of the workpiece. A support portion for positioning the die and the workpiece so that a certain amount of distance occurs;
  The work and the dieFirst, let it be in a state of relative rotation.A circumferential reference position determined corresponding to a joining position or a planned joining position of a ground electrode material to be a ground electrode on the workpiece, and one or a plurality of tool side reference positions defined on the die.Is the angular position signal whenA rotation drive unit for detecting
  AboveBased on angular position signalA control unit that outputs a close-up start signal;
  With this signal output, it has a leaning drive unit that makes the die and the workpiece relatively approach,
  Perform thread rolling on the outer peripheral surface of the workpiece.In spark plug manufacturing equipment,
  After the angular position signal is obtained, the approach start signal is output after being delayed by a predetermined delay angle with respect to the direction of rotation of the die.It is characterized by that.
[0009]
The axial workpiece to be the metal shell of the spark plug according to the present invention is formed by projecting the gas seal portion radially outward on the outer peripheral surface of the base end side of the screw formation scheduled portion, and the axial direction of the workpiece , A certain amount of gap between the end face (hereinafter referred to as a workpiece side positioning end face) facing the screw formation planned portion of the gas seal portion and the end face of the die corresponding to the workpiece side positioning end face (hereinafter referred to as die side positioning end face). The die and the workpiece are positioned so that a distance (hereinafter referred to as a distance between the positioning end faces) is generated. As a result, the thread forming portion of the workpiece is accurately positioned in the axial direction, and the workpiece-side positioning end surface (that is, the surface to be used for sealing with the cylinder head directly or via the gasket) And the thread rolling start position can be kept small within the same product number (product lot).
[0010]
In this state, while rotating the dice and the work relative to each other, on the work, a circumferential reference position determined corresponding to the joining position or the planned joining position of the ground electrode material to be the ground electrode, A relative rotational angle position relationship with the determined one or more tool side reference positions 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 die is adjusted in advance in accordance with the start position (the biting position) of the thread rolling process on the workpiece outer peripheral surface. It is only necessary to set it arbitrarily, and the thread rolling process becomes easy. In addition, it is not necessary to set the die and workpiece visually for each thread rolling process cycle so that the thread rolling process is started from a predetermined rotational angle position with respect to the circumferential reference position, thereby shortening the machining time. Thus, the manufacturing cost can be reduced.
[0011]
When the thread rolling process is performed on the outer peripheral surface of the workpiece, the die and the workpiece are first rotated relative to each other, and in the rotated state, the circumferential reference position and the tool side reference position are set at a predetermined rotation angle. When an angular position signal is detected when the positional relationship is satisfied, and a close-up start signal is output based on this angular position signal, the load on the die is reduced, and the wear of the die is suppressed to extend the life. Can do.
[0012]
Also, the angular position signal that triggers the output of the close-up start signal can use the output signal of the encoder that detects the rotational angular position of the dice, and this encoder is a rotating shaft of the die or an axis that rotates synchronously with this. Installed to detect the rotational angle position. Therefore, the work may be stopped at least after the work is set and before the thread rolling process is started.
[0013]
Then, after the angular position signal is obtained, an 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 dice. This delay angle can be set and detected by using an encoder installed on a rotating shaft of the die 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 rolled product is obtained. Specifically, in a shaft-shaped workpiece that is to be a metal shell of the spark plug, for example, a circumferential direction with reference to a bonding position or a planned bonding position (circumferential reference position) of a ground electrode material that should be a ground electrode. A total of four types of processed products can be obtained in which the positions spaced 90 degrees apart from each other are used as the biting position of the die (starting position of the thread rolling process). 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.
[0014]
Furthermore, when the die 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 the thread rolling process is set in the circumferential direction of the die corresponding to the number of screw threads. A plurality are set at predetermined angular 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.
[0015]
Further, when the die of the present invention is a multi-thread screw die, one of a plurality of angular position signals arriving in a predetermined order in accordance with the relative rotation of the die and the workpiece is randomly selected to output a close-up start signal. By using it, 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 is subjected to thread rolling at the corresponding biting candidate position. Since it is started, five biting candidate positions are randomly used.
[0016]
Further, when the die of the present invention is a multi-thread screw die, when the thread rolling process is repeatedly performed on a plurality of workpieces, each of a plurality of angular position signals corresponding to a plurality of biting candidate positions is a machining cycle. Since the selection sequence of the angular position signals is determined so that the angular position signals are used with a substantially equal probability with the repetition of the above, it is possible to make the wear of the multi-thread screw dies 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.
[0017]
As a method of positioning the thread formation planned part of the workpiece in the axial direction, it is performed at a position different from the screw rolling device, and transported and positioned to the final positioning position in the screw rolling device, and in the screw rolling device. It may be performed directly at the final positioning position. In the former case, in the thread rolling device, the position of the workpiece where the distance between the positioning end surfaces is formed between the workpiece side positioning end surface and the die side positioning end surface is the final positioning position. At another position, the workpiece is preliminarily positioned at a preliminary positioning position that satisfies a certain relationship with the final positioning position, and the workpiece is conveyed and positioned at the final positioning position using the preliminary positioning position. In the latter case, the workpiece is directly positioned at the final positioning position where the distance between the positioning end surfaces is formed between the workpiece positioning end surface and the die positioning end surface in the thread rolling device.
[0018]
In any case, the work can be positioned at the preliminary positioning position or the final positioning position by mounting the work directly or indirectly through another member. As a result, positioning in the axial direction can be performed more accurately, and dimensional variations between the workpiece-side positioning end surface and the thread rolling start position can be further reduced within the same product number (product lot). In this respect, the jig is more effective when it directly holds the workpiece.
[0019]
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 100 includes a support unit 1 that supports a workpiece W, a rotation drive unit 2 that rotates a tool, a contact drive unit 3 that moves the tool toward the circumferential direction of the workpiece W, a rotation drive unit 2, and a contact drive unit 3. And a control unit 4 that issues a control command for thread rolling. The support unit 1, the rotation drive unit 2, and the approach drive unit 3 are collectively referred to as a workpiece processing unit 50. 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.
[0020]
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.
[0021]
As shown in FIG. 11, a gas seal portion W1 is formed on the outer peripheral surface of the workpiece W so as to protrude outward in the radial direction on the proximal end side of the thread formation portion W0 '. In the axial direction of the workpiece W, the end surface of the gas seal portion W1 on the thread formation planned portion W0 ′ side is formed as a workpiece side positioning end surface S, and the end surface of the die 27 corresponding to the workpiece side positioning end surface S is the die side positioning end surface F. The die 27 and the workpiece W are positioned so that a certain amount of distance (positioning end surface distance) h is generated between both end surfaces. In this state, the die 27 is approached from the outer peripheral surface side of the workpiece W and the outer peripheral surface of the workpiece W is subjected to thread rolling. In many cases, the distance h between the positioning end faces is represented by an axial distance between the seating surface S of the gasket G of the workpiece W and the upper end face F of the die 27 as shown in FIG. On the other hand, in the case of the conical sheet type, the gasket P is not used, and the sealing is performed by the tapered surface S ′ of the gas seal portion W1, and therefore the position P where the outer diameter of the tapered surface S ′ is the smallest in the gas seal portion W1. The distance in the axial direction between this position P and the upper end face F of the die 27 is set as the distance h between the positioning end faces.
[0022]
Next, a method for positioning and setting the workpiece W in the axial direction so that the distance h between the positioning end faces is substantially constant will be described. As a method of positioning the thread formation planned portion W0 ′ of the workpiece W in the axial direction, the position is different from the workpiece machining portion 50 in the screw rolling device 100, and the final workpiece machining portion 50 in the screw rolling device 100 is finalized. There are a case where it is conveyed / positioned to a positioning position and a case where it is directly carried out at the final positioning position of the workpiece machining unit 50 in the screw rolling device 100.
[0023]
In FIG. 12, the workpiece W is positioned in the axial direction at a position different from the workpiece processing portion 50 in the screw rolling device 100, and is set on the support portion 1 of the screw rolling device 100 while maintaining the distance h between the positioning end faces. An example is shown. The workpiece W has a workpiece-side positioning end surface S (gasket seating surface) at a holding height H from a reference position GL (for example, the ground surface) at a position different from the workpiece machining section 50 in the screw rolling device 100. It is supported with respect to the support base 10 (jig). The support 10 includes a cylindrical member 10B for receiving and holding the workpiece-side positioning end surface S of the workpiece W, a cylindrical guide member 10A in which the cylindrical member 10B is slidably stored in the axial direction, and a reference It is provided between the position GL and the cylindrical member 10B, and at least includes a fixing member 10C that fixes the cylindrical member 10B. The cylindrical member 10B includes a cylindrical body portion 10B1 into which the thread formation planned portion W0 ′ of the workpiece W can be inserted in the axial direction, and a bottom portion 10B2 configured to close one end side of the cylindrical body portion 10B1, for example, a bolt or a screw. As for fixing member 10C formed with a rod, the screw part is fixed to bottom 10B2.
[0024]
When the workpiece W is set on the support base 10, when the workpiece W is inserted into the cylindrical portion 10B1 of the cylindrical member 10B, the workpiece-side positioning end surface S is received by the opening-side end surface of the cylindrical portion 10B1. At this time, the workpiece-side positioning end surface S is held at a fixed holding height H from the reference position GL (FIG. 12A). In this state, the mandrel type stopper 11 is inserted from above the workpiece W, and the workpiece W is held by the stopper 11. The mandrel type stopper 11 is directly or indirectly attached to a predetermined position of the screw rolling device 100 so that the height in the axial direction with respect to the attachment position to the screw rolling device 100 can be adjusted. It is configured. Here, the height of the stopper 11 in the axial direction is adjusted so that the holding height H (a constant value) corresponds to the predetermined distance h between the positioning end faces (that is, the height of the mounting position on the thread rolling device 100). Adjust). Next, the height-adjusted stopper 11 is conveyed into the workpiece machining unit 50 in the screw rolling device 100 while holding the workpiece W, and is attached to a predetermined position. Then, the workpiece W is positioned and held in the axial direction of the support portion 1 in a state where the distance h between the positioning end faces reflects (transfers) the holding height H reliably (FIG. 12B). The stopper 11 is in a state of being rotatable around the central axis along with the workpiece W in FIG. Instead of adjusting the holding height H and the distance h between the positioning end faces by adjusting the height of the stopper 11 in the axial direction, the stopper 11 is always directly attached to the thread rolling device 100 with the same height position. Alternatively, the fixing member 10C on the side of the support base 10 that receives the workpiece W is screwed in to adjust the holding height H, or a plurality of support bases 10 having different heights H are prepared. By holding the workpiece W with the stopper 11 as well, the positioning h can be positioned with respect to the workpieces W of different types so that the distance h between the positioning end faces is kept substantially constant.
[0025]
FIG. 13 shows a case where the workpiece W is positioned in the axial direction so that the distance h between the positioning end faces is substantially constant when the workpiece W is set on the support portion 1 (see FIG. 1) of the thread rolling device 100. Yes. The workpiece W is supported from below by a mandrel-type stopper 11 (jig) whose height in the axial direction can be adjusted in the support portion 1 of the thread rolling device 100. The stopper 11 has a first cylindrical portion 11A inserted inside the workpiece W, and a notch 11B1 for housing the ground electrode X extending in the axial direction in a part of the circumferential direction. It consists of a second cylindrical portion 11B having an outer diameter received by the lower end surface, and a shaft-shaped portion 11C penetrating the inside of both cylindrical portions 11A and 11B in the axial direction. A plurality of holes 11A0 are provided in the outer circumferential surface of the first cylindrical portion 11A so as to penetrate in the radial direction at predetermined intervals in the circumferential direction. On the other hand, a lid 11C1 having the same diameter as the hole 11A0 is attached to the shaft portion 11C via an elastic member (for example, a compression spring) 11C2. Thereby, the stopper 11 is inserted from the lower side of the workpiece W and is supported so as to be rotatable around the central axis together with the workpiece W. Further, the workpiece W is positioned in the axial direction so that the distance h between the positioning end faces becomes substantially constant by adjusting the elevation of the stopper 11.
[0026]
By adjusting the elevation of the stopper 11 in the axial direction, the distance h between the positioning end surfaces can be kept substantially constant for the workpieces W of different types, and the stopper 11 functions as a jig. In addition, as shown in FIG. 1, the mandrel type stopper 11 may be inserted from the upper side of the workpiece W to support the workpiece W so as to be rotatable around the central axis.
[0027]
By the way, in FIG. 13, the circumferential direction set sensor 12A and the axial direction set sensor 12B are separately provided as the work set detection sensor 12 described above, and both sensor outputs function under AND conditions. The work set signal may be output only when the signal is detected. Of these, the ground electrode material X can be easily detected by providing the circumferential set sensor 12A so as to face the notch 10B1 or 11B1. Further, if the axial set sensor 12B is provided to face the workpiece side positioning end surface S or S '(see FIG. 11), the distance h between the positioning end surfaces can be easily detected.
[0028]
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 and worms and worm wheels 25A, 25B, and 25C (25C is not shown). The rolling round dies 27A, 27B, and 27C (27C not shown) are transmitted to three die rotating shafts 26A, 26B, and 26C (26C not shown). 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).
[0029]
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”. The screw 27a on the outer circumferential surface of the outer surface of the workpiece W comes into contact with the outer circumferential surface of the workpiece W to start the thread rolling process is called “biting”.
[0030]
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.
[0031]
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
[0032]
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.
[0033]
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). ) Again, the control unit 4 outputs a pulse (detection signal) No. 2 of the angular position signal by using the detection signal of the rotational angular position of the die 27 by the encoder 28. 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).
[0034]
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.
[0035]
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.
[0036]
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 biting candidate positions T1 to T5 of the die 27 randomly contribute to the start of the thread rolling process. Uneven wear is prevented.
[0037]
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, a phase difference of 90 ° in the circumferential direction between the biting position of the threaded portion W0 of the workpiece W (screw rolling start position) and the position of the ground electrode material X (circumferential reference position) ( In the rolling round die 27A, four types of spark plug metal shells having a phase difference A, B, C, D of 18 ° 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. Further, 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.
[0038]
Here, the suitability of the threading start positions of the spark plug and the cylinder head will be described with reference to FIG. Generally, 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 thread rolling process start position of the spark plug thread part (male thread) is set to one point, when the spark plug is screwed into the engine cylinder head thread part (female thread) and fixed, The ground electrode X ′ of the spark plug is not always located at a position where the ignition performance is exhibited. In FIG. 11, a spark plug W ′ (shaft workpiece W to be a spark plug metal shell) is prepared in which the position of the ground electrode X ′ and the thread rolling start position of the threaded portion W0 coincide at the A position. Assuming that 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.
[0039]
Therefore, in this embodiment, four types of spark plugs having a phase difference A, B, C, D of 90 ° in the circumferential direction at the thread rolling start position of the threaded portion W0 with respect to the position of the ground electrode X ′. W 'is created. 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 thread rolling start positions A, B, C, and D of the plug W ′ are made to correspond to the screw processing start positions ranges a, b, c, and d of the cylinder head w. As a result, the spark plug W ′ having the thread rolling start positions A, B, C, and D corresponding to the ranges a, b, c, and d of the threading start position of the threaded portion w0 of the cylinder head w is appropriately selected. This makes it easier to set the ground electrode X ′ to the optimum position for ignition. The number of divisions between the thread rolling start positions A, B, C, and D of the threaded portion W0 of the spark plug W ′ and the ranges a, b, c, and d of the threading start position of the threaded portion w0 of the cylinder head w. Can be changed as appropriate.
[0040]
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 the present embodiment), the encoder sets the delay angle of 90 ° set based on the biting candidate position. It counts using the detection signal of the rotation angle position by 28. 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'. Note that the delay angle in the rotation direction is not limited to 90 °, and can be set arbitrarily according to the desired thread rolling 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.
[0041]
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).
[0042]
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.
[0043]
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 for the total number of 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.
[0044]
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 (n is any one of 1 to 5) (S51), and 1 is stored in the counter Kn corresponding to the angular position signal No.n at the end of the thread rolling process. Are added (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 signal (S5) that appears after the work set. 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.
[0045]
(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.
[0046]
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.
[0047]
The number of thread rolling dies in the present invention may be two in addition to three.
[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 schematic view of positioning rolling.
FIG. 10 is a schematic diagram showing the compatibility of the threading start position between the spark plug and the cylinder head.
11 is a schematic diagram showing a state in which the positional relationship between the dice and the workpiece in FIG. 2 is viewed from another direction.
12 is a cross-sectional view showing a first embodiment for setting a work on the thread rolling device of FIG. 1;
FIGS. 13A and 13B are a cross-sectional view and a perspective view showing a second embodiment in which a work is set on the thread rolling device of FIG.
[Explanation of symbols]
100 Screw rolling equipment
50 Workpiece processing part
1 Supporting part
10 Support stand (jig)
11 Mandrel type stopper (jig)
2 Rotation drive part
26 Dies rotation axis
27 Dice
28 Encoder
3 Drive unit
4 Control unit
W Workpiece (Axis-shaped work to be a metal shell)
W0 thread
W0 ’thread formation planned part
W1 Gas seal part
X Ground electrode material (circumferential reference position)
T1-T5 biting candidate position (tool side reference position)
F Die upper end surface (Die side positioning end surface)
S Gasket seating surface (workpiece side positioning end surface)
S 'Tapered surface (Workpiece side positioning end surface)
h Distance between positioning end faces

Claims (17)

A shaft-shaped workpiece that is to be the metal shell of the spark plug, and a workpiece in which a gas seal portion protrudes outward in the radial direction on the outer peripheral surface of the base end side of the screw formation scheduled portion is formed around its central axis. While being held rotatably,
In the axial direction of the workpiece, it corresponds to the workpiece side positioning end surface which is the end surface of the gas seal portion on the side where the screw is to be formed , and the workpiece side positioning end surface in a die for thread rolling the outer peripheral surface of the workpiece. Positioning the die and the workpiece so that a certain amount of distance between the positioning end faces occurs between the end face that is the die end positioning end face ,
The workpiece and the die were first rotated relative to each other, and in the rotated state , the workpiece was determined corresponding to the bonding position or planned bonding position of the ground electrode material to be the ground electrode on the workpiece. An angular position signal is detected when a circumferential reference position and one or more tool-side reference positions defined on the die satisfy a predetermined rotational angular position relationship ;
In the spark plug manufacturing method in which a close-up start signal is output based on the angular position signal, the die and the workpiece are relatively approached by this signal output, and the outer peripheral surface of the workpiece is subjected to thread rolling .
A method of manufacturing a spark plug , wherein after the angular position signal is obtained, the approach start signal is output with a predetermined delay angle with respect to the direction of rotation of the die . Said angular position signal is installed in the shaft rotating synchronously rotating shaft or to the die, the manufacturing method of the spark plug of claim 1, wherein emitted on the basis of the output of the encoder for detecting the rotational angular position of the die .   The spark plug manufacturing method according to claim 2, wherein the work is stopped at least after the work is set and before the thread rolling process is started. The spark plug manufacturing method according to any one of claims 1 to 3, 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 a rotating shaft of the die or a shaft that rotates in synchronization with the die, and an output of the encoder is used as a trigger for the approach start signal . 2. A method for producing a spark plug according to item 1 . The die is a multi-thread screw die, and is set as the tool-side reference position, and the biting candidate positions for starting the thread rolling process are set at predetermined angular intervals in the circumferential direction of the die corresponding to the number of threads. a plurality of sets, corresponding to that of one or more of the plurality of biting candidate positions, producing a spark plug according to any one of the angular positions claims 1 and so the signal is outputted 5 Method. The spark plug manufacturing method according to claim 6 , wherein the angular position signal is output for each of the biting candidate positions. The spark according to claim 6 or 7 , wherein one of the plurality of angular position signals arriving in a predetermined order with relative rotation between the die and the workpiece is randomly selected and used for outputting the approach start signal. Plug manufacturing method. The indu start signal, among the plurality of angular position signals, the spark plug according to any one of claims 6-8 is output when it detects having a predetermined timing relationship when viewed from the reference time Production method. The spark plug manufacturing method according to claim 9 , wherein the approach start signal is output based on the angular position signal that first arrives after completion of setting of the workpiece. When the thread rolling process is repeatedly performed 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 method for manufacturing a spark plug according to claim 6 or 7 , wherein a selection sequence of the angular position signals is defined as follows. 12. The spark plug according to claim 11 , 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. Manufacturing method. The spark plug manufacturing method according to claim 11 , 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. In the screw rolling device, the workpiece positioning position where the distance between the positioning end surfaces is formed between the workpiece side positioning end surface and the die side positioning end surface is set as a final positioning position. at the position and the final positioning position and the workpiece to the preliminary positioning position that satisfies the predetermined relationship and prepositioning of claims 1 to 13 for conveying and positioning the workpiece to said final positioning position using the preposition position The manufacturing method of the spark plug of any one of Claims 1 . In said thread rolling device, the final positioning position where the distance between the registration edge surface is formed between the workpiece-side registration edge face and the die-side positioning end face of claims 1 to 13 for positioning the workpiece directly The manufacturing method of the spark plug of any one of Claims 1 . The spark plug manufacturing method according to claim 14 or 15 , wherein the workpiece is positioned at the preliminary positioning position or the final positioning position by mounting the workpiece on a jig that holds the workpiece directly or indirectly through another member. Method. A shaft-shaped workpiece that is to be the metal shell of the spark plug, and a workpiece in which a gas seal portion is formed to protrude radially outward on the outer peripheral surface of the base end side of the portion where the screw is to be formed, around its central axis While holding it rotatable,
In the axial direction of the workpiece, between the end surface of the gas seal portion on the side where the thread formation is scheduled and the end surface corresponding to the workpiece-side positioning end surface in the die for thread rolling the outer peripheral surface of the workpiece. A support portion for positioning the die and the workpiece so that a certain amount of distance occurs;
The workpiece and the die were first rotated relative to each other, and in the rotated state , the workpiece was determined corresponding to the bonding position or planned bonding position of the ground electrode material to be the ground electrode on the workpiece. A rotational drive unit that detects an angular position signal when a circumferential reference position and one or more tool-side reference positions defined on the die 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 that makes the die and the workpiece relatively approach,
In the spark plug manufacturing apparatus that performs thread rolling on the outer peripheral surface of the workpiece ,
An apparatus for manufacturing a spark plug , wherein after the angular position signal is obtained, the approach start signal is output with a delay by a predetermined delay angle with respect to the direction of rotation of the die .

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