Ignition coil bank-winding method

Abstract: An ignition coil winding method for spirally winding an element wire in banks of wire turns one by one around coil bobbin provides in particular that a nozzle can vertically move toward and away from a coil bobbin according to a changing winding radius and can swing in the direction normal to the longitudinal axis of the bobbin to maintain constant tension of the element wire. This method also uses a nozzle whose opening diameter is 2 to 6 times larger than that of the element wire to eliminate oscillation of the element wire in the nozzle opening.

Description: BACKGROUND OF THE INVENTION The present invention relates to a method of winding a secondary coil of an engine igniting coil device. Japanese laid-open patent No. 60-107813 discloses a bank winding method applied for manufacturing a secondary coil of a compact engine ignition coil device having a necessary dielectric strength of the coil interlayer insulation. According to this bank winding method, an element wire being fed from a nozzle reciprocating in the coil winding direction for a distance of a specified width is suitably tensioned and wound spirally in banks of turns one by one in both forward and reverse directions on a coil bobbin coaxially connected to a rotating shaft. The conventional bank winding method forms a coil on a coil bobbin by winding an element wire in layers around the bobbin in both forward and reverse directions by the reciprocal movement of the nozzle in parallel to the longitudinal axis of the bobbin. Consequently, a nozzle-to-bobbin distance (distance from a nozzle tip to a bending point of an element wire to form a new turn of a coil on the bobbin) and a wire-to-nozzle angle (angle formed by the element wire with the nozzle outlet axis) varies according to the changing radius of a coil being formed on the bobbin, causing fluctuation of tension in the element wire. In short, the conventional bank winding method applied for manufacturing an engine ignition coil device has the following problems to be solved. The first problem of the conventional bank winding method for winding an element wire in banks of turns a around coil bobbin by using a nozzle reciprocating parallel to the longitudinal axis of the coil bobbin is that the nozzle-to-bobbin distance and the wire-to-nozzle angle vary and make the tension of the wire unstable, resulting in loosening and/or falling-down of wire turns of the coil. The second problem is that the conventional bank winding method may be accompanied by a remarkable variation of the nozzle-to-bobbin distance and the wire-to-nozzle angle, in particular, when winding a tensioned fine element wire (e.g., a wire of 0.05 to 0.07 mm in diameter) in banks of turns one over another around the coil bobbin in both forward and backward directions. In this case, the fine wire unsteadily oscillates in a relatively large outlet of the nozzle, causing the falling-down of the turns in the coil being formed on the bobbin. EP-A-O 750 324 discloses a method of bank winding of an engine igniting coil, by which a wire tensioned with a specified force is fed from a nozzle reciprocating for a specified distance at a specified pitch along a longitudinal axis of a coil bobbin and wound spirally in layers of wire turns one over another in forward an reverse directions wherein the nozzle movable toward and away from the coil bobbin to always maintain a constant distance from the nozzle to a current winding point of the element wire to form a new turn of a coil on the bobbin. There, no spool feeding the wire is shown. DE-A-34 33 724 discloses a method of bank winding a coil by which a wire is fed from a roller wherein the roller can swing in a direction perpendicular to the longitudinal axis of a coil bobbin to always maintain a constant angle between the wire and an axis. There, the spool feeding the wire is not driven by a motor. In view of the foregoing, it is an object of the invention to provide an improved bank winding method of forming a secondary coil on a secondary coil bobbin for an engine igniting coil, which is capable to feed an element wire, preferably a non-oil coated wire, to coil bobbin more smoothly. This object is achived by a method in accordance with claim 1 and 2. In the method of the invention the element wire is fed with constant tension controlled by rotation of the spool and/or the tensioning device through the nozzle head reciprocally moving a specified distance along the rotation axis of the coil bobbin. Further, the wire is spirally wound in layers of wire turns one by one at a specified pitch around the coil bobbin coaxially attached to the rotating shaft in such a way that the nozzle-to-bobbin distance and the wire-to-nozzle angle may be always constant by axially moving the nozzle toward and away from the bobbin according to a changing winding radius and by swinging the wire in the direction normal to the nozzle axis, thus preventing the banks of wire turns from being loosened and falling-down during the winding operation. Preferably, the outlet opening of the nozzle has a diameter 2 to 6 times larger than that of an element wire to be wound into a coil. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of a coil winding machine for bank winding of an engine igniting coil according to the present invention. Fig. 2 is a front view of the coil winding machine of Fig. 1. Fig. 3 is a perspective view of the coil winding machine of Fig. 1. Fig. 4 is an end view for explaining a method of bank winding of a coil according to the present invention. Fig. 5 is a side view for explaining a method of bank winding of a coil 1 according to the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will be described in detail by way of example and with reference to the accompanying drawings. Figs. 1 to 3 are illustrative of an example of coil winding machine for realizing the bank winding of an engine ignition coil by the bank winding method according to the present invention. The shown machine is of multi-unit type that is capable of simultaneously forming a plurality of engine ignition coils. The operation of each coil winding unit of the machine is as follows: An element wire 3 being fed from a spool 1 through a tensioning device 2 and a nozzle 4 reciprocating in the coil winding direction for a distance of a specified width is spirally wound in banks of turns one by one in both forward and reverse directions to form a coil on a rotating coil bobbin 6 coaxially attached to a rotating shaft 5 of a driving portion 8 which is driven under the control of a controller 7. Fig. 4 shows the coil forming process in which an element wire 3 is wound in banks of wire turns one by one around a coil bobbin 6 in the forward direction of ascending (upward slope) bank-winding with an increasing winding diameter and the reverse direction of descending (downward slope) bank-winding with a decreasing winding diameter by driving a nozzle 4 to reciprocally move a specified distance of width "w" corresponding to a bank length at a specified pitch. The bobbin 6 has a plurality of fine grooves 9 formed in an axial direction on its body for preventing collapse of banks of wire turns. As shown in Fig. 5, a coil being formed on a coil bobbin 6 by spirally winding thereon an element wire 3 varies its diameter from a least diameter D1 to a maximum diameter D2, thereby the element wire 3 may have different lengths ℓ1 and ℓ2 (distances from a nozzle 4 to wire bending points "a" and "b" on the bank-winding section) and different angles 1 and 2 formed by the wire with the axis of the nozzle 4 at the least winding diameter D1 and the maximum winding diameter D2 respectively. Consequently, the bank winding of an element wire around the coil bobbin by the nozzle 4 simply reciprocating along the longitudinal axis of the bobbin is accompanied by variation of the nozzle-to-bobbin distance ℓ and the wire-to-nozzle angle . This causes the element wire to vary its tension, resulting in loosening and/or falling-down of wire turns in the coil formed. Therefore, the method according to the present invention is to vertically move the nozzle 4 toward and away from the coil bobbin in synchronism with winding of the element wire around the bobbin under the control of the controller 7 so that the distance ℓ from the nozzle 4 to the wire bending point may be maintained always at a constant specified value. The nozzle 4 is also moved left to right and reverse in synchronism with winding of the element wire around the bobbin under the control of the controller 7 so that the angle  of the element wire to the nozzle axis may be maintained always at a constant specified value. The nozzle 4 can move vertically and transversely to always maintain the constant distance ℓ and the constant angle  of the element wire, thus assuring feeding the element wire 3 with a constant tensioning force. This can effectively prevent loosening of wire turns and/or falling-down of the banks in the coil formed on the bobbin 6. Usually, an element wire 3 is coated with oil to be smoothly fed from the spool 1 by the effect of drawing force from the winding side. The winding method according to the present invention is intended to use an element wire 3 not coated with oil to prevent the collapse of banks resulted from slip-down of wire turns therein during the process of spirally winding the wire .around the bobbin. To smoothly feed the not-oil-coated element wire 3, the spool 1 is provided with a motor 10 for rotating the spool 1 in synchronism with winding the coil wire around the bobbin under the control of the controller 7. Between the spool 1 and the tensioning device 2, a cushion roller 11 is disposed to absorb the shock that may be produced when drawing the element wire 3 from the spool 1. The combination of the rotatable spool 1 with the cushioning roller 11 allows the element wire 3 to be fed always with constant tension, making it possible to form a reliable coil on the bobbin with no loosening of wire turns and/or no collapse of the banks of the wire turns thereof. The process of spirally winding an element wire 3 in layers one by one in both forwarding and backward directions also provides that the number of wire turns in banks in the reverse direction of descending spiral winding with a decreasing winding diameter is larger than that in the forward direction of ascending spiral winding with an increasing winding diameter. Namely, a coil may be formed on the coil bobbin by placing thereon, for example, 50 turns of the element wire in banks in the forward winding direction and 53 to 58 turns of the wire in banks in the reverse winding direction. This method can form a reliable foundation of a bank slope by placing a larger number of turns on the coil bobbin in the reverse descending winding direction and by further spiral winding the wire over the upward slope of firmly wound banks, thus preventing the occurrence of falling-down of the wire turns during the winding operation. This design solution in combination with the before-described means for maintaining constant tension in the element wire to be wound on the bobbin has an increased effect to prevent collapse of the banks of wire turns. As shown in Fig. 4, the bobbin is provided with a plurality of fine grooves in which an excess of wire turns in the forward winding direction is accommodated to effectively prevent collapse of the banks of wire turns during the cail-forming process. Thus, the nozzle 4 allows the element wire 3 to smoothly pass through its outlet at a least necessary clearance that may also prevent the oscillation of the wire therein while being wound spirally in layers one over another in both forward and reverse directions on the coil bobbin 3. As be apparent from the foregoing, the ignition coil winding method according to the present invention can form a reliable coil on a coil bobbin with no collapse of banks of wire turns by winding an element wire spirally in layers one by one around the coil bobbin in both forward and reverse direction thereon in such a way that the nozzle-to-bobbin distance and the wire-to-nozzle angle may be always maintained at constant specified values by axially moving the nozzle toward and away from the bobbin according to a changing winding radius and by swinging the wire in the direction normal to the nozzle axis, thus realizing adaptively winding the wire around the bobbin with a constant tension and with no fear of loosening and falling-down of the banks of wire turns in the coil during the winding operation. The number of wire turns in the reverse direction of descending spiral winding with a decreasing winding diameter is larger than that in the forward direction of ascending spiral winding with an increasing winding diameter. Therefore, a reliable foundation of a bank slope by placing a larger number of turns on the coil bobbin in the reverse descending winding direction and by further spiral winding the wire over the upward slope of firmly wound banks can be formed, thus preventing the occurrence of falling-down of the wire turns during the winding operation. The winding method according to the present invention is intended to use a not-oil-coated element wire that can be smoothly uncoiled from a rotatable spool being protected against a shock by a cushion member. The combination of the rotatable spool with the cushion roller allows the not-oil-coated element wire to be fed always with a constant tension. This makes it possible to wind a coil on the bobbin with no loosening of wire turns and/or no collapse of the banks of the wire turns. The ignition coil bank-winding method according to the present invention uses a nozzle whose outlet opening has a diameter being 2 to 6 times larger than the diameter of an element wire, thus the nozzle allows the element wire to smoothly pass through the nozzle at a least necessary clearance that may also prevent the oscillation of the wire therein while being wound spirally in layers one over another in both forward and backward directions on the coil bobbin. This can effectively prevent collapse of banks of wire turns during the coil forming process.

Claims: A method of bank winding of a engine igniting coil, by which an element wire (3) tensioned with a specified force by a tensioning device (2) is fed from a spool (1) through a nozzle (4) reciprocating for a specified distance (w) at a specified pitch along a longitudinal axis of a coil bobbin (6) and wound spirally in layers of wire turns one over another in forward and reverse directions on the coil bobbin (6) coaxially attached to a rotating shaft (5), wherein the nozzle (4) is also movable toward and away from the coil bobbin (6) to always maintain a constant distance (I) from the nozzle (4) to a current winding point of the element wire (3) to form a new turn of a coil on the bobbin, characterized in that the spool (1), when feeding the element wire (3), is rotated by a motor (10) in synchronism with winding the element wire (3) onto the bobbin (6). A method of bank winding of an engine igniting coil, by which an element wire (3) tensioned with a specified force by a tensioning device (2) is fed from a spool (1) through a nozzle (4) reciprocating for a specified distance (w) at a specified pitch along a longitudinal axis of a coil bobbin (6) and wound spirally in layers of wire turns one over another in forward and reverse directions on the coil bobbin (6) coaxially attached to a rotating shaft (5), wherein the nozzle (4) can swing in a direction perpendicular to the longitudinal axis of a coil bobbin (6) to always maintain a constant angle () between the element wire (3) and the nozzle axis, characterized in that the spool (1), when feeding the element wire (3), is rotated by a motor (10) in synchronism with winding the element wire (3) onto the bobbin (6). A method of bank-winding of an engine igniting coil as defined in any one of claims 1 and 2, characterized in that a not-oil-coated element wire is used.

Inventors: YUKITAKE KIKUO, YUKITAKE, KIKUO, Yukitake, Kikuo, c/o Toyo Denso K.K.
Applicants: TOYO DENSO KK, TOYO DENSO KABUSHIKI KAISHA
Application year: 1998
Main classification: H01F41
IPC codes: H01F38, H01F41