JP2013168560A - Ignition coil for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition coil of which not only the shape can be reduced in size but also the ignition energy can be improved.SOLUTION: An ignition coil comprises a primary coil L1 in which ON/OFF control is performed on an electrification state, a secondary coil L2 electromagnetically coupled to the primary coil, and a central iron core CO forming a closed magnetic path of magnetic flux interlinked to the primary coil and the secondary coil. In the center core CO, connecting faces of a first core CO1 and a second core CO2 are abutted directly or indirectly and in the first core CO1, a proximate part continued to the connecting face with the second core CO2 is formed thick orthogonally to a magnetic flux direction.

Description

  The present invention relates to an ignition coil used for an internal combustion engine such as an automobile engine, and more particularly to a small and high-performance closed magnetic circuit type ignition coil.

  In general, an internal combustion engine such as an engine employs a system in which an ignition coil is inserted into a plug hole adjacent to a combustion chamber, and an ignition plug attached to the bottom of the plug hole is driven. This type of ignition coil includes a primary coil that receives battery voltage and a secondary coil that generates a high voltage when the current of the primary coil is interrupted. The primary coil and the secondary coil have almost the entire length. There are roughly classified into a pencil type (open magnetic circuit type) disposed inside the plug hole and a closed magnetic circuit type in which the entire primary coil and secondary coil are disposed outside the plug hole to form a closed magnetic circuit.

  The pencil type is excellent in that the occupied space is narrow because there are few parts exposed from the plug hole, but the magnetic path of the primary coil and secondary coil must be an open magnetic path, so the energy at the time of ignition energy generation There is a problem that the loss (power loss) is not small.

  In this regard, the closed magnetic circuit type can suppress the power loss and generate the necessary ignition energy, can smoothly realize the combustion control such as lean combustion and EGR control, and can reduce the fuel consumption and the pollution of the automobile. The request can be met (Patent Documents 1 to 3).

JP 2011-151181 A JP 2011-003812 A JP 2008-166649 A

  However, for the closed magnetic circuit type, there is a strong demand to further increase the ignition energy while reducing the size of the shape. However, increasing the ignition energy by increasing the size of the primary coil or the secondary coil has no meaning contrary to the demand for reducing the size of the ignition coil.

  Moreover, if the overall shape and device configuration of the ignition coil are complicated, even if the size is reduced as a whole, the manufacturing cost and the like cannot be increased and the market demand cannot be met.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an ignition coil that can not only reduce the size but also increase ignition energy.

  In order to achieve the above object, the present invention provides a primary coil whose ON / OFF state is controlled, a secondary coil that is electromagnetically coupled to the primary coil, and a closed magnetic circuit of magnetic flux that links the primary coil and the secondary coil. The central core is divided into a plurality of parts, and the adjacent two split cores are configured such that their connection surfaces directly or indirectly contact each other, In one or both of the split cores, a proximity portion that is continuous with the connection surface is formed to be thick, being orthogonal or inclined to the magnetic flux direction.

  In the present invention, it is preferable that a permanent magnet is disposed on the connection surface so that two adjacent divided cores are in contact with each other indirectly. Further, it is preferable that the connection surface is configured to have an inclination angle of 20 ° or less with respect to a theoretical magnetic flux direction circulating in the closed magnetic circuit.

  The central iron core of the present invention is typically composed of a substantially rectangular parallelepiped first core, a substantially gate-shaped second core, and a thin plate-like permanent magnet MG. Forming. In this case, the first core is formed with a thick proximity portion in the bottom direction continuously to the connection surface with the second core with the permanent magnet interposed therebetween, and the bottom surface of the first core except for the proximity portion. Is preferably formed flat.

  The primary bobbin around which the primary winding W1 is wound is inserted into the secondary bobbin around which the secondary winding of the secondary coil is wound. It is preferable that one core is inserted and the second core disposed outside the secondary coil and the connecting surface of the first core are in direct or indirect contact with each other. Moreover, it is preferable that the central iron core is configured by laminating electromagnetic steel sheets.

  According to the present invention described above, it is possible to realize an ignition coil that can not only reduce the size but also increase the ignition energy.

It is drawing which shows the whole shape of the ignition coil which concerns on an Example, and the shape of each part. It is drawing explaining the internal circuit structure and center iron core of an ignition coil. It is a result of a simulation experiment about the structure of the center core of an Example and a comparative example. It is drawing which shows the use condition of an ignition coil. It is drawing which shows the result of a performance test.

  Hereinafter, the present invention will be described in more detail based on examples. FIG. 1 is a drawing showing the overall shape of the ignition coil CL and the shape of each part according to the embodiment. FIG. 1A is an assembled state in which the coil assembly 3 is accommodated in the box-shaped coil case 1. Is shown.

  As illustrated, a terminal case 2 that accommodates the connection terminals T1 to T3 is fixed to one end portion of the coil case 1, and a mounting portion 1b into which a mounting bolt is inserted is formed at the other end portion of the coil case 1. ing. Then, the ignition coil CL is completed by filling the coil case 1 with a thermosetting resin.

  FIG. 2 is a diagram for explaining the internal circuit configuration of the ignition coil CL and the central iron core CO that is a characteristic component. As shown in FIG. 2A, the ignition coil CL includes a primary coil L1, a secondary coil L2, a central iron core CO that forms a closed magnetic path of magnetic flux that links the primary coil L1 and the secondary coil L2, and a primary coil. A transistor Tr that controls ON / OFF of the coil L1 and a high-voltage diode D that controls the ignition direction in one direction are built in.

  The ignition coil CL includes a battery terminal T1 that receives a DC voltage, a control terminal T2 that receives an ignition signal from an ECU (Engine Control Unit), and a ground terminal T3. These three input terminals Is arranged in a terminal case 2 fixed to one end (right end) of the coil case 1 shown in FIG.

  And the output voltage of the secondary coil L2 is output from the high voltage output terminal T4 (refer FIG.1 (f)) arrange | positioned at the bottom face of the coil case 1, and this high voltage output is supplied to the ignition plug PG. Necessary ignition discharge operation is realized.

  The primary coil L1, the secondary coil L2, and the central iron core CO are integrated as a whole to form a coil assembly 3, which is arranged in the center of the coil case 1 (see FIG. 1A). A high voltage diode D (FIG. 1B) and a transistor Tr (not shown) are disposed between the coil assembly 3 and the terminal case 2.

  As shown in FIG. 1 (f) and FIG. 2 (c), the central iron core CO is composed of a substantially rectangular parallelepiped first core CO1, a substantially gate-shaped second core CO2, and a thin plate-like permanent magnet MG. As a whole, a closed magnetic circuit having an angular cross section is formed. Here, the first core CO1 and the second core CO2 are configured by laminating electromagnetic steel plates having the shape shown in FIG. A silicon steel plate is typically used as the electromagnetic steel plate.

  The permanent magnet MG secures a wide usable area (linear part) of the magnetic hysteresis curve (HB curve) by forming a magnetic field opposite to the magnetic field generated by the primary coil L1.

  The primary coil L1 is configured by winding a primary winding W1 around a primary bobbin B1 shown in FIG. 1G capable of accommodating the first core CO1 (see FIG. 2D). On the other hand, the secondary coil L2 is configured by winding a secondary winding W2 around a secondary bobbin B2 (see FIG. 1 (f)) that can accommodate the primary coil L1. The completed secondary coil L2 is inserted from the left side of FIG. 2D and disposed outside the primary coil L1.

  The first core CO1 of the present embodiment has the distal end portion and the proximal end portion of the first core CO1 at both ends in the length direction of the primary coil L1 and the secondary coil L2 in a state where the first core CO1 is accommodated in the primary bobbin B1. The exposed dimensions are set (see FIG. 2D). Therefore, in the state where the permanent magnet MG is arranged at the distal end portion (right side in the drawing) of the exposed first core CO1, the second core CO2 corresponds to the distal end surface SL and the base end surfaces FA, F1, F2 of the first core CO1. By bringing the surfaces into contact, the central iron core CO is in a completed state. To be precise, the front end surface SL of the first core CO1 is brought into contact with the corresponding surface of the second core CO2 with the permanent magnet MG interposed therebetween.

  FIG. 2B is a central iron core (comparative example) having a normal configuration, and is shown for comparison with the central iron core CO (example) of FIG. The central iron core CO of the embodiment is common to the central iron core of the comparative example in that it is composed of the first core CO1, the second core CO2, and the permanent magnet MG, but the shape of the first core CO1 is different from the comparative example. Notably different.

  That is, the bottom surface of the first core of the comparative example shown in FIG. 2 (b) extends in the left-right direction (the magnetic flux direction of the primary coil L1) and is formed flat, whereas the first core of the example. The bottom surface of the CO1 has a non-flat shape with a projecting portion PR projecting downward at a tip portion (right side in the drawing) perpendicular to the magnetic flux direction.

  By adopting such a configuration, if the magnetic material is thickened by tilting in the magnetic flux direction (typically orthogonal) at the discontinuous portion of the closed magnetic circuit, the leakage magnetic flux can be suppressed, and the energy can be reduced. This is because the loss can be effectively suppressed. This effect was clarified for the first time by the present inventor's research, and FIG. 3 shows only a part of the data showing this effect, and shows a simulation experiment using the Finite Element Method (FEM). Results are shown.

  As shown in FIG. 3A and FIG. 3B, when the central cores CO of the example and the comparative example are compared, in the example in which the magnetic material is thickly formed perpendicular to the magnetic flux direction, the magnetic flux concentration at the tip is Is eliminated, and it is confirmed that the leakage magnetic flux is reduced (see FIG. 3A). In addition, as shown in FIG.2 (c), 1st core CO1 of this Example is formed in the left-right center part thinner than the 1st core of the comparative example shown in FIG.2 (b) (W1- δ2) Since the magnetic path cross-sectional area A decreases accordingly, it is considered that the magnetic resistance Rm (Rm∝1 / A) increases. However, according to a performance experiment described later by the present inventor, it has been confirmed that the electrical performance higher than that of the comparative example is exhibited regardless of such a change in magnetic resistance.

  In the case of the embodiment, the inclination angle θ is steeply formed on the inclined surface SL that is a contact surface between the first core CO1 and the second core CO2 and the permanent magnet MG is disposed therebetween. (See FIG. 2 (d)). The inclination angle θ is preferably set to 20 ° or less with respect to the thickness direction of the first core CO1 (theoretical magnetic flux direction circulating in the closed magnetic circuit and in the vertical direction in the figure), and more preferably Is set to about 12 to 18 °. Note that the inclination angle of the comparative example is about 21 to 22 °.

  As described above, in the present embodiment, the inclined surface SL on which the permanent magnet MG is disposed is set to a steep inclination angle of 20 ° or less, so that the left and right central portion BY of the first core CO1 is formed thin. However, the contact area of the permanent magnet MG can be sufficiently secured, and a desired magnetic hysteresis curve can be realized.

  Further, as shown in FIG. 2D, the base end portion of the first core CO1 includes a first inclined surface F that is continuous with the upper flat surface FA, and a second inclined surface F2 that is directed to the left and right center portion BY. A character-shaped cut groove is formed, and a sufficient contact area with the contact surface of the second core CO2 is ensured. Further, the first core CO1 shown in FIG. 2D has a sufficient contact area between the wiring cable connecting the wiring groove LN and the ground terminal T3 by forming the wiring groove LN on the bottom surface of the protrusion PR. Is secured.

  By the way, in the example used for the simulation experiment, the thickness of the left and right central part and the base end part of the second core CO2 is the same as in the comparative example, and the magnetic path cross-sectional area is the same. On the other hand, the base end portion of the second core CO2 has a length (L + δ3) in the vertical direction slightly longer than that of the comparative example (+ δ3), and sufficient space for the primary bobbin B1 and the primary winding W1. (See FIGS. 2B and 2C).

  Further, in the example, when the entire left and right center part BY of the first core CO1 is thinner than the comparative example (−δ2), and the entire center iron core CO is evaluated, the height in the vertical direction ( H−δ1) is lower than the comparative example by a predetermined value δ1, contributing to downsizing of the coil assembly 3 and suppression of the amount of magnetic material used.

  Corresponding to the configuration of the first core CO1 described above, the primary bobbin B1 includes a cylindrical main body 10 around which the primary winding W1 is wound, and the tip of the first core CO1, as shown in FIG. The front end portion 11 from which the surface SL is exposed and the base end portion 12 from which the base end surfaces FA, F1, F2 of the first core CO1 are exposed are configured. The distal end portion 11 and the proximal end portion 12 both have a U-shaped outline in a front view, and are configured to support the bottom surface and the side surface of the first core CO1. Further, a locking piece TG for fixing the winding start line and the winding end line of the primary winding W1 is formed at the tip portion 11.

  As shown in FIG. 2D, the bottom surface of the distal end portion 11 is set lower than the bottom surface of the main body portion 10 corresponding to the bottom surface of the protruding portion PR of the first core CO1. On the other hand, the bottom surface of the base end portion 12 is continuous with the bottom surface of the main body portion 10 and forms the same plane. Note that a part of the bottom surface of the distal end portion 11 is opened, so that the wiring groove LN and the ground terminal T3 can be electrically connected.

  Hereinafter, a method for assembling the ignition coil will be described for confirmation. The primary coil W1 is wound around the primary bobbin B1 shown in FIG. 1 (g) to complete the primary coil L1, and then the secondary coil L2 is disposed outside the primary coil L1. The secondary coil L2 is configured by winding the secondary winding W2 around the secondary bobbin B2. By inserting the secondary bobbin B2 from the base end side of the primary bobbin B1, the secondary coil L2 The secondary coil L2 is disposed outside.

  Next, in this state, the first core CO1 of the central iron core CO is inserted into the primary bobbin B1. In the insertion completed state, the back side of the tip surface SL of the first core CO1 and the bottom surface of the protrusion PR are in contact with the inner surface of the tip 11 of the primary bobbin B1 (FIG. 2D).

  In this accommodated state, the distal end portion and the proximal end portion of the first core CO1 are exposed from the primary bobbin B1 and the secondary bobbin B2, so that the permanent magnet MG is disposed on the exposed surface of the first core CO1. By bringing the corresponding surfaces of the two-core CO2 into contact with each other, the central iron core CO is in a completed state.

  Thereafter, when the protective cover 20 is disposed on the upper side of the second core CO2, the coil assembly 3 is obtained. And when this coil assembly 3 is accommodated in the coil case 1, it will be in the assembly | attachment state of Fig.1 (a).

  The secondary coil L2 of the coil assembly 3 outputs a lead wire LD for deriving its output voltage, which is in contact with the high-voltage terminal T4 in the assembled state of FIG. The electrical connection is complete.

  The ignition coil CL configured as described above is inserted into the plug hole HO with its lower end covered with the insulating elastomer material 30, and is fixed to the engine block using a bolt BT or the like (FIG. 5). reference). Note that a conductive spring (not shown) is disposed inside the elastomer material 30, and electrical connection between the high voltage terminal T4 and the spark plug PG is realized.

  Finally, a performance experiment confirming the technical significance of the present invention will be described with reference to FIG. FIG. 6 (a) shows the secondary voltage when the energization is cut off in the experimental circuit in which both ends of the secondary coil L2 are terminated with a 20 pF capacitor. Is shown on the vertical axis. Under normal operating conditions, the primary current of the cut-off timing is about 4 to 6 A. Therefore, it is confirmed that the present embodiment, in which the device configuration is downsized, exhibits the same performance as the comparative example of the conventional configuration.

  6 (b) to 6 (d) show the time until the secondary current disappears in the experimental circuit in which both ends of the secondary coil L2 are terminated at 5 kΩ with the value of the primary current at the time of energization interruption as the horizontal axis. The discharge time T2 (FIG. 6B), the secondary current value I2 at the time of interrupting the primary current I2 (FIG. 6C), and the discharge energy E2 until the secondary current disappears (FIG. 6D), respectively, This is shown on the vertical axis.

  In any performance, it has been proved that it is not different from the comparative example under normal operating conditions or superior to the comparative example, and the excellent effect of the present invention is confirmed.

  Although the embodiments of the present invention have been specifically described above, the specific description is not particularly intended to limit the present invention and can be appropriately changed.

L1 Primary coil L2 Secondary coil CO Center iron core CO1 Split core CO2 Split core PR Thick part

Claims (7)

It has a primary coil whose ON / OFF state is controlled, a secondary coil that is electromagnetically coupled to the primary coil, and a central iron core that forms a closed magnetic path of magnetic flux interlinking with the primary coil and the secondary coil. ,
The central core is divided into a plurality of parts, and the adjacent two split cores are configured such that their connection surfaces are directly or indirectly abutted,
One or both of the split cores have an adjacent portion that is continuous with the connection surface and is formed with a thickness that is orthogonal to or inclined with respect to the magnetic flux direction.   The ignition coil according to claim 1, wherein two adjacent cores are indirectly in contact with each other by disposing a permanent magnet on the connection surface.   The ignition coil according to claim 1, wherein the connection surface is configured to have an inclination angle of 20 ° or less with respect to a theoretical magnetic flux direction circulating in a closed magnetic circuit.   2. The central iron core is constituted by a substantially rectangular parallelepiped first core, a substantially gate-shaped second core, and a thin plate-like permanent magnet MG, and forms a closed magnetic circuit having an angular cross section as a whole. The ignition coil in any one of -3.   The first core is formed with a thick adjacent portion in the bottom direction continuously to the connection surface with the second core with the permanent magnet interposed therebetween, and the bottom surface of the first core is flat except for the proximity portion. The ignition coil according to claim 4 formed. The primary bobbin around which the primary winding W1 is wound is inserted into the secondary bobbin around which the secondary winding of the secondary coil is wound, and the first core is inserted into the primary bobbin. Is inserted and configured,
The ignition coil according to claim 4 or 5, wherein a second core disposed outside the secondary coil and a connection surface of the first core are in direct or indirect contact.   The ignition coil according to any one of claims 1 to 6, wherein the central iron core is configured by laminating electromagnetic steel sheets.