Patent Publication Number: US-2018047503-A1

Title: Ignition device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority based on 35 USC 119 from prior Japanese Patent Applications Nos. 2016-156221 filed on Aug. 9, 2016, and 2017-135149 filed on Jul. 11, 2017, entitled “IGNITION DEVICE”, the entire contents of which are herein incorporated by reference. 
     BACKGROUND 
     The disclosure relates to an ignition device that causes a plug to ignite with a high voltage generated on a secondary ignition coil when a current in a primary ignition coil is intermittently interrupted. 
     An ignition device disclosed in Japanese Patent Application Publication No. H05-248334 has been known as an ignition device.  FIG. 4  illustrates the internal-combustion engine ignition device described in Japanese Patent Application Publication No. H05-248334. 
     In  FIG. 4 , primary winding P 1  and secondary winding S 1  of ignition transformer T 1  wind in opposite directions and perform flyback operation. Igniter control circuit  11  turns off igniter switch Q 1  in response to an inputted ignition signal. Then, a current flowing from battery BT through primary winding P 1  to igniter switch Q 1  is interrupted. At this time, interruption of the current flowing through primary winding P 1  induces a high voltage between both ends of secondary winding S 1 . The high voltage generated across secondary winding S 1  causes plug  12  to ignite to thus drive the internal-combustion engine. 
     In addition,  FIG. 5  illustrates another example of an ignition device of a related art. The ignition device in  FIG. 5  is for driving a multicylinder engine (illustrated is a four-cylinder engine) and is provided with plugs  12 - 1  to  12 - 4  the number of which corresponds to the number of cylinders. A secondary side of ignition transformer T 2  is provided with four secondary windings S 2 a to S 2 d. Switches SW 1  to SW 4  and plugs  12 - 1  to  12 - 4  are connected to corresponding secondary windings S 2 a to S 2 d. Each of switches SW 1  to SW 4  includes a semiconductor element such as a MOSFET. The switches SW 1  to SW 4  are turned on or off by rotation in order to cause plugs  12 - 1  to  12 - 4  to ignite one after another with time lags. 
     However, the ignition devices in  FIGS. 4 and 5  has a risk that, since the high voltages generated on secondary windings S 1  and S 2 a to S 2 d are applied to diode D 1  and switches SW 1  to SW 4 , those semiconductor elements may be broken. Consequently, the conventional ignition devices have to use semiconductor elements having high breakdown voltage, and this increases the cost. 
     SUMMARY 
     One or more embodiments provide an ignition device that causes an ignition plug to ignite that comprises an ignition transformer that includes a primary winding and a secondary winding that are electromagnetically coupled to each other, a battery connected to a first end of the primary winding, a switch that is connected to a second end of the primary winding and is turned on or off in response to an ignition signal, a saturable reactor that includes a saturable core and includes a first winding with first and second ends, and a second winding with a first and second ends, the first and second windings electromagnetically coupled to each other, the first end of the first winding connected to the first end of the second winding, the second end of the first winding connected to the ignition plug, and a reset circuit that applies a reset voltage to the first and second ends of the second winding, the reset voltage being a voltage to switch a magnetization status of the saturable core between a saturated state and an unsaturated state. 
     One or more embodiments provide an ignition device that causes ignition plugs to ignite that comprises an ignition transformer that includes a primary winding with a first and second ends and a secondary winding with first and second ends, the primary and secondary windings electromagnetically coupled to each other, a battery connected to the first end of the primary winding, a switch that is connected to the second end of the primary winding and is turned on or off in response to an ignition signal, saturable reactors, the number of which corresponds to the number of the ignition plugs, the saturable reactors each including a saturable core and including a first winding with a first and a second ends and a second winding with a first and a second ends, the first and second windings electromagnetically coupled to each other, the first end of the first winding connected to the first end of the second winding, the second end of the first winding connected to the ignition plug, and reset circuits, the number of which corresponds to the number of the saturable reactors, the reset circuits each applying a reset voltage to the first and second ends of the second winding, the reset voltage being a voltage to switch a magnetization status of the saturable core between a saturated state and an unsaturated state. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a circuit configuration of an ignition device according to Example 1 of the present invention; 
         FIG. 2  is a diagram illustrating a circuit configuration of an ignition device according to Example 2 of the present invention; 
         FIG. 3  is a timing chart of four reset signals for resetting four saturable reactors, which are provided corresponding to four cylinders in the ignition device according to Example 2 of the present invention; 
         FIG. 4  is a diagram illustrating an example of a conventional ignition device; and 
         FIG. 5  is a diagram illustrating another example of a conventional ignition device. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments are explained with referring to drawings. In the respective drawings referenced herein, the same constituents are designated by the same reference numerals and duplicate explanation concerning the same constituents may be omitted. All of the drawings are provided to illustrate the respective examples only. No dimensional proportions in the drawings shall impose a restriction on the embodiments. For this reason, specific dimensions and the like should be interpreted with the following descriptions taken into consideration. In addition, the drawings include parts whose dimensional relationship and ratios are different from one drawing to another. 
     EXAMPLE 1 
       FIG. 1  is a diagram illustrating a circuit configuration of an ignition device according to Example 1 of the present invention. The ignition device of Example 1 in  FIG. 1  differs from a conventional ignition device in  FIG. 4  in a configuration of a secondary side of ignition transformer T 3 . Now the configuration of this part is thus described. 
     Ignition transformer T 3  has primary winding P 3  and secondary winding S 3  that are electromagnetically coupled to each other. 
     In saturable reactor SL, first winding L 1  and second winding L 2  are wound on an un-illustrated saturable core including magnetic material and are electromagnetically coupled to each other. One end of first winding L 1  is connected to one end of secondary winding S 3 , and the other end of first winding L 1  is connected to one end of plug  12 . The other end of plug  12  is grounded. Both ends of second winding L 2  are connected to reset circuit  13 . Saturable reactor SL uses a voltage applied from reset circuit  13  to second winding L 2  in order to switch a magnetization status of the saturable core to a saturated state or an unsaturated state. In the saturated state, the saturable core is not magnetized; thus, the inductance of primary winding L 1  is significantly decreased. In the unsaturated state, the saturable core is magnetized; thus, the inductance of primary winding L 1  is significantly increased. 
     In reset circuit  13 , a reset voltage for resetting the magnetization of the saturable core is applied to second winding L 2 . Once the reset voltage is applied to second winding L 2 , the saturable core is magnetized. This means that the magnetization of the saturable core is reset. Once the magnetization of the saturable core is reset, the magnetization status of the saturable core is changed into an unsaturated area. This significantly increases the inductance of primary winding L 1 . 
     Next, operations of the ignition device according to Example 1, which is formed as the above, are described. First, igniter control circuit  11  turns off igniter switch Q 1  with an inputted ignition signal. Then, a current flowing from battery BT through primary winding P 3  of ignition transformer T 3  to igniter switch Q 1  is interrupted. 
     At this time, a high voltage is applied to one side of primary winding P 3  where its winding begins (marked with a filled circle), whereby a high voltage is generated on one side of secondary winding S 3  where its winding begins (marked with a filled circle). In this case, when the high voltage pulse generated in secondary winding S 3  of ignition transformer T 3  is applied to saturable reactor SL, since the magnetization status of the saturable core is now the unsaturated area, the inductance of primary winding L 1  is very high. Hence, no current flows through primary winding L 1 , and thus saturable reactor SL is changed into a switched-off state. 
     Thereafter, the high voltage pulse causes the magnetization status of the saturable core to be a saturated area, and the inductance of primary winding L 1  is rapidly decreased. Hence, the current flows through primary winding L 1 , and thus saturable reactor SL is changed into a switched-on state. Applying the high voltage generated in secondary winding S 3  to plug  12  causes plug  12  to ignite. The ignition of plug  12  may include at least one of firing and sparking. 
     Next, igniter control circuit  11  turns on igniter switch Q 1  with an inputted ignition signal. This makes the high voltage pulse of ignition transformer T 3  be turned off, and the polarity of the high voltage pulse inverts. While the polarity of the high voltage pulse is inverting, the reset voltage from reset circuit  13  resets the magnetization of the saturable core. In other words, since the reset voltage changes the magnetization status of the saturable core into the unsaturated area, and thus the inductance of primary winding L 1  is very high, no current flows through primary winding L 1 , whereby the switch of saturable reactor SL is turned off. 
     In this way, saturable reactor SL operates as a switch circuit that turns on or off the high voltage generated on secondary winding S 3  in order to apply the high voltage to plug  12  to cause plug  12  to ignite. 
     In addition, because saturable reactor SL includes the saturable core, which is made of the magnetic material, and first winding L 1  and second winding L 2 , it is very rare that saturable reactor SL is broken by the high voltage generated on secondary winding S 3 . Hence, this ignition device has the high voltage resistance and can reduce the cost. 
     EXAMPLE 2 
       FIG. 2  is a diagram illustrating a circuit configuration of an ignition device according to Example 2 of the present invention. The ignition device according to Example 1 in  FIG. 1  includes one plug; however, the ignition device according to Example 2 has a characteristic that the ignition device is provided with four plugs  12 - 1  to  12 - 4  corresponding to a four-cylinder engine. The operation for making each plug be ignited is the same as that in Example 1. In Example 2, reset signals RS 1  to RS 4  from reset controller  15  cause four plugs  12 - 1  to  12 - 4  to ignite by rotation. 
     Four saturable reactors SL 1  to SL 4  are provided corresponding to four plugs  12 - 1  to  12 - 4 . On a saturable core of saturable reactor SL 1 , first winding L 1  and second winding L 2  are wound and electromagnetically coupled to each other. On a saturable core of saturable reactor SL 2 , first winding L 3  and second winding L 4  are wound and electromagnetically coupled to each other. On a saturable core of saturable reactor SL 3 , first winding L 5  and second winding L 6  are wound and electromagnetically coupled to each other. On a saturable core of saturable reactor SL 4 , first winding L 7  and second winding L 8  are wound and electromagnetically coupled to each other. 
     One end of first winding L 1  is connected to one end of secondary winding S 4 , and the other end of first winding L 1  is connected to one end of plug  12 - 1 . The other end of plug  12 - 1  is grounded. 
     One end of first winding L 3  is connected to one end of secondary winding S 4 , and the other end of first winding L 3  is connected to one end of plug  12 - 2 . The other end of plug  12 - 2  is grounded. 
     One end of first winding L 5  is connected to one end of secondary winding S 4 , and the other end of first winding L 5  is connected to one end of plug  12 - 3 . The other end of plug  12 - 3  is grounded. 
     One end of first winding L 7  is connected to one end of secondary winding S 4 , and the other end of first winding L 7  is connected to one end of plug  12 - 4 . The other end of plug  12 - 4  is grounded. 
     Four reset circuits  13 - 1  to  13 - 4  are provided corresponding to four saturable reactors SL 1  to SL 4 . Reset circuit  13 - 1  applies a reset voltage on both ends of second winding L 2 . Reset circuit  13 - 2  applies a reset voltage on both ends of second winding L 4 . Reset circuit  13 - 3  applies a reset voltage on both ends of second winding L 6 . Reset circuit  13 - 4  applies a reset voltage on both ends of second winding L 8 . 
     Reset controller  15  controls driving of each of four reset circuits  13 - 1  to  13 - 4  by rotation. 
     Next, operations of the ignition device according to Example 2, which is formed as the above, are described with reference to a timing chart of the reset signals illustrated in  FIG. 3 . 
     First, igniter control circuit  11  turns off igniter switch Q 1  with an inputted ignition signal. Then, a current flowing from battery BT through primary winding P 4  of ignition transformer T 4  to igniter switch Q 1  is interrupted. 
     This causes a high voltage pulse generated on second winding S 4  of ignition transformer T 4  to be applied to one ends of primary windings L 1 , L 3 , L 5  and L 7  of saturable reactors SL 1  to SL 4 . 
     At time t 1 , reset controller  15  transmits reset pulse RS 1  to reset circuit  13 - 1 , and thus reset circuit  13 - 1  supplies the reset voltage to secondary winding L 2  of saturable reactor SL 1 . The magnetization status of the saturable core of saturable reactor SL 1  is now the unsaturated area, and the inductance of primary winding L 1  is very high. Hence, the switch of saturable reactor SL 1  is turned off. 
     Thereafter, the high voltage pulse changes the magnetization status of the saturable core of saturable reactor SL 1  into the saturated area, and thus the inductance of primary winding L 1  is rapidly decreased. Hence, the switch of saturable reactor SL 1  is turned on, and thus plug  12 - 1  is ignited. 
     Next, at time t 2 , reset controller  15  transmits reset pulse RS 2  to reset circuit  13 - 2 , and thus reset circuit  13 - 2  supplies the reset voltage to saturable reactor SL 2 . The magnetization status of the saturable core of saturable reactor SL 2  is now the unsaturated area, and the inductance is very high. Hence, the switch of saturable reactor SL 2  is turned off. 
     Thereafter, the high voltage pulse changes the magnetization status of the saturable core of saturable reactor SL 2  into the saturated area, and thus the inductance is rapidly decreased. Hence, the switch of saturable reactor SL 2  is turned on, and thus plug  12 - 2  is ignited. 
     Next, at time t 3 , reset controller  15  transmits reset pulse RS 3  to reset circuit  13 - 3 , and thus reset circuit  13 - 3  supplies the reset voltage to saturable reactor SL 3 . The magnetization status of the saturable core of saturable reactor SL 3  is now the unsaturated area, and the inductance is very high. Hence, the switch of saturable reactor SL 3  is turned off. 
     Thereafter, the high voltage pulse changes the magnetization status of the saturable core of saturable reactor SL 3  into the saturated area, and thus the inductance is rapidly decreased. Hence, the switch of saturable reactor SL 3  is turned on, and thus plug  12 - 3  is ignited. 
     Next, at time t 4 , reset controller  15  transmits reset pulse RS 4  to reset circuit  13 - 4 , and thus reset circuit  13 - 4  supplies the reset voltage to saturable reactor SL 4 . The magnetization status of the saturable core of saturable reactor SL 4  is now the unsaturated area, and the inductance is very high. Hence, the switch of saturable reactor SL 4  is turned off. 
     Thereafter, the high voltage pulse changes the magnetization status of the saturable core of saturable reactor SL 4  into the saturated area, and thus the inductance is rapidly decreased. Hence, the switch of saturable reactor SL 4  is turned on, and thus plug  12 - 4  is ignited. 
     In this way, the ignition device according to Example 2 enables plugs  12 - 1  to  12 - 4  to be ignited by rotation with time lags. 
     In addition, since saturable reactors SL 1  to SL 4  includes the saturable core, which is made of the magnetic material, and first windings L 1 , L 3 , L 5  and L 7  and second windings L 2 , L 4 , L 6  and L 8 , it is very rare that saturable reactors SL 1  to SL 4  are broken by the high voltage generated on secondary winding S 4 . Hence, this ignition device has the high voltage resistance and can reduce the cost. 
     According to one or more embodiments, once a high voltage pulse generated on a secondary winding of an ignition transformer is applied to a saturable reactor, a magnetization status of a saturable core is changed into an unsaturated area, and the inductance is very high. Hence, a switch of the saturable reactor is turned off. Thereafter, the high voltage pulse changes the magnetization status of the saturable core into a saturated area, and thus the inductance is rapidly decreased. Hence, the switch of the saturable reactor is turned on, and thus a plug is ignited. While the polarity of the high voltage pulse is inverting after the high voltage pulse of the transformer is turned off, applying the reset voltage from reset circuit resets the magnetization of the saturable core. 
     With using the saturable reactor in such a way, the ignition device according to one or more embodiments have the high voltage resistance and can reduce the cost. 
     The invention includes other embodiments in addition to the above-described embodiments without departing from the spirit of the invention. The embodiments are to be considered in all respects as illustrative, and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description. Hence, all configurations including the meaning and range within equivalent arrangements of the claims are intended to be embraced in the invention.