This application is based on and claims the benefit of priority from earlier Japanese Patent Application No. 2017-112441 filed on Jun. 7, 2017, the description of which is incorporated herein by reference.
The present disclosure relates to an ignition device operable to generate a spark discharge at a spark plug.
Conventionally, an ignition device is known, which includes a main ignition circuit operable to generate a spark discharge at a spark plug through energization control of a primary coil of ignition coils and an energy input circuit operable to input electrical energy to the primary coil during the spark discharge (see, for example, Japanese Patent Application Laid-Open Publication No. 2015-200284). In the ignition device disclosed in Japanese Patent Application Laid-Open Publication No. 2015-200284, the spark discharge initiated by activation of the main ignition circuit is continued by the energy input circuit passing through a secondary coil of the ignition coils a secondary current having the same polarity as the secondary current generated upon activation of the main ignition circuit.
Ignition energy required for combustion may vary with environment in which the ignition is carried out by the ignition device, such as an internal-combustion engine load, an engine speed, the presence or absence of supercharging or exhaust gas recirculation (EGR), lean-burn or the like. An optimum ignition method may be different for different environments. Even though the ignition device as disclosed Japanese Patent Application Laid-Open Publication No. 2015-200284 is configured such that the main ignition by induction discharge and the ignition by energy input can be carried out by a main ignition circuit and an energy input circuit, respectively, there is still room for improvement.
In view of the above, an ignition device capable of selectively performing more ignition methods is desired.
One aspect of the disclosure provides an ignition device for generating a spark discharge at a spark plug based on a first voltage and a second voltage higher than the first voltage, the first voltage being supplied from a first supply, the second voltage being supplied from a second supply. The ignition device includes: the second supply; a primary coil including a center tap, a first terminal on a ground (GND) side of the center tap, and a second terminal on a first-supply side of the center tap; a secondary coil electromagnetically coupled to the primary coil and electrically connected to the spark plug; a first switch configured to make or break an electrical connection between the first terminal and GND; a second switch configured to make or break an electrical connection between the second supply and the center tap; a third switch configured to pass or interrupt a current from the second terminal to the first supply; and a controller configured to control an on/off state of each of the first switch, the second switch, and the third switch.
With this configuration, the on/off state of each of the first switch, the second switch, and the third switch is controlled by the controller. This allows the ignition device to select one of the following three ignition methods in response to engine operating condition and carry out the selected ignition method.
The second switch breaks the electrical connection between the second supply and the center tap, the third switch makes the electrical connection between the first supply and the second terminal, and the first switch makes the electrical connection between the first terminal and GND, thereby allowing the primary current to flow from the second terminal of the primary coil to the first terminal. Thereafter, the first switch breaks the electrical connection between the first terminal and GND, thereby generating a high voltage across the secondary coil. This allows the “main ignition by induction discharge” at the spark plug to be implemented.
After initiation of the main ignition by induction discharge, the first switch is placed in the off state (the disconnected state), the third switch is placed in the on state (the connected state), and the second switch makes the electrical connection between the second supply and the center tap, thereby allowing the primary current to flow from the center tap of the primary coil to the second terminal (energy input). The second supply then supplies the second voltage higher than the first voltage and the number of turns from the center tap to the second terminal is less than the number of turns from the first terminal to the second terminal. This can provide a current flow at a higher voltage than a discharge sustainable voltage Vm that is a voltage required to sustain the discharge at the spark plug, and an additional secondary current flows through the secondary coil in the same direction as the secondary current flows through the secondary coil at the time of the main ignition by induction discharge. Thereafter, the secondary current can be continued by controlling the second switch alternately to the on state and the off state to thereby control the secondary current to a target current that can sustain the discharge, which allows the “ignition by energy input” at the spark plug to be implemented.
After initiation of the main ignition by induction discharge, the third switch is placed in the off state (the disconnected state), the second switch is placed in the on state (the connected state), and the first switch makes the electrical connection between the first terminal and GND, thereby allowing the primary current to flow from the center tap of the primary coil to the first terminal (rapid energization). The second supply then supplies the second voltage higher than the first voltage and the number of turns from the center tap of the primary coil to the first terminal is less than the number of turns from the second terminal to the first terminal. This can provide a higher rate of increase in the primary current as compared to the case of the main ignition by induction discharge, which allows the primary current to rapidly flow through the primary coil in the same direction as the primary current flows through the primary coil at the time of the main ignition by induction discharge. Thereafter, a high voltage is generated across the secondary coil by the first switch breaking the electrical connection between the first terminal and GND, which implements the multiple ignition by rapid energization. The rapid energization and the induction discharge at the spark plug are repeated alternately by controlling the first switch alternately to the on state and the off state, which can implement the “multiple ignition by rapid energization” at the spark plug. As above, selecting and performing one of the above three ignition methods allows the ignition to be carried out with optimal power consumption.
With reference to the accompanying drawings, hereinafter are described several embodiments of the present disclosure. Substantially common elements throughout the embodiments are assigned the same numbers and will not be redundantly described. In one embodiment of the present disclosure, an engine may be a direct cylinder injection type engine that can run lean. The engine includes a turbulent flow controller for generating a turbulent flow, such as a tumble flow, a swirl flow or the like, of an air-fuel mixture within a cylinder. The ignition device is operable to ignite the air-fuel mixture in a combustion chamber at a predefined timing. The ignition device is a direct ignition (DI) type ignition device using an ignition coil corresponding to a spark plug for a respective one of multiple cylinders of the engine.
As shown in
The ECU 70 is configured to output the main ignition signal IGT and the energy input signal IGW in response to engine parameters, such as a warming up state, an engine speed, an engine load or the like, acquired from various sensors, and an engine control state (the presence or absence of lean combustion, the magnitude of the turbulent flow or the like).
The ignition device 10 includes the primary coil 11, the secondary coil 21, switching elements 31-33, a boost circuit 50, diodes 41-44, current sensing resistors 47, 48, and a control circuit 60. A spark plug 80 is provided for each cylinder of the engine. The primary coil 11 and the secondary coil 21 are provided for each spark plug 80. In the following description, a configuration corresponding to one of the spark plugs 80 will be described as a representative example. Components of the ignition device 10 are housed within a case containing the primary coil 11 and the secondary coil 21.
The spark plug 80, which has a well-known configuration, includes a central electrode electrically connected to one of ends of the secondary coil 21 via an output terminal 71, and an outside electrode electrically connected to ground (GND) via an engine cylinder head or the like. The other end of the secondary coil 21 is electrically connected to ground via the diode 44 and the current sensing resistor 48. An anode of the diode 44 is electrically connected to the secondary coil 21, and a cathode of the diode 44 is electrically connected to the current sensing resistor 48. The current sensing resistor 48 is operable to detect a secondary current flow though the secondary coil 21. An output of the current sensing resistor 48 is fed to the control circuit 60. The diode 44 inhibits a spark discharge from an undesired voltage generated during energization of the primary coil 11. The spark plug 80 generates a spark discharge between the central electrode and the outside electrode from electrical energy generated across the secondary coil 21.
The ignition coils include the primary coil 11 and the secondary coil 21 electromagnetically coupled to the primary coil 11. The number of turns in the secondary coil 21 is greater than the number of turns in the primary coil 11.
The primary coil 11 has the source terminal 12, a GND terminal 14, a center tap 16. A portion of the primary coil 11 between the source terminal 12 and the center tap 16 is a first winding 11a and a portion of the primary coil 11 between the center tap 16 and the GND terminal 14 is a second winding 11b.
The source terminal 12 (as a second terminal) is electrically connected via the switching element 33 and the diode 43 to a battery 82. The battery 82 (as a first supply) may be a well-known lead battery that supplies a voltage of 12 V (as a first voltage). An anode of the diode 43 is electrically connected to the battery 82, and a cathode of the diode 43 is electrically connected to the source terminal 12. The switching element 33 is a semiconductor switching element, such as a power transistor or a metal-oxide semiconductor (MOS) transistor, and is electrically connected in parallel with the diode 43. An on/off state of the switching element 33 is controlled by the control circuit 60. The diode 43 may be a parasitic diode of the MOS transistor. The switching element 33 and the diode 43 form a third switch operable to admit or interrupt a current flow from the source terminal 12 to the battery 82.
The GND terminal 14 (as a first terminal) of the primary coil 11 is electrically connected to the switching element 31. The switching element 31 (as a first switch) is a semiconductor switching element, such as a power transistor or a metal-oxide semiconductor (MOS) transistor. An output terminal of the switching element 31 is electrically connected to GND via the current sensing resistor 47 (as a current detecting circuit). The switching element 31 is operable to make or break an electrical connection between the GND terminal 14 and GND in response to a signal from the control circuit 60. The current sensing resistor 47 is operable to detect a primary coil current flowing through the switching element 31. An output of the current sensing resistor 47 is fed to the control circuit 60.
The center tap 16 of the primary coil 11 is electrically connected to the switching element 32 via the diode 42. An anode of the diode 42 is electrically connected to the switching element 32, and a cathode of the diode 42 is electrically connected to the center tap 16. The switching element 32 (as a second switch) is a semiconductor switching element, such as a power transistor or a MOS transistor. An input terminal of the switching element 32 is electrically connected via the boost circuit 50 to the battery 82. The switching element 32 is operable to make or break an electrical connection between the boost circuit 50 and the center tap 16 in response to a signal from the control circuit 60. A cathode of the freewheeling diode 41 is electrically connected between the diode 42 and the center tap 16. An anode of the freewheeling diode 41 is electrically connected to GND.
The boost circuit 50 (as a second supply) includes a choke coil 51, a switching element 52, a capacitor 53, and a diode 54. The choke coil 51 is electrically connected to the battery 82. The switching element 52 is a semiconductor switching element, such as a power transistor or a MOS transistor. The switching element 52 is operable to pass and block a current from the battery 82 to the choke coil 51. An on/off state of the switching element 52 is controlled by the control circuit 60. Electrical energy stored in the choke coil 51 is charged in the capacitor 53 by controlling the on/off state of the switching element 52. The diode 54 is operable to block the electrical energy stored in the capacitor 53 from flowing back to the choke coil 51. By controlling the switching element 32 to the on state, the boost circuit 50 supplies a stepped-up voltage of from tens to hundreds of volts (as a second voltage) to the center tap 16.
The control circuit 60 (as a controller) includes an input-output interface, a drive circuit and others. The control circuit 60 is configured to control an on/off state of each of switching elements 31-33, 52 in response to signals from the ECU 70 and outputs of the current sensing resistors 47, 48. The control circuit 60 selects one of three ignition methods, that is, main ignition by induction discharge, ignition by energy input, and multiple ignition by rapid energization.
The ignition device 10 includes a freewheeling diode 41. Therefore, in the ignition by energy input, upon the switching element 32 being placed in the disconnected state, a freewheeling current flows through a freewheeling current path: GND->the freewheeling diode 41->the center tap 16->the source terminal 12->the switching element 33->the battery 82->GND. This can suppress a rapid decrease in the primary current I12, which can make it easy to control the secondary current I22 to a predetermined value.
Thereafter, the control circuit 60 controls the switching element 32 alternately to the on state and the off state during a time period in which the energy input signal IGW from the ECU 70 is high (H). The boost circuit 50 supplies a stepped-up voltage higher than the battery voltage and the number of turns in the first winding 11a through which the primary current I12 flows is less than the number of turns in the primary coil 11 (see
The control circuit 60 is configured to feedback control the on/off state of the switching element 32 such that the secondary current I22 detected by the current sensing resistor 48 is maintained between a lower limit Ith1 and an upper limit Ith2. The lower limit Ith1 and the upper limit Ith2 may be fixed values or may be variably set depending on the engine operating condition. At the time instant when the energy input signal IGW becomes low (L), the control circuit 60 controls the switching element 32 to the off state. Then, the control circuit 60 controls the switching element 33 to the off state. In an alternative embodiment, the control circuit 60 may be configured to feedforward control the on/off state of the switching element 32 such that the secondary current I22 is maintained between the lower limit Ith1 and the upper limit Ith2.
Thereafter, the control circuit 60 controls the switching element 31 to the on state during a time period in which the multiple ignition signal is high (H). The boost circuit 50 supplies a stepped-up voltage higher than the battery voltage and the number of turns in the second winding 11b through which the primary current I13 flows is less than the number of turns in the primary coil 11 (see
The embodiment set forth above can provide the following advantages.
(A1) The switching element 32 breaks an electrical connection between the boost circuit 50 and the center tap 16, the diode 43 makes an electrical connection between the battery 82 and the source terminal 12, and the switching element 31 makes an electrical connection between the GND terminal 14 and GND, thereby allowing the primary current I11 to flow from the source terminal 12 of the primary coil 11 to the GND terminal 14. Thereafter, the switching element 31 breaks the electrical connection between the GND terminal 14 and GND, thereby generating a high voltage across the secondary coil 21. This allows the main ignition by induction discharge at the spark plug 80 to be implemented.
(A2) After initiation of the main ignition by induction discharge, the switching element 31 is placed in the off state (the disconnected state), the switching element 33 is placed in the on state (the connected state), and the switching element 32 makes the electrical connection between the boost circuit 50 and the center tap 16, thereby allowing the primary current I12 to flow from the center tap 16 of the primary coil 11 to the source terminal 12 of the first winding 11a (energy input). The boost circuit 50 then supplies a stepped-up voltage higher than the battery voltage and the number of turns from the center tap 16 of the primary coil 11 to the source terminal 12 is less than the number of turns from the GND terminal 14 to the source terminal 12. This can provide a current flow at a higher voltage than a discharge sustainable voltage Vm that is a voltage required to sustain the discharge at the spark plug 80, and an additional secondary current I22 flows through the secondary coil 21 in the same direction as the secondary current flows through the secondary coil 21 at the time of the main ignition by induction discharge. Thereafter, the secondary current I22 can be continued by controlling the switching element 32 alternately to the on state and the off state, which allows the ignition by energy input at the spark plug 80 to be implemented.
(A3) After initiation of the main ignition by induction discharge, the switching element 33 is placed in the off state (the disconnected state), the switching element 32 is placed in the on state (the connected state), and the switching element 31 makes the electrical connection between the GND terminal 14 and GND, thereby allowing the primary current I13 to flow from the center tap 16 of the primary coil 11 to the GND terminal 14 through the second winding 11b (rapid energization). The boost circuit 50 then supplies a stepped-up voltage higher than the battery voltage and the number of turns from the center tap 16 of the primary coil 11 to the GND terminal 14 is less than the number of turns from the source terminal 12 to the GND terminal 14. This can provide a higher rate of increase in the primary current I13 as compared to the case of the main ignition by induction discharge, which allows the primary current I13 to rapidly flow through the primary coil 11 in the same direction as the primary current flows through the primary coil 11 at the time of the main ignition by induction discharge. Thereafter, a high voltage is generated across the secondary coil 21 by the switching element 31 breaking the electrical connection between the GND terminal 14 and GND, which implements the multiple ignition by rapid energization. The rapid energization of the second winding 11b and the induction discharge at the spark plug 80 are repeated alternately by controlling the switching element 31 alternately to the on state and the off state, which can implement the multiple ignition by rapid energization at the spark plug 80.
(A4) During the multiple ignition by rapid energization, the primary current I13 is allowed to flow through the second winding 11b only, which can reduce the impedance of the second winding 11b as compared to when the primary current flows through the entire primary coil 11. This can reduce the amount of time needed to charge the second winding 11b, thereby allowing the ignition to be carried out intermittently at short time intervals. Therefore, where the airflow velocity in the engine is low as compared to when the ignition by energy input is carried out, the flame warmed by the ignitions will not be swept away by the airflow even in the case that there is a spacing between the successive ignitions, so that the ignition flame will likely dwell in the vicinity of the spark plug. A succession of spark discharges allows the ignition flame to be superimposed, which facilitates combustion. A subsequent spark discharge is allowed to occur until the generated ignition flame is blown out and the combustion can therefore be continued.
(A5) The current is allowed to flow from the battery 82 to the source terminal 12 via the diode 43. Therefore, the switching element 33 does not need to be controlled to carry out the main ignition by induction discharge. That is, to carry out the main ignition by induction discharge, the switching element 32 is placed in the disconnected state and the switching element 31 is placed in the connected state, which can pass the primary current I11 from the source terminal 12 of the primary coil 11 to the GND terminal 14. To carry out the ignition by energy input, the switching element 31 is placed in the disconnected state, the switching element 33 is placed in the connected state, and the switching element 32 is placed in the connected state, which can pass the primary current I12 from the center tap 16 of the primary coil 11 to the source terminal 12. To carry out the multiple ignition by rapid energization, the switching element 33 is placed in the disconnected state, the switching element 32 is placed in the connected state, and the switching element 31 is placed in the connected state, which can pass the primary current I13 from the center tap 16 of the primary coil 11 to the GND terminal 14.
(A6) The ignition device 10 includes a freewheeling diode 41. A cathode of the freewheeling diode 41 is electrically connected between the diode 42 and the center tap 16. An anode of the freewheeling diode 41 is electrically connected to GND. Therefore, in the ignition by energy input, upon the switching element 32 being placed in the disconnected state, a freewheeling current flows through a freewheeling current path: GND->the freewheeling diode 41->the center tap 16->the source terminal 12->the switching element 33->the battery 82->GND. This can suppress a rapid decrease in the primary current I12, which can make it easy to continue the secondary current I22 and sustain the spark discharge.
(A7) The ignition is carried out by the control circuit 60 according to one of the three ignition methods selected in response to an environment in which the ignition is carried out at the spark plug 80. An environment in which the ignition is carried out at the spark plug 80. Therefore, the ignition method suitable in an environment in which the ignition is carried out at the spark plug 80 can be carried out with optimal power consumption.
Numerous modifications, alterations, and changes to the described embodiment are possible without departing from the scope of the present invention, as defined in the appended claims. Similar elements to those of the described embodiment are assigned the same numbers and will not be redundantly described.
(M1) As shown in
In this configuration, to carry out the main ignition by induction discharge, the switching element 32 is placed in the disconnected state, the switch 133 is placed in the connected state, and the switching element 31 is placed in the connected state, which can pass the primary current I11 from the source terminal 12 of the primary coil 11 to the GND terminal 14. To carry out the ignition by energy input, the switching element 31 is placed in the disconnected state, the switch 133 is placed in the connected state, and the switching element 32 is placed in the connected state, which can pass the primary current I12 from the center tap 16 of the primary coil 11 to the source terminal 12. To carry out the multiple ignition by rapid energization, the switch 133 is placed in the disconnected state, the switching element 32 is placed in the connected state, and the switching element 31 is placed in the connected state, which can pass the primary current I13 from the center tap 16 of the primary coil 11 to the GND terminal 14. Therefore, the ignition can be carried out with optimal power consumption.
In the above configuration, a three-state analog switching element may be used as the switch 133. That is, the switch 133 only has to be configured such that it can pass the current from the battery 82 to the source terminal 12 and can switch between a passing and a blocking state for a current from the source terminal 12 to the battery 82.
(M2)
With this configuration, it is possible to store electrical energy in the second winding 11b of the primary coil 11 while inhibiting the primary current I13 from becoming excessively large. In addition, heat generation of the switching element 31 can be suppressed as compared to when the primary current I13 is controlled by controlling the magnitude of the gate voltage of the switching element 31 and adjusting a turn-on voltage and a switching activation level of the switching element 31. This can inhibit excessive temperature rise of the switching element 31 and can simplify a cooling structure for the switching element 31. Upon the switching element 32 being placed in the disconnected state, a freewheeling current flows through a freewheeling current path: GND->the freewheeling diode 41->the center tap 16->the GND terminal 14->the switching element 31->GND (see
(M3) As shown in
(M4) As shown in
(M5) As shown in
With this configuration, the magnitude of voltage applied to the center tap 16 can be changed and the ignition of each method can be carried out at reduced power. For example, in the ignition by energy input, the switching element 32A making or braking the electrical connection between the boost circuit 50A and the center tap 16 allows the primary current flowing through the first winding 11a, thus the secondary current flowing through the secondary coil 21, to be increased. The engine speed is thus increased, so that even in an ignition environment where flame generated by the spark discharge tends to be blown out, the combustion of fuel is allowed to be continued. In the multiple ignition by rapid energization, if the voltage applied to the center tap 16 is too high, a voltage across the diode 44 generated upon initiation of energization of the second winding 11b may exceed its withstand voltage. Therefore, in the multiple ignition by rapid energization, the switching element 32 making or braking the electrical connection between the boost circuit 50 and the center tap 16 can inhibit occurrence of a discharge of reversed polarity at the spark plug 80.
(M6) The ECU 70 may be configured to cause the control circuit 60 to carry out any two of the three ignition methods.
(M7) The ECU 70 (as a controller) may be configured to further include all or some of the functions of the control circuit 60.
(M8) The ignition device 10 may be applied to an engine without the turbulent flow controller. The ignition device 10 may be applied to a spark ignition engine using fuel other than gasoline or mixed fuel with gasoline.
Number | Date | Country | Kind |
---|---|---|---|
2017-112441 | Jun 2017 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
6675784 | Nagase | Jan 2004 | B2 |
7392798 | Wada | Jul 2008 | B2 |
8861175 | Godo | Oct 2014 | B2 |
20160084215 | Kondou | Mar 2016 | A1 |
20160201637 | Sekine | Jul 2016 | A1 |
20170022960 | Takeda | Jan 2017 | A1 |
Number | Date | Country |
---|---|---|
2007-092605 | Apr 2007 | JP |
2015-200284 | Nov 2015 | JP |
2016-053358 | Apr 2016 | JP |
Number | Date | Country | |
---|---|---|---|
20180358782 A1 | Dec 2018 | US |