Patent Publication Number: US-7581534-B2

Title: Internal combustion engine ignition device

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an internal combustion engine ignition device, for example, mounted on a vehicle, and particularly to an internal combustion engine ignition device that generates an ignition high voltage across the secondary coil of an ignition coil, by flowing and interrupting an electric current for the primary coil of the ignition coil by use of a switching element. 
   2. Description of the Related Art 
   In a conventional internal combustion engine ignition device, an ion signal and an ignition signal are multiplexed and outputted on a coil-driver input signal line, and in the case where the ion signal is outputted, masking is performed so that the switching element does not turn on (for example, refer to Japanese Patent Laid-Open Pub. No. 2004-156608, Pages 17 and 18, FIGS. 49 and 50). 
   In the conventional internal combustion engine ignition device, there has been a problem that, in the case where, when the ion signal and the ignition signal are outputted at the coil-driver input signal line, the inside of the engine compartment becomes high-temperature, thereby causing pre-ignition, or a smolder occurs around the ignition plug, thereby producing soot between the electrodes, causing a leakage electric current to flow, and causing a pseudo ion current to flow constantly, it is required that the dynamic range of the input voltage be set wide in order to detect the ion current even at the timing when the ignition signal is supplied; as a result, the circuit scale of the ECU (Electronic Control Unit) becomes large, thereby causing the cost hike. 
   Moreover, there has been a problem that, in the case where a certain factor such as interruption of the primary-coil current causes a difference between the ground potential for the ECU and the ground potential for the coil driver, the ion signal cannot accurately be transferred to the ECU. 
   SUMMARY OF THE INVENTION 
   The present invention has been implemented in order to solve the foregoing problems; the objective of the present invention is to provide an internal combustion engine ignition device that can securely detect the ion current even at the timing when the ignition signal is supplied and that improves the functionality of the ignition system by enlarging at low cost the region in which the ion current can be detected. 
   An internal combustion engine ignition device according to the present invention includes an ignition coil having a primary coil and a secondary coil and a switching element that generates an ignition high voltage across the secondary coil of the ignition coil by flowing and interrupting a primary-coil current of the ignition coil; the internal combustion engine ignition device further includes an ECU (electronic control unit) including a pulse generation circuit that supplies a coil-driver input signal line with a single pulse signal having an extremely short duration or a plurality of pulse signals, as an energization start signal Igt 1  or a de-energization signal Igt 2 ; a pulse detection circuit that stores the energization start signal and the de-energization signal, that recognizes the single pulse signal or the plurality of pulse signals, received by way of the coil-driver input signal line from the pulse generation circuit, as the energization start signal or the de-energization signal, and that supplies an ignition signal to the switching element; an ion bias circuit that is connected to a low-voltage side of the secondary coil and generates an ion current; an ion-current detection circuit that detects an ion current flowing through the secondary coil; an ion-current output circuit that outputs an ion signal at the coil-driver input signal line, based on an output signal of the ion-current detection circuit; and an ion-signal detection/control circuit that is included in the ECU and that detects and controls an output signal of the ion-current output circuit. The internal combustion engine ignition device is configured in such a way that, at a timing when the pulse generation circuit outputs neither the energization start signal nor the de-energization signal, the ion-signal detection/control circuit sets an input voltage Igt of a coil driver to a high level, and at a timing when the pulse generation circuit outputs the energization start signal or the de-energization signal, the input voltage Igt of the coil driver is lowered for an extremely short time from the high level to a low level, so that the pulse detection circuit recognizes the change in the input voltage Igt as the energization start signal or the de-energization signal and supplies an ignition signal to the switching element, and in such a way that, at a timing except the timing when the energization start signal and the de-energization signal is supplied to the pulse detection circuit, the ion-current output circuit outputs an ion signal at the coil-driver input signal line, based on an ion current detected by the ion-current detection circuit. 
   According to the present invention, an internal combustion engine ignition device can be obtained in which, even in the case where the ignition signal is supplied when, the inside of the engine compartment becomes high-temperature, thereby causing pre-ignition, or a smolder around the ignition plug causes soot or the like in the space between the electrodes, thereby causing a leakage electric current to flow, whereby a pseudo ion current always flows, it is not required to make the dynamic range of the input voltage Igt wide, an ion current can accurately be detected by a 5-Volt system, and, at low cost, an ion-current detection region is enlarged and the functionality of the ignition system is enhanced. 
   Moreover, at the timing when the pulse generation circuit outputs neither the energization start signal nor the de-energization signal, the input voltage Igt of the coil driver is set to a high level (from 5 V to 14 V), so that the ion signal can accurately be transferred to the ECU, even in the case where a difference between the ground potential for the ECU and the ground potential for the coil driver is caused, for example, at the timing of interruption of the primary-coil current. 
   The foregoing and other object, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic block diagram illustrating principal parts of an internal combustion engine ignition device according to Embodiment 1 of the present invention; 
       FIG. 2  is a detailed circuit diagram of an internal combustion engine ignition device according to Embodiment 1 of the present invention; 
       FIG. 3  is an example of timing chart representing waveforms at various operational points in Embodiment 1 of the present invention; 
       FIG. 4  is a circuit diagram illustrating a variant example of Embodiment 1 of the present invention, in the case where an ion-signal detection/control circuit is digitized; 
       FIG. 5  is an example of timing chart representing waveforms at various operational points in Embodiment 1, in the case where an ion-signal detection/control circuit is digitized; 
       FIG. 6  is another example of timing chart representing waveforms at various operational points in Embodiment 1 of the present invention; 
       FIG. 7  is another example of timing chart representing waveforms at various operational points in Embodiment 1 of the present invention; 
       FIG. 8  is a set of charts each representing the waveform of a pulse signal according to Embodiment 2 of the present invention; 
       FIG. 9  is a set of charts each representing the waveform of a pulse signal according to Embodiment 4 of the present invention; 
       FIG. 10  is an example of timing chart representing waveforms at various operational points in Embodiment 5 of the present invention; 
       FIG. 11  is an example of timing chart representing waveforms at various operational points in Embodiment 6 of the present invention; 
       FIG. 12  is a schematic block diagram illustrating principal parts of an internal combustion engine ignition device according to Embodiment 7 of the present invention; 
       FIG. 13  is a detailed circuit diagram of an internal combustion engine ignition device according to Embodiment 7 of the present invention; and 
       FIG. 14  is a timing chart representing waveforms at various operational points in Embodiment 7 of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the present invention will be explained below with reference to the accompanying drawings. 
   Embodiment 1 
     FIGS. 1 and 2  are circuit block diagrams illustrating an internal combustion engine ignition device according to Embodiment 1 of the present invention;  FIG. 1  is a schematic block diagram illustrating principal parts of Embodiment 1;  FIG. 2  is a detailed circuit diagram for the principal parts illustrated in  FIG. 1 . In the first place, the principal parts of Embodiment 1 of the present invention will be explained with reference to  FIG. 1 . 
   As illustrated in  FIG. 1 , the internal combustion engine ignition device according to Embodiment 1 of the present invention is provided with an ignition coil  1  having a primary coil  2  and a secondary coil  3 , a pulse generation circuit  201  that is incorporated in an electronic control unit (hereinafter, referred to also as ECU)  200  and outputs an energization start signal Igt 1  and a de-energization signal Igt 2 , and an NPN transistor  202  that supplies the later stage with a signal, based on the energization start signal Igt 1  and the de-energization signal Igt 2  that are outputted by the pulse generation circuit  201 . In addition, the foregoing internal combustion engine ignition device is provided with a pulse detection circuit  7  that stores the energization start signal Igt 1  and the de-energization signal Igt 2 , recognizes a signal, supplied from the collector of the NPN transistor  202  to the pulse detection circuit  7  by way of a resistor  204  and an input impedance  6  inside a coil driver  400 , as the energization start signal Igt 1  or the de-energization signal Igt 2 , and supplies the later stage with an ignition signal; a switching element  5  that, based on the output signal of the pulse detection circuit  7 , flows and interrupts a primary-coil current I 1  for the primary coil  2  of the ignition coil so as to generate a high voltage, for igniting an ignition plug  4 , across the secondary coil  3  of the ignition coil  1 ; an ion bias circuit  8  for generating an ion current, which is connected to the low-voltage side of the secondary coil  3 ; an ion-current detection circuit  9  that detects an ion current generated after the execution of ignition and outputs the ion current to the later stage; an ion-current-output current mirror circuit  10  that outputs an ion current, based on the output signal of the ion-current detection circuit  9 ; and an ion-signal detection/control circuit  300  that detects and controls the output signal of the ion-current-output current mirror circuit  10 . 
   The internal combustion engine ignition device is configured in such a way that, at the timing when the pulse generation circuit  201  outputs neither the energization start signal Igt 1  nor the de-energization signal Igt 2 , the ion-signal detection/control circuit  300  inside the ECU sets an input voltage Igt of the coil driver  400  to a high level (from 5 V to 14 V), and at the timing when the pulse generation circuit  201  outputs the energization start signal Igt 1  or the de-energization signal Igt 2 , the ion-signal detection/control circuit  300  lowers for an extremely short time the input voltage Igt of the coil driver  400  from the high level (from 5 V to 14 V) to a low level (0 V), so that the pulse detection circuit  7  recognizes the change in the input voltage Igt as the energization start signal Igt 1  or the de-energization signal Igt 2  and supplies an ignition signal to the switching element  5 , thereby driving the switching element  5 . 
   The pulse detection circuit  7  is a circuit in which the energization start signal Igt 1  and the de-energization signal Igt 2  are stored. 
   The ion bias circuit  8  is a bias circuit for making an ion current flow. The ion-current detection circuit  9  supplies the ion-current-output current mirror circuit  10  with an ion current. The ion-current detection circuit  9  is activated at the timing when an ion current flows, and then the ion-current-output current mirror circuit  10  is activated. The ion-current-output current mirror circuit  10  extracts an electric current equivalent to the ion current from the ECU  200 . In addition, the input voltage Igt of the coil driver  400  at this timing is given by the following equation:
 
 Igt ≈the voltage of the internal power source of the ECU 200−(ION×the resistance value of a resistor 203)
 
   As a result, the ion-signal detection/control circuit  300  is activated, and the ion current is transferred to the ion-signal detection/control circuit  300 . 
   By performing an analysis based on the ion current, the in-cylinder combustion condition is ascertained. 
   Next, the internal combustion engine ignition device according to Embodiment 1 will be described more specifically, with reference to  FIG. 2 . The reference characters the same as those in  FIG. 1  denote the same or equivalent constituent elements. 
   As illustrated in  FIG. 2 , the internal combustion engine ignition device according to Embodiment 1 includes the ECU  200 , the ignition coil  1 , the pulse detection circuit  7 , the switching element  5 , the ion bias circuit  8 , the ion-current detection circuit  9 , and the ion-current-output current mirror circuit  10 . The ignition coil  1  having the primary coil  2  and the secondary coil  3  is connected to a power-source terminal VB. The ignition plug  4  is connected to the high-voltage side of the secondary coil  3 . The ECU  200  has the pulse generation circuit  201  and the ion-signal detection/control circuit  300 ; the pulse generation circuit  201  supplies to an input terminal  400 a of the coil driver  400  the energization start signal Igt 1  and the de-energization signal Igt 2  that are a single pulse having an extremely short duration or a plurality of pulses, by way of the NPN transistor  202  and the resistor  204 . In addition, the pulse generation circuit  201  supplies the energization start signal Igt 1  and the de-energization signal Igt 2  also to the gate of a P-channel MOSFET  302 , described later, in the ion-signal detection/control circuit  300 . 
   At the timing when neither the energization start signal Igt 1  nor the de-energization signal Igt 2  is supplied to the NPN transistor  202  and the P-channel MOSFET  302 , the input voltage Igt of the coil driver  400  is set to a high level (from 5 V to 14 V), and at the timing when the pulse generation circuit  201  supplies the energization start signal Igt 1  or the de-energization signal Igt 2  to the NPN transistor  202  and the P-channel MOSFET  302 , the NPN transistor  202  turns on and the P-channel MOSFET  302  turns off, thereby lowering for an extremely short time the input voltage Igt of the coil driver  400  from the high level (from 5 V to 14 V) to a low level (0 V), so that a signal is supplied to the pulse detection circuit  7 . 
   The pulse detection circuit  7  is a circuit in which the energization start signal Igt 1  and the de-energization signal Igt 2  are stored; the pulse detection circuit  7  recognizes the signal received from the pulse generation circuit  201  as the energization start signal Igt 1  or the de-energization signal Igt 2  and supplies an ignition signal to the switching element  5  in the later stage, thereby driving the switching element  5 . 
   The switching element  5  is, for example, an IGBT (insulated gate bipolar transistor (IGBT); the gate terminal is connected to the pulse detection circuit  7 , the collector terminal is connected to the primary coil  2  of the ignition coil  1 , and the emitter terminal is connected to the reference potential point GND. The ion bias circuit  8  is connected to the low-voltage side of the secondary coil  3 . 
   The ion bias circuit  8  is configured in such a way as to have an output terminal  8   a  and an input terminal  8   b.  The output terminal  8   a  is connected to the ion-current detection circuit  9  in the later stage, and the input terminal  8   b  is connected to the low-voltage side of the secondary coil  3 . 
   The ion-current detection circuit  9  is connected to the ion-current-output current mirror circuit  10  and the ion bias circuit  8 . 
   The ion-current-output current mirror circuit  10  is configured in such a way as to have an output terminal  10   a  and an input terminal  10   b.  The output terminal  10   a  is connected to the input impedance  6  and the pulse detection circuit  7 , and the input terminal  10   b  is connected to the ion-current detection circuit  9 . 
   Next, the inner configuration of the ion-signal detection/control circuit  300  will be explained. The ion-signal detection/control circuit  300  is configured with an internal power source  301 , the P-channel MOSFET  302 , a current mirror circuit  305  including PNP transistors  303  and  304 , ion-current detection resistor  306 , and an ion-signal control circuit  309 . The gate of the P-channel MOSFET  302  in the ion-signal detection/control circuit  300  is connected to the pulse generation circuit  201 ; the drain is connected to the emitters of the PNP transistors  303  and  304 ; the source is connected to the internal power source  301 . The internal power source  301  is a stabilized power source. The base of the PNP transistor  303  is connected to the base of the PNP transistor  304 , and the collector of the PNP transistor  303  is connected to the ion-current detection resistor  306  and the ion-signal control circuit  309 . The base of the PNP transistor  304  is connected to the collector of the PNP transistor  304  and the resistor  203 . The other terminal of the ion-current detection resistor  306  is connected to the ground GND. 
     FIG. 3  is a timing chart representing waveforms at various points in Embodiment 1; the operation of the internal combustion engine ignition device illustrated in  FIG. 2  will be explained with reference to the timing chart. During the time period between the time points t 1  and t 2 , the pulse generation circuit  201  supplies the NPN transistor  202  and the P-channel MOSFET  302  with the energization start signal Igt 1  (here, represented as a single pulse) having an extremely short duration. At the timing when neither the energization start signal Igt 1  nor the de-energization signal Igt 2  is supplied to the NPN transistor  202  and the P-channel MOSFET  302 , the input voltage Igt of the coil driver  400  is set to a high level (from 5 V to 14 V), and at the timing when the pulse generation circuit  201  supplies the energization start signal Igt 1  or the de-energization signal Igt 2  to the NPN transistor  202  and the P-channel MOSFET  302 , the NPN transistor  202  turns on and the P-channel MOSFET  302  turns off, thereby lowering for an extremely short time the input voltage Igt of the coil driver  400  from the high level (from 5 V to 14 V) to a low level (0 V), so that a pulse signal is supplied to the pulse detection circuit  7 . The pulse detection circuit  7  recognizes the pulse signal supplied from the pulse generation circuit  201  as the energization start signal Igt 1  and, at the time point t 2 , supplies an ignition signal to the input terminal (the gate, in this case) of the switching element  5  in the later stage, so that the switching element  5  turns on, whereupon the primary-coil current I 1  starts to flow through the primary coil  2  of the ignition coil  1 . 
   After that, during the time period between the time points t 3  and t 4 , the pulse generation circuit  201  supplies the NPN transistor  202  and the P-channel MOSFET  302  with the de-energization signal Igt 2  (here, represented as a single pulse) having an extremely short duration. The pulse detection circuit  7  recognizes the pulse signal received from the pulse generation circuit  201  as the de-energization signal Igt 2  and, at the time point t 4 , interrupts the ignition signal that has been supplied to the switching element  5  in the later stage. At the time point t 4  when, due to the interruption of the voltage supply to the input terminal (here, the gate) of the switching element  5 , the switching element  5  turns off, the primary-coil current I 1  flowing in the primary coil  2  is interrupted, whereby a high voltage is generated at the collector (here, represented as C) of the switching element  5 . 
   The energy is converted through the secondary coil  3 , whereby a negative voltage is induced at the high-voltage side of the secondary coil  3 . On that occasion, a high voltage is applied to the low-voltage side of the secondary coil and a voltage is applied across a Zener diode  83  through a diode  81 , whereby a capacitor  84  is charged. In the case where the negative voltage, which is large enough to break the insulation in the gap of the ignition plug  4 , is generated, a discharge takes place, and, after the time point t 4 , a secondary-coil current flows from the ignition plug  4  to the ground GND by way of the secondary coil  3 , the diode  81 , and the Zener diode  83 . 
   At the time instant t 5  when the discharge is completed, the voltage charged across the capacitor  84  causes an ion current to start to flow through the secondary coil  3  by the intermediary of a resistor  82 . The ion-current detection circuit  9  is activated at this time instant, and then the ion-current-output current mirror circuit  10  is activated. An N-channel MOSFET  101  in the ion-current-output current mirror circuit  10  extracts a drain current, corresponding to the ion current that flows through an N-channel MOSFET  102 , from the current mirror circuit  305  in the ion-signal detection/control circuit  300 . 
   As a result, the current mirror circuit  305  in the ion-signal detection/control circuit  300  is activated, and the collector current, corresponding to the ion current that flows through the PNP transistor  304 , flows through the PNP transistor  303  in the current mirror circuit  305 . The outputted current is converted into a voltage by the ion-current detection resistor  306  and transferred, as an analogue signal, to the ion-signal control circuit  309 . 
   In addition, in the foregoing internal combustion engine ignition device according to Embodiment 1, by replacing the ion-signal detection/control circuit  300  by an ion-signal detection/control circuit (digital-type)  300 ′ illustrated in  FIG. 4 , the detection and control of an ion current can digitally be performed. 
   The digital-type ion-signal detection/control circuit  300 ′ will be explained. 
   In  FIG. 4 , the ion-signal detection/control circuit (digital-type)  300 ′ is configured with the internal power source  301 , the P-channel MOSFET  302 , the current mirror circuit  305  including the PNP transistors  303  and  304 , the ion-current detection resistor  306 , a comparator circuit  307 , a reference voltage  308 , and the ion-signal control circuit  309 . The gate of the P-channel MOSFET  302  is connected to an unillustrated pulse generation circuit  201 ; the drain is connected to the emitters of the PNP transistors  303  and  304 ; the source is connected to the internal power source  301 . The internal power source  301  is a stabilized power source. The base of the PNP transistor  303  is connected to the base of the PNP transistor  304 , and the collector of the PNP transistor  303  is connected to the ion-current detection resistor  306 . The base of the PNP transistor  304  is connected to the collector of the PNP transistor  304  and the resistor  203 . The other terminal of the ion-current detection resistor  306  is connected to the ground GND. The input terminal (+) of the comparator circuit  307  is connected to the ion-current detection resistor  306 ; the input terminal (−) is connected to the reference voltage (Vth)  308 ; the output terminal of the comparator circuit  307  is connected to the ion-signal control circuit  309 . 
     FIG. 5  is a timing chart representing waveforms at various points in the case where the ion-signal detection/control circuit  300  is replaced by the digital-type ion-signal detection/control circuit  300 ′. During the time period between the time points t 5  and t 6 , in which the analogue signal obtained by converting an ion current into a voltage by the ion-current detection resistor  306  exceeds the reference voltage (Vth)  308 , the comparator circuit  307  outputs a pulse as a digital signal to the ion-signal control circuit  309 . In addition, the operation up to the time point when the ion current is supplied to the ion-current detection resistor  306  is the same as that represented in  FIG. 3 ; therefore, the explanation therefor will be omitted. 
   In the internal combustion engine ignition device, according to Embodiment 1 of the present invention, configured as described above, even in the case where, as represented by a timing chart in  FIG. 6 , the inside of the engine compartment becomes high-temperature, whereby pre-ignition causes an ion current to occur during the time period between the time points t 3  and t 4 , which is earlier than the normal timing, the ion-current-output current mirror circuit  10  can be activated by setting the input voltage Igt of the coil driver  400  to a high level (from 5 V to 14 V) at the timing except the timing when the pulse generation circuit  201  supplies the energization start signal Igt 1  or the de-energization signal Igt 2  to the NPN transistor  202  and the P-channel MOSFET  302 . As a result, even during the time period in which the primary-coil current I 1  flows, the outputted ion current can be transferred to the ion-signal control circuit  309 , whereby it is made possible to enlarge the region in which the ion current can be detected. 
   Moreover, even in the case where, as represented by a timing chart in  FIG. 7 , a smolder around the ignition plug causes soot or the like to be produced in the space between the electrodes and a leakage electric current to flow, whereby a pseudo ion current always flows, and even in the case where the inside of the engine compartment becomes high-temperature, whereby pre-ignition causes an ion current to occur at the timing which is earlier than the normal timing, an ion current can accurately be detected by a 5-volt system, without expanding the dynamic range of the input voltage Igt, although the high level of the input voltage Igt is lowered. 
   Embodiment 2 
   An internal combustion engine ignition device according to Embodiment 2 of the present invention is configured in such a way that, in the foregoing Embodiment 1, as an example represented in  FIG. 8 , the pulse generation circuit  201  outputs an energization start signal Igt 1 ′ and a de-energization signal Igt 2 ′ that are different from each other in pulse width (refer to  FIG. 8A ), or the pulse generation circuit  201  outputs an energization start signal Igt 1 ″ and a de-energization signal Igt 2 ″ that are different from each other in the number of pulses (refer to  FIG. 8B ). 
   According to Embodiment 2, the pulse detection circuit  7  can readily distinguish between the energization start signal Igt 1 ′ and the de-energization signal Igt 2 ′ that are outputted from the pulse generation circuit  201 . 
   Embodiment 3 
   An internal combustion engine ignition device according to Embodiment 3 of the present invention is configured in such a way that, in the foregoing Embodiment 1, the value of the input impedance  6  in the coil driver  400  is set to be extremely large compared with the value of the resistor  204  in the ECU  200 . 
   According to Embodiment 3, even in the case where, while the pulse generation circuit generates the energization start signal Igt 1  or the de-energization signal Igt 2 , an ion current flows, no electric current flows in the ion-current-output current mirror circuit  10 ; therefore, the pulse generation circuit  201  can stably supply the energization start signal Igt 1  and the de-energization signal Igt 2 , and the ion detection can stably be performed without affecting the ignition signal. 
   Embodiment 4 
   An internal combustion engine ignition device according to Embodiment 4 of the present invention is configured in such a way that, in the foregoing Embodiment 1, as an example represented in  FIG. 9 , the pulse generation circuit  201  outputs an energization start signal Igt 1 ′″ and a de-energization signal Igt 2 ′″ that are signals each including at least two kinds of pulse widths (for example, a combination signal, having a width of several tens microseconds, consisting of a low-frequency pulse signal and a high-frequency pulse signal), and provision is made for the pulse detection circuit  7  that detects the fact that the pulse signals are inputted in predetermined order. 
   According to Embodiment 4, even in the case where noise such as a surge voltage intrudes in the input signal line of the coil driver  400 , the noise is not recognized as the energization start signal or the de-energization signal because high-frequency noise and low-frequency noise each include continuous noise signals that are of the same frequency; therefore, problems such as re-energization of the primary coil and erroneous ignition can be avoided. 
   Embodiment 5 
   An internal combustion engine ignition device according to Embodiment 5 is configured in such a way that, in the foregoing Embodiment 1, provision is made, in the coil driver  400 , for a response circuit that transmits a signal that indicates the start of energization, in a constant time after detecting the fact that the pulse generation circuit  201  has supplied the energization start signal Igt 1  to the pulse detection circuit  7 , and provision is made, in the ECU  200 , for a response monitoring circuit that detects the signal transmitted by the response circuit. 
     FIG. 10  is a timing chart representing waveforms at various points in Embodiment 5. 
   According to Embodiment 5, during the time period between the time points t 1  and t 2  in the timing chart in  FIG. 10 , the pulse detection circuit  7  detects the energization start signal Igt 1 ′, and the response circuit transmits a response signal Igt 3  to the Igt 1  line. The response monitoring circuit detects the response signal Igt 3 , and the operation status detected by the response monitoring circuit and the operation status indicated by the ECU  200  are compared, so that it can be determined whether or not the coil driver operates normally. 
   Embodiment 6 
   An internal combustion engine ignition device according to Embodiment 6 of the present invention is configured in such a way that, in the foregoing Embodiment 5, provision is made, in the ECU  200 , for a function for recurrently transmitting the same signal in the case where the operation status detected by the response monitoring circuit is different from a predetermined operation status. 
     FIG. 11  is a timing chart representing waveforms at various points in Embodiment 6. 
   According to Embodiment 6, even in the case where, during the time period between the time points t 1  and t 2  in the timing chart represented in  FIG. 11 , a normal signal transfer from the pulse generation circuit  201  to the pulse detection circuit  7  cannot be performed, the response circuit does not transmit the response signal Igt 3  to the Igt 1  line; thus, by making the response monitoring circuit in the ECU  200  detect the foregoing fact that a normal signal transfer cannot be performed and supply, during the recurrent time period between the time points t 5  and t 6 , the energization start signal Igt 1 ′ to the pulse detection circuit  207 , the operational accuracy of the coil driver can be enhanced. 
   Embodiment 7 
     FIGS. 12 and 13  are circuit block diagrams illustrating an internal combustion engine ignition device according to Embodiment 7 of the present invention;  FIG. 12  is a schematic block diagram illustrating principal parts of Embodiment 7;  FIG. 13  is a detailed circuit diagram for the principal parts illustrated in  FIG. 12 . In the first place, the principal parts of Embodiment 7 of the present invention will be explained with reference to  FIG. 12 . 
   As illustrated in  FIG. 12 , the internal combustion engine ignition device according to Embodiment 7 of the present invention is provided with a coil  700  including a coil driver, a pulse generation circuit  501  that is incorporated in an ECU  500  and outputs an energization start signal Igt 1  and a de-energization signal Igt 2 , an NPN transistor  502  that supplies a signal to the coil  700  including a coil driver, based on the energization start signal Igt 1  and the de-energization signal Igt 2  that are outputted by the pulse generation circuit  501 , and a coil-output-signal detection/control circuit  600  that detects and controls the output signal of the coil  700  including a coil driver. In the coil  700  including a coil driver, the energization start signal Igt 1  and the de-energization signal Igt 2  are stored; a signal, supplied from the collector of the NPN transistor  502  by way of a resistor  504 , is recognized as the energization start signal Igt 1  or the de-energization signal Igt 2 ; an ignition signal is supplied to a switching element, thereby flowing and interrupting a primary-coil current I 1  for the primary coil of an ignition coil so as to generate a high voltage for igniting the ignition plug  14 ; and a signal, outputted when the coil  700  including a coil driver is activated, is detected and outputted to the ECU  500 . 
   At the timing when the pulse generation circuit  501  outputs neither the energization start signal Igt 1  nor the de-energization signal Igt 2 , the input voltage Igt of the coil  700  including a coil driver is set to a high level (from 5 V to 14 V), and at the timing when the pulse generation circuit  501  outputs the energization start signal Igt 1  or the de-energization signal Igt 2 , the input voltage Igt of the coil  700  including a coil driver is lowered for an extremely short time from the high level (from 5 V to 14 V) to a low level (0 V), so that the coil  700  including a coil driver recognizes the change in the input voltage Igt as the energization start signal Igt 1  or the de-energization signal Igt 2  and flows and interrupts the primary-coil current I 1  so as to generate a high voltage for igniting the ignition plug  14 . 
   The coil  700  including a coil driver detects a signal outputted through a series of operations thereof and extracts a constant current I 3  from the ECU  500 . 
   In addition, the input voltage Igt of the coil  700  including a coil driver at this timing is given by the following equation:
 
 Igt ≈the voltage of the internal power source of the ECU 500−(the constant current  I 3×the resistance value of a resistor 503)
 
   As a result, a coil-output-signal detection/control circuit  600  is activated, and a coil output signal is transferred to the coil-output-signal detection/control circuit  600 . 
   By performing an analysis based on the coil output signal, a malfunction of the coil  700  including a coil driver is detected. 
   Next, the internal combustion engine ignition device according to Embodiment 7, in the case where the primary-coil current I 1  is utilized as the signal that is detected by the coil  700  including a coil driver, will be described specifically, with reference to  FIG. 13 . As illustrated in  FIG. 13 , the internal combustion engine ignition device according to Embodiment 7 includes the ECU  500 , an ignition coil  11 , a pulse detection circuit  17 , a switching element  15 , and a coil-output-signal detection circuit  19 . The ignition coil  11  having a primary coil  12  and a secondary coil  13  is connected to a power-source terminal VB. The ignition plug  14  is connected to the high-voltage side of the secondary coil  13 . The ECU  500  has the pulse generation circuit  501  and the coil-output-signal detection/control circuit  600 ; by way of the NPN transistor  502  and the resistor  504 , the pulse generation circuit  501  supplies to an input terminal  800   a  of a coil driver  800  the energization start signal Igt 1  and the de-energization signal Igt 2  that each are a single pulse having an extremely short duration or a plurality of pulses. At the timing when neither the energization start signal Igt 1  nor the de-energization signal Igt 2  is supplied to the NPN transistor  502  and a P-channel MOSFET  602 , the input voltage Igt of the coil driver  800  is set to a high level (from 5 V to 14 V), and at the timing when the pulse generation circuit  501  supplies the energization start signal Igt 1  or the de-energization signal Igt 2  to the NPN transistor  502  and the P-channel MOSFET  602 , the NPN transistor  502  turns on and the P-channel MOSFET  302  turns off, thereby lowering for an extremely short time the input voltage Igt of the coil driver  800  from the high level (from 5 V to 14 V) to a low level (0 V), so that a signal is supplied to the pulse detection circuit  17 . 
   The pulse detection circuit  17  is a circuit in which the energization start signal Igt 1  and the de-energization signal Igt 2  are stored; the pulse detection circuit  17  recognizes the signal received from the pulse generation circuit  501  as the energization start signal Igt 1  or the de-energization signal Igt 2  and supplies an ignition signal to the switching element  15  in the later stage, thereby driving the switching element  15 . The switching element  15  is, for example, an IGBT (insulated gate bipolar transistor (IGBT); the gate terminal is connected to the pulse detection circuit  17 , the collector terminal is connected to the primary coil  12  of the ignition coil  11 , and the emitter terminal is connected to a detection resistor  18  and the coil-output-signal detection circuit  19 . The other terminal of the detection resistor  18  is connected to the reference potential point GND. 
   The coil-output-signal detection circuit  19  is configured in such a way as to have an output terminal  19   a  and an input terminal  19   b.  The output terminal  19   a  is connected to an input impedance  16  and the pulse detection circuit  17 , and the input terminal  19   b  is connected to the emitter terminal of the switching element  15  and the detection resistor  18 . The coil-output-signal detection circuit  19  is configured with a current mirror circuit  192  including N-channel MOSFETs  190  and  191 , an internal power source  193 , a current source  194 , a P-channel MOSFET  195 , an AND circuit  196 , and a window comparator circuit  199  including comparator circuits  197  and  198 . 
   The gate of the N-channel MOSFET  190  is connected to the gate of the N-channel MOSFET  191 ; the drain is connected to the output terminal  19   a;  the source is connected to the ground GND. The gate of the N-channel MOSFET  191  is connected to the drain of the N-channel MOSFET  191 , the current source  194 , and the source of the P-channel MOSFET  195 . The other terminal of the current source  194  is connected to the internal power source  193 . The internal power source  193  is a stabilized power source. The gate of the P-channel MOSFET  195  is connected to the output terminal of the AND circuit  196 , and the drain is connected to the ground GND. One input terminal of the AND circuit  196  is connected to the output terminal of the comparator circuit  197 ; the other input terminal is connected to the output terminal of the comparator circuit  198 . The input terminal (+) of the comparator circuit  197  is connected to the input terminal  19   b;  the input terminal (−) is connected to a reference voltage (Vth 1 ). The input terminal (+) of the comparator circuit  198  is connected to a reference voltage (Vth 2 ); the input terminal (−) is connected to the input terminal  19   b.    
   Next, the inner configuration of the coil-output-signal detection/control circuit  600  will be explained. The coil-output-signal detection/control circuit  600  is provided with an internal power source  601 , the P-channel MOSFET  602 , a current mirror circuit  605  including PNP transistors  603  and  604 , a coil-output-signal detection resistor  606 , and a coil-output-signal control circuit  609 . 
   The gate of the P-channel MOSFET  602  is connected to the pulse generation circuit  501 ; the drain is connected to the emitters of the PNP transistors  603  and  604 ; the source is connected to the internal power source  601 . The internal power source  601  is a stabilized power source. The base of the PNP transistor  603  is connected to the base of the PNP transistor  604 , and the collector of the PNP transistor  603  is connected to the coil-output-signal detection resistor  606  and the coil-output-signal control circuit  609 . The base of the PNP transistor  604  is connected to the collector of the PNP transistor  604  and a resistor  503 . The other terminal of the coil-output-signal detection resistor  606  is connected to the ground GND. 
     FIG. 14  is a timing chart representing waveforms at various points in Embodiment 7; the operation of the internal combustion engine ignition device illustrated in  FIG. 12  will be explained with reference to the timing chart. During the time period between the time points t 1  and t 2 , the pulse generation circuit  501  supplies the NPN transistor  502  and the P-channel MOSFET  602  with the energization start signal Igt 1  (here, represented as a single pulse) having an extremely short duration. At the timing when neither the energization start signal Igt 1  nor the de-energization signal Igt 2  is supplied to the NPN transistor  502  and the P-channel MOSFET  602 , the input voltage Igt of the coil driver  800  is set to a high level (from 5 V to 14 V), and at the timing when the pulse generation circuit  501  supplies the energization start signal Igt 1  or the de-energization signal Igt 2  to the NPN transistor  502  and the P-channel MOSFET  602 , the NPN transistor  502  turns on and the P-channel MOSFET  602  turns off, thereby lowering for an extremely short time the input voltage Igt of the coil driver  800  from the high level (from 5 V to 14 V) to a low level (0 V), so that a pulse signal is supplied to the pulse detection circuit  17 . The pulse detection circuit  17  recognizes the pulse signal supplied from the pulse generation circuit  501  as the energization start signal Igt 1  and, at the time point t 2 , supplies an ignition signal to the input terminal (the gate, in this case) of the switching element  15  in the later stage, so that the switching element  15  turns on, whereupon the primary-coil current I 1  starts to flow through the primary coil  12  of the ignition coil  11 . 
   After that, at the time point t 3  when a voltage Vdet, which is produced when the primary-coil current I 1  flows through the detection resistor  18 , is between Vth 1  and Vth 2 , the output of the window comparator circuit  199  becomes high-level, whereby the P-channel MOSFET  195  turns off. The constant current I 3  is supplied from the current source  194  to the current mirror circuit  192  at this time instant, and then the current mirror circuit  192  is activated. The N-channel MOSFET  190  in the current mirror circuit  192  extracts a drain current, corresponding to the constant current I 3  that flows through the N-channel MOSFET  191 , from the current mirror circuit  605  in the coil-output-signal detection/control circuit  600 . 
   As a result, the current mirror circuit  605  in the coil-output-signal detection/control circuit  600  is activated, and the collector current, corresponding to the constant current I 3  that flows through the PNP transistor  604 , flows through the PNP transistor  603  in the current mirror circuit  605 . The outputted current is converted into a voltage by the coil-output-signal detection resistor  606  and transferred to the coil-output-signal control circuit  609 . 
   After that, at the time point t 4  when the voltage Vdet is larger than Vth 2 , the output of the window comparator circuit  199  becomes low-level, whereby the P-channel MOSFET  195  turns on. The gate voltages of the N-channel MOSFETs  190  and  191  become low-level at this time instant, and then the operation of the current mirror circuit  192  stops. On that occasion, the current supply to the coil-output-signal detection resistor  606  stops. 
   As described above, in the internal combustion engine ignition device according to Embodiment 7, in the case where some sort of failure such as breakage of the primary coil  12  is caused in the coil  700  including a coil driver, the ECU  500  can detect the abnormality and can perform a failure diagnosis. 
   Moreover, by, as the coil output signal to be detected, utilizing a primary-coil voltage, a secondary-coil current, a secondary-coil voltage, or the like, the failure diagnosis on the coil  700  including a coil driver can widely be performed. 
   In addition, the foregoing Embodiments 2 to 6 are applicable not only to Embodiment 1 but also to Embodiment 7. 
   Various modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this is not limited to the illustrative embodiments set forth herein.