Abstract:
An internal combustion engine controller that drives an electromagnetic load is provided for improving a fault diagnosis precision of the electromagnetic load and stabilizing a high-speed control without influence of noises even if the drive cycle of the electromagnetic load is short. The internal combustion engine controller has high reliability in a fault diagnosis for a circuit to regenerate counter electromotive energy. The internal combustion engine controller comprises a current source or a voltage source for controlling a potential of the diagnosis position in order to ensure a high-precision fault diagnosis even if the drive cycle of the electromagnetic load, such as the fuel injector, in the internal combustion engine is shortened. Diagnosis timing is optimally set or the number of determinations for averaging is increased in order to ensure the high-precision fault diagnosis without being influenced by unexpected disturbance such as noises. In the fault diagnosis of the regeneration circuit into the booster circuit, an input/output voltage or the regeneration current of a driving switching element of the electromagnetic load is detected.

Description:
CLAIM OF PRIORITY 
       [0001]    The present application claims priority from Japanese Patent Application JP 2008-011584 filed on Jan. 22, 2008, the content of which is hereby incorporated by reference into this application. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to internal combustion engine controllers for automobiles, motorcycles, farm vehicles, industrial machines, or ships which use gasoline or light oil as fuel. More particularly, the present invention relates to electromagnetic load controllers, such as fuel injectors, which are driven by a battery voltage or a boosted battery voltage, and driving and fault diagnosis of the controllers. 
       BACKGROUND OF THE INVENTION 
       [0003]    The internal combustion engine controllers for automobiles, motorcycles, farm vehicles, industrial machines, or ships which use gasoline or light oil as fuel are equipped with an injector (fuel injector) that injects fuel directly into cylinders to improve fuel consumption and engine output. Such a direct fuel injector uses high-pressure fuel and therefore requires a large amount of energy for valve opening operation. The direct fuel injector also requires having a short time for the energy to be supplied and interrupted in order to respond to an improvement in control performance (response) and to a high-speed rotation (high-speed control). That is, it is necessary to interrupt a current flowing in an electromagnetic load in a short time. Japanese Patent No. 3871168 discloses a conventional internal combustion engine controller that controls fuel injection. 
         [0004]    In order to interrupt the current in the electromagnetic load in a short time and rapidly remove (consume) the large amount of energy from the electromagnetic load, a system has been proposed, for example, which transforms the energy into a heat energy using the Zener diode effect in a drive circuit. JP-A-2001-234793 discloses another system which regenerates the energy stored in the electromagnetic load into a booster circuit. The latter system may regenerate the energy using a regeneration element such as a regeneration diode. This system is widely utilized in direct-injection engines using gasoline as fuel because the system can relatively reduce heat generation in the drive circuit where a large current flows. 
         [0005]    If some fault, such as battery short (short circuit to battery), ground short (short circuit to ground), short circuit to high-side driver, or open state, occurs in the electromagnetic load during driving or interrupting of the electromagnetic load, it is necessary to detect and diagnose the fault immediately. However, in a case of short drive cycle (that is, when the rotating speed of the internal combustion engine increases), the conventional internal combustion engine controllers cannot set a fault-detection timing control properly, and a diagnosis circuit may misdiagnose that short-circuit to a battery has occurred, for example, although the drive circuit and the electromagnetic load are normal. Moreover, an improvement in controllability may fail because it takes long time to return the potential of a diagnosis position to an initial state. In addition, the diagnosis circuit may misdiagnose due to unexpected disturbance such as noises. 
         [0006]    Besides, if the regeneration element breaks down by overload energy, the energy cannot be regenerated, resulting in a possible serious accident, such as heat generation or ignition of the device. 
         [0007]    An object of the present invention is to provide an internal combustion engine controller that drives an electromagnetic load such as an injector (fuel injector), improving a fault diagnosis precision of the electromagnetic load and stabilizing a high-speed control even when the rotating speed of an internal combustion engine becomes higher, that is, when the drive cycle of the electromagnetic load becomes shorter. 
         [0008]    Another object of the present invention is to provide an internal combustion engine controller that is not influenced by noises. 
         [0009]    Still another object of the present invention is to provide an internal combustion engine controller having a booster circuit of a battery voltage, with high reliability in fault diagnosis for a circuit that regenerates counter electromotive energy into the booster circuit as the counter electromotive energy is generated in driving of the electromagnetic load. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention has a feature that a current source or a voltage source is provided for controlling a potential of the diagnosis position in order to ensure a high-precision fault diagnosis even if the drive cycle of the electromagnetic load, such as the fuel injector, in the internal combustion engine is shortened. The present invention also has a feature that diagnosis timing is optimally set or the number of determinations for averaging is increased in order to ensure the high-precision fault diagnosis without being influenced by unexpected disturbance such as noises. 
         [0011]    In the fault diagnosis of the regeneration circuit into the booster circuit, the above object can be achieved by detecting an input/output voltage or the regeneration current of a driving switching element of the electromagnetic load. 
         [0012]    More specifically, the electromagnetic load controller according to the present invention is basically configured as follows. 
         [0013]    The electromagnetic load controller comprises an electromagnetic load; a power supply for the electromagnetic load; a driver for the electromagnetic load, disposed at either or both of between the power supply and the electromagnetic load and between the electromagnetic load and the ground; a switching element for the driver; diagnosing means for diagnosing a fault of a circuit configuration by detecting a voltage abnormality between the electromagnetic load and the switching element; and at least one of means for rapidly attenuating a counter electromotive energy that is generated at the time of an interruption of the electromagnetic load, means for setting a time zone for detecting the voltage abnormality, and means for confirming the voltage abnormality. 
         [0014]    The internal combustion engine controller that drives the electromagnetic load can ensure the reliability and precision of the fault diagnosis of the electromagnetic load even when the drive cycle of the internal combustion engine becomes shorter. In addition, the high-precision fault diagnosis can be ensured without being influenced by the noises. Further, more improvement in safety can be expected because of the reliable fault diagnosis of the circuit that regenerates the counter electromotive energy into the booster circuit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a circuit configuration diagram of an internal combustion engine controller in accordance with a first embodiment of the present invention; 
           [0016]      FIG. 2  is a circuit configuration diagram of an internal combustion engine controller in accordance with a second embodiment of the present invention; 
           [0017]      FIG. 3  shows an example of an operating waveform of a circuit in the internal combustion engine controller in accordance with the first embodiment; 
           [0018]      FIG. 4  is a circuit configuration diagram of an internal combustion engine controller in accordance with a third embodiment of the present invention; 
           [0019]      FIG. 5  shows an example of an operating waveform of a circuit in the internal combustion engine controller in accordance with the third embodiment; 
           [0020]      FIG. 6  is a circuit configuration diagram of an internal combustion engine controller in accordance with a fourth embodiment of the present invention; 
           [0021]      FIG. 7  shows an example of an operating waveform of a circuit in the internal combustion engine controller in accordance with the fourth embodiment; 
           [0022]      FIG. 8  is a circuit configuration diagram of an internal combustion engine controller in accordance with a fifth embodiment of the present invention; 
           [0023]      FIG. 9  shows an example of an operating waveform of a circuit in the internal combustion engine controller in accordance with the fifth embodiment; 
           [0024]      FIG. 10  is a circuit configuration diagram of an internal combustion engine controller in accordance with a sixth embodiment of the present invention; 
           [0025]      FIG. 11  shows an example of an operating waveform of a circuit in the internal combustion engine controller in accordance with the sixth embodiment; 
           [0026]      FIG. 12  is a circuit configuration diagram of an internal combustion engine controller in accordance with a seventh embodiment of the present invention; 
           [0027]      FIG. 13  shows an example of an operating waveform of a circuit in the internal combustion engine controller in accordance with the seventh embodiment; 
           [0028]      FIG. 14  is a circuit configuration diagram of an internal combustion engine controller in accordance with an eighth embodiment of the present invention; 
           [0029]      FIG. 15  is a circuit configuration diagram of an internal combustion engine controller in accordance with a ninth embodiment of the present invention; 
           [0030]      FIG. 16  shows an example of an operating waveform of a circuit in the internal combustion engine controller in accordance with the eighth embodiment; 
           [0031]      FIG. 17  shows an example of an operating waveform of a circuit in the internal combustion engine controller in accordance with the ninth embodiment; 
           [0032]      FIG. 18  a circuit configuration diagram of an internal combustion engine controller without a first current-source controller in the first embodiment; and 
           [0033]      FIG. 19  shows an example of an operating waveform of a circuit in the internal combustion engine controller without the first current-source controller in the first embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    A description will be given below of embodiments of an internal combustion engine controller in accordance with the present invention with reference to the accompanying drawings. 
       First Embodiment 
       [0035]    An internal combustion engine controller in accordance with a first embodiment of the present invention will be described with reference to  FIGS. 1 and 3 . 
         [0036]      FIG. 1  shows a circuit configuration of an internal combustion engine controller  2  which includes a battery voltage  1 , a booster circuit  3  that boosts the battery voltage  1 , and an electromagnetic load  5  that is located between the booster circuit  3  and a ground  37 . 
         [0037]    The internal combustion engine controller  2  also includes a high-side driver  4  between the battery voltage  1  and the electromagnetic load  5 , and a low-side driver  10  between the ground  37  and the electromagnetic load  5 . The high-side driver  4  and the low-side driver  10  are drivers for the electromagnetic load  5 , and comprise switching elements (for example, FETs) As used herein, “high side (upper or upstream side)” and “low side (lower or downstream side)” means, respectively, the battery voltage  1  side and the ground  37  side in relation to the electromagnetic load  5 . 
         [0038]    The internal combustion engine controller  2  further includes a microprocessor  30 , a logical circuit  31 , a drive signal generator for high-side driver  28 , and a drive signal generator for low-side driver  12 . The internal combustion engine controller  2  also includes a voltage detector  15  and a diagnosis circuit  25  for diagnosing a fault of the electromagnetic load  5 . 
         [0039]    The booster circuit  3  boosts a battery voltage  1 , and the boosted voltage is applied to the electromagnetic load  5  through the high-side driver  4  and the low-side driver  10 . An electromagnetic load current  5 A that flows through the electromagnetic load  5 , such as an injector, increases in a short time by the boosted voltage. In this way, the internal combustion engine controller  2  drives the high-side driver  4  and the low-side driver  10  to drive the electromagnetic load  5 . This process will be described below. A control signal  29  is output from the microprocessor  30  and input to the logical circuit  31 . On the basis of the control signal  29 , the logical circuit  31  outputs a logical drive signal for high-side driver  26  and a first logical drive signal for low-side driver  13  to a drive signal generator for high-side driver  28  and a drive signal generator for low-side driver  12 , respectively. The drive signal generators  28  and  12  generate an analog drive signal for high-side driver  27  and an analog drive signal for low-side driver  11  on the basis of the input logical signals  26  and  13 . The analog drive signals  27  and  11  energize the high-side driver  4  and the low-side driver  10 , allowing the electromagnetic load current  5 A to flow in the electromagnetic load  5 , which then gets to drive. 
         [0040]    The electromagnetic load current  5 A is relatively large enough to drive a valving element (for example, to open a valve) of the electromagnetic load  5 , such as an injector, with a good response. After the electromagnetic load  5  is driven, an amount of current which continuously maintains the state of the driven valving element is supplied to the electromagnetic load  5  for a given period of time. In this case, the state of the driven electromagnetic load  5  is maintained with the drive signal for low-side driver  11  kept on (that is, the low-side driver  10  is on), the drive signal for high-side driver  27  kept off (the high-side driver  4  is off), and the electromagnetic load  5  chopped by a chopping signal generator  108 . A chopping signal  109  is output from the logical circuit  31  according to the control signal  29  from the microprocessor  30 . The details will be described later with reference to  FIG. 3 . 
         [0041]    The fault diagnosis of the electromagnetic load  5  is performed by the diagnosis circuit  25 . The voltage detector  15  detects a drain voltage  46  of the low-side driver  10 , and outputs a diagnosis flag signal  14  to the diagnosis circuit  25 . 
         [0042]    For example, if the drain voltage  46  of the low-side driver  10  increases close to the battery voltage  1  and exceeds a threshold of battery short, the diagnosis circuit  25  determines that the electromagnetic load  5  is short-circuited to battery. 
         [0043]    On the other hand, if the drain voltage  46  of the low-side driver  10  decreases close to the voltage of the ground level and falls below a threshold of ground short, the diagnosis circuit  25  determines that the electromagnetic load  5  is short-circuited to ground. 
         [0044]    The internal combustion engine controller  2  further includes a first current source controller  18 , a second current source controller  20 , and a drive signal selector for current control  111 . The first current source controller  18  includes a first current source  17 . The second current source controller  20  includes a second current source  19  and a third current source  21 . The drive signal selector  111  selectively switches and controls the current sources  17 ,  19 , and  21  of the first and second current source controllers  18  and  20 , respectively, according to an output signal from the drain voltage detector  15 . 
         [0045]    The second current source controller  20  detects the drain voltage of the electromagnetic load  5  on the switching element (low-side driver  10 ) side, and keeps the drain voltage at a given voltage level when the electromagnetic load  5  is driving. For example, if the drain voltage is low, the third current source  21  (current source at the power supply side) is turned on by the drain voltage detector  15  and the drive signal selector for current control  111  to increase the drain voltage. If the drain voltage is high, the second current source  19  (current source at the ground side) is turned on to decrease the drain voltage. In this way, the second current source controller  20  keeps the drain voltage at a given level. The second current source  19  is connected to the ground side in this case, resulting in a gradual decrease of the drain voltage to converge at the given level. 
         [0046]    The first current source  17 , which is included in the first current source controller  18 , rapidly attenuates a jumping voltage caused by a counter electromotive energy generated at the drain side of the low-side driver  10 . The counter electromotive energy is generated by the electromagnetic load  5  when current through the electromagnetic load  5  is interrupted (that is, when the electromagnetic load  5  stops driving or when high-side and low-side drivers  4  and  10  turn off). The rapid attenuation of the counter electromotive energy prevents misdiagnoses of battery short at timing when the voltage detector  15  detects the battery short or the ground short. The battery short and the ground short are detected when the control signal  29  from the microprocessor  30  rises, that is, when the electromagnetic load  5  starts driving (when the high-side and low-side drivers  4  and  10  turn on). The details will be described below with reference to timing charts in  FIGS. 3 and 19 . 
         [0047]    The first current source  17 , which is included in the first current source controller  18 , is disposed between the drain side of the low-side driver  10  and the ground as with the second current source  19  included in the second current source controller  20 . A difference of the second current source  19  and the first current source  17  is that the second current source  19  is a sink current source for convergence which converges the drain voltage at a given level whereas the first current source  17  rapidly attenuates a counter electromotive energy (rapidly attenuates a first counter drain voltage). As a result, the second current source  19  and the first current source  17  are different in the characteristics. 
         [0048]    The internal combustion engine controller  2  is equipped with an upper capacitor of electromagnetic load for noise or surge  7  and a lower capacitor of electromagnetic load for noise or surge  9  in order to protect the input and output signal of the electromagnetic load  5  from disturbance, such as surge or noise from the external. 
         [0049]    The internal combustion engine controller  2  further comprises a rectification diode  6  and a regeneration diode  8 . The rectification diode  6  prevents a backflow of current when the electromagnetic load  5  is chopped. The regeneration diode  8  regenerates a current generated by a counter electromotive energy of the low-side driver  10  into the booster circuit  3  when the analog drive signal for low-side driver  11  turns off at the falling edge of the control signal  29 . 
         [0050]    The operation of the internal combustion engine controller in accordance with a first embodiment will be described with reference to timing charts shown in  FIG. 3 . 
         [0051]    When the control signal  29  output from the microprocessor  30  turns on, the drive signals of the low-side driver  10  and the high-side driver  4  (that is, the analog drive signal for low-side driver  11  and the analog drive signal for high-side driver  27 ) turn on and the electromagnetic load current  5 A flows through the electromagnetic load  5 . 
         [0052]    The battery voltage  1  boosted by the booster circuit  3  increases the electromagnetic load current  5 A in a short time up to a threshold of peak current  100  during a peak-current flow period in an initial energization stage. The electromagnetic load current  5 A stops flowing at the threshold of peak current  100 , which is predetermined. After reaching the threshold of peak current  100 , the electromagnetic load current  5 A transfers in a retention state, and is chopped by the chopping signal generator  108  after the high-side driver  4  turns off (current for high side  81 A turns off). In this situation, a wave form of the upper voltage of the electromagnetic load  103  is shown in  FIG. 3 . When the operation of the electromagnetic load  5  is finished, the electromagnetic load current  5 A is rapidly interrupted in a short current-down period in order to quickly return the electromagnetic load  5  to the initial state. 
         [0053]    When the control signal  29  turns off, the analog drive signal for the low-side driver  11  turns off at the falling edge of the control signal  29 . The counter electromotive energy is generated by the electromagnetic load  5  at the drain side of the low-side driver  10  at the falling edge  39  of the drive signal (gate signal) for low-side driver  11 . The drain voltage for low-side driver  46  jumps up to a specific voltage (a jumping voltage  300 ) due to the counter electromotive energy. The jumping voltage  300  is stored in the lower capacitor of electromagnetic load for noise or surge  9 . Simultaneously, the jumping voltage  300  is input to the voltage detector  15  as the drain voltage for low-side driver  46 . Then, the first current source controller  18  and the second current source controller  20  are controlled by the drive signal selector for current control  111 , according to a result of detection by the voltage detector  15 . 
         [0054]    If the drain voltage for low-side driver  46  exceeds a threshold for battery short  104 , as shown in  FIG. 3 , a first current source control signal  16  is output as a high signal from the drive signal selector for current control  111 , turning the first current source  17  on. As a result, the drain voltage for low-side driver  46  discharges electric charges stored in the lower capacitor of electromagnetic load for noise or surge  9  and rapidly attenuates the jumping voltage  300 . Then, when the drain voltage for low-side driver  46  becomes the threshold for battery short  104  or lower, the first current source control signal  16  gets to low by the drive signal selector for current control  111 , and the first current source  17  turns off. A second current source control signal  24  is output as high from the drive signal selector for current control  111  at a falling edge for first current source signal  33 , and the second current source  19  turns on. As a result, the drain voltage for low-side driver  46  dramatically attenuates without extreme decreasing and converges on a default drain voltage for low-side driver  105  to reach a steady state. 
         [0055]    Timing to diagnose whether the state is battery short or not is synchronized with the rising edge of the control signal  29 . Because of a rapid start-up of the electromagnetic load  5  or generation of the counter electromotive energy, determination of battery short is difficult at any timing except for the rising edge of the control signal  29 . If the drain voltage for low-side driver  46  exceeds the threshold for battery short  104  at this detection timing of battery short  116 , it is determined that the state is battery short. 
         [0056]    According to this embodiment, even if the drain voltage for low-side driver  46  jumps up to a specific voltage by the counter electromotive energy and is charged in the lower capacitor of electromagnetic load for noise or surge  9 , the charged voltage can be rapidly attenuated before the detection timing of battery short  116 . 
         [0057]    Accordingly, even if the rotating speed of the internal combustion engine increases and the drive cycle of the control signal  29  becomes shorter, resulting in a short interval of the detection timing of battery short  116 , the electromagnetic load  5  can be diagnosed with high precision and controlled at high speed without misdiagnosing that the state is battery short although the drive circuit and the electromagnetic load  5  are normal. 
         [0058]    The method described above makes it possible that the current from the first current source  17  can flow only when the drain voltage for low-side driver  46  jumps up to the specific voltage due to the counter electromotive energy. This leads to an advantage of reduction in the heat generation. 
         [0059]    In a configuration where the first current source controller  18  (including the first current source  17 ) is not provided and only the second current source controller  20  (including the second current source  19  and the third current source  21 ) is provided, that is, in a configuration shown in  FIG. 18 , the rapid attenuation of the counter electromotive energy (the rapid attenuation of the first counter drain voltage  300 ) described above cannot be expected. In  FIG. 18 , the same symbols as in the first embodiment denote elements identical with or common to those in the first embodiment. In the state shown in  FIG. 18 , even if the current passing through the electromagnetic load  5  is interrupted and the first counter drain voltage is detected by the drain voltage detector  15  to turn the second current source  19  on, the second current source  19  cannot rapidly discharge the voltage generated by the counter electromotive energy, which has been charged in the lower capacitor of electromagnetic load for noise or surge  9 , because of the characteristics. Therefore, the first counter drain voltage of the counter electromotive energy gradually attenuates and reaches a given drain voltage as the attenuation curve  300  in timing charts shown in  FIG. 19 . 
         [0060]    In this case, if the rotating speed of the internal combustion engine increases and the drive cycle of the control signal  29  becomes shorter, resulting in a short interval of the detection timing of battery short  116 , the possibility increases that the state comes to the detection timing of battery short  116  while the drain voltage of the counter electromotive energy is still not below the threshold for battery short and that the state is misdiagnosed as battery short although the drive circuit and the electromagnetic load  5  are normal. 
       Second Embodiment 
       [0061]    With reference to  FIG. 2 , a description will be given of an internal combustion engine controller in accordance with a second embodiment of the present invention. 
         [0062]    In the configuration of this embodiment, the first current source  17  shown in  FIG. 1  is replaced with a first resistor for current source  32 . The first resistor for current source  32  functions as a sink current resistor. The drain voltage for low-side driver  46 , which has been charged in the lower capacitor of electromagnetic load for noise or surge  9 , is consumed and discharged by the first resistor for current source  32 . Therefore, the drain voltage for low-side driver  46  can rapidly attenuate as in the timing charts of the first embodiment shown in  FIG. 3 . Accordingly, the same advantages as in the first embodiment can be obtained in this configuration. 
       Third Embodiment 
       [0063]    With reference to  FIGS. 4 and 5 , a description will be given of an internal combustion engine controller in accordance with a third embodiment of the present invention. 
         [0064]    In the configuration of this embodiment, the positions of the diagnosis circuit  25  and its peripheral circuits in the first embodiment ( FIG. 1 ) are changed from the downstream side of the electromagnetic load  5  to the upstream side thereof as shown in  FIG. 4 . The peripheral circuits include the first current source controller  18 , the second current source controller  20 , the voltage detector  15 , and the drive signal selector for current control  111 . In the first embodiment, the fault diagnosis of the electromagnetic load  5  is performed by detecting the drain voltage for low-side driver  46 . In this embodiment, the fault diagnosis of the electromagnetic load  5  is performed by means of detection of a drain voltage for high-side driver  114  by the voltage detector  15  and a diagnosis by the diagnosis circuit  25 . 
         [0065]    Waveforms according to the operation in this embodiment are shown in timing charts of  FIG. 5 . The drain voltage for high-side driver  114  increases up to the jumping voltage  300  due to the counter electromotive energy at a falling edge for gate signal of high-side driver  48 . At this moment, the first current source control signal  16  is output as high from the drive signal selector for current control  111 , turning the first current source  17  on, and rapidly attenuating the drain voltage for high-side driver  114 . Then, the drain voltage for high-side driver  114  becomes equal to the threshold for battery short  104  or lower, making the first current source control signal  16  low, and turning the first current source  17  off. Meanwhile, the second current source control signal  24  is output as high from the drive signal selector for current control  111  at the falling edge for first current source signal  33 , turning the second current source  19  on in this embodiment. As a result, the drain voltage for high-side driver  114  converges on a default drain voltage for high-side driver  106 . 
         [0066]    As described above, the operation in this embodiment is substantially identical with that in the first embodiment except that the drain voltage for low-side driver  46  is replaced with the drain voltage for high-side driver  114 . Accordingly, in the configuration of this embodiment, as in the first embodiment, even if the rotating speed of the internal combustion engine increases and the drive cycle of the control signal  29  becomes shorter, resulting in a short interval of the detection timing of battery short  116 , the electromagnetic load  5  can be diagnosed with high precision and controlled at high speed without misdiagnosing that the state is battery short although the drive circuit and the electromagnetic load  5  are normal. 
       Fourth Embodiment 
       [0067]    With reference to  FIGS. 6 and 7 , a description will be given of an internal combustion engine controller in accordance with a fourth embodiment of the present invention. The first to third embodiments show the examples of the device that is capable of preventing misdiagnoses in a detection of battery short. This example shows an example of a device that is capable of preventing misdiagnoses in a detection of ground short. 
         [0068]    As shown in  FIG. 6 , an internal combustion engine controller  2  according to this embodiment does not include a lower capacitor of electromagnetic load for noise or surge  9 , a low-side driver  10 , and a drive signal generator for low-side driver  12 , which are located downstream of the electromagnetic load  5 , in the internal combustion engine controller  2  of the third embodiment shown in  FIG. 4 . 
         [0069]    The logical circuit  31  receives the control signal  29  from the microprocessor  30 , and outputs the logical drive signal for high-side driver  26  to the drive signal generator for high-side driver  28 . After receiving the logical drive signal for high-side driver  26 , the drive signal generator for high-side driver  28  outputs the analog drive signal for high-side driver  27  to the high-side driver  4 . The high-side driver  4  is driven by the analog drive signal for high-side driver  27  and allows the electromagnetic load current  5 A to flow in the electromagnetic load  5 . The fault diagnosis of the electromagnetic load  5  is performed by means of detection of a source voltage  115  of the high-side driver  4  by the voltage detector  15  and a diagnosis by the diagnosis circuit  25 . 
         [0070]    The operation of the internal combustion engine controller in accordance with this embodiment will be described with reference to timing charts shown in  FIG. 7 . 
         [0071]    When the control signal  29  from the microprocessor  30  turns on, the drive signal of the high-side driver  4 , that is, the analog drive signal for high-side driver  27  turns on, and the electromagnetic load current  5 A flows through the electromagnetic load  5 . 
         [0072]    When the control signal  29  turns off, the gate signal of the high-side driver  4  turns off. At the falling edge for gate signal of high-side driver  48 , the source voltage  115  of the high-side driver  4  drops down to a specific voltage (a falling voltage  302 ) due to the counter electromotive energy. The electric charges in the upper capacitor of electromagnetic load for noise or surge  7  are discharged and decreased due to the falling voltage  302 . At the same time, the falling voltage  302  is input to the voltage detector  15  as the source voltage for high-side driver  115 . Then, the first current source controller  18  and the second current source controller  20  are controlled by the drive signal selector for current control  111  according to a result of the detection by the voltage detector  15 . 
         [0073]    When the source voltage for high-side driver  115  is lower than a threshold for ground short  44 , the first current source control signal  16  is output as high from the drive signal selector for current control  111 , turning the first current source  17  on. As a result, the source voltage for high-side driver  115  rapidly increases as shown in  FIG. 7 . When the source voltage for high-side driver  115  becomes equal to the threshold for ground short  44  or higher, the first current source control signal  16  becomes low and the first current source  17  turns off. At this falling edge for first current source signal  33 , the second current source control signal  24  is output as high from the drive signal selector for current control  111  and the third current source  21  turns on. As a result, the source voltage for high-side driver  115  converges on a default source voltage for high-side driver  107 . 
         [0074]    Timing to diagnose whether the state is ground short or not is, as well as the timing of the diagnosis of battery short in the first embodiment, synchronized with the rising edge of the control signal  29 . If the source voltage for high-side driver  115  falls below the threshold for ground short  44  at this detection timing of ground short, it is determined that the state is ground short. 
         [0075]    However, through the above operation, the discharged voltage can rapidly increase before the detection timing of ground short even if the source voltage for high-side driver  115  decreases to a specific voltage due to the counter electromotive energy to discharge the upper capacitor of electromagnetic load for noise or surge  7 . 
         [0076]    Accordingly, even if the rotating speed of the internal combustion engine increases and the drive cycle of the control signal  29  becomes shorter, resulting in a short interval of the detection timing of ground short, the electromagnetic load  5  can be diagnosed with high precision and controlled at high speed without misdiagnosing that the state is ground short although the drive circuit and the electromagnetic load  5  are normal. 
       Fifth Embodiment 
       [0077]    With reference to  FIGS. 8 and 9 , a description will be given of an internal combustion engine controller in accordance with a fifth embodiment of the present invention. 
         [0078]    The internal combustion engine controller  2  in accordance with this embodiment has the same circuit configuration as that of the first embodiment, except for the following matters. The internal combustion engine controller  2  of this embodiment does not include the regeneration diode  8  and the chopping signal generator  108  shown in  FIG. 1  (however, the regeneration diode  8  and the chopping signal generator  108  may be provided), and is provided with a filter time generator  50 , a diagnosis window signal generator  58 , and a delay time selector  301 , which will be described below. 
         [0079]    A given delay time is provided in the first logical drive signal for low-side driver  13  by the filter time generator  50  and becomes high or low with a delay from the rising edge or the falling edge of the control signal  29 . The delay time is short not to affect the high-speed operation of the internal combustion engine having the internal combustion engine controller  2 . The first logical drive signal for low-side driver  13  with the delay time, that is, a second logical drive signal for low-side driver  13   a  is input to the drive signal generator for low-side driver  12 . As a result, the delay time same as the above-mentioned delay time is provided between the control signal  29  and the analog drive signal for low-side driver  11 . During the delay time, the control of the electromagnetic load current  5 A does not start even if the control signal  29  is input, and the potential level of the drain voltage for low-side driver  46  does not fluctuate. 
         [0080]    The delay time generated by the filter time generator  50  is input to the diagnosis window signal generator  58 . A diagnosis window signal  112  is output from the diagnosis window signal generator  58  only during the delay time, and then input to the diagnosis circuit  25 . In the diagnosis circuit  25 , a diagnosis counter operates while the diagnosis window signal  112  is on, and counts a time while the drain voltage for low-side driver  46  exceeds the threshold for battery short or falls below the threshold for ground short. 
         [0081]      FIG. 9  shows timing charts when disturbance, such as noises, interferes the drain voltage for low-side driver  46  in the internal combustion engine controller  2  having the above circuit configuration. The diagnosis of battery short or ground short of the electromagnetic load  5  is triggered by a rising edge  51  for the control signal  29  and synchronized with the rising edge of the clock signals while the diagnosis window signal  112  is on. The diagnosis window signal  112  turns on at the rising edge  51  for the control signal  29  and turns off at the rising edge  53  for the analog drive signal for the low-side driver  11 . The analog drive signal for the low-side driver  11  is delayed by a delay time  56  from the rising edge  51  for control signal  29 . That is, the diagnosis window signal  112  is on during the delay time  56 . 
         [0082]    When the diagnosis window signal  112  is on, the diagnosis counter of the diagnosis circuit  25  counts a time while the drain voltage for low-side driver  46  exceeds the threshold for battery short or falls below the threshold for ground short as described above, and then diagnoses the battery short or the ground short. In the diagnosis, if the number of counting up of the diagnosis counter is less than a predetermined diagnosis count number, the diagnosis flag signal  14  is not output. The predetermined diagnosis count number can be set in advance, for example, so as to be equal to the number of times which the clock signal rises during the delay time  56 . 
         [0083]      FIG. 9  shows a case in which the drain voltage for low-side driver  46  increases due to an interference of noises. The predetermined diagnosis count number is set to be 12 times in advance. As shown in  FIG. 9 , the drain voltage for low-side driver  46  suffers an electric potential change by noise  113 . While the drain voltage for low-side driver  46  exceeds the threshold for battery short  104 , the diagnosis counter counts up from an initial counter condition  54  in synchronization with the rising edge of the clock signal. Counting up is twice in  FIG. 9 , a first counter condition  74  and a second counter condition  55 . Since the number of this counting up is less than the predetermined diagnosis count number, the diagnosis flag signal  14  is not output. Therefore, the electric potential change by noise  113  is not diagnosed as battery short, preventing misdiagnosis. 
         [0084]    If the number of the counting up is equal to the predetermined diagnosis count number (12 times in this embodiment) or more, the diagnosis flag signal  14  turns on at the rising edge  53  for the analog drive signal for low-side driver  11 , and the state is diagnosed as battery short. 
         [0085]    The above description refers to a case in which the drain voltage for low-side driver  46  increases due to the noises. Similarly, in the case where the drain voltage for low-side driver  46  decreases, comparing the number of the counting up to the predetermined diagnosis count number while the diagnosis window signal  112  is on prevents misdiagnosis as ground short. Through the above method, it is possible to prevent the misdiagnosis that the state of the electromagnetic load  5  is battery short or ground short, caused by an unexpected disturbance such as noise. 
         [0086]    In the internal combustion engine controller  2  in accordance with this embodiment, the delay time  56  can be changed by the delay time selector  301  shown in  FIG. 8  and the conditions to turn on the diagnosis flag signal  14  also can be changed by varying the predetermined diagnosis count number. Accordingly, the internal combustion engine controller  2  has advantage that misdiagnosis can be prevented under the diverse conditions by changing the delay time  56  or the predetermined diagnosis count number. 
       Sixth Embodiment 
       [0087]    With reference to  FIGS. 10 and 11 , a description will be given of an internal combustion engine controller in accordance with a sixth embodiment of the present invention. This embodiment is an example of an internal combustion engine controller which can detect a breakdown or open state of a regeneration diode. 
         [0088]    The internal combustion engine controller  2  in accordance with this embodiment has the same circuit configuration as that of the first embodiment, except for the following matters. The internal combustion engine controller  2  of this embodiment does not include the chopping signal generator  108  shown in  FIG. 1  (however, the chopping signal generator  108  may be provided), being provided with an active clamper  61  described below and the voltage detector  15  detecting the gate signal  11  of the low side drier  10 . 
         [0089]    The active clamper  61  supplies a current to the gate of the low-side driver  10 , forcing the gate signal high and turning the low-side driver  10  on if the drain voltage for low-side driver  46  exceeds a specified value. 
         [0090]    The diagnosis circuit  25  inputs the diagnosis flag signal  14  from the voltage detector  15  and the first logical drive signal for low-side driver  13  from the logical circuit  31 , and compares these two signals with each other to detect the breakdown or open state of the regeneration diode  8 . 
         [0091]    With reference to  FIG. 11 , a description will be given of a case in which the regeneration diode  8  is in the breakdown or open state. It is assumed that the regeneration diode  8  is broken down or opened during the regeneration diode breakdown time  62 . Normally, the drain voltage  46  for low-side driver rises up to the booster voltage  63  due to the regeneration diode  8 . However, if the regeneration diode  8  is broken down or opened, the counter electromotive energy cannot be regenerated in the booster circuit  3  during the regeneration diode breakdown time  62 , causing the drain voltage for low-side driver  46  to increase beyond the booster voltage  63 . When the drain voltage for low-side driver  46  exceeds a predetermined second threshold for regeneration diode breakdown detection  70 , the active clamper  61  turns on. Then, a current is supplied from the drain of the low-side driver  10  to the gate thereof, and the analog drive signal for low-side driver  11 , that is, the gate signal of the low-side driver  10  is forcedly raised at least during a filter time  65 , which is described later. As a result, the low-side driver  10  turns on and the jumped counter electromotive energy is clamped to a clamp voltage  64 . 
         [0092]    Now, a description will be given of a method for detecting the breakdown or open state of the regeneration diode  8 . 
         [0093]    The jumped counter electromotive energy is clamped to the clamp voltage  64 . In this situation, the gate signal is raised as described above. The voltage detector  15  detects the gate signal and outputs the diagnosis flag signal  14  as high if the gate signal is beyond a predetermined first threshold for regeneration diode breakdown detection  66 . A period of time after the gate signal is forcedly raised until the diagnosis flag signal  14  is output as high is called “filter time  65 .” 
         [0094]    On the other hand, when the gate signal is forcedly raised by the active clamper  61 , the control signal  29  is always low as shown in  FIG. 11 . Accordingly, the first logical drive signal for low-side driver  13 , which is controlled by the control signal  29 , is also always low. 
         [0095]    Therefore, the diagnosis circuit  25  detects a state in which the diagnosis flag signal  14  is high and the first logical drive signal for low-side driver  13  is low. This is a state in which the gate signal is raised during the filter time  65  although the control signal of the low-side driver  10  is low. This means that the active clamper  61  is in operation and the regeneration diode  8  is broken down or opened. In this way, the diagnosis circuit  25  can detect the brake down or open state of the regeneration diode  8  with high precision. 
         [0096]    Further, in order to ensure a high detection precision even if disturbance, such as noises, occurs in the gate of the low-side driver  10 , the state of the regeneration diode  8  is detected within the filter time  65  from the falling edge of the analog drive signal for low-side driver  11 . 
       Seventh Embodiment 
       [0097]    With reference to  FIGS. 12 and 13 , a description will be given of an internal combustion engine controller in accordance with a seventh embodiment of the present invention. This embodiment is another example of the internal combustion engine controller which can detect the breakdown or open state of the regeneration diode. As a detecting method, while the voltage of the gate signal of the low-side driver  10  is used in the sixth embodiment, the drain voltage  46  for the low-side driver  10  is used in this embodiment. The operation of the first and second current source controllers  18 ,  20  and the regeneration diode  8  is identical with that in the first embodiment. 
         [0098]      FIG. 12  is a diagram showing a circuit of an internal combustion engine controller  2  in accordance with this embodiment. A difference from the sixth embodiment is that the drain voltage  46  for the low-side driver  10  is input to the voltage detector  15 . Timing charts shown in  FIG. 13  are identical with those in the sixth embodiment. 
         [0099]    As described in the sixth embodiment, if the regeneration diode  8  is broken down or opened, the counter electromotive energy cannot be regenerated in the booster circuit  3  during the regeneration diode breakdown time  62  as shown in  FIG. 13 . This makes the drain voltage for low-side driver  46  exceed the second threshold for regeneration diode breakdown detection  70  and jump up to the clamp voltage  64 . 
         [0100]    Now, a description will be given of a method for detecting the breakdown or open state of the regeneration diode  8  in this embodiment. The jumped drain voltage for low-side driver  46  is detected by the voltage detector  15 . Then, when the drain voltage for low-side driver  46  exceeds the second threshold for regeneration diode breakdown detection  70 , the diagnosis flag signal  14  is output to the diagnosis circuit  25 . The diagnosis circuit  25  outputs the diagnosis flag signal  14  as high. As a result, the brake down or open state of the regeneration diode  8  can be detected. 
         [0101]    Moreover, in order to ensure a high detection precision even if disturbance, such as noises, occurs in the gate of the low-side driver  10 , the state of the regeneration diode  8  is detected within the filter time  65  from the falling edge of the analog drive signal for low-side driver  11 . 
         [0102]    By the process mentioned above, the brake down or open state of the regeneration diode  8  can be detected with higher precision. 
       Eighth Embodiment 
       [0103]    With reference to  FIGS. 14 and 16 , a description will be given of an internal combustion engine controller in accordance with an eighth embodiment of the present invention. This embodiment is another example of the internal combustion engine controller which can detect the breakdown or open state of the regeneration diode. As a detecting method, a reverse current of a current flowing between the booster circuit  3  and the high-side driver  4  is detected. The current flowing between the booster circuit  3  and the high-side driver  4  is hereinafter referred to as “current for high side.” 
         [0104]      FIG. 14  is a diagram showing a circuit of an internal combustion engine controller  2  in accordance with this embodiment. A difference from the seventh embodiment is that a current detection resistor  81  and a current detector  80  are disposed between the booster circuit  3  and the high-side driver  4 , and that a current detected by the current detector  80  is input to the voltage detector  15 . The first current source controller  18 , the second current source controller  20 , the first current source  17 , the second current source  19 , the third current source  21 , and the drive signal selector for current control  111  are omitted from the description. Timing charts shown in  FIG. 16  are the same as those of the seventh embodiment, except for a waveform of the current for high side  81 A which is added to  FIG. 16 . The current for high side  81 A flows through the current detection resistor  81 . 
         [0105]    As described in the sixth and seventh embodiments, if the regeneration diode  8  is broken down or opened, the counter electromotive energy cannot be regenerated into the booster circuit  3  during the regeneration diode breakdown time  62 , as shown in  FIG. 16 . As a result, the drain voltage for low-side driver  46  exceeds the second threshold for regeneration diode breakdown detection  70  and jumps up to the clamp voltage  64 . 
         [0106]    Now, a description will be given of a method for detecting the breakdown or open state of the regeneration diode  8  in this embodiment. As shown in  FIG. 16 , when the control signal  29  and the analog drive signal for low-side driver  11  turns on, the current for high side  81 A flows from the upstream side to the downstream side, showing a waveform of a peak current  84 . When the analog drive signal for low-side driver  11  turns off, in a normal case, a regeneration current flows through the regeneration diode  8  and the current for high side  81 A, which flows through the current detection resistor  81 , becomes the reverse current  85 . 
         [0107]    However, if the regeneration diode  8  is broken down or opened, the reverse current  85  does not flow through the current detection resistor  81  because the regeneration current cannot flow. In the waveform of the current for high side  81 A in  FIG. 16 , the dotted line indicates the reverse current  85  that should flow when the regeneration diode  8  is normal. Therefore, the current detector  80  does not detect the reverse current  85 , leading to the detection of the brake down or open state of the regeneration diode  8 . 
       Ninth Embodiment 
       [0108]    With reference to  FIGS. 15 and 17 , a description will be given of an internal combustion engine controller in accordance with a ninth embodiment of the present invention. This embodiment is another example of the internal combustion engine controller which can detect the breakdown or open state of the regeneration diode. As a detecting method, the regeneration current is detected. 
         [0109]      FIG. 15  is a diagram showing a circuit of an internal combustion engine controller  2  in accordance with this embodiment. The internal combustion engine controller  2  is the same as that of the eighth embodiment shown in  FIG. 14 , except for the locations of the current detector  80  and the current detection resistor  81 . The current detector  80  and the current detection resistor  81  are located between the regeneration diode  8  and the low-side driver  10 . The regeneration current  81 B flows through the current detection resistor  81 . Timing charts shown in  FIG. 17  are same as those of the eighth embodiment, except that a waveform of the regeneration current  81 B substitutes for that of the current for high side  81 A. 
         [0110]    As described in the eighth embodiment, when the analog drive signal for low-side driver  11  turns off, in a normal case, the regeneration current  81 B flows through the regeneration diode  8  as well as through the current detection resistor  81 . 
         [0111]    However, if the regeneration diode  8  is broken down or opened, the regeneration current  81 B does not flow through the current detection resistor  81 . In the waveform of the regeneration current  81 B in  FIG. 17 , the dotted line indicates the regeneration current that should flow when the regeneration diode  8  is normal. Therefore, the current detector  80  does not detect the regeneration current  81 B, leading to the detection of the brake down or open state of the regeneration diode  8 . 
         [0112]    The present invention relates to internal combustion engine controllers which drive an electromagnetic load, such as a fuel injector, by a battery voltage or a boosted battery voltage in automobiles, motorcycles, farm vehicles, industrial machines, or ships which use gasoline or light oil as fuel. In addition, the present invention is applied to controllers whose drive cycle changes, such as internal combustion engines, requiring a high diagnosis performance.