Patent Publication Number: US-8989994-B2

Title: System and method for fault diagnosis in fuel injection system

Description:
TECHNICAL FIELD 
     The present disclosure relates to a fuel injection system and more particularly to a control system and a method for fault diagnosis in the fuel injection system. 
     BACKGROUND 
     Internal combustion engines use fuel injectors to deliver fuel under pressure to one or more cylinders. Such fuel injectors utilize actuators which are operated by an engine control to deliver measured quantities of fuel to the cylinders, in synchronism with movement of pistons within the cylinders. The timing of fuel injection and the quantity of fuel injected during each injection operation affect the efficiency of the engine and the emissions therefrom. Further, it is required to sequence the injection of the fuel by each fuel injector for sustainable operation of the engine. 
     During operation of the engine, there may be a fault due to short-circuiting of the fuel injectors to ground or engine chassis. In fuel injection system, with the fuel injectors sharing connections, the short-circuiting of one of the fuel injectors may lead to unintended actuation of associated fuel injectors. This unintended injection may result in unwanted forces and lead to damage to engine&#39;s components. 
     US Patent Application No. 20080212246 discloses systems and methods for detecting a short in an electrical distribution system. A determination is made as to whether a short condition is satisfied based on a change in a voltage in a wire harness coupled to a first side of a switch. The determination of whether a short exists is made in response to determining whether the short condition has been satisfied for at least a threshold time. The threshold time is dependent on a change in a voltage of the wire harness coupled to a second side of the switch. 
     SUMMARY 
     In an aspect, the present disclosure provides a method for fault diagnosis in a fuel injection system having first and second fuel injectors. The method includes initiating a current flow in the first and second fuel injectors. Further, a rise duration of the current flow to reach a threshold level is measured. The method further includes comparing the rise duration and a preset duration. The fuel injection system is controlled based on the comparison. 
     In another aspect, the present disclosure provides a control system for fault diagnosis in the fuel injection system having the first and second fuel injectors. The control system includes a first module configured to initiate current flow in the first and second fuel injectors. The control system includes a second module configured to measure a rise duration of the current flow, from the first and second fuel injectors, to reach a threshold level. The control system further includes a third module configured to compare the rise duration and a preset duration. Further, the control system includes a fourth module configured to control the fuel injection system based at least on the comparison. 
     Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a engine system with a fuel injection system, according to an aspect of the present disclosure; 
         FIG. 2  illustrates a driver circuit in the fuel injection system, according to an aspect of the present disclosure; and 
         FIG. 3  illustrates a process flow for fault diagnosis in the fuel injection system, according to an aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure will now be described in detail with reference being made to accompanying figures. Referring to  FIG. 1 , an engine system  100 , such as an automotive vehicle or construction machinery engine is generally shown. The engine system  100  may include may include an engine block  101  having a number of cylinders disposed in any one of an inline configuration, a V-configuration, a W-configuration, or an X-configuration, etc. For the purpose of clear illustration,  FIG. 1  shows only one cylinder set having a first cylinder  102  and a second cylinder  104 . However, the engine block  101  may include a plurality of cylinder sets, each with the first cylinder  102  and the second cylinder  104 , as illustrated in  FIG. 2 . Each of the first and the second cylinders  102 ,  104  include respective pistons  106 , which reciprocates in the corresponding cylinders due to pressure energy generated by combustion of fuel inside the cylinders. 
     Further, as illustrated in  FIG. 1 , the engine system  100  includes a fuel injection system  108  which supplies the fuel into the cylinders  102 ,  104 . For example, the fuel injection system  108  may be employed in a diesel engine to inject diesel fuel, or in a spark ignited internal combustion engine to inject combustible gasoline. The fuel injection system  108  include an injector bank  110  having a first fuel injector  112  and a second fuel injector  114 , in association with the first cylinder  102  and the second cylinder  104 , respectively. The fuel injectors  112 ,  114  may be electrically actuable to inject the fuel into the cylinders  102 ,  104 . In an embodiment, as illustrated in  FIG. 2 , the fuel injection system  108  may include a plurality of injector banks  110  associated with each cylinder set. Also, the injector banks  110  may include more than two fuel injectors, depending on the number of cylinders in each cylinder set. 
     In an embodiment of the present disclosure, the fuel injection system  108  may employ a driver circuit  116  for each of the injector banks  110 . The driver circuit  116  may be associated with the injector bank  110 , to monitor and control the first and second fuel injectors  112 ,  114 . The driver circuit  116  may form a part of an Engine Control Module (ECM)  118 . The ECM  118  may, typically, include a microprocessor and a memory which are arranged to perform various routines to control the operation of the engine system  100 . For example, the ECM  118  may be configured to monitor engine speed and load, and provide the feedback to the driver circuit  116  to control the timing of operation and the amount of fuel supplied to the fuel injectors  112 ,  114 . Further, the driver circuit  116  receives signals indicating the reciprocation of the pistons  106  in the first and the second cylinders  102 ,  104 , and accordingly actuates the fuel injectors  112 ,  114  to supply the fuel. 
     Typically, each of the fuel injectors  112 ,  114 , in the injector bank  110 , includes an injection valve  120  and an actuator  122 . The actuator  122  may be any one of a solenoid coil, piezoelectric actuator, or the like. The actuator  122  may be operable by the driver circuit  116  to cause the injector valve  120  to open and close, in order to control the injection of the fuel into the associated cylinders. 
       FIG. 2  illustrates a detailed embodiment of the driver circuit  116 . The driver circuit  116  may include a power source  124 . In an embodiment, the power source  124  may be a combination of, for example, but not limited to, a battery  126 , and a High Voltage Power Supply (HVPS)  128  working in conjunction, via a current mirror  129  and a pair of diodes  130 . Such an arrangement may provide voltage proportional to the load by the fuel injectors  112 ,  114 . The driver circuit  116  may also include a boost circuit  115  which amplifies the power from the power source  124 , as shown in  FIG. 1 . The driver circuit  116  may also include means for noise suppression, such as, a capacitor, or like connected to the power source  124 . 
     The driver circuit  116  includes a first selector switch  132  and a second selector switch  134 , disposed in a low-side, that is, between the first fuel injector  112  and the second fuel injector  114 , respectively, and the power source  124 . The first and second selector switches  132 ,  134  may be connected to first terminals  136  of the first and second fuel injectors  112 ,  114 , and controllably connect and disconnect the first and second fuel injectors  112 ,  114  to and from the power source  124 . Further, the driver circuit  116  may include a multiplexed switch  138  disposed in a high-side, and connected to second terminals  140  of the first and second fuel injectors  112 ,  114  to controllably connect and disconnect the first and second fuel injectors  112 ,  114  to and from the power source  124 . 
     In an embodiment of the present disclosure, the first and second selector switches  132 ,  134  are field effect transistors (FET&#39;s) with a drain connected to the power source  124 . Similarly, the multiplexed switch  138  may also be a field effect transistor (FET) with a drain in connection with the power source  124 . In an embodiment, the driver circuit  116  of the present disclosure may use n-type MOSFET as switches  132 ,  134 ,  138 . It will be apparent to a person ordinarily skilled in the art, the fuel injection system  108  of the present disclosure have the injector banks  110  share the low-side. That is, each of the injector banks  110  is connected to the same first and second selector switches  132 ,  134 . Further, the fuel injectors  112 ,  114  in each of the injector bank  110  share a common multiplexed switch  138  in the high-side. 
     The driver circuit  116  may include diodes  142  connected between the first terminals  136  of the first and second fuel injectors  112 ,  114  and the power source  124 . The diodes  142  may allow the current flow from the high-side to the low-side via the fuel injectors  112 ,  114 . The driver circuit  116  may also include diodes  144  to ensure unidirectional current flow through the fuel injectors  112 ,  114 . 
     In an embodiment, the driver circuit  116  of the present disclosure includes a control system  200  for controlling the fuel injection system  108 . Generally, the control system  200  may be a combination of, but not limited to, a processor, a Read Only Memory, a Random-Access Memory, a Logic Unit, etc. The control system  200  may primarily control the first and second selector switches  132 ,  134  and the multiplexed switch  138  in order to control the current flow through the driver circuit  116 , and therefore the fuel injectors  112 ,  114  for injection of the fuel. 
     The control system  200  may be operable to selectively trigger the first and second fuel injectors  112 ,  114  at desired points in time, by closing the multiplexed switch  138  while operating the first and second selector switches  132 ,  134  in alternating on and off states, whereby a first average magnitude of current is supplied to the first fuel injector  112  during a first period of time and a second average magnitude of current is supplied to the second fuel injector  114  during a second period of time subsequent to the first period of time. 
     According to an embodiment, the control system  200  may further be configured for fault diagnosis in the fuel injection system  108 . For example, the control system  200  may help to diagnose the fault condition due to either of the first and second fuel injectors,  112 ,  114  of the fuel injection system  108  being short-circuited to ground or engine chassis of the engine block  101 . 
     The control system  200  may include a first module  202  to close the multiplexed switch  138  along with the first and second selector switches  132 ,  134 , and thus initiates a current flow in the driver circuit  116 . In an embodiment, the first module  202  may close the switches  132 ,  134 ,  138  for a pre-selected time in order to cause the current flow for this pre-selected time duration. The first module  202  may also be configured to ensure that the current flow is initiated before the timed actuation of the first and second fuel injectors  112 ,  114 , as determined by ECM  118 . Further, the current flow may be limited not to cause the actuation of the actuators  122  in the first and second fuel injectors  112 ,  114  for fuel injection. 
     Further, the control system  200  may include a second module  204  to measure rise duration of the current flow, that is, the time for the current flow from the first and second fuel injectors  112 ,  114  to reach a predetermined threshold level. For example, the threshold level may be equivalent to peak value of voltage of the current waveform passing from the first and second fuel injectors  112 ,  114 . The current level may be measured by using a current-sensing circuit, and further means may be provided to indicate when the threshold level is reached. Also, the rise duration may be measured by any known process in the art, such as, but not limited to, using a counting circuit or the like. 
     The control system  200  may further include a third module  206  to compare the measured rise duration with a preset duration. The preset duration of the current flow may be defined during normal operation of the fuel injection system  108 , that is, when neither of the first and second fuel injectors  112 ,  114  are short-circuited to the ground or the engine chassis. For this purpose, the third module  206  may include an arithmetic logic unit (ALU), such as, an adder circuit, etc. The third module  206  may further generate a fault signal based on the comparison. Specifically, the third module  206  may be configured to generate the fault signal when the rise duration is greater than the preset duration. Here, the fault signal may be indicative of a short-circuited fuel injector out of the first and second fuel injectors  112 ,  114 . This is because, if any of the first and second fuel injectors  112 ,  114  is short-circuited, the current waveform may take longer to reach the threshold level, resulting in the rise duration to be greater than the preset duration. In a further embodiment, the third module  206  may be configured to generate the fault signal when the rise duration is greater than the preset duration by more than a tolerance limit. The tolerance limit may be set over the threshold level, so as to avoid unwanted fault signals for each current cycle with the rise duration above the threshold level. 
     Further, the control system  200  may include a fourth module  208  to control the fuel injection system  108 . The fourth module  208  may control the fuel injection system  108  based on the comparison performed by the third module  206 . In particular, the fourth module  208  may be configured to disable the fuel injection system  108 , in response to the fault signal. The fourth module  208  may achieve this by opening the first and second selector switches  132 ,  134  and/or the multiplexed switch  138 , associated with the first and second fuel injectors  112 ,  114  of the fuel injection system  108 . 
     In an embodiment, the first module  202  may be configured to initiate a current flow from the first and second fuel injectors  112 ,  114  for a preselected target current level, that is, the threshold level. Further, the second module  204  may be configured to switch open the second selector switch  134 , when the combined current flow reaches the threshold level. The third module  206  may indicate whether the combined current level reaches the threshold level in the allowable duration or not. If the combined current level did not reach the threshold level in the allowable duration, the third module  206  may generate a fault signal. 
     For this purpose, the driver circuit  116  may employ a counter which generates the fault signal if the count exceeds a predetermined count for the current level to reach the threshold level. Further, the fourth module  208  may be configured to control the fuel injection system  108  based on the indication and/or the fault signal. In an exemplary configuration, the fourth module  208  may be configured to shut-off the fuel injection system  108  in case of the fault signal. 
     In an exemplary configuration, the rise duration for the combined current level to reach the threshold level may be very high when neither of the first and second fuel injectors  112 ,  114  are shorted. There may a worst case scenario that the current level never reaches the threshold level, including but not limited to the high inductance of the first and second fuel injectors  112 ,  114 . In such cases, the control system  200  may incorporate tolerances for slow current rise duration, and generate the fault signal. 
     INDUSTRIAL APPLICABILITY 
     The industrial applicability of the system described herein will be readily appreciated from the foregoing discussion. The fuel injection system  108  of the present disclosure may be employed in any machine, such as, but not limited to, an automobile, an earth-moving machine like a loader, an excavator, a tractor, etc. Typically, such machines include electrical distribution system with wire harnesses, which in turn may include multiple wires for establishing electrical connections between devices in the machine. For example, the electrical distribution system may connect the power source to devices such as the starter, lights, and radio. For example, the electrical distribution system may also be utilized for connecting the fuel injectors  112 ,  114  of the fuel injection system  108  to the power source  124 . 
     During operation, one or more wires of the wire harness in the electrical distribution system may be subject to a short. A short generally results from a significant drop in the impedance of a device connected to the electrical distribution system. This may result in continuous current flow through the short-circuited device, and may affect the operation of the electrical distribution system. Failure to detect a short may potentially damage the electrical distribution system and/or devices connected to such electrical distribution system. 
     For example, the wires connected to the first terminals  136  or the second terminals  140  of the fuel injectors  112 ,  114  may be short-circuited to ground or the engine chassis. The ECM  118  may command the injection of the fuel in the first cylinder  102 . Accordingly, the driver circuit  116  may close the multiplexed switch  138 , and subsequently the first selector switch  132  to create a path for current flow through the first fuel injector  112 . But with the short-circuited second fuel injector  114 , the current will also flow through the second fuel injector  114  and cause unintended injection of the fuel in the second cylinder  104 . 
     Further, the driver circuit  116  may not be able to drive down the current because of the short-circuited fuel injector, that is, the current decay is slowed. So, the current flow through the short-circuited fuel injector will be for excessively long duration, and therefore lead to large quantity of unintended fuel injection in the associated cylinder. The mistimed combustion of such large quantity of fuel may result in forces which may damage some components of the engine such as connecting rod, piston, crankshaft, etc. 
     There have, in the past, been some efforts made towards protecting the engine due to possible damages due to mistimed injection because of the short-circuiting of the fuel injectors. Such methods have taken various forms, including mechanical and electrical arrangements that may be complex and expensive. These methods mostly involve measuring voltage at the selector switch in a period immediately following end of the current, or by detecting current through the fuel injectors above the highest allowable limit. Therefore, such methods detect the faults too late to prevent the engine damage. 
     The present disclosure provides a method of diagnosing such fault conditions at the beginning of the fuel injection event, and thereby eliminate chances of unintended fuel injection by shutting-off the fuel injection system  108  in case of any fault. This method has been described by means of a process flow  300 , as illustrated in  FIG. 3 . 
     In step  302 , the process flow involves initiating a current flow in the first and second fuel injectors  112 ,  114 . The current flow may be initiated in the first and second fuel injectors for a preselected time. Further, in step  304 , rise duration for the current flow, from the first and second fuel injectors  112 ,  114 , is measured to reach a threshold level. Subsequently, in step  306 , the measured rise duration is compared with a preset duration. Based on the comparison, a fault signal is generated when the rise duration is greater than the preset duration, the fault signal being indicative of a short-circuited fuel injector. Finally, in step  308 , the fuel injection system  108  may be controlled based at least on the comparison. Specifically, the first and second fuel injectors  112 ,  114  may be disabled in response to the fault signal. 
     The method, described in process flow  300 , may be achieved by means of the control system  200  of the present disclosure. The control system  200  may be configured for fault diagnosis in the fuel injection system  108 . In an exemplary embodiment, the control system  200  may close the switches  132 ,  134  and  138 , and pass a combined current through the fuel injectors  112 ,  114  of about 1 A (or 0.5 A nominal for each fuel injector), with a rise duration of approximately 10 micro-seconds to reach the threshold level, in case of no fuel injector being short-circuited. The preset duration for the current waveform to reach the threshold level is set at around 14 micro-seconds. The control system  200  measures the rise duration for the current waveform, and generate the fault signal when the rise duration is greater than 14 micro-seconds. The control system  200 , then, disables the fuel injectors  112 ,  114  and prevents further fuel injection and possible damage to the engine. 
     In an alternative method, the current flow through the first and second fuel injectors  112 ,  114  may be initiated for a preselected threshold level. If the current flow did not reach the threshold level with in the preset duration, the fault signal is generated indicative of the short-circuited fuel injector. In this example configuration, the control system  200  allows 14 micro-seconds for the combined current to reach the threshold value of 1 A to be sensed. If subsequent to 14 micro-seconds, the combined current level is not equal or greater than 1 A, further fuel injection is disabled. 
     The method of the present disclosure may be implemented by configuring the existing Field-programmable gate array (FPGA) to carry out the task of the control system  200 . Further, the specific rise duration ranges may be determined for differentiating between the normal operating condition and the short-circuited condition for all operating conditions of the fuel injectors in the fuel injection system  108 . In an embodiment, the control system  200  may be programmed to stop further fuel injection after determination of the fault condition, but continue attempts to check for the fault condition, and permanently shut-off the fuel injection system  108  and ultimately the engine system  100  after repeated encountering of the fault condition. 
     Although the embodiments of this disclosure as described herein may be incorporated without departing from the scope of the following claims, it will be apparent to a person skilled in the art that various modifications and variations can be made. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.