Fuel injection control device

Abstract

Provided is a fuel injection control device capable of ensuring abnormality diagnosis accuracy with less processing load. The fuel injection control device according to the present invention acquires, as a first sampling value, a drive voltage at a first predetermined time point when a first predetermined time has elapsed from a time point when energization to a fuel injection valve was stopped, and acquires, as a second sampling value, a drive voltage measured at a second predetermined time point when a second predetermined time has elapsed from a time point at which energization to the fuel injection valve was stopped. Then, a noise determination value is calculated using the first sampling value and the second sampling value, whether or not the noise determination value satisfies a noise determination condition is determined by comparing the noise determination value with a noise determination threshold, and abnormality diagnosis is performed when the noise determination value satisfies the noise determination condition.

Description

fuel injection control device

[0001] The present invention relates to a fuel injection control device for controlling a fuel injection valve of an internal combustion engine.

[0002] In a conventional method for detecting an abnormality in voltage information, which is the basis for correcting the fuel injection amount of a fuel injector, the voltage difference between the downstream voltage and the upstream voltage of the fuel injector is compared with a threshold value at a predetermined time point after the end of the control period of voltage supply, and the abnormality of the voltage information is determined based on the result. This abnormality determination method can improve the accuracy of abnormality diagnosis by obtaining as many sampled values ​​of the voltage difference as possible from the end of the control period of voltage supply to the predetermined time point.

[0003] Patent Document 1 discloses a technique for accurately determining whether or not the valve body of a fuel injection valve is seated, in which after stopping the supply of current to an electromagnetic actuator, the value of a monitored voltage derived as a back electromotive force is acquired multiple times, and an interpolated line passing through the estimated seating period is generated using sampled values ​​from among the multiple sampled values ​​that belong to a period outside a predetermined estimated seating period, and whether or not the valve body is seated is determined based on a comparison between the multiple sampled values ​​that belong to the estimated seating period and the interpolated line.

[0004] JP 2016-211452 A

[0005] However, the conventional method of acquiring as many sampled values ​​as possible has the problem that the computational load is large and it is difficult to reduce the load.On the other hand, if the number of sampled values ​​is reduced, if the timing of acquiring a sampled value coincides with the timing of noise occurrence, the voltage information may be determined to be abnormal, and it is necessary to eliminate factors that could lead to a misdiagnosis.

[0006] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a fuel injection control device that can ensure the accuracy of abnormality diagnosis with a smaller processing load.

[0007] The fuel injection control device of the present invention that solves the above problem is a fuel injection control device that controls a fuel injection valve of an internal combustion engine, and includes: an input voltage processing unit that detects a drive voltage of the fuel injection valve; and an abnormality diagnosis unit that performs an abnormality diagnosis of a drive circuit of the fuel injection valve based on the drive voltage, wherein the input voltage processing unit obtains, as a first sampled value, the drive voltage at a first predetermined time point when a first predetermined time has elapsed since the supply of current to the fuel injection valve was stopped; obtains, as a second sampled value, the drive voltage measured at a second predetermined time point when a second predetermined time longer than the first predetermined time has elapsed since the supply of current to the fuel injection valve was stopped; calculates a noise judgment value using the first sampled value and the second sampled value; and compares the noise judgment value with a noise judgment threshold to determine whether the noise judgment value satisfies a noise judgment condition; and the abnormality diagnosis unit performs the abnormality diagnosis when the noise judgment value satisfies the noise judgment condition.

[0008] According to the present invention, it is possible to obtain a fuel injection control device that can ensure the accuracy of abnormality diagnosis with a smaller processing load. Further features related to the present invention will become apparent from the description of the present specification and the accompanying drawings. Furthermore, problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments.

[0009] 1 is a diagram showing the basic configuration of an internal combustion engine equipped with a fuel injection control device according to a first embodiment. FIG. 2 is a block diagram illustrating the configuration of the fuel injection control device shown in FIG. 1. FIG. 3 is a flowchart illustrating a method for diagnosing a valve closure detection circuit of a fuel injection valve. FIG. 4 is a timing chart illustrating calculation example 1 of a noise judgment value. FIG. 5 is a timing chart illustrating calculation example 2 of a noise judgment value. FIG. 6 is a timing chart illustrating calculation example 3 of a noise judgment value. FIG. 7 is a graph showing a state diagram of a valve closure detection circuit and a change in drive voltage when the valve is closed. FIG. 8 is a graph showing a state diagram of a valve closure detection circuit and a change in drive voltage when the valve is closed. FIG. 9 is a flowchart illustrating a method for shifting the timing of acquiring a sampling value. FIG. 10 is a diagram illustrating a state in which the timing of acquiring a sampling value and the timing of ignition overlap. FIG. 11 is a diagram illustrating a state in which the timing of acquiring a sampling value is shifted.

[0010] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements may be designated by the same numerals. Note that the accompanying drawings show embodiments and implementation examples according to the principles of the present disclosure, but these are for understanding the present disclosure and are not to be used to interpret the present disclosure in a limiting manner. The descriptions in this specification are merely typical examples and are not intended to limit the scope or application of the present disclosure in any way.

[0011] Although the present embodiment has been described in sufficient detail to enable those skilled in the art to implement the present disclosure, it should be understood that other implementations and forms are possible, and that changes in configuration and structure and substitutions of various elements are possible without departing from the scope and spirit of the technical ideas of the present disclosure. Therefore, the following description should not be interpreted as being limited thereto.

[0012] [First Embodiment] FIG. 1 shows the basic configuration of an internal combustion engine equipped with a fuel injection control device according to a first embodiment of the present invention.

[0013] The internal combustion engine 101 of this embodiment is a prime mover mounted on a vehicle such as an automobile or a hybrid automobile, and includes a piston 102, an intake valve 103, and an exhaust valve 104 within a cylinder. As an example, the internal combustion engine 101 can be an internal combustion engine having a plurality of cylinders, for example, four cylinders (#1 to #4), but Fig. 1 illustrates only one of the plurality of cylinders.

[0014] Each cylinder of the internal combustion engine 101 is equipped with a fuel injection valve 105 that directly injects fuel into the combustion chamber within the cylinder, and the cylinder head is equipped with an ignition plug 106 and an ignition coil 107. The water jacket of the cylinder is equipped with a coolant temperature sensor 108. A crank angle sensor 11 that measures the crankshaft angle of the internal combustion engine 101 is attached to the crankcase of the internal combustion engine 101.

[0015] An ECU (Engine Control Unit) 109 is provided as a control unit for controlling the internal combustion engine 101. The ECU 109 is configured by, for example, a microcomputer having a central processing unit (CPU) and memories such as RAM and ROM. A crank angle sensor 11 and an accelerator position sensor 12 that measures the position of the accelerator operated by the driver are connected to the ECU 109. Detection signals from the crank angle sensor 11 and the accelerator position sensor 12 are input to a fuel injection control device 109A of the ECU 109.

[0016] An intake pipe 110 for introducing air to be drawn into the internal combustion engine 101 is provided upstream of the intake valve 103, and an exhaust pipe 111 for exhausting air from the cylinder is provided downstream of the exhaust valve 104. A three-way catalyst 112 for purifying the exhaust gas and an oxygen sensor 113 are provided on the exhaust pipe 111. A collector 115, a throttle valve 119, and an air flow meter 120 are also provided in the intake pipe 110.

[0017] Air drawn into the internal combustion engine 101 is introduced into the intake pipe 110 via an air flow meter 120, a throttle valve 119, and a collector 115, and is then supplied to a combustion chamber 121 via an intake valve 103. An output signal from the air flow meter 120 is supplied to a fuel injection control device 109A of the ECU 109.

[0018] Fuel used in the internal combustion engine 101 is sent from a fuel tank 123 by a low-pressure fuel pump 124 to a high-pressure fuel pump 125 provided in the internal combustion engine 101. The high-pressure fuel pump 125 increases the pressure of the fuel introduced therein by power transmitted from an exhaust camshaft (not shown) of an exhaust cam 128. Specifically, the pressure of the fuel introduced into the high-pressure fuel pump 125 is increased by moving a plunger provided in the high-pressure fuel pump 125 up and down. Based on a control command value from the ECU 109, an open / close valve provided at the intake port of the high-pressure fuel pump 125 is controlled by a solenoid so that the pressure of the fuel discharged from the high-pressure fuel pump 125 becomes a desired pressure. The pressurized fuel is sent to a fuel injection valve 105 via a high-pressure fuel pipe 129, and the fuel injection valve 105 injects the fuel into the combustion chamber 121 based on a command from a fuel injection control device 109A provided in the ECU 109.

[0019] The internal combustion engine 101 is provided with a fuel pressure sensor 13 that measures the pressure in a high-pressure fuel pipe 129 in order to control the high-pressure fuel pump 125. The fuel injection control device 109A of the ECU 109 is configured to perform so-called feedback control based on the output of this fuel pressure sensor 13 so as to maintain the fuel pressure in the high-pressure fuel pipe 129 at a desired pressure. As described above, the internal combustion engine 101 is equipped with an ignition plug 106 and an ignition coil 107, and the ECU 109 controls the energization of the ignition coil 107 and the ignition by the spark plug 106 based on the output from the fuel pressure sensor 13. As a result, the intake air and fuel are combusted in the combustion chamber 121 by a spark emitted from the spark plug 106, and the resulting pressure pushes down the piston 102.

[0020] Exhaust gas generated by combustion is discharged into an exhaust pipe 111 via an exhaust valve 104, purified by the catalytic action of a three-way catalyst 112, and then discharged to the outside. The oxygen concentration of the exhaust gas is measured by an oxygen sensor 113 provided upstream of the three-way catalyst 112. An output signal from the oxygen sensor 113 is supplied to a fuel injection control device 109A of the ECU 109.

[0021] The control of the ECU 109 will be described in more detail. The ECU 109 calculates the torque required by the internal combustion engine 101 from the signal of the accelerator position sensor 12, and determines whether the engine is in an idling state. The ECU 109 also has the function of calculating the rotational speed of the internal combustion engine 101 (hereinafter referred to as engine speed) from the signal of the crank angle sensor 11, and determining whether the three-way catalyst 112 is warmed up from the coolant temperature of the internal combustion engine 101 obtained from the water temperature sensor 108 and the elapsed time since the start of the internal combustion engine 101, etc.

[0022] In addition, the ECU 109 calculates the amount of intake air required for the internal combustion engine 101 based on the required torque of the internal combustion engine 101 described above, and outputs an opening signal corresponding to the amount to the throttle valve 119. The fuel injection control device 109A calculates the amount of fuel corresponding to the amount of intake air, and outputs a corresponding fuel injection signal to the fuel injection valve 105, and further outputs an ignition signal to the ignition coil 107.

[0023] Next, the configuration of the fuel injection control device 109A of the ECU 109 shown in FIG. 1 will be described with reference to the block diagram of FIG.

[0024] The fuel injection control device 109A includes a drive IC 200, an engine state detection unit 201, a pulse signal calculation unit 202, a drive waveform command unit 203, a drive voltage input unit 207, an input voltage processing unit 204, an abnormality diagnosis unit 212, and a fuel injection amount correction unit 213. The drive IC 200 is a drive control unit that is responsible for overall control of the fuel injection control device 109A. The engine state detection unit 201 collects various information such as the engine speed, intake air amount, coolant temperature, fuel pressure, and fault state of the internal combustion engine 101, and provides the information to each unit.

[0025] The pulse signal calculation unit 202 calculates a pulse width Wp of an injection pulse Sp that defines the fuel injection period of the fuel injection valve 105 based on various information obtained from the engine state detection unit 201, and outputs the injection pulse Sp having the pulse width Wp. The drive waveform command unit 203 calculates a command value Swf related to the waveform of a drive current Id that is supplied to open or keep the fuel injection valve 105 open, and outputs the command value Swf to the drive IC 200. The drive waveform command unit 203 controls the waveform of the drive current Id, so that the drive IC 200 can appropriately set the valve disc lift amount and valve closing timing, and precisely control the fuel injection amount.

[0026] The drive voltage input unit 207 is connected to the high and low sides of the fuel injector 105 and supplies a drive voltage to the fuel injector 105. The drive voltage input unit 207 is turned on and off in accordance with a control signal from the drive IC 200, and switches the supply of a drive current Id to the fuel injector 105. The drive IC 200 switches the drive voltage input unit 207 on and off based on the injection pulse Sp calculated by the pulse signal calculation unit 202 and the drive current waveform command value Swf calculated by the drive waveform command unit 203, and applies a boost voltage Vboost or a battery voltage Vbat to the fuel injector 105, thereby controlling the drive current Id supplied to the fuel injector 105. The drive voltage input unit 207 is a drive circuit for the fuel injector 105 and includes a valve closure detection circuit that detects whether the fuel injector 105 is closed.

[0027] The fuel injection amount correction unit 213 determines the correction of the fuel injection amount to be performed in the internal combustion engine 101 and generates a signal for performing the correction. The fuel injection amount correction unit 213 generates a signal for correcting the fuel injection amount based on information on the drive signal to the fuel injection valve 105 from the drive voltage input unit 207 and information on the engine state from the engine state detection unit 201.

[0028] The input voltage processing unit 204 detects the drive voltage of the fuel injection valve 105. After stopping the supply of current to the fuel injection valve 105, the input voltage processing unit 204 acquires the value of the voltage generated as back electromotive force (hereinafter also referred to as the voltage difference of the drive voltage) from the drive voltage input unit 207 a predetermined number of times at predetermined acquisition timings. The input voltage processing unit 204 sets the acquisition timing and the number of samplings, which are the number of acquisition times, for acquiring the voltage difference of the drive voltage of the fuel injection valve 105 (diagnostic differential voltage) as a sampling value.

[0029] The sampled value of the voltage difference is the voltage difference (INJ_L-INJ_H) between the drive voltage on the Hi side (INJ_H) and the drive voltage on the Low side (INJ_L) of the fuel injection valve 105 at a predetermined time point p (interruption) when a predetermined time tp has elapsed since the end point tp0 of the control period of the voltage supply (the point when the injection pulse is switched from ON to OFF). The timing of acquiring the sampled value is set based on a value calculated in accordance with the operating state of the internal combustion engine 101.

[0030] The number of samplings is set in advance and stored in the memory of the ECU 109. In this embodiment, the number of samplings is set to two as the minimum number of measurements. That is, the voltage differences measured at a first predetermined time point p1, which is a first predetermined time tp1 elapsed from the end point tp0 of the control period of the voltage supply (the time when the supply of current to the fuel injection valve 105 is stopped), and at a second predetermined time point p2, which is a second predetermined time tp2 longer than the first predetermined time tp1 elapsed from the end point tp0 of the control period of the voltage supply, are acquired as the sampled values ​​V1 and V2. The first predetermined time tp1 and the second predetermined time tp2 are each adjusted according to the operating state of the internal combustion engine 101.

[0031] The input voltage processing unit 204 measures the voltage difference at a set acquisition timing and acquires it as a sampling value. The input voltage processing unit 204 calculates a noise judgment value using information on the acquired sampling value of the voltage difference. The noise judgment value is a value used to remove noise from the sampling value and to determine the presence or absence of noise.

[0032] The input voltage processing unit 204 calculates a noise judgment value, such as an average value, a difference, a ratio, or a predicted value, using a first sampling value V1 measured at a first predetermined time point p1 and a second sampling value V2 measured at a second predetermined time point p2. Then, the input voltage processing unit 204 obtains a noise judgment threshold value and compares the noise judgment value with the noise judgment threshold value to determine whether the noise judgment value satisfies the noise judgment condition.

[0033] The input voltage processing unit 204 determines whether or not noise is mixed into the sampled value based on the comparison result between the noise judgment threshold and the noise judgment value. If the input voltage processing unit 204 determines that the noise judgment value does not satisfy the noise judgment condition, it determines that noise is mixed in, and performs adjustment processing to change the setting of the acquisition timing of the next sampled value.

[0034] In this adjustment process, for example, if the ignition timing obtained from the engine state detection unit 201 overlaps with the voltage acquisition timing obtained by the input voltage processing unit 204, the input voltage processing unit 204 performs a process of changing the setting of the acquisition timing of the first sampling value V1 or the acquisition timing of the second sampling value V2 so that the voltage acquisition timing is different from the ignition timing.

[0035] The input voltage processing unit 204 determines, based on the determination result of whether or not noise is mixed in, whether or not to diagnose the state of the valve closure detection circuit of the fuel injection valve 105. When the input voltage processing unit 204 determines that the state of the valve closure detection circuit of the fuel injection valve 105 should be diagnosed, the abnormality diagnosis unit 212 performs abnormality diagnosis using the first sampled value V1 and the second sampled value V2. On the other hand, when the input voltage processing unit 204 determines that the state of the valve closure detection circuit of the fuel injection valve 105 should not be diagnosed, the abnormality diagnosis unit 212 skips and does not perform the abnormality diagnosis.

[0036] When performing an abnormality diagnosis, the abnormality diagnosis unit 212 compares the first sampled value V1 and the second sampled value V2 with a diagnostic upper limit threshold Vth_d1, which is a High_input threshold, and a diagnostic lower limit threshold Vth_d2, which is a Low_input threshold. If both the first sampled value V1 and the second sampled value V2 are greater than the diagnostic upper limit threshold Vth_d1 or both are smaller than the diagnostic lower limit threshold Vth_d2, the abnormality diagnosis unit 212 determines that a malfunction has occurred in the valve closure detection circuit of the fuel injection valve 105. The diagnostic upper limit threshold Vth_d1 and the diagnostic lower limit threshold Vth_d2 are set based on values ​​calculated according to the operating state of the internal combustion engine 101.

[0037] 3 is a flowchart illustrating the contents of a method for diagnosing a closed valve detection circuit of a fuel injection valve. The fuel injection control device 109A executes the flow shown in FIG. 3 as a stationary task C_n in a predetermined programming cycle.

[0038] First, the input voltage processing unit 204 of the fuel injection control device 109A acquires the driving voltage at a first predetermined time point p1, which is a first predetermined time tp1 after the end time t0 of the control period of the voltage supply, as a first sampling value V1, and acquires the driving voltage at a second predetermined time point p2, which is a second predetermined time tp2 longer than the first predetermined time, after the end time of the control period of the voltage supply, as a second sampling value V2 (S301).

[0039] Then, the input voltage processing unit 204 calculates a noise judgment value Va, which is a diagnostic judgment voltage after noise processing, using the first sampled value V1 and the second sampled value V2 (S302). For example, in calculation example 1, in order to remove noise from the sampled values, the average value of the first sampled value V1 and the second sampled value V2 is calculated, and this average value is set as the noise judgment value Va1.

[0040] In calculation example 2, in order to determine whether or not there is noise in the sampled value, the second sampled value is predicted from the first sampled value V1, and the difference or ratio between the predicted value V2' of the second sampled value and the actual measurement value V2 of the second sampled value that is actually measured is calculated and set as the noise determination value Va2. In calculation example 3, in order to determine whether or not there is noise in the sampled value, the difference or ratio between the first sampled value V1 and the second sampled value V2 is calculated and set as the noise determination value Va3.

[0041] Next, the input voltage processing unit 204 calculates the noise determination threshold Vth_n (S303). The input voltage processing unit 204 calculates the noise determination threshold Vth_n based on the engine operating state. The input voltage processing unit 204 has a calculation table set according to, for example, the engine load, and calculates the noise determination threshold Vth_n by referring to this calculation table.

[0042] The input voltage processing unit 204 then uses the noise judgment threshold Vth_n to determine whether the noise judgment value Va satisfies the noise judgment condition (S304). For example, the noise judgment value Va is compared with the noise judgment threshold Vth_n. If the noise judgment value Va is outside the range of the noise judgment threshold Vth_n, it is determined that the noise judgment condition is not satisfied (NO in S304). If the noise judgment value Va is within the range of the noise judgment threshold Vth_n, it is determined that the noise judgment condition is satisfied (YES in S304).

[0043] Here, the noise determination condition determination process in step S304 will be described with reference to FIGS.

[0044] 4 is a timing chart illustrating a first calculation example of the noise judgment value. The noise judgment value is calculated for each steady task C_n. In the first calculation example of the noise judgment value, the noise judgment value Va is calculated by averaging Va1 of the first sampled value V1 and the second sampled value V2 (Va1=(V1+V2) / 2).

[0045] 4(3), if this average value Va1 is within the range between the upper noise determination threshold Vth_n1 and the lower noise determination threshold Vth_n2 (average value determination threshold range), it is determined that the noise determination condition is met (YES in S304). On the other hand, if the average value Va1 is not within the range between the upper noise determination threshold Vth_n1 and the lower noise determination threshold Vth_n2, it is determined that the noise determination condition is not met (NO in S304).

[0046] 4(2), the second sampled value V2 is lower than the predetermined differential voltage lower limit V_min. Therefore, in a comparative example in which the condition for abnormality diagnosis is that both the first sampled value V1 and the second sampled value V2 are between the differential voltage upper limit V_max and the differential voltage lower limit V_min, it is determined that abnormality diagnosis cannot be performed.

[0047] In contrast, in the present embodiment using the noise judgment value of calculation example 1, although the second sampling value V2 is below the differential voltage lower limit value V_min, the average value Va1 is within the range between the noise judgment upper limit threshold Vth_n1 and the noise judgment lower limit threshold Vth_n2, so it is determined that abnormality diagnosis can be performed.

[0048] In this calculation example 1, the first sampled value V1 and the second sampled value V2 are averaged, and noise contained in the first sampled value V1 and the second sampled value V2 can be removed.

[0049] 5 is a timing chart illustrating a second calculation example of the noise judgment value. In this second calculation example of the noise judgment value, a predicted value V2' of the second sampled value is calculated from the first sampled value V1. The predicted value V2' of the second sampled value can be calculated by referring to a table map that is set in advance based on the first sampled value V1 and engine operating conditions such as the engine load.

[0050] Next, the difference or ratio between the predicted value V2' of the second sampled value and the actual measurement value V2 of the second sampled value that is actually measured is calculated and set as the noise judgment value Va2. For example, if the noise judgment value Va2 is the difference δ between the predicted value V2' and the actual measurement value V2, and the difference δ is smaller than the threshold value δth, it is determined that the noise judgment condition is met (YES in S304). On the other hand, if the difference δ is larger than the threshold value δth, it is determined that the sampled value contains noise and does not satisfy the noise judgment condition (NO in S304).

[0051] 5A, the actual measurement value V2 of the second sampling value is between the upper limit V_max and the lower limit V_min of the differential voltage, and the difference value δ1, which is the noise determination value Va2, is smaller than the threshold value δth. Therefore, it is determined that the noise determination condition is met (YES in S304).

[0052] On the other hand, in the example shown in FIG. 5 (2), the actual measurement value V2 of the second sampled value contains noise, and the difference δ2 is greater than the threshold value δth. Therefore, it is determined that the sampled value contains noise and does not satisfy the noise determination condition (NO in S304). Therefore, when the process finally proceeds to the abnormality diagnosis skip (S308), the abnormality diagnosis in this task is not performed, and it is possible to prevent the input voltage processing unit 204 from erroneously determining that the output of the valve close detection circuit is abnormal. Note that when the noise determination value Va2 is a ratio, for example, if the ratio of the second sampled value V2 to the actual measurement value is within a threshold range of 90% to 110%, it is determined that the noise determination condition is satisfied (YES in S304).

[0053] 6 is a timing chart illustrating calculation example 3 of the noise judgment value. In calculation example 3 of the noise judgment value, the difference or ratio between the first sampled value V1 and the second sampled value V2 is set as the noise judgment value Va3.

[0054] For example, if the difference δ between the first sampled value V1 and the second sampled value V2 is set as the noise determination value Va3, when the difference δ is within the range of the threshold δth, it is determined that the noise determination condition is met (YES in S304) and the process proceeds to abnormality diagnosis (S305).On the other hand, when the difference δ is outside the range of the threshold δth, it is determined that the sampled value contains noise and does not meet the noise determination condition (NO in S304).

[0055] 6A, the first sampled value V1 and the second sampled value V2 are between the upper limit V_max and the lower limit V_min of the differential voltage, and the difference value δ3, which is the noise judgment value Va3, is within the range of the threshold δth. Therefore, it is determined that the noise judgment condition is met (YES in S304).

[0056] 6(2), the second sampled value V2 is smaller than the differential voltage lower limit V_min, the difference δ4 is large, and it is outside the range of the threshold δth. Therefore, it is determined that the sampled value contains noise and does not satisfy the noise determination condition (NO in S304). Therefore, when the process finally proceeds to skip abnormality diagnosis (S308), abnormality diagnosis in this task is not performed, and it is possible to prevent the input voltage processing unit 204 from erroneously determining that the output of the valve close detection circuit is abnormal.

[0057] In addition, when the noise judgment value Va3 is a ratio, for example, if it is within a threshold range of 90% to 110% of the second sampling value V2 that does not contain noise, it is judged to meet the noise judgment condition (YES in S304).

[0058] 3. When the input voltage processing unit 204 determines that the noise determination condition is not satisfied (NO in S304), it performs processing to count the number n of times that the noise determination condition is not satisfied (S305). In S305, each time the input voltage processing unit 204 determines that the noise determination condition is not satisfied, it increments the counter by one and adds 1 to the number n (n+1).

[0059] Then, the number of times n measured in S305 that the noise judgment condition was not met is compared with a preset abnormality diagnosis implementation judgment threshold nth (number of times), and it is determined whether the number of times n that the noise judgment condition was not met is equal to or greater than the abnormality diagnosis implementation judgment threshold nth (S306).

[0060] If the number of times n that the noise determination condition is not satisfied is less than the abnormality diagnosis execution determination threshold nth (NO in S306), the input voltage processing unit 204 determines that abnormality diagnosis cannot be executed.

[0061] On the other hand, if the number of times n that it is determined that the noise determination condition is not satisfied is equal to or greater than the abnormality diagnosis implementation determination threshold nth (YES in S306), the input voltage processing unit 204 determines that abnormality diagnosis can be implemented.

[0062] Furthermore, if the input voltage processing unit 204 determines that the noise determination condition is satisfied (YES in S304), it performs processing to reset the number of times n that the noise determination condition is not satisfied to 0 (S307).Then, the input voltage processing unit 204 determines that an abnormality diagnosis can be performed.

[0063] When the input voltage processing unit 204 determines that the abnormality diagnosis can be performed, the abnormality diagnosis unit 212 of the fuel injection control device 109A performs the abnormality diagnosis to diagnose whether or not there is an abnormality in the valve closing detection circuit of the fuel injection valve 105 (S309). On the other hand, when the input voltage processing unit 204 determines that the abnormality diagnosis cannot be performed, the abnormality diagnosis unit 212 skips the abnormality diagnosis in this routine and does not perform it (S308).

[0064] In the abnormality diagnosis (S309), the sampled value is compared with a diagnostic threshold value to diagnose whether an abnormality has occurred in the closed valve detection circuit. Specifically, if both the first sampled value V1 and the second sampled value V2 are greater than a predetermined upper diagnostic threshold value or smaller than a predetermined lower diagnostic threshold value, it is determined that an abnormality has occurred in the closed valve detection circuit.

[0065] Figure 7 is a graph showing a state diagram of the valve closure detection circuit and the change in drive voltage when the valve is closed. Figure 7(1) shows the state of the valve closure detection circuit when there is a break or GND short in the wiring INJ_H connected to the high side of the fuel injection valve 105, or when there is a VCC short in the wiring INJ_L. Figure 7(2) shows the change in drive voltage in the state of Figure 7(1).

[0066] As shown in Fig. 7(1), if there is a break or a GND short in the wiring INJ_H connected to the High side of the fuel injection valve 105, or if there is a VCC short in the wiring INJ_L, the INJ drive voltage is fixed to the High side and does not become less than the diagnostic upper limit threshold Vth_d1, as shown in Fig. 7(2). Therefore, if both the first sampled value V1 and the second sampled value V2 are greater than the diagnostic upper limit threshold Vth_d1, it is determined that an abnormality has occurred in the valve close detection circuit.

[0067] Figure 8 is a graph showing a state diagram of the valve closure detection circuit and the change in drive voltage when the valve is closed. Figure 8(1) shows the state of the valve closure detection circuit when there is a break or GND short in the wiring INJ_L connected to the low side of the fuel injection valve 105, or when there is a VCC short in the wiring INJ_H. Figure 8(2) is a graph showing the change in drive voltage in the state of Figure 8(1).

[0068] As shown in Fig. 8(1), if there is a break or a GND short in the wiring INJ_L connected to the low side of the fuel injection valve 105, or if there is a VCC short in the wiring INJ_H, the INJ drive voltage is fixed to the low side and does not exceed the diagnostic lower limit threshold Vth_d2, as shown in Fig. 8(2). Therefore, if both the first sampled value V1 and the second sampled value V2 are smaller than the diagnostic lower limit threshold Vth_d2, it is determined that an abnormality has occurred in the valve close detection circuit.

[0069] If it is determined in the process of S304 that the noise determination condition is not satisfied (NO in S304) and it is determined that the number of times n that it has been determined that the noise determination condition is not satisfied is less than the abnormality diagnosis implementation determination threshold nth (NO in S306), the abnormality diagnosis determination is skipped and not executed in this steady task (S308). The input voltage processing unit 204 determines that the noise determination value Va is outside the range of the noise determination threshold Vth_n and that noise has been mixed into the sampled value, and performs adjustment processing to change the setting of the acquisition timing of the next sampled value to be acquired.

[0070] The input voltage processing unit 204 adjusts at least one of the first predetermined time tp1 and the second predetermined time tp2 set in the current steady task C_n to be longer or shorter, and changes the setting to an acquisition timing different from the acquisition timing of the sampling value determined to contain noise. Then, from the next time onwards, the sampling value is acquired at the acquisition timing after the change in setting.

[0071] When determining to skip the abnormality diagnosis (S306), the input voltage processing unit 204 compares the voltage acquisition timing with the ignition timing, and if the comparison is within a predetermined range, performs processing to shift the voltage acquisition timing the next time the voltage is acquired. For example, if the acquisition timing of the first sampled value V1 (first predetermined time point p1) or the acquisition timing of the second sampled value V2 (second predetermined time point p2) overlaps with the ignition timing p3, the input voltage processing unit 204 changes the setting of the acquisition timing of the first sampled value V1 or the acquisition timing of the second sampled value V2 so that the timing will differ from the ignition timing from the next time onwards.

[0072] FIG. 9 is a flowchart illustrating a method for shifting the timing at which sampling values ​​are obtained.

[0073] The input voltage processing unit 204 calculates the elapsed time tp3' from the end point tp0 of the control period of the voltage supply (when the injection pulse switches from ON to OFF) using the elapsed time tp3 from the steady task C_n to the ignition timing p3. Here, the input voltage processing unit 204 calculates the elapsed time tp3' from the end point tp0 of the control period of the voltage supply to the ignition timing p3 by calculating the elapsed time from the steady task C_n to the end point tp0 of the control period of the voltage supply and subtracting it from the elapsed time tp3 from the steady task C_n to the ignition timing p3 (S901).

[0074] The input voltage processing unit 204 calculates a first shift judgment value λ1, which is the time difference between the first predetermined time point p1, which is the timing at which the first sampling value V1 is acquired, and the ignition timing p3, and a second shift judgment value λ2, which is the time difference between the second predetermined time p2, which is the timing at which the second sampling value is acquired, and the ignition timing p3 (S902).

[0075] The first shift determination value λ1 is calculated by subtracting the first predetermined time tp1 from the elapsed time tp3' (λ1 = |tp3' - tp1|), and the second shift determination value λ2 is calculated by subtracting the second predetermined time tp2 from the elapsed time tp3' (λ2 = |tp3' - tp2|).

[0076] Next, the input voltage processing unit 204 determines whether the first shift determination value λ1 and the second shift determination value λ2 are within a threshold range between a predetermined upper determination limit and a predetermined lower determination limit (S903). The upper determination limit and the lower determination limit for each predetermined time point in one ejection pulse are set to be the same.

[0077] If at least one of the first shift determination value λ1 and the second shift determination value λ2 is within the threshold range, it is determined that the voltage acquisition timing overlaps with the ignition timing p3, and the voltage acquisition timing is changed (S905). The voltage acquisition timing is changed by lengthening or shortening the predetermined time for which the shift determination value λ is within the threshold range. On the other hand, if neither the first shift determination value λ1 nor the second shift determination value λ2 is within the threshold range, it is determined that the voltage acquisition timing does not overlap with the ignition timing p3, and the setting of the voltage acquisition timing is not changed (S904).

[0078] FIG. 10 is a diagram illustrating a state in which the timing of acquiring the sampled values ​​overlaps with the ignition timing, and FIG. 11 is a diagram illustrating a state in which the timing of acquiring the sampled values ​​is shifted from the ignition timing.

[0079] The input voltage processing unit 204 calculates the first shift judgment value λ1 and the second shift judgment value λ2 in the steady task C_n, and determines whether each of them falls within the threshold range between the judgment upper limit value and the judgment lower limit value in the next steady task C_n+1.

[0080] 10, in the steady task C_n, the difference between the first predetermined time point p1 and the ignition timing p3 is large, but the difference between the second predetermined time point p2 and the ignition timing p3 is small. Therefore, in the steady task C_n+1, the first shift determination value λ1 is determined to be greater than the determination upper limit value, and it is determined that the first predetermined time point p1 and the ignition timing p3 do not overlap. Therefore, the shift determination flag for the first predetermined time point p1 is not set, and it is determined that the first predetermined time point p1, which is the timing for obtaining the first sampled value V1, will not be shifted.

[0081] On the other hand, in the steady task C_n+1, it is determined that the second shift determination value λ2 is within the threshold range between the upper determination limit value and the determination threshold value, and it is determined that the second predetermined time point p2 and the ignition timing p3 overlap. Therefore, the shift determination flag for the second predetermined time point p2 is set, and it is determined that the second predetermined time point p2, which is the timing for acquiring the second sampled value V2, should be shifted. Here, the second predetermined time point p2 is adjusted, for example, to lengthen the second predetermined time tp2.

[0082] In the example shown in Fig. 11, in the steady task C_n, the acquisition timing of the second sampled value V2 is changed to a second predetermined time point p2', and the difference between the second predetermined time point p2 and the ignition timing p3 is larger than in the example shown in Fig. 10. Therefore, in the steady task C_n+1, the second shift determination value λ2 is determined to be greater than the determination upper limit value, that is, outside the threshold range, and it is determined that the second predetermined time point p2 and the ignition timing p3 do not overlap. Therefore, the shift determination flag for the second predetermined time point p2 is cleared, and it is determined that the second predetermined time point p2 will not be shifted.

[0083] According to the fuel injection control device 109A of this embodiment, the number of sampling points is set to two, and whether or not to perform abnormality diagnosis is determined using the first sampled value and the second sampled value. Therefore, the accuracy of abnormality diagnosis can be ensured with a smaller processing load.

[0084] According to the fuel injection control device 109A of this embodiment, a noise judgment value is calculated and compared with a noise judgment threshold value to determine whether or not the noise judgment condition is met. If the noise judgment condition is not met, the abnormality diagnosis is skipped and not performed. Therefore, abnormality diagnosis in this task is not performed, and it is possible to prevent the input voltage processing unit 204 from erroneously determining that the output of the valve close detection circuit is abnormal. Note that, although the above embodiment has been described using an example in which the minimum number of sampling points is two, three sampling points may also be used, and similarly to the case in which two sampling points are used, it is possible to ensure the accuracy of abnormality diagnosis with a small processing load.

[0085] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various design modifications can be made without departing from the spirit of the present invention as defined in the claims. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0086] 101...internal combustion engine, 109A...fuel injection control device, 201...engine state detection unit, 202...pulse signal calculation unit, 202...pulse signal calculation unit, 203...drive waveform command unit, 204...input voltage processing unit, 207...drive voltage input unit, 212...abnormality diagnosis unit, 213...fuel injection amount correction unit, tp1...first predetermined time, tp2...second predetermined time, p1...first predetermined time point, p2...second a predetermined time point, p3...ignition timing, V_max...differential voltage upper limit value, V_min...differential voltage lower limit value, V1...first sampling value, V2...second sampling value, Vth_d1...diagnosis upper limit threshold (High_input threshold), Vth_d2...diagnosis lower limit threshold (Low_input threshold), Vth_n1...noise judgment upper limit threshold, Vth_n2...noise judgment lower limit threshold, C_n...steady task

Claims

1. A fuel injection control device that controls a fuel injection valve of an internal combustion engine, comprising: an input voltage processing unit that detects a drive voltage of the fuel injection valve; and an abnormality diagnosis unit that performs an abnormality diagnosis of a drive circuit of the fuel injection valve based on the drive voltage, wherein the input voltage processing unit obtains, as a first sampling value, the drive voltage at a first predetermined time point when a first predetermined time has elapsed since the supply of current to the fuel injection valve is stopped, and obtains, as a second sampling value, the drive voltage measured at a second predetermined time point when a second predetermined time longer than the first predetermined time has elapsed since the supply of current to the fuel injection valve is stopped, and calculates a noise judgment value using the first sampling value and the second sampling value, and compares the noise judgment value with a noise judgment threshold to determine whether or not the noise judgment value satisfies a noise judgment condition, and the abnormality diagnosis unit performs the abnormality diagnosis if the noise judgment value satisfies the noise judgment condition.

2. The fuel injection control device according to claim 1, characterized in that the input voltage processing unit calculates a predicted value of the second sampling value based on the first sampling value, and the difference or ratio between the predicted value and the actual measured value of the second sampling value is set as the noise judgment value.

3. The fuel injection control device according to claim 1, wherein the input voltage processing section sets the average value of the first sampled value and the second sampled value as the noise judgment value.

4. The fuel injection control device according to claim 1, wherein the input voltage processing section sets the difference or ratio between the first sampled value and the second sampled value as the noise judgment value.

5. The fuel injection control device according to claim 1, wherein the input voltage processing section adjusts at least one of the first predetermined time and the second predetermined time in accordance with an operating state of the internal combustion engine.

6. The fuel injection control device according to claim 5, characterized in that, when it is determined that the noise judgment value does not satisfy the noise judgment condition, the input voltage processing unit performs an adjustment process of changing the settings of the acquisition timing of the first sampling value and the second sampling value by lengthening or shortening at least one of the first specified time and the second specified time.

7. The fuel injection control device according to claim 6, characterized in that, when the timing of acquiring the first sampling value or the timing of acquiring the second sampling value overlaps with the timing of the ignition timing of the internal combustion engine, the input voltage processing unit changes the setting of the timing of acquiring the first sampling value or the setting of the timing of acquiring the second sampling value so that the timing is different from the timing of the ignition timing of the internal combustion engine.