JP6926852B2 - Electronic control device - Google Patents

Description

The present invention relates to an electronic control device.

As one of the exhaust gas aftertreatment systems for diesel engines for automobiles, there is a urea SCR (Selective Catalytic Reduction) system. In the urea SCR system, urea water is injected from an injector into the exhaust gas discharged from the internal combustion engine and added to purify the nitrogen oxides (hereinafter referred to as NOx) contained in the exhaust gas. In the urea SCR system, there is a risk of failure due to a short circuit or disconnection in the injector drive circuit. If a failure occurs in the drive circuit, urea water cannot be properly added to the exhaust gas, resulting in the inability to purify NOx. Therefore, a mechanism for detecting a failure of the drive circuit is required. As a method of detecting a failure of a drive circuit, for example, in Patent Document 1, the drive current during the energization period of the drive circuit is monitored, and it is specified that the failure occurs when the current value of the drive current deviates from a predetermined range. There is a way to do it.

Japanese Unexamined Patent Publication No. 2002-227698

However, when the above method is applied to a urea SCR system, if the injection amount required for one injection is small, the energization period becomes short, and it is not possible to secure a sufficient period for monitoring the drive current. Therefore, there is a problem that it is not possible to determine whether or not the current value of the drive current is out of the predetermined range, and it is not possible to detect a failure.

The present invention has been made in view of the above circumstances, and an object of the present invention is to secure a sufficient period for monitoring a physical quantity according to an energized state of an injector to a drive circuit, and to appropriately detect a failure of the drive circuit. The purpose is to provide an electronic control device that can be used.

According to the invention described in claim 1, the control unit (18) controls energization of the drive circuit (19) of the injector (9) that injects urea water into the exhaust gas discharged from the internal combustion engine (2). , The physical quantity during the energization period or the non-energization period of the drive circuit is monitored to detect the failure of the drive circuit. The control unit adjusts the energization period or the non-energization period per injection, and detects a failure of the drive circuit. By adjusting the energization period or non-energization period per injection to a period in which a failure of the drive circuit can be detected by monitoring the physical quantity during the energization period or non-energization period of the drive circuit, the drive circuit Failure can be detected appropriately. In the configuration in which urea water is injected and added to the exhaust gas discharged from the internal combustion engine to purify the NOx contained in the exhaust gas, the added urea water is immediately hydrolyzed to ammonia without being used for NOx purification. Since it is later accumulated in the reduction catalyst, even if the injection timing of urea water is delayed, NOx cannot be purified. By paying attention to this point and adjusting the energization period or the non-energization period per injection, it is possible to appropriately detect the failure of the drive circuit without hindering the purification of NOx.

The figure which shows the whole structure of the exhaust gas purification system of 1st Embodiment Functional block diagram of urea water addition system Functional block diagram of electronic control device Flowchart showing injector drive processing Flowchart showing battery short circuit detection process Timing chart Timing chart Flowchart showing injector drive processing Flowchart showing ground short detection processing Timing chart Timing chart Functional block diagram of the electronic control device of the second embodiment Flowchart showing injector drive processing Flowchart showing ground short detection processing Timing chart Timing chart

(First Embodiment)
Hereinafter, the first embodiment of the present invention will be described with reference to FIGS. 1 to 11. As shown in FIG. 1, the exhaust gas purification system 1 of an internal combustion engine injects urea water into the exhaust gas discharged from an internal combustion engine 2 composed of, for example, a diesel engine for an automobile, and adds NOx contained in the exhaust gas. Includes a urea SCR system for purification. The exhaust gas of the internal combustion engine 2 flows through the exhaust path 4 formed by the exhaust pipe 3, is purified in the middle of the exhaust gas, and is discharged to the atmosphere. The exhaust gas purification system 1 may be applied not only to a diesel engine for an automobile but also to a gasoline engine, a gas turbine engine, etc., and is not limited to an internal combustion engine for an automobile, for example, a stationary internal combustion engine such as a power generation unit. It may be applied to an institution.

The urea water addition system 5 is a system for adding urea water to the exhaust flowing in the exhaust path 4 in the exhaust purification system 1, and includes a urea water tank 6, a urea water pump 7, a urea water pipe 8, and an injector 9. , And a reduction catalyst 10. The urea water tank 6 stores an aqueous solution of urea, which is urea water. When the urea water pump 7 is energized, the urea water stored in the urea water tank 6 is discharged into the urea water path 11 composed of the urea water pipe 8 and supplied to the injector 9. The injection port at the tip of the injector 9 penetrates the exhaust pipe 3 and is exposed in the exhaust path 4, and when energized, the injector 9 injects the urea water supplied from the urea water pump 7 through the urea water path 11. Urea water is added to the exhaust gas that is injected from the mouth into the exhaust path 4 and is discharged from the internal combustion engine 2 and flows through the exhaust path 4. The added urea water is not immediately used for purifying NOx contained in the exhaust gas, but is hydrolyzed to ammonia and then accumulated in the reduction catalyst 10. When the exhaust gas and urea water mixed in the exhaust path 4 flow into the reduction catalyst 10, NOx contained in the exhaust gas is purified by chemically reacting with urea contained in the urea water in the reduction catalyst 10.

As shown in FIG. 2, the urea water addition system 5 has an electronic control device 12, an inlet side NOx sensor 13, an outlet side NOx sensor 14, an inlet side temperature sensor 15, and an outlet side as an electrical configuration. It has a temperature sensor 16 and a pressure sensor 17. The inlet-side NOx sensor 13 and the inlet-side temperature sensor 15 are provided between the internal combustion engine 2 and the reduction catalyst 10 in the exhaust path 4, and are provided on the inlet side of the reduction catalyst 10 in the flow direction of the exhaust gas flowing in the exhaust path 4. Has been done. The inlet-side NOx sensor 13 detects the concentration of NOx contained in the exhaust gas flowing into the reduction catalyst 10, and outputs a detection signal indicating the detected concentration of NOx to the electronic control device 12. The inlet side temperature sensor 15 detects the temperature of the exhaust gas flowing into the reduction catalyst 10, and outputs a detection signal indicating the detected exhaust gas temperature to the electronic control device 12.

The outlet-side NOx sensor 14 and the outlet-side temperature sensor 16 are provided between the reduction catalyst 10 and the atmosphere side in the exhaust path 4, and are provided on the outlet side of the reduction catalyst 10 in the flow direction of the exhaust gas flowing in the exhaust path 4. ing. The outlet-side NOx sensor 14 detects the concentration of NOx contained in the exhaust gas flowing out from the reduction catalyst 10, and outputs a detection signal indicating the detected concentration of NOx to the electronic control device 12. The outlet side temperature sensor 16 detects the temperature of the exhaust gas flowing out from the reduction catalyst 10, and outputs a detection signal indicating the detected exhaust gas temperature to the electronic control device 12.

The pressure sensor 17 is provided in the middle of the urea water pipe 8, detects the pressure of the urea water discharged from the urea water pump 7, and sends a detection signal indicating the detected pressure of the urea water to the electronic control device 12. Output.

In the above configuration, the temperature of the reduction catalyst 10 is indirectly detected by the temperature sensors 14 and 16 provided on the inlet side and the outlet side of the reduction catalyst 10, respectively, but the inlet side or the outlet side of the reduction catalyst 10 is detected. The temperature of the reduction catalyst 10 may be indirectly detected by a temperature sensor provided on any one of the above. Further, the temperature of the reduction catalyst 10 may be directly detected by the temperature sensor provided on the reduction catalyst 10.

The electronic control device 12 has a microcomputer (hereinafter referred to as a microcomputer) 18 (corresponding to a control unit) having a CPU, a ROM, a RAM, and an I / O, and is a computer program stored in the ROM. Is executed to control the urea water addition system 5. When the detection signals are input from the various sensors 13 to 17 described above, the microcomputer 18 specifies the NOx concentration, the exhaust temperature, and the pressure of the urea water from the input detection signals to perform various controls. The microcomputer 18 outputs an energization signal to the urea water pump 7 to control the discharge of urea water from the urea water pump 7, and outputs an energization signal to the injector 9 to control the injection of urea water from the injector 9. do.

Here, the drive circuit for driving the injector 9 will be described. As shown in FIG. 3, the drive circuit 19 of the injector 9 has a coil 20 which is a component of the electromagnet actuator, and when the output of the energization signal from the microcomputer 18 to the injector 9 is started and the energization is started, the energization is started. The injection of urea water from the injector 9 is started. Further, the drive circuit 19 stops the output of the energization signal from the microcomputer 18 to the injector 9, and when the energization to the drive circuit 19 is stopped, the injection of urea water from the injector 9 is stopped.

The electronic control device 12 described above includes a high-side switch circuit 21 and a low-side switch circuit 22 as a configuration for controlling the drive circuit 19. The high-side switch circuit 21 is connected to one end side of the coil 20 and switches and controls the power supplied from the vehicle-mounted battery 23 according to a control signal input from the microcomputer 18, so that the current value of the drive current flowing through the coil 20 is changed. It operates so as to reach a preset target current value. The target current value is a current value of a drive current that can hold the fuel injection valve of the injector 9 in the valve open state.

The low-side switch circuit 22 is connected to the other end side of the coil 20, and is turned on in the energized state of the coil 20 according to the control signal input from the microcomputer 18, so as to discharge the drive current flowing through the coil 20. Operate. The low side switch circuit 22 is grounded via the current detection circuit 24. The current detection circuit 24 is, for example, a circuit including a resistor, and outputs the current value of the current flowing through the resistor to the microcomputer 18. The microcomputer 18 inputs the current value of the current flowing through the resistor from the current detection circuit 24, and detects the current value of the drive current flowing through the coil 20.

When the microcomputer 18 starts energizing the drive circuit 19, the microcomputer 18 detects a failure due to a short circuit or disconnection in the drive circuit 19 by using the current value input from the current detection circuit 24. That is, when a short circuit or disconnection failure occurs in the drive circuit 19, the current value of the drive current flowing through the coil 20 (corresponding to the physical quantity during the energization period) becomes abnormal, so that the microcomputer 18 inputs from the current detection circuit 24. By monitoring the current value of the drive current according to the current value to be applied and determining whether the current value of the drive current is normal or abnormal, it is possible to detect a failure of the drive circuit 19. The microcomputer 18 monitors the drive current during the energization period of the drive circuit 19, and determines that the current value of the drive current does not exceed the preset current threshold for detecting the battery short, and the battery short occurs. On the other hand, if it is determined that the current value of the drive current exceeds the current threshold for detecting the battery short circuit, it is determined that the battery short circuit has occurred. Further, when the microcomputer 18 determines that the current value of the drive current during the energization period of the drive circuit 19 exceeds the preset current threshold value for ground short circuit detection, it is specified that the ground short circuit has not occurred. On the other hand, if it is determined that the current value of the drive current does not exceed the current threshold value for detecting the ground short, it is determined that the ground short has occurred.

It should be noted that the rise of the drive current varies due to the variation in the voltage of the vehicle-mounted battery 23, the variation in the impedance of the coil 20, the variation in the parts of the high-side switch circuit 21, the low-side switch circuit 22, and the current detection circuit 24, and the like. It is preferable to set the current threshold value for short circuit detection in consideration of the above-mentioned variation. For example, it is preferable to sample the tendency of the rise of the drive current for each fuel injection valve in advance, obtain the range of variation in the rise of the normal drive current, and set the current threshold value for short circuit detection according to the range of the obtained variation. .. Further, the timing for comparing the current value of the drive current and the current threshold value for short circuit detection may be set in consideration of the above-mentioned variation.

In such a method of monitoring the drive current during the energization period of the drive circuit 19 and comparing the current value of the drive current with the current threshold value to detect a failure, the injection amount required for one injection is small. If the energization period becomes short, it is not possible to secure a sufficient period for monitoring the drive current. The microcomputer 18 performs the following processing in consideration of this point.

Next, the operation of the above configuration will be described with reference to FIGS. 4 to 11. Here, a method of detecting a battery short circuit and a method of detecting a ground short circuit will be described.

(1) Method of Detecting Battery Short In the method of detecting a battery short, the microcomputer 18 performs an injector drive process and a battery short detection process.
As shown in FIG. 4, when the injector drive process is started, the microcomputer 18 sets the injection request integration period to "0" and initializes it (S1), and waits for the occurrence of the injection request event (S2). When the microcomputer 18 determines that the injection request event has occurred (S2: YES), the microcomputer 18 specifies the injection request period due to the occurrence of the injection request event, adds the injection request period to the injection request integration period at that time, and injects. Update the required integration period (S3). The microcomputer 18 compares the updated injection request integration period with the preset first set period (S4). The first setting period is, for example, 10 milliseconds.

When the microcomputer 18 determines that the injection request integration period does not exceed the first set period (S4: NO), the microcomputer 18 returns to step S2 described above, and repeats step S2 and subsequent steps. When the microcomputer 18 determines that the injection request integration period has exceeded the first set period (S4: YES), the microcomputer 18 outputs an energization signal to the injector 9 over the injection request integration period exceeding the first set period. The drive circuit 19 is energized (S5) over the injection request integration period, and the injector drive process is completed.

As shown in FIG. 5, when the battery short-circuit detection process is started, the microcomputer 18 determines whether or not the drive circuit 19 is in the energization period (S11). When the microcomputer 18 determines that the drive circuit 19 is being energized (S11: YES), the microcomputer 18 specifies the current value of the drive current flowing through the coil 20 according to the current value input from the current detection circuit 24, and specifies the current value. The current value of the drive current is compared with the current threshold value for detecting a battery short circuit (S12). The current threshold for detecting a battery short is, for example, 2.5 amps.

When the microcomputer 18 determines that the current value of the drive current does not exceed the current threshold value for detecting the battery short circuit (S12: NO), it determines whether or not the drive circuit 19 is in the non-energized period (S13). .. When the microcomputer 18 determines that the drive circuit 19 is not in the non-energized period (S13: NO), the microcomputer 18 returns to the above-mentioned step S12 and repeats the steps S12 and subsequent steps. When the microcomputer 18 determines that the drive circuit 19 is in the non-energized period (S13: YES), it identifies that the battery short circuit has not occurred, identifies it as normal (S14), and performs the battery short circuit detection process. finish. On the other hand, when the microcomputer 18 determines that the current value of the drive current exceeds the current threshold value for detecting the battery short circuit (S12: YES), it identifies that the battery short circuit has occurred (S15), and performs the battery short circuit detection process. To finish.

That is, as shown in FIG. 6, in the microcomputer 18, in the configuration in which the drive circuit 19 is energized each time an injection request event occurs (t1, t2, ... T5, t6), the injection amount required for one injection is If the amount is small and the energization period per injection is less than a predetermined period, it is not possible to secure a sufficient period for monitoring the drive current. As a result, even if a battery short occurs, the current value of the drive current does not exceed the current threshold value for detecting the battery short, so that the occurrence of the battery short cannot be specified.

On the other hand, in the present embodiment, as shown in FIG. 7, the microcomputer 18 does not energize the drive circuit 19 every time an injection request event occurs, but calculates the injection request integration period as described above. By energizing the drive circuit 19 when the injection request integration period exceeds the first set period (t1, t2), the energization period per injection can be made longer than the predetermined period, and the drive current can be extended. It is possible to secure a sufficient period for monitoring. That is, by summarizing the injection timings due to the occurrence of the five injection request events shown in FIG. 6 into one, it is possible to sufficiently secure the period for monitoring the drive current. As a result, when a battery short occurs, the current value of the drive current exceeds the current threshold for detecting the battery short, and it is determined that the current value of the drive current exceeds the current threshold for detecting the battery short. , It becomes possible to identify the occurrence of a battery short circuit.

(2) Method for Detecting Ground Short The microcomputer 18 has a ground short detection mask period, and performs injector drive processing and ground short detection processing.
As shown in FIG. 8, when the injector drive process is started, the microcomputer 18 performs the same process as the injector drive process in the above-described method for detecting a battery short circuit (S21 to S25). The second set period to be compared with the injection request integration period is, for example, 10 milliseconds, as in the first set period.

As shown in FIG. 9, when the ground short detection process is started, the microcomputer 18 performs the same process as the battery short detection process of the above-described method for detecting a battery short (S31 to S35). In this case, the microcomputer 18 compares the current value of the drive current flowing through the coil 20 according to the current value input from the current detection circuit 24 with the current threshold value for detecting a ground short (S32). The current threshold for detecting a ground short is, for example, 0.2 amperes.

The microcomputer 18 determines that the current value of the drive current exceeds the current threshold value for detecting a ground short circuit (S32: NO), and determines that the drive circuit 19 is in the non-energized period (S33: YES). It is specified that no ground short has occurred, it is specified as normal (S34), and the ground short detection process is terminated. On the other hand, when the microcomputer 18 determines that the current value of the drive current does not exceed the current threshold value for detecting the ground short (S32: YES), it identifies that the ground short has occurred (S35), and performs the ground short detection process. To finish.

That is, as shown in FIG. 10, in the microcomputer 18, in the configuration in which the drive circuit 19 is energized each time an injection request event occurs (t1, t2, ... T5, t6), the injection amount required for one injection is If the amount is small and the energization period per injection is less than a predetermined period, it is not possible to secure a sufficient period for monitoring the drive current. As a result, if the ground short detection mask period is set longer than the energization period, it is not possible to identify the factor that the current value of the drive current does not exceed the current threshold value for ground short detection even if the ground short occurs. , The occurrence of ground short cannot be specified.

On the other hand, in the present embodiment, as shown in FIG. 11, the microcomputer 18 does not energize the drive circuit 19 every time an injection request event occurs, but calculates the injection request integration period as described above. By energizing the drive circuit 19 when the injection request integration period exceeds the second set period, the energization period per injection can be made longer than the predetermined period, and the period for monitoring the drive current can be set. It can be secured sufficiently. That is, by summarizing the injection timings due to the occurrence of the five injection request events shown in FIG. 10 into one, it is possible to sufficiently secure the period for monitoring the drive current. As a result, even if a ground short detection mask period is provided, if a ground short occurs, the current value of the drive current will not exceed the current threshold value for detecting the battery short even during the energization period, and the current value of the drive current will increase. By determining that the current threshold value for detecting a ground short is not exceeded, the occurrence of a ground short can be identified.

As described above, according to the first embodiment, the following effects can be obtained.
In the electronic control device 12, the injection timing due to the occurrence of a plurality of injection request events is summarized into one, and the energization period per one injection is adjusted to be long. A sufficient period for monitoring the drive current can be secured, and a failure of the drive circuit 19 can be appropriately detected. In the urea SCR system, which purifies NOx contained in the exhaust gas by injecting urea water into the exhaust gas discharged from the internal combustion engine 2, the added urea water is not immediately used for purifying NOx and is added to ammonia. Since it is decomposed and then accumulated in the reduction catalyst 10, even if the injection timing of urea water is delayed, NOx cannot be purified. By paying attention to this point and adjusting the energization period per injection, it is possible to appropriately detect the failure of the drive circuit 19 without hindering the purification of NOx.

Further, when the injection request integration period is calculated by integrating the injection request period for each occurrence of the injection request event and it is determined that the calculated injection request integration period exceeds the set period, a plurality of injection request events are performed. The injection timing due to the generation is summarized at one time. By freely adjusting the set period, the period for monitoring the drive current can be freely adjusted, and even if the current threshold value for detection varies, it can be easily dealt with.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. 12 to 16. The same parts as those in the first embodiment described above will be omitted, and different parts will be described. The first embodiment is configured to monitor the drive current, while the second embodiment is configured to monitor the terminal voltage.

As shown in FIG. 12, the electronic control device 31 includes a microcomputer 32 (corresponding to a control unit), a high-side switch circuit 21 described in the first embodiment, a low-side switch circuit 22, and a current detection circuit 24. In addition, it has a terminal voltage detection circuit 25. The terminal voltage detection circuit 25 outputs the voltage value of the terminal voltage applied to the coil 20 to the microcomputer 32. The microcomputer 32 detects the voltage value of the terminal voltage applied to the coil 20 by inputting the voltage value of the terminal voltage applied to the coil 20 from the terminal voltage detection circuit 25.

When the energization of the drive circuit 19 is stopped, the microcomputer 32 uses the voltage value input from the terminal voltage detection circuit 25 to detect a failure due to a short circuit or disconnection in the drive circuit 19. That is, when a short circuit or disconnection failure occurs in the drive circuit 19, the voltage value of the terminal voltage applied to the coil 20 (corresponding to the physical amount during the non-energized period) becomes abnormal, so that the microcomputer 18 detects the terminal voltage. The voltage value of the terminal voltage is monitored by the voltage value input from the circuit 25, it is determined whether the voltage value of the terminal voltage is normal or abnormal, and a failure of the drive circuit 19 can be detected. The microcomputer 18 monitors the terminal voltage during the non-energization period of the drive circuit 19, and if it is determined that the voltage value of the terminal voltage exceeds the preset voltage threshold for detecting a ground short, a ground short occurs. On the other hand, if it is determined that the voltage value of the terminal voltage does not exceed the voltage threshold for detecting the ground short, it is specified that the ground short has occurred.

As shown in FIG. 13, when the injector drive process is started, the microcomputer 32 performs the same process as the injector drive process of the method of detecting a short circuit based on the current value of the drive current described above (S41 to S45). The third set period to be compared with the injection request integration period is, for example, 10 milliseconds, as in the first set period and the second set period.

As shown in FIG. 14, when the ground short detection process is started, the microcomputer 32 determines whether or not the drive circuit 19 is in the non-energized period (S51). When the microcomputer 32 determines that the drive circuit 19 is in the non-energized period (S51: YES), the microcomputer 32 grounds the voltage value of the terminal voltage applied to the coil 20 according to the voltage value input from the terminal voltage detection circuit 25. Compare with the voltage threshold for short circuit detection (S52). The voltage threshold value for detecting a ground short is, for example, 0.5 volt.

When the microcomputer 32 determines that the voltage value of the terminal voltage exceeds the voltage threshold value for detecting a ground short circuit (S52: NO), it determines whether or not the drive circuit 19 is being energized (S13). When the microcomputer 32 determines that the drive circuit 19 is not in the energization period (S53: NO), the microcomputer 32 returns to the above-mentioned step S52 and repeats the steps S52 and subsequent steps. When the microcomputer 32 determines that the drive circuit 19 is being energized (S53: YES), it identifies that a ground short has not occurred, identifies it as normal (S54), and ends the ground short detection process. do. On the other hand, when the microcomputer 32 determines that the voltage value of the terminal voltage does not exceed the voltage threshold value for detecting the ground short (S52: YES), it identifies that the ground short has occurred (S55), and performs the battery short detection processing. To finish.

That is, as shown in FIG. 15, in the configuration in which the drive circuit 19 is energized each time an injection request event occurs in the microcomputer 32 (t1, t2, ... T5, t6), the injection amount required for one injection is If the amount is small and the non-energization period per injection is less than a predetermined period, it is not possible to secure a sufficient period for monitoring the terminal voltage. As a result, even if a ground short occurs, the terminal voltage does not drop below the voltage threshold value for detecting the ground short, so that the occurrence of the ground short cannot be specified.

On the other hand, in the present embodiment, as shown in FIG. 16, in the microcomputer 32, instead of energizing the drive circuit 19 every time an injection request event occurs, the injection request integration period is calculated as described above. By energizing the drive circuit 19 when the injection request integration period exceeds the third set period (t1, t2), the non-energization period per injection can be made longer than the predetermined period, and the terminal A sufficient period for monitoring the voltage can be secured. That is, by summarizing the injection timings due to the occurrence of the five injection request events shown in FIG. 15 into one, it is possible to sufficiently secure the period for monitoring the terminal voltage. As a result, when a ground short occurs, the voltage value of the terminal voltage drops to less than the voltage threshold for detecting the ground short, and it is determined that the voltage value of the terminal voltage drops to the voltage threshold for detecting the ground short. By doing so, it becomes possible to identify the occurrence of a ground short.

As described above, according to the second embodiment, the same effect as that of the first embodiment can be obtained even in the configuration of monitoring the terminal voltage instead of monitoring the drive current. That is, in the electronic control device 31, the period for monitoring the terminal voltage is sufficiently set by collecting the injection timings due to the occurrence of a plurality of injection request events into one and adjusting the non-energization period per injection for a long time. It can be secured, and the failure of the drive circuit 19 can be appropriately detected.

(Other embodiments)
The present disclosure has been described in accordance with the examples, but it is understood that the present disclosure is not limited to the examples and structures. The present disclosure also includes various modifications and modifications within a uniform range. In addition, various combinations and forms, as well as other combinations and forms containing only one element, more or less, are also within the scope of the present disclosure.
The first setting period, the second setting period, the third setting period, the current threshold value, and the voltage threshold value may be values other than those illustrated.

In the drawings, 12 and 31 are electronic control devices, 2 is an internal combustion engine, 9 is an injector, 18 and 32 are microcomputers (control units), and 19 is a drive circuit.

Claims (8)

Controls the energization of the drive circuit (19) of the injector (9) that injects urea water into the exhaust discharged from the internal combustion engine (2), and monitors the physical quantity during the energization period or non-energization period of the drive circuit. A control unit (18) for detecting a failure of the drive circuit is provided.
An electronic control device that adjusts the energization period or non-energization period per injection and detects a failure of the drive circuit. The electronic control device according to claim 1, wherein when the energization period per injection from the injector is less than a predetermined period, the energization period per injection is adjusted to be longer than the predetermined period. The electronic control device according to claim 2, wherein the energization period per injection is adjusted to be longer than a predetermined period by collecting the injection timings due to the occurrence of a plurality of injection request events into one. The electronic control device according to claim 1, wherein when the non-energized period per injection from the injector is less than a predetermined period, the non-energized period per injection is adjusted to be longer than the predetermined period. The electronic control device according to claim 4, wherein the non-energized period per injection is adjusted to be longer than a predetermined period by collecting the injection timings due to the occurrence of a plurality of injection request events into one. When the injection request integration period is calculated by integrating the injection request period each time an injection request event occurs and it is determined that the calculated injection request integration period exceeds the set period, multiple injection request events occur. The electronic control device according to claim 3 or 5, wherein the injection timing is summarized at one time. The electronic control device according to any one of claims 1 to 6, wherein the drive current is monitored as a physical quantity during the energization period or the non-energization period of the drive circuit. The electronic control device according to any one of claims 1 to 6, wherein the terminal voltage is monitored as a physical quantity during the energization period or the non-energization period of the drive circuit.

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