JP2006009598A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device capable of appropriately performing regeneration processing even when abnormality occurs in a differential pressure detector. <P>SOLUTION: A microcomputer 19 stores the injection quantity of main injection at this point of time as a learning injection quantity when an engine is put in an idling state after a change-over switch is pressed to output a setting signal. When the differential pressure indicated by a sensor signal from a differential pressure sensor 31 is outside a predetermined range during the drive of the engine 2, the microcomputer 19 determines that abnormality has occurred in the differential pressure sensor 31. The injection quantity of main injection at the point of time is compared with the upper limit injection quantity with a predetermined quantity added to the stored learning injection quantity, and when the injection quantity of main injection is larger than the upper limit injection quantity, post-injection is instructed to a drive unit 18. At this time, the injection timing and injection quantity of post-injection are computed based on the difference quantity of two above-mentioned injection quantities. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection device for a vehicle diesel engine.

2. Description of the Related Art Conventionally, exhaust purification apparatuses that capture and purify particulates (particulate matter) contained in exhaust gas from a vehicle diesel engine are known. For example, the exhaust purification device of Patent Document 1 includes a differential pressure detector that detects a pressure loss when exhaust gas passes through a filter that captures particulates, and the pressure loss detected by the detector is exhausted. Correction is made based on the temperature of the gas, the engine speed, and the number of regeneration times of the filter, and the amount of particulates captured by the filter is accurately calculated. When the calculated amount of particulates exceeds a predetermined amount, the conventional apparatus turns on a lamp indicating that the filter regeneration process is necessary, and the filter regeneration process is performed by the user to remove the captured particulates. Encourage
JP-A-7-11935

  However, in the conventional apparatus, when an abnormality occurs in the differential pressure detector, the amount of particulate trapped by the exhaust gas purification apparatus cannot be calculated, and the regeneration process cannot be performed appropriately. For this, there may be a method of providing a plurality of differential pressure detectors and calculating the amount of captured particulates using the detection results from a normal differential pressure detector. It becomes complicated and is not preferable in terms of design and cost.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel injection device capable of appropriately performing the regeneration process even when an abnormality occurs in the differential pressure detector.

  In order to achieve the above object, a fuel injection device according to claim 1 is a fuel injection device in a diesel engine mounted on a vehicle, and particles contained in exhaust gas from the engine are disposed at a subsequent stage of the diesel engine. An exhaust purification device that captures the particulate matter is connected, and includes a differential pressure detector that detects a pressure difference between the exhaust gas flowing into the device and the exhaust gas flowing out from the device, and the fuel injection device includes a differential pressure detector When the pressure difference detected by the engine exceeds a predetermined pressure difference, in addition to fuel injection that generates driving force in the diesel engine, fuel injection that burns particulate matter trapped in the exhaust purification device is performed. When the diesel engine is in an idling state when an abnormality occurs in the pressure detector, the amount of fuel injection that causes the engine to generate a driving force is measured. In addition, when the measured injection amount exceeds the set upper limit injection amount, fuel injection is performed to burn particulate matter trapped in the exhaust purification device regardless of the detection result of the differential pressure detector. An abnormality control means is provided.

  When the trapped amount of particulate matter in the exhaust purification device increases, the fluid resistance when exhaust from the diesel engine passes through the device increases, and the energy required for the exhaust gas to pass through the exhaust purification device increases. It must be supplied from a diesel engine. That is, even in the case of the same engine speed, it is necessary to increase the amount of fuel injection that causes the diesel engine to generate driving force (generate energy) as the amount of particulate matter trapped in the exhaust purification device increases. In the fuel injection device of the present invention, when the diesel engine is in an idling state, the abnormality control means measures an injection amount of fuel injection that causes the engine to generate a driving force. When the measured injection amount exceeds the set upper limit injection amount, that is, when the trapped amount of particulate matter in the exhaust purification device exceeds the set upper limit injection amount and the corresponding trap amount, there is a difference. Regardless of the detection result of the pressure detector, fuel injection for burning the particulate matter captured by the exhaust gas purification device is performed. Thus, the fuel injection device can appropriately perform the regeneration process for the exhaust gas purification device even when an abnormality occurs in the differential pressure detector.

  According to a second aspect of the present invention, the abnormality control means generates a driving force when the diesel engine is in an idling state when the trapped amount of particulate matter in the exhaust purification device is substantially zero. It is desirable to set the injection amount obtained by adding the predetermined amount to the measured injection amount as the upper limit injection amount while measuring the injection amount of the fuel injection. As a result, the upper limit injection amount, which is a criterion for determining whether or not to perform the regeneration process for the exhaust purification device, is appropriately set based on the case where there is no energy loss when the exhaust from the diesel engine passes through the exhaust purification device. The injection amount can be set.

  According to a third aspect of the present invention, it is desirable for the abnormality control means to vary the predetermined amount based on the temperature of the coolant that cools the diesel engine. Immediately after starting the vehicle, the differential pressure detector may not be able to accurately measure the pressure difference due to initialization operations of various in-vehicle devices. Based on the temperature of the coolant that cools the diesel engine, it is possible to set an appropriate upper limit injection amount in view of the initialization operation immediately after the vehicle is started, etc. by making the predetermined amount variable. Become.

  As described in claim 4, it is desirable that the abnormality control means sets the predetermined injection amount as the upper limit injection amount. This eliminates the need for dedicated hardware and software for setting the upper limit injection amount, which is preferable in terms of design and cost.

  It is desirable to provide an instruction means for instructing to set the upper limit injection amount, and when the abnormality control means receives an instruction from the instruction means, it is desirable to set the upper limit injection amount. Thus, the abnormality control means can reliably set the upper limit injection amount at an appropriate time according to the instruction from the instruction means.

  Preferably, the instructing means instructs to set the upper limit injection amount immediately after the exhaust purification device is replaced or immediately after the combustion of the particulate matter is completed. . Immediately after replacing the exhaust purification device or immediately after burning the particulate matter captured by the exhaust purification device, the particulate matter is not captured by the device, and a more appropriate upper limit injection amount can be set. It is.

  According to the seventh aspect of the present invention, the abnormality control means is based on the difference between the upper limit injection amount and the injection amount of the fuel injection that causes the engine to generate driving force in the idling state of the diesel engine. It is desirable to determine the fuel injection timing and the fuel injection amount of the fuel injection for burning the particulate matter trapped in the fuel. As described above, when the amount of trapped particulate matter in the exhaust purification device increases, the amount of fuel injection that causes the diesel engine to generate driving force also increases. This means that the larger the difference amount described above, the larger the trapped amount of particulate matter in the exhaust gas purification device. By using the difference amount, the particulate matter trapped in the exhaust gas purification device. It is possible to determine an appropriate fuel injection timing and fuel injection amount in the fuel injection for burning the fuel.

  According to the eighth aspect of the present invention, the abnormality control means sets a plurality of upper limit injection amounts, and each of the set upper limit injection amounts and fuel injection for generating driving force in the engine in an idling state of the diesel engine The fuel injection timing and the fuel injection amount for fuel injection for burning the particulate matter trapped by the exhaust gas purification device may be determined based on the injection amount. As described above, regarding the fuel injection for burning the particulate matter trapped by the exhaust purification device, it is necessary to determine the injection timing and the injection amount according to the trapped amount of the particulate matter in the device. By setting a plurality of upper limit injection amounts, the fuel injection amount that generates driving force in the diesel engine is selected according to the trapped amount of particulate matter in the exhaust emission control device corresponding to the upper limit injection amount closest to the injection amount. Thus, it is possible to determine an appropriate fuel injection timing and fuel injection amount in the fuel injection for burning the particulate matter captured by the exhaust gas purification device.

  According to a ninth aspect of the present invention, in the idling state of the diesel engine, the abnormality control means sets the engine speed to a predetermined value even if the injection amount of fuel injection that causes the engine to generate driving force is the upper limit of idle control. When the target rotational speed is not reached, it is desirable to perform fuel injection for burning the particulate matter trapped in the exhaust purification device. This is because it is clear that a large amount of particulate matter is trapped in the exhaust purification device when the engine speed does not reach the predetermined target speed even when the above-mentioned injection amount is set to the upper limit of idle control. is there.

  According to a tenth aspect of the present invention, the abnormality control means desirably determines that an abnormality has occurred in the differential pressure detector when the detection result of the differential pressure detector is outside a predetermined range. This is because when the detection result of the differential pressure detector is outside the predetermined range, it is clear that an abnormality has occurred in the differential pressure detector.

  According to the eleventh aspect, when the diesel engine is in an idling state, the abnormality control means measures the fuel injection amount that causes the engine to generate a driving force, and the measured injection amount sets the upper limit injection amount. If it exceeds, it is desirable to determine that an abnormality has occurred in the differential pressure detector. Even if the detected value by the differential pressure detector belongs to the predetermined range and the detected pressure difference is less than the predetermined pressure difference, the fuel injection for generating the driving force in the engine in the idling state of the diesel engine is performed. This is because when the injection amount exceeds the upper limit injection amount, an abnormality occurs in the differential pressure detector, and accurate detection is not performed.

  FIG. 1 is a block diagram showing an overall configuration of a fuel injection device according to an embodiment of the present invention. The fuel injection device 1 is applied to a fuel injection device of an engine 2 that is a diesel engine mounted on a vehicle. An exhaust purification device 3 is connected to the rear stage of the engine 2, and exhaust gas discharged from the engine is purified by the exhaust purification device 3 and then released to the outside of the vehicle.

  First, the configuration and operation of the exhaust purification device 3 will be described.

  As shown in FIG. 1, the exhaust purification device 3 sucks exhaust gas discharged from the engine 2, passes through a filter (not shown), and captures particulates (particulate matter) contained in the exhaust gas. Purify exhaust gas. The purified exhaust gas is discharged outside the vehicle. The particulate matter captured by the filter is configured to be burned and removed (recyclable) by passing exhaust gas containing fuel vapor through an oxidation catalyst (not shown) provided in the apparatus. Is done. Further, the exhaust purification device 3 includes a differential pressure sensor 31 that detects a pressure difference (hereinafter referred to as a differential pressure) between the exhaust gas sucked from the engine 2 and the exhaust gas discharged to the outside of the vehicle, and outputs the sensor from the sensor. It transmits also to the fuel-injection apparatus 1 as a signal.

  Next, the configuration and operation of the fuel injection device 1 will be described.

  As shown in FIG. 1, the high-pressure fuel pump 11 is an in-vehicle supply pump, and pumps up fuel stored in a fuel tank (not shown) mounted on the vehicle to increase the pressure to a target pressure (several hundred to several thousand atmospheres). And output as high-pressure fuel. Note that the target pressure described above can be changed.

  The common rail 12 stores the high-pressure fuel output from the high-pressure fuel pump 11 and pumps the stored high-pressure fuel to each of injectors A13 to D16 described later. A pressure sensor (not shown) is attached to the common rail 12, and the pressure of the high-pressure fuel stored in the common rail 12 is also detected by the sensor.

  Each of the injectors A13 to D16 includes an electromagnetic fuel injection valve (not shown). When a drive current is supplied, the injector A13 to D16 opens the injection valve, and the high pressure fuel pumped from the common rail 12 is supplied to the first cylinder 21 of the engine 2. -Injection into a combustion chamber (not shown) in each of the fourth cylinders 24. The above-described fuel injection valve may be a mechanical fuel injection valve that operates by a cam or the like.

  The injection control ECU 17 includes a drive unit 18 that supplies a drive current to each of the injectors A13 to D16, and a microcomputer 19 that instructs the drive unit 18 to supply a drive current to each of the injectors A13 to D16. Control fuel injection performed by D16. The injection control ECU 17 includes a drive signal line 1A to 1D for instructing the drive unit 18 to supply drive current to each of the injectors A13 to D16, and a drive unit 18 to the injector 19 to the injector A13. A single diagnostic signal line 1E is provided for notifying that driving current is supplied to D16. Hereinafter, operations of the drive unit 18 and the microcomputer 19 will be described in detail.

  The drive unit 18 includes a drive current output circuit 1F and a drive current detection circuit 1G. When a Hi signal is output to each of the drive signal lines 1A to 1D, the drive current output circuit 1F is activated, and each of the injectors A13 to D16. Supply drive current to When the drive current detection circuit 1G detects that the drive current is output from the drive current output circuit 1F, the drive current detection circuit 1G outputs a Hi signal to the diagnosis signal line 1E. When the drive current reaches the maximum (peak), the diagnosis signal line A Low signal is output to 1E. That is, when the drive current is normally supplied to the injectors A13 to D16, the drive current detection circuit 1G outputs a pulse to the diagnosis signal line 1E. Note that while the drive current is not output from the drive current output circuit 1F, the drive current detection circuit 1G outputs a Low signal to the diagnosis signal line 1E. FIG. 2 shows an example of a signal output to each drive signal line, a drive current output from the drive unit 18, and a pulse output to the diagnosis signal line 1E.

  The microcomputer 19 is composed of a known computer, and includes an accelerator sensor (not shown) that detects the degree of depression of the accelerator pedal, a speed sensor (not shown) that detects the speed of the engine 2, and crankshafts (not shown) in each cylinder of the engine 2. Based on various sensor signals acquired from a rotation angle sensor (not shown) that detects the rotation angle, the drive unit 18 is instructed to drive each of the injectors A13 to D16.

  Specifically, the microcomputer 19 describes three fuel injections performed in the compression process of each cylinder of the engine 2 and one fuel injection performed in the combustion process (hereinafter referred to as main injection) from the acquired various sensor signals. ) And the injection timing and the injection amount are calculated. When it is determined from the sensor signal acquired from the rotation angle sensor that each cylinder of the engine 2 has entered the calculated injection timing, the microcomputer 19 injects fuel into the cylinder among the drive signal lines 1A to 1D. The Hi signal is output to the drive signal line corresponding to the injector that performs the operation only for the period corresponding to the calculated injection amount, and the drive unit 18 is instructed to perform the fuel injection to the cylinder. Since the engine 2 of the present embodiment is a diesel engine, combustion occurs immediately after the main injection for each cylinder is performed, and a driving force is generated on the crankshaft of the cylinder. That is, the three fuel injections performed in the compression process and the one main injection performed in the combustion process are mainly fuel injections that cause the engine 2 to generate a driving force.

  Further, when the amount of particulates captured by the exhaust purification device 3 exceeds a predetermined amount, the microcomputer 19 burns the particulates captured by the exhaust purification device 3 in the exhaust process of each cylinder of the engine 2. The drive unit 18 is instructed to perform fuel injection called post injection for removal (regeneration processing).

  Specifically, the microcomputer 19 acquires a sensor signal output from the differential pressure sensor 31, and calculates the amount of particulate trapped by the exhaust purification device 3 from the differential pressure indicated by the signal. When the calculated amount of particulates exceeds a predetermined amount, the microcomputer 19 determines that it is necessary to perform post-injection, and in addition to the above-described differential pressure, the temperature of exhaust gas detected by a temperature sensor or pressure sensor (not shown). The post-injection injection timing and the injection amount are calculated based on the engine pressure detected by the engine, the pressure, and the engine speed. When it is determined from the sensor signal acquired from the rotation angle sensor that each cylinder of the engine 2 has entered the calculated post injection timing, the microcomputer 19 performs the post injection among the drive signal lines 1A to 1D. The Hi signal is output to the corresponding drive signal line for a period corresponding to the calculated post injection amount. The above-described post-injection is a fuel injection that does not cause the engine 2 to generate a driving force (not related to the generation of the driving force).

  In particular, in the present embodiment, when an abnormality occurs in the differential pressure sensor 31, the microcomputer 19 determines whether or not to perform the post injection based on the injection amount of the main injection at the time point and a learning injection amount described later, The injection timing and amount of post injection are calculated.

  Specifically, immediately after the exhaust purification device 3 is replaced, the microcomputer 19 monitors the number of revolutions of the engine 2 from the sensor signal of the number of revolutions sensor when a not-shown replacement switch is pressed and a setting signal is output. To do. When it is determined from the above-described rotation speed that the engine 2 is in an idling state, the microcomputer 19 stores the injection amount of the main injection at the time as the learned injection amount. When the differential pressure indicated by the sensor signal from the differential pressure sensor 31 is outside a predetermined range during the driving of the engine 2 (for example, the sensor signal is equal to the GND voltage or the power supply voltage, and the differential pressure indicated by the signal is negative) The microcomputer 19 determines that an abnormality has occurred in the differential pressure sensor 31. Then, the injection amount of the main injection at the time point is compared with the upper limit injection amount obtained by adding a predetermined amount to the stored learned injection amount. If the injection amount of the main injection is larger than the upper limit injection amount, the drive unit 18 Direct post injection. At that time, the post injection timing and the injection amount are also calculated based on the difference between the two injection amounts described above. Regarding the calculation of the injection timing and the injection amount of the post injection, the temperature and pressure of the exhaust gas detected by the above-described temperature sensor and pressure sensor, the engine speed detected by the rotation speed sensor, and the like are also taken into consideration.

  Note that the microcomputer 19 instructs the drive unit 18 to inject fuel so that the operation process in each cylinder of the engine 2 is shifted for each process. For example, when the first cylinder 21 of the engine 2 is in the intake process, the second cylinder 22 is in the exhaust process, the third cylinder 23 is in the combustion process, and the fourth cylinder 24 is in the compression process. Further, the microcomputer 19 calculates a target pressure based on a sensor signal from the rotation speed sensor or the pressure sensor of the common rail 12 and instructs the high-pressure fuel pump 11 of the target pressure. In addition, a control signal for controlling a super-absorber (not shown), an exhaust gas circulation device (EGR), an intake throttle valve, and the like, and a control signal for controlling various relays such as a radiator fan relay (not shown) are also output.

  FIG. 3 is a flowchart regarding the process in which the fuel injection device 1 of the present embodiment stores the learning injection amount. The processing of this flowchart is started when the microcomputer 19 acquires the setting signal output from the replacement switch immediately after the exhaust purification device 3 is replaced.

  In step 301, the microcomputer 19 acquires a sensor signal output from the rotation speed sensor, and determines whether or not the engine 2 is in an idling state from the sensor signal. If it is determined that the engine 2 is idling, the routine proceeds to step 302. Otherwise, the above determination is repeated until it is determined that the engine 2 is in the idling state. In step 302, the injection amount of the main injection at that time is stored as a learning injection amount.

  FIG. 4 is a flowchart regarding a process in which the fuel injection device 1 of the present embodiment performs post injection. The process of this flowchart is executed by the microcomputer 19 every predetermined time.

  In step 401, the microcomputer 19 acquires a sensor signal output from the differential pressure sensor 31. In step 402, it is determined whether or not the differential pressure indicated by the sensor signal acquired from the differential pressure sensor 31 in step 401 is within a predetermined range, that is, whether or not the differential pressure sensor 31 is normal. If the above-described differential pressure is within the predetermined range, that is, if it is determined that the differential pressure sensor 31 is normal, the process proceeds to step 403. If it is determined that the above-described differential pressure is outside the predetermined range, that is, it is determined that an abnormality has occurred in the differential pressure sensor 31, the process proceeds to step 406.

  In step 403, the amount of particulate trapped by the exhaust purification device 3 is calculated from the sensor signal acquired from the differential pressure sensor 31 in step 401. In step 404, it is determined whether the amount of particulates calculated in step 403 exceeds a predetermined amount. If it exceeds the predetermined amount, the process proceeds to step 405, and based on the differential pressure indicated by the differential pressure sensor 31 acquired in step 401, the temperature or pressure of the exhaust gas detected by the temperature sensor or the pressure sensor, and the rotation speed sensor detect it. The post-injection injection timing and injection amount are calculated in consideration of the engine speed and the like, and the routine proceeds to step 410. If the calculated amount of particulates is equal to or less than the predetermined amount, the process ends.

  On the other hand, in step 406, the injection amount of the main injection at the time is acquired. In step 407, a predetermined amount is added to the stored learning injection amount, and the upper limit injection amount is calculated (set). Thereby, it is possible to calculate (set) an appropriate upper limit injection amount that is a criterion for determining whether or not to perform post injection.

  In step 408, it is determined whether or not the injection amount of the main injection acquired in step 406 is larger than the learning injection amount calculated in step 407. If it is larger than the above-described upper limit injection amount, the process proceeds to step 409, where the temperature sensor or pressure sensor detects based on the difference amount between the main injection amount acquired in step 406 and the upper limit injection amount calculated in step 407. The post-injection injection timing and injection amount are calculated in consideration of the exhaust gas temperature and pressure, the engine speed detected by the engine speed sensor, etc., and the routine proceeds to step 410. By using the difference amount described above, it is possible to appropriately calculate the injection timing and the injection amount of the post injection. When the injection amount of the main injection is smaller than the above-described upper limit injection amount, the process is terminated.

  In step 410, the post injection is instructed to the drive unit 18 based on the injection timing and the injection amount of the post injection calculated in step 405 or step 409.

  As described above, the fuel injection device according to the present embodiment performs post injection when an abnormality occurs in the differential pressure sensor 31 when the injection amount of the main injection at the time exceeds the calculated upper limit injection amount. . Thus, even when an abnormality occurs in the differential pressure sensor 31 for some reason, it is possible to determine whether to perform post injection based on the injection amount of the main injection and the calculated upper limit injection amount. In other words, in the present fuel injection device, even when an abnormality occurs in the differential pressure sensor 31, it is possible to appropriately perform a regeneration process in which post injection is performed and the particulate matter captured by the exhaust gas purification device 3 is burned and removed. it can.

  Next, a first modification of the present embodiment will be described. The fuel injection device of this modification is different from the above-described embodiment in that the upper limit injection amount is calculated according to the water temperature of the cooling water (coolant) of the engine 2.

  The engine 2 of this modification includes a water temperature sensor (not shown) that detects the coolant temperature of the engine in addition to the functions of the above-described embodiment, and outputs the coolant temperature of the engine 2 as a sensor signal.

  The microcomputer 19 of the present modification calculates the above-described upper limit injection amount according to the coolant temperature of the engine 2. Specifically, the microcomputer 19 stores a correction injection amount corresponding to the coolant temperature of the engine 2. When the differential pressure indicated by the sensor signal from the differential pressure sensor 31 is outside the predetermined range, the microcomputer 19 reads the corrected injection amount corresponding to the water temperature indicated by the sensor signal of the water temperature sensor and adds it to the stored learning injection amount. The upper limit injection amount is calculated (variable). Then, when the injection amount of the main injection is larger than the calculated upper limit injection amount, the post injection is instructed to the drive unit 18. At that time, the post injection timing and the injection amount are also calculated based on the difference between the two injection amounts described above. As shown in FIG. 5, the corrected injection amount is set so as to increase as the coolant temperature of the engine 2 decreases, and is calculated when the coolant temperature of the engine 2 is low. The weight of the corrected injection amount that occupies the upper limit injection amount increases.

  Other configurations and operations are the same as those in the above-described embodiment, and thus description thereof is omitted.

  FIG. 6 is a flowchart relating to a process in which the fuel injection device 1 of the present modification performs post injection. The processing of this flowchart is provided with a step of reading out the correction injection amount corresponding to the water temperature indicated by the sensor signal from the water temperature sensor with respect to the flowchart of FIG. 4 of the above-described embodiment. Furthermore, instead of the step of adding a predetermined amount to the stored learning injection amount and calculating the upper limit injection amount, the step of adding the correction injection amount to the stored learning injection amount and calculating the upper limit injection amount Provide. In other words, all processes other than steps 607 and 608 are the same as those in the flowchart of FIG.

  In step 607, the microcomputer 19 reads the corrected injection amount corresponding to the water temperature indicated by the sensor signal from the water temperature sensor. In step 608, the stored learning injection amount is added to the corrected injection amount read in step 607 to calculate the upper limit injection amount.

  As described above, in the fuel injection device according to the present modification, the correction injection amount corresponding to the coolant temperature of the engine 2 is prepared, and the correction injection amount corresponding to the water temperature is added to the learning injection amount to obtain the upper limit injection. The amount is calculated (variable). Immediately after starting the vehicle, the differential pressure sensor 31 may not be able to accurately measure the aforementioned differential pressure due to initialization operations of various in-vehicle devices. By adding the corrected injection amount corresponding to the coolant temperature of the cooling water of the engine 2 to the learning injection amount and calculating the upper limit injection amount, it is possible to set the upper limit injection amount in consideration of the initialization operation immediately after the vehicle is started. it can.

  Next, a second modification of the present embodiment will be described. The fuel injection device of this modification is different from the above-described embodiment in that the upper limit injection amount is determined in advance as a predetermined injection amount.

  The microcomputer 19 of this modification does not store the learning injection amount in the above-described embodiment, but stores a predetermined injection amount as an upper limit injection amount in advance. When the differential pressure indicated by the sensor signal from the differential pressure sensor 31 is outside the predetermined range, the microcomputer 19 compares the injection amount of the main injection at that time with the upper limit injection amount stored in advance, When the injection amount is larger than the upper limit injection amount, the post injection is instructed to the drive unit 18. At that time, the post injection timing and the injection amount are also calculated based on the difference between the two injection amounts described above. In the fuel injection device 1 of the present modification, since the learning injection amount is not stored, a replacement switch is not necessary.

  Other configurations and operations are the same as those in the above-described embodiment, and thus description thereof is omitted.

  FIG. 7 is a flowchart relating to a process in which the fuel injection device 1 of the present modification performs post injection. The process of this flowchart is performed by adding a predetermined amount to the stored learning injection amount in the flowchart of FIG. 4 of the above-described embodiment, and calculating the upper limit injection amount instead of the step of calculating the upper limit injection amount. A reading step is provided. In other words, all processes other than step 707 are the same as those in the flowchart of FIG.

  Thus, in the fuel injection device of this modification, the learning injection amount is not stored, and the predetermined injection amount is stored in the microcomputer 19 as the upper limit injection amount. This eliminates the need for dedicated hardware and software for calculating the upper limit injection amount, which is preferable in terms of design and cost.

  In the embodiment and the modification described above, a single upper limit injection amount is calculated from the stored learned injection amount, and based on the main injection amount and the single upper limit injection amount when an abnormality occurs in the differential pressure sensor 31. Thus, whether or not post injection can be executed and the injection timing and amount of post injection were determined. However, even if a plurality of upper limit injection amounts are calculated and the injection amount of the main injection and the calculated upper limit injection amounts are determined, whether or not the post injection can be executed and the injection timing and the injection amount of the post injection are determined. good. Even in this case, the injection timing and the injection amount of the post injection can be appropriately determined from the injection amount of the main injection and each of the plurality of upper limit injection amounts. In the above-described embodiment, the learning injection amount is stored immediately after the exhaust purification device 3 is replaced. However, the learning injection amount may be stored immediately after the regeneration process is completed.

  Furthermore, in the above-described embodiment and each modification, when the differential pressure indicated by the sensor signal from the differential pressure sensor 31 is outside the predetermined range, it is determined that an abnormality has occurred in the sensor. However, when the engine 2 is in an idling state, the engine 2 does not reach the predetermined target speed even if the main injection quantity is maximized (the upper limit injection quantity during idle control). Alternatively, it may be determined that an abnormality has occurred in the differential pressure sensor 31. In this case, an abnormality occurs in the differential pressure sensor 31 and accurate detection is not performed. Therefore, it is assumed that post injection is not performed even though many particulates are captured in the exhaust purification device 3. This is because it is considered. Further, when the differential pressure is within a predetermined range, and the differential pressure does not indicate the accumulation of particulates over a predetermined amount, and the injection amount at idling of the engine 2 is equal to or higher than the upper limit injection amount, It may be determined that the differential pressure sensor is abnormal.

  In the above-described embodiment and each modification, the upper limit injection amount is calculated from the stored learned injection amount, or the predetermined injection amount is stored in advance as the upper limit injection amount. However, the main injection amount at the time when the setting signal is output from the replacement switch may be calculated as the upper limit injection amount. Thereby, the upper limit injection amount can be calculated more easily, which is preferable in terms of design and cost.

  In the above-described embodiment and each modified example, the injection control ECU 17 causes the injectors A13 to D16 to perform fuel injection up to five times including post injection in each operation cycle of each cylinder of the engine 2. However, the present invention is not limited to this, and a larger number of fuel injections may be performed. Alternatively, only a smaller number of fuel injections may be performed. Further, the post injection may be performed in a plurality of times.

  Finally, in the above-described embodiment and each modified example, the present fuel injection device is applied to the fuel injection device of a diesel engine mounted on a vehicle. However, the present invention is not limited to this, and is mounted on a railway or an aircraft. The present invention can also be suitably used for a diesel engine fuel injection device. However, it is noted that the most preferable case is a case where the present invention is applied to a fuel injection device of a diesel engine mounted on a vehicle.

1 is a block diagram illustrating an overall configuration of a fuel injection device according to an embodiment of the present invention. In the fuel injection device of this embodiment, it is a figure which shows an example of the signal output to a drive signal line, the drive current which a drive unit outputs, and the pulse output to a diagnosis signal line. It is a flowchart regarding the process which the fuel-injection apparatus of this embodiment memorize | stores the learning injection quantity. It is a flowchart regarding the process which the fuel-injection apparatus of this embodiment performs post injection. It is a graph which shows the relationship between the water temperature of engine cooling water, and the magnitude | size of correction | amendment injection quantity of the fuel-injection apparatus in a 1st modification. It is a flowchart regarding the process in which the fuel-injection apparatus in a 1st modification performs post injection. It is a flowchart regarding the process in which the fuel-injection apparatus in a 2nd modification performs post-injection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel injection apparatus 11 ... High pressure fuel pump 12 ... Common rail 13-16 ... Injector AD
17 ... Injection control ECU
18 ... Drive unit 19 ... Microcomputer 1A-1D ... Drive signal line AD
DESCRIPTION OF SYMBOLS 1E ... Diagnostic signal line 1F ... Drive current output circuit 1G ... Drive current detection circuit 2 ... Engine 21-24 ... 1st cylinder-4th cylinder 3 ... Exhaust gas purification device 31 ... Differential pressure sensor

Claims (11)

A fuel injection device for a diesel engine mounted on a vehicle, wherein an exhaust gas purification device that captures particulate matter contained in exhaust gas from the engine is connected to the downstream of the diesel engine and flows into the device And a differential pressure detector that detects a pressure difference between the exhaust gas flowing out of the apparatus and the exhaust gas, and the fuel injection device detects that the pressure difference detected by the differential pressure detector exceeds a predetermined pressure difference. In addition to fuel injection for generating driving force in the diesel engine, fuel injection for burning particulate matter captured by the exhaust purification device is performed.
When an abnormality occurs in the differential pressure detector, when the diesel engine is in an idling state, the fuel injection amount that causes the engine to generate a driving force is measured, and the measured injection amount is set to a set upper limit injection. A fuel comprising an abnormality control means for performing fuel injection for burning particulate matter trapped in the exhaust gas purification device when the amount exceeds the amount, regardless of the detection result of the differential pressure detector Injection device. The abnormality control means determines an injection amount of fuel injection that causes the engine to generate a driving force when the diesel engine is in an idling state when the trapped amount of particulate matter in the exhaust purification device is substantially zero. 2. The fuel injection device according to claim 1, wherein the fuel injection device is configured to set an injection amount obtained by adding a predetermined amount to the measured injection amount as the upper limit injection amount. 3. The fuel injection device according to claim 2, wherein the abnormality control unit varies the predetermined amount based on a temperature of a coolant that cools the diesel engine. 2. The fuel injection device according to claim 1, wherein the abnormality control means sets a predetermined injection amount as the upper limit injection amount. Instructing means to instruct to set the upper limit injection amount,
4. The fuel injection device according to claim 2, wherein the abnormality control unit sets the upper limit injection amount when receiving the instruction from the instruction unit. 5. The instructing means instructs to set the upper limit injection amount either immediately after the exhaust purification device is replaced or immediately after the combustion of the particulate matter is completed. Fuel injectors. The abnormality control means is configured to detect particles captured by the exhaust emission control device based on a difference amount between the upper limit injection amount and an injection amount of fuel injection that causes the engine to generate driving force in an idling state of the diesel engine. The fuel injection device according to any one of claims 1 to 6, wherein a fuel injection timing and a fuel injection amount of fuel injection for burning the particulate matter are determined. The abnormality control means sets a plurality of the upper limit injection amounts, and sets each of the set upper limit injection amounts and an injection amount of fuel injection that causes the engine to generate driving force in an idling state of the diesel engine. 7. The fuel injection according to claim 1, wherein a fuel injection timing and a fuel injection amount for fuel injection for burning the particulate matter captured by the exhaust gas purification device are determined based on the fuel injection timing. apparatus. In the idling state of the diesel engine, the abnormality control means is configured such that the engine speed does not reach a predetermined target speed even if the fuel injection amount that causes the engine to generate driving force is set to the upper limit of idle control. 9. The fuel injection device according to claim 1, wherein fuel injection is performed to burn the particulate matter trapped by the exhaust purification device. 10. The abnormality control unit according to claim 1, wherein when the detection result of the differential pressure detector is outside a predetermined range, the abnormality control means determines that an abnormality has occurred in the differential pressure detector. The fuel injection device according to claim 1. When the diesel engine is in an idling state, the abnormality control unit measures an injection amount of fuel injection that causes the engine to generate a driving force, and when the measured injection amount exceeds the upper limit injection amount, The fuel injection device according to any one of claims 1 to 10, wherein it is determined that an abnormality has occurred in the differential pressure detector.

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