JP6512066B2 - Fuel injection state estimation device - Google Patents

Description

  The present invention relates to an apparatus for estimating a fuel injection state when injecting fuel from a fuel injection valve.

  In order to control the output torque and emission state of the internal combustion engine with high precision, it is important to control the injection state of the fuel injected from the fuel injection valve precisely, such as the injection start timing, maximum injection rate arrival timing and injection amount. It is. Therefore, conventionally, there has been proposed a technique for detecting the actual injection state by detecting the pressure (fuel pressure) of the fuel in the fuel supply path which fluctuates with the injection. For example, the actual injection start timing is detected by detecting the timing when the fuel pressure starts to fall with the start of injection, or the actual maximum injection rate is detected by detecting the amount of fuel pressure drop (maximum pressure drop amount). It detects (refer patent document 1).

  In the invention described in Patent Document 1, a fuel pressure sensor is attached to a fuel injection valve, and a fuel pressure fluctuation caused by fuel injection is detected by the fuel pressure sensor. The fuel pressure fluctuation detected at this time is influenced not only by the fuel pressure generated by the fuel injection but also by various disturbance factors. Disturbance factors include, for example, variation in pressure fluctuation caused by variation in pumping amount each time fuel is pumped from the fuel supply pump to the common rail, and dispersion in diameter of orifice passing when flowing from the common rail to the fuel injection valve. The pressure fluctuation variation derived from it etc. are mentioned. Therefore, the fuel pressure fluctuation caused by the fuel injection is affected by such a disturbance factor. Therefore, the fuel pressure fluctuation due to the fuel injection is detected in consideration of the disturbance factor. Specifically, it is determined whether fuel injection has actually been performed, using a threshold for assuming that the fuel pressure fluctuation is due to the injection. This threshold is set in consideration of a plurality of disturbance factors.

JP 2008-144749 A

  By the way, during driving of a vehicle, there is a larger proportion of routinely performed transient traveling in which the traveling speed fluctuates than in steady traveling where the traveling speed is always constant. During such transient travel, a small amount of fuel injection (micro injection) may be commanded. When it is determined using a threshold whether or not the micro injection is actually implemented, for example, when the injection amount at the time of the micro injection decreases due to the aging of the fuel injection valve, etc. The relationship with the threshold value can not be a predetermined relationship that determines that the fuel injection is actually performed (for example, when the parameter is a fuel pressure value, the fuel pressure value decreased by the microinjection can not fall below the threshold value) Even if the micro injection is actually performed, it may be determined that the micro injection has not been performed. In this case, the fuel injection state estimation device can not estimate the fuel injection state when the small injection is performed.

  The present invention has been made to solve the above-described problems, and its main object is to provide a fuel injection state estimation device capable of estimating a fuel injection state at the time of performing a small injection up to a smaller amount of injection. It is to do.

  The present invention is a fuel injection state estimation device, which includes a pressure accumulation container for accumulating pressure supplied from a fuel supply pump, a fuel pipe connected to a discharge port of the pressure accumulation container, and the pressure accumulation container through the fuel pipe. A fuel injection valve having an injection hole for injecting supplied fuel and a valve body for opening and closing the injection hole, and a fuel supply path from the discharge port to the injection hole to detect a fuel pressure; The present invention is applied to a fuel injection system including a fuel pressure sensor that outputs a sensor waveform representing a change in fuel pressure caused by fuel injection, and represents a fluctuation in the fuel pressure caused by the fuel injection from the fuel injection valve. A fuel injection determination unit that determines that fuel has been injected from the fuel injection valve on the condition that the relationship between the parameter and the first threshold has become a predetermined relationship; and the fuel injection determination unit The injection state estimation which estimates the fuel injection state from the injection hole based on the sensor waveform outputted from the fuel pressure sensor within the fuel injection period when it is judged that the fuel is injected from the injection valve A fuel cut-off determining unit that determines a fuel cut-off state for stopping fuel injection by the fuel injection valve; and a target that controls the fuel pressure to a target pressure A pressure control unit, and a fuel supply stop unit for stopping the fuel supply by the fuel supply pump, wherein the fuel injection determination unit is determined by the fuel cut determination unit to be in the fuel cut state, and the fuel Provided that the fuel supply by the fuel supply pump is stopped by the supply stop unit, and the fuel pressure is controlled to the target pressure by the target pressure control unit. A small amount of fuel is injected in a single stage from the fuel injection valve, and the parameter representing the fluctuation of the fuel pressure due to the single stage injection, and the determination that fuel is injected more easily than the first threshold are set It is characterized in that it is determined that the fuel is injected from the fuel injection valve on condition that the relationship with the second threshold has become the predetermined relationship.

  The fuel injection determination unit included in the present fuel injection state estimation device injects a small amount of fuel from the fuel injection valve in a single stage, on the condition that a plurality of conditions are satisfied. Fuel injection on condition that the relationship between the parameter representing the fluctuation of fuel pressure due to single-stage injection and the second threshold set so that it is determined that fuel is injected more easily than the first threshold becomes a predetermined relationship It is determined that fuel has been injected from the valve. At this time, the plurality of conditions are determined by the fuel cut determination unit to be in the fuel cut state by the fuel cut determination unit, and the fuel supply stop unit stops the fuel supply by the fuel supply pump, and the target pressure control unit It corresponds to being controlled by The first threshold and the second threshold are thresholds in consideration of a plurality of disturbance factors that affect fuel pressure fluctuation other than fuel injection.

  Here, when a small amount of single-stage injection is performed in this control, a plurality of conditions are satisfied, so the number of disturbance factors to be considered is compared with the number of disturbance factors generated during normal fuel injection You can do less. Specifically, since the fuel supply by the fuel supply pump is stopped, the variation of the pressure fluctuation caused by the variation of the pumping amount of the fuel from the fuel supply pump does not occur. Further, by injecting a small amount of fuel in a single stage, no error occurs when correcting the influence on the fuel pressure caused by the fuel injection immediately before. Since a small amount of fuel injection can be performed in a state in which a plurality of disturbance factors are suppressed as described above, even if the second threshold set so that it is determined that fuel has been injected more easily than the first threshold is used It can suppress that the judgment accuracy that injection was carried out falls. Then, it becomes easy to determine that the fuel is injected by using the second threshold value, and it becomes possible to determine that the injection is performed with a smaller amount of fuel. In addition, even in a situation where the injection amount decreases due to aging or the like, it can be determined by the above control that a small amount of fuel injection has been implemented, and the fuel injection state at the time of the small amount of fuel injection can be estimated. It becomes possible.

It is a schematic block diagram of the fuel injection system concerning this embodiment. It is a figure showing the fuel pressure waveform which arises by the fuel injection carried out at the time of usual run. It is a figure showing how often micro injection is commanded at the time of transient travel. It is the figure which showed the fuel pressure waveform which arises by implementing the micro single stage injection which concerns on this embodiment. 5 is a control flowchart executed by the ECU according to the present embodiment. It is the figure which showed that the detection rate of micro injection improved by control concerning this embodiment.

  Hereinafter, the present embodiment will be described based on the drawings. FIG. 1 shows a fuel injection system 10 of the present embodiment.

  The pressure accumulation type fuel injection system 10 includes a fuel supply pump 16, a common rail (corresponding to a pressure accumulation container) 20, a pressure sensor 206, a pressure reducing valve 30, a fuel injection valve 40, an electronic control unit (ECU: Electronic Control Unit) 50, and an electronic drive. A fuel injection device (EDU: Electronic Driving Unit) 52 or the like injects fuel to each cylinder of a four-cylinder diesel engine (hereinafter referred to as an engine) (not shown) as an internal combustion engine. In addition, in order to avoid the complexity of a figure, in FIG. 1, only the control signal line from EDU 52 to one fuel injection valve 40 and the injection piping 202 from common rail 20 to one fuel injection valve 40 are shown. There is.

  The fuel filter 14 removes foreign matter in the fuel which the fuel supply pump 16 sucks from the fuel tank 12. The fuel supply pump 16 incorporates a feed pump for drawing in fuel from the fuel tank 12, pressurizes the drawn fuel, and discharges it to the common rail 20 through the supply pipe 200.

  The fuel supply pump 16 is a known pump that pressurizes the fuel sucked into the pressurizing chamber by reciprocating movement of the plunger as the cam of the camshaft rotates. The ECU 50 controls the metering valve 18 of the fuel supply pump 16 to regulate the amount of intake of the fuel that the fuel supply pump 16 sucks in the suction stroke. Then, the amount of discharge of fuel from the fuel supply pump 16 is adjusted by adjusting the amount of intake.

  The common rail 20 accumulates the fuel discharged by the fuel supply pump 16, holds the fuel pressure at a predetermined high pressure according to the engine operating condition, and supplies the fuel to the fuel injection valve 40 through the injection pipe 202. Note that a fuel supply path for allowing fuel to flow from the common rail 20 to the injection holes 41 is constituted by the high pressure passage provided in the injection piping 202 and the fuel injection valve 40.

  The pressure reducing valve 30 is an electromagnetic valve that is opened by energization control and discharges the fuel in the common rail 20 to the low pressure side return pipe 204.

  The fuel injection valve 40 is mounted on each cylinder of a four-cylinder diesel engine, and injects the fuel accumulated in the common rail 20 from the injection hole 41 into the cylinder. The fuel injection valve 40 performs multistage injection including pilot injection and post injection before and after main injection in one combustion cycle based on the operating state of the engine. The fuel injection valve 40 is a known electromagnetically driven injection valve that controls the fuel injection amount by controlling the pressure of the back pressure chamber that applies fuel pressure to the nozzle needle in the valve closing direction. The electromagnetic drive unit of the fuel injection valve 40 is configured of a piezo actuator or an electromagnetic coil. Further, in the fuel injection system 10 according to the present embodiment, a pressure sensor 206 (corresponding to a fuel pressure sensor) is provided in the vicinity of the fuel injection valve 40, in particular, at the fuel inlet thereof. The pressure sensor 206 outputs a signal corresponding to the injection operation of the fuel injection valve 40 relating to the predetermined injection and the pressure fluctuation state due to the actual injection.

  The back pressure control valve 42 opens when the pressure in the back pressure chamber of the fuel injection valve 40 exceeds a predetermined pressure, and discharges the fuel in the back pressure chamber to the return pipe 204. This prevents the pressure in the back pressure chamber of the fuel injection valve 40 from exceeding the predetermined pressure.

  The ECU 50 mainly includes a microcomputer (microcomputer) mainly having a CPU, a ROM, a RAM, a rewritable nonvolatile memory such as a flash memory, and an input / output interface.

  The ECU 50 includes various sensors such as a pressure sensor 206, a rotational speed sensor 60 for detecting the rotational speed of the engine, a speed sensor 62 for detecting the traveling speed of the vehicle, and an accelerator sensor 64 for detecting an accelerator opening which is an operation amount of an accelerator pedal. The target injection state (number of injection stages, injection start point, injection end point, injection amount, etc.) is calculated from the output signal of For example, the optimal injection state corresponding to the engine load calculated from the engine rotational speed and the operation amount of the accelerator pedal is stored in the ROM or the flash memory as an injection state map. Then, based on the current engine load and engine rotational speed, the target injection state is calculated with reference to the injection state map.

  Then, an injection command signal is set based on the calculated target injection state. For example, an injection command signal corresponding to a target injection state is stored in the storage device as a command map, and the injection command signal is set with reference to the command map based on the calculated target injection state. As described above, the injection command signal corresponding to the engine load and the engine rotational speed is set and output from the ECU 50 to the fuel injection valve 40.

  The ECU 50 executes various controls of the fuel injection system 10 by executing a control program stored in the ROM or the flash memory in addition to the above control. For example, the ECU 50 controls the discharge amount of the fuel supply pump 16 and the opening and closing of the pressure reducing valve 30, and detects the fuel pressure in the injection pipe 202 detected from the output signal of the pressure sensor 206 (actual fuel pressure) Feedback (F / B) control is performed to make the actual fuel pressure follow the target fuel pressure based on the differential pressure with the target fuel pressure set based on the above.

  The ECU 50 corresponds to a fuel injection determination unit, an injection state estimation unit, a fuel cut determination unit, a fuel supply stop unit, a target pressure control unit, and a correction unit.

  The EDU 52 is a drive device for supplying a drive current or a drive voltage to the pressure reducing valve 30 and the fuel injection valve 40 based on a control signal output from the ECU 50.

  The pressure sensor 206 according to the present embodiment detects the fluctuation of the actual fuel pressure in the injection pipe 202. The fuel pressure fluctuation detected at this time is affected not only by the actual fuel pressure generated by the fuel injection but also by various disturbance factors. Disturbance factors include: (1) variation in fuel pressure fluctuation due to variation in pumping amount each time fuel is pumped from the fuel supply pump 16 to the common rail 20, (2) when fuel flows from the common rail 20 to the fuel injection valve 40 Variations in fuel pressure due to variations in the diameter of the orifice passing through, (3) Correction error that occurs when correcting the effect on fuel pressure caused by, for example, pilot injection being performed just before pilot injection, (4) Adjustment error of each actual fuel pressure detected by the pressure sensor 206 provided in the injection piping 202, (5) Individual differences within the allowable error range at the time of manufacturing even if the same amount of fuel is injected by each fuel injection valve 40 And an error in the fluctuation of the actual fuel pressure that occurs due to the presence of

  Therefore, even if the actual fuel pressure is to be F / B controlled to the target fuel pressure, the actual fuel pressure fluctuates around the target fuel pressure due to the plurality of disturbance factors. Therefore, as shown in FIG. 2, the first predetermined range assumed as the fluctuation range of the actual fuel pressure generated by the plurality of disturbance factors affecting the actual fuel pressure is set so that the target fuel pressure is centered. Then, when the actual fuel pressure falls within the first predetermined range, it is determined that the actual fuel pressure is controlled to the target fuel pressure.

  Even when fuel injection is carried out, the above-mentioned disturbance factors (1) to (5) affect the fuel pressure fluctuation generated at that time, so the fuel pressure fluctuation due to fuel injection is detected in consideration of the disturbance factor It will be. However, in consideration of the case where disturbance factors not assumed other than disturbance factors (1) to (5) affect the fuel pressure, it is set lower than the lower limit value of the first predetermined range as described in FIG. The first threshold is used to determine whether fuel injection has actually been performed.

  By the way, during driving of the vehicle, the transient traveling in which the traveling speed fluctuates is more frequently performed on a daily basis than the steady traveling in which the traveling speed is always constant. Such transient data are shown in FIG. When the vehicle is in a transient running state, a small amount of fuel injection (micro injection) may be commanded so that F / B control is difficult to make the fuel injection amount follow the target injection amount. Such small injections have an opportunity to be implemented when the vehicle speed begins to decrease and the rotational speed of the engine begins to decrease. More specifically, there is an opportunity for the micro injection to be carried out when a state in which the current opening degree of the accelerator detected by the acceleration sensor 64 is reduced by a predetermined opening degree is maintained.

  When it is determined using the first threshold whether or not such a small injection is actually implemented, for example, when the injection amount at the time of the small injection decreases due to the aged deterioration of the fuel injection valve 40, the decrease is caused by the small injection The actual fuel pressure can not fall below the first threshold, and it may be determined that the micro injection has not been performed even if the micro injection has actually been performed. In this case, the ECU 50 can not estimate the fuel injection state when the small injection is performed.

  As a countermeasure against this, in the present embodiment, the fuel injection state at the time of the small injection is learned in a state where the fuel pressure fluctuation is small. Specifically, after determining that the fuel cut state (state in which the fuel injection by the fuel injection valve 40 is stopped), the ECU 50 stops the fuel supply from the fuel supply pump 16 and determines the pressure The actual fuel pressure detected by the sensor 206 is controlled to a learning fuel pressure described later. A small amount of fuel is injected in a single stage (small single stage injection) on condition that these controls are performed. At this time, a second threshold is provided instead of the first threshold provided to determine whether fuel injection has been performed during normal travel.

  At the time of micro single stage injection, the fuel supply from the fuel supply pump 16 is stopped. For this reason, the pressure propagation caused by the fuel supply from the fuel supply pump 16 and the error in the fuel pressure fluctuation caused by the diameter of the orifice provided between the common rail 20 and the injection pipe 202 being different for each injection pipe 202 Will not occur. Further, by adopting single-stage injection, it is not necessary to take into consideration the correction error that occurs when correcting the influence on the fuel pressure caused by the execution of the pilot injection and the like immediately before. Therefore, the second threshold is set on the assumption of disturbance factors (4) and (5) without assuming those disturbance factors (1), (2) and (3). Therefore, the second threshold is set as a value larger than the first threshold as described in FIG. Thus, when the minute single-stage injection is performed, the fuel pressure becomes smaller than the second threshold value, and the ECU 50 can determine that the minute injection has been performed from the fuel injection valve 40.

  Next, an example of fuel injection state estimation control executed by the ECU 50 will be described using the flowchart of FIG. 5. Note that the series of processes shown in FIG. 5 are repeatedly executed by the ECU 50 at predetermined intervals while the ECU 50 is powered on.

  First, in step S100, it is determined whether the engine is in the fuel cut state. When it is determined that the engine is not in the fuel cut state (S100: NO), this control is ended. If it is determined that the engine is in the fuel cut state (S100: YES), the process proceeds to step S110.

  In step S110, it is determined which fuel pressure level of the fuel injection state needs to be estimated, and the fuel pressure is set as a learning fuel pressure. Then, the actual fuel pressure detected by the pressure sensor 206 is controlled to the learning fuel pressure. In step S120, it is determined whether the actual fuel pressure has reached the learning fuel pressure. Specifically, it is determined whether the actual fuel pressure of the majority of the cylinders has reached the learning fuel pressure. If it is determined that the actual fuel pressure has not reached the learning fuel pressure (S120: NO), the process returns to step S110, and the process of controlling the actual fuel pressure to the learning fuel pressure is continued. If it is determined that the actual fuel pressure is controlled to the learning fuel pressure (S120: YES), the process proceeds to step S130, and the fuel supply from the fuel supply pump 16 is stopped.

  Then, in step S140, the disturbance factors (1), (2), and (3) are not assumed, and the disturbance factors (4) and (5) are set on the basis of the learning fuel pressure. (2) It is determined whether the fuel pressure falls within a predetermined range (see FIG. 4). When it is determined that the actual fuel pressure is not within the second predetermined range (S140: NO), this control is ended. This is because disturbance factors other than the disturbance factors (4) and (5) are considered to occur and there is a possibility that the fuel injection state at the time of minute single stage injection may not be estimated normally. If it is determined that the actual fuel pressure is within the second predetermined range (S140: YES), the process proceeds to step S150.

  If an instantaneous large change occurs in the actual fuel pressure, the determination process in step S140 may fail to capture the instantaneous change. Therefore, in step S150, the differential value of the actual fuel pressure detected by the pressure sensor 206 is calculated, and in step S160, whether or not the variation of the calculated differential value falls within a third predetermined range centered on 0 Determine When it is determined that the fuel pressure does not fall within the third predetermined range (S160: NO), this control is ended. This is because it is conceivable that a disturbance factor causing instantaneous large fluctuation in actual fuel pressure is generated, and there is a possibility that the fuel injection state at the time of minute single-stage injection can not be normally estimated. If it is determined that the fuel pressure is within the third predetermined range (S160: YES), the process proceeds to step S170.

  In step S170, the first threshold value for determining whether fuel injection has been performed from the fuel injection valve 40 is changed to a second threshold value. Then, in step S180, a minute single-stage injection is performed from the fuel injection valve 40, and in step S190, it is determined whether the actual fuel pressure has become lower than a second threshold. When it is determined that the fuel pressure is not lower than the second threshold (S190: NO), this control is ended. If it is determined that the actual fuel pressure is lower than the second threshold (S190: YES), the process proceeds to step S200, and the fuel injection state is estimated based on the fuel pressure waveform output by the pressure sensor 206, and the fuel After storing the injection state, the present control is ended.

  After completion of the control, assume that the vehicle normally travels, and at that time, a command is issued to inject a fuel injection amount substantially the same as the fuel injection amount at the time when the small single-stage injection is performed in this control. In this case, the fuel injection state stored in step S200 is acquired, and the injection command signal stored in the command map is corrected based on the acquired fuel injection state. At this time, the fuel injection state at the time of small injection is not estimated. This is because, during transient travel, fuel is supplied from the fuel supply pump 16 and so on, and there are many disturbance factors compared to the situation where minute single-stage injection is performed, so the fuel injection state by minute injection is more accurate It is because it is difficult to estimate.

  According to the above configuration, the present embodiment has the following effects.

  -As the small single-stage injection can be performed in the situation where the disturbance factors (1) to (3) are suppressed, the fuel injection is performed even if the second threshold set larger than the first threshold is used. It can suppress that the judgment accuracy of the thing falls. Then, it becomes easy to determine that the fuel is injected by using the second threshold value, and it becomes possible to determine that the injection is performed with a smaller amount of fuel. In addition, even in a situation where the injection amount decreases due to aging or the like, it is possible to determine that the minute single-stage injection has been performed by the above control, and it is possible to estimate the fuel injection state at the time of the minute single-stage injection Become. The result of actually carrying out this control is shown in FIG. The horizontal axis in the upper diagram of FIG. 6 is the required injection amount, and the vertical axis is the difference between the required injection amount and the actual injection amount. The horizontal axis in the lower part of FIG. 6 represents the required injection amount, and the vertical axis represents the fuel injection detection rate. Compared with normal travel, in this control, even if the required injection amount is small, it is possible to inject without a large difference in the actual injection amount (see the upper diagram in FIG. 6), and at a minute amount It shows that even fuel injection can be detected with high accuracy (see the lower figure in Fig. 6).

  The second threshold is set in consideration of the adjustment error of the pressure sensor 206 and the error caused by the individual difference of the fuel injection valve 40 as a disturbance factor. This makes it possible to determine with high accuracy whether or not a small amount of fuel injection has been performed.

  The first threshold is a variation error of the actual fuel pressure derived from the variation of the orifice diameter in addition to the error caused by the adjustment error of the pressure sensor 206 and the individual difference of the fuel injection valve 40. Correction error that occurs when it is corrected to remove the influence on the actual fuel pressure caused by the above, and fuel pressure fluctuation variation derived from variation in pumping amount each time fuel is pumped from the fuel supply pump 16 to the common rail 20; The first threshold is set taking into account the disturbance factor. This makes it possible to more accurately determine the fuel injection during normal driving.

  When the injection of approximately the same amount as the small single-stage injection performed in the fuel cut state is performed, the injection command signal is corrected based on the fuel injection state estimated during the small single-stage injection. This makes it possible to control the injection state more accurately in the case of a small amount of fuel injection which is carried out during transient travel. Also, during transient traveling, estimation of the fuel injection state is not performed. As a result, when it is difficult to accurately estimate the fuel injection state, it is possible not to estimate the injection state.

  The above embodiment can be modified as follows.

  In the flowchart of FIG. 5, it is determined in step S120 whether or not the actual fuel pressure of a majority of the cylinders has reached the learning fuel pressure. It is not necessary to carry out the above determination about this. For example, it may be determined that the actual fuel pressure is controlled to the learning fuel pressure when the first predetermined time has elapsed since the process of controlling the actual fuel pressure to the learning fuel pressure in step S110.

  After the fuel supply stop process from the fuel supply pump 16 is performed in step S130, it is determined in step S140 whether the actual fuel pressure is within the second predetermined range. In addition, after the calculation process of calculating the differential value of the actual fuel pressure detected by the pressure sensor 206 in step S150, whether the variation of the calculated differential value falls within the third predetermined range in step S160 The decision processing of whether or not it was carried out. These inner steps S140 to S160 need not necessarily be performed. For example, after the fuel supply stop process from the fuel supply pump 16 is executed, it is determined that the fluctuation range of the fuel pressure is narrowed so as to fall within the second predetermined range and the third predetermined range when the second predetermined time elapses. May be

  In the above embodiment, when the actual fuel pressure becomes smaller than the first threshold value, it is determined that the fuel is injected from the fuel injection valve 40. Further, when the fuel cut is performed and the fuel supply from the fuel supply pump 16 is stopped, the second threshold is set instead of the first threshold, and the actual fuel pressure becomes smaller than the second threshold, It was determined that a small amount of fuel was injected from the fuel injection valve 40. Regarding this, the fuel injection determination is not limited to the determination based on the fluctuation of the actual fuel pressure. For example, the derivative value of the actual fuel pressure is calculated, and the calculated derivative value is the third threshold value set during normal travel or the fuel cut state, and is set by stopping the fuel supply from the fuel supply pump 16 It may be determined that fuel has been injected from the fuel injection valve 40 when it has become lower than the fourth threshold. By calculating the derivative value of the actual fuel pressure, it is possible to accurately grasp the fluctuation of the actual fuel pressure due to the fuel injection. Therefore, it can be determined with high accuracy that fuel has been injected by the fuel injection valve 40. In addition, since the fourth threshold is set larger than the third threshold, it can be determined that fuel is injected more easily in the case of using the fourth threshold than in the case of using the third threshold.

  In the above embodiment, the fuel cut is performed, the fuel supply from the fuel supply pump 16 is stopped, and the first threshold for determining the fuel injection is reset to the second threshold, and then the minute single-stage injection is performed. It has been determined whether fuel injection has been implemented. At this time, when it is estimated that the disturbance factor affects the change in the actual fuel pressure when setting the first threshold value to the second threshold value, the change is also reflected in the first threshold value. You may When such a process is performed, it is possible to more accurately perform the fuel injection determination at the time of normal injection.

  In the above embodiment, the first threshold is set on the assumption of disturbance factors (1) to (5). About this, for example, the first threshold value is set assuming disturbance factors (1) to (4), and the combination thereof is not limited. Also, the second threshold is set assuming (4) and (5). About this matter, there is no restriction | limiting in the combination in the range which does not assume disturbance factors (1)-(3), such as setting a 2nd threshold value supposing only (4), for example.

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection system, 16 ... Fuel supply pump, 20 ... Common rail, 40 ... Fuel injection valve, 41 ... Injection hole, 50 ... ECU, 202 ... Injection piping, 206 ... Pressure sensor.

Claims (7)

An accumulator vessel (20) for accumulating fuel supplied from the fuel supply pump (16);
A fuel pipe (202) connected to the discharge port of the pressure accumulation container;
An injection hole (41) for injecting fuel supplied from the pressure accumulation container through the fuel pipe, and a fuel injection valve (40) having a valve body for opening and closing the injection hole;
A fuel pressure sensor (206 provided in a fuel supply path (40, 202) from the discharge port to the injection hole to detect fuel pressure and expressing a change in fuel pressure caused by fuel injection (206 )When,
Applied to a fuel injection system (10) equipped with
It is determined that the fuel is injected from the fuel injection valve on the condition that the relation between the first threshold and the parameter representing the fluctuation of the fuel pressure due to the fuel injection from the fuel injection valve becomes a predetermined relation. A fuel injection determination unit,
Wherein when the fuel injection determination unit fuel from said fuel injection valve is determined to have been injected, based on the sensor waveform fuel is output from the fuel pressure sensor within the period that has been injected, fuel from the injection hole An injection state estimation unit that estimates a fuel injection state, which is the number of injection stages, the injection start point, the injection end point, or the injection amount ;
A correction unit that corrects an injection command signal for commanding fuel injection based on the fuel injection state estimated by the injection state estimation unit;
A fuel injection state estimation device (50) comprising
A fuel cut determination unit that determines a fuel cut state in which fuel injection by the fuel injection valve is stopped;
A target pressure control unit that controls the fuel pressure to a target pressure;
A fuel supply stop unit for stopping the fuel supply by the fuel supply pump;
Equipped with
The fuel injection determination unit is determined by the fuel cut determination unit to be in the fuel cut state, and the fuel supply stop unit stops the fuel supply by the fuel supply pump, and the target pressure control unit controls the fuel Under the condition that the pressure is controlled to the target pressure, a minute amount of fuel is injected from the fuel injection valve in a single stage, and the parameter representing the fluctuation of the fuel pressure caused by the single stage injection and the first parameter Regardless of whether or not the relationship with the threshold has become the predetermined relationship, the relationship between the parameter and a second threshold set so that it is determined that fuel has been injected more easily than the first threshold has become the predetermined relationship. On the condition that fuel is injected from the fuel injection valve ,
If it is determined by the fuel injection determination unit that the small amount of fuel has been injected in a single stage, and the fuel injection state at the single stage injection is estimated by the injection state estimation unit, the single unit injection thereafter When performing injection of approximately the same injection amount as stage injection, the estimation by the injection state estimation unit is not performed, and the correction unit performs the correction based on the fuel injection state estimated during the single stage injection. The fuel injection state estimation device characterized by implementing . The fuel pipe from the pressure accumulation container to the fuel inlet of the fuel injection valve is provided with an orifice;
The second threshold value is a fluctuation error of the fuel pressure derived from the dispersion of the diameter of the orifice which passes when the fuel is supplied from the pressure accumulation container to the fuel supply path, and the second threshold value is caused by the fuel injection performed immediately before. The fuel pressure is not considered, taking into account the effect on the fuel pressure caused by an error that occurs when removing the influence on the fuel pressure and the variation in the fuel supply amount each time the fuel supply pump supplies the pressure storage container. The fuel injection state estimation device according to claim 1 , wherein an error caused by individual differences of the injection valve is set in consideration of one of disturbance factors affecting the fuel pressure. The fuel pipe from the pressure accumulation container to the fuel inlet of the fuel injection valve is provided with an orifice;
The first threshold value is one of disturbance factors that affect the fuel pressure due to a fluctuation error of the fuel pressure derived from the variation of the diameter of the orifice passing when the fuel is supplied from the pressure accumulation container to the fuel supply path. 3. The fuel injection state estimation device according to claim 1, wherein the fuel injection state estimation device is set in consideration of the above. The first threshold value is set in consideration of an error generated when removing the influence on the fuel pressure by the fuel injection performed immediately before as one of the disturbance factors affecting the fuel pressure. The fuel injection state estimation device according to any one of claims 1 to 3 . The first threshold value is set in consideration of variation in fuel supply amount at each time of supplying the pressure accumulation container from the fuel supply pump as one of disturbance factors affecting the fuel pressure. The fuel injection state estimation device according to any one of claims 1 to 4 . Wherein the first threshold value, any one of claims 1 to 5, characterized in that set in consideration of an error caused by individual differences the fuel injection valve has a single disturbance factor affecting the fuel pressure 1 The fuel-injection-state estimation apparatus as described in a term. A differential value calculation unit configured to calculate a differential value of the fuel pressure detected by the fuel pressure sensor;
The parameter indicates the differential value of the fuel pressure calculated by the differential value calculation unit,
When the differential value of the fuel pressure is smaller than the first threshold value or the differential value of the fuel pressure is smaller than the second threshold value , the fuel injection determination unit has the predetermined relationship Judge
The fuel injection state estimation device according to any one of claims 1 to 6 , wherein the second threshold is set larger than the first threshold.