JP4506661B2 - Fuel injection control device - Google Patents

Description

  The present invention relates to a pressure accumulation chamber that stores fuel in a high pressure state, a fuel pump that pressurizes fuel into the pressure accumulation chamber, a fuel injection valve that injects fuel in the pressure accumulation chamber, and a detection that detects fuel pressure in the pressure accumulation chamber And a fuel injection control device that feedback-controls the detected fuel pressure to a target value.

  As this type of fuel injection control device, a fuel injection control device for a common rail type diesel engine that stores high-pressure fuel in a common rail (pressure accumulation chamber) common to each cylinder and injects fuel in the common rail via a fuel injection valve is well known. It is. In this fuel injection control device, the fuel pressure in the common rail is controlled to follow the target value (target fuel pressure) by operating the fuel pump that pumps up the fuel in the fuel tank and supplies it to the common rail.

  By the way, at the time of deceleration when the accelerator pedal is released, the command value (command injection amount) of the injection amount decreases. As a result, the amount of fuel flowing out from the common rail is reduced, so that the amount of fuel pressurized and supplied by the fuel pump may become surplus fuel. When surplus fuel is supplied to the common rail, the fuel pressure in the common rail cannot be made to follow the target fuel pressure.

  Therefore, conventionally, as can be seen from, for example, Patent Document 1 below, it has also been proposed that the amount of decrease in the command injection amount during deceleration is made smaller than that set in accordance with the operation amount of the accelerator pedal. As a result, the fuel in the common rail flows out into the combustion chamber of the diesel engine by fuel injection, so that the fuel pressure in the common rail can be quickly reduced even during deceleration.

However, there are various restrictions on performing the fuel injection during deceleration. For example, from the viewpoint of avoiding deterioration of exhaust characteristics or inducing fuel into engine oil, restrictions such as limiting this to the vicinity of compression top dead center as to when the fuel can be injected during deceleration. There is. Due to such restrictions, it is difficult to sufficiently perform the fuel injection in a region where the rotational speed of the output shaft of the diesel engine is high, and as a result, there is a possibility that the followability to the target fuel pressure by the feedback control may be reduced.
JP 2004-156578 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel injection control capable of maintaining a higher followability to a target fuel pressure when a demand for reducing the output torque of a diesel engine occurs. To provide an apparatus.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

The invention according to claim 1 is a pressure accumulation chamber that stores fuel in a high pressure state, a fuel pump that pressurizes fuel into the pressure accumulation chamber, a fuel injection valve that injects fuel in the pressure accumulation chamber, and a fuel pressure in the pressure accumulation chamber In a fuel injection control apparatus that is applied to an internal combustion engine that includes a detection means for detecting the feedback, and that performs feedback control of the detected fuel pressure to a target value, a determination means that determines whether or not there is a request to reduce the output torque of the internal combustion engine; When it is determined by the determining means that there is a reduction request, the differential pressure of the detected fuel pressure with respect to the target value as the calculation parameter used for the calculation of the feedback control, and the calculation used for the calculation of the feedback control forcibly reduced the discharge amount of the fuel pump by forcibly increases with the pressure difference reduction degree command value of the injection amount for the fuel injection valve Characterized in that it comprises a reducing means for.

  In the above configuration, when it is determined that there is a request to reduce the output torque, the discharge amount of the fuel pump is forcibly reduced by correcting the calculation parameter according to the degree of decrease in the command value of the injection amount. For this reason, even if the injection amount decreases due to a request to reduce the output torque, it can be suitably avoided that the fuel pressure in the pressure accumulating chamber greatly exceeds the target value.

In particular, since the calculation parameter is a parameter located downstream of the target fuel pressure setting, even if the degree of decrease in the target fuel pressure is small compared to the degree of decrease in the injection amount, the calculation parameter is used. The discharge amount of the pump can be appropriately reduced according to the output torque reduction request.
According to a second aspect of the present invention, there is provided a pressure accumulation chamber for storing fuel in a high pressure state, a fuel pump for pressurizing and supplying fuel into the pressure accumulation chamber, a fuel injection valve for injecting fuel in the pressure accumulation chamber, and a fuel pressure in the pressure accumulation chamber In a fuel injection control apparatus that is applied to an internal combustion engine that includes a detection means for detecting the feedback, and that performs feedback control of the detected fuel pressure to a target value, a determination means that determines whether or not there is a request to reduce the output torque of the internal combustion engine; When the determination means determines that there is a reduction request, either the calculation parameter used for the calculation of the feedback control or the calculation parameter used for the calculation of the operation amount of the fuel pump after the calculation is used as the injection amount for the fuel injection valve. Reducing means for forcibly reducing the discharge amount of the fuel pump by correcting according to the reduction degree of the command value of Means for calculating an annealing value with a reduced degree of change based on an operation amount of the accelerator operating member, and making the determination based on a difference between the operation amount of the accelerator pedal and the annealing value. It is characterized by that.
In the above configuration, when it is determined that there is a request to reduce the output torque, the discharge amount of the fuel pump is forcibly reduced by correcting the calculation parameter according to the degree of decrease in the command value of the injection amount. For this reason, even if the injection amount decreases due to a request to reduce the output torque, it can be suitably avoided that the fuel pressure in the pressure accumulating chamber greatly exceeds the target value.
In particular, since the calculation parameter is a parameter located downstream of the target fuel pressure setting, even if the degree of decrease in the target fuel pressure is small compared to the degree of decrease in the injection amount, the calculation parameter is used. The discharge amount of the pump can be appropriately reduced according to the output torque reduction request.
Further, the deceleration side operation of the accelerator operating member is a request for reducing the output torque itself during autonomous driving in which the user operates the accelerator operating member. For this reason, in the said structure, the presence or absence of a reduction request | requirement can be determined appropriately at the time of autonomous driving. In addition, the amount of data stored in the storage means can be reduced as compared with the case where the reduction request is quantified as the change rate of the operation amount of the accelerator operation member. This is because when the change speed is used, it is necessary to store a large number of sampling values of the operation amount in the storage means.
The reducing means may forcibly increase the differential pressure of the detected fuel pressure with respect to the target value, and forcibly increasing the differential pressure used for the calculation of the feedback control.
According to a third aspect of the present invention, a pressure accumulating chamber for storing fuel in a high pressure state, a fuel pump for pressurizing and supplying the fuel into the pressure accumulating chamber, a fuel injection valve for injecting fuel in the pressure accumulating chamber, and a fuel pressure in the pressure accumulating chamber In a fuel injection control apparatus that is applied to an internal combustion engine that includes a detection means for detecting the feedback, and that performs feedback control of the detected fuel pressure to a target value, a determination means that determines whether or not there is a request to reduce the output torque of the internal combustion engine; When the determination means determines that there is a reduction request, either the calculation parameter used for the calculation of the feedback control or the calculation parameter used for the calculation of the operation amount of the fuel pump after the calculation is used as the injection amount for the fuel injection valve. Reducing means for forcibly reducing the discharge amount of the fuel pump by correcting according to the reduction degree of the command value of Whether or not there is a request for reduction of the output torque of the combustion engine, it is determined whether or not there is a request for gradual reduction in which the degree of decrease in the target value is small relative to the degree of reduction in the fuel injection amount through the fuel injection valve. And
In the above configuration, when it is determined that there is a request to reduce the output torque, the discharge amount of the fuel pump is forcibly reduced by correcting the calculation parameter according to the degree of decrease in the command value of the injection amount. For this reason, even if the injection amount decreases due to a request to reduce the output torque, it can be suitably avoided that the fuel pressure in the pressure accumulating chamber greatly exceeds the target value.
In particular, since the calculation parameter is a parameter located downstream of the target fuel pressure setting, even if the degree of decrease in the target fuel pressure is small compared to the degree of decrease in the injection amount, the calculation parameter is used. The discharge amount of the pump can be appropriately reduced according to the output torque reduction request.
In particular, at the time of a slow reduction request where the degree of decrease in the target value is small relative to the degree of decrease in the injection amount, there is a possibility that the discharge amount of the fuel pump cannot be reduced sufficiently because the target fuel pressure does not decrease much. By correcting the calculation parameters, the discharge amount of the fuel pump can be sufficiently reduced even in such a region.
The reducing means may forcibly increase the differential pressure of the detected fuel pressure with respect to the target value, and forcibly increasing the differential pressure used for the calculation of the feedback control.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the reduction means forcibly reduces and corrects the target value using the target value as the calculation parameter. To do.

  In the above configuration, the discharge amount of the fuel pump is reduced by feedback control so as to reduce the actual fuel pressure by forcibly correcting the target value.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the reduction means calculates a smoothed value whose degree of change is relaxed based on a command value of the injection amount. And means for calculating a difference between the command value and the smoothing value as the degree of decrease.

  When quantifying the degree of decrease in the command value of the injection amount based on the sampling value of the command value, if this is quantified as the change rate of the command value, it is necessary to store a large number of sampling values in the storage means. In this regard, in the above configuration, by providing the means for calculating the smoothing value, it is possible to appropriately quantify the degree of decrease in the command value while suppressing an increase in the amount of data stored in the storage means.

According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the reduction means determines that the reduction is required, and the rotational speed of the output shaft of the internal combustion engine is predetermined. The forcible reduction is performed when the speed is higher than a predetermined speed.

  In the region where the rotation speed of the output shaft is high, the target value of the fuel pressure is normally set to be small with respect to the decrease in the injection amount with respect to the request for a gradual reduction in the output torque. For this reason, if a request for moderate reduction of the output torque is made in this region, there is a possibility that the discharge amount of the fuel pump cannot be sufficiently reduced because there is little decrease in the target value of the fuel pressure. In this regard, in the above configuration, by correcting the calculation parameter, the discharge amount of the fuel pump can be sufficiently reduced even in such a region.

The invention according to claim 7 is the invention according to any one of claims 1 to 6 , wherein the reducing means determines that the request for reduction is present and the fuel pressure is equal to or higher than a predetermined pressure. It is characterized by a forced reduction.

  In a region where the target value of the fuel pressure in the pressure accumulating chamber is large, the target value of the fuel pressure is normally set small for the reduction of the injection amount, in response to a request for a moderate reduction of the output torque. For this reason, if a request for moderate reduction of the output torque is made in this region, there is a possibility that the discharge amount of the fuel pump cannot be sufficiently reduced because there is little decrease in the target value of the fuel pressure. In this regard, in the above configuration, by correcting the calculation parameter, the discharge amount of the fuel pump can be sufficiently reduced even in such a region.

The invention according to an eighth aspect is characterized in that, in the invention according to any one of the first to seventh aspects, the determination means makes the determination based on a deceleration side operation of an accelerator operation member.

  The deceleration-side operation of the accelerator operation member is a request for reducing the output torque itself during autonomous driving in which the user operates the accelerator operation member. For this reason, in the said structure, the presence or absence of a reduction request | requirement can be determined appropriately at the time of autonomous driving.

The invention according to claim 9 is the invention according to any one of claims 1 to 7 , wherein the determination means performs the determination based on a decrease in a command value of an injection amount for the fuel injection valve. .

  When a request for reducing the output torque occurs, the command value for the injection amount decreases. For this reason, in the said structure, the presence or absence of a reduction request | requirement can be determined appropriately based on the reduction | decrease in the command value of injection quantity.

(First embodiment)
Hereinafter, a first embodiment in which a fuel injection control device according to the present invention is applied to a fuel injection control device of a diesel engine will be described with reference to the drawings.

  FIG. 1 shows the overall configuration of the engine system according to the present embodiment.

  As shown in the figure, the fuel in the fuel tank 2 is pumped up by the fuel pump 6 through the fuel filter 4. The fuel pump 6 is powered by a crankshaft 8 that is an output shaft of a diesel engine and discharges fuel. Specifically, the fuel pump 6 includes an intake metering valve 10. The intake metering valve 10 adjusts the amount of fuel discharged from the fuel pump 6 by adjusting the amount of fuel sucked. That is, the amount of fuel discharged to the outside is determined by operating the intake metering valve 10. Further, the fuel pump 6 includes two plungers, and these plungers reciprocate between a top dead center and a bottom dead center, whereby fuel is sucked and discharged.

  The fuel discharged from the fuel pump 6 is pressurized and supplied (pumped) to the common rail 12. The common rail 12 stores the fuel pumped from the fuel pump 6 in a high pressure state and supplies the fuel to the fuel injection valve 16 of each cylinder (here, four cylinders are illustrated) via the high pressure fuel passage 14. The fuel injection valve 16 is connected to the fuel tank 2 via a low pressure fuel passage 18.

  The engine system includes various sensors that detect the operating state of the diesel engine, such as a fuel pressure sensor 20 that detects the fuel pressure in the common rail 12 and a crank angle sensor 22 that detects the rotation angle of the crankshaft 8. Further, the engine system includes an accelerator sensor 24 that detects an operation amount of an accelerator pedal operated in response to a user's acceleration request.

  On the other hand, the electronic control unit (ECU 30) is composed mainly of a microcomputer, takes in the detection results of the various sensors, and controls the output of the diesel engine based on this.

  The ECU 30 performs fuel injection control so as to appropriately control the output of the diesel engine. In this fuel injection control, the fuel pressure in the common rail 12 is feedback-controlled to a target value (target fuel pressure) set according to the operation state of the diesel engine. This will be described in detail below.

  FIG. 2 is a functional block diagram of processing related to feedback control of the target fuel pressure in the common rail 12 among the processing performed by the ECU 30.

  The filter B2 performs a smoothing process for reducing the degree of change of the A / D conversion value in order to remove noise from the A / D conversion value of the output of the accelerator sensor 24, and the degree of change of the A / D conversion value is reduced. (Hereinafter, accelerator pedal operation amount ACCP) is calculated.

  The injection amount calculation unit B4 is based on the rotational speed of the crankshaft 8 based on the detected value of the crank angle sensor 22 and the operation amount of the accelerator pedal calculated by the filter B2, and a command value for the injection amount for the fuel injection valve ( (Command injection amount) is calculated as a map.

  The target fuel pressure calculation unit B6 calculates a target fuel pressure based on the command injection amount and the rotation speed.

  Based on the target fuel pressure and the fuel pressure detected by the fuel pressure sensor 20, the differential pressure calculation unit B8 calculates a differential pressure between the actual fuel pressure and the target fuel pressure. This differential pressure is taken into the proportional term calculation unit B10, the differential term calculation unit B12, and the integral term calculation unit B14. Here, the proportional term calculation unit B10 calculates the proportional term by multiplying the differential pressure by the proportional gain. The differential term calculation unit B12 calculates the differential term by multiplying the time differential value of the differential pressure by the differential gain. Further, the integral term calculation unit B14 calculates the integral term by multiplying the time integral value of the differential pressure by the reciprocal of the integral gain.

  The target change calculation unit B16 calculates the change amount of the target fuel pressure. The fuel conversion unit B18 converts the change amount of the target fuel pressure into the fuel amount so as to calculate the fuel amount required to actually change the fuel pressure in the common rail 12 by the change amount of the target fuel pressure. In this conversion, the value “E / V” obtained by dividing the volume expansion coefficient E of the fuel by the sum V of the volume of the fuel passage between the fuel pump 6 and the common rail 12 and the volume of the common rail 12 is the amount of change in the target fuel pressure. By multiplying by.

  The proportional term, the differential term, the integral term, and the fuel amount converted by the fuel conversion unit B18 are added by the adding unit B20. The output of the adding unit B20 becomes a command value (command discharge amount) of the discharge amount for the fuel pump 6.

  The drive current conversion unit B22 converts the command discharge amount into a drive current value of the fuel pump 6 required for discharging from the fuel pump 6 (more precisely, a drive current value of the intake metering valve 10). . Here, the command discharge amount is converted into a drive current value using, for example, an “n” -order (n ≧ 1) polynomial for the command discharge amount. The fuel pump 6 is operated based on the drive current value calculated by the drive current conversion unit B22.

  By the way, at the time of the rapid deceleration request | requirement in which an accelerator pedal is released rapidly (at the time of the rapid reduction request | requirement of the output torque of a diesel engine), command injection quantity and target fuel pressure fall. For this reason, since the actual fuel pressure greatly exceeds the target fuel pressure, the command discharge amount calculated by feedback control decreases. However, since the fuel that has already been sucked into the fuel pump 6 before the command discharge amount decreases is pumped to the common rail 12, the fuel pressure in the common rail 12 increases. Furthermore, since the fuel that can supplement the fuel flowing out from the common rail 12 before the request is calculated by the integral term, the decrease in the command discharge amount may be delayed for the sudden deceleration request. is there. Therefore, in the present embodiment, when a sudden deceleration request is made, the followability of the fuel pressure in the common rail 12 is improved in the manner shown in FIG.

  FIG. 3 (a) shows the change of the operation amount of the accelerator pedal, FIG. 3 (b) shows the change of the fuel pressure in the common rail 12, and FIG. 3 (c) shows the change of the command injection amount. Incidentally, in FIG. 3B, the solid line indicates the actual fuel pressure, and the alternate long and short dash line indicates the transition of the target fuel pressure.

  At time t1 when the accelerator pedal is suddenly released, the command injection amount calculated by the injection amount calculation unit B4 of FIG. 2 is rapidly decreased as shown by a broken line in FIG. In this case, as shown by a broken line in FIG. 3B, an overshoot occurs in which the actual fuel pressure greatly exceeds the target fuel pressure. For this reason, in the present embodiment, in order to suppress a decrease in the command injection amount calculated by the injection amount calculation unit B4, as shown by a solid line in FIG. This avoids overshooting of the fuel pressure as shown by the solid line in FIG.

  On the other hand, at the time of a slow deceleration request where the accelerator pedal is released slowly (when a gentle reduction of the output torque of the diesel engine is requested), the command injection amount gradually decreases in the high load high rotation region of the diesel engine. The degree of decrease in the target fuel pressure is smaller than the degree of decrease in the command injection amount. This is because the change in the target fuel pressure with respect to the change in the command injection amount is set to be smaller as the rotational speed of the crankshaft 8 is higher in the target fuel pressure calculation unit B6 shown in FIG. Incidentally, in FIG. 2, the map of the target fuel pressure calculation unit B6 shows a portion where the change in the command injection amount is equal to or less than a predetermined value (the target fuel pressure also decreases sharply when the command injection amount decreases rapidly).

  For this reason, even if a slow deceleration request occurs, the command discharge amount calculated by feedback control hardly decreases for a while. That is, if the target fuel pressure hardly changes, the differential pressure of the detected fuel pressure with respect to the target fuel pressure also does not change for a while, and during this time, the discharge amount according to the injection amount before the slow deceleration request is calculated by the integral term. Become. For this reason, the command discharge amount calculated by the feedback control is sufficiently decreased after the detected pressure is greatly exceeded the target fuel pressure and the differential pressure is increased. Therefore, in this case, the overshoot of the fuel pressure is inevitable. However, in this case, it is difficult to avoid overshoot by letting fuel flow out of the common rail 12 in the manner shown in FIG. This is because if the decrease in the command injection amount during the slow deceleration is suppressed, it is not possible to sufficiently respond to the slow deceleration request, and the decrease in the command discharge amount calculated by feedback control is slow. Incidentally, it is conceivable to inject the fuel without contributing to the generation of the output torque of the crankshaft 8, but in this case, the exhaust characteristics are deteriorated.

  Therefore, in the present embodiment, the command discharge amount of the fuel pump 6 is forcibly reduced by correcting the calculation parameter used for the calculation of the feedback control according to the decrease degree of the command injection amount when the slow deceleration is requested. Specifically, the calculation parameter is set as the target fuel pressure, and this is corrected to decrease in accordance with the degree of decrease in the command injection amount. In order to perform such control, the present embodiment includes a processing unit shown in FIG.

  That is, the annealing processing unit B24 calculates the annealing value QFINSM in which the degree of change in the command injection amount is reduced. The calculation method of this annealing process is, for example, a weight that multiplies the previous sampling value QFIN (i-1) and the current sampling value QFIN (i) of the command injection amount by the normalized weights a and b. What is necessary is just to carry out by average processing. Here, in the weighted average value “a × QFIN (i−1) + b × QFIN (i)”, it is desirable that “a> b”. For example, a first-order lag filter may be used instead of the weighted average process.

  The correction amount calculation unit B28 calculates the correction amount by subtracting the command injection amount QFIN from the smoothed value QFINSM and multiplying by the proportionality constant K. The switching unit B30 switches whether or not to use the correction amount calculated by the correction amount calculation unit B28.

  The torque reduction request determination unit B32 determines whether or not it is a slow deceleration request, and switches the switching unit B30 to use the correction amount when the slow deceleration request is made.

  Here, processing performed by the annealing processing unit B24, the correction amount calculation unit B28, the switching unit B30, and the torque reduction request determination unit B32 will be further described with reference to FIG.

  FIG. 4 shows a procedure of processing related to fuel pressure control at the time of a slow deceleration request according to the present embodiment. This process is repeatedly executed at a predetermined cycle.

  In this series of processing, first, in step S10, the operation amount and rotation speed of the accelerator pedal, the fuel pressure detected by the fuel pressure sensor 20, and the command injection amount QFIN are captured. In a succeeding step S12, it is determined whether or not the change amount of the accelerator pedal operation amount is not less than the lower limit value α1 and not more than the upper limit value β1 (processing of the torque reduction request determination unit B32). Here, the lower limit value α1 is for determining slow deceleration. That is, at the time of sudden deceleration (the amount of change in the accelerator operation amount is negative and its absolute value is large), the processing shown in FIG. 3 is performed, so that the target fuel pressure should be corrected only for slow deceleration. The lower limit value α1 is provided. On the other hand, the upper limit value β1 is provided in order to avoid a minute change in the operation amount of the accelerator pedal being determined as a deceleration request even though there is no deceleration request.

  In the subsequent step S14, it is determined whether or not the operation range is a predetermined operation region in which the degree of decrease in the target fuel pressure is small relative to the degree of decrease in the command injection amount. As shown in FIG. 5, the predetermined operation region is a region where the rotational speed is equal to or higher than a predetermined speed and the detected fuel pressure is equal to or higher than a predetermined pressure.

  If it is determined that it is in the predetermined operation range, in step S16, an annealing value is calculated based on the command injection amount (processing by the annealing processing unit B24). In step S18, a correction amount is calculated from the command injection amount and the annealing value (processing of the correction amount calculation unit B28). Further, in step S20, the target fuel pressure is corrected to be lowered by subtracting the correction amount from the target fuel pressure calculated by the target fuel pressure calculation unit B6 of FIG.

  When a negative determination is made in step S12 or step S14 or when the process of step S20 is completed, this series of processes is temporarily ended.

  FIG. 6 illustrates a change in fuel pressure when a slow deceleration request is made by the above processing.

  6 (a) shows the change in the amount of operation of the accelerator pedal, FIG. 6 (b) shows the change in the command injection amount, FIG. 6 (c) shows the change in the rotational speed, and FIG. ) Shows the transition of the correction amount, and FIG. 6E shows the transition of the fuel pressure.

  As shown in the figure, when the accelerator pedal operation amount starts to gradually decrease at time t2, calculation of the smoothed value QFINSM is started, and thereby calculation of the correction amount is also started. Therefore, the basic value of the target fuel pressure calculated by the target fuel pressure calculation unit B6 indicated by the two-dot chain line in FIG. 6E is corrected by the correction amount, and is indicated by the one-dot chain line in FIG. This is the final target fuel pressure. As a result, immediately after the request for slow deceleration occurs, the actual fuel pressure indicated by the solid line in FIG. 6 (e) exceeds the target fuel pressure, so that the command discharge amount calculated by the feedback control is reduced. Fuel pressure overshoot can be avoided.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) When a slow deceleration request is made, the target fuel pressure is forcibly corrected to decrease, so that the differential pressure between the actual fuel pressure and the target fuel pressure increases, so that the fuel pump 6 discharges by feedback control to reduce the actual fuel pressure. The amount decreases.

  (2) The correction amount for correcting the target fuel pressure to be lowered was calculated based on the difference between the command injection amount and the smoothed value. Here, when the correction amount is calculated based on the change rate of the command injection amount, it is necessary to store a large number of sampling values of the command injection amount in the storage means. In this regard, in the present embodiment, by calculating the annealing value, it is possible to appropriately calculate the correction amount while suppressing an increase in the amount of data stored in the storage unit.

  (3) At the time of slow deceleration, the target fuel pressure is corrected to be lowered in an operation region where the rotational speed of the crankshaft 8 of the diesel engine is equal to or higher than a predetermined speed and the fuel pressure is equal to or higher than a predetermined pressure. In such a region, since the degree of decrease in the target fuel pressure is small relative to the degree of decrease in the command injection amount, fuel pressure overshoot is likely to occur. On the other hand, in this embodiment, overshoot can be suitably suppressed by correcting the target fuel pressure to be lowered in this operating region.

  (4) Based on the change speed of the operation amount of the accelerator pedal, whether or not there is a request for slow deceleration is determined. Thereby, the presence or absence of the slow deceleration request | requirement can be determined appropriately.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 7 shows a procedure of processing relating to fuel pressure control at the time of a slow deceleration request according to the present embodiment. This process is repeatedly executed by the ECU 30, for example, at a predetermined cycle. In FIG. 7, the same steps as those in FIG. 4 are given the same step numbers for the sake of convenience.

  In this series of processes, the process of step S10 in FIG. 4 is first performed. In the subsequent step S11, based on the amount of operation of the accelerator pedal, a smoothed value with the degree of change in the amount of operation being relaxed is calculated. This process can be performed by the same process as step S16 of FIG. In the subsequent step S12a, it is determined whether or not the difference of the accelerator pedal operation amount ACCP with respect to the smoothed value ACCPSM is not less than the lower limit value α2 and not more than the upper limit value β2. This step 12a is a process performed for the same purpose as step S12 of FIG. 4, and the lower limit value α2 and the upper limit value β2 are provided for the same purpose as the lower limit value α1 and the upper limit value β1, respectively. .

  If an affirmative determination is made in step S12a, it is determined that a slow deceleration request is being made, and the processes of steps S14 to S20 in FIG. 4 are performed.

  According to the present embodiment described above, the following effects can be obtained in addition to the effects (1) to (3) of the first embodiment.

  (5) Based on the difference between the operation amount of the accelerator pedal and the tempered value, whether or not there is a request for slow deceleration is determined. Thereby, the presence or absence of the slow deceleration request | requirement can be determined appropriately. In addition, the amount of data stored in the storage means can be reduced as compared with the case where the slow deceleration request is quantified as the change speed of the operation amount of the accelerator pedal. This is because when the change speed is used, it is necessary to store a large number of sampling values of the operation amount in the storage means.

(Third embodiment)
Hereinafter, the third embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 8 shows a procedure of processing relating to fuel pressure control at the time of a slow deceleration request according to the present embodiment. This process is repeatedly executed by the ECU 30, for example, at a predetermined cycle. In FIG. 8, the same steps as those in FIG. 4 are given the same step numbers for the sake of convenience.

  In this series of processes, first, in step S10a, the rotational speed of the crankshaft 8, the fuel pressure detected by the fuel pressure sensor 20, and the command injection amount are captured. In subsequent step S12b, it is determined whether or not the change amount of the command injection amount is not less than the lower limit value α3 and not more than the upper limit value β3. This step 12b is a process performed for the same purpose as step S12 of FIG. 4, and the lower limit value α3 and the upper limit value β3 are provided for the same purpose as the lower limit value α1 and the upper limit value β1, respectively. .

  If an affirmative determination is made in step S12b, it is determined that a slow deceleration request is being made, and the processes of steps S14 to S20 in FIG. 4 are performed.

  According to the present embodiment described above, the following effects can be obtained in addition to the effects (1) to (3) of the first embodiment.

  (6) By determining whether there is a slow deceleration request based on the decrease rate of the command injection amount, it is possible to appropriately determine whether there is a slow deceleration request.

(Fourth embodiment)
Hereinafter, the fourth embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  In the present embodiment, in order to forcibly reduce the command discharge amount of the fuel pump 6, the calculation parameter to be corrected is the calculation fuel pressure used for feedback control, and this is corrected to increase.

  FIG. 9 shows a functional block diagram of processing relating to feedback control of the target fuel pressure in the present embodiment. In FIG. 9, the same functional blocks as those in FIG. 2 are given the same reference numerals for the sake of convenience.

  As illustrated, the correction amount calculated by the correction amount calculation unit B28 is added to the detected value of the fuel pressure detected by the fuel pressure sensor 20. As a result, the differential pressure ΔPC that is the differential pressure of the detected fuel pressure with respect to the target fuel pressure and that is used for the calculation of feedback control increases. For this reason, in order to reduce the actual fuel pressure, the command discharge amount is reduced by feedback control.

  According to the present embodiment described above, the same effects as those of the first embodiment can be obtained.

(Fifth embodiment)
Hereinafter, a fifth embodiment will be described with reference to the drawings, focusing on differences from the first embodiment.

  In the present embodiment, a calculation parameter to be corrected for forcibly reducing the command discharge amount of the fuel pump 6 is set as an integral term, and this is corrected to decrease.

  In FIG. 10, the functional block diagram of the process regarding the feedback control of the target fuel pressure in this embodiment is shown. In FIG. 10, the same functional blocks as those of FIG.

  As illustrated, the integral term is corrected to decrease by the correction amount calculated by the correction amount calculation unit B28. As a result, the command discharge amount decreases.

  According to the present embodiment described above, the same effects as those of the first embodiment can be obtained.

(Sixth embodiment)
Hereinafter, the sixth embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  In the present embodiment, the target fuel pressure reduction correction is performed not only when a slow deceleration request is made but also when the vehicle approaches a gentle downhill when the vehicle is traveling at a constant speed by cruise control. That is, in this case, since a request for moderate reduction of the output torque of the diesel engine is made, the same problem as in the first embodiment is caused.

  FIG. 11 shows a functional block diagram of processing particularly during cruise control among the processing related to feedback control of the target fuel pressure in the present embodiment. In FIG. 11, functional blocks that perform the same processing as in FIG. 2 are given the same reference numerals for convenience.

  As shown in the figure, the cruise torque calculation unit B34 calculates the cruise torque CRT based on the target value of the vehicle traveling speed (vehicle speed) and the actual vehicle speed. The cruise injection amount calculation unit B36 calculates a command injection amount based on the cruise torque. On the other hand, the torque reduction request determination unit B32 determines whether or not there is a request for slow reduction of the output torque of the diesel engine based on the change amount of the cruise torque, and based on this, determines whether or not to perform the target fuel pressure decrease correction by the correction amount. decide.

  According to the present embodiment described above, the same effects as those of the first embodiment can be obtained.

(Other embodiments)
Each of the above embodiments may be modified as follows.

  -The determination method of the presence or absence of the slow deceleration request | requirement in 2nd Embodiment or 3rd Embodiment may be applied to 4th Embodiment or 5th Embodiment.

  In the sixth embodiment, the method of the fourth embodiment or the fifth embodiment may be used to forcibly reduce the command discharge amount of the fuel pump 6.

  The discharge amount of the fuel pump 6 may be forcibly reduced by correcting the calculation parameters used for the feedback control calculation not only when the output torque is requested to be gently reduced but also when the output torque is requested to be reduced.

  -The feedback control method is not limited to those exemplified in the above embodiments. For example, the feedforward term based on the change amount of the target fuel pressure may not be provided. In particular, when the design of the calculation method related to feedback control is changed to a configuration that does not include a feed-forward term based on the injection amount, the amount of fuel outflow from the common rail 12 due to fuel injection is controlled by feedback control of the detected fuel pressure to the target fuel pressure. Compensated. Therefore, since the change in the injection amount appears as a change in the fuel pressure and is reflected in the feedback control, the command discharge amount can be reduced in a region where the degree of decrease in the target fuel pressure is small relative to the degree of decrease in the command injection amount. Can not. Therefore, in such a case, the application of the present invention is generally effective.

  The correction amount calculation method is not limited to the one exemplified in the above embodiments. For example, a correction value that increases as the rate of decrease in the command injection amount increases may be calculated by multiplying the rate of change in the command injection amount by a proportional coefficient.

  The parameter to be corrected in order to forcibly reduce the discharge amount of the fuel pump 6 when the output torque is requested to be moderately reduced is not limited to that used for the calculation of the feedback control, but the parameter of the fuel pump 6 after the calculation It may be a calculation parameter (including the operation amount itself) used for calculation of the operation amount. However, when integral control is included in the feedback control, if the discharge amount is excessively reduced, the integral term remains a large value, so that the fuel pressure may overshoot as soon as correction of the calculation parameter is stopped. For this reason, in this case, the correction is limited to such an extent that the overshoot at the time of the slow reduction request can be suppressed, and the opportunity for the integral term to decrease as the detected fuel pressure exceeds the target fuel pressure remains. It is desirable.

  In each of the above embodiments, the pressure reducing valve that forcibly flows the fuel in the common rail 12 to the fuel tank 2 is not provided, but the present invention is not limited to this. For example, in a configuration including a pressure reducing valve, when there is a request for rapid reduction of the output torque, the pressure reducing valve may be opened instead of the process shown in FIG. Even in this case, when the output torque is required to be moderately reduced, the number of operations of the pressure reducing valve can be reduced by using the method exemplified in each of the above embodiments. Can be suppressed.

  -The target fuel pressure calculation method is not limited to using a two-dimensional map with the command injection amount and the rotational speed as inputs. For example, the operation amount of the accelerator pedal may be used instead of the command injection amount. Even in this case, in the high speed region, etc., the reduction degree of the target fuel pressure tends to be set smaller than the reduction degree of the operation amount of the accelerator pedal and the reduction degree of the command injection amount. The application of the invention is effective.

  -Not only a diesel engine but a cylinder injection type gasoline engine may be used, for example.

The figure which shows the whole structure of the engine system concerning 1st Embodiment. The functional block diagram of the process regarding the feedback control of the fuel pressure in the embodiment. The time chart which shows the control method of the fuel pressure at the time of the rapid deceleration request | requirement in the embodiment. The flowchart which shows the process sequence concerning control of the fuel pressure at the time of the slow deceleration request | requirement in the embodiment. The figure which shows the area | region which performs the fall correction | amendment of a target fuel pressure at the time of the slow deceleration request | requirement in the same embodiment. The time chart which illustrates the control aspect of the fuel pressure at the time of the slow deceleration request | requirement in the embodiment. The flowchart which shows the process sequence concerning control of the fuel pressure at the time of the slow deceleration request | requirement in 2nd Embodiment. The flowchart which shows the process sequence concerning control of the fuel pressure at the time of the slow deceleration request | requirement in 3rd Embodiment. The functional block diagram of the process regarding the feedback control of the fuel pressure in 4th Embodiment. The functional block diagram of the process regarding the feedback control of the fuel pressure in 5th Embodiment. The functional block diagram of the process regarding the feedback control of the fuel pressure in 6th Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Fuel tank, 6 ... Fuel pump, 12 ... Common rail, 16 ... Fuel injection valve, 20 ... Fuel pressure sensor, 30 ... ECU (fuel injection control apparatus).

Claims (9)

A pressure accumulating chamber for storing fuel in a high pressure state, a fuel pump for pressurizing and supplying the fuel into the pressure accumulating chamber, a fuel injection valve for injecting fuel in the pressure accumulating chamber, and a detecting means for detecting the fuel pressure in the pressure accumulating chamber. In a fuel injection control device that is applied to an internal combustion engine and feedback-controls the detected fuel pressure to a target value,
Determining means for determining whether or not there is a request to reduce the output torque of the internal combustion engine;
When it is determined by the determining means that there is a reduction request, the differential pressure of the detected fuel pressure with respect to the target value as the calculation parameter used for the calculation of the feedback control, and the calculation used for the calculation of the feedback control Fuel injection, comprising: a reduction means for forcibly decreasing the discharge amount of the fuel pump by forcibly increasing the differential pressure in accordance with the degree of decrease in the command value of the injection amount for the fuel injection valve. Control device. A pressure accumulating chamber for storing fuel in a high pressure state, a fuel pump for pressurizing and supplying the fuel into the pressure accumulating chamber, a fuel injection valve for injecting fuel in the pressure accumulating chamber, and a detecting means for detecting the fuel pressure in the pressure accumulating chamber. In a fuel injection control device that is applied to an internal combustion engine and feedback-controls the detected fuel pressure to a target value,
Determining means for determining whether or not there is a request to reduce the output torque of the internal combustion engine;
When the determination means determines that there is a reduction request, either the calculation parameter used for the calculation of the feedback control or the calculation parameter used for the calculation of the operation amount of the fuel pump after the calculation is used as the injection amount for the fuel injection valve. Reducing means for forcibly reducing the discharge amount of the fuel pump by correcting according to the degree of decrease of the command value,
The determination means includes means for calculating an annealing value whose degree of change is reduced based on an operation amount of the accelerator operation member, and the determination is performed based on a difference between the operation amount of the accelerator pedal and the annealing value. A fuel injection control device characterized in that the fuel injection control device is provided. A pressure accumulating chamber for storing fuel in a high pressure state, a fuel pump for pressurizing and supplying the fuel into the pressure accumulating chamber, a fuel injection valve for injecting fuel in the pressure accumulating chamber, and a detecting means for detecting the fuel pressure in the pressure accumulating chamber. In a fuel injection control device that is applied to an internal combustion engine and feedback-controls the detected fuel pressure to a target value,
Determining means for determining whether or not there is a request to reduce the output torque of the internal combustion engine;
When the determination means determines that there is a reduction request, either the calculation parameter used for the calculation of the feedback control or the calculation parameter used for the calculation of the operation amount of the fuel pump after the calculation is used as the injection amount for the fuel injection valve. Reducing means for forcibly reducing the discharge amount of the fuel pump by correcting according to the degree of decrease of the command value,
The determination means determines whether or not there is a gradual reduction request in which the degree of decrease in the target value is small relative to the degree of reduction in the fuel injection amount via the fuel injection valve as the presence or absence of a request to reduce the output torque of the internal combustion engine. What is claimed is: 1. A fuel injection control apparatus comprising: The fuel injection control apparatus according to any one of claims 1 to 3, wherein the reducing means forcibly reduces and corrects the target value using the target value as the calculation parameter . The reducing means includes means for calculating an annealing value whose degree of change is relaxed based on a command value of the injection amount, and means for calculating a difference between the command value and the annealing value as the degree of reduction. The fuel injection control device according to any one of claims 1 to 4, further comprising: The said reduction means performs the said forced reduction when it is judged that the said reduction request | requirement exists and the rotational speed of the output shaft of the said internal combustion engine is more than a predetermined speed. 6. The fuel injection control device according to any one of 5 above . The said reduction | decrease means performs the said forced reduction | decrease when it is judged that the said reduction request | requirement exists and the said fuel pressure is more than a predetermined pressure, The said reduction | decrease means characterized by the above-mentioned. Fuel injection control device. The fuel injection control device according to claim 1, wherein the determination unit performs the determination based on a deceleration side operation of an accelerator operation member . The fuel injection control device according to claim 1, wherein the determination unit performs the determination based on a decrease in a command value of an injection amount for the fuel injection valve .

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