JP2011106414A - Fuel injection control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device capable of enhancing the accuracy of fuel injection and relaxing the processing load. <P>SOLUTION: The fuel injection control device is to be used in a fuel injection system arranged so that the fuel fed with pressure by a fuel pump 12 having a plunger 30 is stored in a common rail 2 and the fuel stored in the common rail 2 is injected by an injector 4 into each cylinder of an internal combustion engine, wherein the pressure Pc1 in the common rail 2 at the injection starting time t1 is presumed from the pressure sensing value Pc0 of the common rail 2 at the pressure feed starting time t0 when the fuel pump 12 starts feeding the fuel with pressure, the position of the plunger 30 at the pressure feed starting time t0, and the position of the plunger 30 at the injection starting time t1 when the injector 4 starts injecting the fuel. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel injection control device used in a fuel injection system that stores high-pressure fuel pumped by a fuel pump in a common rail and injects high-pressure fuel stored in the common rail.

  Conventionally, this type of fuel injection control apparatus has a command injection period, which is a period for injecting fuel from an injector, based on a required injection amount that is a required injection amount and a rail pressure that is a fuel pressure in a common rail. decide.

  Here, in order to accurately determine the command injection period and improve the fuel injection control accuracy, it is important to accurately grasp the rail pressure at the actual injection start time. However, when fuel is being pumped from the fuel pump to the common rail, the rail pressure increases as the fuel is pumped. Therefore, if the fuel injection timing from the injector overlaps with the fuel pump timing from the fuel pump, the actual injection It becomes difficult to accurately grasp the rail pressure at the start time.

  In view of this point, in the prior art of Patent Document 1, the rail pressure is detected at the command injection start time, and the rail pressure increase amount from the command injection start time to the actual injection start time is determined as the displacement mode of the plunger of the fuel pump. The rail pressure at the actual injection start time is estimated by adding the calculated rail pressure increase amount to the rail pressure detection value at the command injection start timing. The command injection start time is a time for instructing the injector to start fuel injection.

JP 2007-126980 A

  However, in the prior art disclosed in Patent Document 1, since the rail pressure is detected at the command injection start time, there is an extremely short time difference corresponding to the response delay of the injector between the rail pressure detection time and the actual injection start time. Only. Here, the response delay of the injector means that a delay occurs from when the injector is instructed to start injection to when the injection is actually started (see FIGS. 3A and 3B described later).

  Therefore, in the prior art of Patent Document 1, a series of arithmetic processing such as calculation of rail pressure at the start of actual injection based on the detection result of rail pressure and determination of a command injection period based on the calculation result are performed using actual fuel. Must be done almost simultaneously with the injection. In other words, the process for determining the command injection period cannot be performed with sufficient time for actual fuel injection.

  As a result, the conventional technique of Patent Document 1 has a problem that the processing load increases because the determination process of the command injection period must be performed in a very short period.

  The present invention has been made in view of the above points, and has an object to improve the accuracy of fuel injection and reduce the processing load.

In order to achieve the above object, in the invention described in claim 1, the fuel pumped by the fuel pump (12) having the plunger (30) is stored in the common rail (2), and the fuel stored in the common rail (2) is stored. A fuel injection control device used in a fuel injection system for injecting into a cylinder of an internal combustion engine with an injector (4),
The pressure detection value (Pc0) of the common rail (2) at the pumping start time (t0) when the fuel pump (12) starts pumping the fuel, the position of the plunger (30) at the pumping start time (t0), and the injector (4 ) Estimates the pressure (Pc1) of the common rail (2) at the injection start time (t1) based on the position of the plunger (30) at the injection start time (t1) at which the fuel injection starts. .

  According to this, as in the above-described prior art, the pressure (Pc1) of the common rail (2) at the injection start time (t1) is determined based on the pressure detection value (Pc0) of the common rail (2) and the position of the plunger (30). Since it estimates, the precision of fuel injection can be improved.

  Further, since the pressure detection value (Pc0) of the common rail (2) is the one at the pumping start time (t0), the injection start is compared with the above-described conventional technique using the pressure detection value at the command injection start timing (ti). The processing load for estimating the pressure (Pc1) of the common rail (2) at the time point (t1) can be reduced (see FIG. 3 described later).

According to a second aspect of the present invention, in the fuel injection control device according to the first aspect, the position of the plunger (30) at the pumping start time (t0) and the position of the plunger (30) at the injection start time (t1) On the basis of the pressure increase amount (ΔPc) of the common rail (2) from the pumping start time (t0) to the injection start time (t1),
The pressure (Pc1) of the common rail (2) at the injection start time (t1) is estimated by adding the pressure increase amount (ΔPc) to the pressure detection value (Pc0). Thereby, the precision of fuel injection can be raised more.

According to a third aspect of the present invention, in the fuel injection control device according to the second aspect, the position of the plunger (30) at the pumping start time (t0) and the position of the plunger (30) at the injection start time (t1) Based on the above, the fuel pumping amount (Qpump) from the fuel pump (12) to the common rail (2) from the pumping start time (t0) to the injection start time (t1) is obtained.
The pressure increase amount (ΔPc) is obtained based on the pumping amount (Qpump).

  Thereby, the amount of pressure increase (ΔPc) of the common rail (2) from the pumping start time (t0) to the injection start time (t1) can be obtained with high accuracy.

  According to a fourth aspect of the present invention, in the fuel injection control device according to the third aspect, when the previous injection is performed between the pressure start time (t0) and the injection start time (t1), the pumping amount ( The fuel change amount (ΔQ) of the common rail (2) from the pumping start time (t0) to the injection start time (t1) is obtained by subtracting the required injection amount (Qinj) at the previous injection from Qpump), and the fuel change The pressure increase amount (ΔPc) is obtained based on the amount (ΔQ).

  Thereby, when the fuel pump (12) performs fuel pumping once when performing fuel injection a plurality of times, the accuracy of fuel injection can be improved.

According to a fifth aspect of the present invention, in the fuel injection control device according to any one of the second to fourth aspects, a correction corresponding to a fuel leakage amount in the fuel injection system with respect to the pressure increase amount (ΔPc). To obtain the corrected pressure increase amount (ΔPc ′),
The pressure of the common rail (2) at the injection start time (t1) is estimated by adding the corrected pressure increase amount (ΔPc ′) to the detected pressure value (Pc0).

  Thereby, the estimation precision of the pressure of the common rail (2) at the injection start time (t1) can be improved.

According to the sixth aspect of the present invention, the fuel pumped by the fuel pump (12) having the plunger (30) is stored in the common rail (2), and the fuel stored in the common rail (2) is stored in the internal combustion engine by the injector (4). A fuel injection control device used in a fuel injection system for injecting into a cylinder of
The pressure detection value (Pc0) of the common rail (2) at the pumping start time (t0) when the fuel pump (12) starts pumping the fuel, and the injector (4) starts fuel injection from the pumping start time (t0). The pressure (Pc1) of the common rail (2) at the injection start time (t1) is estimated based on the pressure increase amount (ΔPc) of the common rail (2) until the injection start time (t1). Thereby, the same effect as that of the invention described in claim 1 can be obtained.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

1 is an overall configuration diagram of a fuel injection system according to a first embodiment of the present invention. It is sectional drawing of the high pressure pump of FIG. It is a time chart which shows the action | operation in 1st Embodiment of this invention. It is a flowchart which shows the arithmetic processing which calculates | requires the rail pressure in the injection start time. It is a time chart which shows the action | operation in 2nd Embodiment of this invention.

(First embodiment)
The first embodiment of the present invention will be described below. FIG. 1 is an overall configuration diagram showing a common rail fuel injection system in the present embodiment. As shown in FIG. 1, the common rail type fuel injection system injects fuel into a vehicular diesel engine (not shown). As a fuel supply pump 1, a common rail 2, an EDU 3, an injector 4, and a fuel injection control device. Engine ECU 5 and the like.

  The fuel supply pump 1 pumps high-pressure fuel to the common rail 2. Specifically, the fuel supply pump 1 is a high-pressure pump 11 that pumps fuel from a fuel tank 7 through a fuel filter 6, and a high-pressure fuel pump that pressurizes fuel supplied from the low-pressure pump 11 and pumps the fuel to the common rail 2. A pump 12 and a suction metering valve 13 for adjusting the flow rate of fuel supplied from the low pressure pump 11 to the high pressure pump 12 are provided.

  The fuel supply pump 1 is an assembly in which a low pressure pump 11, a high pressure pump 12, and a suction metering valve 13 are accommodated in a common main body housing. The fuel tank 7 and the fuel filter 6 are disposed outside the main body housing.

  As shown in FIG. 2, the housing of the fuel supply pump 1 includes an aluminum housing 20, an aluminum bearing cover 21, and a pair of ferrous metal cylinder heads 22. A cam chamber 23 in which a cam ring (to be described later) is accommodated is formed at the center of the housing 20, and cylinder chambers 24 in which cylinders (to be described later) are accommodated are formed on both sides of the cam chamber 23 in the housing 20. .

  The cylinder head 22 includes a cylinder head main body 220 that is located outside the housing 20 and closes the cylinder chamber 24, and a cylindrical cylinder 221 that protrudes from the cylinder head main body 220 and is accommodated in the cylinder chamber 24. ing. In the following description, as necessary, the cylinder chamber 24 positioned on the top of the heaven region is referred to as the first cylinder chamber 24a, and the cylinder chamber 24 positioned on the lower side in the vertical direction is referred to as the second cylinder chamber 24b.

  The cam shaft 25 is made of iron-based metal, is rotatably supported by the housing 20 and the bearing cover 21 via the journal 26, and is driven to rotate by a diesel engine (not shown). The cam shaft 25 and the bearing cover 21 are sealed with an oil seal 27. A cam 28 having a circular cross section is formed eccentrically with respect to the cam shaft 25 at an intermediate portion in the axial direction of the cam shaft 25.

  A cam ring 29 that revolves around the cam shaft 25 is fitted to the outer periphery of the cam 28. The cam ring 29 includes a cam ring main body 290 and a bush 291 integrated with the cam ring main body 290. More specifically, the cam ring body 290 is made of an iron-based metal, has an outer shape of a quadrangular prism, and has a circular through hole. The bush 291 is formed in a cylindrical shape from copper, aluminum, or resin, and is press-fitted into a through hole of the cam ring body 290 so as to be slidable with the cam 28. The cam 28 and the cam ring 29 are accommodated in the cam chamber 23.

  On both sides of the cam ring 29, iron-based metal plungers 30 that reciprocate following the revolution of the cam ring 29 are arranged. The plunger 30 includes a columnar portion 300 that is reciprocally inserted into the cylinder 221 and a hook-shaped plunger head 301 that is disposed in the cam chamber 23 and is opposed to the cam ring 29. In the following description, as necessary, the plunger 30 positioned on the upside of the sky is referred to as a first plunger 30a, and the plunger 30 positioned on the downside of the top and bottom is referred to as a second plunger 30b.

  The spring 31 disposed on the outer peripheral side of the cylinder 221 is sandwiched between the cylinder head main body 220 and the plunger head 301. The spring 30 urges the plunger 30 toward the cam ring 29 so that the plunger head 301 is pressed against the cam ring 29. The contact surface between the cam ring 29 and the plunger head 301 is formed in a flat shape, so that the rotation of the cam ring 29 is prevented, so that the cam ring 29 rotates while sliding with the plunger head 301 as the cam 28 rotates. Revolve without any problems.

  In the cylinder head 22, a fuel pressurizing chamber 32 whose volume changes with the reciprocation of the plunger 30, and an inlet side check valve 33 that allows only the flow of fuel from the low-pressure pump described later to the fuel pressurizing chamber 32. , And an outlet check valve 34 that allows only the flow of fuel from the fuel pressurizing chamber 32 to the common rail 2 is provided.

  Accordingly, when the plunger 30 reaches the bottom dead center and starts to be displaced toward the top dead center, the fuel pumping from the high pressure pump 12 to the common rail 2 is started. Here, the bottom dead center is a position when the plunger 30 is displaced most toward the cam ring 29 and the fuel pressurizing chamber 32 reaches the maximum volume.

  Thus, in this embodiment, the pumping start time at which fuel pumping from the high pressure pump 12 to the common rail 2 is started coincides with the bottom dead center point at which the plunger 30 reaches the bottom dead center.

  One end of the camshaft 25 is coupled to a low pressure pump 11 constituted by an inner gear type trochoid pump. The low-pressure pump 11 is housed in the pump cover 35 so as to be freely rotatable. The low-pressure pump 11 is driven to rotate by the camshaft 25 so as to pressurize and discharge the fuel sucked from the fuel tank, and the discharge pressure increases as the rotational speed of the internal combustion engine increases.

  The fuel discharged from the low-pressure pump 11 is supplied to the fuel pressurizing chamber 32 through a fuel passage (not shown) and an inlet side check valve 33. An intake metering valve 13 (not shown in FIG. 2) for adjusting the amount of fuel supplied to the fuel pressurizing chamber 32 according to the operating state of the internal combustion engine is provided in the middle of the fuel passage. Yes. The suction metering valve 13 may be either a normally open type or a normally closed type.

  A part of the fuel discharged from the low-pressure pump 11 is supplied to the cam chamber 23 via a lubricating fuel supply passage 36 formed in the housing 20. An end portion of the lubricating fuel supply passage 36 is opened at a position facing the cam chamber 23.

  A return fuel passage (not shown) that opens to a position facing the first cylinder chamber 24a is formed in the housing 20, and an overflow pipe (not shown) is press-fitted into the return fuel passage. Further, the overflow pipe is connected to the fuel tank 7 via a return pipe 14 shown in FIG.

  The camshaft 25 is driven by a diesel engine. In the present embodiment, the camshaft 25 is connected to the crankshaft 8 via a speed reduction mechanism (not shown) that reduces the rotation of the crankshaft 8 of the engine to ½. For this reason, when the crankshaft 8 rotates once (360 ° CA), the camshaft 25 rotates 1/2.

  A common rail 2 shown in FIG. 1 is a livestock pressure means that holds and stores high-pressure fuel supplied from the fuel supply pump 1 at a target pressure (hereinafter referred to as target rail pressure). This target rail pressure is determined by the engine ECU 5 based on the operation state of the diesel engine such as an accelerator opening signal and an engine speed signal, for example.

  Further, a pressure limiter (not shown) that opens when the fuel pressure in the common rail 2 (hereinafter referred to as rail pressure) exceeds a predetermined upper limit value and releases the rail pressure is attached to the common rail 2. It has been. The fuel that has flowed out of the pressure limiter is returned to the fuel tank 7 via a fuel pipe (not shown).

  Furthermore, a rail pressure sensor 40 is attached to the common rail 2, and a signal corresponding to the actual rail pressure (hereinafter referred to as an actual rail pressure) is input to the engine ECU 5.

  The EDU 3 is a drive device that outputs an open / close signal (drive current) for opening and closing the nozzle hole of the injector 4 to the injector 4 based on a drive signal input from the engine ECU 5.

  High pressure fuel is introduced into the injector 4 from the common rail 2 through the fuel pipe 15, and surplus fuel inside the injector 4 is returned to the fuel tank 7 through the fuel pipe 16. The injector 4 is attached to the cylinder head of the diesel engine, and the injection hole is opened and closed based on an opening / closing signal input from the EDU 3. When the injection hole is opened, fuel is injected from the injection hole into the combustion chamber of the diesel engine. Is supposed to be injected.

  The injector 4 is attached to each cylinder (four cylinders in this embodiment) of the diesel engine, and high pressure fuel is supplied to each injector 4 via each fuel pipe 15.

  The engine ECU 5 includes a microcomputer including a CPU, ROM, EEPROM, RAM, and the like (not shown), and performs arithmetic processing according to a program stored in the microcomputer.

  Signals are input to the engine ECU 5 from sensors, and the engine ECU 5 determines the optimal injection timing, injection amount, etc. according to the operating state of the diesel engine based on these input signals and the like. Then, each injector 4 is driven.

  Further, the engine ECU 5 calculates the target discharge amount of the high-pressure pump 12 so that the actual rail pressure of the common rail 2 detected by the rail pressure sensor 40 follows the target rail pressure corresponding to the injection pressure, and performs intake metering. The valve 13 is driven to feedback control the rail pressure.

  Here, as sensors, for example, in addition to the rail pressure sensor 40 described above, a crank angle sensor 41 that detects the rotation angle of the crankshaft 8 of the engine, a vehicle speed sensor 42 that detects the vehicle speed, and a temperature of engine cooling water are detected. A cooling water temperature sensor 43 that detects the temperature of the fuel in the fuel supply pump 1, an accelerator opening sensor 45 that detects the amount of depression of the accelerator pedal of the vehicle (hereinafter referred to as accelerator opening), and the like. ing.

  FIG. 3 is a time chart showing the operation in the above configuration. The engine ECU 5 performs fuel injection amount control for each cylinder from the operating state of the engine as follows. First, the engine ECU 5 determines the engine speed obtained from the pulse signal input from the crank angle sensor 41, the accelerator opening input from the accelerator opening sensor 45, and the engine coolant temperature input from the coolant temperature sensor 43. Then, using the fuel temperature input from the fuel temperature sensor 44, a required injection amount (refer to the hatching region Qinj in FIG. 3B) that is an injection amount required from the operating state of the engine is calculated.

  Subsequently, the engine ECU 5 uses the engine speed determined from the pulse signal input from the crank angle sensor 41 and the accelerator opening input from the accelerator opening sensor 45 to determine the command injection start timing (FIG. 3A). The time ti is calculated, and the rail pressure (see the pressure Pc1 in FIG. 3 (e)) and the required injection amount at the actual injection start time (see the time t1 in FIG. 3 (b)) are calculated. A command injection period (refer to the period Tinj in FIG. 3A) corresponding to the energization time of the drive current to the injector 4 is calculated.

  Here, the command injection start time is a time for instructing the injector 4 to start fuel injection. The actual injection start time is a time when fuel injection from the injector 4 is actually started. Since the injector 4 has a response delay, the actual injection start time is delayed with respect to the command injection start time (see FIGS. 3A and 3B).

  Then, the engine ECU 5 outputs a pulsed drive current to the EDU 3 according to the command injection start timing and the command injection period (see FIG. 3A). When the EDU 3 opens and closes each injector 4, fuel is injected from each injector 4 into the cylinder of the engine, and the engine operates.

  In the present embodiment, as described above, the diesel engine has four cylinders, the high-pressure pump 12 has two cylinders, and when the crankshaft 8 of the diesel engine makes one revolution, the camshaft 25 of the high-pressure pump 12 makes a half revolution. For this reason, when the injector 4 performs the fuel injection twice, the high-pressure pump 12 performs the two-injection one-pressure feeding operation in which the fuel pressure feeding is performed once.

  Here, the “rail pressure at the command injection start time” used in the calculation of the command injection period described above is obtained by the arithmetic processing shown in the flowchart of FIG. The calculation process of FIG. 4 is executed in the engine ECU 5 and is started when the engine ECU 5 is turned on by operating a key switch (not shown) when the diesel engine is started, and is operated when the diesel engine is stopped. When the power supply to the engine ECU 5 is stopped, the process is terminated.

  First, in step S100, the actual rail pressure Pc0 (FIG. 3) at the bottom dead center point t0 (FIG. 3) is acquired based on the pressure detection value of the rail pressure sensor 40. Here, the bottom dead center point t0 refers to the time when one of the first and second plungers 30a, 30b has reached the bottom dead center. As described above, in the present embodiment, the bottom dead center time t0 is also the pumping start time. Whether or not the plunger 30 is at bottom dead center can be determined based on the rotation angle of the crankshaft 8 of the engine detected by the crank angle sensor 41.

  Subsequently, in step S110, the required injection amount Qinj (FIG. 3) calculated at the time of the previous injection (first injection) is acquired. Subsequently, in step S120, a time Tpump (FIG. 3) from the bottom dead center time t0 to the next actual injection start time t1 (FIG. 3) is obtained. The actual injection start time t1 can be obtained by adding the response delay time of the injector 4 to the command injection start timing ti. The command injection start timing ti is calculated using the engine speed and the accelerator opening as described above.

  The response delay time of the injector 4 is a delay time at the actual injection start time with respect to the command injection start timing. The response delay time of the injector 4 depends on the rail pressure. In addition, the response delay time of the injector 4 changes due to pressure pulsation caused by the previous injection. Therefore, the response delay time of the injector 4 can be calculated based on the time interval from the previous injection to the next injection and the actual rail pressure Pc0.

  Subsequently, in step S130, a fuel pumping amount Qpump (FIG. 3) which is a pumping amount of fuel to the common rail 2 until the time Tpump elapses from the bottom dead center time t0 (that is, until the actual injection start time t1) is obtained. Specifically, the positions of the first and second plungers 30a and 30b at the bottom dead center time t0, and the first and second times when the time Tpump has elapsed from the bottom dead center time t0 (that is, the actual injection start time t1). The positions of the plungers 30a and 30b are obtained, and the fuel pumping amount Qpump is obtained based on the positions of the first and second plungers 30a and 30b.

  Here, the positions of the first and second plungers 30a and 30b when the time Tpump has elapsed from the bottom dead center point t0 can be obtained based on the rotation angle of the cam shaft 25 corresponding to the time Tpump. The rotation angle of the camshaft 25 corresponding to the time Tpump can be obtained based on the time Tpump and the engine speed.

  Further, the fuel pressure feed amount Qpump is the sum of the oil feed amount by the first plunger 30a and the oil feed amount by the second plunger 30b, and corresponds to the area of the hatched region in FIG. 3D in the example of FIG. .

  Subsequently, in step S140, based on the fuel pumping amount Qpump and the required injection amount Qinj at the previous injection, the pressure increase of the common rail 2 until the time Tpump elapses from the bottom dead center time t0 (that is, until the actual injection start time t1). A rail pressure increase amount ΔPc (FIG. 3), which is an amount, is obtained. Specifically, first, by subtracting the required injection amount Qinj at the previous injection from the fuel pumping amount Qpump, the common rail until the time Tpump elapses from the bottom dead center time t0 (that is, until the actual injection start time t1). 2 is obtained, and the rail pressure increase amount ΔPc is obtained based on the fuel change amount ΔQ and a map or calculation formula stored in advance in the ECU 5.

  Here, the map or calculation formula stored in advance in the ECU 5 indicates the relationship between the fuel change amount ΔQ and the rail pressure increase amount ΔPc. When the required injection amount Qinj exceeds the fuel pumping amount Qpump, the fuel change amount ΔQ and the rail pressure increase amount ΔPc are negative values.

  Subsequently, in step S150, correction corresponding to the mechanical loss (fuel leakage amount) in the injector 4 or the high-pressure pump 12 is performed on the rail pressure increase amount ΔPc to obtain the corrected rail pressure increase amount ΔPc ′. In step S150, a correction corresponding to the pressure loss in each piping portion may be performed.

  In step S160, the rail pressure Pc1 (FIG. 3) at the next actual injection start time t1 is obtained by adding the corrected rail pressure increase ΔPc ′ to the actual rail pressure Pc0 at the bottom dead center time t0.

  According to the present embodiment, the rail pressure Pc1 at the injection start time point t1 is estimated based on the pressure detection value Pc0 of the common rail 2 and the position of the plunger 30 as in the above-described conventional technique, so that the accuracy of fuel injection can be improved. it can.

  Furthermore, since the pressure detection value Pc0 of the common rail 2 is used at the pumping start time, that is, the bottom dead center time t0, compared with the above-described conventional technique using the pressure detection value at the command injection start timing ti, at the injection start time t1. The processing load for estimating the rail pressure Pc1 can be reduced (see FIG. 3).

  In particular, in the present embodiment, as in steps S140 and S160, the actual injection start from the pumping start time t0 based on the position of the plunger 30 at the pumping start time t0 and the position of the plunger 30 at the actual injection start time t1. Since the rail pressure increase amount ΔPc up to the time point t1 is obtained and the rail pressure increase amount ΔPc is added to the pressure detection value Pc0 to estimate the rail pressure Pc1 at the actual injection start time point t1, the fuel injection accuracy is further improved. Can do.

  In addition, in the present embodiment, as in steps S130 and S140, the actual injection start from the pumping start time t0 based on the position of the plunger 30 at the pumping start time t0 and the position of the plunger 30 at the actual injection start time t1. Since the fuel pumping amount Qpump up to the time point t1 is obtained and the pressure increase amount ΔPc is determined based on the fuel pumping amount Qpump, the pressure increase amount ΔPc of the common rail 2 from the pumping start point t0 to the actual injection start point t1 is accurately determined. be able to.

  Further, in this embodiment, as in steps S150 and S160, correction corresponding to the amount of fuel leakage in the fuel injection system is performed on the pressure increase amount ΔPc, and the corrected pressure increase amount ΔPc ′ is set to the point at which pumping starts. Since the pressure of the common rail 2 at the injection start time t1 is estimated by adding to the pressure detection value Pc0 at t0, it is possible to improve the estimation accuracy of the pressure of the common rail 2 at the injection start time t1.

(Second Embodiment)
In the first embodiment, the two-injection one-pressure feeding operation is performed. In this embodiment, as shown in FIG. 5, the one-injection one-pressure feeding operation is performed. That is, in the present embodiment, the camshaft 25 of the high-pressure pump 12 is configured to rotate once when the crankshaft 8 of the diesel engine rotates once (360 ° CA).

  Also in the present embodiment, the rail pressure Pc1 at the next actual injection start time t1 can be estimated based on the actual rail pressure Pc0 at the bottom dead center time t0, which is the pumping start time, as in the first embodiment. It is possible to reduce the load of calculation processing for the command injection period in the engine ECU 5.

  Incidentally, in the present embodiment, since the previous injection is completed before the bottom dead center point t0, the required injection amount Qinj subtracted from the fuel pumping amount Qpump in step S140 becomes zero.

(Other embodiments)
In each of the above embodiments, in step S130, the fuel pumping amount Qpump is obtained based only on the positions of the first and second plungers 30a and 30b. However, the positions and suctions of the first and second plungers 30a and 30b are determined. The fuel pumping amount Qpump may be obtained based on the opening of the metering valve 13.

  In each of the above embodiments, the intake metering valve 13 is provided at the fuel inlet of the high-pressure pump 12, and the fuel flow supplied from the low-pressure pump 11 to the high-pressure pump 12 is adjusted by the intake metering valve 13. The flow rate of fuel to be pumped from the pump 12 to the common rail 2 is adjusted. A discharge amount control valve is provided at the fuel outlet of the high pressure pump 12, and the flow rate of fuel to be pumped from the high pressure pump 12 to the common rail 2 is adjusted by the discharge amount control valve. You may make it do. In this case, the time when the discharge amount control valve is opened is the pressure start time.

  In each of the above embodiments, in steps S130 and S140, the fuel pumping amount Qpump is obtained based on the position of the plunger 30, and the rail pressure increase amount ΔPc is obtained based on the fuel pumping amount Qpump. However, the fuel pumping amount Qpump is not necessarily calculated. The rail pressure increase amount ΔPc may be obtained based on the position of the plunger 30 and a map stored in the engine ECU 5 in advance. Here, the map stored in advance in the engine ECU 5 only needs to indicate the relationship between the position of the plunger 30 and the rail pressure increase amount ΔPc.

  In each of the above embodiments, the present invention is applied to a fuel injection system that injects a required injection amount of fuel at one time. However, the required injection amount of fuel is divided into pre-injection, main injection, and after injection. The present invention can also be applied to a fuel injection system that injects fuel.

  Moreover, in each said embodiment, although this invention is applied to the diesel engine, this invention is applicable to various internal combustion engines, such as a cylinder injection type gasoline engine, for example, without being limited to this.

2 Common rail 4 Injector 12 High-pressure pump (fuel pump)
30 Plunger Pc0 Actual rail pressure at the start of pumping (pressure detection value)
Pc1 Rail pressure at the start of injection Qpump Fuel pumping amount t0 Pumping start point t1 Injection start point ΔPc Pressure increase

Claims (6)

Fuel that is pumped by a fuel pump (12) having a plunger (30) is stored in a common rail (2), and the fuel stored in the common rail (2) is injected into a cylinder of an internal combustion engine by an injector (4) A fuel injection control device used in an injection system,
The pressure detection value (Pc0) of the common rail (2) at the pumping start time (t0) when the fuel pump (12) starts pumping the fuel, and the position of the plunger (30) at the pumping start time (t0) And the position of the plunger (30) at the injection start time (t1) at which the injector (4) starts the fuel injection, the pressure of the common rail (2) at the injection start time (t1) ( A fuel injection control device that estimates Pc1). Based on the position of the plunger (30) at the pumping start time (t0) and the position of the plunger (30) at the injection start time (t1), the injection start time ( The amount of pressure increase (ΔPc) of the common rail (2) until t1) is obtained,
The pressure (Pc1) of the common rail (2) at the injection start time (t1) is estimated by adding the pressure increase amount (ΔPc) to the pressure detection value (Pc0). The fuel injection control device described. Based on the position of the plunger (30) at the pumping start time (t0) and the position of the plunger (30) at the injection start time (t1), the injection start time ( The fuel pumping amount (Qpump) from the fuel pump (12) to the common rail (2) until t1) is determined.
The fuel injection control device according to claim 2, wherein the pressure increase amount (ΔPc) is obtained based on the pumping amount (Qpump).   When the previous injection is performed between the pumping start time (t0) and the injection start time (t1), the required injection amount (Qinj) at the time of the previous injection is subtracted from the pumping amount (Qpump). To determine the fuel change amount (ΔQ) of the common rail (2) from the pressure start time (t0) to the injection start time (t1), and the pressure increase amount (ΔPc) based on the fuel change amount (ΔQ). The fuel injection control device according to claim 3, wherein: A corrected pressure increase amount (ΔPc ′) is obtained by performing correction corresponding to the fuel leak amount in the fuel injection system on the pressure increase amount (ΔPc),
The pressure of the common rail (2) at the injection start time (t1) is estimated by adding the corrected pressure increase amount (ΔPc ') to the pressure detection value (Pc0). 5. The fuel injection control device according to any one of items 4 to 4. Fuel that is pumped by a fuel pump (12) having a plunger (30) is stored in a common rail (2), and the fuel stored in the common rail (2) is injected into a cylinder of an internal combustion engine by an injector (4) A fuel injection control device used in an injection system,
The pressure detection value (Pc0) of the common rail (2) at the pumping start time (t0) when the fuel pump (12) starts pumping the fuel, and the injector (4) from the pumping start time (t0) Based on the pressure increase amount (ΔPc) of the common rail (2) up to the injection start time (t1) at which fuel injection is started, the pressure (Pc1) of the common rail (2) at the injection start time (t1) is determined. A fuel injection control device characterized by estimating.

Images