JP4640019B2 - Fuel injection control device - Google Patents

Description

  The present invention relates to a fuel injection control device.

  In order to inject fuel directly into the cylinder of an engine, it is necessary to increase the fuel supplied to each fuel injection valve to a high pressure, and a high-pressure fuel injection device for that purpose is known.

  The high-pressure fuel injection device includes a low-pressure pump that pumps fuel in a fuel tank and a high-pressure pump that further pressurizes the low-pressure fuel. The low pressure pump is driven by an electric motor, and the high pressure pump is driven by an engine. The fuel pumped by the high pressure pump during the engine operation is maintained in a high pressure state in the delivery pipe. The high-pressure fuel is injected into the cylinder through each fuel injection valve.

  By the way, when the engine is stopped, the high-pressure pump and the low-pressure pump are stopped, and the fuel injection through the fuel injection valve is stopped. For this reason, the high-pressure fuel is sealed in the delivery pipe. The temperature of the fuel in the delivery pipe gradually decreases with time.

  The fuel is thermally contracted as the temperature decreases, and the fuel pressure in the delivery pipe decreases. It has been confirmed that a temperature change of 10 ° C. causes a volume change of about 1%, which results in a pressure change of about 8 MPa. As described above, the decrease in the fuel pressure accompanying the temperature decrease is relatively rapid. For this reason, when the fuel drops to a predetermined temperature, the fuel pressure in the delivery pipe may be lower than the saturated vapor pressure at the predetermined temperature. Then, vapor (fuel vapor) can be generated in the delivery pipe. When vapor is formed in the delivery pipe, the pressure in the delivery pipe thereafter changes in the vicinity of the saturated vapor pressure at each temperature as the temperature decreases, and the vapor space gradually increases in the delivery pipe. Thus, a large space may be formed in the delivery pipe when the engine is started.

  If such a space exists, the inside of the delivery pipe cannot be increased to a desired pressure.

Therefore, in the conventional fuel injection device, the vapor generation state is determined from the pressure increase state of the low pressure pump / high pressure pump and the change in the fuel temperature while the engine is stopped. When the vapor generation is determined, the fuel pressure is the rated pressure of the low pressure pump ( The fuel injection is started when it becomes close to 0.35 MPa) (see Patent Document 1).
Japanese Patent Laid-Open No. 2003-120460

  However, the above-described conventional device determines whether or not vapor is generated based on the pressure increase state of the fuel pressure. Therefore, it cannot be determined unless the low pressure pump is driven or the high pressure pump is driven by cranking. Judgment time is required.

  The present invention has been made paying attention to such conventional problems. When the engine is started, it is determined in a short time whether or not vapor has occurred in the fuel injection mechanism. It aims at providing the fuel-injection control apparatus which can crush reliably.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

The present invention includes a pump (11, 21) for increasing the pressure of fuel, a delivery pipe (31) for supplying fuel increased in pressure by the pump (11, 21) to a fuel injection valve (32a-32d), Pressure detection means (51 / step S12) for detecting the pressure of the fuel in the delivery pipe (31) while the engine is stopped, and temperature detection for detecting the temperature of the fuel in the delivery pipe (31) while the engine is stopped Means (51 / step S21), saturated vapor pressure calculating means (step S23) for calculating the saturated vapor pressure of the fuel at the detected temperature, and vapor generation when the detected fuel pressure is lower than the calculated saturated vapor pressure And a vapor determination means (step S24) for determining the amount of vapor generated when vapor generation is determined based on the calculated saturated vapor pressure and the detected fuel pressure. Vapor amount estimating means (steps S251 to S252), vapor crushing cranking calculating means (step S253) for calculating the number or time of cranking necessary for crushing the estimated vapor, and after performing the calculated cranking And fuel injection means (step S83) for starting stratification and starting fuel injection.

According to the present invention, when the engine is stopped, vapor generation is determined based on whether or not the fuel pressure in the delivery pipe is lower than the saturated vapor pressure of the fuel calculated based on the temperature of the fuel in the delivery pipe. The occurrence of vapor can be quickly determined. And when vapor | steam generation | occurrence | production was determined, since cranking required in order to crush vapor | steam is performed, fuel injection is started and stratification start is performed , Therefore Vapor can be crushed reliably.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing a first embodiment of a fuel injection control device according to the present invention.

  The fuel injection device 1 includes a fuel pumping unit 10, a fuel high pressure unit 20, and a high pressure fuel injection unit 30.

  The fuel pumping unit 10 includes a feed pump (low pressure pump) 11, a pressure regulator 12, a fuel filter 13, and a fuel tank 14.

  The fuel tank 14 stores fuel and houses the feed pump 11 and the pressure regulator 12. The feed pump 11 is driven by the electric motor 11 a and supplies the fuel in the fuel tank 14 to the fuel high pressure unit 20 via the fuel supply passage 15. The fuel filter 13 is disposed upstream and downstream of the feed pump 11, respectively. The pressure regulator 12 is provided in a return passage 16 branched from the fuel supply passage 15, and returns excess fuel to the fuel tank 14 so that the discharge pressure of the feed pump 11 does not exceed a certain pressure. A damper 16 is provided in the fuel supply passage 15. The damper 16 suppresses pressure pulsation in the fuel supply passage 15.

  The fuel high pressure unit 20 includes a plunger pump (high pressure pump) 21, an intake check valve 22, a spill adjustment solenoid 23, and a discharge check valve 24.

  The plunger pump 21 includes a cylinder 21a, a plunger 21b, and a spring 21c. The plunger 21b reciprocates in the cylinder 21a. The plunger 21b follows the peripheral surface of the pump drive cam 25 (plate cam). The pump drive cam 25 is formed integrally with the intake valve camshaft 26. The intake valve camshaft 26 is driven by a crankshaft via a chain or a belt. The spring 21 c biases the plunger 21 b toward the peripheral surface of the cam 25.

  The suction check valve 22 is provided on the suction side of the cylinder 21a. The intake check valve 22 prevents the fuel from flowing back from the cylinder 21a to the fuel pumping unit 10.

  The spill adjustment solenoid 23 controls the spill shaft 23a. The spill shaft 23a forcibly opens the suction check valve 22. When the intake check valve 22 is forcibly opened by the spill shaft 23 a, the fuel in the cylinder 21 a is returned to the fuel tank 14 through the spill passage 27.

  The discharge check valve 24 is provided on the discharge side of the cylinder 21a. The discharge check valve 24 prevents fuel from flowing back from the high-pressure fuel injection unit 30 to the cylinder 21a.

  When the plunger 21b descends following the circumferential surface of the pump drive cam 25, the low pressure fuel from the feed pump 11 fills the cylinder 21a via the intake check valve 22. When the plunger 21b rises following the peripheral surface of the pump drive cam 25, the pressure of the fuel in the cylinder 21a rises, the discharge check valve 24 is opened, and the high-pressure fuel is delivered via the orifice 28 to the delivery pipe 31. To increase the pressure in the delivery pipe 31. The discharge amount of the plunger pump 21 is controlled by a spill adjustment solenoid 23. That is, when the opening time of the suction check valve 22 by the spill shaft 23a is lengthened when the plunger 21b rises, the amount of fuel returned to the fuel tank 14 through the spill passage 27 increases, and the discharge amount of the plunger pump 21 That is, the amount of fuel supplied to the delivery pipe 31 decreases. Conversely, if the opening time of the intake check valve 22 by the spill shaft 23a is shortened, the amount of fuel returned to the fuel tank 14 through the spill passage 27 is reduced, and the discharge amount of the plunger pump 21, that is, the fuel to the delivery pipe 31 is reduced. Supply is increased.

  The high-pressure fuel injection unit 30 includes a delivery pipe 31 and high-pressure fuel injection valves 32a to 32d.

  The delivery pipe 31 stores high-pressure fuel discharged from the plunger pump 21. The high-pressure fuel stored in the delivery pipe 31 is directly injected into the engine cylinder from the high-pressure fuel injection valves 32a to 32d.

  The delivery pipe 31 includes a safety valve 33. The safety valve 33 opens when the fuel pressure in the delivery pipe 31 exceeds the allowable pressure, and returns a part of the high-pressure fuel in the delivery pipe 31 to the fuel tank 14.

  The temperature and pressure of the fuel in the delivery pipe 31 are detected by a temperature / pressure sensor 51. The sensor may be detected by a plurality of sensors that detect temperature and pressure, respectively, or may calculate (indirectly detect) temperature from pressure, for example.

  The controller 50 inputs signals from a temperature pressure sensor 51, a crankshaft position sensor 52, a camshaft position sensor 53, a cooling water temperature sensor 54, and an intake air temperature (outside air temperature) sensor 55, and receives an electric motor 11a, a spill adjustment solenoid 23, a high pressure. The fuel injection valves 32a to 32d are controlled. A REF signal described later is a signal from the crankshaft position sensor 52 and the camshaft position sensor 53.

  The controller 50 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The controller 50 may be composed of a plurality of microcomputers.

  In order to start the engine stratified, it is necessary to inject fuel in the compression stroke, and the fuel must be kept at a high pressure.

  However, when the engine stops, the fuel pressure in the delivery pipe decreases as described above, and vapor may be generated. When the vapor is generated, the pressure in the delivery pipe cannot be sufficiently increased.

  Therefore, in order to start stratification, the vapor must be crushed in a short time from the start of cranking to the injection of fuel.

  Therefore, in the present invention, the vapor is crushed in a short time so that the stratification can be started, and when it is determined that the vapor cannot be crushed, the homogeneous start is performed in which the fuel is injected in the intake stroke.

  Hereinafter, specific control contents of the controller 50 will be described.

  FIG. 2 is a flowchart showing a method for calculating the fuel pressure. During the key-on, the controller 50 always calculates the fuel pressure PF at intervals of 2 milliseconds according to this flowchart.

  In step S <b> 11, the controller 50 inputs a signal from the fuel pressure sensor 51.

  In step S12, the controller 50 calculates the fuel pressure PF by performing a weighted average process on the input signal.

  FIG. 3 is a flowchart showing a method for determining whether or not cold stratification can be started. The controller 50 executes before starting cranking at the start of cold stratification.

  In step S21, the controller 50 detects the fuel temperature TF (° C.), the cooling water temperature Tw (° C.), and the outside air temperature TA (° C.). These are done while the engine is stopped. That is, when the engine rotates, the plunger pump 21 is also operated thereby, and the pressure in the delivery pipe is increased. Therefore, the presence or absence of vapor can be determined more accurately by detecting the engine while it is stopped.

  In step S22, the controller 50 detects the engine rotational speed Ne (rpm) and determines whether or not it is less than 50 rpm. If it is less than 50 rpm, the process proceeds to step S23, and if it is 50 rpm or more, this process is exited.

  In step S23, the controller 50 obtains the gasoline saturated vapor pressure PFVAP at the fuel temperature TF detected in step S21. Specifically, the saturated vapor pressure PFVAP is obtained based on the map shown in FIG. 8 stored in advance in the ROM of the controller 50. This map is set in advance through experiments.

  In step S24, the controller 50 determines whether or not vapor is likely to be generated. Specifically, the determination is made based on whether or not the fuel pressure PF obtained in step S12 is equal to or lower than the saturated vapor pressure PFVAP. That is, vapor is not generated if the fuel pressure PF at a certain fuel temperature TF is higher than the saturated vapor pressure PFVAP, but vapor can be generated if the fuel pressure PF is lower than the saturated vapor pressure PFVAP. When there is a possibility of vapor generation, the process proceeds to step S25, and when there is no possibility of vapor generation, the process is exited.

  In step S25, the controller 50 determines whether or not the fuel pressure can be increased to a state where a cold stratification start is possible. Specific contents will be described later.

  In step S26, the controller 50 determines the conditions under which cold stratification can be started. Specific contents will be described later.

  FIG. 4 is a flowchart illustrating a subroutine for determining whether or not the fuel pressure can be increased to a state where cold stratification can be started.

  Although it has been determined in step S24 that vapor can be generated, if this vapor exists, the fuel pressure cannot be increased to a state where cold stratification can be started. Therefore, in this routine, the generated paper volume Vvap is obtained, and the number of cranking times (hereinafter referred to as “vapor crushing cranking times”) NCRVAP required to crush the vapor Vvap is obtained. If the fuel pressure is smaller than the number of cranking times RNCR performed to boost the fuel pressure to a state where cold stratification can be started, it is determined that the vapor can be crushed. Details are as follows.

  In step S251, the controller 50 calculates the volume change ΔVgas + vap of gasoline + vapor at the fuel pressure PF using the following equation.

  This formula is a modification of the following general formula of the volume change ΔV with respect to the pressure change ΔP.

  In step S252, the controller 50 calculates the paper volume Vvap generated at this time by the following equation.

  Here, RVvapgas is a volume ratio (constant value) obtained by experiment, and is 0.25 as an example.

  In step S253, the controller 50 obtains the paper crushing cranking count NCRVAP for crushing the generated paper Vvap. Specifically, it is obtained based on the map shown in FIG. 9 stored in advance in the ROM of the controller 50. This map is set in advance through experiments.

  In step S254, the controller 50 obtains the cranking frequency RNCR to be performed to increase the fuel pressure to a state where cold stratification start is possible based on the cooling water temperature Tw at that time. Specifically, it is obtained based on the map shown in FIG. 10 stored in advance in the ROM of the controller 50. This map is set in advance through experiments.

  In step S255, the controller 50 determines whether or not the vapor is crushed during cranking to increase the fuel pressure in the delivery pipe to a state where cold stratification can be started. If the vapor can be crushed, the pressure can be increased. At this time, the process proceeds to step S256. When the vapor cannot be crushed, it is considered that the pressure increase is insufficient. At this time, the process proceeds to step S257.

  In step S256, the controller 50 sets the flag # FSTRPFOK = 1.

  In step S257, the controller 50 sets flag # FSTRPFOK = 0.

  FIG. 5 is a flowchart showing a subroutine for determining whether or not a condition for enabling cold stratification is satisfied.

  In step S261, the controller 50 determines whether or not the coolant temperature Tw is within the range of TwSSTL to TwSSTH. If it is within the range, the process proceeds to step S262, and if it is out of the range, the process proceeds to step S264.

  In step S262, the controller 50 determines whether or not the outside air temperature TA is within the range of TASSTL to TASSTH. If it is within the range, the process proceeds to step S263, and if it is out of the range, the process proceeds to step S264.

  In step S263, the controller 50 sets a flag # FSTRSTOK = 1 because it is possible to start cold stratification.

  In step S264, the controller 50 sets a flag # FSTRSTOK = 0 because cold stratification start is impossible.

  FIG. 6 is a flowchart of cranking in which the pressure in the delivery pipe is increased by the fuel discharged from the high-pressure fuel pump without injecting the fuel (in a fail cut state) at the time of starting the engine.

  In step S71, the controller 50 increments the REF position passage counter REFCNT.

  In step S72, the controller 50 determines whether or not the counter REFCNT has become twice or more the number of times of cranking RNCR performed to increase the fuel pressure to a state where cold stratification can be started. The reason why it is doubled is that the number of times REFCNT is counted in one cycle is twice that of cranking.

  Until step S72 is established, steps S71 → S72 → S73 are repeated, and when step S72 is established, the process proceeds to step S71 → S72 → S74, and the process proceeds to the start process of step S80.

  FIG. 7 is a flowchart of processing for actually starting the engine upon completion of cranking.

  In step S81, the controller 50 determines whether or not the flag # FSTRPFOK = 1. If # FSTRPFOK = 1, the process proceeds to step S82. If # FSTRPFOK = 0, the process proceeds to step S84.

  In step S82, the controller 50 determines whether or not the flag # FSTRSTOK = 1. If # FSTRSTOK = 1, the process proceeds to step S83. If # FSTRSTOK = 0, the process proceeds to step S84.

  In step S83, the controller 50 cancels the fail cut and starts stratification at the stratified fuel injection timing and ignition timing.

  In step S84, the controller 50 cancels the fail cut and performs a homogeneous start at a uniform fuel injection timing and ignition timing.

  According to the present embodiment, the temperature and pressure of the fuel in the delivery pipe are detected, and it is determined whether or not vapor is generated in the delivery pipe based on them. it can. There is no need to add a special mechanism.

  When vapor generation is determined, the amount of vapor is estimated, the number of crankings required to crush the vapor is calculated, and fuel is injected after cranking, so the pressure in the delivery pipe is reduced. High pressure can be ensured.

  Further, the stratification start can be reliably performed by starting the stratification only when the vapor is crushed during cranking in order to increase the fuel pressure in the delivery pipe to a state where the cold stratification start is possible.

(Second Embodiment)
In the first embodiment, in order to facilitate understanding, the description has been given assuming that the saturated vapor pressure line of gasoline is one as shown in FIG. However, the actual saturated vapor pressure line is not one, but there are different saturated vapor pressure lines depending on the gasoline properties as shown in FIG. In FIG. 12, the saturated vapor pressure line of winter gasoline is shown by a solid line, and the saturated vapor pressure line of summer gasoline is shown by a one-dot chain line.

  On the premise of winter gasoline with a lot of volatile components, if the amount of vapor generated in summer gasoline is estimated, the amount of vapor generated is estimated to be large and unnecessarily cranked. On the other hand, assuming summer gasoline with a small amount of volatile components, if the amount of vapor generated in winter gasoline is estimated, the amount of vapor generated is estimated to be small and the vapor cannot be crushed.

  Therefore, in the second embodiment, assuming that winter gasoline is used, and vapor generation can be estimated even if the predetermined conditions are met, it is determined that the gasoline is low in volatile components, and the determination result is learned. Therefore, the number of cranking at the next start is made appropriate. Specific contents will be described with reference to the flowchart of FIG.

  In step S91, the controller 50 determines whether or not the outside air temperature TA exceeds the learning permission temperature TALRN. That is, it determines whether it is summer or winter. When the outside temperature TA exceeds the learning permission temperature TALRN, the process proceeds to step S92, and when it does not exceed, the routine is exited.

  In step S92, the controller 50 determines whether or not the coolant temperature Tw exceeds the learning permission temperature TwLRN. That is, it is determined whether or not the engine has been warmed up. When the cooling water temperature Tw exceeds the learning permission temperature TwLRN, the process proceeds to step S93, and when it does not exceed, the routine is exited.

  In step S93, the controller 50 determines whether or not the fuel pressure PF is equal to or lower than the saturated vapor pressure PFVAP. This is a condition where vapor can be generated. In other words, if vapor generation does not occur normally, but the conditions under which vapor can be generated are satisfied, it is considered that vapor generation is estimated from the saturated vapor pressure line of winter gasoline in summer. If so, the process proceeds to step S94. Otherwise, the routine is exited.

  In step S94, the controller 50 sets (PFVAP-PF) × GRVP, shifts the saturated vapor pressure line downward, and determines the presence or absence of vapor generation based on the learned saturated vapor pressure line at the next and subsequent startups.

  According to the present embodiment, the number of crankings at the start can be made appropriate by learning the fuel properties.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea, and it is obvious that these are equivalent to the present invention.

  For example, in the first embodiment, the number of times of cranking is obtained, but the duration of cranking may be obtained.

  In the second embodiment, the learning permission is determined based on the outside air temperature and the cooling water temperature. For example, instead of the outside air temperature, the initial value of the cooling water temperature is determined, the summer / winter season is determined, or the process from the start of the engine. The engine warm-up may be determined according to time.

It is a figure showing a 1st embodiment of a vapor generation judging device of a fuel injection mechanism by the present invention. It is a flowchart which shows the calculation method of fuel pressure. It is a flowchart which shows the determination method whether a cold stratification start is possible. It is a flowchart which shows the determination subroutine whether a fuel pressure can be pressure | voltage-risen to the state which can be cold-stratified start-up. It is a flowchart which shows the judgment subroutine whether it has the conditions which can perform cold stratification start. 6 is a flowchart of cranking in which the pressure in the delivery pipe is increased by the fuel discharged from the high-pressure fuel pump without injecting fuel (in a fail cut state) at the time of engine start. It is a flowchart of the process which actually starts an engine in response to completion | finish of cranking. It is a figure which shows the saturated vapor pressure characteristic of gasoline. It is a figure which shows the relationship between the amount of vapor generation, and the frequency of vapor squashing cranking. It is a figure which shows the relationship between cooling water temperature and the frequency | count of cranking performed in order to raise | lift a fuel pressure to the state which can be cold-stratified start. It is a figure which shows the learning routine of saturated vapor pressure. It is a figure which shows the saturated vapor pressure characteristic of winter gasoline and summer gasoline.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection apparatus 10 Fuel pumping part 11 Feed pump (low pressure pump)
20 Fuel high pressure part 21 Plunger pump (high pressure pump)
DESCRIPTION OF SYMBOLS 30 High pressure fuel injection part 31 Delivery pipe 32a-32d High pressure fuel injection valve 50 Controller 51 Temperature pressure sensor (pressure detection means / temperature detection means)
Step S12 Pressure detection means Step S21 Temperature detection means Step S23 Saturated vapor pressure calculation means Step S24 Vapor determination means Steps S251 and S252 Vapor amount estimation means Step S253 Vapor collapse cranking calculation means Step S254 Stratification start cranking calculation means Step S255 Stratification start Permission means Step S83 Fuel injection means Steps S91, S92 Learning permission means Step S94 Saturated vapor pressure learning means

Claims (5)

A pump to increase the pressure of the fuel;
A delivery pipe for supplying the fuel pressurized by the pump to the fuel injection valve;
Pressure detecting means for detecting the pressure of the fuel in the delivery pipe while the engine is stopped;
Temperature detecting means for detecting the temperature of the fuel in the delivery pipe while the engine is stopped;
A saturated vapor pressure calculating means for calculating the saturated vapor pressure of the fuel at the detected temperature;
Vapor determining means for determining vapor generation when the detected fuel pressure is lower than the calculated saturated vapor pressure;
A vapor amount estimating means for estimating a vapor generation amount based on the calculated saturated vapor pressure and the detected fuel pressure when vapor generation is determined;
Vapor crushing cranking calculating means for calculating the number of times or time of cranking necessary for crushing the estimated vapor;
Fuel injection means for starting stratification by starting fuel injection after performing the calculated cranking;
A fuel injection control device comprising: Stratification start cranking calculation means for calculating the number of times or time of cranking required for stratification start based on the engine water temperature;
Stratification start permission means for permitting stratification start when the vapor crushing cranking number or time is smaller than the stratification start cranking number or time;
With
The fuel injection means starts fuel injection after performing stratified start cranking frequency or time cranking when stratified start is permitted,
The fuel injection control device according to claim 1. Learning permission means for determining learning permission;
Saturated vapor pressure learning means for updating the fuel pressure in the delivery pipe so as to decrease the value of the saturated vapor pressure when the fuel pressure in the delivery pipe does not reach the saturated vapor pressure at the fuel temperature at that time even in the learning permission state;
The fuel injection control device according to claim 1, further comprising: The learning permission means permits learning when the outside air temperature or the engine water temperature exceeds a predetermined value.
The fuel injection control device according to claim 3. The learning permission means permits learning when the engine warm-up is determined.
The fuel injection control device according to claim 3 or 4, characterized by the above.

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