JP2000257495A - Fuel injection method for engine and its apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide fuel injection method and an apparatus for it, capable of starting the fuel injection at a target injection start timing, regardless of the temperature or the properties of the fuel by finding the real fuel injection start timing from a pressure drop start timing and pulsation cycle calculated, based on a detected common rail pressure. SOLUTION: A pressure drop start timing td and a cycle ΔT of the pulsation generated during the pressure drop are calculated from the decline curve of a common rail pressure Pr. By retrograding for a time by a half of the pulsation cycle ΔT from the pressure drop start timing td, the actual fuel injection start timing t1 can be found. A fall time t0 of the command pulse output from a controller is controlled, such that an actual fuel injection start timing t1 agrees with a target fuel injection start timing tb found from running condition of the engine. The fuel injection start timing t1 is controlled accurately, based on the pulsation cycle ΔT which reflects the temperature and properties of the fuel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for fuel injection of an engine for injecting fuel stored in a common rail in an accumulated state from an injector into a combustion chamber.

[0002]

2. Description of the Related Art A common rail fuel injection system has been used as a system for increasing the injection pressure of an engine for fuel injection and optimally controlling injection conditions such as fuel injection timing and injection amount according to the operating state of the engine. Are known. The common rail fuel injection system stores fuel pressurized to a predetermined pressure by a fuel pump in a common rail in an accumulated pressure state, and stores the stored pressurized fuel in an engine operating state such as a fuel injection amount and a fuel injection timing by a controller. This is a system in which each injector injects fuel into the combustion chamber under optimum fuel injection conditions. In the fuel flow path from the common rail to the injection hole of each injector through the fuel supply pipe, a fuel pressure equivalent to the injection pressure is constantly applied, and each injector passes or blocks the fuel supplied through the fuel supply pipe. Valve that operates as follows. The controller controls the pressure of the common rail and the operation of the solenoid valve of each injector so that the pressurized fuel is injected in each injector under optimal injection conditions for the operating state of the engine.

FIG. 2 is a diagram showing an outline of a common rail fuel injection system. In the common rail fuel injection system, the fuel in the fuel tank 4 is supplied through a filter 5 and a feed pump 6 to a fuel pump 8 which is, for example, a plunger-type variable displacement high-pressure pump through a fuel pipe 7. The fuel pump 8 is driven by the output of the engine, raises the fuel pressure to a required predetermined pressure, and supplies the fuel to the common rail 2 through the fuel pipe 9. The fuel pump 8 is provided with a flow control valve 14 for maintaining the fuel pressure in the common rail 2 at a predetermined pressure. The fuel relieved from the fuel pump 8 returns to the fuel tank 4 through the return pipe 10. The fuel in the common rail 2
The fuel is supplied to a plurality of injectors 1 through a fuel supply pipe 3. Among the fuel supplied from the fuel supply pipe 3 to the injector 1, the fuel not consumed for injection into the combustion chamber returns to the fuel tank 4 through the return pipe 11.

A controller 12 which is an electronic control unit
Includes an engine cylinder discrimination sensor and an engine speed Ne.
Angle sensor for detecting the pressure and top dead center (TDC), the accelerator opening sensor for detecting the accelerator pedal depression amount Acc, the water temperature sensor for detecting the cooling water temperature Tw, and the pressure in the intake pipe. From various sensors for detecting the operating state of the engine, such as a pressure sensor in the intake pipe, for example. Common rail 2
Is provided with a pressure sensor 13.
The detection signal of the fuel pressure in the common rail 2 detected by the controller 12 is sent to the controller 12. Controller 12
Controls the fuel injection conditions by the injector 1, that is, the fuel injection timing (injection start timing and period) and the injection amount based on these signals so that the engine output becomes the optimum output in accordance with the operating state. I do. The fuel in the common rail 2 is consumed by the injector 1 injecting the fuel,
Although the fuel pressure in the common rail decreases, the controller 1
2 is to control the discharge amount by the flow control valve 14 of the fuel pump 8 in order to keep the fuel pressure in the common rail 2 constant or to obtain the required fuel injection pressure according to the operating state of the engine. To control the pressure.

FIG. 3 is a longitudinal sectional view showing an example of an injector used in a common rail type fuel injection system. The injector 1 is hermetically attached to a hole provided in a base such as a cylinder head (not shown) by a seal member. A fuel supply pipe 3 is connected to an upper side of the injector 1 via a fuel inlet joint 20. The fuel passages 21 and 2 are provided inside the main body of the injector 1.
2, the fuel supply pipe 3 and the fuel passage 21,
A fuel flow path is formed from 22. The fuel supplied through the fuel flow path is injected into the combustion chamber through a fuel reservoir 23 and a passage around the needle valve 24 from an injection hole 25 opened when the needle valve 24 is lifted.

[0006] The injector 1 is provided with a balance chamber type needle valve lift mechanism for controlling the lift of the needle valve 24. That is, an electromagnetic valve 26 is provided at the uppermost part of the injector 1, and a control current corresponding to a command pulse of the controller 12 is sent to a solenoid 28 of the electromagnetic valve 26 through a signal line 27. When the solenoid 28 is excited, the armature 29 rises and opens the on-off valve 32 provided at the end of the fuel passage 31, so that the fuel pressure of the fuel supplied from the fuel passage to the balance chamber 30 decreases the fuel pressure of the fuel passage 31. Be released through. A control piston 34 is provided in a hollow hole 33 formed inside the main body of the injector 1 so as to be able to move up and down. The control piston 3 is controlled by the force based on the reduced pressure in the balance chamber 30 and the spring force of the return spring 35.
The control piston 34 rises because the force for pushing up the control piston 34 based on the fuel pressure acting on the tapered surface 36 facing the fuel reservoir 23 is greater than the pushing force acting on 4. As a result, the needle valve 24 is lifted, and fuel is injected from the injection hole 25. Fuel injection timing is needle valve 24
The fuel injection amount is determined by the fuel pressure in the fuel passage and the lift of the needle valve 24 (lift amount, lift period).

In general, the fuel injection amount of the injector 1 and the pulse width P of a command pulse output by the controller 12
The relationship with w is determined using the fuel pressure Pr (fuel pressure in the common rail 2, hereinafter referred to as “rail pressure”) as a parameter. Assuming that the rail pressure Pr is constant, the fuel injection amount increases as the pulse width Pw increases, and even with the same pulse width Pw, the fuel injection amount increases as the rail pressure Pr increases. On the other hand, since the fuel injection is started or stopped with a certain time delay with respect to the falling time and the rising time of the command pulse, by controlling the timing when the command pulse is turned on or off,
It is possible to control the injection timing. The fuel injection amount for each combustion cycle is calculated based on the operating state of the engine and the basic injection amount characteristic map. Engine speed N
e and the basic injection amount, the accelerator pedal depression amount A
A certain relation is given in advance as a map using c as a parameter.

In a conventional common rail fuel injection system, the fuel injection start timing is calculated by calculating a phase difference from a preset crank angle (for example, TDC) by a crank angle sensor, and fuel is injected at a predetermined timing. The controller outputs a command pulse that determines the drive current to the solenoid valve 26 of the injector 1 as described above. By the way, the time interval from the output timing of the command pulse to the operation of the injector 1, that is, the fuel injection delay time tends to gradually increase in any injector due to a mechanical time lag caused by wear of each operating portion or the like. In some cases, the difference between the target fuel injection start timing and the actual fuel injection start timing causes deterioration of smoke in the exhaust gas. Further, since the injection delay time differs depending on the individual difference of the injector 1, the injection start timing of each cylinder differs, and the combustion balance between the cylinders is disrupted, thereby causing the engine rotation fluctuation, noise and vibration.

In a fuel injection device for an engine to which a common rail type fuel injection system is applied, the following proposal has been made as one of measures for controlling the fuel injection start timing with high accuracy. According to this proposal, the pressure of the common rail is controlled according to the operating state of the engine,
From the pressure data detected by the pressure sensor provided on the common rail, the descent start time at which the fuel pressure in the common rail drops due to fuel injection from the injector is detected. The actual fuel injection start timing is calculated by moving the propagation time of the pressure wave backward, and the next fuel injection is calculated based on the difference between the calculated fuel injection start timing and the target value of the fuel injection start timing. The target injection start timing at the time is corrected (see Japanese Patent Application Laid-Open No. 10-47137).

From the start of fuel injection from the injector to the time when the pressure sensor provided on the common rail detects a drop in rail pressure, the change in pressure propagates from the injector to the fuel and reaches the pressure sensor. Lag, ie, pressure drop delay. The actual fuel injection start timing is estimated in consideration of the pressure drop delay time, which is the propagation delay of the pressure wave, and the target fuel injection start timing is feedback-controlled based on the estimated fuel injection start timing. According to this proposal, the valve opening timing of each cylinder is measured and the fuel injection start timing is controlled without providing a lift sensor for each cylinder.

In the above proposal, the pressure drop delay time is set to an experimental value obtained experimentally or a fixed value obtained in consideration of the pressure propagation distance, the general density of fuel, and the like. I have. However, when the pressure drop delay time is used as an experimental value, the amount of data becomes too large when trying to reflect the temperature and the properties of the fuel, and the calculated value is obtained by interpolating for a condition different from the data collection condition. Is merely an estimate and still contains errors. When the pressure drop delay time is set to a fixed value, it is difficult to set the fixed value. That is, the fuel density greatly depends on the fuel temperature (in Hokkaido and the Tohoku region, the temperature falls significantly below the freezing point in winter and can reach as high as 40 ° C in summer). (For example, No. 2 light oil, No. 3 light oil, etc. are used depending on the area), the fuel density differs.

Further, there is a method in which the mechanical manufacturing variation and the deterioration with time of the injector are calculated based on the elapsed time of the actual fuel injection start timing from the ON time of the drive signal to the injector. When trying to detect the above elapsed time from the fuel injection start timing estimated by the conventional method of estimating the actual fuel injection start timing, when the stored pressure propagation time is simply used, the pressure propagation time is as described above. Since errors are included, it is difficult to accurately detect deterioration with time and manufacturing variations.

[0013] A sensor is provided on a component that actually operates upon fuel injection of the injector, for example, a needle,
It is conceivable to accurately detect the fuel injection start timing.
However, this method is not practical because it is necessary to dispose the lift sensors by the number of cylinders and immediately raises the cost of the fuel injection device. Further, in the electronic control type controller, the number of sensor input units is increased by the number of cylinders, so that a drastic change in specifications of the input / output unit is forced.

[0014]

In the fuel injection of an engine to which the common rail type fuel injection system is applied, the pressure sensor detects the fuel pressure of the common rail, which decreases due to the fuel injection from the injector. it can. By detecting the change in the common rail pressure that decreases after fuel injection from the injector, the pressure drop delay time from the actual fuel injection start time to the rail pressure drop start time is set as a value that reflects the temperature and properties of the fuel. There are issues that need to be solved in terms of what you want.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems. In a common rail type fuel injection system, attention is paid to the fact that the common rail pressure decreases with the fuel injection after the start of fuel injection. Based on the data on the common rail pressure detected by the pressure sensor, based on the start timing of the common rail pressure drop, regardless of the temperature and properties of the fuel, without adding special equipment or equipment and changing the specifications It is an object of the present invention to provide an engine fuel injection method and apparatus capable of accurately determining the fuel injection start timing of the engine.

According to the present invention, fuel delivered by a fuel pump is stored in a common rail in a pressure-accumulated state, and fuel supplied from the common rail through a fuel supply pipe is injected into a combustion chamber from an injector driven based on an injection command signal. Then, based on the actual fuel injection start time calculated from the start time of the pressure drop of the common rail that drops with fuel injection and the cycle of the pulsation that appears in the pressure of the common rail that drops with the fuel injection. The present invention relates to a fuel injection method for an engine, which comprises controlling the output timing of an injection command signal.

Further, the present invention provides a common rail for storing fuel delivered by a fuel pump in an accumulated state, an injector for injecting fuel supplied from the common rail through a fuel supply pipe into a combustion chamber, and detecting a pressure of the common rail. A pressure sensor, and a controller for outputting an injection command signal for injecting fuel from the injector, wherein the controller starts dropping the pressure of the common rail, which drops with the fuel injection, and drops with the fuel injection. The present invention relates to a fuel injection device for an engine, which controls the output timing of the injection command signal based on the actual fuel injection start timing calculated from the pulsation cycle appearing in the common rail pressure.

According to the fuel injection method and apparatus for an engine according to the present invention, a certain delay time (injection delay time) from the on time of the injection command signal output by the controller.
After the actual fuel injection, the common rail pressure starts to drop after another delay time (pressure drop delay time). From the fluctuation of the common rail pressure detected by the pressure sensor, the commencement time of the common rail pressure drop and the pulsation cycle are calculated. The pulsation of the common rail pressure is
Since the pressure wave is considered to be caused by the reciprocating propagation of the pressure wave from the tip of the injector nozzle through the fuel supply pipe to the common rail pressure sensor installation position, the pressure drop delay time is obtained from the pulsation, and The actual fuel injection start timing is obtained as the time that precedes the pressure drop delay time. The output timing of the injection command signal to the injector is controlled so that the actual fuel injection start timing becomes the target fuel injection start timing.

In the fuel injection method and the apparatus for the engine, a target fuel injection start timing to be injected from the injector is determined based on an operation state of the engine, and the actual fuel injection start timing is determined by the target fuel injection start timing. The output timing of the injection command signal is controlled to coincide with the timing.

In addition, the actual fuel injection start timing is calculated as a timing that is half the period of the pulsation cycle from the start timing of the decrease of the common rail pressure. The pulsation of the rail pressure is considered to be caused by the reciprocating propagation of the pressure wave from the nozzle tip of the injector through the fuel supply pipe to the pressure sensor installation position of the common rail, and is formed at the nozzle tip of the injector. The time required for the change in pressure drop due to the injection of fuel from the injection hole to propagate from the injector to the fuel in the fuel supply pipe and reach the pressure sensor installed on the common rail is half the period of the pulsation cycle. Conceivable.

[0021]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a fuel injection method for an engine according to an embodiment of the present invention; The injector shown in FIG. 2 or the injector shown in FIG. 3 can be used as it is for the common rail type fuel injection system applied to the engine fuel injection device according to the present invention and the injector used for the fuel injection device. In the description of the example, a detailed description is omitted again. FIG. 1 shows the supply or supply of a control current (voltage) to a solenoid valve 26 of an injector 1 over a certain period (or crank angle) before a compression top dead center of a combustion cycle in a fuel injection device for an engine according to the present invention. A command pulse as an injection command signal for controlling the stop, a fuel injection rate q for injecting fuel from the injector 1 into the combustion chamber, and a fuel pressure (rail pressure) P on the common rail 2
It is a graph which shows r and its differential value.

For each cylinder, an injection command signal is output when the command pulse falls (ON) at time t ₀ before the top dead center, and a drive signal for causing the injector 1 to perform fuel injection is sent from the controller 12. Can be Solenoid 2 of solenoid valve 26 provided in injector 1
A drive current flows through 8, the pressure of the working fluid in the balance chamber 30 is released, the needle valve 24 lifts, and fuel is injected from an injection hole 25 formed at the tip of the injector 1. As can be seen from the rise of the fuel injection rate q shown in FIG. 1, the fuel injection starts at time t ₁ (fuel injection time) after the injection delay time Δt ₁ from time t _0, and has a pulse width Pw of the command pulse. Accordingly, fuel is injected over a predetermined fuel injection period. The rail pressure Pr does not immediately decrease even when the fuel injection is started, and the time t
_It begins to drop at _d (rail pressure drop start time) and continues to drop gradually as fuel injection progresses.

Engine speed Ne and accelerator operation amount Ac
From the operation state of the operation state engine detected by the sensor etc., and the command value ΔTb to date back to the top dead center is calculated based on a map that is prepared in advance, is set the basic target injection start timing t _b . The injection delay time Δt ₁ usually shows a different value for each injector 1. Note that the variable displacement fuel pump 8 is controlled so that the rail pressure Pr itself matches the target rail pressure calculated based on data such as a map prepared in advance by the controller 12 in accordance with the operating state of the engine. And the flow control valve 14 is controlled.

The actual pressure of the common rail 2, that is, the rail pressure Pr is sequentially detected by the pressure sensor 13.
In this fuel injection device, from the data of the rail pressure Pr detected by the pressure sensor 13, the start time of the fall of the rail pressure Pr and the cycle of the pulsation during the fall of the rail pressure Pr are calculated, and the start time of the fall of the rail pressure Pr is calculated. The actual fuel injection start timing is estimated from the pulsation cycle. A DSP (Digital Signal Proc) that can be processed in parallel with the CPU to calculate the start time of the drop of the rail pressure Pr and the pulsation cycle during the drop of the rail pressure Pr.
ESSOR) processes a large amount of data in a short processing time with respect to the rail pressure Pr. Buffering of rail pressure data by the DSP is started when the ON (falling) of the command pulse of the injector 1 is detected, and thereafter sampled at, for example, a 100 KHz cycle, stored in a memory in the controller 12, and stored in the memory of the controller 12. This operation is performed until Pr is sufficiently reduced and vibration is confirmed.

The present applicant has already applied for patents (Japanese Patent Application Nos. Hei 9-277974 and Hei 10 ₎ to calculate the start time t _d of the rail pressure Pr of the common rail accompanying fuel injection.
184210). The calculation method disclosed in Japanese Patent Application No. 9-277974 will be briefly described below. Since the data of the rail pressure Pr includes noise, the data of the rail pressure Pr is smoothed by performing filtering such as performing a moving average process. Among the data started to be acquired from the time t ₀ , the rail pressure Pr has little fluctuation in the initial fixed period during the injection delay time Δt ₁ , and by taking the average of the pressure during this period, the common rail 2 before the fuel injection is obtained. The average pressure Pa can be determined. Further, since the acquired rail pressure data is discrete value data with the passage of time, the time differential of the rail pressure Pr is calculated by taking the difference between adjacent data values.

In a graph using time and the common rail pressure as the coordinate axes, the time derivative whose time derivative is the smallest between time t ₄ when the rail pressure Pr starts to decrease from the average pressure Pa and first takes a minimum value is shown. A time t _{3 at} which the pressure drop of the rail pressure Pr is the largest is calculated, and a time t ₃
By the linear regression calculation based on the time at several points before and after ₃ and the data at that time, the rail pressure P at time t ₃ is obtained.
An approximate straight line Ld (tangent at the inflection point of the descent curve) of the descent curve of r is obtained. Straight line L representing the average pressure Pa before the start of injection
The time t _{2 at} the intersection of the approximate straight line Ld and the point p (shown by a dashed line parallel to the time axis in FIG.
It can be regarded as the _d . Although a linear regression line is used as an approximation of the curve in which the common rail pressure decreases, a higher-order approximate curve may be used.

As another method of calculating the descent start time t _d of the rail pressure Pr, for example, the least square method is used based on the data of the rail pressure Pr from time t ₀ to time t ₄ when the first minimum value is obtained. Approximate straight line Le of the drop curve of the rail pressure Pr (in FIG. 1,
Seeking shown by two-dot chain line), the difference between the rail pressure Pr in the period from time t ₀ to time t ₄ the approximate straight line Le is a method regarded as falling start timing t _d of the rail pressure Pr time of maximum (Japanese Patent Application No. 10-184210).

The thus obtained rail pressure Pr
The injection delay time Δt ₁ from the fall time t ₀ of the command pulse to the actual fuel injection start time t _{1 with} respect to the descent start time t _d is calculated by a predetermined map or function. The parameters that determine the injection delay time Δt ₁ are the value of the descent start time t _d itself (the slower the descent start time t _d , the larger the injection delay time Δt ₁ tends to be) and the magnitude of the rail pressure Pr (pressure propagation Effect of speed), cylinder number (injection delay time Δt ₁ is greater for cylinders farther from pressure sensor 13 provided on common rail 2)
It is.

Rail pressure Pr after fuel injection is started
Descends with pulsation. This pressure fluctuation is such that when high-pressure fuel is introduced into the injector 1 from the common rail 2, a pressure reflected wave generated according to the shape of the fuel passage returns to the common rail 2, and the reflected wave is further transmitted to the common rail 2 and the injector 1. It is considered that this is caused by reciprocation in the propagation path including the fuel supply pipe 3 between. Rail pressure Pr detected by the pressure sensor 13 and subjected to smoothing processing
When the differential value is obtained, the time at which the maximum value of the rail pressure Pr is reached is the zero-cross time t ₅ or t ₆ at which the differential value changes from positive to negative (or the zero-cross time of the approximate straight line if there is no zero-cross point). ). The pulsation cycle ΔT is calculated as the time interval between the zero cross times t ₅ and t ₆ adjacent to the rail pressure Pr. It is needless to say that the time when the local minimum value is taken may be detected instead of the time when the local maximum value is taken.

When the pulsation cycle ΔT of the rail pressure Pr is calculated, the actual fuel injection start timing t ₁ can be estimated by the following equation. t ₁ = t _d −ΔT × (1/2) Since the pulsation period ΔT is the time for the pressure wave to reciprocate on the propagation path, the time t ₁ at which the fuel injection is actually started is provided on the common rail 2. When the pressure sensor 13 detects a pressure wave caused by injecting fuel from the injection hole formed at the tip of the nozzle in the injector 1 (descent start time t _d ), the pressure wave is one-way in the propagation path. (Half of the pulsation period ΔT, ie,
This is a time that is traced back by the pressure drop delay time). The injection start time t ₁ obtained in this way is compared with the target fuel injection start time t _b obtained from the operation state of the engine, and based on the time difference between the two, the injection start time t ₁ is changed to the target fuel injection start time t _{b The} falling time t ₀ of the command pulse is determined so as to coincide with _b .

In the example shown in FIG.
Fall time t₀Is the injection start time t ₁From injection delay time
Δt₁The injection command signal (command pulse
Output time t)₀Is determined. That is, the time before correction
t₀For (t_b-T₁) When delayed by the time interval
Period is the final command pulse in the next fuel injection.
Falling time t₀Is determined as Like this
Command pulse output at the output timing determined by
In order to inject fuel at the target fuel injection start time,
Drive current is supplied to the solenoid 28 of the solenoid valve 26 of the ejector 1.
Be paid. Fall time t of the command pulse₀,Goal
Fuel injection start time t_b, And start of drop of rail pressure Pr
From the period to the period determined based on the pulsation cycle
Required actual fuel injection start timing t₁It turns out that
Therefore, mechanical delay of each injector and aging degradation
Is always present, the actual fuel injection start timing t₁
Is the target fuel injection start timing t_bCommand to match
Pulse falling time t ₀Is determined.

In a common rail type fuel injection system, generally, a plurality of injectors 1 are provided as shown in FIG. 2, and a controller obtains an actual fuel injection start timing t ₁ for each injector ₁ to obtain an actual fuel injection timing. and it determines the output timing of the injection command signal as timing predated the injection delay time Delta] t ₁ from the start time t _1. The engine fuel injection method and apparatus according to the present invention are particularly suitable for a common rail fuel injection system of a diesel engine, but can also be applied to other fuel injection systems having a similar structure such as a direct injection gasoline engine. Needless to say,

[0033]

The fuel injection method and apparatus for an engine according to the present invention are configured as described above and have the following effects. That is, according to the fuel injection method and apparatus for an engine according to the present invention, the period of the pulsation of the common rail is detected, and the propagation time from the injector to the pressure sensor disposed on the common rail is determined based on the period. Since the actual fuel injection start timing is obtained by calculation based on the pressure drop start timing, it is possible to always obtain an accurate fuel injection start timing irrespective of a change in fuel temperature or a change in fuel properties. Even when feedback control of injector operation is performed so that fuel is injected at the target fuel injection start timing determined according to the operating state of the engine, fuel is always accurately injected at the target injection start timing regardless of fuel properties. can do. In addition, even if the same engine has a different engine due to a variation in the injection delay time of each injector or a change in the diameter of the same injector, even if the same engine is used, the combustion timing of each cylinder is disturbed, and the exhaust gas such as smoke is generated. Although gas performance has deteriorated and engine noise and vibration have occurred, according to the fuel injection method or device according to the present invention, the fuel injection in each injector is always the optimal target injection determined based on the operating state of the engine. Since this can be performed at the start time, it is possible to prevent deterioration of the exhaust gas performance of the engine and noise and vibration of the engine. Further, a new sensor is not required for determining the fuel injection start timing, and when calculating the actual fuel injection start timing, a pressure sensor for detecting the common rail pressure used in the existing common rail system is used. Since only the obtained detection data is processed, it is possible to avoid an increase in the number of parts, which is a factor of increasing the manufacturing cost of the fuel injection device.

[Brief description of the drawings]

FIG. 1 is a graph illustrating changes over time of a command pulse, a fuel injection rate, and a common rail pressure in a fuel injection method and device according to the present invention.

FIG. 2 is a schematic diagram showing a common rail type fuel injection system.

FIG. 3 is a sectional view showing an example of an injector to which the common rail type fuel injection system shown in FIG. 2 is applied.

[Explanation of symbols]

1 injector 2 common rail 3 fuel supply pipe 8 fuel pump 12 controller 13 a pressure sensor 24 the needle valve 25 the injection hole 26 output timing of the electromagnetic valve Pr rail pressure (common rail pressure) Pa before the fuel injection common rail mean pressure t ₀ injection command signal t ₁ the actual fuel injection start timing t _b basic target injection start timing Δt ₁ injection delay time

Claims (6)

[Claims] 1. A fuel pumped by a fuel pump is stored in a common rail in a pressure-accumulated state, and fuel supplied from the common rail through a fuel supply pipe is injected into a combustion chamber from an injector driven based on an injection command signal.
The injection command is based on the actual fuel injection start time calculated from the start time of the common rail pressure dropping along with the fuel injection and the pulsation cycle appearing in the common rail pressure falling along with the fuel injection. A fuel injection method for an engine, comprising controlling the output timing of a signal. 2. A target fuel injection start timing to be injected from the injector is determined based on an operation state of the engine, and the injection command is set so that the actual fuel injection start timing coincides with the target fuel injection start timing. 2. The method according to claim 1, further comprising controlling the output timing of the signal. 3. The fuel injection start timing according to claim 1, wherein the actual fuel injection start timing is calculated as a timing going back half a time of the pulsation cycle from the start timing of the decrease of the common rail pressure. Engine fuel injection method. 4. A common rail for storing fuel delivered by a fuel pump in an accumulated state, an injector for injecting fuel supplied from the common rail through a fuel supply pipe into a combustion chamber, a pressure sensor for detecting a pressure of the common rail, A controller for outputting an injection command signal for injecting fuel from the injector, the controller comprising: a start time of a decrease in the pressure of the common rail that decreases with the fuel injection; and a pressure of the common rail that decreases with the fuel injection. A fuel injection device for an engine, comprising: controlling the output timing of the injection command signal based on the actual fuel injection start timing calculated from the pulsation cycle appearing in (1). 5. The controller according to claim 1, wherein the controller determines a target fuel injection start timing based on an operation state of the engine, and controls the injector so that the actual fuel injection start timing coincides with the target fuel injection start timing. 5. The fuel injection device for an engine according to claim 4, comprising controlling the output timing of a drive signal. 6. The controller according to claim 4, wherein the controller calculates the actual fuel injection start timing as a timing which is half a period of the pulsation cycle from the start timing of the decrease of the common rail pressure. The fuel injection device for an engine according to claim 1.