JPH1047137A - Control method for fuel injection timing of internal combustion engine and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a fuel injection timing by measuring a valve opening timing in each cylinder without installing a lift sensor in each cylinder concerning a control method for a fuel injection time of an internal combustion engine and its device. SOLUTION: A timing toc when the pressure value of a pressure sensor provided on a common rail decreases after an injection from an injector is detected, and the propagation time δtt D of a pressure wave from an injection nozzle to the common rail is made to retroact to the timing toc to compute the start timing tos of actual fuel injection, and a difference between the start timing tos of actual fuel injection and the target value to of the injection start time is stored, and the target injection timing in the case of next injection is corrected by this stored value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a diesel engine,
In particular, the present invention relates to a method and an apparatus for controlling a fuel injection timing of an internal combustion engine such as an automobile diesel engine.

[0002]

2. Description of the Related Art In a fuel injection internal combustion engine for an automobile, the fuel injection timing affects the optimum combustion operation of the engine. That is, if the fuel injection timing deviates from the optimum value, problems such as an increase in the amount of harmful components in the exhaust gas and an increase in noise occur, so that it is necessary to control the fuel injection timing optimally. Therefore, in the case of an electronically controlled internal combustion engine, a map including the engine speed and the load for the fuel injection timing is provided.
During the operation of the engine, the fuel injection timing corresponding to the rotation speed and the load is calculated from a map, and the fuel injector is driven so as to obtain the calculated fuel injection timing. However, the fuel injection timing calculated from the map is deviated from that for performing the optimal combustion operation of the internal combustion engine due to individual fluctuations and aging of the injector. Therefore, there is a possibility that the amount of the harmful component in the exhaust gas increases or the noise increases.

In JP-A-1-52570, a lift (head) sensor is provided for a needle for opening and closing the injection nozzle of each fuel injector, and the valve opening timing of the needle is obtained from the output value of the lift sensor to obtain a target injection start time. An apparatus that corrects the injection start timing by calculating a difference from the timing has been proposed.

[0004]

Problems to be Solved by the Invention
In the publication, it is necessary to install a lift sensor for each injector of each cylinder in order to know the actual valve opening timing of the needle of each cylinder. Since the lift sensor is expensive, the cost increase by installing the lift sensor for each cylinder is large.

It is an object of the present invention to measure the valve opening timing of each cylinder without increasing the number of sensors and control the fuel injection timing.

[0006]

According to the first and fourth aspects of the present invention, the pressure sensor provided on the common rail detects a change timing of the common rail pressure caused by the injection from the injector. Since the correction term for the target injection start timing is calculated by considering the propagation time of the pressure wave from the common rail to the nozzle seat of the electronic control injector, the lift sensor is not provided for each cylinder. The fuel injection timing can be accurately corrected, and there is an effect of simplifying the configuration and reducing costs.

According to the second aspect of the present invention, by calculating the propagation time by a predetermined calculation formula, it is possible to grasp the propagation time without actually measuring it, and it is possible to improve the efficiency. By actually measuring the propagation time according to the third aspect of the invention, the propagation time can be accurately grasped irrespective of the difference between individuals.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 denotes a multi-cylinder,
For example, it is an electronically controlled fuel injector provided in each cylinder of a four-cylinder diesel engine, and is connected to a common rail 3 by a high-pressure pipe 2. A fuel pump 4 is connected to the common rail 3, and fuel in a fuel tank 5 is supplied to the common rail 3. The fuel pump 4 incorporates a well-known pressure control mechanism, whereby the fuel pressure in the common rail 3 is controlled to a predetermined value according to operating conditions.

Reference numeral 6 denotes a control circuit for operating the injector 1, which is configured as a microcomputer system. A pressure sensor 7 is provided on the common rail 3. The pressure sensor 7 detects the pressure of the fuel charged in the common rail 3. A signal corresponding to the fuel pressure in the common rail 3 from the pressure sensor 7 is sent to the control circuit 6. As will be described later, the actual start of fuel injection from the injector is to correct the propagation time of the pressure wave in the high-pressure fuel pipe and the injection nozzle from the timing of the fuel pressure drop in the common rail 3 detected by the pressure sensor 7. Can be grasped.

The control circuit 6 includes, in addition to the pressure sensor 7, a crank angle sensor 8 for generating a pulse signal corresponding to a rotation angle of the crankshaft of the engine, for example, every 30 ° and 720 °.
A load sensor 9 including a sensor for detecting a rotation angle of an injection control lever of a fuel injection pump (not shown) or a sensor for detecting an amount of depression of an accelerator pedal is connected, and necessary arithmetic processing is executed according to a program based on signals from these sensors. Then, a fuel injection signal for driving the injector 1 of each cylinder is formed.

FIG. 2 shows a detailed configuration of the injector 1.
The main body injector 1 includes a housing 10 and a housing 1.
, A needle body 12 fixed to the end of the needle body 12, a distance piece 14, and a needle hole 12 of the needle body 12.
-1, a needle spring 18 for urging the needle 16 to close the valve, and a command piston slidably fitted in a command piston hole 10-1 of the housing 10. 20 and housing 10
A solenoid 22 fixed to the other end of the solenoid 22;
, An armature portion 24 ′ opposed to the solenoid valve 22 is integrally formed, and a control valve 24 fitted slidably up and down in the hole 10-2 of the housing 10 and a control valve 24 are separated from the solenoid 22. And an energizing armature spring 28. Further, in order to cancel the hydraulic pressure applied to the lower surface of the valve portion 24 ″ of the control valve 24, the needle body 12 having the balance rod 26 having the same diameter as the seat diameter of the valve portion 24 ′ forms a needle hole 30; The lower end forms a nozzle seat 32, and the nozzle seat 32 extends to the nozzle 34 at the lower end of the needle body 12. The needle spring 18 urges the needle 16 so that the lower end thereof is seated on the nozzle seat 32. The upper end of the needle hole 30 forms a fuel reservoir 40 around the enlarged diameter portion of the upper end of the needle 16. The fuel pressure in the fuel reservoir 40 generates a force that lifts the needle 16 against the spring 18. The needle hole 30 is in the needle body 1.
2. It is communicated with a high-pressure fuel passage 42 formed through the distance piece 14 and the housing 10. The high-pressure fuel passage 42 is connected to the high-pressure pipe 2 extending from the common rail 3.
Connected to.

A control chamber 44 is formed at the upper end of the command piston 20 facing the needle 16, and the control chamber 44 is connected to the high-pressure pipe 2 via a throttle 46. A control port 48 formed in the housing 10 has a lower end opened to the control chamber 44 and an upper end opposed to the valve portion 24 ″ at the lower end of the control valve 24. The control valve 24 is closed by the spring 28. And the low pressure chamber 50 formed around the valve portion 24 ″ of the control valve 24 is controlled by the control port 48.
Disconnected from This low pressure chamber 50 is provided with a low pressure passage 52.
Is connected to the fuel tank via

When the solenoid 22 is demagnetized, the spring 28 lowers the control valve 24 so that the valve 2
4 "closes the control port 48. On the other hand, the high-pressure fuel in the high-pressure pipe 2 is introduced into the fuel storage chamber 40 through the high-pressure passage 42 and urges the needle 16 in the valve opening direction. Introduced into the control room 44 via the control port 48,
The needle 16 is urged to close the valve via the command piston 20. Therefore, the valve opening force and the valve closing force by the high-pressure fuel are canceled, and the needle 16 is eventually closed by the spring 18.

When the solenoid 22 is excited, the armature 24 'is displaced upward against the spring 28, the valve portion 24 "of the control valve 24 is lifted from the control port 48, and fuel flows from the control chamber 44 to the low pressure pipe side. Therefore, the force for lowering the needle 16 in the control chamber 44 is weakened, and the needle 16 is moved by the fuel pressure in the fuel storage chamber 40.
Is lifted from the valve seat 32 against the spring 18, and fuel is injected from the nozzle 34.

The predetermined pressure of the common rail 3 is controlled by an injector.
1 by performing the fuel injection from FIG.
(E)). Common level detected by pressure sensor 7
The pressure drop of the valve 3 starts the valve opening of the injector 1 (need
Pressure wave from the point of time when the lift of the
Is delayed by the time until the propagation. This delay time Δt
_DIs generally a piping system (high pressure passage 42, high pressure piping 2, and
Determined by the elastic properties of Monrail 3) and the properties of the fuel
Diameter D, length l, longitudinal elastic modulus E, flow path (piping) support
For each part where the constant C and the wall thickness e are changed
(N) and can be obtained by the following equation.

[0016]

(Equation 1)

Here, γ: fuel density, k: body expansion coefficient,
g: The acceleration of gravity. It should be noted that Δt can also be obtained by experiment in an actual machine. That is, the actual injection timing can be grasped by moving the time backward by Δt _D from the point of time when the pressure of the common rail 3 drops. In the present invention, the desired injection operation is realized by controlling the actual injection timing grasped in this way to be the target injection timing.

Next, the fuel injection operation by the control circuit 4 will be described with reference to the flowcharts of FIGS. 3 and 4 and the timing chart of FIG. FIG. 3 shows a fuel injection routine, which is executed at every predetermined crank angle from the crank angle sensor 8, for example, every time a pulse signal arrives at every 30 ° of the crank angle. In step 100, it is determined whether or not it is the first cylinder injection calculation timing. In a diesel engine, fuel injection is executed immediately before the compression top dead center of each cylinder, and the injection calculation is set to be a timing before the injection timing with a necessary margin. In FIG. 5, the injection calculation timing t _c is shown in FIG. Similarly, in step 102, it is determined whether or not it is the injection calculation timing of the second cylinder.
In step 106, it is determined whether it is the injection calculation timing of the third cylinder. In step 106, it is determined whether it is the injection calculation timing of the fourth cylinder.

If it is determined in step 100 that the timing for calculating the fuel injection of the first cylinder has been reached, the routine proceeds to step 108, where the calculation of the fuel injection amount Q is performed. As is well known, there is a map (fuel injection amount map) of the fuel injection amount for a combination of a large number of values of the engine speed and the engine load.
Then, the interpolation calculation of the fuel injection amount Q with respect to the engine speed and the load value at that time is executed.

In step 110, a calculation of a target value t ₀ of the injection start timing (timing of opening the needle 16 of the injector 1) is executed. As is well known, a map of an optimum injection start timing value (injection start timing map) for a combination of a large number of values of the engine speed and the engine load is provided. An interpolation calculation of the fuel start timing is executed.

In step 112, the target value t ₀ of the injection start timing calculated in step 110 minus the error correction value Δt ₀ is replaced with the target value t ₀ of the injection start timing. As will be described later, the error correction value Δt ₀ is the actual value _tom and the target value _tom of the injection start timing obtained from the pressure drop of the common rail 3 in the previous injection (720 ° before the crank angle) of the first cylinder. ₀ (step 15 in FIG. 4).
0).

In step 114, the calculation of the start timing t _i of the drive signal of the injector 1 for starting the injection at the target injection start timing t ₀ calculated in step 112 is shown.
That is, the control valve 24 is lifted from the time when the drive signal of the injector 1 is output until the needle 16 actually passes through the lift, whereby the command piston 20 is lifted and transmitted to the needle 16 with a series of operations. There is a delay time. The start time t _i is the target injection start time t ₀
Is subtracted from this time Δt _F ((e) in FIG. 5). The value of Δt _F can be determined by a test using an actual device.

Step 116 shows the calculation of the time t _e at which the drive signal of the injector 1 is turned off. This time t _e is calculated as the time required to inject the amount Q of fuel calculated in step 108 from the time t _i when the injector 1 is turned on. In step 118, the on time t _i and the off time t _e of the drive signal of the injector 1 are set in a time coincidence register provided in the control circuit 6. The time coincidence register turns on the drive signal of the injector when the time t _i arrives and turns off the drive signal of the injector when the time t _e arrives (see FIG. 5B).

Step 120 shows the calculation of the start time t _A of the pressure detection period T of the common rail 3 by the injection of the first cylinder, and step 122 shows the calculation of the end time t _B ((c) of FIG. 5).
FIG. 5E shows a change in the pressure of the common rail 3. As described above, after the time Δt _D required for the pressure propagation determined by the above equation from the start of fuel injection, the pressure drop is _reduced (t _{oc in} FIG. 5E). Can be seen. Step 120, 122 in the appropriate time range t _A ~t _B after the start of injection descent time t _oc of the pressure can be predicted reliably contain is set. Steps
At 124, times t _A and t _B are set. That is, the control circuit 6 includes a comparison register (not shown), and when the time t _A arrives, sets a flag indicating the pressure drop detection period of the cylinder in FIG.
(C) The flag F is reset when the time t _B comes. Therefore, it is possible to determine whether or not it is during the common rail pressure drop detection period after the injection of the first cylinder by the state of the flag F.

The processing when it is determined in steps 102, 104 and 106 of FIG. 3 that it is the injection calculation timing for the cylinders 2, 3 and 4, respectively, is the same as the processing in steps 108 to 124, respectively. This makes it possible to control the fuel injection timing and the fuel injection amount independently for each cylinder. In addition, a common rail pressure drop detection period after injection can be set for each cylinder.

FIG. 4 shows the detection of the pressure drop and the calculation of the correction value Δt of the fuel injection time accompanying the detection. This routine is a time interruption routine executed at predetermined time intervals (for example, every 0.1 millisecond). In step 140, it is determined whether or not it is during the pressure drop detection period of the common rail 3 after the injection of the first cylinder. Therefore, steps 120 to 12 in FIG.
4 to determine whether the flag F = 1. If it is determined that the period is the pressure drop detection period of the common rail 3 after the injection of the first cylinder (F = 1), step 142
The process proceeds, been determined whether the detection of the pressure drop has already been, if the detection of the pressure drop not yet been proceeds to step 143, the detection value P of the common rail pressure by the pressure sensor 7 is P _i It is taken in. In step 144, it is determined whether or not the current pressure detection value _Pi is smaller than the previous pressure detection value _Pi-1 (0.1 milliseconds ago). P _i <
If it is not _Pi-1 , it is determined that the pressure drop of the common rail 3 due to the injection of the injector 1 has not yet occurred, and the routine proceeds to step 145, where _Pi-1 is updated with _Pi , and the value of _Pi-1 is The next time (ie after 0.1 ms), step 144
Used in.

In step 144, P_i<P_i-1The judgment is
Common rail 3 caused by injection of injector 1
Since the pressure drop of
It shows that it occurred before passing through the routine. At this time
Proceed to step 146, where the timer (the control circuit 6
The value t of the free-run timer (not shown) provided is t _OC
Can be put in. This t_OCIs the value of como in (e) of FIG.
Rail pressure starts to drop from the previous constant value
Corresponds to a point in time. Next, proceed to step 148,
Pressure drop start time t_ocFrom Δt_DSubtracted
Is the actual start time of the fuel injection that caused this pressure drop
t_omIs calculated as That is, Δt_DIs the injector
From the start of valve opening in 1 until the pressure wave propagates to the pressure sensor 7
Time and the common rail pressure drop
Time t_ocFrom Δt_DOpen the actual valve when the time goes up
It can be grasped as the start time. Steps
In 150, the actual start time t thus obtained is_omFrom
It is calculated based on the engine speed and load (step 10 in FIG. 3).
8) Target valve opening time t₀Is the injection start time supplement
Positive amount Δt₀This is the smell of the next injection of the first cylinder
In step 112 of FIG.₀of
Used for correction.

In step 152, the period of detecting the pressure drop of the common rail due to the injection of the second cylinder, in step 154, the period of detecting the pressure drop of the common rail due to the injection of the third cylinder, and in step 156, the pressure drop of the common rail due to the injection of the fourth cylinder If it is determined in each of the detection periods, and if a positive determination is made, the steps 142 to 15 of the first cylinder are respectively performed.
According to the same procedure as that of 0, detection of the pressure drop timing t _oc of each cylinder and calculation of the injection start time correction amount Δt ₀ are performed.
Each of the third and fourth cylinders is used in the next injection.

In FIG. 5D, the solid line represents the change in the actual injection rate due to the injection from the injector 1, and the broken line represents the change in the target injection rate. Even in the change of the actual injection rate change and the target injection rate of deviation, such as solid and broken lines, FIG. 3, the target injection start timing t ₀ the actual injection start timing t _om the control of FIG. 4 It can be made to match, and the injection rate characteristics can also be made to match the target characteristics.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fuel injection device of the present invention.

FIG. 2 is a partial detailed view of FIG. 1;

FIG. 3 is a flowchart of a fuel injection routine.

FIG. 4 is a flowchart of a pressure drop detection routine.

FIG. 5 is an operation timing chart of the fuel injection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Injector 3 ... Common rail 6 ... Control circuit 7 ... Pressure sensor 16 ... Needle 34 ... Nozzle

Claims (4)

[Claims] 1. A fuel injection system comprising: a common rail for accumulating pressurized fuel; an electronic control injector for each cylinder; and a high pressure pipe connecting the common rail to the electronic control injector. In the fuel injection start timing control method for the internal combustion engine, which calculates the fuel injection start timing correction term according to the difference between the fuel injection start timing command and the fuel injection start timing command, the pressure sensor is provided on the common rail, and the fuel injection start timing after the injection from the injector is provided. The change timing of the output of the pressure sensor is measured, and the calculation of the fuel injection start timing correction term is based on the propagation of the pressure wave from the common rail to the nozzle seat of the electronic control injector on the measured value of the output change timing of the pressure sensor. A fuel injection timing control method for an internal combustion engine, which is performed by considering time. 2. The fuel injection timing control method for an internal combustion engine according to claim 1, wherein said propagation time is calculated by a predetermined calculation formula. 3. The method according to claim 1, wherein the propagation time is obtained by a test using an actual machine. 4. A common rail for accumulating pressurized fuel, an injection nozzle for injecting a fuel injection amount in the common rail to each cylinder of the internal combustion engine and intermittently injecting fuel in response to an electric signal, and a common rail and an injection nozzle. A high-pressure fuel pipe that communicates with a pressure sensor that is disposed in the common rail and detects a fuel injection amount pressure in the common rail; and an injection signal generation circuit that outputs an electric signal that controls the injection timing of the injection nozzle. Detecting means for detecting when the pressure detected by the pressure sensor starts to change after outputting the electric signal; and a pressure wave in the high-pressure fuel pipe and the injection nozzle with respect to the start time of the change in pressure. Means for calculating the actual fuel injection start timing by correcting the propagation time of the fuel injection, and an injection start timing based on the injection signal from the injection signal generation circuit. An internal combustion engine comprising: means for storing a difference between the calculated value and the calculated value of the actual injection start timing; and means for correcting the timing of the injection signal by the injection signal generating means in the next injection based on the stored difference. Fuel injection timing control device.