JP2970368B2 - Fuel injection timing measurement method and injection timing control device for diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a fuel injection timing of a diesel engine and an injection timing control device.

[0002]

2. Description of the Related Art Light fuels and heavy fuels are generally supplied to diesel engines. Heavy fuels and light fuels are set so as to inject fuel at the same time due to differences in viscosity and the like. However, there is a time difference in the actual fuel injection, and when switching from heavy fuel to light fuel, the injection timing tends to be delayed. Even if the fuel injection start timing does not change much, if the injection that substantially supplies most of the fuel is delayed, the combustion will not proceed unless measures such as advancing the fuel injection timing are taken. Becomes stable,
In the worst case, the engine may misfire.

Therefore, for example, Japanese Patent Application Laid-Open No. 61-275570
In the device disclosed in the above publication, the output of the lift sensor that detects the lift of the needle valve of the fuel injection valve is filtered to remove noise, and the output delay due to the filter is corrected, and this and the crank angle of the engine are corrected. By calculating the fuel injection timing from the reference position and performing feedback control on the injection timing so that this injection timing matches the target injection timing, even if the fuel used changes, the injection timing can be accurately grasped, and the fuel injection timing can be determined. Even if the properties fluctuate, stable combustion is always maintained.

[0004]

However, even if the lift of the needle valve is detected, not all the fuel is injected at the moment when the lift is started, but the fuel injection continues for a certain period. Detecting the moment when the lift is started does not always correspond to the correct fuel injection timing. It is also conceivable that the injection timing is recognized when there is a certain amount of lift. However, since the injection characteristics change depending on the operating state, for example, in FIG. In this case, the actual fuel injection timing (the center position of the total injection amount)
In the section A, it is almost in the middle, but in the section B, it is behind the middle.

Therefore, if the injection timing is not determined based on the characteristics of the actual fuel injection amount, even if the fuel injection timing is feedback-controlled as described above, it is not always possible to obtain proper combustion.

Accordingly, it is an object of the present invention to always accurately detect the fuel injection timing and to appropriately control the fuel injection timing based on the detection.

[0007]

A first invention is shown in FIG.
As shown in (A), means 1 for pumping fuel in synchronism with engine rotation, means 2 for controlling target injection timing of fuel in accordance with an operation state, and a fuel injection valve for injecting this fuel into a combustion chamber 3, the fuel injection pressure of the fuel injection valve is detected while the reference crank angle of the engine is detected, and this injection pressure is compared with a comparison reference value, and the injection pressure exceeds the comparison reference value. A fuel injection timing measurement method for a diesel engine, wherein a fuel injection timing is calculated from a median value of a period in which the fuel injection is performed and a fuel injection timing is calculated from the median value and a reference crank angle.

In a second aspect based on the first aspect, the comparison reference value increases in accordance with the engine speed and the fuel injection amount.

[0009] In the third invention, as shown in FIG.
A means 1 for pumping the fuel in synchronization with the engine rotation, a means 2 for controlling a target injection timing of the fuel in accordance with an operation state,
In a diesel engine having a fuel injection valve 3 for injecting this fuel into a combustion chamber, a means 4 for detecting a reference crank angle of the engine, a means 5 for detecting a fuel injection pressure of the fuel injection valve 3, A means 6 for comparing the pressure with the comparison reference value, a means 7 for determining a center value during a period when the injection pressure exceeds the comparison reference value, and a means 8 for calculating the main fuel injection timing from the center value and the reference crank angle. And a means 9 for correcting the fuel injection timing so that the calculated fuel main injection timing matches the target fuel injection timing.

[0010]

According to the first aspect of the present invention, the central value of the period during which the fuel injection pressure exceeds the comparison reference value is determined as the substantial fuel injection timing. Even if the correspondence between the actual injection timing and the actual injection timing is different, the injection timing of the main injection can always be correctly measured.

In the second invention, even if the fuel injection pressure fluctuates according to the engine speed or the injection amount, the comparison reference value is made to correspond to this, so that the main injection timing is accurately detected under all operating conditions. be able to.

In the third aspect of the present invention, the actual fuel injection, that is, the injection timing of the main injection is correctly determined, and the fuel injection timing is corrected based on this. Even if the injection timing fluctuates, the injection timing can always be matched with the target injection timing, and stable combustion can be maintained even when the fuel is switched.

[0013]

Embodiments of the present invention will be described below. 10 is an engine body of a diesel engine, 11 is an intake passage, 1
An exhaust passage 2 is supercharged by a turbocharger 13. An exhaust gas recirculation passage 14 is an exhaust gas recirculation control valve 15.
Thus, the amount of exhaust gas recirculated to the intake passage 11 is controlled. At the time of exhaust gas recirculation, the throttle valve 16 interposed in the intake passage 12 is throttled.

A fuel injection valve 18 for directly injecting fuel into a combustion chamber 17 of the engine body 1 is provided, and fuel from a fuel injection pump 19 is supplied to the fuel injection valve 18. The fuel injection pump 19 operates the plunger 20 in synchronization with the engine speed to increase the pressure of the fuel pressurized by the feed pump 21 and to pump the fuel to the fuel injection valve 18 of each cylinder near the compression top dead center. The fuel injection amount changes depending on the position of the control sleeve 22, and the position of the control sleeve 22 is controlled by a governor electric 23 which is operated by a signal from the control device 25.

The control device 25 calculates a basic fuel injection amount based on a signal from an accelerator sensor 26 for detecting an accelerator opening and an engine speed signal, thereby controlling the governor electric 23.

In order to correct the basic fuel injection amount and to control the exhaust gas recirculation amount, the control device 25 sends a signal representative of the operating state as well as the accelerator opening and the rotational speed, as well as the reference crank of the engine. A reference crank angle signal from a crank angle sensor 27 that outputs an angle signal, a vehicle speed signal, and a signal from a transmission switch are input. Furthermore, a signal from a sensor 29 for detecting the position of the control sleeve and a sensor 30 for detecting the fuel temperature for measuring the actual fuel injection amount of the fuel injection pump 19, and the needle lift of the fuel injection valve 17 of the engine body 1 Signals from a sensor 31 for detecting the amount and a sensor 32 for detecting the temperature of the engine cooling water are also input. Also,
An air flow meter 33 for detecting the mass flow rate of the engine intake air is attached to the intake passage 11, and also receives this intake air amount signal.

The controller 25 detects the actual air-fuel ratio from the signals from the air flow meter 33 and the control sleeve position sensor 29, and the detected air-fuel ratio does not become lower than a predetermined value (the air-fuel ratio does not become higher than a certain value). As described above, the maximum injection amount with respect to the basic injection amount of the fuel is regulated, and the smoke generated during the maximum fuel injection is always suppressed to a certain value or less. Further, a duty control of the negative pressure control valve 34 for controlling the drive negative pressure of the exhaust gas recirculation control valve 15 and a first control for simultaneously controlling the drive negative pressure of the throttle valve 16 are performed.
The opening degree of the solenoid valve 38 and the second solenoid valve 39 is controlled, so that optimal exhaust gas recirculation is performed in accordance with the operation state in order to reduce NOx, and fuel leakage when the engine is stopped is prevented. The fuel cut valve 37 is closed when the engine is stopped.

Further, the controller 25 controls the fuel injection pump 1
The fuel injection signal, which is basically set according to the engine speed, is transmitted to the needle lift sensor 31 in order to optimally perform feedback control of the injection timing of the fuel injected from the fuel injection valve 9.
And the main injection timing signal calculated from the signal of the crank angle sensor 27, the opening degree of the timing control valve 35 is controlled by this correction signal, and the pressure applied to the timer piston 36 is changed.
By moving 6 and adjusting the fuel injection timing,
Even if the injection characteristics (injection amount and injection timing) of the fuel supplied to the engine change, control is performed so that stable combustion is always ensured. The movement of the timer piston 36 causes the cam roller 41 with respect to the cam 40 to be displaced in the rotation direction of the cam 40, thereby advancing or retarding the fuel injection timing.

Control contents for controlling the injection timing so as to always maintain the proper fuel injection timing even when the fuel injection characteristics change will be described with reference to the flowcharts of FIGS.

First, FIG. 3 shows a routine for calculating a fuel injection timing signal. In step 11, the engine speed N and the target fuel injection amount _QSOL are read. Although not shown, the value of Q _SOL is calculated based on the engine speed N and the accelerator opening, and increases as the accelerator opening increases and the engine speed decreases.

In step 12, the basic fuel injection timing IT _SOL is determined from the N and Q _SOL from the map shown in FIG. Further, at step 13, the fuel injection timing correction value ΔI
T _SOL is calculated as ΔIT _SOL = IT _SOL −IT _IST . This IT _IST is the position of the center of gravity of the main injection of fuel injection and represents the substantial center position (cam angle) of fuel injection.
FIG. 4 shows specific contents.

In step 14, IT _SOL = IT _SOL -ΔIT _SOL is calculated as a fuel injection timing signal, and is output to the timing control valve 35 to control the fuel injection timing.

Next, a routine for calculating the position of the center of gravity of the injection at the main injection timing of the fuel will be described with reference to FIG.

In step 21, the needle lift sensor 31
Reads the output voltage V _{N / L,} and the engine speed N and the target injection amount Q _SOL, sliced from these N and Q _SOL, from the map shown in FIG. 6, as the comparison reference value of the output voltage of the needle lift sensor 31 Find level A. As shown in FIG. 7, this slice level A is for defining the calculation condition of the cam angle position that is the center of gravity of the fuel injection. The slice level A increases as both the rotation speed N and the target injection amount Q _SOL increase ( High). This is because as the rotation speed and the fuel injection amount increase, the injection pressure relatively increases, and the output voltage of the needle lift sensor 31 also increases. Therefore, the slice level A has a relatively low value in the low rotation and low injection range.

In step 23, the output voltage V _{N / L of the} needle lift sensor 31 is compared with the slice level A,
When the output voltage V _{N / L} exceeds the slice level A with the fuel injection by the lift of the fuel injection valve 18, the process proceeds to step 24 to start counting by the first timer T ₁ .

Furthermore, V _{N / L} at step 25 waits until drops below A, After lower than the slice level A, starts a second timer count T ₂ (step 25, 26). The timers T ₁ and T ₂ stop counting when the output of the reference crank angle sensor 27 is determined and the reference crank angle is reached (steps 27 and 2).
8). Then, in step 29, these timers T ₁ , T ₂
From the count values T ₁ , T ₂ (time) and the engine speed (rotation speed per minute) N at that time,
Crank angle IT until each timer stops
_IST 1 and IT _IST 2 are calculated.

IT _IST 1 = (N / 60) × 360 × T ₁ IT _IST 2 = (N / 60) × 360 × T ₂ Thus, when IT _IST 1 and IT _IST 2 are obtained, Center of gravity of main fuel injection (cam angle) IT _IST
Is calculated as IT _IST = (IT _IST 1 + IT _IST 2) / 2. This is the output voltage of the needle lift sensor 31 is V _{N / L} corresponds to a central value of the period exceeds the slice level A (advance angle from the reference crank angle). In this case, in FIG.
The cam angle (corresponding to the crank angle) at which 0% is injected is a position slightly advanced by the crank angle from the position of the center of gravity.

FIG. 8 shows the relationship between the cam angle when the injection amount actually reaches 50% and the cam angle for detecting the center of gravity position of the needle lift sensor 31.
For every 500 rpm from 0 rpm to 2500 rpm, the fuel injection amount is set to 5, 20, 35, 50 (mm ³ /
(st) represents the state when changed. In this case, as the rotational speed increases and the fuel injection amount increases, the cam angle at the center of gravity position becomes relatively larger than the cam angle at the time of 50% injection.

As can be understood from these facts, the position of the center of gravity of the fuel injection substantially corresponds to the center of the main injection of the fuel. Therefore, by grasping the position of the center of gravity, the actual fuel injection timing can be correctly judged.

Therefore, the calculated IT
_{From the IST} , the correction amount ΔIT _SOL in FIG.
If the fuel injection timing is output as IT _SOL = IT _SOL −ΔIT _SOL , it is possible to control the fuel injection timing that correctly reflects the main injection of the fuel.

As a result, even if the needle lift characteristic changes during the crank angle period during which fuel is injected (for example, only a small amount of lift is maintained, or the lift characteristic changes from a small amount of lift to a large amount of lift). Thus, the actual injection timing can always be accurately detected.

Therefore, for example, if the main injection actually delays, the injection timing corresponding to the delay can be detected. Therefore, the control signal of the timing control valve 35 for controlling the position of the timer piston 36 by the feedback control is determined by the delay of the main injection. Thus, the injection timing can be corrected to the leading side, the delay of the injection timing can be eliminated, and the combustion of the engine can be stabilized.

Further, if the actual main injection timing is relatively advanced, the correction is made in the direction of delaying the injection timing accordingly, and thus the proper injection timing can always be maintained.

[0034]

As described above, the first aspect of the present invention provides a means for feeding fuel in synchronism with the rotation of the engine, a means for controlling a target injection timing of fuel in accordance with an operation state, and a method for transferring this fuel to a combustion chamber. In a diesel engine equipped with a fuel injection valve that injects fuel, while detecting the reference crank angle of the engine, the fuel injection pressure of the fuel injection valve is detected, and this injection pressure is compared with a comparison reference value. Since the center value of the period during which the reference value is exceeded is determined, and the main injection timing of the fuel is calculated from the center value and the reference crank angle,
Since the center value of the period during which the fuel injection pressure is higher than the comparison reference value is determined as the substantial fuel injection timing, the fuel injection characteristics change and the correspondence between the injection start timing and the substantial injection timing is determined. , The injection timing of the main injection can always be correctly measured.

According to a second aspect of the present invention, in the first aspect, the comparison reference value is increased in accordance with the engine speed and the fuel injection amount.
Even if the fuel injection pressure fluctuates, the comparison reference value corresponds to this, so that the main injection timing can be accurately detected under all operating conditions.

According to a third aspect of the present invention, there is provided a means for pumping fuel in synchronization with engine rotation, a means for controlling a target injection timing of fuel in accordance with an operating state, a fuel injection valve for injecting the fuel into a combustion chamber, and Means for detecting the reference crank angle of the engine, means for detecting the fuel injection pressure of the fuel injector, means for comparing the injection pressure with a comparison reference value, and Means for calculating the center value of the period exceeding the value, means for calculating the main fuel injection timing from the center value and the reference crank angle, and setting such that the calculated main fuel injection timing matches the target fuel injection timing. Because of the provision of the means for correcting the fuel injection timing, even if the fuel injection characteristics change and the actual injection timing fluctuates, this is correctly grasped and always coincides with the target injection timing. Bets can be always maintained stable combustion, it is possible to improve the fuel economy and exhaust compositions.

[Brief description of the drawings]

FIG. 1 is a block diagram of the present invention, wherein (A) is the first invention,
(B) shows the third invention.

FIG. 2 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart showing a control operation for calculating a fuel injection timing.

FIG. 4 is a flowchart showing a control operation for calculating a main injection timing.

FIG. 5 is a characteristic diagram of a target injection timing obtained from a rotation speed and an injection amount.

FIG. 6 is a characteristic diagram of a slice level obtained from a rotation speed and an injection amount.

FIG. 7 is an explanatory diagram showing a fuel injection waveform and a needle lift sensor waveform.

FIG. 8 shows the cam angle of the center-of-gravity position detection of the needle lift sensor and the fuel injection amount when the rotation speed and the injection amount are changed.
It is explanatory drawing which shows the relationship with the cam angle at the time of 0%.

FIG. 9 is an explanatory diagram showing a relationship between fuel injection characteristics and actual injection timing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Engine main body 11 Intake passage 12 Exhaust passage 18 Fuel injection valve 19 Fuel injection pump 25 Controller 31 Needle lift sensor 35 Timing control valve 36 Timer piston 40 Cam 41 Cam roller

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiichi Inoue Nissan Motor Co., Ltd. 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture (56) References JP-A-59-113254 (JP, A) JP-A-4- 60168 (JP, A) Japanese Utility Model 3-104174 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F02M 65/00 301 F02D 41/00-41/40

Claims (3)

(57) [Claims] 1. A diesel engine comprising: means for pumping fuel in synchronization with engine rotation; means for controlling a target injection timing of fuel in accordance with an operation state; and a fuel injection valve for injecting the fuel into a combustion chamber. In the engine, while detecting the reference crank angle of the engine, the fuel injection pressure of the fuel injection valve is detected, and this injection pressure is compared with a comparison reference value, and the central value of the period when the injection pressure exceeds the comparison reference value is detected. And calculating a main injection timing of the fuel from the center value and the reference crank angle. 2. The method according to claim 1, wherein the comparison reference value increases in accordance with an engine speed and a fuel injection amount. 3. A diesel engine comprising: means for pumping fuel in synchronization with engine rotation; means for controlling a target injection timing of fuel in accordance with an operation state; and a fuel injection valve for injecting the fuel into a combustion chamber. In the engine, a means for detecting a reference crank angle of the engine, a means for detecting a fuel injection pressure of a fuel injection valve, a means for comparing the injection pressure with a comparison reference value, and an injection pressure exceeding the comparison reference value Means for calculating the center value of the fuel injection period, means for calculating the main fuel injection timing from the center value and the reference crank angle, and setting the fuel injection timing so that the calculated fuel main injection timing matches the target fuel injection timing. A fuel injection timing control device for a diesel engine, comprising: a correction unit.