JPH0842376A - Controller of pressure accumulating-type fuel injection system - Google Patents

Abstract

PURPOSE:To prevent fluctuation of output caused by change of the fuel temperature by taking the temporary target injection amount as the target injection amount to be determined by the correction factor of specific gravity of fuel according to the engine speed and the load when the fuel temperature is deviated from the predetermined range. CONSTITUTION:A controller is provided with a pressure sensor 6 provided on a common rail 5 to which high pressure fuel is supplied, a temperature sensor 12 provided on a fuel tank 1, a rational sensor 13, an engine load sensor 14, and a top dead center sensor 15, and the output signals are input into a controller 7. The temporary fuel injection amount Q' and the temporary fuel injection pressure P1' are found on the basis of the engine speed and the load of an engine. When the fuel temperature is within the normal temperature range, Q' and P1' are respectively set as target values. When the temperature is deviated from the normal temperature range, the value obtained by dividing Q' by the temperature correction factor K of the fuel specific gravity is set to the target injection amount, or the value obtained by multiplying the reciprocal of the square of P1' is set to the target injection pressure according to the engine speed and the load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for a pressure accumulation type fuel injection system, and more specifically, in an internal combustion engine equipped with a pressure accumulation type fuel injection system, a pressure accumulation type for correcting a fuel injection amount according to a change in fuel temperature. The present invention relates to a control device for a fuel injection system.

[0002]

2. Description of the Related Art An internal combustion engine equipped with a pressure accumulating fuel injection system in which a common rail is mounted between a fuel pump and a fuel injection nozzle has been conventionally used. In this pressure-accumulation fuel injection system, the target fuel injection amount Q and the target injection pressure P _i according to the engine speed and the load (generally, the accelerator opening) are set in advance in a map, and the fuel injection is performed based on the signal from the load sensor. PID (proportional-integral-derivative) control is performed so that the pressure (that is, the pressure in the common rail) P _I becomes the target injection pressure P _I , while the fuel injection amount becomes the target fuel injection amount Q by the following equation. The injection period (lift period of the needle valve of the injection nozzle) is calculated based on this, and the energization time to the solenoid valve provided in the injection nozzle is controlled.

[0003] Where A is the nozzle area, α is the flow coefficient, γ is the fuel specific gravity, Δ
P is a value obtained by subtracting the cylinder pressure P ₂ from the fuel injection pressure P _1, may be approximately [Delta] P ≒ P _1. By the way, while the output of the engine is determined by the net fuel mass, the fuel injected from the fuel injection nozzle depends on the lift height and lift period of the needle valve, so the injection amount is determined by the volume.

Therefore, in the pressure-accumulation fuel injection system in which a relatively large amount of fuel leaks from the injection nozzle, the leaked fuel is recirculated to the fuel tank, so that the fuel temperature rises with the operation of the engine and becomes high, resulting in a temperature change. Accordingly, there is a problem that proper output control cannot be performed unless the fuel specific gravity γ is also corrected. Therefore, measures have been proposed in the past when the specific gravity of fuel has changed. For example, the means disclosed in JP-A-4-103849 uses a two-stage lift type fuel injection nozzle, and controls the correction coefficient map for the basic injection amount and the basic injection timing when the fuel changes from the basic specific gravity. The basic injection amount and the basic injection timing are obtained from the accelerator opening and the engine rotation speed stored in the device, the temperature-corrected specific gravity is obtained from the specific gravity sensor and the temperature sensor attached to the fuel tank, and the volume is calculated from the correction coefficient map. The fuel injection amount, the fuel injection timing, and the initial lift amount are calculated, and the fuel injection nozzle is controlled.

[0005]

By the way, the correcting means described in the above publication corrects the fuel injection amount only by controlling the length of the injection period (the lift period of the needle valve of the injection nozzle). ing. Therefore, exhaust emissions (smoke emissions such as NO _X), relative to the optimum injection period determined by the fuel economy properties, there is a problem that optimum control can be obtained. More specifically, in the high-speed / high-load operation region, when the fuel temperature rises (that is, the fuel specific gravity decreases) and a substantial decrease in the fuel injection amount is attempted to be corrected, the injection is performed with respect to the piston speed. The period becomes too long, and exhaust gas characteristics and fuel efficiency characteristics deteriorate. This becomes more remarkable in the pressure-accumulation fuel injection system in which a large amount of fuel leaks from the injection nozzle (that is, a large amount of fuel that has once been heated to a high temperature is returned to the fuel tank).

The present invention has been made in view of the above problems. By correcting the optimum fuel injection amount according to the operating condition of the engine, the exhaust gas characteristic and the fuel consumption characteristic are not deteriorated. An object of the present invention is to provide a control device for a pressure-accumulation fuel injection system that prevents output fluctuations due to changes in fuel temperature.

[0007]

SUMMARY OF THE INVENTION To achieve the above object, a control device for a pressure accumulation type fuel injection system according to the present invention is a control device for a pressure accumulation type fuel injection system. The temporary target values of the fuel injection amount and the fuel injection pressure are obtained from the map determined in advance, and when the fuel temperature is within the predetermined standard temperature range, the temporary target value is set to the respective target injection amount and target injection. When the pressure is set and the fuel temperature deviates from the standard temperature range, if the rotational speed and the load of the engine are equal to or less than a set value, a value obtained by dividing the temporary target injection amount by a fuel temperature correction coefficient is used as the target injection. In addition, the temporary target value injection pressure is set as the target injection pressure, and when the engine speed or the load is equal to or higher than a set value, the temporary target injection amount is set as the target injection amount, and the temporary target is set. Before injection pressure The value obtained by multiplying the square of the reciprocal of the temperature correction coefficient as a target injection pressure, and controls the fuel injection amount and the fuel injection pressure.

[0008] The standard temperature range of the fuel is not constant depending on the area of use and the state of use, but generally, the temperature t is set within the standard temperature range (for example, 30 to 40 ° C).
It can be set to a range of ₀ ± 10 ° C. However, the present invention is not limited to this, and can be appropriately determined based on actual practice. When the specific gravity with respect to the temperature t ₀ is γ ₀ , the specific gravity of the fuel at the actual temperature te is γ, the correction coefficient is K, and a is a constant determined from the physical properties of the light oil, the specific gravity γ is γ = K × γ ₀ K = it can be determined by _{1-a (te -t 0)} .

The injection pressure, the energization time of the electromagnetic valve of the injection nozzle, the injection timing, etc. can be determined by the same means as in the prior art. Furthermore, the map may be modified in various ways, for example, when the map is created in consideration of the performance of the internal combustion engine used, restrictions due to restrictions on exhaust gas temperature, and restrictions on durability such as cylinder internal pressure.

The rotation sensor for detecting the rotational speed of the engine used in the present invention, the load sensor for detecting the load of the engine, the temperature sensor for detecting the temperature of the fuel, and the pressure sensor for detecting the fuel injection pressure are all conventional. What is used for control of an engine can be used.

[0011]

When the fuel temperature is within the predetermined range, the fuel temperature is controlled based on the temporary target injection amount obtained from the map or the formula using the engine speed and load as parameters, and the fuel temperature deviates from the range. In this case, if the engine speed and the load are equal to or lower than the predetermined set values, the temporary target injection amount is set as the target injection amount determined by the correction coefficient K of the specific gravity of the fuel, and the engine speed is set to the predetermined value. If it is equal to or higher than the set value (high speed rotation number), the temporary target injection pressure is set to the correction coefficient K.
The means for determining by the above corrects the optimum fuel injection amount according to the operating condition of the internal combustion engine, thereby preventing the fluctuation of the output due to the change of the fuel temperature without deteriorating the exhaust gas characteristic and the fuel consumption characteristic. be able to.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the accompanying drawings with reference to the accompanying drawings. The fuel injection system in this embodiment shown in FIG. 1 sends fuel pumped by a feed pump 2 from a fuel tank 1 of a diesel engine (not shown) to a high-pressure pump 3 to switch high-pressure pressurized fuel to three-way. It is supplied to the common rail 5 via a pressure control solenoid valve 4 composed of a valve. A pressure sensor 6 is attached to the common rail 5, and the pressure signal detected here is a control device 7.
Is input to

The high-pressure fuel stored in the common rail 5 is
It is sent to the fuel injection nozzle 9 through the fuel passage 8 and the fuel is injected from an injection port (not shown). In the fuel injection nozzle 9,
An electromagnetic leak valve 10 is attached, and the leaked fuel is returned to the fuel tank 1 via the return passage 11. A temperature sensor 12 is attached to the fuel tank 1, and the detected fuel temperature is input to the control device 7. In this embodiment, a 6-cylinder engine is used, and the dotted line portion where the return passage 11 crosses the fuel injection nozzle 9 is connected to each of the fuel injection nozzles 9. It is shown that.

In addition to the pressure signal and the temperature signal, the control device 7 detects a rotation sensor 13 for detecting the rotation speed of the engine, a load sensor 14 for detecting the engine load, and a top dead center of a piston (not shown). The signal from the top dead center sensor 15 is input. In this embodiment, the load sensor 14 is an accelerator sensor that detects the accelerator opening. The fuel pressure in the common rail 5 is controlled by controlling the pressure control solenoid valve 4 so that the pressure signal from the pressure sensor 6 matches the set pressure. The pressure control solenoid valve 4 is preferably controlled by PID control.
Further, the injection period T _D of the fuel injection nozzle and the injection timing T _INJ
Are controlled based on the signals from the sensors 6, 12, 13, 14, and 15.

Next, the operation of the control device 7 will be described with reference to the flow charts shown in FIGS. The main mode shown in FIG. 2 and the sub mode shown in FIG. 3 are processed in parallel by performing time sharing for several msec. When the flow of the main mode is started, in step 1, the rotation speed Ne of the engine is detected by the rotation sensor 13, the accelerator opening _VL is detected by the load sensor 14 in step 2, and the temperature sensor 12 is used in step 3. The fuel temperature Tf is detected, and the temporary target injection amount Q'is obtained from a predetermined map from the rotational speed Ne and the accelerator opening _VL read in step 4.

Next, at step 5, the fuel temperature Tf
Is _{below the} lower limit of standard temperature T _0MIN (eg, 25 ° C.) and lower than the upper limit of standard temperature T _0MAX (eg, 45 ° C.), and if a positive result is obtained, the pressure correction coefficient K _{P is set} to 1 in step 6. Then, if a negative result is obtained, step 7 is executed. In step 7, it is judged whether or not it is in the range of the region F (shown in FIG. 2) of the map 1 in which the relationship between the engine speed Ne and the accelerator opening degree _VL is obtained, and a negative result is obtained. In step 8, the square root of the temperature correction coefficient K of the specific gravity of the fuel is calculated, the pressure correction coefficient K _P of the fuel is obtained, and the process proceeds to step 9. The temperature correction coefficient K of the fuel specific gravity γ used in this example was calculated from the following equation.

K = 1-a (Tf-Tf ₀ ) where a is a constant and Tf ₀ is a standard temperature (for example, 35
° C). If a positive result is obtained in step 7, the target injection amount Q is obtained by dividing the temporary target injection amount Q'by the temperature correction temperature K in step 10, and the pressure correction coefficient K _{P is set} to 1 in step 11, Twelve are executed.

In step 9, the target injection amount Q
Is set to the tentative target injection amount Q ', and in step 12, the energization time T of the electromagnetic leak valve 10 of the fuel injection nozzle 9 is set.
_D is obtained, and in step 13, the injection timing T _INJ is obtained from the injection timing map determined by the rotation speed Ne and the accelerator opening degree _VL . In this case, it is obvious that the injection timing T _INJ is not a single type but a plurality (6 in this embodiment) shifted by the phase for each cylinder. And step
At 14, the electromagnetic leak valve 10 of the fuel injection nozzle 9 is energized from the injection timing T _INJ for the energization time T _D to inject fuel, and the process returns to step 1.

When step 8 is executed, the control device 7 starts the sub mode shown in FIG. 3 at the same time as the main mode. When the sub mode is started, the rotational speed Ne, accelerator opening _{VL, and} fuel temperature Tf information detected in the main mode are shared in step S1, and step S2 is performed.
In the rotational speed Ne, determine the temporary target injection pressure P _I 'from a predetermined injection pressure map according to the accelerator opening V _L, in step S3, the provisional target injection pressure to the pressure correction coefficient K _P which is set in the main mode P _I ′ Is multiplied to obtain the target injection pressure P _I , the pressure sensor 6 detects the injection pressure P _i in step S4, and in step S5, the pressure control electromagnetic wave is adjusted so that the injection pressure P _i matches the target injection pressure P _I. The valve 4 is controlled, and the process returns to step S1.
As described above, the control is performed by changing the fuel injection condition according to the operating state of the engine, so that it is possible to prevent the output fluctuation due to the change of the fuel temperature without deteriorating the exhaust gas characteristic and the fuel consumption characteristic.

[0020]

As described above, since the control device for the pressure-accumulation type fuel injection system of the present invention is constructed, the control of the fuel injection nozzle and the fuel injection are performed by the combination of the detected engine speed, engine load and fuel temperature. By controlling the pressure, it is possible to prevent the output fluctuation due to the change of the fuel temperature without deteriorating the exhaust gas characteristic and the fuel consumption characteristic over the entire range of the operating condition of the engine.

[Brief description of drawings]

FIG. 1 is a control system diagram of a control device for a pressure-accumulation fuel injection system according to an embodiment of the present invention.

FIG. 2 is a flowchart of a main mode control operation of the control device shown in FIG.

FIG. 3 is a flowchart of a sub mode control operation of the control device shown in FIG.

[Explanation of symbols]

1 Fuel Tank 2 Feed Pump 3 High Pressure Pump 4 Pressure Control Solenoid Valve 5 Common Rail 6 Pressure Sensor 7 Control Device 8 Fuel Passage 9 Fuel Injection Nozzle 10 Electromagnetic Leak Valve 11 Return Passage 12 Temperature Sensor 13 Rotation Sensor 14 Load Sensor 15 Top Dead point sensor F region K temperature correction coefficient K _P pressure correction coefficient Ne speed P _i injection pressure P _I target injection pressure P _I 'temporary target injection pressure Q target injection amount Q' temporary target injection amount T _D energization time Tf fuel temperature Tf ₀ Standard temperature T _INJ Injection timing T _0MIN Standard temperature lower limit T _0MAX Standard temperature upper limit _VL Accelerator opening γ Fuel specific gravity

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location F02M 47/00 E 61/10 D

Claims (2)

[Claims] 1. A control device for a pressure-accumulation fuel injection system, comprising:
Obtaining a temporary target value of the fuel injection amount and the fuel injection pressure from a map predetermined by the rotational speed and load of the engine, and when the fuel temperature is within a predetermined standard temperature range, the temporary target value With the target injection amount and the target injection pressure, when the fuel temperature deviates from the standard temperature range,
When the engine speed and load are equal to or lower than the set values, the value obtained by dividing the temporary target injection amount by the fuel temperature correction coefficient is set as the target injection amount, and the temporary target value injection pressure is set to the target injection pressure. When the rotational speed or the load of the engine is equal to or more than a set value, the temporary target injection amount is set as the target injection amount, and the temporary target injection pressure is multiplied by the reciprocal of the square of the temperature correction coefficient. A control device for an accumulator fuel injection system, which controls a fuel injection amount and a fuel injection pressure with a value as a target injection pressure. 2. The map according to claim 1, wherein the set rotational speed is set lower as the load detection value increases, and a map is formed when the injection period is adjusted by the lift of the fuel injection nozzle and when it is adjusted by the injection pressure. Accumulator fuel injection system control device.