JP2890898B2 - Pressurized fuel control device - Google Patents

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 pressurized fuel supplied to an internal combustion engine, and more particularly, to a pressurized fuel control system for directly injecting fuel into a cylinder.

[0002]

2. Description of the Related Art As one method of realizing lean combustion for improving properties of exhaust gas discharged from an internal combustion engine, a method of directly injecting fuel into a cylinder is known.
In order to accurately control the amount of fuel injected into a cylinder in this method, a fuel injection control device called a common rail system has been proposed.

That is, fuel is pressurized to about 20 M pascal by a fuel pump driven by an internal combustion engine and held in a pressure accumulating chamber. The pressurized fuel is injected into the cylinder by a fuel injection valve provided for each cylinder. In order to accurately control the amount of injected fuel, it is necessary to maintain the pressure in the accumulator at a constant level. For this purpose, a pressure detector for detecting the pressure in the accumulator and a fuel supply amount controller are provided.

The applicant of the present application has already proposed a pressurized fuel control device using a fuel pump integrally incorporating an overflow valve using a piezo as an actuator as a fuel supply amount control means (Japanese Patent Application No. Hei. 096498). FIG. 6 is a configuration diagram of a pressurized fuel control device using an overflow valve according to the proposal of the present applicant. An overflow valve unit 207 includes a fuel pump 208.
An overflow valve 2071 for returning the fuel pressurized in the fuel tank 210 to the fuel tank 210 and a piezo actuator 2072 for adjusting the opening degree of the overflow valve 2071 are integrally incorporated.

The fuel pressurized by the fuel pump 208 is held in a pressure accumulating chamber 220. The fuel pressure P _R, which is held in the accumulator 220 is detected by the accumulator pressure detector 204,
The comparison unit 252 compares the target pressure _PT set by the pressure accumulation chamber pressure setting unit 251 with the target pressure _PT . Pressure deviation ΔP calculated in comparison unit 251 the absolute value of the pressure deviation is equal to or larger than the predetermined value K _P is determined by the determination unit 253.

When the value is larger than the predetermined value K _P , the full-open or full-close command is output to the overflow valve 2071 by the full-open or full-close setting unit 254. If the value is smaller than the predetermined value K _P, the opening of the overflow valve 2071 is integratedly controlled by the integral control unit 255 according to the pressure deviation. The opening command of the overflow valve 2071 is output as a ratio (hereinafter referred to as a duty ratio) of a time required to open the overflow valve 2071 in a time required for one rotation of the fuel pump 208.

[0007] The driving unit 209 controls the piezo 207.
The overflow valve 2071 is closed by bringing 2 into a charged state, and the overflow valve 2071 is opened by bringing the piezo 2072 into a discharged state.

[0008]

SUMMARY OF THE INVENTION However, this system
The control method has the following problems. That is, the fuel in the accumulator 220
Charge pressure P_RQuickly to the target pressure P_TA predetermined value K
_PIs set to be small, the fuel pressure P_RIs the target pressure
P_TOverflow valve 2072 repeatedly opens and closes when approaching
Fuel pressure P_RCauses hunting.

Conversely, a predetermined value K is used to prevent hunting.
If you set larger _P is, a long time is required until the fuel pressure P _R to reach the target pressure P _T, the exact amount of fuel from being injected. FIG. 5 shows the fuel pressure P _R according to the predetermined value K _P.
FIG. 4B illustrates the response when the predetermined value K _P is small, and FIG. 4C illustrates the response when the predetermined value K _P is large.

[0010] The present invention has been made in view of the above problems, it is possible not only to increase the fuel pressure P _R to rapidly target pressure P _T, overshoot or that no fuel pressure control of occurrence of hunting It is intended to provide a device.

[0011]

FIG. 1 is a basic configuration diagram of a pressurized fuel control device according to the present invention, wherein a rotational speed detecting means 101 for detecting the rotational speed of an internal combustion engine, and a load of the internal combustion engine are detected. Load detecting means 102 and rotational speed detecting means 101
Fuel injection means 103 for calculating the amount of fuel to be injected into the cylinder based on the rotational speed detected in step 1 and the load detected by the load detection means 102, and pressure accumulation chamber pressure detection means for detecting the pressure of the pressure accumulation chamber 104 and target pressure
And the accumulator pressure detected by the accumulator pressure detector
Fills the accumulator with fuel of target pressure
Calculated by the fuel amount required for
By adding the injection quantity of fuel supply fuel amount calculating means 105 for calculating a fuel amount to be supplied to the pressure accumulating chamber, the amount of supplied fuel
The supplied fuel amount and the fuel po
A duty ratio calculating means for calculating a duty ratio representing an overflow valve opening time per one rotation of the fuel pump, which is a ratio to a fuel amount discharged from the pump, and a duty ratio calculated by the duty ratio calculating means. An overflow valve unit 107 in which an overflow valve for determining a valve time and a valve closing time is incorporated.

[0012]

In the pressurized fuel control device according to the present invention,
After supplying fuel according to the operating state to the internal combustion engine, a fuel supply amount required to maintain the fuel in the accumulator at the target pressure is determined, and the fuel is driven by a piezo actuator so that the fuel amount is supplied to the accumulator. The opening of the overflow valve is controlled.

[0013]

FIG. 2 is a hardware configuration diagram of a pressurized fuel control device according to the present invention, and an example of a four-cylinder internal combustion engine will be described. The cylinder block 251 of the internal combustion engine has four cylinders 2511, 2512, 2513, and 2514. Each cylinder is provided with a fuel injection valve 2521, 2522, 2523, and 2524 that injects fuel directly into the cylinder.

The fuel injection valves 2521, 2522, 2523
And 2524 have four fuel supply pipes 2201, 2202, 2203 and 2204 branched from the pressure accumulation chamber 220.
Is connected. In the accumulator 220, a fuel pressure detector 204 for measuring the fuel pressure in the accumulator is installed.

The cylinders 2511, 2512, 2513
And 2514, an intake pipe 260 is connected to supply combustion air. Since the intake pressure is proportional to the load of the internal combustion engine, the output of the intake pressure detector 202 installed in the manifold of the intake pipe 260 Functions as a signal representing the load of the internal combustion engine. The fuel in the fuel tank 210 is supplied to the fuel pump 208 via the booster pump 211, and is pressurized to 20M Pascal or more. The pressurized fuel is supplied to the accumulator 220 and the overflow valve 2071
Is returned to the fuel tank 210.

That is, by adjusting the opening of the overflow valve 2071, the amount of fuel supplied to the accumulator 220 can be controlled. The overflow valve 2071 is opened and closed by a piezo actuator 2072, but cannot be set to an intermediate opening, and the opening is controlled by controlling the ratio (duty ratio) of the valve opening time and the valve closing time.

The fuel pump 208 includes an overflow valve 2071
In general, the piezo actuator 2072 is integrally formed with the overflow valve unit 207 integrally formed. A first cam angle sensor 2011 and 30 for transmitting a pulse at every 720 ° cam angle, for example, is provided to a distributor 230 which sequentially gives an ignition signal to an ignition plug (not shown) attached to each of the cylinders 2521, 2522, 2523 and 2524. A second cam angle sensor 2012 that oscillates a pulse for each cam angle is attached.

Control device 2 for controlling pressure in accumulator 220
Reference numeral 60 denotes a microcomputer system, for example, and a CPU 2602 and a RAM 260
3, ROM 2604, input interface 2605, and output interface 2606 are connected.
The input interface 2605 is connected to the first and second cam angle sensors 2011 and 2012 and the analog / digital converter 2607.

This analog / digital converter 2607
Includes a fuel pressure detector 204 and an intake pressure detector 202
Are connected, converted to digital signals, and
0 is taken in. The opening degree command of the overflow valve 2071 output from the output interface 2606 is
Is supplied to the piezo actuator 2072 via the.

A control program is stored in a ROM 2604, and an input interface 26 is stored in a RAM 2603.
The detected value captured through the interface 05, the overflow valve opening command value output from the output interface 2606, and the like are stored. The actual control calculation is executed in the CPU 2602. FIG. 3 is a functional diagram of the control calculation executed in the CPU 2602.

As a function of the internal combustion engine speed Ne determined by the pulse transmitted from the first cam angle sensor 2011 and the intake pressure Pm detected by the intake pressure detector 202, the amount of fuel injected V _INJ to the internal combustion engine is determined. The calculation is performed by the injection fuel calculation unit 303. Fuel compression ratio as a function of the additive average value of the atmospheric pressure P ₀ detected with the fuel pressure P _R detected by the atmospheric pressure detector 3501 by the fuel pressure detector 204 mounted to the accumulator 220 beta
Is calculated by the compression ratio calculation unit 3052.

In addition to the fuel pressure P _R , the atmospheric pressure P _0, and the fuel compression ratio β, the accumulation chamber target pressure _PT set by the accumulation chamber target pressure setting section 3053 is used as the accumulation chamber fuel balance calculation section 305.
4 and the following processing is executed. That is, the atmospheric pressure P required to fill the accumulator with fuel at the target pressure _PT.
V _R20 the volume of fuel at _0, the decrease volume when compressing the fuel volume V _R20 at atmospheric pressure P ₀ to the target pressure P _T [Delta] V, the volume of the V _CR accumulator chamber, the compression ratio of the fuel beta, and Then, the following equation is established.

[0023] _{V CR = V R20 - ΔV (} 1) ΔV = β · V R20 · (P T -P 0) (2) However, the compression ratio β is a function of the arithmetic mean of the target pressure P _T and the atmospheric pressure P ₀ Is calculated as (1) and (2) is solved for V _R20, the following expression is obtained.

V _R20 = V _CR / {1−β · (P _T −P ₀ )} (3) Further, the fuel amount V _RI remaining in the accumulator can be obtained by the following equation. _{V RI = V CR / {1-} β · (P R -P 0)} (4) The actually accumulating by subtracting the amount of fuel returning to the fuel tank through the overflow valve from a quantity of fuel discharged from the fuel pump Assuming that the amount of fuel supplied to the chamber is V _S , the fuel balance of the accumulator is expressed by the following equation.

V _R20 = V _RI + V _S −V _INJ (5) By solving equation (5) for the supplied fuel amount V _S , the following equation is obtained. V _S = V _R20 −V _RI + V _INJ (6) Then, in the fuel pump discharge fuel amount calculation unit 3055,
The discharged fuel amount is calculated as follows.

Assuming that the nominal discharge amount of the fuel pump is V _P , the volumetric efficiency is η, and the rotational speed of the fuel pump is N _P , the fuel amount V _F actually discharged from the fuel pump is expressed by the following equation. . _{V F = V P · η (} N P) (7) above atmospheric pressure detector 3501, the compression ratio calculating unit 3052, accumulator target pressure setting section 3053, accumulator fuel balance computation section 3
054 and the fuel pump discharge fuel amount calculation unit 3055 constitute supply fuel calculation means. Since the fuel pump is usually to be driven by an internal combustion engine, the fuel pump speed N _P is equal to the engine speed Ne.

Next, the duty ratio calculation unit 306
Pump discharge V_FAnd fuel supply V _SThe ratio of
The tee ratio DR is calculated by the following equation. DR = V_S/ V_F (8) Therefore, the overflow valve is calculated based on the calculated duty ratio DR.
Control the pressure in the accumulator to the target pressure.
Can be

FIG. 4 shows a routine for controlling the pressure of the accumulator, which is executed as an interrupt process each time a pulse signal is input from the cam angle sensor 2012, for example.
In step 401, via the analog / digital converter 2607 and the input interface 2605, the pressure accumulating chamber pressure P _R , the intake pipe pressure Pm, and the pulses oscillated from the cam angle sensors 2011 and 2012 are read.

The rotational speed N _P of the rotational speed Ne and the fuel pump of the internal combustion engine based on the pulses from the cam angle sensor 2011 and 2012 is determined. In step 402, the fuel injection amount V _INJ into the cylinder is calculated as a function of the rotational speed Ne of the internal combustion engine and the intake pipe pressure Pm. Next, at steps 403 and 404, _VR20 and _VR1 are calculated based on the equations (3) and (4).

Further, in step 405, the fuel amount V _S discharged from the fuel pump is determined based on the equation (7). Then, in step 406, the duty ratio DR for the overflow valve control is calculated based on the equation (8).
Then, in steps 407 to 411, the duty ratio is protected so as not to be 10% or less and 90% or more.
From 06, a duty ratio DR is output.

FIG. 5A is a graph showing the pressure control response of the accumulator by the pressurized fuel control device according to the present invention, and shows the fuel supply amount necessary to maintain the target pressure from the fuel balance in the accumulator. Since the duty ratio for overflow valve control is determined based on this, overshoot or hunting does not occur even though the pressure in the accumulator reaches the target pressure quickly, and controllability is improved. It indicates that you want to.

In this embodiment, the load of the internal combustion engine is detected based on the intake pipe pressure. However, the load may be determined based on the throttle valve opening, the output torque of the internal combustion engine, and the like. Although the fuel injection amount and the volumetric efficiency of the fuel pump are expressed as functions, they may be stored in the ROM 2604 as a map of arguments.

Further, the so-called proportional-integral control which has been used in the past and the control method according to the present invention are used together, and the control method according to the present invention is used when the absolute value of the deviation from the target pressure is equal to or more than a predetermined value. When the value is equal to or less than the predetermined value, it is possible to secure so-called robustness by using the proportional integral control.

[0034]

As described above, according to the present invention, the duty ratio for controlling the overflow valve is determined based on the fuel balance in the accumulator, so that the target pressure can be quickly reached and the target pressure can be overshot or hunted. And the amount of fuel injected into the cylinder can be maintained at a predetermined value.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of a pressurized fuel control device according to the present invention.

FIG. 2 is a hardware configuration diagram of an embodiment of a pressurized fuel control device according to the present invention.

FIG. 3 is a functional diagram of an embodiment of the pressurized fuel control device according to the present invention.

FIG. 4 is a flowchart of a control routine.

FIG. 5 is an explanatory diagram of a pressure response of a pressure storage chamber.

FIG. 6 is a functional diagram of a conventional pressurized fuel control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 ... Rotation speed detection means 102 ... Load detection means 103 ... Injected fuel amount calculation means 104 ... Accumulation chamber pressure detection means 105 ... Supply fuel amount calculation means 106 ... Duty ratio calculation means 107 ... Fuel supply amount control means

Claims (1)

(57) [Claims] 1. A rotational speed detecting means for detecting a rotational speed of an internal combustion engine, a load detecting means for detecting a load of the internal combustion engine, a rotational speed detected by the rotational speed detecting means and a detection by the load detecting means. Injection fuel calculating means for calculating the amount of fuel to be injected into the cylinder based on the applied load; accumulator pressure detecting means for detecting pressure in the accumulator; target pressure and pressure detected by the accumulator pressure detecting means. Storage
Accumulation chamber determined by pressure chamber pressure and target pressure fuel
Fuel amount required to fill the fuel and the injected fuel amount calculating means
By adding the computed fuel injection amount in the fuel supply amount calculating means for calculating a fuel amount to be supplied to the accumulating chamber, a supply fuel amount calculated in the fuel supply amount calculation means
A duty ratio calculating means for calculating a duty ratio representing an overflow valve opening time per one rotation of the fuel pump, which is a ratio with respect to a fuel amount discharged from the fuel pump, and a duty ratio calculated by the duty ratio calculating means. An overflow valve unit incorporating an overflow valve for determining a valve time and a valve closing time.