JPH09256886A - Fuel injection controller for direct injection type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely control a fuel injection quantity by computing a differential pressure between a cylinder internal pressure computed according to an operating condition and a fuel pressure supplied to an injector, computing a fuel injection rate on the basis of the differential pressure, and correcting a valve opening time of the injector on the basis of the fuel injection rate. SOLUTION: In a direct injection type engine provided with a throttle valve 101 throttling an intake passage in compliance with an operating condition and an injector 102 injecting fuel into a cylinder, a valve opening time of the injector 102 is controlled by means of a fuel injection quantity controlling means 103 according to the operating condition. The direct injection type engine is also provided with a cylinder internal pressure computing means 104, which computes a pressure inside the cylinder according to the operating condition, and a differential pressure between the computed cylinder internal pressure and a fuel pressure fed to the injector 102 is computed by means of the differential pressure computing means 105. On the basis of the computed differential pressure, a fuel injection rate is computed by means of a fuel injection rate computing means 106, and then, a valve opening time of the injector 102 is corrected by means of a fuel injection quantity correcting means 107 on the basis of the fuel injection rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a fuel injection control device for a direct injection type engine.

[0002]

2. Description of the Related Art In a direct injection engine having an injector for directly injecting fuel into a cylinder, the injector is composed of an electromagnetic fuel injection valve, and the valve opening time (injection pulse width) of the injector is 0 depending on the operating state. Some include a fuel injection amount control device that performs duty control between 100% and 100%.

In the conventional direct injection type engine, the fuel pressure introduced to the injector is adjusted via the pressure regulator so that the pressure difference from the atmospheric pressure becomes constant.

[0004]

By the way, in a spark ignition engine equipped with an injector for injecting fuel into an intake pipe, the fuel pressure introduced to the injector becomes a back pressure of the injector via a pressure regulator and a negative pressure of the intake pipe. It is adjusted so that the differential pressure of is constant. As a result, the injection rate of the injector (the amount of fuel injected per unit time) is kept constant, and the valve opening time T of the injector is maintained.
The required fuel amount can be obtained by controlling i.

However, in a direct injection type engine,
Since the in-cylinder pressure, which is the back pressure of the injector, changes according to the crank angle at which fuel injection is performed and the intake pipe negative pressure, even if the injector valve opening time Ti is the same, the injector injection rate increases and decreases There is a problem that is not obtained.

In response to this, Japanese Patent Laid-Open No. 4-116243
In a fuel injection control device for a direct injection engine disclosed in Japanese Patent Laid-Open Publication, a sensor for detecting the in-cylinder pressure is provided, and the valve opening time Ti of the injector is corrected based on the detected in-cylinder pressure. .

However, the provision of the in-cylinder pressure sensor may complicate the structure and raise the cost of the product.

The present invention has been made in view of the above problems, and an object thereof is to accurately control the fuel injection amount in a fuel injection control device for a direct injection type engine without using a cylinder pressure sensor. .

[0009]

A fuel injection control device for a direct injection type engine according to a first aspect of the present invention, as shown in FIG.
Throttle valve 10 that throttles the intake passage according to operating conditions
1, an injector 102 for injecting fuel into the cylinder, and a fuel injection amount control means 103 for controlling the valve opening time Ti of the injector 101 according to the detected operating state, and a fuel injection control device for a direct injection engine. In the in-cylinder pressure calculating means 104 for calculating the in-cylinder pressure Pc according to the detected operating state, and the differential pressure for calculating the differential pressure Pf between the calculated in-cylinder pressure Pc and the fuel pressure supplied to the injector 101. Calculation means 105, fuel injection rate calculation means 106 for calculating the fuel injection rate K based on the calculated differential pressure Pf, and fuel for correcting the valve opening time Ti of the injector 101 based on the calculated fuel injection rate K. And an injection amount correction means 107.

According to a second aspect of the present invention, there is provided a fuel injection control device for a direct injection engine, wherein in the first aspect of the invention, a crank angle detecting means for detecting a crank angle, a detected crank angle and a downstream side of a throttle valve are provided. An in-cylinder pressure calculating means for calculating the in-cylinder pressure Pc in accordance with the intake pipe negative pressure generated in.

A fuel injection control device for a direct injection type engine according to a third aspect is the fuel injection control device according to the second aspect, wherein the intake air amount detecting means for detecting the intake air amount and the minimum flow passage area of the intake pipe are detected. And a suction negative pressure calculation means for calculating the intake pipe negative pressure generated on the downstream side of the throttle valve according to the detected intake air amount and the minimum flow passage area.

A fuel injection control device for a direct injection type engine according to a fourth aspect is the fuel injection control device according to any one of the first to third aspects, for determining the fuel injection timing from the engine speed. And in-cylinder pressure calculation means for calculating the in-cylinder pressure Pc according to the determined fuel injection timing and the intake pipe negative pressure generated on the downstream side of the throttle valve.

[0013]

In the fuel injection control device for a direct injection type engine according to claim 1, the fuel of the injector 101 changes as the pressure Pc in the cylinder, which is the back pressure of the injector 101, changes according to the operating state of the engine. The injection rate changes. Therefore, the amount of fuel injected from the injector 101 into the cylinder in one cycle increases or decreases according to the pressure Pc in the cylinder even if the valve opening time of the injector 101 is the same.

In the present invention, the pressure Pc in the cylinder is calculated according to the detected operating state, and the differential pressure Pf between the calculated cylinder pressure Pc and the fuel pressure supplied to the injector 101 is calculated and calculated. The fuel injection rate K is calculated based on the differential pressure Pf,
Since the valve opening time Ti of the injector 101 is corrected based on the calculated fuel injection rate K, the valve opening time of the injector 101 can be corrected appropriately. Therefore, the cost of the product can be reduced without providing the in-cylinder pressure sensor unlike the conventional device.

In the fuel injection control device for the direct injection engine according to the second aspect, the cylinder pressure Pc is calculated according to the detected crank angle and the intake pipe negative pressure generated on the downstream side of the throttle valve. Therefore, the cost of the product can be reduced without providing the in-cylinder pressure sensor unlike the conventional device.

In the fuel injection control device for a direct injection type engine according to claim 3, the intake pipe negative pressure generated downstream of the throttle valve is calculated according to the detected intake air amount and the minimum flow passage area. The cost of the product can be reduced without providing a sensor for detecting the negative pressure of the pipe.

In the fuel injection control device for the direct injection engine according to the fourth aspect, in-cylinder pressure Pc is calculated in accordance with the determined fuel injection timing and the intake pipe negative pressure generated on the downstream side of the throttle valve. The valve opening time of the injector can be appropriately corrected. Therefore, the cost of the product can be reduced without providing the in-cylinder pressure sensor unlike the conventional device.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, an engine 1 mounted on a vehicle has an intake port 3 as an intake valve 2 is opened.
The intake air is drawn into the cylinder 4 from the injector 1 at the same time.
Fuel is directly injected into the cylinder 4 from No. 4. The air-fuel mixture formed by the intake air and the injected fuel is compressed by the piston 5, ignited and burned by the ignition plug 6, and the exhaust gas is exhausted through the exhaust port 8 as the exhaust valve 7 is opened. Each of these strokes is continuously repeated.

A three-way catalyst 17, 18 is provided in the exhaust passage 9.
Are installed to oxidize HC and CO in the exhaust gas and reduce NOx.

Intake air is taken into each cylinder 4 from the air cleaner 21, through the intake duct 22, the throttle chamber 23, the intake pipe 26 and the intake ports 3.

The throttle chamber 23 is provided with a throttle valve 30 which is opened and closed by an accelerator pedal.

A bypass passage 35 is provided which connects the upstream side and the downstream side of the throttle valve 30 of the intake passage 20. An electromagnetic auxiliary air valve (ISC) 36 is provided in the middle of the bypass passage 35.

The auxiliary air valve 36 has an opening time of 0 to 10
The duty is controlled between 0%, and the idle rotation speed of the engine 1 is feedback-controlled to a target value by adjusting the intake air amount according to the engine operating state when the throttle valve 30 is closed. There is.

As shown in FIG. 2, the fuel tank 59
Is pumped up through a low-pressure fuel pump 58 and sent to a high-pressure fuel pump 57. The high-pressure fuel pump 57 sends the pressurized fuel to the pressure accumulating chamber 56, and pressurizes the fuel from the pressure accumulating chamber 56 to the injector 14 of each cylinder. The fuel pressure in the pressure accumulator 56 is adjusted via a pressure regulator (not shown) so that the pressure difference from the atmospheric pressure becomes a predetermined value. Excess fuel sent from the high-pressure fuel pump 57 to the accumulator chamber 56 is returned to the fuel tank 59 through the fuel return passage 58.

The injector 14 has a valve opening time of 0 to
The duty is controlled between 100%, the valve is opened by a pulse signal sent from the control unit 13, and the fuel is directly injected into the cylinder 4. Injector 14
Is controlled so that the intake valve 2 opens and intake air flows from the intake port 3 into the cylinder 4, so that intake air and fuel are mixed.

The control unit 13 controls the intake air amount Q detected by the air flow meter 40, the throttle opening TVO detected by the throttle opening sensor 42, and the engine rotation speed Ne detected by the engine rotation speed sensor 41.
And the cooling water temperature Tw detected by the cooling water temperature sensor 43 and the like, and the injector 14 is input according to these operating states.
The injection pulse width Ti is controlled.

By the way, in such a fuel injection device having the direct injection type injector 14, as the back pressure of the injector 14, the pressure Pc in the cylinder changes in accordance with the operating state of the engine 1. Injector 1
The fuel injection rate of No. 4 changes. Therefore, the injector 1
There is a problem that the amount of fuel injected into the cylinder 4 in 4 to 1 cycles increases or decreases according to the pressure Pc in the cylinder even if the valve opening time of the injector 14 is the same.

The present invention deals with this by inputting the crank angle θ detected by the crank angle sensor 10 in the control unit 13, and based on the crank angle θ and the average value P of the negative pressure generated in the intake pipe 26. The fuel injection rate K of the injector 14 is calculated, and the valve opening time of the injector 14 is corrected.

The flow chart of FIG. 3 shows the injector 1
4 shows a program for calculating the injection pulse width Ti of No. 4, which is executed at regular intervals.

To explain this, first, Step
At 1, the crank angle θ and the intake pipe negative pressure average value P are input.

Here, the intake pipe negative pressure average value P is calculated by a routine shown in FIG. 6 as described later.

Then, in Step 2, the stroke amount y at the crank angle θ is calculated according to the following equation. However,
S is the total stroke amount, and L is the length of the connecting rod 19.

Y = (S / 2 + L) −cos θ− (L ² −sin ² θ) ^1/2 (1) Subsequently, in Step 3, the in-cylinder volume V at the stroke amount y is calculated according to the following equation. However, Vcyl is the cylinder stroke volume, and Vcomb is the length of the combustion chamber volume.

V = Vcyl × (y / S) + Vcomb (2) Next, in Step 4, the cylinder pressure Pc is calculated from the intake pipe negative pressure P and the cylinder volume V according to the following equation. However, Vivc
Is the in-cylinder volume at the closing timing of the intake valve 2, and k is the specific heat ratio.

Pc = (Vivc / V) × P (3) FIG. 4 shows the relationship between the cylinder pressure Pc and the crank angle θ.
Cylinder pressure Pc is determined by the crank angle θ at the piston bottom dead center (BD
It has a characteristic that it gradually increases from C) toward the piston top dead center (TDC) and rises sharply near the top dead center.

Then, in Step 5, the injector 1
The pressure difference Pf between the fuel pressure introduced to the cylinder No. 4 and the cylinder pressure Pc is calculated.

Then, in Step 6, the injection rate K is calculated based on the differential pressure Pf according to the following equation. However, K0 is the differential pressure P
It is the injection rate at 0.

K = K0 × (Pf / P0) ^1/2 (4) FIG. 5 shows the relationship between the injection rate K and the differential pressure P0. The injection rate K has a characteristic that it gradually increases as the differential pressure Pf increases.

Then, in Step 7, the final fuel pulse width Ti is calculated by the following equation based on the required fuel amount Tp, the injection rate K and the invalid injection time Ts according to the following equation.

Ti = (Tp / K) + Ts (5) Here, the required fuel amount Tp is calculated according to the following equation in another routine. Here, Kp is a constant, and COEF is the sum of various correction coefficients using the cooling water temperature Tw and the like as parameters.

Tp = Kp × Q / Ne × COEF (6) A pulse signal corresponding to the fuel injection amount Ti thus calculated is output to each injector 14 to control the fuel injection.

As described above, the fuel injection rate K of the injector 14 is calculated based on the crank angle θ detected by the crank angle sensor 10 and the average value P of the negative pressure generated in the intake pipe 26, and the valve opening time of the injector 14 is calculated. Can be accurately corrected. Therefore, unlike the conventional device, it is not necessary to provide the in-cylinder pressure sensor, and the cost of the product can be reduced.

The flowchart of FIG. 6 shows a routine for calculating the intake pipe negative pressure average value P, which is executed by the control unit 13 at regular intervals.

To explain this, first, Step
11, crank angle θ, intake air amount Q, cooling water temperature T
Input w, throttle opening α, opening β of the auxiliary air valve 36, and engine speed Ne.

Then, in step 12, the fresh air ratio rotational speed portion ηn is obtained by searching based on the table shown in FIG. 7 based on the engine rotational speed Ne.

Subsequently, in Step 13, the opening area of the throttle valve 30 is obtained by searching based on the table shown in FIG. 8 with the throttle opening α, and the auxiliary air valve 36
Based on the table shown in FIG. 9, the opening area of the auxiliary air valve 36 is searched to find the opening area of the throttle valve 30 and the opening area of the auxiliary air valve 36, and the total air passage area AA is calculated. Ask.

Subsequently, at Step 14, the opening rotational speed air flow rate index AADNV is calculated by the following equation based on the engine rotational speed Ne and the air passage total area AA. However, Ve is the total displacement of the engine.

AADNV = AA / (Ne × Ve) (7) Subsequently, in Step 15, the opening rotational speed air flow rate QHO is searched by the opening rotational speed air flow rate index AADNV based on the table shown in FIG. Ask.

Then, in Step 16, the fresh air ratio flow rate ηq is obtained by searching based on the table shown in FIG. 11 by the opening rotational speed air flow rate QH0.

Subsequently, in Step 17, the fresh air ratio η is calculated by the following equation based on the fresh air ratio rotational speed component ηn and the fresh air ratio flow rate ηq.

Η = ηn × (1−ηq) + ηq (8) Then, the suction negative pressure P is calculated by the following equation from the intake air amount Q, the cooling water temperature Tw, and the fresh air ratio η. Where Vcyl is the cylinder stroke volume and ρ is the air density.

P = (Q × Tw) / (Vcyl × ρ × η) (9) As described above, the intake pipe negative pressure average value P is calculated based on the detected engine operating state, and the injector 14 The valve opening time of can be properly corrected. Therefore,
The cost of the product can be reduced without providing a sensor for detecting the intake pipe negative pressure.

Next, as another embodiment, in the control unit, the fuel injection rate K of the injector is determined based on the determined fuel injection start crank angle (fuel injection timing) θinj and the average value P of the negative pressure generated in the intake pipe. And calculate
The valve opening time of the injector may be corrected.

The flowchart of FIG. 12 shows a program for calculating the injection pulse width Ti of the injector, which is executed at regular intervals. The parts corresponding to those in FIG. 3 are designated by the same reference numerals.

To explain this, first, Step
At 1 ′, the fuel injection start crank angle θinj and the intake pipe negative pressure average value P determined by another routine are input.

Subsequently, in Step 2 ', the stroke amount y at the fuel injection start crank angle θinj is calculated according to the following equation.
Is calculated. However, S is the total stroke amount, and L is the length of the connecting rod.

Y = (S / 2 + L) −cos θinj− (L ² −sin ² θinj) ^1/2 (1) Subsequently, in Step 3, the in-cylinder volume V at the stroke amount y is calculated according to the following equation. However, Vcyl is the cylinder stroke volume, and Vcomb is the length of the combustion chamber volume.

V = Vcyl × (y / S) + Vcomb (2) Subsequently, in Step 4, the cylinder pressure Pc is calculated from the intake pipe negative pressure P and the cylinder volume V according to the following equation. However, Vivc
Is the in-cylinder volume at the closing timing of the intake valve, and k is the specific heat ratio.

Pc = (Vivc / V) × P (3) Then, in Step 5, the differential pressure Pf between the fuel pressure guided to the injector and the in-cylinder pressure Pc is calculated.

Then, in Step 6, the injection rate K is calculated based on the differential pressure Pf according to the following equation. However, K0 is the differential pressure P
It is the injection rate at 0.

K = K0 × (Pf / P0) ^1/2 (4) Then, at Step 7, the final fuel pulse width Ti is calculated according to the following equation as the required fuel amount Tp, the injection rate K and the invalid injection time Ts. The following formula is used to calculate.

Ti = (Tp / K) + Ts (5) A pulse signal corresponding to the calculated fuel injection amount Ti is output to each injector to control the fuel injection.

The fuel injection rate K of the injector is calculated based on the fuel injection start crank angle θinj thus determined and the average value P of the negative pressure generated in the intake pipe, and the valve opening time of the injector is appropriately corrected. can do. Therefore, without providing an in-cylinder pressure sensor unlike the conventional device,
Product cost can be reduced.

[0065]

As described above, according to the fuel injection control device for the direct injection type engine according to the first aspect, the in-cylinder pressure Pc is calculated according to the detected operating state, and the calculated in-cylinder pressure is calculated. The differential pressure Pf between Pc and the fuel pressure supplied to the injector is calculated, the fuel injection rate K is calculated based on the calculated differential pressure Pf, and the valve opening time of the injector is calculated based on the calculated fuel injection rate K. Since Ti is corrected, the valve opening time of the injector can be corrected appropriately. Therefore, it is not necessary to provide an in-cylinder pressure sensor as in the conventional device, and the cost of the product can be reduced.

According to the fuel injection control device for the direct injection type engine of the second aspect, the cylinder pressure Pc is calculated according to the detected crank angle and the intake pipe negative pressure generated on the downstream side of the throttle valve. The cost of the product can be reduced without providing the in-cylinder pressure sensor unlike the conventional device.

According to the fuel injection control device for the direct injection type engine of the third aspect, the intake pipe negative pressure generated downstream of the throttle valve is calculated according to the detected intake air amount and the minimum flow passage area. , The cost of the product can be reduced without providing a sensor for detecting the negative pressure of the intake pipe.

According to the fuel injection control device for the direct injection type engine of the fourth aspect, the cylinder pressure Pc is calculated according to the determined fuel injection timing and the intake pipe negative pressure generated on the downstream side of the throttle valve. Therefore, unlike the conventional device, the cost of the product can be reduced without providing the in-cylinder pressure sensor.

[Brief description of drawings]

FIG. 1 is a system diagram of an engine showing an embodiment of the present invention.

FIG. 2 is a system diagram of a fuel supply system.

FIG. 3 is a flowchart for similarly calculating a fuel injection pulse width Ti.

FIG. 4 is a characteristic diagram showing the relationship of the cylinder pressure Pc with respect to the crank angle θ.

FIG. 5 is a characteristic diagram showing the relationship between the injection rate K and the differential pressure Pf.

FIG. 6 is a flowchart for calculating the same suction negative pressure average value P.

FIG. 7 is a characteristic diagram similarly showing an opening degree of a fresh air ratio rotational speed portion ηn with respect to an engine rotational speed Ne.

FIG. 8 is a characteristic diagram showing the opening of the throttle opening area with respect to the throttle opening α.

FIG. 9 is a characteristic diagram showing the relationship between the auxiliary air valve opening area β and the auxiliary air valve opening area.

FIG. 10 is a characteristic diagram showing a relationship between the opening rotational speed air flow rate QAD and the opening rotational speed air flow index AADN.

FIG. 11 is a characteristic diagram showing the relationship between the opening rotation speed air flow rate QH0 and the fresh air ratio flow rate ηq.

FIG. 12 is a flowchart for calculating a fuel injection pulse width Ti according to another embodiment.

FIG. 13 is a claim correspondence diagram showing the invention according to claim 1;

[Explanation of symbols]

 1 engine 2 intake valve 4 cylinder 5 piston 10 crank angle sensor 13 control unit 14 injector 20 intake passage 26 intake pipe 30 throttle valve 31 control valve 35 bypass passage 36 auxiliary air valve 40 air flow meter 42 throttle opening sensor 101 throttle valve 102 injector 103 fuel injection amount control means 104 in-cylinder pressure calculation means 105 differential pressure calculation means 106 fuel injection rate calculation means 107 fuel injection amount correction means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F02D 45/00 366 F02D 45/00 366Z 368 368S

Claims (4)

[Claims] 1. A throttle valve that throttles an intake passage according to an operating condition, an injector that injects fuel into a cylinder, and a valve opening time T of the injector according to a detected operating condition.
In a fuel injection control device for a direct injection engine, which includes a fuel injection amount control means for controlling i, an in-cylinder pressure calculation means for calculating an in-cylinder pressure Pc according to a detected operating state, and a calculated in-cylinder pressure A differential pressure calculating means for calculating a differential pressure Pf between Pc and the fuel pressure supplied to the injector; a fuel injection rate calculating means for calculating a fuel injection rate K based on the calculated differential pressure Pf; A fuel injection control device for a direct injection engine, comprising: a fuel injection amount correction means for correcting the valve opening time Ti of the injector based on the injection rate K. 2. A crank angle detecting means for detecting a crank angle, and an in-cylinder pressure calculating means for calculating a cylinder pressure Pc according to the detected crank angle and an intake pipe negative pressure generated on a downstream side of a throttle valve. The fuel injection control device for the direct injection engine according to claim 1, further comprising: 3. An intake air amount detection means for detecting an intake air amount, a minimum flow passage area detection means for detecting a minimum flow passage area of an intake pipe, and a detected intake air amount and a minimum flow passage area according to the detected intake air amount. The fuel injection control device for a direct injection engine according to claim 2, further comprising: intake negative pressure calculating means for calculating an intake pipe negative pressure generated on the downstream side of the throttle valve. 4. A fuel injection timing determining means for determining a fuel injection timing from an engine speed, and a cylinder pressure Pc calculated in accordance with the determined fuel injection timing and an intake pipe negative pressure generated downstream of a throttle valve. A fuel injection control device for a direct injection engine according to any one of claims 1 to 3, further comprising: in-cylinder pressure calculating means.