JPH1136935A - Fuel supply system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly make a fuel injection amount agreed with a target value, and to improve the stability of combustion by detecting or estimating the pulsation of the fuel supply pressure, and correcting a fuel injection time on the basis of the same. SOLUTION: A fuel supply pump 5 is driven in synchronization with the rotation of an engine 6, and the discharge pressure thereof is pulsated in synchronization with the rotation. The pressure of the discharge fuel is regulated by a high pressure regulator 7, but the pulsation is not completely extinguished. In a controller, the fuel discharge pressure regulated by the high pressure regulator 7 (in a period just before the injection), is detected by a fuel pressure sensor, and the fuel injection time, that is, a basic fuel injection pulse width operated on the basis of the operating condition, is corrected by the fuel discharge pressure on the basis of the difference between the target fuel pressure and the real fuel pressure. That is, when the real fuel pressure is higher than the target fuel pressure, the basic fuel injection time is corrected to be shorter, and when the real fuel pressure is lower than the same, the basic fuel injection time is corrected to be longer.

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 supply device used for a direct fuel injection type spark ignition internal combustion engine or the like.

[0002]

2. Description of the Related Art The amount of fuel injected into an internal combustion engine is controlled by adjusting the pulse width of a fuel injection valve.
When the fuel injection pressure fluctuates, the injection amount fluctuates even with the same injection pulse width.

Therefore, as disclosed in Japanese Utility Model Application Laid-Open No. 6-58158, a correction value obtained by weighted averaging of the fuel supply pressure is obtained in order to prevent the fluctuation of the injection amount due to the pulsation of the fuel supply pressure. 2. Description of the Related Art There is known a fuel supply apparatus that controls a discharge amount of a fuel supply pump based on the above-described control to secure stable fuel injection characteristics.

[0004]

However, even if the pump discharge amount is controlled by obtaining the average value of the fuel supply pressure as described above, the pulsation of the discharge pressure cannot be completely suppressed due to the structure of the pump. Therefore, even if the injection pulse width of the fuel injection valve is constant, the fluctuation of the fuel injection amount due to the pulsation of the discharge pressure cannot be avoided.

[0005] In particular, in the case of a spark ignition type internal combustion engine in which fuel is directly injected into a cylinder, unlike premixed combustion in which fuel is injected into an intake port, the injection pressure of fuel is relatively high. In addition, the fluctuation range of the injection amount due to the pulsation of the fuel supply pressure increases, and the influence on the combustion characteristics is correspondingly large.

The present invention has been proposed to solve such a problem, and detects or predicts the pulsation of the fuel supply pressure, and corrects the fuel injection time based on the pulsation, so that the fuel injection amount can be accurately determined. The purpose of the present invention is to improve the stability of combustion by making the target value equal to the target value.

[0007]

According to a first aspect of the present invention, there is provided a fuel supply pump for pumping fuel to a fuel injection valve, a means for detecting an operation state, a means for calculating a fuel injection amount according to the operation state, A fuel supply device for an internal combustion engine, comprising: means for controlling an injection time of a fuel injection valve so as to attain a calculated fuel injection amount; means for detecting a fuel supply pressure; Means for setting the supply pressure;
Means are provided for comparing the target fuel supply pressure with the actual fuel supply pressure, and means for correcting the fuel injection time according to the comparison result.

According to a second aspect of the present invention, there is provided a fuel supply pump for pumping fuel to a fuel injection valve, a means for detecting an operation state, a means for calculating a fuel injection amount according to the operation state, and a calculated fuel injection amount. A fuel supply device for an internal combustion engine, comprising: means for controlling an injection time of a fuel injection valve such that a target fuel supply pressure is set according to an operation state; and Means for setting a pulsation pattern of the supply pressure, means for calculating a pulsation width between the target fuel pressure at the fuel injection timing and the fuel pressure obtained from the pulsation pattern, and correcting the fuel injection time according to the pulsation width. Means.

According to a third aspect of the present invention, there is provided a fuel supply pump for pumping fuel to a fuel injection valve, a means for detecting an operation state, a means for calculating a fuel injection amount according to the operation state, and a calculated fuel injection amount. Means for detecting a fuel supply pressure, and means for setting a target fuel supply pressure in accordance with an operating state, in a fuel supply device for an internal combustion engine, comprising: means for controlling an injection time of a fuel injection valve so that Means for setting a pulsation pattern of the fuel supply pressure in accordance with the operation state; means for calculating a deviation amount based on a difference between a target fuel pressure and an actual fuel pressure; and the pulsation based on the deviation amount. Means for correcting and learning the set value of the pattern, means for calculating the pulsation width between the target fuel pressure at the fuel injection timing and the fuel pressure obtained from the learned pulsation pattern, and the fuel injection time according to the pulsation width. And means for correcting.

[0010]

In the first invention, the target fuel pressure according to the operating state is compared with the actual fuel pressure, and if the actual fuel pressure is lower than the target fuel pressure, the fuel injection time is reduced. The injection time is corrected to be longer than the previously calculated target injection time, and if the actual fuel pressure is high, the injection time is corrected to be shorter than the target injection time, thereby causing a pulsation in the fuel pressure from the fuel supply pump. Even if it does, the fuel injection amount can be accurately matched with the target value, the combustion stability is ensured, and the exhaust characteristics and fuel efficiency are improved.

In the second aspect of the present invention, at the timing of fuel injection, a change width between a target fuel pressure according to an operating state and a fuel pressure obtained from a preset fuel pressure pulsation pattern is calculated, For example, when the fuel pressure is lower than the target fuel pressure, the fuel injection time is corrected to be longer by an amount corresponding to the change width, and when the fuel pressure is higher, the fuel injection time is corrected to be shorter. In this way, even if there is a pulsation in the fuel pressure, the fuel injection amount can be accurately matched with the target value.

According to the third aspect of the invention, the set value of the learned pulsation pattern is corrected and updated based on the actual fuel pressure. Therefore, the actual pulsation pattern is always accurately reflected based on the latest information. Even if the pressure pulsation fluctuates due to deterioration of the fuel supply pump or the like, the fuel injection time is accurately corrected.

[0013]

Preferred embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a fuel tank, 2 is a feed pump for pressurizing the fuel at a low pressure, and is driven to rotate by a motor 3. Reference numeral 4 denotes a low pressure regulator for regulating the discharge pressure from the feed pump 2 to a substantially constant low pressure value.

Reference numeral 5 denotes a plunger-type fuel supply pump which is driven to rotate by the engine 6, and further increases the discharge pressure from the feed pump 2. Reference numeral 7 denotes a high-pressure regulator for regulating the discharge pressure from the fuel supply pump 5 to a substantially constant high-pressure value.

The fuel discharged from the fuel supply pump 5 is supplied to the engine 6 from the fuel injection valves 8 provided in the respective cylinders. As shown in FIG. Is controlled according to the injection signal from the controller 10.

In this embodiment, the fuel injection valve 8 is provided so as to inject fuel directly into the combustion chamber.
In the operation region where the engine load is small, fuel is injected in the latter half of the compression stroke, a combustible mixture layer is formed only in a limited space near the spark plug, and the air-fuel ratio exceeds A / F = 40. Even in lean air-fuel mixtures, stratified combustion is performed stably, and in the operating range where the engine load is large, fuel is injected during the intake stroke to promote mixing with air, and a homogeneous air-fuel mixture layer is formed throughout the combustion chamber. It forms and performs homogeneous combustion near the stoichiometric air-fuel ratio to secure high output.

The controller 10 provides signals representative of the operating state of the engine 6 as a rotational speed signal from an engine crank angle sensor 11, an accelerator opening signal from an accelerator opening sensor 12, and a water temperature from an engine cooling water temperature sensor 13. A signal, a throttle opening signal from a throttle opening sensor 15, an intake air amount signal from an air flow meter 16, and the like, and a fuel pressure from a fuel pressure sensor 14 for detecting a fuel discharge pressure from the fuel supply pump 5. A signal is also input, and the fuel injection amount and the injection timing of the fuel injection valve 8 are controlled based on these signals. At the same time, even if there is a fuel discharge pressure pulsation, the fuel injection amount is made to exactly match the target value. The fuel injection time is corrected and controlled according to the discharge pressure.

Here, the control executed by the controller 10 will be described with reference to the flowchart of FIG.

In step 1, the operating state such as the engine speed and load is read, and in step 2, the target fuel pressure Xij in the operating state is calculated from a map as shown in FIG. Next, at step 3, the fuel pressure sensor 1
4 detects the fuel discharge pressure α (at the time immediately before the injection) regulated by the high-pressure regulator 7. The relationship between the fuel pressure α and the sensor output is as shown in FIG.

In step 4, based on the difference between the target fuel pressure and the actual fuel pressure, the fuel injection time, that is, the basic fuel injection pulse width T calculated based on the operating state.
Modify i as follows:

Ti ′ = Ti × (Xij / α) ^1/2 Therefore, if the actual fuel pressure is lower than the target fuel pressure, the corrected injection time Ti ′ becomes the basic fuel injection time T
If the actual fuel pressure is longer than i, the corrected injection time Ti ′ is shorter than Ti, and the corrected injection time Ti ′ controls the opening time of the fuel injection valve 8.

The operation is described as follows.

The fuel supply pump 5 is driven in synchronization with the rotation of the engine 6, and its discharge pressure pulsates in synchronization with the rotation.
The pressure of the discharged fuel is regulated by the high-pressure regulator 7, but the pulsation does not completely disappear. If the fuel pressure supplied to the fuel injection valve 8 differs from the target fuel pressure, the same fuel injection time , The actual fuel injection amount fluctuates.

For example, if the actual fuel pressure is higher than the target fuel pressure, the fuel injection amount increases even during the same injection time. Conversely, if the actual fuel pressure is low, the fuel injection amount decreases.

However, in the present invention, the fuel pressure is detected,
After comparing this with the target fuel pressure, the basic fuel injection time of the fuel injection valve 8 is corrected. That is, when the actual fuel pressure is higher than the target fuel pressure, the basic fuel injection time is corrected to be shorter, and when the actual fuel pressure is lower, the basic fuel injection time is corrected to be longer. Even if the fuel pressure fluctuates in a pulsating manner, the target fuel injection amount can always be obtained accurately.

Next, another embodiment shown in FIG. 6 will be described.

In this embodiment, instead of detecting the actual fuel pressure α, a pulsation pattern of the fuel supply pump according to the operation state is set in a table in advance, and this is compared with a target pressure. The fuel injection time is corrected.

For this reason, first, in step 1, the operating state is detected from various signals representative of the operating state, and in step 2, the target fuel pressure Xij at that time is read in the same manner as described above.

In step 3, the maximum fluctuation width a of the fuel pressure pulsation in the operating state is read from the table shown in FIG. 7 based on the relationship with the target fuel pressure Xij. The pulsation width of the fuel pressure tends to increase as the target fuel pressure increases, and this characteristic is detected in advance and set in a table.

Next, in step 4, the fuel injection timing IT is set based on the operating state, and based on this IT, the correction amount b of the fuel pressure is calculated in step 5 from the table shown in FIG. This is to predict the fuel pressure at the fuel injection timing.

Then, in step 6, a predicted fuel pressure β at the fuel injection timing is calculated from these values as follows.

Β = Xij + a × b Once the predicted fuel pressure β is obtained in this manner, the fuel injection pulse width Ti ′ of the fuel injection valve 8 is calculated based on a comparison between this and the target fuel pressure Xij, and Ti ′ = Ti × (Xij / β) ^1/2 is calculated in step 9.

In this case, instead of measuring the actual fuel pressure, a predicted fuel pressure at the actual fuel injection timing is obtained based on the characteristics of the fuel pressure pulsation set in advance in a table, and the predicted fuel pressure at the actual fuel injection timing is calculated. Since the fuel injection time is corrected based on the comparison, even if the fuel pressure fluctuates, the fuel injection amount can be accurately matched with the target value, and the stability of combustion, fuel consumption, and the composition of exhaust gas are improved. be able to.

Next, another embodiment shown in FIGS. 9 and 10 will be described.

In this embodiment, the fuel pulsation pattern is learned and updated based on the actual fuel pressure, so that the fuel injection time can be corrected more accurately.

FIG. 9 shows a routine for learning.
After detecting the operating state in step 1, the target fuel pressure Xij is read in step 2, and
Then, the actual fuel pressure α is read.

In step 4, the crank angle of 36
In the range of 0 °, the maximum pulsation width A of the fuel pressure is calculated as follows based on the fuel pressure maximum value αmax and the minimum value αmin.

A = (αmax−αmin) / 2 Next, in step 5, the crank angle B which is the first peak of the fuel pressure pulsation in the range of 360 ° of the actually detected crank angle and the crank angle B set on the table are set. The phase difference (difference between the actual value and the table setting value) D of the angle with the crank angle C having the first peak value is calculated as D = BC.

In step 6, the table setting values a and d of the pulsation width and the phase difference are read out. In step 7, these table setting values are set based on the pulsation width A and the phase difference D obtained as described above. The values a and d are learned as follows.

[0041]

(Equation 1)

After learning a 'and d' in this way,
These learning values are updated in step 8 and used for the next control.

That is, FIG. 10 shows a routine for correcting the fuel injection time based on the result learned in this way.

Since this is basically the same control contents as in FIG. 6, only the differences will be described. In step 3, what is read based on the target fuel pressure is the learning value a of the pulsation width, and step 4 At the fuel injection timing IT '
It is corrected based on the learning value as IT ′ = IT + d ′, whereby, in step 5, from the table as shown in FIG.
The correction amount b of the fuel pressure is calculated. In step 6,
From these values, the predicted fuel pressure γ at the fuel injection timing is calculated as γ = Xij + a ′ × b, and based on the comparison between the predicted fuel pressure γ and the target fuel pressure Xij, The fuel injection pulse width Ti ′ is corrected as Ti ′ = Ti × (Xij / γ) ^1/2 .

In this way, the pattern of fuel pulsation is learned and updated based on the actual fuel pressure. Even if the discharge pressure pulsation of the fuel supply pump fluctuates with time, the fuel injection time can be accurately determined. Correction can be made, and the fuel injection amount can always be accurately matched with the target value, thereby improving fuel efficiency and exhaust composition.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of an engine.

FIG. 3 is a flowchart showing control contents.

FIG. 4 is a map of a target fuel pressure.

FIG. 5 is an explanatory diagram showing output characteristics of a fuel pressure sensor.

FIG. 6 is a flowchart showing control contents according to another embodiment.

FIG. 7 is an explanatory diagram showing a variation width of fuel pulsation.

FIG. 8 is an explanatory diagram showing correction characteristics depending on fuel injection timing.

FIG. 9 is a flowchart showing control contents of still another embodiment.

FIG. 10 is also a flowchart.

[Explanation of symbols]

 2 Feed pump 4 Low pressure regulator 5 Fuel supply pump 6 Engine 7 High pressure regulator 8 Fuel injection valve 10 Controller 11 Crank angle sensor 12 Accelerator opening sensor 14 Fuel pressure sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 37/08 F02M 37/08 Z 55/02 310 55/02 310Z

Claims (3)

[Claims] 1. A fuel supply pump for pumping fuel to a fuel injection valve, means for detecting an operation state, means for calculating a fuel injection amount in accordance with the operation state, and a method for calculating the calculated fuel injection amount. A fuel supply device for an internal combustion engine, comprising: means for controlling an injection time of a fuel injection valve; means for detecting a fuel supply pressure; means for setting a target fuel supply pressure in accordance with an operating state; A fuel supply device for an internal combustion engine, comprising: means for comparing a supply pressure with an actual fuel supply pressure; and means for correcting the fuel injection time according to a result of the comparison. 2. A fuel supply pump for pumping fuel to a fuel injection valve, a means for detecting an operation state, a means for calculating a fuel injection amount according to the operation state, and a fuel injection amount calculated based on the calculated fuel injection amount. A fuel supply system for an internal combustion engine, comprising: means for controlling an injection time of a fuel injection valve; means for setting a target fuel supply pressure according to an operation state; and pulsation of the fuel supply pressure according to an operation state. Means for setting a pattern, means for calculating the pulsation width between the target fuel pressure at the fuel injection timing and the fuel pressure determined from the pulsation pattern, and means for correcting the fuel injection time according to the pulsation width. A fuel supply device for an internal combustion engine, comprising: 3. A fuel supply pump for pumping fuel to a fuel injection valve, a means for detecting an operating state, a means for calculating a fuel injection amount according to the operating state, and a means for calculating the calculated fuel injection amount. A fuel supply device for an internal combustion engine, comprising: means for controlling an injection time of a fuel injection valve; means for detecting a fuel supply pressure; means for setting a target fuel supply pressure in accordance with an operation state; Means for setting a pulsation pattern of the fuel supply pressure according to the following formula: means for calculating a deviation amount based on a difference between a target fuel pressure and an actual fuel pressure; and a set value of the pulsation pattern based on the deviation amount. Means for correcting and learning, means for calculating the pulsation width between the target fuel pressure at the fuel injection timing and the fuel pressure obtained from the learning pulsation pattern, and means for correcting the fuel injection time according to the pulsation width. The fuel supply apparatus for an internal combustion engine, characterized in that it comprises.