KR102581410B1 - Fuel injection control device - Google Patents

Abstract

The present invention relates to a fuel injection control device, which includes an engine including an injector that injects fuel into a combustion chamber, a control unit that controls the fuel injection amount of the injector, and an oxygen sensor and a temperature sensor that measure the air-fuel ratio, and the fuel injection mode is HSP. After changing from the mode to the HOM mode, the fuel injection amount is controlled using the correction value that changes according to the deviation of the target air-fuel ratio and the air-fuel ratio until an engine state suitable for using the HOM correction value is reached. It relates to a fuel injection control device that can prevent changes in fuel injection amount, reduce deviation from the target air-fuel ratio, and reduce exhaust gas.

Description

Fuel injection control device {Fuel injection control device}

The present invention relates to a fuel injection control device. More specifically, the present invention relates to a fuel injection control device, and more specifically, when the injection mode is switched, the fuel injection amount is corrected according to the deviation between the target air-fuel ratio and the air-fuel ratio, thereby mitigating sudden changes in the fuel injection amount, and tracking the target air-fuel ratio to reduce exhaust gas. It relates to a fuel injection control device in which emissions can be reduced.

Reducing CO2 emissions, which are identified as the main cause of global warming, is ultimately possible by developing fuel-efficient engines. Against this background, GDI (Gasoline Direct Injection) engines, which have many advantages in terms of fuel economy, output, and eco-friendliness, are emerging.

Unlike MPI (Multi-Point Injection) engines, GDI engines can inject fuel during the compression stroke in addition to the intake stroke. The primary injection in the intake stroke forms a homogeneous lean mixture, and the secondary injection in the compression stroke forms a stratified mixture. The injection method that achieves the overall target air-fuel ratio is called Homogeneous Split Injection (HSP). This can delay the ignition timing more than Homogeneous Injection (HOM), which injects only during the intake stroke. Therefore, HSP mode is very effective in shortening the catalyst activation time by significantly increasing the temperature of the exhaust gas. HSP mode only applies after a cold start until the catalyst is activated.

Meanwhile, fuel loss correction is required after the vehicle is started and before the engine stabilizes, so different fuel correction values are used depending on each fuel injection mode.

However, conventionally, when the fuel injection mode is changed (HSP → HOM) after a cold start and before engine stabilization, the fuel correction value is also immediately converted from the HSP correction value to the HOM correction value, resulting in fuel quantity jumping, resulting in an excessively rich air-fuel ratio. There is a problem with excessive exhaust gas emissions.

In order to improve the problems of the prior art described above, the present invention uses a correction value that changes according to the deviation of the target air-fuel ratio and the air-fuel ratio until an engine state suitable for using the HOM correction value is reached after changing the fuel injection mode. The purpose is to provide a fuel injection control device for preventing sudden changes in fuel injection amount, reducing air-fuel ratio deviation, and reducing exhaust gas by controlling the fuel injection amount.

In order to achieve the above object, a fuel injection control device according to the present invention includes an engine including an injector that injects fuel into a combustion chamber; The fuel from the injector is divided into a Homogeneous Injection (HOM) mode in which fuel is injected only in the suction stroke, and a Homogeneous Split Injection (HSP) mode in which fuel is firstly injected in the suction stroke and secondaryly injected in the compression stroke. A control unit that controls the injection amount; and an oxygen sensor disposed in the exhaust pipe to measure the air-fuel ratio, wherein the control unit controls the fuel injection amount using a preset first correction value in the HSP mode, and controls the fuel injection amount with a preset second correction value in the HOM mode. Controlling the fuel injection amount, when the injection mode is switched from the HSP mode to the HOM mode, a third engine that changes according to the deviation between the air-fuel ratio and the target air-fuel ratio until the deviation between the air-fuel ratio and the target air-fuel ratio becomes 0. The fuel injection amount may be controlled using a correction value.

In addition, the fuel injection control device according to the present invention further includes a temperature sensor that measures the temperature of the oxygen sensor, and the control unit is configured to determine the temperature of the oxygen sensor measured by the temperature sensor when switching the injection mode. When the temperature is below a preset temperature, the fuel injection amount may be controlled by performing feedback control to track the target air-fuel ratio based on the second correction value.

Meanwhile, when switching the injection mode, if the time the HSP mode lasts is shorter than a preset time, the control unit performs feedback control to track the target air-fuel ratio based on the second correction value to determine the fuel injection amount. It may be characterized by controlling.

Additionally, when switching the injection mode, the control unit may control the fuel injection amount using the first correction value when the difference between the air-fuel ratio and the target air-fuel ratio is greater than the value measured immediately before.

Furthermore, when switching the injection mode, the control unit, if the deviation between the air-fuel ratio and the target air-fuel ratio is smaller than the value measured immediately before, the control unit determines the difference between the current air-fuel ratio and the target air-fuel ratio (air-fuel ratio deviation), the maximum value of the air-fuel ratio, and the target air-fuel ratio. It may be characterized by calculating the third correction value as a function of the deviation (maximum air-fuel ratio deviation), the first correction value, and the second correction value.

Here, the third correction value can be calculated according to Equation 1 below.

[Equation 1]

As described above, the fuel injection control device according to the present invention, after the fuel injection mode is changed from HSP mode to HOM mode, the difference between the target air-fuel ratio and the air-fuel ratio is maintained until an engine state suitable for using the HOM correction value is reached. The fuel injection amount can be controlled using a correction value that changes depending on the fuel injection amount. Therefore, there is an effect of preventing a sudden change in fuel injection amount due to a change in injection mode, reducing the deviation between the target air-fuel ratio and the actual air-fuel ratio, and reducing exhaust gas.

Figure 1 is a graph to explain problems with the conventional fuel injection method.
Figure 2 is a block diagram for explaining the configuration of a fuel injection control device according to an embodiment of the present invention.
Figure 3 is a flowchart for explaining a method of controlling the fuel injection amount of the fuel injection control device according to an embodiment of the present invention.
Figure 4 is a graph for explaining fuel injection amount control using the third correction value of the fuel injection control device according to an embodiment of the present invention.
Figure 5 is a graph of experimental results for comparing a conventional fuel injection amount control logic and a fuel injection amount control logic using a fuel injection control device according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. This is not intended to limit the present invention to specific embodiments, and should be interpreted as including all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

In describing the present invention, terms such as first and second may be used to describe various components, but the components may not be limited by the terms. The above terms are solely for the purpose of distinguishing one component from another. For example, a first component may be named a second component, and similarly, the second component may also be named a first component without departing from the scope of the present invention.

The term “and/or” may include any of a plurality of related stated items or a combination of a plurality of related stated items.

When a component is said to be "connected" or "connected" to another component, it means that it may be directly connected to or connected to that other component, but that other components may also exist in between. It can be understood. On the other hand, when a component is referred to as being “directly connected” or “directly connected” to another component, it can be understood that there are no other components in between.

The terms used in this application are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions may include plural expressions, unless the context clearly indicates otherwise.

In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and one or more other features It can be understood that it does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by a person of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries can be interpreted as having meanings consistent with the meanings they have in the context of related technologies, and unless clearly defined in this application, are interpreted as having an ideal or excessively formal meaning. It may not work.

In addition, the following examples are provided to provide a more complete explanation to those with average knowledge in the art, and the shapes and sizes of elements in the drawings may be exaggerated for clearer explanation.

Figure 1 is a graph to explain problems with the conventional fuel injection method.

GDI (Gasoline Direct Injection) engines use Homogeneous Split Injection (HSP), which injects fuel once during the intake stroke and then injects additional fuel once or twice during the compression stroke, and injection only during the intake stroke. Homogeneous Injection (HOM) can be performed.

HSP mode is a fuel injection mode to perform normal combustion even when the ignition timing is delayed for catalyst heating (activation). Therefore, HSP mode is applied only until the catalyst is activated after a cold start, and after the catalyst is activated, the fuel injection mode switches to HOM mode.

The Engine Management System (EMS) adjusts the preset fuel injection amount correction value for each fuel injection mode to minimize fuel loss due to interference with intake air volume calculation that may occur due to foreign substances entering the engine after starting and before engine stabilization. Apply.

In other words, before engine stabilization, in HSP mode, the fuel injection amount correction value (hereinafter referred to as first correction value) appropriate for the HSP mode is applied, and in HOM mode, the fuel injection amount correction value (hereinafter referred to as second correction value) appropriate for HOM mode is applied. do.

However, even if the fuel injection mode is changed from HSP mode to HOM mode, it is preferable that the first correction value is still applied immediately after the mode is changed, and the environment gradually changes over time to an environment suitable for applying the second correction value.

Nevertheless, when changing from HSP mode to HOM mode, if the fuel injection amount correction value is immediately converted from the first correction value to the second correction value, a sudden change in the fuel injection amount occurs (see Figure 1). This sudden change in the fuel amount causes an excessive air-fuel ratio. It causes excessive concentration and exhaust gas emissions.

In order to prevent rapid changes in the fuel injection amount as described above, conventionally, the fuel injection amount was controlled by performing feedback control to track the target air fuel ratio by converging the air-fuel ratio deviation to 0 based on the second correction value. However, even with feedback control, rapid changes in fuel injection amount occur to some extent, and oscillation of fuel injection amount occurs for a certain period of time in transient conditions, so there is a problem of insufficient exhaust gas reduction performance.

Another way to prevent sudden changes in the fuel injection amount is to control the fuel injection amount by continuously using either the first correction value or the second correction value.

However, if only the first correction value is used regardless of the injection mode, a smaller amount of fuel is continuously injected compared to the second correction value, so there is a possibility of unstable idling.

Conversely, if only the second correction value is used regardless of the injection mode, it is difficult to optimize engine performance because too much fuel is injected before catalyst heating during cold start.

Therefore, controlling the fuel injection amount using only one correction value as described above is not appropriate to solve the problems of the prior art, so a new method of fuel injection amount correction is needed.

The present invention discloses a fuel injection control device that can solve the above problems of the prior art.

Figure 2 is a block diagram for explaining the configuration of the fuel injection control device 1 according to an embodiment of the present invention.

The fuel injection control device 1 according to an embodiment of the present invention includes an engine 10 including an injector 100 that injects fuel into a combustion chamber 101, and a control unit 11 that controls the fuel injection amount of the injector 100. ) and an oxygen sensor 13 disposed in the exhaust pipe to measure the air-fuel ratio.

The control unit 11 may control the fuel injection amount of the injector 100 according to the fuel injection mode. Specifically, in HSP mode, the fuel injection amount can be controlled using a preset first correction value, and in HOM mode, the fuel injection amount can be controlled using a preset second correction value.

The oxygen sensor 13 is a component that is placed inside the exhaust pipe and can measure the air fuel ratio (air-to-combustion ratio). In theory, when the weight ratio of air to combustion is 14.7:1, gasoline and oxygen undergo an oxidation reaction and complete combustion, so the catalytic converter can achieve the best purification effect and minimize exhaust gas emissions.

Hereinafter, the air-to-combustion ratio of 14.7:1 is referred to as the “target air-fuel ratio,” the currently measured air-fuel ratio is referred to as the “current air-fuel ratio,” and the deviation between the target air-fuel ratio and the current air-fuel ratio is referred to as the “air-fuel ratio deviation.”

At this time, in order for the oxygen sensor 13 to accurately measure the air-fuel ratio, it must be heated to an appropriate temperature.

The fuel injection control device 1 according to an embodiment of the present invention may further include a temperature sensor 14 that measures the temperature of the oxygen sensor 13.

The temperature sensor 14 is a component that measures whether the temperature of the oxygen sensor 13 has been heated to the appropriate temperature suitable for measuring the air-fuel ratio.

Hereinafter, a specific method by which the fuel injection control device 1 including the above components controls the fuel injection amount will be described in conjunction with FIGS. 3 and 4.

FIG. 3 is a flowchart for explaining a method of controlling the fuel injection amount of the fuel injection control device 1 according to an embodiment of the present invention, and FIG. 4 is a third correction method of the fuel injection control device 1 according to an embodiment of the present invention. This is a graph to explain fuel injection amount control using values.

The control unit 11 may control the fuel injection amount by determining whether the current fuel injection mode is the HSP mode (S101).

Specifically, when the current fuel injection mode is the HSP mode, the fuel injection amount of the injector 100 can be controlled using the first correction value preset for the HSP mode (S102).

HSP mode is a fuel injection mode to perform normal combustion even when the ignition timing is delayed for catalyst heating (activation). Therefore, after catalyst heating is completed, the injection mode can be changed to HOM mode, and in this case, different correction values are used. Use may be necessary. Therefore, when using the first correction value (S102), it can be determined again whether the fuel injection mode continues to be the HSP mode (i.e., whether the first correction value must be continuously used) (S101).

If the current fuel injection mode is not HSP mode, the fuel injection amount can be controlled by determining whether the injection mode changes from HSP mode to HOM mode (S103). Whether or not the injection mode is changed is determined by whether or not catalyst heating is completed.

Specifically, when the fuel injection mode does not change from HSP mode to HOM mode, it is determined that the HOM mode has continued, and the fuel injection amount of the injector 100 can be controlled using the second setting value preset for the HOM mode. Yes. (S104)

Since the injection mode is no longer changed in HOM mode, the second set value can continue to be used. If the catalyst is already sufficiently heated, such as in the case of a non-cold start, fuel may be injected in HOM mode from the beginning without going through HSP mode. In such case, step S104 may be performed.

When the fuel injection mode is changed from HSP mode to HOM mode, it can be determined whether the temperature of the oxygen sensor 13 measured by the temperature sensor 14 is higher than the preset temperature (S105). The oxygen sensor 13 is heated. This is because the correct air-fuel ratio can be measured only when the appropriate temperature is reached.

If the temperature of the oxygen sensor 13 is not higher than the preset temperature, the fuel injection amount can be controlled by performing feedback control to track the target air-fuel ratio based on the second set value suitable for the HOM mode (S107).

When the temperature of the oxygen sensor 13 is sufficiently heated above the preset temperature, the air-fuel ratio can be accurately measured, and step S108, which will be described later, can be performed.

When the fuel injection mode is changed from HSP mode to HOM mode, it can be further determined whether the HSP mode has continued for more than a preset time (S106). If the engine is sufficiently affected by the HSP mode, the third method, which will be described later, This is because it is appropriate to use correction values.

If the HSP mode is performed shorter than the preset time, the fuel injection amount can be controlled by performing feedback control that follows the target air-fuel ratio based on the second set value suitable for the HOM mode (S107).

If the HSP mode continues for more than a preset time, step S108, which will be described later, can be performed because the engine has been sufficiently affected by the HSP mode.

The temperature determination (S105) of the oxygen sensor 13 and the duration determination of the HSP mode (S106) can be made in parallel, and the duration of the HSP mode is determined after the temperature determination (S105) of the oxygen sensor 13 ( S106) does not have to be performed. Therefore, unlike the flowchart of FIG. 3, the duration of the HSP mode (S106) may be determined first, and then the temperature of the oxygen sensor 13 (S105) may be determined.

In other words, “the temperature of the oxygen sensor 13 will be higher than the preset temperature” and “the duration of the HSP mode will be longer than the preset time” are conditions for starting fuel injection amount control according to the present invention, respectively, There is no priority for each condition.

Therefore, if the two conditions are not satisfied, the conventional feedback control is performed (S107), and if the two conditions are satisfied, the feedback control is not performed, and a step is performed to determine whether the air-fuel ratio deviation has reached the maximum value as described below ( S108).

The oxygen sensor 13 can be placed in the exhaust pipe to measure the current air-fuel ratio.

Referring to FIG. 4, the air-fuel ratio deviation, which refers to the difference between the target air-fuel ratio and the current air-fuel ratio measured by the oxygen sensor 13, gradually increases after the injection mode is changed.

After changing the injection mode, the air-fuel ratio deviation reaches the maximum value and then gradually decreases and converges to 0. However, before the air-fuel ratio deviation reaches the maximum value, the air-fuel ratio deviation is not properly measured immediately after changing the injection mode. (Hereinafter, the maximum value of the air-fuel ratio deviation is referred to as 'maximum'. It is called ‘air-fuel ratio deviation’.)

According to the present invention, the third correction value is a value that changes according to the air-fuel ratio deviation, and therefore should be used when the air-fuel ratio deviation can be properly measured.

Therefore, if the periodically measured air-fuel ratio deviation is determined to be before reaching the maximum air-fuel ratio deviation after changing the injection mode (S108), the third correction value cannot be used yet, so the first correction value used in HSP mode is used (S109) ), the fuel injection amount can be controlled using the third correction value after reaching the maximum air-fuel ratio deviation (S110).

Specifically, after switching to the injection mode, if the air-fuel ratio deviation measured at a specific point in time is greater than the air-fuel ratio deviation measured immediately before, it is determined that the maximum air-fuel ratio deviation has not yet been reached (S108) and the fuel injection amount is adjusted using the first correction value. Can be controlled. (S109)

Afterwards, the air-fuel ratio deviation is continuously monitored, and if the air-fuel ratio deviation measured at a specific point in time is smaller than the air-fuel ratio deviation measured immediately before, it is determined that the maximum air-fuel ratio deviation has been reached (S108) and the fuel injection amount can be controlled using the third correction value. (S110)

Here, the third correction value may be calculated as a function of the air-fuel ratio deviation, the maximum air-fuel ratio deviation, the first correction value, and the second correction value.

Specifically, the third correction value can be calculated according to Equation 1 below.

[Equation 1]

According to the above equation, the third correction value is equal to the first correction value at the maximum air-fuel ratio deviation, and becomes equal to the second correction value when the air-fuel ratio deviation converges to 0 over time.

That is, the third correction value starts from the first correction value and converges to the second correction value.

After controlling the fuel injection amount using the third correction value (S110), it can be determined whether the air-fuel ratio deviation is 0. (S111) If the air-fuel ratio deviation is not 0, the third correction value is continued to be used, and the air-fuel ratio deviation is 0. At this point, the fuel injection amount correction using the third correction value ends.

Figure 5 is a graph of experimental results for comparing a conventional fuel injection amount control logic and a fuel injection amount control logic using the fuel injection control device 1 according to an embodiment of the present invention.

In FIG. 5, the left side is an experimental example in which the fuel correction value based on the conventional fuel injection quantity control logic changes over time, and the right side is the fuel correction value based on the logic of the fuel injection control device 1 according to the embodiment of the present invention. This is an example of an experiment that changes over time.

As shown, according to the conventional fuel injection amount control logic, a sudden change (step difference) in the fuel injection amount occurs immediately after the fuel injection mode is changed, but according to the logic of the fuel injection control device 1 according to the embodiment of the present invention, According to this, there is almost no change in fuel injection amount.

According to the comparative experimental example above, when the fuel injection amount is controlled using the fuel injection control device 1 according to the embodiment of the present invention, the sudden change in the fuel injection amount due to the change in fuel injection mode is alleviated, the air-fuel ratio deviation is reduced, and It can be seen that there is an effect of reducing exhaust gas.

Although the present invention has been described in detail through specific examples, this is for detailed explanation of the present invention, and the present invention is not limited thereto, and the present invention is intended to be understood by those skilled in the art within the technical spirit of the present invention. It is clear that modification or improvement is possible.

All simple modifications or changes of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be made clear by the appended claims.

1: Fuel injection control unit
10: engine
11: control unit
13: Oxygen sensor
14: temperature sensor
100: injector
101: combustion chamber

Claims (6)

An engine including an injector that injects fuel into a combustion chamber;
The fuel from the injector is divided into a Homogeneous Injection (HOM) mode in which fuel is injected only in the suction stroke, and a Homogeneous Split Injection (HSP) mode in which fuel is firstly injected in the suction stroke and secondaryly injected in the compression stroke. A control unit that controls the injection amount; and
It includes an oxygen sensor disposed in the exhaust pipe to measure the air-fuel ratio,
The control unit,
In the HSP mode, the fuel injection amount is controlled by a preset first correction value, and in the HOM mode, the fuel injection amount is controlled by a preset second correction value,
When the injection mode is switched from the HSP mode to the HOM mode, the temperature of the oxygen sensor is higher than the preset temperature, and the time for which the HSP mode continues is longer than the preset time, the deviation between the air-fuel ratio and the target air-fuel ratio is 0. A fuel injection control device characterized in that the fuel injection amount is controlled by a third correction value that changes according to the deviation between the air-fuel ratio and the target air-fuel ratio until
According to paragraph 1,
A temperature sensor that measures the temperature of the oxygen sensor;
It further includes,
The control unit,
When the injection mode is switched from the HSP mode to the HOM mode, if the temperature of the oxygen sensor measured by the temperature sensor is below a preset temperature, feedback control is performed to track the target air-fuel ratio based on the second correction value. A fuel injection control device characterized in that it controls the fuel injection amount.
According to paragraph 1,
The control unit,
When the injection mode is switched from the HSP mode to the HOM mode, if the duration of the HSP mode is shorter than a preset time, feedback control to track the target air-fuel ratio is performed based on the second correction value to A fuel injection control device characterized in that it controls the fuel injection amount.
According to paragraph 1,
The control unit,
When the injection mode is switched from the HSP mode to the HOM mode, if the difference between the air-fuel ratio and the target air-fuel ratio is greater than the immediately previously measured value, the fuel injection amount is controlled by the first correction value. controller.
According to paragraph 1,
The control unit,
When the injection mode is switched from the HSP mode to the HOM mode, if the deviation between the air-fuel ratio and the target air-fuel ratio is smaller than the value measured immediately before, the deviation between the current air-fuel ratio and the target air-fuel ratio (air-fuel ratio deviation), the maximum value of the air-fuel ratio, and A fuel injection control device, characterized in that calculating a third correction value as a function of the deviation of the target air-fuel ratio (maximum air-fuel ratio deviation), the first correction value, and the second correction value.
According to clause 5,
The third correction value is calculated according to Equation 1 below.
[Equation 1]