KR20170067330A - Method of learning closing time of injector - Google Patents

Abstract

The present invention relates to an injector closing time learning method for compensating a driving characteristic of an injector which defines a relationship between the injection time of an injector for each cylinder of the internal combustion engine and a valve closing time and correcting the deviation of the closing time of the inter- will be.
In the present invention, a multi-stage injection of fuel including a learning injection mode for injecting fuel by an injector injection time serving as a learning target is performed, and an actual closing time of the injector at the time of learning injection is measured, Accurate information on the relationship between the injector injection time and the closing time can be obtained and accurate learning for correcting the injector closing time deviation can be performed for each cylinder.

Description

{METHOD OF LEARNING CLOSING TIME OF INJECTOR}

The present invention relates to a method of learning a closing time of an injector, and more particularly, to a method of learning the closing time of an injector by compensating a driving characteristic of an injector which defines a relationship between a time of injection of the injector for each cylinder of the internal combustion engine and a valve closing time, The injector closing time learning method for correcting the injector closing time.

When the fuel is supplied to the automotive engine, the amount of supplied fuel is determined by the control unit (ECU), and fuel is injected into the engine by the injector by the determined required fuel amount.

The injector is usually constituted by a solenoid valve. The injector is provided for each cylinder and receives the fuel injection signal from the control unit to inject fuel for a predetermined injection time, thereby supplying fuel to the inside of the engine by the required fuel amount.

As described in Patent Document 1, there is a difference in the injector driving characteristic inherent to the type and the company of the injector. Specifically, as shown in Fig. 3 (a), the injector closing request time according to the fuel amount required for fuel pressure comparison is in a linear relationship that is specific to the type of injector or company. Also, as shown in FIG. 3 (b), the injector closing request time and the injection command time corresponding thereto are also in a specific correspondence relation by the type of the injector or the company. Generally, such characteristic information is stored in a memory inside the control unit at the time of manufacturing the vehicle, and is used to supply fuel to each cylinder by the required fuel amount.

However, even in the case of the same injector, the injector driving characteristics may vary due to manufacturing tolerances, tolerances of the output stage for operating the injectors in the control unit, and the difference in the operating current profile. In particular, when the deviation of the injector driving characteristic related to the injector closing time is not compensated for each cylinder, a variation in the closing time between the injectors occurs for each cylinder, so that despite the injection command based on the same injection time, . That is, it becomes difficult to control the same flow rate between the cylinders.

In order to correct the deviation between the cylinder injection command time and the injector closing time, the actual injector closing time corresponding to the injection command is measured and learned for each cylinder, and thereby the injector driving characteristic shown in FIG. 3 (b) It is necessary to modify the data relating to the injector drive characteristics previously stored, such as curves.

In this learning method, the actual measured value of the injector closing time is fed back to an arbitrary injection time at which the fuel is injected at the time of driving the engine, and then, using the characteristic curve obtained by interpolation based on the measured data value, Thereby compensating the driving characteristics.

Thus, in the prior art, several representative learning operation points are used to compensate through interpolation. Generally, the actual operation point is different from the learning operation point. Therefore, it is difficult to compensate the accurate injector drive characteristic according to the prior art.

Patent Document 1: Published Patent Application No. 2015-0114078 (Oct. 12, 2015)

SUMMARY OF THE INVENTION The present invention has been conceived in order to solve the above-mentioned problems, and it is an object of the present invention to provide a fuel injection control system and a fuel injection control method for injecting fuel, The injector closing time learning method capable of correcting the deviation of the injector closing time between cylinders.

According to an aspect of the present invention, there is provided a method for correcting a deviation of a closing time of an inter-cylinder injector by compensating a driving characteristic of an injector defining a relationship between an injection time of an injector for each cylinder of the internal combustion engine and a valve closing time An injector closing time learning method comprising: setting an injector injection time which is a learning target; Calculating a closing time corresponding to the set injector injection time from the driving characteristic of the existing injector; Injecting the fuel by a closing time corresponding to the amount of fuel obtained by subtracting the calculated closing time from the target closing time corresponding to the total amount of injection required for driving the engine, A multistage fuel injection step; Measuring the closing time of the injector during learning injection; Repeating the multi-stage fuel injection step and the injector closing time measurement to learn the actual injector closing time corresponding to the learning injection time; And terminating the learning of the injector injection time when the predetermined learning completion condition is satisfied and compensating the driving characteristic of the injector by reflecting the learning result.

Preferably, the step of calculating the closing time further includes stopping the learning when it is determined that the injection amount corresponding to the calculated closing time exceeds a predetermined ratio with respect to the total required injection amount.

Preferably, the multi-stage fuel injection step includes the steps of: determining whether or not the engine has entered the catalyst heating mode for heating the exhaust gas processing catalyst by increasing the temperature of the exhaust gas by delaying the ignition timing through the multi-step fuel injection; When it is determined that the catalyst heating mode is entered through the multi-step fuel injection, the injection time in any one of the multi-step injection in the catalyst heating mode is made to be the fuel injection time corresponding to the set injector closing time.

Preferably, it is determined whether or not the injector closing time learning mode is entered according to whether the engine has been started and whether the target fuel pressure has been reached, and the learning method is executed according to the determination result.

Preferably, the step of determining whether the measurement result of the repeatedly measured injector closing time converges within a certain range; And when the measurement result of the injector closing time measured a plurality of times converges within a certain range, if the number of times of measurement of the injector closing time converging within a certain range exceeds the first set value, And determining that the learning completion condition is satisfied.

Determining whether the number of attempts of learning injection exceeds a second set value if the measured result of the injector closing time measured a plurality of times does not converge within a certain range; And determining that learning of the injector injection time which is a learning target has failed and ending the learning of the injector closing time when the number of trial injection attempts exceeds the second set value.

Preferably, when the learning of the injector injection time as the learning target is ended, the injector injection time set as the next learning target is set, and learning of the injector injection time set is advanced, and the learning of all the injector injection time The injector closing time learning mode is terminated.

As described above, according to the injector closing time learning method of the present invention, it is possible to obtain the characteristic relationship between the actual injector injection time and the closing time required for learning by performing the actual injection during the injector injection time which is the learning target.

This improves the accuracy of learning for correcting the injector closing time deviation and improves the performance of correcting the closing time deviation for each cylinder. This also improves the performance of correcting the fuel amount deviation between cylinders.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart schematically illustrating injector fine control logic to which an injector closing time learning method according to the present invention may be applied.
2 is a flowchart showing an injector closing time learning method according to the present invention;
3 is a graph showing the injector drive characteristic.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a flowchart schematically showing injector fine control logic to which an injector closing time learning method according to the present invention can be applied.

1, the control unit installed in the vehicle first sets a required fuel amount required for combustion of the engine (S10). 3 (a), using the linear relationship data of the injector closing demand time relative to the fuel pressure according to the required fuel amount for each cylinder stored in the nonvolatile memory in the control unit, The injector closing request time is calculated (S20). Here, the injector closing time means the time taken for the injector to completely close from immediately after the injector closing command is issued by transmitting a closing signal from the control unit to the injector.

Next, the control unit uses the relationship data of the fuel pressure comparative closing time according to the injector required injection time stored in the nonvolatile memory in the control unit, for example, as the injector driving characteristic curve shown in Fig. 3 (b) A fuel injection time corresponding to the injector closing required time calculated for injection of the fuel amount is calculated (S30).

Then, based on the calculated fuel injection time, the control unit controls the injector for each cylinder to inject the fuel (S40).

On the other hand, in the case of the same injector for each cylinder, the injector driving characteristic may be changed due to the manufacturing tolerance, the tolerance of the output stage for operating the injector in the control unit, and the difference in the operating current profile. As a result, a deviation may occur in the relationship between the injection time and the closing time of the injector for each cylinder.

In order to compensate for this, the actual closing time of the injector is measured for each cylinder in the precise control logic of the injector (S50), and the relationship between the injection time and the actual closing time of each injector is learned (S60). Based on the learning result, the deviation of the closing time of the injector for each cylinder can be eliminated by compensating the injector driving characteristic curve defining the relationship between the injection time and the closing time of the injector for each cylinder (S70).

2 is a flowchart showing an injector closing time learning method according to the present invention. Hereinafter, an embodiment of the injector closing time learning method according to the present invention will be described in detail with reference to the contents of FIG.

Preferably, in the injector closing time learning method according to the present invention, it is determined whether to enter the injector closing time learning mode, and learning of the closing time of the injector can be performed according to the determination result.

To this end, the control unit may determine whether to enter the injector closing time learning mode based on whether the vehicle has been started and reached the target fuel pressure (S100). It is difficult to determine the exact injector driving characteristic in the starting process in which the fuel pressure fluctuates. Accordingly, the injector closing time learning mode is entered (S110) on condition that the startup is completed and the fuel pressure is stabilized in a predetermined range.

After entering the injector closing time learning mode, the control unit sets the injector injection time to be the learning target (S200). The learning objective is the injector injection time required to learn to reduce the deviation of the injector closing time, and it is highly necessary to learn the injector closing time at the low flow rate section requiring precise control.

After the injector injection time which is the learning target is set, the closing time corresponding to the injector injection time set from the driving characteristic data of the injector, which is stored in the nonvolatile memory and defines the relationship between the injection time and the closing time of each injector for each cylinder, The time is calculated (S300).

If it is determined that the injection amount corresponding to the calculated closing time exceeds a predetermined ratio with respect to the total required injection amount, learning can not be performed at the same time as the learning mode described later is executed, so that the learning is interrupted (S400). That is, as described later, the learning method according to the present invention separately includes the learning combustion mode for learning the injector closing time. Therefore, when the total injection amount required at the time of combustion is not sufficient as compared with the learning target injection time , The learning injection amount occupies an excessively large proportion of the total required injection amount in order to learn the injector closing time. In this case, it is difficult to simultaneously learn the injector closing time and the normal combustion, so the learning is stopped.

A learning injection step of calculating a closing time corresponding to an injector injection time which is a learning target and injecting the fuel by the set fuel injection time and a target closing time corresponding to the total required injection amount required for driving the engine, And injecting the fuel by a closing time corresponding to the amount of fuel except for the amount of fuel (step S600).

That is, in order to carry out the learning, the control unit sets the learning injection step for injecting the fuel by the set fuel injection time as one of the above-mentioned multi-step injection mode after switching the fuel injection mode through the injector to the multi-stage injection mode . The remaining injection amounts other than the injection amount required for the above-mentioned learning injection are controlled so as to be injected in the remaining steps excluding the above-mentioned learning injection step among the multistage injection mode.

As a result, the fuel injection can be performed for a specific injector injection time which is a learning target.

On the other hand, in order to activate the catalytic device, there is a case where the ignition timing is delayed by injecting the fuel in a multistage manner through the injector, and the catalyst for treating the exhaust gas is rapidly heated to the activation temperature. When it is determined that the fuel injection mode is under the catalyst heating mode (S500), one of the multi-stage injection modes for catalyst heating is set as the learning injection step for injecting the fuel for the fuel injection time set above (S510).

As a result, the multi-stage fuel injection mode for the catalyst heating mode can be executed, and at the same time, learning injection can be performed for a specific injection time.

The control unit measures the closing time of the actual injector in the learning injection mode during multi-stage fuel injection by the injector (S700). The control unit measures a change in the driving voltage of the injector in order to measure the closing time of the injector. More specifically, a voltage sensor connected to both nodes of the injector is used to sense a voltage consumed in driving the injector. The time at which the slope change of the sensed driving voltage changes from (+) to 0 or (-) is regarded as the closing timing of the injector, and the time from the point at which the injector closing command is issued to the closing point of the injector Measured as injector closing time.

Thus, in the present invention, it is possible to acquire data on the relationship between the actual injector injection time and the closing time, which is a learning target for each cylinder.

In order to carry out the learning, it is possible to repeat the measurement of the actual injector closing time during the learning injection during the multi-stage injection and the multi-stage injection as described above, thereby obtaining reliable results of the injector injection time and the closing time.

Specifically, it is determined whether the actual measured value of the injector closing time obtained by repeatedly performing learning injection converges to a predetermined value or range (S710). If the actual measured value of the injector closing time constantly converges to a predetermined value, it is determined whether the number of measurements of the injector closing time converging at a constant rate exceeds a predetermined first predetermined value (S720). When the number of times of the injector closing time constantly converging to a predetermined value or range exceeds the first predetermined value, a reliable relationship between the injector injection time, which is the learning target, and the closing time is derived and it is determined that the learning is completed , And the relationship between the injector injection time and the closing time derived through the learning result is applied to the injector driving characteristic curve for each cylinder (S800).

If the actual measured value of the injector closing time obtained by repeatedly performing the learning injection does not converge to a predetermined value or range, the number of injections in the learning mode is counted, and the number of injections of the learning mode exceeds the predetermined second set value (S730). When the number of injections in the learning mode exceeds the second set value, it is determined that the learning of the injector closing time, which is the learning target, has failed, and the learning of the injector closing time is terminated without further learning.

When it is determined that the learning of the injector injection time at the initial stage is completed or the learning is failed and the learning of the injector injection time is finished, it is judged whether or not there is an injector injection time interval required for learning next (S900). If it is determined that there is an injector injection time interval required for further learning, the injector injection time corresponding to the learning target is newly set (S1000). Then, the injector closing time learning is performed in association with the newly set injector injection time.

According to the injector closing time learning method of the present invention described above, a multi-stage injection including a learning injection mode corresponding to an injector injection time serving as a learning target is performed during fuel injection using the injector, and the actual closing By measuring the time, data on the exact injector drive characteristic associated with the target specific cylinder injector closing time can be obtained.

Accordingly, the present invention can improve the accuracy of learning for correcting the injector closing time deviation and improve the fuel amount deviation correction between cylinders.

Claims (7)

There is provided a learning method of an injector closing time for compensating a driving characteristic of an injector which defines a relationship between an injection time of an injector for each cylinder of the internal combustion engine and a valve closing time and correcting a deviation of a closing time of the inter-
Setting an injector injection time which is a learning target;
Calculating a closing time corresponding to the set injector injection time from the driving characteristic of the existing injector;
A learning injection step of injecting fuel by the set fuel injection time and a step of injecting fuel by a closing time corresponding to a fuel amount excluding the output closing time from a target closing time corresponding to the total injection amount required for driving the engine Stage fuel injection step;
Measuring a closing time of the injector during the learning injection;
Learning the actual injector closing time corresponding to the learning injection time through the multi-stage fuel injection step and the injector closing time measurement;
And terminating the learning of the injector closing time when the predetermined learning completion condition is satisfied and compensating the driving characteristic of the injector by reflecting the learning result. The method according to claim 1,
Wherein the calculating the closing time comprises:
Further comprising the step of stopping the learning when it is determined that the injection amount corresponding to the calculated closing time exceeds a predetermined ratio with respect to the total required injection amount. The method according to claim 1,
Wherein the multi-stage fuel injection step comprises:
Determining whether the engine has entered a catalyst heating mode for heating the exhaust gas processing catalyst by increasing the temperature of the exhaust gas by delaying the ignition timing through the multi-step fuel injection;
The injection time in any one of the multi-stage injection in the catalyst heating mode is made to be the fuel injection time corresponding to the set injector injection time when it is judged that the mode has entered the catalyst heating mode through the multi-stage fuel injection Characterized in that the injector closing time learning method. The method according to claim 1,
Whether or not the injection mode of the injector has entered the closing time learning mode is determined according to whether the engine has been started and whether the target fuel pressure has been reached, and the learning method is executed according to the determination result. The method according to claim 1,
Determining whether the measured result of the repeatedly measured injector closure time converges within a certain range; And
When the measurement result of the injector closing time measured in the plurality of times converges within a certain range and the number of times of measurement of the injector closing time converging within the predetermined range exceeds the first set value, Further comprising: determining that the learning completion condition is satisfied. The method of claim 5,
Determining whether the number of attempts of learning injection exceeds a second set value if the measured result of the injector closing time measured a plurality of times does not converge within a certain range;
And terminating the learning of the injector injection time by determining that the learning of the injector injection time as the learning target has failed and the learning of the injector injection time is ended when the number of attempts of learning injection exceeds the second set value Time learning method. The method according to claim 5 or 6,
When the learning of the injector injection time which is the learning target is ended, the injector injection time which is the next learning target is set, and the learning of the closing time of the injector injection time is performed,
And terminates the learning mode of the injector closing time when it is determined that learning has been completed with respect to all the injector injection times that become learning targets.

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