JP5448181B2 - Fuel injection control correction method and fuel injection control device - Google Patents

Description

  The present invention relates to a correction method and apparatus for fuel injection control of an internal combustion engine, and more particularly to an improvement in starting characteristics of a diesel engine.

In a diesel engine, starting at an extremely low temperature has a problem that the in-cylinder temperature is low and the fuel is difficult to ignite, resulting in misfire and a long starting time from cranking start to idling rotation. There is something well known from the past.
As a countermeasure against such a problem, for example, it is determined whether or not the engine is in a very low temperature state based on the coolant temperature of the engine coolant, and when it is determined that the engine is in a very low temperature state, the fuel injection amount, the injection timing, Generally, the start-up time is optimized by correcting the fuel injection control such as the fuel injection pressure.
As such injection control based on the water temperature of the engine cooling water, for example, as disclosed in Patent Document 1 or the like, the water temperature of the engine cooling water is substituted for the in-cylinder temperature, and correction control of the fuel injection timing is performed. An apparatus such as this is disclosed.

Japanese Patent Laid-Open No. 11-294228 (page 3-5, FIGS. 1 to 8)

  However, it is difficult to say that the engine cooling water temperature accurately reflects the in-cylinder temperature. Therefore, particularly when the ambient temperature is low, the difference between the engine cooling water temperature and the in-cylinder temperature is significant. Therefore, the correction in the injection control as described above becomes insufficient, and there is a problem that satisfactory starting characteristics cannot be secured.

  The present invention has been made in view of the above circumstances, and provides a fuel injection control correction method and a fuel injection control device that can satisfactorily maintain starting characteristics even when a diesel engine is in an extremely low temperature state.

In order to achieve the above object of the present invention, a fuel injection control correction method according to the present invention comprises:
In a fuel injection control device configured to control a fuel injection operation to the internal combustion engine according to an operating state of the internal combustion engine, the fuel injection operation calculated based on the operating state of the internal combustion engine is controlled. A fuel injection control correction method for correcting a basic control amount used by a correction parameter,
The in-cylinder temperature predicted value of the internal combustion engine as the correction parameter,
The in-cylinder temperature predicted value is sequentially updated by repeatedly adding a predetermined in-cylinder temperature change amount determined according to the rotational speed and injection state of the internal combustion engine to the most recently calculated in-cylinder temperature predicted value. It is configured to be calculated.
In order to achieve the above object of the present invention, a fuel injection control device according to the present invention includes:
The basic control amount used for controlling the fuel injection operation calculated and calculated based on the operating state of the internal combustion engine is corrected by the correction parameter by the electronic control unit so that the fuel injection operation to the internal combustion engine is controlled. A fuel injection control device comprising:
The electronic control unit is
The in-cylinder temperature predicted value of the internal combustion engine as the correction parameter,
The in-cylinder temperature predicted value is sequentially updated by repeatedly adding a predetermined in-cylinder temperature change amount determined according to the rotational speed and injection state of the internal combustion engine to the most recently calculated in-cylinder temperature predicted value. It is configured to be calculated.

According to the present invention, since the predicted value of the in-cylinder temperature is used as the correction parameter, in particular, a value approximated to the actual in-cylinder temperature can be reflected in the fuel injection control at the time of engine start at a low temperature, Therefore, unlike the prior art, the engine can be rotated smoothly and quickly at the time of starting the engine at a low temperature, and the effect of shortening the starting time and reducing the variation in the starting time is achieved.
Furthermore, the effect of reducing the generation time of white smoke and reducing the emission by shortening the starting time and appropriateness can be achieved.

It is a block diagram which shows the structural example of the fuel-injection control apparatus in embodiment of this invention. 2 is a subroutine flowchart showing a schematic procedure of fuel injection control correction processing in the embodiment of the present invention executed by an electronic control unit constituting the fuel injection control device shown in FIG. 1. It is a subroutine flowchart which shows the specific process sequence of the correction parameter calculation calculation process shown by FIG. It is the block diagram which showed the function required for an electronic control unit in order to perform the correction parameter calculation calculation process shown by FIG. 3 using the functional block. It is a characteristic diagram which shows the example of a characteristic by the simulation of the time change of the engine speed at the time of engine starting, the time change of cylinder prediction temperature, and the time change of the detection temperature of a water temperature sensor.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.
The members and arrangements described below do not limit the present invention and can be variously modified within the scope of the gist of the present invention.
Initially, the structural example of the fuel-injection control apparatus in embodiment of this invention is demonstrated, referring FIG.
The fuel injection control device according to the embodiment of the present invention is a so-called common rail fuel injection control device.

  The common rail fuel injection control device includes a plurality of fuel injection valves 2-1 to 2-n that supply fuel to cylinders of the diesel engine 1 and high-pressure fuel that is supplied to the fuel injection valves 2-1 to 2-n. A common rail 3 to be stored; a high-pressure pump 4 that pumps high-pressure fuel to the common rail 3; a feed pump 5 that supplies fuel from the fuel tank 6 to the high-pressure pump 4; and an electronic control unit 11 that executes injection control correction processing, which will be described later. It is divided into two categories. Such a configuration itself is the same as the basic configuration of this type of fuel injection control apparatus that has been well known.

In this configuration, the fuel in the fuel tank 6 is pumped up to the high-pressure pump 4 by the feed pump 5, and the pumped-up fuel is pumped as high-pressure fuel to the common rail 3 by the high-pressure pump 4. Although not shown, a pipe is provided so that excess fuel in the common rail 3 is returned to the fuel tank 6.
The fuel injection valves 2-1 to 2-n are provided for each cylinder of the diesel engine 1, and are supplied with high-pressure fuel from the common rail 3, respectively. The injection operation is controlled.

The electronic control unit 11 has, for example, a microcomputer (not shown) having a known and well-known configuration, a storage element (not shown) such as a RAM and a ROM, and a fuel injection valve 2- A drive circuit (not shown) for driving 1 to 2-n is configured as a main component.
The electronic control unit 11 includes a rotation sensor 12 that detects the engine speed, an accelerator opening sensor 13 that detects the accelerator opening, an outside air temperature sensor 14 that detects the outside air temperature, and the temperature of the cooling water of the diesel engine 1. Detection signals of various sensors such as a water temperature sensor 15 that detects the temperature of the fuel supplied to the fuel injection valves 2-1 to 2-n, and the like are input to be used for engine operation control and injection control. It has become so.

FIG. 2 shows a schematic flowchart of the fuel injection control correction process executed by the electronic control unit 11 in a subroutine flowchart, and the contents thereof will be described below with reference to FIG.
First, when the process is started, a correction parameter calculation calculation process is performed (see step S100 in FIG. 2). The correction parameter is a correction element for correcting the basic control amount described below. It is arbitrary what correction parameter is used and how many correction parameters are used.
In the embodiment of the present invention, the predicted in-cylinder temperature of the diesel engine 1 is set as one of the correction parameters.

Next, calculation of the basic control amount is performed (see step S200 in FIG. 2).
The basic control amount is a plurality of control factors required for fuel injection control, such as fuel injection amount, injection timing, common rail pressure, and the like.
Each of these basic control amounts is calculated by a predetermined procedure using an arithmetic expression, a map, or the like that has been conventionally used.

Next, necessary correction is performed on the basic control amount based on the correction parameter obtained in advance (see step S300 in FIG. 2).
Which basic control amount is used for the correction parameter, and the specific procedure of the correction process is arbitrarily set.
In the embodiment of the present invention, as described above, the in-cylinder temperature predicted value is used for correcting the basic control amount.
After a series of processes, the process returns to the main routine (not shown), and after passing through other necessary processes, the series of processes described above is repeated again.

  FIG. 3 is a subroutine flowchart showing a procedure for calculating the in-cylinder temperature predicted value as the correction parameter described above. FIG. 4 shows the calculation processing for calculating the in-cylinder temperature predicted value shown in FIG. The configuration of the logic formed in the electronic control unit 11 for execution is schematically shown respectively. Hereinafter, the in-cylinder temperature predicted value in the embodiment of the present invention will be described with reference to these drawings. A procedure of the calculation calculation process will be described.

When the processing is started by the electronic control unit 1, it is first determined whether or not the fuel injection control is in the start mode (see step S102 in FIG. 3).
The injection control itself has been performed conventionally, and the control state thereof includes a start mode in which the start of the diesel engine 1 is ensured and the stability is ensured, and a normal state after normal start. The control mode is divided into two, and the calculation processing of the in-cylinder temperature predicted value in the embodiment of the present invention is particularly suitable for being executed in the start mode. It is determined whether the control is in the start mode.

The start mode is injection control that is performed during the period from when cranking is started to when the engine speed of the diesel engine 1 reaches the idle speed.
Further, the in-cylinder temperature predicted value is intended to be used for correcting the basic control amount as described above, particularly in the fuel injection control in the start mode, and therefore the processing shown in FIG. This is executed when the fuel injection control is in the startup mode.

  Therefore, in step S102, when it is determined that the injection control is in the start mode (in the case of YES), the process proceeds to step S104 described below, while in the case where it is determined that the injection mode is not in the start mode (NO). In the case), a series of processes are not executed, and the process returns to the main routine (not shown).

In step S104, the initial value of the engine cooling water temperature is recognized. That is, the water temperature sensor 15 sets the water temperature of the engine coolant detected at this time as an initial value of the in-cylinder temperature predicted value. The initial value of the in-cylinder temperature predicted value may be the engine coolant temperature, in addition to the engine coolant temperature, for example, in the case of a vehicle configured to detect the temperature of the engine lubricant. Is preferred.
After that, cranking becomes possible and cranking is started (see step S106 in FIG. 3).

Next, the engine speed and the number of injections at this time are recognized (see step S108 in FIG. 3). The recognition of the engine speed and the number of injections is used as a parameter for calculating the in-cylinder temperature change amount in step S110 described below.
Here, “the number of injections” in step S108 means the total number of injections from the start of cranking to this point, and is hereinafter referred to as “total number of injections”. The total number of injections is obtained as the product of the engine speed and the elapsed time from the start of cranking. Note that the total number of injections can be calculated by counting the detection signal of a cam sensor (not shown) from the start of cranking, and may be obtained in this way.
The engine speed and the total number of injections obtained at this time obtained as described above are temporarily read and stored in an appropriate storage area (not shown) of the electronic control unit 11.
The engine speed is obtained based on the detection signal of the rotation sensor 12.

Next, using a preset in-cylinder temperature change amount map, the in-cylinder temperature change amount with respect to the total number of injections and the engine speed obtained in step S108 is obtained (see step S110 in FIG. 3).
The in-cylinder temperature change amount map in the embodiment of the present invention is a change characteristic from the start of cranking of the change amount of the in-cylinder temperature of the diesel engine 1 that can occur for various combinations of the engine speed and the total number of injections. Is obtained from simulations and tests, and the data of the change characteristics are mapped.
In addition, instead of the total number of injections, an elapsed time from the start of cranking may be used.

In FIG. 4, functions required for the electronic control unit 11 in order to execute the calculation calculation processing of the in-cylinder temperature predicted value in the embodiment of the present invention by the electronic control unit 11, particularly the above-described step S <b> 110. The block diagram which showed the function required for performing after a process with the functional block is shown, and the function which the electronic control unit 11 has for calculating the above-mentioned in-cylinder temperature change amount is demonstrated.
As shown in FIG. 4, the in-cylinder temperature change amount map 21 as described above is stored in an appropriate storage area of the electronic control unit 11, and the engine speed and the total number of injections are set as described above. When acquired, the in-cylinder temperature change amount with respect to the engine speed and the total number of injections is read from the in-cylinder temperature change amount map 21.
In addition, instead of the total number of injections, an elapsed time from the start of cranking is used, and the in-cylinder temperature change amount map 21 is set to diesel for various combinations of the engine speed and the elapsed time from the start of cranking. It is also preferable that the amount of change in the cylinder temperature of the engine 1 is required.

Returning to the description of the subroutine flowchart in FIG. 3 again, after the in-cylinder temperature change amount is obtained as described above, the calculation of the in-cylinder temperature predicted value is performed (see step S112 in FIG. 3).
That is, the in-cylinder temperature predicted value is obtained by adding the in-cylinder temperature change amount at the time of calculation of the new in-cylinder temperature predicted value to the latest in-cylinder temperature predicted value. By repeating the above, new in-cylinder temperature predicted values are sequentially updated and calculated for each repetition period.

In FIG. 4, the calculation logic of the in-cylinder temperature predicted value is expressed as described below.
That is, an addition element 22 is provided for adding the in-cylinder temperature change amount obtained from the in-cylinder temperature change amount map 21 and the latest predicted in-cylinder temperature, and the addition result of the addition element 22 is the logic switch 23. It is applied to one input side.
The logic switch 23 outputs one of the two inputs. In the embodiment of the present invention, the addition result of the adding element 22 and the in-cylinder temperature initial value (FIG. 3). Step S104) is input. When the ignition (not shown) is turned on (indicated as “IG-ON” in FIG. 4), the in-cylinder temperature initial value is selected and output, while in other states. Are selected and output from the addition result of the adding element 22.

  Further, a delay element 24 is provided between the output side of the logic switch 23 and the adding element 22, and the output of the logic switch 23, that is, the predicted in-cylinder temperature, is used to calculate the next predicted in-cylinder temperature. Therefore, the previous (most recent) in-cylinder predicted value is added to the in-cylinder temperature change amount obtained from the in-cylinder temperature change amount map 21 (see FIG. 4).

3 again, after the in-cylinder temperature predicted value is calculated as described above (see step S112 in FIG. 3), the engine speed Ne should end the start mode in the fuel injection control. It is determined whether or not a predetermined engine speed, that is, the starting cut speed has been exceeded (see step S114 in FIG. 3).
If it is determined in step S114 that the engine speed Ne has exceeded the start-up cut speed (in the case of YES), the process is terminated because it is not in a state suitable for continuing a series of processes. That is, in the embodiment of the present invention, the routine returns to the routine shown in FIG.
On the other hand, if it is determined in step S114 that the engine speed Ne has not yet exceeded the starting cut speed (in the case of NO), the process returns to the previous step S108, and the subsequent processes are repeated. It will be.

Next, with respect to changes in the engine speed at the start of cranking and the like when the predicted in-cylinder temperature obtained as described above is used as a correction parameter in fuel injection control, a characteristic example by simulation shown in FIG. Will be described with reference to FIG. In FIG. 5, the horizontal axis represents the elapsed time from the start of cranking, the right vertical axis represents the in-cylinder temperature prediction value and the engine coolant temperature, and the left vertical axis represents the engine speed. It is meant to be shown.
First, in FIG. 5, an example of a change characteristic of the engine speed at the start of cranking in the conventional apparatus obtained by simulation is indicated by a dotted characteristic line.

  In the conventional apparatus, the water temperature of the engine cooling water is used for the correction process of the fuel injection control, and the in-cylinder temperature is not necessarily reflected appropriately in the correction process. Therefore, in the dotted characteristic line shown in FIG. 5, the change in the engine cooling water temperature is shown in spite of the fact that the actual in-cylinder temperature should have increased after the first explosion 6 seconds after the start. Because it is very small (see the characteristic line of the one-dot chain line in FIG. 5), about 8 to 11 seconds after the start, the engine speed stays below the idle speed and a smooth increase in the engine speed is obtained. It is not possible.

  In contrast, by using the in-cylinder temperature predicted value in the embodiment of the present invention for the correction process of the fuel injection control instead of the engine cooling water temperature, the characteristic line indicated by the solid line in FIG. Thus, unlike the conventional case (see the dotted characteristic line), there is no stagnation of the engine speed between about 8 to 11 seconds after the start, and a quick increase in the engine speed can be obtained. This is because the in-cylinder temperature predicted value, as shown by the two-dot chain line characteristic line in FIG. 5, is different from the conventional engine coolant temperature, and an appropriate rising characteristic is obtained after the engine is started. it is conceivable that.

  In the above-described embodiment of the present invention, in particular, in the fuel injection control at the time of starting, the in-cylinder temperature predicted value is used instead of the engine coolant water temperature used when correcting the basic control amount. As a specific target for the basic control amount, for example, the fuel injection amount, the injection timing, etc. can be considered, but if the engine rotation characteristics at the start can be improved as described above, It is not necessary to be limited to a specific basic control amount, and any basic control amount to be used for correction is arbitrary. Further, in this case, it is not necessary to be limited to the case of using for one basic control amount. In the correction of a plurality of basic control amounts, a cylinder is used instead of the engine cooling water temperature or another correction parameter. Of course, the internal temperature predicted value may be used.

  Since the start characteristics of the diesel engine at an extremely low temperature are improved, it is particularly suitable for a common rail fuel injection control device.

DESCRIPTION OF SYMBOLS 1 ... Diesel engine 2-1-2-n ... Fuel injection valve 3 ... Common rail 11 ... Electronic control unit 12 ... Rotation sensor 13 ... Accelerator opening degree sensor 14 ... Outside temperature sensor 15 ... Water temperature sensor 16 ... Fuel temperature sensor

Claims (7)

In a fuel injection control device configured to control a fuel injection operation to the internal combustion engine according to an operating state of the internal combustion engine, the fuel injection operation calculated based on the operating state of the internal combustion engine is controlled. A fuel injection control correction method for correcting a basic control amount used by a correction parameter,
The in-cylinder temperature predicted value of the internal combustion engine as the correction parameter,
The in-cylinder temperature predicted value is sequentially updated by repeatedly adding a predetermined in-cylinder temperature change amount determined according to the rotational speed and injection state of the internal combustion engine to the most recently calculated in-cylinder temperature predicted value. A fuel injection control correction method characterized by being calculated.   The initial predicted in-cylinder temperature value is obtained by adding a predetermined in-cylinder temperature change amount to a predetermined initial value, and the predetermined initial value is a coolant temperature of the engine cooling water. The fuel injection control correction method according to 1.   The predetermined in-cylinder temperature change amount is determined based on the engine speed and the injection state of the internal combustion engine at the time of calculation based on a preset map of the in-cylinder temperature change amount for various combinations of the engine speed and the injection state. The fuel injection control correction method according to claim 2, wherein the correction method is obtained.   4. The fuel injection control correction method according to claim 3, wherein the injection state is a total number of injections from the start of cranking or an elapsed time. The basic control amount used for controlling the fuel injection operation calculated and calculated based on the operating state of the internal combustion engine is corrected by the correction parameter by the electronic control unit so that the fuel injection operation to the internal combustion engine is controlled. A fuel injection control device comprising:
The electronic control unit is
The in-cylinder temperature predicted value of the internal combustion engine as the correction parameter,
The in-cylinder temperature predicted value is sequentially updated by repeatedly adding a predetermined in-cylinder temperature change amount determined according to the rotational speed and injection state of the internal combustion engine to the most recently calculated in-cylinder temperature predicted value. A fuel injection control device configured to be calculated.   The electronic control unit calculates the first predicted in-cylinder temperature value by adding a predetermined in-cylinder temperature change amount to a predetermined initial value, and uses the engine coolant temperature as the predetermined initial value. 6. The fuel injection control device according to claim 5, wherein the fuel injection control device is configured.   The electronic control unit calculates a predetermined in-cylinder temperature change amount based on a predetermined map of the in-cylinder temperature change amount for various combinations of the engine speed and the injection state, and the engine speed at the time of calculation. The fuel injection control device according to claim 6, wherein the fuel injection control device is configured to calculate based on an injection state.

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