JP2008180111A - Fuel injection control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a decompression property at a cold fuel temperature, and to improve a low noise characteristic. <P>SOLUTION: When it is determined that the fuel temperature is set at a predetermined temperature situation giving damage to an injection system, moderating injection is executed by increasing a moderating amount in moderating control of decelerating injection (S302, S304), and when it is determined that the fuel temperature is set at a predetermined temperature situation causing deterioration of combustion noise, moderating injection is executed by increasing a moderating amount in moderating control of decelerating injection (S306, S308), whereby a decompression property at a low temperature of the fuel temperature can be improved, and a low noise characteristic can be improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to an improvement in rail pressure reduction characteristics and the like in a common rail fuel injection control device.

  As a fuel injection control device for an internal combustion engine such as a diesel engine, the fuel is pressurized by a high-pressure pump, and is pumped and stored in a common rail that is an accumulator, and the accumulated high-pressure fuel is supplied to the injector. The common rail fuel injection control system that enables the injection of high-pressure fuel is known for its excellent fuel efficiency and emission characteristics. Various configurations are proposed and put to practical use to further improve operating characteristics (See, for example, Patent Document 1).

JP 2000-192843 A (page 5-12, FIG. 1 to FIG. 13)

By the way, it has been known that the viscosity increases as the fuel temperature decreases. However, in the common rail fuel injection control device, the rail pressure reduction performance decreases due to the increase in the fuel viscosity. For this reason, in the injection control similar to the normal temperature, the rail pressure may exceed the normal value in some cases, and there is a possibility that the injection system may be seriously damaged.
Further, when the fuel temperature is lowered and the decompression performance is lowered as described above, when fuel is injected from the deceleration state, that is, the non-injection state, the rail pressure is higher than the normal temperature due to the residual pressure in the rail. For this reason, the combustion noise becomes loud, which may lead to a deterioration in low noise characteristics.

  The present invention has been made in view of the above circumstances, and provides a fuel injection control method and apparatus capable of improving low-noise characteristics as well as improving the decompression performance when the fuel temperature is low.

In order to achieve the above object of the present invention, a fuel injection control method according to the present invention comprises:
A fuel injection control method in a fuel injection control device configured to perform smooth injection that gradually performs fuel injection over time at a normal temperature deceleration,
When it is determined that the fuel temperature is in a predetermined temperature state that damages the injection system, the smoothing injection is performed by increasing the amount of annealing.
Further, in order to achieve the object of the present invention, a fuel injection control method in a fuel injection control device configured to perform smooth injection that gradually performs fuel injection over time at the time of normal temperature deceleration,
A configuration in which the smoothing injection is performed by increasing the smoothing amount when it is determined that the fuel temperature is in a predetermined temperature state that causes deterioration of combustion noise is also preferable.
In order to achieve the above object, a fuel injection control device according to the present invention includes:
In addition to having a plurality of fuel injection valves, it has an electronic control unit that controls the operation of the fuel injection valves, and is configured to be able to perform a smooth injection that gradually performs fuel injection over time when decelerating at normal temperature. A fuel injection control device comprising:
The electronic control unit is configured to perform the smoothed injection by increasing the smoothing amount when it is determined that the fuel temperature is in a predetermined temperature state that damages the injection system.
Furthermore, in order to achieve the object of the present invention, the apparatus has a plurality of fuel injection valves and an electronic control unit for controlling the operation of the fuel injection valves, and at the time of normal temperature deceleration, the fuel injection is gradually performed over time. A fuel injection control device configured to be able to perform the smooth injection,
It is also preferable that the electronic control unit is configured to perform the smoothing injection by increasing the smoothing amount when it is determined that the fuel temperature is in a predetermined temperature state that causes deterioration of combustion noise.

  According to the present invention, the deterioration of the depressurization property of the rail pressure due to the fuel temperature is surely suppressed, so that the rail pressure exceeds an appropriate value due to the decrease in the fuel temperature, and the pressure resistance of the components of the fuel injection device is threatened. In addition, it is possible to reliably prevent an increase in combustion noise due to deterioration in decompression performance, and to provide a fuel injection control device with high safety and reliability and low noise. There is an effect.

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 performs smoothing injection control, 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. Better jetting.

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 subroutine flowchart showing the procedure of the fuel injection control process executed by the electronic control unit 11. Hereinafter, the fuel injection control process in the embodiment of the present invention will be described with reference to FIG. explain.
When processing is started by the electronic control unit 11, first, various signals (engine state signals) representing the operation state of the diesel engine 1, that is, the engine speed, the engine coolant temperature, the accelerator opening degree, and the outside air temperature. Are input to a predetermined storage area in the electronic control unit 11 and temporarily stored (see step S100 in FIG. 2).

Next, based on these engine state signals, the required target fuel injection amount is calculated based on a predetermined arithmetic expression (see step S200 in FIG. 2).
Further, the amount of smoothing in the smoothing control performed during deceleration is calculated.
Here, the annealing control refers to a process of slowing a sudden increase in the fuel injection amount or a sudden decrease in the fuel injection amount when the vehicle is suddenly accelerated or decelerated.
The embodiment of the present invention is an example of smoothing control during deceleration, but normally smoothing control is similarly performed during acceleration to prevent occurrence of surging during sudden acceleration.
Next, in step S400, fuel injection with annealing control is performed.

FIG. 3 shows a subroutine flowchart showing a more specific processing procedure of the above-described deceleration injection amount smoothing amount calculation (see step S300 in FIG. 2), and the contents thereof will be described below with reference to FIG. explain.
When the process is started, it is determined whether or not the fuel temperature is in a predetermined temperature state that damages the injection system (see step S302 in FIG. 3).

  Here, the damage caused by the fuel temperature on the injection system specifically refers to the situation described below. That is, when the fuel temperature is lowered, the viscosity of the fuel is increased, thereby reducing the rail pressure reduction property. For this reason, in the injection control similar to the normal temperature, the rail pressure may exceed the normal value in some cases and exceed the pressure resistance of each component constituting the fuel injection control device, leading to mechanical fatigue and the like. When such a state is left unattended, an accident such as breakage of parts occurs at the worst. The damage caused by the fuel temperature on the injection system means such a situation.

  The predetermined temperature state means a case where the fuel temperature is in a temperature or a temperature range that may cause the above situation. Such a temperature or temperature range is preferably set based on experiments, simulation results, and the like. In addition, as a standard of predetermined temperature, it is about -10 degreeC.

If it is determined in step S302 that the fuel temperature is not in a predetermined temperature condition that damages the injection system (in the case of NO), the process proceeds to step S306 described later, while the fuel temperature is When it is determined that the temperature is in a predetermined temperature state that damages the engine (in the case of YES), an increase calculation of the smoothing amount with respect to the deceleration injection amount is performed.
That is, in a state where it is determined that the fuel temperature is equal to or lower than a predetermined temperature that causes damage to the injection system, or is in a predetermined temperature range, the rail pressure can be reduced by the smoothing amount when the fuel temperature is not in such a state. Since it deteriorates, an annealing amount that takes into account a predetermined increase amount is obtained based on a predetermined arithmetic expression, a map, etc. (see step S304 in FIG. 3).

  Here, the annealing amount will be described. First, as described above, the annealing control is performed by suddenly increasing the fuel injection amount or rapidly decreasing the fuel injection amount when the vehicle suddenly accelerates or decelerates. Is a process of slowing down, and it is “annealing” to slow down the sudden increase in fuel injection amount or the sudden decrease in fuel injection amount. Therefore, when the “annealing” is large, in other words, “the amount of annealing” is large, the rapid increase in the fuel injection amount or the decrease in the rapid fuel injection amount is slow. Is larger. That is, if the slowness is large, it can be expressed numerically that the change amount of the fuel injection amount in two consecutive times is smaller.

Therefore, the greater the annealing, that is, the greater the amount of annealing, the smaller the annealing coefficient, if the numerical value, that is, for convenience, is referred to as an “annealing coefficient”.
Therefore, in step S304, to increase the amount of annealing compared to the normal time is to make the change amount of the fuel injection amount slower than the normal time. The better factor is to make it smaller.

Next, in step 306, it is determined whether or not the fuel temperature is in a predetermined temperature state that causes deterioration of combustion noise.
Here, the deterioration of the combustion temperature due to the fuel temperature means that if the rail pressure is reduced due to a decrease in the fuel temperature, as described above, when the fuel is injected from the deceleration state, that is, the non-injection state, the common rail 3 means a phenomenon in which the rail pressure becomes higher than normal temperature due to the residual pressure in 3, and combustion noise becomes louder.

  The predetermined temperature state means a case where the fuel temperature is in a temperature or a temperature range that may cause the above situation. Such a temperature or temperature range is preferably set based on experiments, simulation results, and the like. The standard of the predetermined temperature is about + 20 ° C., and generally, the rail pressure tends to exhibit a decompression property that makes the combustion noise worse when the fuel temperature is lower than this.

  In step S306, if it is determined that the fuel temperature is not within the predetermined temperature or temperature range that causes the combustion noise to deteriorate (in the case of NO), the fuel temperature is reduced as the smoothing amount with respect to the deceleration injection amount. Thus, the normal amount of annealing is calculated without considering the deterioration of the decompression property due to the above, the increase in the combustion temperature, etc. (see step S310 in FIG. 3).

  On the other hand, when it is determined in step S306 that the fuel temperature is in a predetermined temperature state that causes deterioration of combustion noise, that is, in the predetermined temperature or temperature range (in the case of YES), the deceleration injection amount The calculation for increasing the amount of annealing is performed (see step S308 in FIG. 3).

That is, in a state where it is determined that the fuel temperature is equal to or lower than a predetermined temperature that causes deterioration of the combustion temperature, or within a predetermined temperature range, the combustion temperature becomes larger with the amount of annealing when the fuel temperature is not in such a state. Therefore, an amount of annealing that takes into account a predetermined increase amount is obtained based on a predetermined arithmetic expression, a map, and the like.
Note that the map used for calculating the increase in the smoothing amount in the previous step S304 and the map used for calculating the increase in the smoothing amount in step S308 have different fuel temperature conditions for calculation. Therefore, for example, separate maps such as an increase value map for protecting the injection system and an increase value map for reducing combustion noise are prepared. In FIG. 3, in order to indicate that the increase values in steps S304 and S308 are different as described above, the numbers “1” and “2” are shown as subscripts after the phrase “increase value”. .
Then, after the processing of step S308 or step S310, the process returns to the subroutine shown in FIG.

As described above, in the embodiment of the present invention, when it is determined that the fuel temperature is in a predetermined temperature state that causes deterioration of the deceleration performance or increase in combustion noise, the normal smoothing amount is further increased. Thus, by performing the annealing injection, such a situation can be avoided as described below with reference to FIGS. 4 and 5.
First, in FIG. 4, when the accelerator pedal is released for deceleration from an acceleration state where an accelerator pedal (not shown) is depressed, a control signal generated in the electronic control unit 11 correspondingly, that is, The signal corresponding to the change in the required injection amount is indicated by a solid line, and the change in the target injected fuel when the normal smoothing injection is performed at that time is schematically indicated by the dotted line, and the increase in the smoothing amount is The change of the target injected fuel when the smoothed injection is performed is schematically shown by a one-dot chain line.
In FIG. 4, the horizontal direction represents the passage of time, and the vertical direction represents the target fuel injection amount Q.

Further, in FIG. 5, the control signal generated in the same electronic control unit 11 as shown in FIG. 4 is represented by a solid line, and at that time, the normal injection by the normal annealing amount is at a low temperature. An example of the change in the target rail pressure when it is performed is indicated by a dotted line, and the change in the target rail pressure when the smoothing injection is performed at a low temperature when the smoothing amount is increased is indicated by a one-dot chain line. ing.
In the figure, the horizontal direction represents the passage of time, and the vertical direction represents the target rail pressure P.

  Under such a premise, first, for example, assuming that the accelerator pedal depression is released for deceleration from a state where an accelerator pedal (not shown) is depressed, the electronic control unit 11 in FIG. As indicated by the solid line, a control signal that immediately makes the required injection amount zero is generated and used for triggering injection control.

In the case where the fuel temperature is not in a predetermined temperature state that causes deterioration of the depressurization property of the rail pressure, or in the case where the fuel temperature is not in a predetermined temperature state that causes deterioration in combustion noise, that is, at normal temperature, FIG. When the fuel injection amount request signal corresponding to the operation of the accelerator pedal as shown by the solid line is generated, the control signal is generated almost simultaneously up to a predetermined target injection amount Q1 at once. The fuel injection is performed.
After reaching the target fuel injection amount Q1, the remaining fuel is gradually injected (smoothed injection) with a normal smoothing amount (see step S310 in FIG. 3) (see dotted line in FIG. 4). ).

  On the other hand, when the fuel temperature is in a predetermined temperature state that causes deterioration of the depressurization property of the rail pressure, or when the fuel temperature is in a predetermined temperature state that causes deterioration of the combustion noise, first, the control signal Almost simultaneously with the occurrence of the above, the injection is normally performed almost at once without smoothing injection to a predetermined target injection amount Q2 (Q2> Q1). Then, after reaching the target fuel injection amount Q2, the smoothing injection (see step S308 in FIG. 3) with a larger smoothing amount than that in the normal time is performed (see the dashed line in FIG. 4). In other words, the fuel consumption is further increased as compared with the case where the normal injection is performed.

Therefore, when fuel injection ends when the amount of smoothing is increased (see steps S304 and S308 in FIG. 3), fuel injection ends at the normal amount of smoothing (see step S310 in FIG. 3). In comparison, it will be later (see FIG. 4). That is, in FIG. 4, ts> tn.
As a result, the change in the target rail pressure when the smoothing injection is performed with a normal smoothing amount during deceleration when the fuel temperature has decreased to a level that reduces the rail pressure depressurization performance, sometimes overshoots during deceleration. In contrast to the gradual decrease with the chute (see the characteristic line of the dotted line in FIG. 5), when the smoothing injection is performed with the increased smoothing amount, the target rail pressure is Then, it gradually decreases in a state of lowering compared with the case of the normal injection with the normal annealing amount (see the characteristic line of the one-dot chain line in FIG. 5).
In the example of FIG. 5, the upper limit value of the rail pressure is, for example, about 160 MPa (1600 bar), and the lower limit rail pressure is a target rail pressure corresponding to idle operation, and specifically, about 30 MPa. It is.

  Therefore, the rail pressure reduction performance is improved compared to the normal smoothing injection, and the rail pressure is suppressed from being high enough to damage the injection system when the fuel temperature is low. As a result, the increase in combustion noise at low temperatures is suppressed and the low noise characteristics are improved.

In the embodiment of the present invention, one characteristic line is shown as a characteristic line of fuel injection accompanied by an increase in the smoothing amount as shown by a one-dot chain line in FIG. Needless to say, the control is not limited to the annealing control along one characteristic line. For example, it is of course possible to select from a plurality of fuel injection characteristic lines so that the degree of increase in the smoothing amount can be changed according to the fuel temperature. In this case, increase the amount of smoothing to avoid damage to the injection system and increase the amount of smoothing to avoid deterioration of combustion noise when fuel injection is performed by increasing the amount of smoothing. It is preferable to set the fuel injection characteristic line separately when performing fuel injection.
In this case, in a state where the fuel temperature is low enough to cause damage to the injection system, as the fuel temperature decreases, the characteristics of the fuel injection with the smoothed injection corresponding to each temperature are reduced. A plurality of lines exist on the right side of the alternate long and short dash line in FIG. This also applies to the fuel injection characteristic line when the fuel injection is performed by increasing the smoothing amount in order to avoid the deterioration of the combustion noise.

It is a block diagram which shows the structural example of the fuel-injection control apparatus in embodiment of this invention. 3 is a subroutine flowchart showing an overall procedure of fuel injection control processing in the fuel injection control device shown in FIG. 1. 3 is a subroutine flowchart showing a more specific procedure of a deceleration injection amount smoothing amount calculation process shown in the flowchart of FIG. 2. It is explanatory drawing explaining the smoothing injection operation | movement in embodiment of this invention, Comprising: When depression of an accelerator pedal is cancelled | released for the deceleration from the acceleration state where the accelerator pedal was stepped on, it respond | corresponds to electronic FIG. 5 is an explanatory diagram schematically showing changes in injected fuel in fuel injection with normal smoothing injection and changes in injected fuel in fuel injection with increase in smoothing amount, along with control signals generated in the control unit. is there. It is explanatory drawing explaining the change of the rail pressure at the time of the smooth injection in embodiment of this invention, Comprising: The depression of the accelerator pedal is released for deceleration from the acceleration state where the accelerator pedal was stepped on. The change in rail pressure in fuel injection with normal smoothing injection and the change in rail pressure in fuel injection with increase in smoothing amount together with the corresponding control signal generated in the electronic control unit It is explanatory drawing which showed typically.

Explanation of symbols

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 (8)

A fuel injection control method in a fuel injection control device configured to perform smooth injection that gradually performs fuel injection over time at a normal temperature deceleration,
A fuel injection control method, characterized in that, when it is determined that the fuel temperature is in a predetermined temperature state that damages the injection system, the smoothing injection is performed by increasing the amount of annealing.   The fuel injection control method according to claim 1, wherein when it is determined that the fuel temperature is in a predetermined temperature state that causes deterioration of combustion noise, the smoothing injection is performed by increasing the smoothing amount. A fuel injection control method in a fuel injection control device configured to perform smooth injection that gradually performs fuel injection over time at a normal temperature deceleration,
A fuel injection control method comprising performing a smoothing injection by increasing a smoothing amount when it is determined that the fuel temperature is in a predetermined temperature state that causes deterioration of combustion noise.   The fuel injection control method according to any one of claims 1 to 3, wherein the predetermined temperature condition is a state in which the fuel temperature is equal to or lower than a predetermined temperature or falls to a predetermined temperature range. In addition to having a plurality of fuel injection valves, it has an electronic control unit that controls the operation of the fuel injection valves, and is configured to be able to perform a smooth injection that gradually performs fuel injection over time when decelerating at normal temperature. A fuel injection control device comprising:
The electronic control unit is configured to perform the smoothing injection by increasing the smoothing amount when it is determined that the fuel temperature is in a predetermined temperature state that damages the injection system. Injection control device.   The electronic control unit is configured to perform a smoothing injection by increasing a smoothing amount when it is determined that the fuel temperature is in a predetermined temperature state that causes deterioration of combustion noise. 5. The fuel injection control device according to 5. In addition to having a plurality of fuel injection valves, it has an electronic control unit that controls the operation of the fuel injection valves, and is configured to be able to perform a smooth injection that gradually performs fuel injection over time when decelerating at normal temperature. A fuel injection control device comprising:
The electronic control unit is configured to perform a smoothing injection by increasing a smoothing amount when it is determined that the fuel temperature is in a predetermined temperature state that causes deterioration of combustion noise. Injection control device.   The fuel injection control device according to any one of claims 5 to 7, wherein the predetermined temperature state is a state in which the fuel temperature is equal to or lower than a predetermined temperature or a predetermined temperature range.

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