JP3975559B2 - Accumulated fuel injection control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure accumulation type fuel injection control device for an internal combustion engine that controls injection of high pressure fuel once stored in a pressure accumulation chamber, for example, in a diesel engine.
[0002]
[Prior art]
Conventionally, in a diesel engine, for example, in a common rail unit injector, the pressure of the common rail is controlled to a target value according to the operation condition, and the fuel injection amount and the fuel injection timing according to the operation condition are calculated, and the accumulator chamber By performing valve opening control of an injector that injects fuel from the fuel, fuel injection corresponding to operating conditions is performed.
[0003]
The set value of the common rail pressure described above is generally set to be low at low speed and low load and high at high speed and high load in consideration of fuel consumption and combustion noise.
For this reason, for example, during acceleration, it is necessary to increase the common rail pressure from a low pressure to a high pressure. However, since there is a certain delay in the boost response, the injection during this period is performed in order to realize the command injection amount. Has been extended.
[0004]
[Problems to be solved by the invention]
However, in such a case, when conventional general injection start timing control is performed, a problem may occur.
For example, as shown in FIG. 9, this injection start timing control is obtained by calculating an actual injection start timing XTFIN according to the operating state such as the engine speed and taking into account the injection start response delay XTD. ) To determine the timing XTT of the injection start command from the control reference start position, and output the injector drive pulse over the injection command period XTQ corresponding to the injection amount. Incidentally, XTDE is a delay in response to injection end.
[0005]
XTT = 90 ° -XTFIN-XTD (A)
However, if the injection start timing control is performed when the acceleration changes from the steady state, for example, during acceleration, the injection start command timing XTT is the same as that in the steady state, but the injection command period XTQ is extended corresponding to the increasing injection amount. Therefore, the injection center (the center of the actual injection period) and the injection center of gravity (the center of gravity of the area of the injector injection rate) are retarded. Therefore, the combustion center of gravity (the center of gravity of the E / G in-cylinder heat generation rate area) is also retarded. As a result, there is a problem in that combustion efficiency is deteriorated, smoke is increased, and fuel consumption is deteriorated.
[0006]
Further, for example, during deceleration, the vacuum delay, similarly combustion efficiency is deteriorated, NO _X and noises is disadvantageously increased.
As a countermeasure against this, for example, a description in Japanese Patent Laid-Open No. 4-272446 has been proposed. In this technique, the difference between the command value of the common rail pressure and the actual common rail pressure is monitored, and if the difference exceeds a predetermined value, the command value of the injection timing is corrected to advance.
[0007]
However, although this technique solves the above-described problem during acceleration / deceleration, it is necessary to consider all acceleration modes and to match a predetermined value and a correction value (to determine the difference), so that the control is complicated. There has been a problem of further improvement, and further improvement has been desired.
[0008]
The present invention has been made to solve the above-described problem, and an object thereof is to provide an accumulator fuel injection control device for an internal combustion engine that improves the combustion state at the time of transition without complicating the control. .
[0009]
[Means for Solving the Problems]
(1) According to the first aspect of the present invention for achieving the above object, a high-pressure fuel stored in a pressure accumulating chamber (for example, a common rail) is controlled by an internal combustion engine (for example, a diesel engine) by controlling fuel injection means (for example, an injector). And an injection center setting means for setting an injection center between the actual injection start and the injection end of the fuel according to an operating state of the internal combustion engine. Timing setting means for setting the timing of an injection command for the fuel injection means based on the injection center set by the injection center setting means, wherein the injection center setting means is configured to operate each operating state of the internal combustion engine. injection center of the gist accumulator fuel injection control apparatus for an internal combustion engine and setting based on the operating state in the steady state of said internal combustion period That.
[0010]
As shown in FIG. 9, in the conventional injection start timing control, for example, during acceleration, if the injection command period XTQ is extended in consideration of a delay in boost response, the injection center and the injection center of gravity are retarded, The combustion center of gravity shifts and the combustion state deteriorates.
Therefore, in the present invention, the injection center between the actual start and end of fuel injection (that is, the center point between the start and end of injection) is set according to the operating state of the internal combustion engine, and based on this injection center. The timing of the injection command is set.
[0011]
That is, in the present invention, for example, as shown in FIG. 8, the injection center (target injection reference time) TFIN ′ is set, and the injection command timing such as the injection start command timing TT is set so that the injection center does not deviate. Is set. Thus, for example, even when the operating state changes from a steady state to a transient state, the injection center can be set so as not to deviate. As a result, the combustion center of gravity does not deviate and the combustion state does not deteriorate.
[0012]
Thus, for example, during acceleration, even if the injection period becomes longer, the combustion efficiency does not deteriorate, the generation of smoke can be suppressed, and the deterioration of fuel consumption can be prevented. Further, for example, during deceleration, even when short injection period, similarly combustion efficiency without deteriorated, it is possible to prevent an increase of the NO _X and noises.
[0013]
Moreover, if the control is based on the injection center as in the present invention, the timing of fuel injection can be set appropriately in any operating state, so all acceleration modes are studied as in the past. Thus, there is an advantage that the matching between the predetermined value and the correction value performed in this way becomes unnecessary, and the control can be simplified.
[0015]
Moreover, the present invention makes the injection centers in the current operating state (for example, transient state) of the internal combustion engine coincide with each other based on the operating state in the steady state of the internal combustion period, for example. In the transient state, the cause of smoke or deterioration of fuel consumption is that the center of combustion shifts due to the shift of the center of gravity of the injection. Therefore, in the present invention, the center of injection (and hence the center of injection) is prevented from shifting. .
[0016]
In other words, since the combustion state in the steady state is considered to be almost constant, the injection center in the steady state is grasped in advance by experiments, etc., and the injection center is used even in a transient state such as during acceleration. The shift of the center of gravity can be prevented, and deterioration of the combustion state can be prevented.
[0017]
( 2 ) In the invention according to claim 2 , the injection center setting means adjusts the timing of the injection command so that the injection center in the transient state of the internal combustion engine and the injection center in the steady state of the internal combustion period coincide with each other. and gist accumulator fuel injection control apparatus for an internal combustion engine according to claim 1, characterized in that.
[0018]
The present invention exemplifies the invention of claim 1 , and here, the timing of the injection command is adjusted so that the injection center in the transient state coincides with the injection center in the steady state. As a result, the injection center (and hence the injection center of gravity) does not deviate during steady state, acceleration, deceleration, etc., so that the combustion center of gravity does not deviate, and the combustion state can always be kept in a suitable state.
[0019]
( 3 ) In the invention of claim 3 , the timing setting means includes the injection center, an injection command period corresponding to the fuel injection amount, an injection start response delay (deviation between the injection start command and the actual injection start), and based on the injection end response delay (deviation between the actual injection end and the injection end command), the internal combustion engine according to any of the claims 1 or 2, characterized in that to set the timing of injection start instruction The gist of the pressure accumulation type fuel injection control device.
[0020]
The present invention exemplifies the invention of the first or second aspect . For example, the following equation (B) is used to determine the injection center TFIN ′, the injection command period TQ, the injection start response delay TD, and the injection end response delay TDE. Based on this, the timing TT of the injection start command is set. 90 ° indicates a control reference position 90 ° before the top dead center (see FIG. 8).
[0021]
TT = 90 ° −TFIN ′ − (TQ + TDE−TD) / 2−TD (B)
That is, by using each of the above values, the injection command timing is adjusted so that the injection center is not changed, but the same injection center is obtained. Thereby, the deterioration of the combustion state at the time of transition can be prevented.
[0022]
(4) The invention according to claim 4, wherein the timing setting means, timing and the injection start command, on the basis of said injection command period, claim 3, characterized in that to set the timing of the injection end command The pressure accumulation type fuel injection control device for an internal combustion engine as described in 1 above.
[0023]
The present invention exemplifies the invention of claim 3 , and here, the timing of the injection end command is set based on the timing of the injection start command and the injection command period of how long the injection is continued. Yes. Thereby, an injection command can be performed reliably.
( 5 ) The invention of claim 5 is a pressure accumulating chamber for temporarily storing fuel to be supplied to the internal combustion engine in a high pressure state, a fuel pumping means (for example, a pump) for pumping fuel to the pressure accumulating chamber, Pressure detection means (for example, a pressure sensor) for detecting fuel pressure, operation state detection means (for example, a rotational speed sensor or an accelerator sensor) for detecting the operation state of the internal combustion engine, and an operation state detected by the operation state detection means The target pressure calculating means for calculating the target value of the fuel pressure in the pressure accumulating chamber based on the pressure, the target value and the detected value by the pressure detecting means are compared, and the fuel pressure in the pressure accumulating chamber is used as the target value. The fuel injection amount calculation for calculating the target fuel injection amount to the internal combustion engine on the basis of the feedback control means for controlling the drive of the fuel pumping means and the operation condition detected by the operation condition detection means And stage, on the basis of the target fuel injection amount issued the calculated, of the claims 1-4, characterized in that the high-pressure fuel stored in the accumulator chamber and a fuel injection means for injecting into the internal combustion engine The gist of the accumulator fuel injection control device for an internal combustion engine according to any one of the above.
[0024]
The present invention exemplifies a device configuration for performing control by the control device according to claims 1 to 4 described above. Thereby, for example, in a diesel engine, the fuel pressure in the pressure accumulating chamber can be maintained at a desired value, and the target fuel injection amount can be injected and supplied to the internal combustion engine.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example (example) of an embodiment of an accumulator fuel injection control device for an internal combustion engine of the present invention will be described.
[Example]
a) First, a hardware configuration of a common rail fuel injection control device in a diesel engine according to an embodiment of the present invention will be described.
[0026]
FIG. 1 is an explanatory diagram of a configuration of a common rail fuel injection control device including a variable discharge high pressure pump.
The common rail fuel injection control device 1 includes a six-cylinder diesel engine 2, an injector 3 that injects fuel into each cylinder of the diesel engine 2, a common rail 4 that accumulates high-pressure fuel supplied to the injector 3, and a common rail 4. Are provided with a variable discharge high pressure pump 5 for pumping high pressure fuel and an electronic control unit (ECU) 6 for controlling them.
[0027]
The ECU 6 takes in operating conditions such as the state of the diesel engine 2, for example, the detected value of the rotational speed sensor 7 (engine rotational speed Ne) and the detected value of the accelerator sensor 8 (accelerator opening degree Ac), and the combustion state of the diesel engine 2 is determined. A target common rail pressure for realizing an optimal fuel injection pressure is calculated, and the actual common rail pressure (Pc) is maintained at the target common rail pressure based on the detection value of the common rail pressure sensor 9 provided on the common rail 4. The common rail pressure feedback control for driving and controlling the variable discharge high pressure pump 5 is performed.
[0028]
The variable discharge high-pressure pump 5 sucks the fuel stored in the fuel tank 10 through the low-pressure supply pump 11 in accordance with the control command from the ECU 6 and pressurizes the fuel into a high pressure inside itself. Fuel is pumped to the common rail 4 through the supply pipe 12.
[0029]
Each injector 3 is connected by a pipe 13 to a common rail 4 that accumulates high-pressure fuel. Then, by opening and closing the control valve 14 disposed in each injector 3, high-pressure fuel accumulated in the common rail 4 to become the target common rail pressure is injected into the combustion chamber of each cylinder of the diesel engine 2. The
[0030]
The opening / closing operation of the control valve 14 of the injector 3 is executed based on an injector control command (injector drive pulse) from the ECU 6. The injector control command is for adjusting the fuel injection amount and the fuel injection timing, and is calculated based on the detected value from the operating condition detecting means such as the rotational speed sensor 7 and the accelerator sensor 8, and the crank angle sensor 15. And output from the ECU 6 at a predetermined timing based on detection values of the cylinder discrimination sensor 16 and the like.
[0031]
b) Next, the control processing of the present embodiment will be described based on the flowchart of FIG. 2 and the graphs of FIGS.
In step 100 of FIG. 2, the engine speed Ne is detected based on the signal from the speed sensor 7.
[0032]
In the subsequent step 110, the accelerator opening degree Ac is detected based on the signal from the accelerator sensor 8.
In the following step 120, the common rail pressure Pc is detected based on the signal from the common rail pressure sensor 9.
[0033]
In the following step 130, a fuel injection amount (target fuel injection amount) QFIN corresponding to an operating state such as acceleration or deceleration is obtained from the engine speed Ne and the accelerator opening degree Ac using the map shown in FIG.
In the following step 140, a target injection reference time TFIN ′ corresponding to the injection center is obtained from the engine speed Ne and the target fuel injection amount QFIN using the map shown in FIG.
[0034]
In this embodiment, since the injection center in the steady state and the injection center in the transient state are made coincident with each other, the target injection reference timing (injection center) TFIN in the steady state is obtained by an experiment or the like in advance as in the map of FIG. If this is the case, it can be used as the target injection reference timing TFIN ′, which is the injection center at the time of transition.
[0035]
In the subsequent step 150, an injection command period TQ that is an ON period of the injector drive pulse is obtained from the common rail pressure Pc and the target injection amount QFIN using the map shown in FIG.
Therefore, in the steady state, the injection command period TQ indicated by the solid line in FIG. 8 is obtained. For example, during the acceleration, the injection command period TQk indicated by the broken line in FIG. 8 is obtained. TQ is a concept including TQk.
[0036]
In the following step 160, the injection start response delay TD is obtained from the common rail pressure Pc using the map shown in FIG. This injection start response delay TD is a delay time from when the injector drive pulse is turned on until when fuel is actually injected from the injector 3.
[0037]
In the following step 170, an injection end response delay TDE is obtained from the common rail pressure Pc and the injection command period TQ using the map shown in FIG. The injection end response delay TDE is a delay time from when the injector drive pulse is turned off until the actual fuel injection is ended.
[0038]
In the following step 180, the following equation (1) is used to determine the injection time from the control reference position (BTDC 90 ° CR), that is, the control reference position 90 ° before the crank angle top dead center until the injector drive pulse is turned on. A start command period TT is calculated.
TT = 90 ° −TFIN ′ − (TQ + TDE−TD) / 2−TD (1)
That is, since (TQ + TDE−TD) / 2 is a period TJ from the start of injection to the injection center (accordingly, the injection center of gravity) as shown in FIG. 8, the target injection reference timing (injection center) TFIN ′ from 90 °. The injection start command period TT can be obtained by subtracting the period TJ to the injection center and the injection start response delay TD.
[0039]
Therefore, in the steady state, the injection start command period TT shown by the solid line in FIG. 8 is obtained. For example, during acceleration, the injection start command period TTk shown by the broken line in the same figure is obtained. Note that TT is a concept including TTk.
In the following step 190, the injection end command period TTE, which is the time from the control reference position to the OFF of the injector drive pulse, is calculated using the injection start command period TT and the injection command period TQ in the following equation (2).
[0040]
TTE = TT + TQ (2)
In the following step 200, an injector drive pulse is output to the injector 3 at the corresponding crank angle based on the injection start command period TT and the injection end command period TTE obtained by the above-described processing.
[0041]
Specifically, the injector drive pulse is turned on in the injection start command period TT to start fuel injection, and the injector drive pulse is turned off in the injection end command period TTE to end fuel injection. finish.
c) Next, the state of injection by the control of this embodiment described above will be described in comparison with the prior art based on the timing charts of FIGS. In FIGS. 8 and 9, the solid line indicates the steady state (high pressure, high load), and the broken line indicates the transient acceleration (low pressure, high load).
[0042]
As shown in FIG. 9, in the conventional injection start timing control, the injection start command period XTT is set based on the equation (A). For example, when the fuel is increased during acceleration, the injection start command period XTT is changed. Instead, the injection command period TQ is increased to cope with the increase in fuel. However, this causes a shift in the center of gravity of the injection, which may deteriorate the combustion state.
[0043]
On the other hand, in this embodiment, as shown in FIG. 8, the timing of the injector drive pulse is set so that the injection center does not deviate both in the steady state and in the transient state.
That is, in the present embodiment, first, a map is created by previously obtaining the operation state such as the engine speed Ne and the target injection reference time TFIN that is the actual injection center from the data in the steady state. Then, for example, during acceleration, by using a method of matching the target injection reference time TFIN ′ at acceleration and the target injection reference time TFIN ′ at steady state, the target injection reference at the time of transient is obtained using the steady state map. The position TFIN ′ is obtained. Next, the ON / OFF timing of the injector drive pulse is adjusted so that the actual fuel injection state during acceleration is the target injection reference timing (ie, injection center) TFIN ′.
[0044]
That is, at the time of acceleration, as shown by the broken line in FIG. 8, the injection command start timing TTk and the injection command period TQk are calculated and the injector 3 is driven.
As a result, the injection center (and hence the injection center of gravity) does not deviate during steady state and during transition, so that the combustion center of gravity of the engine (E / G) in-cylinder heat generation rate in FIG.
[0045]
Therefore, for example, during acceleration, even if the injection period becomes longer, the combustion efficiency does not deteriorate, the generation of smoke can be suppressed, and the deterioration of fuel consumption can be prevented. Further, for example, during deceleration, even when short injection period, similarly combustion efficiency without deteriorated, it is possible to prevent an increase of the NO _X and noises.
[0046]
In addition, if the control is performed based on the injection center as in the present embodiment, it is possible to suitably cope with any operating state. There is an advantage that matching of correction values is not required and control can be simplified.
[0047]
As mentioned above, although the Example of this invention was described, this invention is not limited to this, The various aspect within the range which does not deviate from the summary can be employ | adopted.
(1) In the above-described embodiment, the positions of the injection center and the injection gravity center coincide with each other.
[0048]
(2) Further, the map for obtaining the injection center is the same in the steady state and the transient state. For example, a plurality of maps are distinguished depending on the operating state by distinguishing between steady state, acceleration and deceleration. (However, not so many) may be used to set the injection center. In this case, the injection center is slightly different depending on the operating state.
[0049]
(3) For example, in the above-described embodiment, the accumulator fuel injection control device has been described. However, the present invention is not limited thereto, and can also be applied to a recording medium storing means for executing the above-described control.
Examples of the recording medium include various recording media such as an electronic control device configured as a microcomputer, a microchip, a floppy disk, a hard disk, and an optical disk.
[0050]
That is, there is no particular limitation as long as it stores a means such as a program that can execute the control of the vehicle control device described above.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating a system according to an embodiment.
FIG. 2 is a flowchart illustrating a control process performed by an ECU in the embodiment.
FIG. 3 is a graph showing a relationship between a target fuel injection amount and an engine speed.
FIG. 4 is a graph showing the relationship between target injection reference timing and engine speed.
FIG. 5 is a graph showing a relationship between an injection command period and a common rail pressure.
FIG. 6 is a graph showing a relationship between an injection start response delay and a common rail pressure.
FIG. 7 is a graph showing a relationship between an injection end response delay and a common rail pressure.
FIG. 8 is a timing chart showing an operation by control of the embodiment.
FIG. 9 is a timing chart showing the operation by the control of the prior art.
[Explanation of symbols]
1 ... Common rail type fuel injection control device,
2 ... Diesel engine,
3 ... Injector,
4 ... Common rail,
5 ... Variable discharge high pressure pump,
6 ... Electronic control unit (ECU),
7 ... Rotational speed sensor,
8 ... accelerator sensor,
9: Common rail pressure sensor,
10 ... Fuel tank,
11 ... Low pressure supply pump,
12 ... supply piping,
13 ... Piping,
14 ... Control valve,
15 ... Crank angle sensor,
16 ... Cylinder discrimination sensor

Claims (5)

In the accumulator fuel injection control device for an internal combustion engine that supplies the high-pressure fuel stored in the accumulator chamber to the internal combustion engine by controlling the fuel injection means.
Injection center setting means for setting the injection center between the actual injection start and the end of injection of the fuel according to the operating state of the internal combustion engine;
Timing setting means for setting the timing of an injection command to the fuel injection means based on the injection center set by the injection center setting means;
Equipped with a,
The injection center setting means sets an injection center in each operation state of the internal combustion engine based on an operation state in a steady state of the internal combustion period;
An accumulator fuel injection control device for an internal combustion engine. The ejection central setting means, an injection center in the transient state of the internal combustion engine, so as to match the injection center in the steady state of said internal combustion period, the claim 1, wherein adjusting the timing of the injection command 2. An accumulator fuel injection control device for an internal combustion engine according to 1. The timing setting means sets the timing of the injection start command based on the injection center, an injection command period corresponding to the fuel injection amount, an injection start response delay, and an injection end response delay. 3. An accumulator fuel injection control device for an internal combustion engine according to claim 1 or 2 . The pressure accumulation type fuel injection for an internal combustion engine according to claim 3 , wherein the timing setting means sets the timing of the injection end command based on the timing of the injection start command and the injection command period. Control device. A pressure accumulation chamber for temporarily storing fuel to be supplied to the internal combustion engine in a high pressure state;
Fuel pumping means for pumping fuel to the pressure accumulation chamber;
Pressure detecting means for detecting fuel pressure in the pressure accumulating chamber;
An operating state detecting means for detecting an operating state of the internal combustion engine;
Target pressure calculating means for calculating a target value of the fuel pressure in the pressure accumulating chamber based on the operating condition detected by the operating condition detecting means;
A feedback control means for comparing the target value with a value detected by the pressure detection means, and driving and controlling the fuel pressure sending means so that the fuel pressure in the pressure accumulating chamber becomes the target value;
Fuel injection amount calculating means for calculating a target fuel injection amount to the internal combustion engine based on the operating condition detected by the operating condition detecting means;
The calculated on the basis of the target fuel injection amount issued, to any of the preceding claims 1-4, characterized in that the high-pressure fuel stored in the accumulator chamber and a fuel injection means for injecting into the internal combustion engine An accumulator fuel injection control device for an internal combustion engine as described.

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