JP4532532B2 - Fuel injection control device and fuel injection system - Google Patents

Description

  The present invention relates to a fuel injection control device that detects a difference between an actual injection amount from a fuel injection valve and a command injection amount and sets an injection amount correction value, and a fuel injection system using the same.

Conventionally, in a diesel engine for a vehicle, pilot injection that performs a very small amount of fuel injection prior to main injection has been performed in order to reduce combustion noise, suppress NOx, and the like.
In this pilot injection, if there is a difference between the fuel injection amount from the fuel injection valve and the command injection amount, there is a problem that the fuel injection accuracy is remarkably lowered and the effect cannot be fully exhibited.

  Therefore, conventionally, for example, during deceleration operation in which the fuel injection amount to the diesel engine becomes zero, the fuel injection valve performs a single fuel injection, and the actual injection from the rotational fluctuation amount of the diesel engine caused by the single injection. It has been proposed to perform fuel injection amount learning control for each cylinder in a procedure that estimates the amount and sets the injection amount correction value based on the difference between the estimated actual injection amount and the command injection amount. (See, for example, Patent Document 1).

In other words, in the proposed learning control, the generated torque generated in the diesel engine by the fuel injection is obtained by multiplying the rotation fluctuation amount generated by the single fuel injection and the engine speed at that time. And in the diesel engine, since the generated torque is proportional to the fuel injection amount from the fuel injection valve, the actual injection amount is estimated from this generated torque, and the deviation between the estimated actual injection amount and the command injection amount is This is set as an injection amount correction value when fuel is supplied to the cylinder.
JP 2005-36788 A

Incidentally, since the fuel injection amount from the fuel injection valve changes in accordance with the fuel injection pressure, it is desirable to execute the learning control as described above for each fuel injection pressure.
For this purpose, when executing the learning control, the learning injection pressure for executing the learning control is set, the fuel injection pressure is controlled to the learning injection pressure, and then the learning control is performed. By executing this, an injection amount correction value may be calculated for each fuel injection pressure.

  However, if the fuel injection pressure is controlled to the learning injection pressure each time the learning control is executed in this way, the fuel injection pressure at the time of learning (learning injection pressure) is the normal injection that does not perform the learning control. It is conceivable that the fuel injection pressure cannot be sufficiently reduced when the learning control is terminated and the normal injection is restarted because the fuel injection pressure becomes too high compared to the current fuel injection pressure.

When normal injection is resumed in a state where the fuel injection pressure is not sufficiently reduced, the operating state such as combustion noise and vibration of the internal combustion engine changes greatly, giving the driver a sense of incongruity.
Also, if the learning injection pressure becomes too high compared to the fuel injection pressure during normal injection, the operation state such as combustion noise and vibration of the internal combustion engine will change greatly even during execution of learning control. In addition, it is possible to give the driver a sense of incongruity.

  The present invention has been made in view of such problems, and learning control for detecting a deviation between the actual injection amount from the fuel injection valve and the command injection amount and setting an injection amount correction value makes the driver, etc. feel uncomfortable. It aims at providing the fuel-injection control apparatus which can be performed for every fuel-injection pressure without giving, and a fuel-injection system using the same.

  In the fuel injection control device according to claim 1, which is made to achieve such an object, the learning condition determination unit determines whether or not a learning condition for the fuel injection amount from the fuel injection valve is satisfied, The injection pressure setting means sets a learning injection pressure for injecting fuel from the fuel injection valve when the learning condition is satisfied.

  When the learning condition determining means determines that the learning condition is satisfied, the learning injection control means causes the injection pressure control means to control the fuel injection pressure to the learning injection pressure, and then the fuel injection valve A learning injection command is output to the fuel injection valve so that fuel is injected from the fuel injection valve by the command injection amount.

  When fuel is injected from the fuel injection valve by the injection command from the learning injection control unit, the correction value setting unit detects the actual injection amount of the injected fuel, and the detected actual injection amount and the command injection are detected. Based on the difference from the amount, an injection amount correction value for fuel injection at the fuel injection pressure corresponding to the learning injection pressure is set.

  Therefore, according to the fuel injection control device of the present invention, the injection amount correction value can be set for each fuel injection pressure set by the injection pressure setting means as the learning injection pressure. The fuel injection amount from the fuel injection valve can be controlled to the optimum value according to the operating state of the internal combustion engine without being affected by the pressure.

  Further, the fuel injection control device of the present invention obtains a pressure difference between the learning injection pressure set by the injection pressure setting means and the target injection pressure controlled by the injection pressure control means when the learning condition is not satisfied, If the pressure difference is greater than or equal to a preset threshold value, learning injection prohibiting means for prohibiting the operation of the learning injection control means is provided.

  Therefore, according to the fuel injection control device of the present invention, the pressure difference between the learning injection pressure and the target injection pressure at the time of normal injection is large. When the state changes greatly, the learning control can be prohibited to prevent the driver from feeling uncomfortable.

  Here, when the learning control is executed or when the normal injection is resumed, the driver feels uncomfortable due to fluctuations in the operation of the internal combustion engine (changes in combustion noise and vibration) caused by the pressure difference. When the surrounding noise is high, it is difficult for the driver to feel uncomfortable.

  For this reason, in the fuel injection control device of the present invention (claim 1), as described in claim 2, the threshold value used by the learning injection prohibiting means for determining the pressure difference is set according to the ambient noise. It is preferable to provide threshold setting means.

  That is, according to the fuel injection control device of the second aspect, when the ambient noise is large and the driver does not feel uncomfortable, a large value is set for the threshold value, and the learning injection prohibiting means controls the learning injection control. The probability that the operation of the means is prohibited can be reduced. Therefore, according to this device, it is possible not only to perform the above-described learning control without giving the driver a feeling of strangeness, but also to increase the probability that the injection amount correction value is updated by the learning control.

Further, in the fuel injection control device according to claim 2, the threshold value setting means may be configured as described in claim 3.
That is, in the fuel injection control device according to claim 3, the threshold value setting means detects the rotational speed of the internal combustion engine or the vehicle speed of the vehicle using the internal combustion engine as a power source as a parameter representing ambient noise, The threshold value is set so that it increases as the detected rotational speed or vehicle speed increases.

  As a result, when the rotational speed and vehicle speed of the internal combustion engine are large and the ambient noise increases, a large value is set for the threshold value, and the probability that the injection amount correction value can be updated by the learning control is as follows. It can be increased more reliably.

On the other hand, in the fuel injection control device according to the fourth aspect, the learning condition determination means determines that the learning condition is satisfied when the internal combustion engine is in the non-injection deceleration state.
For this reason, according to the fuel injection control device of the fourth aspect, the learning control described above can be executed under the condition of less disturbance that changes the operating state of the internal combustion engine, and the injection amount correction value is set to the fuel injection pressure. It becomes possible to set with high precision every time.

  Next, in the fuel injection system according to claim 5, the fuel injection amount from the fuel injection valve that receives fuel supply from the common rail and injects fuel to the internal combustion engine (diesel engine) is described above. It controls by the fuel-injection control apparatus in any one of Claim 4.

  Therefore, according to this fuel injection system, the fuel injection amount from the fuel injection valve, in particular, the minute injection amount by the pilot injection performed before the main injection can be corrected with high accuracy.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing the overall configuration of an accumulator fuel injection system 10 to which the present invention is applied.

  The fuel injection system 10 of this embodiment is for supplying fuel to, for example, a four-cylinder diesel engine 2 for automobiles. The common rail 20 that stores high-pressure fuel and the high-pressure fuel supplied from the common rail 20 are diesel-powered. The fuel injection valve 30 inject | poured into the combustion chamber of each cylinder of the engine 2 and the electronic control unit (ECU) 50 which controls this system are provided.

  Further, in order to supply fuel to the common rail 20, the fuel injection system 10 includes a feed pump 14 that pumps fuel from the fuel tank 12, and a high pressure that pressurizes the fuel supplied from the feed pump 14 and supplies the fuel to the common rail 20. A pump 16 is provided.

  Here, the high-pressure pump 16 is a known pump that pressurizes the fuel sucked into the pressurizing chamber when the plunger reciprocates as the cam of the camshaft rotates. The high-pressure pump 16 is provided with a metering valve 18 for metering the amount of fuel sucked from the feed pump 14 in the suction stroke.

  The common rail 20 is provided with a pressure sensor 22 for detecting internal fuel pressure (common rail pressure) and a pressure reducing valve 24 for reducing the internal fuel pressure by overflowing the internal fuel to the fuel tank 12 side. It has been.

  The diesel engine 2 includes a rotation speed sensor 32 that detects a rotation speed NE, an accelerator sensor 34 that detects an accelerator operation amount (accelerator opening ACC) by a driver, and a coolant. A water temperature sensor 36 for detecting the temperature (cooling water temperature THW), an intake air temperature sensor 38 for detecting the temperature of intake air (intake air temperature TA), and the like are provided.

On the other hand, the ECU 50 is configured by a microcomputer centered on a CPU, ROM, RAM, and the like.
The ECU 50 detects the traveling speed (vehicle speed) of the automobile on which the pressure sensor 22 provided on the common rail 20, the various sensors 32, 34, 36, 38... Provided on the diesel engine 2 and the diesel engine 2 are mounted. Detection signals from the vehicle speed sensor 40 and the like are taken in, and based on these detection signals, the common rail pressure (in other words, the fuel injection pressure from the fuel injection valve 30) and the fuel injection amount from the fuel injection valve 30 are controlled.

That is, the ECU 50
a) A target pressure (in other words, a target injection pressure) of the common rail 20 is calculated based on the operating state of the diesel engine 2, and the metering valve 18 and the pressure reducing valve are set so that the common rail pressure detected by the pressure sensor 22 becomes the target pressure. Common rail pressure control as an injection pressure control means for controlling energization of 24,
b) The fuel injection amount is calculated based on the operating state of the diesel engine 2, and fuel is injected into each cylinder by opening the fuel injection valve 30 of each cylinder for a predetermined time at a predetermined injection timing according to the calculation result. The fuel injection control to be supplied is executed.

In this fuel injection control, the ECU 50 executes pilot injection prior to main injection.
In this pilot injection, the fuel injection accuracy changes greatly due to the difference between the fuel injection command value for the fuel injection valve 30 (command injection amount) and the fuel amount actually injected from the fuel injection valve 30 (actual injection amount). Therefore, the ECU 50 also executes learning control for calculating a deviation between the actual injection amount from the fuel injection valve 30 and the command injection amount as a correction value (injection amount correction value) of the fuel injection amount.

Hereinafter, this learning control will be described in detail with reference to the flowchart shown in FIG.
FIG. 2 shows an injection amount learning routine executed by the ECU 50 at, for example, the injection control timing of each cylinder.

  As shown in FIG. 2, in the injection amount learning routine, first, in S110 (S represents a step), it is determined whether or not a fuel injection amount learning condition is satisfied. In this determination process, for example, when the accelerator opening ACC is zero, the diesel engine 2 enters a deceleration operation, and the fuel injection amount to each cylinder is zero (in other words, the diesel engine 2 is In the non-injection deceleration state), it is determined that the learning condition is satisfied.

  If it is not determined that the learning condition is satisfied in S110, the injection amount learning routine is terminated. If it is determined that the learning condition is satisfied in S110, the process proceeds to S120 and learning is performed in the subsequent processes. It is determined whether or not a target injection pressure (learning injection pressure) for performing the fuel injection is already set.

  If it is determined in S120 that the learning target injection pressure is not set, the process proceeds to S130, and the injection amount correction value should be updated next from the plurality of learning injection pressures to be learned. A learning injection pressure is selected, and the selected learning injection pressure is set as a target pressure (target injection pressure) in the common rail pressure control.

  When the learning injection pressure is set as the target pressure (target injection pressure) in the common rail pressure control in S130, the common rail pressure is controlled to the learning injection pressure by the common rail pressure control separately executed by the ECU 50. It becomes like this.

Next, when it is determined in S120 that the learning target injection pressure is already set, or when the learning target injection pressure is set in S130, the process proceeds to S140.
In S140, the currently set target injection pressure for learning (learning injection pressure) and the target injection pressure for normal operation (normally calculated based on the operation state of the diesel engine 2 by the above-described common rail pressure control) The pressure difference (= the injection pressure for learning−the normal injection pressure) is calculated, and the process proceeds to S150.

  In S150, the vehicle speed detected by the vehicle speed sensor 40 and the threshold value calculation map shown in FIG. Is calculated.

As shown in FIG. 3, the threshold value calculation map is set so that the threshold value increases as the vehicle speed increases with the vehicle speed as a parameter.
Next, when a threshold value is set in S150, the process proceeds to S160, where the set threshold value is compared with the pressure difference calculated in S140, and whether the pressure difference is smaller than the threshold value. Judge whether or not.

  If it is determined in S160 that the pressure difference is smaller than the threshold value, the process proceeds to S170, and the common rail pressure is set to the learning target injection pressure (learning injection pressure) set in S130 by the common rail pressure control. Determine whether it has been reached.

  If the common rail pressure does not reach the learning target injection pressure (learning injection pressure), the injection amount learning routine is terminated, and conversely, the common rail pressure becomes the learning target injection pressure (learning injection pressure). If the fuel injection amount has been reached, the process proceeds to S180, and in order to learn the fuel injection amount, the fuel injection valve 30 of the cylinder that is currently at the fuel injection timing is subjected to fuel injection (single shot) by a preset command injection amount. Injection).

  Next, after the single injection is executed, the amount of change in the operating state of the diesel engine 2 (the amount of change in rotational speed, etc.) is detected in S190. In the subsequent S200, the generated torque of the diesel engine 2 is obtained based on the amount of change detected in S190, the actual injection amount is estimated from the generated torque, and the process proceeds to S210.

  In S210, based on the difference between the actual injection amount obtained in S200 and the command injection amount, when the common rail pressure is the current fuel injection pressure, the fuel injection amount for the cylinder that has performed the single injection this time is corrected. The injection amount correction value is calculated, and the correction value calculation map is updated.

  If the correction value calculation map is updated in S210 as described above, or if it is determined in S160 that the pressure difference is greater than or equal to the threshold value, the process proceeds to S220, where the common rail pressure control is performed. By returning the target pressure (target injection pressure) from the learning injection pressure to the normal operation target injection pressure (normal injection pressure), the common rail pressure control is returned to the normal control, and the injection amount learning routine is terminated.

  As described above, in the fuel injection system 10 of the present embodiment, when the fuel injection amount learning condition is satisfied, the ECU 50 as the fuel injection control device performs the target injection pressure (when the single injection for learning is executed) Learning injection pressure), and the difference between the set learning injection pressure and the target injection pressure (normal injection pressure) when the learning condition is not satisfied (= learning injection pressure−normal injection pressure) is a threshold value. It is judged whether it is less than.

  Then, if the pressure difference is less than the threshold, the ECU 50 waits for the fuel injection pressure (common rail pressure) to be controlled to the learning injection pressure by the common rail pressure control separately executed, and executes the single injection, Based on the amount of change in the operating state of the diesel engine 2 after the single injection, learning control of the fuel injection amount is executed by a procedure of calculating an injection amount correction value at the current fuel injection pressure.

  Therefore, according to the fuel injection system 10 of the present embodiment, the injection amount correction value can be set for each fuel injection pressure, and the fuel injection valve is not affected by the fuel injection pressure during normal operation of the diesel engine 2. It is possible to control the actual injection amount from 30 to an optimum value according to the operating state of the internal combustion engine.

In addition, if the pressure difference is equal to or greater than the threshold value, the ECU 50 stops the learning control.
Therefore, according to the fuel injection system 10 of the present embodiment, when the pressure difference is large and the learning control described above is executed, the operation state of the diesel engine 2 changes greatly after the single injection is executed or after the normal injection is resumed. Can inhibit learning control and prevent the driver from feeling uncomfortable.

  In the present embodiment, the threshold value used to determine whether to execute or prohibit the learning control is set so that the threshold value increases as the vehicle speed increases, using the map shown in FIG. Is done. For this reason, when the vehicle or the like that makes it difficult for the driver or the like to feel the fluctuation in the operation of the diesel engine 2 caused by the pressure difference, the threshold value can be increased to reduce the probability that the learning control is prohibited.

  In the present embodiment, in the injection amount learning routine executed by the ECU 50, the determination process of S110 corresponds to the learning condition determination means of the present invention, and the process of S130 is the injection pressure setting means of the present invention. The processing of S150 corresponds to the threshold value setting means of the present invention, the processing of S140 and S160 corresponds to the learning injection prohibiting means of the present invention, and the processing of S170 and S180 is the learning of the present invention. It corresponds to the injection control means, and the processing of S190 to S210 corresponds to the correction value setting means of the present invention.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various aspect can be taken in the range which does not deviate from the summary of this invention.
For example, in the embodiment described above, the threshold value is set according to the vehicle speed based on the map shown in FIG. 3 in S150 of the injection amount learning routine. However, the threshold value may be set to increase as the rotational speed increases, for example, according to the rotational speed of the diesel engine 2.

  In the above embodiment, in S140 of the injection amount learning routine, a value obtained by subtracting the normal injection pressure from the learning injection pressure (learning injection pressure−normal injection pressure) is calculated as a pressure difference. When it is equal to or higher than the threshold value (in other words, when the learning injection pressure is higher than the threshold value than the normal injection pressure), the learning control is described as being prohibited. The absolute value of the difference from the pressure may be calculated as the pressure difference.

  In this way, even when the learning injection pressure is smaller than the threshold value than the normal injection pressure, the learning control is prohibited, and the fuel injection pressure at the time of restarting the normal injection becomes too low, This makes it possible to prevent the engine 2 from having sufficient fuel.

  On the other hand, in the above embodiment, the diesel engine 2 has been described as performing the so-called deceleration type learning control in which the fuel is injected once and the injection amount correction value is calculated when the diesel engine 2 is in the non-injection deceleration state.

  However, according to the present invention, for example, during idle operation of the diesel engine 2, fuel injection is performed in a plurality of times for each cylinder, and rotation is performed between the cylinders based on the rotational speed and rotational fluctuation of the diesel engine that occurs at that time. A first correction value for smoothing the fluctuation and a second correction value for controlling the average rotation speed of all the cylinders to the target rotation speed (idle rotation speed) are obtained, and these correction values are used as the actual injection amount and the command. Even in the learning control of a method different from the above embodiment, such as learning control for setting a final injection amount correction value as a parameter representing the deviation from the injection amount, it can be applied similarly to the above embodiment. .

  In the above embodiment, the fuel injection system 10 for a diesel engine that supplies the fuel in the common rail 20 to each cylinder of the diesel engine 2 from the fuel injection valve 30 has been described. However, the present invention is directed to the fuel injection for each cylinder. If a valve is provided, even a fuel injection system for a gasoline engine can be applied in the same manner as in the above embodiment.

It is a schematic structure figure showing the composition of the whole fuel injection system of an embodiment. It is a flowchart showing the injection quantity learning routine performed by ECU. It is explanatory drawing showing the map used for calculating a threshold value based on a vehicle speed.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Diesel engine, 10 ... Fuel injection system, 12 ... Fuel tank, 14 ... Feed pump, 16 ... High pressure pump, 18 ... Metering valve, 20 ... Common rail, 22 ... Pressure sensor, 24 ... Pressure reducing valve, 30 ... Fuel injection Valve: 32 ... Rotational speed sensor, 34 ... Accelerator sensor, 36 ... Water temperature sensor, 38 ... Intake temperature sensor, 40 ... Vehicle speed sensor, 50 ... ECU (electronic control unit).

Claims (5)

A fuel injection control device that calculates the fuel injection amount based on the operating state of the internal combustion engine and drives the fuel injection valve according to the calculation result to supply fuel to the internal combustion engine,
Injection pressure control means for controlling the fuel injection pressure from the fuel injection valve to the target injection pressure;
Learning condition determination means for determining whether or not a learning condition for the fuel injection amount from the fuel injection valve is satisfied;
An injection pressure setting means for setting an injection pressure for learning when fuel is injected from the fuel injection valve when the learning condition is satisfied;
When the learning condition determination unit determines that the learning condition is satisfied, the injection pressure control unit controls the fuel injection pressure to the learning injection pressure, and then causes the fuel injection valve to perform learning. Learning injection control means for outputting a fuel injection command and injecting fuel by the command injection amount from the fuel injection valve;
Based on the difference between the actual injection amount and the command injection amount, the actual injection amount of the fuel injected from the fuel injection valve is detected by the injection command from the learning injection control means, and corresponds to the learning injection pressure. Correction value setting means for setting an injection amount correction value when performing fuel injection at the fuel injection pressure;
A pressure difference between the learning injection pressure set by the injection pressure setting means and the target injection pressure controlled by the injection pressure control means when the learning condition is not satisfied is obtained, and the pressure difference is set in advance. Learning injection prohibiting means for prohibiting the operation of the learning injection control means,
A fuel injection control device comprising: Threshold setting means for setting the threshold used by the learning injection prohibiting means for determining the pressure difference so as to increase as the noise increases according to ambient noise;
The fuel injection control device according to claim 1, further comprising:   The threshold value setting means detects the rotational speed of the internal combustion engine or the vehicle speed of the vehicle using the internal combustion engine as a power source as a parameter representing ambient noise, and increases as the rotational speed or vehicle speed increases. The fuel injection control device according to claim 2, wherein the threshold value is set.   The fuel injection according to any one of claims 1 to 3, wherein the learning condition determination unit determines that the learning condition is satisfied when the internal combustion engine is in a non-injection deceleration state. Control device. A fuel supply pump that pressurizes and pumps fuel; and
A common rail for accumulating fuel pumped by the fuel supply pump;
A fuel injection valve for injecting fuel accumulated in the common rail into a cylinder of an internal combustion engine;
A fuel injection control device according to any one of claims 1 to 4,
A fuel injection system comprising:

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