JP5152164B2 - Diesel engine control device - Google Patents

Description

  The present invention relates to a control device for a diesel engine.

  A diesel engine is known in which fuel is supplied by a fuel injection system including a common rail (see, for example, Patent Document 1). In the technique described in Patent Document 1, fuel supplied from a fuel tank is accumulated in a common rail, and the accumulated high-pressure fuel is injected from a fuel injection valve into a combustion chamber of each cylinder. The fuel injection system including the pressure in the common rail (hereinafter referred to as common rail pressure) is controlled by an electronic control unit (ECU).

JP-A-11-93735

  In a diesel engine, after starting the engine at a low temperature and before warming up, a so-called rough idle, which is an unpleasant vibration generation due to instability of idle rotation, and white smoke in exhaust gas may occur. These phenomena are considered to be caused by, for example, variations in fuel injection systems such as variations in injection accuracy, spray deterioration, fluctuations in common rail pressure, and variations in compression in the engine body.

  Therefore, the present invention has been made in view of the above-described problems, and an object thereof is to provide a diesel engine control device that can reduce the generation of rough idle and white smoke.

The present invention employs the following technical means to achieve the above object. That is, in the invention according to the diesel engine control device of the first aspect, the rotation speed fluctuation range obtained by using the rotation speed fluctuation width detecting means after the diesel engine is started exceeds a predetermined fluctuation width threshold, If further cylinder diesel engine is determined to be a semi-misfire state by half misfire determination means, Ru increases the pressure of the rail. Further, the inter-cylinder injection amount correction value is calculated using the inter-cylinder difference in the rotational speed fluctuation of the diesel engine, and the semi-misfire determination means is when the calculated inter-cylinder injection amount correction value is smaller than a predetermined misfire determination threshold value. It is characterized by determining that it is a semi-misfire state .

According to the present invention, when the rotational speed fluctuation range exceeds a predetermined fluctuation range threshold and the cylinder of the diesel engine is in a semi-misfire state, the pressure of the rail is increased so that the fuel spray to the cylinder is extended. Thus, since the fuel state of the engine is improved from the semi-misfire state to the normal combustion state, the generation of rough idle and white smoke can be reduced. Furthermore, the control device for the diesel engine detects a decrease in the fuel injection amount due to the clogging of the injection hole of the fuel injection device that injects the fuel into the cylinder, and a decrease state of the engine compression, and improves these states for combustion. State stabilization can be performed. Here, the semi-misfire state is a state where the degree of misfire is lighter than a complete misfire state including, for example, a state of no fuel injection or a state where the engine is not compressed, and is included between the complete misfire state and the normal combustion state State. Further, according to the present invention, it is possible to determine whether or not each cylinder of the engine is in a semi-misfire state by determining whether or not it is in a semi-misfire state based on the inter-cylinder injection amount correction value. A cylinder in a misfire state can be identified, and control for effectively improving this state can be performed. Therefore, it is possible to expect a highly accurate detection of a decrease in the amount of fuel injection due to clogging of the fuel injection holes or the like, and a decrease in engine compression.

  Further, in the present invention, for example, when the above-mentioned rotation speed fluctuation range is exceeded and the semi-misfire state determination is satisfied, the rail pressure is set by the pressure during normal control, for example, ISC (idle speed control) control. If the semi-misfire state determination is not satisfied, the rail pressure can be controlled to the normal control pressure.

According to a second aspect of the present invention related to the diesel engine control device, after the diesel engine is started, the rotational speed fluctuation range obtained by using the rotational speed fluctuation width detecting means exceeds a predetermined fluctuation width threshold, When it is determined that the engine cylinder is in a semi-misfire state by the semi-misfire determination means, the rail pressure is increased. Further, an air-fuel ratio detection means for detecting the air-fuel ratio in the exhaust of the diesel engine is provided, and even if the rotation speed fluctuation range obtained by the rotation speed fluctuation width detection means is equal to or less than the fluctuation width threshold value, it is obtained by the air-fuel ratio detection means. If the air / fuel ratio is smaller than a predetermined white smoke determination threshold for determining the occurrence of white smoke, and if it is determined by the semi-misfire determination means that the state is a semi-misfire state, the rail pressure is increased. Features.

According to the present invention, when the rotational speed fluctuation range exceeds a predetermined fluctuation range threshold and the cylinder of the diesel engine is in a semi-misfire state, the pressure of the rail is increased so that the fuel spray to the cylinder is extended. Thus, since the fuel state of the engine is improved from the semi-misfire state to the normal combustion state, the generation of rough idle and white smoke can be reduced. Furthermore, the control device for the diesel engine detects a decrease in the fuel injection amount due to the clogging of the injection hole of the fuel injection device that injects the fuel into the cylinder, and a decrease state of the engine compression, and improves these states for combustion. State stabilization can be performed. Further, according to the present invention, even if the rotational speed fluctuation range is equal to or less than the fluctuation range threshold value, the air-fuel ratio is less than the white smoke determination threshold value, and it is determined that the state is a semi-misfire state. A misfire condition can be detected. Furthermore, in this case, by increasing the rail pressure, the fuel state of the engine is improved from the semi-misfire state to the normal combustion state by extending the spray of fuel to the cylinder, thus reducing the generation of white smoke. can do. For example, when the air-fuel ratio obtained by the air-fuel ratio detection means is less than the white smoke determination threshold, the rail pressure is set to the pressure during normal control (for example, the pressure set by ISC (idle speed control) control). When the air-fuel ratio is equal to or higher than the white smoke determination threshold, the rail pressure can be set to the pressure during normal control.

According to a third aspect of the present invention, there is provided a diesel engine control device, wherein after the diesel engine is started, the rotational speed fluctuation range obtained by using the rotational speed fluctuation width detection means exceeds a predetermined fluctuation width threshold, When it is determined that the engine cylinder is in a semi-misfire state by the semi-misfire determination means, the rail pressure is increased. Further, the inter-cylinder injection amount correction value is calculated using the difference between the cylinders in the rotational speed fluctuation of the diesel engine. When the calculated inter-cylinder injection amount correction value is equal to or greater than a predetermined misfire determination threshold, the rail pressure is increased. It is characterized in that no control is performed .

According to the present invention, when the rotational speed fluctuation range exceeds a predetermined fluctuation range threshold and the cylinder of the diesel engine is in a semi-misfire state, the pressure of the rail is increased so that the fuel spray to the cylinder is extended. Thus, since the fuel state of the engine is improved from the semi-misfire state to the normal combustion state, the generation of rough idle and white smoke can be reduced. Furthermore, the control device for the diesel engine detects a decrease in the fuel injection amount due to the clogging of the injection hole of the fuel injection device that injects the fuel into the cylinder, and a decrease state of the engine compression, and improves these states for combustion. State stabilization can be performed. Furthermore, if the inter-cylinder injection amount correction value is an excessive value that is equal to or greater than the misfire determination threshold value, a complete misfire condition may occur.In this case, the rail pressure is increased to extend the fuel injection. However, the fuel is discharged without being burned. However, according to the present invention, by not performing the control for increasing the pressure of the rail, it is possible to avoid such a situation in advance. A reduction in engine control efficiency due to an increase in rail pressure can be avoided.

According to a fourth aspect of the present invention, there is provided a diesel engine control apparatus, wherein after the diesel engine is started, the rotational speed fluctuation range obtained by using the rotational speed fluctuation width detecting means exceeds a predetermined fluctuation width threshold value, and further the diesel engine When it is determined that the engine cylinder is in a semi-misfire state by the semi-misfire determination means, the rail pressure is increased. Furthermore, the fluctuation range of the rotational speed is detected based on a detection result of a knock sensor that detects knocking of the diesel engine .

According to the present invention, when the rotational speed fluctuation range exceeds a predetermined fluctuation range threshold and the cylinder of the diesel engine is in a semi-misfire state, the pressure of the rail is increased so that the fuel spray to the cylinder is extended. Thus, since the fuel state of the engine is improved from the semi-misfire state to the normal combustion state, the generation of rough idle and white smoke can be reduced. Furthermore, the control device for the diesel engine detects a decrease in the fuel injection amount due to the clogging of the injection hole of the fuel injection device that injects the fuel into the cylinder, and a decrease state of the engine compression, and improves these states for combustion. State stabilization can be performed. Furthermore, the fluctuation range of the rotational speed can be detected with excellent accuracy.

The invention according to claim 5 is characterized in that when the cylinder of the diesel engine is determined to be in a semi-misfire state by the semi-misfire determination means, the rail pressure is increased and the fuel injection start timing is delayed. To do. According to this invention, in addition to the control for increasing the rail pressure when the determination of the semi-misfire state is made, by delaying the start timing of the fuel injection, the change in the combustion sound that can be caused by the increase in the rail pressure is suppressed. Can be suppressed. Therefore, in addition to reducing the rough idle and alleviating the semi-misfire state, it is possible to improve the quietness of the engine by reducing the change in combustion noise .

According to a sixth aspect of the present invention, there is provided a diesel engine that is obtained using the air-fuel ratio detecting means even when the rotational speed fluctuation width obtained using the rotational speed fluctuation width detecting means is equal to or less than a predetermined fluctuation width threshold value. If the air-fuel ratio of the exhaust gas is smaller than the white smoke determination threshold determined in advance to determine the generation of white smoke, and if it is determined by the semi-misfire determination means that it is in a semi-misfire state, the rail pressure is increased. When the air-fuel ratio obtained by the air-fuel ratio detection means is equal to or greater than the white smoke determination threshold, control for increasing the rail pressure is not performed.
According to a seventh aspect of the present invention, when the air-fuel ratio obtained by the air-fuel ratio detection means is equal to or greater than the white smoke determination threshold value, the control for increasing the rail pressure is not performed.

According to the sixth and seventh aspects of the present invention, when it is determined that rough idle and white smoke are not generated, the control for increasing the rail pressure is not performed, thereby increasing the useless rail pressure. Reduction in engine control efficiency and increase in combustion noise can be avoided.

The invention described in claim 8 is characterized in that the fluctuation range of the rotational speed is detected based on the measured value of the rotational speed sensor for measuring the rotational speed of the diesel engine. According to the present invention, the fluctuation range of the rotational speed can be detected with excellent accuracy.

The invention according to claim 9 detects the fluctuation range of the rotational speed based on the detection result of the knock sensor for detecting knocking of the diesel engine. According to the present invention, the fluctuation range of the rotational speed can be detected with excellent accuracy.

It is a block diagram showing the structure of the control apparatus of the diesel engine in 1st Embodiment of this invention. It is a flowchart showing the process which the control apparatus of a diesel engine performs. It is a logic figure showing the raise process of the common rail pressure which the control apparatus of a diesel engine performs. It is a logic diagram showing the injection start timing retard process which the control apparatus of a diesel engine performs. It is a graph showing the effect which the raise processing of the common rail pressure by the control apparatus of a diesel engine has. It is the graph which showed the relationship between the crank angle at the time of normal control implementation by the control apparatus of a diesel engine, and cylinder internal pressure. It is the graph which showed the relationship between the crank angle at the time of execution of the common rail pressure raise process by the control apparatus of a diesel engine, and a cylinder internal pressure. It is the graph which showed the relationship between the crank angle at the time of the injection start timing retard process implementation by the control apparatus of a diesel engine, and a cylinder internal pressure.

(First embodiment)
A first embodiment of the present invention will be described with reference to the drawings. The diesel engine control device 1 (hereinafter also simply referred to as the control device 1) supplies fuel to a diesel engine 2 for automobiles (hereinafter also simply referred to as the engine 2). FIG. 1 is a block diagram showing the configuration of a control device 1 for a diesel engine.

  As shown in FIG. 1, the control device 1 includes a fuel tank 3 containing fuel, a high-pressure pump 5 that pressurizes the fuel in the fuel tank 3, and a common rail 6 that accumulates high-pressure fuel supplied from the high-pressure pump 5. The fuel injection valve 12 for injecting the high-pressure fuel supplied from the common rail 6 into the combustion chamber of each cylinder 11 and the ECU 4 for controlling the operation of each part of the present apparatus are provided. In FIG. 1, the solid line arrow indicates the fuel flow direction, the broken line arrow indicates the intake flow, and the alternate long and short dash line arrow indicates the exhaust flow.

  The engine 2 to be controlled by the control device 1 is provided with a plurality of cylinders 11 (four cylinders in this embodiment) serving as combustion chambers, and fuel is injected into the fuel chambers of the cylinders 11. A fuel injection valve 12 is provided.

  The fuel injection valve 12 is, for example, an electromagnetically driven injection valve that controls the axial movement of a nozzle needle that opens and closes an injection hole for injecting fuel into a combustion chamber by the pressure in the control chamber. The fuel injection valve 12 is connected to a common rail 6 serving as a pressure accumulation pipe common to each cylinder 11. Basically, fuel in the common rail 6 is transferred from the fuel injection valve 12 while the electromagnetic valve for injection control is open. It is injected into each cylinder 11 of the engine 2. The common rail 6 continuously accumulates fuel having a relatively high pressure that enables such fuel injection.

  The high-pressure pump 5 incorporates a feed pump that pumps fuel from the fuel tank 3. The high-pressure pump 5 is a pump that pressurizes the fuel sucked into the pressurizing chamber when the built-in plunger reciprocates with the rotation of the cam of the camshaft synchronized with the rotation of the engine 2. Further, the high pressure pump 5 includes a metering valve (not shown) for metering the amount of fuel sucked from the feed pump in the suction stroke of one cycle of the engine 2. By controlling on / off of the metering valve, the amount of fuel discharged from the discharge port of the high-pressure pump 5 toward the common rail 6 is adjusted. The high pressure pump 5 sucks fuel from the fuel tank 3 through a filter, raises the fuel to a required predetermined pressure, and supplies the fuel to the common rail 6.

  The common rail 6 is provided with a relief valve (not shown). For example, when the fuel pressure in the common rail 6 (common rail pressure Pc) increases excessively, the relief valve is opened. As a result, the high-pressure fuel in the common rail 6 is returned to the fuel tank 3 through the return pipe, and the pressure in the common rail 6 decreases.

  The ECU 4 is composed of a microcomputer centered on a CPU, ROM, RAM, flash memory, and the like. The ECU 4 includes a pressure sensor 13 that detects the fuel pressure inside the common rail 6 (common rail pressure Pc), a start switch 14 that detects on / off of the engine start, a rotational speed sensor 21 that measures the rotational speed of the engine 2, and the engine 2. A coolant temperature sensor 22 that detects the coolant temperature of the engine 2, and an air-fuel ratio sensor (hereinafter referred to as A / F sensor 23) that detects a signal for calculating an air-fuel ratio (hereinafter also referred to as A / F value) in the exhaust gas of the engine 2 ), Taking in detection signals from various sensors such as the accelerator sensor 24 for detecting the operation amount of the accelerator pedal, and performing various controls such as the discharge amount of the high-pressure pump 5, the fuel injection amount from the fuel injection valve 12, and the fuel injection start timing. carry out. The ECU 4 can control the common rail pressure by controlling the discharge amount of the high-pressure pump 5.

  Further, the rotation speed sensor 21 may be constituted by a crank angle sensor and a cam angle sensor. In this case, the crank angle sensor is provided in the vicinity of a pulsar provided on the crankshaft of the engine 2 and detects the rotation angle of the crankshaft. The rotation of the crankshaft is transmitted via a timing belt or the like to a camshaft for opening / closing an intake valve and an exhaust valve (both not shown). The camshaft is set to rotate at a rotational speed that is 1/2 of that of the crankshaft. A cam angle sensor is provided in the vicinity of the pulsar provided on the camshaft. The ECU 4 can calculate the engine speed NE, the crank angle, the cam angle, and the top dead center of the piston in each cylinder 11 from the pulse signals output from the crank angle sensor and the cam angle sensor.

  In the fuel injection control, the ECU 4 feedback-controls the pressure in the common rail 6 (common rail pressure Pc) to a target common rail pressure set according to the operating state of the engine 2 and the like.

  In this feedback control, first, the target value of the pressure in the common rail 6 based on the injection amount for generating the required torque corresponding to the operation amount of the accelerator pedal detected by the accelerator sensor 24 and the rotational speed of the crankshaft. (Target common rail pressure) is calculated. Then, based on the difference between the actual fuel pressure detected by the pressure sensor 13 and the target common rail pressure, a command value (command discharge amount) of the discharge amount of the high-pressure pump 5 is calculated. Specifically, the calculation of the discharge amount is performed based on PID control in order to feedback-control the detected fuel pressure to the target common rail pressure. That is, the proportional term, the differential term, and the integral term are calculated based on the above difference, and the command discharge amount is calculated from these. Then, the ECU 4 calculates a drive current value (specifically, a drive current value of the metering valve) of the high-pressure pump 5 according to the command discharge amount. The ECU 4 controls the high-pressure pump 5 (specifically, a metering valve) based on the calculated drive current value.

  In this way, the common rail pressure Pc can be controlled to the target common rail pressure. Based on the common rail pressure Pc controlled in this way and the command value (command injection amount) of the injection amount for the fuel injection valve 12, the command value (command injection period) for the injection period for the fuel injection valve 12 is calculated, thereby fuel injection. Control can be performed.

  Further, the ECU 4 detects a rotational fluctuation for each explosion stroke of each cylinder 11 when the engine 2 is idling. Then, the ECU 4 compares the detected value of the rotational speed fluctuation of each cylinder 11 with the average value of the rotational speed fluctuations of all the cylinders, and optimizes each cylinder 11 so as to smooth the rotational speed fluctuation between the cylinders. Rotational speed variation inter-cylinder correction (FCCB) is performed to individually adjust the fuel injection amount.

  Specifically, the ECU 4 calculates the instantaneous rotational speed for each explosion stroke of each cylinder 11 by calculating the interval time of the pulse signal acquired from the crank angle sensor, and a pulse between BTDC 90 ° CA and ATDC 90 ° CA. The maximum value of the signal interval time is read as the minimum rotational speed of the cylinder in question (hereinafter referred to as the minimum rotational speed NL). Further, the ECU 4 reads the minimum value of the interval time of the pulse signal between BTDC 90 ° CA and ATDC 90 ° CA as the maximum rotational speed (hereinafter referred to as the maximum rotational speed NH) of the cylinder. However, NL and NH do not necessarily need to be the minimum rotation speed and the maximum rotation speed, and may be a low rotation speed and a high rotation speed that represent the rotation speed fluctuation of the cylinder.

  Then, after performing these calculations for each cylinder, the ECU 4 calculates a cylinder-by-cylinder speed difference ΔNK, which is the difference between the maximum speed NH of each cylinder 11 and the minimum speed NL of each cylinder 11. Thereby, the ECU 4 calculates the detected value of the rotational speed fluctuation of each cylinder 11 and calculates the average value ΣΔNK of the rotational speed fluctuation of all the cylinders.

  That is, the ECU 4 averages the rotational speed fluctuations of all the cylinders, calculates the average value of the rotational speed fluctuations of all the cylinders, and then detects the rotational speed fluctuation value of each cylinder 11 and the average value of the rotational speed fluctuations of all the cylinders. From this, the deviation of the rotational speed variation between the cylinders is calculated. Then, the ECU 4 sets the injection amount correction value for each cylinder corresponding to the injection amount or the injection command pulse width (fuel injection index value) calculated for each cylinder so that the rotational speed fluctuation between the cylinders is smoothed. Calculate every time. This inter-cylinder injection amount correction value is the FCCB value.

  Further, the ECU 4 sets the average engine speed in order to adjust the average engine speed (average idling speed), which is the current engine speed NE, to the target speed (target idling speed) when the engine 2 is idling. Average engine speed correction (ISC control) is performed uniformly for all cylinders with respect to the deviation ΔNE from the target speed. Specifically, the actual rotational speed NE of the engine 2 is compared with the target rotational speed, and a correction amount for the injection amount or the injection command pulse width (fuel injection index value) corresponding to the rotational speed difference ΔNE is calculated. . This correction amount is called an ISC correction amount.

  Then, the ECU 4 learns, as a learning value for each cylinder, a value obtained by adding the ISC correction amount that is obtained uniformly for all cylinders to the FCCB value that is obtained for each cylinder. The calculated learning value is stored in the ECU 4. In the fuel injection control, the ECU 4 corrects the injection amount injected from the fuel injection valve 12 based on the stored learning value, thereby compensating for an error in the fuel injection amount caused by deterioration of the fuel injection valve 12 over time. To do.

  Next, processing executed by the control device 1 will be described based on the flowchart shown in FIG. This process is repeatedly executed every predetermined time after the ignition switch of the automobile is turned on. First, in step 10, it is determined based on a detection signal from the start switch 14 whether or not the engine 2 has started. If the engine 2 has been started, the process proceeds to step 20. If the engine 2 has not been started, step 10 is executed again.

  In step 20, it is determined based on the detection signal of the accelerator sensor 24 and the vehicle speed signal detected by the vehicle speed sensor 25 whether or not the vehicle is in an idle state. If it is in the idling stop state, the process proceeds to step 30, and if it is not in the idling stop state, step 60 described later is executed.

  In step 30, the rotational speed sensor 21 detects the rotational speed of the engine 2 for a predetermined time, and detects a fluctuation range ΔNE of the rotational speed during the predetermined time. It is determined whether or not the rotational speed fluctuation range ΔNE exceeds a predetermined reference value KR. This KR is a reference value determined so that it can be determined that rough idle (unpleasant vibration caused by instability of idle rotation) can occur when ΔNE is exceeded. When ΔNE exceeds KR, the process proceeds to step 40, and when it is equal to or less than KR, the process proceeds to step 35.

  Next, in step 40, it is determined whether or not the FCCB value calculated as described above is smaller than a predetermined reference value KFCCB. This KFCCB is a reference value determined so that when the FCCB value is smaller, it can be determined that the cylinder is in a semi-misfire state. This semi-misfire state is a state in which the degree of misfire is lighter than a complete misfire state including, for example, a fuel non-injection state or a compression loss state of the engine 2, and is included between a complete misfire state and a normal combustion state It is. Therefore, KFCCB defined for determining the semi-misfire state is a guard value set to a value smaller than the guard value for determining the complete misfire state. If the FCCB value is less than KFCCB, the process proceeds to step 50. If the FCCB value is greater than or equal to KFCCB, the process proceeds to step 60.

  In step 50, the common rail pressure Pc is set higher by ΔP than the target common rail pressure P calculated during normal control as described above. That is, in step 50, a process of increasing Pc to P + ΔP is performed. The ECU 4 controls the metering valve of the high-pressure pump 5 as the pressure raising means so that the common rail pressure Pc becomes a pressure obtained by adding ΔP to the target common rail pressure P set according to the operating state of the engine 2 or the like. Further, in step 50, processing for delaying the start timing of fuel injection is performed. The ECU 4 controls the operation of the fuel injection valve 12 so that the start timing of the fuel injection discharged from the fuel injection valve 12 is delayed by ΔTIM time with respect to the fuel injection timing (target injection start timing TIM) during normal control. .

  If NO in step 30, the process proceeds to step 35, and it is determined whether or not the A / F value in the exhaust gas detected using the A / F sensor 23 is less than a predetermined reference value KAFR. To do. This KAFR is a boundary value determined so that it can be determined that white smoke can be generated when the A / F value is further decreased. If the A / F value is less than KAFR, the process proceeds to step 40, and if it is greater than or equal to KAFR, the process proceeds to step 60. In step 60, a process of setting the common rail pressure to the target common rail pressure P calculated during normal control is performed. In step 60, the fuel injection start timing is set to the target injection start timing TIM during normal control.

  Next, the processing executed by the control device 1 for the diesel engine will be further described based on the logic diagrams shown in FIGS. 3 and 4. FIG. 3 is a logic diagram illustrating the common rail pressure Pc increasing process executed by the control device 1. FIG. 4 is a logic diagram showing the injection start timing retard process executed by the control device 1. First, the process of setting the common rail pressure Pc (= P + ΔP) in the process of step 50 in the flowchart of FIG. 2 will be described.

  In step R1 in FIG. 3, ΔP is set based on the engine coolant temperature detected by the coolant temperature sensor 22 and the elapsed time after the engine 2 is started (hereinafter referred to as the elapsed time after engine startup). Specifically, the increase ΔP of the common rail pressure is set using a map representing the correlation between the engine coolant temperature and the elapsed time after engine start and ΔP. For example, ΔP tends to be set larger as the engine coolant temperature is lower, and tends to be set larger as the elapsed time after engine startup is shorter. The above map is stored in the ROM of the ECU 4.

  Next, in the process of R2, the normal common rail pressure P is set by the above ISC control. In the process of R3, ΔP calculated in the process of R1 and P set in the process of R2 are added to set P + ΔP as the common rail pressure Pc. The processing of step 50 in the flowchart of FIG. 2 is based on the precondition that ΔNE> KR and FCCB value <KFCCB, or A / F value <KAFR and FCCB value <KFCCB (YES in step 30 and step 40). YES, or YES in step 35 and YES in step 40). The calculation in this case is such that B1 and C1 are connected in SW1 of FIG. 3 and B2 and C2 are connected in SW2, and ΔP calculated in the process of R1 and P set in the process of R2 are added. It becomes logic.

  Next, a process of setting the common rail pressure Pc (= P) in the process of step 60 in the flowchart of FIG. 2 will be described. In this case, P set in step R2 is set as the common rail pressure Pc as it is. The processing of step 60 in the flowchart of FIG. 2 is based on the precondition that ΔNE ≦ KNE, and A / F value ≧ KAFR, FCCB value ≧ KFCCB, in the case of not idling (NO in step 20). (NO in step 30 and NO in step 35, or NO in step 40). The calculation in this case includes a flow in which A1 and C1 are connected in SW1 in FIG. 3 and A2 and C2 are connected in SW2, and a flow in which B1 and C1 are connected in SW1 and A2 and C2 are connected in SW2. In any case, ΔP is not added to P set in the process of R2.

  Next, a process of retarding the fuel injection start timing (delaying ΔTIM time with respect to the normal injection start timing) in the process of step 50 in the flowchart of FIG. 2 will be described. This process is also performed with the same logic as the process of increasing the common rail pressure Pc. In the process of R4 in FIG. 4, ΔTIM is set based on the common rail pressure Pc and the engine speed NE. Specifically, the delay time ΔTIM of the injection start timing is set using a map representing the correlation between the common rail pressure and engine speed and ΔTIM. The above map is stored in the ROM of the ECU 4.

  Next, in the process of R5, the target injection start timing TIM during the normal control is set. In the process of R6, ΔTIM calculated in the process of R4 and the TIM set in the process of R5 are added, and TIM + ΔTIM is set as the fuel injection start timing Ti. The processing of step 50 in the flowchart of FIG. 2 is based on the precondition that ΔNE> KR and FCCB value <KFCCB, or A / F value <KAFR and FCCB value <KFCCB (YES in step 30 and step 40). YES, or YES in step 35 and YES in step 40). The processing in this case is a logic in which B1 and C1 are connected in SW1 in FIG. 4 and B2 and C2 are connected in SW2, and ΔTIM calculated in the process of R4 and the TIM set in the process of R5 are added. It becomes.

  Next, a process of setting the injection start timing Ti (= TIM) in the process of step 60 in the flowchart of FIG. 2 will be described. In this case, the TIM set in the step R5 is set as the injection start timing Ti as it is. The processing of step 60 in the flowchart of FIG. 2 is based on the precondition that ΔNE ≦ KNE, and A / F value ≧ KAFR, FCCB value ≧ KFCCB, in the case of not idling (NO in step 20). (NO in step 30 and NO in step 35, or NO in step 40). The processing in this case is as follows: A1 and C1 are connected in SW1 of FIG. 4 and A2 and C2 are connected in SW2, B1 and C1 are connected in SW1, and A2 and C2 are connected in SW2. In any case, ΔTIM is not added to the TIM set in step R5.

  Below, the experimental result which verifies the effect which the control apparatus 1 of a diesel engine show | plays is demonstrated with reference to FIG. FIG. 5 is a graph showing the effect produced by the common rail pressure increasing process by the control device 1.

  When the common rail pressure Pc is set to the pressure P set by the above ISC control (in FIG. 5, “conventional control: indicated pressure Pc = P” is displayed), the common rail pressure Pc is set to ΔP ( For example, the correlation between the fluctuation of the common rail pressure (ΔPC) and the fluctuation range ΔNE of the rotational speed is shown for each of the cases where the pressure is high (in FIG. 5, “application control: indicated pressure Pc = P + ΔP”). It was measured. Measurement conditions were set to start when the vehicle was idle at an outside air temperature of 0 ° C. and a cooling water temperature of 5 to 15 ° C. It is considered that the fluctuation of the common rail pressure Pc occurs due to the low temperature environment, parts and control variations, and the fluctuation width ΔNE of the rotational speed is increased due to the fluctuation. As can be seen from FIG. 5, the control range of the present application in which the common rail pressure Pc is set higher is significantly smaller in the fluctuation range ΔNE of the rotational speed with respect to the fluctuation (ΔPC) of the common rail pressure. This result confirms that rough idling and generation of white smoke can be reduced by performing control for setting a pressure increase of ΔP with respect to the target common rail pressure P in the control device 1 of the diesel engine.

  Below, the effect which the control apparatus 1 of a diesel engine implement | achieves the raise process of said common rail pressure and injection start timing retard process is demonstrated with reference to FIGS. FIG. 6 is a graph showing the relationship between the crank angle and the cylinder internal pressure during normal control by the control device 1. FIG. 7 is a graph showing the relationship between the crank angle and the cylinder internal pressure when the control device 1 performs the common rail pressure increasing process. FIG. 8 is a graph showing the relationship between the crank angle and the cylinder internal pressure when the control device 1 performs the injection start timing retard process. In each graph, the fuel injection pulse width and the injection start timing are drawn together.

  During normal control, the cylinder pressure varies with respect to the crank angle as shown in FIG. By performing the fuel injection by the fuel injection pulse starting at the target injection start timing TIM shown in FIG. 6, the cylinder internal pressure rises again at the crank angle beyond the parabolic peak so as to draw a parabola. The transition will decrease.

  On the other hand, when the common rail pressure Pc is made higher than the target common rail pressure P by ΔP by the process of increasing the common rail pressure, the cylinder internal pressure is again reduced at a crank angle smaller than that in the normal control of FIG. 6 as shown in FIG. As the value rises, a transition in which the peak value is higher than that in FIG. 6 is drawn. Thereby, combustion becomes earlier than the time of the normal control of FIG. 6, and the combustion state is improved. In FIG. 7, a portion indicated by a two-dot chain line corresponds to a transition portion of the cylinder pressure generated by the fuel injection during the normal control shown in FIG. 6.

  As described above, according to the process of increasing the common rail pressure, rapid combustion may occur due to rapid combustion, and a high-pitched combustion sound similar to a metallic sound may be generated. Therefore, if the injection start timing Ti is delayed by ΔTIM from the target injection start timing TIM by the injection start timing retard process, the cylinder pressure rises again at a crank angle larger than the process of FIG. 7 as shown in FIG. Then, a transition in which the peak value is lower than that in FIG. 7 is drawn. As a result, the combustion is delayed with respect to the processing in FIG. Therefore, the change in the combustion noise caused by the sudden combustion change in FIG. 7 is alleviated, and the combustion noise in the common rail pressure increase process is improved. In FIG. 8, a portion indicated by a two-dot chain line corresponds to a transition portion of the in-cylinder pressure generated by the execution of the common rail pressure increasing process shown in FIG.

  According to the above-described embodiment, the diesel engine control device 1 detects the rotational speed sensor 21 (the rotational speed fluctuation width detection) that detects the rotational speed fluctuation range ΔNE of the engine 2 to which the fuel accumulated in the common rail 6 is supplied. Means) and a semi-misfire determination step (semi-misfire determination means, step 40) for determining whether or not each cylinder 11 of the engine 2 into which the fuel is injected is in a semi-misfire state. After starting the diesel engine 2, the control device 1 determines that the rotational speed fluctuation range ΔNE obtained using the rotational speed sensor 21 exceeds a predetermined fluctuation width threshold value KR, and the cylinder 11 of the engine 2 is subjected to a semi-misfire determination step. When it determines with it being a semi-misfire state, the pressure of the common rail 6 is raised. At this time, the common rail pressure Pc is higher than the pressure at the time of normal control, for example, the pressure set by ISC (idle speed control) control. If the semi-misfire state determination is not satisfied, the common rail pressure Pc Is controlled to the target common rail pressure P during the normal control.

  According to this, when the rotation speed fluctuation range ΔNE exceeds a predetermined fluctuation range threshold value KR and the cylinder 11 of the engine 2 is in a semi-misfire state, the common rail pressure is increased, thereby spraying fuel into the cylinder 11. The fuel state of the engine 2 is improved from the semi-misfire state to the normal combustion state by extending. For this reason, rough idle and white smoke generation can be reduced. Further, the control device 1 detects a decrease in the fuel injection amount due to the clogging of the injection hole of the fuel injection valve 12 that injects the fuel into the cylinder 11 and a decrease state of the engine compression, and improves these states to perform combustion. State stabilization can be performed. In this way, the control device 1 determines that the cause of the rough idle and white smoke generation is a complete misfire state (misfire state including no fuel injection state and engine compression loss state) and other misfire states. A semi-misfire state (a state included between a complete misfire state and a normal combustion state) with a lighter misfire degree than that of the misfire state is determined and determined to reduce the generation of rough idols and white smoke that are highly effective. ing.

  Further, in the present embodiment, the pressure of the common rail 6 is increased when it is determined that the state is a semi-misfire state. Therefore, the fuel flowing into the cylinder can be spread over a wide range in the cylinder by the increase in the pressure. become. Therefore, the combustion state in the cylinder can be improved without correcting the fuel injection amount positively. Further, according to this function and effect, the fuel injection pulse width during the common rail pressure increase process can be made smaller than the target injection pulse width during normal control. Thereby, in addition to the effect of improving the combustion state, the fuel injection amount can be reduced, which can contribute to the improvement of fuel consumption.

  Further, the control device 1 detects the fluctuation range ΔNE of the rotational speed based on the measured value of the rotational speed sensor 21 that measures the rotational speed of the engine 2 after the engine 2 is started and when the vehicle is idled. According to this, since the rotational speed of the engine 2 is directly measured by the rotational speed sensor 21, the rotational speed fluctuation range ΔNE can be detected with high accuracy.

  The semi-misfire determination step (step 40) as the semi-misfire determination means is a semi-misfire state based on the inter-cylinder injection amount correction value (FCCB value) calculated using the inter-cylinder difference in the rotational speed fluctuation of the diesel engine 2. If the calculated FCCB value is smaller than a predetermined misfire determination threshold value KFCCB, it is determined that the state is a semi-misfire state.

  According to this, since it can be determined whether or not each cylinder 11 of the engine 2 is in a semi-misfire state by determining whether or not it is in a semi-misfire state based on the inter-cylinder injection amount correction value. A cylinder that is in a misfire state can be identified, and control that effectively improves this state can be reliably performed. Therefore, highly accurate detection of a semi-misfire state including a decrease in the fuel injection amount due to clogging of the fuel injection holes and a state where the engine compression is reduced can be expected.

  In addition, when the cylinder 11 of the diesel engine 2 is determined to be in a semi-misfire state by the semi-misfire determination step, the control device 1 increases the pressure of the common rail 6 and other than the cylinder determined to be in the semi-misfire determination state. Control is performed to delay the fuel injection start timing by ΔTIM from the target injection start timing TIM. According to this, in addition to the control for increasing the common rail pressure when the determination of the semi-misfire state is made, the control for delaying the start timing of the fuel injection causes a change in combustion noise that may be caused by the increase in the common rail pressure Pc (for example, (High-pitched combustion sound similar to metal sound) can be suppressed. Therefore, in addition to reducing rough idle and alleviating the semi-misfire state, it contributes to improving the quietness of the engine 2 by suppressing combustion noise.

  Further, the control device 1 is obtained using the A / F sensor 23 (air-fuel ratio detecting means) even if the rotational speed fluctuation range ΔNE obtained using the rotational speed sensor 21 is equal to or less than the fluctuation width threshold KR. The A / F value (air / fuel ratio) of the exhaust of the engine 2 is smaller than the white smoke determination threshold value KAFR set in advance for determining the generation of white smoke, and it is further determined that the engine is in a semi-misfire state by the semi-misfire determination step. If so, implement control to increase common rail pressure.

  According to this, even when the rotation speed fluctuation range ΔNE is equal to or less than the fluctuation width threshold value KR and there is little fluctuation in the rotation speed, it is determined that the A / F value is less than the white smoke determination threshold value KAFR and is in a semi-misfire state. Thus, it is possible to detect a state where white smoke can be generated and a semi-misfire state, and to improve the detection ability of the state. Further, in this case, by increasing the common rail pressure, the fuel state is improved as described above, so that the generation of white smoke can be reduced.

  Further, when the A / F value (air-fuel ratio) obtained using the A / F sensor 23 (air-fuel ratio detecting means) is equal to or higher than the white smoke determination threshold KAFR, the control device 1 increases the pressure of the common rail. Without control, the target common rail pressure P is controlled. According to this, when it is determined that rough idle and white smoke are not generated, the target common rail pressure P is controlled to reduce the efficiency of engine control and the change in combustion sound due to the increase in the common rail pressure. Can be avoided.

  Further, the control device 1 calculates an inter-cylinder injection amount correction value (FCCB value) using the inter-cylinder difference of the rotational speed variation of the diesel engine, and the calculated FCCB value is equal to or greater than a predetermined misfire determination threshold value KFCCB. In some cases, the target common rail pressure P is controlled without increasing the common rail pressure.

  When the FCCB value is an excessive value equal to or greater than the misfire determination threshold value KFCCB, a complete misfire state may be present. In this case, even if the rail pressure is increased to extend the fuel injection, the fuel is not combusted and is discharged wastefully. Therefore, according to this control, such a useless pressure increase can be avoided in advance, so that a decrease in engine control efficiency can be avoided.

(Other embodiments)
The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  For example, the fluctuation range ΔNE in the rotational speed of the engine 2 may be detected based on the detection result of the knock sensor 26 that detects knocking of the engine 2. According to this, the fluctuation range of the rotation speed can be detected with excellent accuracy. For example, a map representing the correlation between the detection result of the knock sensor 26 and the fluctuation range in the rotation speed is stored in advance, and the detection result of the knock sensor 26 is applied to the map to detect the fluctuation width ΔNE of the rotation speed.

  Further, the control device 1 may increase the common rail pressure in accordance with the detected rotational speed fluctuation range ΔNE. According to this, it can contribute to reduction of rough idle.

  Further, the control device 1 may increase the common rail pressure according to the exhaust A / F value obtained by using the A / F sensor 23. According to this, it can reduce that excess unburned fuel contains in exhaust_gas | exhaustion.

  Further, the control device 1 may set the pressure increase ΔP in the common rail pressure increase process to be larger as the engine coolant temperature is lower. According to this, it becomes possible to set a preferable increase width ΔP according to the state of the engine 2. That is, it is possible to reduce a situation in which rough idols and white smoke cannot be sufficiently reduced due to lack of the rising width ΔP, or that the rising noise ΔP becomes excessive and the combustion noise and fuel consumption are deteriorated more than necessary.

  Further, the control device 1 sets the pressure increase width ΔP in the common rail pressure increase process to be larger as the elapsed time after engine start is shorter. According to this, a suitable increase width ΔP can be set according to the state of the engine 2. That is, there is no case where the rising width ΔP is insufficient and the rough idle and white smoke cannot be sufficiently reduced, or the rising width ΔP becomes excessive, and the combustion noise and fuel consumption are not deteriorated more than necessary.

DESCRIPTION OF SYMBOLS 1 ... Control apparatus of diesel engine 2 ... Diesel engine 3 ... Fuel tank 4 ... ECU
5 ... High pressure pump 6 ... Common rail (rail)
DESCRIPTION OF SYMBOLS 11 ... Cylinder 12 ... Fuel-injection valve 13 ... Pressure sensor 14 ... Start switch 21 ... Speed sensor (rotation speed fluctuation detection means)
23. A / F sensor (air-fuel ratio detecting means)
26 ... Knock sensor

Claims (9)

A rotation speed fluctuation detecting means for detecting a fluctuation width of a rotation speed of a diesel engine to which fuel accumulated in the rail is supplied;
Semi-misfire determination means for determining whether or not each cylinder of the diesel engine into which fuel is injected is in a semi-misfire state,
After the start of the diesel engine, the rotation speed fluctuation range obtained by the rotation speed fluctuation detection means exceeds a predetermined fluctuation width threshold, and the cylinder of the diesel engine is in a semi-misfire state by the semi-misfire determination means. If it is determined that there is, increase the rail pressure ,
Further, an inter-cylinder injection amount correction value is calculated using the inter-cylinder difference in the rotational speed variation of the diesel engine, and the semi-misfire determination means determines that the calculated inter-cylinder injection amount correction value is greater than a predetermined misfire determination threshold value. A control device for a diesel engine, characterized in that it is determined that the vehicle is in a semi-misfire state when it is small . A rotation speed fluctuation detecting means for detecting a fluctuation width of a rotation speed of a diesel engine to which fuel accumulated in the rail is supplied;
Semi-misfire determination means for determining whether or not each cylinder of the diesel engine into which fuel is injected is in a semi-misfire state,
After the start of the diesel engine, the rotation speed fluctuation range obtained by the rotation speed fluctuation detection means exceeds a predetermined fluctuation width threshold, and the cylinder of the diesel engine is in a semi-misfire state by the semi-misfire determination means. If it is determined that there is, increase the rail pressure ,
Further comprising air-fuel ratio detection means for detecting an air-fuel ratio in the exhaust of the diesel engine,
Even if the rotational speed fluctuation range obtained by the rotational speed fluctuation detecting means is equal to or less than the fluctuation width threshold value, the air-fuel ratio obtained by the air-fuel ratio detecting means is predetermined in order to determine the generation of white smoke. The diesel engine control device is configured to increase the rail pressure when the semi-misfire determination means determines that the semi-misfire state is smaller than the white smoke determination threshold . A rotation speed fluctuation detecting means for detecting a fluctuation width of a rotation speed of a diesel engine to which fuel accumulated in the rail is supplied;
Semi-misfire determination means for determining whether or not each cylinder of the diesel engine into which fuel is injected is in a semi-misfire state,
After the start of the diesel engine, the rotation speed fluctuation range obtained by the rotation speed fluctuation detection means exceeds a predetermined fluctuation width threshold, and the cylinder of the diesel engine is in a semi-misfire state by the semi-misfire determination means. If it is determined that there is, increase the rail pressure ,
Further, an inter-cylinder injection amount correction value is calculated using a difference between cylinders in the rotational speed fluctuation of the diesel engine, and when the calculated inter-cylinder injection amount correction value is equal to or greater than a predetermined misfire determination threshold value, the rail pressure A control device for a diesel engine, characterized by not performing control to raise the engine. A rotation speed fluctuation detecting means for detecting a fluctuation width of a rotation speed of a diesel engine to which fuel accumulated in the rail is supplied;
Semi-misfire determination means for determining whether or not each cylinder of the diesel engine into which fuel is injected is in a semi-misfire state,
After the start of the diesel engine, the rotation speed fluctuation range obtained by the rotation speed fluctuation detection means exceeds a predetermined fluctuation width threshold, and the cylinder of the diesel engine is in a semi-misfire state by the semi-misfire determination means. If it is determined that there is, increase the rail pressure ,
A knock sensor for detecting knocking of the diesel engine;
The control device for a diesel engine, wherein the rotation speed fluctuation detecting means detects the rotation speed fluctuation width based on a detection result by the knock sensor . The fuel injection start timing is delayed while the pressure of the rail is increased when the cylinder of the diesel engine is determined to be in a semi-misfire state by the semi-misfire determination means. Item 5. The diesel engine control device according to any one of Items 4 to 6. Further comprising air-fuel ratio detection means for detecting an air-fuel ratio in the exhaust of the diesel engine,
Even if the rotational speed fluctuation range obtained by the rotational speed fluctuation detecting means is equal to or less than the fluctuation width threshold value, the air-fuel ratio obtained by the air-fuel ratio detecting means is predetermined in order to determine the generation of white smoke. If it is smaller than the determined white smoke determination threshold and is further determined to be a semi-misfire state by the semi-misfire determination means, the rail pressure is increased,
The control for increasing the pressure of the rail is not performed when the air-fuel ratio obtained by the air-fuel ratio detection means is equal to or greater than the white smoke determination threshold value. diesel engine control device according to an item or. 3. The diesel engine according to claim 2, wherein control for increasing the pressure of the rail is not performed when the air-fuel ratio obtained by the air-fuel ratio detection unit is equal to or greater than the white smoke determination threshold value . Control device. A rotational speed sensor for measuring the rotational speed of the diesel engine;
The diesel engine control according to any one of claims 1 to 4, wherein the rotation speed fluctuation detecting means detects the rotation speed fluctuation width based on a measurement value of the rotation speed sensor. apparatus. A knock sensor for detecting knocking of the diesel engine;
The diesel engine control device according to any one of claims 1 to 3, wherein the rotation speed fluctuation detecting means detects the rotation speed fluctuation width based on a detection result of the knock sensor. .

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