JP2009008060A - Diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a satisfactory starting operation by clearly setting a changing time point and a change of common rail pressure in the starting operation of an engine. <P>SOLUTION: The diesel engine equipped with a common rail has a construction characterized in that a correction means is provided for increase correction of the rail pressure p of the common rail in the vicinity of a position where an initial explosion state is detected from a change of engine rotation speed n in the starting operation of the engine. Further, the diesel engine equipped with the common rail has a construction characterized in that a pressurization means is provided for gradually raising the rail pressure p of the common rail while the engine reaches a constant speed range from a cranking range through an acceleration range in a cold starting operation of the engine. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

 The present invention relates to a diesel engine. In particular, it relates to rail pressure control for common ales.

In recent years, as one of the fuel injection devices for supplying and injecting fuel to an engine, high pressure fuel is temporarily stored in a fuel passage of a common rail, and then an injection nozzle having a plurality of solenoid valves connected to the common rail is provided. Various types of so-called common rail fuel injection devices that can be controlled and simultaneously injected have been proposed and are well known and well known. (For example, see Patent Document 1)
By the way, in such a common rail type fuel injection device, how stable and surely the common rail pressure, that is, the common rail pressure is set as the target pressure greatly affects the quality of the injection characteristics. In, various control is performed on the assumption that the operation characteristics such as opening of a pressure control valve having an electromagnetic valve are assumed in advance.

In reality, variations may occur depending on the individual pressure control valves, and depending on the various operating conditions of the fuel injection device, the original stable and reliable injection control can be performed even if there are variations in these characteristics. An operation control method and a fuel injection device capable of appropriately controlling the common rail pressure are provided, and at the start of the engine, the common rail pressure is reduced from the initial explosion of the engine to at least the idling state. As the control, there is disclosed a control that can realize stable and reliable fuel injection control by performing control with good responsiveness. (For example, see Patent Document 2)
Japanese Patent Laid-Open No. 10-54318 JP 2002-339830 A

  However, as described above, in the engine starting state, the common rail pressure is stable in the idling state when the common rail pressure is controlled from the initial explosion of the engine until at least the idling state is stabilized. However, there is a problem that the change point is unclear until it is done, and the change content that the control with good responsiveness is performed lacks concreteness.

  Therefore, the present invention makes it possible to perform a good start operation by clearly setting the change point and contents of the common rail pressure during the start operation of the engine.

  According to the first aspect of the present invention, in a diesel engine equipped with a common rail, the rail pressure (p) of the common rail is increased before and after the position where the initial explosion state is detected by a change in the engine speed (n) during the start-up operation of the engine. It is set as the structure of the diesel engine characterized by providing the correction means to correct pressure.

  With this configuration, when starting the engine, when it is determined that the engine is in the initial explosion state by detecting an increase in the engine speed (n), an increase rate, or the like, the position at the time of the determination is determined. Before and after, the rail pressure (p) of the common rail for accumulating fuel is corrected to be increased by the correcting means, so that accurate fuel injection can be performed under severe conditions during the start operation.

  According to the invention of claim 2, in a diesel engine equipped with a common rail, the rail pressure (p) of the common rail is gradually increased while the engine reaches a constant speed region from the cranking region through the acceleration region during low temperature start operation. It is set as the structure of the diesel engine characterized by providing the pressure | voltage rise means.

  With such a configuration, when the engine is started at a low temperature, the rail pressure (p) of the common rail for accumulating fuel is gradually increased between the cranking region and the acceleration region due to the increase in the engine speed (n). By boosting the pressure by the boosting means, it is possible to perform fuel injection accurately for particularly severe conditions during the low temperature start operation.

  According to the first aspect of the present invention, as described above, when it is determined that the engine is in the initial explosion state due to a change in the engine speed (n) when starting the engine, the position at the time of the determination is determined. By increasing the rail pressure (p) of the common rail before and after, there is no difficulty that there is no ambiguity about the time of change of the rail pressure (p) and lack of concreteness about the content of the change as in the past, and at the time of starting operation Accurate fuel injection can be performed under severe conditions, and startability can be improved and white smoke at the start can be reduced.

  In the invention of claim 2, as described above, when the engine is started at a low temperature, the rail pressure (p) of the common rail is set between the cranking region and the acceleration region due to the increase in the engine speed (n). By gradually increasing the pressure, the rail pressure (p) is increased before ignition at low temperatures, and the unburned fuel does not collide with the piston wall to lower the temperature and deteriorate the startability. Accurate fuel injection can be performed under particularly severe conditions during operation, and startability can be improved and white smoke at start-up can be suppressed to improve ignitability.

  In the diesel engine using the common rail system, correction means is provided for correcting the rail pressure p of the common rail to increase and decrease before and after the position where the initial explosion state is detected by the change in the engine speed n during the start operation of the engine. Further, in the diesel engine using the common rail system, there is provided a boosting means for gradually increasing the rail pressure p of the common rail while reaching the constant speed region from the cranking region through the acceleration region during the low temperature start operation of the engine.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 4, the diesel engine 1 is a multi-cylinder type common rail system in which a cylinder head 3 is disposed at the top of the cylinder block 2, an oil pan 4 is disposed at the bottom, and a gear case 5 and a radiator fan 6 are disposed at the front. The flywheel 7 is disposed at the rear, and the intake manifold 8 is connected to the intake side of the cylinder head 3 and the common rail 10 is mounted on the upper position of the cylinder block 2 below the intake manifold 8. .

  As shown in FIG. 5, an outline of a common rail fuel injection device will be described with reference to a system diagram. The common rail type (accumulation type fuel injection) is performed via a common rail 10 (accumulation chamber) having a required pressure for fuel supply to a fuel injection device that injects fuel into each cylinder.

  The fuel in the fuel tank 11 is sucked into the high pressure pump 13 driven by the engine 1 through the fuel filter 12 through the suction passage, and the high pressure fuel pressurized by the high pressure pump 13 is guided to the common rail 10 through the discharge passage 14. It is stored.

The high-pressure fuel in the common rail 10 is supplied to the fuel injection valves 17 corresponding to the number of cylinders through the high-pressure fuel supply passages 16, and the fuel injection valves 17 for each cylinder based on commands from the engine control unit 18 (hereinafter referred to as ECU). Is opened, high pressure fuel is injected and supplied into each combustion chamber of the engine 1, and surplus fuel (return fuel) in each fuel injection valve 17 is guided to a common return passage 20 by each return passage 19,
The return passage 20 returns the fuel tank 11.

  Further, in order to control the fuel pressure (rail pressure) in the common rail 10, a pressure control valve 21 is provided in the high-pressure pump 13, and this pressure control valve 21 is sent from the high-pressure pump 13 to the fuel tank 11 by a duty signal from the ECU 18. This adjusts the flow area of the return passage 20 for surplus fuel to the rail, and the rail pressure p can be controlled by adjusting the fuel discharge amount to the common rail 10 side.

  Specifically, the target rail pressure p is set according to the engine operating conditions, and the rail pressure p is set via the pressure control valve 21 so that the rail pressure p detected by the rail pressure sensor 22 matches the target rail pressure p. Feedback control.

  As shown in FIG. 6, the ECU 18 of the common rail diesel engine 1 in an agricultural vehicle has three types of control modes, a traveling mode M1, a normal working mode M2, and a heavy working mode M3, in relation to the rotational speed and the output torque.

  The traveling mode M1 is used when traveling without farming as droop control in which the output fluctuates due to fluctuations in the rotational speed. For example, when the traveling speed is reduced or stopped by applying a brake, As the traveling load increases, the engine speed decreases, so the traveling speed can be reduced or stopped safely.

  The normal work mode M2 is used when performing normal farm work as isochronous control in which the rotation speed is constant and the output is changed according to the load even when the load fluctuates. Sometimes, when the cultivated land is hard and resistance is applied to the cultivating blade, the combine makes it easy for the operator to control the output and maintain the number of rotations even when there is a lot of harvest during harvesting and the load increases.

  In the heavy work mode M3, as in the normal work mode M2, the isochronous control that changes the output according to the load at a constant rotation speed even when the load fluctuates, and when the load limit is approached, the rotation speed is increased to increase the output. Control with heavy load control, especially used when farming near the load limit.For example, when plowing with a tractor, engine output even when encountering hard cultivated land Increases beyond the normal limit, so work is not interrupted.

  These work modes M1, M2, and M3 are configured to be switched by an operation of a work mode changeover switch, a shift operation of a travel shift lever, an operation of turning on and off a work clutch, or the like.

  Conventionally, in a diesel engine, it is known to perform pilot injection that injects a small amount of fuel in a pulse manner prior to main injection, thereby shortening the ignition delay and reducing the so-called knocking noise peculiar to the diesel engine. .

  This pilot injection is performed once or twice before the main injection. However, by using the system of the common rail 10, the state of the pilot injection is changed according to the state of the engine. The generation of white smoke or black smoke due to noise reduction or incomplete combustion can be suppressed.

  As shown in FIG. 1, when a start-up operation is performed in the common rail type diesel engine 1, if it is determined that the initial explosion state is detected by detecting an increase in the engine speed n, an increase rate, or the like, before the determined time point. Then, by increasing the rail pressure p of the common rail 10, which was low, by the correcting means by the ECU 18 or the like after the judgment, the fuel injection valve 17 accurately injects the fuel into the severe condition during the starting operation. Therefore, it is possible to improve startability and reduce white smoke at the start.

  Further, as shown in FIG. 2, when the low temperature start operation is performed in the common rail type diesel engine 1, the flowchart of FIG. 3 is shown while the cranking region due to the increase in the engine speed n reaches the constant speed region through the acceleration region. As shown in the figure, the rail pressure p of the common rail 10 is gradually increased by the pressure increasing means by the ECU 18 or the like according to the increase rate of the engine speed n at the low temperature due to the water temperature. The fuel injection valve 17 performs accurate fuel injection for particularly severe conditions during low-temperature starting operation without increasing the pressure p and causing unburned fuel to collide with the piston wall to lower the temperature and deteriorate startability. It is possible to improve the startability, suppress white smoke at the start, and improve the ignitability.

  Further, during the start-up operation of the engine 1 as described above, as shown in FIG. 7, the initial explosion state is determined by detecting the increase or increase rate of the engine speed n, and by this determination, the in-cylinder ambient temperature can be combusted. It is determined that the engine is in a state, and the initial explosion state does not occur due to the control of the starting operation time, etc. as in the past, by correcting the increase in the fuel injection amount form that was small before the determination point, after the determination point Since excessive fuel injection can be prevented in a difficult state, the total amount of fuel required for starting and the total amount of black smoke discharged at starting can be reduced.

  Originally, the responsiveness to the operation of the operator is one of the performances required for the engine. By increasing this responsiveness, the accelerator operation is suddenly performed immediately after the engine is started at a low temperature. When doing so, it can cause problems such as misfires and white smoke.

  For this reason, in the common rail type diesel engine 1, the fuel injection amount in the ECU 18 at the time of no load after the start is monitored, so that the current state of the engine 1 is heavy even at the time of no load such as immediately after the start at a low temperature. Since it can be determined that the injection amount increases, as shown in FIG. 8, the correction of the smoke limit s that restricts the injection amount as the fuel injection amount increases is performed strongly, thereby suppressing the occurrence of misfire and white smoke. This can be dealt with by responsiveness according to the state.

  The smoke limit s originally is a function for suppressing the occurrence of smoke due to the fuel injection amount being too large with respect to the increase in the engine speed n when a sudden accelerator change occurs at no load or the like. When the smoke amount increases depending on the state of the engine, it is necessary to further increase the map correction amount of the smoke limit s.

  Further, as described above, by monitoring the fuel injection amount in the ECU 18 at the time of no load after the start in the engine 1, the current state of the engine 1 is heavy even at the time of no load such as immediately after the start at a low temperature. Since it can be determined that the fuel injection amount increases, an accelerator that lowers the responsiveness according to the state of the engine 1 as the fuel injection amount that requires the smoke limit s increases as shown in FIG. By performing the smoothing control f strongly, it is possible to cope with a sudden accelerator change with better response in accordance with the state of the engine 1 by suppressing the occurrence of misfire and white smoke.

  Further, in the common rail diesel engine 1, conventionally, when the fuel temperature at the inlet of the high pressure pump 13 is too high, if the fuel is returned to the fuel tank 11 more than necessary and cooled in the return passage 20 too much, the heat efficiency is lost. When the fuel is at a low temperature, n-paraffin may precipitate as wax crystals, which may block the fuel filter 12 and hinder the operation.

  For this reason, as shown in FIG. 10, the return passage 20 is provided with a thermo-stud type flow path switching valve 23, and the return point of the leaked fuel by the flow path switching valve 23 depends on the temperature. Since the return point of the leaked fuel can be made variable depending on the temperature by returning the fuel filter 12 to the front of the fuel filter 12 when the temperature is low and to the back of the fuel filter 12 when the temperature is low. It is possible to adjust the fuel temperature to an appropriate temperature and perform a good operation.

  Conventionally, in an electronically controlled fuel injection engine, various catalyst regeneration operations have been carried out depending on the engine environment, one of which is the exhaust gas temperature rise due to post injection, but it is the extreme of the minimum value of nozzle opening. In the case of a small amount of injection, the injection amount and the presence or absence of injection are likely to be unstable.

  Therefore, in the common rail diesel engine 1 equipped with a DPF (particulate filter), the presence or absence of post-injection is made variable for each cylinder of the engine. For example, when the post-injection amount is extremely small, post-injection is performed. It is also possible to increase the injection amount per cylinder by reducing the number of cylinders. In this way, by making it possible to increase or decrease the number of cylinders that perform post-injection, by making it possible to adjust the injection amount per cylinder, it is possible to reliably perform post-injection and appropriately adjust the temperature. Can be controlled.

  In addition, in an electronically controlled fuel injection engine, various fuel injection corrections are performed depending on the engine environment. An example in which a work machine load is incorporated into the engine environment to perform control specific to agricultural machinery is shown below. Few.

  For this reason, as shown in FIG. 11, in the combine, the start timing of the cutting load is predicted by a sensor provided for detecting and predicting the start of rice cutting at the tip of the cutting unit, and in the tractor, the rotary case Since the start of the tillage load is predicted by a sensor provided to detect and predict the timing when the rotary contacts the ground on the lower surface etc., control correction etc. can be started from the start of prediction, so load It is possible to reduce the response delay of engine control at the start of work where conditions change greatly. For example, it is possible to optimize the EGR rate and boost pressure, switch the operation mode, reduce sudden torque fluctuations, etc. it can.

  In this way, by attaching a sensor for predicting the start time of the work load to the work machine itself, it is possible to detect the start time of the work load with high accuracy and to predict the start time of the work load. The control setting can be easily switched, and the fuel injection set value can be smoothly corrected under the condition that the load factor changes greatly.

  In addition, when climbing or descending on a farm vehicle 24 by going over a fence or the like, conventionally, the accelerator opening is manually adjusted according to the operator's judgment to ensure workability and safety. In such an operation, when an operator's judgment mistake occurs, the safety is hindered.

  For this reason, as shown in FIG. 12, when the inclination angle instruction value of the inclination sensor 25 provided on the farm vehicle 24 is equal to or greater than a set value, it is determined that the vehicle is climbing or descending according to the information of the inclination sensor 25. By controlling so that the accelerator opening is automatically kept low without waiting for the judgment and operation by the operator, it is possible to reduce the engine speed n and perform an operation that ensures workability and safety.

  Further, as described above, the engine speed is determined by determining whether the vehicle is climbing or descending based on the information of the inclination sensor 25 provided on the farm vehicle 24 and automatically controlling the accelerator opening without waiting for the determination and operation by the operator. When the operation of the accelerator is performed within a few seconds before the inclination angle is detected in an operation in which n is reduced and workability and safety are ensured, automatic accelerator opening based on information from the inclination sensor 25 is performed. Priority is given to manual operation according to the operator's intention.

  Further, as described above, the engine speed is determined by determining whether the vehicle is climbing or descending based on the information of the inclination sensor 25 provided on the farm vehicle 24 and automatically controlling the accelerator opening without waiting for the determination and operation by the operator. In the case where the operation is performed by reducing n and ensuring workability and safety, control is performed to lower the accelerator opening during traveling, but control is performed to increase the accelerator opening during climbing operation. In the operation mode, the work performance can be maintained by increasing the accelerator opening.

  Further, when turning during the operation of the farm vehicle 24 or the like, conventionally, since the throttle is controlled by the actuator by the signal of the potentiometer, there is a problem that the response delay in changing the engine speed n is large. It was.

  Therefore, as shown in FIG. 13, when a turning signal t and a steering angle signal h are inputted to the ECU 26 on the vehicle body side during work, these signals are sent to the ECU 18 on the engine 1 side by CAN communication, and the potentiometer Control for changing the decrease rate of the engine speed n by the turning angle of the steering wheel is performed independently of the throttle position of the vehicle, thereby reducing response delay and improving the operability of the operator.

  It can also be used for general vehicles such as farm vehicles such as tractors and combines.

The diagram which shows the rail pressure increase state by the first explosion state detection at the time of engine starting operation. The diagram which shows the rail pressure increase state by rotation increase at the time of engine low temperature start driving | operation. The flowchart which shows the pressure | voltage rise procedure of rail pressure by rotation speed increase at the time of water temperature low temperature. The side view which shows the whole structure in a common rail type | mold multi-cylinder diesel engine. The system figure which shows the pressure accumulation type fuel injection diesel engine by a common rail. The diagram which shows the relationship between the engine speed and output torque by three types of control modes. The diagram which shows the increase state of the injection quantity by the detection of the first explosion state at the time of engine starting operation. The diagram which shows the state of correction | amendment of the smoke limit with respect to the fuel injection quantity at the time of no load. The diagram which shows the state which strengthens smoothing control when there is much fuel injection quantity at the time of no load. The block diagram which shows the state which changes the leak fuel return point of an engine with temperature. The diagram which shows the state which estimates a workload start with a sensor and reduces response delay. The side view which shows the state of the farm vehicle which attached the sensor which detects an inclination angle. The block diagram which shows the circuit which changes an engine speed by the input of a turning signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Common rail type diesel engine n Engine speed 10 Common rail p Rail pressure 11 Fuel tank 12 Fuel filter 13 High pressure pump 17 Fuel injection valve 18 ECU
20 Return passage

Claims (2)

  In a diesel engine equipped with a common rail, a correction means is provided for correcting the rail pressure (p) of the common rail before and after the position where the initial explosion state is detected by a change in the engine speed (n) during start-up operation of the engine. Diesel engine characterized by that.   A diesel engine equipped with a common rail is provided with a boosting means for gradually increasing the rail pressure (p) of the common rail while reaching the constant speed region from the cranking region through the acceleration region during low temperature start operation of the engine. A featured diesel engine.

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