JP2006029094A - Pressure accumulating fuel injector and internal combustion engine having its pressure accumulating fuel injector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure accumulating fuel injector and an internal combustion engine having its pressure accumulating fuel injector, capable of providing a proper fuel injection quantity, by highly accurately adjusting common rail internal pressure. <P>SOLUTION: An engine has a common rail type fuel injector, and is respectively equipped with actuators 88 and 89, by constituting a fuel force feed high pressure pump 8 of two pump groups 8A and 8B. In operation being relatively a little in a fuel injection quantity, one is stopped among the two actuators 88 and 89, and fuel force feed operation is performed from only the other actuator 89, to thereby reduce capacity of a fuel flowing space reaching a delivery part from a suction part of the high pressure pump 8. Thus, a quantity adjusting error in the whole high pressure pump 8 can be reduced, and fuel quantity adjusting accuracy can be improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pressure accumulation type (common rail type) fuel injection device including a pressure accumulation pipe (so-called common rail) applied to a fuel supply system of an internal combustion engine (for example, a diesel engine), and an internal combustion engine including the pressure accumulation type fuel injection device. Related. In particular, the present invention relates to a measure for enabling the common rail internal pressure to be adjusted with high accuracy.

  Conventionally, as a fuel supply system for a multi-cylinder diesel engine or the like, an accumulator type fuel injection device superior in controllability compared to a mechanical fuel injection pump-nozzle method has been proposed (for example, Patent Document 1 and Patent below) Reference 2).

  This type of fuel injection device stores fuel pressurized to a predetermined pressure by a high-pressure pump in a common rail, and injects fuel stored in the common rail from a predetermined injector into a combustion chamber in accordance with fuel injection timing. It has become. In addition, the controller performs arithmetic processing to control fuel pressure in the common rail (hereinafter referred to as common rail internal pressure) and control of each injector so that fuel is injected under optimal injection conditions for the engine operating state.

  As described above, the pressure accumulation type fuel injection device is excellent in controllability because the fuel injection pressure determined by the common rail internal pressure can be controlled in accordance with the operating state of the engine in addition to the fuel injection amount and the injection timing. It has been attracting attention as an injection device.

Further, as a high-pressure pump used in this type of pressure accumulation fuel injection device, for example, as disclosed in Patent Document 3 below, one having a plurality of fuel pumping systems is known.
JP 2000-18052 A JP 2003-328830 A JP 2004-84538 A

  By the way, the engine performance is greatly influenced by the common rail internal pressure, and in order to achieve high engine output, low fuel consumption, and low emissions, it is necessary to control from a wide common rail pressure to a high common rail pressure with high accuracy depending on the driving conditions. There is. However, in order to control the common rail internal pressure widely in the entire engine operation region, it is necessary to increase the capacity of the fuel sent from the pump to the rail, particularly in order to achieve a high common rail internal pressure under high speed and high injection amount conditions. As described above, when the amount of fuel sent from the pump to the rail (hereinafter referred to as “pump discharge amount”) is increased, the plunger diameter and lift amount of the pump are increased and the control accuracy of the discharge amount becomes rough. As a result, the common rail internal pressure control accuracy deteriorates. Has the problem.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an accumulator fuel injection device capable of adjusting the common rail internal pressure with high accuracy in the entire engine operation region, and an accumulator fuel injection thereof. An object of the present invention is to provide an internal combustion engine provided with the device.

-Summary of invention-
The solution of the present invention taken to achieve the above object is to forcibly stop a part of the fuel pumping system with respect to the accumulator fuel injection apparatus having a high-pressure pump having a plurality of fuel pumping systems. The purpose is to reduce pump discharge capacity, improve pump discharge control accuracy, and improve rail pressure control accuracy.

-Solution-
Specifically, the present invention relates to a fuel pumping unit that pumps fuel, a common rail that stores fuel pumped from the fuel pumping unit, and fuel that is supplied from the common rail is injected toward the combustion chamber of the internal combustion engine. A pressure accumulation type fuel injection device including a fuel injection valve is assumed. In the accumulator fuel injection device, the fuel pumping means is provided with a plurality of fuel pumping units having pumping paths independent from each other. When the fuel requirement amount of the internal combustion engine is equal to or less than a predetermined amount, a part of the fuel pumping unit is forcibly stopped and the fuel pumping operation for the common rail is performed only by the remaining fuel pumping units. Is provided.

  Due to this specific matter, for example, when the internal combustion engine is operating at a high speed and the required fuel amount of the internal combustion engine exceeds a predetermined amount (for example, this required fuel amount cannot be obtained unless all the fuel pumping units are driven). In this case, the fuel pumping operation for the common rail is performed by driving all the fuel pumping units. On the other hand, for example, when the internal combustion engine is operating at a low speed and the required fuel amount of the internal combustion engine is equal to or less than a predetermined amount (when the required fuel amount can be obtained by only driving some of the fuel pumping units). In this case, the pressure feeding unit control means forcibly stops some of the fuel pressure feeding units. Thereby, the fuel pumping operation with respect to the common rail is performed only by the remaining fuel pumping units. In this way, when the fuel pumping operation with respect to the common rail is performed only by the remaining fuel pumping units, the discharge amount from the fuel pumping means (fuel pump) is 1 / compared to the case where all the fuel pumping units are driven. 2 and less. As a result, the metering error in the entire fuel pumping means can be reduced, and metering accuracy can be improved. For example, if one fuel pumping unit is forcibly stopped while two fuel pumping units may cause a metering error of several percent, both fuel pumping units are driven. The metering error is halved as compared to the case of the above. Accordingly, the common rail internal pressure control error is also halved.

  As the switching control of the number of drive of the fuel pumping unit by the pumping unit control means, specifically, an operation of driving all the fuel pumping units according to the operating rotational speed of the internal combustion engine and the fuel injection amount of the fuel injection valve; The operation for forcibly stopping some of the fuel pumping units is switched. For example, a map for setting the number of drive of the fuel pumping unit according to the operating speed and the fuel injection amount is prepared, and the map of the fuel pumping unit is prepared from this map according to the detected operating speed and the fuel injection amount. There are things that set the number of drives. It is also possible to use the engine output torque instead of the fuel injection amount for detecting the engine operating state.

  In addition, as the operation when the control operation by the pressure-feeding unit control means is forcibly canceled, the following operation is listed. Transient determination means for determining whether or not the operation of the internal combustion engine is in a transient state is provided. When the pumping unit control means receives a signal from the transient determining means and the operation of the internal combustion engine is in a transient state, the operation for forcibly stopping some of the fuel pumping units is canceled and all the fuel pumping units are released. Is driven to perform fuel pumping operation on the common rail. For example, during a transition, such as when a request to rapidly increase the rotational speed of the internal combustion engine occurs, all fuel pumping units are driven to perform fuel pumping operation to the common rail regardless of the detected value of the common rail internal pressure, etc. Let it be done.

  Furthermore, when the number of fuel pumping units to be driven is switched by the pumping unit control means, the determination value for performing the switching determination is provided with hysteresis. Thereby, it is possible to avoid the hunting phenomenon that frequently causes the switching operation of the number of drive of the fuel pumping unit, and to maintain the stability of the driving operation of the fuel pumping means.

  In addition, an internal combustion engine including the pressure accumulating fuel injection device according to any one of the above-described solving means is also within the scope of the technical idea of the present invention.

  As described above, in the present invention, with respect to an accumulator fuel injection apparatus having a fuel pumping means having a plurality of fuel pump units independent from each other, a part of the fuel pumping system is forcibly stopped to improve metering accuracy. Can be planned. As a result, the common rail internal pressure can be maintained at the target pressure with high accuracy, and as a result, the fuel injection amount from the fuel injection valve can be appropriately controlled.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment demonstrates the case where this invention is applied to the pressure accumulation type fuel-injection apparatus with which the fuel supply system of the 6-cylinder marine diesel engine was equipped.

-Description of fuel injection system configuration-
First, the overall configuration of the fuel injection device applied to the engine according to the present embodiment will be described. FIG. 1 shows a pressure accumulation type fuel injection device provided in a 6-cylinder marine diesel engine.

  This accumulator fuel injection device includes a plurality of fuel injection valves (hereinafter referred to as injectors) 1, 1,... Attached corresponding to each cylinder of a diesel engine (hereinafter simply referred to as an engine), and a relatively high pressure ( A common rail 2 for accumulating high-pressure fuel having a common rail internal pressure (for example, 100 MPa), and a high-pressure pump as a fuel pump that pressurizes fuel sucked from a fuel tank 4 via a low-pressure pump (feed pump) 6 and discharges the fuel into the common rail 2 (Fuel pumping means in the present invention) 8 and a controller (ECU) 12 for electronically controlling the injectors 1, 1,.

  The high-pressure pump 8 is a so-called plunger-type supply fuel supply pump that is driven by an engine, for example, and boosts the fuel to a high pressure determined based on an operating state or the like and supplies the fuel to the common rail 2 through the fuel supply pipe 9. For example, the high-pressure pump 8 is connected to a crankshaft of the engine via a gear so that power can be transmitted. As another configuration for transmitting the power, a pulley is provided on each of the drive shaft of the high-pressure pump 8 and the crankshaft of the engine, and a belt is placed on the pulley so that the power can be transmitted, or a sprocket is provided on each shaft. It is also possible to provide a power transmission by linking a chain to the sprocket.

  Each of the injectors 1, 1,... Is attached to the downstream end of a fuel pipe that communicates with the common rail 2. The fuel injection from the injector 1 is controlled, for example, by energizing and stopping energization (ON / OFF) of an electromagnetic valve for injection control (not shown) integrated in the injector. That is, the injector 1 injects the high-pressure fuel supplied from the common rail 2 toward the combustion chamber of the engine while the injection control electromagnetic valve is open.

  The controller 12 receives various engine information such as the engine speed and engine load, and provides the injection control solenoid valve with the optimal fuel injection timing and fuel injection amount determined from these signals. Output a control signal. At the same time, the controller 12 outputs a control signal to the high pressure pump 8 so that the fuel injection pressure becomes an optimum value according to the engine speed and the engine load. Further, a pressure sensor 13 for detecting the common rail internal pressure is attached to the common rail 2, and the high pressure pump is set so that the signal of the pressure sensor 13 becomes an optimum value set in advance according to the engine speed and the engine load. The amount of fuel discharged from 8 to the common rail 2 is controlled.

  The fuel supply operation to each injector 1 is performed from the common rail 2 through the branch pipe 3 constituting a part of the fuel flow path. That is, the fuel taken out from the fuel tank 4 through the filter 5 by the low-pressure pump 6 and pressurized to a predetermined suction pressure is sent to the high-pressure pump 8 through the fuel pipe 7. The fuel supplied to the high-pressure pump 8 is stored in the common rail 2 in a state where the pressure is increased to a predetermined pressure, and is supplied from the common rail 2 to the injectors 1, 1,. A plurality of injectors 1 are provided according to the type of engine (the number of cylinders, six cylinders in this embodiment), and the fuel supplied from the common rail 2 is optimally injected at the optimal injection timing under the control of the controller 12. The quantity is injected into the corresponding combustion chamber. Since the injection pressure of the fuel injected from the injector 1 is substantially equal to the pressure of the fuel stored in the common rail 2, the pressure in the common rail 2 is controlled to control the fuel injection pressure.

  Further, of the fuel supplied from the branch pipe 3 to the injector 1, the fuel that was not spent for injection into the combustion chamber and the excess fuel when the common rail internal pressure excessively rises are returned to the fuel tank 4 through the return pipe 11. .

  Information on the cylinder number and the crank angle is input to the controller 12, which is an electronic control unit. The controller 12 sets a target fuel injection condition (for example, target fuel injection timing, target fuel injection amount, target common rail internal pressure) that is predetermined based on the engine operating state so that the engine output becomes an optimum output that matches the operating state. As a function, the target fuel injection conditions (that is, the fuel injection timing and the injection amount by the injector 1) corresponding to signals representing the current engine operating state detected by various sensors are obtained by calculation, and the conditions Thus, the operation of the injector 1 and the fuel pressure in the common rail are controlled so that fuel injection is performed.

  FIG. 2 is a control block of the controller 12 for determining the fuel injection amount. As shown in FIG. 2, the calculation of the fuel injection amount is performed by the command rotational speed calculation means 12A receiving the opening signal of the regulator operated by the user, and the command rotational speed calculation means 12A corresponds to the opening of the regulator. Command rotation speed "is calculated. Then, the injection amount calculation means 12B calculates the fuel injection amount so that the engine rotation speed becomes the command rotation speed. In the injector 1 of the engine (internal combustion engine) E, the fuel injection operation is performed with the fuel injection amount obtained by this calculation. In this state, the rotational speed calculation means 12C calculates the actual engine rotational speed, and this actual engine Comparing the rotational speed with the command rotational speed, the fuel injection amount is corrected (feedback control) so that the actual engine rotational speed approaches the command rotational speed.

  The feature of this embodiment is that the driving state of the high-pressure pump 8 can be switched according to the operating state of the engine E. Before describing the switching operation of the driving state of the high-pressure pump 8, the schematic configuration of the high-pressure pump 8 will be described.

-Description of high-pressure pump 8-
FIG. 3 is a diagram schematically showing a schematic configuration of the high-pressure pump 8 and a connection state of the low-pressure pump 6 and the common rail 2 to the high-pressure pump 8. As shown in FIG. 3, the high-pressure pump 8 includes first to sixth six pump mechanisms 81 to 86. That is, the pump mechanisms 81 to 86 are configured by six cylinders and pistons that reciprocate within the cylinders, and the first to sixth pump chambers 81a to 86a are formed in the pump mechanisms 81 to 86, respectively. ing.

  The pump mechanisms 81 to 86 perform the fuel pressure feeding operation at different timings. Specifically, after the fuel pumping operation of the first pump mechanism 81 is performed, the fuel pumping operation of the fourth pump mechanism 84 is performed, and thereafter, the second, fifth, third, and sixth pump mechanisms 82, The fuel pumping operation is performed in the order of 85, 83, 86. In the high-pressure pump 8, the rotational speed of the drive shaft matches the rotational speed of the crankshaft of the engine, and the fuel pumping operation is performed six times by one revolution of the crankshaft (one revolution of the drive shaft of the high-pressure pump 8: 360 °). Is configured to be performed. In other words, one of the pump mechanisms 81 to 86 performs one fuel pressure feeding operation every 60 ° rotation of the crankshaft.

  Further, these six pump mechanisms 81 to 86 are grouped into first and second two pump groups (fuel pumping units referred to in the present invention) 8A and 8B. Specifically, the first to third pump mechanisms 81, 82, and 83 are grouped so as to be the first pump group 8A, and the fourth to sixth pump mechanisms 84, 85, and 86 are the second pump group 8B. ing. For this reason, the discharge-side piping 61 of the low-pressure pump 6 is branched into two low-pressure piping 62 and 63 of the first and second systems, and the first low-pressure piping 62 is further connected to the first to third pump mechanisms 81, 82 and 83. Are branched into three branch pipes 62a, 62b, and 62c, respectively, and are individually connected to the first to third pump chambers 81a, 82a, and 83a. Similarly, the second low-pressure pipe 63 is branched into three branch pipes 63a, 63b, 63c corresponding to the fourth to sixth pump mechanisms 84, 85, 86, and the fourth to sixth pump chambers 84a, 84a, 85a and 86a are individually connected. Each of the branch pipes 62a to 62c and 63a to 63c is provided with a check valve for preventing a back flow of fuel from the pump chambers 81a to 86a to the low pressure pump 6 side. The discharge sides of the pump chambers 81a to 86a are connected to merging spaces 87 and 87 provided for the groups 8A and 8B. The merging spaces 87 and 87 are connected to the common rail 2 via the fuel supply pipe 9. It is connected. A check valve is provided on the discharge side of each of the pump chambers 81a to 86a to prevent the fuel from flowing back from the merge spaces 87 and 87 to the pump chambers 81a to 86a.

  The first low pressure pipe 62 and the second low pressure pipe 63 are provided with first and second discharge amount control actuators 88 and 89, respectively. These actuators 88 and 89 are provided with needle valves 88a and 89a which can be freely moved in and out of the low pressure pipes 62 and 63, and the opening areas of the low pressure pipes 62 and 63 are made variable by the protruding amount of the needle valves 88a and 89a, thereby the pump chamber. The common rail internal pressure can be adjusted by adjusting the amount of fuel supplied to 81a to 86a. That is, the lower the common rail internal pressure, the larger the opening area of the low-pressure pipes 62, 63 and the amount of fuel supplied to the pump chambers 81a to 86a is increased, thereby increasing the common rail internal pressure to the target pressure.

  The controller 12 includes a pumping unit control means 12D for controlling the fuel pumping operation of the pump groups 8A and 8B. In other words, the pumping unit control means 12D drives both the first pump group 8A and the second pump group 8B, and forcibly stops the first pump group 8A and drives only the second pump group 8B. Switching between cases.

  Specifically, the pressure feeding unit control means 12D controls the needle valve protrusion amounts of the discharge amount control actuators 88 and 89. When the opening area of the low-pressure pipes 62 and 63 is increased by reducing the protruding amount of the needle valve, fuel pumping from the pump group increases, and conversely, the protruding amount of the needle valve is increased. When the opening area of the low pressure pipes 62 and 63 is reduced, fuel pumping from the pump group is reduced. Further, when the needle valve protrusion amount is maximized, the low pressure pipes 62 and 63 are fully closed, and fuel is not pumped from the pump group, that is, the pump group is stopped.

  More specifically, the pressure-feeding unit control means 12D receives an engine speed signal, a fuel injection amount signal, etc., for example, when the engine E is operating at a high speed and the fuel requirement amount of the engine E is in both pump groups 8A, 8B. If it is not possible to drive the two, the pump groups 8A and 8B are driven to perform the fuel pressure feeding operation with respect to the common rail 2 (hereinafter referred to as the both actuator driving state). On the other hand, for example, when the engine is operating at a low speed and the required fuel pumping amount of the engine can be obtained only by driving one pump group 8B, the first pump group 8A is forcibly stopped. (The first low pressure pipe 62 is fully closed by maximizing the needle valve protrusion amount of the first discharge amount control actuator 88: hereinafter referred to as a one-side actuator drive state). As a result, the fuel pumping operation for the common rail 2 is performed only by the second pump group 8B.

  As described above, when the fuel pumping operation with respect to the common rail 2 is performed by only one pump group 8B, the metering accuracy can be improved as compared with the case where both pump groups 8A and 8B are driven. I have to. For example, assuming that the pump maximum discharge amount is 101 / min when both the first and second pump groups are used and the pump discharge amount is controlled from 0 to the maximum value, the current needs to be changed from 0 to 2A. The control resolution of the pump is 51 / min / A. When only the second pump group is used, the pump maximum discharge amount is 51 / min and 1/2, but the current for controlling the pump discharge amount from 0 to the maximum value does not change from 0 to 2A. As a result, the pump control The resolution is 2.51 / min / A and 1/2. That is, since the discharge amount change with respect to the actuator driving current is halved, the control resolution can be improved and the metering accuracy can be improved.

  FIG. 4 shows a map for switching between the two actuator driving states and the one-side actuator driving state in accordance with the engine speed and the fuel injection amount. In this map, a region A (a region with a dashed diagonal line) indicates a region in which both actuators are driven (two actuator regions), and a region B (a region with a dashed-dotted diagonal line) indicates a one-side actuator driving state (second actuator region). A state in which only the actuator 89 is driven: 1 actuator region) is shown. In this way, both the actuator driving state and the one-side actuator driving state are switched according to the engine speed and the fuel injection amount.

  Further, as shown in FIG. 5, when the pumping unit control means 12D switches the number of pump groups 8A and 8B to be driven, a hysteresis is given to the determination value for performing the switching determination. In FIG. 5 as well, the two actuator areas are indicated by broken diagonal lines, and the one actuator area is indicated by one-dot chain line.

  As described above, by providing hysteresis to the determination value, it is possible to avoid the hunting phenomenon that frequently causes the switching operation of the number of driving of the pump groups 8A and 8B, and the stability of the driving operation of the high-pressure pump 8. Can be maintained. In this embodiment, the hysteresis width (width B1 in FIG. 5) in the one-side actuator driving state is set to about half of the hysteresis width (width A1 in FIG. 5) in both actuator driving states. Thereby, the control accuracy can be improved.

  Further, in this embodiment, the controller 12 includes the transient determination means 12E, and the control of the pressure feeding unit control means 12D can be forcibly stopped by a signal from the transient determination means 12E. Specifically, for example, the transient determination means 12E can detect that the regulator opening degree has suddenly increased (a request to suddenly increase the engine speed), and whether the operation of the engine E is in a transient state. It is determined whether or not. Upon receiving the transient determination signal from the transient determination unit 12E, the pumping unit control unit 12D cancels the operation of forcibly stopping a part of the pump groups, so that both the pump groups 8A and 8B are brought together. The fuel pumping operation is performed on the common rail 2 by driving. As a result, it is possible to quickly respond to the above request (request for rapidly increasing the engine speed).

-Other embodiments-
In the embodiment described above, the case where the present invention is applied to a 6-cylinder marine diesel engine has been described. The present invention is not limited to this, and can be applied to various types of engines such as a four-cylinder marine diesel engine. Further, the present invention is not limited to marine engines but can be applied to engines used for other purposes such as vehicles.

  Further, in the above embodiment, the pump mechanisms 81 to 86 are divided into two groups, and two actuators 88 and 89 are provided. However, the pump mechanisms are divided into three or more groups and three or more actuators are provided. The metering accuracy may be improved by selectively driving only some of these actuators.

It is a figure which shows the pressure accumulation type fuel injection apparatus which concerns on embodiment. It is a control block diagram for determining the fuel injection amount. It is a figure which shows typically schematic structure of a high pressure pump and the low pressure pump and common rail which this high pressure pump connects. It is a figure which shows the map for switching a both actuator drive state and a one-side actuator drive state. It is a figure which shows the hysteresis of the switching determination value at the time of switching the number of the pump groups to drive.

Explanation of symbols

1 Injector (fuel injection valve)
2 Common rail 8 High-pressure pump (fuel pressure feeding means)
8A 1st pump chamber group (fuel pumping unit)
8B Second pump chamber group (fuel pumping unit)
12D Pressure feed unit control means 12E Transient judgment means E Engine (internal combustion engine)

Claims (6)

An accumulator comprising fuel pumping means for pumping fuel, a common rail for storing fuel pumped from the fuel pumping means, and a fuel injection valve for injecting fuel supplied from the common rail toward the combustion chamber of the internal combustion engine In the fuel injection device,
While the fuel pumping means includes a plurality of fuel pumping units having pumping paths independent of each other,
When the required fuel amount of the internal combustion engine is equal to or less than a predetermined amount, a pressure feeding unit control unit is provided that forcibly stops some of the fuel pressure feeding units and performs a fuel pressure feeding operation on the common rail only by the remaining fuel pressure feeding units. An accumulator fuel injection device characterized by comprising: The pressure accumulation type fuel injection device according to claim 1,
The pressure feeding unit control means switches between an operation for driving all the fuel pressure feeding units and an operation for forcibly stopping a part of the fuel pressure feeding units according to the operating rotational speed of the internal combustion engine and the fuel injection amount of the fuel injection valve. The pressure accumulation type fuel injection device characterized by being constituted. The pressure accumulation type fuel injection device according to claim 1,
The pressure feeding unit control means switches between an operation for driving all the fuel pressure feeding units and an operation for forcibly stopping a part of the fuel pressure feeding units according to the operating rotational speed of the internal combustion engine and the engine output torque of the fuel injection valve. The pressure accumulation type fuel injection device characterized by being constituted. In the pressure accumulation type fuel injection device according to claim 1, 2, or 3,
A transient determination means for determining whether or not the operation of the internal combustion engine is in a transient state;
The pressure feeding unit control means receives a signal from the transient judging means, and when the operation of the internal combustion engine is in a transient state, cancels the operation of forcibly stopping some of the fuel pressure feeding units and drives all the fuel pressure feeding units. Thus, the pressure accumulation type fuel injection device is configured to perform a fuel pressure feeding operation on the common rail. In the accumulator fuel injection device according to claim 1, 2, 3, or 4,
The pressure-accumulating fuel injection device is characterized in that the pressure-feeding unit control means is configured to give hysteresis to a determination value for performing the switching determination when the number of fuel pumping units to be driven is switched.   An internal combustion engine comprising the pressure accumulation type fuel injection device according to any one of claims 1 to 5.

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