JP2004124842A - Fuel injection device for common rail system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively correct a variation in a fuel injection amount from an injector occurring accompanying fluctuation in rail pressure. <P>SOLUTION: The common rail type fuel injection device 1 controls a fuel injection movement of the injector 3 by adjusting back pressure from high pressure fuel given to a nozzle needle 34 by a fuel releasing mechanism 41 including an electrostrictive actuator 42. Fluctuation in fuel injection occurring due to the fluctuation in rail pressure is regarded as a difference between a target rail pressure of the common rail 4 and an actual fuel injection pressure. According to this difference, driving voltage impressed by the electrostrictive actuator 42 is controlled, and the fluctuation of the fuel injection amount of the injector due to the fluctuation in the rail pressure is effectively suppressed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Patent Document 1]
JP 2001-355538 A
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel injection device for a common rail system.
[0003]
[Prior art]
As a fuel injection device for an internal combustion engine, a common rail type fuel injection device configured to inject high pressure fuel stored in a common rail by a high pressure pump into a corresponding cylinder by an injector provided for each cylinder. Has been put to practical use. Conventional injectors used in this type of fuel injection device disclose a needle valve by applying back pressure to the needle valve with high-pressure fuel supplied from a common rail as disclosed in Patent Document 1. The high-pressure fuel is released to the low-pressure side of the fuel by using an electromagnetic valve or the like to lower the level of the back pressure applied to the needle valve, lift the needle valve, and thereby lift the needle valve from the injector. The fuel injection is performed.
[0004]
[Problems to be solved by the invention]
Since the fuel injection device for the common rail system is configured as described above, the pressure of the high-pressure fuel stored in the common rail decreases every time fuel is injected from the injector, and the pressure in the fuel injection device for the multi-cylinder internal combustion engine is reduced. The common rail pressure is constantly and irregularly changed due to pulsation caused by a plurality of injectors performing operations for injecting fuel into corresponding cylinders at mutually different timings. As a result, if the opening and closing control of the solenoid valve for controlling the injection of the injector is performed based on the assumption that the common rail pressure is controlled to the control target value, the required target injection amount cannot be accurately obtained from the injector. There is a problem that.
[0005]
In order to solve this problem, means for correcting in the area of the control program of the solenoid valve in consideration of the characteristics of the control solenoid valve for the injector is known. However, a control solenoid valve for releasing high-pressure fuel that gives back pressure to the needle valve of the injector to the low-pressure side of the fuel has a variation in initial performance and a large variation in durability deterioration. Therefore, according to this conventional technique, it is necessary to check the characteristics of each of the control solenoid valves and reflect the characteristics in the control program, so that the pulsation of the rail pressure affects the fuel injection amount control. There is a problem that it is extremely difficult to perform satisfactory correction.
[0006]
An object of the present invention is to provide a fuel injection device for a common rail system that can solve the above-described problems in the related art.
[0007]
[Means for Solving the Problems]
According to an embodiment of the present invention, there is provided a fuel injector comprising: a plurality of injectors for injecting and supplying high-pressure fuel accumulated in a common rail into each cylinder of an internal combustion engine; The fuel injection device for a common rail system, wherein the fuel injection operation is controlled by adjusting a back pressure applied to the valve member by the fuel by a fuel relief mechanism including an electrostrictive actuator. A rail pressure detecting means for outputting a pressure signal corresponding to the pressure of the high-pressure fuel in the internal combustion engine, and at least one signal indicating an operating state of the internal combustion engine and the pressure signal required for fuel injection in response to the pressure signal. A first calculating means for calculating an energization period of the electrostrictive actuator; a target rail pressure of the common rail and an actual fuel injection; A second calculating means for calculating a correction voltage value corresponding to a difference from the pressure, and a driving voltage corrected by the correction voltage value in response to the first and second calculating means, calculated by the first calculating means. A fuel injection device for a common rail system, comprising: a drive circuit for applying voltage to the electrostrictive actuator only during an energization period.
[0008]
The electrostrictive actuator can be configured using, for example, a piezo element, and can expand and contract according to the level of the applied voltage to position the valve body. A drive voltage of a level reflecting the rail pressure is given to the electrostrictive actuator by using the correction voltage value. Therefore, when the rail pressure is large without correcting the energization period, the escape amount is large, and when the rail pressure is small. Thus, the valve body can be driven with high responsiveness so that the amount of escape is reduced. As a result, it is possible to effectively correct the amount of change in the fuel injection amount caused by the change in the rail pressure.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.
[0010]
FIG. 1 is a configuration diagram showing an example of an embodiment of a fuel injection device for a common rail system according to the present invention. In the common rail type fuel injection device 1 shown in FIG. 1, the fuel stored in the fuel tank T is sent to a common rail 4 to which a plurality of injectors 3 are connected via a high-pressure pump 2 if its configuration is roughly described. The operation of an electrostrictive actuator (not shown) built in the injector 3 is controlled by the control unit 5 so that the fuel injection from the injector 3 is controlled. In the present embodiment, the injector 3 is attached to each cylinder (not shown) of a multi-cylinder internal combustion engine for driving a vehicle, and the common rail fuel injection device 1 controls the injection of each cylinder of this internal combustion engine for a vehicle. The fuel is injected and supplied into the combustion chamber.
[0011]
Hereinafter, the configuration of the common rail fuel injection device 1 will be described more specifically. A fuel pipe 8 is disposed between the fuel tank T and the low-pressure side of the high-pressure pump 2. In the middle of the fuel pipe 8, in order from the fuel tank T side, for removing dust and the like in the fuel. The filter 6 and the low pressure control solenoid valve 7 are provided. A fuel temperature sensor 9 is provided at an appropriate position on the fuel pipe 8 between the filter 6 and the low-pressure control solenoid valve 7, and a temperature of the fuel passing through the fuel pipe 8 from the fuel temperature sensor 9. Is output, and the fuel temperature signal SA is input to the control unit 5 described later. Further, a mechanical low-pressure control valve 10 is provided at an appropriate position of the fuel pipe 8 between the filter 6 and the low-pressure control solenoid valve 7 so that the fuel pressure in the fuel pipe 8 is reduced to a predetermined valve opening pressure. Then, the mechanical low pressure control valve 10 is opened, and the fuel in the fuel pipe 8 between the low pressure control solenoid valve 7 and the filter 6 is discharged into the fuel tank T.
[0012]
The high pressure side of the high pressure pump 2 is directly connected to the input end 4A of the common rail 4 by a fuel pipe 13. The outlet end 4B of the common rail 4 is connected to the fuel tank T by a fuel pipe 14 provided with a high-pressure control solenoid valve 11 on the way. The common rail 4 is provided with a rail pressure sensor 12 for detecting the pressure (rail pressure) of the high-pressure fuel in the common rail 4 at an appropriate position, and a rail indicating the rail pressure output from the rail pressure sensor 12. The pressure signal SB is input to the control unit 5.
[0013]
The control unit 5 executes software, which will be described later, to control the operations of the low-pressure control solenoid valve 7, the high-pressure control solenoid valve 11, and the unillustrated electrostrictive actuators of the injector 3. Specifically, for example, It comprises a so-called microcontroller and various interface circuits. The control unit 5 receives the fuel temperature signal SA and the rail pressure signal SB from the fuel temperature sensor 9 and the rail pressure sensor 12 as described above, and also supplies fuel by the common rail fuel injection device 1. An engine speed signal Ne indicating the number of revolutions of an internal combustion engine (not shown), an accelerator opening signal Acc indicating an accelerator opening determined by the amount of depression of an accelerator pedal (not shown), and the time of starting the vehicle. A position information signal Key of a so-called ignition engine key (not shown) to be used is inputted.
[0014]
The low-pressure control solenoid valve 7 and the high-pressure control solenoid valve 11 are provided for setting the rail pressure of the common rail 4 to a required target rail pressure value, and both are controlled by the control unit 5.
[0015]
FIG. 2 is a sectional view of the injector 3 shown in FIG. The injector 3 will be described with reference to FIG.
[0016]
The injector 3 has an injector body 32 attached to the rear side of the nozzle body 31. A guide groove 33 formed over the nozzle body 31 and the injector body 32 allows the nozzle needle 34 to move in the axial direction. Are mated.
[0017]
An oil reservoir 35 is formed in the nozzle body 31 so as to surround the distal end portion 34A of the nozzle needle 34. An injection hole 36 communicating with the oil reservoir chamber 35 is formed at the distal end of the nozzle body 31. ing. When the tip portion 34A of the nozzle needle 34 is seated on the seat portion 35A of the oil reservoir chamber 35, the injection hole 36 is configured to be closed by the tip portion 34A of the nozzle needle 34.
[0018]
In the injector body 32, a control chamber 37 is formed so as to surround the rear end portion 34B of the nozzle needle 34 so as to be continuous with the guide groove 33. The control chamber 37 is connected to a supply oil passage 39 through an orifice 38. ing. The supply oil passage 39 is connected to the oil reservoir chamber 35 via a fuel passage 40, and a high-pressure fuel from a common rail is supplied to a port 39A of the supply oil passage 39.
[0019]
A fuel release mechanism 41 for releasing high-pressure fuel in the control chamber 37 to the low-pressure side of the fuel is provided in the injector body 32. The fuel release mechanism 41 includes a fuel release chamber 45 having a fuel release port 45A connected to the low-pressure side of the fuel, an electrostrictive actuator 42 configured using a piezo element, and an axial And an anchor 43 configured to extend and retract.
[0020]
The distal end portion 43A of the anchor 43 serving as a valve body has a conical shape, and the fuel release chamber 45 has a valve seat portion 46 formed in a shape corresponding to the distal end portion 43A of the anchor 43. The valve seat 46 is connected to the control chamber 37 via the orifice 44, and the anchor 43 is extended by the electrostrictive actuator 42, so that the distal end 43 A is seated on the valve seat 46 and the control chamber 37 is connected to the control chamber 37. The communication state with the fuel release chamber 45 is shut off. On the other hand, by shortening the anchor 43 by the electrostrictive actuator 42, a gap is generated between the distal end portion 43A and the valve seat portion 46 in accordance with the shortening amount, thereby releasing high-pressure fuel in the control chamber 37 as fuel. The pressure in the control chamber 37 can be reduced by escaping into the chamber 45.
[0021]
The nozzle needle 34 has a pressure receiving area of the high-pressure fuel at the distal end portion 34A smaller than a pressure-receiving area of the high-pressure fuel at the rear end portion 34B. When the pressure decreases, the nozzle needle 34 is lifted to perform fuel injection.
[0022]
FIG. 3 is a block diagram functionally showing the configuration of the control unit 5. Here, of the configuration of the control unit 5, only a functional part for controlling one of the plurality of injectors 3 is shown. In FIG. 3, reference numeral 51 is used to calculate an energization period of the electrostrictive actuator 42 necessary for fuel injection corresponding to these in response to the rail pressure signal SB, the engine speed signal Ne, and the accelerator opening signal Acc. Is a current supply period calculation unit. Here, according to the load state and the rail pressure at that time, it is necessary to secure a fuel release time from the control chamber 37 to the fuel release chamber 45 necessary for injecting and supplying necessary fuel into the corresponding cylinder. The energization period of the electrostrictive actuator 42 is calculated, and an energization control signal SC indicating the calculation result is output.
[0023]
52 drives the electrostrictive actuator 42 in response to a target rail pressure signal SD indicating a target rail pressure which is a target pressure value of the high-pressure fuel in the common rail 4 and an actual injection pressure signal SE indicating an actual fuel injection pressure. Is a drive voltage calculation unit for calculating the value of the optimum drive voltage. The drive voltage calculation unit 52 calculates a drive voltage value required to secure a required target injection amount from the target rail pressure and the actual injection pressure at that time, and performs voltage control indicating the calculation result. The signal SF is output.
[0024]
The positive electrode of the battery BT is connected to one drive terminal 42A of the electrostrictive actuator 42, and the negative electrode is connected to the other drive terminal 42B of the electrostrictive actuator 42 via a drive circuit 53. The drive circuit 53 receives an energization control signal SC and a voltage control signal SF. The drive circuit 53 applies a drive voltage having a level according to the voltage control signal SF to the electrostrictive actuator 42 for a period according to the energization control signal SC. Is configured.
[0025]
As a result, when the tip 43A separates from the valve seat 46 in response to the energization control signal SC and releases high-pressure fuel in the control chamber 37 to the fuel release chamber 45, the amount of retreat of the tip 43A (the amount of the anchor 43 The amount of shortening is controlled by the voltage control signal SF according to the actual injection amount at that time. That is, when the actual injection amount is small, the voltage applied to the electrostrictive actuator 42 is increased to increase the retreat amount of the distal end portion 43A, to increase the gap between the distal end portion 43A and the peripheral edge 46A, and to increase the unit time. The applied voltage control is performed so that the fuel injection amount per hit increases. On the other hand, when the actual injection amount is large, the voltage applied to the electrostrictive actuator 42 is reduced to reduce the amount of retreat of the distal end 43A, reduce the gap between the distal end 43A and the peripheral edge 46A, and reduce The applied voltage control is performed such that the fuel injection amount of the fuel cell decreases.
[0026]
As described above, the amount of the high-pressure fuel released from the control chamber 37 is configured to be performed by using the electrostrictive actuator 42, and the drive voltage of the electrostrictive actuator 42 is controlled according to the target rail pressure and the actual injection amount. Therefore, the fuel injection amount at that time can be controlled with extremely high responsiveness so that the required injection amount can be obtained. Therefore, even if the rail pressure causes pulsation due to fuel injection, the voltage applied to the electrostrictive actuator 42 is controlled in response to the pulsation, and a highly accurate fuel injection control operation can be realized.
[0027]
FIG. 4 is a flowchart for explaining another embodiment of the present invention. The flowchart shown in FIG. 4 shows another example of the drive control of the electrostrictive actuator 42 by the control unit 5, and the control unit 5 executes a control program set in advance to drive the electrostrictive actuator 42. It is intended to be controlled.
[0028]
In step S11, the target rail pressure (P0) is set, and in step S12, the actual injection pressure (Pa) from an actual injection pressure sensor (not shown) is read. In step S13, it is determined whether or not Pa <P0. If Pa ≧ P0, the determination result in step S13 is NO, and the process proceeds to step S14.
[0029]
In step S14, the value of the drive voltage applied to the electrostrictive actuator 42 is set to a predetermined specified voltage, and the process proceeds to step S15.
[0030]
Step S15 is a step showing a function corresponding to the energization period calculation unit 51 shown in FIG. 3, and applies the drive voltage of the level set in Step S14 to the electrostrictive actuator 42 at a predetermined timing for a predetermined period. Thus, a required fuel injection operation is performed.
[0031]
On the other hand, if Pa <P0 in step S13, the determination result in step S13 is YES, and the process proceeds to step S16. In step S16, a correction voltage value according to the pressure difference between Pa and P0 is calculated, and in the next step S17, the drive voltage level of the electrostrictive actuator 42 is corrected by correcting the correction voltage value with respect to a predetermined specified voltage. Set. Thereafter, the process proceeds to step S15, in which the driving voltage at the corrected level is applied to the electrostrictive actuator 42 at a required timing for a required period, and a fuel injection operation is performed. Even if the rail pressure causes pulsation due to fuel injection, the voltage applied to the electrostrictive actuator 42 is controlled in response to the pulsation, and a highly accurate fuel injection control operation can be realized.
[0032]
【The invention's effect】
According to the present invention, as described above, the fuel injection operation from the injector is controlled by the back pressure adjusting device including the electrostrictive actuator, and the variation of the fuel injection amount caused by the variation of the rail pressure is controlled by the target rail of the common rail. The fuel injection amount from the injector is determined according to the difference by controlling the drive voltage applied to the electrostrictive actuator according to the difference and adjusting the back pressure according to the difference. Therefore, it is possible to effectively suppress the fluctuation of the fuel injection amount from the injector due to the fluctuation of the rail pressure.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an example of an embodiment of a fuel injection device for a common rail system according to the present invention.
FIG. 2 is a sectional view of the injector shown in FIG. 1;
FIG. 3 is a block diagram functionally showing a configuration of a control unit.
FIG. 4 is a flowchart for explaining another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Common rail type fuel injection device 3 Injector 4 Common rail 5 Control unit 34 Nozzle needle 37 Control room 41 Fuel escape mechanism 42 Electrostrictive actuator 43 Anchor 43A Tip 45 Fuel escape chamber 46 Valve seat 51 Energization period calculation unit 52 Drive voltage calculation unit 53 Drive circuit Acc Accelerator opening signal Ne Engine speed signal SA Fuel temperature signal SB Rail pressure signal SD Target rail pressure signal SE Actual injection pressure signal

Claims (1)

A plurality of injectors for injecting and supplying high-pressure fuel accumulated in the common rail into each cylinder of the internal combustion engine, wherein the plurality of injectors each provide a back pressure applied to a valve member by the high-pressure fuel to an electrostrictive actuator. A fuel injection device for a common rail system configured to be able to control the fuel injection operation by adjusting the fuel injection mechanism comprising:
Rail pressure detecting means for outputting a pressure signal corresponding to the pressure of the high-pressure fuel in the common rail,
First calculating means for calculating an energization period of the electrostrictive actuator necessary for fuel injection in response to at least one signal indicating an operation state of the internal combustion engine and the pressure signal;
Second calculating means for calculating a correction voltage value according to a difference between the target rail pressure of the common rail and an actual fuel injection pressure;
And a drive circuit for applying a drive voltage corrected by the correction voltage value in response to the first and second calculation means to the electrostrictive actuator for an energization period calculated by the first calculation means. A fuel injection device for a common rail system.

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