JPH11236847A - Fuel injection device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly control a working fluid pressure for determining a fuel injection amount by a method wherein a gain in PID control of a deviation between a pressure of working fluid and a pressure of a target working fluid pressure is varied according to the operation state of a feel injection amount. SOLUTION: The control gain of a PID control element 35 to perform PID operation of a pressure deviation ΔPr is varied according to the operation state of an engine of some an idle or a non idle operation state, a pressure deviation between the pressure of working fluid and a target working fluid pressure, or the pressure change of working fluid. When a pressure control valve 64 is controlled based on PID operation such that the pressure Pr of working fluid coincides with a target working fluid pressure Prt, the working fluid pressure is further and properly controlled according to an operation state, an amount of fuel injected from an injector to a combustion chamber is further properly controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for an engine having an injector for injecting fuel based on the operating state of the engine.

[0002]

2. Description of the Related Art Conventionally, there has been provided an injector having a needle valve for raising and lowering the inside of a main body to control opening and closing of an injection hole, and an electromagnetic valve for supplying a drive current for controlling a working fluid for raising and lowering the needle valve. 2. Description of the Related Art There is known a fuel injection system for an engine in which a controller controls a fuel injection timing and a fuel injection amount injected from the injector according to an operation state of the engine.

The fuel injection system includes an injector having a working fluid as a working oil such as an engine oil, a solenoid valve for controlling the flow of the working oil into a main body, and a pressure-intensifying piston operated by the working oil.
A system in which the fuel in the booster chamber is boosted by a booster piston, the needle valve is raised and lowered by the pressure of the boosted fuel, and the fuel is injected from an injection hole opened by the needle valve; The working fluid is high-pressure fuel stored in a common rail, and an injector having a control pressure chamber formed in the main body is provided to control the inflow and outflow of high-pressure fuel to and from the control pressure chamber.
There is a system in which a needle valve is raised and lowered based on the pressure of the high-pressure fuel, and high-pressure fuel is injected from an injection hole opened by the needle valve.

FIG. 10 shows a fuel injection system for an engine in which an injector of the former type is incorporated. Recent engines are multi-cylinder engines such as four-cylinder and six-cylinder engines in order to obtain high output, and each cylinder is provided with an injector 1 for injecting fuel into a combustion chamber. In the fuel injection system shown in FIG. 10, the fuel in the fuel tank 52 is supplied to the common rail 51, which is a common passage for supplying fuel, through the fuel filter 54 by driving the fuel pump 53. The common rail 51 is connected to the injector 1 of each cylinder.
Are connected to the fuel supply port 11 and the fuel discharge port 12. That is, the injector 1 is disposed on the common rail 51 in which fuel at a predetermined pressure is constantly supplied to the fuel supply port 11 and the fuel discharge port 12 thereof. Fuel not consumed by each injector 1 is collected in the fuel tank 52 through the fuel collection passage 55.

A working fluid, ie, working oil, from a high-pressure oil manifold 56 is introduced into the injector 1 through a solenoid valve 10 in order to increase the fuel injection pressure. Oil from an oil reservoir 57 is supplied to the high-pressure oil manifold 56 through an oil supply path 61 by operation of an oil pump 58, and an oil cooler 59 and an oil filter 60 are provided in the oil supply path 61. The oil supply passage 61 branches into a lubrication system passage 67 leading to the oil gallery 62 and a working oil system passage 66 leading to the high-pressure oil pump 63. A high-pressure oil pump 63 is provided in the working oil passage 66, and the supply of oil from the high-pressure oil pump 63 to the high-pressure oil manifold 56 is controlled by controlling the amount of working oil leaked by the pressure control valve 64. . The controller 50 is configured to control the pressure control valve 64 and control the solenoid valve 10 of the injector 1. The controller 50 receives, as the operating state of the engine, the engine speed detected by the speed sensor 68, the accelerator opening detected by the accelerator depression amount sensor 69, and the crank angle detected by the crank angle sensor 70. I have.
The controller 50 includes a high-pressure oil manifold 5.
The operating oil pressure of the high-pressure oil manifold 56 detected by the pressure sensor 71 installed at 6 is input. The crank angle detected by the crank angle sensor 70 is determined by the drive current and the detection signal of each sensor for detecting that the piston has reached the compression top dead center of the piston or the predetermined position before the compression top dead center in each cylinder. Is used to control the power supply start timing and power supply period. The pressure control valve 64 is a normally-open or normally-closed control valve, and its opening is controlled by a control signal from the controller 50.
Excess high-pressure oil from the return passage 65
Through the oil reservoir 57. The temperature of the working oil is detected by an oil temperature sensor 72.

FIG. 11 is a sectional view of the injector 1 used in the fuel injection system shown in FIG. The main body of the injector 1 has a nozzle main body 2 having an injection hole 13 for injecting fuel at the tip, a solenoid main body 3 having a solenoid as an electromagnetic actuator 15, an injector main body 4, and a fuel supply main body 5. . The injector 1 is driven by the pressure increasing chamber 7 to which the fuel from the common rail 51 is supplied, the pressure chamber 8 to which the working fluid is supplied, and the working fluid supplied to the pressure chamber 8 to increase the pressure of the fuel in the pressure increasing chamber 7. The case 6 includes a pressure booster piston 9, a return spring 17 that returns the pressure booster piston 9, and a fuel supply port 11 and a fuel discharge port 12 that open to a common rail 51 to form a fuel chamber 20. . The needle valve 23 moves up and down based on the pressure of the fuel from the pressure increasing chamber 7 to open and close the injection hole 13. The electromagnetic valve 10 has a valve body 16 that is operated by an electromagnetic actuator 15 to control the supply of the working fluid to the pressure chamber 8. The booster piston 9
A large-diameter portion 25 slidably fitted into a hollow hole 26 formed in the main body and forming a part of a wall surface of the pressure chamber 8;
A small-diameter portion 2 slidably fitted in a hollow hole 27 formed in the fuel supply body and forming a part of a wall surface of the pressure increasing chamber 7.
It consists of four.

In such a pressure-intensifying piston type injector, the fuel injection pressure from the injection hole is determined by the pressure in the high-pressure oil manifold 56, that is, the rail pressure. Therefore, in order to obtain the target fuel injection amount,
The rail pressure is controlled so that the actual rail pressure becomes the target rail pressure. The rail pressure is controlled by means such as controlling the opening of the pressure control valve 64 (for example, the duty ratio of the pulse current for valve opening control). The target rail pressure is calculated based on the target fuel injection amount and the actual engine speed so that the target fuel injection amount determined according to the operating state of the engine is injected within a predetermined period (within a predetermined crank angle range). Is determined based on In a normal operation state, the target fuel injection amount is determined based mainly on the engine speed and the accelerator depression amount based on a predetermined map or the like so that the output characteristics and the exhaust characteristics of the engine are optimized. However, it is preferable that the engine speed be constant in the idling state.
The target fuel injection amount is determined such that the actual engine speed is equal to the target engine speed. The solenoid valve of the injector is driven so that the fuel of the target fuel injection amount thus determined is actually injected under the actual rail pressure.

In the rail pressure control for controlling the actual rail pressure to become the target rail pressure, PID control is employed. That is, the correction amount obtained by the proportional operation (P control), the integral operation (I control), and the differential operation (D control) of the pressure deviation of the actual rail pressure from the target rail pressure is added to the target rail pressure, and the correction is performed. By calculating the duty ratio of the control current that drives the pressure control valve with respect to the measured rail pressure, periodic changes in rail pressure, rail pressure offset, and delay in following a sudden change are prevented. .

In such rail pressure control, PI
If the gain of the D control is constant, it is not possible to perform optimal rail pressure control according to all operating regions of the engine. For example, in the normal operation state of the engine, it is preferable to set a relatively large gain in order to improve the followability of the actual rail pressure. PI
When applied to the D control, there is a problem that the fluctuation of the actual rail pressure becomes too large. In addition, even in the normal operation state of the engine, if the pressure difference between the actual rail pressure and the target rail pressure is large, hunting occurs in the rail pressure when the pressure deviation is small. Furthermore, it has been found that, when the gain is set corresponding to the case where the actual rail pressure is increased, when the rail pressure is decreased, the magnitude of the undershoot of the rail pressure is increased and the rail pressure is excessively decreased. .
In this case, since the pressure for opening the valves such as the pressure-intensifying piston and the needle valve of the injector cannot be obtained, the fuel is not injected into each cylinder and the engine is stalled.

In the PID control of the rail pressure of the engine, changing the gain of the PID control is disclosed in JP-A-6-93914. In the PID control disclosed in this publication, the PID constant (gain) setting means sets the gain of the PID control at the start of the engine to be larger than the gain at the time of normal operation. When the engine is started, the actual fuel injection pressure tends to be lower than the target injection pressure because the discharge pressure of the high-pressure pump for the working fluid is not sufficiently high.
Since the gain of the D control is set to be large, the actual fuel injection pressure is increased to the target fuel injection pressure in a short time.

[0011]

As described above, when the engine is in the idle operation state and the non-idle operation state,
The gain of the PID control of the working fluid pressure according to the operating state of the engine, such as when the deviation between the target value and the actual value of the working fluid pressure is large or small, or when the working fluid pressure rises and falls. There is a problem to be solved in that the hydraulic fluid pressure is changed and the working fluid pressure is controlled to follow the target pressure in accordance with the operating state of the engine, so that the optimum control of the output characteristics and exhaust gas characteristics of the engine is realized. .

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to determine whether or not the engine is in an idle operation state.
PID operation in which the pressure deviation is a control deviation according to the magnitude of the pressure deviation between the actual pressure of the working fluid and the target hydraulic fluid pressure, or the operating state of the engine, ie, whether the pressure of the working fluid is increasing or decreasing. An object of the present invention is to provide a fuel injection device for an engine capable of optimally controlling the working fluid pressure according to the operating state of the engine by changing the characteristics of the control of the working fluid pressure based on the engine.

The present invention provides an injector for injecting fuel into a combustion chamber of an engine, a pressure control valve for controlling a pressure of a working fluid supplied to the injector for controlling fuel injection pressure, and detecting an operating state of the engine. And a pressure deviation between the pressure of the working fluid and the target working fluid pressure is set as a control deviation such that the pressure of the working fluid coincides with a target working fluid pressure determined according to an operation state of the engine. A controller for controlling the pressure control valve based on a PID operation, wherein the controller is in an idle or non-idle operating state, the pressure deviation between the pressure of the working fluid and the target working fluid pressure, or a pressure of the working fluid. Changing the control gain of the PID operation in accordance with any of the operating states of the engine. It relates to a fuel injection system of the engine.

In the fuel injection device for an engine, the controller may control the PID when the operating state of the engine is the idle operating state more than when the operating state of the engine is the non-idling operating state.
The control gain of the operation is set to a small value.

In this fuel injection device for an engine, the detection means includes a rotation speed sensor for detecting a rotation speed of the engine and an accelerator depression amount sensor for detecting an accelerator depression amount. When the rotation speed of the engine is within a predetermined range and the accelerator depression amount detected by the accelerator depression amount sensor is equal to or less than a predetermined value, the operating state of the engine is changed to the idle operation. The state is determined.

In the fuel injection device for an engine, when the absolute value of the pressure deviation between the pressure of the working fluid and the target working fluid pressure is small,
The P value is greater than when the absolute value of the pressure deviation is large.
The control gain of the ID operation is set to a small value.

In the fuel injection device for an engine, the controller may set the control gain of the PID operation to be smaller when the pressure of the working fluid is decreasing than when the pressure of the working fluid is increasing. Set to a value.

In the fuel injection device for an engine, the controller corrects the target working fluid pressure by a correction amount obtained by the PID operation, and determines a predetermined relationship in accordance with the corrected target working fluid pressure. The pressure control valve is controlled by an operation amount obtained based on the above. The operation amount is a duty ratio of a control pulse current for determining an opening degree of the pressure control valve.

In this fuel injection device for an engine, the working fluid is engine oil or fuel. When the working fluid is engine oil, the injector includes a nozzle having an injection hole for injecting fuel, a booster chamber formed in the main body and supplied with fuel from a common rail, and an injector formed in the main body. A pressure chamber to which a working fluid is supplied, a pressure-increasing piston driven up and down based on the pressure action of the working fluid in the pressure chamber to increase the pressure of the fuel in the pressure-increasing chamber, A needle valve for raising and lowering the inside of the main body to open and close the injection hole, and a case arranged on the outer periphery of the main body to form a fuel chamber and having a fuel supply port and a fuel discharge port opened to the common rail. , And an electromagnetic valve driven by a drive current supplied from the controller to control a pressure action of the working fluid in the pressure chamber.

According to the present invention, as described above, the controller is capable of controlling the idling or non-idling operation state, the pressure deviation between the working fluid pressure and the target working fluid pressure,
Alternatively, the control gain of the PID operation of the pressure deviation is changed in accordance with any one of the operating states of the engine due to a change in the pressure of the working fluid. In any of these operating states, the pressure control valve is controlled based on the PID operation using the pressure deviation as the control deviation so that the pressure of the working fluid matches the target working fluid pressure determined according to the operating state of the engine. When controlling, the working fluid pressure is controlled more appropriately and quickly according to the operating condition. Therefore, the injection pressure of the fuel is appropriately controlled based on the working fluid pressure thus controlled, so that the injection amount of the fuel from the injector to the combustion chamber is more appropriately controlled.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a fuel injection device for an engine according to the present invention will be described with reference to the accompanying drawings. In the embodiment of the present invention, the specific structure of the fuel injection system of the engine and the injector used in the system is applied to the fuel injection system shown in FIG. 10 and employs the injector shown in FIG. Can be. That is, also in the fuel injection device for an engine according to the present invention, a needle valve for raising and lowering the inside of the main body to control the opening and closing of the injection hole and an electromagnetic actuator for supplying a drive current for controlling a working fluid for raising and lowering the needle valve are provided. And a controller that controls the amount of fuel injected from the injector according to the operating state of the engine. In the following description, FIG.
The same reference numerals as those used in FIGS. 10 and 11 are used for components and parts corresponding to those shown in FIGS.

FIG. 1 is a block diagram of rail pressure control which is a working fluid pressure of a fuel injection device for an engine according to the present invention. In the rail pressure control shown in FIG. 1, the engine speed Ne obtained by a signal from the speed sensor 68 included in the engine operating state detecting means and an input of a final target fuel injection amount Qf described later are received. The first target rail pressure calculating means 31 outputs the target rail pressure Prt in the non-idling operation state. On the other hand, based on the oil temperature To obtained from the signal from the oil temperature sensor 72, the second target rail pressure calculating means 32 outputs the target rail pressure Prt in the idling operation state. The idling determination means 33 determines whether the engine is in an idling operation state or a non-idling operation state based on the engine speed Ne and the accelerator depression amount Ac obtained from a signal from the accelerator depression amount sensor 69, and based on the determination result. The switch 34 is operated to output the target rail pressure Prt from the first target rail pressure calculation means 31 when the engine is in the idling operation state, and to output the second target rail pressure calculation means 32 when the engine is in the non-idle operation state. From the target rail pressure Prt.

The target rail pressure P which is the output of the switch 34
rt and a pressure deviation ΔPr between the actual rail pressure Pr detected by the pressure sensor 71 are obtained.
The corrected rail pressure is obtained by the PID operation of the ID control element 35. The final target rail pressure (the function g of the pressure deviation ΔPr) as the sum of the target rail pressure Prt as the feedforward term and the corrected rail pressure as the correction term
(Calculated as ΔPr) is input to the duty ratio determining means 36 of the pressure control valve 64, and the opening degree (or the average opening degree) of the pressure control valve 64 corresponding to the final target rail pressure is determined from a predetermined map. The duty ratio Dpr that determines the valve time is determined. The controller 50 outputs a control current to the pressure control valve 64 with the duty ratio Dpr to control the amount of high-pressure oil leaking from the pressure control valve 64, so that the oil pressure in the high-pressure oil manifold 56 becomes the target rail pressure Prt. Is controlled as follows.

FIG. 2 is a block diagram for outputting the final target fuel injection amount Qf in FIG. Based on the engine speed Ne detected by the speed sensor 68 and the accelerator pedal depression amount Ac detected by the accelerator pedal depression amount sensor 69, the first basic fuel injection amount calculation means 40 having a predetermined map is used for the basic fuel injection amount calculation. Calculate the quantity Qb. A plurality of maps are prepared in advance in the basic fuel injection amount calculating means 40 according to the oil temperature To. On the other hand, based on the oil temperature To detected by the oil temperature sensor 72, the second basic fuel injection amount calculating means 41 having a predetermined map calculates the basic fuel injection amount Qi in the idling operation state. The engine speed Ne detected by the speed sensor 68 in the idling operation state and a reference idling operation speed Ni
The corrected fuel injection amount calculation means 42 calculates the corrected fuel injection amount ΔQ based on a predetermined map based on the rotational speed deviation ΔN from the above. The corrected fuel injection amount ΔQ is a correction amount obtained by the PID operation of the PID control element for the rotation speed deviation ΔN. When the idling determining means 33 determines that the operating state of the engine is the non-idling operating state, the controller 50 controls the switch 43 to change the basic fuel injection amount Qb from the basic fuel injection amount calculating means 40 to the final target fuel injection amount. Qf, and when the idling determining means 33 determines that the operating state of the engine is the idling operating state, the switch 43 is controlled to control the basic fuel injection amount calculating means 41.
Is output as a final target fuel injection amount Qf.

In the engine fuel injection device, the controller 50 controls the engine based on the operating state of the engine, that is, the engine speed Ne detected by the engine speed sensor 68 and the accelerator pedal depression Ac detected by the accelerator pedal depression sensor 69. To determine the basic fuel injection amount. Further, the controller 50 stores in advance a reference fuel injection characteristic between the reference energization period of the drive current and the fuel injection amount to be injected.

FIG. 3 is a flowchart showing a main routine of the fuel injection system for an engine according to the present invention.
This flowchart consists of the following steps. (1) An idle operation flag is determined (steps 1 and 2).
Abbreviated as S1. same as below). That is, the value of the flag that is different between the idle operation state and the non-idle operation state of the engine is determined. (2) The final target fuel injection amount Qf is determined (S2).
The amount of fuel to be injected in one fuel injection is determined based on the relationship of a predetermined map or the like according to the operating state of the engine such as the engine speed Ne and the accelerator depression amount Ac. (3) The target rail pressure Prt is determined (S3). S
If it is determined that the operating state of the engine is the idle operating state based on the result of 1, the target rail pressure Prt is determined so as to compensate for the viscosity of the working fluid. (4) The pressure control valve 64 is controlled (S4). That is, the duty ratio of the control current to the pressure control valve 64 is determined so that the target rail pressure Prt is obtained based on the deviation between the target rail pressure Prt and the actual rail pressure Pr, and the pressure control valve 64 leaks. Determine the amount of oil leak. (5) The injector 1 is driven (S5). That is, the drive pulse width Pw for driving the solenoid valve 10 of the injector 1 is determined based on the final target fuel injection amount Qf, the actual rail pressure Pr, and the viscosity of the working fluid, and the injector 1 is driven by the drive pulse width Pw. Driven.

The details of the steps S1 to S5 will be described below in order. FIG. 4 is a flowchart showing a routine (S1) for determining an idle operation flag in the main routine shown in FIG. (1) The operating state of the engine is read (S10).
That is, the engine speed Ne obtained by the signal from the rotation speed sensor 68 and the accelerator depression amount Ac obtained by the signal from the accelerator depression amount sensor 69 are periodically read into the controller 50. (2) When the accelerator depression amount Ac corresponds to the accelerator depression amount in the low-load operation state, the magnitude of the accelerator depression amount Ac is compared with a predetermined value Acl (S11). (3) If it is determined in step S11 that the accelerator depression amount Ac is smaller than Ac1, the engine speed N
It is determined whether or not e is within a range of a predetermined rotation speed between predetermined rotation speeds Nl and Nh (S1).
2). (4) If the determination in S12 is YES, 1 is assigned to the idle operation flag FlagI, and it is determined that the engine is in the idle operation state (S13). (5) If the determination in S11 or S12 is NO, 0 is substituted for the idle operation flag FlagI to determine that the engine is in the non-idle operation state (S14). ).

FIG. 5 is a flowchart showing a routine (S2) for determining the final target fuel injection amount Qf in the main routine shown in FIG. 3, and comprises the following steps. (1) The operating state of the engine is read (S20).
That is, the controller 50 periodically reads the engine speed Ne obtained from the signal from the rotation speed sensor 68 and the accelerator depression amount Ac obtained from the signal from the accelerator depression amount sensor 69. (2) It is determined whether or not the idle operation flag FlagI is 1, and it is determined whether or not the operation state of the engine is the idle operation (S21). (3) If the determination in S21 is YES, the target fuel injection amount Qi during idling operation according to the temperature To of the working fluid oil is calculated based on a predetermined relationship such as a map (S22). ). (4) The deviation of the engine speed is obtained by the following equation, and is substituted as the speed deviation ΔN (S23). Here, Ni is a reference rotational speed that determines the idling operation state of the engine. ΔN ← Ne−Ni (5) The final target fuel injection amount Qf is calculated as P
It is obtained by correcting the target fuel injection amount Qi by feedback control based on the ID operation (S2
4). Qf ← Qi + Kp × ΔN + Ki × ∫ΔNdt + Kd ×
(DΔN / dt) (6) If the determination result in S21 is NO, the engine is in the non-idle operation state, and the final target fuel injection amount Qf is, as usual, the engine speed Ne and the accelerator depression amount. It is obtained from a predetermined relationship such as a map based on Ac (S25).

FIG. 6 is a flowchart showing a routine (S3) for setting the target rail pressure Prt in the main routine shown in FIG. 3, and comprises the following steps. (1) Engine speed Ne, final target fuel injection amount Qf,
And the oil temperature To are read (S30). (2) It is determined whether or not the idle operation flag FlagI is 1, and it is determined whether or not the operation state of the engine is the idle operation (S31). (3) If the determination in S31 is YES, S30
The target rail pressure Prt is set based on a predetermined relationship such as a map based on the oil temperature To read in step (S32). That is, when the operation state of the engine is the idling operation, the target rail pressure Prt is determined only by the oil temperature To, and the target rail pressure Prt is not determined by information such as the engine speed. (4) If the determination in S31 is NO, the engine speed Ne and the final target fuel injection amount Q read in S30
Based on f and the oil temperature To, a target rail pressure Prt is set from a predetermined relationship such as a map (S33).

FIG. 7 is a flowchart showing a pressure control valve driving routine (S4) in the main routine shown in FIG. 3, and comprises the following steps. (1) From the target rail pressure Prt determined in S32 and S33 and the pressure sensor 71 to the controller 50
Is read in (S4).
0). (2) The deviation between the target rail pressure Prt read in S40 and the actual rail pressure Pr is calculated by the following equation, and the calculation result is substituted for the pressure deviation ΔPr (S41). ΔPr ← Pr−Prt (3) It is determined whether or not the idling operation flag FlagI is 1, that is, whether or not the operation state of the engine is the idling operation state (S42). (4) If it is determined in step S42 that the engine operation state is the idle operation state, each gain of the PID control for obtaining the correction amount of the rail pressure Pr is determined by the gain characteristic G1 shown in FIG. Determine the gain (S4
3). In the idling operation, too fast response is not required, so the gain (absolute value) determined by the gain characteristic G1 is determined to be a small value in any of the PID operations. (5) If it is determined in S42 that the engine operation state is the non-idle operation state, the pressure deviation ΔPr between the rail pressure Pr and the target rail pressure Prt is larger than a predetermined relatively large pressure deviation ΔPrh. It is determined whether or not this is the case (S44). (6) YES in S44 (that is, pressure deviation ΔPr> ΔPr)
If h) is determined, each gain of the PID control that determines the correction amount of the rail pressure Pr is determined to the gain determined by the gain characteristic G2 shown in FIG. 9 (S45). (7) NO in S44 (that is, pressure deviation ΔPr ≦ ΔPr
If h) is determined, it is determined whether the pressure deviation ΔPr between the rail pressure Pr and the target rail pressure Prt is larger than a predetermined relatively small pressure deviation ΔPrl (S46). (8) YES in S46 (that is, pressure deviation ΔPr <ΔPr
If it is determined to be 1), each gain of the PID control that determines the correction amount of the rail pressure Pr is determined to be the gain determined by the gain characteristic G3 shown in FIG. 9 (S47). (9) NO in S46 (that is, ΔPrl ≦ pressure deviation ΔPr
If it is determined that .ltoreq..DELTA.Prh, the gain of the PID control for determining the correction amount of the rail pressure Pr is determined to be the gain determined by the gain characteristic G4 shown in FIG. 9 (S48). (10) Using the gains determined by the gain characteristics G1 to G4 in S43, S45, S47, and S48, respectively, the duty ratio Dpr of the drive pulse current supplied to the pressure control valve 64 is determined by the target rail pressure Prt and S41. It is obtained as a function fn of the sum of the calculated pressure deviation ΔPr and the feedback control amount based on the PID operation (S49). Dpr ← fn [Prt + Gp × ΔPr + Gi × ∫ΔPr
dt + Gd × (dΔPrt / dt)] Here, Gp is the gain of the proportional control (P control) multiplied by the pressure deviation ΔPr, and Gi is the gain of the integral control (I control) multiplied by the integral value of the pressure deviation ΔPr. Yes,
Gd is the gain of the differential control (D control) multiplied by the differential value of the pressure deviation ΔPr. (11) The pressure control valve 64 is driven according to the duty ratio Dpr obtained in S49. That is, the pressure control valve 6
4 is supplied with a drive pulse current having a duty ratio Dpr determined in S49, the amount of leakage of the working oil from the high-pressure oil pump 63 through the pressure control valve 64 is determined, and as a result, the high-pressure oil manifold 56 The supplied working oil amount is controlled, and the rail pressure Pr in the high-pressure oil manifold 56 is controlled (S4).
3).

FIG. 9 is a graph showing the relationship between the pressure deviation ΔPr and the correction amount (for example, the correction amount by proportional control). The gain Gp during the idling operation is determined by a gain characteristic G1.
Of the gain Gp as shown by a gentle slope.
(The absolute value) is a small value. Pressure deviation ΔPr is Δ
The gain Gp when it is larger than Prh is equal to the pressure deviation ΔP
The gain is set to a value slightly larger in absolute value than the gain Gp when r is smaller than ΔPrl. Pressure deviation ΔPr
Is greater than or equal to ΔPrl and less than or equal to ΔPrh, as indicated by the slope of the gain characteristic G4, the gain is set to a value smaller than the gain in the case of the gain characteristics G2 and G3, so that the control is performed gently. The correction amount for the pressure deviation ΔPr by the integral control (I control) and the correction amount by the differential control (D control) are obtained in the same manner as in FIG.

FIG. 8 is a flowchart showing the injector driving routine (S5) in the main routine shown in FIG. 3, and comprises the following steps. (1) The final target fuel injection amount Qf, the actual rail pressure Pr, and the oil temperature To are read (S60). (2) The pulse width Pw of the control current applied to the injector 1 is determined (S61). That is, the actual rail pressure Pr
Under the condition of the oil temperature To and the oil temperature To, the drive pulse width Pw is determined as a period for supplying the drive pulse current of the solenoid valve 10 of the injector 1 necessary for the injector 1 to inject the fuel of the final target fuel injection amount Qf. . (3) The injector 1 is driven by the control current having the drive pulse width Pw obtained in S61 (S62). That is, a control current having a drive pulse width Pw is supplied to the solenoid valve 10 of the injector 1, and the solenoid valve 10
Operates, the injection hole 13 of the injector 1 is opened, and fuel is injected into the combustion chamber.

As described above, in the fuel injection system of the engine, the controller 50 performs the PID operation when the engine is in the operating state or the idle operating state more than when the engine is in the non-idling operating state. Since the control gain is set to a small value, the fluctuation of the actual rail pressure Pr is suppressed, and as a result, the fuel injection amount from the injector 1 becomes appropriate. Also, the controller 50
When the absolute value of the pressure deviation ΔPr between the actual rail pressure Pr and the target rail pressure Prt is small, the control gain of the PID operation is set to a smaller value than when the absolute value of the pressure deviation ΔPr is large. When it is small, it is possible to prevent hunting of the rail pressure Pr from occurring. Further, the controller 50 controls the rail pressure Pr.
When the rail pressure Pr is decreasing, the control gain of the PID operation is set to a smaller value than when the rail pressure Pr is increasing. The situation where the needle valve 23 of the injector 1 does not open can be avoided.

[0034]

The fuel injection device for an engine according to the present invention is configured as described above, so that the controller operates in an idle or non-idle operating state, a pressure deviation between the pressure of the working fluid and the target working fluid pressure, or By changing the control gain of the PID operation of the pressure deviation in accordance with one of the engine operating conditions due to the pressure change of the working fluid, the pressure deviation is controlled so that the pressure of the working fluid matches the target working fluid pressure. When controlling the pressure control valve based on the PID operation described above, the working fluid pressure can be controlled more appropriately and quickly according to the operating state. Therefore, the injection pressure of the fuel is appropriately controlled based on the working fluid pressure thus controlled, so that the injection amount of the fuel injected from the injector into the combustion chamber is more appropriately controlled. Fluctuation of the engine speed in the idling operation state, hunting in the idling operation state and the normal operation state, or stall of the engine can be prevented, and stable and appropriate fuel injection of the engine can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of rail pressure control of a fuel injection control device for an engine according to the present invention.

FIG. 2 is a block diagram for outputting a final target fuel injection amount Qf in FIG. 1;

FIG. 3 is a flowchart showing a main routine of an engine fuel injection device according to the present invention.

FIG. 4 is a flowchart showing a routine for determining an idle operation flag in the main routine shown in FIG. 3;

FIG. 5 is a flowchart showing a routine for determining a final target fuel injection amount in the main routine shown in FIG. 3;

FIG. 6 is a flowchart showing a routine for setting a target rail pressure in the main routine shown in FIG. 3;

FIG. 7 is a flowchart showing a driving routine of a pressure control valve in the main routine shown in FIG. 3;

FIG. 8 is a flowchart showing a routine for driving an injector in the main routine shown in FIG. 3;

9 is a graph illustrating an example of a relationship between a pressure deviation and a correction amount employed in a pressure control valve driving routine illustrated in FIG. 7;

FIG. 10 is a diagram illustrating an example of a fuel injection system in an engine.

11 is a cross-sectional view of an injector used in the fuel injection system shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 injector 2 nozzle body 3 solenoid body 4 injector body 5 fuel supply body 6 case 7 booster chamber 8 pressure chamber 9 booster piston 10 solenoid valve 11 fuel supply port 12 fuel outlet 13 injection hole 15 electromagnetic actuator 20 fuel chamber 23 needle Valve 31 First target rail pressure calculating means 32 Second target rail pressure calculating means 33 Idle determining means 35 PID control element 36 Duty ratio determining means 50 Controller 51 Common rail 56 High pressure oil manifold 63 High pressure oil pump 64 Pressure control valve 68 Revolution sensor 69 accelerator depression amount sensor 71 pressure sensor 72 oil temperature sensor Ne engine speed Ac accelerator depression amount Pr rail pressure Prt target rail pressure Qb basic fuel injection amount (non-idle operation state) Qi basic fuel injection The amount (idling) Qf final target fuel injection amount Pw driving pulse width Dpr duty ratio

Claims (9)

[Claims] An injector for injecting fuel into a combustion chamber of an engine, a pressure control valve for controlling a pressure of a working fluid supplied to the injector for controlling an injection pressure of the fuel, and a detection for detecting an operating state of the engine. Means, and a PID operation using a pressure deviation between the pressure of the working fluid and the target working fluid pressure as a control deviation so that the pressure of the working fluid matches a target working fluid pressure determined according to an operating state of the engine. A controller that controls the pressure control valve based on the pressure difference between the working fluid pressure and the target working fluid pressure, or a change in the working fluid pressure. Changing the control gain of the PID operation in accordance with one of the operating states of the engine. Injection device. 2. The controller according to claim 1, wherein the controller sets the control gain of the PID operation to a smaller value when the operation state of the engine is the idle operation state than when the operation state of the engine is the non-idle operation state. The fuel injection device for an engine according to claim 1, comprising setting. 3. The detecting means includes a rotation speed sensor for detecting a rotation speed of the engine and an accelerator depression amount sensor for detecting an accelerator depression amount.
When the rotation speed of the engine detected by the rotation speed sensor is within a predetermined range and the accelerator depression amount detected by the accelerator depression amount sensor is equal to or less than a predetermined value, 3. The fuel injection device for an engine according to claim 2, comprising determining an operation state from the idle operation state. 4. The PID operation of the PID operation when the absolute value of the pressure difference between the pressure of the working fluid and the target working fluid pressure is smaller than when the absolute value of the pressure difference is larger. 2. The engine fuel injection device according to claim 1, wherein the control gain is set to a small value. 5. The controller according to claim 1, wherein the controller sets the control gain of the PID operation to a smaller value when the pressure of the working fluid is decreasing than when the pressure of the working fluid is increasing. The fuel injection device for an engine according to claim 1, wherein 6. The controller according to claim 1, wherein the controller corrects the target working fluid pressure with a correction amount obtained by the PID operation, and obtains an operation based on a predetermined relationship according to the corrected target working fluid pressure. 6. The fuel injection device for an engine according to claim 1, comprising controlling the pressure control valve by an amount. 7. The fuel injection device for an engine according to claim 6, wherein the operation amount is a duty ratio of a control pulse current for determining an opening of the pressure control valve. 8. The fuel injection device for an engine according to claim 1, wherein the working fluid is engine oil or fuel. 9. The injector is formed with a nozzle having an injection hole for injecting fuel, a pressure increasing chamber formed in a main body and supplied with fuel from a common rail, and an injector formed in the main body and supplied with the working fluid. A pressure chamber, a pressure-increasing piston driven up and down based on the pressure action of the working fluid in the pressure chamber to increase the pressure of the fuel in the pressure-intensifying chamber, A needle valve that moves up and down to open and close the injection hole, a case that is disposed on the outer periphery of the main body to form a fuel chamber, and that has a fuel supply port and a fuel discharge port that open to the common rail;
And an electromagnetic valve driven by a drive current supplied from the controller to control a pressure action of the working fluid in the pressure chamber.
A fuel injection device for an engine according to any one of claims 8 to 13.