JP3944143B2 - Accumulated fuel injection internal combustion engine and fuel control method thereof - Google Patents

Description

  The present invention is applied to an accumulator fuel injection diesel engine, and accumulates fuel pressurized by a fuel pump in a common rail, and is provided in a fuel injection pipe connecting the common rail and a fuel injection valve of an engine (internal combustion engine). The present invention relates to an accumulator type fuel injection internal combustion engine configured to inject pressurized fuel in the common rail from a fuel injection valve into a combustion chamber of an engine by controlling opening and closing of the electromagnetic valve, and a fuel control method for the internal combustion engine.

  An electromagnetic valve provided in the fuel injection pipe for accumulating fuel pressurized by a fuel pump in a common rail, sending high-pressure fuel in the common rail to a fuel injection valve of an engine (internal combustion engine) through the fuel injection pipe In recent years, an accumulator fuel-injection diesel engine that controls the fuel injection timing and the injection amount from the fuel injection valve to the combustion chamber of the engine by opening and closing the engine has been realized as an engine that can realize both high thermal efficiency and low NOx. Many have been adopted.

In such an accumulator type fuel injection diesel engine, pulsation due to reciprocation of a plunger of a fuel pump, pressure fluctuation due to fuel injection from a fuel injection valve provided in each cylinder of the engine, pressure due to shock wave movement (sonic speed) in the common rail The fuel pressure in the common rail fluctuates greatly due to fluctuations and the like.
As one of means for obtaining a uniform fuel pressure by suppressing the fluctuation of the fuel pressure in the common rail, a technique of Patent Document 1 (Japanese Patent Laid-Open No. 2003-106208) is provided.
In Patent Document 1, the influence of pressure fluctuation due to pulsation due to reciprocation of the plunger in the common rail, pressure fluctuation due to fuel injection, pressure fluctuation due to shock wave movement, etc. is eliminated, the fuel pressure in the common rail is made uniform, The fuel injection from the injection valve can be controlled with high accuracy, and a control block diagram thereof is shown in FIG.

  In FIG. 11, 04 is a rail pressure sensor that detects the pressure in the common rail, 08 is a fuel injection pressure sensor that detects the pressure of high-pressure fuel pumped from the common rail to the fuel injection valve of the engine, and 06 is the fuel pressure at the fuel pump outlet. The pressure detection value of the pressure fluctuation due to the shock wave movement in the common rail from the rail pressure sensor 04, the pressure fluctuation detection value due to the fuel injection from the fuel injection pressure sensor 08, and the pump pressure sensor 06 The pulsation pressure fluctuation detection value due to the reciprocating motion of the fuel plunger, that is, disturbance, is input to the adder 016, added by the adder 016, and input to the adder / subtracter 014 described later.

10 is a difference between a common rail pressure (hereinafter referred to as rail pressure) detection value P ₁ detected and fed back by the rail pressure sensor 04 and a rail pressure target value P ₀ which is a preset reference rail pressure. The pressure ΔP (ΔP = P ₁ −P ₀ ) is calculated. The differential pressure ΔP is input to the PID control unit 11, and PID (proportional, integral, differential) calculation is performed in the PID control unit 11.
020 is a multi-dimensional map, and the feedforward amount is set corresponding to engine operating conditions such as engine load, rotation speed, supply air temperature, exhaust temperature, etc., and adapted to each engine operating condition by engine test operation. The feedforward amount is obtained and mapped.

014 is an adder / subtracter that adds and subtracts the disturbance S, the feedback output ΔP _p from the PID control unit 11 and the feedforward amount ΔP _f from the multidimensional map 020, and incorporates the disturbance S. A correction amount ΔP _c for the common rail internal pressure P ₁ is calculated and input to the solenoid valve controller 015.
In the solenoid valve controller 015, a control current adjustment amount of the common rail pressure control solenoid valve 0109 corresponding to the correction amount ΔP _c is calculated and transmitted to the solenoid valve 0109. The opening degree of the solenoid valve 0109 is It is adjusted to an opening corresponding to the correction amount [Delta] P _c. As a result, the common rail internal pressure P ₁ is maintained at the target value P ₀ and pressure fluctuations due to the influence of the disturbance S are removed.

JP 2003-106208 A

In the case of controlling the pressure in the common rail to the target value P _0, the pressure difference ΔP between the detection value P ₁ and the target value P ₀ of the rail pressure PID (proportional, integral, differential) calculation alms, after the PID calculation If you obtain a correction amount [Delta] p _c by the difference between the feedback output [Delta] p _p and the disturbance S performs feedback for adjusting the degree of opening of the solenoid valve, than the period of pressure fluctuations in the response speed in the common rail of the feedback output after PID calculation Since it is slow, the pressure control in the common rail cannot be performed with high accuracy.
However, in the technique of Patent Document 1, the multi-dimensional map in which the feed-forward amount is set corresponding to the engine operating condition is used, and the feed-forward amount is set in the multi-dimensional map as the feedback output after the PID calculation. Since the feedforward amount is added, the delay in the response speed of the feedback output due to the PID calculation can be supplemented, and the above-described problems related to the pressure control in the common rail can be solved.

However, in the technique of Patent Document 1, a feedforward amount adapted to engine operating conditions such as engine load, rotation speed, supply air temperature, exhaust temperature and the like is obtained by a trial operation of the engine and is converted into a multidimensional map. In addition, it is necessary to obtain specific numerical values of the multidimensional map manually while the engine is running, and a great deal of labor is required to create the multidimensional map.
In addition, in the conventional technique (the technique of Patent Document 1), when creating a multidimensional map, it is not possible to deal with a periodic disturbance due to an unexpected factor, and such a periodic disturbance is not possible. When this occurs, the control performance of the pressure control in the common rail is greatly reduced.
Furthermore, in this conventional technology, since it is impossible to obtain data for creating a multidimensional map in the entire limited operating range from the viewpoint of engine strength, it is not possible to create a multidimensional map in the entire operating range of the engine. Difficult.
And so on.

  Therefore, in view of the problems of the prior art, the present invention makes it possible to control the pressure in the common rail with simple means without requiring manual operation, without acquiring data by a trial operation of the engine, and unexpected disturbance acts. However, it is possible to control the pressure in the common rail in response to the disturbance, and to provide a fuel control method and apparatus for an accumulator type fuel injection internal combustion engine capable of realizing highly accurate pressure control in the common rail in the entire operating range of the engine. The purpose is to do.

The present invention achieves such an object, and accumulates fuel pressurized by a fuel pump in a common rail, and connects the common rail to a fuel injection valve of an engine (internal combustion engine). In the fuel control method for an accumulator type fuel injection internal combustion engine configured such that the pressurized fuel in the common rail can be injected into the combustion chamber of the engine from the fuel injection valve by opening and closing the valve by a fuel injection control device. A fuel pressure in the common rail is detected to calculate a differential pressure (ΔP = P ₁ −P ₀ ) between the fuel pressure detection value (P ₁ ) and a preset target value (P ₀ ) of the fuel pressure; said difference portion feedforward amount ([delta] P _i) as the predetermined crank angle every memory of the engine pressure ([Delta] P), and accumulation, the differential pressure said feedforward amount ([delta] P _i) of ([Delta] P) Parts in PID (proportional, integral, derivative) and performing adding the feedback output subjected to control ([Delta] P _p) is repeated so as to correspond to the crank angle of the engine equalization control of the common rail pressure .

In this invention, preferably, the feedback output (ΔP _p ) and the feedforward amount (δP) obtained by applying the PID control to disturbance (S) such as fuel pressure fluctuation acting on the common rail and the fuel system connected thereto. _i ) is added and subtracted to calculate the correction amount of the pressure in the common rail including the disturbance.
More preferably, the feed and forward quantity sum of the feedback output which has been subjected to ([delta] P _i) and the PID control ([Delta] P _p) and a certain proportion of the feed forward amount and ([delta] P _i) and the feedback output ([Delta] P _p) (ΔP _i / ΔP _p ) is greatly increased at the beginning of the control and decreased with time.

Further, as an invention of an apparatus for carrying out the method invention, in an accumulator type fuel injection internal combustion engine having a common rail, a rail pressure sensor for detecting a fuel pressure in the common rail, and a fuel pressure detection input from the rail pressure sensor An adder / subtractor for calculating a differential pressure (ΔP = P ₁ −P ₀ ) between a value (P ₁ ) and a preset target value (P ₀ ) of the fuel pressure, and output from the adder / subtracter A part of the differential pressure (ΔP) is stored and stored as a feed forward amount (δP _i ) for each predetermined crank angle of the engine, and a PID (proportional, integral) is stored in the remaining portion of the differential pressure (ΔP). , Derivative) control, and a second adder / subtracter for adding and subtracting the feedforward amount (δP _i ) to and from the feedback output (ΔP _p ) from the PID controller. Foix Pressurizing the amount de feedback output from ([delta] P _i) and the PID control unit ([Delta] P _p), subtracts the common rail pressure control device that performs equalization control of pressure in the common rail is repeated in correspondence with the crank angle of the engine It is characterized by having.
Preferably, the common rail pressure control device receives a disturbance (S) such as a fuel pressure fluctuation acting on the common rail and a fuel system connected thereto, and inputs a second adder / subtractor to the disturbance. (S), the feedback output (ΔP _p ), and the feedforward amount (δP _i ) are added and subtracted to calculate the correction amount of the common rail internal pressure including the disturbance.

  In controlling the pressure in the common rail by controlling the pressure in the common rail, the pressure fluctuation in the common rail is several tens of msec. Therefore, the control cycle needs to be performed in several msec. Because the time constant of the solenoid valve, which is the internal pressure adjusting means, is as slow as 80 to 100 msec, the response speed is slow only by PID (proportional, integral, differential) control by the PID control unit, and it is practical to control the pressure in the common rail. Impossible.

However, according to this method and apparatus invention, the difference between the fuel pressure detection value (P ₁ ) in the common rail calculated by the first adder / subtractor and the preset target value (P ₀ ) of the fuel pressure. A part of the pressure (ΔP = P ₁ −P ₀ ) is stored and accumulated in the accumulation buffer accumulating unit for each predetermined crank angle of the engine as a feed forward amount (δP _i ).
In the second adder / subtracter, the PID control unit stores the feedback output (ΔP _p ) in which the remainder of the differential pressure (ΔP) is subjected to PID (proportional, integral, derivative) control in the cumulative buffer storage unit. Then, the accumulated feed forward amount (δP _i ) is added for each crank angle, and the correction amount of the pressure in the common rail is calculated. At this time, preferably, disturbance (S) such as fuel pressure fluctuation acting on the common rail and the fuel system connected thereto is added to the value obtained by adding the feedforward amount (δP _i ) to the feedback output (ΔP _p ). Is added and subtracted to obtain the correction amount for the pressure in the common rail.

Such percentage (δP i _/ ΔP _p the amount the feedforward ([delta] P _i) and the feedback output ([Delta] P _p) at the time summing crank angle every feedback output feedforward amount to (ΔP _p) (δP i) ) Is increased in the first half of a cycle with a large delay due to PID control to compensate for the delay due to PID control. Then, the rate (δP _i / ΔP _p ) is decreased as the later stage of the cycle in which the influence of the delay due to the PID control becomes smaller.
By performing such control, the delay due to PID control is eliminated by adding the feedforward amount (δP _i ) stored and accumulated in the accumulation buffer accumulation unit to the feedback output (ΔP _p ) of PID control. It becomes possible.

Further, according to this invention, a part of the differential pressure (ΔP = P ₁ −P ₀ ) between the fuel pressure detection value (P ₁ ) in the common rail and the target value (P ₀ ) of the fuel pressure is converted into the feedforward amount. (δP _i ) is stored and accumulated in the accumulation buffer accumulating unit for each predetermined crank angle of the engine, and the feedforward amount (δP _i ) is subjected to PID control on the remainder of the differential pressure (ΔP). Since the feedback output (ΔP _p ) is added for each crank angle and the correction amount of the pressure in the common rail is calculated, a test run of the engine is performed and a multidimensional map is created from the test run data as in the technique of Patent Document 1. Thus, the feedforward amount can be obtained without requiring labor and time-consuming manual work, and the pressure in the common rail can be controlled by a very simple means.

Further, according to this invention, even if an unexpected disturbance enters during the pressure control in the common rail, the multi-dimensional map is created in advance as in the technique of Patent Document 1, so that the disturbance cannot be dealt with. The control performance of the pressure control in the common rail is not significantly reduced, and the gain of the feed forward amount (δP _i ) stored and accumulated in the accumulation buffer accumulation unit is advanced, so that the disturbance can be freely controlled. Corresponding control is possible.
Further, unlike the prior art, it is not necessary to perform a test run of the engine and create a multi-dimensional map from the test run data, and during operation of the engine, the cumulative buffer storage unit stores the engine at every predetermined crank angle. By adding the stored and accumulated feed forward amount (δP _i ) to the feedback output (ΔP _p ) subjected to PID control for each crank angle, and calculating the correction amount of the common rail internal pressure, Can be easily controlled.

In this invention, the following first to fifth means are preferable.
That is, the first means stores an initial value of the differential pressure (ΔP), and after a certain time when the fuel pressure detection value (P ₁ ) periodically changes, the feedforward amount (δP _i ) and Calculation of feedback output (ΔP _p ) by PID control is started.
According to the first means, since the pressure in the common rail is unstable and an excessive control deviation is likely to occur at the initial stage immediately after the control power is turned on, such as when the engine is started, the differential pressure (ΔP) Is stored, and after the control power supply is turned on, the fuel pressure detection value (P ₁ ) changes periodically after a certain period of time, and then the feedforward amount (δP _i ) and feedback output by PID control Since the calculation of (ΔP _p ) is started and the control shifts to the pressure control in the common rail, the influence of an excessive control deviation on the pressure control in the common rail at the initial time can be avoided.

Second means calculates the amount of the feed-forward ([delta] P _i) and the immediately preceding cycle feedforward amount ([delta] P _i-1) shift amount between _{E r (= δP i -δP i} -1), the common rail pressure When the control origin position is detected, the shift amount is initialized to be close to 0 (E _r ← 0), and the continuity of the feedforward amount (δP _i ) at the origin position is maintained.
According to the second means, the deviation of one cycle formed between immediately after the origin detection and immediately before the origin detection of the feedforward amount stored and accumulated in the accumulation buffer accumulation unit corresponding to the crank angle is calculated as the origin. It is corrected by initializing the deviation amount to be close to 0 (E _r ← 0) at the time of position detection, and the continuity of the feedforward amount (δP _i ) at the origin position can be maintained to prevent a decrease in control performance. .

The third means calculates the sum of squares (ΣΔP) of the differential pressure (ΔP) in a plurality of past cycles, and equalizes the pressure in the common rail when the sum of squares (ΣΔP) starts to increase. Interrupt control.
According to the third means, when the sum of squares (ΣΔP) of the differential pressure (ΔP) in a plurality of past cycles tends to increase beyond the reference value, the pressure equalization control in the common rail is interrupted. The divergence of the control value due to disturbance can be avoided, and the common rail pressure control can be stabilized.

A fourth means uses a feedback output (ΔP _p ) that has been subjected to the PID control by interpolation between the two points using two feed points (δP _i ) sampled at constant crank angles. The crank angle corresponding to time is calculated.
According to the fourth means, the feedback output (ΔP _p ) of the PID control is performed by interpolation between the two points using the values of the two points sampled at constant crank angles of the feed forward amount (δP _i ). The time-dependent crank angle is calculated and the time of the feedback output (ΔP _p ) is corrected, whereby the change of the feedforward amount (δP _i ) is changed to the crank angle base, and the change of the feedback output (ΔP _p ) The time gap of being a base can be eliminated.

The fifth means calculates a time change rate (ΔP ₀ / Δt) of the target value (P ₀ ), and a feedforward amount correction value (δP _si ) based on the time change rate (ΔP ₀ / Δt). And the correction value (δP _si ) is added to the feedforward amount (δP _i ).
According to the fifth means, the time change rate (ΔP ₀ / Δt) of the target value (P ₀ ) is calculated, and the feedforward amount (δP _si ) is corrected based on the time change rate (ΔP ₀ / Δt). By calculating the amount and adding the correction amount to the feedforward amount (δP _si ), the upper limit of the pressure in the common rail gradually increases during transitional periods such as when the engine is suddenly loaded or rapidly started. The target value (P ₀ ) can also be changed according to the behavior state of the engine, and even in a transient state such as a step response and a ramp response of the target value (P ₀ ), it is possible to repeatedly control the pressure in the common rail. Good trackability can be maintained.

According to the present invention, the delay due to PID control can be eliminated by adding the feedforward amount (δP _i ) stored and accumulated in the accumulation buffer accumulation unit to the feedback output (ΔP _p ) of PID control. Thus, pressure control in the common rail can be performed with high accuracy.
Further, according to the present invention, the feedforward amount (δP _i ) stored and accumulated in the accumulation buffer accumulating unit is added to the feedback output (ΔP _p ) of the PID control, and the correction amount of the common rail internal pressure is calculated. Therefore, it is possible to obtain the feedforward amount without the need for labor and time-consuming manual work such as creating a multidimensional map from engine test operation data as in the prior art. The internal pressure can be controlled.

Even if an unexpected disturbance enters during pressure control in the common rail, the gain can be freely controlled by advancing the gain of the feedforward amount (δP _i ) stored and accumulated in the accumulation buffer accumulation unit. Can be controlled to maintain good common rail pressure control performance.
Further, during engine operation, the feedforward amount (δP _i ) stored and accumulated in the accumulation buffer accumulation unit for each predetermined crank angle of the engine is added to the feedback output (ΔP _p ) of PID control for each crank angle. Since the correction amount of the pressure in the common rail is calculated and the pressure control in the common rail is performed, the pressure control in the common rail can be easily performed in the entire operation range of the engine.

  Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this example are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.

  FIG. 1 is an overall configuration diagram of a fuel control device for an accumulator fuel injection diesel engine according to an embodiment of the present invention, and FIG. 2 is a control block diagram of the common rail fuel pressure control device according to the embodiment. 3 is a flowchart of PID control, FIG. 4 is a flowchart of feedforward amount control, and FIG. 5 is a flowchart of initialization setting. 6A and 6B are diagrams for explaining the discontinuous adjustment of the feedforward amount, and FIGS. 7A and 7B are diagrams for explaining the time difference adjustment between the PID control and the feedforward control. 8 is a diagram for explaining fuel pressure fluctuation in the common rail. FIG. 9 is a flowchart of the pressure equalization control interruption operation in the common rail using the square sum of the differential pressures. FIG. 10 is a control block diagram of another embodiment in which target value control of common rail internal pressure is added.

In FIG. 1 showing a fuel control apparatus according to an embodiment of the present invention, 100 is an engine (diesel engine), 103 is a piston of the engine 100, 104 is a crankshaft, and 102 is a combustion formed in a space above the piston 103. It is a room. Reference numeral 101 denotes a fuel injection valve, which is a known multi-injection type fuel injection valve configured to push up the needle valve 101b with the pressure of high-pressure fuel and inject the fuel into the combustion chamber 102 from the injection hole 101a. is there.
Reference numeral 105 denotes a high-pressure common rail for accumulating high-pressure side fuel, and reference numeral 106 denotes a low-pressure common rail for accumulating low-pressure side fuel.

Reference numeral 127 denotes a fuel tank. A high pressure pump 107 sucks the fuel in the fuel tank 127 through the high pressure side fuel pipe 122 and pressurizes the fuel into a high pressure, and pushes the fuel into the high pressure common rail 105 through the high pressure discharge pipe 123. A low-pressure pump 108 sucks the fuel in the fuel tank 127 through the low-pressure side fuel pipe 124, pressurizes the fuel to a pressure lower than that of the high-pressure pump 107, and pushes the fuel into the low-pressure common rail 106 through the low-pressure discharge pipe 125. Is.
Reference numeral 109 denotes a high-pressure side throttle valve provided in the high-pressure side fuel pipe 122, which controls the fuel flow rate of the high-pressure pump 107 by a control signal from the common rail pressure control device 1 described later. Reference numeral 110 denotes a low-pressure side throttle valve provided in the low-pressure side fuel pipe 124, which controls the fuel flow rate of the low-pressure pump 108 by a control signal from the common rail pressure control device 1 described later.

  Reference numeral 2 denotes a fuel injection control device that performs control to be described later. 112 is a high pressure side injection control valve, an inlet port is connected to the high pressure injection pipe 115 connected to the high pressure common rail 105 outlet side, and an outlet port is connected to the fuel injection valve 101 side via the high pressure injection pipe 116; By switching the connection between the inlet port and the outlet port according to the control signal 120 from the fuel injection control device 2, the injection from the fuel injection valve 101 of the high-pressure fuel accumulated in the high-pressure common rail 105 is controlled. ing.

113 is a low pressure side injection control valve, the inlet port is connected to the low pressure injection pipe 119 connected to the low pressure common rail 106 outlet side, the outlet port is connected to the fuel injection valve 101 side via the low pressure injection pipe 116a, By switching the connection between the inlet port and the outlet port in accordance with a control signal 121 from the fuel injection control device 2, the injection from the fuel injection valve 101 of the high-pressure fuel accumulated in the low-pressure common rail 106 is controlled. ing. The drain port of the low pressure side injection control valve 113 is connected to the fuel tank 127 via a drain pipe 126, and the connection between the inlet port and the outlet port is controlled by a control signal from the fuel injection control device 2. In addition, by switching the connection between the outlet port on the fuel injection valve 101 side and the drain port, injection of the low-pressure fuel accumulated in the low-pressure common rail 106 from the fuel injection valve 101 is controlled.
A check valve 114 is provided in the low pressure injection pipe 119 and allows only the flow of fuel from the low pressure common rail 106 side to the low pressure side injection control valve 113 side. A check valve 111 is provided in the drain pipe 126 and allows only the flow of fuel from the low pressure side injection control valve 113 side to the fuel tank 127 side.

  Reference numeral 4 denotes a high-pressure rail pressure sensor that detects the pressure in the high-pressure common rail 105, and reference numeral 5 denotes a low-pressure rail pressure sensor that detects the pressure in the low-pressure common rail 106. The pressure detection value in the high-pressure common rail 105 from the high-pressure rail pressure sensor 4 and the pressure detection value in the low-pressure common rail 106 from the low-pressure rail pressure sensor 5 are detected values of pressure fluctuations due to shock wave movement in the high-pressure common rail 105. The detected value of the pressure fluctuation due to the shock wave movement in the low-pressure common rail 105 is input to the common rail control device 1.

8 is a fuel injection pressure sensor for detecting the fuel injection pressure at the inlet of the fuel injection valve 101, 6 is a high pressure pump pressure sensor for detecting the fuel pressure at the outlet of the high pressure pump 107, and 7 is a fuel pressure at the outlet of the low pressure pump 108. Pulsating pressure fluctuation detection value due to reciprocation of the high pressure pump plunger from the high pressure pump pressure sensor 6 and pulsation pressure fluctuation detection value due to the reciprocation of the low pressure pump plunger from the low pressure pump pressure sensor 7. Is input to the common rail control device 1.
Reference numeral 3 denotes a crank angle sensor that detects a crank angle of the engine 100, and a crank angle detection value from the crank angle sensor 3 is input to the common rail control device 1 and the fuel injection control device 2.

Next, the operation of the fuel control apparatus will be described with reference to FIGS.
The detected value Pd of pressure fluctuation due to shock wave movement in the high pressure common rail 105 from the high pressure rail pressure sensor 4 or the detected value Pd of pressure fluctuation due to shock wave movement in the low pressure common rail 106 from the low pressure rail pressure sensor 5 is the common rail control device 1. To the adder 16.
Further, the pressure fluctuation detection value Pp due to fuel injection from the fuel injection pressure sensor 8 and the pulsation pressure fluctuation detection value due to reciprocation of the plunger of the high pressure pump 107 from the high pressure pump pressure sensor 6, or the low pressure pump pressure sensor 7. The pulsation pressure fluctuation detection value Ps due to the reciprocating motion of the plunger of the low pressure pump 108 is input to the adder 16.
In the adder 16, the periodic disturbance S (S = Pd + Pp + Ps) is calculated by adding the pressure fluctuation detection value Pd due to the shock wave movement, the pressure fluctuation detection value Pp due to fuel injection, and the pulsation pressure fluctuation detection value Ps. , Input to the adder / subtractor 14 described later.

The following description of the operation is performed when the common rail pressure on the high-pressure common rail 105 side is controlled, but the same operation as that on the high-pressure common rail 105 side is performed on the low-pressure common rail 106 side.
As shown in FIG. 8, the throttle valve 109 (high-pressure side throttle valve) opens and closes like B, and the common rail pressure P ₁ causes a pressure fluctuation like A due to the periodic disturbance S. In such an embodiment, to remove variations in the common rail pressure P ₁ by repeating the control described below.
First, in order to avoid the occurrence of a control deviation due to unstable pressure in the common rail at the initial stage immediately after turning on the control power source, such as when the engine is started, as shown in FIG. The initial value Ffbuf (i) of the accumulation buffer) is stored, and calculation of feedback output by the feedforward amount and PID control is started after a certain time when the fuel pressure detection value (P ₁ ) changes periodically. .
Thus, the fuel pressure detection value P ₁ from becoming periodically change after a predetermined time after turning the control power, the pressure control in the common rail to start calculation of the feedback output by the feedforward quantity and PID control Since the shift is made, it is possible to avoid the influence of the excessive control deviation on the pressure control in the common rail at the initial time immediately after the control power is turned on, such as when the engine is started.

That the pressure (hereinafter rail pressure in the high pressure common rail 105 which is fed back is detected at the target value of the high-pressure rail pressure P ₀ and the high-pressure rail pressure sensor 4 which is the reference rail pressure, which is preset by the operating conditions of the engine 100 ) detection value _{P 1} is the pressure common rail pressure control device 1 is input to the subtractor 10 (step of FIG. 3 (1)).
The adder / subtracter 10 calculates a differential pressure ΔP (ΔP = P ₁ −P ₀ ) between the rail pressure detection value P ₁ and the target value P ₀ of the high-pressure rail pressure (step (2) in FIG. )).
A part of the differential pressure ΔP is input to the feed forward gain setting unit 12, and the remaining part is input to the PID control unit 11 by a calculation as described later (step (3) in FIG. 3).

The PID control unit 11 performs a PID (proportional, integral, derivative) operation on the remaining part of the differential pressure ΔP according to the following equation (1) to calculate a feedback output ΔP _p .
ΔP _p = KP × ΔP + KI × ∫ (ΔP) + KD (dΔP / dt) (1)
Here, KP, KI, and KD are PID gains. The feedforward gain setting unit 12 performs origin detection (step (1) in FIG. 4) and then feeds for each crank angle according to the following equation (2). The forward amount δP _i is calculated (step (2) in FIG. 4).
δP _i = ΔP × KF (2)
Here, KF is a forward gain. This feed forward amount δP _i is stored and accumulated in the accumulation buffer accumulating unit 13 as an accumulation buffer Fval by the following equations (3) and (4) for each predetermined crank angle ( Steps (3) and (4) in FIG.
Fbuf (i) ← δP _i + Fbuf (i) (3)
Fval ← Fbuf (i) (4)

The feedback output ΔP _p and the cumulative buffer Fval (feed forward amount) are input to the adder / subtractor 14 from time to time, and the adder / subtracter 14 adds the cumulative buffer Fval to the feedback output ΔP _p and the following ( 5) summing each crank angle by equation calculates a correction amount U of the common rail pressure P ₁ (step of FIG. 3 (4)).
U ← ΔP _p + Fval (5)
Further, the adder / subtractor 14 corrects the correction amount U of the common rail internal pressure P ₁ by the periodic disturbance S (S = Pd + Pp + Ps) according to the following equation (6), and the solenoid valve controller 15 To enter.
U ← SU (6)
The electromagnetic valve controller 15 calculates a control current adjustment amount of the common rail pressure control electromagnetic valve 109 corresponding to the correction amount U and transmits the calculated control current adjustment amount to the electromagnetic valve 109. As a result, the opening degree of the electromagnetic valve 109 is adjusted to an opening degree corresponding to the correction amount U, the common rail internal pressure P ₁ is held at the target value P _0, and the pressure fluctuation due to the influence of the periodic disturbance S Is removed.

In the common rail pressure control in the fuel control apparatus as described above, in this embodiment, the cumulative buffer Fval (added to the feedback output ΔP _p , that is, the cumulative buffer Fval ( The ratio (Fval / ΔP _p ) between the feed forward amount) and the feedback output ΔP _p is increased in the first half of the cycle where the delay due to the PID control calculation in the PID control unit 11 is large, and the delay due to the PID control is complemented. Then, the rate (Fval / ΔP _p ) is decreased as the later stage of the cycle in which the influence of the delay due to the PID control becomes small, so that the feedback output ΔP _p finally becomes equal to the periodic disturbance S. To control.
By performing such control, the delay due to PID control is eliminated by adding the accumulated buffer Fval (feed forward amount) stored and accumulated in the accumulated buffer accumulating unit 13 to the feedback output ΔP _p of PID control. It becomes possible.
Further, according to this embodiment, even when the disturbance S enters an unexpected time, the gain of the accumulated buffer Fval (feed forward amount) stored and accumulated in the accumulated buffer accumulating unit 13 is advanced. Thus, control corresponding to the disturbance S can be performed freely, and deterioration of the control performance of the common rail pressure control can be prevented.

Next, in the common rail pressure control in the fuel control device, as shown in FIG. 6, the origin detection of the accumulated buffer Fval (feed forward amount) stored and accumulated in the accumulated buffer accumulating unit 13 corresponding to the crank angle is performed. There is a shift of one cycle formed immediately after (Fbuf (0)) and immediately before the origin detection (Fbuf (n-1)).
In order to cope with this, a deviation amount E _r between the cumulative buffer (feed forward amount) (Fbuf (0)) immediately after the origin detection and the cumulative buffer (feed forward amount) (Fbuf (n−1)) one cycle before. (= Fbuf (0) −Fbuf (n−1)) is calculated, and when the origin position of the common rail pressure control is detected, the shift amount is initialized to be close to 0 (E _r ← 0), and the feed at the origin position is initialized. By maintaining the continuity of the forward amount, deterioration of the control performance is prevented.

In the common rail pressure control in the fuel control device, if the above repeated control is performed permanently, the control sensitivity becomes high, and the common rail pressure slightly fluctuates due to the influence of the control system disturbance in the accumulation buffer. In order to suppress this, the following control is performed.
That is, the sum of squares (ΣΔP) of the differential pressure ΔP in a plurality of past cycles is calculated, and when the sum of squares (ΣΔP) starts to increase, the pressure control of the pressure in the common rail is interrupted.
Specifically, as shown in FIG. 9, it is determined whether the square sum σP of the pressure fluctuation in the common rail 105 calculated in step (1) in FIG. 9 is within the allowable range σColor (σP <σColor). If it is within the allowable range σColor, the repeated control is interrupted.
By controlling in this way, the divergence of the control value due to disturbance can be avoided, and the common rail pressure control can be stabilized.

In the common rail pressure control in the fuel control device, the PID control is based on the time function, whereas the feed forward amount accumulation buffer is stored and accumulated for each crank angle. In order to correct the deviation, the following control is performed.
That is, as shown in FIG. 7, from the change in the cumulative buffer Fbuf with respect to the crank angle shown in (A), using two values Fbuf (i) and Fbuf (i + 1) sampled at constant crank angles, As in (B), the crank angle corresponding to the PID control time is calculated by interpolating the two points with a straight line.
By controlling in this way, it is possible to eliminate a time lag that the accumulated buffer change of the buffer feedforward amount is based on the crank angle and the change of the feedback output is based on the time.

In the common rail internal pressure control in the fuel control apparatus, the upper limit of the common rail internal pressure gradually increases during a transitional period such as when the engine is suddenly loaded or rapidly started, so that the target value P ₀ is also changed. Therefore, the following target value correction control is performed.
That is, as shown in FIG. 10, the target value correction unit 30 calculates the rate of change of the target value P ₀ (NW) with time, that is, the differential value dP ₀ / dt and the secondary differential value d ² P ₀ / dt ² .
Then, the cumulative buffer correction value Ftrans = f (dP ₀ / dt, d ² P ₀ / dt ² ) (7)
The adder 31 adds the cumulative buffer Fval from the cumulative buffer storage unit 13 and the cumulative buffer correction value Ftrans, and sends this addition value (Fval + Ftrans) to the adder / subtractor 14, Additionally, in the subtractor 14, like the embodiment of FIG. 2, the feedback output [Delta] p _p and the disturbance S and pressure from the PID controller 11, subtraction and calculates the correction amount U by the following equation (8),
U ← S− (ΔP _p + Fval + Ftrans)
The correction amount U is input to the solenoid valve controller 15.

If ask this configuration, obtain a correction amount Ftrans of the accumulation buffer based on said time rate of change by calculating the time rate of change of the target value P ₀ (feed forward amount), the correction amount of the accumulation buffer (feedforward amount by the summing performed to), sudden load application of the engine, corresponding to the upper limit of the common rail pressure P ₁ increases gradually in rapid activation such transitional target value P ₀ be the engine can be varied by behavior state, the step response of the target value P _0, the transient state of the lamp and answers, maintaining good trackability of the repetitive control of the common rail pressure.

  According to the present invention, it is possible to perform the pressure equalization control of the pressure in the common rail with simple means without requiring manual labor associated with data acquisition by engine test operation, and even if an unexpected disturbance acts, To provide an accumulator type fuel injection internal combustion engine that can perform pressure control in a common rail in response to a disturbance without lowering the control performance, and can realize highly accurate pressure control in the common rail in the entire operation range of the engine. Can do.

1 is an overall configuration diagram of a fuel control device for an accumulator fuel injection diesel engine according to an embodiment of the present invention. It is a control block diagram of the fuel pressure control apparatus in a common rail in the said Example. It is a flowchart of PID control. It is a flowchart of feedforward amount control. It is a flowchart of initialization setting. (A), (B) is an explanatory diagram of the discontinuous adjustment of the feedforward amount. (A), (B) is an explanatory diagram of the time difference adjustment between PID control and feedforward control. It is a diagram for explanation of the fuel pressure fluctuation in the common rail. The flowchart of the equalization control interruption operation | movement of the pressure in a common rail using the square sum of a differential pressure is shown. It is a control block diagram of the other Example which added target value control of the pressure in a common rail. It is a figure corresponding to FIG. 1 which shows a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Common rail control apparatus 2 Fuel injection control apparatus 3 Crank angle sensor 4 High pressure rail pressure sensor 5 Low pressure rail pressure sensor 6 High pressure pump pressure sensor 7 Low pressure pump pressure sensor 8 Fuel injection pressure sensor 10 Addition / subtraction unit 11 PID control unit 12 Feed forward Gain setting unit 13 Cumulative buffer storage unit 14 Addition / subtraction unit 15 Solenoid valve controller 16 Adder 100 Engine (diesel engine)
101 Fuel injection valve 102 Combustion chamber 104 Crankshaft 105 High pressure common rail 106 Low pressure common rail 107 High pressure pump 108 Low pressure pump 109 High pressure side throttle valve 110 Low pressure side throttle valve 112 High pressure side injection control valve 113 Low pressure side injection control valve

Claims (10)

The fuel pressurized by the fuel pump is accumulated in the common rail, and the solenoid valve provided in the fuel injection pipe connecting the common rail and the fuel injection valve of the engine (internal combustion engine) is controlled to be opened and closed by the fuel injection control device. In the fuel control method for an accumulator type fuel injection internal combustion engine configured to be able to inject pressurized fuel in the common rail from the fuel injection valve into a combustion chamber of an engine, the fuel pressure in the common rail is detected and the fuel is detected. A differential pressure (ΔP = P ₁ −P ₀ ) between a pressure detection value (P ₁ ) and a preset target value (P ₀ ) of the fuel pressure is calculated, and a part of the differential pressure (ΔP) is fed A forward amount (δP _i ) is stored and stored for each predetermined crank angle of the engine, and the feed forward amount (δP _i ) is stored in the remainder of the differential pressure (ΔP) as a PID (proportional, integral, derivative) control. A fuel control method for an accumulator fuel-injection internal combustion engine, characterized by repeatedly adding to a controlled feedback output (ΔP _p ) in accordance with the crank angle of the engine to perform equalization control of the pressure in the common rail. . The feedback output (ΔP _p ) and the feedforward amount (δP _i ) subjected to the PID control are added to or subtracted from disturbance (S) such as fuel pressure fluctuation acting on the common rail and the fuel system connected thereto. 2. The fuel control method for an accumulator fuel-injected internal combustion engine according to claim 1, wherein a correction amount of the pressure in the common rail including the disturbance is calculated. The feedforward quantity to the sum of ([delta] P _i) and the feedback output which has been subjected to the PID control ([Delta] P _p) is constant, the feed forward amount ([delta] P _i) and the feedback output ([Delta] P _p) ratio of ([delta] P _i / the [Delta] p _p), the fuel control method for an accumulator fuel injection internal combustion engine according to claim 1, wherein the allowed to small with the lapse of increased time to the original control. An initial value of the differential pressure (ΔP) is stored, and after a predetermined time when the fuel pressure detection value (P ₁ ) periodically changes, the feedforward amount (δP _i ) and the feedback output (ΔP) by PID control are stored. _2. The fuel control method for an accumulator type fuel injection internal combustion engine according to claim 1, wherein calculation of _p ) is started. Weight the feed-forward ([delta] P _i) and calculates feedforward amount of 1 cycle before the ([delta] P _i-1) shift amount between _{E r (= δP i -δP i} -1), when the common rail pressure control of the origin position detection 2. The accumulator fuel injection according to claim 1, wherein the deviation amount is initialized to be close to 0 (E _r ← 0) to maintain the continuity of the feedforward amount (δP _i ) at the origin position. A fuel control method for an internal combustion engine.   Calculating the sum of squares (ΣΔP) of the differential pressure (ΔP) in a plurality of past cycles, and interrupting the equalization control of the pressure in the common rail when the sum of squares (ΣΔP) starts to increase. 2. The fuel control method for an accumulator type fuel injection internal combustion engine according to claim 1, wherein Using the values of two points sampled at a constant crank angle of the feed forward amount (δP _i ), the time corresponding crank angle of the feedback output (ΔP _p ) subjected to the PID control by interpolation between the two points is calculated. The fuel control method for an accumulator fuel-injected internal combustion engine according to claim 1, wherein the fuel control method is calculated. A time change rate (ΔP ₀ / Δt) of the target value (P ₀ ) is calculated, and a correction value (δP _si ) of the feedforward amount is calculated based on the time change rate (ΔP ₀ / Δt), and the correction is performed. 2. The fuel control method for an accumulator type fuel injection internal combustion engine according to claim 1, wherein a value (δP _si ) is added to the feedforward amount (δP _i ). The fuel pressurized by the fuel pump is accumulated in the common rail, and the solenoid valve provided in the fuel injection pipe connecting the common rail and the fuel injection valve of the engine (internal combustion engine) is controlled to be opened and closed by the fuel injection control device. In the accumulator type fuel injection internal combustion engine configured to inject pressurized fuel in the common rail from the fuel injection valve into a combustion chamber of the engine, a rail pressure sensor for detecting fuel pressure in the common rail, and the rail An adder / subtractor for calculating a differential pressure (ΔP = P ₁ −P ₀ ) between a fuel pressure detection value (P ₁ ) input from the pressure sensor and a preset target value (P ₀ ) of the fuel pressure; Accumulated buffer accumulation for storing and accumulating a part of the differential pressure (ΔP) output from the adder / subtractor as a feed forward amount (δP _i ) for each predetermined crank angle of the engine Part,
A PID control unit that performs PID (proportional, integral, differential) control on the remainder of the differential pressure (ΔP), and the feedforward amount (δP _i ) is added to or subtracted from the feedback output (ΔP _p ) from the PID control unit And adding and subtracting the feedforward amount (δP _i ) and the feedback output (ΔP _p ) from the PID controller in accordance with the crank angle of the engine. An accumulator fuel injection internal combustion engine comprising a common rail pressure control device that performs equalization control of pressure in the common rail. The common rail pressure control device receives a disturbance (S) such as a fuel pressure fluctuation acting on the common rail and a fuel system connected thereto, and inputs a second adder / subtractor to the disturbance (S). 10. The correction amount of the pressure in the common rail including the disturbance is calculated by adding and subtracting a feedback output (ΔP _p ) and a feed forward amount (δP _i ). Accumulated fuel injection internal combustion engine.

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