JP5514173B2 - Fuel pump control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel pump control device for an internal combustion engine that controls a drive operation amount of a fuel pump that supplies fuel to a fuel injection valve.

  As this type of control device, there is one that controls the fuel pump drive operation amount according to the fuel consumption from the fuel injection valve (actual engine load), but the fuel pressure is controlled by the response delay of the control system and the fuel pump. Sometimes it was difficult to maintain properly.

  For this reason, in Patent Document 1, the fluctuation of the intake pipe pressure is predicted based on the accelerator operation amount, and the drive voltage of the electric fuel pump is controlled based on the predicted intake pipe pressure. The intended technique is disclosed.

JP-A-9-170467

  In Patent Document 1, since the fuel pump drive operation amount is calculated based on the required engine load, such as the accelerator opening, the fuel injection amount (actual Engine load) decreases.

  As a result, the amount of fuel discharged from the fuel pump driven by the operation amount based on the required load becomes excessive, causing a deviation between the target fuel pressure and the actual fuel pressure, resulting in deterioration of exhaust emission, fuel consumption, and output performance. was there.

  In order to solve such a conventional problem, an object of the present invention is to drive a fuel pump so that the fuel pressure is properly maintained even when the atmospheric pressure changes.

For this reason, the present invention
A demand load detecting means for detecting a demand load of the engine; and a drive operation amount calculating means for calculating a drive operation amount of the fuel pump based on at least the detected demand load, wherein the fuel pump is driven by the drive operation amount. A fuel pump control apparatus for an internal combustion engine that includes the following means.

Atmospheric pressure detection means for detecting atmospheric pressure
Drive operation amount correction means for correcting the required load based on the detected atmospheric pressure to estimate an actual engine load and calculating a drive operation amount based on the estimated engine load and the engine rotation speed

  While ensuring high responsiveness by setting the drive operation amount based on the required load, by correcting the drive operation amount based on the atmospheric pressure detection value, the drive operation amount commensurate with the actual engine load even if the atmospheric pressure changes The engine performance such as exhaust emission, fuel consumption, and output performance is improved.

The figure which shows the fuel pump control apparatus of the internal combustion engine for vehicles which concerns on embodiment. A flowchart showing a first embodiment of calculation of a driving voltage (driving operation amount) of a fuel pump Flow chart of a subroutine for calculating an atmospheric pressure correction coefficient based on the detection value of the atmospheric pressure sensor Diagram showing the relationship between the target fuel pressure FPTRP and the feedforward manipulated variable FPFFVOL Flowchart showing a second embodiment of calculation of drive voltage (drive operation amount) of the fuel pump Flowchart of a subroutine for estimating and calculating the atmospheric pressure correction coefficient based on the engine operating state

Embodiments of the present invention will be described below.
FIG. 1 is a diagram illustrating a fuel supply system of an internal combustion engine for a vehicle including a fuel pump control device according to an embodiment.

In FIG. 1, a fuel tank 1 is a tank for storing fuel of an engine (internal combustion engine) 10, and is disposed, for example, under a rear seat of a vehicle.
The fuel tank 1 is provided with a fuel filler opening 3 that is closed by a fuel filler cap 2, and the fuel filler cap 2 is removed to replenish fuel from the fuel filler inlet 3.

An electric fuel pump 4 is installed in the fuel tank 1 by a bracket (not shown).
The fuel pump 4 is an electric pump of, for example, a turbine type that sucks gasoline in the fuel tank 1 from a suction port and discharges it from the discharge port, and one end of a fuel pipe 5a is connected to the discharge port.

  The other end of the fuel pipe 5a passes a fuel flow from the fuel pump 4 toward a fuel injection valve 9 to be described later, and a check valve that blocks a flow (back flow) from the fuel injection valve 9 toward the fuel pump 4. 7 inlet side is connected.

The fuel pipe 5a, the fuel pipe 5b, and the fuel gallery pipe 8 form a fuel supply passage from the fuel pump 4 toward the fuel injection valve 9.
The fuel gallery pipe 8 is provided with the same number of injection valve connection portions 8a as the number of cylinders (4 cylinders in the present embodiment) along the extending direction, and each injection valve connection portion 8a includes a fuel injection valve. Nine fuel intakes are connected to each other.

  The fuel injection valve 9 is an electromagnetic fuel injection valve in which when a magnetic attractive force is generated by energization of an electromagnetic coil, a valve body biased in a valve closing direction by a spring lifts and injects fuel.

The fuel injection valve 9 is installed at each intake port portion of each cylinder of the engine 10 and injects fuel into each cylinder.
Further, a relief pipe 12 is provided for communicating the inside of the fuel gallery pipe 8 and the inside of the fuel tank 1, and a relief valve 13 is interposed in the middle of the relief pipe 12.

  The relief valve 13 is urged in the valve closing direction by an elastic body, and is a mechanical check valve that relieves the fuel in the fuel gallery pipe 8 into the fuel tank 1, and the fuel power in the fuel gallery pipe 8. Is provided to prevent the pressure from becoming larger than the valve opening pressure (allowable upper limit pressure).

  An electronic control unit (ECU) 11 incorporating a microcomputer individually outputs a valve opening control pulse signal to each of the fuel injection valves 9 to control the fuel injection amount and injection timing of each fuel injection valve 9. .

Detection signals from various sensors are input to the electronic control unit 11.
The various sensors include an air flow meter 21 that detects the intake air flow rate of the engine 10, a crank angle sensor 22 that outputs a detection signal for each predetermined crank angle position, a water temperature sensor 23 that detects a cooling water temperature Tw of the engine 10, In addition to a fuel pressure sensor 24 that detects the pressure of the fuel in the fuel gallery pipe 8, a fuel temperature sensor 25 that detects the temperature of the fuel in the fuel gallery pipe 8, an air-fuel ratio sensor 26 that detects the air-fuel ratio from the exhaust components, As sensors relating to drive control of the fuel pump 4, a throttle sensor 27 that detects the opening (throttle opening) of a throttle valve (not shown) of the engine 10, an atmospheric pressure sensor 28 that detects atmospheric pressure, and the like are provided.

  Then, the electronic control unit 11 sets the injection pulse width corresponding to the amount of fuel that can form the target air-fuel ratio mixture from the air flow meter 21, the crank angle sensor 22, the water temperature sensor 23, the air-fuel ratio sensor 26, and the like. And the valve opening control pulse signal having the injection pulse width is output to each fuel injection valve 9. The electronic control unit (ECU) 11 performs other engine control (ignition timing, throttle control) and the like.

The pump control unit (PCU) 14 controls the fuel pressure by controlling the fuel discharge amount of the fuel pump 4 by controlling the drive voltage (drive operation amount) to the fuel pump 4.
Here, the drive voltage of the fuel pump 4 is set so that the fuel pressure can be properly maintained even when the atmospheric pressure changes.

FIG. 2 is a flowchart showing a first embodiment for calculating the drive voltage (drive operation amount) of the fuel pump 4.
In the first embodiment, the feedforward manipulated variable FPFFVOL of the drive voltage of the fuel pump 4 with respect to the target fuel pressure FPTRP is calculated according to the following linear expression.

FPFFVOL = FPGAIN × FPPTRP + FPOFS (1)
Here, the gain (inclination) FPGAIN and the offset FPOFS are set as follows based on the engine operating state.

  In step S1, a corrected engine load obtained by correcting the required load of the engine to match the actual load according to a change in atmospheric pressure or the like is calculated according to the following equation. The post-correction engine load corresponds to the fuel injection amount from the fuel injection valve 9 once (in each intake stroke).

TQHHOS = TQH0 × INJPAMS × INJFER (2)
TQHHOS: engine load after correction
TQH0: throttle opening (required load)
INJPAMS: atmospheric pressure correction factor
INJFER: fuel equivalent ratio Here, the atmospheric pressure correction coefficient INJPAM is detected by the atmospheric pressure sensor 28 as shown in the flowchart of the subroutine shown in FIG. 3 when the atmospheric pressure sensor 28 is provided as described above. The atmospheric pressure correction coefficient INJPAMS is calculated so as to decrease as the atmospheric pressure decreases.

  Even at the same throttle opening, the lower the atmospheric pressure, the lower the intake pressure (intake air amount), and the fuel injection amount (actual load) decreases accordingly. The decrease is corrected.

  Further, the fuel equivalent ratio is set for correction in the operation region where the target air-fuel ratio deviates from the reference air-fuel ratio, for example, the stoichiometric air-fuel ratio. For example, it is set to 1 in the operation region at the reference air-fuel ratio, but in a region where the fuel injection amount is increased and the air-fuel ratio is richer than the reference air-fuel ratio, such as at high load, 1 is set according to the concentrated air-fuel ratio. In a region that is set to a larger value and is operated at a lean air-fuel ratio that is smaller than the reference air-fuel ratio, the value is set to a value smaller than 1 in accordance with the lean air-fuel ratio.

In this way, it is possible to calculate the corrected engine load TQHHOS commensurate with the actual load (fuel injection amount).
In step S2, based on the corrected engine load TQHHOS and the engine speed Ne, the gain FPGAIN of the FF manipulated variable calculation formula (1) is calculated from a map set as shown in the figure. In the map, the gain FPGAIN is set to increase as the output increases from a small output region such as an idle to a medium to high output region and a fully open output region.

  In step S3, the offset FPOFS of the above-described FF manipulated variable calculation formula (1) is calculated from the map set as shown in the figure based on the corrected engine load TQHHOS and the engine speed Ne. In the map, the offset amount FPOFS is set to increase as the output increases from a small output region such as an idle to a medium to high output region and a fully open output region.

  In step S4, the feedforward manipulated variable FPFFVOL of the drive voltage of the fuel pump 4 with respect to the target fuel pressure FPTRP is calculated by the following equation (1) using the gain FPGAIN and the offset FPOFS calculated in steps S2 and S3.

FPFFVOL = FPGAIN × FPPTRP + FPOFS (1)
FIG. 4 shows the relationship between the target fuel pressure FPTRP and the feedforward manipulated variable FPFFVOL.

  For simplicity, the feedforward manipulated variable FPFFVOL may be directly applied to the fuel pump 4 as a drive voltage (operated variable). However, the difference between the target fuel pressure and the actual fuel pressure caused by the performance variation of the fuel pump 4 or the like. In order to correct, it is preferable to perform feedback control by calculating a feedback operation amount as follows.

  In step S5, based on the deviation between the target fuel pressure FPTRP and the actual fuel pressure FPREP detected by the fuel pressure sensor 24, the feedback manipulated variable FPFBVOL of the drive voltage of the fuel pump 4 is calculated. For example, the feedback manipulated variable FPFBVOL is set to a larger value as the deviation ΔP (= FPPTRP−FPREP) is larger.

  In step S6, based on the feedforward manipulated variable FPFFVOL and the feedback manipulated variable FPFBVOL, the final drive manipulated variable FPVOL of the fuel pump 4 is calculated as shown in the following equation (3) and output to the fuel pump 4.

FPVOL = FPFFVOL + FPFBVOL (3)
According to the first embodiment, the fuel pressure can be controlled with high response to the response delay of the control system and the fuel pump by setting the feedforward operation amount of the fuel pump drive based on the required load of the engine. .

  On the other hand, when the atmospheric pressure decreases due to high altitude traveling or the like, it is possible to control the fuel pressure to be decreased by correcting the feedforward operation amount to decrease by the atmospheric pressure correction coefficient INJPAMs that decreases as the atmospheric pressure decreases. As a result, reduction correction is made to an appropriate fuel injection amount commensurate with the required load that decreases as the atmospheric pressure decreases.

Thereby, engine performance, such as exhaust emission, fuel consumption, and output performance, can be maintained satisfactorily.
In the present embodiment, the feedforward manipulated variable is defined by a linear expression with respect to the target fuel pressure, and the gain and offset are set for each engine output based on the corrected engine load and engine speed. The feedforward manipulated variable can be calculated with high accuracy by a simple arithmetic expression.

Next, a second embodiment for calculating the drive voltage (drive operation amount) of the fuel pump 4 will be described with reference to the flowchart of FIG.
In step S21, as in step S1 of FIG. 2, the corrected engine load TQHHOS (one fuel of the fuel injection valve 9) is obtained by correcting the required load of the engine to match the actual load according to changes in atmospheric pressure or the like. (Injection amount) is calculated.

In step S22, an estimated value FPQEV of the fuel flow consumed by the fuel injection valve 9 is calculated from the following equation based on the corrected engine load TQHHOS and the engine speed Ne.
FPQEV = k × TQHHOS × Ne
However, k is the number of injections per engine revolution, and in the case of a 4-cycle engine, the total number of fuel injection valves n / 2 (k = 2 in the example of FIG. 1).
In step S23, the feedforward manipulated variable FPFFVOL of the drive voltage of the fuel pump 4 is searched from the map set as shown on the basis of the fuel flow rate estimated value FPQEV and the target fuel pressure FPTRP.

  Here, since the feedforward manipulated variable FPFFVOL is larger as the fuel flow rate estimated value FPQEV is larger and the target fuel pressure FPTRP is larger, the required value of the fuel discharge amount from the fuel pump 4 is increased. It is set to increase.

  In step S24, the feedback drive operation amount FPFBVOL of the drive voltage of the fuel pump 4 is calculated based on the deviation between the target fuel pressure FPTRP and the actual fuel pressure FPREP as in step S5 of FIG.

  In step S15, as in step S6 of FIG. 2, the feedforward manipulated variable FPFFVOL and the feedback drive manipulated variable FPFBVOL are added to calculate the final drive manipulated variable FPVOL of the fuel pump 4, and the fuel pump 4 Output.

  According to the second embodiment, as in the first embodiment, the feedforward operation amount for driving the fuel pump is set on the basis of the required load of the engine, so that the response delay of the control system and the fuel pump can be prevented. The fuel pressure can be controlled with high response.

On the other hand, by correcting the feedforward operation amount so as to match the engine load corresponding to the actual load based on the atmospheric pressure, it is possible to control the fuel pressure to an appropriate value even when the atmospheric pressure changes, such as traveling at high altitude.
Thereby, engine performance, such as exhaust emission, fuel consumption, and output performance, can be maintained satisfactorily.

  In this embodiment, the fuel flow rate (fuel consumption) is estimated based on the corrected engine load and the engine speed, and the feedforward manipulated variable is calculated with high accuracy based on the estimated fuel flow rate and the target fuel pressure. be able to.

  FIG. 6 shows a flowchart for estimating and calculating the atmospheric pressure correction coefficient INJPAMS based on the engine operating state when no atmospheric pressure sensor is provided. The estimated atmospheric pressure correction coefficient INJPAMS can be used in the first embodiment (step S1 in FIG. 2) and the second embodiment (step S21 in FIG. 5).

In step S31, it is determined whether the engine is in an engine starting state. If the engine is not in an engine starting state, the process proceeds to step S32 to determine whether the engine is in a transient operation state.
When it is determined that the engine is in a starting state or when the engine is in a transient operation state, the process proceeds to step S33, and the atmospheric pressure correction coefficient INJPAMS is set while maintaining the previous value. The previous value is the latest value calculated in steps S34 and S35 described later.

If it is determined that the engine is not in the engine start state or the transient operation state and is in the steady operation state, the process proceeds to step S34 and subsequent steps, and the atmospheric pressure correction coefficient INJPAMS is estimated.
First, in step S34, the required basic injection amount TTP is calculated based on the throttle opening TQH0 as the required load of the engine.

  The required basic injection amount TPP is a value calculated so that a reference air-fuel ratio (for example, theoretical air-fuel ratio) is obtained with a cylinder intake air amount corresponding to the throttle opening TQH0 in steady running on a low-level flat road. Since the engine travel speed Ne is substantially constant according to the throttle opening TQH0 because the condition is steady running on a low-level flat road, the cylinder intake air amount is determined only by the throttle opening TQH0, and the required basic injection amount. TPP can be determined. However, since the engine speed Ne may change due to a difference in road surface frictional resistance or the like, the required basic injection amount TPP may be calculated more accurately based on the throttle opening TQH0 and the engine speed Ne. Good.

  In step S35, the actual basic injection amount TP corresponding to the reference air-fuel ratio calculated based on the intake air flow rate detected by the air flow meter 21 and the engine rotational speed Ne is compared with the required basic injection amount TPP. The atmospheric pressure correction coefficient INJPAMS is calculated.

  In other words, the required basic injection amount TPP calculated based on the throttle opening QH0 (and the engine speed Ne) decreases the mass intake air amount due to the decrease in atmospheric pressure even if the altitude increases and the atmospheric pressure decreases. Is not reflected. That is, if the throttle opening QH0 is the same, the same value is obtained even if the atmospheric pressure in the cylinder drops.

  On the other hand, since the intake air flow rate detected by the air flow meter 21 is a mass flow rate, an intake air flow rate that decreases as the atmospheric pressure decreases is detected for the same throttle opening QH0.

Therefore, the atmospheric pressure can be estimated by comparing the required basic injection amount TP and the actual basic injection amount TPP, and the atmospheric pressure correction coefficient INJPAMS can be calculated by the following equation (4).
INJPAMS = TP / TTP (4)
By performing such estimation, the atmospheric pressure correction coefficient can be set without providing an atmospheric pressure sensor, and the fuel pump drive operation amount can be corrected based on the atmospheric pressure at low cost.

Further, technical ideas other than the claims that can be grasped from the above embodiment will be described together with the effects thereof.
(A) In a steady operation state of the engine, the atmospheric pressure correction coefficient is calculated by comparing the fuel injection amount calculated based on the required load with the fuel injection amount calculated based on the actually detected engine load;
The drive operation amount correction means corrects the drive operation amount based on the atmospheric pressure correction coefficient.

  In this way, it is possible to correct the fuel pump drive operation amount based on atmospheric pressure at low cost.

DESCRIPTION OF SYMBOLS 1 ... Fuel tank, 4 ... Fuel pump, 5a, 5b ... Fuel pipe, 8 ... Fuel gallery pipe, 9 ... Fuel injection valve, 10 ... Internal combustion engine, 11 ... Electronic control unit, 12 ... Relief pipe, 13 ... Relief valve, DESCRIPTION OF SYMBOLS 14 ... Pump control unit, 21 ... Air flow meter, 22 ... Crank angle sensor, 24 ... Fuel pressure sensor, 27 ... Throttle sensor, 28 ... Atmospheric pressure sensor

Claims (2)

A required load detecting means for detecting a required load of the engine;
Drive operation amount calculation means for calculating a drive operation amount of the fuel pump based on at least the detected required load;
A fuel pump control device for an internal combustion engine that drives the fuel pump by a drive operation amount,
Atmospheric pressure detection means for detecting atmospheric pressure;
A drive operation amount correction unit that corrects the required load based on the detected atmospheric pressure to estimate an actual engine load, and calculates a drive operation amount based on the estimated engine load and the engine rotation speed ; ,
A fuel pump control device for an internal combustion engine, comprising: 2. The fuel pump control device for an internal combustion engine according to claim 1, wherein the drive operation amount correction unit corrects the drive operation amount so as to decrease as the detected value of the atmospheric pressure decreases.

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