JPH03258964A - Fuel supply device for mixed fuel engine - Google Patents

Abstract

PURPOSE:To reduce any fuel temperature rise in a fuel tank by determining a fuel supply quantity based on a detected result of a mixture rate, performing a fuel supply control, and driving a fuel supply means in a specified work quantity for a specified time in the case when a fuel mixture rate changes at a specified speed. CONSTITUTION:When a blend rate is detected in an ECU 14, a compensation coefficient of the blend rate corresponding thereto is calculated. The driving time of an injector is then calculated. In the case of a normal operation, the ECU 14 judges sudden change of the blend rate, and if sudden change is not present, it calculates a fuel consumption from the driving time of an injector and engine speed. The work quantity is calculated in this way so as to drive a fuel pump 26 based thereon. Then it calculates and determines a control value at the time of an normal operation so as to perform the driving control of an ISC valve 10, an ignition plug 44 and the like. In the case when the blend rate is suddenly changed, the ECU 14 commands drive in a fuel driving ratio to the fuel pump 26. As a result, fuel pressure in a feedline 27 is increased instantaneously, delay of supply is prevented at the transient time of fuel. Accordingly, any fuel temperature rise inside the fuel tank and delay of fuel supply can be prevented by proper fuel supply.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fuel supply device for a mixed fuel engine installed in an automobile or the like.

<Prior Art> In recent years, an increasing number of spark ignition engines are operated using fuels other than gasoline, such as methanol and ethanol. Engines using these fuels (so-called alternative fuels) have come into use due to concerns about the stable supply of gasoline, which is a fossil fuel.

However, it is currently difficult to operate engines solely on alternative fuels due to backwardness in the distribution system and lack of absolute quantities, especially for those installed in means of transportation such as automobiles that are not operated stationary. There was also a risk that the vehicle would become undriveable at the destination.

Therefore, in cars, etc., mixed fuel engines (Flexib
Equipped with a fuel engine (hereinafter abbreviated as FFE) is being considered. A mixed fuel vehicle equipped with this FFE (Flexible Fuel
Vehicles (hereinafter abbreviated as FFV) are designed to run on gasoline or alternative fuels, but can be run by supplying (refueling) with available fuel depending on the time and situation.

In FFE, the stoichiometric air-fuel ratio differs depending on the fuel used (for example, gasoline and methanol have a stoichiometric air-fuel ratio of 14.
7:1 to 6.4:1), the mixture ratio of the air-fuel mixture supplied to the combustion chamber must also be changed.Changing the mixture ratio can be done using an electronic fuel injection system (Electronic fuel injection system).
Controlled Fuel Injection D
In an engine equipped with an ECI (hereinafter abbreviated as ECI), this is done by controlling the fuel injection amount (for boat fishing, the valve opening duty, which is the average opening amount of the fuel injection valve). The fuel pump (generally an electric fuel pump), which is the fuel supply means for supplying fuel to the fuel injection valves, is equipped with a pump with a high discharge amount commensurate with the amount of fuel used when the stoichiometric air-fuel ratio is high. has been done.

<Problem to be solved by the invention> In automobiles equipped with ECI, in order to accurately control the fuel injection amount, the fuel delivery pressure (hereinafter referred to as fuel pressure) is
constant (in the L-Jetronic system, 2.55 kg/
cxr~3.35kg/cm". Therefore, an electric fuel pump (hereinafter referred to as fuel pump) supplies a sufficient amount of fuel to the fuel line, and a fuel pressure regulator removes excess fuel. The fuel is returned to the fuel tank.

However, in FFE, as described above, a fuel pump with a discharge amount commensurate with the amount of fuel used when the stoichiometric air-fuel ratio is high is used.

Therefore, when the stoichiometric air-fuel ratio is low, the amount of fuel used naturally decreases, and the amount of fuel (surplus fuel) that flows back into the fuel tank increases.This tendency becomes noticeable when idling or driving at low speeds, and the fuel line Most of the large amount of fuel supplied to the tank will flow back into the fuel tank.

On the other hand, a portion of the fuel line often reaches a very high temperature due to an increase in temperature in the engine room (so-called hot soak phenomenon) immediately after high-speed driving.

Due to these synergistic effects, the temperature of the fuel in the fuel tank (hereinafter abbreviated as fuel temperature) increases abnormally, increasing the amount of evaporated fuel gas generated in the fuel tank, and causing damage to fuel piping, etc. In particular, when the mixing ratio of methanol to gasoline is around 30%, so-called azeotropy occurs, so vapor lock phenomenon often occurs.

Normally, the evaporated fuel gas is temporarily adsorbed in the canister and then supplied to the combustion chamber from the intake passage. However, if the amount of evaporated fuel gas generated is extremely large, it is necessary to increase the capacity of the canister or take other measures. Furthermore, if vapor lock occurs, there is a fear that restarting the engine may become difficult.

The present invention has been made in view of the above circumstances, and has an object to reduce the rise in fuel temperature in the fuel tank by controlling the drive of the fuel supply means according to the amount of fuel injected from the fuel injection valve in FFE. The purpose is to

Means for Solving the Problem> Therefore, in order to solve this problem, the present invention provides a fuel supply device for a mixed fuel engine in which different types of fuels are mixed and supplied to a combustion chamber for combustion, comprising: A fuel supply means capable of varying the fuel supply amount; a mixture ratio detection means for detecting the mixture ratio of the different types of fuel; and a fuel supply amount determined based on the detection result of the mixture ratio detection means to supply the fuel. and drive control means for driving the fuel supply means at a predetermined amount of work for a predetermined time when the fuel mixture ratio changes at a predetermined speed in a direction in which the amount of required fuel increases. The present invention proposes a fuel supply device for a mixed fuel engine with characteristics.

For example, when using fuel with a low stoichiometric air-fuel ratio,
The fuel supply amount is determined based on the detection result of the mixture ratio detection means, and the fuel supply means such as a fuel pump is driven and controlled so that the discharge amount, that is, the recirculation amount of fuel is reduced. Furthermore, in a transient situation where fuel with a low stoichiometric air-fuel ratio is switched to fuel with a high stoichiometric air-fuel ratio, the fuel supply means is temporarily driven at full capacity to ensure the amount of feed.

<Example> An embodiment of the present invention will be specifically described based on the drawings.

Fig. 1 conceptually shows the hardware configuration of an embodiment in which the fuel supply device according to the present invention is applied to an FFV equipped with a gasoline-methanol type FFE, and Fig. 2 shows a control flowchart in this embodiment. This is an indication. In addition, Fig. 3 shows a blend rate correction coefficient search map, Fig. 4 shows a required fuel discharge amount search map, and Figs. 5 and 6 show flow rate characteristic maps in fuel pump duty drive control. and a control block diaphragm.

In Fig. 1, E is the NA (N
This is a normal aspiration type automotive FFE (hereinafter referred to as an engine), and an intake manifold 1 has an intake pipe 3 with an air cleaner box 2 attached to its upstream side, and a surge chamber 4.
are connected via. An air cleaner 5 is housed in the air cleaner box 2, and an atmospheric pressure sensor 6 is housed inside the air cleaner box 2.
Karman vortex type air flow sensor (AF
S) 7 and an intake temperature sensor 8 are provided. intake pipe 3
includes a throttle valve 9 driven by an accelerator wire (not shown) and a bypass type I5C (Idle Speed).
ed Con-Lrol ) valve 10 is provided in the figure, 11 is an FI for promoting warm-up operation.
AV (Fast Idle Air Valve)
) and is incorporated into the ISC valve 10.

The throttle valve 9 is provided with a potentiometer-type throttle position sensor 12 and an idle switch 13, and the opening degree information and idle state detection information of the throttle valve 9 are sent to the ECU, which is the control center in this embodiment.
(Electronic Control
t) 14. Incidentally, detection signals from each of the aforementioned sensors 6, 7, and 8 are also sent to the ECU 14. In the ISC valve 10, a built-in step motor 10a rotates in response to a command from the ECU 14 to increase or decrease the amount of intake air during idling operation.

The engine E of this embodiment is a so-called MPI (Multi
The engine is of the type engine, and the intake manifold 1 is provided with fuel injectors 15 for the number of cylinders. fuel injector 1
5 is connected to the ECU via an injector driver (not shown).
It is duty-driven by the command from 14. Engine E has a cooling water temperature sensor 16. In addition to the knock sensor 17,
Crank angle sensor 18 and TDC (TopDedCen
ter) sensors 19 and the like are attached, and detection signals from these sensors 16 to 19 are input to the ECU 14.

An 02 sensor 21 is attached to the exhaust manifold 20 to detect the oxygen concentration in the exhaust gas, and a detection signal is sent to the ECU 14. A warm-up catalytic converter 22 and a catalytic converter (three-way catalyst) 23 are located downstream of the exhaust manifold 20.
A main muffler 24 is connected via the main muffler 24.

Next, the fuel system in this embodiment will be explained.

Fuel is supplied from the fuel tank 25, which is built in the fuel tank.
It is sucked up by a so-called in-tank fuel pump (hereinafter referred to as a fuel pump) 26 and supplied to a fuel feed line (hereinafter referred to as a feed line) 27. At the most upstream part of the feed line 27, a fuel filter 28 is provided. is provided to separate foreign substances from the fuel.

A fuel collector 29 is provided downstream of the filter 28 on the downstream side of the feed line 27, and there is a fuel composition sensor (hereinafter referred to as a blend ratio sensor) 30 serving as a mixture ratio detection means, and a fuel collector 29 that detects the fuel temperature. Fuel temperature sensor (hereinafter referred to as fuel temperature sensor)
31 is attached.

The blend ratio sensor 30 detects the mixing ratio (0 to 100%) of methanol to gasoline in the fuel, and the fuel temperature sensor 31 in this embodiment is the blend ratio sensor 3o.
It is provided to perform temperature correction on the detected value.

On the downstream side of the feed line is a fuel injector 15.
Main branch to 32. It branches into three directions: a sub-branch 34 to a cold start injector 33 attached to the surge chamber 4; and a waste branch 36 to a fuel pressure regulator 35 serving as fuel pressure adjustment means. A fuel return line (hereinafter referred to as return line) 37 that returns excess fuel to the fuel tank 25 is connected to the fuel pressure regulator 35. In the figure, 38 is a vacuum line for correcting the negative pressure of the fuel pressure regulator 35. It is a hose and is connected to the surge chamber 4.

On the other hand, a purge line 40 is connected to the upper part of the fuel tank 25 to guide the evaporated fuel gas to the surge chamber 4 via a canister 39.

Inside the purge line 40 are a two-way valve 41 and an EC.
An electromagnetic purge control valve 42 controlled by U14 is provided.

In the figure, 43 is a ventilation hose that guides blow-by gas to the surge chamber 4, and 44 is a ventilation hose that guides blow-by gas to the surge chamber 4, and 44 is a ventilation hose that
o5itive Crankcase VenLira
-Lion) valve. 45 is a breather hose. Further, 46 is an ignition plug, and 47 is an ignition coil that supplies high voltage current to the ignition plug 46. The ignition coil 47 is driven by the ECU 14 via an ignition driver (not shown).

The control of this embodiment will be explained below with reference to the flowchart of FIG. Note that a symbol (Sl.

S2. ) corresponds to the symbol written at the end of the explanatory text.

In the FFV of this embodiment, control by the ECU 14 is started by turning on an ignition key (not shown).

After starting control, the ECU 14 first resets various control flags, initializes the RAM, etc., in other words, initializes. When S1 initialization is completed,
The ECU 14 detects the blend ratio (hereinafter referred to as blend ratio) of methanol to gasoline (hereinafter referred to as blend ratio) by correcting the data input from the blend ratio sensor 30 and the fuel temperature data from the fuel temperature sensor 31. Rate B is a value from O to 1. -
・When the S2 blend rate B is detected, next, the ECU 14
calculates the blend rate correction coefficient Ke corresponding to the blend rate B from the blend rate correction coefficient search map shown in FIG.
...S3 Next, the ECU 14 calculates the basic driving time Ts (see/5t
roke) is determined using the following formula.

Here, the symbols in the formula indicate the following values.

Q,: Intake air i per step (1/5 stroke
) α,: Air density (g/l) αf: Fuel density (g/cc) A/F: Theoretical air-fuel ratio (14,7> G1: Injector gain (CC/!IE) 1' during basic drive i'r8 may be calculated digitally using the following formula.

're = A/N(n) X P CX K INJ
X K8 Here, the symbols in the formula indicate the following values.

A/N (n): Number of AFS output pulses (1/5
trokelP, :AFS output pulse constant (1/
pulseKINJ: Drive time conversion coefficient (anus/l)・
-84 After determining the basic drive time T, the ECU 14 then determines the injector drive time T I N J using the following formula.

T I NJ = T a X K + T O Here, the symbols in the formula indicate the following values.

K: Correction coefficient (A/F, F/B, learning, intake temperature, etc.) To: Injector invalid drive time...S5 After determining the injector drive time T I N J, EC
Next, U14 indicates that the engine rotation speed NE is the predetermined stop rotation speed N.
ES engineering. It is determined whether or not it is 2 or less. Stop rotation speed N
Es□. 2 is a number lower than the idling speed,
Stop rotation speed N, s. If it is less than P, engine E
This means that the vehicle is not operating normally. ...S
6Nε〉Nε5techniques. In case 2, that is, when the engine is in normal operation, the ECU 14 next determines whether or not the blend ratio B is changing suddenly using the determination formula described below.

B (n) >B (n-1) X (1+a) Here, the symbols in the formula indicate the following values.

B(n): Blend ratio B(n-
1): Previously measured blend rate a: Blend rate sudden change judgment ratio (increasing type) When the above formula holds true,
The following situations are possible. The vehicle has been driven with 100% gasoline, and 100% methanol is injected into the fuel tank 25 at the filling station.

Then, in the feed line 27, gasoline and methanol are temporarily mixed, and the fuel is exchanged. As a result, the blend ratio B changes instantaneously within the fuel collector 29, and the output value of the blend ratio sensor 30 also changes suddenly. Needless to say, the above determination is positive only when the mixture ratio changes in a direction in which the required fuel increases, and becomes negative when it decreases. -S7 In step S7, if the determination formula is not satisfied, that is, if the blend ratio B has not suddenly changed, then ECtJ 14 uses the injector drive time r81TINJ and the engine rotation speed NE to calculate the fuel amount from the formula below. Consumption amount QINJ (
+/kl).

Here, the symbols in the formula indicate the following values.

GINJ: Injector gain (cc/mi
n)...S8 N cy I: Number of cylinders When fuel consumption Q I N J is obtained, ECU 14
Next, the required fuel discharge amount QPUMP (+/b) is searched from the required fuel discharge amount search map shown in FIG.
...S9 required fuel discharge amount Q
When PUMP is obtained, the ECU 14 next compares the drive duty of the fuel pump 26 from the flow rate characteristic map shown in FIG.

Search for (%). ...Once the S10 drive duty ratio Dp, that is, the amount of work is obtained, the ECU
14 drives the fuel pump 26 based on this amount of work.

In this embodiment, in this case, as shown in FIG.
Meanwhile, a duty drive signal is sent to the power transistor 48, and the current from the power source 49 is supplied to the fuel pump 26 at this duty ratio Dp. As a result, the fuel pump 26
The rotation speed (discharge amount) of the fuel changes, and the amount of fuel fed to the feed line 27, that is, the return line 37 or 26.
Driving stop and various learning data (fuel injection and fuel tank 2)
Since the reflux amount to 5 changes, there is B of quantity learning data, ignition timing learning data, etc.
- Save to 3ll URAM, etc.
-...When the S14 fuel pump 26 starts driving, the EC
1J14 then performs control during normal operation, that is, after calculating and determining control values such as bypass air amount, fuel QM amount, 9 ignition timing, etc., performs drive control of ISC valve 10° fuel injector 151 spark plug 44, etc.・・・
S12 Next, the ECU 14 turns the ignition key OFF.
If it is not in the OFF state, that is, if the operation is continuing, the process returns to step 82 described above, and the control is repeated from the detection of the blend ratio B.・・・
・In step 313, if the ignition key is in the OFF state, the ECU 14 performs key-OFF control, that is, if the determination formula is satisfied in the step of the fuel pump S7, that is, the blend ratio B increases the required fuel amount. If there is a sudden change in direction, the ECTJ 14 commands the fuel pump 26 to drive at a duty ratio of 100%, that is, drive at full drive ratio (hereinafter referred to as full drive). As a result, the fuel pressure in the feed line 27 rises instantaneously, and a delay in feeding during fuel transients is prevented.In this embodiment, the time for full drive is 1 second to
2 seconds, after which normal drive control is performed according to the amount of fuel used. ...515 Meanwhile, at step S6, NE≦
When it is NESTOP, that is, when the engine is not operating normally, the ECU 14 next determines whether the starter switch is in the ON state (the ignition key is in the ○N position).・-・S16 starter switch is O
When in the N state, the ECtJ 14 performs startup control after driving the fuel pump 26 in steps S17 to S21 or S23, that is, driving the cold start injector 33, fixed ignition timing control, etc.
Since the steps 17 to S21 and S23 have the same contents as the steps 87 to Sll and S15 described above, description of the control contents will be omitted. In this case as well, when the startup control ends, the ECU 14 moves to step S13. ...-516~323 On the other hand, when the starter switch is in the OFF state in step S16, the ECU 14 performs engine stop control, that is, stops learning control, saves various learning data in BURAM, etc. After that, the process moves to step S13.
-S24 In this embodiment, as described above, the fuel injection amount in the FFV is determined according to the fuel blend ratio B, and the fuel pump is drive-controlled based on the determined fuel injection amount, so for example, When the mixture ratio of gasoline is high, the discharge amount of the fuel pump 26 is reduced to keep the fuel temperature in the fuel tank 25 low, while when the mixture ratio of methanol is high, the discharge amount of the fuel pump 26 is reduced.
It has become possible to increase the discharge amount of No. 6 and secure the amount of fuel supplied during high-speed operation, etc., without using special parts. In addition, by temporarily driving the fuel pump at full capacity during the time when the fuel used was switched from gasoline to methanol, deterioration in drivability due to supply delays was prevented.

Incidentally, as a side effect of this embodiment, it became possible to reduce the rate at which the fuel pump 26 was operated in vain, and it was possible to reduce power consumption.

This completes the description of the specific embodiment of the present invention, but the aspects of the present invention are not limited to this embodiment. For example, in the above embodiment, a DC motor is used as the drive source of the fuel pump serving as the fuel supply means, Although this is carried out by duty ratio control, voltage control or frequency control using an AC motor may also be used.

Further, in the above embodiment, the present invention is applied to a NA gasoline-methanol type FFV, but it may also be applied to an FFV equipped with a turbocharged FFE or a gasoline-ethanol type FFV, or a two-cycle FFE is used. The present invention may be applied to a mounted FFV or the like.Furthermore, the present invention may be applied not to an FFV FFE but to a marine FFE or the like.

On the other hand, regarding the amount of work when the blend ratio B suddenly changes, in the above embodiment, driving was performed at a duty ratio of 100%, that is, full drive, but driving at other amounts of work such as 50% or 80% was also possible. Also, although the overcontrol time was set to 1 to 2 seconds in the above embodiment, it is also possible to set the time arbitrarily depending on the degree of sudden change.

<Effects of the Invention> According to the fuel supply device for a mixed fuel engine according to the present invention, the mixing ratio of different fuels is detected to determine the fuel supply amount, and the drive control of the fuel supply means is performed. The proper fuel supply or reflux is now performed according to the mixture ratio of the fuel tank, and problems caused by the rise in fuel temperature in the fuel tank no longer occur, while the mixture ratio suddenly changes in the direction of increasing the amount of fuel required. Since over-control is performed when such a situation occurs, it is possible to prevent malfunctions caused by feed delays.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing the hardware configuration of an embodiment in which a fuel supply device according to the present invention is applied to an FFV equipped with a gasoline-methanol type FFE, and FIG. 2 is a control flowchart in this embodiment. . In addition, Fig. 3 is a map for searching the blend rate correction coefficient, Fig. 4 is a map for searching the required fuel discharge amount, and Figs. 5 and 6 are flow rate characteristic maps in duty drive control of the fuel pump. and a control block diaphragm. In the drawings, E is the engine, 14 is the ECU, 15 is the fuel injector 25 is the fuel tank, 26 is the in-tank fuel pump, 27 is the fuel feed line, 28 is the fuel filter, 30 is the fuel composition sensor, and 31 is the fuel composition sensor. Fuel temperature sensor, 32 is the main branch, 33 is the cold start injector, 34 is the sub-branch, 35 is the fuel pressure regulator, 36 is the waste branch, 37 is the fuel return line, 39 is the canister, 40 is the barge line, 48 is the power transistor; 49 is a power supply;

Claims (1)

[Scope of Claims] A fuel supply device for a mixed fuel engine in which different types of fuel are mixed and supplied to a combustion chamber for combustion, comprising: a fuel supply means capable of varying the amount of fuel supplied; a mixture ratio detection means for detecting a mixture ratio of fuel; a fuel supply amount is determined based on the detection result of the mixture ratio detection means, and drive control of the fuel supply means is performed; 1. A fuel supply device for a mixed fuel engine, comprising drive control means for driving the fuel supply means with a predetermined amount of work for a predetermined time when the amount of fuel changes at a predetermined speed in the direction of increasing the fuel amount.