JPH03260349A - Method for starting engine at low temperature - Google Patents

Abstract

PURPOSE:To frequently replace staying fuel with new fuel so as to improve low temperature startability by driving a start injector only for an exchange time of fuel when an engine reaches a predetermined drive mode after a blend rate of mixed fuel is rapidly changed. CONSTITUTION:Fuel is supplied to the intake path 102 of an engine 101 by both main and start injectors 103, 104 of a fuel supply system 107 after a blend rate of gasoline of the fuel to methanol is detected by a blend rate sensor 105. On the other hand, both injectors 103, 104 are drive-controlled respectively by a control means 106. In the control means 106, at least the start injector 104 is driven in a low temperature start mode at the time of starting the engine 101 at a low temperature. Here the start injector 104 is driven only for a fuel exchange time, when the engine reaches a predetermined drive mode after the blend rate of fuel is rapidly changed, in a control means 108.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for starting an engine at a low temperature, and more particularly, to a method for starting an engine at a low temperature by controlling the drive of both the main and start injectors of the fuel supply system of the engine at the time of starting the engine at a low temperature. .

(Prior Art) Methanol has recently attracted attention as a low-pollution fuel, and methanol engines are being developed.

However, it is almost impossible to immediately switch the fuel used in all automobiles from gasoline to methanol, and it is expected that methanol fuel and gasoline fuel will be mixed, at least temporarily, during the switching period.

Gasoline fuel is used to deal with such situations.

It has been proposed to introduce a vehicle (hereinafter simply referred to as FFV) that can use either methanol fuel, that is, has flexibility in the fuel used.

By the way, methanol used in such an FFV has inferior volatility compared to gasoline. For this reason, problems tend to occur particularly in startability during low-temperature starting.

As a solution to this problem, it has been proposed to install a start injector 7 for cold start in addition to the main injector 6 in the fuel supply system F of the engine, as shown in FIG. The fuel supply system F here pressurizes the fuel in the fuel tank 1 with the fuel pump 2 and transfers it to the blend ratio sensor 3.
The fuel that has passed through the fuel pipes 4 is returned to the fuel tank 1 via the fuel pressure regulator 5.

A fuel pipe 8 extends from approximately the center of the fuel pipe 4, and a start injector 7 is connected to the tip of the fuel pipe 8.

Each main injector 6 is disposed at each branch of the intake manifold, and a single start injector 7 is attached to an enlarged diameter section of the intake system.

Here, each main injector 6 is a throttle type valve with a relatively small injection angle, and the start injector is a throttle type valve with a relatively large injection angle, and the start injector with excellent fuel atomization characteristics is driven at a low temperature start. This promotes fuel vaporization and improves starting performance.

(Problem to be Solved by the Invention) The fuel supply system F as shown in FIG. to drive.

Therefore, when the engine is started by cranking at room temperature, that is, other than when starting at a low temperature, the start injector 7 is not driven, and the fuel remaining in the fuel pipe 8 and the start injector 7 remains as is.

Suppose that fuels with different blend ratios are replenished in this state. If a cold start is performed after a while, fuel at the blend ratio before refilling remains in the start injector, so this is assumed to be the new fuel blend ratio and fuel is injected. More than quantity.

This is a problem as starting performance tends to deteriorate due to fuel fogging of the plug at low temperatures.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for starting an engine at low temperature, which can improve the low temperature startability of an engine equipped with a start injector.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a fuel supply system that supplies fuel whose blend ratio is detected by a blend ratio sensor to an engine through a main injector and a start injector; A control means for driving an injector and driving at least the start injector in a low temperature start mode when the engine is started at a low temperature is used, and after the blend ratio of fuel in the fuel supply system suddenly changes, the engine is brought into a predetermined drive mode. The control means drives the start injector for a fuel exchange time when the fuel change time is reached.

(Function) After the blend ratio of fuel in the fuel supply system suddenly changes,
When the engine reaches a predetermined drive mode, the control means drives the start injector for the fuel exchange time, so that the start injector is always supplied with fuel at the new blend ratio detected by the blend ratio sensor. It becomes like this.

(Example) Hereinafter, a method for starting an engine at a low temperature according to the present invention will be described.

In this method, as shown in FIG. 1, the fuel whose blend ratio is detected by the blend ratio sensor 105 is supplied to the intake air @ 102 of the engine 101 using the main injector 103 and the start injector 104 of the fuel supply system 1.07. by the control means 106.

The main and start injectors 103 and 104 are driven and controlled.

In particular, the control means 106 keeps both injectors 103, 104 inoperative at time 10, when no cranking is taking place, as shown in FIG. At the time tl when both the starting information input when cranking the engine 101 and the low temperature information indicating that the engine is in a low temperature atmosphere are received, at least (in Fig. 2, the main injector 103 is also activated). ) The start injector 104 is driven in the low temperature starting mode M s (a predetermined driving time Ts and a predetermined injection amount are set).

Further, when the blend ratio B of the fuel in the fuel supply system 107 suddenly changes at time t3, the control means 105 controls the timing t3 after which the engine reaches the predetermined drive mode M1.
Wait for 4.

From that time point t4, the start injector 104 is operated in the fuel exchange mode M c (the predetermined drive time T8 and the predetermined injection amount are set) for the predetermined drive time T and I, even in non-low temperature conditions, for the predetermined fuel exchange time T and I. drive.

In this way, when the engine 101 is at a low temperature, the start injector 104 is driven in the low temperature starting mode Ms, and even when the engine is warmed up, when the blend ratio B suddenly changes, the engine reaches the predetermined drive mode M1. Then, the start injector 104 is driven in the fuel exchange mode Mc for the fuel exchange time TR.

Therefore, the fuel in the start injector 104 and the fuel pipe section following it can always be the same as that supplied to the main injector, and the control means 106
The fuel amount etc. calculated based on the blend ratio taken in will be the appropriate value.

Next, an engine control device for an FFV vehicle that employs the low-temperature engine starting method of the present invention will be described with reference to FIG.

Here, the combustion chamber 11 of the engine 10 is communicated with the intake air 12 and the exhaust path 13 in a timely manner. The intake passage 12 includes an air cleaner 14, a first intake pipe 15. Expansion pipe 16, second intake pipe 17
The exhaust path 13 is formed by a first exhaust pipe 18. catalyst 1
9, a second exhaust pipe 20, and a muffler 21.

Inside the air cleaner 14, an air flow sensor 22 that outputs passing air amount information, an atmospheric pressure sensor 23 that outputs atmospheric pressure information, and an atmospheric temperature sensor 24 that outputs air temperature information are arranged, and these are connected to an engine control unit (hereinafter simply referred to as controller) 25.

A start injector 45 and a throttle valve 26 are installed in the expansion pipe I6, and a throttle position sensor 27 is installed in the opposing valve.
6 controls the idle position of the controller 25 via the idle speed control motor (ISC motor) 28.
It is configured to be controlled by.

! A water jacket is provided opposite to a part of the @2 intake pipe 17, and a water temperature sensor 29 is attached thereto.

An O sensor 30 is installed in the middle of the first exhaust pipe 18 to output air-fuel ratio information in the exhaust gas.

Furthermore, a fuel injection valve 31 connected to the fuel supply system F is attached to the end of the intake air 812. This fuel injection valve 3
1 is sequentially connected to a branch pipe 32 and a fuel pipe 33 forming a fuel supply path.

Each branch pipe 32 connects the fuel injection valve 31 to a fuel pipe 33 . The fuel pipe 33 transfers fuel from the fuel tank 35 to the fuel pump 34.
The fuel is pressurized by the fuel and introduced into each main injector 31 and the start engine 45 through the blend rate sensor 43.

In addition, the main injector 31 and the start engine 4
5 is constructed similarly to that of FIG.

Further, the fuel pipe 31 is arranged so that a portion of unused fuel is returned to the tank 35 via a fuel pressure regulator 36 for adjusting fuel pressure. Here, each main injector 31 is arranged in the intake boat of each cylinder, and the start injector 45 is configured to inject fuel into the expansion pipe 16 at a relatively large injection angle.

The blend rate sensor 43 has a well-known configuration in which an optical system detects refractive index information that changes depending on the fuel blend rate, and photoelectrically converts the change in the amount of light and outputs it.

Further, the regulator 36 is configured to increase or decrease the boost pressure, that is, the fuel pressure depending on the load.

In FIG. 3, reference numeral 37 indicates a crank angle sensor that outputs crank information, and reference numeral 38 indicates a top dead center sensor that outputs top dead center information of the first cylinder.

The controller 25 includes a control circuit 39, a memory circuit 4o, an input/output circuit 41, and drive circuits 42 and 44.

Here, the Ill@path 39 receives each input signal from each sensor, processes these according to the control program shown in FIGS. 4, 5, and 6, and sends the control signal to the drive circuit 42.
Output to 4.

The storage circuit 40 stores the control programs of the main control process and start injector drive process shown in FIGS. 4, 5, and 6, and also stores the drive time Ts and fuel exchange time T R used during the control. , water temperature Tw, and other values.

The input/output port #41 operates to take in the output signals of the above-mentioned sensors as appropriate, and also sends various control signals to the main and start injectors 3 via the control circuits 42 and 44.
Output at 1.45.

Here, the operation of the controller 25 is shown in FIGS. 4 and 5.
This will be explained together with the control program shown in FIG.

When a key switch of the engine (not shown) is turned on, the controller enters the main routine, and when a cranking signal is input, the controller enters the start injector drive routine.

In the main routine, the controller 25 first takes in each measured value from the output of each sensor, keeps the set values and the like at initial values, and enters the blend ratio calculation routine in step a2.

In the blend rate calculation routine, first the blend rate sensor 4
When proceeding to Step 6 a3, which takes in the blend ratio B8 from 3 and updates it as the current blend ratio B, here, the engine rotation speed N8 is taken in, and this is the engine operation determination rotation speed N□a. It is determined whether or not the value exceeds 2.

When step a4 is reached during engine rotation, the blend ratio B and various correction coefficients are appropriately taken in, and various processes such as calculation of drive time Ts, fuel injection amount, and ignition timing calculation in low temperature start mode Ms are performed.

Here, the cylinder discrimination signal, crank angle, main injector] 03 injection time width and intake air amount A/N (n)
, atmospheric temperature, atmospheric pressure, cooling water temperature TW, etc. are taken in and used according to the output signals of each sensor.

When step alO is reached, the start injector firing routine (see FIG. 5) is entered.

Here, the current blend rate B (t) is determined, and then the change ΔB in the reblend rate is determined from the difference between this and the previous blend rate B (t-1), and the process proceeds to step b3.

Here, it is determined whether the change ΔB in the blend ratio exceeds a specified value ΔBα, which is a determination value for a sudden change in the blend ratio, and if the change is not sudden, the process returns, and if the change is sudden, the process proceeds to step b4.

In step b4, it is determined whether the current engine drive is in the engine brake mode, that is, drive mode M1, and the internal state returns to the main drive mode M1, and if it is in drive mode M1, step Proceed to b5.

Here, the start injector 45 is operated at a predetermined injection amount,
It is driven for a predetermined fuel exchange time TR and then returns to the main.

Thereby, the old fuel accumulated in the branch pipe 32 and the start injector 45 can be consumed and replaced with new fuel.

During this time, the amount of fuel injected by the main injector 31 is cut due to engine braking in a main injector drive routine (not shown).

After this, the process reaches step b6, where it is determined whether the key is off or not. While the key is not off, return to step a2,
When the key is turned off, the process reaches step a6, where, for example, various data are stored in a non-volatile memory, and the process ends.

When the engine is stopped from step a3 and step a7 is reached, the process waits for the starter switch to be turned on, and while the starter switch is off, step a8 is reached. Here, a predetermined process associated with stopping the engine is performed, and when the switch is turned on, the process proceeds to step a9. In step a9, various processes associated with starting are performed, and the process proceeds to step a5.

When the starter is turned on during this main routine and a crank signal is received, the process proceeds to the process of driving the start injector 45 shown in FIG. 6.

Here, the cranking switch is waited for to be turned on, and when it is turned on, the process proceeds to step c2, where the driving time Ts of the low temperature starting mode Ms is calculated based on the water temperature TV and stored in a predetermined area. Further, when step C3 is reached, the process continues to drive the start injector 45 for a driving time Ts, and then returns to the main process.

In addition, the start injector 45 in the low temperature start mode Ms
While the main injector 31 is driving, the injection amount of the main injector 31 is calculated to be reduced by a predetermined amount based on the injection amount of the start injector 45, and the injection is performed.

In the above description, the drive mode M1 is set to the time of engine braking, but instead of this, the drive mode M1 may be set to the time when the vehicle is stopped and idling, or other modes.

(Effects of the Invention) As described above, in the method of the present invention, when the engine reaches a predetermined drive mode, the start injector is driven in the fuel exchange mode for the fuel exchange time, so that no fuel remains in the start injector and its vicinity. It is possible to frequently replace the existing fuel with new fuel, and it is possible to improve the deterioration in startability caused by the blend ratio drift during cold start by the start injector.

[Brief explanation of drawings]

Fig. 1 is a block diagram explaining the method of the present invention, Fig. 2 is a waveform chart illustrating the operation of fuel supply over time according to the method of the present invention, and Fig. 3 is a schematic configuration of an engine control device adopting the method of the present invention. 4, 5, and 6 are flowcharts of the control program used in the engine control process performed by the device in FIG. 3, and FIG. 7 is a schematic diagram of the engine fuel supply system using the conventional method. It shows. 1.10...Engine, 3,1.02...Intake path,
103.31...Main injector, 104.45
...Start injector, 1.05,43...Blend rate sensor, ]-06,25...Control means, 10
7. F...Fuel supply system, 29...Water temperature sensor, M
e...fuel exchange mode, Ms...low temperature start mode,
Ml... Drive mode-TR... Fuel change time. Porridge 6 figure

Claims (1)

[Claims] a fuel supply system that supplies fuel whose blend ratio is detected by a blend ratio sensor to the engine through a main injector and a start injector; and a fuel supply system that drives and controls the main injector and drives at least the start injector in a low temperature start mode when starting the engine at a low temperature. and a control means for driving the start injector for a fuel exchange time when the engine reaches a predetermined drive mode after the blend ratio of fuel in the fuel supply system suddenly changes. A method for starting an engine at low temperature.