JPH03260348A - Method for starting engine at low temperature - Google Patents

Abstract

PURPOSE:To eliminate deterioration of startability due to shift of blend rate in mixed fuel by drive-controlling a start injector in fuel exchange mode only for a predetermined time, even at the time of non-low temperature starting, when start information is received by a control means. 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 to methanol is detected by a blend rate sensor 105. On the other hand, both the 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 low temperature starting of the engine 101. Here the start injector 104 is driven in a fuel exchange mode only for a predetermined time, even at the time of no-low temperature starting, when start information is received by 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 conceivable that methanol fuel and gasoline fuel will coexist at least temporarily during the switching period.

In order to cope with such a situation, it has been proposed to introduce a vehicle (hereinafter simply referred to as F F V) that can use either gasoline fuel or 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 the start injector 7 is attached to a single, enlarged diameter portion 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 has caused problems such as fuel fogging of the plug and poor starting performance.

An object of the present invention is to provide a method for starting a low-temperature engine that can improve the low-temperature startability of an engine equipped with a start injector.

(Means for Solving the Problems) In order to remotely achieve the above-mentioned 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 the main injector and driving at least the start injector in a low temperature start mode when the engine is started at a low temperature, and when the control means receives start information, the start injector is activated even during a non-low temperature start. It is characterized by being driven in fuel exchange mode for a predetermined period of time.

(Function) When the control means receives start information, the start injector is driven in the fuel exchange mode for a predetermined period of time even during non-low-temperature start, so that the start injector is always detected by the blend rate sensor and confirmed by the control means. The fuel with the blend ratio specified will be replaced and supplied.

(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, fuel whose blend ratio is detected by a blend ratio sensor 105 is supplied to the intake passage 102 of the engine 101 by the main injector 103 and the start injector 104 of the fuel supply system 107. , a control means 106 drives and controls the main and start injectors 103 and 104.

In particular, the control means 106 is as shown in FIG.

At time 10 when cranking is not being performed, both injectors 103 and 104 are kept inactive. Engine】0
At the time tl when both the starting information input during cranking in step 1 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 driven. ) The start injector 104 is driven in the low temperature starting mode M s (predetermined flow rate and time Ts), and the control means 1
When 06 receives start information, the start injector 104 is set to the fuel exchange mode Me for a predetermined drive time Tst even during non-low temperature start (indicated by a two-dot chain line in FIG. 2).
Drive it with.

After inputting the starting information, a time point t2. after the drive time T s , T s 1 has elapsed. At t3, the control means 106 drives only the main injector 103 and enters normal operation.

In this way, after the engine 101 starts cranking, the start injector 104 is driven in the fuel exchange mode Mc during the elapse of the drive time T s , so that fine fuel particles are supplied to the engine. Then,
This improves ignitability, the fuel is quickly ignited, and the air-fuel mixture in the engine 101 is stably combusted.

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 passage 12 and the exhaust passage 13 in a timely manner. The intake passage 12 includes an air cleaner 14, a first intake pipe 15, an expansion pipe 16, and a 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 inside the expansion pipe 16, and a throttle position sensor 27 is installed oppositely to the opposite 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 second intake pipe 17, and a water temperature sensor 29 is attached thereto.

An 02 sensor 30 is installed in the middle of the first exhaust pipe 18 to output air-fuel ratio information in the exhaust gas.

Further, a fuel injection valve 31 connected to a fuel supply system F is attached to an end of the intake passage 12. 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 main injector 31 to a fuel pipe 33. The fuel pipe 33 pressurizes the fuel in the fuel tank 35 with the fuel pump 34 and passes it through the blend rate sensor 43 to each main injector 31 and the start engine 45.
In addition, the main injector 31 and the start engine 4
5 is constructed similarly to that of FIG.

Further, the fuel pipe 33 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 at the intake port 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 40, an input/output circuit 41, and drive circuits 42 and 44.

Here, the control circuit 32 receives each input signal from each sensor, processes these in accordance with the control program shown in FIGS. 5 and 6, and outputs control signals to the drive circuits 42 and 44.

The storage circuit 40 stores each control program of the main control process and the main and start injector drive process shown in FIGS. 5 and 6, and also stores drive times Ts, Ts, water temperature Tw, etc. used during control. It has an area to capture the value of.

The input/output circuit 41 operates to appropriately receive the output signals of the respective sensors mentioned above, and also sends various control signals to the main and start injectors 3 via drive circuits 42 and 44.
Output at 1.45.

Here, the operation of the controller 25 will be explained together with the control programs shown in FIGS. 5 and 6.

When a key switch of the engine (not shown) is turned on, the controller enters the main routine, and upon input of a cranking signal, the controller proceeds to processing for driving the start injector 45.

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
The blend rate B8 from 3 is taken in and updated as the current blend rate B.

Proceeding to step a3, here, the engine rotation speed N is taken in, and this is the engine operation determination rotation speed N25TOP.
It is determined whether or not it has rotated -L times.

When step a4 is reached when the engine is rotating, the blend ratio B and various correction coefficients are taken in as appropriate, and the driving times Ts and Ts in the low temperature start mode Ms and the fuel exchange mode Mc are calculated, the fuel injection amount is calculated, and the ignition timing is calculated. Performs various processes such as calculation.

Here, cylinder identification confidence, crank angle, main injector 103 injection time width, intake air amount A(n), atmospheric temperature, atmospheric pressure, cooling water temperature TW, etc. are output signals from each sensor. be imported and used accordingly.

When step a5 is reached, it is determined whether or not the key is off, and unless the key is off, the process returns to step a2, and when the key is off, 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, predetermined processing associated with the engine stop is performed at step a8, and when the starter switch is turned on, the process proceeds to step a9.

In step a9, various processes associated with starting are performed, and step a
We will proceed to step 5.

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, when the cranking switch is turned on, the process proceeds to step b2, where the water temperature T7 is taken in and it is determined whether the water temperature T7 has fallen below the specified value A. If not, the process proceeds to step b6, and if it has, the process proceeds to step b4.

In step b4, the driving time Ts of the low temperature starting mode l<Ms is determined based on the water temperature T, based on a predetermined map, for example.

Driving time T of the start injector 45 in FIG. 4(a)
5. Calculate the data using the calculation map and store it in a predetermined area. Furthermore, when step b5 is reached, the process continues to drive the start injector 45 for the drive time TS, and then returns to the main process.

On the other hand, while the water temperature T is not exactly below the specified value A, step b6 is reached, and the drive time Ts+ of the start injector 45 in the fuel exchange mode Me is determined based on the water temperature TV according to a predetermined map, for example, FIG. ) start injector 4
The opening time Ts of No. 5 is obtained from the calculation map and stored in a predetermined area.

Further, when step b7 is reached, the process continues to drive the start injector 45 for a driving time Ts, and then returns to the main process. As a result, the old fuel that has accumulated in the start injector 45 and the fuel path connected thereto is replaced with new fuel.

In addition, in fuel exchange mode Mc, start injector 45
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 low-temperature engine starting method adopted by the device shown in Figure 3,
Although the number of stop strokes NM and N5 have been set as the stop time Tα, depending on the situation, it may be set as a set time, and further may be set based on the water temperature value.

(Effects of the Invention) As described above, in the method of the present invention, when the control means receives low temperature information, the start injector is driven in the low temperature start mode, and when the control means does not receive low temperature information but simply receives the start information, the control means drives the start injector in the low temperature start mode, and when the control means does not receive low temperature information but simply receives start information, it drives the start injector in the low temperature start mode. Since the start injector is driven in exchange mode, old fuel that has accumulated in the start injector and the fuel path connected to it is always replaced with new fuel that is detected by the blend ratio sensor.

When starting at low temperatures using the start injector, it is possible to improve the deterioration of startability due to blend ratio deviation6.

[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. Figures 4(a) and 4(b) are maps for calculating the drive time of the start injector in low-temperature starting mode and fuel exchange mode, and Figures 5 and 6 are engine control processing performed by the device in Figure 3. The flowchart of the control program used, FIG. 7, shows a schematic diagram of the fuel supply system of the engine using the conventional method. King, 10...Engine, 3,102...Intake path, 1
03.31... Main injector, 104.45.
...Start injector, 106.25...Control means, 107. F...Fuel supply system, 29...Water temperature sensor, Ts, Ts,...Driving time, F7...Water temperature.

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. A method for starting an engine at a low temperature, characterized in that the start injector is driven in a fuel exchange mode for a predetermined time even during a non-low temperature start, when the control means receives start information.