JPH03260350A - Method for starting engine at low temperature - Google Patents

Abstract

PURPOSE:To preheat the interior of a combustion chamber while eliminating fuel cover on a spark plug so as to improve low temperature startability by holding a fuel supply means inoperative until the lapse of a stop period after which an engine is considered to be easily started. CONSTITUTION:An injector 4 is arranged in an intake path 3 connected to the combustion chamber 2 of an engine 1, and further a spark plug 5 is arranged in the combustion chamber 2. The injector 4 is drive-controlled through a fuel supply means 7 and further the spark plug 5 is drive-controlled through an ignition means 8, by a control means 6. Here the control means 6 holds the injector 4 and the spark plug 5 respectively inoperative when the engine 1 is not in cranking. The fuel supply means 7 is held inoperative further with the spark plug 5 drive-controlled when start information and low temperature information are respectively input at cranking time. Further the injector 4 is drive-controlled when a stop period passes after the start information is input.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for starting an engine driven by mixed fuel at low temperatures.

(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.

During the switching period, it is expected that methanol fuel and gasoline fuel will be mixed temporarily.

Gasoline fuel is used to deal with such situations.

Either methanol fuel can be used, ie.

Vehicles with flexibility in fuel usage (hereinafter simply referred to as FFV)
is proposed to be introduced.

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 for cold start in addition to the main injector. The main injector here 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.The start injector, which has excellent fuel atomization characteristics, is driven at low temperature startup. Efforts are being made to improve startability.

(Problem to be Solved by the Invention) However, during a cold start, the fuel supplied to the combustion chamber by cranking does not burn at all until the first explosion occurs, and this fuel causes the spark plug in the combustion chamber to ignite. This has caused a fogging condition, making it increasingly difficult to start methanol engines. Note that this deterioration in startability due to fuel fogging of the ignition plug also occurs in the case of ordinary gasoline engines, and is a similar problem.

An object of the present invention is to provide a method for starting an engine at low temperature, which can improve cold startability.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides an intake system that guides air and fuel into the combustion chamber of an engine, a fuel supply means attached to the intake system, and a fuel supply means for the intake system. and a control means for controlling the fuel supply means, and when the control means receives both the low temperature information and the start information, the fuel supply means is deactivated until a stop period during which it is deemed that starting the engine has been facilitated has elapsed. It is characterized by:

(Function) When the control means receives both the low temperature information and the start information, the fuel supply means is deactivated until the stop period during which it is considered that the engine starts easily has elapsed, so that the spark plug is turned off during that time. The combustion chamber is not covered with fuel, and the temperature inside the combustion chamber can be increased by cranking during the stop time.6 (Example) The low temperature starting method of the engine according to the present invention will be explained below. .

In this method, as shown in FIG. 1, an injector 4 is disposed oppositely on an intake passage 3 that can communicate with a combustion chamber 2 of an engine l, a spark plug 5 is disposed in the combustion chamber 2, and a spark plug 5 is disposed in the combustion chamber 2. The means 6 drives and controls the fuel supply means 7 that drives the injector 4 and the ignition means 8 that drives the spark plug 5.

In particular, the control means 6 keeps both the injector 4 and the spark plug 5 inoperative at time 10 when the engine is not cranking, as shown in FIG. At time t1, both the starting information input during engine cranking and the low temperature information indicating that the engine is in a low temperature atmosphere are received.

The fuel supply means 7 is kept inactive and the spark plug 5 is driven via the ignition means 8. At time t2 after the stop time Tα has elapsed after inputting the start information, the injector 4 is driven via the fuel supply means 7, the ignition plug 5 is driven via the ignition means 8, and normal operation begins.

In this way, after starting cranking of engine 1,
During the elapse of the stop time Tα, the temperature inside the combustion chamber 2 increases due to the pumping operation and the ignition operation of the spark plug 5, making it easier to vaporize the fuel. When fuel supply to the combustion chamber 2 is started at time t2, the fuel is quickly vaporized and ignited, and the air-fuel mixture in the combustion chamber 2 is 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, a catalyst 1
9. The second exhaust pipe 20 and the muffler 21 form a blockage.

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.

Furthermore, a main injector 31 connected to a fuel supply system F is attached to an end of the intake passage 12.

This main injector 31 is connected to a branch pipe 3 forming a fuel supply path.
2 and a fuel pipe 33 in sequence.

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.
lead to. Furthermore, 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 has a relatively large injection angle.
The blend rate sensor 43 is configured to inject fuel into the interior of the fuel cell 6. The blend rate sensor 43 is a well-known sensor that uses an optical system to detect refractive index information that changes depending on the blend rate of the fuel, photoelectrically converts the change in light amount, and outputs it. Take the configuration of Furthermore,
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 39 receives each input signal from each sensor, processes these in accordance with the control programs shown in FIGS. 5, 6, and 7 (a) and (b) to generate control signals. It outputs via drive circuits 42 and 44.

The memory circuit 40 is shown in FIGS. 5, 6, and 7 (a) and (b).
The main and start injector stop processing and injector drive processing control programs are stored in accordance with the control program shown in , and the stop stroke N, , N, , injection time is stored as the drive stop period used during control. 1
@ Contains an area to capture Tr, water temperature Tw, and other values.

The input/output circuit 41 operates to appropriately take in the output signals of the respective sensors described above, and outputs various control signals via the drive circuits 42 and 44.

Here, the operation of the controller 25 will be explained together with the control programs shown in FIGS. 5, 6, 7(a) and 7(b).

When a key switch of the engine (not shown) is turned on, the controller and each sensor start driving. First, the controller 25 maintains each set value, measured value, etc. at the initial value and enters a blend ratio calculation routine in step a2.

In the blend rate calculation routine, first the blend rate sensor 4
The blend rate B5 from 3 is taken in and updated as the current blend rate B.

Proceeding to step a3, here the engine rotation speed N2
This is the engine operation judgment rotation speed N□1゜2
Determine whether or not it exceeds.

When step a4 is reached when the engine is rotating, the blend ratio B and various correction coefficients are appropriately taken in, and various processes such as fuel injection amount calculation and ignition timing calculation are performed.

Here, the cylinder discrimination signal, crank angle, main injector injection time width TI, intake air amount A/N (n), atmospheric temperature, atmospheric pressure, cooling water temperature Tw, etc. are determined according to the output signals of each sensor. It is taken in and used. step a5
When the key is reached, it is determined whether the key is off or not, 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, 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 and a crank signal is received during this main routine, the stop process shown in FIG. 6 begins.

Here, by turning on the cranking switch, the water temperature Tw and the set water temperature data A, which is the determination value for stopping the initial injection, are taken in from the water temperature sensor 29.

In step b4, the number N2 of each main and start injection stop strokes is stored in the memory circuit 40 in advance. From the calculation map of N5, the number of stopping strokes NM and Ns are calculated according to the current water temperature Tw.

Furthermore, in step b6, a stop flag for the movement of both the main and start injectors is set for the number of stop strokes NM, N5, and the process returns to the main routine.

Through this process, the start injector 45 here stops injection until the stroke counter counts the number of stop strokes N8, and each main injector 31 stops injection until the stroke counter counts the number of stop strokes NM. becomes.

On the other hand, when a reference signal for each cylinder, which is one of the crank signals, is input during the main routine, the main injector fuel injection valve driving process shown in FIG. 7(a) begins.

First, the injection time width T1 for the main injector is read from a predetermined area, and it is determined whether the stop flag of the main injector is on or not (see step c2). Here, when the flag is OFF, the program returns as is, and when the flag is ON, the injection time width T□ is set in the injection timer of each main injector 31, and the program returns to main.

Similarly, when a reference signal for each cylinder, which is one of the crank signals, is input during the main routine, the process enters the start injector fuel injection valve drive process shown in FIG. 7(b).

First, it is determined whether or not warm-up has been completed. If warm-up is completed, the start injector 45 is turned off and the process returns to main. If warm-up has not been completed, the process proceeds to step d2, and the continuous injection amount (flow rate) for the start injector is started from a predetermined area. ) and determines whether the stop flag of the start injector is on or not (see step d3).Here, if the stop flag is off, the program returns as is, and if it is on, the start injector 45 is turned on and returns to the main process. .

In the low-temperature engine starting method adopted by the device shown in Figure 3,
Although the number of stop strokes NM and Ns have been set as the stop time Tα, depending on the situation, it may be set as a set time, or it may be further set based on a water temperature value.

(Effects of the Invention) As described above, in the method of the present invention, when the control means receives the low temperature information and the start information, the fuel supply means is deactivated until the stop period during which it is considered that engine starting is facilitated has elapsed. Therefore, the spark plug will not be covered with fuel during that period, and the temperature in the combustion chamber can be expected to rise due to cranking during the stop period, and when fuel is injected after the stop period, the fuel will be quickly injected. The mixture is ignited to ensure combustion of the air-fuel mixture in the combustion chamber, improving low-temperature startability.

[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 the fuel supply means and ignition means over time according to the method of the present invention, and Fig. 3 is an engine control using the method of the present invention. A schematic configuration diagram of the device, Figures 4 (a) and (b) are characteristic diagrams of maps for calculating the main and start stop strokes, Figures 5, 6, and 7 (a), (b). ) is the third
3 shows a flowchart of a control program used in engine control processing performed by the device shown in the figure. 1.10...Engine, 2...Combustion chamber, 3,12
...Intake path, 4,31...Main injector, 5
, 45... Start injector, 6, 25... Control means, 7... Fuel supply means, 8... Ignition means, 2
9... Water temperature sensor, Tα... Stop time, NM, N,
...Number of stop strokes. Water temperature T9 Figure 1 Temperature T. Fig. %

Claims (1)

[Claims] An intake system that guides air and fuel into the combustion chamber of the engine, a fuel supply means attached to the intake system, and a control means for controlling the fuel supply means are used, and the control means transmits both low temperature information and starting information. A method for starting an engine at a low temperature, characterized in that the fuel supply means is deactivated until a stop period during which starting of the engine is deemed to have been facilitated has elapsed.