JPH02188646A - Supply of engine fuel - Google Patents

Abstract

PURPOSE:To obtain a good air-fuel-mixed state over a wide operation range in an independent, cylinder-to-cylinder injection system, in which fuel is injected in a synchronized manner with a suction stroke, by sending the injected fuel onto a combustion chamber side, taking advantage of an air flow-velocity at which no wall surface slagging is formed. CONSTITUTION:In controlling a fuel injection valve 7, which is arranged at a suction port, based on output signals from an engine speed sensor 8, a crank angle sensor 9, a cooling water temperature sensor 10, and an inlet sensor 11, a range of the air flow velocity, that is lower than a critical air flow velocity Vpc, in which no wall surface slagging takes place to an inlet pipe of an injected fuel passage, is obtained first from sine-wave-resembled air flow velocity characteristics in the vicinity of the inlet valve in the range from valve-opening to valve-closing of the inlet valve in each cylinder. Next, a valve-opening position of a fuel injection valve 7 is decided, based on an air feeding valve opening position corresponding to the air flow velocity lower than Vpc. When the range of the air flow velocity lower than Vpc varies because of a change in the engine speed, the starting time of the valve opening of the fuel injection valve 7 is varied, according to the variation of the range.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fuel supply method for an engine, and in particular to a fuel supply method suitable for an electronically controlled fuel injection system of a cylinder independent injection method in which fuel is injected for each cylinder. Regarding.

[Conventional technology]

Previously, the fuel supply method of the cylinder-specific independent injection method used simultaneous injection control in which fuel was injected into each cylinder at the same time.
Recently, instead of this, there has been a shift to sequential injection control in which fuel injection timing is controlled for each cylinder. This sequential control is evaluated as having the advantage of injecting a more accurate amount of fuel without waste than simultaneous injection. When adopting this sequential control, it is ideal to inject fuel during the intake stroke from the viewpoint of control responsiveness during acceleration and deceleration, but conventionally, from the standpoint of fuel atomization and better mixture formation, For example, as described in the magazine "Internal Combustion Engine J (VO1, 25, NQ321°L986.8), pages 39 to 46, the injection timing is set mainly before the intake stroke of the relevant cylinder, in other words. In other words, conventionally, taking into consideration that the atomization of the injected fuel from the fuel injection valve was insufficient, the injected fuel was set during the intake stroke by injecting the fuel before the intake stroke. Once it was attached to the manifold wall near the boat, a portion of it was evaporated due to wall temperature, and then atomization was promoted by the high-speed airflow from the valve when the intake valve began to open.

However, recently, atomization technology in fuel injection valves has improved,
Even if fuel injection is started during the intake stroke, a fairly good air-fuel mixture can now be formed, so a system in which fuel is injected during the intake stroke of each cylinder is being put into practical use.

[Problem to be solved by the invention]

However, this method of injecting fuel during the intake stroke had the following points to be improved. Below, the problem to be solved will be explained based on FIGS. 7 and 8.

FIG. 7 shows the fuel injection state when the throttle valve 2 has a small opening and is in a low speed rotation range. The amount of air sucked into the engine (cylinder) 1 is adjusted by a throttle valve 2, and passes through an intake path 3.
It is guided when the intake valve 4 opens. The fuel injected from the fuel injection valve 5 during this intake stroke is aimed at the vicinity of the center of the bulk of the intake valve 4. As shown in FIG. 7, when the throttle valve 2 has a small opening (low speed rotation range), the intake path
The air flow velocity is small, and the injected fuel is not affected much by the air flow, resulting in good injection operation.

However, as shown in Fig. 8, when the throttle valve 2 is in the middle or large opening or in the high speed rotation range, the air flow velocity in the intake passage 3 becomes large.
The injected fuel is pushed and bent by the air flow and collides with the wall of the intake passage 3 as shown in the figure, causing a phenomenon in which much of the fuel adheres to the wall and flows into the cylinder (combustion chamber) 1 in a liquid state. Such a phenomenon causes the mixture concentration in the cylinder 1 to become non-uniform, which hinders good combustion.

The present invention has been made in view of the above points, and its purpose is to employ fuel injection control during the intake stroke that has excellent fuel control responsiveness, while solving the conventional problems with this method. It is an object of the present invention to provide a fuel supply method that can satisfactorily form a mixture over a wide operating range.

[Means to solve the problem]

In order to achieve the above object, the present invention is configured as follows.

First, the first invention relates to a method, and in a fuel supply method using a cylinder independent injection method in which fuel is injected into each cylinder in synchronization with the intake stroke, the intake valve in each cylinder is controlled from the start of opening to the closing of the intake valve. Based on the sinusoidal air flow velocity characteristics near the intake valves, we found in advance the air flow velocity range below the critical air flow velocity VPC in which the injected fuel does not adhere to the intake passage wall, and responded to the air flow velocity range below this critical air flow velocity VPC. The opening timing of the fuel injection valve is set based on the intake valve opening position, and the critical air flow velocity V is set based on the change in engine speed.
When the air flow velocity range below the PC changes, the fuel injection control is performed by changing the valve opening timing of the fuel injection valve in response to the change.

Similar to the first invention, the second invention is based on the sinusoidal air flow velocity characteristic near the intake valve from the start of opening to the end of opening of the intake valve in each cylinder. The unique feature is that an air flow velocity range below the critical air flow velocity VPC in which no adhesion to the intake passage wall occurs is found in advance, and then the fuel injection timing during the intake stroke is determined as follows.

That is, in the present invention, the valve opening end timing of the fuel injection valve is determined based on the intake valve open position in the air flow velocity region related to the latter half of the sinusoidal air flow velocity characteristic in the air flow velocity region below the critical air flow velocity VPC. By adding the fuel injection valve opening time predetermined from the engine condition to the determined fuel injection valve opening end timing, the fuel injection valve opening start timing is automatically determined, and the fuel injection valve opening timing is automatically determined. This method was used to control injection.

[Effect]

Prior to a detailed explanation of the present invention, first, in order to facilitate understanding of the content of each invention, we will first explain how the intake valve of the engine operates during the intake valve opening operation (from the start of opening to the closing of the intake valve of each cylinder). The sinusoidal air flow rate characteristic V p ' occurring in the vicinity (near the intake port) will be explained with reference to FIG.

Figure 1 shows the air flow velocity characteristic Vp' during the intake valve opening period.
, where the horizontal axis represents the intake valve position during the intake valve opening operation period by the crank angle θC. Ns, Nx, N
s is each engine rotation speed, and the engine rotation speed is N i
< N z < Na The *Vp' characteristic is such that when the intake valve is open for the period shown in the figure, with respect to the engine crank angle Oc, the intake valve vicinity ( The air flow velocity Vp at the intake port section changes sinusoidally. In this air flow velocity characteristic V p ', the position of VPC is the critical air flow velocity that deflects the injected fuel and causes it to adhere to the wall surface of the intake passage. Since the air velocity characteristics are sinusoidal, V
Intake valve opens even in air flow velocity range below PC (air flow velocity characteristics)
Occurs in the first and second half of

The air flow velocity characteristic V p ' increases as the engine speed increases, that is, as the downward speed of the piston increases. Therefore, if 1) fuel injection is always started at a crank angle of C1, the engine speed will be changed from N1 to
When increasing from N2 to N8, the air flow velocity Vp
increases as Vpn → Vpx → Vpδ, and as a result,
In the rotation range of Nt and Ns, the critical flow velocity VPC that does not cause wall adhesion is exceeded, and wall adhesion phenomenon occurs. Note that as the engine speed increases, the air flow velocity region below VPC becomes narrower in both the first half and the second half.

In order to eliminate this problem of wall adhesion, the first aspect of the present invention. This becomes possible if a method like the second invention is used.

That is, in the first invention, the sinusoidal air flow velocity characteristic Vp
', the air flow velocity below the above-mentioned critical flow velocity VPC is found in advance, and the fuel injection valve opening (injection) start timing is set based on the intake valve opening position (crank angle) corresponding to this VPC. The injected fuel can be sent to the relevant cylinder (the cylinder during the intake stroke) at an air flow velocity that does not cause adhesion. As is clear from FIG. 1, the air flow velocity region below this critical air flow velocity Vp changes depending on the engine speed.
When the air flow velocity range below C changes, the opening timing of the fuel injection valve changes accordingly, so even if the engine speed changes, the intake valve open position is always synchronized to the critical air flow velocity below VPC. control to start fuel injection. Specifically, for example, as shown in FIG. 1, when the engine speed is N1. Nx.

No matter where in the N3 region, the air flow velocity Vpz is always
If you want to inject fuel when (Vpt<VPC), at a rotation speed of Nt, with a crank angle of 0c,
The injection is set to start at Ocx at rotation speed 2, and at Ocs at rotation speed Na.

Note that the opening time (injection time) of the fuel injector is generally determined by the engine operating conditions (for example, intake air amount, etc.), so once the timing to start opening the injector is determined as described above, this By adding the valve opening time to , the timing at which the fuel injection valve ends to open is automatically determined. This valve opening end timing is determined because as the opening time of the fuel injection valve becomes longer, fuel may be injected continuously over the air flow velocity range above the critical air flow velocity Vpa, and even in the air flow velocity range above VPC. In that case, the opening timing of the fuel injection valve may be advanced to the crank angle at which the intake valve finally begins to open.

Furthermore, even if part of the opening time of the fuel injector is in the air flow velocity range slightly higher than VPC, it is not a big problem because if the amount of fuel adhering to the wall is small, it will be peeled off based on evaporation and air flow velocity. .

In addition, in the example shown in Fig. 1, the opening timing of the fuel injection valve is determined at a position related to the first half of the air flow rate characteristic (intake valve operation) Vp', but when It may be determined in the basin below the VPC of the position.

Next, the second invention will be explained based on FIG.

In the second invention, the valve opening end timing occe of the fuel injection valve is determined based on the intake valve open position in the air flow velocity region related to the latter half of the air flow velocity characteristic Vp' in the air flow velocity region below the critical air flow velocity VPC.
is determined. Then, the valve opening end timing θc8 of this determination
In addition, the opening time Ti of the fuel injector, which is predetermined from the engine condition, is added, and the opening start timing O of the fuel injector is automatically determined.
cn is determined.

Even in this fuel supply method, if the injector opening end timing OC is set at the crank angle Oce just before the intake valve closes, the injector opening start timing OCn can also be adjusted to the engine rotational speed Nl, Nz. , the critical air velocity VP regardless of Ns
It can be placed in the air flow velocity range below C.

Also in this second invention, since the injected fuel is placed in an airflow having a velocity lower than the critical air flow velocity VPC, it is possible to almost completely prevent the injected fuel from adhering to the wall surface. There are the following advantages when the valve time is short.

In other words, if fuel is injected in the first half of the air flow rate characteristic (intake valve opening operation) during light load, if the injection time is short and the intake stroke time is long, as shown in Figure 3. As shown in (a), the mixture concentration exhibits a so-called reverse stratification, in which the concentration is higher at the bottom of the combustion chamber and thinner at the top. As a result, problems such as the mixture concentration around the ignition plug becoming thinner and ignitability are likely to occur.1.To solve this problem, if the opening timing of the injection valve is determined in the latter half of the intake stroke as in the present invention, the injection By delaying the time, the mixture concentration above the combustion chamber (around the spark plug) can be enriched when the engine is young, as shown in FIG. 3(b), which has the advantage of greatly improving ignitability and combustibility.

Note that if the injection valve opening end timing OCe is set to a position with some margin from just before the intake valve closes, the injection valve opening start timing will be at OCn' as shown in FIG. In this case, for example, in the case of engine rotation speed N2, the indicated value ΔOc
During this period, the critical flow velocity VPC is exceeded, and during this period, the injected fuel adheres to the wall surface, but the proportion thereof is small. On the other hand, in the engine rotation speed range N3, the ratio of wall adhesion increases, but in such a high speed rotation range, even if wall adhesion occurs, the air flow velocity is high, so the fuel is stripped from the wall.
Since the particles are re-atomized, there is not much of a problem.6 Furthermore, a control means may be provided to change the opening timing of the fuel injection valve during the intake stroke in accordance with the engine speed. If the data of the injection valve opening start timing for carrying out the above-mentioned first or second invention is set in this control means in accordance with the engine speed range, the above-mentioned first or second invention. It becomes possible to perform each action of the second invention.

〔Example〕

An embodiment of the present invention will be described based on FIG.

FIG. 2 is a system schematic diagram of the fuel injection control system of this embodiment.

Reference numeral 7 in FIG. 2 denotes a fuel injection valve (InJ) of an independent injection method for each cylinder, and in the figure, the fuel injection valves for each cylinder are shown as one block. The mounting structure of this fuel injection valve 7 is as follows:
For example, similar to the fuel injection valve 5 shown in FIGS. 7 and 8,
An intake port injection method (or manifold injection method) is adopted.

The controller 6 that controls the fuel injection valve 7 has a built-in microcomputer (?gt calculating means), and has a built-in microcomputer (?gt calculation means), and detects the detected value N of the engine rotation speed sensor 8, the detected value Oc from the crank angle sensor 9, and the detected value Oc from the engine coolant temperature sensor 10. Detected value Tw
, the detected value Qa from the intake sensor 11 is input. Based on these detection signals, the controller 6 calculates the valve opening start timing and valve opening time of the fuel injection valve 7 by calculation or map search, and sends a drive signal for executing this to the fuel injection valve 7.
Output to. Specifically, the valve opening time Ti of the injection valve 7 is determined from the intake air iQa, the engine cooling water temperature Tw, etc., and the timing to start opening the injection valve 7 is determined from the engine rotation speed and the like. The opening timing of the injection valve 7 is during the intake stroke of the relevant cylinder, and as described in detail in the [Function] section of the invention based on FIG. Among the air flow velocity characteristics V p ', the air flow velocity region (below the critical air flow velocity VPC) in which the injected fuel hardly adheres to the intake passage wall surface
For example, as shown in Fig. 1, in the first half of the air flow velocity characteristic Vp', in other words, in the first half of the intake valve opening operation (intake stroke), when the engine speed is N1. is the intake valve open position (crank angle) Oct, in the case of Nz, θc2, and in the case of N8, the position of OCR is the timing to start opening of the injection valve 7.

With such a configuration, when the engine 9 is in operation, the controller 6 determines the opening timing of the injection valve based on the engine speed N by calculation or by searching a predetermined map. When the crank angle corresponding to the opening start timing of the injection valve is detected, a valve opening command is output from the controller 6 to the injection valve 7 of the corresponding (intake stroke), and fuel injection is executed for a predetermined period of time. Fuel injection is performed.

According to such a fuel injection method, even if fuel is injected during the intake stroke, most of the injected fuel is sent to the cylinders over a wide engine speed range at an air velocity that does not cause wall adhesion. The air-fuel mixture can always be formed well over a wide operating range.

Furthermore, Figure 5 shows an example of the map search method.
Q with engine speed N and Qa/N (Qa is intake air amount)
By creating a cn map, injection valve start timing control can be easily performed. FIG. 6 shows a method for determining the valve opening time Ti, which can be performed in substantially the same manner as in FIG. 5.

〔Effect of the invention〕

As described above, according to the present invention, in the cylinder-by-cylinder independent injection system in which fuel is injected in synchronization with the intake stroke.

The injected fuel is sent to the engine combustion chamber (cylinder) side at an air velocity that does not cause wall adhesion, so the mixture formation is good over a wide range of engine operation, promoting combustion and stability. In turn, it is possible to improve engine output, make exhaust cleaner, and reduce fuel consumption.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example of setting the air flow velocity characteristics during the intake stroke and the opening timing of the injection valve of the present invention, Fig. 2 is a system overview diagram as an embodiment of the present invention, and Fig. 3 is an illustration of the air flow rate characteristic during the intake stroke. An explanatory diagram showing the distribution state of the air-fuel mixture concentration in the engine combustion chamber during a stroke, FIG. 4 is an explanatory diagram showing an example of setting the opening start timing of the injection valve, which is another example of the present invention, and FIG. 5 is an explanatory diagram showing the above-mentioned example. An explanatory diagram showing a map search method for the injection valve opening start time Ocn in the embodiment, FIG. 6 is an explanatory diagram showing a map search method for the injection valve opening time Ti in the above embodiment, and FIGS. 7 and 8 are It is an explanatory view showing the behavioral state of fuel injection from a conventional injection valve. 1...Cylinder, 3...Intake path, 4...Intake valve, 5,
7...Fuel injection valve, 6...Controller (fuel injection start timing and injection time calculation means), 8...Engine speed sensor, 9...Crank angle sensor, 11...
Intake sensor, Vp'...air flow rate characteristics, VPC...
Critical air flow velocity, Och* Ocx+ Ocs+...O
cn...Injection valve opening start timing.

Claims (1)

[Claims] 1. In a fuel supply method using a cylinder independent injection method in which fuel is injected into each cylinder in synchronization with the intake stroke, the intake valve in each cylinder from the start of opening to the closing of the intake valve. From the nearby sinusoidal air flow velocity characteristics, an air flow velocity range below the critical air flow velocity V_P_C in which the injected fuel does not adhere to the intake passage wall is found in advance, and the intake valve opening position corresponding to the air flow velocity range below this critical air flow velocity V_P_C is determined. The valve opening start timing of the fuel injector is set based on this, and when the air flow velocity range below the critical air flow velocity V_P_C changes due to a change in engine speed, the fuel injection valve opening start timing is set based on this. A fuel supply method for an engine characterized by controlling fuel injection by changing the fuel injection. 2. In a fuel supply method using a cylinder independent injection method in which fuel is injected into each cylinder in synchronization with the intake stroke, a sinusoidal air wave near the intake valve in each cylinder from the start of opening to the closing of the intake valve. From the flow velocity characteristics, an air flow velocity range below the critical air flow velocity V_P_C in which the injected fuel does not adhere to the intake passage wall is found in advance, and within this air flow velocity range below the critical air velocity V_P_C, the second half of the sinusoidal air flow velocity characteristic is Determine the opening end timing of the fuel injector based on the intake valve open position in the relevant air flow velocity range, and at the determined opening end timing of the fuel injector,
A method for supplying fuel to an engine, characterized in that the opening timing of the fuel injector is automatically determined by adding a predetermined opening time of the fuel injector based on the engine state, and fuel injection control is performed.