JPH02112667A - Air assist type electronic control fuel injection system - Google Patents

Abstract

PURPOSE:To keep off any mixture rarefaction at acceleration as well as to make an effect of fuel atomization utilizable to the largest extent by closing an assist air control valve for a period of valve closing time operated when turning to an accelerated state. CONSTITUTION:When an engine accelerated state is detected by an intake pipe pressure signal being outputted by a vacuum sensor 7 at a microcomputer 27, valve closing time of a control valve 25 is calculated on the basis evaporableness of fuel stuck to an intake pipe inner wall being discriminated out of an engine driven state. Then, the control valve 25 is closed for a period of this valve closing time, and the full or partial assist air is stopped for a while as long as the irreducible minimum of requirement and thereby a spray angle of an air assist type fuel injection valve 9 is contracted. Accordingly, during the while, fuel is not stuck to the intake pipe inner wall, thus any sluggishness of engine output due to lean mixture ratio will not occur there. Therefore an effect of fuel atomization owing to the air assist is utilizable to the largest extent in the case other than the accelerated state.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is an electronically controlled fuel injection device (hereinafter referred to as EFI) for an internal combustion engine, which is an auxiliary fuel injection device for promoting fuel vaporization. This invention relates to an improvement in an EFI that uses an air flow (hereinafter referred to as an air-assisted EFI).

(Prior art) As a conventional technology of air-assisted EFI, Japanese Patent Application Laid-open No. 57
There is one described in Japanese Patent No.-143158. Fig. 15 shows the outline thereof, 1 is an intake valve, 2 is a cylinder head, 3 is a piston, 4 is an intake port, 5 is a surge tank, 6 is a throttle valve, 7 is an intake pipe negative pressure sensor, 8 is an air flow sensor, 9 is an air-assisted fuel injection valve, 1.
0 is piping, 11 is an electric air pump, 12 is a linear solenoid valve, 13 is an assist air inlet, 14 is a throttle switch, 15 is a rotation speed sensor (an electromagnetic pickup attached to the distributor 18 of the engine), l
6 is a water temperature sensor, and 17 is a microcomputer.

Air-assisted EFI supplies an auxiliary air flow (referred to as assist air) led from upstream of the throttle valve to the injection valve in order to make the fuel particles injected from the fuel injection valve finer. However, simply obtaining airflow by using the pressure difference before and after the throttle valve may not be able to obtain a sufficient flow rate as assist air, so the conventional technology described above , at startup or under high load when the differential pressure across the throttle valve is small,
Alternatively, various sensors detect when the cooling water temperature is extremely low, and the electric air pump 11 is driven based on judgment and instructions from the computer 17, and the linear solenoid valve 12 is appropriately throttled to allow assist air to flow to the fuel injection valve 9. is increasing.

[Problem to be solved by the invention]

In terms of being able to make fuel particles finer and reducing hydrocarbons and carbon monoxide in exhaust gas,
Air-assisted EFI has a remarkable effect, but for example, when accelerating a car equipped with it, the throttle valve opens and the amount of intake air increases, and the signal from the air flow sensor that detects this causes the computer to control the injection valve. Even if you increase the amount of fuel coming out of the engine, depending on the condition of the engine, the air-fuel mixture that actually enters the engine from the intake valve may become temporarily lean, making it impossible to obtain a sharp increase in output and reducing drivability. It turned out that there was a problem. Therefore, when we investigated the cause of such a phenomenon, we found that, as shown in Figure 14 (B), in the air-assisted EFI, the assist air promotes atomization of the fuel, but on the other hand,
Since the spray angle is expanded compared to the case where air assist is not used as shown in FIG. , it adheres to the pipe wall as if it were wet, so in a steady state such as constant speed operation, there is a balance between the amount newly deposited and the amount that evaporates on the intake air, so it does not cause any problems. , as the amount of fuel increases during acceleration, the amount of fuel adhering to the pipe wall may temporarily increase, and depending on the engine condition, the amount of fuel entering the combustion chamber may not increase much. In this case, the amount can be increased significantly without such problems, and furthermore, when accelerating, the throttle valve expands and the pressure near the intake port is often close to atmospheric pressure, so there is no risk of pressure on the pipe wall. As a result, the mixture may be temporarily diluted in the combustion chamber due to two reasons: less evaporation of the adhering liquid fuel; as a countermeasure, during acceleration, My first thought was to stop air assist all together.

However, there is a problem that if air assist is stopped, the atomization of the fuel does not proceed, and on the other hand, there is a problem that the engine is in a state where the adhering fuel is likely to vaporize.
When the intake pipe negative pressure is large, the temperature of the intake air is high, the temperature of the cooling water is high, or the engine is rotating at high speed, the amount of fuel that adheres to the intake pipe wall due to acceleration increases. It has been found that even if the air assist increases, it is not a big problem because the vaporization is fast. Therefore, in such conditions, it is thought to be a good idea to take advantage of the advantages of air assist as much as possible. I came up with the idea of reducing the air assist stop time as much as possible.

Therefore, in the present invention, the problem to be solved is to provide a means that can prevent the dilution of the air-fuel mixture during acceleration and make maximum use of the effect of atomization of fuel by air assist. do.

[Means to solve the problem]

As a configuration of the invention for solving the above-mentioned problems, the present invention includes a fuel injection valve, and assist air is injected into the fuel injection valve to promote vaporization of the fuel injected from the injection valve, as shown in FIG. It has a pipe for supplying the valve, a control valve provided in the middle of the pipe, and a control means for controlling opening and closing of the control valve, and the control means includes an acceleration detection means for detecting an acceleration state of the engine. and a valve-closing time calculation means for calculating the valve-closing time of the control valve based on the ease of evaporation of the fuel adhering to the inner wall of the intake pipe, which is determined from the engine operating state, and the valve-closing time calculation means calculates the valve-closing time of the control valve based on the ease with which fuel adhering to the inner wall of the intake pipe evaporates, which is determined from the engine operating state. Air-assisted electronically controlled fuel injection for an internal combustion engine, characterized in that by closing the control valve for a valve-closing time calculated when , all or part of the assist air is stopped during that time. Provide equipment.

[For production]

Since the present invention has the above configuration, assist air is sent to the fuel injection valve through the control valve and its piping, which are normally open while the engine is operating, to promote atomization and vaporization of the injected fuel spray. At the same time, the latent heat of vaporization of the fuel cools the intake air and increases the engine's intake efficiency. However, when the engine accelerates, the amount of fuel adhering to the intake pipe wall temporarily increases, causing the mixture ratio to decrease. In order to stop the supply of assist air for a minimum period of time or reduce it to a level that does not cause any problems, when the acceleration detection means detects the acceleration state of the engine, the engine The valve closing time calculating means calculates the closing time of the control valve based on the ease with which fuel adhering to the inner wall of the intake pipe evaporates, which is determined from the operating status of to stop all or part of the assist air and reduce the spray angle of the injection valve. Therefore, during this period, fuel does not adhere to the inner wall of the intake pipe, and the increase in engine output does not slow down due to dilution of the mixture ratio, so that deterioration in drivability can be prevented.

〔Example〕

In FIG. 1 showing an embodiment of the present invention, parts similar to those in FIG. 15 already described are given the same reference numerals. The engine 21 shown in this embodiment has a relatively thin and long straight intake manifold 22 rising from the intake boat 4.
Since the air-assisted fuel injection valve 9 is provided upstream, the distance from the injection valve 9 to the intake port 4 is long (
It has become. Therefore, when air assist is stopped, the fuel spray discharged from the injection valve 9 becomes a thin streak and
However, when assist air is sent, the spray angle of the fuel expands, and almost all of the injected fuel reaches the inner wall 23 of the intake manifold 22 or the intake port 4.
will now collide with the wall. If the amount of fuel is increased for acceleration when the engine is in a state where the fuel adhering to the inner wall 23 etc. is difficult to vaporize, the problem described above will occur. During constant speed operation, the adhering fuel evaporates and the temperature of the intake air decreases, increasing the engine's intake efficiency and preventing non-king, increasing output in the low and medium speed range. There is a big advantage in doing so. In addition to assist air atomizing the fuel and promoting vaporization, air assist was also stopped as much as possible (this is also the reason why it is not done).

Next, 24 is an electromagnetic air pump installed in the assist air piping 10 as necessary, and when the throttle valve 6 is closed to a certain extent and there is a pressure difference across it, a sufficient amount of assist air is supplied from the intake port 13. There is no need to operate it as it is sent to the piping 10, but when the throttle valve 6 approaches full open, the differential pressure across it becomes small and the assist air tends to be insufficient, so it may be necessary to provide air assist even under high load conditions. For example, the electromagnetic air pump 24 is provided to forcibly feed assist air into the piping 10.

25 is an assist air control valve (referred to as an air assist valve)
In this example, a solenoid valve is shown, but it goes without saying that a diaphragm valve operated using intake pipe negative pressure may also be used. 26 is a linear throttle sensor attached to the operating mechanism of the throttle valve 6, which detects the opening degree of the throttle valve.

27 is a microcomputer as a control means, 28 is its input port, 29 is also an output port, 30 is a memory, and 31 is a central processing unit (CPU). Further, 32 is an intake air temperature sensor provided in the intake passage;
is an air cleaner.

In the operating state, the engine rotation speed signal N0 is output by the rotation speed sensor 15, the intake pipe pressure signal P is output by the negative pressure sensor 7, and the engine cooling water temperature signal T is output by the water temperature sensor 16. , the intake air temperature signal T output by the intake temperature sensor 32
a. Furthermore, each of the throttle valve opening signals Te output from the linear throttle sensor 26 is input to the microcomputer 27 from the input boat 2, the data is stored in the memory 30, and other data set in the memory are input. At the same time, the CPU 31 performs arithmetic processing to control the fuel injection amount in the injection valve 9 and the supply and stop of assist air in the air assist valve 25, respectively, based on the output signal appearing on the output boat 29. Furthermore, if necessary, the electromagnetic pump 24 is driven and controlled to replenish assist air in a situation where it is insufficient.

The control procedure for the air assist valve 25 is as shown in FIG. The rate of change ΔP of P is calculated and input into the memory 30 (step 101). Furthermore, this differential pressure Δ
Regarding the change in P, the difference between the previous and current values of each ΔP, that is, the rate of change in ΔP, is calculated and manually stored in the memory 30 (step 102).

In the main routine 200 shown in FIG. 3, the value of ΔP is first compared with a preset value A to determine whether the vehicle is in an acceleration state (step 201).

If ΔP>A, it is determined that the vehicle is in an acceleration state, and the process proceeds to step 202. Furthermore, in order to determine whether or not it is the initial stage of acceleration, the value of ΔΔP is compared with 0, and ΔΔP>
If it is 0, it is determined that the acceleration is in the initial stage, and step 203
Proceed to. Note that if the answer in step 201 or 202 is NO, the process enters return in step 205.

In step 203, the value of intake pipe pressure P is read and an index value is determined. As shown in FIG. 5, the index value of 2 is 1. when the negative pressure is large. The map in the memory 30 is set as a function of the pressure P such that the value of 9 increases as the negative pressure decreases (the value of P increases).

As for the index value, the smaller the negative pressure in the intake manifold 22 and the closer the pressure P is to atmospheric pressure, the more difficult it is for the fuel adhering to the inner wall 23 to vaporize, and the more the amount of fuel adhering to the wall surface becomes. This value not only indicates the degree of difficulty in vaporization, but also estimates the amount of attached fuel. Next, in step 204, the index value is multiplied by ΔP, which is a numerical value indicating the degree of acceleration (if the degree of acceleration is large, the air assist stop time should be lengthened), and the air assist The closing time of the valve 25, that is, the air assist stop time T is determined, and the process returns in step 205.

300 shown in FIG. 4 is a 4 m5ec routine, and in step 301 it is determined whether the closing time T of the air assist valve 25 is O or not. When T=O, air assist valve 25 is ON.
(remains open), and if T>0, subtract 4 m5ec from T in 302 and proceed to 303. Therefore, when the stop time T is set during acceleration, the air assist valve 25 is turned off (closed) for the time T, and the air assist is stopped.

The above describes the case where the closing time of the air assist valve 25 is determined based on the intake pipe pressure P, but the degree of difficulty in vaporizing the fuel adhering to the inner wall of the intake pipe is an index for determining the closing time of the air assist valve. , or a numerical value corresponding to the amount of adhering fuel (such as the above-mentioned index value) can be calculated from other data, and some examples will be described below.

6 to 8 are based on the slot valve opening signal Te output from the linear throttle sensor 26 attached to the shaft of the throttle valve 6, instead of the intake pipe pressure P in the examples shown in FIGS. 2 to 5. This is an example in which the closing time T of the air assist valve 25 is determined by calculating the index value KO, which is a numerical value corresponding to the amount of adhering fuel.

In the 360° routine 400 shown in FIG.
The difference ΔTe in the throttle valve opening degree T9 and its rate of change ΔΔTe are calculated for each rotation, and the main routine 50 shown in FIG.
0, ΔT9 is compared with the set value A (step 501),
It is determined whether the rate of change ΔΔTθ is greater than O (502)
, if it is large, compare it with the map shown in Figure 8 in the memory and calculate 9 as the index value corresponding to the amount of adhering fuel.
03), and this is multiplied by ΔTθ to determine the closing time T of the air assist valve 25 (504). After T is calculated, the process is the same as in the above example, and the air assist valve 25 is controlled to open and close in accordance with the procedure shown in FIG.

In the example described above, the air assist valve closing time T is determined based only on the intake pipe pressure P or the throttle valve opening Te, but the engine rotation speed N.

If the above calculation result is corrected using other data such as
A more desirable value of T is determined. This is because when the engine is rotating at high speed, the flow velocity of the intake air increases, and the adhering fuel vaporizes more rapidly than when the engine is rotating at low speed. This is because there is no problem even if the closing time T of the assist valve is made slightly shorter, and the air assist stop time can be shortened to the limit to make the most of the air assist effect.

As an example, control using the intake pipe pressure P and the engine speed N0 is shown in FIGS. 9 and 10. The matters explained in FIGS. 2 to 5 will be omitted since they are redundant. 9 is the same as the above-mentioned FIG. 3 up to step 202, and calculating the index value Kp from the intake pipe pressure P is also the same as in FIG. 5. However, in step 203 of FIG. 9, a correction value is further read from the engine speed N, using a map such as that shown in FIG. The index value is □.

The subsequent control procedures, such as calculating the desired T from K, are the same as those already described, so their description will be omitted.

(Usually, the correction value used for multiplication is a decimal number less than 1, and the correction value used for addition is a negative value.) Next, considering the engine cooling water temperature Tw, this is also similar to the engine speed N. Similar characteristics can be seen.

In other words, a high cooling water temperature also means that the inner wall temperature of the intake manifold 22 and intake boat 4 is high.
Under such conditions, the adhering fuel vaporizes more rapidly than when the inner wall temperature is low.

Therefore, the index value calculated based on the intake pipe pressure P can be corrected to a more desirable value by adding 8 to the correction value determined from the engine cooling water temperature T1 (based on a map as shown in FIG. 12). This procedure is shown in FIG. 11, but since it can be understood from the above explanation regarding FIG. 9, detailed explanation will be omitted.

Furthermore, the engine cooling water temperature T1. Figure 13 shows a control procedure for correcting θ (Figure 8) to the index value calculated based on the throttle valve opening T9 to a more desirable value by adding 1 (Figure 12) to the correction value obtained from I. .

Since the contents can be understood by reading the above explanation, detailed explanation will be omitted.

In addition to the above, the intake temperature TA detected by the intake temperature sensor 32 also includes the engine speed N0, the engine cooling water temperature T,
Since it has properties similar to 4 and A, it can be used to obtain a correction value and calculate a desirable index value for shortening the air assist valve closing time T as much as possible.

In the above explanation, intake pipe pressure P or throttle valve opening T
Calculate the index value or KQ based on Although the procedure for finding a desirable index value has been explained, it is also possible to determine the index value of the air assist valve occlusion time based on N-, Th, or TA, even if the accuracy is superior or inferior. It is also possible to find a more desirable index value by multiplying or adding the correction value calculated based on P or Tθ.

As a matter of course, the air assist valve 25 is closed during the closing time T, but this does not mean that the pipe 10 is completely closed. If it is desired to allow a small amount of assist air to flow even during the closing time T, a suitable bypass can be provided either inside or outside of the valve 25.

〔Effect of the invention〕

The present invention solves the problem of air-assisted fuel injection valves during acceleration by stopping the assist air for the minimum amount of time necessary, so it is possible to make maximum use of the advantages of air assist. possible. In other words, the atomization and vaporization of the fuel spray are promoted, and the resulting improvement in combustion reduces the amount of hydrocarbons and carbon monoxide in the exhaust gas, and the cooling effect of the intake air due to the vaporization of the fuel increases the intake efficiency. Output increases.

On the other hand, during acceleration, by stopping all or part of the supply of assist air for the minimum necessary time, the spray angle is made small, preventing fuel from adhering to the inner wall of the intake pipe, and improving the mixture ratio. It is possible to prevent the slowdown in output growth due to dilution and maintain good drivability.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view showing an embodiment of the present invention, FIGS. 2 to 4 are flowcharts showing an example of control, FIG. 5 is a map used therein, and FIGS. 6 and 7 are FIG. 8 is a flowchart showing a control example, FIG. 9 is a flowchart showing another control example, FIG. 10 is a map thereof, FIG. 11 is a flowchart showing another control example, and FIG. 12 is a flowchart showing another control example. That map, No. 13
14 is an explanatory diagram showing the difference depending on the presence or absence of air assist in the fuel injection valve. FIG. 15 is a partial cross-sectional view illustrating the conventional air assist II EFI. The figure is a schematic diagram illustrating essential constituent elements of the present invention. 1...Intake valve, 4...Intake port, 6
... Throttle valve, 7... Intake pipe pressure sensor, 9... Air-assisted fuel injection valve, 10... Piping, 15... Rotation speed sensor, 16... Water temperature sensor, 17.27 ...Microcomputer, 22...Intake manifold, 24...Electromagnetic air pump, 25...
Air assist valve, 26--Linear throttle sensor, 32--Intake air temperature sensor. Go to 360° routine Electric air pump system (B) Fig. 14 9... Air assist type fuel injection valve 19... Intake pipe wall control means Fig. 16

Claims (1)

[Claims] A fuel injection valve, a pipe for supplying assist air to the injection valve to promote vaporization of the fuel injected from the injection valve, a control valve provided in the middle of the pipe, and the control valve. It has a control means for controlling opening and closing, and the control means has an acceleration detection means for detecting an acceleration state of the engine, and an acceleration detection means for detecting an acceleration state of the engine, and a control means for controlling the ease of evaporation of fuel adhering to the inner wall of the intake pipe, which is determined from the engine operating state. and a valve-closing time calculation means for calculating the valve-closing time of the control valve based on the calculated valve-closing time when the engine is in an accelerating state. 1. An air-assisted electronically controlled fuel injection system for an internal combustion engine, characterized in that all or part of the fuel injection system is stopped.