JPS63230935A - Fuel injector for engine - Google Patents

Abstract

PURPOSE:To prevent considerable shift of air-fuel ratio by varying the upper limit being set on a detection value of intake air quantity or operated fuel injection quantity according to the temperature of combustion chamber. CONSTITUTION:Injection quantity of a fuel injection valve 25 arranged in an intake path 12 is controlled by a controller 100 which receives intake air quantity signal from an air flow sensor 20. The controller 100 receives a signal from a water temperature sensor 24 and varies an upper limit being set on a detected intake air quantity signal or an operated fuel injection quantity according to cooling water temperature. In other word, the upper limit is set higher for lower cooling water temperature. Consequently, a proper upper limit can be set according to the density of air, and considerable shift of air-fuel ratio can be prevented when a throttle valve is fully opened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is an engine that sets a fuel injection amount based on an intake air amount detected by an airflow sensor, and supplies fuel to the engine using the fuel injection amount. It relates to a fuel injection device.

(Prior Art) In engines in which fuel is supplied by a fuel injection device, an electronic control unit (control unit) using a microcomputer normally determines the fuel injection amount based on the amount of intake air detected by an air flow sensor. is set. Then, the drive control of the fuel injection valve is performed by an injection pulse signal having a pulse width corresponding to the fuel injection amount, and an amount of fuel corresponding to the operating state of the engine is injected from the fuel injection valve and supplied to the engine. Ru. In such engines, the airflow sensors used to detect the amount of intake air are those that detect the mass flow rate of intake air such as a movable vane type or hot wire type, and those that detect the volumetric flow rate of intake air such as the Karman vortex type. It can be broadly divided into those that detect When such an air flow sensor is used, for example, as shown in FIG.
The detection signal supplied from the air flow sensor to the control unit is the intake air IQ (g/sec).
, the value of engine rotation speed N is N,,N,,N,,N4
and N6, for example 1000.1500.2000.2
500 and 3000 (rpm), and the intake negative pressure B (-
mml (g) increases as it approaches the atmospheric side, but if an airflow sensor that detects mass flow rate is used, the throttle valve may be in a fully open state or an opening state close to that. When the intake negative pressure B assumes the maximum value Bm or a value close to it, and the engine speed N is in a low rotation range, particularly near N or N2, , the amount of intake air that is taken out due to the extremely large influence of intake pulsation. may become excessive compared to the amount of intake air actually taken into the combustion chamber. In addition, when the throttle valve is suddenly opened to a fully open state or close to it, the detected intake air amount Q may differ from the actual intake air amount due to a sudden change in the flow of intake air in the intake passage. In some cases, the amount of intake air sucked into the combustion chamber becomes excessive.

If the intake air 1iQ detected by the airflow sensor becomes excessive compared to the amount of intake air actually taken into the combustion chamber when the throttle valve is fully open or close to it, the control unit will The set fuel injection amount is excessively increased from the appropriate value, and the air-fuel ratio of the air-fuel mixture used for combustion deviates significantly from the target value to the rich side.

Therefore, conventionally, when such an air flow sensor is used, the fuel consumption is calculated based on the intake air IQ detected by the air flow sensor, as shown in Japanese Patent Laid-Open No. 55-98624, for example. An upper limit value for the injection amount is set according to the engine speed N, and when the fuel injection amount exceeds the upper limit value, an injection pulse signal having a pulse width corresponding to the upper limit value is formed instead. , it has been proposed to supply it to the fuel injection valve. Separately, an upper limit Qm for the intake air amount Q detected by the air flow sensor is set according to the engine speed N, and when the intake air amount Q exceeds the upper limit Qm, the intake air 1i
It has been considered to set the fuel injection amount using the upper limit value Qm instead of Q.

Note that the upper limit Qm set for the intake air amount Q is:
For example, when the throttle valve is fully open,
It is set as the maximum amount of intake air that can actually be taken into the combustion chamber, and as shown in FIG. 5 and FIG.
:l, N4 and N.

, the upper limit Qm of the intake air IQ is, respectively,
Qt, Qz, Qz, Qa and Q.

(Problem to be Solved by the Invention) Generally, when the engine is warmed up and in a relatively high temperature state, the density of the intake air taken into the combustion chamber is relatively small; When the engine is in a low-temperature state that has not yet been warmed up, the density of the intake air is relatively high, so when the engine is in a low-temperature state, there is more air inside the combustion chamber than when it is in a high-temperature state. The weight of the intake air that can be filled is relatively large. Therefore, as described above, if the upper limit value for the intake air amount detected by the air flow sensor or the fuel injection amount set based on it is set based on, for example, when the engine is in a high temperature state, When the temperature is low, the intake air amount or fuel injection amount will be set lower than the appropriate amount due to the upper limit value, and the air-fuel ratio will deviate to the lean side from the target value when the throttle valve is fully open. There is a risk that it will happen.

Conversely, if the upper limit value is set based on when the engine is in a low temperature state, when the engine is in a high temperature state, the intake air amount or fuel injection amount will be set larger than the appropriate amount due to the upper limit value. There is a bottom where the air-fuel ratio deviates from the target value to the Lynch side, such as when the throttle valve is fully open.

If the air-fuel ratio deviates significantly from the target value in this way, there is a risk that problems such as driving performance, running performance, exhaust gas purification performance, etc. will deteriorate.

In view of these points, the present invention sets the fuel injection amount based on the intake air amount detected by the air flow sensor, and supplies fuel by the fuel injection (2). It is an object of the present invention to provide a fuel injection device for an engine in which an upper limit value for a fuel injection amount is appropriately set so that an air-fuel ratio does not deviate greatly from a target value.

(Means for Solving the Problems) In order to achieve the above-mentioned object, a fuel injection device for an engine according to the present invention, as shown in the basic configuration in FIG. 1, includes a fuel injection means for supplying fuel to the engine. , an intake air amount detection means for detecting the amount of intake air drawn into the combustion chamber of the engine, an information detection means for detecting the temperature of the combustion chamber or information related thereto, and an intake air amount detected by the intake air amount detection means. upper limit value setting means for setting an upper limit value for the fuel injection amount calculated based on the intake air amount detected by the intake air amount detection means, and an upper limit value set by the upper limit value setting means; Upper limit value correction means corrects based on the temperature of the combustion chamber detected by the information detection means or information related thereto; and the intake air amount detected by the intake air amount detection means is equal to or less than the upper limit value corrected by the upper limit value correction means. In this case, the fuel injection amount is set based on the detected intake air amount, and when the intake air amount detected by the intake air amount detection means exceeds the corrected upper limit value, the fuel injection amount is set based on the upper limit value. , a state in which the fuel injection means performs fuel injection with a set fuel injection amount, or after calculating the fuel injection amount based on the intake air amount detected by the intake air amount detection means, the calculated fuel When the injection amount is less than the upper limit corrected by the upper limit value correction means, the calculated fuel injection amount is used, and when the fuel injection amount exceeds the corrected upper limit value, the fuel injection is performed using the corrected upper limit value. and a fuel injection amount control means that causes the injection means to perform a state, and the upper limit value correction means adjusts the upper limit value set by the upper limit value setting means when the temperature of the combustion chamber is relatively low and when the temperature is relatively high. The correction is made to be larger than .

(Function) In the engine fuel injection device having the above-described configuration, the upper limit value correcting means is configured to adjust the upper limit value setting means based on the temperature of the combustion chamber detected by the information detection means or information related thereto. The upper limit value for the set intake air amount or fuel injection (2) is corrected to be larger when the temperature of the combustion chamber is relatively low than when it is relatively high.

Therefore, when the engine is in a low temperature state and the density of intake air taken into the combustion chamber is high, when the engine is in a high temperature state and the density of intake air taken into the combustion chamber is low, In comparison, the upper limit value for the intake air amount or fuel injection amount is set large.

By setting the upper limit values for the intake air amount or fuel injection amount to vary according to the temperature of the combustion chamber, when the throttle valve is in the fully open state or an opening state in the vicinity thereof, This prevents the air-fuel ratio from deviating significantly from the target value due to excessive or insufficient fuel injection amount.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows an example of an engine fuel injection device according to the present invention, together with an engine to which it is applied. In FIG. 2, an intake passage 12 that guides intake air from an air cleaner 11 into a combustion chamber 14 of an engine body 10 is provided with a throttle valve 16 that is interlocked with an accelerator pedal. The opening degree of this throttle valve 16 is determined by the throttle opening sensor 18.
A detection signal St corresponding to the opening of the throttle valve 16 is obtained from the throttle opening sensor 18, and is supplied to the control unit 100, which will be described in detail later.

A hot wire type air flow sensor 20 for detecting the amount of intake air is disposed upstream of a portion of the intake passage 12 where the throttle valve 16 is disposed. This air flow sensor 20 has a platinum hot wire 20a that is heated with electricity, and detects the amount of intake air by utilizing the change in resistance value of the hot wire 20a according to the flow velocity of intake air flowing through the intake passage 12. It is made to be. A detection signal Sa corresponding to the detected amount of intake air is supplied from the air flow sensor 20 to the control unit 100. Further, a surge tank 22 having a relatively large volume is provided downstream of the portion of the intake passage 12 where the throttle valve 16 is disposed, and a fuel injection valve is provided further downstream of the surge tank 22. 25 have been temporarily installed.

The fuel injection valve 25 is electronically controlled, and is opened according to the pulse width of the injection pulse signal Pc supplied from the control unit 100, and the fuel injection valve 25 is opened in accordance with the pulse width of the injection pulse signal Pc supplied from the control unit 100, and the fuel injection valve 25 is pressurized and pressure-fed from the fuel supply system. intermittently injects at predetermined timing toward the intake port of the combustion chamber 14,
A mixture is formed to be combusted within the combustion chamber 14. The air-fuel mixture is drawn into the combustion chamber 14 via the intake valve 27, ignited by the spark plug 28, and combusted. Exhaust gas generated by combustion of the air-fuel mixture in the combustion chamber 14 is discharged into the exhaust passage 26 via the exhaust valve 29.

Further, in relation to the crank mechanism 33 that converts the reciprocating motion of the piston 31 in the engine body IO into rotational motion,
A rotation speed sensor 30 that detects the engine rotation speed is arranged, and a detection signal Sn corresponding to the engine rotation speed is supplied from the rotation speed sensor 30 to the control unit 100.

The control unit 100 receives the above-mentioned detection signals Sa,
In addition to Sn and St, a detection signal Sf corresponding to the temperature of the intake air obtained from the intake air temperature sensor 19 provided between the air cleaner 11 and the air flow sensor 20 in the intake passage 12, and a water temperature provided in the engine body 10. Various detection signals such as a detection signal Sw corresponding to the engine cooling water temperature obtained from the sensor 24 are supplied, and other detection signals Sx necessary for engine control are also supplied, and the voltage Vd of the battery 35 is applied.

The control unit 100 controls the fuel injection amount in the fuel injection valve 25 based on the various detection signals Sa, Sn, St, 3f, Sw, Sx, etc. described above, that is,
The air-fuel ratio of the air-fuel mixture that is subjected to combustion in the combustion chamber 14 is controlled.

In this example, based on the time when the engine is sufficiently warmed up and in a high temperature state (for example, a state of 806C or higher), the engine speed is adjusted according to the engine speed N as shown in FIG. 6 above. Upper limit Qm (Q+, Q2, Q3.Q
a, etc.) are stored in advance in the built-in memory as an upper limit value map.

Further, the built-in memory stores an upper limit correction coefficient map as shown in FIG. 3, which corresponds to the engine cooling water temperature Tw corresponding to the temperature of the combustion chamber 14. The upper limit correction coefficient hw is set to 1.2 when the value of the cooling water temperature Tw has not reached a predetermined value TI, for example, 50 ('C), and to T2 when the cooling water temperature TwO value is T9 or higher, for example, When the temperature is less than 80 ('C), the higher the cooling water temperature Tw, the smaller the value;
When the value is 0 (0C) or more, the value is set to 1.

The control unit lOO takes in the upper limit value Qm corresponding to the engine rotational speed N at which the detection signal Sn is generated from the above-mentioned upper limit value map, and also takes in the upper limit value Qm corresponding to the engine rotation speed N at which the detection signal Sn occurs from the above-mentioned upper limit value correction coefficient map. A new upper limit value Qh is set by taking in the upper limit value correction coefficient hW and multiplying the upper limit value Qm corresponding to the engine speed N by the upper limit value correction coefficient hw, and temporarily stores it in the built-in memory.

When the control unit lOO controls the air-fuel ratio, the detection signal Sn indicates the engine rotation speed N, and the detection signal Sa indicates the intake air IQ when the intake air i1Q is below the upper limit value Qh. and when the intake air IQ exceeds the upper limit value Qh, the upper limit value Qh is used to calculate the basic fuel injection ff1Tp, and the detection signals St', Sr, Sw and Sx
The injection amount correction coefficient CX is set according to the engine operating state based on the voltage Vd, and the invalid injection I is set based on the voltage Vd.
Cv is set, and the invalid injection lcv is added to the value obtained by multiplying the basic fuel injection amount Tp by the injection amount correction coefficient Cx to set the fuel injection amount Ti.

Subsequently, the control unit 100 controls the fuel injection lT
An injection pulse signal Pc having a pulse width corresponding to i is formed and supplied to the fuel injection valve 25 at a predetermined timing, for example, in synchronization with the engine rotation speed.
5 to perform fuel injection with fuel injection lTi.

In this way, the upper limit Qm for the intake air amount Q is set according to the engine speed N, and the upper limit Qm is corrected according to the cooling water temperature Tw to set a new upper limit Qh.
By setting the newly set upper limit Qh, the newly set upper limit value Qh corresponds to the density of the intake air actually drawn into the combustion chamber 14. Therefore, throttle valve 1
6 is in a fully open state or an opening state close to it, it is avoided that the fuel injection amount Ti is determined to be too large or too small, and the air-fuel ratio deviates greatly from the target value, thereby improving driving performance, etc. It will be done.

The control unit 100 that performs the above-described control is configured using, for example, a microcomputer, and an example of a program executed by the microcomputer in such a case, mainly for fuel injection amount control, is shown in FIG. This will be explained with reference to a flowchart.

This program starts a and takes in the detection signals Sa, Sf, Sn, SL, Sw, and Sx in process 101, and in the subsequent process 102, the upper limit value map as shown in the above-mentioned FIG. Based on this, an upper limit value Qm corresponding to the engine rotational speed N at which the detection signal Sn is detected is set, and in process 103, the upper limit value correction coefficient map as shown in FIG. Based on this, an upper limit correction coefficient hw is set according to the cooling water temperature Tw at which the detection signal Sw is detected.

Then, continuing (in process 105, process 102
By multiplying the upper limit value Qm set in step 103 by the upper limit correction coefficient hw set in process 103, the upper limit value Qm is corrected and a new upper limit value Qh is set.
Proceed to step 6. In decision 106, the detection signal S
It is determined whether or not the intake air IQ generated by a is less than the upper limit value Qh set in process 105, and the intake air iQ
If it is determined that the intake air IQ exceeds the upper limit value Qh, in the subsequent process 107, the intake air iQ is replaced with the upper limit value Qh, and the process proceeds to process 10B, and in the decision 106, it is determined that the intake air IQ is less than the upper limit value Qh. In this case, process 1 is executed without going through process 1゜7.
Proceed to 08.

In the process 10B, the basic fuel injection ff1Tp is determined according to the detection signal Sa as the intake air NQ or the intake air amount Q replaced by the upper limit Qh in the process 107, and the detection signal Sn as the default engine rotational speed N. T
It is set by calculating p=KX口/N (where K is a constant). In the next step 109, an injection amount correction coefficient Cx is set based on the intake air temperature at which the detection signal sf indicates a storm, the engine cooling water temperature Tw at which the detection signal Sw indicates a storm, the atmospheric pressure at which the detection signal Sx causes a storm, etc. In the subsequent process 111, an invalid injection amount Cv is set based on the voltage Vd of the battery 35.

Then, in the next process 112, the fuel injection lT
i is set by calculating T i = T p If it is determined that this is the case, an injection pulse signal Pc having a pulse width corresponding to the fuel injection amount Ti is formed in process 114, and is supplied to the fuel injection valve 25, and the process returns to the original state. Thereby,
Fuel injection with a fuel injection amount Ti is performed by the fuel injection valve 25, and an amount of fuel corresponding to the operating state of the engine is supplied to the engine.

In the above example, the upper limit Qm for the intake air IQ detected by the detection signal Sa is set according to the engine speed N, and is corrected according to the cooling water temperature Tw. However, the fuel injection device for the engine according to the present invention does not necessarily have to be configured in this way, and an upper limit value for the basic fuel injection mTp or the fuel injection lTi is set according to the engine speed N, and the upper limit value is set depending on the cooling water temperature Tw. The correction may be made accordingly.

Further, in the above example, the upper limit value Qm is corrected based on the engine cooling water temperature Tw when the detection signal SW is detected, but it is not necessary to do so, for example. The −L limit value Qm may be corrected based on the intake air temperature at which the detection signal Sf is detected, the atmospheric pressure at which one of the detection signals SX is detected, or the like.

However, depending on the mounting position of the intake air temperature sensor 19 and atmospheric pressure sensor, the intake air temperature and atmospheric pressure detected by them may not necessarily accurately represent the temperature and pressure of the intake air drawn into the combustion chamber 14. Therefore, the density of the intake air actually taken into the combustion chamber 14 can be reduced by
Furthermore, in order to properly detect the temperature, it is preferable to perform the detection based on the engine cooling water temperature Tw, as in the above-mentioned example.

(Effects of the Invention) As is clear from the above description, the engine fuel injection device according to the present invention sets the fuel injection amount based on the intake air amount detected by the air flow sensor, and also sets the fuel injection amount based on the intake air amount detected by the air flow sensor. It was made to provide fuel supply,
Moreover, the upper limit value for the intake air amount or fuel injection amount is set to change depending on the temperature of the combustion chamber, so the upper limit value corresponds to the density of the intake air actually taken into the combustion chamber. Become. As a result, it is possible to prevent the air-fuel ratio from deviating significantly from the target value due to excessive or insufficient fuel injection amount when the throttle valve is fully open, etc., thereby improving driving performance, exhaust purification performance, etc. be able to.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram showing the present invention in accordance with the claims, FIG. 2 is a schematic configuration diagram showing an example of an engine fuel injection device according to the present invention, and FIG. 3 is the same as shown in FIG. FIG. 4 is a flowchart showing an example of a program executed by a microcomputer when a microcomputer is used in the control unit shown in FIG. and FIG. 6 are characteristic diagrams for explaining the upper limit value set for the intake air amount, respectively. In the figure, 10 is the engine body, 20 is the air flow sensor,
24 is a water temperature sensor, 25 is a fuel injection valve, 30 is a rotation speed sensor, and 100 is a control unit. Fig. 1 Fig. 3 IT2 Tw ('C) Fig. 2 Fig. 5 m Fig. 6 8 (-""9) N (rpm)

Claims (1)

[Claims] a fuel injection means for supplying fuel to the engine; an intake air amount detection means for detecting the amount of intake air taken into the combustion chamber of the engine; and an information detection means for detecting the temperature of the combustion chamber or information related thereto; Upper limit value setting means for setting an upper limit value for the intake air amount detected by the intake air amount detection means or an upper limit value for the fuel injection amount calculated based on the intake air amount detected by the intake air amount detection means; , the upper limit value set by the upper limit value setting means is determined based on the temperature of the combustion chamber detected by the information detection means or information related thereto, when the temperature of the combustion chamber is relatively low. When the intake air amount detected by the upper limit value correction means and the intake air amount detection means is smaller than the upper limit value corrected by the upper limit value correction means,
The fuel injection amount is set based on the intake air amount, and when the detected intake air amount exceeds the corrected upper limit value, the fuel injection amount is set based on the upper limit value, and the fuel injection amount is set based on the above-mentioned upper limit value. After the fuel injection amount is calculated based on the intake air amount detected by the intake air amount detection means, the calculated fuel injection amount is When the fuel injection amount is below the upper limit corrected by the upper limit correction means, the calculated fuel injection amount is used, and when the calculated fuel injection amount exceeds the corrected upper limit, the fuel injection is performed using the upper limit. 1. A fuel injection device for an engine, comprising: fuel injection amount control means that causes the fuel injection means to perform a state.