JPS60153444A - Fuel feed device for engine - Google Patents

Abstract

PURPOSE:To prevent an air-fuel mixture from coming into being overlean, by detecting a specified operating region where output of a suction temperature sensor shows a higher value than that in the actual suction temperature, while releasing a degree of suction temperature compensation to a fuel feed quantity. CONSTITUTION:When a suction temperature compensating circuit 17 judges a fact that an ignition switch 9 is turned to ON and a warm start from each A/D conversion output N, Tw out of an engine speed sensor 10 and a water temperature sensor 7, it sets a setting value K to a timer, then reads the A/D conversion output of an outside air sensor 11. And stored it into a register To, while it subtracts the setting value K one by one therefrom. The circuit 17 finds a proper suction temperature equivalent value from the To and the Tw, storing the value into the register Ta and outputting, then it compensates a fuel feed quantity from a map 14 at an operation circuit 20 by way of an A/D converter 18 and a function generator circuit 19. Next, when a timer setting value K comes to nil, the circuit 17 outputs the A/D conversion output value Ta of a suction temperature sensor 8 as it is, and compensates it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel supply device for an engine.

[Prior art]

Generally, a fuel supply device for an engine attempts to efficiently operate the engine by supplying an amount of fuel to the engine according to the amount of intake air. For example, in an engine's carburetor, the amount of fuel introduced is controlled by the venturi negative pressure in the intake passage, and in an engine's fuel injection device, the amount of intake air is detected by an air flow sensor, and the amount of intake air is controlled according to the output of the sensor. The fuel injection amount is controlled. However, in this case, if the fuel supply amount is controlled simply by the venturi negative pressure or according to the output of the airflow sensor, the venturi negative pressure changes with the intake flow rate as a parameter, and the airflow sensor normally , Karman vortex type to detect the volumetric flow rate of intake air.

Since speed density type and vane type sensors are used, a problem arises in that the air-fuel ratio of the mixture deviates from the set value when the intake air temperature changes and the intake air density changes.

In order to solve this problem, conventionally, an intake air temperature sensor is installed in the middle of the intake passage, and the fuel supply amount is corrected and controlled based on the sensor's output. There is one shown in Japanese Patent Application Laid-Open No. 57-51299. However, in conventional fuel supply systems that perform such intake temperature correction, engine output may decrease or engine stall may occur during warm start, excitation, acceleration, and the like.

As a result of intensive research aimed at preventing engine output reduction and engine stalling, the inventor of the present invention discovered that the following causes the output reduction and engine stalling. That is, FIG. 1 shows temporal changes in the intake air temperature a in the intake passage, the output of the intake air temperature sensor, the engine cooling water temperature C, and the outside air temperature d. According to Figure 1, when the engine is cold started, the intake air temperature sensor detects the intake air temperature (see the dashed line a in the figure) without delay, as shown by the solid line in the figure, while the engine cooling water As shown by the solid line C in the figure, the temperature rises immediately after the engine starts, and becomes almost constant at about 80°C. Once the engine is stopped, the cooling water temperature C gradually decreases from about 80°C, but at that time, the intake air in the intake passage is heated by this high temperature engine cooling water, and the intake air temperature a is about 30°C. The temperature rises significantly from the current state, and the temperature of the intake temperature sensor itself, which is in contact with this high-temperature intake air, also becomes high. When the engine is started, that is, warm-started, in this condition, low-temperature outside air as shown by the broken line d in the figure is sucked into the intake passage, and the intake air temperature a immediately decreases to its original temperature of about 30°C. However, as mentioned above, since the intake air temperature sensor itself is at a high temperature when the engine is stopped,
A detection delay occurs in the sensor, and the sensor generates an output corresponding to a temperature higher than the actual intake air temperature a. Therefore, when the intake temperature of the fuel supply amount is corrected based on the output of this intake temperature sensor, the correction control becomes over-controlled and the fuel supply amount decreases, which causes the air-fuel ratio of the air-fuel mixture to become over-lean and the engine output. The vehicle may drop or the engine may stall. That is, a sudden increase in the amount of intake air and a delay in the detection of the intake air temperature sensor at that time cause a decrease in engine output and engine failure.

[Purpose of the invention]

In view of this, the present invention aims to provide an engine fuel supply device that can prevent a decrease in engine output and the occurrence of engine stalling.

[Structure of the invention]

Therefore, the present invention provides an engine fuel supply system in which an intake temperature sensor is disposed in the intake passage of the engine, and the intake temperature is corrected for the fuel supply amount based on the output of the sensor. detects a specific operating region in which the intake air temperature is higher than the intake temperature of This is how it was done.

〔Example〕

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

FIGS. 2 and 3 show an engine fuel supply system according to an embodiment of the present invention, and this is an example applied to an engine fuel injection system. In the figure, 1 is an engine, 2 is an intake passage of the engine 1, 2a is an intake air heating part formed in the middle of the intake passage 2 and heats intake air, 3 is a fuel injection valve disposed in the middle of the intake passage 2, 4 is a throttle valve, 5 is an air cleaner, 6 is a negative pressure sensor which is a speed density type air flow sensor disposed downstream of the throttle in the intake passage 2, and 8 is disposed near the engine 1 in the intake passage 2 to detect the intake air temperature. 9 is an ignition switch, IO is a rotational speed sensor, and 12 is a control circuit that receives the outputs of the sensors 6.8 to 10 and controls the fuel injection amount.

Further, FIG. 3 shows a more detailed configuration of the control circuit 12. In the figure, the same reference numerals as in FIG. 2 indicate the same parts as in the same figure, 13 is an A/D converter that A/D converts the re-outputs of the rotation speed sensor 10 and the negative pressure sensor 6, and 14 is the engine rotation speed. A basic fuel injection pulse generation circuit that has a pulse width map of basic fuel injection pulses with and negative pressure as parameters, and generates a basic fuel injection pulse width according to the A/D conversion outputs of both the sensors 6.10. , 15 connects the output of the circuit 14 to D/
This is a D/A converter that performs A conversion.

Further, 16 is an A/D converter that A/D converts the re-outputs of the intake air temperature sensor 8 and the rotation speed sensor 10, and 17 is an A/D converter that receives the A/D conversion outputs of both the sensors 8 and 10 and the output of the ignition switch 9. Tsutomi outputs the A/D conversion output of the intake temperature sensor 8 as it is, and on the other hand, when the intake temperature at the time of starting is higher than the intake temperature at the time of engine stop, it is a constant value for a predetermined time after starting. Intake temperature correction circuit 18 consisting of a CPU that outputs the A/D conversion output of the intake temperature sensor 8
19 is a D/A converter that D/A converts the output of the intake air temperature correction circuit 17, and 19 is a D/A converter that converts the output of the intake air temperature sensor 17 into D/A. As shown in FIG. 4, the higher the intake air temperature, the smaller the value. 20 is the function generating circuit that outputs the correction coefficient D
21 is an arithmetic circuit that multiplies and corrects the /A converted basic fuel injection pulse width by the output of the function generating circuit 19; .

In the above configuration, the basic fuel injection pulse generation circuit 14 serves as a fuel supply amount adjustment device for adjusting the amount of fuel supplied to the engine, and the function generation circuit 19 and the calculation circuit 20 is a correction means that corrects and controls the fuel supply amount adjustment device so that the fuel supply amount decreases as the intake temperature increases, based on the output of the intake temperature sensor.
Furthermore, the intake air temperature correction circuit 17 receives the detection output of the specific operating state detection means and the specific operating state detection means for detecting an operating state in which the intake air temperature corresponding to the intake air temperature sensor output is higher than the actual intake air temperature, and performs the correction control described above. This is a release means that divides by M.

Next, the general operation of this device will be explained using FIG. 3.

When the engine is cranked, the negative pressure sensor 6 measures the intake negative pressure downstream of the throttle valve 4, the intake air temperature sensor 8 measures the intake air temperature when the intake air is heated and is drawn into the engine, and the rotational speed sensor 10 measures the engine speed. The re-outputs of the negative pressure sensor 6 and rotation speed sensor 10 are A/D converted by an A/D converter 13 and then input to a basic fuel injection pulse generation circuit 14. Then, this basic fuel injection pulse generation circuit 14 determines the pulse width of the basic fuel injection pulse according to the engine speed and the intake negative pressure, converts it into a D/A converter 15, and then converts it into an arithmetic circuit. Enter 20. On the other hand, the re-outputs of the intake temperature sensor 8 and rotation speed sensor 0 are A/D converted by an A/D converter 16 and then applied to an intake temperature correction circuit 17. When the ignition signal is input, the intake air temperature correction circuit 17 determines whether the air intake air temperature when the engine is started is higher than the air intake air temperature when the engine is stopped.

If the intake temperature when the engine is started is not higher than that when the engine is stopped, the intake temperature correction circuit 17
directly outputs the A/D conversion output of D/A converter 1B.
After D/A conversion, it is input to the function generating circuit 19, which generates a correction coefficient (see FIG. 4) corresponding to the intake air temperature sensor output and adds it to the arithmetic circuit 20. Then, this arithmetic circuit 20 corrects the pulse width of the basic fuel injection pulse using the correction coefficient, and injector drive circuit 21
applies a fuel injection pulse with a corrected pulse width to the fuel injection valve 3, whereby the fuel injection amount is corrected and controlled to be smaller as the intake air temperature rises in accordance with the intake air temperature sensor output.

On the other hand, if the intake temperature when the engine is started is higher than that when the engine is stopped, the intake temperature correction circuit 17 replaces the A/D conversion output of the intake temperature sensor 8 with the current A/D conversion output for a predetermined period of time after the engine is started.
The output of the intake temperature sensor when the engine is stopped is a constant value, and the function generating circuit 19 outputs a correction coefficient according to the output of the intake temperature sensor when the engine is stopped, and as a result, the fuel injection amount is adjusted to the same value as when the engine is stopped. The intake air temperature is corrected according to the intake air temperature. In this manner, when the intake air temperature is high when the engine is started, the correction control of the fuel injection amount based on the intake air temperature sensor output at that time is canceled for a predetermined period of time.

Next, using the flowchart in FIG. 5, the intake air temperature correction circuit 1
7 will be explained in detail.

When the ignition signal from the ignition switch 9 is applied to the intake temperature correction circuit 17, the ignition signal from the ignition switch 9 is 0.
Read the conversion output N and set it as the set value, for example 500r.
pm or more, it is determined whether the engine has started or not (step 30), the process waits in step 30 described above until the engine starts, and when the engine starts, it is determined YES in step 30 and step 31 Then, the A/D conversion output of the intake air temperature sensor 8 is read and stored in the register Ta, and the difference between the intake air temperature in this register Ta and the intake air temperature when the engine is stopped in the static memory Tm, which will be described later, is calculated. , and it is determined whether it is greater than or equal to the set value C (step 32).

Then, the above intake air temperature difference (T a - T m) is the set value C
If it is larger, the intake temperature correction circuit 17 makes a YES determination in step 32, proceeds to step 33, sets the set value T to the timer, and then sets the timer value T to 0.
(step 34), and subtracts 1 from the timer value T (step 35).
The value of a is rewritten with the intake temperature 1 when the engine is stopped in the static memory Tm (step 36), and this register Ta
The temperature of the intake air in the air is output (step 37), and the process returns to step 34, and the route from steps 34 to 37 is repeated.

Then, when the timer value becomes 0, in step 34 above, Y
It is determined as ES and the process proceeds to step 38, where the register T is
In step 39, the value in the static memory Tm is rewritten with the value in a, and the A/D conversion output of the intake air temperature sensor 8 is newly read and stored in the register Ta.
), output the intake air temperature in the register Ta, and step 3
Return to 4.

Further, if the intake air temperature difference (Ta-Tm) is smaller than the setting 1thC, the intake air temperature correction circuit 17
If the answer is No, the process proceeds through steps 38, 39 and 37, and in this case as well, the value in the static memory Tm is rewritten with the value in the register Ta, and the newly read intake air temperature in the register Ta is output as is.

In the device of this embodiment as described above, if the intake air temperature at the time of engine startup is higher than the intake air temperature at engine stop and there is a risk of a detection delay in the intake air temperature sensor, the intake air temperature is stopped for a predetermined period of time. Instead of the intake temperature sensor output when the engine is stopped, the intake temperature correction for the fuel injection amount is performed based on the intake air temperature sensor output when the engine is stopped, which is a constant value. The injection amount does not decrease, and as a result, the air-fuel ratio of the air-fuel mixture is prevented from becoming overly lean, and a decrease in engine output and occurrence of engine stalling can be prevented.

Incidentally, in the above embodiment, the intake air correction of the fuel injection amount is canceled at the time of starting when the intake air temperature is large compared to the intake air temperature when the engine is stopped, but the present invention detects the time at the time of starting when the engine cooling water temperature is high and adjusts the fuel injection amount. The intake correction of the injection amount may be canceled. FIG. 6 shows the calculation of the intake temperature correction circuit 17 in another embodiment of the present invention, in which the intake temperature correction according to the output of the intake temperature sensor is canceled at the time of starting when the engine coolant temperature is high (at the time of m start excitation). The flow of processing is shown.

Next, using FIG. 6, the intake temperature correction circuit 17 in this device
The arithmetic processing operation will be explained. Intake Temperature Correction 3 When the ignition signal is applied to the circuit 17, the intake temperature correction circuit 17 first determines whether or not the engine has started (step 30), and if the engine has started, it determines YES in step 30 above. The process advances to step 40, where the output of the water temperature sensor (see broken line 7 in Fig. 2-3) is read and stored in the register Tw.
Based on the determination of whether the value of is greater than or equal to the set value C, it is determined whether or not it is time for a warm start of the engine (step 41).

When the engine is warmly started, the intake temperature correction circuit 17
The determination in step 41 is YES and the process proceeds to step 42, where the timer is set to a set value T, and then it is determined whether the timer value is 0 or not (step 43), and the timer value T is changed to 1. step 44), and then read the A/D conversion output of the outside temperature sensor (see broken line 11 in Figures 2 and 3) and store it in register TO (step 45), and then subtract the value of this register To and the above register. Find an appropriate value from the value in Ta and store it in register Ta (step 46), and output the value in register Ta as the intake air temperature sensor output value (step 48).
), the process returns to step 43 and repeats the above operation. Here, the above-mentioned appropriate value is determined, for example, from the stored contents of both registers To and Tw (Tw-To) using the characteristics shown in FIG. 7, that is, the outside temperature is corrected by the water temperature. That's fine.

When the value of the above-mentioned timer reaches O, the intake temperature correction circuit 1
7 makes a YES determination in step 43 and proceeds to step 47, where the A/D conversion output of the intake temperature sensor 8 is read and stored in register Ta, and proceeds to step 48, where the intake temperature sensor output in register Ta is read. Output.

Note that in the above two embodiments, the specific operating conditions in which the intake air temperature correction of the fuel injection amount should be canceled are detected as the starting time when the difference in intake air temperature from when the engine is stopped is large, or the starting time when the engine cooling water temperature is high. However, this specific operating state may be simply at the time of starting or during acceleration; in any case, an operating state in which the intake air temperature corresponding to the output of the intake air temperature sensor is higher than the actual intake air temperature must be detected. Ba5 Good.

Further, in the above embodiment, a fuel injection device for an engine has been described, but the present invention can of course be similarly applied to a carburetor for an engine. Furthermore, the air flow sensor may be of a Karman vortex type or a Hoehn type instead of a speed density type.

Furthermore, in the above two embodiments, instead of the intake temperature sensor output at that time in a specific operating range, the intake temperature sensor output value when the engine is stopped or the outside temperature corrected by the water temperature is used to correct the intake temperature of the fuel injection amount. I tried to do it, but
The intake temperature correction of the fuel injection amount in this specific operating range may be performed using the intake air temperature sensor output value of another operating range, the outside temperature, or a fixed value instead of the intake air temperature sensor at that time. The amount of intake temperature correction may not be performed at all, that is, it may be simply canceled.

〔Effect of the invention〕

As described above, according to the present invention, there is provided an engine fuel supply system in which an intake temperature sensor is disposed in the intake passage of the engine, and the intake temperature is corrected for the fuel supply amount according to the output of the sensor. A specific operating region in which the output of the temperature sensor shows a value higher than the actual intake air temperature is detected, and the above-mentioned intake temperature correction is canceled in the specific operating region, so that the intake temperature correction of the fuel supply amount is not overcontrolled. This has the effect of preventing the air-fuel mixture from becoming overly lean without reducing the amount of fuel, thereby preventing a drop in engine output and engine stalling.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the present invention, FIG. 2 is a schematic configuration diagram of an engine fuel supply system according to an embodiment of the present invention,
FIG. 3 is a detailed configuration diagram of the above device, FIG. 4 is a diagram showing the input/output characteristics of the function generation circuit 19 in the above device, and FIG. 5 is a flowchart 1 of the calculation process of the intake temperature correction circuit 17 in the above device. FIG. 6 is a diagram showing a flowchart 1 of the calculation process of the intake temperature correction circuit 17 in another embodiment of the present invention, and FIG. 7 is a diagram for explaining the operation of the intake temperature correction circuit 17. This is a diagram. 7 1...Engine, 8...Intake temperature sensor, 14...
Basic fuel injection pulse generation means (fuel supply amount adjustment device),
17... Intake temperature correction circuit (specific operating state detection means. Release means), 19... Function generation circuit (correction means), z
O... Arithmetic circuit (correction means). Patent applicant Toyo Kogyo Co., Ltd. agent Patent attorney Ken Hayase - 8 Figure 1 C Time - Figure 2

Claims (1)

[Claims] (11) A fuel supply amount adjustment device that adjusts the amount of fuel supplied to the engine; an intake air temperature sensor that is disposed in the intake passage of the engine to detect the intake air temperature; a correction means for correcting and controlling the fuel supply amount adjustment device so that the fuel supply amount is reduced; and a specific driving state detection means for detecting an operating state in which the intake air temperature corresponding to the output of the intake air temperature sensor is higher than the actual intake air temperature. and,
A fuel supply device for an engine, comprising a canceling means for canceling the correction control in response to a detection output of the specific driving state detecting means.