JPS60153443A - Fuel feed device for engine - Google Patents

Abstract

PURPOSE:To prevent an air-fuel mixture from coming into being overlean, by controlling a degree of suction temperature compensation to a fundamental fuel injection feed quantity at a time when detecting a specified operating region where a variation in a suction temperature sensor is more than the setting value. CONSTITUTION:A suction temperature compensating circuit 17 judges an engine start when an ignition switch 9 is turned on and an A/D conversion output N out of an engine speed sensor 10 becomes more than the specified value, then stores each A/D conversion output out of a suction temperature sensor 8 and an outside temperature sensor 11 into each of registers Ta and To at a specified time interval, and calculates a variation in an output difference between both sensors 10 and 11. And, when the variation is larger than the setting value, it outputs the suction temperature sensor output Ta in time of the engine stop stored in memory, and compensates a fundamental fuel feed quantity from a map 4 at an operation circuit 20 by way of a D/A converter 18 and a function generator 19. Likewise, when the variation is smaller than the setting value, at that point, it outputs the read suction temperature sensor output Ta as it is.

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, with conventional fuel supply systems that compensate for the intake air temperature, engine output may decrease during warm starts, acceleration, etc.
Engine stalls sometimes occurred.

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 Fig. 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, and on the other hand, 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 this 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 this state, and the intake temperature sensor itself, which is in contact with this high-temperature intake air, also becomes high temperature. When the engine is started in this condition, that is, warm-started, 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, there is a detection delay in the sensor, and the sensor outputs an output corresponding to a temperature higher than the actual intake air temperature a. This will occur. 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 overcontrol 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 engine may slow down or stall. That is, a sudden increase in the amount of intake air and a delay in detection by the intake air temperature sensor at that time cause a decrease in engine output and engine stalling.

[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]

By the way, if we consider the intake air temperature sensor output shown in Figure 1 in more detail, we can see that when the rate of change in the sensor output is large, the air-fuel ratio of the air-fuel mixture becomes over-lean, causing a drop in engine output and engine stalling. I understand.

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. A specific operating range in which the air-fuel ratio is equal to or higher than a set value is detected, and the intake temperature correction is limited in the specific operating range, thereby preventing the air-fuel ratio of the air-fuel mixture from becoming over-lean.

〔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, l 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, 10 is a rotation speed sensor, 11 is an outside temperature sensor, and 12 is a control circuit that receives the outputs of the above-mentioned sensors 6.8 to 11 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 converts both the power of the rotation speed sensor +10 and the negative pressure sensor 6 into A/D, 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 and 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 converts each output of the intake temperature sensor 81, rotation speed sensor 10, and outside temperature sensor 11 into A/D;
17 receives the A/D conversion output of each sensor 8, 10.11 and the output of the ignition switch 9, and when the rate of change of the temperature difference between the intake air temperature and the outside air temperature is less than a set value, The A/D conversion output of the intake temperature sensor 8 when the engine is stopped is output as is, and when the rate of change of the temperature difference is greater than or equal to the set value, the A/D conversion output of the intake air temperature sensor 8 when the engine is stopped is output instead of the A/D conversion output of the intake air temperature sensor 8 at that time. An intake temperature correction circuit consisting of a CPU that outputs a D-converted output, 18 a D/A converter that converts the output of the intake temperature correction circuit 17 into D/A, and 19 the D/A converted intake temperature sensor output. A function generating circuit 20 outputs a correction coefficient that becomes smaller as the intake air temperature increases as shown in FIG. An arithmetic circuit 21 for performing multiplication correction is an injector drive circuit that drives the fuel injection valve 3 according to the output of the arithmetic circuit 20.

In the above configuration, the basic fuel injection pulse generation circuit 14 serves as a fuel supply amount adjustment device that adjusts the amount of fuel supplied to the engine, and the function generation circuit 19 and calculation circuit 20 function as an intake temperature sensor. The intake temperature correction circuit 17 serves as a correction means for correcting and controlling the fuel supply amount adjustment device so that the fuel supply amount decreases as the intake temperature rises based on the output of the intake temperature sensor. specific operating state detection means for detecting an operating state that exceeds a value;
and a limiting means for limiting the above-mentioned correction control in response to the detection output of the specific driving state detecting means.

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 rotation speed sensor 0 measures the engine speed. The outside temperature sensor 1 detects the temperature of the outside air, and the re-outputs of the negative pressure sensor 6 and rotation speed sensor 0 are A/D converted by the A/D converter 13, and then a basic fuel injection pulse is generated. The signal is input to the 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, each output of the intake temperature sensor 82, rotation speed sensor 0, and outside temperature sensor 1 is A/D converted by the A/D converter 16, and then applied to the intake temperature correction circuit 17. When the ignition signal from the ignition switch 9 is input,
The intake temperature correction circuit 17 determines whether the rate of change of the difference between the re-outputs of the intake temperature sensor 8 and the outside temperature sensor 1 is greater than a set value.

If the rate of change of the difference in the re-output is smaller than the set value, the intake temperature correction circuit 17 outputs the A/D conversion output of the intake temperature sensor 8 as it is, and the D/A converter 18 outputs the A/D conversion output. After conversion, it is input to the function generation circuit 19, and the circuit 1
9 is a correction coefficient corresponding to the intake air temperature sensor output (see Figure 4)
and add it to the arithmetic circuit 20. Then, the arithmetic circuit 20 corrects the pulse width of the basic fuel injection pulse using the correction coefficient, and the injection valve drive circuit 21 applies a fuel injection pulse with the corrected pulse width to the fuel injection valve 3, thereby injecting fuel. The amount is corrected and controlled to be smaller as the intake temperature is higher, depending on the output of the intake air temperature sensor.

On the other hand, if the rate of change of the difference between the re-outputs of the intake temperature sensor 8 and the outside temperature sensor 11 is larger than the set value, the intake temperature correction circuit 17 replaces the output of the intake temperature sensor 8 at that time with a constant value. Outputs the A/D conversion output of the intake air temperature sensor 8 when the engine is stopped, and the function generating circuit 19 outputs a correction coefficient having a value corresponding to the output of the intake air temperature sensor when the engine is stopped,
As a result, the fuel injection amount is corrected for the intake air temperature based on the intake air temperature when the engine is stopped. In this way, when the rate of change in the difference between the intake air temperature sensor output and the outside air temperature sensor output is large, the correction control of the fuel injection amount is restricted.

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 intake temperature correction circuit 17 first reads the A/D conversion output N of the rotation speed sensor 10 and determines whether it is above a set value, for example 500 rpm. From the determination whether or not the engine has started, it is determined whether or not the engine has started (step 30), and the step 30 described above is performed until the engine starts.
When the engine starts, press Y at step 30 above.
It is determined as ES and the process proceeds to the next step, reads the A/D conversion outputs of the intake air temperature sensor 8 and the outside air temperature sensor 11, and stores them in registers Ta and To (step 31.32). Memory the value of Tam
, Tom (step 33), read the A/D conversion outputs of the intake air temperature sensor 8 and the outside air temperature sensor 11 again and store them in registers 1, Ta and To (step 34 and 35), then register Step 36: Calculate the rate of change of the difference between the outputs of both sensors using the formula -(Tam-rom)-(Ta-To) from the values of Ta, To and memories Tam and Tom.
), and further stores the memory Ta using the values of registers Ta and To.
The values of m and Tom are updated (step 37), and it is determined whether the rate of change K is greater than the set value C (step 38).

If the rate of change K is greater than the set value C, the intake temperature correction circuit 17 makes a YES determination in step 38 and proceeds to step 39, where the engine stop temperature stored in the static memory Tm, which will be described later, is The value of the register Ta is updated with the intake air temperature sensor output, the intake air temperature in the register Ta is output (step 40), and the process returns to step 34, and the route from steps 34 to 40 is repeated.

If the rate of change K is smaller than the set value C, the intake temperature correction circuit 17 makes a negative determination in step 38 and proceeds to step 41, where the intake air temperature correction circuit 17 makes a negative determination in step 38 and proceeds to step 41. After storing the air temperature sensor output in the static memory Tm, in step 40, the intake air temperature in the register Ta is output.

In the device of this embodiment as described above, when the difference between the intake temperature sensor output and the outside temperature sensor output has a large rate of change, the intake temperature sensor output at that time is replaced with the intake temperature sensor output when the engine is stopped, which is a constant value. Since the intake temperature of the fuel injection amount is corrected based on the output, the correction control of the fuel injection amount will not become overcontrolled and the injection amount will become smaller.
As a result, it is possible to prevent the air-fuel ratio of the air-fuel mixture from becoming overly lean, thereby preventing a decrease in engine output and occurrence of engine stalling.

By the way, in the above embodiment, the intake temperature correction of the fuel injection amount is performed using the intake temperature sensor output when the engine is stopped in a specific operating state where the rate of change of the difference between the intake temperature sensor output and the outside temperature sensor output is large. In this particular operating state, the intake air temperature correction for the fuel injection amount may be performed using the outside air temperature corrected by the engine cooling water temperature.

FIG. 6 shows the outside temperature T in the above-mentioned specific operating state.

The flowchart of the calculation process of the intake temperature correction circuit 17 in another embodiment of the present invention is shown in which the intake temperature correction circuit 17 corrects the fuel injection amount using the water temperature Tw. In the figures, the same symbols as in Fig. 5 indicate the same things as in the same figure,
42 is the output To of the outside temperature sensor lI and the water temperature sensor (second
．． For example, from the difference between the output Tw of
This is a step of determining an appropriate value Ta of the intake air temperature sensor output using the characteristics shown in the figure, that is, storing the value obtained by correcting the outside air temperature To with the water temperature Tw in the register Ta as the intake air temperature sensor output.

Since the operation of the device of this embodiment can be easily understood,
A detailed explanation thereof will be omitted.

Note that in the above two embodiments, the intake temperature correction of the fuel injection amount based on the intake temperature sensor output at that time is canceled in a specific operating range, and instead, the intake temperature sensor output or outside temperature when the engine is stopped is corrected using water temperature. However, the intake temperature correction of the fuel injection amount in this specific operating range is performed using the intake air temperature sensor output value, outside air temperature, or fixed value in other operating ranges. Alternatively, the intake temperature correction for the fuel injection amount may not be performed at all, or instead of canceling the intake temperature correction for the fuel injection amount, the intake air temperature sensor output may be corrected and the intake air temperature correction may be performed after the correction. The intake temperature correction may be performed based on the output of the intake air temperature sensor, and in any case, the intake air temperature correction may be limited in this specific operating region.

In addition, in the above two embodiments, a driving state in which the rate of change of the difference between the intake air temperature sensor output and the outside air temperature sensor output is large is detected as a specific driving state in which the intake air temperature correction of the fuel injection amount should be restricted. As the specific driving state, a driving state in which the rate of change in the intake air temperature sensor output is large may be detected.

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. Also, the air flow sensor may be of force 5 Le Mans vortex type or vane type instead of speed density type.

(Effects of the Invention) As described above, according to the present invention, an intake air temperature sensor is disposed in the intake passage of the engine, and the fuel supply amount is corrected for the intake air temperature based on the output of the sensor. The device detects a specific operating region in which the rate of change in the intake air temperature sensor output is large, and limits the above-mentioned intake air temperature correction in that specific operating area, so that the intake air temperature correction of the fuel supply amount becomes overcontrolled and the fuel is reduced. The amount does not decrease, and as a result, the air-fuel mixture is prevented from becoming overly lean, which has the effect of preventing a decrease in engine output and the occurrence of engine stalling.

[Brief explanation of the drawing]

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 generating circuit 19 in the above device, and FIG. FIG. 6 is a flowchart of the arithmetic processing 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. 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. Limiting means), 19... Function generation circuit (correction means), 2
0... Arithmetic circuit (correction means). Patent applicant: Toyo Kogyo Co., Ltd. Representative Patent attorney Ken Hayase - 7

Claims (1)

[Claims] (1) A fuel supply amount adjustment device that adjusts the amount of fuel supplied to the engine, an intake air temperature sensor that is installed in the intake passage of the engine and that detects the intake air salinity, and an intake air temperature that is determined based on the output of the intake air temperature sensor. a correction means for correcting and controlling the fuel supply amount adjusting device so that the fuel supply amount decreases as the fuel supply amount increases; a specific driving state detecting means for detecting a driving state in which the rate of change in the output of the intake air temperature sensor is equal to or higher than a set value; 1. A fuel supply device for an engine, comprising: limiting means for receiving the detection output of the specific driving state detecting means and limiting the correction control.