JPH08189391A - Fuel feed device for internal combustion engine - Google Patents

Abstract

PURPOSE: To provide an excellent responsiveness by injecting and feeding fuel at a regulated pressure with a specified pressure difference between the pressure and atmospheric pressure and, based on an intake air amount and rotational speed of an engine, opening a valve for an injection time proportionally to a basic fuel injection amount according to a cylinder intake air amount so as to eliminate both negative intake pressure and pressure sensor. CONSTITUTION: Fuel sucked by a fuel pump 5 in a fuel tank 4 is regulated by a pressure regulator to a specified pressure, and fed to a fuel injection nozzle 3. When a difference between atmospheric pressure as a reference pressure and a fuel pressure becomes over a specified limit, a return path 1 to return fuel to the fuel tank is opened to regulate the pressure difference at a constant. Also a control unit 9 sets the valve opening time (pulse width) of the fuel injection nozzle 3 based on the detection signals from sensors 12 and 13. Then a pressure difference correction coefficient obtained by an engine speed and a throttle valve opening is set so that the amount of increase is corrected to lower level according to an sucked air negative pressure produced for each operating condition. Thus an injection time can be corrected responsively as well as in high altitude.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply device for an internal combustion engine, and more particularly to a fuel supply device having a structure in which the fuel injection pressure is adjusted by a pressure regulator that keeps the differential pressure with respect to atmospheric pressure constant.

[0002]

2. Description of the Related Art Conventionally, as an electronically controlled fuel injection device for an internal combustion engine, a pressure regulator is used to control the pressure of the fuel supplied to the fuel injection valve so that the injection amount per unit time in the electromagnetic fuel injection valve becomes constant. Adjusted by
There is known a structure in which the fuel injected and supplied to the engine is metered by the pulse width of the injection pulse signal given to the fuel injection valve (valve opening control time of the injection valve).

The pressure regulator adjusts the amount of fuel returned to the fuel tank via the return passage so that the pressure difference between the fuel pressure and the pressure in the injection hole of the injection valve (boost pressure of the engine) is kept constant. In general, it is installed in the fuel pipe near the fuel injection valve. By the way, when the above-mentioned pressure regulator is arranged in the vicinity of the engine, the fuel returned to the fuel tank for adjusting the fuel pressure in the pressure regulator absorbs the heat of the engine and the temperature rise in the fuel tank is prevented. Cause.

Therefore, a system in which a pressure regulator is provided in the fuel tank and the fuel is circulated in the fuel tank so that the fuel returned from the pressure regulator does not cause a temperature rise in the fuel tank. Is being developed. By the way, even in the structure in which the pressure regulator is internally provided in the fuel tank as described above, in order to adjust the fuel pressure to a desired value,
It is necessary to introduce the pressure of the injection hole of the injection valve (boost pressure of the engine) as the reference pressure of the pressure regulator,
It is necessary to install negative pressure piping for a long time to guide the boost pressure of the engine to the pressure regulator in the tank.

That is, if the pressure regulator is installed in the fuel tank, the temperature rise in the fuel tank can be prevented, and a long return passage for returning the fuel from the pressure regulator into the tank is not necessary, but instead,
There is no improvement in the piping configuration, such as the need for long piping for introducing the boost pressure as the reference pressure, which leads to poor responsiveness.

Therefore, the negative pressure pipe is abolished and the pressure adjusting chamber of the pressure regulator is opened to the atmosphere to set the reference pressure to atmospheric pressure. In this case, the fuel injection pressure becomes a constant differential pressure with reference to atmospheric pressure. Since the differential pressure to the injection hole is not constant because it is adjusted to, the fuel pressure and the intake negative pressure (boost pressure) are measured using a pressure sensor, and the injection pulse width (injection time) is measured based on the differential pressure. There is a method in which the correction is made (see Japanese Patent Laid-Open No. 64-73133).

[0007]

However, the method using the pressure sensor as described above is costly. The present invention has been made in view of the above problems,
An object of the present invention is to provide a fuel supply device for an internal combustion engine, which is capable of correcting the fuel injection time without using a pressure sensor in the fuel injection in which the pressure difference with respect to the atmospheric pressure is constant, and reduces the cost.

[0008]

Therefore, in the fuel supply system for an internal combustion engine according to the invention of claim 1, as shown in FIG. 1, the supply pressure is adjusted by a pressure regulator for adjusting the differential pressure from the atmospheric pressure to a constant value. Of the intake air flow rate of the engine in a fuel supply device of an internal combustion engine configured to supply the fuel to the fuel injection valve, and to supply the fuel measured by the opening time of the fuel injection valve to the engine. Detection means, engine rotation speed detection means for detecting the engine rotation speed, throttle valve opening degree detection means for detecting the opening degree of a throttle valve interposed in the intake system of the engine, and the detected intake air flow rate Basic fuel injection time setting means for setting a basic fuel injection time corresponding to the basic fuel injection amount based on the engine rotation speed, and based on the detected engine rotation speed and throttle valve opening. And a differential pressure correction coefficient setting means for setting a correction coefficient corresponding to the estimated differential pressure for each operating state, and a basic fuel injection time set for each operating state is corrected by the set differential pressure correction coefficient. Fuel injection time setting means for setting the fuel injection time according to the value, and fuel injection amount control for controlling the fuel injection amount by opening the fuel injection valve for the fuel injection time set by the fuel injection time setting means. Means and are included.

[0009]

According to the first aspect of the invention, the fuel is injected and supplied at a pressure adjusted so as to have a constant differential pressure with respect to the atmospheric pressure, and the fuel injection time is corrected as follows. First, the basic fuel injection time setting means sets the basic fuel injection time based on the intake air flow rate and the rotational speed of the engine, for example, in proportion to the basic fuel injection amount corresponding to the cylinder intake air amount. .

The basic fuel injection time corresponds to the basic fuel injection amount when the fuel supply pressure (the differential pressure across the injection hole portion) is constant (P ₀ ), but it is actually the injection hole. Although the portion is at the intake negative pressure, the fuel supply pressure adjusted by the pressure regulator is adjusted so as to have a constant differential pressure with respect to the atmospheric pressure, and therefore the atmospheric pressure is higher than the constant pressure P _0. Therefore, the fuel is injected at a higher fuel pressure by the pressure difference between the suction negative pressure of the injection hole and the intake negative pressure.

Therefore, in response to the intake negative pressure in the injection hole portion that occurs for each operating state determined by the throttle opening and the engine rotation speed, the fuel pressure is increased by the differential pressure of the fuel pressure that is increased with respect to the atmospheric pressure. By setting a differential pressure correction coefficient to reduce the fuel injection amount to be corrected, and opening the fuel injection valve for the fuel injection time for which the basic fuel injection time is corrected by the differential pressure correction coefficient to perform fuel injection, It is possible to adjust the fuel injection amount.

With this structure, the intake negative pressure piping is not required and the pressure sensor is not required, so that the cost can be reduced and the response is excellent. In addition, since the air density decreases even when the atmospheric pressure decreases when traveling at high altitudes, the throttle valve opening is increased for the same required output, so the value reduced as the differential pressure correction coefficient. Is set, the high altitude correction is automatically performed.

According to the second aspect of the present invention, the pressure regulator is provided in the fuel tank, so that the entire apparatus is downsized.

[0014]

Embodiments of the present invention will be described below. In FIG. 2 showing an embodiment, an intake manifold 2 of an internal combustion engine 1
A fuel injection valve 3 is provided in each of the branch portions.
The fuel injection valve 3 is an electromagnetic fuel injection valve that is opened by lifting a valve body biased in a valve closing direction by a magnetic attraction force of an electromagnetic coil.

The fuel sucked by a fuel pump 5 provided in a fuel tank 4 is supplied to the fuel injection valve 3 after being adjusted to a predetermined pressure by a pressure regulator 6 also provided in the fuel tank 4. It has become so. In the pressure regulator 6, the reference pressure chamber 6a separated from the fuel chamber by the diaphragm is opened to the atmospheric pressure outside the fuel tank 4, and the atmospheric pressure and the fuel pressure as the reference pressure are set. When the pressure difference becomes equal to or higher than a certain value, the return passage 7 for returning the fuel into the fuel tank 4 is opened, and the pressure difference is adjusted so as to be kept constant.

The fuel whose pressure has been adjusted by the pressure regulator 6 is supplied to the fuel injection valve 3 via a fuel supply pipe 8. According to the above fuel supply system,
The pressure regulator 6 adjusts the pressure by adjusting the amount of fuel returned to the fuel tank 4, but the fuel returned to the fuel tank 4 is the fuel immediately after being discharged from the fuel pump 5, and is the heat of the engine 1. Since the unaffected fuel is returned to the fuel tank 4, the temperature of the fuel tank 4 does not rise due to the fuel returned from the pressure regulator 6.

Further, since the pressure regulator 6 uses the atmospheric pressure as the reference pressure, it does not require a long pipe as in the case where the reference pressure is the boost pressure of the engine (pressure in the injection hole of the injection valve), and there is no need for piping space. Can be saved and the cost can be reduced. The energization of the electromagnetic coil of the fuel injection valve 3 is controlled by the injection pulse signal sent from the control unit 9, and the fuel is metered and supplied according to the pulse width (valve opening control time) of the injection pulse signal. It

In the intake system of the engine, an air flow meter 10 for detecting the intake air flow rate Q, a throttle valve 11 for controlling the intake air flow rate, and a throttle sensor mounted on the throttle valve 11 for detecting the throttle valve opening TVO. A crank angle sensor 13 for detecting the engine rotation speed Ne is provided on the distributor or the camshaft.

The control unit 9 having a built-in microcomputer sets the pulse width of the fuel injection valve (valve opening time of the fuel injection valve) according to the flow chart shown in FIG. 3 based on the detection signals from the sensors. To explain based on the drawings, a signal of the intake air flow rate Q from the air flow meter 10 input in step (denoted as S in the figure. The same applies hereinafter) and the engine rotation speed Ne from the crank angle sensor 13 input in step 2 will be described. In step 3, the basic fuel injection pulse width Tp (← K × Q / Ne: K is a constant) is calculated on the basis of the above signal.

In step 4, a signal of the throttle valve opening TVO is input from the throttle sensor 12. Step 5
Then, the engine speed Ne and the throttle valve opening TVO
The differential pressure correction coefficient KVC is retrieved from the map table based on The differential pressure correction coefficient KVC corresponds to the intake negative pressure in the injection hole portion generated for each operating state determined by the engine rotation speed Ne and the throttle valve opening TVO, and corresponds to the increase in the fuel injection pressure indicated by the hatched portion in FIG. The differential pressure correction coefficient is set so as to reduce the amount by a minute. Specifically, the pressure difference relative to the intake negative pressure P _B of the fuel supply pressure to be adjusted by the pressure regulator 6 when the intake negative pressure P _B of the injection hole of the fuel injection valve in FIG. As P _1, also the fuel supply When the constant differential pressure of the pressure with respect to the atmospheric pressure is P ₀ , the differential pressure correction coefficient KVC is set as KVC = P ₀ / P ₁ .

In step 6, the basic fuel injection pulse width Tp set in step 3 is set to the differential pressure correction coefficient K.
It is corrected to a value Tp 'multiplied by VC. In step 7, the correction coefficient COEF for correcting the corrected basic fuel injection pulse width Tp at the water temperature, the transient state, etc., and the air-fuel ratio of the intake air-fuel mixture detected via the oxygen concentration in the exhaust gas, etc. The air-fuel ratio feedback correction coefficient α, which is set for the fuel injection valve operation delay Ts caused by the battery voltage,
And the like, and the final fuel injection pulse width Ti is calculated by the following equation.

Ti = Tp '× COEF × α + Ts If the fuel injection valve 3 is controlled to open based on the injection pulse width Ti set by the above equation, the required fuel amount indicated by the injection pulse width Ti is changed to the pressure regulator 6 It is possible to inject and supply under the adjusted pressure of. Step 8
Then, set the injection pulse width Tis in the register,
When a predetermined injection timing is reached, an injection pulse signal having the injection pulse width Ti is output to the fuel injection valve 3 to perform fuel injection.

With this configuration, the pressure regulator 6 is housed in the fuel tank 4, piping for guiding the intake negative pressure in the injection hole of the fuel injection valve to the pressure regulator is not necessary, and the intake negative pressure is detected. No pressure sensor is required, and the cost can be reduced. In the present invention, when the differential pressure correction coefficient is set, the throttle valve opening TVO is used as a value representing the engine load, and therefore the basic fuel injection pulse width Tp obtained in step 3 is used (with the engine rotation speed Ne). Compared with the case, there are the following advantages.

For example, when traveling at high altitudes, the air density decreases, but when the differential pressure correction coefficient is set with reference to normal lowland traveling, the same required output and therefore the same Tp are set for the conditions. At the time of traveling at high altitude, the atmospheric pressure is lower than that at low altitude, so if the intake negative pressure is the same, the fuel supply pressure for the intake negative pressure of the injection hole of the fuel injection valve will decrease. Actually, since the throttle valve opening degree is increased to compensate for the decrease in the air density due to the decrease in the atmospheric pressure due to the decrease in the atmospheric pressure, the present invention sets the differential pressure correction coefficient to be decreased accordingly. As a result, high altitude correction is automatically performed.

However, if the differential pressure correction coefficient is set using the basic fuel injection pulse width Tp under the same conditions, the differential pressure correction coefficient for Tp that is the same as during lowland running will be set even during highland running. Therefore, the correction for the decrease in the air density is not performed, and the fuel injection amount becomes excessive. Further, even in the case where only the intake pressure is detected and the differential pressure correction coefficient is set, the air density correction at the time of traveling at high altitude cannot be performed. Therefore, in order to improve the accuracy, a pressure sensor for detecting the atmospheric pressure is separately provided. Will be needed. In this regard, the present invention
It is possible to perform correction including high-altitude correction with high responsiveness without using two pressure sensors and only by software processing.

[0026]

As described above, according to the fuel supply device for an internal combustion engine according to the invention of claim 1, the fuel pressure is adjusted while keeping the differential pressure with respect to the atmospheric pressure constant, thereby eliminating the need for a pipe for introducing the intake negative pressure. On the other hand, the fuel injection time can be corrected with good responsiveness including the altitude correction by setting the differential pressure correction coefficient based on the throttle valve opening and the engine speed without using a pressure sensor. Therefore, the cost can be significantly reduced.

According to the second aspect of the invention, the pressure regulator is provided in the fuel tank, so that the entire apparatus can be significantly downsized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of the invention of claim 1.

FIG. 2 is a system schematic diagram showing one embodiment of the present invention.

FIG. 3 is a flowchart showing correction control of an injection pulse width.

FIG. 4 is a diagram showing a relationship between each pressure and a fuel injection pressure.

[Explanation of symbols]

 1 Internal Combustion Engine 2 Intake Manifold 3 Fuel Injection Valve 4 Fuel Tank 6 Pressure Regulator 9 Control Unit 10 Air Flow Meter 11 Throttle Valve 12 Throttle Sensor 13 Crank Angle Sensor

Claims (2)

[Claims] 1. A fuel whose supply pressure has been adjusted by a pressure regulator that adjusts a differential pressure from atmospheric pressure to a fuel injection valve, and the fuel which is measured by the opening time of the fuel injection valve is supplied to an engine. In a fuel supply device for an internal combustion engine configured to supply, an intake air flow rate detection means for detecting an intake air flow rate of the engine, an engine rotation speed detection means for detecting an engine rotation speed, and a throttle provided in an intake system of the engine. Throttle valve opening degree detecting means for detecting a valve opening degree, and basic fuel injection time setting means for setting a basic fuel injection time corresponding to a basic fuel injection amount based on the detected intake air flow rate and engine speed A differential pressure correction coefficient setting means for setting a correction coefficient according to the differential pressure estimated based on the detected engine speed and throttle valve opening for each operating state, The fuel injection time setting means for setting the fuel injection time according to the value obtained by correcting the basic fuel injection time set for each operation state with the set differential pressure correction coefficient, and the fuel injection time setting means for setting the fuel injection time. A fuel supply device for an internal combustion engine, comprising: a fuel injection amount control means for controlling a fuel injection amount by opening a fuel injection valve for a fuel injection time. 2. A fuel supply apparatus for an internal combustion engine, wherein the pressure regulator is provided in a fuel tank, and a reference pressure chamber for pressure adjustment is opened to atmospheric pressure outside the fuel tank.