JPH08193551A - Fuel supply system of internal combustion engine - Google Patents

Abstract

PURPOSE: To enable it to detect any mixture of gas accurately by calculating a variation of fuel pressure in time of opening or closing a fuel injection valve, and on the basis of the variation, judging of whether there is any gas in a fuel supply route or not. CONSTITUTION: An electronic control circuit 17 finds a basic injection pulse out of intake air quantity and engine speed, calculating a request injection pulse, and it also compensates this request injection pulse according to the actual fuel pressure, thereby calculating the corrected injection pulse. In this case, when gas is not mixed in a fuel supply route 5, the actual fuel pressure goes down in a moment in time of injection starting, and it instantaneously goes up in time of injection ending, but when the gas is mixed in the fuel supply route 5, it is almost constant or slightly varied, therefore first of all, pressure of fuel in the fuel supply route 5 is detected by a fuel pressure detecting means. Then, at the time of opening or closing a fuel injection valve 4, a variation of the pressure detected by the fuel pressure detecting means is calculated, and on the basis of the variation, a fact of whether there is the gas in this supply route 5 or not is judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply system for an internal combustion engine which supplies fuel to each cylinder of the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as a device of this type, a fuel supply means for supplying fuel to a fuel injection valve through a predetermined fuel supply passage, and a fuel pressure detection for detecting the pressure of the fuel in the fuel supply passage. Means for opening and closing the fuel injection valve in synchronization with the rotation of the internal combustion engine, and fuel injection means for injecting the fuel supplied through the fuel supply passage into each cylinder of the internal combustion engine,
Those equipped with are known. Further, in this type of device, for example, as described in JP-A-6-50230, the pressure of fuel in the fuel supply passage is detected by a pressure sensor (fuel pressure detection means), and the output signal of this pressure sensor is output. It is also considered that the pressure applied to the fuel pump (fuel supply means) is controlled based on this to control the pressure in the fuel supply passage to a predetermined value.

[0003]

However, there is a possibility that air will be mixed into the fuel supply passage during manufacturing or maintenance of the internal combustion engine. Further, if the internal combustion engine is operated under high load when the outside temperature is high, vapor (fuel vapor) may be generated from the fuel. In this way, if gas such as air or vapor is mixed in the fuel supply passage, these gases may also be injected from the fuel injection valve, and the air-fuel ratio may become lean.

Therefore, the present invention has been made for the purpose of providing a fuel supply device capable of satisfactorily detecting that gas is mixed in the fuel supply passage.

[0005]

In order to achieve the above object, the invention according to claim 1 supplies a fuel to a fuel injection valve through a predetermined fuel supply passage, as illustrated in FIG. Supply means, fuel pressure detecting means for detecting the pressure of the fuel in the fuel supply path, and opening and closing of the fuel injection valve in synchronization with the rotation of the internal combustion engine, and fuel supplied through the fuel supply path. A fuel injection device for injecting into each cylinder of the internal combustion engine, and a fuel supply device for an internal combustion engine, wherein the fuel pressure detection means is provided when the fuel injection valve is opened or closed by the fuel injection means. Pressure fluctuation calculating means for calculating the detected pressure fluctuation amount, and gas presence / absence judging means for judging whether or not gas exists in the fuel supply path based on the pressure fluctuation amount calculated by the pressure fluctuation calculating means. ,
The gist is a fuel supply device for an internal combustion engine, which is characterized by including the following.

According to a second aspect of the present invention, when the gas presence / absence determining means determines the presence of gas, the fuel supply means increases the fuel supply pressure. The fuel supply device of

According to a third aspect of the present invention, a plurality of the fuel injection valves are provided, and when the gas presence / absence determination means determines the presence of gas, the fuel injection means determines the number of fuel injection valves that are simultaneously opened. The fuel supply device for an internal combustion engine according to claim 1 is characterized in that the number is increased.

[0008]

In the invention according to claim 1 thus constructed, the fuel supply means supplies the fuel to the fuel injection valve through the predetermined fuel supply passage. The fuel injection means opens and closes the fuel injection valve in synchronization with the rotation of the internal combustion engine, and injects the fuel supplied through the fuel supply passage into each cylinder of the internal combustion engine. On the other hand, the fuel pressure detection means
The pressure of the fuel in the fuel supply passage is detected, and the pressure fluctuation calculation means calculates the fluctuation amount of the pressure detected by the fuel pressure detection means when the fuel injection valve is opened or closed.

Here, when the fuel injection valve is opened and fuel injection is started, the pressure of the fuel in the fuel supply passage drops instantaneously. Further, when the fuel injection valve is closed and the fuel injection is completed, the pressure of the fuel in the fuel supply passage instantaneously rises. The pressure fluctuation calculating means usually calculates the fluctuation amount of this pressure.

However, when gas is mixed in the fuel supply passage, the pressure fluctuation is buffered by the gas and becomes small.
Therefore, the gas presence / absence determining means determines whether or not gas is present in the fuel supply path based on the amount of pressure fluctuation calculated by the pressure fluctuation calculating means. Therefore, in the present invention, it is possible to satisfactorily detect that gas is mixed in the fuel supply path.

In the second aspect of the invention, when the gas presence / absence determining means determines the presence of gas, the fuel supply means increases the fuel supply pressure. Then, the pressure of the fuel in the fuel supply passage increases. Further, when the pressure of the fuel rises, the vapor is likely to be liquefied and the air is easily dissolved in the fuel. Then, gas such as vapor and air can be discharged together with the fuel earlier than the fuel injection valve.

Therefore, in the present invention, in addition to the effect of the invention described in claim 1, the effect that the gas existing in the fuel supply passage can be eliminated at an early stage is obtained. Therefore, the operating state of the internal combustion engine can be quickly returned to the normal state. In the invention according to claim 3, a plurality of the fuel injection valves are provided, and when the gas presence / absence determining means determines the presence of gas, the fuel injecting means increases the number of fuel injection valves that are simultaneously opened. When the number of fuel injection valves that are opened at the same time increases, the fuel pressure drops more rapidly when the valves are opened. Then, the gas in the fuel supply path is
The fuel is easily discharged through the fuel injection valve.

Therefore, in the present invention, in addition to the effect of the invention described in claim 1, the effect that the gas existing in the fuel supply passage can be eliminated at an early stage is obtained. Therefore, the operating state of the internal combustion engine can be quickly returned to the normal state.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a fuel supply system for an internal combustion engine of the first embodiment. As shown in FIG. 1, an intake passage 2 and an exhaust passage 3 are connected to an engine 1 as an internal combustion engine, and a fuel injection valve 4 is arranged in the intake passage 2. A fuel supply path 5 is connected to the fuel injection valve 4, and the fuel stored in the fuel tank 6 is supplied to the fuel supply path 5 with a fuel pump (FP) 7 as a fuel supply means.
Is supplied via Fuel filters 8 and 9 are provided upstream and downstream of the fuel pump 7 to filter the fuel supplied from the fuel tank 6. Also, the fuel pump 7
Is a well-known device that supplies fuel by rotation of a motor (not shown), and the fuel supply amount (corresponding to the supply pressure) changes according to the voltage Vfp applied to this motor.

Next, in the fuel supply passage 5, a differential pressure as fuel pressure detecting means for measuring the differential pressure between the fuel pressure in the fuel supply passage 5 and the intake pipe pressure (hereinafter referred to as fuel pressure). The sensor 12 is attached. The differential pressure sensor 12 is mounted downstream of the fuel filter 9 and at a position as close to the fuel injection valve 4 as possible. The differential pressure sensor 12
Is a known pressure sensor that is configured by using the atmospheric pressure (intake pipe pressure) in the intake passage 2 as a reference pressure instead of the vacuum in a normal pressure sensor that uses vacuum as a reference pressure.

On the other hand, in the intake passage 2 of the engine 1, an air flow meter 14 for detecting the intake air amount Q is arranged downstream of the air cleaner 13, and the air flow meter 1 is provided.
In the intake passage 2 downstream of 4 and upstream of the fuel injection valve 4, a throttle valve 15 that opens and closes in response to an operation of an accelerator (not shown) is provided.

DC- for applying a DC voltage to the fuel pump 7.
A control signal is input from the electronic control circuit 17 to the DC converter 16 and the fuel injection valve 4, and the electronic control circuit 17 controls the fuel supply amount by the fuel pump 7 and the fuel injection amount by the fuel injection valve 4. The control with the injection timing is executed. The DC-DC converter 16 is a well-known one in which the average output voltage changes according to a control signal instructed by the electronic control circuit 17, and the motor rotation speed of the fuel pump 7 is controlled by this. Further, instead of the DC-DC converter 16, a PWM type device (well-known) that controls the ON-OFF duty of the power source to change the average voltage may be used.

The electronic control circuit 17 includes the differential pressure sensor 12 and the air flow meter 14, the rotation sensor 19 for detecting the engine rotation speed N and the crank angle of the engine 1, and the cooling water temperature of the engine 1. Detection signals from various sensors such as a water temperature sensor 22 and an intake air temperature sensor 23 that detects the temperature of intake air taken into the intake passage 2 are input. Then, the electronic control circuit 17, based on the detection signals of these sensors, as described later, the fuel pump 7
And various control by the fuel injection valve 4 is performed.

On the other hand, the evaporated gas generated in the fuel tank 6 is adsorbed by the charcoal canister 32 through the passage 31. When the valve 33 is opened by the electronic control circuit 17, it is introduced into the intake passage 2 through the passages 34 and 35.
Further, the electronic control circuit 17 receives the voltage of a battery (not shown) and measures the voltage. Further, the electronic control circuit 17 also detects ON / OFF of a starter (not shown).

The electronic control circuit 17 for performing the above control includes a CPU 60 for executing various arithmetic processes, a ROM 61 for storing various control programs and maps, a RAM 62 for storing input data and temporary storage data, and an input / output interface (I / O interface). ) 63, 64 as main parts.

Next, the operation of the present apparatus thus constructed will be described. FIG. 2 shows a DC-applied to the fuel pump 7.
7 is a flowchart showing a fuel supply amount control process for controlling the fuel supply amount by adjusting the output average voltage of the DC converter 16. The electronic control circuit 17 repeatedly executes this process at regular intervals.

When the processing is started, the electronic control circuit 17
First, in step 102, a load signal corresponding to the load of the engine 1 is read. In this example, as the load signal, the engine speed N detected through the rotation sensor 19 and the intake air amount Q detected through the air flow meter 14 are used.
Are using. In addition to this, the intake pipe pressure or the throttle opening may be used as the load signal.

Next, at step 103, the differential pressure sensor 12
The actual fuel pressure (actual fuel pressure) Pf at that time is calculated based on the detection signal of. In the following step 105, the correction term Vfpci to be used later is calculated according to the load signal read in step 102. Here, the correction term Vfp
ci is calculated using a three-dimensional map as illustrated in FIG. 3, for example.

As shown in FIG. 3, in general, in this type of map, the larger N and the larger Q / N, the more Vfpc.
i is set to be large. This is because the change in the fuel injection amount is likely to be large under high rotation and high load conditions, and in order to follow it, the fuel supply amount from the fuel pump 7,
That is, it is necessary to change the applied voltage Vfp to the fuel pump 7 quickly.

Next, at step 106, the actual fuel pressure P
f is compared with the target fuel pressure Po. Then, the process proceeds to step 107, 108, or 109 depending on the size. The method of setting the target fuel pressure Po will be described in detail later. If it is determined in step 106 that Pf> Po,
The process proceeds to step 107 and Vfp = Vfp (i = 1)-
Vfpci (Vfp (i-1) is the previous value of Vfp) is used to decrease and correct the voltage Vfp applied to the fuel pump 7, and the process is temporarily terminated. When it is determined that Pf <Po in step 106, the process proceeds to step 108 and Vfp = V
Fuel pump 7 according to the formula fp (i-1) + Vfpci
The voltage Vfp applied to is corrected to be increased, and the process is temporarily terminated. When it is determined in step 106 that Pf = Po, the process proceeds to step 109, and the applied voltage Vfp to the fuel pump 7 is Vfp.
Is maintained at the same value as the previous calculated value, and the processing is temporarily terminated (Vfp = Vfp (i-1)).

FIG. 4 is a flow chart showing a fuel injection control process for outputting an injection pulse to drive the fuel injection valve 4 to open. The electronic control circuit 17 includes a rotation sensor 19
This processing is executed at every predetermined crank angle in synchronization with the detection signal of. When the process is started, first, in step 203, the basic injection pulse tp is calculated. This process is a well-known process for obtaining the basic injection pulse tp from the intake air amount Q obtained by the air flow meter 14 and the engine rotation speed N obtained by the rotation sensor 19. The basic injection pulse tp may be obtained from the intake pipe pressure and the engine rotation speed N, the throttle opening and the engine rotation speed N, and the like, as is well known.

At step 204, various correction values for correcting tp are calculated. These are all well-known items such as warm-up correction according to the output of the water temperature sensor 22, and in the following step 205, the total ftotal of the various correction values is calculated. In the following step 206, te = tp × ftot
The required injection pulse te is calculated by the equation al.

Subsequently, at step 215, the required injection pulse te is corrected according to the actual fuel pressure Pf calculated in the process of FIG. 2 to calculate the corrected injection pulse tpf. this is,
This is because the required injection pulse te and the like are values obtained on the basis of when the fuel pressure is the target fuel pressure Po and need to be corrected according to the actual fuel pressure Pf. The corrected injection pulse tpf is calculated by the following formula.

Tpf = Pf / Po × te In the following step 216, the invalid injection pulse tv is calculated. The invalid injection pulse tv is a time during which the injection is not actually performed due to the response delay of the fuel injection with respect to the change of the injection pulse, and the invalid injection pulse tv is well known according to the battery voltage and the actual fuel pressure Pf. Is calculated by a two-dimensional map of Further, in the following step 217, the final injection pulse ti is calculated by adding the invalid injection pulse tv to the corrected injection pulse tpf. And the following step 218
Then, in synchronism with the fuel injection timing calculated in another routine (not shown), the injection pulse is output to the fuel injection valve 4 during the final injection pulse ti calculated in step 217, and the process is temporarily terminated. To do. Then, the fuel injection valve 4 injects an amount of fuel according to the operating state of the engine 1.

Next, the main part of the present invention. A process of detecting that gas such as air or vapor (fuel vapor) is mixed in the fuel supply path 5 and a process corresponding to the detection result will be described. When gas is not mixed in the fuel supply passage 5, the behavior of the actual fuel pressure Pf in the fuel supply passage 5 is as illustrated in FIG. 5 (A). That is, at the start of injection (injection pulse: OFF → ON), the actual fuel pressure Pf instantaneously drops,
At the end of injection (injection pulse: ON → OFF), it instantaneously rises. This is because the liquid fuel is incompressible, and at the start of injection, the pressure drop due to the injection of fuel has an effect, and at the end of injection, the fuel injection valve 4 is suddenly closed. This is because On the other hand, the fuel pressure behavior when gas is mixed in the fuel supply passage 5 is shown in FIG.
As shown in FIG. That is, regardless of the presence or absence of injection, it is almost constant or only a slight change occurs. This is because gases such as air and vapor are compressible, and the pressure fluctuations are buffered by these gases.

FIGS. 6 to 8 are flow charts showing a gas detecting process for detecting that gas such as air or vapor is mixed in the fuel supply passage 5 by utilizing the above characteristics. The process of FIG. 6 is performed at the timing when the injection pulse changes from OFF (closed valve) to ON (open valve) or from ON to OFF,
Treated as an interrupt.

When the processing is started, the electronic control circuit 17
First, in step 302, it is determined whether the interrupt has occurred when the injection pulse is OFF → ON timing or ON → OFF timing. When it is determined that the injection pulse is from OFF to ON timing, the routine proceeds to step 303, where the actual fuel pressure Pf at that moment is substituted into the falling fuel pressure PBOT, and the processing is temporarily terminated. If it is determined that the injection pulse is ON → OFF timing, the routine proceeds to step 304, where the actual fuel pressure Pf at that moment is substituted into the ascending fuel pressure PTOP, and the processing is once terminated.

Further, the electronic control circuit 17 has
Alternatively, the processing of FIG. 7 is repeatedly executed for each constant number of rotations. In this process, the normal fuel pressure (normal fuel pressure) POPN in which the injection pulse does not change is obtained. When the process is started, first, at step 322, it is determined whether or not a predetermined time (1 to several ms) has elapsed since the injection pulse changed (OFF → ON or ON → OFF). This is because there is a possibility that the actual fuel pressure Pf due to the injection fluctuates during the above-mentioned predetermined time after the injection pulse changes.

When an affirmative decision is made in step 322, the routine proceeds to step 323, where the actual fuel pressure Pf at that moment is substituted into the normal fuel pressure POPN and the processing is once terminated. Step 32
When a negative determination is made in 2, there is a possibility that the actual fuel pressure Pf at that moment is still fluctuating, so the process is terminated without changing the value of the normal fuel pressure POPN.

Furthermore, the electronic control circuit 17 is
Alternatively, the process of FIG. 8 is repeatedly executed for every constant number of rotations. In this process, it is determined whether or not gas is mixed in the fuel supply path 5 based on the calculation results of the processes of FIGS.
When the processing is started, first, in step 342, PTOP-
It is determined whether POPN is smaller than a predetermined value K ₁ . If an affirmative determination is made here, it is determined that gas is mixed in the fuel supply passage 5, and the process proceeds to step 345 described later. The predetermined value K ₁ is larger than the fluctuation of the actual fuel pressure Pf at the end of fuel injection (injection pulse: ON → OFF) when gas is mixed in the fuel supply path 5, and is larger than the fluctuation when gas is not mixed. Use a small value.

When a negative determination is made in step 342, the process proceeds to step 343, and it is determined whether POPN-PBOT is smaller than a predetermined value K ₂ . If an affirmative determination is made here, it is determined that gas is mixed in the fuel supply passage 5, and the process proceeds to step 345 described later. The predetermined value K ₂ is set at the start of injection when the gas is mixed in the fuel supply passage 5 (injection pulse: O
The value is larger than the fluctuation of the actual fuel pressure Pf in FF → ON) and larger than the fluctuation when the gas is not mixed.

If a negative decision is made also in step 341,
It can be determined that the gas is not mixed in the fuel supply path 5. Therefore, the processing shifts to step 344, the flag fR representing it is set to "1", and the processing is once terminated. On the other hand, if an affirmative decision is made in step 342 or 343, there is a possibility that gas is mixed, so in step 345 fR = 0 is set and the processing is temporarily terminated.

The rising fuel pressure PTOP and the falling fuel pressure PBO
Since T measures instantaneous pressure, it may not be possible to obtain a peak value depending on the timing of processing. Therefore, fR = 0 may be set only when both conditions corresponding to steps 342 and 343 are satisfied, or fR = 0 may be set only when the condition is satisfied several times.
Further, the judgment may be made only on either the PTOP side or the PBOT side. Even in this case, it is possible to detect that gas such as air or vapor is mixed in the fuel supply passage 5.

In this embodiment, the following control is executed based on the presence / absence of gas mixture detected in this way. FIG. 9 is a flowchart showing a target fuel pressure setting process for setting the target fuel pressure Po based on the presence or absence of gas mixture.
It should be noted that the electronic control circuit 17 repeatedly executes this processing at fixed time intervals or at fixed rotation speeds.

When the processing is started, first, step 902
Then, it is determined whether or not the flag fR is "1". fR =
If 1 (YES), go to step 903, fR = 0 (N
If it is O), the process proceeds to step 904. In step 903, the target fuel pressure K ₃ is set when the gas is not mixed in the fuel supply passage 5. In step 904, the target fuel pressure K ₄ when gas is mixed is set. Where K ₃ ≤ K ₄
(For example, K ₃ = 200 to 300 KPa, K ₄ =
300 to 400 KPa). This is because by increasing the fuel pressure, air can be dissolved in the fuel and vapor can be liquefied, and gas such as air and vapor can be discharged together with the fuel earlier than the fuel injection valve 4. Because you can Note that K ₃ and K ₄ are not constant values, and may be variable depending on the load within the range of K ₃ ≦ K ₄ .

For this reason, in the present embodiment, it is possible to favorably detect that gas is mixed in the fuel supply passage 5, and to quickly eliminate gas such as air and vapor existing in the fuel supply passage 5. You can Therefore, even if gas is mixed in the fuel supply passage 5, the operating state of the engine 1 can be returned to the normal state early. In the above embodiment, the processing of FIG. 4 corresponds to the fuel injection means, the processing of FIGS. 6 and 7 corresponds to the pressure fluctuation calculation means, and the processing of FIG. 8 corresponds to the gas presence / absence determination means.

Further, depending on the characteristics of the engine 1, FIG.
As illustrated in (C), the actual fuel pressure Pf may decrease during injection. In such a case, the normal fuel pressure POPN may be calculated individually when the injection pulse is ON and when it is OFF. In that case, POP when the injection pulse is OFF
It is desirable to compare N with the falling fuel pressure PBOT, and POPN when ON and the rising fuel pressure PTOP. This is the actual fuel pressure P
The fluctuation amount of f becomes large, and the presence or absence of gas such as vapor can be accurately determined. Further, since the normal fuel pressure POPN is a steady value, a predetermined number of Pf when Yes is obtained in step 322 may be taken and the average thereof may be used as POPN. Especially when the actual fuel pressure Pf decreases during injection, such as when the volume of the fuel supply system is small (Fig. 5 (C)).
May require such processing to calculate the normal fuel pressure POPN.

Furthermore, in the above embodiment, the correction term Vfp
Although ci is obtained by a two-dimensional map, it may be set according to a change in the value of the injection amount (= requested injection pulse te × engine speed N). In this case, as illustrated in the following table, Vfpci is increased as the change amount of te × N increases.

[0044]

[Table 1]

Next, a second embodiment of the present invention will be described. FIG. 10 is an explanatory diagram showing the configuration around the fuel injection valve 115 of the second embodiment. The present embodiment is an example applied to a 4-cylinder engine. Further, the fuel supply system of the present embodiment is constructed in substantially the same manner as the first embodiment except for the part shown in FIG.

As shown in FIG. 10, in this embodiment, a fuel delivery pipe 111 is connected to the tip of the fuel supply passage 5. The fuel delivery pipe 111 is horizontally arranged above the intake passage 2, and fuel is supplied from the fuel tank 6 through the fuel supply passage 5. An auxiliary delivery pipe 11 is provided above the fuel delivery pipe 111.
3 are arranged in parallel. This auxiliary delivery pipe 1
13 is connected to the fuel supply path 5 via a branch pipe 114 on the upstream side of the fuel delivery pipe 111.

On the lower surface of the fuel delivery pipe 111, four fuel injection valves 115 for injecting fuel into the intake manifolds of the cylinders # 1 to # 4 (not shown) of the engine 1 are provided.
Are attached via respective cylindrical connectors 116. The connector 116 of each fuel injection valve 115 extends to the upper part inside the fuel delivery pipe 111, and the fuel suction port 117 at the upper end of each connector 116 is located at the upper part inside the fuel delivery pipe 111. Further, the fuel delivery pipe 111 and the auxiliary delivery pipe 1
It communicates with 13 through the throttle pipe 118. The throttle pipe 118 is located right above the fuel injection valve 115 farthest from the branch pipe 114, and the auxiliary delivery pipe 1 is provided.
It extends to the upper part in 13. Therefore, the vapor or the like accumulated in the upper portion of the auxiliary delivery pipe 113 is easily sucked into the connector 116 of the fuel injection valve 115 through the throttle pipe 118. Further, the fuel delivery pipe 111 includes the fuel delivery pipe 111.
A pressure sensor 119 for detecting the absolute pressure of the fuel inside is provided.

Next, the structure of the electronic control circuit 121 for controlling each fuel injection valve 115 will be described. Electronic control circuit 121
Is mainly composed of a microcomputer 122 including a ROM, a RAM, a CPU, etc. The microcomputer 122 independently drives four fuel injection valves 115 via four drive circuits 123. Further, the detection signal of the pressure sensor 119 is detected by the electronic control circuit 1 together with the detection signals of the air flow meter 14, the rotation sensor 19, the water temperature sensor 22, the intake air temperature sensor 23, etc., which are similar to those of the first embodiment.
21 has been entered.

The electronic control circuit 121 is usually the engine 1
Independent injection, group injection, or simultaneous injection is executed according to the operating state of. Here, the independent injection means each cylinder #
Fuel injection valve 115 corresponding to the start of the intake stroke of 1 to # 4
Is an injection method in which a fuel is driven to inject fuel. Group injection refers to dividing the cylinders of a four-cylinder engine into two groups (hence one group has two cylinders), and each group has two cylinders.
This is an injection method in which fuel is injected into each cylinder at the same timing every 360 ° C. Simultaneous injection means 720 ° C.
This is an injection method in which fuel is injected into all cylinders for each A at the same timing. Note that the process of switching the injection method when gas is not mixed in the fuel supply passage 5, the fuel delivery pipe 111, and the auxiliary delivery pipe 113 (hereinafter referred to as the fuel supply passage 5 system) is well known, and therefore will not be described here in detail. I won't mention it. The process of switching the injection method when gas is mixed will be described below.

First, the electronic control circuit 121 is shown in FIGS.
Performing the same gas detection process as described in,
Flag fR is set according to the presence or absence of gas in the fuel supply line 5 system
are doing. In this embodiment, the pressure sensor 119
By detecting the absolute pressure in the fuel delivery pipe 111
However, this absolute pressure is also illustrated in Figs. 5 (A) and 5 (B).
Changes almost the same as. Therefore, the flow of FIGS.
Chart is a predetermined value K ₁ , K₂ Such as making changes
It can be applied to this embodiment as it is.

As in this embodiment, in the structure in which the auxiliary delivery pipe 113 is arranged directly above the fuel delivery pipe 111 and the two are communicated with each other by the throttle pipe 118, the fuel delivery pipe 111 generated while the engine is stopped. The vapor and the like in the inside are collected in the auxiliary delivery pipe 113 through the throttle pipe 118, and are collected in the upper part of the auxiliary delivery pipe 113. Therefore, in order to discharge the vapor and the like, the fuel is sucked out by the injection of the fuel injection valve 115, and the pressure in the auxiliary delivery pipe 113 (hereinafter referred to as gas pressure) and the fuel delivery pipe at the time of fuel injection are increased. The pressure difference with the pressure in 111 (hereinafter referred to as fuel pressure) may be increased.

Therefore, in the injection method switching process of this embodiment, when gas is mixed in the fuel supply path 5 system, there is a situation in which a large amount of fuel is sucked out by one injection and the decrease range of the fuel pressure due to the injection becomes large. As can be obtained, the independent injection is switched to the group injection, or the group injection is switched to the simultaneous injection. Switching to any of these injection methods doubles the number of fuel injection valves 115 that are simultaneously driven by one injection. Therefore, FIG.
As illustrated in (A) and (B), after the injection system is switched at the time point t1, the decrease width of the fuel pressure is significantly increased, and the differential pressure between the gas pressure and the fuel pressure is significantly increased. At the same time, the suction of fuel per injection is significantly increased. This effectively promotes the discharge of vapor,
The discharge of vapor etc. can be completed within an extremely short time. It should be noted that FIG. 11A shows a case where the independent injection is switched to the group injection, and FIG. 11B shows a case where the group injection is switched to the simultaneous injection.

FIG. 12 is a flow chart showing the injection method switching processing of this embodiment. The electronic control circuit 121
Repeats this process at regular intervals or at regular revolutions. When the process starts, first, step 100
At step 2, it is judged whether the flag fR is "1". f
When R = 0, it is considered that air, vapor, etc. are not mixed in the fuel supply path 5 system, so the process of step 1003 is executed and the process is temporarily terminated. This step 1003
Then, it switches to the normal injection method (hereinafter referred to as the normal injection method) according to the operating state of the engine 1 and continues if the normal injection method is being executed. On the other hand, if it is determined in step 1002 that the flag fR = 1, that is, if it is considered that air, vapor, or the like is mixed in the fuel supply path 5 system, then in step 1004, the injection method is set to the following emission promotion method. After switching to, the processing is temporarily terminated. That is, when the normal injection method is the independent injection, it is switched to the group injection, and when the normal injection method is the group injection, it is switched to the simultaneous injection.

Therefore, the above process effectively promotes the discharge of gas such as vapor and air, and the discharge of gas can be completed within an extremely short time. Therefore, even if gas is mixed in the fuel supply passage 5, the operating state of the engine 1 can be returned to the normal state early.

When the independent injection is switched to the simultaneous injection, the number of fuel injection valves simultaneously driven by one injection becomes four times. Therefore, as illustrated in FIG. 11C, the width of decrease in the fuel pressure is further increased, and the vapor or the like can be discharged more satisfactorily. Therefore, in step 1004, the independent injection may be switched to the simultaneous injection. Further, the amount of change in the fuel pressure when the fuel injection valve 115 is opened / closed (for example, the above-mentioned PTOP-POPN, P
It may be determined whether to switch the independent injection to the group injection or the simultaneous injection according to (the value corresponding to OPN-PBOT).

Furthermore, the second embodiment is an example in which the present invention is applied to a 4-cylinder engine, but it can be similarly applied to an engine having 5 or more cylinders. For example, when applied to a 6-cylinder engine, group injection may be divided into two groups or three groups. Further, in a multi-cylinder engine, when the normal injection method is group injection, the number of fuel injection valves 115 that are simultaneously driven in one injection may be increased by switching the number of groups of group injection.

In the second embodiment, the auxiliary delivery pipe 113 is provided directly above the fuel delivery pipe 111.
Are arranged and communicated with each other by the squeezing pipe 118 to collect the vapor and the like on the side of the auxiliary delivery pipe 113. However, the auxiliary delivery pipe 113 is abolished and the capacity of the fuel delivery pipe 111 is increased to exclusively. It is also possible to have a configuration in which vapor or the like is stored in the upper part inside the fuel delivery pipe 111. Furthermore, in the second embodiment,
Although all the connectors 116 of each fuel injection valve 115 are extended to the upper part in the fuel delivery pipe 111, the connector 116 of at least one fuel injection valve 115 may be extended to the upper part in the fuel delivery pipe 111. By doing so, the vapor or the like is satisfactorily discharged through the extended connector 116.

The present invention is not limited to the above embodiments, and can be implemented in various modes without departing from the gist of the present invention. For example, the absolute pressure of the fuel supply path 5 and the fuel delivery pipe 111
The differential pressure between the intake passage 2 and the intake passage 2 also shows the same fluctuation as in FIG. Therefore, even if a pressure sensor (which detects an absolute pressure) is used instead of the differential pressure sensor 12 of the first embodiment, or a differential pressure sensor is used instead of the pressure sensor 119 of the second embodiment, the vapor is similarly obtained. Etc. can be detected.

However, when a pressure sensor is used, it is necessary to convert the absolute pressure into a differential pressure when calculating the correction injection pulse tpf and the like. This conversion can be performed by a known method using parameters such as the detection signal of the air flow meter 14 and the engine rotation speed N. It should be noted that the discharge or removal of air, vapor, etc. described in each of the above-described embodiments may be forcedly performed during vehicle maintenance. This can be achieved by providing a vehicle equipped with the engine 1 with a test terminal and forcibly setting the flag fR to "0" when the terminal is turned on. Also,
A configuration for discharging the vapor or the like may not be provided in particular, and when the mixture of the vapor or the like is detected (fR = 0), an abnormality notifying means such as an EMG lamp may be driven to notify the abnormality.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a fuel supply system for an internal combustion engine of a first embodiment.

FIG. 2 is a flowchart showing a fuel supply amount control process of the first embodiment.

FIG. 3 is a map used in the fuel supply amount control process.

FIG. 4 is a flowchart showing a fuel injection control process of the first embodiment.

FIG. 5 is a time chart showing the behavior of the actual fuel pressure in the fuel supply passage of the first embodiment.

FIG. 6 is a flowchart showing a process of calculating a rising fuel pressure and a falling fuel pressure in the gas detection process of the first embodiment.

FIG. 7 is a flowchart showing a normal-time fuel pressure calculation process of the gas detection process of the first embodiment.

FIG. 8 is a flowchart showing a gas presence / absence determination process of the gas detection process of the first embodiment.

FIG. 9 is a flowchart showing a target fuel pressure setting process of the first embodiment.

FIG. 10 is an explanatory diagram showing a configuration around a fuel injection valve of a fuel supply device according to a second embodiment.

FIG. 11 is a time chart showing changes in fuel pressure according to the injection method of the second embodiment.

FIG. 12 is a flowchart showing an injection method switching process of the second embodiment.

FIG. 13 is a diagram illustrating the configuration of the present invention.

[Explanation of symbols]

1 ... Engine 2 ... Intake passage 3
... Exhaust passage 4 ... Fuel injection valve 5 ... Fuel supply passage 6
… Fuel tank 7… Fuel pump 12… Differential pressure sensor 1
4 ... Air flow meter 17 ... Electronic control circuit 19 ... Rotation sensor 2
2 ... Water temperature sensor 23 ... Intake temperature sensor 111 ... Fuel delivery pipe 113 ... Auxiliary delivery pipe 115 ... Fuel injection valve 119 ... Pressure sensor 121 ... Electronic control circuit

Claims (3)

[Claims] 1. A fuel supply means for supplying fuel to a fuel injection valve via a predetermined fuel supply path, a fuel pressure detection means for detecting a pressure of fuel in the fuel supply path, and a rotation speed of the internal combustion engine. A fuel supply device for an internal combustion engine, comprising: a fuel injection unit that synchronously opens and closes the fuel injection valve and injects fuel supplied through the fuel supply path into each cylinder of the internal combustion engine, When the fuel injection valve is opened or closed by the injection means, the pressure fluctuation calculation means calculates the fluctuation quantity of the pressure detected by the fuel pressure detection means, and the fluctuation quantity of the pressure calculated by the pressure fluctuation calculation means. Based on
A fuel supply device for an internal combustion engine, comprising: a gas presence / absence determining means for determining whether or not gas is present in the fuel supply path. 2. The fuel supply apparatus for an internal combustion engine according to claim 1, wherein the fuel supply means increases the fuel supply pressure when the gas presence / absence determination means determines the presence of gas. 3. A plurality of fuel injection valves are provided, and when the gas presence / absence determination means determines the presence of gas, the fuel injection means increases the number of fuel injection valves opened simultaneously. The fuel supply system for an internal combustion engine according to claim 1.