JPH01313637A - Fuel pressure controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To precisely control the fuel pressure according to the vapor generation state by switching the fuel pressure from a high pressure side to a low pressure side when an internal combustion engine completes the starting operation and the temperature rises over a prescribed temperature and the feedback control quantity reduces by a prescribed quantity. CONSTITUTION:A control unit 31 detects the completion of start from the signals of a starter switch 42 and a revolution speed sensor 43 and detects the rise of the temperature of an engine 1 over a prescribed temperature from the signal of a water temperature sensor 39, and then judges the generation of vapor due to the high temperature start. In this state, the feedback control quantity of the air-fuel ratio is reduced by a prescribed quantity on the basis of the output of an O2 sensor 44, an electromagnetic control valve 22 is duty-ratio- controlled, and the control pressure supplied into the negative pressure chamber A of a pressure regulator 6 is controlled so that the fuel pressure supplied into and injector 7 becomes a low pressure from the high pressure side. Thus, the fuel pressure can be controlled precisely according to the vapor generation state.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an internal combustion engine such as a vehicle engine, and in particular controls the air-fuel ratio by controlling the fuel pressure applied to the fuel injection valve during high-temperature startup. The present invention relates to such a fuel pressure control device.

[Prior Art] Generally, when an internal combustion engine, for example a vehicle engine, is restarted at a high temperature, fuel vapor may be generated in a fuel injection valve or a fuel supply pipe. When vapor is generated, the fuel injected from the injector contains the vapor, and the amount of fuel injected decreases, resulting in a lean air-fuel ratio.

For this reason, there is a risk that the idling of the engine may become unstable or that starting problems such as engine stalling may occur.

Therefore, by installing a well-known pressure regulator in the injector and introducing atmospheric pressure into the negative positive chamber of the pressure regulator when the engine starts at high temperature, the fuel pressure applied to the injector (hereinafter referred to as "fuel pressure") is reduced to the atmospheric pressure on the high pressure side. This was done to suppress the generation of vapor.

However, in the above fuel pressure control, when returning the fuel pressure that was switched to the high pressure side to the normal intake pipe negative pressure on the low pressure side, the fuel pressure was simply switched based on the time elapsed since the engine started. . Therefore, depending on the degree of vapor generation, the fuel pressure may become too high or too low. Therefore, there is a possibility that the air-fuel ratio becomes overlifted or overlean, resulting in problems such as unstable idling and engine stalling.

Therefore, in Japanese Patent Application Laid-Open No. 62-87638, a fuel pressure control device for an internal combustion engine was proposed to solve the above-mentioned problem of fuel pressure control by the pressure regulator.

This fuel pressure control device maintains the engine cooling water temperature at a predetermined temperature (10
a water temperature sensor that determines whether the water temperature is above 0°C; a starter that detects when the engine is started; a pressure regulator that controls the fuel injection pressure of the fuel injection valve, that is, the fuel pressure; (A negative pressure control valve (VSV) that controls the control pressure on a duty basis, and a VSV that detects the air-fuel ratio from the concentration of a specific component (02) in the exhaust gas.)
The duty ratio of the negative pressure control valve is controlled so that when the output of the 02 sensor changes from a lean signal to a rich signal during a high temperature start, the fuel pressure is gradually changed from atmospheric pressure to intake pipe negative pressure. It is composed of

[Problem to be solved by the invention] However, in the conventional fuel pressure control device for an internal combustion engine, the
The duty ratio of the negative pressure control valve was simply controlled so that when the output of the second sensor changed from a lean signal to a rich signal, the fuel pressure was gradually changed from atmospheric pressure to intake pipe negative pressure.

For this reason, noise may be superimposed on the 02 sensor when the engine starts at a high temperature, or a rich signal may be output from the 02 sensor due to a sudden increase in the amount of fuel supplied to the engine, even during vapor generation. However, this resulted in a malfunction in which the fuel pressure was lowered. As a result,
There was a risk that further vapor would be generated, causing problems such as unstable idling and engine stalling.

This invention has been made in view of the above-mentioned circumstances, and its purpose is to prevent noise from being superimposed on the air-fuel ratio detection means when the internal combustion engine is started at a high temperature, or from a sudden increase in the amount of fuel supplied to the internal combustion engine. An object of the present invention is to provide a fuel pressure control device for an internal combustion engine, which can prevent malfunctions in which the fuel pressure is lowered even when vapor is generated, and can perform good fuel pressure control. .

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a starting detection means for detecting the starting time of the internal combustion engine, an engine temperature detection means for detecting the temperature of the internal combustion engine, and an internal combustion engine temperature detection means for detecting the temperature of the internal combustion engine. A pressure regulator that adjusts the fuel pressure applied to a fuel injection valve provided in the engine, a control pressure changing means that duty-controls the control pressure applied to a negative positive chamber of the pressure regulator, and exhaust gas discharged from the internal combustion engine. In a fuel pressure control device for an internal combustion engine, the fuel pressure control device includes an air-fuel ratio detection means for detecting an air-fuel ratio from the concentration of a specific component in the air-fuel ratio, and an air-fuel ratio feedback control means for feedback-controlling the air-fuel ratio based on a detection signal of the air-fuel ratio detection means. , a start completion determination means for determining whether the start of the internal combustion engine is complete based on the detection signal of the start detection means; and a temperature determination means for determining whether the internal combustion engine is at a predetermined temperature or higher based on the detection signal of the crotch temperature detection means. When the determination conditions based on the start completion determination means and the temperature determination means are both satisfied and the feedback control amount by the air-fuel ratio feedback control means is reduced by a predetermined amount, control is performed to switch the fuel pressure from the high pressure side to the low pressure side. and fuel pressure control means for controlling the duty ratio of the pressure changing means.

[Operation] Therefore, the determination conditions based on the start completion determination means and the temperature determination means are both satisfied, that is, the internal combustion engine completes the start and enters the predetermined temperature state, and the feedback control by the air-fuel ratio feedback control means is satisfied. When the flI amount is reduced by a predetermined amount, the fuel pressure control means controls the duty ratio of the control pressure changing means to switch the fuel pressure from the high pressure side to the low pressure side at that point, and changes the fuel pressure to the negative pressure chamber of the pressure regulator. Duty control is applied to the control pressure introduced.

As a result, the fuel pressure applied to the fuel injection valve is switched from the high pressure side to the low pressure side, and the fuel pressure is controlled according to the generation of vapor.

[Example] Hereinafter, an example embodying the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of an engine 1 as an internal combustion engine mounted at the front of a vehicle and equipment related to the engine 1. As shown in FIG. The engine l has an intake pipe 1a for inhaling air.
and an exhaust pipe 1b for discharging exhaust gas.

In FIG. 1, a fuel tank 2 is provided at a location away from the engine 1, and a pipe 2a is led out from the fuel tank 2. This pipe 2a is connected to the suction side of a fuel pump 3 provided near the fuel tank 2. A fuel filter 4 is connected to the discharge side of the fuel pump 3 through a pipe 3a, and is provided near the engine 1 at the front of the vehicle.
is connected. A fuel supply pipe 5 is led out from the fuel filter 4, and one end of the vibrator 5 is connected to a pressure regulator 6.

Further, an injector 7 serving as a fuel injection valve for injecting and supplying fuel to the vicinity of the intake valve IC of the engine 1 is provided in the middle of the fuel supply pipe 5. Therefore, when the fuel pump 3 is operated, the fuel stored in the fuel tank 2 is transferred to the injector 7 via the fuel filter 4.
and is injected from the injector 7. Further, the fuel that is not injected from the injector 7 behind the fuel supplied to the injector tube is sent to the pressure regulator 6 via the fuel supply pipe 5.

As shown in FIGS. 1 and 2, two diaphragms 8.9, a first and a second diaphragm, are provided within the pressure regulator 6. Then, the housing 6a of the pressure regulator 6 is connected to the first one from above by each diaphragm 8.9.
The fuel chamber is divided into a negative pressure chamber A, a second negative pressure chamber B, and a fuel chamber C. Note that in this embodiment, the first diaphragm 8
The effective pressure receiving area of the second diaphragm 9 is larger than that of the second diaphragm 9.

The hanging 6a of the fuel chamber C includes a pipe 10a forming a fuel inlet port IO for introducing fuel into the fuel chamber C;
Fuel return port 1 for discharging fuel from fuel chamber C
A pipe lla forming one pipe is provided respectively. An injector 7 is connected to the pipe 10a via a fuel supply pipe 5. Further, one end of a fuel return pipe 12 is connected to the pipe lla, and the other end of the return pipe 12 is connected to the fuel tank 2.

As shown in FIG. 2, a rigid body 13 fixed to the second diaphragm 9 and a rigid body 14 fixed to the fuel return port ti are provided in the fuel chamber C. A control valve 15 is constituted by both open bodies 13 and 14.

Further, a transmission plate 16 is fixed to the first diaphragm 8. This transmission plate 16 is connected to the rigid body 13 via a rigid transmission rod 17.

Therefore, the transmission plate 16 and the rigid body 13 are movable together. Further, a spring 18 is provided in the first negative pressure chamber A to bias the first diaphragm 8 toward the second negative pressure chamber B. Therefore, based on the biasing force of the spring 18, the transmission plate 16, the transmission rod 17, and the rigid body 13 are pressed downward, thereby acting on the control valve 15 in the closing direction.

As shown in FIG. 1.2, one end of a pipe 19a forming the first pressure guiding section 19 is connected to the housing 6a of the second negative pressure chamber B. As shown in FIG. The second negative pressure chamber B is communicated with a surge tank 20 provided in the middle of the intake pipe 1a through this pipe 19a. As a result, the second negative pressure chamber B is always supplied with the intake pipe negative pressure as it is.

Further, as shown in FIG. 1.2, one end of a pipe 21a forming the second pressure guiding section 21 is connected to the housing 6a of the first negative pressure chamber A. The other end of the pipe 21a is connected to an electromagnetic control valve 22 as control pressure changing means for duty-controlling the control pressure introduced into each negative pressure chamber of the pressure regulator 6. This electromagnetic control valve 22 is
This is a well-known duty control valve for controlling fuel pressure applied to an injector. The electromagnetic control valve 22 operates based on a control signal from a control unit 31 that constitutes an air-fuel ratio feedback control means, a start completion determination means, a temperature determination means, and a fuel pressure control means. Then, by the operation of the electromagnetic control valve 22, the pressure introduced into the first negative pressure chamber A via the second pressure guiding part 21 is increased between the intake pipe negative pressure on the low pressure side and the atmospheric pressure on the high pressure side. It is set to change continuously.

FIG. 3 shows a well-known configuration of the electromagnetic control valve 22. As shown in FIG. That is, the electromagnetic control valve 22 has a pressure guiding path 22a.

22b and an atmospheric pressure guiding path 22c, and further includes an electromagnetic coil 23, a valve 24, and a spring 25. The pressure guiding path 22a communicates with the first negative pressure chamber A of the pressure regulator 6. Then, by demagnetizing the electromagnetic coil 23, the valve 24 is pressed based on the biasing force of the spring 25, and one end of the atmospheric pressure passage 22c is closed, and the other door pressure passages 22a and 22b are closed. communicated. Also, by energizing the electromagnetic coil 23, the valve 24
is attracted to the electromagnetic coil 23 against the biasing force of the spring 25, and one end of the atmospheric pressure guiding path 22c is opened and the pressure guiding path 2
2a is communicated with the atmospheric pressure path 22c, and communication between both door pressure paths 22a and 22b is cut off.

FIG. 4 shows the control voltage applied from the control unit 31 to the electromagnetic coil 23 in order to control the operation of the electromagnetic control valve 22. In this embodiment, the ratio of the on time TON to the constant period T, that is, the duty ratio TON/T
So-called pulse width modulation PWM is performed to control the operation of the electromagnetic control valve 22.

When the duty ratio TON/T is 0%, the two door pressure paths 22a and 22b are in communication with each other, and the intake pipe negative pressure is directly supplied to the first negative pressure chamber A of the pressure regulator 6. On the other hand, the duty ratio TON/T is 1
00%, the communication between both door pressure paths 22a and 22b is cut off, and the pressure path 22a and the atmospheric pressure path 22 are disconnected.
c, and atmospheric pressure is supplied to the first negative pressure chamber A. That is, by changing the duty ratio TON/T between 0 and 100%, the pressure supplied to the first negative pressure chamber A changes linearly as shown in FIG. 5.

Next, the electrical configuration of this fuel pressure control device will be explained.

The control unit 31 is mainly composed of a microcomputer, and includes a central processing unit (CPU) 32 that executes calculations as is well known, and a readable/writable random access memory (RAM) 33 that temporarily stores data. A read-only memory (ROM) 34 that stores programs and data used by the CPU 32, an input port 35 that inputs various control signals, and outputs drive signals according to the calculation results executed by the CPU 32. Output boat 36 and CP
It is composed of a bus 37 that electrically connects U32, RAM 33, ROM 34, input boat 35, and output boat 36 to each other.

In addition, the input boat 35 of the control unit 31 has
When the intake temperature sensor 38 detects the intake temperature TA of the air taken into the engine 1, the water temperature sensor 39 detects the cooling water temperature TW of the engine 1, and the throttle valve 26 provided in the intake pipe la is fully closed. The idle switch 40 is turned on when the transmission (the path shown) is in the neutral position or the clutch (the path shown) is disengaged, and the neutral switch 41 is turned on when the engine starter (the path shown) is in operation. The air-fuel ratio A/F is determined by an operating starter switch 42, a rotation speed sensor 43 that detects the engine rotation speed N, and a rotation speed sensor 43 that is attached to the exhaust pipe 1b near the exhaust valve 1d and detects the oxygen concentration in the exhaust gas.
0 as an air-fuel ratio detection means to detect rich/lean
2 sensor 44 and a well-known air flow meter 45 that is provided in the intake pipe la and detects intake IQ are connected to each other. And each of these sensors and each switch 3
Detection signals 8 to 45 are input to the control unit 31. In this embodiment, the intake air temperature sensor 38 and the water temperature sensor 39 constitute an engine temperature detection means, and the starter switch 42 and the rotational speed sensor 43 constitute a starting time detection means.

In addition, the output boat 36 of the control unit 31 has
The injector 7 and the electromagnetic control valve 22 are connected to each other. Then, the control unit 31 controls the operation of the injector 7 and the electromagnetic control valve 22 based on detection signals from each sensor and each switch 38 to 45. That is, the fuel injection timing of the injector 7 is controlled, and the duty ratio TON/T given to the electromagnetic control valve 22 is controlled.

Then, from the control unit 31 to the electromagnetic control valve 22
By controlling the duty ratio TON/'r given to 0%, intake pipe negative pressure is introduced into both page pressure chambers A and B of the pressure regulator 6. Therefore, there is no pressure difference between the upper and lower sides of the diaphragm 8, and the fuel pressure applied to the injector becomes equal to the biasing force of the spring 18 minus the negative pressure in the intake pipe (for example, 2.55 kg/cm2).

That is, as shown in graph a of FIG. 6, the pressure regulator 6 performs normal operation.

On the other hand, by controlling the duty ratio TON/T given to the electromagnetic control valve 22 from the control unit 31 to 100%, atmospheric pressure is introduced into the first negative pressure chamber A of the pressure regulator 6, and the second negative pressure is Intake pipe negative pressure is introduced into chamber B. Therefore, due to the difference in the pressure receiving areas of the diaphragms 8 and 9, a downward force is applied to each member 16, 17.13, that is, in a direction to close the control valve 15. Therefore, the fuel pressure applied to the injector 7 is the pressure when the intake pipe negative pressure is introduced into both page pressure chambers A and B (for example, 2.55 kg/c
m2) higher pressure (e.g. 3.00-4゜00k
g/cm2). That is, as shown in graph b of FIG. 6, the pressure regulator 6 operates to obtain the maximum fuel pressure.

In this embodiment, the pressure introduced into the first negative pressure chamber A is gradually changed from atmospheric pressure on the high pressure side to intake pipe negative pressure on the low pressure side by the electromagnetic control valve 22. 7, the fuel pressure applied to the intake pipe is gradually changed from atmospheric pressure to normal intake pipe negative and positive.

Here, fuel injection control will be explained according to the flowchart of FIG. This control program is executed at predetermined intervals.

First, in step 101, the control unit 31 manually inputs detection signals from each sensor and each switch 38 to 45, and outputs intake air amount Q, intake air temperature TA, cooling water? jLTW,
The air-fuel ratio A/F, engine speed N, etc. are calculated respectively.

Next, in step 102, the control unit 31 calculates the basic injection ITP of the injector based on the intake air i1Q and the engine speed N.

Subsequently, in step 103, the control unit 31 calculates the feedback correction amount KWA excluding the feedback control IKFB. This feedback correction amount KWA is calculated based on the intake air temperature TA, the cooling water temperature TW, and the like.

Furthermore, in step 104, the control unit 3
1 determines whether the air-fuel ratio A/F feedback condition is satisfied. For example, if the cooling water temperature TW is above a predetermined value, 0
It is assumed that the feedback condition is satisfied when the two sensors 44 are not out of order. Then, when the feedback condition is satisfied, the control unit 31 moves to step 105 to perform feedback control [tKF
Calculate B.

Here, feedback control 11f! The calculation of i<pB will be explained.

That is, the 02 sensor 44 at the time of the previous program execution
If the detection signal of the 02 sensor 44 instructs the air-fuel ratio A/F to be rich, and the detection signal of the 02 sensor 44 during the current program execution instructs the air-fuel ratio A/F to be lean, the control unit 31 performs skip control. 5% to the feedback control IKFB during the previous program execution.
Add.

KFB=KFB (i-1)+5 (%) Furthermore, when the detection signal of the 02 sensor 44 instructs a change in the air-fuel ratio A/F from lean to rich, the control unit 3
1 is the feedback control ff during the previous program execution
Subtract 5% from 1KFB.

KFB=KFB (i-1)-5(%) Furthermore, if the detection signal of the 02 sensor 44 instructs the air-fuel ratio A/F to be lean following the previous program execution, the control unit 31 performs integral control. By doing so, 2% is added to the feedback control IKFB during the previous program execution.

KFB=KFB (i-1)+2 (%) Normally, feedback control IKFB has a value close to 0%. and,
If the predetermined basic air-fuel ratio becomes lean for some reason, the feedback control KFB changes significantly to a positive value. Furthermore, when the basic air-fuel ratio becomes rich, the feedback control 1KFB changes significantly to a negative value.

Next, the control unit 31 moves to step 106, and changes the basic injection amount TP to the feedback correction amount KWA,
The final injection fftTinj is calculated by correcting based on the feedback system 1iKFB and adding the injector invalid injection time TV which changes depending on the voltage.

100 +KWA[! 10 KFB Tinj = x'rp+'rv Furthermore, the control unit 31 moves to step 107 and operates the injector 7 based on the final injection amount Tinj.

On the other hand, if the air-fuel ratio A/F feedback condition is not satisfied in step 104, the control unit 31 moves to step 108, and the feedback control I
Set KFB to 0%.

Thereafter, the control unit 31 performs step 106.
The process moves to step 107 and each process is sequentially executed.

Next, the operation of the fuel pressure control device configured as described above will be explained with reference to the flowchart of FIG. 8 and the time charts of FIGS. 9 and 10.

In step 201, the control unit 31 determines whether starting of the engine 1 is completed.

That is, in this embodiment, the control unit 31
determines whether the engine starter is in operation based on the detection signal of the starter switch 42 and whether or not the engine speed N has reached a predetermined value based on the detection signal of the rotation speed sensor 43. Based on the determination result, it is determined whether the engine 1 has started.

Then, if the engine starter is in operation and the engine speed N has not reached the predetermined value and the start has not been completed, the control unit 31 moves to step 202.

In step 202, control unit 31 sets FLAG to "1". This F■, AC increases the duty ratio TON/T that controls the electromagnetic control valve 22,
FLAG for determining holding and lowering.

Next, the control unit 31 performs step 203.2.
Move to 04. Then, in step 203, the control unit 31 determines whether the cooling water temperature TW is higher than a predetermined value α based on the detection signal of the water temperature sensor 39. Further, in step 204, the control unit 31 adjusts the intake air temperature TA based on the detection signal of the intake air temperature sensor 38.
is higher than a predetermined value β.

Then, if the cooling water temperature TW and the intake temperature TA are higher than the predetermined values α and β, respectively, a high temperature start occurs, and the control unit 31 moves to step 205 and sets the duty ratio TON/T of the electromagnetic control valve 22 to 100%. Set.

As a result, the fuel pressure applied to the injector 7 is set to atmospheric pressure on the high pressure side.

Further, if at least one of the cooling water temperature TW and the intake air temperature TA is lower than the predetermined values α and β, a low temperature start occurs, and the control unit 31 moves to step 206 and sets the duty ratio TON/T of the electromagnetic control valve 22 to 0. Set to %.

As a result, the pressure regulator 6 is brought into a normal operating state, and the fuel pressure applied to the injector 7 is set to the intake pipe negative pressure on the low pressure side.

On the other hand, in step 201, if the engine start is in operation and the engine speed N has reached a predetermined value, and the start is complete, the control unit 31 performs step 201.
1 to steps 207 and 208.

In step 207, the control unit 31 determines whether the 02 sensor 44 is out of order. or,
In step 208, the control unit 31 determines whether feedback control of the air-fuel ratio A/F is being executed.

This is a process for determining the timing to start lowering the duty ratio TON/T based on the feedback control IIKFB in each process described later.

Then, if the 02 sensor 44 is out of order and feedback control of the air-fuel ratio A/F is impossible, or if feedback control has not started, the control unit 31 moves to step 209.

In step 209, the control unit 31 determines whether a predetermined time (4 minutes in this case) has elapsed since the start of the engine 1 in order to start lowering the duty ratio TON/T based only on the time elapsed since the start of the engine l. . This is a process performed in order to uniformly lower the duty ratio TON/T when feedback control is difficult, that is, when the timing to start lowering the duty ratio TON/T cannot be determined based on the feedback control amount KFB. . In other words, if the duty ratio TOJII/T cannot be lowered and the fuel pressure is kept at high atmospheric pressure, the fuel pressure will remain high even though the paper has completely cleared by 1, and the air-fuel ratio A/F will become rich. This results in problems such as deterioration of exhaust gas. The process in step 209 is to prevent the above-mentioned problems.

In this embodiment, the predetermined time from start-up was set to 4 minutes, but the predetermined time may be any time that allows the paper to come out reliably, and can be set according to the displacement of the engine, etc. do it.

Also, in steps 207 and 208, the 02 sensor 44
If there is no failure in the air-fuel ratio A/F and feedback control of the air-fuel ratio A/F is possible and feedback control has started, the control unit 31 moves to step 210.

In step 210, the control unit 31 determines whether the feedback system 11iKFB is Nil by 10% or more, that is, whether KFB≦−10%. For example, as shown at time t1 in FIG. 9, the feedback control IKFB is set to 10%.
If the above amount of fuel is reduced, the amount of fuel injected from the injector 7 becomes rich due to the influence of the high fuel pressure due to the removal of the paper, and the control unit 31 proceeds to step 211.

In step 211, the control unit 31 sets the duty ratio TON/T to a predetermined value in the subsequent process.
Reset FLAG to "O" to lower ir.

Also, in step 209, if 4 minutes have elapsed since the start of engine l, the control unit 31 proceeds to step 211 and sets FLAG to "0".
”. If 4 minutes have not elapsed since the start of the engine 1, the current status is maintained without any action being taken and the process is terminated.

In this embodiment, the reduction value of the feedback control amount KFB is set to 10%, but this value may be set to an appropriate value depending on the displacement of the engine 1, etc.

Also, in step 210, feedback control IK
If FB is not performing MIt of 10% or more,
The control unit 31 moves to step 212.

In step 212, the control unit 31 determines whether the feedback control IKFB has been increased by 10% or more, that is, whether KFB≧lO%. For example, as shown at time t2 in FIG. 10, the feedback control amount KFB is 10%.
If the amount has been increased more than that, paper will have been generated and the fuel pressure will have become lower than the required value. Therefore, the control unit 31 moves to step 213 and sets FLAG to "2" in order to increase the duty ratio T''ON/T by a predetermined amount γ in the subsequent processing.

In this embodiment, the increase value of the feedback control amount KFB is set to 10%, but this value may be set to an appropriate value depending on the displacement of the engine 1, etc.

Subsequently, the control unit 31 moves from step 213 to step 214.

In addition, in steps 210 and 212, if the feedback control ff1KFB has not increased the Ml by 10% or more and the feedback control 1iKFI3 has not increased the amount by 10% or more, the control unit 3
1 maintains FLAG as it is and moves to step 214.

In step 214, the control unit 31 determines whether FLAG is "0", "1", or "2".

Here, if FLAG is "0", the paper has come out and the air-fuel ratio has become rich due to the influence of high fuel pressure, and it is necessary to lower the fuel pressure by lowering the duty ratio TON/T. becomes. Therefore, for example, time t1 to t2 in FIG. 9, time t1 to t2 in FIG. t3～
As shown at timing t4, the control unit 31 proceeds to step 215 and gradually decreases the duty ratio TON/T by a predetermined amount γ. At this time, as shown in the timings of time t2 in FIG. 9 and time t4 in FIG. 1θ, when the duty ratio TON/T becomes smaller than 0%, the duty ratio TON/T is held at 0%.

As a result, as shown in FIGS. 9 and 10, the fuel pressure gradually decreases in response to changes in the duty ratio TON/T. Therefore, the fuel pressure after the paper comes out can be kept in a good state. Therefore, it is possible to prevent the air-fuel ratio from becoming overlifted, and it is possible to prevent problems such as unstable idling and engine stalling.

Further, when FLAG is "2", paper is generated and the air-fuel ratio A/F is in a lean state, and it is necessary to increase the fuel pressure by increasing the duty ratio TON/T. Therefore, for example, from time t2 in FIG.
As shown at timing t3, the control unit 31 moves to step 216 and sets the duty ratio TON/
T is gradually increased by a predetermined amount T. At this time, if the duty ratio TON/T becomes larger than 100%, the duty ratio TON/T is maintained at 100%.

As a result, as shown in the timing from time t2 to time t3 in FIG. 10, the fuel pressure gradually increases in accordance with the change in the duty ratio TON/T, and the generation of paper is suppressed. Therefore, the fuel pressure can be maintained at a good level without paper. Therefore, it is possible to prevent the air-fuel ratio from becoming overly lean, and it is possible to prevent problems such as unstable idling and engine stalling.

Further, when FLAG is "1", there is no request to change the fuel pressure, and the duty ratio TON/T is maintained at its current state. Therefore, the control unit 31 maintains the current duty ratio TON/T and ends the process.

As described above, in this embodiment, the engine 1 is started at a high temperature, and the air-fuel ratio A/F feedback control (nl
When the iKFI3 is reliably reduced by a predetermined amount, that is, 10%, the fuel pressure is gradually lowered from the atmospheric pressure on the high pressure side to the intake pipe negative pressure on the low pressure side. Therefore, simply 02
Unlike conventional fuel pressure control devices that are configured to gradually switch the fuel pressure from atmospheric pressure to intake pipe negative pressure when the sensor output changes from a lean signal to a rich signal, this system prevents malfunctions of the device itself. can do. That is, in this embodiment, if noise is superimposed on the 02 sensor 44 or if the amount of fuel is suddenly increased during racing, etc., the detection signal of the 02 sensor 44 indicates the air-fuel ratio A/F from lean to rich. Even if the fuel pressure is switched in this manner, the fuel pressure is not immediately lowered, and it is possible to prevent a malfunction in which the fuel pressure is lowered even during vapor generation during a high-temperature start. Therefore, accurate fuel pressure control can be performed depending on the paper generation situation.

As a result, it is possible to prevent problems such as more paper being generated when the engine 1 is started at a high temperature, resulting in unstable idling or engine stalling.

Furthermore, in this embodiment, if the 02 sensor 44 is out of order or the air-fuel ratio A/F feedback control is not performed, the elapsed time (4
The configuration is such that the fuel pressure is uniformly lowered based on the time (minutes). Therefore, even when the 02 sensor 44 fails or feedback control is not executed, the fuel pressure will not remain high forever even though the paper has completely come out.

Therefore, it is possible to minimize the occurrence of problems such as deterioration of exhaust gas due to the air-fuel ratio A/F becoming richer than necessary.

Note that this invention is not limited to the above embodiments,
The present invention can be implemented as follows by changing a part of the structure as appropriate without departing from the spirit of the invention.

(1) In the above embodiment, the pressure regulator 6 is provided in three chambers, the first and second negative and positive chambers A and B, and the fuel chamber C, as shown in FIG. 1.2. However, as shown in Figure 11.12, the negative pressure chamber and fuel chamber E
The well-known pressure regulator 27 may be provided in two chambers separated from each other.

(2) In the above embodiment, duty control was carried out to gradually reduce the fuel pressure from the atmospheric pressure on the high pressure side to the intake pipe negative pressure on the low pressure side. Duty control may also be used.

(3) In the embodiment described above, the starter switch 42 and the rotational speed sensor 43 constitute the starting detection means for detecting when the engine I is started, but the starting detection means may be composed of other devices.

(4) In the embodiment described above, the engine temperature detection means for detecting the temperature state of the engine 1 is configured by the intake air temperature sensor 38 and the water temperature sensor 39, but the engine temperature detection means may be configured by other devices.

[Effects of the Invention] As detailed above, according to the present invention, noise is superimposed on the air-fuel ratio detection means when the internal combustion engine is started at a high temperature, and the amount of fuel supplied to the internal combustion engine is suddenly increased. In this case, it is possible to prevent a malfunction in which the fuel pressure is lowered even when vapor is being generated, and it is possible to perform accurate fuel pressure control depending on the vapor generation state.

[Brief explanation of the drawing]

1 to 10 are drawings showing an embodiment embodying the present invention, and FIG. 1 is a schematic configuration explanatory diagram of a fuel pressure control device in an engine mounted at the front of a vehicle, and FIG. is a longitudinal sectional view of the pressure regulator, Fig. 3 is a longitudinal sectional view of the electromagnetic control valve, Fig. 4 is a time chart explaining the control B voltage applied to the electromagnetic control valve, and Fig. 5 is a diagram for controlling the electromagnetic control valve. A graph showing the relationship between the duty ratio and the control pressure introduced into the negative pressure chamber of the pressure regulator,
Fig. 6 is a graph showing the relationship between the intake pipe negative pressure introduced into the negative pressure chamber of the pressure regulator and the fuel pressure applied to the injector, Fig. 7 is a flowchart explaining well-known fuel injection control, and Fig. 8 is this implementation. A flowchart explaining the operation of the example fuel pressure control device, FIGS. 9 and 10 show the feedback control amount, duty ratio, fuel pressure, and FLAG.
It is a time chart explaining the relationship. 11 and 12 are drawings showing another embodiment embodying the present invention. FIG. 12 is a longitudinal sectional view of a known pressure regulator. In the figure, l is an engine as an internal combustion engine, 6.27 is a pressure regulator, 7 is an injector as a fuel injection valve, 22 is an electromagnetic control valve as a control pressure changing means, 31
38 is an intake temperature sensor; 39 is a water temperature sensor; 38 and 39 are engine temperature detection means; ing),
42 is a starter switch, 43 is a rotation speed sensor (42 and 43 constitute a detection means at the time of starting), 44 is an 02 sensor as an air-fuel ratio detection means, A is a first negative pressure chamber, and B is a second , D is the negative pressure chamber, A/F is the air-fuel ratio, KFB is the feedback control amount, and TON/T is the duty ratio.

Claims (1)

[Scope of Claims] 1. Start detection means for detecting the start of the internal combustion engine; engine temperature detection means for detecting the temperature of the internal combustion engine; and detection means for detecting the fuel pressure applied to the fuel injection valve provided in the internal combustion engine. a pressure regulator for adjusting the pressure; a control pressure changing means for duty-controlling the control pressure introduced into the negative pressure chamber of the pressure regulator; and an air-fuel ratio for detecting the air-fuel ratio from the concentration of a specific component in the exhaust gas discharged from the internal combustion engine. A fuel pressure control device for an internal combustion engine, comprising: a detection means; and an air-fuel ratio feedback control means for feedback-controlling the air-fuel ratio based on a detection signal of the air-fuel ratio detection means; a starting completion determining means for determining whether starting of the internal combustion engine is complete; a temperature determining means for determining that the internal combustion engine is at a predetermined temperature or higher based on a detection signal of the engine temperature detecting means; the starting completion determining means; The control pressure changing means switches the fuel pressure from the high pressure side to the low pressure side when the judgment conditions based on the temperature judgment means are both satisfied and the feedback control amount by the air-fuel ratio feedback control means is reduced by a predetermined amount. 1. A fuel pressure control device for an internal combustion engine, comprising fuel pressure control means for controlling a duty ratio.