JPS6287638A - Fuel pressure controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent an unstable idling state and an engine stall from occurring, by having control pressure to be led into a pressure regulator when output of an air-fuel ratio sensor is selected from lean to rich at the time of high temperature starting, duty-controlled by a negative pressure control valve. CONSTITUTION:In the case where vapor is generated in a fuel system at the time of high temperature starting, if an output signal out of an oxygen sensor 16 is a lean signal, a duty ratio of a negative pressure control valve VSV15 is set to 100% by a command out of a control circuit 11 and control pressure to be led into a diaphragm chamber of a pressure regulator 12 is set to atmo spheric pressure. And, when output of the oxygen sensor 16 is selected from a lean signal to a rich signal, from that point of time, the duty ratio of the VSV15 is made so as to be lowered from the 100% by degrees, and when then the specified time elapses, the duty ratio is set to 0%. With this constitution, fuel pressure is gradually lowered from the high pressure side to the low pres sure side so that a large variation in the air-fuel ratio is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a fuel pressure control device that controls an air-fuel ratio by controlling the fuel pressure applied to a fuel injection valve when an internal combustion engine is started at a high temperature. Generally, when an engine is stopped after operating under high load for a long period of time, the engine may become hot and vapor may be generated in the fuel piping of the fuel injection device. In an engine that supplies fuel 11ffi in proportion to the injection time, even if the fuel injection time is the same, the fuel supply i decreases by the amount of vapor, and as a sufficient amount of fuel is not supplied, the air-fuel ratio becomes over-lean, making it impossible to start. F1 is not present or has completed starting.
*JJ stage idle operation becomes unstable and often causes engine stall.

This fuel pressure control device has a fuel nosher regulator in order to keep the fuel injection 0Affi from the fuel I+1 injection valve constant for a certain period of time. By introducing a negative pressure, the fuel pressure is controlled so as to keep the differential pressure between the fuel and the intake pipes constant (Japanese Patent Laid-Open No. 59-96439).

On the other hand, at high temperature restart, the intake pipe negative pressure introduced into the diaphragm chamber of the pressure regulator is reduced to negative pressure 1i11.
By switching to atmospheric pressure using the vsv c vacuum comb switching valve (111 valve), only the intake pipe negative pressure valve limits the fuel pressure applied to the fuel injection valve for a predetermined period of time after the high-temperature start, thereby reducing the air-fuel ratio due to the vapor generation. I'm trying to avoid overleaning.

If the high-temperature start restart time is shortened, that is, when it is assumed that most of the vapor in the fuel pipe has disappeared, the control pressure introduced into the pressure regulator, atmospheric pressure, is switched to the intake pipe negative pressure, and the fuel injection is stopped. The valve's fuel pressure is restored to normal operating conditions.

Problems to be Solved by the Invention However, in conventional fuel pressure control devices for internal combustion engines, when the control pressure introduced into the diaphragm chamber of the pressure regulator is set to atmospheric pressure immediately after a high-temperature start, the fuel pressure increases. As the vapor in the fuel pipe gradually disappears, the air-fuel ratio gradually shifts from normal to rich, and just before the time for setting the control pressure to atmospheric pressure has passed, it becomes overrich, resulting in poor fuel efficiency. As the situation worsened, problems such as unstable idling and engine stalling occurred.

Conversely, if the control pressure introduced into the pressure regulator's diaphragm chamber is set to atmospheric pressure, and the fuel pressure increase time is set short enough to prevent the air-fuel ratio from becoming overrich, the control pressure introduced into the pressure regulator will increase. At the stage of switching from atmospheric pressure to intake pipe negative pressure, the air-fuel ratio becomes A-bar lean, and the idle state becomes unstable and L
This may cause an engine stall.

The present invention was made in order to solve these conventional problems.The present invention has been made in order to solve the problems of the conventional art. The purpose is to avoid overrich or overlean air-fuel ratio by gradually switching the duty ratio of the 1III111 valve from the atmospheric pressure side to the intake pipe negative pressure side.

Means for Solving the Problems The fuel pressure control device for an internal combustion engine according to the present invention includes an engine temperature determining means for determining whether the temperature of the engine is higher than a predetermined temperature, and a starting time detecting means for detecting when the engine is started. , a pressure regulator that controls the fuel injection pressure of the fuel injection valve, a negative pressure control valve that duty-controls the control pressure guided to the diaphragm chamber of the pressure regulator, and an air-fuel ratio that detects the air-fuel ratio from the concentration of specific components in the exhaust gas. sensor, and is configured to gradually control the control pressure from atmospheric pressure to intake pipe negative pressure when the output of the air-fuel ratio sensor switches from a lean signal to a rich signal during a high temperature start.

According to the present invention, when it is detected that the engine is starting at a high temperature based on the engine temperature determining means and the starting time detecting means, if the output of the air-fuel ratio sensor is lean, the negative pressure control valve releases the brake lever 1. Control 2I leading to the diaphragm chamber of the fregulator
Set the t pressure to atmospheric pressure.

When the output of the air-fuel ratio sensor changes from lean to rich during high-temperature startup, the control pressure led from the negative pressure control valve to the diaphragm chamber of the pressure regulator is switched to duty control from the atmospheric pressure side to the intake pipe side.

When it is assumed that most of the vapor in the fuel pipe has disappeared during high-temperature startup, the control pressure led from the negative pressure control valve to the diaphragm chamber of the pressure regulator is set to the normal control pressure.

Actual M example Embodiments of the present invention will be explained based on the drawings.

In FIG. 1, 1 is an engine body, 2 is a cylinder, 3 is a piston, 4 is an intake valve, 5 is an exhaust valve, and 6 is a spark plug. A fuel injection valve 10 is provided in the vicinity of the intake boat 9 of the intake pipe 8. The fuel injection valve 10 injects a predetermined amount of fuel according to a command from a control circuit 11 consisting of a microcomputer. The fuel injection amount of the fuel injection valve 10 is proportional to the fuel injection time, and for this purpose, the differential pressure between the fuel pressure of the fuel injection valve 10 and the intake pipe negative pressure is set to a predetermined value (for example, 2.55 Ny/
A pressure regulator 12 is provided for setting ai).

The main body of the pressure V generator 12 is defined by a diaphragm (not shown) into a fuel chamber and a diaphragm chamber,
The diaphragm chamber is provided with a diaphragm spring that introduces control pressure from the VSV15 as a negative pressure control valve, while also closing the fuel return circuit of the fuel chamber on the opposite side via the diaphragm. There is. When the diaphragm chamber is open to the atmosphere,
When the fuel pressure in the fuel chamber exceeds, for example, 2°55/9/ctA, the diaphragm is pushed up against the diaphragm spring and the fuel returns to the fuel tank through the return circuit. When the intake pipe negative pressure is introduced into the diaphragm chamber, the fuel returns to the fuel tank at a fuel pressure that is lower by the intake pipe negative pressure than when the diaphragm chamber is opened to the atmosphere.

Intake pipe negative pressure in a surge tank 14 on the downstream side of a throttle valve (not shown) installed in the intake pipe 8 is introduced into the diaphragm chamber of the pressure regulator 12 via the VSV 15. The duty ratio of VSV15 is controlled by the command from the control circuit 11, and the duty ratio is normally set to 0%.
0 pressure in the intake pipe is introduced into the diaphragm j1 chamber of the pressure regulator 12.

Therefore, if vapor is generated in the fuel system during a high-temperature start, if the output of the oxygen sensor 16 as an air-fuel ratio sensor is a lean signal, the command from the control circuit 11 will cause the V
The duty ratio of the SV 15 is set to 100%, and the control pressure introduced into the diaphragm chamber of the pressure regulator 12 is set to atmospheric pressure. When the output of the oxygen sensor 16 switches from a lean signal to a rich signal, from that point on, the duty ratio of the VSV 15 is gradually lowered (decreased Q) from 100% to 0% by a command from the well control circuit 11, thereby changing from lean to rich. After a predetermined period of time has elapsed from the time of switching to rich, the duty ratio is set to 0%, that is, the control pressure introduced into the pressure regulator 12 is set to the intake pipe negative pressure. During normal operation, the control circuit 11 performs feedback control of the air-fuel ratio based on the power of the oxygen sensor 16.

Next, an example of the fuel pressure control of the fuel pressure control device in this embodiment will be explained based on the flowcharts shown in FIGS. 2 to 4.

Figure 2 shows the engine starting routine.

First, in step 20, it is determined whether the starter is on or not. If the starter is off, the process proceeds to step 23, where the duty ratio of the VSV 15 is set to 0%, that is, the control pressure guided to the pressure regulator 12 is set to 0%. Set the intake pipe to negative pressure. If the starter is turned on in step 20, the process proceeds to step 21, where it is determined whether the separate cooling water temperature detected by a water temperature sensor (not shown) is 100° C. or higher. If the engine water temperature is less than 100° C. in step 21, the process proceeds to step 23, where the duty ratio of the VSV 15 is set to 0%. Conversely, if the engine cold water temperature is 100° C. or higher, the process proceeds to step 22, where the duty ratio of the VSV 15 is set to 100%. However, when the engine cooling water temperature is over 100℃ during the opening operation,
This state is considered as a high temperature start, and the duty ratio of VSV15 is set to 100%, and the pressure regulator 12 is
By setting the υ control pressure introduced into the diaphragm chamber at atmospheric pressure gQ, the lean air-fuel ratio due to paper generated in the fuel pipe is directed to the air-fuel ratio ridge side.

In FIG. 3, the main route which controls the fuel pressure of the pressure regulator 12 is controlled by the VSV 15. The machine starts at step 30f! It is determined whether 1111210 seconds have elapsed or not, and if 10 seconds have not elapsed, the process proceeds to step 39, and the R1 time lag is exited from tL. In other words, VS
By setting the duty ratio of V15 to 100%, the control pressure introduced into the diaphragm chamber of the pressure regulator 12 is set to atmospheric pressure 1 to increase the fuel pressure. When 10 seconds have elapsed after starting the engine, the process proceeds to step 31, where it is determined whether or not the signal FLR is set, indicating that the air-fuel ratio has been switched from lean to rich. Flag F
If the LR is down, the program proceeds to step 32, where it is determined whether the air-fuel ratio is rich or not, and if the air-fuel ratio is close to 1, the program proceeds to step 39, where a lean flag is set. If the air-fuel ratio is rich in step 32, the routine proceeds to step 33, where it is determined whether or not the lean flag is raised, and if the lean flag is lowered, this routine is ended. On the other hand, if the lean flag is raised, the flow advances to step 34 and the flag FLR is raised.

When the flag FLR is set, the interrupt routine shown in FIG. [VS for each CA
The duty control counter value of V15 is incremented by +1.

Next, in step 35, the duty control counter value becomes 1.
It is determined whether or not the value is 0 or more, and if the duty control counter (shift is 10 or more), the process proceeds to step 36 and the VSV15
The duty ratio of is subtracted by 2%, and the duty control counter value is set to O at that point. Next, if the flags FL and R are set according to the interrupt routine shown in FIG. 4, the duty control counter value is incremented by 1 at every fixed time or every fixed crank angle. If the duty control power "Kunta value is 10 or more, the duty ratio is roughly subtracted by 2% in step 36, and the duty control counter value is set to O again.
l: Set.

In this way, the flag F L is set 10 seconds after the high temperature start.
If R is set, the duty ratio of VSV15 is gradually subtracted by 2% under predetermined conditions.

As the duty ratio gradually decreases, the control pressure of the pressure regulator 12 gradually approaches the intake pipe negative pressure from atmospheric pressure, and the air-fuel ratio is controlled within a predetermined range. In step 37, the duty ratio is further reduced to O.
If it is determined that the value is below, the process proceeds to step 38, where the duty ratio is set to a fixed state of 0%.

FIG. 5 shows a graph comparing conventional fuel pressure control and fuel pressure duty control according to this embodiment. In this example, if the air-fuel ratio is lean immediately after a high-temperature restart, the fuel pressure will be increased by 100% of the duty ratio.
(B), when the air-fuel ratio gradually becomes richer as time passes after startup and the oxygen sensor 16 outputs a rich signal (B)
, this rich signal is set as - and the duty ratio of VSV15 is gradually reduced from 100% to 0% (between 8 and 0).
. When the duty control of the VSV 15 is completed (C), the fuel pressure increase at the time of high temperature start is completed, and thereby a predetermined air-fuel ratio is set by normal fuel pressure control.

Q ;j'3, In this embodiment, the starter and engine cooling water It? However, in the present invention, an ignition switch, an intake temperature sensor, or the like may be used to detect a high temperature start.

Effects of the Invention According to the present invention, when the output of the air-fuel ratio sensor switches from lean to rich during high-temperature startup, the control pressure introduced to the pressure regulator is duty-controlled by the 0-pressure control valve, and the fuel pressure is changed from the high pressure side to the low pressure side. Since the air-fuel ratio is gradually decreased toward the side, it is possible to avoid large fluctuations in the air-fuel ratio and reliably prevent unstable idling conditions and engine stalls caused by over-rich or over-lean conditions.

In addition, the rich signal from the air-fuel ratio sensor after a high-temperature restart is used as a trigger to start duty control of the negative pressure control valve, so even if the air-fuel ratio varies slightly depending on the engine starting condition and fuel scale, the viscosity remains constant. Fuel pressure control can be performed.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, and FIG. 2 is a schematic diagram showing an embodiment of the present invention (excluding the start operation routine).
[Coachyard, Fig. 3 is a flowchart showing the main routine in the embodiment of the present invention, Fig. 4 does not show the interrupt routine in the embodiment of the invention) [-] - chart, Fig. 5 is a flowchart showing the main routine in the embodiment of the invention. This is a graph showing the fuel pressure control characteristics of the example compared with the conventional example. 1...Opening/opening body, 4...Intake valve, 5...
- Exhaust valve, 8... Intake pipe, 9... Intake boat, 10... Fuel injection valve, 11... Control circuit, 12... Pressure regulator, 14... Surge tank, 15... - Negative pressure control valve (VSV), 16... sky ratio sensor (oxygen sensor).

Claims (1)

[Claims] an engine temperature determination means for determining whether the engine temperature is higher than a predetermined temperature; a start detection means for detecting when the engine is started;
A pressure regulator that controls the fuel injection pressure of the fuel injection valve, a negative pressure control valve that controls the duty of the control pressure guided to the diaphragm chamber of the pressure regulator, and an air-fuel ratio sensor that detects the air-fuel ratio from the concentration of a specific component in the exhaust gas. and controlling the duty ratio of the negative pressure control valve so that the control pressure is gradually switched from atmospheric pressure to intake pipe negative pressure when the output of the air-fuel ratio sensor changes from a lean signal to a rich signal during a high temperature start. A fuel pressure control device for an internal combustion engine, characterized in that: