JP2000073901A - Fuel supply control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the operating efficiency by providing a determining means for determining the generation of foam in the fuel to be injected in an Atkinson' s cycle engine, and operating a foam generation restricting means so as to prevent the generation of foam when the generation of foam is detected. SOLUTION: In an Atkinson's cycle engine, of which compression starting time is delayed by shifting the closing timing of an intake valve 2 to a delay angle side so that a part of the air sucked into a cylinder 1 once is pushed back to the inside of an intake port 8, since the expansion volume becomes larger than the intake air volume, expansion energy by combustion can be recovered more as the kinetic energy, and energy efficiency of the engine can be improved. At this stage, an ECU 18 determines the fuel temperature and the existence of foam on the basis of the signal from an intake port sensor 9 and a fuel temperature sensor 16 or the like. In the case where the generation of foam is determined, fuel pressure is raised by a fuel pressure adjusting valve 14 so as to prevent the generation of foam in the fuel to be injected.

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 achieves an Atokinson cycle by setting a valve timing of an intake valve specially (this is called an Atkinson cycle engine).

[0002]

2. Description of the Related Art Higher efficiency of an internal combustion engine is desired.
Atkinson cycle engines in which the suction volume is smaller than the expansion volume have attracted attention as one of the things that can achieve this. According to the Atkinson cycle engine, since the expansion volume is larger than the suction volume, more expansion energy due to combustion can be recovered as kinetic energy, and the energy efficiency of the engine can be improved.

[0003] As this Atkinson cycle engine, there is an engine utilizing a late closing action of an intake valve. By shifting the closing timing of the intake valve to the retard side, a part of the air once sucked into the cylinder is pushed back into the intake port, and the compression start timing is delayed more than usual. Therefore, in the Atkinson cycle engine, the volume in the cylinder at the start of compression becomes the substantial intake volume. On the other hand, since the expansion volume after combustion is determined by the opening timing of the exhaust valve, when the piston is near the bottom dead center so that it can be used even near the state where the stroke volume in the cylinder is maximum, Open the exhaust valve. By the action of the intake valve and the exhaust valve as described above, an Atkinson cycle in which the suction volume is smaller than the expansion volume is achieved using the same cylinder as the conventional one, and high efficiency can be obtained.

A mechanism (VVT) for adjusting the valve timing so that the closing timing of the intake valve is continuously variable.
In an internal combustion engine equipped with a throttle valve, it is possible to realize an Atkinson cycle by changing the closing timing of the intake valve to adjust the output, and to pump the intake air which occurs in the output adjustment by the conventional throttle valve. Since the loss can be reduced, this also leads to higher efficiency of the internal combustion engine.

[0005]

However, since the intake gas blown back into the intake port by the late closing action of the intake valve is once sucked into the cylinder, heat transfer from the inner wall surface of the cylinder and the intake air It is heated by passing through a valve throttle. When the intake gas having a high temperature is blown back into the intake port, the intake port may be several tens degrees Celsius higher than that of a normal engine. This allows fuel supply lines,
The temperature of the fuel injector or carburetor rises, and some of the fuel inside the fuel vaporizes and becomes bubbles.As a result, air bubbles are discharged from the fuel injection holes of the fuel injector and the carburetor, and necessary fuel is injected. There is a problem that it is difficult to accurately inject the amount.

SUMMARY OF THE INVENTION Accordingly, the present invention provides an internal combustion engine that achieves an Atkinson cycle utilizing a late closing action of an intake valve, which reduces the accuracy of fuel injection control due to fuel vaporization in a fuel supply line including the vicinity of a fuel injection hole. It is intended to prevent it.

When it is difficult to directly measure the temperature of the fuel injector, it is assumed that the temperature of the fuel injector is in a high temperature state by estimating the temperature from an ambient temperature such as a measurable cooling water temperature and an intake air temperature. When it is determined that the fuel pressure is increased by changing the set pressure of the pressure regulator, the reduced pressure boiling of the fuel can be suppressed, and the engine which is in a high temperature state can be easily restarted. Publication No.
As described in Japanese Patent Application Laid-Open No. 12031, these prior arts are intended to solve the problem of restarting an engine that has become hot due to high output operation or the like.
The present invention differs from the present invention in the prerequisite problem.

[0008]

According to the present invention, there is provided a fuel supply control device for an internal combustion engine as claimed in the claims as means for solving the above-mentioned problems.

According to the first aspect of the present invention, the detecting means and the determining means for determining that bubbles are generated in the fuel injected by the Atkinson cycle engine, and the bubble generation suppressing means for positively preventing the generation of bubbles. When it is determined that air bubbles are generated, the suppression means is operated to prevent the generation of air bubbles. According to the second aspect, the Atkinson cycle engine is provided with a fuel pressure adjusting mechanism, thereby increasing the fuel pressure in the fuel supply line, thereby suppressing the generation of bubbles in the fuel. According to the third aspect, the fuel supply line or the bypass line branching from the vicinity of the fuel injection hole is provided. By circulating the fuel through the bypass line, the temperature of the portion in contact with the fuel and the temperature of the injected fuel are reduced. Since it is lowered, it is possible to prevent the generation of bubbles in the fuel.

The means for detecting, judging, and suppressing the generation of air bubbles is the same as that of the ordinary internal combustion engine provided with the valve timing adjusting means, which is changed to an Atkinson cycle engine by changing the valve timing. Can also be applied. According to claim 5, the pressure and the temperature of the fuel in the fuel supply line are:
The electronic control unit refers to a built-in map value and performs optimal control so as to suppress generation of bubbles.

Each of the fuel supply control devices according to the sixth to fifteenth aspects is characterized by a measuring means for estimating whether or not bubbles are generated in the injected fuel. In claim 6, the lubricating oil temperature is detected, in claim 7, the cooling water temperature is detected, in claim 8, the intake air temperature is detected, and in claim 9, the temperature of the fuel supply line or the housing near the line is detected. And claim 1
At 0, the temperature of the fuel in the fuel supply line is directly detected, at 11th temperature of the intake port is detected, at 12th temperature of the fuel injector is detected, and at 13th, the carburetor is detected. The electric resistance value of the solenoid in the fuel injector is detected in claim 14, and the pattern of the air-fuel ratio signal of the air-fuel ratio detection means provided in the exhaust passage is detected in claim 15, Based on each detection signal, it can be estimated whether or not bubbles are generated in the injected fuel.

As described above, according to the present invention, in an internal combustion engine that realizes an Atkinson cycle by an intake valve late closing action, high-temperature intake gas is generated in fuel in a fuel injector, a carburetor, or the like by blowing back. By suppressing bubbles, accurate fuel injection amount control can be achieved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) The structure and operation of a first embodiment of the present invention will be described with reference to FIGS. FIG.
1 shows a configuration of the gasoline engine 100 according to the first embodiment.
The gasoline engine 100 includes an intake valve 2 provided in a cylinder 1 at a cylinder head.
And an intake valve cam 3 for opening and closing the intake valve 2, an air-fuel ratio sensor (A / F sensor) 5 provided in an exhaust passage 4 common to all cylinders 1, and an intake passage 6 common to all cylinders 1. An intake air temperature sensor 7 provided, an intake port 8 branching from the intake passage 6 toward each cylinder 1, an intake port temperature sensor 9 provided in each intake port 8, and a water temperature provided in the cooling water jacket 10. Sensor 11 and fuel tank 12
Pump 13 for pressurizing the fuel and the fuel pressure regulating valve 1
4, a fuel temperature sensor 16 provided on the line 15, a fuel injector 17, and an electronic control unit (EC) for controlling them.
U) 18 and a piston 19 in the cylinder 1 and the like.

First, the operation of the Atkinson cycle and the problems occurring in this cycle will be specifically described with reference to FIG. The feature of the Atkinson cycle is that the intake and exhaust volumes are different. The expansion volume is larger than the intake volume, so that more expansion energy of the combustion gas can be extracted as work. This cycle is realized by the late closing of the intake valve 2. In the first embodiment, the shape of the intake valve cam 3 causes the intake valve 2 to close later than a normal engine. As a result, a part of the intake gas 20 once sucked into the cylinder is pushed back into the intake port 8 by the piston 19 which has begun to rise from the bottom dead center, and then the intake valve 2 is closed. The process begins. As a result, the suction volume is relatively small, and a relatively large amount of work can be obtained in the expansion stroke even with the combustion gas generated by the small amount of intake gas.

The same applies to a variable displacement Atkinson cycle engine provided with a variable intake valve operating timing mechanism (VVT) so that the intake valve closes at an arbitrary timing instead of the specially shaped intake valve cam 3. I can say. In the Atkinson cycle engine, the intake gas 20 which flows into the cylinder 1 to receive heat transfer from the wall surface thereof or is heated to a high temperature by the throttle action of the intake valve 2 is returned to the intake port 8. This high-temperature intake gas 20 is supplied to the intake port 8
To heat the fuel injectors and the fuel injectors, the temperature of which is several tens of degrees Celsius higher than that of a normal engine.
May be higher. As a result, the temperature of the fuel in the fuel injector 17 or the fuel supply line 15 becomes high, and bubbles are generated. When the fuel is injected, the bubbles are also injected, so that the injection amount cannot be accurately controlled. There is.

Therefore, in the first embodiment of the present invention,
To address this problem in an Atkinson cycle engine, a water temperature sensor 11, an intake temperature sensor 7, an intake port temperature sensor 9, a fuel temperature sensor 16, an A / F
At least one of the signals from the sensor 5 is used to determine the fuel temperature or the presence or absence of air bubbles, and the fuel pressure is increased using the fuel pressure adjusting valve 14 in response to the fuel pressure and the fuel is injected from the fuel injector 17 or carburetor. This is to prevent bubbles from being generated in the previous fuel.

FIG. 3 shows a control procedure executed by the ECU 18 for this purpose. The level of the pressure applied to the fuel is determined by the ECU 18 reading from a steam diagram incorporated as a map in accordance with the boiling point of the fuel, and control is executed by changing the set pressure of the fuel pressure regulating valve 14. . Since gasoline etc., which is fuel, is a mixture,
As shown in FIG. 4, even if the pressure is constant, the boiling point differs for each component. Therefore, the fuel pressure is determined from the fuel temperature and the partial pressure of each component.

Also, in the Atkinson cycle engine, the fuel in the fuel injector 17 and the carburetor often becomes the highest temperature, and bubbles are generated there. Therefore, these parts are exposed to temperature such as a thermistor or a thermocouple. It is effective to provide a measuring means.

In the above-described method, the generation of steam in the fuel in the fuel injector 17 and the carburetor is estimated from the signals of the various temperature sensors, but the A / F sensor 5 provided in the exhaust passage 4 is used. When used, whether or not steam has actually been generated in the fuel can be read from the waveform of the signal of the A / F sensor 5. FIG. 5 shows the signal waveform of the A / F sensor at the time when bubbles start to be generated in the fuel. The characteristic of this signal waveform is that the signal value of the A / F sensor 5 is changed from the stoichiometric air-fuel ratio (14.5) to the air. It is to come off in excess. This is because the fuel injector 17 simultaneously discharges bubbles during fuel injection, resulting in insufficient fuel supply.

When air bubbles are generated inside the fuel injector 17, the largest amount of air bubbles are generated from the highest temperature among the fuel injectors 17 provided for each cylinder 1. Therefore, this fuel injector When combustion occurs in the cylinder 1 (# 2) corresponding to 17, a relatively large signal indicating the above-mentioned excess air is generated as indicated by P in FIG. Also,
Even in the same cylinder 1 (# 1), a variation (unevenness) as shown as D in FIG. 5 occurs between the signals of excessive air generated in each cycle. The ECU 18 recognizes the occurrence of bubbles from such a signal.

Second Embodiment The configuration and operation of a second embodiment of the present invention will be described with reference to FIGS. FIG. 6 shows the configuration of a gasoline engine 200 according to the second embodiment. The gasoline engine 200 has an intake valve 21, an intake valve cam 22, an A / F sensor 2
3, an intake air temperature sensor 24, an intake port 25, an intake port temperature sensor 26, a water temperature sensor 27, a fuel pump 28, a fuel pressure regulating valve 29, and a fuel supply line 30.
, Fuel temperature sensor 31 and fuel injector 3
2 and an ECU 33, and further includes a fuel return bypass 34 for returning excess fuel from the fuel injector 32, and a fuel return amount adjusting valve 35 provided in the middle thereof.

The means and method for determining whether or not air bubbles are generated in the fuel supplied from the fuel supply line 30 to the fuel injector 32 are the same as those in the first embodiment. , Intake air temperature sensor 24
, Intake port temperature sensor 26, and fuel temperature sensor 31
And at least one of the signals from the A / F sensor 23 to determine the fuel temperature and the presence or absence of bubbles. However, the means for preventing the generation of bubbles in the fuel based on these signals is different from that of the first embodiment.

The feature of the means for suppressing the generation of bubbles according to the second embodiment is that a fuel bypass line is provided so as to branch off from a fuel supply line or a fuel passage near the fuel supply line, and fuel is circulated through the bypass line. This is to reduce the temperature of the fuel to be injected and prevent the generation of bubbles due to the rise in the temperature of the fuel. The bypass line used for lowering (cooling) the temperature of the fuel is the fuel return bypass 34 in the example shown in FIG. 6, and the amount of the fuel returned to the fuel tank through the bypass line is automatically set as described later. Adjusted.

FIG. 7 shows a control flow of the second embodiment. In the second embodiment, the fuel temperature is adjusted by the flow rate of the fuel sent to the fuel return bypass (bypass line) 34. When fuel is supplied to the bypass line 34 or its flow rate is increased, the ECU 33 determines whether or not the flow rate of the bypass line 34 is sufficient by means for recognizing whether or not bubbles are generated inside the fuel. The flow rates of the fuel supply line 30 and the bypass line 34 are adjusted by the fuel pressure adjusting valve 29 and the fuel return amount adjusting valve 35.
The criterion for determining whether the flow rate is sufficient is determined by the boiling point (see FIG. 4) for each fuel component, as in the first embodiment.

In the case of an Atkinson cycle engine, since the fuel in the fuel injector 32 and the carburetor often has the highest temperature, it is effective to provide a fuel return bypass 34 for these components. FIG.
In the example shown in FIG. 5, the fuel return bypass 34 branches off from the inside of the fuel injector 32 of each cylinder, which is the end point of the fuel supply line 30, and the fuel in the fuel injector 32 at a high temperature has a relatively small amount of fuel. By bypassing even a part of the flow rate, it is possible to effectively lower the fuel temperature and prevent the generation of bubbles.

(Third Embodiment) The configuration and operation of a third embodiment of the present invention will be described with reference to FIG. Although the first and second embodiments mainly describe the entire system, the third embodiment particularly relates to a temperature measuring means for determining whether or not bubbles are generated in the fuel in the fuel injector. .

In recent internal combustion engines, a fuel injector is often provided in place of the carburetor in order to realize accurate fuel supply. As shown in FIG.
The fuel injector 41 supplies the fuel to the combustion chamber by opening and closing the needle valve 42 to inject fuel.
The fuel supply amount is adjusted according to the length of the valve opening time of the needle valve 42. Since many mechanisms using the solenoid 43 open and close the needle valve 42, the third embodiment attempts to measure the temperature of the fuel injector 41 from a change in the internal resistance of the solenoid 43.

Generally, the resistance of a conductive wire used for a solenoid increases as the temperature increases. Since the rate of increase in resistance due to temperature is determined by the material of the conductive wire, the solenoid 43
The resistance value of the conductive wire is measured by the current detecting means 44,
The ECU 42 can estimate the temperature of the fuel injector 41 based on the change in the resistance value. Therefore, in the third embodiment, it is not necessary to provide the fuel injector 42 with a new temperature measuring device such as a thermocouple.
In addition, the fuel injector 41 where air bubbles are most likely to be generated
Since the temperature of the fuel in the vicinity of the injection hole can be accurately estimated, there is an advantage that accurate fuel pressure and temperature control can be performed.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a first embodiment.

FIG. 2 is a conceptual diagram showing the operation of the Atkinson cycle.

FIG. 3 is a flowchart illustrating a control procedure according to the first embodiment.

FIG. 4 is a diagram showing a component composition of each fuel boiling point.

FIG. 5 is a time chart showing a signal of an A / F sensor when bubbles occur in fuel.

FIG. 6 is a system configuration diagram of a second embodiment.

FIG. 7 is a flowchart illustrating a control procedure according to the second embodiment.

FIG. 8 is a system configuration diagram showing a part of the configuration of the second embodiment in an enlarged manner.

FIG. 9 is a system configuration diagram of a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cylinder 2, 21 ... Intake valve 3, 22 ... Intake valve cam 4 ... Exhaust passage 5, 23 ... Air-fuel ratio sensor (A / F sensor) 6 ... Intake passage 7, 24 ... Intake temperature sensor 8, 25 ... Intake port 9, 26 ... intake port temperature sensor 11, 27 ... cooling water temperature sensor 13, 28 ... fuel pump 14 ... fuel pressure regulating valve 15, 30 ... fuel supply line 16, 31 ... fuel temperature sensor 17, 32, 32a to 32d ... fuel Injectors 18, 33 Electronic control unit (ECU) 20 Intake gas 100, 200 Gasoline engine 34 Fuel return bypass 35 Fuel return amount adjustment valve 41 Fuel injector 42 Needle valve 43 Solenoid 44 Current detection means 45 ... Electronic control unit (ECU)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 19/06 F02M 19/06 A 31/20 31/20 E 69/00 340 69/00 340Z (72) Inventor Osamu Fujishiro 14 Iwatani, Shimowasukamachi, Nishio City, Aichi Prefecture Inside the Japan Auto Parts Research Institute, Inc. (72) Inventor Tokio Obama 14 Iwatani, Shimotsukamachi, Nishio City, Aichi Prefecture, The Japan Auto Parts Research Institute (72) ) Inventor Seiko Watanabe 14 Iwatani, Shimowasumi-cho, Nishio-shi, Aichi Prefecture Inside the Japan Auto Parts Research Institute, Inc. (72) Inventor Hirohiko Hirose 1 Toyota-cho, Toyota-shi, Aichi Prefecture F-term (reference) 3G016 AA02 AA19 BA38 DA01 GA03 3G301 HA01 HA19 JA00 LB06 PA00Z PA10Z PB00Z PB01Z PB08Z PD03Z PE08Z PG00Z

Claims (15)

[Claims] Atkinson wherein a part of air sucked into a space in a cylinder is pushed back into an intake port by a late closing action of an intake valve so that a substantial suction volume in the cylinder becomes smaller than an expansion volume. In an internal combustion engine capable of achieving a cycle, detecting means and determining means for determining that air bubbles have been generated in the injected fuel, and at least positively preventing the generation of air bubbles by the determination result A fuel supply control device for an internal combustion engine, comprising one bubble generation suppressing means. 2. The fuel supply line according to claim 1, further comprising a fuel pressure adjusting mechanism capable of changing a fuel pressure of the fuel supply line, wherein the fuel pressure adjusting mechanism is capable of changing a fuel pressure of the fuel supply line. A fuel supply control device for an internal combustion engine, wherein the pressure of fuel in the fuel supply line is increased to prevent bubbles from being generated in the fuel in the fuel supply line. 3. The fuel cell according to claim 1, wherein a bypass line is provided as the bubble generation suppressing means, the bypass line branching from a passage portion extending from a fuel supply line to a fuel injection hole, and the fuel is recirculated by the bypass line. A fuel supply control device for an internal combustion engine, wherein a temperature of fuel in a portion from a supply line to the fuel injection hole is reduced to prevent bubbles from being generated in the injected fuel. 4. The method according to claim 1, wherein
At least valve timing adjustment means capable of changing the closing timing of the intake valve is provided, and a part of the air sucked into the space in the cylinder is changed by the change of the closing timing of the intake valve. A fuel supply control device for an internal combustion engine adapted to achieve an Atkinson cycle pushed back to a port. 5. The method according to claim 1, wherein
An electronic control device that stores fuel temperature-steam pressure characteristics is provided, and as the bubble generation suppressing means, the stored fuel characteristic values are compared with actual measured values of fuel temperature and pressure. And a fuel supply control device for the internal combustion engine that controls the pressure and temperature of the fuel in the fuel supply line to optimal values. 6. The method according to claim 1, wherein
A fuel supply control device for an internal combustion engine, comprising: a measuring means capable of detecting a lubricating oil temperature as the detecting means, and estimating the generation of bubbles in the injected fuel from the lubricating oil temperature detected by the measuring means. 7. The method according to claim 1, wherein
A fuel supply control device for an internal combustion engine, comprising: a measuring means capable of detecting a cooling water temperature as the detecting means; and estimating generation of bubbles in injected fuel from a cooling water temperature detected by the measuring means. 8. The method according to claim 1, wherein
A fuel supply control device for an internal combustion engine, comprising: a measurement unit capable of detecting an intake air temperature as the detection unit; and estimating the generation of bubbles in the injected fuel from the intake air temperature detected by the measurement unit. 9. The method according to claim 1, wherein
Measuring means capable of detecting the temperature of the fuel supply line or the housing near the line as the detecting means,
A fuel supply control device for an internal combustion engine for estimating generation of bubbles in injected fuel from a temperature detected by the measuring means. 10. The fuel supply system according to claim 1, further comprising a measuring means for directly detecting a temperature of the fuel in the fuel supply line as the detecting means, wherein the temperature of the fuel detected by the measuring means is detected. A fuel supply control device for an internal combustion engine that estimates the generation of bubbles in injected fuel from a temperature. 11. The intake port according to claim 1, further comprising: a measuring unit configured to detect a temperature of the intake port as the detecting unit. A fuel supply control device for an internal combustion engine that estimates the generation of bubbles in fuel. 12. The fuel injector according to any one of claims 1 to 5, further comprising a measuring means for detecting a temperature of a fuel injector as the detecting means, wherein the temperature detected by the measuring means is included in the fuel injector. A fuel supply control device for an internal combustion engine that estimates the generation of bubbles in fuel. 13. The carburetor according to claim 1, further comprising: a measuring unit configured to detect a temperature of the carburetor as the detecting unit, wherein the temperature of the fuel contained in the carburetor is determined based on the temperature detected by the measuring unit. A fuel supply control device for an internal combustion engine that estimates the generation of air bubbles. 14. The fuel injector according to claim 1, further comprising a solenoid provided in the fuel injector as the detection means, and detecting a change in the electric resistance of the solenoid to detect bubbles in the fuel in the fuel injector. A fuel supply control device for an internal combustion engine that estimates occurrence. 15. An air-fuel ratio detecting means according to claim 1, further comprising an air-fuel ratio detecting means provided in an exhaust passage as said detecting means, wherein the fuel is injected from a pattern of an air-fuel ratio signal output by said air-fuel ratio detecting means. A fuel supply control device for an internal combustion engine that estimates the generation of bubbles in fuel.