JPH029094Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a fuel supply system for an internal combustion engine, and in particular to a so-called single-point injection electronic control system that distributes fuel to multiple cylinders using one or two injectors. An injector suitable for use in an automobile engine equipped with a fuel injection device, which injects pressurized fuel to form an air-fuel mixture, is opened and closed in accordance with engine operating conditions and is located upstream of the throttle valve. The present invention relates to an improvement in a fuel supply system for an internal combustion engine installed in a fuel supply system for an internal combustion engine.

For injecting pressurized fuel to form a mixture,
2. Description of the Related Art A one-point injection type electronically controlled fuel injection device is known in which one or two injectors are arranged upstream of a throttle valve and the opening and closing of the injector is controlled according to the operating state of the engine. For example, as shown in FIG. 1, this works in conjunction with a fuel pump 14 for pressurizing the fuel in the fuel tank 12 to a predetermined pressure, and an accelerator pedal (not shown) for controlling the flow rate of intake air. Throttle valve 18 that opens and closes
The throttle body 16 is equipped with a throttle body 16, the throttle sensor 19 detects the opening degree of the throttle valve 18, and the fuel pump 14 is installed upstream of the throttle valve 18. , an injector 22 for injecting pressurized fuel supplied via the pressurized fuel passage 20 to form an air-fuel mixture, which is controlled to open and close depending on the engine operating state.
, a fuel pressure regulator 24 for maintaining the pressure of the pressurized fuel injected by the injector 22 at a predetermined value, and a fuel pressure regulator 24 for returning the remaining fuel not injected by the injector 22 to the fuel tank 12 from the fuel pressure regulator 24. return fuel passage 26
and an intake temperature sensor 28 for detecting the temperature of intake air taken into the throttle body 16.
and the intake pipe 3 downstream of the throttle body 16.
a negative pressure sensor 32 disposed at the engine 10 for detecting intake pipe negative pressure; and an igniter 34 for generating an ignition signal to be given to a spark plug (not shown) disposed in each cylinder of the engine 10. A water temperature sensor 36 is installed in the cylinder block of the engine 10 to detect the engine cooling water temperature, and a water temperature sensor 36 is installed in the exhaust pipe 38 to detect the rich lean state of the air-fuel ratio from the residual oxygen concentration in the exhaust gas. An exhaust gas sensor 40 for detection and a battery 42
and, for example, determine the basic injection amount according to the engine load detected by the negative pressure sensor 32 and the engine rotation speed detected from the output of the igniter 34,
This is the output of the intake temperature sensor 28 and the water temperature sensor 3.
6 outputs, exhaust gas sensor 40 outputs, battery 42
and an electronic control unit (hereinafter referred to as ECU) 44 that determines the fuel injection amount by correcting it according to the voltage, etc. of It is configured.

According to such a single point injection type electronically controlled fuel injection device, the configuration is smaller than that of a so-called multipoint injection type electronically controlled fuel injection device which is provided with an injector that injects pressurized fuel to each cylinder of the engine. It has the characteristics of being simple and having low production costs.

However, in this one-point injection type electronically controlled fuel injection system, only the injector 22 provided upstream of the throttle valve 18 covers the entire operating range. In engine operating ranges where the injection amount and intake air amount are small, most of the fuel injected from the injector 22 temporarily adheres to the wall surface of the throttle body 16 or the top surface of the throttle valve 18, forming a so-called wall flow and flowing along with the intake air. The air is inhaled into the intake pipe 30. At this time, the amount of intake air is small, the intake air flow rate is slow except for the end face of the throttle valve 18, and the difference from the end face of the valve is large, so the fuel atomization performance is poor and the mixture of fuel and air is highly uneven. In particular, the engine becomes unstable during idle operation. Conventionally, countermeasures have been taken to prevent this by making the air-fuel ratio richer than the stoichiometric air-fuel ratio and increasing the idle rotation speed above the standard value, but this not only increases fuel consumption but also There were also problems with exhaust gas control.

In order to solve these problems, JP-A-57-
It is conceivable to install an injector on the downstream side of the throttle valve as in 10764, but this not only increases the production cost due to the use of a large number of expensive injectors, but also makes it difficult to use two injectors when the engine is running. The problem is that it is difficult to adapt and control the method.

The present invention was made to solve the problems of the conventional technology, and it is possible to control the air-fuel ratio in a simple way without making the air-fuel ratio richer than the stoichiometric air-fuel ratio or increasing the idle rotation speed above the reference value. A fuel for an internal combustion engine that can stabilize the operating state of the engine at low speeds by using an auxiliary fuel supply mechanism, thereby reducing fuel consumption and simplifying the exhaust gas purification device. The purpose is to provide a feeding device.

The present invention is applied to a fuel supply system for an internal combustion engine, in which an injector that injects pressurized fuel to form an air-fuel mixture and whose opening and closing are controlled according to engine operating conditions is disposed upstream of a throttle valve. ,
a low-speed fuel passage into which a portion of the return fuel of the pressurized fuel supplied to the injector is introduced; an air bleed for mixing air into the fuel in the low-speed fuel passage; and an air bleed for mixing air into the fuel in the low-speed fuel passage. a slow port and an idle port for supplying fuel to the downstream side near the throttle valve;
including an idle adjustment screw for adjusting the flow rate of fuel supplied from the idle port, and a solenoid valve for opening the low speed fuel passage at low speed,
The above object is achieved by providing an auxiliary fuel supply mechanism for supplying a portion of the return fuel to the vicinity of the throttle valve during predetermined operating conditions including low speed. Alternatively, a portion of the return fuel is introduced into the low-speed fuel passage through a float chamber, and an acceleration fuel passage into which a portion of the fuel in the float chamber is introduced into the auxiliary fuel supply mechanism; By including an acceleration pump for pressurizing the inside of the acceleration fuel passage and an acceleration nozzle for supplying the fuel pressurized by the acceleration pump to the upstream side near the throttle valve, the engine during acceleration can be In addition to stabilizing the operating state of the engine and improving transient performance, it also eliminates the need for increased acceleration in the injector, greatly simplifying control.

Further, the structure of the auxiliary fuel supply mechanism is simplified by directly introducing a portion of the return fuel into the low-speed fuel passage and by causing the solenoid valve to gradually open the low-speed fuel passage during low speed. It has become.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electronically controlled one-point injection type fuel injection system for an automobile engine, in which a fuel supply system for an internal combustion engine according to the present invention is adopted, will be described in detail below with reference to the drawings.

As shown in FIG. 2, the first embodiment of the present invention has a fuel tank 12, a fuel pump 14, a throttle body 16, a throttle valve 18, a throttle sensor 19, and a high-pressure fuel passage 2, which are similar to the conventional example.
0, injector 22, fuel pressure regulator 24,
return fuel passage 26, intake temperature sensor 28, intake pipe 30, negative pressure sensor 32, igniter 34, water temperature sensor 36, exhaust pipe 38, exhaust gas sensor 40,
In the single point injection type electronically controlled fuel injection system for the automobile engine 10 including the battery 42 and the ECU 44, a portion of the return fuel from the return fuel passage 26 is further introduced into the throttle body 16 via the float valve 52. , a float chamber 56 in which a float 54 is floated and communicated with the inside of the throttle body 16 through a ventilation pipe 55.
and a low-speed fuel passage 60 into which a portion of the fuel in the float chamber 56 is introduced via the low-speed jet 58.
and a slow port 64 and an idle port 66 for supplying the fuel in the low-speed fuel passage 60 into which air has been mixed through the air bleed 62 to the downstream side near the throttle valve 18, and an idle adjustment screw 68 for adjusting the flow rate of fuel supplied by the
An auxiliary fuel supply mechanism 50 is provided which includes a solenoid valve 70 for opening the low-speed fuel passage 60 at low speeds using the output of the ECU 44.

The ECU 44, as shown in detail in FIG.
a basic calculation circuit 72 for determining a basic injection amount according to the engine rotational speed N detected from the intake pipe negative pressure output from the negative pressure sensor 32 and the ignition signal Ig output from the igniter 34; The obtained basic injection amount is sent to the intake air temperature sensor 28.
To determine the fuel injection amount by correcting it in accordance with the intake air temperature as the output, the engine cooling water temperature as the output of the water temperature sensor 36, the air-fuel ratio as the output of the exhaust gas sensor 40, and the throttle valve opening θ as the output of the throttle sensor 19. a first comparator circuit 76 that outputs a high level signal when the engine speed N detected from the output of the igniter 34 exceeds a predetermined value _N1 ; and the throttle sensor 19.
The output throttle valve opening θ is the first predetermined value θ ₁
a second comparison circuit 78 that outputs a high level signal when the throttle valve opening degree θ exceeds the first predetermined value θ ₁ ; A third comparison circuit 80 outputs a high level signal when the value θ ₂ is exceeded, and the output of the first comparison circuit 76 and the second comparison circuit 78
An OR circuit 82 that outputs the logical sum of outputs, and
an AND circuit 84 that outputs the logical product of the output of the circuit 82 and the output of the correction calculation circuit 74;
a first drive circuit 86 for driving the injector 22 with the output of the first comparator circuit 86; circuit 88
and a second drive circuit 90 for driving the solenoid valve 70 with the output of the solenoid valve 70.

The first to third comparison circuits 76, 78, 80 and the second drive circuit 90 surrounded by broken lines in FIG.
Specifically, it is constructed as shown in FIG. 4. For example, the first comparison circuit 76 is comprised of a waveform shaping circuit 76a, a monostable circuit 76b, a low-pass filter 76c, and a comparator 76d.

Therefore, input from the igniter 34,
The ignition signal Ig as shown in FIG. 5A is waveform-shaped by the waveform shaping circuit 76a of the first comparison circuit 76 to become a signal as shown in FIG. 5B, and further,
The monostable circuit 76b produces a signal as shown in FIG. 5C, and the low-pass filter 76c produces a voltage signal _VN corresponding to the engine rotational speed N as shown in FIG. 5D. This engine rotational voltage signal _VN is compared with a predetermined voltage _VN1 corresponding to a predetermined rotational speed _N1 set in the comparator 76d, and as shown in FIG.
If higher than N ₁ , the high level signal
The low level signal is input to the OR circuit 82 and the NOR circuit ₈₈ ;
The signal is input to the OR circuit 82 and the NOR circuit 88. Further, the throttle valve opening voltage signal V〓 inputted from the throttle sensor 19 is
As shown in FIG. 7, the throttle valve angle θ
is larger than the second predetermined value θ ₂ , both the second comparison circuit 78 and the third comparison circuit 80 output high-level signals, and the throttle valve opening θ
is less than θ ₂ and greater than θ ₁ , the second comparison circuit 78
, a high level signal is output from the third comparison circuit 80, and a low level signal is output from the third comparison circuit 80. Also, when the throttle valve opening θ is less than the predetermined opening θ ₁ , the second comparison circuit 78 and the third comparison circuit 80 output a low level signal. A low level signal is output from both comparison circuits 80. Therefore, the NOR circuit 88 is
Only when the engine rotational speed N is _N1 or less and the throttle valve opening θ is _θ2 or less, a high level signal is output, the second drive circuit 90 opens the solenoid valve 70, and the slow port 64 And fuel is supplied from the idle port 66. On the other hand, the OR circuit 82 outputs a low level signal only under the conditions that the engine rotational speed N is less than _N1 and the throttle valve opening θ is less than _θ1 , and at this time, the output of the AND circuit 84 is a low level signal. Therefore, the injector 22 is closed and fuel injection from the injector 22 is stopped.

The operation of the first embodiment will be explained below.

First, under normal engine operating conditions, the
The ECU 44 includes the throttle sensor 19, the intake air temperature sensor 28, the negative pressure sensor 32, and the igniter 3.
4. The valve opening time of the injector 22 is controlled according to output signals from the water temperature sensor 36, exhaust gas sensor 40, etc. Therefore, the fuel pressurized by the fuel pump 14 from the fuel tank 12 and supplied to the injector 22 via the pressurized fuel passage 20 is injected into the air passage section of the throttle body 16, and the remaining fuel is transferred to the fuel pressure regulator. 24 and is returned to the fuel tank 12. Further, when the level of the float 54 in the float chamber 56 is decreasing, a portion of the return fuel also flows into the float chamber 56 until the level reaches a certain level.

The fuel injected from the injector 22 is
The gas is mixed with air, passes from the throttle body 16 through the intake pipe 30, and is combusted in the combustion chamber within the engine 10, and the exhaust gas is discharged from the exhaust pipe 38.

On the other hand, when the engine is in an operating state near a low speed range, that is, when the engine speed N is below the predetermined value _N1 and the throttle valve opening θ is below the predetermined value _θ2 , the ECU 44 The solenoid valve 70 is opened, thereby causing the float chamber 5 to open.
6 is metered by the low-speed jet 58, passes through the low-speed fuel passage 60, and along the way there is an air bleed 62.
The air is mixed with air and supplied into the intake pipe 30 from the slow port 64 and the idle port 66.

Further, when the throttle valve opening degree θ becomes less than or equal to a smaller first predetermined value θ ₁ , the ECU 44 closes the injector 22 and fuel is supplied only from the slow port 64 and the idle port 66.

In this embodiment, the auxiliary fuel supply mechanism 50 supplies only low-speed fuel, so the auxiliary fuel supply mechanism is relatively simple.

Next, we will discuss one example of an automobile engine in which the second embodiment of the fuel supply device for an internal combustion engine according to the present invention is adopted.
A second embodiment of the point injection type electronically controlled fuel injection device will be described in detail.

As shown in FIG. 8, this embodiment has a fuel tank 12 and a fuel pump 14 similar to those of the first embodiment.
, throttle body 16, throttle valve 18, throttle sensor 19, pressurized fuel passage 20, injector 22, fuel pressure regulator 24, return fuel passage 26, intake temperature sensor 28, and intake pipe 30. , negative pressure sensor 32, igniter 34, water temperature sensor 36, and exhaust pipe 38
, an exhaust gas sensor 40, a battery 43,
ECU44, float valve 52, float 54,
Ventilation pipe 55, float chamber 56, low speed jet 5
8. 1 of the automobile engine 10 equipped with an auxiliary fuel supply mechanism 50 consisting of a low-speed fuel passage 60, an air bleed 62, a slow port 64, an idle port 66, an idle adjustment screw 68, and a solenoid valve 70.
In the point injection type electronically controlled fuel injection device, the auxiliary fuel supply mechanism 50 further includes an acceleration fuel passage 9 into which a part of the fuel in the float chamber 56 is introduced.
2, an acceleration pump 94 for pressurizing the inside of the acceleration fuel passage 92 during acceleration, and an acceleration nozzle 96 for supplying the fuel pressurized by the acceleration pump 94 to the upstream side near the throttle valve 18. It was added. The other configurations are the same as those of the first embodiment, so explanations will be omitted.

In this embodiment, as in the first embodiment, not only fuel is supplied from the slow port 64 and the idle port 66 during low speeds, but also acceleration fuel is supplied during acceleration when the acceleration pump 94 operates. Ru. Therefore, during acceleration, acceleration fuel is immediately supplied, and the transient response is improved compared to the case where the injector 22 increases the amount of acceleration fuel. Further, it is no longer necessary to perform acceleration increase with the injector 22, and the injector 22
control can be simplified.

In each of the above embodiments, the auxiliary fuel supply mechanism 50 includes the float chamber 56, so the control of the auxiliary fuel supply mechanism 50 is as follows:
It is only necessary to control the opening and closing of the solenoid valve 70, and the control is very simple. Furthermore, it is easy to adapt to the engine. Note that the configuration of the auxiliary fuel supply mechanism is not limited to this, and for example, the auxiliary fuel supply mechanism may include a low-speed fuel passage provided with one air bleed passage into which a portion of the return fuel is directly introduced, and the low-speed A slow port and an idle port for supplying fuel in the fuel passage to the downstream side near the throttle valve, and an opening located at the slow port position,
for gradually opening the low speed fuel passage at low speeds;
It is also possible to simplify the configuration of the auxiliary fuel supply mechanism by including a linearly controlled solenoid valve.

Further, in each of the above embodiments, the engine load is detected using the negative pressure sensor 32 and the intake air temperature sensor 28, but the method of detecting the engine load is not limited to this, and for example, It is also possible to directly detect the intake air flow rate of the engine using an air flow meter incorporating an intake air temperature sensor.

As explained above, according to the present invention, by using an auxiliary fuel supply mechanism that is simple to control, operation in the low speed range is more stable than before, and especially in idling operation, a leaner air-fuel ratio and low rotation speed can be achieved. This has the excellent effect of improving fuel efficiency and simplifying the exhaust gas purification device.

An example of changes in carbon dioxide concentration and intake pipe negative pressure during idling operation in the conventional example and the first embodiment of the present invention is shown in FIG. 9 for comparison. As is clear from FIG. 9, it is clear that in the case of the present invention, the fluctuations in carbon dioxide concentration and intake pipe negative pressure are smaller than in the conventional example, and the engine rotation is stable.

[Brief explanation of the drawing]

FIG. 1 is a sectional view, including a partial block diagram, showing the configuration of a conventional single-point injection type electronically controlled fuel injection device for an automobile engine, and FIG. 2 is a fuel supply device for an internal combustion engine according to the present invention. FIG. 3 is a cross-sectional view, including a partial block diagram, showing the configuration of a first embodiment of a single-point electronically controlled fuel injection system for an automobile engine, in which the fuel injection device used in the first embodiment is FIG. 4 is a block diagram showing the overall configuration of the electronic control unit, and FIG. 4 is an electric circuit diagram showing the configuration of the main parts. FIG. 6 is a diagram showing the operating state of the first comparison circuit used in the electronic control unit, and FIG. 7 is a diagram showing the operating state of the second and third comparison circuits. Figure 8 shows a fuel supply system for an internal combustion engine according to the present invention.
FIG. 9 is a cross-sectional view, partially including a block diagram, showing the configuration of a second embodiment of a single-point electronically controlled fuel injection system for an automobile engine. FIG. 3 is a diagram comparing and showing changes in carbon dioxide concentration and intake pipe negative pressure in an idling state. DESCRIPTION OF SYMBOLS 10... Engine, 16... Throttle body, 18... Throttle valve, 19... Throttle sensor, 20... Pressurized fuel passage, 22... Injector, 24... Fuel pressure regulator, 26...
... Return fuel passage, 32 ... Negative pressure sensor, 34
...Igniter, 44 ...Electronic control unit, 5
0... Auxiliary fuel supply mechanism, 56... Float chamber,
60...Low speed fuel passage, 62...Air bleed,
64... Slow port, 66... Idle port, 68... Idle adjustment screw, 70... Solenoid valve, 92... Acceleration fuel passage, 94... Acceleration pump, 96... Acceleration nozzle.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) An injector that injects pressurized fuel to form an air-fuel mixture and is controlled to open and close according to engine operating conditions is disposed upstream of the throttle valve. A fuel supply system for an internal combustion engine, comprising: a low-speed fuel passage into which a portion of the return fuel of the pressurized fuel supplied to the injector is introduced; an air bleed for mixing air into the fuel in the low-speed fuel passage; a slow port and an idle port for supplying fuel mixed with air by air bleed to the downstream side near the throttle valve; an idle adjustment screw for adjusting the flow rate of the fuel supplied from the idle port; and a solenoid valve for opening the low-speed fuel passage at low speeds, and an auxiliary fuel supply mechanism for supplying a portion of the return fuel to the vicinity of the throttle valve during predetermined operating conditions including low speeds. A fuel supply device for an internal combustion engine, characterized by: (2) an acceleration fuel passage through which a part of the return fuel is introduced into the low-speed fuel passage via a float chamber, and a part of the fuel in the float chamber is introduced into the auxiliary fuel supply mechanism; The utility model registration request includes an acceleration pump for pressurizing the inside of the acceleration fuel passage, and an acceleration nozzle for supplying the fuel pressurized by the acceleration pump to the upstream side near the throttle valve. A fuel supply device for an internal combustion engine according to scope 1. (3) A portion of the return fuel is directly introduced into the low-speed fuel passage, and the solenoid valve gradually opens the low-speed fuel passage during low speed. Fuel supply device for the internal combustion engine described.