JPH055474A - Fuel pressure control device for engine - Google Patents

Abstract

PURPOSE:To improve startability at the time of starting an engine by preventing narrowness of an injection angle of fuel injected from an injector in the case of fuel at a very low temperature, improving a condition of a mixture, stabilizing a combustion condition in a combustion chamber, and shortening an intake time of fuel into the combustion chamber, in a temperature condition of fuel. CONSTITUTION:At the time of low temperature of both intake air and cooling water, in an idling condition of an engine, a controller 25 judges fuel at a low temperature and in high viscosity by a signal from each sensor. A vacuum switching valve(VSV) 19, connected to a pressure regulator 11, is actuated by an electric signal from this controller 25, and a negative pressure passage to the pressure regulator 11 is switched to release control gas, applied to a chamber 14 of the pressure regulator 11, to the atmospheric pressure from an existing negative pressure. In this way, a pressure of fuel is increased to spread an injection angle of fuel from an injector 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine fuel pressure control device applicable to a single point injection type engine.

[0002]

2. Description of the Related Art A conventional example of a single point injection (hereinafter referred to as SPI) type engine will be described with reference to FIG. 1 is a throttle body, 2 is an intake passage,
3 is a water jacket. An injector 4 is attached to the inside of the throttle body 1 toward the downstream side, and a throttle valve 5 is provided on the downstream side so as to rotate about a throttle shaft 6 as a rotation center. Reference numeral 7 is a throttle sensor that outputs the opening degree of the throttle valve 5 as an electric displacement amount. A fuel tank 9 is connected to the injector 4 via a pipe 8 having a fuel pump (not shown). Further, a pipe 10 communicating with the pipe 8 is connected to the chamber 12 of the pressure regulator 11.

A chamber 14 partitioned by a diaphragm 13 is provided inside the pressure regulator 11.
The chamber 14 has its tip end communicated with a negative pressure passage 15 which is opened in the intake passage 2 downstream of the throttle valve 5. A valve body 16 is provided inside the chamber 12 so that the conduit 10 and the fuel return passage 17 for returning the surplus fuel to the fuel tank 9 are communicated with or cut off from each other. Reference numeral 18 denotes a spring that acts to urge the diaphragm 13 toward the valve body 16 to cut off the communication between the conduit 10 and the fuel return passage 17.

As described above, in the SPI engine in which the injector 4 is installed upstream of the throttle valve 5 and the fuel supplied from the fuel tank 9 is injected, an intake negative pressure value as a control gas and a spring are used. Pipe line 10 and fuel recirculation line 17 that connect and block by the balance with the elastic force of 18
As a result, the injection pressure of the injector 4 is maintained at a constant value.
The fuel injected from the injector 4 by this action is
Normally, a high-speed air flow sufficiently mixes with air, and atomization and atomization are sufficiently promoted by the time they enter the combustion chamber of each cylinder.

[0005]

However, when the fuel is in an extremely low temperature such as after parking in an extremely cold region, the viscosity of the fuel becomes high, so that the injection angle of the fuel injected from the needle valve of the injector 4 is increased. Is narrower than when the fuel is at a high temperature. For this reason, even in an engine in which fuel is injected aiming at the peripheral portion of the throttle valve 5 when the engine is in the idling state, the injection angle of the fuel becomes narrow, so the injected fuel is injected into the throttle valve 5. It will collide with and adhere to the surface.
As a result, it takes time to inject the fuel into the combustion chamber required by the engine, which delays the engine start time. This is due to the fact that the injection pressure of the injector 4 is maintained at a constant value, so this injection pressure can be changed appropriately as necessary.
If improvements for this purpose can be made with minor changes, it can be installed on existing vehicles, and there are advantages that many parts are common to vehicles of non-cold region specifications.

Among the prior arts, there is a mechanism disclosed in Japanese Patent Laid-Open No. 60-32972 as a mechanism for changing the injection pressure of an injector, and a mechanism for providing a bypass passage in the fuel passage is actually open. -54267 publication. Those disclosed in these publications are also excellent in achieving their respective purposes, but as a solution to the problem caused by the increase in the viscosity of the fuel in the extremely cold regions where the present invention has a problem to be solved. Further, with respect to the point that this is carried out with a slight improvement to the existing vehicle, the configurations disclosed in these publications cannot be used as they are.

The present invention has been made in view of the problems existing in the above-mentioned prior art, and prevents the narrowing of the emission angle of the fuel injected from the injector when the fuel is extremely low temperature under the fuel temperature condition. The purpose is to improve the startability at the time of engine star by improving the state of the air-fuel mixture to stabilize the combustion state in the combustion chamber and shortening the intake time of fuel into the combustion chamber. ..

[0008]

As a means for solving the above problems, the present invention is installed in an intake passage collecting portion,
In an engine fuel pressure control device comprising an injector that opens a valve to inject fuel by an injection signal from a controller and injects fuel, and a pressure regulator that regulates the fuel pressure applied to the injector to a constant value. A vacuum switching valve that is switched by a signal from the controller is connected to the chamber, and by the vacuum switching valve,
As a control gas to the chamber, a negative pressure of intake air and an atmosphere are switched and supplied.

[0009]

With the above structure, when the intake air temperature and the cooling water temperature are both low and the engine is idling,
The controller determines that the temperature of the fuel is low and the viscosity of the fuel is strong based on the signals from the intake air temperature sensor, the water temperature sensor, the throttle sensor, etc., and outputs an output signal that is connected to the pressure regulator. By operating the vacuum switching valve, the negative pressure passage to the pressure regulator is switched, and the negative pressure applied to the pressure regulator is released to atmospheric pressure, thereby increasing the fuel pressure and expanding the fuel injection angle from the injector. The fuel pressure is controlled to recover the injection angle.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG. Reference numeral 1 is a throttle body, 2 is an intake passage, and 3 is a water jacket. An injector 4 is attached inside the throttle body 1 toward the downstream side, and a throttle valve 5 is arranged downstream of the injector 4 about a throttle shaft 6 as a rotation center. Reference numeral 7 is a throttle sensor that outputs the opening degree of the throttle valve 5 as an electric displacement amount. A fuel tank 9 is connected to the injector 4 via a pipe 8 having a fuel pump (not shown). Further, a pipe 10 communicating with the pipe 8 is connected to the chamber 12 of the pressure regulator 11.

A chamber 14 partitioned by a diaphragm 13 is provided inside the pressure regulator 11.
The chamber 14 has a tip end opened to the downstream side of the throttle valve 5 in the intake passage 2 and communicated with a negative pressure passage 15 to which a vacuum switching valve (VSV) 19 is connected. A valve element 16 is provided inside the chamber 12, and a pipe 10 and a fuel return passage for returning excess fuel to the fuel tank 9.
It is designed to communicate with 17 and shut off. Reference numeral 18 urges the diaphragm 13 toward the valve body 16 side to connect the pipe 10 and the fuel return passage.
It is a spring that acts to block communication with 18.

The vacuum switching valve 19 includes ports 20 and 21 for connecting two parts of the divided negative pressure passage 15.
And a port 22 opening to the atmosphere,
When the solenoid 23 is excited, the valve 24
It connects 1 and 22. This operation is performed by a command from the controller 25, as will be described later. On the input side of the controller 25, in addition to the above-mentioned throttle sensor 7, a pressure sensor 26 for detecting the pressure in the intake passage 2, a water temperature sensor 27 for detecting the temperature of the cooling water, an air flow meter 28 for outputting the intake air amount, An intake air temperature sensor 29 that is attached to the air flow meter 28 to detect the intake air temperature and an ignition coil 30 that outputs the engine speed are connected. Reference numeral 31 is an ignition switch, and 32 is a battery serving as a power source.

In this device thus constructed, the controller 25 determines the basic injection amount (injection time) at that time from the status of the output signals of the above-mentioned sensors, and determines the correction injection amount for this basic injection amount. And outputs the injection amount signal of the injector 4. That is, the injector 4 injects the fuel sent from the fuel tank 9, and the signal of the intake air amount from the air flow meter 28 and the signal of the engine speed by the primary signal of the ignition coil 30 are sent to the controller 25. The basic injection amount (injection time) is determined by the controller, and signals from each sensor are sent to the controller 25,
25 controls the valve of the injector 4 to determine the corrected injection amount with respect to the basic injection amount.

The pressure regulator 11 connected to the injector 4 by the negative pressure passage 15 is adjusted so that the fuel pressure applied to the injector 4 (the difference between the intake pipe internal pressure and the fuel pressure) becomes constant. The pressure regulator 11 communicates with the fuel tank 9 so as to correspond to the negative pressure in the intake passage 2 from the negative pressure passage 15 so as to decrease the fuel pressure when the negative pressure becomes strong and increase the fuel pressure when the negative pressure becomes weak. Fuel return path
The fuel pressure is controlled by adjusting the opening and closing of 17 passages.

2 (a) and 2 (b) show the relationship between fuel temperature and pressure. That is, when the fuel is at extremely low temperature (both intake air temperature and water temperature are low and the engine is idling), as shown in (a), when the fuel pressure is the same, the temperature of the fuel is extremely low and that of normal temperature. In comparison, the injection angle of the injector 4 becomes narrower at the extremely low temperature than at the normal high temperature. Further, the relationship between the injection angle of the injector 4 and the fuel pressure is such that the injection angle widens when the fuel pressure is high and narrows when the fuel pressure is low, as shown in FIG. The present invention utilizes the relationship between the injection angle of the injector 4, the temperature of the fuel, and the fuel pressure, and prevents the narrowing of the injection angle of the injector 4 by increasing the fuel pressure even when the fuel has an extremely low temperature. Is.

A signal indicating that the engine is idling is transmitted from the throttle sensor 7 to the controller 24, and a detection value indicating that the intake temperature is low from the intake temperature sensor 29 in the air flow meter 28 and the water jacket. When the detected value that the cooling water temperature is low is transmitted to the controller 25 from the water temperature sensor 27 installed in the controller 3, and when both detected values are lower than the predetermined value, the controller 25 determines the temperature of the fuel supplied to the injector 4. Is extremely low temperature and the viscosity of the fuel is high. Based on this determination, the vacuum switching valve 19 opens the chamber 14 of the pressure regulator 11 to the atmosphere,
17 is closed and the injection pressure of the injector 4 is increased. If the injection pressure of the injector 4 rises, the injection angle of the injector 4 becomes wider as described in (a) and (b) of FIG.

3 and 4 are pressure regulators.
The two states by the operation of 11 are shown in FIG.
The intake valve negative pressure acts on the valve body 16 to open it, and the pipe 10 and the fuel return passage 17 are shown in communication with each other. FIG. 4 shows that the valve body 16 closes and the pipe 10 and the fuel return passage 17 are closed. It shows where the road 17 is cut off.

The steps 40 to 45 shown in FIG.
The controller 24 of the engine fuel pressure control device according to the present invention
It is a flowchart figure which shows the determination and control in.
The controller 24 first compares the detected value of the intake air temperature with a predetermined value (step 41), and if the detected value is less than the predetermined value, then compares the detected value of the water temperature with the predetermined value (step 4).
2). If the water temperature is also below the predetermined value, it is judged whether the engine is in the idling state or not by the detection signal from the throttle sensor 7 (step 43). If it is in the idling state, the vacuum switching valve 19 is operated. If "NO" is output in the above determination process, the vacuum switching valve 19 is stopped (step 45).
That is, the operation condition of the vacuum switching valve 19 is that both the intake air temperature and the water temperature are low and the engine is in the idling state. If the above conditions are not satisfied, the vacuum switching valve 19 will not operate.

FIG. 6 is a graph showing the relationship between the fuel injection amount and the injection time, assuming that the fuel injection amount becomes large when the fuel pressure is large. In this figure, negative pressure a and negative pressure b
Is a vacuum switching valve of the device according to the present invention.
It is a pressure value switched by the operation of 19, and it can be seen that the same injection amount can be obtained in a shorter time than the conventional one (Tb, Ta <Tf) in relation to the injection time.

[0020]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, it is possible to prevent narrowing of the injection angle of the fuel injected from the injector by increasing the fuel pressure even when the fuel is extremely low temperature. It is possible to improve the state of the air-fuel mixture and stabilize the combustion state in the combustion chamber by recovering the normal injection angle. Also, by increasing the fuel pressure,
The intake time of fuel into the combustion chamber is shortened, and the startability at engine start is improved. As for the structure, the conventional vehicle can be improved simply by adding a vacuum switching valve and a sensor, so that it can be easily applied to an existing vehicle.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a fuel temperature and a fuel pressure at a fuel injection angle of an injector.

FIG. 3 is a cross-sectional view showing an operating state of a pressure regulator.

FIG. 4 is a cross-sectional view showing an operating state of the pressure regulator different from that of FIG.

FIG. 5 is a flowchart showing the controller's judgment and control state.

FIG. 6 is a graph showing a relationship between a fuel injection amount and an injection time.

FIG. 7 is a system diagram showing a conventional example of an SPI engine.

[Explanation of symbols]

 1 Throttle body 2 Intake passage 4 Injector 5 Throttle valve 7 Throttle sensor 8 Pipe line 9 Fuel tank 10 Pipe line 11 Pressure regulator 12 Chamber 14 Chamber 15 Negative pressure passage 16 Valve body 17 Fuel return passage 19 Vacuum switching valve 25 Controller 26 Pressure sensor 27 Water temperature sensor 28 Air flow meter 29 Intake air temperature sensor 30 Ignition coil

Claims (1)

Claim: What is claimed is: 1. An injector, which is installed in an intake passage collecting part, opens a valve in response to an injection signal from a controller and injects fuel, and a pressure regulator which adjusts a fuel pressure applied to the injector to a constant value. In a fuel pressure control device for an engine comprising, a vacuum switching valve that is switched by a signal from the controller is connected to a chamber that receives an intake negative pressure of the pressure regulator, and by the vacuum switching valve, as control gas to the chamber, An engine fuel pressure control device characterized in that it is configured to supply a negative pressure of intake air and an atmosphere by switching.