JPH08165967A - Fuel injection device - Google Patents

Abstract

PURPOSE: To reduce the size of a system and to simplify an oil pressure passage by providing a first piezoelement to change a pressure in a pressure chamber through expansion and contraction, a second piezoelement to change a pressure in a fuel chamber through expansion and contraction, and injecting air-fuel mixture in a combustion chamber through control of energization to each of the piezoelements. CONSTITUTION: When a pressure in a combustion chamber 25 is lower than a pressure in a mixing chamber 20, with a voltage being applied on a first piezoelement 21 and the element 21 being expanded, pressure in a pressure chamber 33 is pressurized and the valve body of a moving body 24 is opened, and fuel is injected in the combustion chamber 25 through an injection nozzle 16. A pressure in the mixing chamber 20 and a pressure in the combustion chamber 25 are made approximately equal to each other. When a pressure in the mixing chamber 20 attains a given pressure, gas in the combustion chamber 25 is charged in the mixing chamber 20. In which case, when a voltage is applied on a second piezoelement 22 and the element 22 is expanded, fuel in a fuel chamber 17 is compressed. When a pressure in the fuel chamber 17 is increased to a value higher than the opening pressure of a check valve 19, the check valve 19 is opened and fuel is fed in the mixing chamber 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for injecting fuel into a combustion chamber, and more particularly to a fuel injection device for injecting a mixture of fuel and air into a combustion chamber of an internal combustion engine.

[0002]

2. Description of the Related Art As a conventional fuel injection device for injecting fuel into a combustion chamber of an internal combustion engine, a technique disclosed in Japanese Patent Publication No. 2-500925 is known. FIG. 5 shows a block diagram of the fuel injection device disclosed in the above publication. This technology is provided with a pump for delivering fuel, a unit for taking out compressed gas from the combustion chamber, a gas tank for storing gas, and a unit for blowing out gas and the delivered fuel. The blow-off valve 50 is provided with a take-out unit, a valve-side chamber 51 as a blow-out unit, and a chamber 52 on the side away from the valve, and the valve 5 is opened to the combustion chamber 53.
4 controls the gas exchange between the combustion chamber 53 and the valve-side chamber 51, the valve-side chamber 51 is used as a gas tank for the gas taken out of the combustion chamber 53, and the valve 54 is separated from the valve. The valve-side chamber 51 is operated by a piston 55 that is a drive means that divides the side chamber 52, and the valve-side chamber 51 is connected to the chamber 52 on the side separated from the valve via a check valve 56 and separated from the valve. The fuel injection device is characterized in that the pressure generating unit 57 sends fuel to the side chamber 52.

[0003]

However, in the above-mentioned prior art, the pressure generating unit 57 is externally required to control the operation of the piston 55, which is the driving means of the fuel injection device, and therefore the entire system is provided. Becomes large, and the hydraulic passage becomes complicated.

[0004] Therefore, it is a technical object of the present invention to provide a fuel injection device which enables downsizing of a system and simplification of a hydraulic passage.

[0005]

In order to solve the above-mentioned problems, the invention of claim 1 is arranged between a pressurizing means for pressurizing fuel and the pressurizing means and a combustion chamber of an internal combustion engine. A fuel injection device comprising a fuel injection valve and drive means connected to the fuel injection valve, wherein the fuel injection valve is connected to an input port connected to an output side of the pressurizing means and a combustion chamber. And a movable member having a valve body that opens and closes between the injection port and the combustion chamber at one end, and a pressure chamber is formed between the other end of the movable member and the pressure of the pressure chamber by expansion and contraction. , A fuel chamber formed between the input port and the injection port, a second piezo element for changing the pressure of the fuel chamber by expansion and contraction, the input port and the fuel chamber And is opened at a pressure lower than the pressure applied by the pressurizing means. A first check valve that allows only the flow of fuel from the input port to the injection port, and a pressure that is arranged between the fuel chamber and the injection port and that is higher than the valve opening pressure of the first check valve. A second check valve that opens at the same time and allows only the flow of fuel from the fuel chamber to the injection port;
A mixing chamber formed between the check valve and the injection port, and the drive means is connected to each of the first piezo element and the second piezo element, and applies a voltage. I chose

In addition to the invention of claim 1, in claim 2, the driving means applies a voltage in a direction in which the first piezo element extends when the pressure in the combustion chamber is lower than the pressure in the mixing chamber,
When the pressure in the mixing chamber is a predetermined pressure, the power supply to the first piezo element is stopped.

[0007]

According to the present invention, for example, when the pressure in the combustion chamber is lower than the pressure in the mixing chamber, the driving means applies a voltage to the first piezo element to extend the first piezo element. First
The expansion of the piezo element pressurizes the pressure in the pressure chamber, opens the valve member of the movable member, and connects the injection port and the combustion chamber. When the injection port and the combustion chamber are in communication, the pressure in the mixing chamber and the pressure in the combustion chamber become substantially the same, and when the pressure in the mixing chamber reaches a predetermined pressure, the gas in the combustion chamber is charged in the mixing chamber.
Then, when the energization of the first piezo element is stopped, the valve body is closed to disconnect the mixing chamber and the combustion chamber. Second by driving means
When a voltage is applied to the piezo element, the second piezo element expands and the fuel in the fuel chamber is compressed, and when the pressure in the fuel chamber becomes higher than the opening pressure of the second check valve, the second check valve opens. Fuel is supplied into the mixing chamber. At this time, the driving means is the first
The piezoelectric element may be energized or de-energized.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

The fuel injection device 10 of this embodiment is arranged between a fuel tank 11 for storing fuel, a fuel pump 13 as a pressurizing means for pressurizing the fuel in the fuel tank 11, and a combustion chamber of an internal combustion engine. A fuel injection valve 12 provided and a drive circuit 1 as a drive means for driving the valve action of the fuel injection valve 12.
The fuel injection valve 12, which is a main part of the present invention, includes an input port 15 for taking in fuel, an injection port 16 for injecting fuel, an injection port 16 at one end, and a combustion chamber 25.
The pressure chamber 33 is provided between the movable member 24 including the outer opening valve formed by the valve body 16a that opens and closes the space between the movable member 24 and the other end of the movable member 24.
And a fuel chamber 17 formed between the input port 15 and the injection port 16, and a first piezo element 21 that changes the pressure of the pressure chamber 33 by expansion and contraction, and a fuel chamber 17 that changes the pressure of the fuel chamber 17 by expansion and contraction. 2 piezo elements 22 and input port 15
Check valve 1 which is interposed between the fuel chamber 17 and the fuel chamber 17, opens at a pressure lower than the pressure of the fuel pump 13, and allows only the flow of fuel from the input port 15 to the injection port 16.
8 and between the fuel chamber 17 and the injection port 16, the valve opens at a pressure higher than the valve opening pressure of the first check valve 18, and allows only the flow of fuel from the fuel chamber 17 to the injection port 16. The second check valve 19 and the mixing chamber 20 formed between the second check valve 19 and the injection port 16 are provided.

Here, one end of each of the first piezo element 21 and the second piezo element 22 is fixed to a partition portion 34 formed substantially in the center of the fuel injection valve 12, and the partition portion 34 is attached to the fuel injection valve 12. It is fixed inside. A first piston 21a and a second piston 22a are formed at the other ends of the first piezo element 21 and the second piezo element 22, respectively.

The fuel in the fuel tank 11 is sent to the input port 15 of the fuel injection valve 12 by the fuel pump 13. The spring force of the first check valve 18 is set to be equal to or lower than the pump pressure of the fuel pump 13, so that the fuel is supplied from the input port 15 to the fuel chamber 17 via the filter 23 and the first check valve 18. Has become. The check valve 32 arranged between the fuel pump 13 and the input port 15 opens when the pressure between the fuel pump 13 and the fuel injection valve 12 exceeds a predetermined pressure, and returns the fuel to the fuel tank 11. It is provided. Further, the spring force of the second check valve 19 is set to a value larger than the pump pressure of the fuel pump 13, and the valve is opened only when the pressure of the fuel chamber 17 becomes equal to or higher than the spring force of the second check valve 19. It is supposed to do.

Here, the expansion amount of the piezo elements 21, 22 due to the application of the voltage from the drive circuit 14 is not so large that the valve body 16a in the injection port 16 sufficiently opens the open valve, so that the first piezo element 21. By making the diameter formed by the first piston formed at the tip of the movable member 24 larger than the diameter formed by the movable member 24, the stroke amount of the movable member 24 becomes a sufficient value for opening the valve body 16a. . In this embodiment, the diameter formed by the first piston 21a is four times the diameter formed by the other end of the movable member 24, and the area ratio is 16 times. For example, when the stroke amount when the first piezo element 21 is energized is 0.06 mm, the stroke amount of the movable member 24 is 0.96 mm, and the valve body 16a can reliably open the valve.

In the present embodiment, the timing of energization from the drive circuit 14 to the first piezo element 21 and the second piezo element 22 is the angle of the crankshaft (not shown), the ignition timing,
And the pressure in the combustion chamber 25.

Next, the operation of the fuel injection device 10 in the combustion chamber of any one cylinder of this embodiment will be described with reference to FIGS. 2 and 3.
This will be described using the time chart of. In FIG. 3, the horizontal axis shows the crank angle, and the vertical axis shows the pressures of the combustion chamber 25 and the mixing chamber 20. Intake in each cylinder while the crankshaft makes two revolutions, that is, when the crank angle is from 0 ° to 720 ° →
The cycle of compression → expansion → exhaust is performed. Although the fuel injection device for a 4-cycle internal combustion engine is shown in this embodiment, it is also possible to use the fuel injection device of the present invention for a 2-cycle internal combustion engine.

First, as the crankshaft rotates, the crank angle changes and the pressure in the combustion chamber 25 changes. When the pressure in the combustion chamber 25 reaches an angle (eg, 280 °) estimated to reach a predetermined pressure, the drive circuit 14 energizes the first piezo element 21. The pressure in the pressure chamber 33 increases due to the expansion of the first piezo element 21.
When the pressure of 3 overcomes the spring force of the spring 35, the movable member 24 moves downward in FIG. 1, the valve body 16a opens the outer valve, and the combustion chamber 25 and the mixing chamber 20 communicate with each other.
Since the pressure in the mixing chamber 20 is higher than the pressure in the combustion chamber 25 at the beginning, the air-fuel mixture in the mixing chamber 20 is injected into the combustion chamber 25.

The pressure in the combustion chamber 25 gradually increases as the piston sliding in the combustion chamber 25 approaches the top dead center.
When the crank angle (for example, 320 °) at which the pressures of the combustion chamber 25 and the mixing chamber 20 are estimated to be equal to each other is reached, the combustion chamber 2
The gas in 5 is charged into the mixing chamber 20.

Next, the crank angle (eg, 3) at which the amount of gas charged in the mixing chamber 20 is estimated to be a predetermined amount.
40 °), the drive circuit 14 stops energizing the first piezo element 21 and the valve body 16a of the injection port 16 closes the open valve. When the piston sliding in the combustion chamber 25 crosses the top dead center and reaches a crank angle (for example, 380 °) at which the pressure in the combustion chamber 25 starts to decrease, the drive circuit 14 energizes the second piezo element 22.

When the second piezo element 22 extends, the fuel chamber 17
When the pressure in the fuel chamber 17 rises and the pressure in the fuel chamber 17 overcomes the spring force of the second check valve 19, the second check valve 19 opens and the fuel in the fuel chamber 17 enters the mixing chamber 20. Sent. The amount of fuel sent from the fuel chamber 17 to the mixing chamber 20 can be controlled by repeating energization / de-energization of the second piezo element 22. In FIGS. 2 and 3, the fuel injection time is TF ₁ And two patterns of TF ₂ are shown.

In the present embodiment, the drive circuit 14 does not energize the first and second piezo elements 21, 22 at the same time, but the energization timing changes depending on the running conditions of the vehicle. And the second piezo element 21,
It is also possible to energize 22 simultaneously.

Here, the drive circuit 14 in the present embodiment.
4 is a circuit connected to the battery 27 via the ignition switch 26 as shown in FIG. 4, and energizes the DC-DC converter 28 as a booster and the first and second piezo elements 21, 22. It is composed of first and second energizing switches 29 and 30, and each energizing switch 29, 30 is generated by a signal from the engine control computer 31.
When 30 is turned on, a constant voltage is applied to each piezo element 21, 22.

According to the present invention, the unit for feeding the fuel in the fuel chamber 17 to the mixing chamber 20 is provided inside the fuel injection valve 12, and the unit for reducing the size of the fuel injection device is provided. It will be possible.

[0022]

[Effect] According to the fuel injection device of the present invention, a special injection mechanism such as a compressor for injecting the air-fuel mixture into the combustion chamber is unnecessary by utilizing the pressure change of the combustion chamber, and the fuel injection valve can be easily installed. Since the injection mechanism having a different structure is provided, it is possible to prevent the system from increasing in size.

[Brief description of drawings]

FIG. 1 is a sectional view of a fuel injection device according to an embodiment of the present invention.

FIG. 2 is an operation time chart of the fuel injection device in the present embodiment.

FIG. 3 is an operation time chart of the fuel injection device in the present embodiment.

FIG. 4 is a circuit diagram of a drive circuit of this embodiment.

FIG. 5 is a configuration diagram of a conventional fuel injection device.

[Explanation of symbols]

10 ... Fuel injection device 11 ... Fuel tank 12 ... Fuel injection valve 13 ... Fuel pump 14 ... Drive circuit 15 ... Input port 16 ... Injection port 17 ... Fuel chamber 18 ... First check valve 19 ... Second
Check valve 20 ... Mixing chamber 21 ... First
Piezo element 22 ... Second piezo element 23 ... Filter 24 ... Movable member 25 ... Combustion chamber 26 ... Ignition switch 27 ... Battery 28 ... DC-DC converter 29 ... First
Energizing switch 30 ... Second energizing switch 31 ... Engine control computer 32 ... Check valve 33 ... Pressure chamber 34 ... Compartment 35 ... Spring

Claims (2)

[Claims] 1. A pressurizing means for pressurizing fuel, a fuel injection valve disposed between the pressurizing means and a combustion chamber of an internal combustion engine,
A fuel injection device comprising drive means connected to the fuel injection valve, wherein the fuel injection valve includes an input port connected to an output side of the pressurizing means, and an injection port connected to a combustion chamber. A first member that forms a pressure chamber between a movable member that has a valve body that opens and closes between the injection port and the combustion chamber at one end, and the other end of the movable member, and changes the pressure of the pressure chamber by expansion and contraction; A piezo element, a fuel chamber formed between the input port and the injection port, a second piezo element that pressurizes the pressure of the fuel chamber by expansion and contraction, and an interposing between the input port and the fuel chamber. A first check valve inserted between the fuel chamber and the injection port, the first check valve being opened at a pressure lower than the pressure of the pressurizing means and allowing only the flow of fuel from the input port to the injection port; And is opened at a pressure higher than the opening pressure of the first check valve. And a second check valve that allows only the flow of fuel from the fuel chamber to the injection port, and a mixing chamber formed between the second check valve and the injection port, The driving means is connected to each of the first piezo element and the second piezo element, and applies a voltage to the fuel injection device. 2. The fuel injection device according to claim 1, wherein the drive means applies a voltage in a direction in which the first piezo element extends when the pressure in the combustion chamber is lower than the pressure in the mixing chamber, and the mixing is performed. A fuel injection device, wherein energization to the first piezo element is stopped when the pressure in the chamber reaches a predetermined pressure.