JPH0635859B2 - Fuel pressure control valve - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fuel pressure regulating valve.

[Prior Art] A fuel pressure regulating valve is used in a fuel injection system to maintain an appropriate fuel pressure supplied to the injection valve. An example of a conventional pressure control valve is shown in FIG.

(Nippon Denso Public Technical Report, October 20, 1982).

The pressure regulating valve has a cylindrical case 1, and the case 1 is divided into a back pressure chamber A and a fuel pressure chamber B by a diaphragm 2 provided across the cylindrical case 1. A pressure introducing pipe 11 is connected to the back pressure chamber A, and the internal pressure of an engine intake pipe provided with a fuel injection valve is introduced. The back pressure chamber A is provided with a coil spring 3 and pushes the valve member 4 provided at the center of the diaphragm 2 toward the fuel pressure chamber B side.

A fuel supply pipe 12 and a fuel return pipe 13 are provided in the fuel pressure chamber B.
The valve member 4 is in contact with the opening of the return pipe 13 to close it. The fuel supply pipe 12
Is connected to the fuel pump, and an injection valve is installed on the way.

When the fuel pressure in the fuel pressure chamber B rises, the diaphragm 2 is deformed toward the back pressure chamber A side against the spring force of the spring 3, the fuel return pipe 13 is opened, and the fuel pressure is quickly lowered. At this time, since the fuel pressure receiving area and the back pressure receiving area are the same, the fuel pressure supplied to the fuel injection valve has a constant value corresponding to the spring force of the spring 3 even when the intake pipe pressure fluctuates. The differential pressure is always kept high.

[Problems to be Solved by the Invention] By the way, in order to cope with various operating states of the engine, it is required to make the adjustment range of the fuel injection valve as wide as possible. In this case, the amount of injected fuel is adjusted by changing the valve opening time of the injection valve while maintaining a constant injection differential pressure by the conventional pressure adjusting valve.

However, with this method, there is a limit to the expansion of the metering range, and the amount of injected fuel tends to be insufficient in the region where the engine load is large and the intake pipe pressure is high, while on the other hand, in the region where the engine load is small and the intake pipe pressure is low There was a problem that it became overkill.

In view of the above problem, the present invention positively changes the pressure difference between the fuel pressure and the intake pipe pressure, that is, the injection pressure difference, so as to expand the metering range of the fuel injection valve with a relatively simple structure. The purpose is to provide a pressure regulating valve.

[Means for Solving Problems] The configuration of the present invention will be described with reference to FIG.
Is divided into two pressure chambers by a diaphragm 2 provided across it. The intake pipe pressure of the engine is introduced into one pressure chamber A to form a back pressure chamber, and the diaphragm 2 is provided on the other pressure chamber side. There is provided a spring member 3 for pushing. The other pressure chamber has two chambers B due to the side wall 5 that expands and contracts.
The side wall 5 has one end joined to the diaphragm 2 and the other end joined to the case wall facing the diaphragm 2.

A fuel supply passage 14 and a fuel return passage 13 are opened in one of the two chambers to form a fuel pressure chamber B, and the fuel return passage is opened and closed by a valve member 4 provided integrally with the diaphragm 2. The other C of the two chambers is connected to the atmosphere.

[Operation and Effect] In the regulating valve having the above structure, the pressure receiving area S1 of the diaphragm 2 facing the pressure chamber A and the pressure receiving area S of the diaphragm 2 facing the fuel pressure chamber B are shown.
Unlike 2, S1> S2.

Then, the pressure change in the pressure chamber A becomes S1 / S2 times in the fuel pressure chamber B, and the pressure difference between the two chambers A and B becomes
S1 corresponding to the pressure change of
It changes with the slope of / S2.

As a result, the injection differential pressure of the fuel injection valve is reduced when the engine load is low with a low intake pipe pressure, enabling injection at a lower flow rate, while the injection differential pressure is increased when the engine load is high with a high intake pipe pressure. As a result, a higher flow rate injection is possible. Thus, the metering range of the injection valve is expanded.

[Embodiment] In FIG. 1, a case 1 of a pressure control valve is formed by caulking and connecting a cylindrical upper half portion and a lower half portion, which are closed at one end. A diaphragm 2 is provided across the inside of the case 1, and an outer peripheral edge of the diaphragm 2 is sandwiched between the connecting portions. A hole is formed in the center of the diaphragm 2, and a valve member 4 is provided by sandwiching the peripheral edge of the hole from above and below.

The valve member 4 has a valve body 41 in the center of the lower surface, and the valve body 41 is composed of a spherical upper half portion and a plate-like lower half portion, and the upper half portion is rotatably held by the valve member 4. There is. In the back pressure chamber A formed above the diaphragm 2, a coil spring 3 is provided between the case 1 and the valve member 4. In the back pressure chamber A, a pressure introducing pipe 11 reaching the engine intake pipe is opened. The above structure is basically the same as the conventional example.

In the pressure chamber formed below the diaphragm 2, a cylindrical metal bellows 5 is provided, the upper end of the bellows 5 is joined to the outer peripheral edge of the valve member 4, and the lower end is attached to the case bottom wall. It is joined. Bellows 5 is diaphragm 2
It freely expands and contracts with the deformation of the. Thus, the fuel pressure chamber B is formed inside the bellows 5, while the atmosphere chamber C is formed outside the bellows 5. That is,
A fuel return pipe 13 is provided in the center of the fuel pressure chamber B, and the valve body 41 is in contact with the opening of the tip end of the fuel return pipe 13 to close it.

A plurality of fuel supply ports 1 are provided around the fuel return pipe 13.
4 is provided. The air chamber C is a ventilation hole 1 provided on the case wall.
5 communicates with the atmosphere. According to the above structure, the pressure receiving area S1 of the diaphragm 2 facing the back pressure chamber A and the pressure receiving area S2 facing the fuel pressure chamber B are different, and S1> S2.

When the fuel pressure in the fuel pressure chamber B rises and the pressure applied to this and the atmospheric pressure becomes larger than the force applied to the back pressure and the spring force of the spring 3, the diaphragm 2 is deformed and moves upward, and the return pipe 1
The opening of 3 is opened, and the fuel pressure is reduced. As a result, the diaphragm 2 is deformed downward again, thus
The forces applied to both sides of the diaphragm 2 are always in balance.

By the way, in the present invention, since the pressure receiving areas S1 and S2 of the back pressure chamber A and the fuel pressure chamber B are made different as described above,
The pressure change in the back pressure chamber A is S1 / in the fuel pressure chamber B.
S2 times. Therefore, the pressure difference between the two chambers A and B is
Does not become constant with a change in the pressure of S, and as shown in FIG. 2 line y, S increases with the increase of the back pressure, that is, the pressure in the intake pipe.
It increases with a slope of 1 / S2. The line x in the figure shows the change in the differential pressure by the conventional adjusting valve, and in this case, the differential pressure is the constant pressure P0 corresponding to the spring force of the spring 3.

Thus, according to the present invention, the injection differential pressure of the fuel injection valve is reduced when the engine load is low when the intake pipe pressure is low, and injection at a lower flow rate is possible, while the above is performed when the engine load is high when the intake pipe pressure is high. The injection pressure difference rises, and a higher flow rate injection becomes possible.

[Brief description of drawings]

FIG. 1 is an overall sectional view of a pressure regulating valve according to the present invention, FIG. 2 is a graph showing the back pressure dependency of the differential pressure between the back pressure chamber and the fuel pressure chamber, and FIG. 3 is a conventional pressure regulating valve. FIG. 1 ... Case 11 ... Intake pipe pressure introduction pipe 13 ... Fuel return pipe 14 ... Fuel supply port 15 ... Vent hole 2 ... Diaphragm 3 ... Spring member 4 ... Valve member 5 ... Bellows (side wall) A: Back pressure chamber B: Fuel pressure chamber C: Atmosphere chamber

Claims (3)

[Claims] 1. A diaphragm provided across a tubular case divides the inside of the case into two pressure chambers, and one of the pressure chambers introduces an intake pipe pressure of the engine to form a back pressure chamber and the other of the diaphragms. A spring member for urging the other pressure chamber toward the pressure chamber side is provided, and the other pressure chamber is joined by a side wall which is joined to the diaphragm at one end and is joined at the other end to the case wall facing the diaphragm and expands and contracts as the diaphragm moves. It is divided into chambers, and a fuel supply passage and a fuel return passage are opened in one chamber to form a fuel pressure chamber, and the fuel return passage is opened and closed by a valve member integrally provided on the diaphragm. And fuel pressure control valve. 2. The fuel pressure regulating valve according to claim 1, wherein the side wall is constituted by a cylindrical bellows concentrically provided in the other pressure chamber. 3. The fuel according to claim 1, wherein one of the two chambers defined by the side wall is the fuel pressure chamber and the other chamber is an atmospheric chamber introduced with atmospheric air. Pressure regulating valve.