JPS6337264B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for keeping a fuel injection valve differential pressure constant in a valve that injects fuel into an intake pipe of an internal combustion engine.

In a so-called electronically controlled fuel injection engine that increases or decreases the fuel injection amount while detecting the intake air flow rate of the engine, accurate control of the fuel injection amount is required.

Therefore, the fuel injection valve is usually configured with an on-off type solenoid valve, and the absolute sum of the pressure before and after the valve (that is, the fuel injection differential pressure) is kept constant, so that fuel is always injected at a constant flow rate when the valve is opened. At the same time, the fuel injection amount is precisely controlled by increasing or decreasing the valve opening time.

As a device to keep this fuel injection differential pressure constant,
For example, there is one shown in FIG.

First, fuel pumped from the electromagnetic fuel pump 1 passes through the fuel pipe 2 and reaches the regulator 3.

This regulator 3 detects the intake pipe negative pressure P ₂ in the engine operating state at that time, and depending on the magnitude of the negative pressure value, the spring 5 is activated via the diaphragm valve 4.
The fuel is returned to the fuel tank according to the balance.

For example, when the intake pipe negative pressure _P2 , which is the discharge side pressure of the fuel injection valve 6, increases, the flow rate of fuel returning to the tank increases, and the supply side pressure _P1 of the fuel injection valve 6 increases.
decreases, so the differential pressure before and after the fuel injection pressure (that is, the fuel injection differential pressure) is kept constant.

At that time, the fluctuation range of intake pipe negative pressure _P2 (0 in absolute pressure)
~0.85Kg/cm ² ), and in order to keep the differential pressure before and after this constant, this pressure difference should be 2 to 3Kg/cm 2 ).
The discharge pressure of the fuel pump 1 is set relatively high to the extent that cm ² .

Therefore, the fuel pump 1 is required to have a relatively high discharge pressure, and the injection valve 6 is required to have high pressure resistance, so there is a limit to how they can be made smaller and lighter.

The present invention was made in view of the above-mentioned circumstances, and provides a device that can maintain a constant pressure difference across a fuel injection valve (i.e., fuel injection pressure difference) even when using a fuel pump with a relatively low discharge pressure. The purpose is to obtain.

In order to achieve the above object, the present invention includes a bypass passage that bypasses the throttle valve and connects to the intake pipe of the engine, an orifice installed in the passage, and a sonic orifice installed downstream of the bypass passage. An electromagnetic fuel injection valve opened and installed between the orifices, means for supplying fuel at a constant pressure to the injection valve, and a control circuit for increasing/decreasing the opening time of the injection valve were provided.

The following will be explained based on the drawings. FIG. 2 is a schematic diagram showing an embodiment of the present invention.

In the figure, 11 is an air cleaner, 12 is an engine main body, and 13 is an intake pipe that sends intake air that has passed through the air cleaner 11 to the engine main body 12.

A throttle valve 14 and a bypass passage 15 bypassing the valve 14 are attached to the intake pipe 13.

An orifice 16 is provided on the inlet side 15a of the bypass passage 15, and a sonic orifice 17 is provided on the outlet side 15b.

As shown in FIG. 3, when the intake pipe negative pressure _P2 downstream of the throttle valve 14 reaches a predetermined value or more, the air flow velocity reaches the sonic velocity at the sonic orifice 17 and becomes constant, so the bypass passage The flow rate of air flowing through the orifice 15 is constant, and as a result, the pressure on the upstream side of the orifice 16 is constant atmospheric pressure.
The negative pressure _P3 in the bypass passage sandwiched between the two also remains constant.

The value of this negative pressure P ₃ decreases as the inner diameter of the orifice 16 is increased, so if the characteristics of the Sonic orifice 17 and the orifice 16 are appropriately selected, the value of the negative pressure P ₃ can be set to an arbitrary value (P ₀ ). .

A fuel injection valve 18, which is an on-off type electromagnetic valve, is open and attached to a bypass passage 15 sandwiched between an orifice 16 and a sonic orifice 17. 19 to 21 in the figure constitute means for supplying fuel at a constant pressure to the fuel injection valve 18;
9 is a fuel pump that pumps fuel from a fuel tank (not shown); 20 is a pressure regulating device that regulates relatively high pressure fuel from the fuel pump 19 to a constant pressure _P4 ; and 21 is a fuel injection device for injecting fuel from the pressure regulating device. This is a fuel tube that leads to valve 18.

That is, the pressure on the discharge side of the fuel injection valve 18 is a negative pressure _P3 in the bypass passage, and the pressure on the supply side is a constant pressure _P4 .

Therefore, when the intake pipe negative pressure P ₂ is equal to or higher than a predetermined value (in the low-medium load region) when the negative pressure P ₃ is constant, the pressure difference before and after that is always constant regardless of the intake pipe negative pressure P ₂ . becomes constant.

In this case, since the fuel injection differential pressure is constant, the fuel injection flow rate as an average value can be accurately controlled simply by increasing or decreasing the opening time of the fuel injection valve 18 using the control circuit 22.

The injected fuel is atomized by the sonic orifice 17, and further enters the intake pipe 13 downstream of the throttle valve from the bypass passage 15, and then enters the engine body 12.
However, in order to further promote atomization of the fuel, the outlet side 15b of the bypass passage 15 is connected to the intake pipe 13 near the downstream side of the throttle valve 14 where the flow velocity is high.

On the other hand, when the intake pipe negative pressure P ₂ where the negative pressure P ₃ fluctuates is lower than the predetermined value (high load region), a signal stored in the table in advance, or a signal from the negative pressure sensor or throttle valve opening sensor is sent. Based on this, the fuel injection amount is adjusted by relatively increasing (decreasing) the opening time of the fuel injection valve 18 according to the value of the negative pressure _P3 (in other words, as the injection differential pressure decreases). Can be controlled accurately.

Here, since the value of negative pressure _P3 , which is the pressure on the discharge side of the fuel injection valve 18, is always stable, the discharge pressure of the fuel pump 19 is also significantly lowered compared to the conventional one, and as a result, the fuel injection valve 18 is not required to have such high pressure resistance performance, and the fuel pump 19, fuel injection valve 18, etc. can be made smaller and lighter.

As shown in FIG. 4, the fuel flow characteristics A1 and A2 as average values for the opening rate of the fuel injection valve in this embodiment have a slope that is smaller than that of the characteristic A3 of the conventional device.

Therefore, in this embodiment, the fuel flow rate can be increased or decreased more finely than in the past for the same variable width of the valve opening rate, and the flow rate can be controlled more accurately.

In particular, under no-load conditions, where the fuel flow rate is relatively small and the differential pressure across the fuel injection valve is relatively large in the conventional device, the effect of accurate flow rate control by this embodiment is extremely large, compared to the conventional device. The internal combustion engine can be controlled more appropriately.

Furthermore, in this embodiment, since the air-fuel mixture passes through the sonic orifice 17 and is sucked into the engine body, the atomization characteristics of the air-fuel mixture are improved.

FIG. 5 is a sectional view showing the main parts of another embodiment of the present invention.

In this embodiment, a fuel injection valve 31 is installed with a direct opening into an intake pipe 32, and a sonic orifice 33 is provided in a fuel discharge passage 31a of the injector 31, and further upstream of the sonic orifice, this fuel discharge By connecting the passage 31a to the intake pipe upstream of the throttle valve and downstream of the air cleaner through an orifice 34, a portion of the bypass passage described above is integrated with the passage 31a in the fuel injection valve.

In addition to the effects similar to those of the above-mentioned embodiments, this embodiment allows the overall size of the device to be reduced due to its integrated structure, which provides excellent equipment and cost efficiency, and is of high practical value.

As explained above, in the present invention, the differential pressure across the fuel injection valve (that is, the fuel injection differential pressure) can be kept at a constant small value, so it is possible to use a fuel pump with a relatively low discharge pressure. Fuel pumps, fuel injection valves, etc. can be made smaller and lighter.

Additionally, since the fuel injection valve is operated with a smaller differential pressure across the front and rear than in the past, the fuel injection flow rate can be controlled more accurately.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a conventional device, FIG. 2 is a schematic diagram showing an embodiment of the present invention, and FIGS.
The figure is a characteristic diagram showing the function of each part, and FIG. 5 is a sectional view showing the main parts of another embodiment of the present invention. 12...Engine body, 13...Intake pipe, 14
... Throttle valve, 15 ... Bypass passage,
16... Orifice, 17... Sonic orifice, 18... Fuel injection valve, 19... Fuel pump,
20...Pressure regulation device, 22...Control circuit, 31...Fuel injection valve, 31a...Fuel discharge passage, 32...Intake pipe, 33...Sonic orifice.

Claims (1)

[Scope of Claims] 1. A bypass passage connected to the intake pipe of the engine by bypassing the throttle valve, an orifice installed in the passage, a Sonic orifice installed downstream thereof, and between the two orifices. A fuel injection valve supply pressure control device comprising an electromagnetic fuel injection valve mounted in an open state, means for supplying fuel at a constant pressure to the injection valve, and a control circuit for increasing/decreasing the opening time of the injection valve. 2. The fuel injection valve supply pressure control device according to claim 1, wherein a portion of the bypass passage is formed integrally with a fuel discharge passage within the fuel injection valve. 3. Claims in which the control circuit is configured to increase or decrease the valve opening time according to the intake pipe negative pressure in a region where the differential pressure across the fuel injection valve fluctuates according to the intake pipe negative pressure. 2. The fuel injection valve supply pressure control device according to claim 1 or 2.