JPH03124955A - Fuel feeder - Google Patents

Abstract

PURPOSE:To prevent the heating of fuel by engine radiation by providing a relief valve opened at the fixed value or below of the fuel pressure and relieving part of the fuel in a fuel feed passage on the fuel feed passage in a fuel tank or at a position near it, and opening the relief flow path of the relief valve in the fuel tank. CONSTITUTION:When an engine load is reduced, a throttle valve 3 is rotated in the closing direction, and the engine intake pressure is reduced. A pressure control valve 4 returns most of the fuel F fed via a fuel feed passage 61 to a fuel tank T to reduce the fuel pressure after the engine intake pressure. When the fuel pressure is decreased from a fixed value, a relief valve 5 is opened, and most of the fuel discharged from a fuel pump 1 is immediately returned to the fuel tank T without being sent to a fuel control valve 4. A large quantity of fuel F is not sent wastefully near a high-temperature engine, the heating of the fuel F is prevented, and the temperature rise in the fuel tank T is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel supply device, and more particularly to a fuel supply device that can prevent a rise in temperature within a fuel tank.

[Prior Art] To explain a general fuel supply device, fuel is supplied from a fuel pump provided in a fuel tank to a fuel injection valve installed in an engine intake passage downstream of a throttle valve. This fuel pump is normally driven at a constant rotation by an on-vehicle battery, and sucks in and discharges fuel at a constant volume. On the other hand, a pressure control valve is provided near the fuel injection valve, and the difference between the intake pressure and the fuel pressure is always adjusted to be constant, regardless of fluctuations in the engine intake pressure that change depending on the engine load.

That is, when the engine load is low, the above-mentioned intake pressure decreases. Therefore, the pressure control valve returns most of the fuel discharged and supplied at a constant volume to the fuel tank, thereby reducing the fuel pressure accordingly.

[Problems to be Solved by the Invention] In such a conventional fuel supply device, when the engine is left in an idling state, most of the fuel delivered from the fuel pump is returned to the fuel tank after reaching the vicinity of the engine. Many modern engines are V-type, and the number of auxiliary machines is also increasing, so they tend to run hotter.
The fuel is heated by heat radiation from the engine and returned to the fuel tank.
As a result, the temperature inside the tank rises rapidly. There is a concern that this increase in tank temperature may cause fuel vapor to increase beyond the capacity of the charcoal canister and be dissipated into the atmosphere.

Therefore, for example, Japanese Utility Model Application Publication No. 50-76220 or Nippon Denso Technical Report No. 50-059 (November 15, 1986) describes how to calculate the engine load based on the amount of throttle valve depression, engine intake pressure, and rotation speed. A system has been proposed in which the rotational speed of the fuel pump is lowered during low load conditions, thereby reducing the amount of fuel that is wasted and returned to the pressure control valve near the engine. However, in such a device,
Since sensors and motor rotation control circuits are required, the configuration becomes complicated and costs increase.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fuel supply device that does not require any sensors or circuits, has a simple and inexpensive configuration, and can prevent an increase in the internal temperature of a fuel tank.

[Means for Solving the Problems] To explain the present invention in detail, it includes a fuel pump 1 installed in a fuel tank T, which sucks in fuel F and supplies it to a fuel supply path 61; The fuel injection valve 2 injects the fuel F into the engine intake passage 7, and the fuel supply passage 61 is provided near the fuel injection valve 2 to keep the difference between the engine intake pressure and the fuel pressure constant. In a fuel supply control device equipped with a pressure control valve 4 that returns a portion of the fuel that has reached the fuel tank T, the fuel pressure is below a certain value in the fuel supply path 61 in or near the fuel tank T. A relief valve 5 for relieving a portion of the fuel in the fuel supply passage 61 is provided, and the relief flow passage 51 of the relief valve 5 is opened into the fuel tank T.

[Operation] In the fuel supply system having the above configuration, when the engine load decreases, the throttle valve 3 rotates in the closing direction, and the engine intake pressure decreases. The pressure control valve 4 is connected to the fuel supply path 61
Most of the fuel F that has reached this point is returned to the fuel tank T, and the fuel pressure is lowered to follow the engine intake pressure. When the fuel pressure falls below a certain value, the relief valve 5 opens and most of the fuel discharged from the fuel pump 1 is immediately returned to the fuel tank T without going to the pressure control valve 4.

Therefore, a large amount of fuel F is not wasted and sent to the vicinity of the high-temperature engine, thereby preventing the fuel F from being heated and preventing a rise in temperature within the fuel tank T.

[Embodiment] In FIG. 1, a fuel pump 1 is provided in a fuel tank T with its lower half immersed in fuel F, and the fuel pump 1 is energized by an enclosed vehicle battery and operates at a constant rotation speed. , the fuel F taken in through the filter 12 on the lower surface is discharged from the discharge pipe 11 at the center of the top surface.

The discharge pipe 11 is connected to a relief valve 5 whose details will be described later.
A fuel supply pipe 61 extends from the relief valve 5 to the outside of the tank T. The fuel supply pipe 61 passes through a filter 63 and reaches the fuel injection valve 2 provided on the wall of the engine intake pipe 7 . The fuel injection valve 2 is located downstream of the throttle valve 3.

The fuel supply pipe 61 branches downstream of the filter 63 and is connected to a pressure control valve 4 near the engine, and a fuel return pipe 62 that returns to the fuel tank T extends from the pressure control valve 4.

Input pressure in the engine intake pipe 7 downstream of the throttle valve 3 is fed back to both valves 4 through a pressure guiding pipe 41, and the fuel pressure is controlled so as to always maintain a constant difference from the intake pressure.

In other words, when the engine load decreases and the intake pressure decreases, a large amount of fuel F is returned, causing the fuel pressure to fall accordingly, and when the engine load increases and the intake pressure increases, the amount of fuel returned is reduced to lower the fuel pressure. to rise.

FIG. 2 shows details of the relief valve 5. The relief valve 5 has a sealed housing 52, and the inside of the housing 52 is partitioned into left and right by a diaphragm 53. and,
A coil spring 54 is disposed inside the left side space S1 of the housing 52 between the diaphragm 53 and the right side space S2.
A cylindrical body 55 forming a relief flow path 51 therein is provided so as to open through the side surface of the housing 52 . A rod-shaped valve body 56 whose base end is fixed to the diaphragm 53 is inserted into the cylindrical body 55. The tip of the valve body 56 protrudes from the outer opening of the cylindrical body 55 and is formed into a trapezoidal shape, with its outer periphery serving as a sealing surface 56a, while the outer opening edge of the cylindrical body 55 has an inclined surface along the trapezoidal tip. It is molded to form a sealing surface 55a.

A through hole 551 is formed in the side wall of the cylindrical body 55 and communicates with the inside of the right side space S2, and the discharge pipe 11 of the fuel pump 1 and one end of the fuel supply pipe 61 are connected to the space S2 and opened. There is. Therefore, when the fuel pressure is decreasing, the valve body 55 is moved by the coil spring 54 together with the diaphragm 53.
is pushed toward the right side space S2, and its stepped base end comes into contact with the inner opening end surface of the cylindrical body. In this state, as shown in the figure, the sealing surface 56a of the valve body 56 is separated from the sealing surface 55a of the cylinder opening, and the fuel supply pipe 6 is separated from the discharge pipe 11.
1 is relieved into the fuel tank T through the relief passage 51 on the outer periphery of the valve body 56 through the through hole 551 (arrow in the figure).

In the fuel supply system having the above structure, when the engine is under high load, the throttle valve 3 opens wide, and the intake pressure downstream thereof rises to near atmospheric pressure. Therefore, the fuel pressure in this case is maintained high (approximately 2.5 kg) by the pressure control valve 4, and as a result, the diaphragm 53 and the valve body 56 in the relief valve 5 move toward the left side space S1 against the coil spring 54. The sealing surface 56a is pushed away, and the sealing surface 56a comes into close contact with the cylinder sealing surface 55a, and the relief flow 851 is closed.

In this state, the amount of fuel that reaches the pressure control valve 4 and is returned is small, and sufficient fuel is supplied to the fuel injection valve 2 and injected into the intake pipe 7.

When the engine is in a low load state, the opening of the throttle valve 3 becomes smaller and the intake pressure decreases. Since the injection amount of the fuel injection valve 2 also decreases, the pressure control valve 4 returns a large amount of fuel F to lower the fuel pressure (approximately 2.0 O
lqr/cxl). Here, the valve body 56 of the above-mentioned relief valve 5 opens due to the decrease in fuel pressure, and the surplus fuel F is relieved into the fuel tank T through the relief passage 51, and does not go to the above-mentioned pressure control valve 4. . Therefore, in order to maintain the fuel pressure at a predetermined level, the pressure control valve 4 returns a small amount of fuel F, and as a result, the amount of fuel F heated by the engine's heat radiation and returned is reduced, and as a result, a temperature rise in the fuel tank T is prevented. Ru.

Although the relief valve does not necessarily need to be provided inside the fuel tank, it is advantageous in that the relief flow path can be opened directly into the tank without using a pipe line.

[Effects of the Invention] As described above, according to the fuel supply device of the present invention, the amount of fuel returned from the pressure control valve near the engine can be significantly reduced in a low engine load state, thereby preventing fuel heating due to engine heat radiation. As a result, the rise in the internal temperature of the fuel tank can be suppressed.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of a fuel supply device showing one embodiment of the present invention, and FIG. 2 is a sectional view of a relief valve. 1... Fuel pump 2... Fuel injection valve 3... Throttle valve 4... Pressure control valve 5... Relief valve 51... Relief flow path 53... Diaphragm 54... Coil spring 56 ... Valve body 61 ... Fuel supply pipe (fuel supply path) 62 ... Fuel return pipe 7 ... Engine intake pipe (engine intake path) T ... Fuel tank

Claims (1)

[Claims] A fuel pump is installed inside the fuel tank and sucks in fuel and sends it to the fuel supply path, a fuel injection valve injects the fuel that has arrived through the fuel supply path into the engine intake path, and controls the engine intake pressure and fuel pressure. In a fuel supply control device comprising a pressure control valve that returns part of the fuel that has reached the fuel supply path to the fuel tank in order to keep the difference constant, the fuel supply control device is provided with a pressure control valve that returns a part of the fuel that has reached the fuel supply path to the fuel tank. A relief valve that opens when the fuel pressure is below a certain value to relieve a part of the fuel in the fuel supply passage is provided in the passage, and a relief flow passage of the relief valve is opened into the fuel tank. fuel supply device.