Fuel supply unit for vehicle

Abstract: The invention promotes separation of returned fuel into liquid fuel and gases. A base plate 34 of a fuel pump assembly 33 is attached, from the lower side, to a rear part of a bottom 30 of a fuel tank 1. A fuel pump 1 and a strainer 4 communicating with an inlet port 3 are housed in the fuel tank 1. A small partition 36 made of an elastic material such as rubber covers the front, right and left sides of the strainer 4, and partially supports a fuel-adsorbing member 35 arranged on the strainer 4. The fuel-adsorbing member 36 is a spongy filter made of stainless steel coils and having a great number of minute pores, adsorbs the fuel returned via a fuel return pipe 10, and separates the fuel into gases and liquid fuel. The liquid fuel remains adsorbed onto the fuel-adsorbing member 35 and stays near the strainer 4.

Description: This invention relates to a fuel supply unit for supplying fuel to a fuel supply system of an engine from a fuel tank mounted on a vehicle such as a motorcycle. Japanese Patent Laid-Open Publication No. Sho. 63-227949 discloses a fuel supply unit for a vehicle, in which a fuel tank houses a subsidiary tank, which encloses a fuel pump. A fuel return pipe communicates with the fuel pump via an open end thereof. Fig. 6 schematically shows the configuration of a fuel supply unit including an in-tank type fuel pump and applied to a motorcycle. Referring to Fig. 6, a fuel pump 2 is housed in a fuel tank 1 at a rear bottom thereof, and is connected at its inlet port 3 to a strainer 4 having a resin mesh filter for removing foreign matter. A discharge pipe 5 extending from a discharge port of the fuel pump 2 introduces fuel to a throttle body 7 outside the fuel tank 1 via a high pressure fuel filter 6. The fuel is then injected by fuel injectors into combustion chambers of an engine. Part of the fuel is returned as surplus fuel to an area near the strainer 4 by a pressure regulator 9 of the throttle body 7 via a connecting hose 10a and a fuel return pipe 10. In the foregoing related art, the fuel returned via the fuel return pipe contains a lot of gases. The fuel pump draws up such returned fuel when the fuel in either the fuel tank or the subsidiary tank is reduced nearly to a lower limit. Therefore, the engine sometimes suffers from surge. In such a case, the mesh filter in the strainer does not contribute to separation of gases from the fuel. When accelerating, decelerating or turning, a motorcycle changes its posture extensively compared with a four-wheel vehicle. In such a case, the motorcycle engine tends to suffer from surge because the level of the fuel varies in the fuel tank. There has been a strong demand for preventing the surge caused by the foregoing reasons. DE 195 23 634 A discloses a fuel pump that is surrounded by spongy dampening means. In order to overcome the foregoing problems, the invention provides a fuel supply unit according to claim 1. The fuel-adsorbing member is made of a spongy material which is full of minute pores and is elastic and flexible, can attract fuel thereonto, and can separate gases from the returned fuel. The fuel-adsorbing member may be constituted by a natural material, a foamed synthetic resin material, or a metallic material. For example, it may be made of a corrosion-resistant metal. In the specification, the terms "forward direction" and "rear direction" represent the directions in which the vehicle runs, and "upward direction" and "downward direction" represent the directions with respect to the vehicle standing. Preferably, in the fuel supply unit a partition is disposed in the fuel tank in order to separate at least an area near the inlet port of the fuel pump and the area in front of the inlet port. The fuel-adsorbing member is supported by the partition. Preferably the fuel supply unit is designed for a motorcycle. According to the invention the spongy fuel-adsorbing member is disposed between the strainer and the tip of the fuel return pipe, thereby enabling the air-fuel mixture returned via the fuel return pipe to be separated into gases and liquid fuel. The liquid fuel is adsorbed onto the fuel-adsorbing member and usually stays near the strainer. Even when the amount of fuel is reduced nearly to the lower limit, it is possible to supply the foregoing liquid fuel to the fuel tank from the adsorbing member, so that the engine can be protected against surge. Further, the liquid fuel adsorbed onto the fuel-adsorbing member remains around the strainer, which allows the fuel to be supplied substantially without being affected by the varying posture of the running vehicle. The fuel-adsorbing member is easily manufactured using a spongy material such as a foamed synthetic resin material which is elastic, so that it is resistant to vibrations and effective in suppressing noise. Alternatively, a fuel-adsorbing member made of a corrosion-resistant metal and having good heat conductivity is sufficiently durable to returned acidic fuel, and can cool the adsorbed fuel. In accordance with a preferred embodiment of the invention, the partition in the fuel tank divides at least the area near the inlet port of the fuel pump and the area in front of the inlet port. Therefore, even if the vehicle is suddenly decelerated due to braking , a fuel level can be maintained substantially normal near the inlet port of the fuel tank, thereby protecting the engine against surge. Further, the fuel-adsorbing member supported on the partition can be easily arranged near the strainer. When the fuel supply unit is applied to a motorcycle whose posture is extensively variable during running, the engine thereof can be protected against surge. Therefore, the fuel supply unit is preferable for motorcycles. Embodiments of the invention will be described in reference to the enclosed drawings. Fig. 1 is a cross-sectional view of the fuel supply unit according to the embodiment of the invention. Fig. 2 is a side view of the motorcycle to which the invention is applied. Fig. 3 is a side view of the fuel pump assembly. Fig. 4 is a rear view of the fuel pump assembly. Fig. 5 is a bottom view of the fuel pump assembly. Fig. 6 is a schematic view of the fuel supply unit applied to a motorcycle in the related art. Components identical to those of the related art are assigned reference numerals identical to those in Fig. 6. Referring to Fig. 2 first of all, the motorcycle 2 is provided with a V-type four-cycle engine 13 arranged between front and rear wheels 11 and 12. A main frame 14 suspending and supporting the engine 13 includes a pair of members extending from a head pipe 15 and over the engine 13 toward the rear of the motorcycle 2. A fuel tank 1 is supported on the main frame 14. A bottom of the fuel tank 1 is partially raised to define a space thereunder. An air cleaner 16 housed in the foregoing space introduces air into respective cylinders of the engine 13, using a down-draft system. Fuel in the fuel tank 1 is simultaneously supplied to the cylinders via a throttle body 7 (shown in Fig. 1). Part of the fuel is brought back to the fuel tank 1 as returned fuel from the throttle body 7, as will be described later. The throttle body 7 is similar to that shown in Fig. 6, and its detailed structure and piping arrangement with the fuel tank 1 will not be described here. In Fig. 2, reference numeral 20 represents a steering handle, 21 represents a front fork, 22 represents a seat rail support obliquely and upward extending from the rear part of the main frame 14 toward the rear part of the motorcycle, 23 represents a rear cowl, and 25 represents rear swing arms. The rear swing arms 25 are directly attached at their front ends to a rear part of a casing 26 constituting the engine 13 so as to turn freely. The casing 26 is split into upper and lower parts. A crankshaft 27, a main shaft 28, an output sprocket shaft (countershaft) 29, a pivot shaft 25a and so on are arranged substantially straight on a split surface 13a. Referring to Fig. 1, the bottom 30 of the fuel tank 1 slopes moderately obliquely downward and rearward, and a rear part 31 of the bottom 30 is flat. A fuel pump assembly 33 is attached from a lower side to an opening 32 formed on the rear part 31, and is covered by a base plate 34. As shown in Figs. 3 to 5, the fuel pump assembly 33 includes the fuel pump 2, strainer 4, high-pressure fuel filter 6, fuel return pipe 10, fuel-adsorbing member 35, partition 36 and so on which are collectively and compactly disposed on the base plate 34. The fuel pump 2 is supported by a stay 37 projecting from the center of the base plate 34 so as to be sloped obliquely forward. The high-pressure fuel filter 6 is disposed on the stay 37 at a position opposite to the fuel pump 2. A discharge port of the fuel pump 2 and an inlet port of the high-pressure fuel filter 6 are connected using a discharge pipe 5. An outlet port of the high-pressure fuel filter 6 communicates via a pipe 38 with a joint pipe of a branch terminal 39 arranged on the base plate 34. High-pressure fuel is supplied to the throttle body 7 via the branch terminal 39. The inlet port 3 of the fuel pump 2 is directly connected to the strainer 4, which includes a well-known mesh filter in order to remove foreign matter such as metal powders from the fuel. A fuel-adsorbing member 35 of stainless steel is positioned on the strainer 4. Specifically, the fuel-adsorbing member 35 is constituted by a stainless steel wire or strip coil which is wound to form a ring, or entwined to form a block, e.g., it is similar to a metallic scrubbing brush known as a household article. The fuel-adsorbing member 35 is porous and elastic, i.e., it is full of minute pores compared with the meshes of the metal filter attached to the strainer 4, and has a total hollow area much larger than that of the mesh metal filter, which enables separation of the returned fuel into gases and liquid fuel. The partition 36 is made of a relatively flexible material such as rubber, and is slightly larger than the strainer 4, but is relatively small compared with a partition constituting a conventional sub-tank. The partition 36 has a height which is sufficient to cover front parts of the inlet port 3, strainer 4, and fuel-adsorbing member 35. The partition 36 extends upward from the base plate 34 in order to cover the lower side of the fuel pump 2, and the front, right and left sides of the strainer 4. Further, the right and left sides 40 of the partition 36 cover the right and left sides of the fuel-adsorbing member 35, and are open at the rear and top. The partition 36 is integral with a holding member 41 which extends across and above upper parts of the sides 40, and holds an upper part of the fuel-adsorbing member 35. The upper part of the fuel-adsorbing member 35 is exposed except for an area held by the holding member 41. One end 42 of the fuel return pipe 10 in the shape of an inverted letter U extends downward to face the exposed area of the fuel-adsorbing member 35. The other end of the fuel return pipe 10 is connected to an upper end of the joint pipe 43 extending vertically through the base plate 34. The lower end of the joint pipe 43, not shown, is connected to the throttle body 7 via a connection hose (similar to the hose 10a shown in Fig. 6). In Figs. 3 and 4, reference numeral 44 represents conductors for the fuel pump 2, and 45 presents a bolt hole into which a bolt 46 projecting downward from the peripheral surface of the base plate 43 is fitted and fastened by a nut 47. The operation of the embodiment will be described hereinafter. As shown in Fig. 1, the fuel housed in the fuel tank 1 is drawn up by the fuel pump 2, and is introduced to the throttle body 7 via the strainer 4 and inlet port 3 substantially at the bottom of the fuel tank 1, and via the high-pressure fuel filter 6. The fuel returned and discharged onto the fuel-adsorbing member 35 via the tip 42 of the fuel return pipe 10 contains a relatively large amount of gases. However, the gases pass through the pores of the fuel-adsorbing member and are sifted from the returned fuel, so that the fuel remains adsorbed on the fuel-adsorbing member 35 as liquid fuel, and stays near the strainer 4. Even when the fuel is reduced nearly to the lower limit in the fuel tank 1, the liquid fuel free from gases is supplied to the strainer 4 from the fuel-adsorbing member 35. Therefore, the engine is effectively protected against surge which is caused by gases contained in the fuel. Further, the foregoing fuel remains adsorbed onto the fuel-adsorbing member 35, and is slow to move even when the posture of the vehicle is changed. Therefore, even if ripples are caused on the surface of fuel around the fuel-adsorbing member 35, they can be stabilized by the fuel supplied from the fuel-adsorbing member 35. In this embodiment, the fuel-adsorbing member 35 is a spongy filter made of stainless steel which is resistant to strong acidic fuel and is very durable. The stainless steel has a good heat conductivity so that the fuel-adsorbing member 35 can efficiently cool the fuel sticking thereon. This is very effective in separating gases from the returned hot fuel, in suppressing lowering of the fuel pressure, and improving fuel supplying efficiency. The partition 36 separates the strainer 4 and the area in front of the strainer 4 to the predetermined height, which is effective in keeping the surface of the fuel from rippling near the strainer 4 even when the posture of the vehicle is varied. Particularly, the fuel tends to move quickly forward when the motorcycle is suddenly braked. The partition 36 is effective in suppressing changes on the surface of the fuel near the strainer 4 which is present between the partition 36 and the rear wall of the fuel tank 1. The partition 36 made of an elastic material such as rubber can suppress noise caused if it comes into contact with the fuel pump 2 or the strainer 4 when the fuel tank 1 is vibrated by the running vehicle. The partition 36 reliably supports the fuel-adsorbing member 35 which is elastic and is easily deformed, so that it is possible to efficiently prevent noise caused when these members come into contact with each other. Further, the partition 36 is positioned near the fuel pump assembly 33 which is independent from the bottom 30 of the fuel tank 1. Therefore, it is not necessary to press-form the partition 36 into a complicated shape, and the fuel pump assembly 33 can be supported on the flat portion 31 of the bottom 30. The flat portion 31 is easy to shape, which means that the fuel tank 1 can be easily formed. The fuel-adsorbing member may be realized using felt-like metal wool made by weaving and shrinking minute metal fibers as thin as hairs, or using a woven or non-woven cloth of metal fibers, or using a mesh obtained by knitting the metal fibers. Further, synthetic resin sponge such as foamed polyurethane or natural sponge or rubber sponge may be usable as the fuel-adsorbing member. Alternatively, fuel may be supplied on the basis of a natural air intake system using a carburetor in place of fuel injection. Further, the fuel pump may be disposed outside the fuel tank instead of the in-tank system employed in the embodiment. In addition, the fuel supply unit is applicable to various types of vehicles such as four-wheel vehicles as well as motorcycles. The invention promotes separation of returned fuel into liquid fuel and gases. A base plate 34 of a fuel pump assembly 33 is attached, from the lower side, to a rear part of a bottom 30 of a fuel tank 1. A fuel pump 1 and a strainer 4 communicating with an inlet port 3 are housed in the fuel tank 1. A small partition 36 made of an elastic material such as rubber covers the front, right and left sides of the strainer 4, and partially supports a fuel-adsorbing member 35 arranged on the strainer 4. The fuel-adsorbing member 36 is a spongy filter made of stainless steel coils and having a great number of minute pores, adsorbs the fuel returned via a fuel return pipe 10, and separates the fuel into gases and liquid fuel. The liquid fuel remains adsorbed onto the fuel-adsorbing member 35 and stays near the strainer 4.

Claims: A fuel supply unit for a vehicle, comprising: a fuel tank (1); a fuel pump (2) for providing a fuel supply system of the vehicle with fuel introduced from said fuel tank via a strainer (4) disposed therein; a fuel return pipe (10) for returning surplus fuel from said fuel supply system to said fuel tank; and a spongy fuel-adsorbing member (35) disposed between said strainer and a tip of said fuel return pipe; the upper side of the spongy fuel-adsorbing member (35) being exposed into the fuel tank (1). The fuel supply unit according to claim 1, wherein said fuel-adsorbing member (35) is made of a corrosion-resistant material. The fuel supply unit according to claim 1, wherein a partition (36) is disposed in said fuel tank (1) in order to separate at least an area near an inlet port (3) of said fuel pump (2) and an area in front of said inlet port. The fuel supply unit according to claim 3, wherein said fuel-adsorbing member (35) is supported by said partition (36). The fuel supply unit according to any of claims 1 to 4, wherein the fuel supply unit is designed for a motorcycle. The fuel supply unit according to one of the preceding claims, wherein the spongy fuel-absorbing member (35) is offset from the fuel pump (1).

Inventors: DAZAI MASAYUKI, NAKASHIMA TAI, ONO NOBUO, YOSHIKI HIROTO, DAZAI, MASAYUKI, NAKASHIMA, TAI, ONO, NOBUO, YOSHIKI, HIROTO
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1998
Main classification: F02M37
IPC codes: F02M37, B60K15