Fuel pump

Abstract

A fuel pump comprising a pump body (1), a ring (4) housed in a recess (10) of the pump body (1), the recess (10) opening on one side to the outside of the pump body (1) and on the other side into a compression chamber (2), a piston (3) movable in translation within the ring (4) to compress fuel in the compression chamber (2), the ring (4) being press-fitted into the recess (10) by two bulges (41, 42) projecting from a cylindrical outer surface of the ring (4), the pump being characterized in that a first of the bulges (41) at a first end (43) of the ring (4) on the side of the compression chamber (2) is located at a distance from the end of the ring (4) of between 20% and 40% of the length of the ring (4). Figure for the abbreviation: Fig. 3

Description

Title of the invention: Fuel pump technical field

[0001] The invention generally relates to the field of fuel pumps for internal combustion engines, and in particular fuel pumps for supplying liquid fuel under high pressure for direct injection into the engine. Previous technique

[0002] Fuel systems in modern gasoline-powered internal combustion engines, particularly those for the automotive market, utilize direct gasoline injection, in which fuel injectors are used to inject fuel directly into the engine's combustion chambers. In such direct injection systems, fuel from the tank is supplied by a low-pressure fuel pump integrated into the tank. This low-pressure pump is generally electric and supplies a high-pressure pump, which typically comprises a movable pump piston within a pump body. The pump piston is actuated by a camshaft of the internal combustion engine to increase the fuel pressure in a pumping chamber of the pump body. The high-pressure fuel is then distributed to the injectors, which control the injection of fuel directly into the engine's combustion chamber.Such a pump has a non-return valve between the low-pressure circuit and the pumping chamber. The non-return valve allows fuel to enter the pumping chamber and prevents it from entering when the piston rises and compresses the fuel.

[0003] Document WO 2023 / 105024 A1 shows such a pump. Figure 1 reproduces a similar pump. A piston 101 is slidably mounted via a ring 107 in a pump body 102 in which a compression chamber 103 is provided. The fuel supply to the compression chamber 103 is achieved through an inlet assembly that is housed partly in the body 102 and partly in an inlet sleeve 104 of substantially cylindrical shape and with its axis perpendicular to the axis of the piston 101. A non-return valve 105 is located in the inlet sleeve 104 and is retained by a ring 106, which is welded by a weld 106' to the pump body 102 at the outlet of the inlet sleeve 104. The inlet sleeve 104 is also welded to the pump body by weld 104'. An output connector 110 is fixed by a 110' solder joint opposite the input connector in the same axis.

[0004] The ring 107 is housed in a recess in the body 102 by a press fit and is abutted against a shoulder at a first end of the recess on the side of the Compression chamber 103. Furthermore, a crimp 108 is formed on the body and fits into a groove in the ring 107 at a second end of the housing opposite the first end, so as to retain the ring 107 against extraction from the housing. The ring has two annular bulges 109 near the first and second ends respectively, on which the press-fit assembly is performed.

[0005] The piston operation must be perfectly controlled. If the fit between the piston and the ring is too small, the piston may seize and become blocked, resulting in a fuel supply interruption. If the fit is too large, the fuel leakage rate between the piston and the ring may be excessive, given the high pressure level in the compression chamber.

[0006] In the pump assembly process, the inlet assembly and outlet connector are welded after the ring and piston have been mounted. However, it has been observed that the welds can cause deformations of the pump body, which in turn deform the ring, particularly because the first bulge is located in a weld alignment between the inlet assembly and the outlet connector. The clearance between the piston and the ring is therefore poorly controlled. Description of the invention

[0007] The invention aims to provide a fuel pump in which the geometric and dimensional characteristics of the piston guidance are controlled.

[0008] With these objectives in view, the invention relates to a fuel pump comprising a pump body, a ring housed in a housing of the pump body, the housing opening on one side to the outside of the pump body and on the other side into a compression chamber, a piston movable in translation in the ring to compress fuel in the compression chamber, the ring being in press-fit mounting in the housing by two bulges projecting from a cylindrical outer surface of the ring, the pump being characterized in that a first of the bulges at a first end of the ring on the side of the compression chamber is located at a distance from the first end of the ring of between 20% and 40% of the length of the ring.

[0009] By positioning the first bulge at this distance, it is located further from the first end than in the prior art, thus placing it at a greater distance from the areas subject to the influence of weld-induced deformations. The inventors found that this displacement was able to reduce the deformations undergone by the ring, measured on the ring's inner diameter, by 30 to 50%. By reducing the deformations, the clearance between the ring and the piston is more reliably ensured, and the risk of piston seizure in the pump is minimized. A distance greater than 40% may weaken the guidance of the ring in the housing with the risk of it moving into slight misalignment during the operation of the pump.

[0010] According to a preferred feature, the first bulge is located at a distance from the end of the ring between 25% and 35% of the length of the ring.

[0011] According to an improvement, the outer diameter of the ring is between 150% and 200% of the piston diameter, preferably between 165% and 190%. The inventors observed that a thicker ring wall deformed less, but that a larger ring diameter was subjected to greater stresses in the direction of ring extraction from the pump body, due to the fuel pressure exerted on the first end from the compression chamber. This is all the more evident given the market trend towards increasing pump operating pressure, with a nominal pressure of 500 bar or more. The values ​​indicated represent an acceptable compromise between the ring's strength and the extraction stresses.

[0012] According to one design, the pump body around the housing is substantially cylindrical with the same axis as the housing, the wall thickness of the ring being between 20% and 35% of the body thickness, preferably greater than 25%. The body diameter is substantially limited by space constraints. Within these limits, a balance must be found between the wall thicknesses of the ring and the body. Indeed, the press-fit insertion of the ring puts stress on the body, which must resist this force, whereas it is advantageous to have a thick ring to minimize deformation. The inventors have found that this balance is achieved with the values ​​indicated above.

[0013] According to a design feature, the housing has a shoulder against which the ring abuts at its first end. This shoulder determines the position of the ring when it is forced into the housing.

[0014] According to one design feature, the body includes a collar formed by crimping against a second end of the ring opposite the first end to immobilize the ring. In addition to retaining the ring in the housing by the tight fit, the collar prevents the ring from being extracted. The collar is formed after the ring is inserted, by deforming the body at the periphery of the second end.

[0015] According to a constructive arrangement, the ring has a rebate at the second end, the collar fitting into the rebate.

[0016] According to an improvement, the compression chamber is in communication with an outlet fitting fixed opposite the compression chamber to the pump body by welding. The outlet fitting is, for example, suitable for receiving the connection of a pipe by screwing on a nut. The outlet fitting is centered towards the compression chamber, which requires that the welds of the outlet fitting on the body are opposite the ring.

[0017] According to an improvement, the pump comprises an inlet assembly facing the compression chamber, the inlet assembly having a sleeve welded to the pump body. As with the outlet fitting, the inlet assembly is centered towards the compression chamber, which also requires that the welds securing the outlet assembly to the body are aligned with the ring. Brief description of the figures

[0018] The invention will be better understood and other features and advantages will become apparent upon reading the following description, the description referring to the accompanying drawings, among which: • [Fig. 1] is a cross-sectional view of a pump according to the prior art; • [Fig.2] is a view of detail II of [Fig.1]; • the [Fig.3] that a partial cross-sectional view of a palm according to a first mode realization of the invention; • [Fig.4] is a cross-sectional view of a ring used in the pump of [Fig.3]. Detailed description

[0019] A fuel pump according to a first embodiment of the invention is shown in Figures 3 and 4. The fuel pump comprises a pump body 1, a piston 3 mounted to slide via a ring 4 in the pump body 1 in which a compression chamber 2 is provided. Fuel enters the compression chamber 2 via an inlet assembly 5 which fits into an inlet housing, defined by the body and by an inlet sleeve 50 with an axis perpendicular to the axis of the piston 3. The fuel compressed by the piston 3 is expelled from the compression chamber 2 via an outlet assembly 13 arranged in an outlet housing and comprising an outlet valve, generally in the form of a non-return valve (not shown) and then an outlet nipple 6. The outlet assembly 13 supplies the pressurized fuel from the compression chamber 2 to injectors via lines, not shown, connected to the outlet nipple 6.For example, the non-return module includes for this purpose a spherical obturator held under pressure on a seat by a spring. The ball lifts from the seat and allows the passage of liquid fuel to the nipple 6 when the fuel pressure in the chamber exceeds the spring force / pressure downstream of the non-return valve.

[0020] The configuration and operation of the input and output assemblies are only briefly described because these components are well known in the field, and may be particularly similar to those described in WO 2023 / 105024 A1.

[0021] The fuel supply to the pump is achieved via a supply chamber 18, to which the fuel is supplied, in communication with the inlet housing by a supply channel 20.

[0022] The inlet assembly 5 further includes a non-return valve 22 to allow fuel to flow from the inlet housing 5 to the compression chamber 2 and to block fuel flow in the opposite direction. The non-return valve 22 is located in the inlet housing 104 and is retained by a ring 26, which includes fuel passage holes.

[0023] The input assembly 5 includes an actuator 28 cooperating with a movable needle 30, projecting towards the output housing 6. The actuator 28 typically includes a movable armature to which the needle 30 is attached. The armature is attracted by the magnetic field generated by a coil assembly with a pole piece, when energized, thus moving the needle to the left in the plane of [Fig.3].

[0024] The check valve 22 comprises a seat element 22a having through holes 22b which cooperates with a flexible obturator 23 located on one side of the seat element 22a. A cage is mounted on the obturator 23 and is fixed to the same side of the seat element 22a (e.g., by welding). The cage limits the bending of the obturator 23 in the opening direction, i.e., away from the seat element 22a. The obturator 23 is therefore open by default and is closed by energizing the actuator 28.

[0025] The inlet housing is delimited by the sleeve 50 fixed to the pump body 1 by a weld 5'. The ring 4 is housed in a recess 10 of the pump body 1, the recess 10 opening on one side to the outside of the pump body 1 and on the other side into the compression chamber 2. The translation of the piston 3 in the ring 4 allows the fuel to be compressed in the compression chamber 2. The compression chamber 2 is in communication with the outlet fitting 6 fixed opposite the compression chamber 2 on the pump body 1 by a weld 6'.

[0026] The ring 4 is press-fitted into the housing 10 by two bulges 41, 42 projecting from a cylindrical outer surface of the ring 4. Furthermore, the housing 10 has a shoulder against which the ring 4 abuts at a first end 43 of the ring 4 on the side of the compression chamber 2. A first of the bulges 41 is located at the first end 43 of the ring 4, at a distance dl from the end of the ring 4 of between 20% and 40% of the length of the ring 4, preferably between 25% and 35% of the length 1 of the ring 4. The second bulge 42 is located at a second end 44 of the ring 4 opposite the first end 43 at a distance d2 between 10% and 25% of the length 1 of the ring 4. The thickness of the bulges 41, 42 is, for example, 0.1 mm to 0.2 mm. The axial length of the bulges can be on the order of 0.4 to 0.8 mm.

[0027] The ring 4 has a rebate 45 at a second end 44 of the ring 4 opposite the first end 43. The body 1 has a collar 11 obtained by crimping and which fits into the rebate 45, in support to immobilize the ring 4.

[0028] The outer diameter of the ring 4 is between 145% and 200% of the diameter of the piston 3, preferably between 150% and 190%. The same pump body 1 can accommodate different piston 3 diameters. The ring 4 then serves as an adapter for the housing 10, whose diameter is fixed, to allow the production of pumps with different characteristics from the same bodies.

[0029] The pump body 1 around the housing 10 is substantially cylindrical with the same axis as the housing 10. The wall thickness of the ring 4 is between 20% and 35% of the thickness of the body 1, preferably greater than 25%.

[0030] During assembly, the ring 4 is first pressed into the housing 10 until the first end 43 is abutted against the shoulder. The collar 11 is then formed by crimping. Next, the ring 4 is fitted to the piston 3 by lapping the inner surface. A piston assembly 30, incorporating the piston 3 and a sealing cover 29, is positioned by inserting the piston 3 into the ring 4. This piston assembly 30 is then fixed to the body 1 by welding the sealing cover 29 to it via weld 29'. The inlet assembly 5 is also positioned and welded, either before or after the outlet fitting 6, which is also welded to the body 1.

[0031] In operation, a cam, not shown, acts indirectly on the piston 3 to move it in the ring 4 in an alternating manner, so that fuel is drawn in via the inlet assembly 5 and is discharged via the outlet fitting 6, in a manner known per se.

[0032] Several pumps have been manufactured, one according to the prior art and the other according to the new embodiment. According to the prior art, the circularity error averaged 4.7 µm on the inner diameter of the ring 4. With the embodiment according to the invention, the circularity error was less than 2 µm on the inner diameter of the ring 4. The new characteristics conferred to the pump thus make it possible to significantly reduce circularity errors, and therefore the risk of piston seizure.

Claims

Demands

1. Fuel pump comprising a pump body (1), a ring (4) housed in a housing (10) of the pump body (1), the housing (10) opening on one side to the outside of the pump body (1) and on the other side into a compression chamber (2), a piston (3) movable in translation in the ring (4) to compress fuel in the compression chamber (2), the ring (4) being press-fitted in the housing (10) by two bulges (41, 42) projecting from a cylindrical outer surface of the ring (4), the pump being characterized in that a first of the bulges (41) at a first end (43) of the ring (4) on the side of the compression chamber (2) is located at a distance from the end of the ring (4) of between 20% and 40% of the length of the ring (4).

2. Pump according to claim 1, wherein the first bulge is located at a distance from the end of the ring (4) between 25% and 35% of the length of the ring (4).

3. Pump according to any one of the preceding claims, wherein the outside diameter of the ring (4) is between 145% and 200% of the diameter of the piston (3), preferably between 150% and 190%.

4. Pump according to any one of the preceding claims, wherein the pump body (1) around the housing (10) is substantially cylindrical with the same axis as the housing (10), the wall thickness of the ring (4) being between 20% and 35% of the thickness of the body (1), preferably greater than 25%.

5. Pump according to any one of the preceding claims, wherein the housing (10) has a shoulder against which the ring (4) abuts at the first end (43).

6. Pump according to any one of the preceding claims, in which the body (1) has a collar (11) obtained by crimping against a second end (44) of the ring (4) opposite the first end (43) to immobilize the ring (4).

7. Pump according to claim 6, in which the ring (4) has a rebate (45) at the second end (44), the collar (11) fitting into the rebate (45).

8. A pump according to any one of the preceding claims, wherein the compression chamber (2) is in communication with a fitting 8 outlet (6) fixed opposite the compression chamber (2) on the pump body (1) by welding.

9. Pump according to any one of the preceding claims, characterized in that it comprises an inlet assembly (5) opposite the compression chamber (2), the inlet assembly (5) comprising an inlet sleeve (50) fixed to the pump body (1) by welding.