FUEL PUMP FOR DIRECT FUEL INJECTION FOR ENGINES

Description

technical field

[0001] The invention relates to a fuel pump for direct fuel injection for internal combustion engines. 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 deliver 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 typically electric and feeds a high-pressure pump, which typically consists of a pump piston moving within a pump body. The pump piston is driven by a camshaft of the internal combustion engine to increase 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.

[0003] Document EP 3 715 619 A1 shows an example of this type of pump. An example is also reproduced on the figure 1The movement of the piston 101 in the pumping chamber 1050 is provided by the camshaft 102 against a spring 103 which tends to keep one end of the piston 101 bearing against a cam of the camshaft 102. The spring is of the helical compression type and bears on one side against a seat 104 fixed on the body 105 of the pump and on the other side against a retaining washer 106 connected to the end of the piston 101 by connecting means 107. The connecting means comprise two conical half-rings 1071 engaging with a recess 1072 at the end of the piston and a conical housing 1073 carried by the retaining washer 106 in which the conical half-rings 1071 are housed. The slope of the cone of the housing 1073 is oriented in such a way that the action of the spring 103 on the retaining washer 106 is blocked by the conical half-rings 1071 wedged in the housing 1073.

[0004] While these retention mechanisms are effective, they do have some drawbacks. The assembly process is complex. The spring and retaining washer must be positioned around the piston, and then the spring compressed to create enough space for the conical half-rings. The spring compression can then be released, allowing the retaining washer to secure the conical half-rings. It has also been observed that only one half-ring is sometimes installed, and this defect is often only detected later, resulting in high intervention costs. Furthermore, the surfaces of the bearing cavity, the conical half-rings, and the housing are machined and quite precise, leading to high production costs. Another example of a fuel pump is shown in document DE 103 45 061 A1. Description of the invention

[0005] It is therefore an objective of the invention to provide a fuel pump for direct fuel injection for internal combustion engines whose construction is reliable and simple and with minimized costs.

[0006] With these objectives in mind, the invention relates to a fuel pump for direct fuel injection for internal combustion engines, the pump comprising a pump body, a pumping chamber in which a piston is mounted to slide, a spring bearing on one side on the pump body and on the other side on an end of the piston protruding out of the pump body by means of a retaining washer and connecting means between the retaining washer and the end of the piston, the pump being characterized in that the connecting means comprise a plurality of fingers originating from a ring of the retaining washer and arranged to protrude towards a central axis of the ring, one end of the fingers fitting into a circular groove of the piston and being held by the spring bearing against a shoulder delimiting the circular groove.

[0007] Thanks to the invention, the retaining washer is secured without the need for any other parts. The risk of missing parts is therefore eliminated. The fact that the connection to the piston is made by fingers, which are separate components, allows for easy assembly: the retaining washer is inserted onto the piston, and the fingers spread apart until they reach the groove. There, the tips of the fingers are inserted into the groove and lock the retaining washer in place. This assembly is simple to produce, reliable, and the retaining washer can be manufactured using inexpensive cutting and stamping operations.

[0008] According to an advantageous feature, the finger tips are flexibly movable relative to the ring. The finger tips return spontaneously into the circular groove when the retaining washer is inserted onto the piston.

[0009] According to an improvement, the fingers are angled relative to a plane perpendicular to the central axis, oriented to create a buttress against the piston in the circular groove when the spring presses on the retaining washer. Thus, the greater the force exerted on the retaining washer to pull it away from the piston, the more the tips of the fingers are pressed into the groove. The fingers, distributed around the groove, balance each other. The resulting retention force is very high.

[0010] In particular, the inclination of the fingers is between 15 and 35°, preferably between 20° and 30°.

[0011] According to a design feature, the diameter of the groove bottom is smaller than the piston end diameter by a factor of between 2 and 10%, preferably between 4 and 5% of the end diameter. This ensures that the groove depth is sufficient to retain the retaining washer without excessively weakening the piston.

[0012] According to other provisions: The retaining washer has a guide ring extending along the central axis of the ring along the spring to center the spring on the retaining washer. It is ensured that the spring is properly centered on the retaining washer. The retaining washer has an annular base connected to the ring to receive the spring. The ring is connected to the ring. The piston has a flange designed to bear against the pump body and limit the piston's stroke when the retaining washer is engaged on the piston. The piston may already be at the bottom of the pumping chamber, but sometimes this is too deep to allow the retaining washer to be inserted onto the piston. By providing a flange, the piston's stop position is determined independently. The pump has a seat that receives the spring and bears against the pump body; the seat has a sleeve on which the spring is centered and which surrounds the piston.

[0013] The invention also relates to a method of assembling a pump as defined above, in which the piston is inserted into the chamber, the spring is placed around the piston, the retaining washer is placed on the spring, and the retaining washer is pressed to compress the spring until the fingers spread against the piston and return to the circular groove. This method is simpler than that of the prior art. Brief description of the figures

[0014] The invention will be better understood and other features and advantages will become apparent upon reading the following description, the description referring to the attached drawings, among which: there figure 1 is a detailed cross-sectional view of a pump according to the prior art; the figure 2 is similar to the figure 1 during a pump assembly phase according to an embodiment of the invention; the figure 3is a view similar to the figure 2 after the pump has been installed; the figure 4 is a cross-sectional and perspective view of the end of a piston and a retaining washer of the pump of the figure 3 ; there figure 5 is a perspective view of the retaining puck of the figure 4 ; there figure 6 is a longitudinal cross-sectional view of the retaining washer of the figure 5 . Detailed description

[0015] A fuel pump for direct fuel injection for internal combustion engines according to an embodiment of the invention is shown in the figures 2 to 6The pump comprises a pump body 5, a pumping chamber 50 in which a piston 1 is slidably mounted, and a spring 3 bearing on the pump body 5 via a seat 4 and on one end 10 of the piston 1 protruding from the pump body 5 via a retaining washer 6. The retaining washer 6 has an annular flange 61 having a central axis A for receiving the spring 3. The retaining washer 6 further comprises a guide ring 62 also having the central axis A as its axis and extending along the spring 3 from the flange 61 to center the spring 3 on the retaining washer 6, and in particular on the flange 61. The guide ring 62 has a substantially frustoconical shape. The crown 62 is extended by a ring 63 which also has the central axis A as its axis and extends in a plane raised relative to the plane of the sole 61.

[0016] Connecting means 7 are provided between the retaining washer 6 and the end 10 of the piston 1. The connecting means 7 comprise a plurality of fingers 70 extending from the ring 63 of the retaining washer 6 and arranged projecting towards the central axis A, inclined with a base connected to the ring 63 closer to the pump body 5 than the ends 700 of the fingers 70 in contact with the piston 1. The end 700 of the fingers 70 fits into a circular groove 71 of the piston 1 and is held by the spring 3 bearing against a shoulder 710 delimiting the circular groove 71. The end 700 of the fingers 70 is flexibly movable relative to the ring 63, as will be better seen in connection with the description of the pump assembly.In other words, the fingers 70 are inclined with respect to a plane perpendicular to the central axis A, being oriented to create a buttress against the piston 1 in the circular groove 71 when the spring 3 presses on the retaining washer 6. The inclination of the fingers 70 is typically between 24 and 30°.

[0017] A bottom diameter 710 of the circular groove 71 is less than an end diameter of the piston 1 by a value between 4 and 5% of the end diameter.

[0018] The piston 1 has a collar 11 intended to bear against the pump body 5 and limit the stroke of the piston 1 when the retaining washer 6 is engaged on the piston 1. The collar 11 could be replaced by an elastic ring inserted in a groove.

[0019] The seat 4, which receives the spring 3, rests on and is fixed to the pump body 5. The seat 4 has a sleeve 40 on which the spring 3 is centered and which surrounds the piston 1. Optionally, stop means (not shown) may be housed between the body and the piston 1 so as to limit the stroke of the piston 1 against the spring 3.

[0020] To assemble the pump, the piston 1 is inserted into the chamber until the flange 11 against the pump body 5 is stopped. The seat 4 is then fixed to the body around the piston 1. The spring 3 is placed around the piston 1, bearing against the seat 4. The retaining washer 6 is placed on the spring 3, and the retaining washer 6 is pressed to compress the spring 3. The fingers 70 then extend elastically under the action of the end 10 of the piston 1 until they reach the circular groove 71. The elastic return of the fingers 70 pushes their ends into the circular groove 71 until they rest against the bottom of the circular groove 71. The spring 3 can then be released; its action is taken up by the retaining washer 6, which rests against the bottom of the circular groove 71 and the shoulder 710.

Claims

1. A fuel pump for direct fuel injection for internal combustion engines, the pump comprising a pump body (5), a pumping chamber (50), in which a piston (1) is slidingly fitted, a spring (3) bearing on the one hand on the pump body (5) and on the other hand at one end (10) of the piston (1) protruding out of the pump body (5) via a retaining washer (6) and joining means (7) between the retaining washer (6) and the end (10) of the piston (1), the pump being characterised in that the joining means (7) comprise a plurality of fingers (70) originating from a ring (63) of the retaining washer (6) and arranged so as to protrude towards a central axis (A) of the ring (63), one end (700) of the fingers (70) being accommodated in a circular groove (71) of the piston (1) and being held by the spring (3) so as to bear against a shoulder (710) delimiting the circular groove (71), the fingers (70) being inclined relative to a plane perpendicular to the central axis (A), being oriented to produce a buttress against the piston (1) in the circular groove (71) when the spring (3) bears on the retaining washer (6).

2. The pump according to Claim 1, wherein the end (700) of the fingers (70) is flexibly mobile relative to the ring (63).

3. The pump according to Claim 1 or 2, wherein the inclination of the fingers (70) is between 15 and 35°, preferably between 20° and 30°.

4. The pump according to one of the preceding claims, wherein the diameter of the bottom of the groove is less than the end diameter of the piston (1) by a value of between 2 and 10 %, preferably between 4 and 5 % of the end diameter.

5. The pump according to one of the preceding claims, wherein the retaining washer (6) comprises a guide crown (62) extending according to the central axis (A) of the ring (63) along the spring (3) to centre the spring (3) on the retaining washer (6).

6. The pump according to Claim 5, wherein the retaining washer (6) comprises an annular-shaped flange (61) joined to the crown (62) for receiving the spring (3).

7. The pump according to Claim 5 or 6, wherein the ring (63) is joined to the crown (62).

8. The pump according to one of the preceding claims, wherein the piston (1) comprises a collar (11) intended to come to bear against the pump body (5) and limit the stroke of the piston (1) when the retaining washer (6) engages on the piston (1).

9. The pump according to one of the preceding claims, characterised in that it comprises a seat (4) receiving the spring (3) and bearing on the pump body (5), the seat (4) comprising a sleeve (40) on which the spring (3) is centred and which surrounds the piston (1).

10. A method of assembling a pump according to one of the preceding claims, characterised in that the piston (1) is introduced into the chamber, the spring (3) is placed around the piston (1), the retaining washer (6) is placed on the spring (3), and pressure is applied to the retaining washer (6) to compress the spring (3) until the fingers (70) spread apart against the piston (1) and then recover to enter the circular groove (71).