Fuel pump for direct injection of fuel for internal combustion engines

Abstract

A fuel pump for direct fuel injection of an internal combustion engine, the fuel pump comprising: a pump body (5); a pumping chamber (50) in which the piston (1) is fitted in a slidable manner; the invention relates to a pump (1) for a motor vehicle, comprising a pump body (5) and a piston (1), a spring (3) which is mounted on the pump body (5) on one side and on one end (10) of the piston (1) on the other side, the end (10) protruding out of the pump body (5) via a retaining washer (6) and a connecting device (7) connecting the retaining washer (6) to the end (10) of the piston (1). The connection means (7) comprise a plurality of fingers (70) originating from a ring (63) of the retaining washer (6) and arranged to protrude towards a central axis (A) of said ring (63), one end (700) of said fingers (70) being housed in a circular groove (71) of the piston (1) and held by the spring (3) so as to abut against a shoulder (710) defining said circular groove (71). A method of assembling a pump.

Description

Technical Field

[0001] The invention relates to a fuel pump for direct fuel injection of an internal combustion engine. Background Art

[0002] Fuel systems in modern petroleum-fueled internal combustion engines, particularly those used in the automotive market, use direct petroleum injection, in which a fuel injector is used to inject fuel directly into the combustion chamber of the engine. In such a direct injection system, fuel from a fuel tank is supplied by a low-pressure fuel pump incorporated into the fuel tank. This low-pressure pump is typically electric and feeds a high-pressure pump, which typically includes a pump piston that moves within a pump body. The pump piston is actuated by the camshaft of the internal combustion engine in order to raise the fuel pressure in the pumping chamber of the pump body. The fuel at high pressure is then distributed to an injector that controls the injection of the fuel directly into the combustion chamber of the engine.

[0003] An example of a pump of this type is disclosed in document EP 3 715 619 A1. Figure 1 The example is also reproduced in . The 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 against a cam of the camshaft 102. The spring is of the spiral compression type and bears on the one hand on a seat 104 fixed to the body 105 of the pump and on the other hand on a retaining washer 106 connected to the end of the piston 101 by a connecting device 107. The connecting device comprises two conical half-rings 1071, which engage with a notch 1072 at the end of the piston, and a conical socket 1073, which is carried by the retaining washer 106 that receives the conical half-rings 1071. The gradient of the cone of the socket 1073 is oriented so that the action of the spring 103 on the retaining washer 106 is blocked by the conical half-rings 1071 wedged into the socket 1073.

[0004] Although these retaining devices are effective, they have many disadvantages. In fact, it will be noted that the assembly operation is complicated. This is because the spring and the retaining washer must be placed around the piston, and then the spring must be compressed in order to free up enough space to introduce the conical half ring. The compression of the spring can then be released so that the retaining washer moves to capture the conical half ring. It will also be noted that it may happen that only a single half ring is placed in place and that the fault may only be detected with delay, resulting in high intervention costs. In addition, the surfaces of the notch, the conical half ring and the socket are relatively accurately machined surfaces, resulting in high production costs. Summary of the invention

[0005] It is therefore an object of the present invention to provide a fuel pump for direct fuel injection of an internal combustion engine which is of simple and reliable construction and which minimizes costs.

[0006] With these objectives in mind, the present invention relates to a fuel pump for direct fuel injection of an internal combustion engine, the pump comprising: a pump body; a pumping chamber in which a piston is slidingly mounted; a spring, which is supported on the pump body on the one hand and on one end of the piston on the other hand, the spring protruding out of the pump body via a retaining washer; and a connecting device, which is located between the retaining washer and the end of the piston, the pump being characterized in that the connecting device comprises a plurality of fingers, which originate from a ring of the retaining washer and are arranged to protrude towards the central axis of the ring, one end of the fingers being accommodated in a circular groove of the piston and being retained by the spring so as to abut against a shoulder defining the circular groove.

[0007] According to the invention, no further components are required to fix the retaining washer. Therefore, there is no risk of missing parts. Assembly is easy in the case where the engagement to the piston is achieved using fingers (i.e. separate elements), wherein the retaining washer is introduced onto the piston and the fingers spread out until they reach the grooves. Once there, the ends of the fingers are housed in the grooves, thus locking the retaining washer in place. Assembly in this way is simple and reliable, and the retaining washer can be obtained by inexpensive cutting and pressing operations.

[0008] According to an advantageous feature, the end of the finger moves flexibly relative to the ring. During the introduction of the retaining washer onto the piston, the recovery of the end of the finger when reaching the circular groove occurs spontaneously.

[0009] According to one refinement, the fingers are inclined relative to a plane perpendicular to the central axis and are oriented so as to produce a support against the piston in the circular groove when the spring bears on the retaining washer. In this way, the more the retaining washer is subjected to forces tending to extract it from the piston, the more the ends of the fingers are pressed into the groove. The fingers distributed around the groove balance each other. The retaining force thus obtained is very strong.

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

[0011] According to one constructional arrangement, the diameter of the bottom of the groove is smaller than the end diameter of the piston by a value between 2% and 10% of the end diameter and preferably between 4% and 5% of the end diameter. It is thus ensured that the depth of the groove is sufficient to retain the retaining washer without excessively weakening the piston.

[0012] According to other arrangements:

[0013] the retaining washer comprises a guiding crown which extends along the spring according to the central axis of the ring in order to center the spring on the retaining washer, thus ensuring that the spring is well centered on the retaining washer;

[0014] The retaining washer includes an annular flange engaged to the crown to receive the spring;

[0015] The ring is joined to the crown;

[0016] The piston comprises a collar which is intended to abut against the pump body and limit the travel of the piston when the retaining washer is engaged on the piston; the piston could already abut against the bottom of the pumping chamber, but sometimes the latter is too deep to introduce the retaining washer onto the piston. By providing a collar, the abutment position of the piston is determined independently;

[0017] The pump comprises a seat receiving the spring and bearing on the pump body, the seat comprising a sleeve on which the spring is centered and surrounds the piston.

[0018] The invention also provides a method of assembling a pump as described above, according to which a piston is introduced into the chamber, a spring is placed around the piston, a retaining washer is placed on the spring, and pressure is applied to the retaining washer to compress the spring until the fingers spread apart against the piston and then recover to enter the circular groove. This method is simpler than the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be better understood, and other features and advantages will become apparent, by reading the following description with reference to the accompanying drawings, in which:

[0020] Figure 1 is a detailed cross-sectional view of a pump according to the prior art;

[0021] Figure 2 is according to one embodiment of the invention during the pump assembly phase similar to Figure 1 's view;

[0022] Figure 3 It is similar to the one after assembling the pump. Figure 2 's view;

[0023] Figure 4 yes Figure 3 A cutaway perspective view of an end of a piston and a retaining washer of a pump;

[0024] Figure 5 yes Figure 4 A three-dimensional view of a retaining washer;

[0025] Figure 6 yes Figure 5 Longitudinal cross-sectional view of the retaining washer. DETAILED DESCRIPTION

[0026] Figures 2 to 6A fuel pump for direct fuel injection of an internal combustion engine according to one embodiment of the invention is shown. The pump comprises a pump body 5, a pumping chamber 50 in which a piston 1 is slidingly mounted, a spring 3, which is supported on the pump body 5 via a seat 4 on the one hand and on the other hand at one end 10 of the piston 1, which protrudes outside the pump body 5 via a retaining washer 6. The retaining washer 6 comprises an annular flange 61 with a center axis A for receiving the spring 3. The retaining washer 6 also comprises a guiding crown 62, the axis of which is also the center axis A and which extends from the flange 61 along the spring 3 to center the spring 3 on the retaining washer 6 and in particular on the flange 61. The shape of the guiding crown 62 is substantially frustoconical. The crown 62 is extended by means of a ring 63, the axis of which is also the center axis A and extends in a plane that is elevated relative to the plane of the flange 61.

[0027] The connection device 7 is arranged between the retaining washer 6 and the end 10 of the piston 1. The connection device 7 comprises a plurality of fingers 70 originating from the ring 63 of the retaining washer 6 and arranged to protrude towards the central axis A, while being inclined, wherein the base engaging the ring 63 is closer to the pump body 5 than the end 700 of the finger 70 (which end contacts the piston 1). The end 700 of the finger 70 is housed in a circular groove 71 of the piston 1 and is held by the spring 3 so as to abut against a shoulder 710 defining the circular groove 71. The end 700 of the finger 70 moves flexibly relative to the ring 63, as will be better seen with respect to the description of the pump assembly. In other words, the finger 70 is inclined relative to a plane perpendicular to the central axis A, and when the spring 3 bears on the retaining washer 6, the finger 70 is oriented so as to create a support against the piston 1 in the circular groove 71. The inclination of the finger 70 is typically between 24° and 30°.

[0028] The diameter of the bottom 710 of the circular groove 71 is smaller than the end diameter of the piston 1 by a value between 4% and 5% of the end diameter.

[0029] The piston 1 comprises a collar 11 intended to bear against the pump body 5 and limit the travel of the piston 1 when the retaining washer 6 is engaged on the piston 1. The collar 11 may be replaced by an elastic ring inserted in the groove.

[0030] The seat 4 housing the spring 3 bears against and is fixed to the pump body 5. The seat 4 comprises a sleeve 40 on which the spring 3 is centred and which surrounds the piston 1. Optionally, a stop means (not shown) may be housed between the body and the piston 1 to limit the travel of the piston 1 against the spring 3.

[0031] To assemble the pump, the piston 1 is introduced into the chamber with the collar 11 against the pump body 5, the seat 4 is fixed around the piston 1 on the body, the spring 3 is placed around the piston 1 to bear against the seat 4, the retaining washer 6 is placed on the spring 3, and pressure is applied to the retaining washer 6 to compress the spring 3. The fingers 70 then spread elastically under the action of the end 10 of the piston 1 until they reach the circular groove 71. The elastic return movement of the fingers 70 pushes their ends into the circular groove 71 until they bear against the bottom of the circular groove 71. The spring 3 can then be released, its action being taken over by the retaining washer 6, which bears against the bottom of the circular groove 71 and the shoulder 710.

Claims

1. A fuel pump for direct fuel injection of an internal combustion engine, the pump comprising: A pump body (5); a pumping chamber (50), in which a piston (1) is slidably mounted; a spring (3), which is supported on the pump body (5) on the one hand and on one end (10) of the piston (1) on the other hand, the end (10) extending out of the pump body (5) via a retaining washer (6) and a connecting device (7) located between the retaining washer (6) and the end (10) of the piston (1), the pump being characterized in that the connecting device (7) includes a plurality of fingers (70) originating from the retaining washer (6). The ring (63) of the retaining washer (6) is arranged to protrude towards the central axis (A) of the ring (63), one end (700) of the finger (70) is accommodated in the circular groove (71) of the piston (1) and is retained by the spring (3) so as to abut against the shoulder (710) defining the circular groove (71), the finger (70) being inclined relative to a plane perpendicular to the central axis (A) and being oriented to create a support member in the circular groove (71) against the piston (1) when the spring (3) bears on the retaining washer (6).

2. The pump according to claim 1, wherein The ends (700) of the fingers (70) move flexibly 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. A pump according to any one of the preceding claims, wherein The diameter of the bottom of the groove is smaller than the end diameter of the piston (1) by a value between 2% and 10% of the end diameter, preferably between 4% and 5% of the end diameter.

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

6. The pump according to claim 5, wherein The retaining washer (6) comprises an annular flange (61) engaged to the crown (62) to receive the spring (3).

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

8. A pump according to any one of the preceding claims, wherein The piston (1) comprises a collar (11) intended to abut against the pump body (5) and limit the travel of the piston (1) when the retaining washer (6) is engaged on the piston (1).

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

10. A method of assembling a pump according to any 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).

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