Fuel pump for direct fuel injection for internal combustion engines with a retaining washer

Abstract

A fuel pump for direct fuel injection for internal combustion engines comprising a pump body, a pumping chamber in which a piston (1) is slidably mounted, a spring (3) bearing on the one hand on the pump body and on the other hand at an end (10) of the piston (1) projecting out of the pump body via a retaining washer (6) and means of connection between the retaining washer (6) and the end (10) of the piston (1), the retaining means (7) comprising a circular groove (71) at the end (10) of the piston (1), the pump being characterized in that the retaining means (7) further comprise a clearance (72) made in the retaining washer (6) allowing the end (10) of the piston (1) to pass into the clearance (72), and a notch (73) in the retaining washer (6) housed in the circular groove (71) connected to the clearance (72) by a slot (74) which is narrower than the outer diameter of the piston (1) at the end (10) but wider than the diameter of the bottom of the groove (71).

Description

[0001] FUEL PUMP FOR DIRECT FUEL INJECTION FOR INTERNAL COMBUSTION ENGINES WITH RETAINING WASHER

[0002] Technical field

[0003] The invention relates to a fuel pump for direct fuel injection for internal combustion engines with a retaining washer for spring action on a piston of the pump. It also relates to the retaining washer and a method of mounting the washer.

[0004] Prior art

[0005] 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 usually electric and powers a high-pressure pump that typically includes a movable pump piston within a pump housing. The pump piston is actuated by a camshaft of the internal combustion engine to raise the fuel pressure in a pump chamber of the pump housing. The high-pressure fuel is then delivered to the injectors, which control the injection of fuel directly into the engine's combustion chamber.

[0006] Document EP 3 715 619 A1 shows an example of such a pump. An example is also reproduced in Figure 1. 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 resting on a cam of the camshaft 102. The spring is of the helical compression type and bears on the one hand on a seat 104 fixed on 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 connecting means 107. The connecting means comprise two conical half-rings 1071 engaged with an imprint 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 such 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.

[0007] Although these retaining means are effective, they have some drawbacks. Assembly operations are complex. The spring and retaining washer must be placed around the piston, then the spring must be compressed to create enough space to insert the tapered half-rings. The spring compression can then be released so that the retaining washer can trap the tapered half-rings. It is also noted that sometimes only one half-ring is placed and this defect is only detected late, resulting in high repair costs. In addition, the surfaces of the cavity, the tapered half-rings and the housing are machined and fairly precise surfaces, which results in high production costs.

[0008] Statement of the invention

[0009] 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.

[0010] With these objectives in view, 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 slidably mounted, a spring bearing on the one hand on the pump body and on the other hand at one end of the piston projecting from the pump body by means of a retaining washer and connecting means between the retaining washer and the end of the piston, the retaining means comprising a circular groove at the end of the piston, the retaining means further comprising a clearance made in the washer allowing the end of the piston to pass into the clearance, and a notch in the washer housed in the circular groove and connected to the clearance by a groove narrower than the outside diameter of the piston at the end but wider than the diameter of the bottom of the groove,the retaining washer comprising a seat on which the spring rests, the seat being annular in shape and located in a plane passing through the bulge or located beyond the end of the piston, the pump being characterized in that the retaining washer further comprises a guide ring of substantially frustoconical shape and extending along the spring from the seat to center the spring on the retaining washer.,

[0011] With these retaining means, the number of parts is reduced compared to the prior art, by eliminating two parts. In addition, the retaining washer can be manufactured by a cutting and cold heading process, which reduces the number of machining operations. By providing a clearance, the washer can be introduced at the end of the piston through the clearance and then inserted into the groove to be retained there. The integrity of the periphery of the washer on which the spring rests is preserved. There is no longer any risk of a part of the retaining means being forgotten. With the annular-shaped seat, the spring rests regularly on the entire periphery of the washer. With the guide ring, the washer has an omega-shaped section. This ensures natural stability of the washer with a center of thrust of the spring offset from an instantaneous center of rotation of the washer on the piston at the level of the groove.In addition, the guide ring allows easy insertion of the washer onto the end of the spring while ensuring permanent centering of the spring and the retaining washer. In addition, the connection between the central part and the seat by a truncated cone-shaped ring optimizes the use of material and provides the lightest possible washer. The lightness of the washer is an important objective because it is subjected to strong accelerations during pump operation. Reducing its mass reduces the effort required to set it in motion.

[0012] According to an improvement, the retaining means further comprise an imprint on the washer around the notch in which a bulge of the piston between the groove and the end of the piston is housed, a neck at the outlet of the imprint in the groove being of a width smaller than a diameter of the bulge. This ensures that as long as the washer is resting on the imprint, the latter cannot disengage radially from the groove. Indeed, in a radial movement, the neck abuts against the bulge and thus stops the radial movement of the washer. As the spring presses the washer against the imprint, there is thus no risk of disassembly of the washer.

[0013] According to a constructive arrangement, the impression has a depth of between 0.05 and 1 mm, preferably between 0.2 and 0.5 mm.

[0014] Preferably, the indentation has a depth between 0.3 and 0.4 mm. These values ​​provide a good compromise between the effectiveness of retaining the washer in the groove and ease of insertion. Indeed, the deeper the indentation, the more retention is guaranteed, but the more delicate the insertion. In addition, the deeper the indentation, the thicker the washer must be, which makes it heavier and compromises the dynamic operation of the pump.

[0015] According to a constructive arrangement, the washer is arranged in the groove with an axial clearance, the clearance being greater than the depth of the impression. This clearance allows the axial offset of the washer during insertion to allow the neck to pass beyond the groove in the radial movement in order to reach the position in which, by an axial movement, the bulge is housed in the impression. After the assembly operation, this clearance is no longer used, the axial position of the washer being determined by the spring which maintains it with the impression in abutment against the bulge.

[0016] According to a constructive arrangement, the truncated cone crown has a cone angle between an axis of the cone and a generator of between 20° and 30°.

[0017] According to a constructive arrangement, the ratio of the diameter of the retaining washer to the thickness of the washer at the seat is between 10 and 20, preferably between 13 and 17. This achieves a good balance between lightness and strength.

[0018] According to a constructive arrangement, the ratio of the diameter of the retaining washer to the diameter of the piston is between 3 and 5, preferably between 3.5 and 4.

[0019] According to a constructive arrangement, the ratio of the diameter of the piston to the diameter of the bottom of the circular groove is between 1.4 and 1.7, preferably between 1.5 and 1.6. This provides a good balance between retaining the washer and resistance of the piston. The invention also relates to a retaining washer intended for a pump as described above.

[0020] The invention also relates to a method of mounting a pump as described above, characterized in that the piston is introduced into the chamber, the spring is placed around the piston, the spring is pressed to compress it, the retaining washer is engaged with the end of the piston through the clearance, the washer is shifted transversely to engage the groove through the groove then the notch and the spring is released so that it presses on the washer and the piston. These operations can be carried out manually, but preferably they will be automated.

[0021] Brief description of the figures

[0022] The invention will be better understood and other features and advantages will appear on reading the description which follows, the description making reference to the appended drawings among which:

[0023] • Figure 1 is a view of a pump according to the prior art;

[0024] • Figure 2 is a perspective and axial sectional view of part of a pump according to a first embodiment of the invention;

[0025] • Figure 3 is a side view of the assembly of a piston and a retaining washer for the assembly of Figure 2;

[0026] • Figure 4 is a perspective view from below of the assembly of Figure 3;

[0027] • Figure 5 is a perspective view from below of the retaining washer in the assembly of Figure 2;

[0028] • Figure 6 is an axial sectional view of the washer of Figure 5;

[0029] • Figure 7 is a bottom view of the retaining washer of Figure 5.

[0030] Detailed description

[0031] A fuel pump for direct fuel injection for internal combustion engines according to one embodiment of the invention is partially shown in Figures 2 to 6. The pump comprises a pump body, not shown, a pumping chamber, not shown, in which a piston 1 is slidably mounted, a spring 3 bearing on the one hand on the pump body and on the other hand at one end 10 of the piston 1 projecting from the pump body by means of a retaining washer 6. The retaining washer 6 comprises a seat 61 of annular shape 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 seat 61 to center the spring 3 on the retaining washer 6, and in particular on the seat 61.The guide ring 62 has a substantially truncated cone shape with a cone angle between the central axis A and a generatrix of between 20° and 30°, for example 23°. The ring 62 is extended by a ring 63 also having the central axis A as its axis and extending in a plane raised relative to the plane of the seat 61.

[0032] Connecting means 7 are provided between the retaining washer 6 and the end 10 of the piston 1. The connecting means 7 comprise a circular groove 71 at the end 10 of the piston 1, such that the groove 71 delimits a bulge 11 of the piston 1 between the groove 71 and the end 10 of the piston 1. The retaining means 7 further comprise a clearance 72 made in the retaining washer 6 allowing the end 10 of the piston 1 to pass through the clearance 72, a notch 73 in the retaining washer 6 housed in the circular groove 71 connected to the clearance 72 by a groove 74 narrower than the outside diameter of the piston 1 at the end 10 but wider than the diameter of the bottom of the groove 71, and an imprint 75 on the retaining washer 6 around the notch 73 in which the bulge 11 is housed. The imprint 75 is circular in shape.As can be seen in particular in Figure 4, a neck 76 at the outlet of the imprint 75 in the groove 74 has a width referenced "O" smaller than a diameter of the bulge 11 referenced "B". It will also be noted that in the variant, the clearance 72 extends in the relief / curvature of the retaining washer 6, from the seat 61 (of which it trims the inner periphery) through the crown 62 and the ring 63, to the passage 74. This arrangement of the clearance makes it possible to achieve a clearance of greater size than if it were in a single plane, without compromising the mechanical strength of the retaining washer 6. An axial clearance marked "J" remains on an upper face of the retaining washer 6 and a rear flank of the groove 71. This clearance is greater than the depth "M" of the imprint 75.

[0033] To assemble the pump, the piston 1 is inserted into the chamber, the spring 3 is placed around the piston 1, the spring 3 is pressed to compress it and press against the pump body, the retaining washer 6 is engaged with the end 10 of the piston 1 through the clearance 72, the retaining washer 6 is shifted transversely to engage the groove 71 through the groove 74 and then the notch 73, and the spring 3 is released so that it presses on the retaining washer 6 and the piston 1.

[0034] In operation, the imprint 75 of the retaining washer 6 is held in abutment against the flank 712 of the groove 71 on the bulge side 11.

[0035] The ratio of the diameter of the retaining washer to the thickness of the washer at the seat is for example 14.5.

[0036] The ratio of the diameter of the retaining washer to the diameter of the piston is for example 3.6.

[0037] The ratio of the piston diameter to the diameter of the bottom of the circular groove is for example 1.55.

Claims

Claims 1. Fuel pump for direct fuel injection for internal combustion engines, the pump comprising a pump body, a pumping chamber in which a piston (1) is slidably mounted, a spring (3) bearing on the one hand on the pump body and on the other hand at one end (10) of the piston (1) projecting from the pump body by means of a retaining washer (6) and connecting means between the retaining washer (6) and the end (10) of the piston (1), the retaining means (7) comprising a circular groove (71) at the end (10) of the piston (1), the retaining means (7) further comprising a clearance (72) made in the retaining washer (6) allowing the end (10) of the piston (1) to pass into the clearance (72),and a notch (73) in the retaining washer (6) housed in the circular groove (71) and connected to the clearance (72) by a groove (74) narrower than the outside diameter of the piston (1) at the end (10) but wider than the diameter of the bottom of the groove (71), the retaining washer (6) comprising a seat (61) having a central axis (A) on which the spring (3) bears, the seat (61) being annular in shape and located in a plane passing through the bulge (11) or located beyond the end (10) of the piston (1), the pump being characterized in that the retaining washer further comprises a guide ring (62) of substantially frustoconical shape and extending along the spring (3) from the seat (61) to center the spring (3) on the retaining washer (6)., 2. Pump according to claim 1, in which the retaining means (7) further comprise an imprint (75) on the retaining washer (6) around the notch (73) in which a bulge (11) of the piston (1) between the groove (71) and the end (10) of the piston (1) is housed, a neck (76) at the outlet of the imprint (75) in the groove (74) being of a width smaller than a diameter of the bulge (11).

3. Pump according to claim 2, wherein the imprint (75) has a depth of between 0.05 and 1 mm, preferably between 0.2 and 0.5 mm. Pump according to claim 2, wherein the imprint (75) has a depth of between 0.3 and 0.4 mm. Pump according to one of claims 2 to 4, wherein the washer (6) is arranged in the groove (71) with an axial clearance (J), the clearance being greater than the depth of the imprint (75). Pump according to one of the preceding claims, wherein the frustoconical crown has a cone angle between an axis (A) of the cone and a generatrix of between 20° and 30°. Pump according to one of the preceding claims, wherein the ratio of the diameter of the retaining washer to the thickness of the washer at the seat is between 10 and 20, preferably between 13 and 17. Pump according to one of the preceding claims, wherein the ratio of the diameter of the retaining washer to the diameter of the piston is between 3 and 5, preferably between 3.5 and 4.Pump according to one of the preceding claims, in which the ratio of the diameter of the piston to the diameter of the bottom of the circular groove is between 1.4 and 1.7, preferably between 1.5 and 1.

6. Pump according to one of the preceding claims, in which the clearance (72) extends in the relief of the retaining washer (6), of the seat (61) of which it trims the inner periphery, through the crown (62) and a ring (63) extending the crown towards the central axis (A) and extending in a plane raised relative to the plane of the seat (61). Retaining washer intended for a pump according to one of the preceding claims.Method of mounting a pump according to one of the preceding claims, characterized in that the piston (1) is introduced into the chamber, the spring (3) is placed around the piston (1), the spring (3) is pressed to compress it, the retaining washer (6) is engaged with the end (10) of the piston (1) through the clearance (72), the retaining washer (6) is shifted transversely to engage the groove (71) to. through the groove (74) then the notch (73) and the spring (3) is released so that it presses on the retaining washer (6) and the piston (1).

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