Fuel pump with a relief valve

Abstract

Fuel pump comprising a relief valve. The fuel pump includes a compression chamber (10) in which the fuel is pressurized, and a relief valve (2) having an inlet communicating with a high-pressure outlet (13) for releasing fuel. The relief valve (2) is located in a housing (15) and has a shutter (20) held against a seat (220) by a spring (21) supported by a seat ring (22). The relief valve (2) has a guide piece (23) against which the spring (21) bears opposite the shutter (20). The guide piece (23) is slidably mounted in a stop ring (25) fixed in the housing (15) and restricting the sliding of the guide piece (23) against the spring (21). Figure for the abbreviation: Fig. 3

Description

Title of the invention: Fuel pump incorporating a relief valve. Technical field

[0001] The invention relates to a high-pressure fuel pump incorporating a relief valve. • 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.

[0003] Such a pump is known from document WO 2023 / 280929 A1i, in which the pump comprises a body incorporating a compression chamber connected via a valve assembly to an outlet connection leading to a fuel rail where injectors are connected. The fuel is compressed in the compression chamber by a piston actuated by a camshaft. A relief valve is located downstream of the valve assembly to ensure operational safety by limiting the pressure and allowing fuel to return to the compression chamber. The relief valve comprises a needle terminating in a conical bulge held against a seat by a spring acting on the needle. The valve opens when a pressure exceeding a predetermined threshold is present on the needle side and acts on the bulge to lift it from the seat against the spring.

[0004] Other safety valve designs have also been proposed. Document DE 10 2019 200 025 A1 shows a fuel pump in which the relief valve is housed in a bore into which the compression chamber opens radially. The bore is blind, being closed by a bottom, and it contains a spring bearing against the bottom, a slidably mounted stress body in a support, a A ball rests on one end of the actuating body, and a ring has a central seat against which the ball is pressed by the spring. The ring is press-fitted into the bore, and its position determines the spring's compression. The bore opens at the pump outlet.

[0005] US patent 11,015,558 B2 shows a device combining a relief valve and a check valve located on the outlet of a fuel pump. The valve portion includes a housing in which a spring is placed, which acts on a actuating body carrying a ball at its end. The ball bears against a seat carried by a ring press-fitted into the housing.

[0006] It is observed that, in this latter embodiment, the spring can buckle under certain conditions, particularly because the load-bearing body with the ball is free to pivot on the seat. This can lead to impaired operation, including a change in the release pressure, or premature wear. • Description of the invention

[0007] The invention aims to provide a fuel pump incorporating a relief valve that is reliable, durable, allowing adjustment of the release pressure.

[0008] With these objectives in mind, the invention relates to a fuel pump comprising a compression chamber in which the fuel is pressurized, a high-pressure outlet connected to the compression chamber via a non-return valve, and a relief valve having an inlet connected to the high-pressure outlet to release fuel if the pressure exceeds a predetermined threshold, the relief valve being placed in a housing and comprising a shutter pressed against a seat carried by a seat ring by a spring, the pump being characterized in that the relief valve comprises a guide piece on which the spring bears opposite the shutter, the shutter comprising a tail guided in translation within the guide piece,The guide piece is mounted to slide within a stop ring fixed in the housing and limits the sliding of the guide piece against the spring; the relief valve includes means for adjusting the position of the stop ring.

[0009] With such a pump, the spring is mounted on two sliding parts, which prevents it from buckling. This reduces the risk of wear or variation in the release pressure, thus increasing the pump's reliability. Furthermore, since the guide piece is independent of the retaining ring, it is possible to press on the guide piece and thus access the spring's compressive force. This makes it possible to check the valve. It is even possible to calibrate the pressure exerted by the spring by adjusting the position of the retaining means until the desired spring return force is obtained.

[0010] According to one embodiment, the adjustment means are achieved by tightly fitting the retaining ring into the housing. The adjustment is made by the degree to which the retaining ring is inserted into the housing. Once the desired position is reached, tightening the retaining ring in the housing maintains it in position. Alternatively, the retaining ring could be screwed into the housing. The fact that the spring applies a constant force ensures that the retaining ring does not unscrew.

[0011] According to an improvement, the relief valve includes stop means for retaining the guide piece on the obturator and thus trapping the spring. Therefore, the obturator, the spring, and the guide piece can be pre-assembled into a sub-assembly that can be manufactured before insertion into the housing.

[0012] According to a first embodiment, the stop means are formed by a circular groove in the tail and an elastic ring cooperating with the circular groove to prevent the guide piece from sliding on the tail. The elastic ring is placed in the groove when the spring and the guide piece are already in place. It then prevents the guide piece from being extracted from the shutter.

[0013] According to a second embodiment, the stop means comprise a cylindrical head at the end of the tail cooperating with a shoulder of the guide piece, the outer diameter of the head being greater than the inner diameter of the shoulder, with connecting means subdividing the tail into two assembled parts. Thus, the head acts as a stop to the sliding of the guide piece when the shoulder abuts against the head, the tail being reconstituted by means of the connecting means.

[0014] According to an improvement, the retaining ring or guide piece is designed to allow fluid communication between an outlet in the housing and the seat. The retaining ring may, for example, have notches extending along the housing to create a passage on either side of the retaining ring. The fuel released by the relief valve can thus flow towards the outlet in the housing.

[0015] According to a design feature, the outlet of the housing communicates with, or rather opens onto, a supply chamber, said supply chamber being configured to receive the fuel supplying the pump. The supply chamber is connected to the compression chamber via a non-return valve. It is supplied with fuel at low pressure, which allows for rapid fuel flow from the high-pressure seat to the low-pressure seat. Less wear on the seat is also observed due to the different operating conditions. Indeed, the relief valve is less frequently stressed under these operating conditions compared to a return flow to the compression chamber.

[0016] According to one design feature, the shutter includes a centering pin to center the spring. This allows for a large diameter spring without increasing the diameter of the tail. The spring remains guided on the shutter without risk of becoming off-center and rubbing against the housing.

[0017] According to one design feature, the guide piece includes a centering sleeve to guide the radial position of the spring at the point where it bears against the guide piece. At the opposite end of the spring from the centering stud, the sleeve also plays the same role, thus guiding the spring at both ends.

[0018] According to one design feature, the obturator comprises a stress-bearing body carrying a ball bearing against the seat. The ball can be made of high-strength steel or ceramic, and with very precise dimensions to ensure a good seal between its contact with the seat. It is held in place, for example, by crimping.

[0019] According to one design feature, the seat ring carrying the seat is housed at the bottom of the housing in a press fit. This type of assembly provides a suitable seal with a simple installation process.

[0020] The invention also relates to a method of mounting a relief valve on a fuel pump according to the present disclosure, characterized in that it comprises the following steps: - insertion of the seat ring into the housing; - in parallel assembly of a sub-assembly with the obturator, the spring surrounding the tail, the guide piece mounted on the tail and resting on the spring; insertion of the sub-assembly into the housing, the shutter coming to rest on the seat ring; then in any order: - insertion of the stop ring to stop the guide piece at a position providing a predetermined spring compression force; - control of said predetermined compression force by pressing on the guide piece against the spring. • Brief description of the figures

[0021] 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:

[0022] [Fig.1] is a cross-sectional view of a fuel pump according to a first embodiment of the invention along an axial plane of a relief valve;

[0023] [Fig.2] is a view of the pump of [Fig.1] in section along an axial plane of the relief valve substantially at 90° to the cutting plane of [Fig.1];

[0024] [Fig.3] is a view of detail III of [Fig.2];

[0025] [Fig.4] is a perspective view of a subset of the relief valve of [Fig.1] in the detent position;

[0026] [Fig.5] is a view similar to [Fig.4] of the subassembly before the insertion of an elastic ring;

[0027] [Fig.6] is an axial cross-sectional view of the subset of [Fig.6];

[0028] [Fig. 7] is a view similar to [Fig. 6] of the subassembly being assembled in a pump housing;

[0029] [Fig.8] is a view similar to [Fig.7] after assembly of the sub-assembly;

[0030] [Fig.9] is a perspective view of the opening of the housing with the sub-assembly in place;

[0031] [Fig. 10] is a view similar to [Fig. 3] according to a second embodiment of the invention. • Detailed description

[0032] A fuel pump according to a first embodiment of the invention is shown in Figures 1 to 9. The pump comprises a pump body 1 in which are provided a compression chamber 10 in which the fuel is pressurized by a plunger 11 actuated by a camshaft, not shown, a high-pressure outlet 13 made in communication with the compression chamber 10 by means of a non-return valve 12, and a relief valve 2 having an inlet in communication with the high-pressure outlet 13 by means of a channel 14 to release fuel if the pressure exceeds a predetermined threshold. The relief valve 2 is placed in a cylindrical housing 15 extending axially in the pump body 1. The channel 14 opens at the bottom 150 of the housing 15, opposite an outlet 151 which opens into a supply chamber 16 delimited by a bell 160 attached to the pump body 1.The relief valve 2 comprises a shutter 20 which is pressed by a spring 21 against a seat 220 carried by a seat ring 22. The seat ring 22 is drilled in its centre such that the bore 221 is in fluidic communication with the channel 14. The seat 220 is made on the periphery of the bore 221.

[0033] The relief valve 2 comprises a subassembly, as shown in Figures 4 to 6, which includes a guide piece 23 against which the spring 21 bears opposite the obturator 20, the obturator 20 and the spring 21, as well as stop means 24 for retaining the guide piece 23 on the obturator 20 and thus trapping the spring 21. The obturator 20 includes a thrust body 200 carrying a ball 201 opposite the seat ring 22 and thrust against the seat 220, a centering pin 202 for centering the spring 21, a bearing ring 203 against which the spring 21 rests, and a tail 204 guided in translation within the guide piece 23. The bearing ring 203 has two notches 2030 to facilitate the flow of fluid along the obturator 20. The guide piece 23 has a centering sleeve 230 to guide the radial position of the spring 21 at the level of the support on the guide piece 23.

[0034] The guide piece 23 is slidably mounted in a stop ring 25, centered on a cylindrical surface 232 of the guide piece 23, which is limited by a flange 233 forming a shoulder. The stop ring 25 is fixed in the housing 15 and limits the sliding of the guide piece 23 against the spring 21 by abutting against the flange. The relief valve 2 includes means for adjusting the position of the stop ring 25. In this case, the adjustment means are achieved by a tight fit of the stop ring 25 in the housing 15, the stop ring 25 being able to be pushed in more or less deeply into the housing 15. The stop ring 25 also has three notches 250 extending longitudinally to allow fluidic communication on both sides of the stop ring 25, as can be seen in particular on [Fig.9].

[0035] According to the first embodiment, the stop means 24 are formed by a circular groove 240 in the tail 204 and a spring ring 241 cooperating with the circular groove 240 to prevent the sliding of the guide piece 23 on the tail 204, as can be seen in particular in [Fig. 5]. The guide piece 23 has an internal recess 231 such that when it abuts the spring ring 241, the spring ring 241 is housed in the recess 231. The stop means 24 are arranged such that the spring 21 is under slight tension when the guide piece 23 abuts the spring ring 241 (here at a shoulder at the bottom of the recess 231).

[0036] To mount the relief valve 2 on the fuel pump, the following steps are carried out. The sub-assembly is assembled independently with the obturator 20, the spring 21 surrounding the stem 204 and centered on the centering pin 202 of the obturator 20, and the guide piece 23 mounted on the stem 204 and bearing against the spring 21. The guide piece 23 is pressed to compress the spring 21 and allow the insertion of the retaining ring 241 into the circular groove 240. The stop means 24 are then in place, and when the guide piece 23 is released, it bears against the retaining ring 241.

[0037] On the pump body 1, the seat ring 22 is inserted into the housing 15 by force until the ring is against the bottom 150 of the housing 15. Then, the sub-assembly is inserted into the housing 15, the ball 201 of the obturator 20 coming to rest on the seat 220 of the seat ring 22.

[0038] The retaining ring 25 is then slid along the guide piece 23, as shown in [Fig. 7], and the retaining ring 25 is pressed into the housing 15, as shown in [Fig. 8]. The guide piece 23 is then moved away from the ring elastic 241 and is no longer supported there.

[0039] Before, during, or after the insertion of the retaining ring 25, force can be applied to the guide piece 23 to compress the spring 21 to a predetermined force, which determines the release pressure at which the valve opens to allow fuel to pass through. This ensures that the retaining ring 25 holds the spring 21 in the position that allows it to develop the predetermined force. If necessary, the position of the retaining ring 25 is adjusted. The ring is, for example, made of steel and has a diameter 10 mm larger by approximately 25 to 50 µm than the diameter of the housing.

[0040] During operation, the ball 201 is normally held against the seat 220 by the spring 21, which closes the fluid passage from the pump outlet. In the event of excessive pressure at the outlet, the pressure is transmitted via the channel 14 to the ball 201 and tends to lift the ball 201 against the spring 21. At a predetermined pressure threshold, depending on the force exerted by the spring 21, the ball 201 lifts from the seat 220 and allows fuel to pass through. The fuel flows along the obturator 20, along the spring 21, then through the notches 250 of the retaining ring 25 to enter the supply chamber 16.

[0041] In a second embodiment of the relief valve 2”, shown in [Fig. 10], the stop means 24” comprise a cylindrical head 244 at the end of the tail 204”, and connecting means 26 subdividing the tail 204” into two assembled parts 204a, 204b. This replaces the circular groove 240 and the elastic ring 241. In this example, the connecting means 26 are formed by a press fit of the two parts, with a cylindrical stud 260 that fits into a hole 261 at the end of the other part. Alternatively, the two parts could be assembled by screwing. The stud, for example, has a diameter of 2 mm and a length of 2.5 mm, 6 to 10 µm larger than the inside diameter of the hole 261 that receives it. The nipple has an entry chamfer, as does the hole, to facilitate insertion. The operation of the relief valve 2 and the pump remains identical to that described in the first embodiment.

Claims

Demands

1. Fuel pump comprising a compression chamber (10) in which the fuel is pressurized, a high-pressure outlet (13) communicated with the compression chamber (10) via a non-return valve (12), and a relief valve (2) having an inlet communicating with the high-pressure outlet (13) to release fuel if the pressure exceeds a predetermined threshold, the relief valve (2) being located in a housing (15) and comprising a shutter (20) pressed against a seat (220) carried by a seat ring (22) by a spring (21), the pump being characterized in that the relief valve (2) comprises a guide piece (23) against which the spring (21) bears opposite the shutter (20), the shutter (20) comprising a tail (204) guided in translation within the guide piece (23),the guide piece (23) being mounted to slide within a stop ring (25) fixed in the housing (15) and limiting the sliding of the guide piece (23) against the spring (21), the relief valve (2) having means for adjusting the position of the stop ring (25).

2. Pump according to claim 1, wherein the adjustment means are achieved by a tight mounting of the stop ring in the housing (15).

3. Pump according to claim 1 or 2, wherein the relief valve (2) has stop means (24, 24") for retaining the guide piece (23) on the obturator (20) and thus trapping the spring (21).

4. Pump according to claim 3, wherein the stop means (24) are formed by a circular groove (240) which has the tail (204) and an elastic ring (241) cooperating with the circular groove (240) to prevent the sliding of the guide piece (23) on the tail (204).

5. Pump according to claim 3, wherein the stop means (24") comprise a cylindrical head (244) at the end of the tail (204") cooperating with a shoulder (242) of the guide piece (23), the outside diameter of the head (244) being greater than the inside diameter of the shoulder (242) and connecting means (26) subdividing the tail (204") into two assembled parts (204a, 204b).

6. Pump according to any one of the preceding claims, wherein the The stop ring (25) or the guide piece (23) are provided to allow fluidic communication between an outlet (151) of the housing (15) and the seat (220).

7. Pump according to claim 6, wherein the outlet (151) of the housing is in communication with a supply chamber (16), respectively opens onto said supply chamber (16), said supply chamber (16) being configured to receive the fuel supplying the pump.

8. Pump according to any one of the preceding claims, wherein the obturator (20) has a centering pin (202) for centering the spring (21).

9. Pump according to any one of the preceding claims, wherein the guide piece (23) has a centering sleeve (230) to guide the radial position of the spring (21) at the bearing on the guide piece (23).

10. Pump according to any one of the preceding claims, wherein the obturator (20) comprises a stressing body (200) carrying a ball (201) stressed against the seat (220).

11. Pump according to any one of the preceding claims, wherein the seat ring (22) carrying the seat (220) is housed at the bottom of the housing (15) in a tight fit.

12. A method for mounting a relief valve (2) on a fuel pump according to any one of the preceding claims, characterized in that it comprises the following steps: - insertion of the seat ring (22) into the housing (15); - in parallel, assembly of a sub-assembly with the obturator (20), the spring (21) surrounding the tail (204), the guide piece (23) mounted on the tail (204) and bearing on the spring (21); insertion of the sub-assembly into the housing (15), the obturator (20) bearing on the seat ring (22); then in any order: - insertion of the stop ring (25) to stop the guide piece (23) in a position providing a predetermined compression force on the spring (21); - checking said predetermined compression force by pressing on the guide piece (23) against the spring (21).

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