Fuel pump having a relief valve

Abstract

The invention relates to a fuel pump comprising a compression chamber (10) in which the fuel is pressurised, and a relief valve (2) having an inlet in communication with a high-pressure outlet (13) for releasing fuel, wherein the relief valve (2) is placed in a cavity (15) and comprises a closure member (20) urged by a spring (21) to bear against a seat (220) carried by a seat ring (22). The relief valve (2) comprises a guide part (23) against which the spring (21) bears opposite the closure member (20), wherein the guide part (23) is slidably mounted in a stop ring (25) fixed in the cavity (15) and limits the sliding of the guide part (23) against the spring (21).

Description

[0001] Fuel pump with relief valve

[0002] Technical field

[0003] The invention relates to a high pressure fuel pump incorporating a relief valve.

[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] Such a pump is known from document WO 2023 / 280929 A1 in which the pump comprises a body incorporating a compression chamber connected via a valve assembly to an outlet connection 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 placed downstream of the valve assembly to ensure operational safety by limiting the pressure and allowing the fuel to return to the compression chamber. The relief valve comprises a needle ending in a conical bulge held in abutment on a seat by a spring acting on the needle. The valve is opened when a pressure greater than a predetermined threshold prevails on the needle side and acts on the bulge to detach it from the seat against the spring.

[0007] Other designs of safety valve 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 by being closed by a base, and it contains a spring resting on the base, a biasing body slidably mounted in a support, a ball resting on one end of the biasing body and a ring having in its center a seat against which the ball is pressed by the spring. The ring is force-fitted in the bore and its position determines the compression of the spring. The bore opens at the pump outlet. Document US 11,015,558 B2 shows a device combining a relief valve and a non-return valve placed on the outlet of a fuel pump.The valve part comprises a housing in which is placed a spring which acts on a stress body carrying a ball at its end. The ball rests against a seat carried by a ring force-fitted into the housing.

[0008] It is noted that, in this latter embodiment, the spring can buckle under certain conditions, in particular because the stress body with the ball is free to pivot on the seat. This can lead to impaired operation, in particular the modification of the release pressure, or premature wear.

[0009] Statement of the invention

[0010] The invention aims to provide a fuel pump incorporating a relief valve which is reliable, durable, and allows adjustment of the release pressure.

[0011] With these objectives in view, the subject of the invention is 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 discharge valve having an inlet connected to the high-pressure outlet to release fuel if the pressure exceeds a predetermined threshold, the discharge valve being placed in a housing and comprising a shutter urged to bear by a spring against a seat carried by a seat ring, the pump being characterized in that the discharge valve comprises a guide piece on which the spring bears opposite the shutter, the shutter comprising a stem guided in translation in the guide piece,the guide piece being slidably mounted in a stop ring fixed in the housing and limiting the sliding of the guide piece against the spring, the relief valve comprising means for adjusting the position of the stop ring,

[0012] 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 reliability of the pump. In addition, since the guide part is independent of the stop ring, it is possible to press on the guide part and thus access the spring loading 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 stop means until the spring return force is at the desired level.

[0013] According to one embodiment, the adjustment means are achieved by tightly fitting the stop ring in the housing. The adjustment is achieved by the degree to which the stop ring is pushed into the housing. Once the desired position is reached, tightening the stop ring in the housing holds it in position. Alternatively, the stop ring could be screwed into the housing. The fact that the spring applies a constant force ensures that the stop ring does not unscrew. According to an improvement, the relief valve comprises stop means for retaining the guide piece on the shutter and thus trapping the spring. Thus, the shutter, the spring and the guide piece can be pre-assembled into a sub-assembly which can be made before insertion into the housing.

[0014] According to a first embodiment, the stop means are formed by a circular groove which the tail comprises 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.

[0015] 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 outside diameter of the head being greater than the inside diameter of the shoulder, connecting means subdividing the tail into two assembled parts. Thus, the head serves to block the sliding of the guide piece when the shoulder abuts against the head, the tail being reconstituted thanks to the connecting means.

[0016] According to an improvement, the stop ring or the guide piece are provided to allow fluid communication between an outlet of the housing and the seat. The stop ring may for example have notches extending along the housing to create a passage on either side of the stop ring. The fuel released by the release valve can thus flow towards the outlet of the housing.

[0017] According to a constructive arrangement, the outlet of the housing is in communication with a supply chamber, respectively opens onto said 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 under low pressure, which allows rapid exhaust of the fuel from the seat from high pressure to low pressure. There is also less wear on the seat due to different operating conditions. Indeed, the release valve is less often stressed under these operating conditions compared to a return to the compression chamber.

[0018] According to a constructive arrangement, the shutter has a centering stud to center the spring. This allows a large diameter for the spring without increasing the diameter of the tail. The spring remains guided on the shutter without the risk of the spring becoming off-center and rubbing against the housing.

[0019] According to a constructive arrangement, the guide part has a centering sleeve to guide the radial position of the spring at the level of the support on the guide part. At the opposite end of the spring with respect to the centering stud, the sleeve also plays the same role, which allows the spring to be guided at its two ends. According to a constructive arrangement, the shutter has a stress body carrying a ball stressed in support against the seat. The ball can be made of very resistant steel or ceramic, and with very precise dimensions in order to obtain a good seal of its contact with the seat. It is held for example by crimping.

[0020] According to a constructive arrangement, the seat ring carrying the seat is housed at the bottom of the housing in a tight assembly. This type of assembly allows for suitable sealing with simple assembly to be achieved.

[0021] The invention also relates to a method of mounting a relief valve on a fuel pump in accordance with the present disclosure, characterized in that it comprises the following steps:

[0022] - insertion of the seat ring into the housing;

[0023] - in parallel assembly of a sub-assembly with the shutter, 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 resting on the seat ring; then in any order:

[0024] - insertion of the stop ring to stop the guide piece at a position providing a predetermined spring compression force;

[0025] - control of said predetermined compression force by pressing on the guide part against the spring.

[0026] Brief description of the figures

[0027] The invention will be better understood and other features and advantages will appear on reading the description which follows, the description referring to the appended drawings among which: Figure 1 is a sectional view of a fuel pump according to a first embodiment of the invention along an axial plane of a discharge valve; Figure 2 is a view of the pump of Figure 1 in section along an axial plane of the discharge valve substantially at 90° to the sectional plane of Figure 1; Figure 3 is a view of detail III of Figure 2; Figure 4 is a perspective view of a subassembly of the discharge valve of Figure 1 in the relaxed position; Figure 5 is a view similar to Figure 4 of the subassembly before the insertion of an elastic ring; Figure 6 is an axial sectional view of the subassembly of Figure 6; Figure 7 is a view similar to Figure 6 of the subassembly being mounted in a housing of the pump;Figure 8 is a view similar to Figure 7 after mounting the subassembly; Figure 9 is a perspective view of the housing outlet with the subassembly in place; Figure 10 is a view similar to Figure 3 according to a second embodiment of the invention.;

[0028] Detailed description

[0029] 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 placed in communication with the compression chamber 10 via a non-return valve 12, and a discharge valve 2 having an inlet in communication with the high-pressure outlet 13 via a channel 14 to release fuel if the pressure exceeds a predetermined threshold. The discharge valve 2 is placed in a cylindrical housing 15 extending in an axial direction in the pump body 1. The channel 14 opens at a 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 discharge valve 2 comprises a shutter 20 urged to bear by a spring 21 against a seat 220 carried by a seat ring 22. The seat ring 22 is pierced in its center so that the bore 221 is in fluid communication with the channel 14. The seat 220 is made on the periphery of the bore 221.

[0030] The discharge valve 2 comprises a subassembly, as shown in Figures 4 to 6, which comprises a guide piece 23 on which the spring 21 bears opposite the shutter 20, the shutter 20 and the spring 21 as well as stop means 24 making it possible to retain the guide piece 23 on the shutter 20 and thus trap the spring 21. The shutter 20 comprises a biasing body 200 carrying a ball 201 facing the seat ring 22 and biased to bear against the seat 220, a centering stud 202 for centering the spring 21, a bearing crown 203 on which the spring 21 bears, and a tail 204 guided in translation in the guide piece 23. The crown 203 comprises two notches 2030 to facilitate the flow fluid along the shutter 20. The guide piece 23 comprises a centering sleeve 230 to guide the radial position of the spring 21 at the level of the support on the guide piece 23.

[0031] The guide piece 23 is slidably mounted in a stop ring 25 while being centered on a cylindrical surface 232 of the guide piece 23 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 discharge valve 2 comprises means for adjusting the position of the stop ring 25. In this case, the adjustment means are produced by a tight mounting of the stop ring 25 in the housing 15, the stop ring 25 being able to be pushed more or less deeply into the housing 15. The stop ring 25 further comprises three notches 250 extending longitudinally to allow fluid communication on either side of the stop ring 25, as can be seen in particular in FIG. 9.

[0032] According to the first embodiment, the stop means 24 are formed by a circular groove 240 that the tail 204 comprises and an elastic ring 241 cooperating with the circular groove 240 to prevent the guide piece 23 from sliding on the tail 204, as seen in particular in FIG. 5. The guide piece 23 comprises an internal recess 231 such that when it is in abutment against the elastic ring 241, the elastic 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 is in abutment against the elastic ring 241 (here at a shoulder at the bottom of the recess 231).

[0033] For the assembly of the discharge valve 2 on the fuel pump, the following steps are carried out. Independently, the assembly of the subassembly is carried out with the shutter 20, the spring 21 surrounding the stem 204 and centered on the centering stud 202 of the shutter 20, the guide piece 23 mounted on the stem 204 and bearing on the spring 21. The guide piece 23 is pressed so as to compress the spring 21 and allow the insertion of the elastic ring 241 into the circular groove 240. The stop means 24 are then in place, and when the guide piece 23 is released, it comes to bear against the elastic ring 241.

[0034] On the pump body 1, the seat ring 22 is inserted into the housing 15 by force until the ring is in abutment at the bottom 150 of the housing 15. Then, the sub-assembly is inserted into the housing 15, the ball 201 of the shutter 20 coming to bear on the seat 220 of the seat ring 22.

[0035] The stop ring 25 is then placed slidingly on the guide piece 23, as shown in Figure 7, and the stop ring 25 is inserted by force into the housing 15, as shown in Figure 8. The guide piece 23 is then moved away from the elastic ring 241 and is no longer supported there.

[0036] Before, during or after the insertion of the stop ring 25, a force can be exerted on the guide piece 23 in order to compress the spring 21 to a predetermined force, which determines the release pressure at which the valve opens to allow fuel to pass. It is thus checked that the stop ring 25 allows the spring 21 to be held in the position which allows it to develop the predetermined force. If necessary, the position of the stop ring 25 is adjusted. The ring is for example made of steel and has a diameter of 10 mm, approximately 25 to 50 μm greater than the diameter of the housing.

[0037] In operation, the ball 201 is normally pressed against the seat 220 by the spring 21, which closes the fluid passage from the pump outlet. In the case of excessive pressure at the outlet, the pressure is transmitted via the channel 14 to the ball 201 and it tends to lift the ball 201 against the spring 21. At a pressure threshold predetermined as a function of the pressing force of the spring 21, the ball 201 lifts from the seat 220 and allows the fuel to pass. This flows along the shutter 20, along the spring 21, then through the notches 250 of the stop ring 25 to open into the supply chamber 16. In a second embodiment of the discharge valve 2”, shown in Figure 10, the stop means 24” comprise a cylindrical head 244 at the end of the tail 204”, 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 force fit of the two parts, with a cylindrical stud 260 which is housed in a hole 261 at the end of the other part. Alternatively, the two parts could be assembled by screwing. The stud has for example a diameter of 2 mm and a length of 2.5 mm, 6 to 10 μm greater than the internal diameter of the hole 261 which receives it. The stud has an inlet chamfer as does the hole to facilitate insertion. The operation of the discharge valve 2 and the pump remains identical to that described in connection with the first embodiment.

Claims

Claims 1. Fuel pump comprising a compression chamber (10) in which the fuel is pressurized, a high-pressure outlet (13) connected to the compression chamber (10) via a non-return valve (12), and a discharge valve (2) having an inlet connected to the high-pressure outlet (13) to release fuel if the pressure exceeds a predetermined threshold, the discharge valve (2) being placed in a housing (15) and comprising a shutter (20) urged to bear by a spring (21) against a seat (220) carried by a seat ring (22), the pump being characterized in that the discharge valve (2) comprises a guide piece (23) on which the spring (21) bears opposite the shutter (20), the shutter (20) comprising a tail (204) guided in translation in the guide piece (23),the guide piece (23) being slidably mounted in a stop ring (25) fixed in the housing (15) and limiting the sliding of the guide piece (23) against the spring (21), the discharge valve (2) comprising means for adjusting the position of the stop ring (25)., 2. Pump according to claim 1, in which the adjustment means are provided by a tight fitting of the stop ring in the housing (15).

3. Pump according to claim 1 or 2, in which the discharge valve (2) comprises stop means (24, 24") making it possible to retain the guide part (23) on the shutter (20) and thus trap the spring (21).

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

5. Pump according to claim 3, in which the stop means (24") comprise a cylindrical head (244) at the end of the tail (204") cooperating with a shoulder (242) of the guide part (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 one of the preceding claims, in which the stop ring (25) or the guide piece (23) are provided to allow fluid 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 one of the preceding claims, in which the shutter (20) comprises a centering stud (202) for centering the spring (21).

9. Pump according to one of the preceding claims, in which the guide part (23) comprises a centering sleeve (230) for guiding the radial position of the spring (21) at the level of the support on the guide piece (23).

10. Pump according to one of the preceding claims, in which the shutter (20) comprises a stress body (200) carrying a ball (201) stressed to bear against the seat (220).

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

12. Method for mounting a relief valve (2) on a fuel pump according to 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 subassembly with the shutter (20), the spring (21) surrounding the tail (204), the guide piece (23) mounted on the tail (204) and resting on the spring (21); insertion of the subassembly into the housing (15), the shutter (20) resting on the seat ring (22); then in any order: - insertion of the stop ring (25) to stop the guide piece (23) at a position providing a predetermined compression force of the spring (21); - control of said predetermined compression force by pressing on the guide part (23) against the spring (21).

Images