DE102020215411A1 - Piston pump, in particular high-pressure fuel pump for an internal combustion engine - Google Patents

Abstract

The invention relates to a piston pump (16), in particular a high-pressure fuel pump for an internal combustion engine, having a pump housing (26), a pump piston (28) guided in the pump housing (26) and a pump piston (28) which is delimited at least by the pump housing (26) and the pump piston (28). Pumping chamber (38), a seal (43) for sealing the pumping chamber (38) being arranged on the circumference of the pump piston (28), the seal (43) being a sealing ring (44) with a substantially sleeve-shaped, extending along a central longitudinal axis ( 41) extending base section (45), wherein the sealing ring (44) is made of fiber-reinforced plastic, the fibers (49) of which are oriented at least along a predominant part of the circumference of the sealing ring (44) in the circumferential direction (51) of the sealing ring (44). are.

Description

State of the art

The invention relates to a piston pump, in particular a high-pressure fuel pump for an internal combustion engine, according to the preamble of claim 1.

Piston pumps are known from the prior art, which are used, for example, in internal combustion engines with gasoline direct injection. E.g. is off WO 2019/015862 A1 a piston pump is known which has a plastic ring as a seal.

Such plastic rings can be produced, for example, using the “Shield Anguss” spraying process, in which the plastic rings are sprayed over the entire end face in order to achieve good symmetry and low component tolerances. When using fiber-reinforced plastics, the fibers are aligned in the direction of injection and are thus oriented parallel to the central longitudinal axis of the plastic ring. However, particularly at high pressures, the plastic ring may not withstand the prevailing loads over the long term.

Disclosure of Invention

The problem on which the invention is based is solved by a piston pump having the features of claim 1 . Advantageous developments of the invention are specified in the dependent claims.

The piston pump according to the invention, in particular a high-pressure fuel pump for an internal combustion engine, has a pump housing, a pump piston guided in the pump housing (along an axial direction) and a pumping chamber delimited at least by the pump housing and pump piston. A seal for sealing off the pumping chamber is arranged on the circumference of the pump piston, or in other words (radially) between the pump piston and the pump housing. The seal is designed as a sealing ring with an essentially sleeve-shaped base section that extends along a central longitudinal axis. The sealing ring is made of fiber-reinforced plastic, the fibers of which are oriented at least along a predominant part of the circumference of the sealing ring in the circumferential direction of the sealing ring (transverse to the central longitudinal axis).

In this way, the strength, the swelling behavior and the thermal expansion of the sealing ring in the circumferential direction can be improved. Thus, the sealing ring or plastic ring can function under all required operating conditions and withstand the loads that occur.

Various plastics can be used for the sealing ring, for example thermoplastics. The fibers (reinforcing fibers) can have glass and/or carbon fibers or be made of glass and/or carbon fibers. The injection molding material used to manufacture the sealing ring can include plastic and fibers.

As previously explained, the fibers are oriented in the circumferential direction of the sealing ring at least along a predominant part of the circumference of the sealing ring. This means that the fibers are oriented in the circumferential direction, in particular outside the areas of the injection entry point and injection exit point or ventilation point, at which the fibers are deflected. The fibers can be oriented or aligned, for example, at least 50 percent, preferably at least 70 percent, more preferably at least 90 percent of the circumference of the sealing ring in the circumferential direction.

According to a further development, the sealing ring can be formed by means of injection molding, with the sealing ring having a spray entry point (inlet of spray material) and a ventilation point (outlet of gases) or a spray entry point (inlet of spray material) and a spray exit point (outlet of spray material) along the circumferential direction of the sealing ring are offset from one another. Thus, the fibers are laid in the desired direction, namely in the circumferential direction, in any case outside of the spray entry point and ventilation point or spray exit point. The injection direction (“injection direction”) is therefore not axial but radial, with the fibers being aligned in the circumferential direction, for example due to the ring contour specified by the injection mold.

In an embodiment with a spray entry point and a spray exit point, spray material can enter at the spray entry point and exit at the spray exit point. At the spray exit point, the fibers can assume a V-shaped configuration, for example. In an embodiment with a spray entry point and vent point, spray material can enter at the spray entry point, wherein the vent point can be set up in such a way that gases exit there, but no spray material. The fibers of the spray material can meet at the ventilation point, with the fibers being able to assume a disordered or chaotic configuration, for example.

According to a further development, some of the fibers can move along a first ring section of the sealing ring from the spray entry point to the spray exit point or vent point and another or the remaining part of the fibers can extend along a further ring section of the sealing ring from the spray entry point to the spray exit point or vent point. In other words, the fibers or the plastic material with the fibers contained therein can be divided into two strands, with a first strand taking a path from the spray entry point to the spray exit point or vent point and the second strand taking a different path from the spray entry point to the spray exit point or vent point . The two parts of fibers or the two strands meet at the spray exit point or vent point (e.g. in the form of a weld line).

According to a further development, the spray entry point and the spray exit point or ventilation point can enclose an angle α with one another, the angle α being between 160° and 180° (160°≦α≦180°). The spray entry point and spray exit point or ventilation point are approximately opposite one another, so that the “strands” described above take a “similarly long way” from the spray entry point to the spray exit point or ventilation point. The spray entry point and the spray exit point or ventilation point may not lie exactly opposite one another, so that there is no predetermined breaking point, for example. Surprisingly, investigations have shown that an angle of α=175° is ideal. The angle specifications for a refer to the circumference of the sealing ring. In other words, the angle α lies in a plane whose normal vector is the central longitudinal axis of the sealing ring.

According to a development, a web can be formed on the sealing ring at the spray entry point, which extends parallel to the central longitudinal axis of the sealing ring along the outer surface of the sealing ring, in particular along the entire length of the outer surface. In order for as many fibers as possible to lie in the circumferential direction transversely to the center axis, the sprue must be lateral at least over the majority or the entire length of the sealing ring. For this purpose, a web is provided on the side of the sealing ring. The web protrudes radially outwards from the lateral surface of the sealing ring. Thus a film sprue is possible.

According to a development, a further web can be formed on the sealing ring at the spray outlet point, which extends parallel to the central longitudinal axis of the sealing ring along the lateral surface of the sealing ring, in particular along the entire length of the lateral surface. So that as many fibers as possible that meet at the spray outlet point can be collected, the collection or weld seam must take place laterally at least over the majority or the entire length of the sealing ring. For this purpose, a further web is provided on the side of the sealing ring. The other web protrudes radially outwards from the lateral surface of the sealing ring. Thus, the weld seam is not in the functional area of the sealing ring, i.e. not inside the essentially sleeve-shaped base section, but outside of it. On the sealing ring, opposite the first web (film sprue), a further web (seam collector) is provided laterally, in particular over the entire length. As already explained above, the web and the further web are not exactly opposite one another on the circumference of the sealing ring, but are slightly offset from one another.

According to a further development, the sealing ring can have at one axial end or at both axial ends a radially outwardly projecting, circumferential collar which is formed onto the sleeve-shaped base section. In the case of a collar at one axial end, the sealing ring thus has an overall L-shaped cross section or, in the case of a collar in each case at both axial ends, a C-shaped or U-shaped cross section. The stiffness of the sealing ring can be increased by the federal government. In addition, the sealing ring can be centered in the radial direction in the pump housing. This allows the sealing ring to be installed in a fixed position in the pump housing. If the sealing ring only has a collar at one axial end, this can face the conveying chamber or face away from the conveying chamber.

According to a further development, the web, the further web and/or the at least one collar can each have play at their radially outer edge relative to the peripheral wall of the recess accommodating the pump piston, for example play of 0.01 to 1 mm (millimeter). In other words, the elements mentioned have an external dimension, for example an external diameter, which is slightly smaller than the internal diameter of the recess (bore) accommodating these components at the point at which the respective component is seated. This play causes the radial position of the component to adjust to the position of the pump piston. This can result in a uniform and symmetrical gap to the pump piston.

According to a development, a spring element can be arranged on the circumference of the pump piston (between the pump piston and the pump), which acts on the sealing ring, for example presses the sealing ring against a fastening ring. The spring element can bear axially at one end, for example against a guide element, and at the other end can press the sealing ring against a fastening ring. The spring element can be used as a compression spring, in particular as a spring washer or Coil spring, be formed. The spring element can at least partially surround the pump piston. An axial force acts on the sealing ring through the spring element, this force pressing on the axial end face of the sealing ring facing the pumping chamber. The axial force causes the sealing ring to rest on the fastening ring, for example, so that an initial tightness at the static sealing point is ensured.

According to a development, one or more guide elements, a fastening ring, an O-ring and/or a support ring can be provided on the circumference of the pump piston (between the pump piston and the pump housing).

The guide elements are used to guide the pump piston along an axial direction relative to the housing. The guide elements can, for example, each be designed as a guide ring. If two guide elements are provided, one guide element can be arranged in the pump housing, for example in the recess for the pump piston, and the other guide element can be arranged in a seal carrier.

The fastening ring can be arranged on the side of the sealing ring facing away from the conveying space. The fastening ring can form a seat for the sealing ring, so that the sealing ring is secured against axial displacement, in particular away from the pumping chamber.

The O-ring can develop a radial sealing effect. The static sealing point can be supplemented by the O-ring and the sealing effect can be improved. The O-ring is arranged in particular between the radially outer lateral surface of the sealing ring and the pump housing (peripheral wall of the recess for the pump piston).

The support ring can be arranged between the radially outer lateral surface of the sealing ring and the pump housing (peripheral wall of the recess for the pump piston) and can serve as a support ring for the O-ring. This protects the O-ring since damage, such as extrusion of the O-ring, can be prevented. The support ring is arranged in particular on the side of the O-ring facing away from the pumping chamber and can have a triangular profile in cross section. The hypotenuse of the triangular profile may face the O-ring.

• 1 eine schematische Darstellung eines Kraftstoffsystems mit einer Kraftstoff-Hochdruckpumpe in Form einer Kolbenpumpe;
• 2 einen teilweisen Längsschnitt durch die Kolbenpumpe von 1;
• 3 eine vergrößerte Ansicht eines Pumpenkolbens, einer Dichtung, eines Führungselements und eines Befestigungsrings der Kolbenpumpe aus 1;
• 4 eine Ausgestaltungsmöglichkeit der Dichtung aus 3 in einer vergrößerten Schnittansicht mit O-Ring und Stützring;
• 5 die Dichtung der Kolbenpumpe aus 2 in Alleinstellung in einer perspektivischen Ansicht;
• 6 die Dichtung aus 5 in einer schematischen Teilansicht mit dargestellten Fasern; und
• 7 die Dichtung aus 7 in einer schematischen Draufsicht zur Veranschaulichung der Herstellung.

The invention is explained in more detail below with reference to the figures, with identical or functionally identical elements being provided with identical reference symbols, but possibly only once. Show it:

• 1 a schematic representation of a fuel system with a high-pressure fuel pump in the form of a piston pump;
• 2 a partial longitudinal section through the piston pump from 1 ;
• 3 Figure 12 shows an enlarged view of a pump piston, a seal, a guide element and a fastening ring of the piston pump 1 ;
• 4 a design option for the seal 3 in an enlarged sectional view with O-ring and support ring;
• 5 the piston pump seal 2 in isolation in a perspective view;
• 6 the seal off 5 in a schematic partial view with fibers shown; and
• 7 the seal off 7 in a schematic top view to illustrate the production.

A fuel system of an internal combustion engine carries in 1 overall reference numeral 10. It includes a fuel tank 12, from which an electric pre-supply pump 14 delivers the fuel to a piston pump 16 designed as a high-pressure fuel pump. This conveys the fuel further to a high-pressure fuel rail 18 to which a plurality of fuel injectors 20 are connected, which inject the fuel into combustion chambers of the internal combustion engine (not shown).

The piston pump 16 comprises an inlet valve 22, an outlet valve 24, and a pump housing 26. A pump piston 28 is accommodated in this housing such that it can be moved back and forth. The pump piston 28 is set in motion by a drive 30, with the drive 30 in 1 is shown only schematically. The drive 30 can be a camshaft or an eccentric shaft, for example. The inlet valve 22 is designed, for example, as a quantity control valve, through which the quantity of fuel delivered by the piston pump 16 can be adjusted.

The construction of the piston pump 16 is shown in more detail 2 , whereby only the essential components are mentioned below. The pump piston 28 is designed as a stepped piston with an in 2 lower plunger section 32, a guide section 34 adjoining this and an upper end section, not shown in detail. The guide section 34 has a larger diameter than the plunger section 32 and the end section.

The end section and the guide section 34 of the pump piston 28, together with the pump housing 26, delimit a pumping chamber 38, which is not shown in detail. The pump housing 26 can be designed as an overall rotationally symmetrical part. The pump piston 28 is accommodated in the pump housing 26 in a recess 40 which is present there and which is designed as a stepped bore 42 . The bore 42 has several stages (three stages 42', 42'', 42'''; see 2 and 3 ).

A seal 43 is arranged between the guide section 34 of the pump piston 28 and an inner peripheral wall of the bore 42 (step 42"). It seals directly between the pump piston 28 and the pump housing 26, and thus seals the pumping chamber located above the seal 43 (high-pressure area ) compared to the in 2 below the seal 43 arranged area (low pressure area), in which, inter alia, the plunger portion 32 of the pump piston 28 is located.

The seal 43 is designed as a sealing ring 44 with an essentially sleeve-shaped base section 45 extending along a central longitudinal axis 41 . The base section 45 has a cylindrical outer surface or lateral surface 58 . The sealing ring 44 is made of fiber-reinforced plastic, the fibers 49 of which are oriented at least along a predominant part of the circumference in the circumferential direction 51 of the sealing ring 44 (transverse to the central longitudinal axis 41) (cf. 6 and 7 ). The design of the sealing ring 44 is explained in more detail below.

In the example, a guide element 46 that is separate from the sealing ring 44 is arranged between the guide section 34 of the pump piston 28 and the inner circumferential wall of the bore 42 (step 42') (cf. 2 and 3 ). The guide element 46 can be axially adjacent to the sealing ring 44 and is in 2 arranged above the sealing ring 44 (facing the delivery chamber). The guide element 46 is ring-shaped (guide ring) and can be attached to the step 42'.

In the example, the piston pump 16 has a further guide element 48 which is arranged in a seal carrier 50 of the piston pump 16 (see FIG 2 ). The guide element 46 and the further guide element 48 are used to guide the pump piston 28 . The further guide element 48 is ring-shaped (guide ring) and can be fastened to the seal carrier 50 .

The piston pump 16 has a fastening ring 52 for the sealing ring 44 between the guide section 34 of the pump piston 28 and the inner peripheral wall of the bore 42 (step 42'''). The sealing ring 44 rests on the fastening ring 52 . A static sealing point 53 is formed by the contact surfaces of sealing ring 44 and fastening ring 52 (see Fig 3 ). The sealing ring 44, the guide element 46, the further guide element 48 and the fastening ring 52 form a sealing assembly.

At its first axial end 54, the sealing ring 44 has a circumferential collar 56 that protrudes radially outwards (see FIG 3 ) protruding from the base portion 45. The collar 56 protrudes radially beyond the lateral surface 58 . The collar 56 surrounds the sealing ring 44 completely. The collar 56 has radial play 64 on its radially outer edge relative to the peripheral wall of the recess 40 (step 42") that accommodates the pump piston 28 (see FIG 3 ). As a result, the sealing ring 44 can be aligned in the radial direction with respect to the pump piston 28 .

The pressure prevailing in the pumping chamber 38 can reach the lateral surface 58 of the sealing ring 44, so that the sealing wall on the sleeve-shaped section 45 undergoes a radial inward deformation due to the force acting there (not shown). A dynamic sealing point can thus form between the pump piston 28, in particular between the guide section 34, and the sealing ring 44 (radially inner ring edge).

A spring element 47 can optionally be arranged between the pump piston 28 and the pump housing 26 and presses the sealing ring 44 against the fastening ring 52 . The spring element 47 can be arranged between the guide element 46 and the sealing ring 44 in the axial direction of the pump piston 28 . The spring element 47 can be designed as a compression spring in the form of a spring washer or helical spring. The spring element 47 bears axially at one end, in particular on the guide element 46, and at the other end presses the sealing ring 44 against the fastening ring 52.

An O-ring 98 can optionally be arranged between the radially outer lateral surface 58 of the sealing ring 44 and the pump housing 26 (cf. 4 ). This serves to reinforce the static sealing points 53 and improves the seal. In addition, a support ring 99 for the O-ring 98 can be arranged between the radially outer lateral surface 58 of the sealing ring 44 in the pump piston 26 (cf. 4 ). The support ring 99 serves to protect the O-ring 98, for example to prevent the O-ring 98 from being extruded.

Irrespective of this, a peripheral axial collar 76 can optionally be arranged on the sealing ring 44 be (cf. 4 ). The axial collar 76 can adjoin the radially inner lateral surface 70 . This ensures that the force runs optimally through the sealing ring 44 and is introduced exactly into the static sealing point 53 (cf. 3 ).

The further configuration and manufacture of the sealing ring 44 are described below with reference to FIG 5 until 7 explained.

The sealing ring 44 is formed by injection molding, the sealing ring 44 in the example having a spray entry point 80 and a spray exit point 82, which are arranged offset to one another along the circumferential direction 51 of the sealing ring 44 (cf. 7 ). Some of the fibers or reinforcing fibers 49 extend along a first ring section 44' of the sealing ring 44 from the spray entry point 80 to the spray outlet point 82, and another or the remaining part of the fibers 49 extend along a further ring section 44" of the sealing ring 44 from the Spray entry point 80 to spray exit point 82. Instead of the spray exit point 82, a ventilation point can be provided, as explained above (not shown).

The spray entry point 80 and the spray exit point 82 enclose an angle α with one another, wherein the angle α can be between 160° and 180°. In the example, the angle is α = 175° (cf. 7 ).

A web 84 is formed on the sealing ring 44 at the spray entry point 80, which in the example extends parallel to the central longitudinal axis 41 of the sealing ring 44 along the outer lateral surface 58 of the sealing ring 44, namely along the entire length of the lateral surface 58 (cf. 5 and 7 ). In addition, a further web 86 is formed on the sealing ring 44 at the spray outlet point 82, which extends parallel to the central longitudinal axis 41 of the sealing ring 44 along the outer lateral surface 58 of the sealing ring 44, specifically along the entire length of the lateral surface 58 (cf. 5 and 7 ).

In the example, the web 84 and the further web 86 merge into the circumferential collar 56 (cf. 5 ). In the example, the web 84 and the further web 86 protrude the same distance relative to the outer lateral surface 58 as the collar 56. The web 84, the further web 86 and the collar 56 point at their radially outer edge to the peripheral wall of the recess accommodating the pump piston 28 40 a game on.

In 7 , some of which have already been referred to, the manufacture of the sealing ring 44 made of fiber-reinforced plastic by injection molding is shown schematically. The "flow in injection direction" (injection direction) is illustrated by the arrow 90 and the axis 91 . The spraying process starts from there, with the spraying material (plastic with fibers contained therein) passing through a film sprue 94 via the web 84 (“web for the film sprue”) into the body of the sealing ring 44 .

The arrow 92 and the axis 93 illustrate the “flow out spray direction”. There, the injection process of the sealing ring 44 is completed, with the injection material (plastic with fibers contained therein) passing over the further web 86 (“web for weld line collector”) to a weld line collector 95 .

The axes 91 and 93 enclose the angle α already explained above.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2019/015862 A1 [0002]

Claims (10)

Piston pump (16), in particular a high-pressure fuel pump for an internal combustion engine, having a pump housing (26), a pump piston (28) guided in the pump housing (26) and a pumping chamber (38) delimited at least by the pump housing (26) and the pump piston (28). , wherein a seal (43) for sealing the pumping chamber (38) is arranged on the circumference of the pump piston (28), characterized in that the seal (43) is designed as a sealing ring (44) with a substantially sleeve-shaped, extending along a central longitudinal axis (41 ) extending base section (45), wherein the sealing ring (44) is made of fiber-reinforced plastic, the fibers (49) of which are oriented at least along a predominant part of the circumference of the sealing ring (44) in the circumferential direction (51) of the sealing ring (44). . Piston pump (16) after claim 1 , characterized in that the sealing ring (44) is formed by injection molding, the sealing ring (44) having a spray entry point (80) and a vent point or a spray entry point (80) and a spray exit point (82) along the circumferential direction (51) of the sealing ring (44) are offset from one another. Piston pump (16) after claim 2 , characterized in that a part of the fibers (49) extends along a first ring section (44 ') of the sealing ring (44) from the spray inlet point (80) to the spray outlet point (82) or ventilation point and that another or the remaining part of the fibers (49) along a further ring section (44") of the sealing ring (44) from the injection entry point (80) to the injection exit point (82) or ventilation point. Piston pump (16) after claim 2 or 3 , characterized in that the spray entry point (80) and the spray exit point (82) or venting point form an angle (a) with one another, the angle (a) being between 160° and 180°. Piston pump (16) according to one of claims 2 until 4 , characterized in that a web (84) is formed on the sealing ring (44) at the spray entry point (80) and extends parallel to the central longitudinal axis (41) along the outer lateral surface (56) of the sealing ring (44), in particular along the entire Length of the lateral surface (56). Piston pump (16) according to one of claims 2 until 5 , characterized in that a further web (86) is formed on the sealing ring (44) at the spray outlet point (82), which extends parallel to the central longitudinal axis (41) along the outer lateral surface (56) of the sealing ring (44), in particular along the entire length of the lateral surface (56). Piston pump (16) according to one of the preceding claims, characterized in that the sealing ring (44) has a radially outwardly projecting, circumferential collar (56) at one axial end (54) or at both axial ends, which is attached to the sleeve-shaped Base portion (45) is formed. Piston pump (16) according to one of the preceding claims, characterized in that the web (84), the further web (86) and/or the collar (56) at their radially outer edge to the peripheral wall of the recess ( 40) have a backlash. Piston pump (16) according to one of the preceding claims, characterized in that a spring element (47) which acts on the sealing ring (44) is arranged on the circumference of the pump piston (28). Piston pump () according to one of the preceding claims, characterized in that on the circumference of the pump piston (28) one or more guide elements (46, 48), a fastening ring (52), an O-ring (98) and/or a support ring (99 ) are provided.

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