High-pressure accumulator and method for producing a high-pressure accumulator

Abstract

High-pressure accumulator (1) for internal combustion engines for storing high-pressure fuel, wherein the high-pressure accumulator (1) comprises a storage tube (2) with a storage chamber (3) formed in the storage tube (2), wherein the high-pressure accumulator (1) has a supply connection (7) for supplying high-pressure fuel and at least one discharge connection (4) for discharging high-pressure fuel, characterized in that a honeycomb structure (10) is arranged in the storage chamber (3), wherein the storage tube (2) and the honeycomb structure (10) are designed as a single piece.

Description

[0001] The present invention relates to a high-pressure accumulator, in particular for an injection system of an internal combustion engine. Furthermore, the invention relates to a method for producing such a high-pressure accumulator. State of the art

[0002] The invention relates to a high-pressure accumulator, in particular for an injection system for injecting fuel under high pressure into the combustion chamber of an internal combustion engine, and to a method for producing such a high-pressure accumulator.

[0003] High-pressure accumulators are known from the prior art, for example, from DE 10 2008 040 901 A1. The known high-pressure accumulator has a storage chamber for storing high-pressure fuel. In addition to the pump- and injector-side connections, there are also receptacles for add-on components. Typically, the two add-on components, the rail pressure sensor and the pressure control valve or pressure relief valve, are attached to the high-pressure accumulator.

[0004] DE 10 2011 120 924 A1 discloses a device for injecting a pressurized fuel fluid into a combustion chamber, comprising a pressure generator, at least one injector with an injection opening and a fuel line between the pressure generator and the injector, wherein at least one damping element is provided between the pressure generator and the injection opening of the injector.

[0005] DE 10 2005 026 993 A1 shows a fuel injection device for an internal combustion engine with a high-pressure storage chamber

[0006] JP 2014-88 791 A discloses a common rail system for a fuel injection device having a common rail main body forming a pressure storage chamber in which high-pressure fuel is stored.

[0007] CN 2 02 832 918 U shows a high-pressure accumulator for internal combustion engines for storing high-pressure fuel, wherein the high-pressure accumulator comprises a storage tube with a storage space formed in the storage tube, wherein the high-pressure accumulator has a supply connection for supplying high-pressure fuel and at least one discharge connection for discharging high-pressure fuel, and wherein a honeycomb structure is arranged in the storage space.

[0008] The injection system, in particular the high-pressure accumulator and the injectors, are sensitive to pressure fluctuations in that these reduce the service life of the components exposed to them. Disclosure of the invention

[0009] In contrast, the high-pressure accumulator for internal combustion engines according to the invention has reduced stress and consequently a longer service life.

[0010] For this purpose, the high-pressure accumulator comprises a storage tube with a storage chamber formed within the storage tube. The high-pressure accumulator has a supply connection for supplying high-pressure fuel and at least one discharge connection for discharging high-pressure fuel. A honeycomb structure is arranged in the storage chamber, with the storage tube and the honeycomb structure being formed as a single piece. This eliminates the need for complex joining techniques, and the high-pressure accumulator is designed to be particularly rigid. The high-pressure accumulator is manufactured using a 3D printing process; a conventional casting process is not suitable for this purpose.

[0011] The honeycomb structure acts as a throttle during rapid flow through the accumulator chamber, such as when the discharge ports are open, thus dampening pressure fluctuations in the accumulator chamber and also in the components downstream of the discharge ports, such as injectors for injecting fuel into the internal combustion engine. By dampening pressure overshoots, the compressive stress on the components is reduced, thus increasing their service life. Furthermore, the honeycomb structure can also be designed to stiffen the accumulator tube, thereby increasing the strength of the high-pressure accumulator.

[0012] In an advantageous development, the honeycomb structure comprises at least one, but preferably 10 to 15, discs, with several honeycomb-shaped recesses formed in each disc. This dampens the fuel flow through the individual discs. Pressure waves are partially reflected by the discs and overlap, thus attenuating the pressure overshoots.

[0013] Advantageously, the discs are arranged one after the other at the same axial spacing. This ensures that the throttling points are arranged at equal distances along the axial direction of the storage chamber. The pressure oscillations in the storage chamber are thus evenly dampened.

[0014] In advantageous designs, the recesses have the basic shape of a regular hexagon. This provides a particularly favorable throttle geometry with comparatively low weight. In comparison, circular holes do not have a constant web width between the holes and therefore require high local material accumulations.

[0015] Advantageously, the edge length of the regular hexagon is 0.75 mm. This is particularly suitable for a diameter of the essentially cylindrical storage space of approximately 10 mm.

[0016] In advantageous alternative embodiments, the honeycomb structure comprises at least one, but preferably 10 to 15, honeycomb cups. Several honeycomb-shaped recesses are formed in each honeycomb cup. This dampens the fuel flow through the individual honeycomb cups, which act as throttles. Pressure waves are partially reflected by the honeycomb cups and overlap, thereby attenuating pressure overshoots. The fuel flow through the storage chamber can be directed very precisely by the honeycomb cups.

[0017] Advantageously, each honeycomb cup has a head region whose diameter corresponds to the diameter of the storage chamber, preferably approximately 10 mm. Furthermore, each honeycomb cup has a tapered base region. The taper along the axial axis can be conical or curved. The cup shape represents a very good compromise between good flow guidance, good damping function, high rigidity, and low weight.

[0018] In advantageous refinements, the honeycomb cups are arranged such that a head region interacts with a head region of the next honeycomb cup, and a foot region interacts with a foot region of the subsequent honeycomb cup. The honeycomb cups are thus arranged in series in such a way that pressure oscillations are strongly damped when flow passes through the two adjacent head regions. Furthermore, such an arrangement significantly increases the rigidity of the high-pressure accumulator in the axial direction.

[0019] In advantageous designs, the honeycomb cups are 5 mm long. This ensures that the throttle points are arranged at equal intervals in the axial direction of the storage chamber through the head areas. The pressure oscillations in the storage chamber are thus evenly dampened.

[0020] In advantageous designs, the recesses have the basic shape of a regular hexagon. This provides a particularly favorable throttle geometry with comparatively low weight. In comparison, circular holes do not have a constant web width between the holes and therefore require high local material accumulations.

[0021] Advantageously, the edge length of the regular hexagon is 0.75 mm. This is particularly suitable for a storage chamber diameter of approximately 10 mm.

[0022] The high-pressure accumulators described above are manufactured using the 3D printing process, which makes the production of such geometries cost-effective in the first place. The one-piece design of the accumulator tube and honeycomb structure is particularly advantageous, both because it is very cost-effective and because it offers high rigidity. Short description of the drawings

[0023] In the following, exemplary embodiments of the invention are described in more detail with reference to the accompanying drawings. They show: Fig. 1 schematically shows a high-pressure accumulator in longitudinal section, as is known from the prior art, Fig. 2 a section of a half model of a high-pressure accumulator according to the invention in perspective view, with only the essential areas being shown, Fig. 3 a section of another high-pressure accumulator according to the invention as a half model in perspective view, wherein only the essential areas are shown. Embodiments of the invention

[0024] In the longitudinal section of the Fig. 1, 1 denotes a tubular high-pressure accumulator, as is known from the prior art. The high-pressure accumulator 1 has an accumulator tube 2 surrounding a storage chamber 3. The high-pressure accumulator 1 is intended for an injection system for internal combustion engines and is commonly referred to as a rail.

[0025] On the accumulator tube 2 of the high-pressure accumulator 1, a plurality of discharge connections 4 for fuel pressure lines to injectors (not shown) are formed. Furthermore, a supply connection 7 to a high-pressure pump (not shown) is formed on the accumulator tube 2. In addition, receptacles 5 and 6 for add-on components 8 and 9 are formed on the accumulator tube 2. Typically, the add-on component 8 is a rail pressure sensor for determining the pressure in the accumulator chamber 3. And the add-on component 9 is a pressure valve, preferably a pressure regulating valve for regulating the pressure in the accumulator chamber 3. The pressure valve 9 or pressure regulating valve 9 is designed, for example, as an electromagnetic valve and has an electrical connection (not shown) for connection to a control unit (not shown) or a power supply.

[0026] The receiving opening 6 for the pressure valve 9 is connected to a low-pressure connection 34 via a discharge channel 32, so that a fuel quantity diverted via the pressure valve 9 can be directed to a low-pressure return. The discharge channel 32 opens into the receiving opening 6 in such a way that, when the pressure valve 9 is attached to the high-pressure accumulator 1, a seal is ensured between the high-pressure part and the low-pressure part (discharge channel 32).

[0027] In the example, the pressure valve 9 and the rail pressure sensor 8 are arranged at opposite ends of the high-pressure accumulator 1. The distribution of these add-on components 8, 9 on the high-pressure accumulator 1 can, in principle, be freely selected.

[0028] In Fig. Figure 2 shows a section of a high-pressure accumulator 1 according to the invention, cut longitudinally in perspective. The high-pressure accumulator 1 is particularly suitable for a fuel injection system, for example, a common rail system. A high-pressure pump (not shown) delivers fuel under high pressure via the supply connection (not shown) into the high-pressure accumulator 1, from where it is distributed via the discharge connections (not shown) to injectors (not shown) for injection into the combustion chambers of internal combustion engines.

[0029] The high-pressure accumulator 1 has the accumulator tube 2, in which the accumulator chamber 3 is formed for storing the high-pressure fuel. Due to the supply of fuel from the high-pressure pump and the discharge of the fuel to the injectors, operating-point-dependent fuel flow conditions with pressure fluctuations arise in the accumulator chamber 3.

[0030] To dampen these pressure oscillations, a honeycomb structure 10 is arranged in the storage space 3. In the embodiment of the Fig. 2, the honeycomb structure 10 comprises a plurality of axially spaced-apart disks 11, in each of which a plurality of honeycomb-shaped recesses 12 are formed. The disks 11 are preferably arranged at a distance a of at least 5 mm from one another and have a thickness b of 0.5 mm. Furthermore, the honeycomb-shaped recesses 12 for a storage space 3 with a diameter D of approximately 10 mm each advantageously have the shape of a uniform hexagon with an edge length s of 0.75 mm. The web width u of the honeycomb structure 10 between the individual recesses 12 is preferably 0.55 mm.

[0031] The discs 11 divide the accumulator chamber 3 into individual chambers 3a, 3b, etc., which are connected to each other via the reduced cross-section provided by the honeycomb-shaped recesses 12. The honeycomb-shaped recesses 12 therefore represent throttles in the axial flow direction, effectively dampening any pressure overshoots during flow. This dampens the maximum pressure peaks within the high-pressure accumulator 1 and also within the downstream injectors. The service life of these components is accordingly increased.

[0032] Advantageously, the storage tube 2 and the honeycomb structure 10 are formed as a single piece, eliminating the need for complex joining technology. The corresponding manufacturing method is preferably 3D printing; a conventional casting process is not suitable for such geometries in high volumes.

[0033] Fig.3 shows a further embodiment of the high-pressure accumulator 1 with a honeycomb structure 10 in a half-model in perspective view, with only the essential areas being shown. The honeycomb structure 10 of this embodiment comprises honeycomb cups 15 arranged axially next to one another, each cup-shaped with a wide head region 17 and a strongly tapered foot region 16. The individual honeycomb cups 15 are arranged next to one another in such a way that one foot region 16 always interacts with another foot region 16 of the next honeycomb cup 15, and one head region 17 with the next head region 17. At the respective ends of the storage space 3, the foot regions 16 and head regions 17 there are supported on a corresponding shoulder or end face of the storage tube 2.

[0034] Due to the positively locking arrangement of the individual honeycomb cups 15, the honeycomb structure 10 in this embodiment has a high degree of rigidity and thus also increases the strength of the storage tube 2 or of the entire high-pressure accumulator 1, both in the radial and axial directions. The individual honeycomb cups 15 preferably have a length L of 5 mm, with 10 to 15 honeycomb cups 15 advantageously being arranged in a row in the storage chamber 3. Furthermore, the honeycomb-shaped recesses 12 for a storage chamber 3 with a diameter D of approximately 10 mm each advantageously have the shape of a uniform hexagon with an edge length s of 0.75 mm. The web width u of the honeycomb structure 10 between the individual recesses 12 is preferably 0.55 mm.

[0035] In general, a very complex geometry of the honeycomb structure 10 can be realized with the 3D printing process, especially when the honeycomb structure 10 is designed as a single piece with the storage tube 2. The designs described above prove to be particularly effective for damping the pressure oscillations in the storage chamber 3, caused by the periodic delivery of high-pressure fuel from the high-pressure pump via the supply connection 7 and the sudden discharge of fuel via one or more discharge connections 4 to the injectors.

Claims

[1] High-pressure accumulator (1) for internal combustion engines for storing high-pressure fuel, wherein the high-pressure accumulator (1) comprises a storage tube (2) with a storage space (3) formed in the storage tube (2), wherein the high-pressure accumulator (1) has a supply connection (7) for supplying high-pressure fuel and at least one discharge connection (4) for discharging high-pressure fuel, characterized by that a honeycomb structure (10) is arranged in the storage space (3), wherein the storage tube (2) and the honeycomb structure (10) are designed in one piece. [2] High-pressure accumulator (1) according to claim 1, characterized by that the honeycomb structure (10) comprises at least one, preferably 10 to 15 discs (11), wherein a plurality of honeycomb-shaped recesses (12) are formed in each disc (11). [3] High-pressure accumulator (1) according to claim 2, characterized bythat the discs (11) are arranged one after the other with the same axial distance (a). [4] High-pressure accumulator (1) according to claim 2 or 3, characterized by that the recesses (12) have the basic shape of a regular hexagon. [5] High-pressure accumulator (1) according to claim 4, characterized by that the edge length (s) of the regular hexagon is 0.75 mm. [6] High-pressure accumulator (1) according to claim 1, characterized by that the honeycomb structure (10) comprises at least one, preferably 10 to 15 honeycomb cups (15), wherein a plurality of honeycomb-shaped recesses (12) are formed in each honeycomb cup (15). [7] High-pressure accumulator (1) according to claim 6, characterized by that each honeycomb cup (15) has a head region (17) whose diameter corresponds to the diameter of the storage space (3), and that each honeycomb cup (15) has a tapered foot region (16). [8] High-pressure accumulator (1) according to claim 7, characterized bythat the honeycomb cups (15) are arranged such that a head region (17) interacts with a head region (17) and a foot region (16) interacts with a foot region (16). [9] High-pressure accumulator (1) according to one of claims 6 to 8, characterized by that the honeycomb cups (15) have a length (L) of 5 mm. [10] High-pressure accumulator (1) according to one of claims 6 to 9, characterized by that the recesses (12) have the basic shape of a regular hexagon. [11] High-pressure accumulator (1) according to claim 10, characterized by that the edge length (s) of the regular hexagon is 0.75 mm. [12] Method for producing a high-pressure accumulator (1) according to one of claims 1 to 11, wherein the storage tube (2) and the honeycomb structure (10) are made in one piece, characterized by that the high-pressure accumulator (1) is manufactured using a 3D printing process.

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