Patent Application
20200325866
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 a high pressure accumulator of this type.
The invention relates to a high pressure accumulator, in particular for an injection system for injecting fuel at high pressure into the combustion chamber of an internal combustion engine, and to a method for producing a high pressure accumulator of this type.
High pressure accumulators are known from the prior art, for example from DE 10 2008 040 901 A1. The known high pressure accumulator has an accumulator space for storing highly pressurized fuel. Furthermore, there are also receptacles for attachment components in addition to the pump-side and injector-side connectors. Here, the two attachment components of the rail pressure sensor and the pressure control valve or pressure limiting valve are usually attached to the high pressure accumulator.
The injection system, in particular the high pressure accumulator and the injectors, are sensitive to pressure oscillations insofar as the latter reduce the service life of the components which are loaded with them.
In contrast, the high pressure accumulator according to the invention for internal combustion engines has reduced loading and accordingly a longer service life.
To this end, the high pressure accumulator comprises a common rail with an accumulator space which is configured in the common rail. The high pressure accumulator has a feed connector for feeding in highly pressurized fuel and at least one discharge connector for discharging highly pressurized fuel. A honeycomb structure is arranged in the accumulator space.
The honeycomb structure acts as a throttle in the case of a rapid throughflow of the accumulator space, as occurs in the case of open discharge connectors for instance, and therefore damps pressure oscillations in the accumulator space, but also in the components which are connected downstream of the discharge connectors, for example injectors for injecting fuel into the internal combustion engine. The pressure loading of the components is reduced and therefore the service life of the components is increased by way of the damping of the pressure overshoots. Furthermore, the honeycomb structure can also be designed in such a way that it stiffens the common rail and increases the strength of the high pressure accumulator as a result.
In advantageous refinements, the common rail and the honeycomb structure are configured in one piece. As a result, complicated connecting techniques can be dispensed with, and the high pressure accumulator is of particularly rigid configuration. The high pressure accumulator is produced using the 3D printing process; a conventional casting process is not suitable for this purpose.
In one advantageous development, the honeycomb structure comprises at least one, but preferably from 10 to 15 disks, a plurality of honeycomb-shaped recesses being configured in each disk. As a result, the fuel flow through the individual disks is damped. Pressure waves are reflected partially on the disks and are superimposed in such a way that the pressure overshoots are attenuated.
The disks are advantageously lined up one after another in each case at the same axial spacing. As a result, the throttle points are arranged at identical spacings in the axial direction of the accumulator space. The pressure oscillations in the accumulator space are thus damped uniformly.
In advantageous embodiments, the recesses have the basic shape of a regular hexagon. This is a particularly favorable throttle geometry with a comparatively low weight. For comparison purposes, circular bores do not have a constant web width between the bores and accordingly require high material buildups locally.
The edge length of the regular hexagon is advantageously 0.75 mm. This is very suitable, in particular, for a diameter of the substantially cylindrical accumulator space of approximately 10 mm.
In advantageous alternative embodiments, the honeycomb structure comprises at least one, but preferably from 10 to 15 honeycomb cups. A plurality of honeycomb-shaped recesses are configured in each honeycomb cup. As a result, the fuel flow is damped through the individual honeycomb cups which act as throttle points. Pressure waves are reflected partially on the honeycomb cups and are superimposed in such a way that the pressure overshoots are attenuated. The fuel flow through the accumulator space can be steered in a very controlled manner by way of the honeycomb cups.
Each honeycomb cup advantageously has a head region, the diameter of which corresponds to the diameter of the accumulator space, and is preferably approximately 10 mm. Furthermore, each honeycomb cup has a tapered base region. Here, the tapered portion along the axial axis can run in a conical or curved manner. Here, the cup shape is a very satisfactory compromise between satisfactory flow guidance, a satisfactory damping function, a high rigidity and a low weight.
In advantageous developments, the honeycomb cups are arranged in such a way that in each case a head region interacts with a head region of the next honeycomb cup and, correspondingly, a base region interacts with a base region of the adjacent honeycomb cup. As a result, the honeycomb cups are arranged in series in such a way that pronounced damping of pressure oscillations takes place in the case of a throughflow of the two head regions which are arranged next to one another. Furthermore, the rigidity of the high pressure accumulator is also increased considerably in the axial direction by way of an arrangement of this type.
In advantageous embodiments, the honeycomb cups have a length of 5 mm. As a result, the throttle points by way of the head regions are arranged at identical spacings in the axial direction of the accumulator space. The pressure oscillations in the accumulator space are thus damped uniformly.
In advantageous embodiments, the recesses have the basic shape of a regular hexagon. This is a particularly favorable throttle geometry with a comparatively low weight. For comparison purposes, circular bores do not have a constant web width between the bores and accordingly require high material buildups locally.
The edge length of the regular hexagon is advantageously 0.75 mm. This is very suitable, in particular, for a diameter of the accumulator space of approximately 10 mm.
The production of the above-described high pressure accumulators takes place using the 3D printing process which makes the manufacture of geometries of this type inexpensive in the first place. In particular, the single-piece embodiment of the common rail and the honeycomb structure is then particularly advantageous, namely is firstly very inexpensive and secondly has a high rigidity.
In the following text, exemplary embodiments of the invention will be described in greater detail with reference to the appended drawings, in which:
In the longitudinal section of
A plurality of discharge connectors 4 for fuel pressure lines to injectors (not shown) are configured on the common rail 2 of the high pressure accumulator 1. Furthermore, a feed connector 7 to a high pressure pump (not shown) is configured on the common rail 2. In addition, receptacles 5 and 6 for attachment components 8 and 9 are configured on the common rail 2. The attachment component 8 is usually a rail pressure sensor for determining the pressure in the accumulator space 3. In addition, the attachment component 9 is a pressure valve, preferably a pressure control valve for controlling the pressure in the accumulator space 3. The pressure valve 9 or pressure control valve 9 is configured, for example, as an electromagnetic valve and has an electric connector (not shown) for connecting to a control unit or a power supply (not shown).
The receiving opening 6 for the pressure valve 9 is connected via an outlet duct 32 to a low pressure connector 34, with the result that a fuel quantity which is output in a controlled manner via the pressure valve 9 can be guided to a low pressure return line. Here, the outlet duct 32 opens into the receiving opening 6 in such a way that a seal is ensured between the high pressure part and the low pressure part (outlet duct 32) in the case of a pressure valve 9 which is attached to the high pressure accumulator 1.
In the exemplary case, the pressure valve 9 and the rail pressure sensor 8 are arranged at ends of the high pressure accumulator 1 which face away from one another. Here, the distribution of said attachment components 8, 9 on the high pressure accumulator 1 is in principle freely selectable.
The high pressure accumulator 1 has the common rail 2, in which the accumulator space 3 for storing the highly pressurized fuel is configured. Flow conditions of the fuel in the accumulator space 3 which are dependent on the operating point are produced with pressure oscillations on account of the feeding of the fuel from the high pressure pump and the discharge of the fuel to the injectors.
A honeycomb structure 10 is arranged in the accumulator space 3 in order to damp said pressure oscillations. In the embodiment of
The accumulator space 3 is divided by way of the disks 11 into individual chambers 3a, 3b, etc., which are connected to one another via the cross-sectional reduction by way of the honeycomb-shaped recesses 12. Accordingly, the honeycomb-shaped recesses 12 represent throttles in the axial flow direction which effectively damp any pressure overshoots during the throughflow. As a result, the maximum pressure peaks within the high pressure accumulator 1 and also within the downstream injectors are damped. Accordingly, the service life of said components is increased.
The common rail 2 and the honeycomb structure 10 are advantageously configured in one piece, with the result that a complicated connecting technique is not required. The corresponding production process to this end is preferably the 3D printing process; a conventional casting process is not suitable for geometries of this type in high quantities.
On account of the positively locking lining up of the individual honeycomb cups 15, the honeycomb structure 10 in said embodiment has a high rigidity and thus also increases the strength of the common rail 2 or the entire high pressure accumulator 1, both in the radial and in the axial direction. The individual honeycomb cups 15 preferably have a length L of 5 mm, from 10 to 15 honeycomb cups 15 advantageously being lined up in the accumulator space 3. Furthermore, the honeycomb-shaped recesses 12 in each case have the shape of a uniform hexagon with an edge length s of 0.75 mm, in a manner which is advantageous for an accumulator space 3 with a diameter D of approximately 10 mm. Here, the web width u of the honeycomb structure 10 between the individual recesses 12 is preferably 0.55 mm.
In general, a very complex geometry of the honeycomb structure 10 can be realized using the 3D printing process, specifically if the honeycomb structure 10 is configured in one piece with the common rail 2. Here, the above-described embodiments prove particularly effective for damping the pressure oscillations in the accumulator space 3, caused by way of the periodic conveying of highly pressurized fuel from the high pressure pump via the feed connector 7 and the sudden discharge of fuel via one or more discharge connectors 4 to the injectors.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2016 209 423.8 | May 2016 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/058845 | 4/12/2017 | WO | 00 |
