WO2018072994A1

WO2018072994A1 - Pressure sensor for a high-pressure accumulator, and high-pressure accumulator

Info

Publication number: WO2018072994A1
Application number: PCT/EP2017/075102
Authority: WO
Inventors: Paul Hund; Marc Fischer
Original assignee: Robert Bosch Gmbh
Priority date: 2016-10-17
Filing date: 2017-10-04
Publication date: 2018-04-26
Also published as: DE102016220185A1

Abstract

Pressure sensor (8), in particular for a high-pressure accumulator (1) of an injection system for internal combustion engines. Said pressure sensor (8) comprises a housing part (20) and a sensor element (30). A sensor bore (24) is formed in the housing part (20). The sensor bore (24) is subjected to the fluid pressure to be measured. The sensor element (30) is secured to the housing part (20) by a nanofoil (35).

Description

Description title

Pressure sensor for a high pressure accumulator and high pressure accumulator

The present invention relates to a pressure sensor for a

High-pressure accumulator, the high-pressure accumulator in particular for a

Injection system of an internal combustion engine is used. Furthermore, the invention relates to a high-pressure accumulator with such a pressure sensor.

State of the art

The invention relates to a pressure sensor for a high pressure accumulator and a high pressure accumulator with such a pressure sensor. The high-pressure accumulator is suitable in particular for an injection system for injecting fuel under high pressure into the combustion chamber of an internal combustion engine.

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 space for storing high-pressure fuel. Furthermore, in addition to the pump and injector-side connections still recordings for add-on components available. Usually, the two add-on components are rail pressure sensor and pressure control valve or

Pressure relief valve attached to the high-pressure accumulator.

Furthermore, from DE 10 201 1 088 044 A1 a pressure sensor with a

Housing and a housing piece known, wherein the housing piece is welded to the housing. On the housing piece, a sensor element for measuring the pressure of a sensor hole formed in the housing piece is attached. Disclosure of the invention

The pressure sensor according to the invention, in particular for a high-pressure accumulator of an injection system for internal combustion engines, in contrast, has an increased accuracy of measurement by the connection between the

Housing piece and the sensor element is improved.

For this purpose, the pressure sensor comprises a housing piece and a sensor element. In the housing piece a sensor bore is formed. In the sensor bore is the pressure to be measured of a fluid. The sensor element is attached to the housing piece by means of nanofoil.

If high pressure fluid, for example fuel, is present in the sensor bore, the sensor element deforms or warps. The

Sensor element, for example, have strain gauges that measure this Verwolbung or stretching. A controller can in turn determine the pressure of the fluid or fuel in the.

The Nanofoil, a multilayer of highly reactive layers of fabric, results in a very strong and very dense connection between the housing piece and the sensor element. The sensor element can therefore be manufactured in advance in a separate step and thus has the required measuring sensitivity. For the sensor element can thus be used a metal thin-film technology, which is very good for pressure measurement in particular for

High-pressure accumulator is suitable. The sensor element is manufactured in a separate step in order to achieve the required sensitivity again. The layer structure of the sensor element does not take place on a turned semi-finished product or a thick steel wafer, but on a metal foil. The metal foil may have different thicknesses depending on the required sensitivity.

In an advantageous embodiment, the sensor bore is formed as a through hole. The sensor element consequently limits the sensor bore. The pressure of the fluid thus acts directly on the sensor element, so that the

Pressure measurements have a very low inaccuracy. These

Design is suitable for comparatively low pressures. In another advantageous embodiment, the sensor bore as

Blind hole bore executed. As a result, the sensor bore is delimited on the front side by a membrane wall of the housing piece. The pressure of the fluid thus acts on the membrane wall and thus indirectly on the sensor element, which is preferably mounted on the other side of the membrane wall.

This embodiment is suitable for comparatively high pressures.

In advantageous embodiments, the nanofoil consists of Ni / Al, Al / Ti, Zr / Si, Zr / Al / Si or Pd / Al multilayer. These combinations of the individual layers of the

Multilayers are particularly reactive and thus give a particularly good cohesive connection between the housing piece and the

Sensor element. The materials of the multilayer are alternately arranged one above the other in individual layers and, after a starting process, react with one another by ignition, thus generating the required process temperature for joining the housing piece and the sensor element.

In advantageous developments, the sensor element and the

Case on each of the cooperating with the nanofoil surfaces a nickel layer on. The nickel layer is a very good adhesion promoter in interaction with the nanofoil. This increases the strength of the

cohesive connection between the housing piece and the

Sensor element.

The invention further relates to a high-pressure accumulator for storing high-pressure fluid, in particular fuel. Of the

High-pressure accumulator has a pressure sensor, as described above

has been described. Furthermore, the high-pressure accumulator has a storage space formed in a storage tube, a supply port for supplying pressurized fluid and at least one discharge port for discharging high-pressure fluid. The supply port and the discharge port open into the storage space, are thus fluidly connected thereto. The storage space in turn is fluidic with the

Sensor hole connected. As a result, the sensor element also indirectly measures the pressure in the storage space. From the above

Reasons the pressure sensor is suitable for very high fluid pressures, so it is particularly well suited for high-pressure accumulator with correspondingly high pressures. The pressure sensor is particularly suitable for a high-pressure accumulator of an injection system for internal combustion engines, wherein the

High-pressure accumulator stores high-pressure fuel. The

Development of such high-pressure accumulators has the goal increasingly higher

Provide fuel pressures and be able to seal. At the same time the values of these fuel pressures must be measured as accurately as possible over the lifetime in order to obtain a good injection characteristics of the injection system. Therefore, the pressure sensor according to the invention is for such

High-pressure accumulator particularly well suited. This also applies to the following developments.

Brief description of the drawings

Hereinafter, embodiments of the invention below

With reference to the accompanying drawings described in more detail. It shows:

Fig. 1 shows schematically a high-pressure accumulator in longitudinal section, as he from the

Prior art is known,

Fig. 2 shows a pressure sensor according to the invention for a high-pressure accumulator in

Longitudinal section, showing only the essential areas,

3 shows a further pressure sensor according to the invention in longitudinal section, wherein only the essential areas are shown,

Fig. 4 shows a further pressure sensor according to the invention in longitudinal section, wherein only the essential areas are shown.

Embodiments of the invention

In the longitudinal section of Figure 1 is denoted by 1 a rohrformiger high-pressure accumulator, as it is known from the prior art. The high-pressure accumulator 1 has a storage tube 2, which surrounds a storage space 3. The high-pressure accumulator 1 is provided for an injection system for internal combustion engines and is commonly referred to as a rail. On the storage tube 2 of the high pressure accumulator 1 a plurality of discharge ports 4 are formed for fuel pressure lines to injectors, not shown. Furthermore, a supply port 7 is formed to a high-pressure pump, not shown, on the storage tube 2. In addition, receptacles 5 and 6 for attachment components 8 and 9 are formed on the storage tube 2. The attachment component 8 is a pressure sensor for determining the pressure in the storage space 3. And the attachment component 9 is a pressure valve, preferably a pressure control valve for regulating the pressure in the storage space 3. The pressure valve 9 and pressure control valve 9 is designed and has, for example, as an electromagnetic valve a non-illustrated electrical connection for connection to a control unit or a power supply, not shown.

The receiving opening 6 for the pressure valve 9 is connected via a discharge channel 5 with a low-pressure port 5a, so that a controlled via the pressure valve 9 amount of fuel can be passed to a low pressure return. In this case, the drain channel 5 opens into the receiving opening 6, that when attached to the high-pressure accumulator 1 pressure valve 9, a seal between the high pressure part and the low pressure part (drain channel 5) is ensured.

In the example, the pressure valve 9 and the 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 is basically arbitrary.

The high-pressure accumulator 1 is in particular for a fuel injection system,

For example, a common rail system, suitable. From a high-pressure pump, not shown fuel is conveyed under high pressure via the supply port 7 into the storage space 3 of the high-pressure accumulator 1, from where it via the discharge ports 4 to injectors not shown for injection into the

Combustion chambers of internal combustion engines is distributed.

The high-pressure accumulator 1 has the storage tube 2, in which the

Storage space 3 is formed for storing the fuel under high pressure. Due to the supply of fuel from the high-pressure pump and the discharge of the fuel to the injectors arise

operating point-dependent flow conditions of the fuel in the Storage space 3 with pressure oscillations. Therefore, the pressure in the

Storage space 3 to be subject to strong fluctuations. For an optimized injection behavior of the injectors it is necessary the pressure level in the

Memory space 3 to determine as accurately as possible. The demands on the pressure sensor 8 are correspondingly high.

2 shows a pressure sensor 8 of the high-pressure accumulator 1 according to the invention in longitudinal section, wherein only the essential areas are shown. The pressure sensor 8 comprises a housing 10, which has an external thread 1 1. The housing 10 is on the external thread 1 1 in the storage tube 2 of the

Screwed high-pressure accumulator 1 and secured with a nut 12 against loosening. In alternative embodiments, however, housing 10 and storage tube 2 can also be made in one piece. In the housing 10, a longitudinal bore 14 is formed centrally as a through hole, which is hydraulically connected to the storage space 3 for use in a high-pressure accumulator 1 or an extension or a

Partial volume of the storage space 3 represents. In the longitudinal bore 14, a housing piece 20 is pressed. For this purpose, a cylindrical outer surface 21 of the housing piece 20 is provided with an excess with respect to the through hole 14, so that between the outer surface 21 and the through hole 14, a contact pressure is present. This contact pressure is the basis for the interference fit, that is, for the non-positive connection of the housing 10 with the housing piece 20. Alternatively, the housing 10 and the housing piece 20 may also be made in one piece as a housing, or

Housing piece 20 may be screwed into the housing 10.

In the embodiment of Figure 2, the housing piece 20 frontally on its side facing away from the longitudinal bore 14 a membrane wall 23 on. By doing

Housing piece 20, a sensor bore 24 is formed, which in the

Through hole 14 opens. The sensor bore 24 is therefore formed as a blind hole and is bounded by the diaphragm wall 23. On the surface opposite to the sensor bore 24, a sensor element 30 is connected to the membrane wall 23 by means of nanofoil 35 or adhesively bonded to the membrane wall 23. The connection between the housing piece 20 or the membrane wall 23 and the sensor element 30 is produced according to the invention by the reactive nanofoil 35. The Nanofoil 35 consists of multilayers. The multilayers are superimposed thin layers of different, usually two materials. Preferably, nickel and aluminum layers are alternated. Alternatively, the multilayer may also consist of aluminum-titanium, zirconium-silicon, or palladium-aluminum. Also three

different layers are possible, for example zirconium-aluminum-silicon. The multilayers are highly reactive. The start of the reaction is triggered by ignition via, for example, a laser pulse or an electrical impulse.

After starting the process, the different materials of the multilayer react with each other in a few milliseconds and thus generate the required process temperature for joining the various joining partners sensor element 30 and housing piece 20, so that a cohesive connection is formed. The joining partners, for example stainless steel from 1.4542, typically have one

Nickel layer as a "primer" or solder on

Strength of the connection between sensor element 30 and housing piece 20.

3 shows a pressure sensor 8 with a one-piece housing 10. Das

Housing piece 20 is therefore part of the housing 10 and formed as an end piece on this. As a result, the longitudinal bore 14 and the sensor bore 24 can be considered as a bore, although they are provided in the embodiment of Figure 3 with different diameters. The sensor bore 24 is designed as a blind hole, so that the end face of the housing piece 20, the diaphragm wall 23 which limits the sensor bore 24. Opposite to the sensor bore 24, the nanofoil 35 is arranged on the membrane wall 23, which secures the sensor element 30 to the housing part 20.

4 shows a further pressure sensor 8 with a one-piece housing 10. The sensor bore 24 is designed in this embodiment as a through hole, so that the end face of the housing piece 20 has no membrane wall 23.

Consequently, the sensor element 30 or the nanofoil 35 limits the

Sensor bore 24. Usually, the embodiment of Figure 3 is suitable for higher pressures, while the embodiment of Figure 4 achieves more accurate measurements. The sensor element 30 may, for example, comprise strain gauges which detect a deformation or warping. An unillustrated control unit can, starting from this Verwolbung the pressure in the sensor bore 24 and thus in the

Memory space 3 determine.

Claims

claims

1 . Pressure sensor (8), in particular for a high-pressure accumulator (1) of a

Injection system for internal combustion engines, wherein the pressure sensor (8) has a housing piece (20) and a sensor element (30), wherein in the housing piece (20) a sensor bore (24) is formed, wherein in the sensor bore (24) of the pressure to be measured Fluid is applied, characterized in that the sensor element (30) by means of nanofoil (35) on the housing piece (20) is mounted.

Pressure sensor (8) according to claim 1, characterized in that the

Sensor bore (24) is formed as a through hole, wherein the sensor element (30) limits the sensor bore (24).

Pressure sensor (8) according to claim 1, characterized in that the

Sensor bore (24) is designed as a blind hole (24), so that the sensor bore (24) at the end by a membrane wall (23) of the

Housing piece (20) is limited.

Pressure sensor (8) according to claim 3, characterized in that the sensor element (30) on the sensor bore (24) facing away from the membrane wall (23) is mounted.

Pressure sensor (8) according to one of claims 1 to 4, characterized in that the nanofoil (35) consists of Ni / Al, Al / Ti, Zr / Si, Zr / Al / Si or Pd / Al multilayer.

Pressure sensor (8) according to one of claims 1 to 5, characterized in that the sensor element (30) and the housing piece (20) each have a nickel layer on the surfaces cooperating with the nanofoil (35).

7. High-pressure accumulator (1) for storing a fluid under high pressure, in particular fuel, with a pressure sensor (8) according to one of the preceding claims, wherein the high-pressure accumulator 1 formed in a storage tube 2 storage space (3), a

Feed port (7) for supplying high pressure fluid and at least one discharge port (4) for discharging fluid under high pressure, wherein the supply port (7) and the

Discharge port (4) into the storage space (3) open, wherein the

Storage space (3) is fluidly connected to the sensor bore (24).