Protective device
阅读说明:本技术 保护装置 (Protective device ) 是由 C·希尔 于 2018-12-19 设计创作,主要内容包括:本发明涉及一种用于传感器(2)的膜(3)的保护装置(1);传感器(2)确定由作用在膜(3)上的介质所传递的物理参量;保护装置(1)可安装在传感器(2)上;保护装置(1)具有纵向轴线(Z);保护装置(1)在安装在传感器(2)上的状态下保护膜(3)免受至少一个辐射源(9)的电磁辐射;保护装置(1)具有至少一个通道(7),介质在保护装置(1)安装在传感器(2)上的状态下可以通过通道(7)到达膜(3);在保护装置(1)安装在传感器(2)上的状态下,电磁辐射可以在通道(7)中传播;其中,在通道(7)中传播的电磁辐射只有在通道的壁、简称通道壁(71)上进行至少一次反射之后才到达膜(3)。(The invention relates to a protective device (1) for a membrane (3) of a sensor (2); the sensor (2) determines a physical variable transmitted by the medium acting on the membrane (3); the protection device (1) can be mounted on the sensor (2); the protection device (1) has a longitudinal axis (Z); the protection device (1) protects the membrane (3) from electromagnetic radiation of at least one radiation source (9) in the mounted state on the sensor (2); the protective device (1) has at least one passage (7), through which the medium can reach the membrane (3) in the state in which the protective device (1) is mounted on the sensor (2); in the state in which the protection device (1) is mounted on the sensor (2), electromagnetic radiation can propagate in the channel (7); the electromagnetic radiation propagating in the channel (7) reaches the membrane (3) only after at least one reflection at the wall of the channel, briefly the channel wall (71).)
1. A protection device (1) for a membrane (3) of a sensor (2); the sensor (2) determines a physical quantity transmitted by the medium acting on the membrane (3); the protection device (1) can be mounted on the sensor (2); the protection device (1) has a longitudinal axis (Z); the protective device (1) protects the membrane (3) from electromagnetic radiation of at least one radiation source (9) in the mounted state on the sensor (2); the protective device (1) has at least one channel (7), through which channel (7) the medium can reach the membrane (3) in the state in which the protective device (1) is mounted on the sensor (2); and in a state in which the protection device (1) is mounted on the sensor (2), the electromagnetic radiation is able to propagate in the channel (7); characterized in that the electromagnetic radiation propagating in the channel (7) reaches the membrane (3) only after at least one reflection on the wall of the channel, briefly channel wall (71).
2. The protection device (1) according to claim 1, wherein said channel (7) runs substantially v-shaped in at least one cross-sectional view of a section parallel to said longitudinal axis (Z).
3. The protection device (1) according to claim 1, wherein at least one channel (7) runs substantially s-shaped in at least one cross-sectional view of a section parallel to the longitudinal axis (Z).
4. The protection device (1) according to any one of claims 1 to 3, characterized in that the protection device (1) has a surface facing the membrane (3), referred to simply as membrane side (31), in the mounted state; the protective device (1) has a surface facing away from the membrane (3) in the mounted state, referred to as the medium side (41); and the quotient of the sum of the clear contours of the channels (7) on the membrane side (31) or the medium side (41) and the surface area of the membrane (7) is at least 0.25.
5. The protection device (1) according to any one of claims 1 to 4, wherein a channel wall (71), which is a wall inside the channel, has an average roughness of at least 5 microns; and electromagnetic radiation directionally incident on the roughened surface is reflected such that the directional specific gravity of the reflected radiation is less than 80%.
6. The protection device (1) according to any one of claims 1 to 5, characterized in that the protection device (1) is composed of at least two protection device parts (51, 52); the protective device parts (51, 52) are arranged one above the other perpendicular to the longitudinal axis (Z) in the mounted state of the protective device (1); and the protective device parts (51, 52) are connected in a material-fit manner.
7. The protection device (1) according to any one of claims 1 to 6, wherein a channel wall (71), which is a wall inside the channel, has a coating absorbing electromagnetic radiation; the electromagnetic radiation absorbing coating absorbs at least 10% of the incident intensity of the electromagnetic radiation, which means that the reflection intensity is reduced by at least 10% relative to the uncoated channel wall (71).
8. The protection device (1) according to any one of claims 1 to 7, characterized by a channel wall (71), which is a wall inside a channel, having an anti-adhesion coating, wherein particles present in the medium adsorb on the channel wall (71) less than 50% on the uncoated channel wall (71).
9. The protection device (1) according to any one of claims 1 to 8, characterized in that said protection device (1) is made of metal or metal alloy.
10. The protection device (1) according to any one of claims 1 to 8, characterized in that said protection device (1) is made of ceramic.
11. A sensor (2) for determining a physical quantity, which physical quantity is transmitted through a medium; the sensor (2) has a membrane (3), the medium acting on the membrane (3); characterized in that a protection device (1) according to any one of claims 1 to 10 is mounted on the sensor (2).
12. A sensor (2) according to claim 11, characterized in that the sensor (2) is a pressure sensor determining pressure; and a piezoelectric measuring element is arranged in the pressure sensor.
13. A sensor (2) according to claim 11, characterized in that the sensor (2) is arranged in a pressure chamber of an internal combustion engine.
14. A method for manufacturing a protection device (1) according to claim 9, characterized in that the protection device (1) is made by a selective laser melting technique or a laser metal deposition technique or similar, wherein metal powder is partially or completely melted by laser radiation.
Technical Field
The invention relates to a protective device for mounting on a sensor according to the preamble of the independent claim.
Background
The sensor determines a physical quantity and provides a sensor signal corresponding to the physical quantity under ideal conditions. For this purpose, a sensor element which is sensitive to a physical variable is arranged in the sensor. The sensor element is typically protected from certain external influences, such as dust and/or liquids and/or gases and/or electromagnetic radiation, by a protective layer (e.g. a membrane) of the sensor'. Such expressions and/or terms are to be understood as non-exclusive opposites. The membrane is typically made of metal or metal alloy or plastic. The medium is a carrier of a physical parameter and acts on the membrane.
The membrane is exposed to an external influence. External influences refer to temperature, pressure, etc.
The physical quantity is, for example, pressure. If the sensor determines the pressure, the gas or liquid is the carrier of the physical quantity and acts on the membrane. However, the sensor element of the pressure sensor also has a temperature dependency, which represents a disadvantageous effect on the sensor signal.
The thermal energy causing the temperature change is not only transferred by heat conduction through the medium, but also by convection by means of a thermal band, but also by thermal radiation such as electromagnetic radiation. In the following, the term electromagnetic radiation is also used as a synonym for thermal radiation.
When a flame is ignited near the film, the electromagnetic radiation on the film increases rapidly. If the flame is extinguished, the electromagnetic radiation on the film will decrease rapidly. If the electromagnetic radiation thus incident is partially or completely absorbed by the film, the temperature of the film will increase. The increase in temperature of the membrane is at least partially transmitted to the sensor element and thereby influences the determined sensor signal or damages the sensor element. This influence on the sensor signal can lead to an incorrect value being determined for the physical variable, which is no longer the temperature itself at a later time.
The rapidly occurring temperature changes of the material, for example of the membrane or of the sensor element, are also referred to as thermal shocks, and can also occur in other places where a medium burns, for example in the pressure chamber of an internal combustion engine. Internal combustion engines include four-stroke engines and two-stroke engines, such as Wankel engines, Otto engines, diesel engines, and the like. Thermal shock can also occur in other pressurized spaces, such as in gas turbines, jet engines, rocket engines, steam turbines and steamers or within similar structures. Hereinafter, the pressure chamber of the internal combustion engine and the above-described space inside which pressure is filled are collectively referred to as a pressure chamber. Unlike the almost constant ambient temperature, which changes slowly over time, the influence of thermal shocks on the sensor signal of the sensor mounted in the pressure chamber cannot be minimized or can only be insufficiently minimized within the framework of calibration.
Furthermore, if the temperature exceeds the material-dependent threshold of the film material, the film may be damaged by thermal shock. Repeated thermal shock can also lead to film aging and cause damage associated with film aging.
From EP2024710a1 a membrane protection device is known which is fastened to the front region of a sensor provided with a membrane in the front region and which can withstand temperatures of up to 500 ℃. In one embodiment, the membrane protection device has openings, (channels) through which a medium with the information to be measured can pass. The diameter of the channel is chosen such that no flame can pass through it, which means that the film protection is fire-proof.
The disadvantage here is that the electromagnetic radiation from the at least one radiation source on the medium side can act directly on the membrane through the channel, which can cause thermal shocks. This may affect the sensor signal and determine an erroneous value for the physical quantity. Depending on the intensity of the electromagnetic radiation, the electromagnetic radiation may cause damage to the membrane and/or the sensor element.
Disclosure of Invention
It is an object of the present invention to provide a protective device for a membrane of a sensor such that electromagnetic radiation propagating in a channel reaches the membrane only after at least one reflection at the wall of the channel, thereby reducing the intensity of the electromagnetic radiation incident on the membrane. A further object of the invention is to provide a protective device which enables a medium, which is the support for the physical variable to be determined, to act as unimpeded as possible on the membrane.
At least one object of the invention is achieved by the features of the independent claims. The present invention relates to a protective device for a membrane of a sensor; the sensor determines a physical parameter transmitted by the medium acting on the membrane; the protection device may be mounted on the sensor; the protective device has a longitudinal axis; the protective device protects the membrane from electromagnetic radiation of the at least one radiation source in the mounted state on the sensor; the protective device has at least one passage through which the medium can reach the membrane in the state in which the protective device is mounted on the sensor; and in a state in which the protection device is mounted on the sensor, electromagnetic radiation can propagate in the channel; wherein electromagnetic radiation propagating in the channel reaches the membrane only after at least one reflection on the walls of the channel (shortly called channel walls).
Thereby, the intensity of the electromagnetic radiation incident on the membrane will be reduced compared to a protective device having a channel in which the electromagnetic radiation can propagate from the radiation source to the membrane without reflection at the walls of the channel.
The propagation of electromagnetic radiation takes place linearly in space in the form of rays starting from the radiation source.
If electromagnetic radiation (radiation for short) is incident on the protective device, at least one reflection on the wall of the channel (channel wall for short) is required according to the invention in order to reach the membrane from the radiation source. If the radiation is incident on the channel wall, it will be partly absorbed, partly reflected and partly scattered, and re-rayed and linearly propagated from the channel wall.
Reflection of radiation refers to the directional reflection (gerichete reflection) of radiation on a surface, while scattering of radiation refers to the diffuse reflection of radiation on a surface. Absorption refers to the conversion of radiation into thermal energy at a surface, thereby providing thermal energy to the surface.
Thus, after the radiation is incident on the channel wall, the intensity of the radiation propagating in the channel may be reduced. This is due to absorption of a portion of the radiation at the channel walls. This is also due to the partial reflection and scattering of radiation in the following directions: that is, the radiation is emitted again from the feed-through (durchfur hung) in this direction on the side of the protective device facing away from the membrane (simply referred to as the media side), and therefore does not reach the membrane. This is known as backscattering or back reflection.
Only a small fraction of the radiation may be incident on the membrane after only one incidence on the channel walls. A larger portion of the radiation is incident on the channel walls multiple times, where the intensity decreases with each incidence due to the absorption described above. Backscatter and back reflection also reduce the intensity of radiation reaching the film. The radiation reaching the membrane is therefore many times smaller than the radiation reaching the membrane by the protective device according to the prior art.
It is also desirable that the medium should pass through the protection means as unhindered as possible in order to minimize the influence of the geometry of the protection means on the information to be determined. If the flow resistance of the channel is high, pressure variations due to the flow resistance of the medium through the channel act on the membrane with a delay. The flow resistance depends on the net profile of the channel and the length of the path that the medium will take through the channel. The net profile of a channel is the plane in which the channel is projected onto a plane. Therefore, there is a limit frequency for the pressure change, wherein pressure changes which occur more quickly than the inverse of the limit frequency can only be determined with insufficient accuracy over the course of time of the pressure.
Furthermore, the channel has a resonance frequency, since the combination of the protection device and the sensor represents a helmholtz resonator having at least one resonance frequency. The pressure variations occurring along the time scale in the range of the inverse resonance frequency cannot be accurately determined. The resonant frequency depends on the volume between the protection and the membrane and the net profile of the channel. The net profile of a channel is the plane in which the channel is projected onto a plane.
The protective device has a surface of the membrane facing the sensor in the mounted state, which surface is referred to as the membrane side. The side of the protective device facing away from the membrane is referred to as the media side. The through-hole passes from the medium side to the membrane side.
The protective device is designed such that the quotient of the sum of the clear contours of the channels on the membrane side or the medium side and the surface area of the membrane is at least 0.25. The resonant frequency and the limiting frequency are thereby increased and rapid pressure changes occurring, for example, in the internal combustion engine are determined without the influence of the resonant frequency.
Drawings
The present invention is described in exemplary detail below with reference to the attached figures. Wherein:
fig. 1 shows a sectional view of a preferred embodiment of the protective device with a sensor in the mounting section, wherein the sensor is not hatched for the sake of clarity;
fig. 2 shows a cross section through the protective device according to the embodiment shown in fig. 1 parallel to the longitudinal axis;
fig. 3 shows a view of the protection device according to fig. 1;
FIG. 4 shows a cross-sectional view of another embodiment of the protection device with a sensor in the mounting section, where the sensor is not hatched for clarity;
fig. 5 shows a cross section through the protective device according to the embodiment shown in fig. 4 parallel to the longitudinal axis;
fig. 6 shows a view of the protection device according to fig. 4.
Detailed Description
Fig. 1 shows a sectional view of a
The sensor 2 is formed along the longitudinal axis Z in a substantially rod-like manner. The sensor 2 is mounted in the mounting portion 4. Preferably, the sensor 2 is introduced into the mounting portion 4. The mounting portion 4 defines a chamber volume 11 which should be used for determining the physical parameter. In the chamber volume 11 there is a medium, which is a carrier of a physical parameter. On the end of the sensor 2 facing the chamber volume 11, the sensor 2 has a membrane 3 parallel to the first radial axis X and to the second radial axis Y. The longitudinal axis Z, the first radial axis X and the second radial axis Y form an orthogonal system. The first radial axis and the second radial axis form a radial plane XY. The medium acts on the membrane 3.
In one embodiment, the chamber volume is a chamber volume of a pressure chamber of an internal combustion engine.
In the following, a radial plane XY, which is expanded by the first radial axis X and the second radial axis Y, will be described optionally with a radius R and a polar angle W. The radius R, the polar angle W and the longitudinal axis Z form a cylindrical coordinate system.
In a preferred embodiment, the
The
The
In one embodiment, the
In another embodiment, the
In another embodiment, the
The membrane 3, the
At least one
According to the invention, the
There is no straight line connection through the
Fig. 2 shows a first preferred embodiment of the
The
Preferably, a plurality of
In a preferred embodiment, the
In another embodiment, the
In a preferred embodiment, the
Other manufacturing methods, such as laser metal deposition or direct metal deposition, can also be used by the person skilled in the art, in which case the metal powder is brought purposefully through a nozzle to a position and is melted on this position by a laser during transport.
In a particularly preferred embodiment,
Fig. 4 shows a further preferred embodiment of the
The
The
The tank bottom part 51, 52 has a
At least on the
In one embodiment, the
In one embodiment of the
In another embodiment of the
Of course, other arrangements of the
Of course, the person skilled in the art can also configure the
In a preferred embodiment, the sensor is a pressure sensor in which a piezoelectric measuring element is arranged. In the case of a pressure acting on the membrane, the membrane exerts a force on the piezoelectric measuring element, which generates a charge corresponding to the exerted force. This charge is converted by known electronic components and provided as a sensor signal.
List of reference numerals
1 protective device
2 sensor
3 film
4 mounting part
5 tank bottom
6 tank wall
7 channel
9 radiation source
31 film side
35 membrane side volume, membrane volume
Side of 41 Medium
45 chamber volume
51 tank bottom part
52 can bottom part
53 projection
55 intermediate volume
71 channel wall, wall of a channel
Angle of center A
Radius R
W polar angle
X first radial axis
Y second radial axis
Z longitudinal axis.
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