阅读说明：本技术 一种规避液体低温结晶的压力传递腔结构 (Pressure transmission cavity structure for avoiding liquid low-temperature crystallization ) 是由 陈小青 于 2021-09-17 设计创作，主要内容包括：一种规避液体低温结晶的压力传递腔结构,具体涉及汽车零部件领域中的SCR系统中的压力传感器。本结构包括压力传递腔液体入口喉道、压力传递腔空气喉道、压力传递腔A室、压力传递腔B室和应变压力腔,它们共同构建了压力传递腔。所述的压力传递腔液体入口喉道与压力传递腔A室相连通、压力传递腔A室与压力传递腔B室相连通、压力传递腔B室与压力传递腔空气喉道相连通以及压力传递腔空气喉道与应变压力腔相连通,本发明通过次第相互连通的压力传递腔结构设计,规避了液体直接进入压力传感器的应变压力腔内,避免因液体低温变相时体积增大产生的挤压力造成压力传感器应变片损坏,提高了压力传感器对低温的适应性能。(A pressure transmission cavity structure avoiding low-temperature crystallization of liquid specifically relates to a pressure sensor in an SCR system in the field of automobile parts. The structure comprises a liquid inlet throat of a pressure transfer cavity, an air throat of the pressure transfer cavity, a pressure transfer cavity A chamber, a pressure transfer cavity B chamber and a strain pressure cavity, which jointly construct the pressure transfer cavity. The invention avoids liquid from directly entering the strain pressure cavity of the pressure sensor through the structural design of the pressure transmission cavity which is communicated for the second time, avoids the damage of a strain gauge of the pressure sensor caused by extrusion force generated by volume increase when the liquid changes phase at low temperature, and improves the adaptability of the pressure sensor to low temperature.)

1. The invention relates to a pressure transmission cavity structure for avoiding liquid low-temperature crystallization, which is characterized in that: the device comprises a liquid inlet throat (1) of a pressure transfer cavity, an air throat (2) of the pressure transfer cavity, a pressure transfer cavity A chamber (3), a pressure transfer cavity B chamber (4) and a strain pressure cavity (5); the liquid inlet throat (1) of the pressure transfer cavity is communicated with the A chamber (3) of the pressure transfer cavity, the A chamber (3) of the pressure transfer cavity is communicated with the B chamber (4) of the pressure transfer cavity, the B chamber (4) of the pressure transfer cavity is communicated with the air throat (2) of the pressure transfer cavity, the air throat (2) of the pressure transfer cavity is communicated with the strain pressure cavity (5), and the pressure transfer cavity is constructed by the two communicated channels.

2. The pressure transmission cavity structure for avoiding the low-temperature crystallization of the liquid as claimed in claim 1, wherein: the front end of the pressure transmission cavity is provided with a liquid inlet throat (1) of the pressure transmission cavity, the liquid inlet throat (1) of the pressure transmission cavity is a channel with a cylindrical geometric structure, the ratio of the length to the diameter of the channel is larger than 2, the diameter of the channel is between 1.0 and 3.0mm, and the central axis of the channel is in the same direction as and opposite to the direction of gravitational attraction in the liquid inlet direction and is kept within the range of +/-45 degrees of included angle.

3. The pressure transmission cavity structure for avoiding the low-temperature crystallization of the liquid as claimed in claim 1, wherein: the pressure transfer cavity A chamber (3) is next to the pressure transfer cavity liquid inlet throat (1), the pressure transfer cavity B chamber (4) is next to the pressure transfer cavity A chamber, the pressure transfer cavity A chamber (3) is a channel with a cylindrical geometric structure, the diameter of the channel is D1, the volume of the channel is V1, the pressure transfer cavity B chamber is also a channel with a cylindrical geometric structure, the diameter of the channel is D2, the volume of the channel is V2, D1 is larger than D2, and V1 is larger than V2.

4. A pressure transmission cavity structure avoiding liquid low-temperature crystallization according to claim 1 or claim 3, characterized in that: the channel volume of the pressure transmission cavity A chamber (3) is V1, the channel volume of the pressure transmission cavity B chamber (4) is V2, and the quantity relationship of V1 and V2 satisfies the following equation:

V1 =α（k*（V2+V3+v2））- v1

V2 =（V3+v2）/α

wherein the content of the first and second substances,

v3 is the pressure strain chamber volume,

v1 is the channel volume of the pressure transfer chamber liquid inlet throat,

v2 is the channel volume of the pressure transfer chamber air throat,

k is the ratio of the maximum pressure possible for the liquid to be measured to the atmospheric pressure,

alpha is the regulating coefficient of the liquid level height of the liquid in the pressure transmission cavity, and the value is between 0.1 and 1.0.

5. The pressure transmission cavity structure for avoiding the low-temperature crystallization of the liquid as claimed in claim 1, wherein: the pressure transfer cavity air throat (2) is a cylindrical small hole after the pressure transfer cavity B chamber (4) is followed, the diameter of the pressure transfer cavity air throat is less than 1.5mm, and the ratio of the length to the diameter of the channel is more than 3; the air throat (2) of the pressure transfer cavity projects downwards along the channel axis of the air throat and projects upwards along the channel axis of the liquid inlet throat of the pressure transfer cavity, and the projection surfaces of the two do not have intersection at the inlet of the air throat of the pressure transfer cavity.

6. The pressure transmission cavity structure for avoiding the low-temperature crystallization of the liquid as claimed in claim 1, wherein: the strain pressure cavity is arranged behind the air throat (2) of the pressure transmission cavity, and is characterized in that: the geometry of the strain pressure chamber is a disk-like structure with a diameter equal to the area of the bottom of the pressure strain substrate, taking the size of a commercial bridge, and the thickness of the disk is between 0.15 and 0.25 mm.

7. The pressure transmission cavity structure for avoiding the low-temperature crystallization of the liquid as claimed in claim 1, wherein: when the cavity works, the inner surfaces of the air throat (2) of the pressure transmission cavity and the strain pressure cavity (5) are not allowed to contact with the liquid to be detected, and special surface treatment is needed to realize the hydrophobicity or the liquid to be detected; the inner surfaces of the liquid inlet throat (1) of the pressure transmission cavity, the chamber A (3) of the pressure transmission cavity and the chamber B (4) of the pressure transmission cavity need to be contacted with the liquid to be detected, and special surface treatment needs to be carried out, so that the hydrophilicity or the liquid affinity to the liquid to be detected are realized.

Technical Field

The invention relates to the technical field of automobile parts, in particular to an SCR (selective catalytic reduction) system of a commercial vehicle, and more particularly relates to a pressure sensor in the SCR system.

Background

At present, the global treatment method of harmful NOx (nitrogen monoxide and nitrogen dioxide) in automobile exhaust adopts a selective catalytic reduction system called SCR technology. The specific principle is that urea solution is sprayed into mist, then the mist urea particles and NOx particles in tail gas are fully mixed, and harmful NOx is decomposed into N2 and water under the action of a catalyst at a certain temperature, wherein the N2 and the water are harmless substances in the nature. The urea solution, before being atomized, is subjected to a series of physical treatments consisting of pumping the urea liquid out of a storage tank, building up a pressure in a line in front of the nozzle, and finally spraying the atomized urea through the nozzle.

The physical treatment process requires precise electromagnetic control, which inevitably involves monitoring the pressure in the pipeline, thus requiring the use of pressure sensor devices.

Since the urea liquid changes phase at low temperature (around-9 deg.c) to become solid crystal particles. However, the temperature is usually below-30 ℃ in winter, when the commercial vehicle stops working and is exposed to the field, the residual liquid in the pressure cavity of the pressure sensor can generate crystals, and the volume of the crystals is increased compared with the volume of the liquid in the crystal growth process. At a fixed volume, this volume increase process can damage the pressure strain gage, the most important component of the pressure sensor.

Disclosure of Invention

The invention mainly solves the technical problem of providing a structure which avoids the situation that liquid directly enters a strain pressure cavity of a pressure sensor and directly presses a pressure strain gauge, thereby protecting the pressure strain gauge from being possibly damaged due to solid-state phase change of the liquid at low temperature.

In order to achieve the purpose, the invention is realized by adopting the following specific method:

the utility model provides a pressure transmission cavity structure of evading liquid low temperature crystallization which characterized by: the device comprises a pressure transfer cavity liquid inlet throat 1, a pressure transfer cavity air throat 2, a pressure transfer cavity A chamber 3, a pressure transfer cavity B chamber 4 and a strain pressure cavity 5 which jointly construct a pressure transfer cavity.

The pressure transmission cavity liquid inlet throat 1 is communicated with a pressure transmission cavity A chamber 3, the pressure transmission cavity A chamber 3 is communicated with a pressure transmission cavity B chamber 4, the pressure transmission cavity B chamber 4 is communicated with a pressure transmission cavity air throat 2, the pressure transmission cavity air throat 2 is communicated with a strain pressure cavity 5, and the pressure transmission cavities which are communicated with each other at this time form a pressure transmission cavity of the pressure sensor.

The liquid inlet throat 1 of the pressure transmission cavity is a pressure transmission inlet of the pressure transmission cavity, an opening a of the throat is positioned in the liquid to be detected, and the liquid can enter the liquid inlet throat 1 of the pressure transmission cavity due to pressure to play a role in introducing the liquid pressure.

Preferably, the pressure transfer chamber liquid inlet throat 1 is a cylindrical geometry channel with a channel length to diameter ratio greater than 2 and a channel diameter between 1.0 and 3.0 mm.

Preferably, the channel opening direction of the pressure transfer chamber liquid inlet throat 1 is maintained within +/-45 degrees of inclination from the direction of gravity. This angle of inclination is to ensure that air in the pressure transfer chamber will not escape due to buoyancy if it forms bubbles in the liquid.

The pressure transmission cavity A chamber 3 is closely behind the liquid inlet throat 1 of the pressure transmission cavity and is used for connecting the pressure of the liquid inlet throat 1 of the pressure transmission cavity. When the pressure of the measured liquid is proper, the liquid enters the pressure transmission cavity A chamber 3 through the liquid inlet throat 1 of the pressure transmission cavity.

Preferably, the pressure transmission chamber a 3 is a channel with a cylindrical geometry, and the volume of the channel needs to be large enough, which can be measured by the following calculation formula. Assuming that the volume of the pressure transfer cavity A is V1, the volume of the pressure transfer cavity B connected at the back is V2, the volume of the liquid inlet throat 1 of the pressure transfer cavity is V1, the volume of the air throat 2 of the pressure transfer cavity is V2, and the volume of the strain pressure cavity 5 is V3, the following design equation about the volume can be obtained:

V1 =α（k*（V2+V3+v2））- v1

wherein k is the ratio of the maximum pressure of the measured liquid to the atmospheric pressure, and can be regarded as a fixed value. Alpha is the adjustment coefficient of the height of the liquid level in the pressure transmission cavity, the value of alpha is larger than 1 and the larger the value is, the lower the height of the liquid entering the pressure transmission cavity A chamber 3 is.

The pressure transfer chamber B-chamber 4 follows the pressure transfer chamber a-chamber 3 and serves to connect the pressure of the pressure transfer chamber a-chamber 3. When the measured liquid pressure is proper, the liquid passes through the pressure transmission cavity A chamber 3 and enters the pressure transmission cavity B chamber 4.

Preferably, the pressure transfer chamber B-chamber 4 is a channel of cylindrical geometry, the volume of which needs to be designed appropriately to ensure that no liquid enters the pressure transfer chamber air throat 2, and the volume of which can be designed by the following volume design equation:

v2 = (V3 + V2)/α, α is the same as above, and is an adjustment coefficient of the height of the liquid level in the pressure transfer chamber, and the smaller the value of α is less than 1, the higher the height of the liquid entering the pressure transfer chamber B chamber is.

The final value of alpha is influenced by factors such as the overall dimension of the pressure sensor, the dimensions of all parts forming the pressure transmission cavity, the assembly structure among all parts, the required installation position of the pressure sensor, the assembly specification and the like.

Preferably, α ranges from 0.1 to 1.0.

The pressure transfer chamber air throat 2 follows the pressure transfer chamber B chamber 4 and serves to connect the pressure of the pressure transfer chamber B chamber 4. When the measured liquid pressure reaches the designed maximum value, no liquid is allowed to enter the pressure transmission cavity air throat 2.

Preferably, the pressure transfer chamber air throat 2 is a cylindrical orifice with a diameter less than 1.5mm and a channel length to diameter ratio greater than 3.

Preferably, the pressure transfer chamber air throat 2 projects downwardly along its channel axis and the pressure transfer chamber liquid inlet throat 1 projects upwardly along its channel axis, the two projected surfaces not intersecting at the inlet of the pressure transfer chamber air throat 2.

The strain pressure cavity 5 is located behind the air throat 2 of the pressure transfer cavity, and on one hand, the strain pressure cavity is used for communicating and receiving the gas pressure of the air throat 2 of the pressure transfer cavity and providing the geometric space and area requirements needed by the pressure strain gauge b of the pressure sensor. Commercially available pressure sensor pressure strain bridges are available on the market, which typically use circular disks, with a diameter of about 9.50 mm.

Preferably, the geometry of the strain pressure chamber (5) is a disc-like structure with a diameter equal to the area of the bottom of the pressure strain gauge, taking the diameter of a commercially available bridge substrate, the thickness of the disc is between 0.15 and 0.25 mm.

The inner surfaces of the pressure transmission cavity liquid inlet 1, the pressure transmission cavity A chamber 3 and the chamber throat pressure transmission cavity B chamber 4 are in contact with the measured liquid during working and possibly in contact with air during non-working or pressure releasing conditions.

Preferably, the inner surface of the chamber contacting with the liquid is subjected to a special surface treatment to achieve the hydrophilic property or the liquid-affinity property.

Preferably, the inner surface of the chamber body not in contact with the liquid is subjected to a special surface treatment to impart hydrophobic or liquid repellent properties to the surface.

Description of the drawings:

FIG. 1: structure of pressure transmission chamber

1: pressure transfer chamber liquid inlet throat 2: pressure transfer chamber air throat 3: pressure transfer chamber A chamber

4: pressure transmission chamber B chamber 5: strain pressure chamber a: pressure transfer chamber liquid inlet throat opening b: pressure strain gauge c is the projection line of the air throat of the pressure transmission cavity and the liquid inlet throat of the pressure transmission cavity in two directions

FIG. 2: explosion diagram of part

11: bridge fixing ring 12: strain bridge 12 a: ceramic ring 12 b: the circuit 13: o-ring one 14: pressure transmission chamber upper screw 15: and an O-shaped ring II 16: pressure transmission chamber housing 17: o-shaped ring III

FIG. 3: assembly drawing

d: the first thread e: a second thread f: a third thread G: pressure transfer chamber housing interior platform I: pressure transfer chamber upper portion screw platform H: and a second pressure transmission cavity shell internal platform J: pressure transmission cavity shell internal platform III

Detailed Description

Example (b):

the invention discloses a pressure sensor of a pressure transmission cavity structure for avoiding low-temperature crystallization of liquid, and the core idea of the invention is to realize the pressure transmission cavity structure shown in figure 1. As shown in fig. 2 and 3, the strain pressure chamber 5 of the pressure transmission chamber is realized by the upper screw 14 of the pressure transmission chamber, the strain bridge 12 and the pressure transmission chamber housing 16. Specifically, the lower end of the ceramic ring 12a of the strain bridge abuts against the first land G of the pressure transfer chamber housing 16, and the first land I of the upper screw 14 of the pressure transfer chamber abuts against the second land H of the pressure transfer chamber housing 16. The pressure transfer chamber upper screw 14 and the pressure transfer chamber housing 16 together define the pressure transfer chamber a-chamber 3, and specifically, the lowermost end of the pressure transfer chamber upper screw 14 and the land three J of the pressure transfer chamber housing 16 form the pressure transfer chamber a-chamber 3. The upper screw 14 of the pressure transmission cavity is processed to form a B chamber 4 of the pressure transmission cavity, and the liquid inlet throat 1 and the gas throat 2 are respectively processed by a shell 16 of the pressure transmission cavity and the upper screw 14 of the pressure transmission cavity. The first O-ring 13 and the second O-ring 15 realize the sealing of the pressure transmission cavity. The strain bridge 12 is fixed in a threaded three-f connection mode, and the threaded two-e connection mode is used for connecting and fastening a screw rod on the upper portion of the pressure transmission cavity and the shell of the pressure transmission cavity. The connection of the pressure sensor to the outside can also be realized by means of a screw-on connection.