Liquid level detection device based on pressure difference and ultrasonic distance measurement

Abstract

A liquid level detection device based on pressure difference and ultrasonic distance measurement comprises a liquid measuring cavity, a fluid cavity, a pressure bearing mechanism, a cavity shell, an ultrasonic probe and an ultrasonic probe control module. The fluid cavity bears the pressure brought by the height of the liquid level of the measured liquid, and the local position of the liquid changes delta D due to the change delta H of the height H of the measured liquid. The ultrasonic probe is arranged in the fluid cavity, and the distance measurement of the position change delta D is realized under the control of the ultrasonic probe control module. The pressure bearing mechanism bears the pressure brought by the fluid cavity and provides the dependency relationship between delta H and delta D: delta D = f (delta H, T, G) on the premise that the volume V of fluid in the fluid cavity is not changed, T is the environment temperature, and G is the running state of the automobile. The pressure-bearing mechanism is designed around multiple factors of delta D, delta H, T and G and is deconstructed into the following three remarkable characteristics: 1, delta D is remarkably influenced by double factors of delta H and T; 2, the delta D is obviously influenced by double factors of delta H and G; and 3, the delta D is influenced by the combination of delta H, T and G.

Description

Technical Field

[0001] The utility model relates to an SCR system for treating exhaust gas of a commercial vehicle, in particular to a urea quality sensor for the SCR system, and more particularly to an ultrasonic urea liquid level detection device for the SCR system. Background Art

[0002] Regarding liquid level testing technology, the traditional method is to arrange the reed tubes in the direction of the liquid level height and form a circuit in series with the resistor. The circuit board is placed in a sealed protective tube isolated from the measured liquid. Outside the protective tube is a magnetic ring that can float in the measured liquid. The magnetic ring moves due to the rise and fall of the liquid level, thereby connecting the reed tubes at the corresponding positions of the magnetic rings. The circuit resistance values ​​of the reed tubes at different positions will be different after being connected, so they are used to display the liquid level height of the measured liquid.

[0003] Another commonly used technology is ultrasonic direct measurement of liquid level. The specific technical feature is to use the flight speed and flight time of sound waves to infer the height of the liquid. The flight speed can be obtained through a large number of experiments, and the flight time can be obtained through a dedicated flight time (FOT) chip. The liquid level height h is equal to the product of the speed v and the flight time t. The principle is very intuitive.

[0004] Reed tube technology has been tested by the market for decades. Its stability, reliability and liquid level accuracy requirements have been tested. However, the biggest problem is that it uses a large number of reed tubes, and the labor intensity and workload are high. The result of the two is that the cost is relatively high and the market competitiveness is declining year by year. The ultrasonic direct measurement of liquid level technology, when applied to the automotive urea level detection scene, faces the following technical problems: when the urea liquid on the reflective surface goes up and down the steep slope of the car and is accompanied by bumps, the measured liquid surface will tilt, oscillate and splash, causing the test signal to be unstable, attenuated, distorted, etc., resulting in inaccurate and abnormal measurement data, and frequent alarms in the vehicle system; the second technical difficulty is the bubble problem during the urea filling stage: the bubbles adhere to and cover the sound wave sending surface of the transducer for a long time, making it impossible to send and receive ultrasonic signals; the third technical difficulty is the high voltage problem: because the higher the liquid level, the greater the attenuation of the urea liquid to the sound energy, the more energy the transducer needs to inject, and the higher the driving voltage.

[0005] This utility model patented device proposes an indirect, non-contact ultrasonic measurement technology, which achieves stable test scene, high accuracy, low driving voltage, simple electronic and mechanical structure hardware, and simple system software processing of measurement data and strategy algorithms. Summary of the invention

[0006] A liquid level detection device based on pressure difference and ultrasonic distance measurement is characterized in that it includes a liquid measuring cavity, a fluid cavity, a pressure bearing mechanism, a cavity shell, an ultrasonic probe and an ultrasonic probe control module.

[0007] The fluid chamber is placed in the liquid measuring chamber near the bottom area to bear the pressure caused by the liquid level height.

[0008] The pressure-bearing mechanism is connected to the fluid cavity and bears the pressure change of the fluid cavity caused by the change of the liquid level of the liquid in the liquid measuring cavity.

[0009] The ultrasonic probe is partially or completely placed in the fluid cavity; ultrasonic waves are sent, transmitted and received through the fluid in the fluid cavity.

[0010] The ultrasonic probe control module controls the ultrasonic probe to implement ultrasonic distance measurement ΔD, and the distance change ΔD measured by the ultrasonic probe corresponds to the level change ΔH of the measured liquid.

[0011] The liquid level height change ΔH of the measured liquid in the measuring liquid chamber needs to pass through the fluid chamber to transmit the pressure to the pressure-bearing mechanism; the volume of the fluid in the fluid chamber will not be compressed or expanded due to the change ΔH in the liquid level height H, and the pressure difference ΔH is borne by the pressure-bearing mechanism.

[0012] The liquid volume V in the fluid cavity remains constant, and the local position of the liquid may change by ΔD due to a change ΔH in the height H of the measured liquid; the ultrasonic probe is placed in the fluid cavity and captures this position change ΔD under the control of the ultrasonic probe control module.

[0013] The pressure-bearing mechanism provides a dependency relationship between ΔH and ΔD without changing the volume V of the liquid in the fluid cavity, which can be expressed by a functional relationship: ΔD = f (ΔH, T, G), T is the ambient temperature, G is the vehicle operating state, and t is the real time; the function shows that the pressure-bearing mechanism is mainly designed around multiple factors of ΔH, T (t), and G (t). According to its different focuses, the pressure-bearing mechanism can be deconstructed and designed into the following three significant features:

[0014] 1. ΔD is significantly affected by ΔH and T, while the vehicle running state G is ignored;

[0015] 2. ΔD is significantly affected by ΔH and G, while the ambient temperature T is ignored;

[0016] 3. ΔD is jointly affected by ΔH, T and G.

[0017] The ultrasonic probe control module obtains the flight time tf corresponding to ΔD during the operation of the vehicle based on the TOF chip technology.

[0018] The ultrasonic probe control module includes the measured liquid level height H and the change ΔH of the liquid level height H in different application scenarios, the position change ΔD data of the local position of the liquid in the fluid cavity under different temperatures T and different road conditions G, ΔD corresponds to the flight time tf measured by the ultrasonic probe; thus tf corresponds to the characteristics or data of H, ΔH, T and G. The above characteristics or data are processed to realize tf to determine the reading of the measured liquid level height H.

[0019] The cavity shell provides a layout space S for the fluid cavity, the pressure-bearing mechanism and the ultrasonic probe; the layout space S needs to be isolated from the liquid in the liquid measuring cavity and sealed; the layout space S can be a single space or a combination of multiple spaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Attached Figure 1 :Level probe cross section

[0021] 1. Liquid measuring chamber 2. Fluid chamber 3. Pressure bearing mechanism 4. Chamber housing 5. Ultrasonic probe 6. Ultrasonic probe control module

[0022] Attached Figure 2 :Layout space S diagram

[0023] 2. Fluid chamber 3. Pressure bearing mechanism 5. Ultrasonic probe 21. Middle piece A 31. Middle piece B 32. Elastic body S. Layout space

[0024] Attached Figure 3 :Simplified structural cross-section

[0025] 1. Liquid measuring chamber 2, fluid chamber 5, ultrasonic probe 21, middleware AS, layout space

[0026] Attached Figure 4 : Cross-section of air cavity

[0027] 41. Joint 41a. Sealing ring A. 51. Sealing ring BT. Air cavity A. Local position of liquid. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present utility model will be described clearly and completely below in conjunction with the accompanying drawings.

[0029] As attached Figure 1 As shown, a liquid level detection device based on pressure difference and ultrasonic ranging includes a liquid measuring chamber 1, a fluid chamber 2, a pressure bearing mechanism 3, a chamber housing 4, an ultrasonic probe 5 and an ultrasonic probe control module 6.

[0030] As attached Figure 2As shown, the cavity shell 4 provides a layout space S for the fluid cavity 2, the pressure-bearing mechanism 3 and the ultrasonic probe 5; the layout space S, on the one hand, needs to provide a closed isolation space to isolate the liquid to be measured in the liquid measuring cavity 1 and the pressure transmission, and on the other hand, needs to provide a physical space and physical connection for the fluid cavity 2, the pressure-bearing mechanism 3 and the ultrasonic probe 5.

[0031] Specifically, the pressure transmission design between the fluid cavity 2, the pressure bearing mechanism 3, the ultrasonic probe 5 and the liquid measuring cavity 1 in the layout space S is as follows:

[0032] First, the pressure of the liquid measuring chamber 1 is generated by the change in the liquid level ΔH of the measured liquid. The pressure passes through the contact part between the fluid chamber 2 and the liquid measuring chamber 1 and the intermediate piece A21 of both sides to receive the liquid pressure and transmit the pressure to the liquid in the fluid chamber 2.

[0033] The intermediate member A21 may be a film with a sealing function, or a film combination structure with both a sealing function and an elastic function.

[0034] Secondly, the liquid in the fluid chamber 2 bears the pressure of the liquid measuring chamber 1, and the fluid pressure in the fluid chamber 2 is equal everywhere, and the pressure bearing mechanism 3 has a part in contact with the fluid in the fluid chamber 2, and the middle piece B31 between the two bears the pressure in the fluid, and the middle piece B31 transmits the pressure to the elastic body 32 with elastic deformation;

[0035] The elastic body 32 can be a spring with elastic tension or a gas with volume expansion or contraction.

[0036] As attached Figure 3 As shown, in particular, a very simple design is that one end of the fluid chamber 2 is in contact with the measured liquid in the liquid measuring chamber 1 and bears the pressure through the intermediate piece A21, and the other end of the fluid chamber 2 is connected to the atmosphere, then the pressure bearing mechanism 3 can be replaced by the intermediate piece A21.

[0037] Specifically, the sealed isolation design of the fluid chamber 2, the pressure bearing mechanism 3, the ultrasonic probe 5 and the liquid measuring chamber 1 in the layout space S is as follows:

[0038] At the front end of the layout space S, the liquid measuring chamber 1 and the fluid chamber 2 are sealed by a sealing middle piece A21;

[0039] As attached Figure 4 As shown, at the rear end of the layout space S, the cavity housing 4 provides a joint 41, and the joint 41 provides a sealing function, which can be a sealing ring A41a plus a sleeve 41b;

[0040] Preferably, one end of the connector 41 is connected to the air cavity T, and the other end of the connector 41 is connected to the sleeve 41b. The power cord of the ultrasound probe is placed in the hole of the connector 41 and the sleeve 41b needs to be connected to the atmosphere.

[0041] In particular, the ultrasonic probe 5 is mounted to the cavity housing 4 via a sealing ring B51, the front end of the ultrasonic transmitter is placed in the fluid of the fluid cavity 2, and the rear end thereof is isolated in the air cavity T by the sealing ring B51.

[0042] The ultrasonic probe 5 is partially or completely placed in the fluid cavity 2, and sends, transmits and receives ultrasonic waves through the fluid in the fluid cavity 2 to measure distance.

[0043] Preferably, ultrasonic ranging relies on the fluid volume V in the fluid chamber 2 to remain constant, so as to ensure the following:

[0044] First, a constant fluid volume V is convenient for controlling a position change ΔD in a fluid, ΔD corresponding to a change ΔH in the height H of the measured liquid;

[0045] Secondly, a local position of the liquid in the fluid chamber 2 is used to provide ΔD. Corresponding to the ultrasonic ranging technology, preferably, ΔD will be a position change, specifically, a mechanism is displaced ΔD in the fluid of the fluid chamber 2 .

[0046] Third, the constant fluid volume V is convenient for preventing gas substances, such as air, from penetrating into the fluid, which would affect the ranging of the ultrasonic probe.

[0047] Preferably, the ultrasonic probe 5 is placed in the fluid cavity 2 , aligned with the local position A of the liquid, and captures the displacement change ΔD under the control of the ultrasonic probe control module 6 .

[0048] The pressure-bearing mechanism 3 provides a dependency relationship between ΔH and ΔD without changing the liquid volume V in the fluid chamber 2, which can be expressed by a functional relationship: ΔD = f (ΔH, T, G), where T is the ambient temperature and G is the operating state of the vehicle.

[0049] The above function shows that the pressure-bearing mechanism 3 is mainly designed around multiple factors such as ΔH, T, and G. According to different focuses, the pressure-bearing mechanism 3 can be deconstructed and designed into the following three significant features:

[0050] ①, ΔD is significantly affected by ΔH and T, while G is ignored;

[0051] ②, ΔD is significantly affected by ΔH and G, while T is ignored;

[0052] ③. ΔD is jointly affected by ΔH, T and G.

[0053] The pressure-bearing mechanism 3 is connected to the atmosphere in the air cavity T, and is interconnected and interacts with the fluid cavity 2 through the middle piece B31, becoming the key to obtaining the liquid level H and ΔH; the above-mentioned characteristic requirements ①, ②, and ③ can be fully realized by using different existing technologies.

[0054] The ultrasonic probe control module 6 obtains the flight time tf corresponding to ΔD during the operation of the vehicle based on the TOF chip technology;

[0055] Specifically, the flight time can be completed using the TOF chip MS1022 or its upgraded version.

[0056] The ultrasonic probe control module 6 includes the liquid level H of the measured liquid and the change ΔH of the liquid level H in different application scenarios, and the flight time tf measured by the ultrasonic probe 5 under different temperatures T and different road conditions G.

[0057] The features or data of tf and its corresponding H, ΔH, T and G are cleaned, stored, refined and processed to form the functional relationship required to determine H or a single or multiple two-dimensional data table structures.

[0058] Based on the embodiments of the present utility model, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present utility model.

Claims

1. A liquid level detection device based on pressure difference and ultrasonic ranging, characterized in that: The invention comprises a liquid measuring chamber (1), a fluid chamber (2), a pressure bearing mechanism (3), a chamber housing (4), an ultrasonic probe (5) and an ultrasonic probe control module (6); the fluid chamber (2) is arranged near the bottom area of ​​the liquid measuring chamber (1) to bear the pressure caused by the height of the liquid level; the pressure bearing mechanism (3) is connected to the fluid chamber (2) to bear the pressure change of the fluid chamber (2) caused by the change of the liquid level of the liquid measuring chamber (1); the ultrasonic probe (5) is partially or completely arranged in the fluid chamber (2); ultrasonic waves are sent, transmitted and received through the fluid in the fluid chamber (2); the ultrasonic probe control module (6) controls the ultrasonic probe (5) to realize ultrasonic distance measurement ΔD, and the distance change ΔD measured by the ultrasonic probe corresponds to the liquid level change ΔH of the liquid in the liquid measuring chamber (1).

2. The liquid level detection device based on pressure difference and ultrasonic ranging according to claim 1 is characterized in that: The cavity housing (4) provides a layout space (S) for the fluid cavity (2), the pressure-bearing mechanism (3) and the ultrasonic probe (5); the layout space (S) needs to be isolated from the liquid of the measured liquid level and be sealed; the space (S) can be a single space or a combination of multiple spaces.

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