Air flow measuring device for engine test bench

Abstract

The utility model relates to an air flow measuring device for an engine test bench, and relates to the field of engine bench test measuring devices. The device comprises a measuring chamber, a hot film type air flow sensor arranged in the measuring chamber, a signal conditioning circuit electrically connected with the hot film type air flow sensor, and a secondary instrument and / or a rack module electrically connected with the signal conditioning circuit. According to the utility model, the cost is reduced, the calibration steps are reduced, and the operation difficulty is reduced.

Description

Technical Field

[0001] The utility model relates to the field of engine bench test measurement devices, in particular to an air flow measurement device for an engine test bench. Background Art

[0002] At present, there are two main types of air flow meters used in electronically controlled engines: one is a volumetric air flow meter that directly measures the air volume, such as vane type, Karman vortex type, and core type air flow meter. The other is a mass air flow meter that directly measures the air mass flow, such as hot wire type and hot film type air flow meter. Since the engine fuel injection amount is determined by the air mass flow, the volumetric air flow meter does not have the high measurement accuracy of the mass air flow meter.

[0003] During the engine bench test, the air flow measurement is usually carried out by vortex air flow meter and hot film air flow meter. The former is a volumetric air flow meter, and the latter is a mass air flow meter. As mentioned above, hot film air flow meter has the advantages of high measurement accuracy and fast response speed, so it is widely used by engine manufacturers. However, bench hot film air flow meter is expensive, so the test cost is high. In addition, when the key component diaphragm is polluted by air, the measurement accuracy is reduced. The flow meter calibration procedure is complicated and the operation is difficult. When the key component diaphragm is damaged, it cannot be replaced and can only be scrapped. Utility Model Content

[0004] The utility model aims to provide an air flow measurement device for an engine test bench, so as to reduce costs, calibration steps and operation difficulty.

[0005] In order to achieve the above-mentioned purpose, the technical solution of the utility model provides an air flow measurement device for an engine test bench, including a measuring chamber, a hot film air flow sensor arranged in the measuring chamber, a signal conditioning circuit electrically connected to the hot film air flow sensor, and a secondary instrument and / or bench module electrically connected to the signal conditioning circuit.

[0006] Preferably, the hot film air flow sensor is completely or partially placed in the inner cavity of the measuring chamber, and its bottom is located on the center line of the measuring chamber pipeline.

[0007] Preferably, the signal conditioning circuit is provided with a frequency input FI port for electrically connecting the hot film air flow sensor.

[0008] Preferably, the signal conditioning circuit is provided with a communication output RS485 port for electrically connecting to the secondary instrument.

[0009] Preferably, the signal conditioning circuit is provided with a current output AO port for electrically connecting to the rack module.

[0010] Preferably, the signal conditioning circuit is provided with a data storage device for storing data on the correspondence between the frequency signal of the hot film air flow sensor and the air mass flow.

[0011] Compared with the commonly used hot film bench air flow meter in China, such as ABB brand hot film air flow meter, the utility model has the following advantages:

[0012] 1. Lower cost. Hot film air flow sensors are mass-produced, with a stable supply, low average cost, easy-to-design signal conditioning circuits, and low manufacturing costs. The achievable cost is about 1 / 20 of that of ABB air flow meters.

[0013] 2. Easier to replace. The hot film air flow sensor and the measuring cavity are designed to be plug-in connected. After long-term use, the hot film air flow sensor is easily contaminated by air, which affects the measurement accuracy. The sensor can be directly updated and put into use after calibration.

[0014] 3. Correction is more convenient. The secondary instrument of this device provides a parameter setting interface, which can be manually input to store the relationship data between the frequency and air flow of the hot film air flow sensor into the data storage in the signal conditioning circuit. The more signal frequency-flow relationship points stored during calibration, the closer the output flow signal is to the standard value. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of an air flow measurement device for an engine test bench according to the utility model;

[0016] Figure 2 This is a schematic structural diagram of an air flow measurement device for an engine test bench according to the utility model;

[0017] Figure 3 This is a circuit diagram of a frequency input FI port circuit in an air flow measurement device for an engine test bench of the utility model;

[0018] Figure 4 This is a circuit diagram of a main control CPU circuit in an air flow measurement device for an engine test bench of the utility model;

[0019] Figure 5 The utility model is a circuit diagram of a data storage circuit in an air flow measurement device for an engine test bench;

[0020] Figure 6 The utility model discloses a circuit diagram of a current output AO port circuit in an air flow measurement device for an engine test bench.

[0021] Figure numerals: 1. Measuring chamber; 2. Hot film air flow sensor; 3. Secondary instrument; 4. Signal conditioning circuit; 5. Frequency input FI port; 6. Communication output RS485 port; 7. Current output AO port; 8. Data storage device; 9. Test bench module. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0023] The utility model embodiment discloses an air flow measurement device for an engine test bench. The utility model integrates a hot film air flow sensor 2, a measuring chamber 1, a signal conditioning circuit 4, and a secondary instrument 3 and applies them to the test bench. The whole is used as a self-made bench air flow meter, and the test cost is low, the sensor is easy to replace, the air flow data correction is more convenient, and the measurement accuracy is high.

[0024] like Figure 2 As shown, an air flow measurement device for engine bench test includes a hot film air flow sensor 2, a measuring chamber 1, a signal conditioning circuit 4, and a secondary instrument 3, wherein the hot film air flow sensor 2 is partially placed in the inner cavity of the measuring chamber 1, and its bottom is located on the center line of the pipeline of the measuring chamber 1. The hot film air flow sensor 2 obtains the air flow signal frequency, and the signal conditioning circuit 4 is respectively connected to the data channel of the bench module 9 and the secondary instrument 3.

[0025] The signal conditioning circuit 4 includes a frequency input FI port 5, a current output AO port 7, a communication output RS485 port 6, and a data storage device 8 for the relationship between frequency and flow. The frequency input FI port 5 is connected to the hot film air flow sensor 2, and the communication output RS485 port 6 is connected to the secondary instrument 3, so as to measure the air consumption of the engine during the bench test. The current output AO port 7 of the signal conditioning circuit 4 is connected to the bench module 9, and the air mass flow signal is input into the bench module 9 in the form of (4-20) mA current output. The bench module 9 communicates with the bench software through the module driver, so as to facilitate the real-time display of the engine air mass flow.

[0026] When air flows through the measuring chamber 1, the hot film air flow sensor 2 outputs the corresponding frequency signal to the frequency input FI port 5 of the signal conditioning circuit 4 in real time. The frequency signal is processed by the signal conditioning circuit 4 and converted into a mass flow signal, and then synchronously output to the communication output RS485 port 6 and the current output AO port 7 of the signal conditioning circuit 4. After the secondary instrument 3 receives the mass flow signal of the communication output RS485 port 6 of the signal conditioning circuit 4, the real-time air mass flow data is displayed on the instrument LCD screen. After the bench module 9 receives the (4-20) mA current output by the current output AO port 7 of the signal conditioning circuit 4, it is converted into the corresponding air mass flow data and displayed in the bench software of the bench module 9. The bench software refers to the engine bench test software, which is used for communication and control with external instruments and equipment, bench equipment, etc., parameter setting, etc., and can display relevant channel data. For example: Assuming that the air flow meter of the utility model has a range of 0-1000kg / h after being calibrated by a standard flow meter, the linear current range (4-20)mA output by its current output AO port 7 corresponds to the air quality range 0-1000kg / h. The bench software pre-configures the bench module 9 channel used to receive the current signal to also be (4-20)mA corresponding to 0-1000kg / h. In this way, when the bench module 9 receives the corresponding current signal, the corresponding air mass flow value can be displayed on the software channel.

[0027] The data storage device 8 in the signal conditioning circuit 4 is used to store the corresponding relationship data between the frequency signal of the hot film air flow sensor 2 and the air mass flow rate. These data are calibrated by the standard air flow meter of the municipal measurement unit before the device is used. The more frequency-air mass flow data points stored in the data storage device 8 in the signal conditioning circuit 4, the closer the accuracy of the air mass flow signal output by the signal conditioning circuit 4 is to the accuracy of the standard air flow meter, ensuring that the air mass flow accuracy requirements measured by the engine on the test bench are met.

[0028] Among them, FI: Frequency Input frequency input; AO: Analog Output analog output; AI: Analog Input analog input.

[0029] The utility model also provides a signal conditioning circuit diagram, which includes:

[0030] 1. Frequency input FI port circuit

[0031] Description: Reference Figure 3Since the vehicle flow meter sensor used is a passive signal output, R22 is used as a pull-up resistor for pull-up, and the signal is input into the LM193 comparator after filtering through a 47PF capacitor. The circuit uses Z3 for voltage limiting and R28 for current limiting. In order to obtain a clean square wave, DAC_OUT1 is used to set a threshold for the input voltage. For example, when DAC_OUT1 is 1.5V, a voltage below 1.5V is a low level, and a voltage above 1.5V is a high level. This can remove input interference.

[0032] 2. Main control CPU circuit

[0033] Description: Reference Figure 4 The main control CPU uses a 32-bit RAM chip STM32F107. The above figure is the minimum system of this CPU chip. The CPU compares the real-time collected frequency with the standard value to obtain the real-time air mass flow value, and then uses the CPU's DAC pin to output a voltage of 0.4 to 2V according to the proportional relationship. The peripheral V / I circuit is used to output a 4-20mA industrial standard signal for the bench module 9 to collect, and the product provides an RS485 communication interface.

[0034] 3. Data storage circuit

[0035] Description: Reference Figure 5 ,Data storage uses AT24C128 EEPROM memory to store calibration and configuration data.

[0036] 4. Current output AO port circuit

[0037] Description: Reference Figure 6 , the current output circuit uses the TXR111 integrated circuit, which is stable and small in size. The SET pin can be used to match the input voltage ratio. After using a 1K resistor, the air mass flow signal current output Iout = VIN / 1000*10.

[0038] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An air flow measurement device for an engine test bench, characterized in that: The invention comprises a measuring chamber (1), a hot film air flow sensor (2) arranged in the measuring chamber (1), a signal conditioning circuit (4) electrically connected to the hot film air flow sensor (2), and a secondary instrument (3) and / or a bench module (9) electrically connected to the signal conditioning circuit (4).

2. The air flow measurement device for an engine test bench according to claim 1, characterized in that: The hot film air flow sensor (2) is completely or partially placed in the inner cavity of the measuring chamber (1), and its bottom is located on the center line of the pipeline of the measuring chamber (1).

3. The air flow measurement device for an engine test bench according to claim 1, characterized in that: The signal conditioning circuit (4) is provided with a frequency input FI port (5) for electrically connecting to the hot film air flow sensor (2).

4. The air flow measurement device for an engine test bench according to claim 1, characterized in that: The signal conditioning circuit (4) is provided with a communication output RS485 port (6) for electrically connecting to the secondary instrument (3).

5. The air flow measurement device for an engine test bench according to claim 1, characterized in that: The signal conditioning circuit (4) is provided with a current output AO port (7) for electrically connecting to the rack module (9).

6. The air flow measurement device for an engine test bench according to claim 1, characterized in that: The signal conditioning circuit (4) is provided with a data storage device (8) for storing data on the corresponding relationship between the frequency signal of the hot film air flow sensor (2) and the air mass flow.

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