Brake fluid level signal recognition circuit structure with fault diagnosis

Abstract

This utility model discloses a brake fluid level signal recognition circuit structure with fault diagnosis. It includes a fluid level signal recognition module M1 and a fluid level sensor circuit module M2. In the fluid level signal recognition module M1, the power supply V3, diode D1, and resistor R14 connected in series are connected in parallel with the capacitor C5 and resistor R15 connected in series. Resistor R13 is connected in parallel with capacitor C5. A lead between capacitor C5 and resistor R15 serves as the output terminal, connected to the external power supply voltage via diode D1. A lead between resistors R14 and R15 is connected to the fluid level sensor circuit module M2, which includes a fluid level switch SW1. In this utility model, the fluid level signal recognition module detects the potential changes in the fluid level sensor circuit module in real time to determine if there is a fluid leak. It also integrates fault diagnosis for its own internal modules, including disconnection, signal short circuit to ground, and power supply short circuit. These diagnoses improve the safety and reliability of vehicle braking.

Description

Technical Field

[0001] This utility model belongs to the field of passenger vehicle sensor circuit design, specifically relating to a brake fluid level signal recognition circuit structure with fault diagnosis. Background Technology

[0002] Brake fluid level sensors are commonly used in vehicles to monitor the brake fluid level and issue an alarm when the level is too low, which is crucial for driving safety. The brake fluid level sensor operates on the principle of a normally closed electronic alarm. When the fluid level is normal, the reed in the reed switch is attracted by a magnet, closing the circuit and extinguishing the alarm light. When the fluid level drops, the float moves the magnet down, opening the reed and illuminating the alarm light. However, with increasing demands for braking safety in vehicles, existing brake fluid level sensors and detection circuits lack self-diagnostic capabilities, such as diagnosing short circuits and open circuits in the sensor, thus failing to meet vehicle functional safety requirements. Utility Model Content

[0003] To address the problems existing in the background technology, this utility model proposes a brake fluid level signal identification circuit structure with fault diagnosis.

[0004] The technical solution of this utility model is as follows:

[0005] This utility model circuit comprises two parts: a liquid level signal recognition module M1 and a liquid level sensor circuit module M2. The liquid level signal recognition module M1 includes a power supply V3, a diode D1, resistors R13 to R15, a capacitor C5, and a diode D2. The power supply V3, diode D1, and resistor R14 are connected in series, as are the capacitor C5 and resistor R15. The entire series connection of the power supply V3, diode D1, and resistor R14 and the entire series connection of the capacitor C5 and resistor R15 are connected in parallel. Resistor R13 is connected in parallel with capacitor C5. The lead between capacitor C5 and resistor R15 serves as the output terminal of the braking liquid level signal recognition circuit and is simultaneously connected to an external power supply voltage via diode D1. The lead between resistors R14 and R15 is connected to one end of the liquid level sensor circuit module M2, which has a liquid level switch SW1.

[0006] The positive terminal of the power supply V3 is connected to the anode of diode D1, the cathode of diode D1 is connected to resistor R14, and the negative terminal of the power supply V3 is grounded.

[0007] The liquid level sensor circuit module M2 includes a liquid level switch SW1, a resistor R17, and a resistor R16. The liquid level switch SW1 and the resistor R16 are connected in parallel and then connected in series between the resistor R17 and ground. The other end of the resistor R17 is connected between the resistor R14 and the resistor R15 of the liquid level signal recognition module M1.

[0008] It also includes a microcontroller unit (MCU), and the output of the brake fluid level signal recognition circuit is connected to the ADC analog-to-digital converter port MCU_AD_BFLI of the microcontroller unit MCU.

[0009] The liquid level switch SW1 changes synchronously with the liquid level. When the liquid level is normal, the liquid level switch SW1 is closed; when the liquid level drops below the alarm line, the SW1 switch is open.

[0010] The working process of this utility model circuit is as follows: the liquid level signal recognition module M1 detects the potential change in the liquid level sensor circuit module M2 in real time and distinguishes the following working conditions: 1- normal liquid level, 2- abnormal liquid level, 3- short circuit to ground of liquid level signal, 4- short circuit to power supply of liquid level signal, 5- liquid level signal is not connected.

[0011] Specifically, the voltage value U (MCU_AD_BFLI) is received in real time through the ADC analog-to-digital converter port of the microcontroller unit (MCU) and then the following judgment is made:

[0012] When the liquid level switch SW1 in the liquid level sensor is closed, the voltage value U (MCU_AD_BFLI) is U(R17_2)*(R13) / (R13+R15), and U(R17_2)=(V3-VD)* ((R17) / / (R15+R13)) / ((R17) / / (R15+R13)+R14), which is the following formula, then the liquid level is normal.

[0013] U(R17_2)=

[0014] When the liquid level switch SW1 in the liquid level sensor is open, the voltage value U (MCU_AD_BFLI) is 0V, and U(R17_2)=(V3-VD)* ((R17+R16) / / (R15+R13)) / (((R17+R16) / / (R15+R13))+R14)), which is expanded as follows, then the liquid level is abnormal.

[0015] U(R17_2)=

[0016] When the voltage value U (MCU_AD_BFLI) is 0V, the liquid level signal is short-circuited to ground.

[0017] When the voltage value U (MCU_AD_BFLI) is 3.3V plus 0.7V from the constant voltage output source inside the controller, the liquid level signal is short-circuited to the power supply.

[0018] When the voltage value U (MCU_AD_BFLI) is (V3-VD)*(R13 / (R14+R15+R13)), the liquid level signal is not connected.

[0019] In all three cases, a fault injection operation is performed on terminal 2 of resistor R17 in the circuit diagram. The level switch SW1 can be closed or closed.

[0020] Wherein, V3 represents the constant voltage output source inside the controller, with an output voltage of 3.3V, VD represents the forward voltage drop of diode D1 of 0.7V, U(R17_2) represents the voltage at pin 2 of resistor R17, and R13~R17 represent the resistance values ​​of the corresponding resistors R13~R15.

[0021] The circuit in this invention is designed within the controller, which contains an external 12V to 3.3V vehicle power supply module. The controller's internal constant voltage output source can also be an external 3.3V power supply.

[0022] The beneficial effects of this utility model are:

[0023] In this utility model circuit, the liquid level signal recognition module M1 detects the potential change in the liquid level sensor circuit module M2 in real time to determine whether there is a liquid leakage fault. The M1 module integrates internal fault diagnosis of the M2 circuit module, including disconnection, signal short circuit to ground, and power supply short circuit. The above diagnosis improves the safety and reliability of vehicle braking. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a brake fluid level signal recognition circuit with fault diagnosis. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] like Figure 1 As shown, the circuit comprises two parts: a liquid level signal recognition module M1 and a liquid level sensor circuit module M2, as well as a microcontroller unit (MCU). The liquid level signal recognition module M1 includes a power supply V3, a diode D1, resistors R13 to R15, a capacitor C5, and a diode D2. The power supply V3, diode D1, and resistor R14 are connected in series, as are the capacitors C5 and R15. The series connection of the power supply V3, diode D1, and resistor R14 and the series connection of the capacitors C5 and R15 are connected in parallel. Resistor R13 is connected in parallel with capacitor C5. The lead between capacitor C5 and resistor R15 serves as the output terminal of the braking liquid level signal recognition circuit and is simultaneously connected to an external power supply voltage of 3.3V via diode D1. The lead between resistors R14 and R15 is connected to one end of the liquid level sensor circuit module M2, which has a liquid level switch SW1.

[0027] The positive terminal of power supply V3 is connected to the anode of diode D1, the cathode of diode D1 is connected to resistor R14, and the negative terminal of power supply V3 is grounded.

[0028] The liquid level sensor circuit module M2 includes a liquid level switch SW1, a resistor R17, and a resistor R16. The liquid level switch SW1 and the resistor R16 are connected in parallel and then connected in series between the resistor R17 and ground. The other end of the resistor R17 is not connected to the liquid level switch SW1 and the resistor R16, and is connected between the resistor R14 and the resistor R15 of the liquid level signal recognition module M1.

[0029] The output of the brake fluid level signal recognition circuit is connected to the ADC analog-to-digital converter port MCU_AD_BFLI of the microcontroller unit MCU. That is, the voltage is detected in real time through the ADC analog-to-digital converter port MCU_AD_BFLI to determine the brake fluid level signal status.

[0030] like Figure 1 As shown, in the specific implementation, in the liquid level signal recognition module M1, the positive terminal of pin 1 of the power supply V3 is connected to the anode of pin 1 of diode D1, and the cathode of pin 2 of diode D1 is connected to pin 2 of resistor R14. Pin 1 of resistor R14 is connected to pin 1 of resistor R15 and pin 2 of resistor R17. Pin 2 of resistor R15 is connected to pin 1 of resistor R13, pin 1 of diode D2, pin 1 of capacitor C5, and the ADC port MCU_AD_BFLI of the microcontroller unit MCU. Pin 2 of capacitor C5 is grounded, pin 2 of resistor R13 is grounded, and pin 1 of diode D2 is connected to the power supply voltage 3V3.

[0031] like Figure 1 As shown, in the liquid level sensor circuit module M2, pin 1 of resistor R17 is connected to pin 2 of resistor R16 and pin 1 of liquid level switch SW1. Pin 1 of resistor R16 is grounded and pin 2 of liquid level switch SW1 is grounded.

[0032] In this implementation, diodes D1 and D2 are BAS21, resistor R14 has a resistance of 3KΩ, resistor R15 has a resistance of 30KΩ, resistor R13 has a resistance of 100KΩ, resistor R17 has a resistance of 1KΩ, resistor R16 has a resistance of 3.57KΩ, and capacitor C5 has a capacitance of 100nF. The power supply V3 has a voltage of 3.3V. The forward voltage drop of diodes D1 and D2 is 0.7V.

[0033] The liquid level switch SW1 changes synchronously with the liquid level. In the liquid level sensor circuit module M2, when the liquid level is normal, the liquid level switch SW1 is closed; when the liquid level drops below the alarm line, the SW1 switch is open.

[0034] In the circuit design scheme of this utility model, the potential change in the liquid level sensor circuit module M2 is detected in real time by the liquid level signal recognition module M1. The following working conditions of the liquid level sensor can be distinguished by different voltage values: 1- normal liquid level, 2- abnormal liquid level, 3- short circuit to ground of liquid level signal, 4- short circuit of liquid level signal to power supply, 5- liquid level signal is not connected.

[0035] In practice, the voltage value U (MCU_AD_BFLI) is received in real time through the ADC analog-to-digital converter port of the microcontroller unit (MCU) and then the following judgments are made:

[0036] 1) Liquid level is normal:

[0037] SW1 switch in the level sensor is closed:

[0038] In the liquid level sensor circuit module M2, the liquid level sensor resistor R16 is short-circuited to ground. At this time, the voltage at pin 2 of resistor R17 is:

[0039] U(R17_2)=(V3-VD)* ((R17) / / (R15+R13)) / ((R17) / / (R15+R13)+R14)

[0040] U(R17_2)=(3.3V-0.7V)*((1K) / / (30K+100K)) / ((1K) / / (30K+100K)+3K))=0.65V

[0041] In this circuit, / / represents parallel connection and / represents division. When the switch is closed, resistor R16 is short-circuited, so terminal 1 of resistor R17 is grounded. The overall circuit structure is that V3 passes through diode D1 and then through resistor R14 in series, while R15 and R13 are connected in series and then in parallel with R17.

[0042] At this time, the voltage U (MCU_AD_BFLI) at MCU_AD_BFLI is:

[0043] U(MCU_AD_BFLI)= U(R17_2)*(R13) / (R13+R15)= 0.65V*(100K) / (100K+30K)=0.5V

[0044] Therefore, when the voltage value received in real time by the ADC analog-to-digital converter port MCU_AD_BFLI is 0.5V, the brake fluid level signal is normal and the fluid level is normal.

[0045] 2) Abnormal liquid level:

[0046] SW1 switch in the level sensor is off:

[0047] In M2, the level sensor resistor R17 is connected in series with resistor R16. At this time, the voltage at pin 2 of resistor R17 is:

[0048] U(R17_2)=(V3-VD)* ((R17+R16) / / (R15+R13)) / (((R17+R16) / / (R15+R13))+R14))

[0049] U(R17_2)=(3.3V-0.7V)*((1K+3.75K) / / (30K+100K)) / (((1K+3.57K) / / (30K+100K))+3K)=1.56V

[0050] At this time, the voltage U2 at MCU_AD_BFLI is:

[0051] U(MCU_AD_BFLI)= U(R17_2)*(R13) / (R13+R15)= 1.56V*(100K) / (100K+30K)=1.2V

[0052] Therefore, when the voltage value received in real time by the ADC analog-to-digital converter port MCU_AD_BFLI is 1.2V, the brake fluid level signal is abnormal, and the fluid level is abnormal.

[0053] 3) Liquid level signal short circuit to ground:

[0054] When pin 2 of resistor R17 in the liquid level sensor is shorted to ground, U(R17_2) = 0V.

[0055] At this time, the voltage U2 at MCU_AD_BFLI is:

[0056] U(MCU_AD_BFLI)= U(R17_2)*R13 / (R15+R13)=0V*(100K) / (30K+100K)=0V

[0057] Therefore, when the voltage value received in real time by the ADC analog-to-digital converter port MCU_AD_BFLI is 0V, the brake fluid level signal is abnormal and the fluid level signal is short-circuited to ground.

[0058] 4) Liquid level signal short circuit to power supply:

[0059] When pin 2 of resistor R17 in the liquid level sensor is shorted to ground, U(R17_2) = 16V.

[0060] Theoretically, at this point, the voltage U3 at MCU_AD_BFLI is:

[0061] U(MCU_AD_BFLI)= U(R17_2)*R13 / (R15+R13)=16V*(100K) / (30K+100K)=12.3V

[0062] However, because diode D2 clamps the voltage to the 3.3V power supply, the actual voltage at MCU_AD_BFLI is as follows:

[0063] U(MCU_AD_BFLI)=3.3V+0.7V=4V

[0064] Therefore, when the voltage value received in real time by the ADC analog-to-digital converter port MCU_AD_BFLI is 4V, the brake fluid level signal is abnormal, and the fluid level signal is short-circuited to the power supply.

[0065] 5) Liquid level signal is not connected:

[0066] Pin 2 of resistor R17 in the liquid level sensor is disconnected.

[0067] In M2, the level sensor resistor R16 is short-circuited to ground. At this time, the voltage U2 at MCU_AD_BFLI is:

[0068] U(MCU_AD_BFLI)=(V3-VD)* (R13 / (R14+R15+R13))=(3.3V-0.7V)*(100K / (3K+30K+100K))=1.95V.

[0069] Therefore, when the voltage value received in real time by the ADC analog-to-digital converter port MCU_AD_BFLI is 1.95V, the brake fluid level signal is abnormal and the fluid level signal is not connected.

[0070] The final judgment logic of the identification circuit is shown in the table below:

[0071] Table 1

[0072] state U(MCU_AD_BFLI) 1- Normal liquid level 0.4V <U(MCU_AD_BFLI)<0.6V 2-Abnormal liquid level 1.1V<U(MCU_AD_BFLI)<1.3V 3-Liquid level signal short circuit to ground U(MCU_AD_BFLI)<0.1V 4- Liquid level signal short circuit to power supply 3.9V <U(MCU_AD_BFLI)<4.1V 5 - Liquid level signal is not connected 1.85V<U(MCU_AD_BFLI)<2.05V

[0073] By using the table above to make real-time judgments on interface U (MCU_AD_BFLI), the abnormality status and the type of abnormality of the liquid level signal can be obtained instantly.

[0074] Therefore, this utility model uses the liquid level signal recognition module M1 to detect the potential changes in the liquid level sensor circuit module M2 in real time, so as to quickly and accurately determine whether there is a liquid leakage fault in the oil reservoir. Furthermore, the M1 module integrates fault diagnosis for the M2 circuit module, thereby improving the safety and reliability of vehicle braking.

[0075] The above specific embodiments are used to explain and illustrate the present utility model, and are not intended to limit the present utility model. Any modifications and changes made to the present utility model within the spirit and scope of the claims shall fall within the protection scope of the present utility model.

[0076] The above description is only a preferred embodiment of the present utility model. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of the present utility model patent application are included in the scope of the present utility model patent application.

Claims

1. A brake fluid level signal recognition circuit structure with fault diagnosis, characterized by: The system comprises two parts: a liquid level signal recognition module M1 and a liquid level sensor circuit module M2. The liquid level signal recognition module M1 includes a power supply V3, a diode D1, resistors R13 to R15, a capacitor C5, and a diode D2. The power supply V3, diode D1, and resistor R14 are connected in series, as are the capacitor C5 and resistor R15. The entire series connection of the power supply V3, diode D1, and resistor R14 and the entire series connection of the capacitor C5 and resistor R15 are connected in parallel. Resistor R13 is connected in parallel with capacitor C5. The output of the liquid level signal recognition circuit is led out between capacitor C5 and resistor R15 and is simultaneously connected to an external power supply voltage via diode D1. The output of the liquid level sensor circuit module M2, which includes a liquid level switch SW1, is led out between resistors R14 and R15.

2. The brake fluid level signal identification circuit structure with fault diagnosis according to claim 1, characterized in that: The positive terminal of the power supply V3 is connected to the anode of diode D1, the cathode of diode D1 is connected to resistor R14, and the negative terminal of the power supply V3 is grounded.

3. The brake fluid level signal recognition circuit structure with fault diagnosis according to claim 1, characterized in that: The liquid level sensor circuit module M2 includes a liquid level switch SW1, a resistor R17, and a resistor R16. The liquid level switch SW1 and the resistor R16 are connected in parallel and then connected in series between the resistor R17 and ground. The other end of the resistor R17 is connected between the resistor R14 and the resistor R15 of the liquid level signal recognition module M1.

4. The brake fluid level signal recognition circuit structure with fault diagnosis according to claim 1, characterized in that: It also includes a microcontroller unit (MCU), and the output of the brake fluid level signal recognition circuit is connected to the ADC analog-to-digital converter port MCU_AD_BFLI of the microcontroller unit MCU.

5. The brake fluid level signal recognition circuit structure with fault diagnosis according to claim 1, characterized in that: The liquid level switch SW1 changes synchronously with the liquid level. When the liquid level is normal, the liquid level switch SW1 is closed; when the liquid level drops below the alarm line, the SW1 switch is open.

Images