Method for controlling running state of thick film heater

Abstract

The invention relates to a thick film heater running state control method used in a new energy automobile water heating system. The thick film heater based on the method comprises a thick film heating plate used for heating a medium and a control circuit used for controlling the working state of the thick film heating plate. The method comprises the following steps: S1, calculating and determining the resistance value of a thick film heating plate according to basic characteristic parameters and operating conditions of a material; s2, calibrating resistance values of the thick film heating plate under different working conditions; s3, in the actual operation of the heater, the control circuit controls the working state of the thick film heating plate according to the actually collected resistance value of the thick film heating plate; resistance of the thick film heating plate is collected through an internal circuit of the controller, the controller monitors resistance change values of the heater under different operation conditions, whether the heater works or not is determined, dry burning protection is stopped, the thick film heater is controlled to work through the resistance values, control is sensitive and high in precision, and control reliability is improved.

Description

Technical Field

[0001] The invention relates to a method for controlling the operating state of a thick film heater in a water heating system of a new energy vehicle. Background Art

[0002] As new energy vehicles continue to develop towards high energy density, high energy conversion efficiency and high integration, the demand for thermal management of the three-electric system (battery, motor, and electronic control system) is increasing day by day, which has been related to the overall safety and efficiency of new energy vehicles, and has promoted the proposal, upgrade and evolution of integrated thermal management systems. Different integrated thermal management systems can be formed according to different combinations of cabin air conditioning and battery / motor temperature control. The thick film heater has the advantages of high heat exchange efficiency, small size, and light weight due to its simple structure and few heat exchange interfaces. It has the advantages of stable resistance, no power attenuation, low heat capacity and thermal resistance, good controllability, and no starting impact current. It is the preferred heating source component in the thermal management system of new energy vehicles. The disadvantage is that the thick film heating plate has poor anti-dry burning ability. In the absence of protective measures, the surface temperature of the film heating plate will reach more than 500°C after 10S, causing damage to the film heating plate circuit and the heater is prone to failure to heat. At present, thick film heaters control the normal operation of the heater by adding film temperature sensors and controlling water temperature sensors. However, the method of directly determining the working state through temperature sensing and collecting signals has defects such as low response sensitivity and poor installation reliability, which affects the accuracy of actual detection and makes it difficult to guarantee the reliability of control results. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a thick film heater operating state control method which is mainly based on basic material parameters and basic circuit signals of a control circuit and has high detection accuracy and good control stability.

[0004] The thick film heater operating state control method of the present invention is based on a thick film heater comprising a thick film heating plate for heating a medium and a control circuit for controlling the operating state of the thick film heating plate; the method comprises the following steps: S1. Calculate and determine the resistance of the thick film heating plate based on the basic material characteristics and operating conditions, where: Resistance at operating temperature RH=U 2 / P, where U is the actual working voltage and P is the actual power; Resistance at initial temperature RC=U 2 / P(1+TCR(TH-TC)×106), where TCR is the temperature coefficient of resistance, TH is the operating temperature, and TC is the initial temperature; S2. Calibrate the resistance of the thick film heating plate under different working conditions. When the heater is powered on and heating, collect the film temperature of the thick film heater in normal working state, the film temperature when it stops working due to over-temperature, and the film temperature in dry-burning protection state. The resistance values ​​at these temperatures are calibrated as R1, R2, and R3 respectively. S3. During the actual operation of the heater, the control circuit controls the working state of the thick film heating plate according to the actual collected resistance value of the thick film heating plate; when the collected resistance value is lower than R1, the thick film heating plate is powered on and heated normally; when the collected resistance value is higher than R2, the thick film heating plate stops working; when the collected resistance value is higher than R3, a dry-burning protection instruction is issued.

[0005] This patent of the present invention utilizes the stable characteristic of the resistance curve of the thick film heating plate to control the normal operation of the thick film heater and the state of the protection against dry burning of the heater under extreme working conditions; the resistance of the thick film heating plate is collected by the internal circuit of the controller, and the controller monitors the resistance change value of the heater under different operating conditions to determine whether the heater is working, stopped and dry burning protected, thereby realizing resistance value control of the thick film heater. The control is sensitive and precise, and the control reliability is improved. DETAILED DESCRIPTION

[0006] The thick film heater operation state control method of the embodiment of the present invention is a water-heating thick film heater operated in an electric vehicle, comprising a thick film heating plate for heating a medium and a control circuit for controlling the operation state of the thick film heating plate, and the control circuit can be integrated into the vehicle control system; the control method comprises the following steps: S1. Calculate and determine the resistance of the thick film heating plate based on the basic material characteristics and operating conditions, where: Resistance at operating temperature RH=U 2 / P, where U is the actual working voltage and P is the actual power; Resistance at initial temperature RC=U 2 / P(1+TCR(TH-TC)×106), where TCR is the temperature coefficient of resistance, TH is the operating temperature, and TC is the initial temperature; S2. Calibrate the resistance of the thick film heating plate under different temperature conditions. Specifically, during the heating process of the heater, the resistance values ​​of the thick film heater at the normal working film temperature, the film temperature when the temperature stops working due to over-temperature, and the film temperature in the dry-burning protection state are collected and calibrated as R1, R2, and R3 respectively. The higher the temperature, the greater the resistance. In this embodiment, under normal circumstances, the film temperature of the thick film heating plate is 280°C. At this time, the resistance value collected by the control circuit is 30Ω, the corresponding resistance value at the film temperature of 300°C is 32Ω, and the corresponding resistance value at the film temperature of 500°C is 52Ω; at this time, the resistance value of the heater stopping heating is calibrated at 33Ω at R1, and the thick film dry-burning protection resistance value R3 is 52Ω. When the resistance value returns to 32Ω (R1), the heater automatically returns to work.

[0007] S3. During the actual operation of the heater, the control circuit controls the working state of the thick film heating plate according to the actual collected resistance value of the thick film heating plate. When the collected resistance value is lower than R1, the thick film heating plate is powered on and heated normally; when the collected resistance value is higher than R2, the thick film heating plate stops working; when the collected resistance value is higher than R3, a dry-burning protection instruction is issued.

Claims

1. A method for controlling the operating state of a thick film heater, wherein the thick film heater for water heating in an electric vehicle comprises a thick film heating plate for heating a medium and a control circuit for controlling the operating state of the thick film heating plate; wherein the method comprises: The control method includes the following steps: S1. Calculate and determine the resistance of the thick film heating plate based on the basic material characteristics and operating conditions, where: Resistance at operating temperature RH=U 2 / P, where U is the actual working voltage and P is the actual power; Resistance at initial temperature RC=U 2 / P(1+TCR(TH-TC)×106), where TCR is the temperature coefficient of resistance, TH is the operating temperature, and TC is the initial temperature; S2. Calibrate the resistance of the thick film heating plate under different temperature conditions; S3. During the actual operation of the heater, the control circuit controls the working state of the thick film heating plate according to the actually collected resistance value of the thick film heating plate.

2. The thick film heater operation state control method according to claim 1, characterized in that: step S2 The specific calibration method is to collect the resistance values ​​of the thick film heater at the normal working film temperature, the film temperature when the heater stops working due to over-temperature, and the film temperature in the dry-burning protection state during the heating process of the heater, and calibrate them as R1, R2, and R3 respectively.

3. The thick film heater operating state control method according to claim 2, characterized in that: In step S3, the specific control method is that when the collected resistance value is lower than R1, the thick film heating plate is powered on and heated normally; when the collected resistance value is higher than R2, the thick film heating plate stops working; when the collected resistance value is higher than R3, a dry-burning protection instruction is issued.