Heat medium heating device

Abstract

Provided is a heat medium heating device that makes it possible to determine, without increasing the number of temperature sensors, that drift failure is taking place in either an inlet temperature sensor or an outlet temperature sensor. On the basis of the outputs of electric heaters (18, 19) and the temperature Tin detected by an inlet temperature sensor (41), an estimated value Toutest of the temperature of a heat medium flowing out from a heat medium outflow part (17) is calculated. On the basis of the outputs of the electric heaters (18, 19) and the temperature Tout detected by an outlet temperature sensor (42), an estimated value Tinest of the temperature of the heat medium flowing in from a heat medium inflow part (16) is calculated. When the difference between the temperature Tin and the estimated value Tinest or the difference between the temperature Tout and the estimated value Toutest is equal to or greater than a prescribed value, it is determined that an abnormality has taken place in either the inlet temperature sensor (41) or the outlet temperature sensor (42).

Description

Heat medium heating device

[0001] The present invention relates to a heat medium heating device that heats a heat medium flowing through a heat medium flow path by a heating unit.

[0002] Conventionally, this type of heat medium heating device is used, for example, as a heat source for air conditioning (heating) in a vehicle cabin of an electric vehicle or for keeping a battery warm. In this case, the heat medium heating device forms a heat medium flow path in a housing, allows the heat medium to flow through the heat medium flow path from a heat medium inflow portion toward a heat medium outflow portion, and disposes a cylindrical electric heater (heating unit) called a cartridge heater in the heat medium flow path. The heat medium flowing through the heat medium flow path directly touches the heated electric heater to warm the heat medium (see, for example, Patent Document 1).

[0003] In addition, an inlet temperature sensor and an outlet temperature sensor for preventing the heat medium from becoming too hot are attached near the heat medium inflow portion and the heat medium outflow portion of the heat medium heating device, respectively. In this case, each temperature sensor does not directly touch the heat medium, and there is a housing between their heat sensing portions and the heat medium.

[0004] Japanese Patent Publication No. 2016-536197, US Patent No. 10788378

[0005] Here, a failure may occur in the temperature sensor. The contents of this failure include an open failure (disconnection), a short failure (short circuit), a drift failure (offset), a complete fixation, etc. Among these, an open failure and a short failure can be detected electrically, but a drift failure cannot be detected electrically only by the temperature sensor.

[0006] The state of this drift failure is shown in FIG. 6. In this figure, the horizontal axis is the cumulative operation time, and the vertical axis is the temperature. The true value of the temperature of the object that the temperature sensor tries to detect (in this case, the heat medium) is indicated by a broken line L1, and the detected temperature output by the temperature sensor is indicated by a solid line L2. As is clear from this figure, a drift failure is a failure in which an offset occurs between the true value of the temperature of the object that the temperature sensor tries to detect and the detected temperature.

[0007] As mentioned above, this offset fault cannot be electrically detected by the temperature sensor alone. Therefore, a configuration is required, for example, as shown in Patent Document 2, in which two temperature sensors, a main sensor and an auxiliary sensor, are provided for the same detection target (for example, the heat transfer medium flowing out of the heat transfer medium channel), and the fault is detected by checking whether the difference in the detected values ​​of each temperature sensor exceeds a predetermined value.

[0008] Therefore, in order to detect drift failures in a heat transfer medium heating device equipped with inlet and outlet temperature sensors, it was necessary to install at least four temperature sensors: a main inlet temperature sensor, an auxiliary inlet temperature sensor, and a main outlet temperature sensor and an auxiliary outlet temperature sensor. This resulted in an increase in the number of parts and a rise in costs.

[0009] The present invention was made to solve the aforementioned conventional technical problems, and aims to provide a heat transfer medium heating device that can determine whether a drift failure has occurred in either the inlet temperature sensor or the outlet temperature sensor without increasing the number of temperature sensors.

[0010] To solve the above problems, the heat transfer medium heating device of the first invention comprises a heat transfer medium flow path through which the heat transfer medium flows from a heat transfer medium inlet to a heat transfer medium outlet, a heating unit provided in the heat transfer medium flow path, an inlet temperature sensor for detecting the temperature Tin of the heat transfer medium flowing in from the heat transfer medium inlet, an outlet temperature sensor for detecting the temperature Tout of the heat transfer medium flowing out from the heat transfer medium outlet, and a control device for controlling the heating unit based on information from the inlet temperature sensor and the outlet temperature sensor. The control device calculates an estimated value Toutest of the temperature of the heat transfer medium flowing out from the heat transfer medium outlet based on the output of the heating unit and the temperature Tin of the heat transfer medium obtained from the inlet temperature sensor, and calculates an estimated value Tinest of the temperature of the heat transfer medium flowing in from the heat transfer medium inlet based on the output of the heating unit and the temperature Tout of the heat transfer medium obtained from the outlet temperature sensor. The control device determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor if the absolute value of the difference between temperature Tin and estimated value Tinest, or the absolute value of the difference between temperature Tout and estimated value Toutest, is greater than or equal to a predetermined value.

[0011] The heat transfer medium heating device of the second invention is characterized in that the flow rate of the heat transfer medium flowing through the heat transfer medium channel is constant in the above invention.

[0012] The third invention is a heat transfer medium heating device characterized in that, in the first invention, the control device does not generate heat in the heating section, and if the absolute value of the difference between the temperature Tin and the temperature Tout before the heat transfer medium flows through the heat transfer medium channel is greater than or equal to a predetermined value, it determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor.

[0013] The heat transfer medium heating device of the fourth invention comprises a heat transfer medium flow path through which the heat transfer medium flows from a heat transfer medium inlet to a heat transfer medium outlet, a heating unit provided in the heat transfer medium flow path, an inlet temperature sensor for detecting the temperature Tin of the heat transfer medium flowing in from the heat transfer medium inlet, an outlet temperature sensor for detecting the temperature Tout of the heat transfer medium flowing out from the heat transfer medium outlet, and a control device for controlling the heating unit based on information from the inlet temperature sensor and the outlet temperature sensor, wherein the control device does not generate heat in the heating unit and determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor if the absolute value of the difference between the temperature Tin and the temperature Tout before the heat transfer medium flows through the heat transfer medium flow path is greater than or equal to a predetermined value.

[0014] The fifth invention is a heat transfer medium heating device characterized in that, in each of the above inventions, one inlet temperature sensor and one outlet temperature sensor are provided.

[0015] The heat transfer medium heating device of the sixth invention is characterized in that, in the first to third inventions, if the control device determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor, it adopts the higher value of the temperature Tout and the estimated value Toutest and controls the heating unit.

[0016] The seventh invention, a heat transfer medium heating device, is characterized in that, in the above invention, the control device limits the output of the heating section to a level higher than normal when it determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor.

[0017] The eighth invention is a heat transfer medium heating device characterized in that, in the first to third inventions, if the control device determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor, it adopts the higher of the temperature Tin and the estimated value Tinest to control the heating section.

[0018] The heat transfer medium heating device of the ninth invention is characterized in that, in the above invention, the control device limits the output of the heating section more than under normal conditions when it determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor.

[0019] According to the first invention, a heat medium heating device comprising a heat medium flow path through which a heat medium flows from a heat medium inlet to a heat medium outlet, a heating unit provided in the heat medium flow path, an inlet temperature sensor for detecting the temperature Tin of the heat medium flowing in from the heat medium inlet, an outlet temperature sensor for detecting the temperature Tout of the heat medium flowing out from the heat medium outlet, and a control device for controlling the heating unit based on information from the inlet temperature sensor and the outlet temperature sensor, wherein the control device calculates an estimated value Toutest of the temperature of the heat medium flowing out from the heat medium outlet based on the output of the heating unit and the temperature Tin of the heat medium obtained from the inlet temperature sensor, and also calculates the temperature of the heat medium obtained from the output of the heating unit and the outlet temperature sensor. Based on the temperature Tout, an estimated value Tinest, the temperature of the heat medium flowing in from the heat medium inlet, is calculated. If the absolute value of the difference between the temperature Tin and the estimated value Tinest, or the absolute value of the difference between the temperature Tout and the estimated value Toutest, exceeds a predetermined value, it is determined that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor. Therefore, without increasing the number of temperature sensors, as in the fifth invention, it is possible to determine if an abnormality, particularly a drift failure, has occurred in either the inlet temperature sensor or the outlet temperature sensor using only one temperature sensor each, and to take action such as notifying the occurrence of an abnormality, thereby reducing the number of parts and costs.

[0020] In this case, as in the second invention, by keeping the flow rate of the heat transfer medium through the heat transfer medium channel constant, it becomes easier to calculate the estimated values ​​Toutest and Tinest.

[0021] Furthermore, if the control device, as in the third and fourth inventions, does not generate heat in the heating section and determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor when the absolute value of the difference between the temperature Tin and temperature Tout before the heat transfer medium flows through the heat transfer medium channel is greater than or equal to a predetermined value, it becomes possible to determine that an abnormality (drift failure) has occurred in either the inlet temperature sensor or the outlet temperature sensor, which should normally acquire the same value, before startup, and to take measures such as notifying the occurrence of an abnormality.

[0022] Furthermore, as in the sixth or eighth invention, if the control device determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor, it can control the heating unit by adopting the higher value of temperature Tout and estimated value Toutest, or the higher value of temperature Tin and estimated value Tinest, thereby enabling the heat transfer medium heating device to operate safely and continuously without stopping.

[0023] In that case, if the control device is configured to limit the output of the heating section compared to normal operation, as in the seventh and ninth inventions, the operation of the heat transfer medium heating device can be continued more safely.

[0024] This is a perspective view showing the external appearance of a heat transfer medium heating device according to one embodiment to which the present invention is applied. This is a schematic plan cross-sectional view illustrating the flow path of the heat transfer medium inside the heat transfer medium heating device of Figure 1. This is a plan view showing the inside of the heat transfer medium heating device of Figure 1 (perspective view of the control board). This is a circuit block diagram of the control device of the heat transfer medium heating device of Figure 1. This is a flowchart illustrating the operation of the control device of the heat transfer medium heating device of Figure 1. This is a diagram illustrating a drift failure of the temperature sensor.

[0025] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 is a perspective view showing the external appearance of a heat transfer medium heating device 1 according to one embodiment to which the present invention is applied, Figure 2 is a schematic plan cross-sectional view to explain the flow of the heat transfer medium inside the heat transfer medium heating device 1, and Figure 3 is a plan view showing the inside of the main body 3 of the housing 2 with the cover 4 of the heat transfer medium heating device 1 of Figure 1 removed and the control board 21 visible through it.

[0026] (1) Heat transfer medium heating device 1 The heat transfer medium heating device 1 of the embodiment is used to air condition the interior of an electric vehicle (not shown) and to warm the battery of an electric vehicle. The housing 2 consists of a metallic body 3 having high thermal conductivity, such as iron or aluminum, and a metallic cover 4 attached to the body 3. Two flow channels 6 and 7 (also made of metal) are provided in the body 3 of the housing 2, spaced apart from each other by a gap 8, and constitute a part of the body 3. Heat transfer medium flow channels 9 and 11 are configured inside them, respectively. That is, the heat transfer medium flow channels 9 and 11 are arranged side by side in the housing 2, spaced apart from each other by a gap 8.

[0027] A connecting section 13, which has a connecting channel 12 inside, is connected to one end of each of the flow channel sections 6 and 7, forming part of the main body 3, and one end of each of the two heat transfer fluid flow channels 9 and 11 is connected by this connecting channel 12. A heat transfer fluid inlet section 16 for introducing heat transfer fluid is connected to the other end of the heat transfer fluid flow channel 9, and a heat transfer fluid outlet section 17 for releasing heat transfer fluid is connected to the other end of the heat transfer fluid flow channel 11.

[0028] In each figure, 18 and 19 are rod-shaped electric heaters composed of cartridge heaters (cylindrical heaters) in the embodiment, and constitute the heating section in the present invention. In this case, electric heater (electric heater 1) 18 is inserted into one heat transfer medium flow path 9 with a gap between it and the inner surface of the flow path section 6, and electric heater (electric heater 2) 19 is inserted into the other heat transfer medium flow path 11 with a gap between it and the inner surface of the flow path section 7. As a result, each electric heater 18 and 19 are arranged in series with respect to the flow of the heat transfer medium, and the communication flow path 12 in the communication section 13 is located between each electric heater 18 and 19.

[0029] In this embodiment, the connection terminal 18A of the electric heater 18 is drawn out from the flow channel section 6 at one end of the heat transfer medium flow channel 9, and the connection terminal 19A of the electric heater 19 is drawn out from the flow channel section 7 at one end of the heat transfer medium flow channel 11. Sockets 43 and 44 are attached to the outside of each connection terminal 18A and 19A, respectively, and these sockets are electrically connected to the control board 21, which will be described later (Figure 3).

[0030] A control board 21 is mounted on the cover 4 side of each of the flow path sections 6 and 7 within the main body 3, covering the gap 8. This control board 21 is equipped with a power switching element 22 (IGBT1) for controlling the energization of the electric heater 18, a power switching element 23 (IGBT2) for controlling the energization of the electric heater 19, and a power switching element 24 (IGBT3) for adjusting the overall power of each of the electric heaters 18 and 19. In this embodiment, the above-mentioned multiple power switching elements 22 to 24 are composed of IGBTs, but they may also be composed of SiCs.

[0031] Furthermore, the control board 21 is also equipped with a capacitor 26 and a coil 27 that constitutes a noise filter 25. These power switching elements 22 to 24, along with the capacitor 26 and coil 27, etc., constitute a control device 31 (Figure 4) for controlling the electric heaters 18, 19, etc. of the heat transfer medium heating device 1.

[0032] In this embodiment, all power switching elements 22 to 24 are arranged within the interval 8 and are attached to the communication section 13 in a heat exchange relationship. As a result, each power switching element 22 to 24 can exchange heat with the heat transfer medium flowing through the communication channel 12, that is, the heat transfer medium flowing between the electric heater 18 and the electric heater 19.

[0033] Furthermore, the capacitor 26 and the coil 27 are mounted adjacent to each other on the respective flow path sections 6 and 7 sides of the control board 21, and are inserted and positioned within the gap 8 between flow path section 6 (heat transfer fluid flow path 9) and flow path section 7 (heat transfer fluid flow path 11) (Figure 3).

[0034] (2) Inlet temperature sensor 41 and outlet temperature sensor 42 Next, in Figure 3, 41 is the inlet temperature sensor and 42 is the outlet temperature sensor. The inlet temperature sensor 41 is installed in a heat exchange relationship in the flow channel 6 slightly downstream from the heat medium inlet 16 (downstream side in the heat medium flow) to detect the temperature of the heat medium that has flowed into the heat medium flow channel 9 from the heat medium inlet 16. The outlet temperature sensor 42 is installed in a heat exchange relationship in the flow channel 7 slightly upstream from the heat medium outlet 17 (upstream side in the heat medium flow) to detect the temperature of the heat medium that has flowed out from the heat medium outlet 17.

[0035] In this application, the heat transfer medium that flows in from the heat transfer medium inlet 16 refers to the heat transfer medium immediately after it enters the heat transfer medium inlet 16, and the heat transfer medium that flows out from the heat transfer medium outlet 17 refers to the heat transfer medium immediately before it leaves the heat transfer medium outlet 17.

[0036] (3) Control device 31 Next, Figure 4 shows the circuit block of the control device 31. The coil 27 that constitutes the noise filter 25 mentioned above is connected to the HV battery (DC power supply) 46 of the electric vehicle, and the capacitor 26 is connected downstream of this coil 27. The power switching element 22 and the electric heater 18 are connected in series, and the power switching element 23 and the electric heater 19 are connected in series, and these two series circuits are connected in parallel. The power switching element 24 is connected in series with these parallel circuits, and the current sensor 32 is connected in series with the power switching element 24.

[0037] The power switching elements 22 and 23 are connected to the positive side of the capacitor 26, and the current sensor 32 is connected to the negative side. As a result, the currents that flowed through the two power switching elements 22 and 23 merge and flow through the power switching element 24. The current sensor 32 then detects the total current flowing through this power switching element 24.

[0038] In Figure 4, 36 is a control unit composed of a microcomputer, and drivers 37, 38, and 39 are connected to the output of this control unit 36. Driver 37 is connected to the gate of power switching element 22, driver 38 is connected to the gate of power switching element 23, and driver 39 is connected to the gate of power switching element 24.

[0039] The input to the control unit 36 ​​is the output (current value) of the current sensor 32 mentioned above, as well as the outputs (detected temperatures) of the inlet temperature sensor 41 and the outlet temperature sensor 42. In Figure 4, 47 is the LV battery of the electric vehicle, which is the power source for the control unit 36.

[0040] (4) Operation of the heat transfer medium heating device 1 With the above configuration, the operation of the heat transfer medium heating device 1 will now be explained with reference to the flowchart in Figure 5. Note that the heat transfer medium inlet 16 and the heat transfer medium outlet 17 are connected to a heat transfer medium circuit equipped with a pump (not shown).

[0041] (4-1) Abnormality determination before startup by the control device 31 When the electric vehicle is started, the control unit 36 ​​of the control device 31 first determines whether or not a drift failure has occurred in the inlet temperature sensor 41 and the outlet temperature sensor 42 (abnormality determination before startup) before starting the heat transfer medium heating device 1. Based on this abnormality determination before startup, the control unit 36 ​​does not generate heat in the electric heaters 18 and 19 (heating section) and obtains the temperature Tin detected by the inlet temperature sensor 41 (temperature of the heat transfer medium detected by the inlet temperature sensor 41) and the temperature Tout detected by the outlet temperature sensor 42 (temperature of the heat transfer medium detected by the outlet temperature sensor 42) before the heat transfer medium flows through the heat transfer medium flow path 9, the communication flow path 12, and the heat transfer medium flow path 11.

[0042] The detected temperature Tin is information acquired by the control unit 36 ​​(control device 31) from the inlet temperature sensor 41 before the start of the heat transfer medium heating device 1, and the detected temperature Tout is information acquired by the control unit 36 ​​from the outlet temperature sensor 42 before the start of the heat transfer medium heating device 1.

[0043] Then, the control unit 36 of the control device 31 uses the following mathematical formula (I) to determine whether a drift failure (abnormality) has occurred in either the inlet temperature sensor 41 or the outlet temperature sensor 42 before startup. abs(Tin - Tout) < 5K ··· (I)

[0044] That is, the control unit 36 determines whether the absolute value of the difference (Tin - Tout) between the detected temperature Tin (the temperature of the heat medium obtained from the inlet temperature sensor 41) obtained from the inlet temperature sensor 41 and the detected temperature Tout (the temperature of the heat medium obtained from the outlet temperature sensor 42) obtained from the outlet temperature sensor 42 is less than 5K. This 5K is a predetermined value and is a threshold value appropriately set according to the device. And when the absolute value of the difference (Tin - Tout) between the detected temperature Tin and the detected temperature Tout is less than 5K (threshold value), the inlet temperature sensor 41 and the outlet temperature sensor 42 before startup are determined to be normal.

[0045] On the other hand, when the absolute value of the difference (Tin - Tout) between the obtained detected temperature Tin and the detected temperature Tout is 5K or more, the control unit 36 determines that a drift failure (abnormality) has occurred in either the inlet temperature sensor 41 or the outlet temperature sensor 42 before startup. And it displays on the display of the electric vehicle (not shown) that a drift failure has occurred in the inlet temperature sensor 41 and the outlet temperature sensor 42 before startup (abnormality occurrence notification).

[0046] Here, it is assumed that the control unit 36 has determined that the inlet temperature sensor 41 and the outlet temperature sensor 42 are normal before startup and no drift failure (abnormality) has occurred.

[0047] (4 - 2) Control of the electric heaters 18 and 19 by the control device 31 (normal time) Next, the control unit 36 of the control device 31 starts the operation of the heat medium heating device 1. When the heat medium heating device 1 is started, the heat medium (water in the embodiment) flows into the heat medium flow path 9 from the heat medium inflow part 16 by the pump of the aforementioned heat medium circuit. The heat medium that has flowed into the heat medium flow path 9 flows into the heat medium flow path 11 through the communication flow path 12 and flows out from the heat medium outflow part 17 to the aforementioned heat medium circuit. In the embodiment, it is assumed that the flow rate of the heat medium by the pump (flow rate per unit time) is constant.

[0048] The control unit 36 controls the switching of each of the power switching elements 22 to 24 by each of the drivers 37 to 39 based on the outputs of the inlet temperature sensor 41, the outlet temperature sensor 42, and the current sensor 32. As a result, each of the electric heaters 18 and 19 is energized, and the electric heaters 18 and 19 generate heat. Therefore, the heat medium that has flowed into the heat medium flow path 9 from the heat medium inlet portion 16 is heated in the process of passing around the electric heater 18, enters the heat medium flow path 11 through the communication flow path 12, and is further heated in the process of passing around the electric heater 19 and then flows out from the heat medium outlet portion 17.

[0049] In the above-described heat medium circuit, a heater core disposed in the HVAC unit of the electric vehicle is connected, and the heat medium heated by the heat medium heating device 1 is circulated to this heater core by a pump. Since the air supplied into the passenger compartment of the electric vehicle is ventilated through the heater core, the air is thereby heated and the passenger compartment is heated.

[0050] The control unit 36 of the embodiment compares the detected temperature Tout detected by the outlet temperature sensor 42 with a predetermined target value Tset, and performs switching control of the power switching elements 22 and 23 by PID control so that the detected temperature Tout becomes the target value Tset, and controls the energization of each of the electric heaters 18 and 19.

[0051] The currents flowing through these power switching elements 22 and 23 (electric heaters 18 and 19) merge and flow to the power switching element 24. The control unit 36 performs switching control of the power switching element 24 based on this merged current value detected by the current sensor 32, and adjusts the power of each of the electric heaters 18 and 19 as a whole.

[0052] During operation by the control device 31, the control unit 36 of the abnormal determination control device 3 of the control device 31 monitors whether or not a drift failure (abnormality) has occurred in the inlet temperature sensor 41 and the outlet temperature sensor 42 during the operation of the heat medium heating device 1. The abnormal determination in this case will be described while referring to the flowchart of FIG. 5.

[0053] In step S1 of the control device 31, the control unit 36 ​​of the control device 31 acquires the temperature Tin (water temperature: temperature of the heat medium that has flowed into the heat medium inlet 16) detected by the inlet temperature sensor 41 and the temperature Tout (water temperature: temperature of the heat medium that has flowed out from the heat medium outlet 17) detected by the outlet temperature sensor 42.

[0054] Next, in step S2, the control unit 36 ​​acquires the current value detected by the current sensor 32 and the voltage of the HV battery (DC power supply) 46, and in step S3, it calculates the total heater output Q, which is the sum of the electric heaters 18 and 19.

[0055] Next, in step S4, the control unit 36 ​​calculates the estimated temperature of the heat medium flowing in from the heat medium inlet 16, Tinest, and the estimated temperature of the heat medium flowing out from the heat medium outlet 17, Tinest = f(Tout, Q) ... (II) Tinest = f(Tin, Q) ... (III)

[0056] As mentioned above, the flow rate of the heat transfer medium by the pump (flow rate per unit time) is constant. Therefore, if the heater output Q and the detected temperature Tout obtained from the outlet temperature sensor 42 are known, the estimated temperature Tinest of the heat transfer medium flowing in from the heat transfer medium inlet 16 can be calculated by subtracting the temperature rise due to heating by each electric heater 18 and 19 (Equation (II)). Similarly, if the heater output Q and the detected temperature Tin obtained from the inlet temperature sensor 41 are known, the estimated temperature Toutest of the heat transfer medium flowing out from the heat transfer medium outlet 17 can be calculated by adding the temperature rise due to heating by each electric heater 18 and 19 (Equation (III)).

[0057] Next, in step S5, the control unit 36 ​​again obtains the detected temperature Tin from the inlet temperature sensor 41 and the detected temperature Tout from the outlet temperature sensor 42. Then, in step S6, it determines whether a drift failure (abnormality) has occurred in either the inlet temperature sensor 41 or the outlet temperature sensor 42 using the following formulas (IV) and (V): abs(Tinest - Tin) < 5K ... (IV) abs(Toutest - Tout) < 5K ... (V)

[0058] Specifically, the control unit 36 ​​determines whether the absolute value of the difference (Tinest - Tin) between the estimated value Tinest, estimated using formula (II) from the detected temperature Tout obtained from the outlet temperature sensor 42 and the heater output Q, and the detected temperature Tin obtained from the inlet temperature sensor 41, is less than 5K (formula (IV)). The control unit 36 ​​also determines whether the absolute value of the difference (Toutest - Tout) between the estimated value Toutest, estimated using formula (III) from the detected temperature Tin obtained from the inlet temperature sensor 41 and the heater output Q, and the detected temperature Tout obtained from the outlet temperature sensor 42, is less than 5K (formula (V)). This 5K is also a predetermined value and is a threshold that is set appropriately depending on the device.

[0059] Then, if the absolute value of the difference between the estimated value Tinest and the detected temperature Tin (Tinest - Tin) is less than 5K, and the absolute value of the difference between the estimated value Toutest and the detected temperature Tout (Toutest - Tout) is less than 5K, the control unit 36 ​​proceeds to step S7 and determines that the inlet temperature sensor 41 and the outlet temperature sensor 42 are normal.

[0060] On the other hand, if the absolute value of the difference between the estimated value Tinest and the detected temperature Tin (Tinest - Tin) is 5K or more, or if the absolute value of the difference between the estimated value Toutest and the detected temperature Tout (Toutest - Tout) is 5K or more, the control unit 36 ​​proceeds to step S8 and determines that a drift failure (abnormality) has occurred in either the inlet temperature sensor 41 or the outlet temperature sensor 42. Then, it displays on the display of the electric vehicle (not shown) that a drift failure has occurred in either the inlet temperature sensor 41 or the outlet temperature sensor 42 (abnormality notification).

[0061] (4-4) Control of electric heaters 18 and 19 by control device 31 (in case of abnormality) The control unit 36 ​​of the control device 31 also continues operation if it determines that a drift failure (abnormality) has occurred in either the inlet temperature sensor 41 or the outlet temperature sensor 42. In this case, it adopts the higher value between the detected temperature Tout detected by the outlet temperature sensor 42 and the estimated value Toutest, compares the adopted value with the aforementioned target value Tset, and controls the switching of the power switching elements 22 and 23 using PID control so that the adopted value becomes Tset, thereby controlling the power supply to each electric heater 18 and 19.

[0062] In that case, the output of each electric heater 18, 19 is limited compared to the normal operation described above. Possible methods of this limitation include setting the upper limit of the energization rate to each electric heater 18, 19 by the power switching elements 22, 23 to a lower value than in the normal operation, or setting a lower rate of increase in the energization rate.

[0063] As described in detail above, according to the present invention, the control unit 36 ​​of the control device 31 calculates an estimated value Toutest of the temperature of the heat medium flowing out of the heat medium outlet 17 based on the output Q of the electric heaters 18 and 19 and the detected temperature Tin of the heat medium obtained from the inlet temperature sensor 41, and calculates an estimated value Tinest of the temperature of the heat medium flowing in from the heat medium inlet 16 based on the output Q of the electric heaters 18 and 19 and the detected temperature Tout of the heat medium obtained from the outlet temperature sensor 42, and the absolute value of the difference between the detected temperature Tin and the estimated value Tinest, Alternatively, if the absolute value of the difference between the detected temperature Tout and the estimated value Toutest exceeds a predetermined value, it is determined that an abnormality (drift failure) has occurred in either the inlet temperature sensor 41 or the outlet temperature sensor 42. This makes it possible to determine if either the inlet temperature sensor 41 or the outlet temperature sensor 42 is experiencing a drift failure using only one temperature sensor each, without increasing the number of temperature sensors, and to take action such as notifying the system of the abnormality. This reduces the number of parts and lowers costs.

[0064] In this case, by keeping the flow rate of the heat transfer medium constant in the heat transfer medium channel 9, the communication channel 12, and the heat transfer medium channel 11, as in the embodiment, it becomes easier to calculate the estimated value Toutest and the estimated value Tinest.

[0065] Furthermore, in this invention, the control unit 36 ​​of the control device 31 determines that an abnormality has occurred in either the inlet temperature sensor 41 or the outlet temperature sensor 42 if the absolute value of the difference between the detected temperature Tin and the detected temperature Tout before the heat transfer medium flows through the heat transfer medium channel 9 without generating heat in the electric heaters 18 and 19 is greater than or equal to a predetermined value. Therefore, it is possible to determine that an abnormality (drift failure) has occurred in either the inlet temperature sensor 41 or the outlet temperature sensor 42, which should normally acquire the same value, before startup, and to take measures such as notifying the occurrence of an abnormality.

[0066] Furthermore, as in the embodiment, if the control unit 36 ​​of the control device 31 determines that an abnormality has occurred in either the inlet temperature sensor 41 or the outlet temperature sensor 42, it uses the higher of the detected temperature Tout and the estimated value Toutest to control the electric heaters 18 and 19, thereby enabling the heat transfer medium heating device 1 to operate safely and continuously without stopping.

[0067] In that case, if the control unit 36 ​​limits the output of the electric heaters 18 and 19 more than usual, as in the embodiment, the operation of the heat transfer medium heating device 1 can be continued more safely.

[0068] In the embodiment described above, if an abnormality (drift failure) is detected in either the inlet temperature sensor 41 or the outlet temperature sensor 42 during the abnormality detection before startup, only a display is shown. However, in addition to this, when controlling the electric heaters 18 and 19 after startup, even if no abnormality is detected during operation, the higher value is adopted and output limiting is implemented as described above.

[0069] Alternatively, in the abnormality detection before startup, no display may be made, and the control unit 36 ​​may simply store in memory that there is a suspicion of a drift failure (abnormality) in either the inlet temperature sensor 41 or the outlet temperature sensor 42. Then, for example, if it is determined that a drift failure has occurred after startup as described above, the system may perform operation with the aforementioned display and output limiting of the electric heaters 18 and 19.

[0070] In this embodiment, the detected temperature Tout detected by the outlet temperature sensor 42 is compared with the target value Tset, and the power switching elements 22 and 23 are switched to control the power supply to each electric heater 18 and 19. However, in the event of an open fault or short fault in the outlet temperature sensor 42, for example, the power switching elements 22 and 23 may be switched to control the power supply to each electric heater 18 and 19 based on the detected temperature Tin detected by the inlet temperature sensor 41 and the target value Tset.

[0071] In that case, if it is determined that an abnormality (drift failure) has occurred in either the inlet temperature sensor 41 or the outlet temperature sensor 42 during operation, the higher of the detected temperature Tin detected by the inlet temperature sensor 41 and the estimated value Tinest is adopted, and the adopted value is compared with the target value Tset. The power switching elements 22 and 23 are switched to control the power supply to each electric heater 18 and 19 so that the adopted value becomes Tset. In addition, the output limit of the electric heaters 18 and 19 as described above will also be implemented.

[0072] Furthermore, although the embodiment described an example of a heat transfer medium heating device used in the in-vehicle air conditioning of an electric vehicle, the present invention is not limited to this and is effective for heat transfer medium heating devices in various heating systems.

[0073] 1 Heat transfer medium heating device 9, 11 Heat transfer medium flow path 12 Connecting flow path 16 Heat transfer medium inlet 17 Heat transfer medium outlet 18, 19 Electric heater (heating section) 22-24 Power switching element 31 Control device 32 Current sensor 36 Control unit 41 Inlet temperature sensor 42 Outlet temperature sensor 46 HV battery

Claims

1. A heat medium heating device comprising: a heat medium flow path through which a heat medium flows from a heat medium inlet to a heat medium outlet; a heating unit provided in the heat medium flow path; an inlet temperature sensor for detecting the temperature Tin of the heat medium flowing in from the heat medium inlet; an outlet temperature sensor for detecting the temperature Tout of the heat medium flowing out from the heat medium outlet; and a control device for controlling the heating unit based on information from the inlet temperature sensor and the outlet temperature sensor, wherein the control device calculates an estimated value Toutest of the temperature of the heat medium flowing out from the heat medium outlet based on the output of the heating unit and the temperature Tin of the heat medium obtained from the inlet temperature sensor, and calculates an estimated value Tinest of the temperature of the heat medium flowing in from the heat medium inlet based on the output of the heating unit and the temperature Tout of the heat medium obtained from the outlet temperature sensor, A heat transfer medium heating device characterized in that, if the absolute value of the difference between the temperature Tin and the estimated value Tinest, or the absolute value of the difference between the temperature Tout and the estimated value Toutest, exceeds a predetermined value, it is determined that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor.

2. The heat transfer medium heating device according to claim 1, characterized in that the flow rate of the heat transfer medium through the heat transfer medium channel is constant.

3. The heat transfer medium heating device according to claim 1, characterized in that the control device does not generate heat in the heating section, and if the absolute value of the difference between the temperature Tin and the temperature Tout before the heat transfer medium is flowed through the heat transfer medium channel is greater than or equal to a predetermined value, it determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor.

4. A heat medium heating device comprising: a heat medium flow path through which a heat medium flows from a heat medium inlet to a heat medium outlet; a heating unit provided in the heat medium flow path; an inlet temperature sensor for detecting the temperature Tin of the heat medium flowing in from the heat medium inlet; an outlet temperature sensor for detecting the temperature Tout of the heat medium flowing out from the heat medium outlet; and a control device for controlling the heating unit based on information from the inlet temperature sensor and the outlet temperature sensor, wherein the control device determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor if the heating unit does not generate heat and the difference between the temperature Tin and the temperature Tout before the heat medium flows through the heat medium flow path is greater than or equal to a predetermined value.

5. The heat transfer medium heating device according to any one of claims 1 to 4, characterized in that one inlet temperature sensor and one outlet temperature sensor are each provided.

6. The heat transfer medium heating device according to any one of claims 1 to 3, characterized in that when the control device determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor, it adopts the higher value of the temperature Tout and the estimated value Toutest to control the heating unit.

7. The heat transfer medium heating device according to claim 6, characterized in that when the control device determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor, it limits the output of the heating unit to a level higher than under normal conditions.

8. The heat transfer medium heating device according to any one of claims 1 to 3, characterized in that when the control device determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor, it adopts the higher of the temperature Tin and the estimated value Tinest to control the heating unit.

9. The heat transfer medium heating device according to claim 8, characterized in that when the control device determines that an abnormality has occurred in either the inlet temperature sensor or the outlet temperature sensor, it limits the output of the heating unit to a level higher than under normal conditions.

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