JP6119647B2 - Electric vehicle - Google Patents

Description

  The present invention relates to an electric vehicle. The “electric vehicle” in this specification includes an electric vehicle that includes a motor for traveling but does not include an engine, a hybrid vehicle that includes both a motor and an engine, and a fuel cell vehicle.

  The electric vehicle includes a power conversion device that converts the DC power of the battery into AC power and supplies the AC power to the motor. The power conversion device is typically an inverter, but may include a voltage converter that boosts the voltage of the battery and supplies the boosted voltage to the inverter. Since the motor for traveling has a large output, the power conversion device generates a large amount of heat. Therefore, electric vehicles often include a cooler that cools the power conversion device. For example, Patent Document 1 discloses a technique for efficiently operating a cooler of a power converter. The technology includes a temperature sensor that measures the temperature of the power element included in the power conversion device and another temperature sensor that measures the temperature of the refrigerant that cools the power element. The controller of the cooler calculates a heat transfer amount per unit temperature difference transmitted from the power element to the refrigerant based on the temperature of the power element, the refrigerant temperature, and the heat generation amount of the power element, and the heat transfer amount is a predetermined threshold value. If larger than that, the driving force of the circulating pump of the cooler is lowered. The amount of heat generated by the power element is calculated from the motor torque and the rotation speed.

  Patent Documents 2 and 3 disclose techniques for detecting an abnormality of a cooler. Patent Document 2 discloses a technique for detecting an abnormality of a temperature sensor that measures the temperature of a power element. The technology is as follows. The controller estimates the heat generation amount per predetermined time of the power element. The calorific value is estimated based on the magnitude of the current input to the power converter during a predetermined time. Further, the controller obtains the temperature change amount of the power element at a predetermined time by the temperature sensor. The controller stores a two-dimensional map with the heat generation amount of the power element as one axis and the temperature change amount of the power element as the other axis. The two-dimensional map defines a region where it is estimated that an abnormality has occurred in the temperature sensor, and the controller projects the estimated calorific value and the measured temperature change amount onto the two-dimensional map. When the coordinate value is included in the above-described region for a certain period of time, it is determined that the temperature sensor is abnormal.

  The technique of Patent Document 3 is as follows. The electric vehicle disclosed in Patent Document 3 includes a temperature sensor that measures the temperature of the refrigerant, a temperature sensor that measures the temperature of the voltage converter, and a temperature sensor that measures the temperature of the inverter. The flow rate of the refrigerant is estimated from the value. Then, it is determined from the estimated number of rotations of the pump that circulates the refrigerant and whether the abnormality has occurred in the pump or the refrigerant flow path.

JP 2012-151975 A JP 2013-156097 A International Publication WO2012 / 120630

  The present specification also relates to a technique for detecting an abnormality of a temperature sensor provided in a cooler of a power conversion device in an electric vehicle. The present specification provides a technique for detecting an abnormality of a temperature sensor by a method different from the technique described above.

  One embodiment of the electric vehicle disclosed in this specification includes a power conversion device that supplies power to a motor for traveling, two temperature sensors that measure the temperature of a refrigerant that cools the power conversion device, A controller is provided for determining that an abnormality has occurred in the temperature sensor. One temperature sensor (first temperature sensor) measures the temperature of the refrigerant supplied to the power converter. The other temperature sensor (second temperature sensor) measures the temperature of the refrigerant after passing through the power conversion device. The controller calculates the amount of heat absorbed by the refrigerant from the difference between the temperatures measured by the first and second temperature sensors and the flow rate of the refrigerant sent to the power converter. Further, the controller estimates the amount of heat generated by the power conversion device from the current flowing through the power conversion device. When the difference between the calculated heat quantity and the estimated heat quantity exceeds a predetermined heat quantity difference threshold, the controller notifies the first or second temperature sensor that an abnormality has occurred (abnormal Detection signal). The abnormality detection signal is, for example, a signal for turning on a warning light provided in an instrument panel of a vehicle, or a signal for storing an abnormality occurrence in a diagnosis memory. The heat quantity difference threshold value is determined in advance from the specifications of the power conversion device and is stored in the controller.

  Since the electric vehicle estimates the amount of heat generated by the power conversion device and determines the temperature sensor abnormality using the estimated value, the temperature sensor abnormality can be accurately detected. Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a typical block diagram of the electric power system and cooler of the electric vehicle of an Example. It is a flowchart figure which shows the process which detects abnormality of the water temperature sensor of an electric vehicle. It is a graph which shows an example of the influence by the output voltage of a sub battery and the correspondence of a refrigerant | coolant flow volume and a refrigerant | coolant temperature.

  An electric vehicle 200 according to an embodiment will be described with reference to the drawings. FIG. 1 is a schematic block diagram of an electric power system and a cooler of the electric vehicle 200. The electric vehicle 200 according to the embodiment includes a traveling motor 5. The output of the motor 5 is transmitted to the drive wheels 15 and the electric vehicle 200 travels. The motor 5 is typically a three-phase AC motor. Electric power is supplied to the motor 5 from the main battery 3 via the power converter 2. The power conversion device 2 includes a chopper type voltage converter circuit 2a that boosts the voltage of the main battery 3 together with an inverter circuit 2b that converts DC power into AC power. The power of the main battery 3 is boosted by the voltage converter circuit 2 a, converted to three-phase AC power by the inverter circuit 2 b, and supplied to the motor 5. Further, when braking electric vehicle 200, power conversion device 2 converts regenerative power from motor 5 into DC power, and the converted power is stored in main battery 3. In this case, the voltage converter circuit 2a operates as a step-down circuit. The regenerative power from the motor 5 is converted into DC power by the inverter circuit 2 b and then stepped down by the voltage converter circuit 2 a and stored in the main battery 3. Since the voltage converter circuit 2a and the inverter circuit 2b are well-known techniques, detailed description thereof will be omitted in this specification.

  The motor 5 used for traveling of the electric vehicle 200 has a large output to cope with the traveling. Therefore, the power converter 2 that supplies power to the motor 5 generates a large amount of heat. In particular, the power elements used in the voltage converter circuit 2a and the inverter circuit 2b in the power converter 2 generate a large amount of heat. In order to absorb the generated heat, the power converter 2 is provided with a cooler 21. The cooler 21 is disposed adjacent to the power element provided in the power conversion device 2, and the refrigerant passing through the cooler 21 absorbs heat from the power element. The electric vehicle 200 is provided with a refrigerant supply pipe 9 a that supplies refrigerant to the cooler 21 and a refrigerant discharge pipe 9 b that discharges the refrigerant that has passed through the cooler 21. The electric vehicle 200 is also provided with a radiator 4 for radiating heat absorbed by the refrigerant. One end on the upstream side of the refrigerant supply pipe 9 a is connected to the radiator 4, and the other end on the downstream side is connected to the cooler 21 of the power converter 2. One end on the upstream side of the refrigerant discharge pipe 9 b is connected to the cooler 21 of the power converter 2, and the other end on the downstream side is connected to the radiator 4. The refrigerant discharge pipe 9b is provided with a pump 7. The refrigerant is pumped by the pump 7 and circulates between the radiator 4 and the cooler 21 as indicated by an arrow in FIG. The refrigerant absorbs heat by passing through the cooler 21, dissipates heat by passing through the radiator 4, and the refrigerant whose temperature is reduced by the heat release is sent to the cooler 21 again. The power converter 2 is cooled by the circulation of the refrigerant. The refrigerant is a liquid, for example, water or LLC (Long Life Coolant).

  The pump 7 is driven by electric power from the sub battery 6. The sub battery 6 is connected to the main battery 3 through the step-down converter 8. The sub-battery 6 is charged with the electric power from the main battery 3 that has been stepped down by the step-down converter 8 according to the status such as the remaining charge of the sub-battery 6. Although not shown in the drawing, in addition to the pump 7, an audio, an air conditioner, a controller 12 described later, and the like are connected to the sub battery 6. The sub battery 6 supplies power to these devices. Devices to which power is supplied by the sub-battery 6 are collectively referred to as an auxiliary machine, and the sub-battery 6 may be referred to as an auxiliary battery.

  The refrigerant supply pipe 9a is provided with a first water temperature sensor 13 that measures the temperature of the refrigerant supplied to the cooler 21 of the power conversion device 2. On the other hand, the refrigerant discharge pipe 9b is also provided with a second water temperature sensor 14 that measures the temperature of the refrigerant after passing through the cooler 21 of the power conversion device 2. The 1st, 2nd water temperature sensors 13 and 14 are constituted by temperature sensing elements, such as a thermistor, for example. Measurement values measured by the first and second water temperature sensors 13 and 14 are transmitted to the controller 12 described later.

  The electric vehicle 200 includes a controller 12 that detects an abnormality in the first and second water temperature sensors 13 and 14. The controller 12 monitors the temperature measured by the first and second water temperature sensors 13 and 14. In addition, the power converter 2 is provided with a current sensor (not shown) that measures the current flowing to the motor 5. The controller 12 also monitors the current value measured by this current sensor. Furthermore, the controller 12 monitors the output voltage of the sub battery 8. The electric vehicle 200 includes a power controller 18 that comprehensively controls devices such as the power converter 2, the step-down converter 8, and the pump 7. The power controller 18 controls the traveling of the electric vehicle 200 in accordance with the traveling state of the vehicle, the accelerator opening, and the like.

  Moreover, if the controller 12 detects abnormality of the 1st, 2nd water temperature sensors 13 and 14, it will output an abnormality notification signal (it mentions later for details). The output abnormality notification signal is transmitted to the instrument panel 16 and the diagnosis memory 17 provided in the electric vehicle 200. On the instrument panel 16, a warning lamp is turned on in response to the output abnormality notification signal. With this warning light, the driver can know the abnormality of the water temperature sensor. The diagnostic memory 17 stores the output abnormality notification signal. By reading the information stored in the diagnostic memory 17 when the electric vehicle 200 is inspected, the inspection operator can diagnose the abnormality of the water temperature sensor.

  With reference to the flowchart of FIG. 2, the process in which the controller 12 detects abnormality of the water temperature sensor will be described. A series of processes shown in FIG. 2 is repeatedly executed at regular intervals as the electric vehicle 200 starts to travel. First, the controller 12 calculates a temperature difference dT that is the difference between the measured value of the second water temperature sensor 14 and the measured value of the first water temperature sensor 13 (S1). The measured value of the first water temperature sensor 13 is the temperature of the refrigerant before passing through the cooler 21 of the power conversion device 2, and the measured value of the second water temperature sensor 14 has passed through the cooler 21 of the power conversion device 2. It is the temperature of the later refrigerant. Therefore, the temperature difference dT is the temperature of the refrigerant that has risen by absorbing heat from the power conversion device 2.

  Next, the controller 12 calculates the flow rate of the refrigerant flowing through the refrigerant supply pipe 9a and the refrigerant discharge pipe 9b (S2). The refrigerant flow rate is determined according to the output of the pump 7 driven by the command of the power controller 18 described above. When the power controller 18 issues a command to increase the output of the pump 7, the refrigerant flow rate also increases. On the other hand, the power controller 18 monitors the second water temperature sensor 14 (water temperature sensor for measuring the temperature after passing through the cooler 21). When the temperature measured by the second water temperature sensor 14 increases, the power controller 18 increases the output of the pump 7 in order to increase the cooling efficiency of the cooler 21. That is, as shown in FIG. 3, the refrigerant flow rate and the refrigerant temperature (refrigerant temperature after passing through the cooler 21) are controlled by the power controller 18 with a certain correspondence so that the refrigerant flow rate increases as the refrigerant temperature increases. Yes. Here, the pump 7 is driven by electric power from the sub-battery 6. In general, the output voltage of the battery of an electric vehicle always changes. When the output voltage of the sub battery 6 changes, the output of the pump 7 also changes. That is, even when the output command value from the power controller 18 to the pump 7 is the same, if the output voltage of the sub battery 6 decreases, the actual output of the pump 7 also decreases. Therefore, for example, as shown in the graph of FIG. 3, even when the refrigerant temperature is the same, the actual refrigerant flow rate is lower when the output voltage of the sub battery 6 is 11.5 V than when the output voltage is 12 V. In addition to the correspondence between the refrigerant flow rate and the refrigerant temperature, the controller 12 stores a correspondence relationship for calculating the refrigerant flow rate according to the variation in the output voltage of the sub battery 6 in advance. Thus, the controller 12 can estimate the refrigerant flow rate F based on the output voltage of the sub battery 6 and the refrigerant temperature (measured temperature of the second water temperature sensor 14). Note that the correspondence relationship between the refrigerant flow rate and the refrigerant temperature shown in FIG. 3 is schematically represented by a straight line and is not accurate.

Next, the controller 12 calculates the amount of heat absorbed by the refrigerant while it passes through the cooler 21 (hereinafter referred to as heat receiving amount Qw1) (S3). The amount of heat absorbed per unit time of the refrigerant (heat receiving amount Qw1) can be obtained from the temperature of the refrigerant increased by the absorbed amount of heat using the following equation.
(Heat reception amount Qw1) = (refrigerant flow rate F) × (refrigerant specific heat Hc) × (refrigerant density D) × (refrigerant rising temperature dT)
Here, the refrigerant flow rate F is calculated in step S2. The refrigerant rising temperature dT is calculated as the difference between the measured value of the first water temperature sensor 13 and the measured value of the second water temperature sensor 14 in step S1. The controller 12 stores in advance values of the specific heat Hc of the refrigerant and the density D of the refrigerant. Therefore, the heat reception amount Qw1 of the refrigerant can be calculated using the above formula.

  Next, the controller 12 calculates the calorific value Qw2 of the power converter 2 (S4). The power converter 2 generates heat due to loss of electrical energy. The energy loss of the power converter 2 can be estimated from the current flowing through the power converter 2 at a predetermined time, the carrier frequency of the voltage converter circuit 2a and the inverter circuit 2b, and the like. As described above, the current flowing through the power converter 2 is monitored by the controller 12 by the current sensor. Therefore, the loss per unit time is calculated from the estimated loss of the power converter 2, and the heat generation amount Qw2 of the power converter 2 is estimated based on the value. A calculation formula for estimating the heat generation amount Qw2 of the power conversion device 2 is stored in the controller 12 in advance.

  Next, the controller 12 determines whether or not an abnormality has occurred in the first and second water temperature sensors 13 and 14 from the difference between the amount of heat received Qw1 of the refrigerant and the amount of heat generated Qw2 of the power converter 2 (S5). Theoretically, the amount of heat received Qw1 of the refrigerant is equal to the amount of heat generated Qw2 of the power converter 2. Here, if there is a difference between the refrigerant heat reception amount Qw1 and the heat generation amount Qw2 of the power converter 2 that is equal to or greater than a value considering measurement error, the first water temperature sensor 13 that is the basis for calculating the heat reception amount Qw1, Alternatively, it can be estimated that the measured value of the second water temperature sensor 14 is abnormal. Specifically, when the difference between the heat reception amount Qw1 and the heat generation amount Qw2 is larger than a predetermined heat amount difference threshold, the first water temperature sensor 13 or the second water temperature that is the basis for calculating the refrigerant heat reception amount Qw1. The sensor 14 is determined to be abnormal, and the process proceeds to step S6. On the other hand, if the difference between the heat reception amount Qw1 and the heat generation amount Qw2 is equal to or less than the heat amount difference threshold value, it is determined that there is no abnormality in the first and second water temperature sensors 13 and 14 (S7), and the series of processes is terminated. Note that the heat difference threshold is determined by the specifications of the power conversion device 2 and stored in the controller 12.

  If it is determined that there is an abnormality in the first water temperature sensor or the second water temperature sensor 14, the controller 12 outputs an abnormality notification signal (S6). The abnormality notification signal is sent to the instrument panel 16 and the diagnosis memory 17 shown in FIG. When the abnormality notification signal is received, a warning lamp on the instrument panel 16 is turned on. The abnormality notification signal is stored in the diagnosis memory 17. Then, a series of processing ends.

  The “first water temperature sensor” is an example of the “first temperature sensor”, and the “second water temperature sensor” is an example of the “second temperature sensor”.

  Hereinafter, points to be noted regarding the technology shown in the embodiments will be described. In the embodiment, the flow rate of the refrigerant is estimated from the refrigerant temperature and the output voltage of the sub-battery, but the flow rate sensor may be arranged directly inside the refrigerant supply pipe or the refrigerant discharge pipe.

  The power conversion device 2 according to the embodiment includes a voltage converter circuit 2a and an inverter circuit 2b. The calorific value of each circuit may be estimated individually and summed up to obtain the calorific value Qw2 of the power converter 2. By individually estimating the heat generation amounts of the plurality of heat generation sources, the heat generation amount of the power conversion device can be estimated more accurately, and as a result, the accuracy of abnormality detection of the temperature sensor is also improved.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Power converter 2a: Voltage converter circuit 2b: Inverter circuit 3: Main battery 4: Radiator 5: Motor 6: Sub battery 7: Pump 8: Step-down converter 9a: Refrigerant supply pipe 9b: Refrigerant discharge pipe 12: Controller 13: 1st water temperature sensor 14: 2nd water temperature sensor 15: Drive wheel 16: Instrument panel 17: Memory for diagnosis 21: Cooler

Claims (1)

A power converter that supplies power to the motor for traveling;
A first temperature sensor that measures the temperature of the refrigerant supplied to the power converter;
A second temperature sensor that measures the temperature of the refrigerant after passing through the power converter;
A controller for detecting an abnormality of the first or second temperature sensor;
The controller comprises:
Calculating the amount of heat absorbed by the refrigerant from the difference between the temperatures measured by the first and second temperature sensors and the flow rate of the refrigerant sent to the power converter,
Estimate the amount of heat generated by the power converter from the current flowing through the power converter,
When a difference between the calculated heat quantity and the estimated heat quantity exceeds a predetermined heat quantity difference threshold value, a signal notifying that an abnormality has occurred in the first or second temperature sensor is output.
The electric vehicle characterized by the above-mentioned.

Images