JP6245088B2 - Cooler - Google Patents

Description

  The present invention relates to a cooler using a liquid refrigerant. In particular, the present invention relates to a cooler for cooling a semiconductor element.

  In the case of a cooler using a liquid refrigerant, the temperature of the refrigerant may be used for control of the cooler (for example, Patent Documents 1 and 2). Patent Documents 1 and 2 both disclose an inverter cooler for an electric vehicle. The refrigerant is water. The cooler of Patent Document 1 detects a refrigerant circulation failure from the difference between the temperature of the semiconductor element of the inverter and the water temperature (refrigerant temperature). The cooler of patent document 2 estimates the temperature of a semiconductor element from the electric current which flows through the semiconductor element of an inverter. The flow rate of the refrigerant is controlled based on the difference between the temperature of the refrigerant and the estimated temperature of the semiconductor element.

JP 2010-153567 A JP 2012-099694 A

  When the temperature of the refrigerant is used for controlling the cooler, it is desirable that the refrigerant temperature can be measured as accurately as possible. Although it is sufficient if the refrigerant temperature can be directly measured, since the sensor is immersed in a liquid refrigerant, the cost increases due to waterproofing of the sensor. Therefore, a temperature sensor may be attached to a casing through which the refrigerant flows so as not to directly touch the refrigerant, and a measured value of the temperature sensor may be used as the refrigerant temperature. However, in that case, what is directly measured is the temperature of the casing, not the temperature of the refrigerant. It takes time for the heat of the refrigerant to reach the temperature sensor through the housing. This time is hereinafter referred to as time delay. A temperature difference caused by a time delay occurs between the actual temperature of the refrigerant and the measured value of the temperature sensor. The present specification provides a technique for compensating for the temperature difference due to this time delay. In the following, “compensating for a temperature difference due to time delay” may be simply referred to as “compensating for time delay”.

  In an inverter of an electric vehicle, a temperature sensor that measures the temperature of a semiconductor element may be provided. Unlike the temperature sensor attached to the housing, the temperature sensor that measures the temperature of the semiconductor element has the property that the accuracy of the absolute value is not high but the response is good. A typical temperature sensor that measures the temperature of a semiconductor element is a thermistor built in a chip of the semiconductor element.

  In the technology disclosed in this specification, a short-time temperature change obtained from a measurement value of a temperature sensor that measures the temperature of a semiconductor element is regarded as a temperature difference caused by a time delay in the temperature sensor that measures the temperature of the refrigerant. use. Below, in order to distinguish the temperature sensor which measures the temperature of a semiconductor element, and the temperature sensor which measures the temperature of a refrigerant | coolant, the former may be called an element temperature sensor and the latter may be called a refrigerant | coolant temperature sensor.

  The cooler disclosed in this specification is a liquid-cooled cooler that cools a semiconductor element. The cooler includes an element temperature sensor (first temperature sensor), a refrigerant temperature sensor (second temperature sensor), and a corrector. The refrigerant temperature sensor is attached to the cooler casing so as not to touch the liquid refrigerant. The corrector corrects the refrigerant temperature measured by the refrigerant temperature sensor using the measurement value of the element temperature sensor. That is, the time delay in the refrigerant temperature sensor is compensated using the measured value of the element temperature sensor. The corrector stores a time constant when the transfer function of heat from the refrigerant to the second temperature sensor is expressed by a linear model (first-order lag system or second-order lag system). The corrector corrects the measured value of the refrigerant temperature by the following algorithm. The corrector estimates the heat generation amount of the semiconductor element from the current flowing through the semiconductor element. The corrector estimates the amount of change in the refrigerant temperature during the period corresponding to the time constant described above from the estimated calorific value and the measured value of the element temperature sensor. This amount of change corresponds to a temperature difference caused by a time delay. The corrector outputs a value obtained by adding the amount of change to the measured value of the refrigerant temperature sensor as the corrected refrigerant temperature.

  The algorithm for obtaining the amount of change in the refrigerant temperature for a predetermined time from the current flowing through the semiconductor element and the measured value of the element temperature sensor is as follows. By multiplying the measured value of the element temperature sensor by the heat capacity of the semiconductor element (and the surrounding structure), the amount of heat possessed by the semiconductor element (and the surrounding structure) is obtained. With a certain time as a reference (reference time), a change in the amount of heat of the semiconductor element (and its surrounding structure) from the reference time is obtained from a change in the measured value of the element temperature sensor. On the other hand, a change from the reference time of the amount of heat generated by the semiconductor element is obtained from the current flowing through the semiconductor element. The change in the amount of heat generated by the semiconductor element minus the change in the amount of heat that the semiconductor element (and the surrounding structure) has corresponds to the change in the amount of heat transferred to the refrigerant. When the change in the amount of heat transferred to the refrigerant is divided by the heat capacity of the refrigerant, a change in the temperature of the refrigerant based on the change in the amount of heat is obtained. This temperature change is an estimated value of the refrigerant temperature, but since the measured value of the element temperature sensor is used, the absolute value thereof is not accurate. Therefore, low frequency components are removed from the time series data of the estimated values. The remaining high frequency component is the amount of change in the refrigerant temperature in a short time, and this value is accurate. When the “short time” is made to correspond to a time delay until the actual temperature change of the refrigerant is reflected in the measured value of the temperature sensor, the high frequency component becomes an estimated value of the temperature difference caused by the time delay. The corrector compensates the time delay by adding the high-frequency component of the estimated value of the refrigerant temperature obtained from the measured value of the element temperature sensor to the measured value of the refrigerant temperature sensor.

  The algorithm for removing high frequency components is as follows. The mechanism of heat transfer until the temperature change of the refrigerant appears in the measured value of the refrigerant temperature sensor can be modeled by a first-order lag system or a second-order lag system. Here, it is assumed that the model is a first-order lag system. The time constant of the first order lag model is represented by Td. The compensator applies a first-order lag low-pass filter with a time constant Td to the time-series data of the refrigerant temperature change obtained from the measured value of the element temperature sensor. The obtained result is an estimated value of the measured value of the refrigerant temperature sensor including the time delay. Therefore, the remainder obtained by subtracting the temperature change (time-series data) after passing through the low-pass filter from the temperature change before passing through the low-pass filter is an estimated value of the temperature difference due to the time delay.

  With the above algorithm, the corrector compensates for the time delay of the refrigerant temperature sensor. In addition, when the heat transfer mechanism until the temperature change of the refrigerant appears in the measured value of the refrigerant temperature sensor is modeled by a second-order lag system, a second-order low-pass having two time constants of the second-order lag system A filter may be used.

  The cooler disclosed in this specification can estimate the actual refrigerant temperature by compensating for the measurement time delay of the measurement value of the refrigerant temperature sensor provided so as not to directly touch the refrigerant. Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a block diagram of the electric vehicle containing the cooler of an Example. It is a typical perspective view of a cooler and a power converter. It is sectional drawing along the III-III line of FIG. It is sectional drawing along the IV-IV line of FIG. It is an enlarged view of the range of the broken line V of FIG. It is a flowchart figure of the correction process which a compensator performs. It is the graph which showed an example of the effect of amendment.

  A cooler according to an embodiment will be described with reference to the drawings. The cooler 10 of the embodiment is a device that cools the semiconductor elements T <b> 1 to T <b> 8 of the power converter 2. The cooler 10 and the power converter 2 are mounted on the electric vehicle 100. The power converter 2 boosts the power of the main battery 81, further converts it into alternating current, and supplies it to the traveling motor 83.

  Before describing the cooler 10, the circuit configuration of the power converter 2 will be described. The power converter 2 is connected to the main battery 81 via the system main relay 82. The power converter 2 includes a voltage converter circuit 8 and an inverter circuit 9. The power of the main battery 81 is input to the voltage converter circuit 8. The voltage converter circuit 8 performs both a step-up operation for boosting the voltage of the main battery 81 and supplying it to the inverter circuit 9 and a step-down operation for stepping down the voltage of the regenerative power generated by the motor 83 and supplying it to the main battery 81. can do. The voltage converter circuit 8 includes two transistors T7 and T8, two diodes D7 and D8, a reactor 4, and a filter capacitor 3. Two transistors T7 and T8 are connected in series. A diode is connected in antiparallel to each transistor. The high potential end of the series circuit of the transistors is connected to the inverter side output terminal PH of the voltage converter circuit 8. The low potential end of the series circuit is connected to the ground line GL of the voltage converter circuit 8. One end of the reactor 4 is connected to the middle point PM of the series circuit of transistors, and the other end is connected to the battery side input terminal PL of the voltage converter circuit 8. The filter capacitor 3 is connected between the battery side input terminal PL of the voltage converter circuit 8 and the ground line GL. Further, a smoothing capacitor 5 for suppressing the pulsation of the output current of the voltage converter circuit 8 is connected between the inverter side output terminal PH and the ground line GL.

  The voltage of the main battery 81 is boosted and supplied to the inverter circuit 9 by the on / off operation of the transistor T8. The regenerative power input from the inverter circuit side is stepped down by the ON / OFF operation of the transistor T7 and supplied to the main battery 81.

  The inverter circuit 9 will be described. The inverter circuit 9 is a circuit in which three sets of series circuits of two transistors are connected in parallel (T1 and T4, T2 and T5, and T3 and T6). Each diode (D1-D6) is connected in antiparallel to each transistor. An alternating current is output from the middle point of each series circuit by the on / off operation of each transistor. The output alternating current is supplied to the motor 83. A current sensor 16 is provided on the output line of the inverter circuit 9.

  A drive signal (PWM signal) for driving each transistor T1-T8 is generated by the controller 7 and supplied to each transistor. The controller 7 receives a target output of the motor 83 from a host controller (not shown) and controls each switching element so as to realize the target output. Specifically, the controller 7 monitors the output current by the current sensor 16, determines the operation pattern of each transistor so that the output current matches the target value, and outputs a drive signal corresponding to the operation pattern to each transistor. Supply.

  The transistor T5 of the inverter circuit 9 is provided with an element temperature sensor 6a, and the transistor T8 of the voltage converter circuit 8 is provided with an element temperature sensor 6b. Specifically, the transistor T5 (T8) is mounted on a semiconductor substrate, and the element temperature sensor 6a (6b) is built on the same semiconductor substrate. The element temperature sensor 6a (6b) is, for example, a PTC (Positive Temperature Coefficient) thermistor. Since the element temperature sensor 6a (6b) is built in the mounting substrate of the transistor, the temperature of the transistor can be measured without time delay (delay time). However, since the thermistor includes an offset in the measurement value, the absolute value of the measurement value is not very accurate. The measured value of the element temperature sensor 6a (6b) is also sent to the controller 7. The controller 7 monitors the measured value of the element temperature sensor 6a (6b). When the measured value exceeds a predetermined temperature upper limit value, the controller 7 limits the output of the motor 83 to prevent the transistor from overheating. However, as shown in FIG. 1, the inverter circuit 9 has no element temperature sensor other than the transistor T5. For example, when the vehicle gets on the car stop and the motor outputs torque but the wheels do not rotate, the current flows only in a specific transistor. In the case where current is concentrated in a transistor other than the transistor T5 (for example, the transistor T1), the element temperature sensor 6a cannot detect the state of the transistor T1. In preparation for such a case, the controller 7 also monitors the temperature of the refrigerant in the cooler 10. Next, the cooler 10 will be described.

  The power converter 2 is in contact with a cooler 10 for cooling the transistors T1-T8. FIG. 2 is a schematic perspective view of the power converter 2 and the cooler 10. 3 is a cross-sectional view taken along line III-III in FIG. 2, and FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. The cooler 10 will be described with reference to FIGS. The cooler 10 includes a housing 19, a refrigerant temperature sensor 12, a pump 13, a radiator 14, and a circulation path 15. Since the pump 13 is controlled by the controller 7, the controller 7 is also a part of the cooler 10. A symbol Cmd in FIG. 1 means a command value of a pump output sent from the controller 7 to the pump 13. The sign Sn in FIG. 1 means a measured value sent from the refrigerant temperature sensor 12 to the controller 7.

  The refrigerant of the cooler 10 is a liquid. Specifically, the refrigerant is water or LLC (Long Life Coolant). The refrigerant circulates between the casing 19 and the radiator 14 by the pump 13 and the circulation path 15. As shown in FIGS. 3 and 4, a flow path 18 through which the refrigerant passes is formed inside the housing 19. The casing 19 is made of aluminum having a high thermal conductivity. The casing 19 is a flat plate type, and the power converter 2 is attached to one surface thereof. 2 to 4, the power converter 2 is simplified and drawn in a rectangular parallelepiped. The actual power converter 2 has a complicated shape.

  A partition plate 17c is provided inside the housing 19, and the flow path 18 is curved in a U shape with the partition plate 17c interposed therebetween. The refrigerant supplied by the pump 13 flows into the housing 19 from the inflow port 17a. The inflowing refrigerant absorbs heat from the transistors T1 to T8 of the power converter 2 while flowing through the U-shaped flow path 18. The refrigerant whose temperature has increased by absorbing heat is discharged from the housing 19 through the discharge port 17 b and moves to the radiator 14 through the circulation path 15. The refrigerant is cooled by exchanging heat with air in the radiator 14. The refrigerant whose temperature has decreased is sent again to the housing 19 by the pump 13.

  The flow rate of the refrigerant flowing through the flow path 18 is determined by the output of the pump 13. The controller 7 adjusts the output of the pump 13 based on the measured value of the element temperature sensor 6 a (6 b) and the measured value of the refrigerant temperature sensor 12 provided in the housing 19. Further, as described above, the controller 7 limits the output of the motor 83 when the temperature of the transistor rises excessively based on the measured values of the element temperature sensors 6a and 6b and the refrigerant temperature sensor 12.

  As shown in FIGS. 3 and 4, the refrigerant temperature sensor 12 is attached to the outside of the housing 19. In other words, the refrigerant temperature sensor 12 is attached to the housing 19 so as not to touch the liquid refrigerant. As shown in FIG. 4, the casing 19 is composed of a main body 19a and a cover 19b. A gasket 21 is provided between the main body 19a of the housing 19 and the cover 19b, and the airtightness of the flow path 18 is ensured.

  An enlarged view of the range indicated by the broken line V in FIG. 4 is shown in FIG. Since the refrigerant temperature sensor 12 is away from the flow path 18, the influence of the change in the refrigerant temperature is delayed and appears in the measured value of the refrigerant temperature sensor 12. Arrows A1 and A2 in FIG. 5 schematically represent how the heat of the refrigerant is transmitted. That is, the measured value of the refrigerant temperature sensor 12 has a time delay. The controller 7 compensates for the time delay based on the measured value of the element temperature sensor 6a (6b) provided in the transistor T5 (T8). The algorithm will be described next.

  FIG. 6 shows a flowchart of the refrigerant temperature correction process executed by the controller 7. First, the controller 7 reads the measured values of the element temperature sensors 6a and 6b and the refrigerant temperature sensor 12 (S2). Next, the controller 7 specifies the total current flowing through the transistors T1 to T8 by the current sensor 16. The controller 7 calculates the amount of heat generated by the transistors T1-T8 from the total current (S3). Note that the relationship between the current and the amount of heat generation is specified in advance by experiments or the like. On the other hand, the controller 7 obtains the heat quantity of the transistor (and its surrounding structures) from the measured values of the element temperature sensors 6a and 6b, that is, the temperatures of the transistors T5 and T8. Specifically, the controller 7 stores the temperature change of the transistor after that time with reference to the temperature at a specific time, and specifies the amount of heat corresponding to the temperature rise at each time. The amount of heat can be obtained by multiplying the temperature rise by the heat capacity of the transistor (and the surrounding structure). The controller 7 subtracts the amount of heat corresponding to the temperature rise of the transistor from the amount of heat generated by the transistor. The resulting amount of heat corresponds to the amount of heat transferred to the refrigerant. The controller 7 calculates (estimates) the temperature of the refrigerant with respect to the temperature at the reference time by dividing the amount of heat transferred to the refrigerant by the heat capacity of the refrigerant (S4). The temperature of the refrigerant determined in S4 is an estimated value obtained from the current flowing through the transistor and the measured values of the element temperature sensors 6a and 6b. The controller 7 calculates the refrigerant temperature at each time after the reference time. That is, the controller 7 obtains time series data of the estimated value of the refrigerant temperature after the reference time.

  Since the measured values of the element temperature sensors 6a and 6b built in the semiconductor substrate include an offset, the absolute value is not accurate. On the other hand, a short time change is accurately reflected in the measured values of the element temperature sensors 6a and 6b. The controller 7 compensates for the time delay of the refrigerant temperature sensor 12 using this short time change. The controller 7 removes the low frequency component from the time series data of the estimated value of the refrigerant temperature. Specifically, the controller 7 passes the time series data of the estimated value through a low-pass filter, and subtracts the time series data after filtering from the time series data before filtering. The result thus obtained becomes the high frequency component of the estimated value of the refrigerant temperature change. This high frequency component of the estimated value corresponds to a correction value for the measurement value of the refrigerant temperature sensor (S5). Finally, the controller 7 outputs a value obtained by adding the correction value to the measured value of the refrigerant temperature sensor 12 as the corrected refrigerant temperature (S6). This output is sent to the pump control program. In the pump control program, the pump output is adjusted based on the corrected refrigerant temperature.

  The above low-pass filter will be described. For the low-pass filter, a linear model of a heat transfer function until the refrigerant temperature change appears in the measured value of the refrigerant temperature sensor 12 is used. The linear model of the transfer function is typically a first-order lag system or a second-order lag system. Since this linear model is based on the structure of the cooler, it is specified in advance. The result after passing through such a low-pass filter is an estimated value of the measured value of the refrigerant sensor. Since the time series data before filtering is the estimated value of the refrigerant temperature, and the time series data after filtering is the estimated value of the measured value of the refrigerant temperature sensor 12, the result of subtracting the latter from the former is due to a time delay. This corresponds to an estimated value of the temperature difference between the actual temperature of the refrigerant and the measured value. That is, the temperature difference caused by the time delay can be estimated by the above algorithm. The controller 7 compensates for the temperature change corresponding to the delay time with respect to the measured value of the refrigerant temperature sensor 12 by using the measured values of the element temperature sensors 6a and 6b having a quick response.

  FIG. 7 shows an example of temperature correction by the above algorithm. The graph G4 has a different scale from the other graphs (the numerical value is not shown, but the graph G4 corresponds to the right scale and the other graphs correspond to the left scale). The horizontal axis is time. A graph G1 (solid line) indicates a measurement value of the refrigerant temperature sensor 12.

  A graph G2 (broken line) shows the estimated temperature of the refrigerant obtained from the current flowing through the transistor and the measured values of the element temperature sensors 6a and 6b. As described above, the absolute value of the graph G2 is not accurate. A graph G3 (solid line) is obtained by applying a first-order lag filter to the graph G2 with a time constant Td. The time constant Td is a time constant when the heat transfer characteristic until the change in the refrigerant temperature appears in the measurement value of the refrigerant temperature sensor is modeled by a linear delay system. Therefore, the graph G3 corresponds to the estimated value of the measured value of the refrigerant temperature sensor.

  Graph G4 (broken line) is obtained by subtracting graph G3 (estimated value of the refrigerant temperature sensor) from graph G2 (estimated value of the refrigerant temperature). That is, the graph G4 corresponds to the temperature difference between the actual temperature of the refrigerant and the measured value due to the time delay. In other words, the graph G4 corresponds to the correction value of the measured value of the refrigerant temperature sensor.

  A graph G5 (gray straight line) is obtained by adding the graph G4 (correction value) to the graph G1 (measurement value of the refrigerant temperature sensor). Graph G6 (dotted line) is a value (actual refrigerant temperature) obtained by directly measuring the refrigerant temperature for effect verification. It can be seen that the corrected refrigerant temperature (graph G5) is in good agreement with the actual refrigerant temperature (graph G6).

  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 3: Filter capacitor 4: Reactor 5: Smoothing capacitors 6a, 6b: Element temperature sensor 7: Controller 8: Voltage converter circuit 9: Inverter circuit 10: Cooler 12: Refrigerant temperature sensor 13: Pump 14: Radiator 15: Circuit 16: Current sensor 17: Gasket 17a: Inlet 17b: Outlet 17c: Partition plate 18: Channel 19: Housing 19a: Main body 19b: Cover 81: Main battery 82: System main relay 83: Motor 100: Electric vehicle D1-D8: Diode T1-T8: Transistor GL: Ground line PH: Inverter side output terminal PL: Battery side input terminal PM: Middle point

Claims (1)

A liquid-cooled cooler for cooling a semiconductor element,
A first temperature sensor for measuring the temperature of the semiconductor element;
A second temperature sensor attached to the cooler housing so as not to touch the liquid refrigerant;
A corrector for correcting the refrigerant temperature measured by the second temperature sensor;
With
The corrector is
Storing the time constant when the transfer function of heat from the refrigerant to the second temperature sensor is expressed by a linear model;
The amount of heat generated by the semiconductor element is estimated from the current flowing through the semiconductor element,
From the estimated calorific value and the measured value of the first temperature sensor, the amount of change in the refrigerant temperature during the time constant period is estimated,
A value obtained by adding the estimated change amount to the measured value of the second temperature sensor is output as the corrected refrigerant temperature;
A cooler characterized by that.