JP6468142B2 - In-vehicle relay temperature detection system - Google Patents

Description

  The present invention relates to a temperature detection system for an in-vehicle relay connected between a battery and a load.

  In a hybrid vehicle or an electric vehicle, electric power is supplied from a battery to a load such as a rotating electric machine. A relay called a system main relay (SMR) is connected between the two. The connection and disconnection of the battery and the load are switched by the relay.

  If the relay falls into an overheated state, problems such as contact welding / melting may occur. Therefore, temperature monitoring is performed by providing a temperature sensor in the relay. When the relay temperature exceeds a predetermined threshold, overheat protection control such as reducing the current flowing through the relay is executed to suppress the temperature rise of the relay.

  In detecting the temperature of the relay, for example, a thermistor widely used as an in-vehicle temperature sensor is used. When the thermistor detection element is brought into direct contact with the contact part of the relay or the bus bar, it is natural that a large current flows through the thermistor, leading to breakage.For example, the detection element is insulated and this is applied to the conductor part of the relay. Deploy.

  Since the thermistor detects the temperature of the relay through an insulator, it may be difficult to accurately measure the temperature of the relay with good responsiveness. For example, when a large current flows through the relay, the temperature of the relay rapidly increases. At this time, the heat generated from the relay is transferred to the thermistor through heat transfer by the insulator, so that the detected temperature of the thermistor is delayed until it reaches the actual temperature of the relay, and is lower than the actual temperature of the relay. The temperature is output.

  If a temperature lower than the actual temperature of the relay is output, relay overheating may not be detected or detection delay may occur. Therefore, for example, in Patent Documents 1 and 2, correction processing is performed on the detection value of the relay. For example, the correction value is added (accumulated) to the detection value of the relay, and this is output as the temperature value of the relay. In order to reliably avoid overheating of the relay, conventionally, a correction value is uniformly added to a detection value by a thermistor.

JP 2013-158217 A JP 2011-86742 A

  By the way, when the correction value is uniformly added to the detection value of the thermistor, the correction value is also added when the detection value of the thermistor is close to the actual value, for example, when a large current is not flowing through the relay. . In this case, the temperature value finally output as the relay temperature becomes higher than the actual relay temperature by the addition of the correction value. At this time, even if the actual temperature of the relay is less than the heat resistant upper limit temperature of the relay, if the output temperature value exceeds the heat resistant upper limit temperature of the relay, overheat prevention control is executed on the relay, and the load The power supply to will be reduced. Accordingly, an object of the present invention is to provide a temperature detection system for an in-vehicle relay in which temperature correction for the thermistor is not performed inappropriately.

  The present invention relates to a temperature detection system for an in-vehicle relay connected between a battery and a load. The system includes a thermistor that detects the temperature of the relay and a calculation unit. The arithmetic unit adds a correction value to the detection value of the thermistor based on the current flowing through the relay when the average value of the current flowing through the relay in a predetermined period exceeds a threshold, and outputs the correction value as the temperature value of the relay To do.

  According to the present invention, when a large current flows through the relay for a predetermined period, in other words, when the relay is likely to be overheated and the thermistor may detect a temperature lower than actual, A correction value is added to the detected value. By doing so, inappropriate temperature correction for the thermistor is suppressed.

It is a perspective view which illustrates a relay temperature detection system and its peripheral equipment concerning this embodiment. FIG. 2 is an enlarged perspective view of the vicinity of a junction block in FIG. 1. It is a figure which illustrates the temperature detection circuit of a system main relay. It is a figure which illustrates the correction processing flow by a monitoring unit. It is a figure which shows another example of a correction process flow. It is a figure which illustrates the correction value map used by the correction process flow. It is a figure which illustrates the electric current value map used by the correction process flow.

  FIG. 1 illustrates an in-vehicle relay temperature detection system and its peripheral devices according to this embodiment, and FIG. 2 illustrates an enlarged view thereof. In the example of FIGS. 1 and 2, the temperature detection system for the in-vehicle relay is mounted on a battery unit 12 such as a so-called hybrid vehicle or electric vehicle. The temperature detection system of the in-vehicle relay can communicate with a control unit 14 to be described later.

  The battery unit 12 includes an assembled battery (battery) 16, a junction block 18, a monitoring unit 20, and a cooling blower 22. As will be described later, the in-vehicle relay temperature detection system includes a monitoring unit 20 and various sensors (thermistors 24A to 24C, current sensor 26) connected thereto.

  The assembled battery 16 is a stack (stacked body) in which a plurality of battery cells (single batteries) are stacked. These battery cells are comprised from secondary batteries, such as a nickel metal hydride battery or a lithium ion battery, for example.

  For example, the cooling blower 22 takes in air in the passenger compartment and sends the cooling air to the assembled battery 16 through the duct 30. Further, as shown by the arrows in FIGS. 1 and 2, after passing through the assembled battery 16, the cooling air is also supplied to the junction block 18 and the monitoring unit 20 to cool these devices.

  The junction block 18 includes system main relays (or simply called relays) SMRB, SMRG, and SMRP. For example, the junction block 18 is disposed on the duct 30. In the embodiment shown in FIGS. 1 and 2, the system main relays SMRB, SMRG, and SMRP are mounted on the single junction block 18, but this is not restrictive. For example, the junction block 18 may be divided into a plus side junction block on which the plus side relay SMRB is mounted and a minus side junction block on which the minus side relay SMRG and the precharge relay SMRP are mounted.

  System main relays SMRB, SMRG, and SMRP are connected between assembled battery 16 and a load such as a rotating electric machine (not shown), and switch connection and disconnection between assembled battery 16 and the load. Since a large current is supplied from the assembled battery 16 to the bus bars 25A, 25B, 25C and contact portions of the system main relays SMRB, SMRG, SMRP, etc., these conductor portions are made of an insulating material such as resin. Is housed in a casing (not shown).

  As shown in FIG. 3, system main relay SMRB is connected to the plus side of assembled battery 16 (plus side relay), and system main relay SMRG is connected to the minus side of assembled battery 16 (minus side relay). The system main relay SMRP is a so-called precharge relay, which is provided in parallel with the minus-side relay SMRG and is connected in series with a high-resistance resistor R. When the assembled battery 16 (battery) and the load are switched from the disconnected state to the conductive state, the plus-side relay SMRB is switched from OFF to ON, and the precharge relay SMRP is switched from OFF to ON. At this time, since the electric power supplied from the assembled battery 16 flows to the high-resistance resistor R through the precharge relay SMRP, it is possible to avoid a large inrush current from flowing at the beginning of conduction. When the assembled battery 16 and the capacitor in the circuit including the load are sufficiently charged and no inrush current is generated, the precharge relay SMRP is switched from on to off, and the negative relay SMRG is switched from off to on.

  The monitoring unit 20 (calculation unit) monitors the SOC (State of Charge) and temperature of the assembled battery 16. In addition, the monitoring unit 20 monitors the temperature of the system main relays SMRB, SMRG, SMRP. Since the former (monitoring of SOC and temperature of the assembled battery 16) is known, the description thereof is omitted here. The monitoring unit 20 includes, for example, a computer, and a CPU, which is an arithmetic circuit, a storage unit such as a memory, and a device / sensor interface are connected to each other via an internal bus. The monitoring unit 20 is disposed on the duct 30, for example.

  The storage unit of the monitoring unit 20 stores an SOC calculation program for the assembled battery 16, a correction processing program for the detection values of the thermistors 24A to 24C, a correction value map, and a current value map, which will be described later.

  The monitoring unit 20 acquires signals from various sensors via the device / sensor interface. Specifically, various detection signals are acquired from the current sensor 26 and the thermistors 24A to 24C.

  Thermistors 24A to 24C detect the temperatures of system main relays SMRB, SMRG, and SMRP, respectively. In the example shown in FIGS. 1 and 2, the detection elements of the thermistors 24A to 24C are disposed on the bus bars 25A, 25B, and 25C of the system main relays SMRB, SMRG, and SMRP after being covered with insulation.

  Of the system main relays SMRB, SMRG, and SMRP, the thermistor 24C of the precharge relay SMRP may be omitted. That is, as described above, the precharge relay SMRP has a very short connection period, such as being temporarily connected before the minus-side relay SMRG is connected, and the risk of overheating is relatively low. It is considered low. For this reason, the system main relays to be temperature-detected may be narrowed down to the plus side relay SMRB and the minus side relay SMRG.

  The current sensor 26 is provided in the junction block 18 and detects a current flowing through the system main relays SMRB, SMRG, SMRP. The current sensor 26 is composed of, for example, a magnetic balance type current sensor, and detects a current flowing through a bus bar (not shown) connected to the system main relays SMRB, SMRG, SMRP.

  The monitoring unit 20 performs arithmetic processing on signals from the current sensor 26, the thermistors 24A to 24C, etc., and sends the temperature values of the system main relays SMRB, SMRG, SMRP to the control unit 14 via the device / sensor interface.

  Returning to FIG. 1, the control unit 14 is also referred to as an electronic control unit (ECU), and is composed of a computer, for example. That is, in the control unit 14, for example, a CPU that is an arithmetic circuit, a storage unit such as a memory, and a device / sensor interface are connected to each other via an internal bus. The control unit 14 is provided at a position separated from the battery unit 12 (for example, in front of the vehicle) and can communicate with each other via a signal line (indicated by a one-dot chain line).

  The control unit 14 controls the on / off operation of the system main relays SMRB, SMRG, SMRP. Further, the control unit 14 determines whether or not the overheat protection control of the system main relays SMRB, SMRG, SMRP is executable based on the temperature values of the system main relays SMRB, SMRG, SMRP received from the monitoring unit 20. For example, when the temperature value of any one of the system main relays SMRB, SMRG, and SMRP exceeds a predetermined threshold value, the power supplied from the assembled battery 16 to the load is limited (the power is reduced), whereby the system The temperature rise of the main relays SMRB, SMRG, SMRP is suppressed.

<Relay temperature detection system>
The in-vehicle relay temperature detection system according to the present embodiment includes a monitoring unit 20, a current sensor 26, and thermistors 24A to 24C. FIG. 3 illustrates a circuit diagram of the relay temperature detection system. As shown in this figure, the monitoring unit 20 includes a temperature detection circuit 34A including the thermistor 24A, a temperature detection circuit 34B including the thermistor 24B, and a temperature detection circuit 34C including the thermistor 24C. Yes. By providing such a circuit configuration, the detected temperatures of the thermistors 24A to 24C can be independently calculated and acquired by the microcomputer 32 (or multiplexer) of the monitoring unit 20.

  The thermistors 24 </ b> A to 24 </ b> C are thermal elements (detection elements) whose resistance characteristics change according to temperature. Therefore, when a constant voltage is applied to each of the temperature detection circuits 34A to 34C from a voltage source (not shown), the resistance changes due to the temperature change of the thermistors 24A to 24C, and the output voltages (voltage drops) of the thermistors 24A to 24C change. From this voltage change and the temperature-resistance characteristics of the thermistors 24A to 24C stored in the microcomputer 32 or the like in advance, the temperature changes of the heat sources that cause the thermistors 24A to 24C to change in resistance, that is, system main relays SMRB, SMRG, SMRP It can be detected.

  Further, the microcomputer 32 receives a current value flowing from the current sensor 26 to the system main relays SMRB, SMRG, SMRP. The monitoring unit 20 executes a correction process flow to be described later, and adds a correction value to the temperature values detected from the thermistors 24A to 24C based on the current values flowing through the system main relays SMRB, SMRG, SMRP.

<Correction process flow>
FIG. 4 illustrates a temperature correction process flow of the thermistors 24 </ b> A to 24 </ b> C by the monitoring unit 20. This flow is executed independently for each of the system main relays SMRB, SMRG, SMRP, for example. That is, the three flows of the positive relay SMRB, the negative relay SMRG, and the precharge relay SMRP are independently executed by the microcomputer 32 of the monitoring unit 20.

  The correction process flow is roughly divided into two parts, a determination flow (S10 to S20) and a correction flow (S24, S26). In the determination flow, whether or not correction is necessary is determined depending on whether or not the average value of the current flowing through the system main relays SMRB, SMRG, and SMRP in a predetermined period (determination period) exceeds a predetermined threshold. In the correction flow, a process of adding (adding) correction values to the detection values (detection temperatures) of the thermistors 24A to 24C is executed.

  First, the monitoring unit 20 increments the determination period counter (S10). For example, if the counter is an initial value (i = 0), i = 1 at this step.

Subsequently, the monitoring unit 20 acquires a current value IB (i) flowing from the current sensor 26 to the system main relays SMRB, SMRG, SMRP. Furthermore, by adding the integrated value IB ² _sum (i-1) in the square value IB ² (i) the previous counter of the current value IB (i) (i-1 ), the integrated value IB ² _Sum (I) is obtained (S12).

The square value is focused on the point where Joule heat is proportional to the square of the current (Q = RI ² t). Also, the integrated value is taken in order to prevent the process from proceeding to the correction flow when a large current is generated for a short time, that is, when there is no risk of overheating of the system main relays SMRB, SMRG, SMRP. Instead of integrating the square value, the current value may be simply integrated. The initial value IB ² —sum (0) of the integrated value may be zero.

  Next, the monitoring unit 20 determines whether or not the counter i for the determination period has been counted up to a predetermined value k (k is a positive integer) (S14). When the counter i has not been counted up to the predetermined value k, after waiting for a predetermined period (for example, 100 msec) (S16), the process returns to step S10 again, and the counter i is incremented.

When the determination period counter i is counted up to a predetermined value k in step S14, the monitoring unit 20 divides the integrated value IB ² —sum (i = k) of the square of the current by the count number k. An average value IB ² _ave is obtained (S18). Instead of obtaining the square value of the current as the average value, an average value IB_ave of the current value may be obtained.

Next, the monitoring unit 20 determines whether or not the average value IB ² _ave exceeds a predetermined threshold IB ² _Th (> 0) (S20). If it does not exceed, the monitoring unit 20 determines that the correction value does not need to be added, and uses the detected values (detected temperatures) of the thermistors 24A to 24C as the temperatures of the system main relays SMRB, SMRG, SMRP. The data is output to the control unit 14 as it is (S22).

When the average value IB ² _ave exceeds a predetermined threshold value IB ² _Th, a large current flows through the system main relays SMRB, SMRG, SMRP over a predetermined period. In other words, the system main relays SMRB, SMRG, SMRP There is a risk of overheating, and the thermistors 24A to 24C may detect a temperature lower than the actual temperature. The monitoring unit 20 extracts (calls) a correction value using a correction value map as shown in the lower right of FIG. 4 (S24).

  In the correction value map, correction values [° C.] (≧ 0) corresponding to the current values [A] flowing through the system main relays SMRB, SMRG, SMRP are plotted. The relationship between the current value and the correction value may be obtained in advance by experiment, or may be obtained by simulation or the like. Further, a correction value map may be created for each of the plus side relay SMRB, the minus side relay SMRG, and the precharge relay SMRP.

  In step S24, the monitoring unit 20 plots the current values (for example, IB (i = k)) acquired in step S12 on a correction value map, and extracts correction values corresponding to these values. After step S24, the monitoring unit 20 adds the correction value acquired from the correction value map to the detection value (detection temperature) of the thermistors 24A to 24C, and controls this as the temperature value of the system main relays SMRB, SMRG, SMRP. The data is output to the unit 14 (S26). Furthermore, the monitoring unit 20 resets the determination period counter to the initial value (i = 0) (S28), and starts the flow of FIG. 4 again from step S10.

  As described above, by providing a determination flow prior to the addition of the correction value, the correction value addition is avoided when the average value of the current IB flowing through the system main relays SMRB, SMRG, SMRP is equal to or less than the threshold value, and is inappropriate. Temperature correction is suppressed.

Second Embodiment
In the correction processing flow shown in FIG. 4, only the current flowing through the system main relays SMRB, SMRG, and SMRP is referred to when extracting the correction value from the correction value map, but other parameters may be referred to. For example, when air cooling is performed on the system main relays SMRB, SMRG, SMRP, when detecting the temperature of these relays, heat is transferred from the system main relays SMRB, SMRG, SMRP to the thermistors 24A-24C via insulators. In the process, heat is taken away by the cooling air. As a result, the detected temperatures of the thermistors 24A to 24C may be lower than the actual temperatures of the system main relays SMRB, SMRG, and SMRP. Therefore, in extracting the correction value, in addition to the current flowing through the system main relays SMRB, SMRG, SMRP, the temperature of the cooling air supplied to the system main relays SMRB, SMRG, SMRP and the thermistors 24A to 24C may be referred to. .

  For example, in this embodiment, the vehicle-mounted relay temperature detection system includes an intake air temperature sensor 28 in addition to the monitoring unit 20, the current sensor 26, and the thermistors 24A to 24C. The monitoring unit 20 also acquires a detection signal from the intake air temperature sensor 28 in addition to the current sensor 26 and the thermistors 24A to 24C via the device / sensor interface.

  As shown in FIG. 2, the intake air temperature sensor 28 detects the temperature of the intake air taken in by the cooling blower 22. The intake air temperature sensor 28 is composed of, for example, a thermistor, and its detection element is disposed in the duct 30 as indicated by a broken line in FIG.

  As shown in FIGS. 1 and 2, the cooling air taken into the cooling blower 22 is supplied to the junction block 18 and the thermistors 24 </ b> A to 24 </ b> C via the duct 30 and the assembled battery 16. From this, the intake air temperature detected by the intake air temperature sensor 28 can be used as the temperature of the cooling air supplied to the system main relays SMRB, SMRG, SMRP and the thermistors 24A-24C.

  FIG. 5 exemplifies a correction processing flow for obtaining an added value using the current flowing through the system main relays SMRB, SMRG, SMRP and the intake air temperature detected by the intake air temperature sensor 28. The flow in FIG. 5 is obtained by replacing step S24 in FIG. 4 with step S30. Hereinafter, a part of the steps overlapping with those in FIG.

If the average value IB ² _ave at step S20 exceeds a predetermined threshold IB ² - th, the monitoring unit 20, extracts a correction value using the correction value map as shown in FIG. 6 (call) (S30). In the correction value map, the current value [A] flowing through the system main relays SMRB, SMRG, SMRP is plotted in the column (vertical axis), and the intake air temperature Tc [° C.] of the cooling blower 22 is plotted in the row (horizontal axis) The correction value [° C.] (≧ 0) is plotted in the matrix cell. The relationship between the current value and intake air temperature and the correction value may be obtained in advance by experiments, or may be obtained by simulation or the like. Further, a correction value map may be created for each of the plus side relay SMRB, the minus side relay SMRG, and the precharge relay SMRP.

  The monitoring unit 20 plots the current value acquired in step S12 (for example, IB (i = k)) and the intake air temperature detected by the intake air temperature sensor 28 in a correction value map, and sets correction values corresponding to these values. Extract. Further, the monitoring unit 20 adds the correction value acquired from the correction value map to the detection values (detection temperatures) of the thermistors 24A to 24C, and outputs this to the control unit 14 as the temperature values of the system main relays SMRB, SMRG, SMRP. (S26).

<Another example of current value acquisition>
4 and 5, the current flowing through the system main relays SMRB, SMRG, and SMRP is acquired from the current sensor 26. Alternatively, this may be acquired from the current value map shown in FIG. .

  In the current value map, SOC [%] of the assembled battery 16 is plotted on the column (vertical axis), and the output request [kW] (motor required output) of the rotating electrical machine as a load is plotted on the row (horizontal axis). The estimated value [A] of the current flowing through the system main relays SMRB, SMRG, SMRP is plotted in the matrix cell. The relationship between the SOC and the output request and the estimated current value may be obtained in advance by experiments, or may be obtained by simulation or the like.

  The monitoring unit 20 calculates the SOC of the assembled battery 16 from the integrated current and voltage value change of the assembled battery. Further, an output request from the control unit 14 to the rotating electrical machine is acquired. Further, the monitoring unit 20 plots the obtained SOC and output request on a current value map, and extracts (calls) current values (estimated values) corresponding to these values. The extracted current value is used in step S12 and step S24 in FIG. 4 and step S30 in FIG.

  12 battery unit, 14 control unit, 16 assembled battery (battery), 18 junction block, 20 monitoring unit (calculation unit), 22 cooling blower, 24A-24C thermistor, 26 current sensor, 28 intake air temperature sensor, SMRB, SMRG, SMRP System main relay (relay).

Claims (1)

A temperature detection system for an in-vehicle relay connected between a battery and a load,
A thermistor for detecting the temperature of the relay;
A calculation unit that adds a correction value to the detection value of the thermistor based on the current flowing through the relay when an average value of the current flowing through the relay in a predetermined period exceeds a threshold value, and outputs the correction value as a temperature value of the relay; ,
A temperature detection system for an in-vehicle relay, comprising:

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