charger

Abstract

The present application provides a charger capable of properly applying protection. The charger of one aspect of the present application is provided with an accumulated calculation section, a storage section, a first calculation section, a threshold setting section, a detection section, and a reduction section. During the period in which the charger is electrically connected with an external power source, the accumulated calculation section calculates an accumulated value by accumulating the amount of current obtained based on the charging current value with respect to an initial value, and stores the accumulated value as an accumulated capacity. The storage section stores correspondence information including a first correspondence relationship of the battery capacity and a first temperature threshold. Upon the start of charging of the storage battery, the first calculation section calculates the first temperature threshold in the case where the accumulated capacity calculated by the accumulated calculation section is used as the battery capacity, using the first correspondence relationship. The threshold setting section sets the calculated first temperature threshold as a detection threshold. In the case where the component temperature detected by the detection section reaches or exceeds the detection threshold, the reduction section executes reduction of the charging current value.

Description

Technical Field

[0001] This invention relates to a charger. Background Technology

[0002] The charger described in Patent Document 1 detects the temperature of a specified component and reduces the charging current when the detected temperature reaches a fixed component temperature threshold.

[0003] Patent Document 1: Japanese Patent No. 3983681 Summary of the Invention

[0004] The charger contains multiple heat-generating components with varying temperature rise trends. However, it's difficult to design separate temperature sensors for each of these components. Therefore, temperature sensors are typically installed for only a subset of the heat-generating components. Consequently, if a fixed component temperature threshold is used, even if the detected temperature is below that threshold, other components may still exceed it, potentially leading to inadequate charger protection.

[0005] One aspect of the present invention provides a charger capable of appropriately applying protection.

[0006] One aspect of the present invention is a charger that generates a second power to charge a battery based on a first power supplied from an external power source. The charger includes an accumulation calculation unit, a storage unit, a first calculation unit, a threshold setting unit, a detection unit, and a reduction unit. The accumulation calculation unit is configured to calculate an accumulated value based on a charging current value during electrical connection between the charger and the external power source, and to use this accumulated value as the accumulated capacity. The storage unit stores correspondence information including a first correspondence between battery capacity and a first temperature threshold. The first calculation unit is configured to calculate a first temperature threshold when the battery begins charging, using the first correspondence stored in the storage unit, whereby the accumulated capacity calculated by the accumulation calculation unit is used as the battery capacity. The threshold setting unit is configured to set the first temperature threshold calculated by the first calculation unit as a detection threshold when the battery begins charging. The detection unit is configured to detect the component temperature of a heat-generating component included in the charger. The reduction unit is configured to reduce the charging current value when the component temperature detected by the detection unit reaches or exceeds the detection threshold set by the threshold setting unit.

[0007] In one aspect of the charger of the present invention, the cumulative capacity is calculated by accumulating the current during electrical connection with a power supply source. When the charger continuously charges multiple batteries, the calculated cumulative capacity is the cumulative value of the current supplied to the multiple batteries. The temperature of the heating element included in the charger rises to the same level as when charging a battery for which the cumulative capacity is used as capacity. Therefore, the cumulative capacity appropriately represents the temperature state of the heating element included in the charger. By setting a detection threshold based on this cumulative capacity and a first correspondence, the detection threshold can be set according to the temperature state of the heating element included in the charger. For example, sometimes the heating element includes a first component whose temperature is to be detected, and a second component whose temperature may be higher than the detected component. In this case, the temperature of the second component can be estimated based on the cumulative capacity, and the detection threshold can be set such that the temperature of the first component reaches the detection threshold before the temperature of the second component exceeds the allowable temperature. The allowable temperature is an upper limit of the temperature at which the component operates. Furthermore, when the detected component temperature reaches the set detection threshold, the charging current value is reduced, thereby appropriately protecting the charger.

[0008] In addition, the cumulative calculation unit can be configured to subtract a predetermined value from the cumulative value when the charging current value is less than the current threshold during the period when the charger is electrically connected to the external power supply.

[0009] When the charging current is less than the current threshold, the heat-generating components of the charger dissipate heat, causing their temperature to drop. Therefore, while the charger is electrically connected to the current supply source, if the charging current is less than the current threshold, a predetermined value is subtracted from the cumulative value. This allows for the calculation of a more appropriate cumulative value representing the charger's temperature condition, which can then be used as the cumulative capacity value.

[0010] Additionally, it may include an acquisition unit and a second calculation unit. The acquisition unit is configured to acquire the nominal capacity of the battery. The second calculation unit is configured to calculate a first temperature threshold when the nominal capacity acquired by the acquisition unit is used as the battery capacity, using a first correspondence stored in a storage unit. The threshold setting unit may be configured to set the smaller of the first temperature threshold calculated by the first calculation unit and the first temperature threshold calculated by the second calculation unit as the detection threshold.

[0011] The detection threshold is set to the smaller of a first temperature threshold calculated based on the cumulative capacity and a first temperature threshold calculated based on the nominal capacity of the battery. Here, if a higher-capacity battery is charged with the same charging current as a lower-capacity battery, the temperature of the heat-generating components in the charger rises more gradually compared to when charging a lower-capacity battery. However, the degree of this gradual temperature increase varies depending on the heat-generating component. It is possible that the temperature of a first component positioned near the temperature detection unit rises more gradually than that of a second component positioned further away from the temperature detection unit. That is, when charging a high-capacity battery, the temperature of the second component may be higher than that of the first component.

[0012] If the detection threshold is set solely based on cumulative capacity, a larger detection threshold is set when the charger charges the initial battery pack, as the cumulative capacity is relatively small. Therefore, if the initial battery pack has a large capacity, the temperature of the second component may exceed its allowable temperature before the temperature of the first component reaches the detection threshold, potentially failing to properly protect the charger. Conversely, if the detection threshold is set solely based on nominal capacity, a larger threshold is set when charging lower-capacity batteries. Therefore, if the temperature of the second component becomes high while charging a higher-capacity battery, charging a lower-capacity battery may fail to properly protect the charger. Therefore, the smaller of the first temperature threshold calculated based on cumulative capacity and the first temperature threshold calculated based on nominal capacity is set as the detection threshold. This ensures proper protection of the charger regardless of the charging order of the batteries.

[0013] Additionally, the corresponding information may include a second correspondence between battery capacity and a second temperature threshold. The second temperature threshold is less than the first temperature threshold. The first calculation unit may be configured to: when the battery starts charging, use the second correspondence stored in the storage unit to further calculate the second temperature threshold when the cumulative capacity calculated by the cumulative calculation unit is used as the battery capacity. The second calculation unit may be configured to: use the second correspondence stored in the storage unit to further calculate the second temperature threshold when the nominal capacity obtained by the acquisition unit is used as the battery capacity. The threshold setting unit may also be configured to: when the battery starts charging, set the smaller of the second temperature threshold calculated by the first calculation unit and the second temperature threshold calculated by the second calculation unit as a release threshold. The reduction unit may be configured to: after reducing the charging current value, if the component temperature detected by the detection unit is insufficient to meet the release threshold set by the threshold setting unit, deactivate the reduction of the charging current value.

[0014] A first temperature threshold is set as the detection threshold, and a second temperature threshold lower than the first temperature threshold is set as the release threshold. Therefore, if the component temperature reaches or exceeds the detection threshold, the charging current value is reduced; if the component temperature falls below the release threshold, the reduction in charging current value is deactivated. Thus, the reduction in charging current value can be appropriately implemented and deactivated.

[0015] In addition, the reduction unit can be configured such that when the battery starts charging, if the component temperature detected by the detection unit is above the release threshold set by the threshold setting unit, the charging current value is reduced.

[0016] When charging two batteries consecutively, if the charging current is reduced while the first battery is charging, charging of the second battery may begin before the reduction is lifted. In this case, preferably, when the second battery begins charging, the reduction in charging current is lifted only after the component temperature has fallen below a threshold. If the charging current is reduced when the battery begins charging and the threshold is exceeded, the charger can be properly protected even when charging multiple batteries consecutively. Attached Figure Description

[0017] Figure 1 This is a diagram showing the appearance of the charger and battery pack involved in this embodiment.

[0018] Figure 2 This is a block diagram illustrating the electrical structure of the charger and battery pack involved in this embodiment.

[0019] Figure 3 This is a flowchart illustrating the process of calculating the cumulative charging capacity.

[0020] Figure 4A This is a flowchart illustrating a portion of the charging control process.

[0021] Figure 4B This is a flowchart showing the remaining part of the charging control process.

[0022] Figure 5 This is a graph showing the relationship between the first temperature threshold and the second temperature threshold relative to the nominal battery capacity and the cumulative charging capacity.

[0023] Figure 6 This is a graph showing the temperature changes of the diodes and transformers over time and the temperature threshold during the charging of a low-capacity battery.

[0024] Figure 7 This is a graph showing the temperature changes of the diodes and transformers over time and the temperature threshold during the charging of a high-capacity battery.

[0025] Figure 8 This is a graph showing the temperature changes of the diodes and transformers over time during high-capacity battery charging, the temperature threshold during low-capacity charging, and the temperature threshold during high-capacity charging.

[0026] Explanation of reference numerals in the attached figures

[0027] 2…Battery pack, 3…Charger, 21…Battery, 22…Second MPU, 32…First MPU, 22a, 32a…CPU, 22b, 32b…Memory, 23…Second communication unit, 24…Second positive terminal, 25…Second negative terminal, 26…Second signal terminal, 27…Second serial terminal, 31…Power line, 33…First communication unit, 34…First positive terminal, 35…First negative terminal, 36…First signal terminal, 37…First serial terminal, 38…Shunt resistor, 40…Power circuit, 41…Transformer, 42…Diode, 43…Temperature detection unit, 70…External power supply. Detailed Implementation

[0028] Hereinafter, the methods for carrying out the present invention will be described with reference to the accompanying drawings.

[0029] <1. Structure>

[0030] First, refer to Figure 1 and Figure 2 The structure of the charger 3 according to this embodiment will be described. The charger 3 is a device for charging the battery pack 2. The battery pack 2 is installed on the electric work machine and supplies power to the electric work machine. The capacity of the battery pack 2 can be set to various values. That is, the battery pack 2 can have a high capacity or a low capacity. Electric work machines include power tools, gardening tools, lights, vacuum cleaners, etc. Power tools include laser markers, hammer drills, impact screwdrivers, circular saws, etc. Gardening tools include lawnmowers, trimmers, lawnmowers, etc.

[0031] like Figure 1 As shown, the charger 3 includes a first mounting portion 61, a first terminal portion 62, and a power cord 31. The battery pack 2 includes a second mounting portion 51 and a second terminal portion 52.

[0032] A first mounting portion 61 is disposed on the upper surface of the charger 3, and a first terminal portion 62 is disposed on the first mounting portion 61. A second mounting portion 51 is disposed on the back side of the battery pack 2. A second terminal portion 52 is disposed on the second mounting portion 51 and has a plurality of plate-shaped terminals. The first mounting portion 61 is configured with a shape corresponding to the shape of the second mounting portion 51. The first terminal portion 62 has a plurality of terminals configured to engage with the second terminal portion 52.

[0033] The second mounting portion 51 is slidably mounted on the first mounting portion 61. When the second mounting portion 51 is mounted on the first mounting portion 61, the plurality of plate-shaped terminals provided by the second terminal portion 52 engage with the plurality of terminals provided by the first terminal portion 62. As a result, the battery pack 2 is physically connected to the charger 3 and electrically connected to the charger 3.

[0034] Power cord 31 is connected to an external power source 70. The external power source 70 is, for example, a commercial AC 100V power supply. Charger 3 generates a second power source based on the first power supplied from the external power source 70 and supplies the generated second power source to battery pack 2. Furthermore, the external power source 70 is not limited to a commercial power source. The external power source 70 can also be a DC power source, such as a cigar socket power source.

[0035] like Figure 2 As shown, the charger 3 includes a first positive terminal 34, a first negative terminal 35, a first signal terminal 36, and a first serial terminal 37 as multiple terminals included in the first terminal section 62.

[0036] In addition, the charger 3 includes a first MPU 32, a first communication unit 33, a shunt resistor 38, and a power supply circuit 40.

[0037] The power supply circuit 40 is a switching power supply, including a transformer 41, a diode 42, and a temperature detection unit 43. Additionally, the power supply circuit 40 also includes switching elements such as a FET (not shown). The power supply circuit 40 is connected to the first positive terminal 34 and the first negative terminal 35, and supplies the generated second power to the battery pack 2 via the first positive terminal 34 and the first negative terminal 35.

[0038] In detail, transformer 41 steps down the AC voltage of external power supply 70. Diode 42 is connected to the secondary side of transformer 41 and rectifies the AC voltage that has been stepped down by transformer 41. Transformer 41, diode 42, and a switching element (not shown) correspond to the heat-generating components that generate heat due to the charging current output by charger 3.

[0039] The temperature detection unit 43 detects the component temperature Tc of the heat-generating component included in the power supply circuit 40. Specifically, the temperature detection unit 43 is located near the diode 42 and detects the temperature of the diode 42 as the component temperature Tc. Furthermore, the temperature detection unit 43 outputs the detected component temperature Tc to the first MPU 32.

[0040] The temperature sensing unit 43 is, for example, a thermistor. A diode 42, a transformer 41, and the temperature sensing unit 43 are disposed on a substrate. The substrate has a first surface and a second surface. The diode 42 and the transformer 41 are disposed on the first surface of the substrate. The terminals of the diode 42 and the transformer 41 penetrate the substrate and protrude from the second surface, and are soldered to the second surface. The temperature sensing unit 43 is disposed on the second surface of the substrate near the solder portion of the diode 42's terminals.

[0041] Here, it is difficult to place the temperature detection unit 43 near the transformer 41. The inside of the transformer 41 is insulated. If the temperature detection unit 43 is placed on the primary side of the transformer 41, it is difficult to perform insulation design, thus reducing the design freedom of the power supply circuit 40. In addition, since the transformer 41 is a power conversion component, the power wiring pattern occupies a large area of ​​the printed circuit board around the secondary side of the transformer 41. Therefore, if the temperature detection unit 43 is placed on the secondary side of the transformer 41, switching noise is likely to be superimposed on the analog signal output from the temperature detection unit 43. Even the first MPU 32 is prone to false detection of component temperature Tc. To address this, the diode 42 is placed closer to the first MPU 32 than the transformer 41. Therefore, if the temperature detection unit 43 is placed near the diode 42, the wiring from the temperature detection unit 43 to the first MPU 32 is shortened compared to the case where the temperature detection unit 43 is placed near the secondary side of the transformer 41. Therefore, if the temperature sensing unit 43 is positioned near the diode 42, switching noise is less likely to superimpose with the analog signal output from the temperature sensing unit 43. In other words, by positioning the temperature sensing unit 43 near the diode 42, the design freedom of the power supply circuit 40 can be relatively increased, and false detections of component temperature Tc can be suppressed. Furthermore, the placement of the temperature sensing unit 43 is not limited to this. For example, a heat sink can be provided near the diode 42 on the substrate, and the temperature sensing unit 43 can be positioned on the heat sink.

[0042] Shunt resistor 38 is located on the negative line connecting power supply circuit 40 and first negative terminal 35. Shunt resistor 38 detects the value of the charging current (i.e., the charging current value) flowing from charger 3 to battery pack 2 and outputs the detected charging current value Io to first MPU 32.

[0043] The first communication unit 33 is connected to the first serial terminal 37. The first communication unit 33 is a circuit that performs serial communication.

[0044] The first MPU 32 includes a CPU 32a and a memory 32b, and is connected to a first signal terminal 36. The first MPU 32 receives signals from the battery pack 2 and sends signals to the battery pack 2 via the first signal terminal 36. In addition, the first MPU 32 performs serial communication with the battery pack 2 via a first communication unit 33 and a first serial terminal 37.

[0045] Furthermore, the first MPU32 performs cumulative capacity calculation and charging control processing based on various information input to the first MPU32. Specifically, while the power line 31 is electrically connected to the external power supply 70, the first MPU32 performs cumulative capacity calculation based on the input charging current value Io. Additionally, if the first MPU32 detects the installation of the battery pack 2 via the first signal terminal 36, it performs charging control processing based on the input component temperature Tc and the requested current value Id. The cumulative capacity calculation and charging control processing will be described in detail later.

[0046] As a plurality of plate-shaped terminals included in the second terminal section 52, the battery pack 2 includes a second positive terminal 24, a second negative terminal 25, a second signal terminal 26, and a second serial terminal 27. The second positive terminal 24 is connected to the first positive terminal 34. The second negative terminal 25 is connected to the first negative terminal 35. The second signal terminal 26 is connected to the first signal terminal 36. The second serial terminal 27 is connected to the first serial terminal 37.

[0047] In addition, battery pack 2 includes a storage battery 21, a second MPU 22, and a second communication unit 23.

[0048] The battery 21 has multiple battery cells connected in series. The positive terminal of the battery 21 is connected to the second positive terminal 24, and the negative terminal of the battery 21 is connected to the second negative terminal 25.

[0049] The second communication unit 23 is connected to the second serial terminal 27. The second communication unit 23 is a circuit that performs serial communication.

[0050] The second MPU 22 includes a CPU 22a and a memory 22b, and is connected to the second signal terminal 26. The second MPU 22 receives signals from the charger 3 and sends signals to the charger 3 via the second signal terminal 26. In addition, the second MPU 22 performs serial communication with the charger 3 via the second communication unit 23 and the second serial terminal 27.

[0051] Specifically, the second MPU 22 calculates the requested current value Id based on the voltage of the battery 21 during charging. The requested current value Id decreases accordingly as the voltage of the battery 21 increases. Furthermore, the second MPU 22 transmits the calculated requested current value Id to the charger 3 via the second communication unit 23 and the second serial terminal 27.

[0052] <2. Processing>

[0053] <2-1. Cumulative Capacity Calculation Processing>

[0054] Next, refer to Figure 3The flowchart illustrates the cumulative capacity calculation process performed by the first MPU32.

[0055] During the charging process of charger 3, the temperature of heat-generating components such as transformer 41 and diode 42 rises. If the temperature of these heat-generating components rises excessively and exceeds the allowable temperature, charger 3 may malfunction. The allowable temperature is the upper limit of the temperature at which the heat-generating components can operate. Therefore, it is necessary to suppress the charging current Io before the temperature of the heat-generating components rises excessively. Thus, when the component temperature Tc reaches or exceeds the temperature threshold, the first MPU 32 suppresses the charging current Io. However, if the temperature threshold is set to a constant value regardless of the initial temperature state at the start of charging, it may not adequately protect the heat-generating components.

[0056] The temperature rise trend of transformer 41 and diode 42 varies depending on the capacity of battery pack 2. Figure 6 and Figure 7 The temperature changes of the transformer 41 and diode 42 of the charger 3 are shown when the battery packs 2 with lower and higher capacity are charged with the same charging current value Io.

[0057] like Figure 6 and Figure 7 As shown, if the high-capacity battery pack 2 is charged with the same charging current as the low-capacity battery pack 2, the charging time is longer compared to the low-capacity battery pack 2, and the battery voltage rises gradually. Therefore, the amount of electricity supplied from the charger 3 to the high-capacity battery pack 2 increases gradually compared to the amount supplied to the low-capacity battery pack 2. Along with this, the temperature of the transformer 41 and switching elements included in the power supply circuit 40 rises gradually.

[0058] On the other hand, ideally, when charging battery packs 2 of different capacities with the same charging current, the temperature rise rate of diode 42 should remain constant. However, diode 42 is positioned near heat-generating components such as transformer 41, whose temperature rise rate depends on the capacity of battery pack 2. Therefore, in practice, when charging high-capacity battery pack 2 with the same charging current as low-capacity battery pack 2, diode 42 is affected by the heat from surrounding heat-generating components, resulting in a slower temperature rise rate. Consequently, when charging high-capacity battery pack 2, the temperatures of transformer 41 and diode 42 rise more gradually compared to when charging low-capacity battery pack 2. However, compared to the temperature rise of transformer 41, the temperature rise of diode 42 is even more gradual.

[0059] Therefore, as Figure 6 As shown, when a low-capacity battery is being charged, the temperature of diode 42 remains higher than the temperature of transformer 41 until the temperature threshold is reached. On the other hand, as...Figure 7 As shown, when a high-capacity battery is charging, the temperature of diode 42 is higher than that of transformer 41 in the initial stage of charging, but lower than that of transformer 41 before reaching the temperature threshold. Therefore, the temperature of transformer 41 reaches the temperature threshold first. However, as mentioned above, it is difficult to directly detect the temperature of transformer 41.

[0060] Therefore, the first MPU32 estimates the temperature of the transformer 41. Furthermore, a temperature threshold is set such that the temperature of the diode 42 reaches the threshold before the estimated temperature exceeds the permissible temperature. That is, when the diode 42 temperature is high, the first MPU32 sets a smaller temperature threshold compared to when the temperature is low. Specifically, as an indicator of the temperature state of the transformer 41, the first MPU32 calculates the cumulative capacity A1 (Ah). The cumulative capacity A1 is the cumulative value of the capacity charged by the charger 3. For example, if the cumulative capacity A1 is 2Ah, it is estimated that the transformer 41 rises to the same temperature level as when charging a 2Ah battery pack 2.

[0061] If the power cord 31 is connected to the external power supply 70, the first MPU 32 begins to execute the formal processing; if the power cord 31 is disconnected from the external power supply 70, the execution of the formal processing ends. During the period when the charger 3 receives power supplied from the external power supply 70, the first MPU 32 repeatedly executes the processing described later in S10 to S30 at a predetermined processing cycle Ta.

[0062] First, in S10, the first MPU32 determines whether charging is in progress. Specifically, the first MPU32 determines whether the charging current value Io reaches or exceeds the current threshold Itha. The current threshold Itha is set to a value close to 0A, for example, 0.3A. In S10, if it is determined that charging is in progress, the process proceeds to S20; if it is determined that charging is not in progress, the process proceeds to S30.

[0063] In S20, the first MPU32 updates the accumulated capacity A1 to the value obtained by adding the current amount of one processing cycle to the current accumulated capacity A1. The current amount is the value obtained by multiplying the current charging current value Io(A) by the cycle Ta(h). However, if the accumulated capacity A1 reaches the upper limit, the updating of the accumulated capacity A1 stops. The upper limit is, for example, 10Ah.

[0064] In this embodiment, the initial value of the cumulative capacity A1 at the moment when the power cord 31 is connected to the external power supply 70 is set to 0 Ah. However, the initial value is not limited to 0 Ah. For example, the initial value can be estimated based on the cumulative capacity A1 at the moment the power cord 31 was last disconnected from the external power supply 70. Alternatively, the initial value can be estimated based on the component temperature Tc detected by the temperature detection unit 43 at the moment the power cord 31 is connected to the external power supply 70. The process returns to the process in S10 after the processing in S20.

[0065] On the other hand, in S30, the first MPU32 updates the accumulated capacity A1 to the value obtained by subtracting the set value B from the current accumulated capacity A1. Even while the power line 31 is connected to the external power supply 70, the temperature of the components included in the power supply circuit 40 naturally decreases when not charging. The set value B is set based on the natural temperature decrease rate of the power supply circuit 40. For example, if the natural temperature decrease rate of the power supply circuit 40 is equivalent to a decrease of 3.6 Ah per hour, the set value B is set to 3.6 As per second.

[0066] While the charger 3 is electrically connected to the external power supply 70, the first MPU 32 repeatedly executes the processes S10 to S30. Therefore, when the charger 3 continuously charges multiple battery packs 2, the total electrical power supplied to the multiple battery packs 2 is accumulated to calculate the cumulative capacity A1. Thus, the cumulative capacity A1, which appropriately represents the temperature state of the charger 3, can be calculated.

[0067] For example, when three 2Ah battery packs 2 are charged consecutively, the temperature of the heating element rises to the same level as when charging a single 4Ah battery pack 2. If the cumulative capacity A1 is reset for each charge, the cumulative capacity A1 at the start of charging the third battery pack 2 becomes the value calculated cumulatively based on the current supplied to the single 2Ah battery pack 2. Therefore, if the cumulative capacity A1 is reset for each charge, a cumulative capacity A1 that does not properly represent the temperature state of the charger 3 is calculated.

[0068] In contrast, during the period when the charger 3 is electrically connected to the external power supply 70, the current output from the charger 3 is accumulated, and thus, when the third battery pack 2 begins charging, the accumulated capacity A1 obtained by accumulating the current supplied to the two battery packs 2 is calculated. Therefore, the accumulated capacity A1, which appropriately represents the temperature state of the charger 3, can be utilized.

[0069] <2-2. Charging Control Process>

[0070] Next, refer to Figure 4Aand Figure 4B The flowchart illustrates the charging control process performed by the first MPU32. If power line 31 is connected to the external power supply 70, the first MPU32 begins the charging control process; if power line 31 is disconnected from the external power supply 70, the charging control process ends. The first MPU32 performs the charging control process in parallel with the cumulative capacity calculation process.

[0071] In step S100, it is determined whether battery pack 2 is connected to charger 3. If the second signal terminal 26 is connected to the first signal terminal 36, the potential of the first signal terminal 36 changes, thereby changing the potential of the input signal input to the first MPU 32. The first MPU 32 detects the connection of battery pack 2 based on the change in the potential of the input signal input from the first signal terminal 36. In step S100, if the connection of battery pack 2 is detected, the process proceeds to step S110; if the connection of battery pack 2 is not detected, the process of step S100 is repeatedly executed until a connection is detected.

[0072] In S110, initial communication is performed with the battery pack 2 via the first communication unit 33 and the first serial terminal 37, thereby obtaining the nominal battery capacity A2 (Ah) of the battery pack 2 and the requested current value Id.

[0073] As described above, the temperature rise trend of transformer 41 and diode 42 varies depending on the capacity of battery pack 2. Furthermore, as... Figure 7 As shown, if the temperature threshold for charging the high-capacity battery pack 2 is set to the same value as the temperature threshold for charging the low-capacity battery pack 2, it may result in the charger 3 not being properly protected when the high-capacity battery pack 2 is being charged.

[0074] Therefore, such as Figure 8 As shown, when charging the high-capacity battery pack 2, a smaller temperature threshold is preferably set compared to when charging the low-capacity battery pack 2. Therefore, in this embodiment, the first MPU 23 sets the temperature threshold (specifically, the detection threshold THA and the release threshold THB described later) using the nominal battery capacity A2.

[0075] Next, in S120, the current cumulative capacity A1 is obtained. That is, the cumulative capacity A1, which represents the temperature state of the charger 3 at the start of charging, is obtained.

[0076] Next, in S130, the current component temperature Tc is obtained.

[0077] Next, in S140, the first detection candidate threshold Tha_1 and the first release candidate threshold Thb_1 are calculated using the cumulative capacity A1 and corresponding information obtained in S120. For example... Figure 5As shown, the corresponding information corresponds to the relationship between the cumulative capacity A1 and the nominal battery capacity A2 and the temperature threshold, and is stored in memory 32b. Regarding this relationship, the temperature at which the charging current value Io needs to begin decreasing relative to the battery capacity is determined through simulation and experimentation.

[0078] The temperature thresholds include a first temperature threshold Tha and a second temperature threshold Thb. The first temperature threshold Tha is the threshold used to initiate protection of the charger 3 when the component temperature Tc exceeds this value. The second temperature threshold is the threshold used to deactivate protection of the charger 3 when the component temperature Tc is less than this value. The correspondence can be a formula or a table. In this embodiment, the correspondence is represented by a formula. That is, the first formula represents the relationship between the cumulative capacity A1 and the nominal battery capacity A2 and the first temperature threshold Tha, and the second formula represents the relationship between the cumulative capacity A1 and the nominal battery capacity A2 and the second temperature threshold Thb.

[0079] Specifically, such as Figure 5 As shown, the cumulative capacity A1 and nominal battery capacity A2 are divided into four regions: Region I, Region II, Region III, and Region IV. For each region, a first relational expression and a second relational expression are established. Figure 5 In the equations, "x" represents the variable substituted into the cumulative capacity A1 or the nominal battery capacity A2. Additionally, "y1" corresponds to the first temperature threshold Tha, and "y2" corresponds to the second temperature threshold Thb. The slopes of the first and second equations are equal. That is, the first temperature threshold Tha is equivalent to the value obtained by shifting the second temperature threshold Thb by a temperature higher than a specified range.

[0080] The first MPU32 calculates a first temperature threshold Tha corresponding to the cumulative capacity A1 obtained in S120, using Tha_1 as a first detection candidate threshold in the first relational expression. Additionally, it calculates a second temperature threshold Thb corresponding to the cumulative capacity A1, using Thb_1 as a first removal candidate threshold in the second relational expression.

[0081] Next, in S150, similar to S140, the nominal battery capacity A2 obtained in S110 is used to calculate the second detection candidate threshold Tha_2 and the second release candidate threshold Thb_2.

[0082] Next, in S160, it is determined whether the first detection candidate threshold Tha_1 calculated in S140 is less than the second detection candidate threshold Tha_2 calculated in S150. If, in S160, it is determined that the first detection candidate threshold Tha_1 is less than the second detection candidate threshold Tha_2, then in S170, the first detection candidate threshold Tha_1 is set as the detection threshold THA. Conversely, if, in S160, it is determined that the first detection candidate threshold Tha_1 is greater than or equal to the second detection candidate threshold Tha_2, then in S180, the second detection candidate threshold Tha_2 is set as the detection threshold THA. That is, the smaller of the first detection candidate threshold Tha_1 and the second detection candidate threshold Tha_2 is set as the detection threshold THA.

[0083] Next, in S190, it is determined whether the first removal candidate threshold Thb_1 calculated in S140 is less than the second removal candidate threshold Thb_2 calculated in S150. If in S190 it is determined that the first removal candidate threshold Thb_1 is less than the second removal candidate threshold Thb_2, then in S200, the first removal candidate threshold Thb_1 is set as the removal threshold THB. On the other hand, if in S190 it is determined that the first removal candidate threshold Thb_1 is greater than or equal to the second removal candidate threshold Thb_2, then in S210, the second removal candidate threshold Thb_2 is set as the removal threshold THB. That is, the smaller of the first removal candidate threshold Thb_1 and the second removal candidate threshold Thb_2 is set as the removal threshold THB.

[0084] When charger 3 is charging the first battery pack 2, the cumulative capacity A1 is 0 Ah. Therefore, if the detection threshold THA and release threshold THB are set based solely on the cumulative capacity A1, the detection threshold THA and release threshold THB will be set to a larger value. As a result, when the higher-capacity battery pack 2 is initially charged, the temperature of transformer 41 may exceed the allowable temperature before the component temperature Tc reaches the detection threshold THA, potentially leading to inadequate protection of charger 3.

[0085] Furthermore, if the detection threshold THA and release threshold THB are set solely based on the nominal battery capacity A2, then a larger detection threshold THA and release threshold THB will be set when charging the lower-capacity battery pack 2. Therefore, when the charger 3 charges the higher-capacity battery pack 2, causing the transformer 41 to reach a higher temperature, a larger detection threshold THA and release threshold THB will be set when charging the lower-capacity battery pack 2. As a result, during the charging process of the lower-capacity battery pack 2, the temperature of the transformer 41 may exceed the allowable temperature before the component temperature Tc reaches the detection threshold THA, potentially failing to properly protect the charger 3.

[0086] In this embodiment, the smaller of the first detection candidate threshold Tha_1 and the second detection candidate threshold Tha_2 is set as the detection threshold THA, and the smaller of the first release candidate threshold Thb_1 and the second release candidate threshold Thb_2 is set as the release threshold THB. Therefore, regardless of the order in which multiple battery packs 2 of different capacities are charged, the detection threshold THA and the release threshold THB will be set to appropriately protect the charger 3.

[0087] Next, in S220, it is determined whether the component temperature Tc obtained in S130 is less than the set release threshold THB. If in S220 it is determined that the component temperature Tc is above the release threshold THB, the process proceeds to S230.

[0088] In S230, the high temperature indicator is set to ON. The high temperature indicator is used to initiate protection for the charger 3. When the battery pack 2 begins charging, a release threshold THB, which is lower than the detection threshold THA, is used to determine whether to initiate protection for the charger 3. Sometimes, other battery packs 2 are charged before the current charging of the current battery pack 2 begins. Moreover, when other battery packs 2 are charging, the component temperature Tc sometimes reaches or exceeds the detection temperature THA, thus initiating protection for the charger 3. Furthermore, before the component temperature Tc falls below the release threshold THB, that is, during the protection process for the charger 3, the charging of other battery packs 2 sometimes ends. In this case, when the current charging of the current battery pack 2 begins, it is preferable to continue protecting the charger 3 until the component temperature Tc drops to the release threshold THB. Therefore, when the battery pack 2 begins charging, the release threshold THB is used to determine whether to initiate protection for the charger 3.

[0089] Next, in S240, it is determined whether the requested current value Id obtained in S110 is less than the reduced current value Ithb. The reduced current value Ithb is a sufficiently small value that can suppress the temperature rise of the heating component, for example, 2A.

[0090] In S240, if it is determined that the requested current value Id is greater than or equal to the reduced current value Ithb, the process proceeds to S250. In S250, charging begins with a charging current that is lower than the requested current value Id by the reduced current value Ithb. This helps to suppress the temperature rise of the heat-generating components of the charger 3 and protect the charger 3. After the process in S250, the process proceeds to S270.

[0091] On the other hand, in S240, if it is determined that the requested current value Id is less than the reduced current value Ithb, the process proceeds to S260. In S260, charging begins with a charging current equal to the requested current value Id. This is a situation where the charger 3 should be protected, as the requested current value Id is sufficiently small. Therefore, even when charging with a charging current equal to the requested current value Id, the temperature rise of the heat-generating components of the charger 3 can be suppressed, and thus there is no need to reduce the charging current.

[0092] When battery pack 2 is nearly fully charged and the battery voltage is close to the rated voltage, a request current value Id is generated that is less than the reduction current value Ithb. This also occurs when the user is continuously charging (i.e., additional charging), and battery pack 2 is nearly fully charged at the start of charging. Processing proceeds to S270 after processing in S260.

[0093] Furthermore, in S220, if it is determined that the component temperature Tc is less than the release threshold THB, the process proceeds to S260. In this case, the component temperature Tc has sufficiently decreased at the start of charging, so there is no need to protect the charger 3. Therefore, in S260, charging is performed with the charging current of the requested current value Id. After the process in S260, the process proceeds to S270.

[0094] Next, in S270, communication is established with the charging battery pack 2 to obtain the requested current value Id. The requested current value Id decreases as the charging of battery pack 2 progresses. When the requested current value Id becomes 0, the first MPU32 terminates the charging of battery pack 2 and returns to the processing in S100.

[0095] Next, in S280, the component temperature Tc at the current moment is obtained.

[0096] Next, in S290, it is determined whether the high temperature indicator has turned ON. If it is determined in S290 that the high temperature indicator has turned ON, the process proceeds to S300.

[0097] In step S300, it is determined whether the component temperature Tc obtained in step S280 is less than the release threshold THB. That is, it is determined whether the protection for charger 3 can be released. In step S300, if it is determined that the component temperature Tc is less than the release threshold THB, the process proceeds to step S310. In step S310, the high temperature flag is set to OFF and the process proceeds to step S340.

[0098] On the other hand, in S300, if it is determined that the component temperature Tc is above the release threshold THB, the process proceeds to S320. In S320, it is determined whether the requested current value Id obtained in S270 is less than the reduced current value Ithb.

[0099] In S320, if it is determined that the requested current value Id is greater than or equal to the reduced current value Ithb, the process proceeds to S330. In S330, charging continues at a charging current that is lower than the reduced current value Ithb, which is lower than the requested current value Id. After the process in S330, the process returns to S270.

[0100] On the other hand, in S320, if it is determined that the requested current value Id is less than the reduced current value Ithb, the process proceeds to S340. In S340, charging continues at the charging current of the requested current value Id. After the process in S340, the process returns to S270.

[0101] Additionally, in S290, if the high temperature flag is determined to be OFF, the process proceeds to S350. In S350, it is determined whether the component temperature Tc obtained in S280 is less than the detection threshold THA. That is, it is determined whether it is possible to suspend the protection of charger 3.

[0102] In S350, if the component temperature Tc is determined to be above the detection threshold THA, the process proceeds to S360. In S360, it is necessary to start protecting charger 3, so the high temperature indicator is set to ON.

[0103] Next, in S370, it is determined whether the requested current value Id obtained in S270 is less than the reduced current value Ithb.

[0104] In step S370, if it is determined that the requested current value Id is greater than or equal to the reduced current value Ithb, the process proceeds to step S380. In step S380, charging continues at a charging current that is lower than the requested current value Id by the reduced current value Ithb. This suppresses the temperature rise of the heat-generating components of the charger 3 and protects the charger 3.

[0105] On the other hand, in S370, if it is determined that the requested current value Id is less than the reduced current value Ithb, the process proceeds to S390. In S390, charging continues at the charging current of the requested current value Id. This is a case where charger 3 should be protected, as the requested current value Id is sufficiently small, therefore there is no need to reduce the charging current. After processing in S390, the process returns to processing in S270.

[0106] Additionally, in S350, if it is determined that the component temperature Tc is less than the detection threshold THA, the process proceeds to S390. In S390, there is no need to start the protection charger 3; therefore, charging continues at the charging current of the requested current value Id obtained in S270. After the processing in S390, the process returns to the processing in S270.

[0107] <3. Effects>

[0108] According to the first embodiment described above, the following effects can be obtained.

[0109] (1) During the period when the charger 3 is electrically connected to the external power supply 70, the amount of current supplied to the battery pack 2 is cumulatively calculated. From this, a cumulative capacity A1 that appropriately represents the temperature state of the transformer 41 included in the charger 3 is calculated. Furthermore, a detection threshold THA is set based on the cumulative capacity A1 and the first formula. That is, the detection threshold THA is set according to the temperature state of the transformer 41. And, if the detected component temperature Tc is above the set detection threshold THA, the current value Id is requested to be reduced to a reduced current value Ithb. Therefore, the charger 3 can be appropriately protected.

[0110] (2) When the charging current Io is less than the current threshold Itha, the heat-generating component of the charger 3 dissipates heat, causing the temperature of the heat-generating component to decrease. Therefore, while the charger 3 is electrically connected to the external power supply 70, when the charging current Io is less than the current threshold Itha, a predetermined value is subtracted from the cumulative value. As a result, a cumulative value that more appropriately represents the temperature state of the transformer 41 can be calculated as the cumulative capacity value A1.

[0111] (3) The smaller of the first detection candidate threshold Tha_1 calculated based on the cumulative capacity A1 and the second detection candidate threshold Tha_2 calculated based on the nominal battery capacity A2 is set as the detection threshold THA. Thus, regardless of the order in which multiple battery packs 2 of different capacities are charged, the detection threshold THA and the release threshold THB that can properly protect the charger 3 can be set.

[0112] (4) The smaller of the first release candidate threshold Thb_1 and the second release candidate threshold Thb_2 is set as the release threshold THB. Therefore, if the component temperature Tc reaches or exceeds the detection threshold THA, the charging current value Io is reduced; if the component temperature Tc is below the release threshold THB, the reduction of the charging current value Io is deactivated. Thus, the reduction of the charging current value Io can be appropriately implemented and deactivated.

[0113] (5) When battery pack 2 starts charging, if the component temperature Tc is above the release threshold THB, the charging current value Io is reduced. Therefore, even when multiple battery packs 2 are charged continuously, the charger 3 can be properly protected.

[0114] (Other implementation methods)

[0115] The above describes the methods for implementing the present invention, but the present invention is not limited to the above embodiments and can be implemented in various modifications.

[0116] (a) In the above embodiment, the detection threshold THA and the release threshold THB are set using both the cumulative capacity A1 and the nominal battery capacity A2. However, the detection threshold THA and the release threshold THB can also be set using only the cumulative capacity A1. Although the charger 3 can be more properly protected by using both the cumulative capacity A1 and the nominal battery capacity A2, the charger 3 can also be protected using only the cumulative capacity A1.

[0117] (b) In the above embodiment, the first detection candidate threshold Tha_1 and the first release candidate threshold Thb_1 are calculated using the accumulated capacity A1 at the start of charging, but the present invention is not limited thereto. Alternatively, during the charging process, the first detection candidate threshold Tha_1 and the first release candidate threshold Thb_1 can be calculated using the real-time accumulated capacity A1, and the detection threshold THA and the release threshold THB can also be calculated. For example, during the charging process, the first detection candidate threshold Tha_1 and the first release candidate threshold Thb_1 can be calculated using the real-time accumulated capacity A1 at predetermined time intervals, and the detection threshold THA and the release threshold THB can also be calculated.

[0118] (c) Multiple structural elements may achieve the multiple functions of one structural element in the above embodiments, or multiple structural elements may achieve the single function of one structural element. Alternatively, one structural element may achieve multiple functions of multiple structural elements, or one structural element may achieve the single function achieved by multiple structural elements. Furthermore, a portion of the structure in the above embodiments may be omitted. Additionally, at least a portion of the structure in the above embodiments may be added to or replaced with other structures in the above embodiments.

[0119] (d) In addition to the charger described above, the present invention can be implemented in various ways, such as a system in which the charger is a structural element, a program for enabling a computer to function as the charger, a recording medium of a non-transferable actual state, such as a semiconductor memory for recording the program, and a method for protecting the charger.

Claims

1. A charger that generates a second power for charging a battery based on a first power supplied from an external power source, characterized in that, The charger has the following features: The cumulative calculation unit is configured to calculate a cumulative value by accumulating the current obtained based on the charging current value for an initial value during the period when the charger is electrically connected to the external power source, and to use the cumulative value as the cumulative capacity. The storage unit stores correspondence information including a first correspondence between battery capacity and a first temperature threshold, wherein the first correspondence includes a specific range in which the first temperature threshold decreases as the battery capacity increases. The first calculation unit is configured to: when the battery starts charging, use the first correspondence stored in the storage unit to calculate a first temperature threshold when the cumulative capacity calculated by the cumulative calculation unit is used as the battery capacity; when the cumulative capacity is in the specific range, the larger the cumulative capacity, the smaller the first temperature threshold is calculated. The threshold setting unit is configured to set the first temperature threshold calculated by the first calculation unit as the detection threshold when the battery starts charging. The detection unit is configured to: detect the component temperature of a heat-generating component included in the charger; and The reduction unit is configured to reduce the charging current value when the component temperature detected by the detection unit reaches or exceeds the detection threshold set by the threshold setting unit.

2. The charger according to claim 1, characterized in that, The cumulative calculation unit is configured to subtract a predetermined value from the cumulative value when the charging current value is less than a current threshold during the period when the charger is electrically connected to the external power source.

3. The charger according to claim 1 or 2, characterized in that, The charger also features: An acquisition unit configured to acquire the nominal capacity of the battery; and The second calculation unit is configured to calculate a first temperature threshold when the nominal capacity obtained by the acquisition unit is used as the battery capacity, using the first correspondence stored in the storage unit. The threshold setting unit is configured to set the smaller of the first temperature threshold calculated by the first calculation unit and the first temperature threshold calculated by the second calculation unit as the detection threshold.

4. The charger according to claim 3, characterized in that, The corresponding information includes a second correspondence between the battery capacity and a second temperature threshold, wherein the second temperature threshold is less than the first temperature threshold. The first calculation unit is configured to: when the battery starts charging, use the second correspondence stored in the storage unit to further calculate the second temperature threshold when the cumulative capacity calculated by the cumulative calculation unit is used as the battery capacity. The second calculation unit is configured to further calculate the second temperature threshold when the nominal capacity obtained by the acquisition unit is used as the battery capacity, using the second correspondence stored in the storage unit. The threshold setting unit is further configured to: when the battery starts charging, set the smaller of the second temperature threshold calculated by the first calculation unit and the second temperature threshold calculated by the second calculation unit as the release threshold. The reduction unit is configured such that, after reducing the charging current value, if the component temperature detected by the detection unit is less than the release threshold set by the threshold setting unit, the reduction of the charging current value is released.

5. The charger according to claim 4, characterized in that, The reduction unit is configured such that when the battery starts charging, if the component temperature detected by the detection unit is above the release threshold set by the threshold setting unit, the charging current value is reduced.

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