JP2014072975A - Charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charger which can perform safe and reliable charging by detecting failure of a plurality of cells constituting a secondary battery, when charging a secondary battery built in a battery pack used in an electric tool.SOLUTION: A charger for a battery pack used as a drive source of a cordless electric tool includes a terminal for receiving an over discharge signal. Originally, the over discharge signal is outputted from the battery pack to the electric tool when the voltage of at least one battery cell is equal to or lower than a predetermined voltage, and the tool side interrupts power supply from the battery pack in response to the over discharge signal. The charger is provided with a terminal for receiving the over discharge signal, and is configured to perform charging with a first charging curent for a predetermined time when charging is started, and to stop charging if the over discharge signal is received from the battery pack via the terminal even after elapsing the predetermined time.

Description

  The present invention relates to a charging device for charging a secondary battery such as a lithium ion secondary battery.

  In this technical field, secondary batteries of various types and voltages have been used for a long time in order to use the power tool cordlessly. In order to charge these secondary batteries appropriately, an initial charging step is used. A technique for discriminating a battery type and the like and controlling subsequent charging conditions using the result is proposed (for example, see Patent Document 1 below). In addition, in the technical field, there is a strong demand for high power and large capacity, and a battery pack for a cordless power tool that incorporates a lithium ion battery with a high output density is widespread.

JP 2002-367682 A

  In the current mainstream lithium ion batteries, etc., the purpose is to extend the battery life, and it is required to set the charging conditions appropriately according to the state of the secondary battery than before, and the battery life has been reached. It is also necessary to detect the battery early. Here, as a simple charging method suitable for a lithium ion battery or the like, the above-described conventional technique is applied. At the start of charging, charging is performed with a small charging current, and the battery reaches a predetermined battery voltage even after a predetermined time. If not, it is easy to consider a method in which it is determined that the battery has reached the end of its life, and charging is stopped without performing subsequent main charging. In such a charge control method, for example, when the battery pack is configured to connect a plurality of battery cells in series and the number of connected cells is small, charging is performed simply by monitoring the battery voltage. Thus, it is possible to determine the life battery and perform charging. However, in a battery pack used as a drive source for a cordless electric tool, as described above, a large number of battery cells tend to be connected to cope with high power and large capacity. In the battery pack comprising the above, it is difficult to determine the battery that has reached the end of life and to set suitable charging conditions by the method of simply monitoring the battery voltage described above.

  Here, for example, in a battery pack incorporating a battery set in which 10 battery cells are connected in series, if the battery pack does not reach 30 V (3 V per cell) after charging for a predetermined time, the battery life or failure is set. In this case, even if one of the battery cells connected in series fails in a short state, the other cells have a slightly higher voltage (3.33V (30V / 9 cells) per cell). As a result, an equivalent output is generated. Therefore, it is impossible to sufficiently determine the battery life or the situation having a failed battery cell.

  This is a problem that becomes conspicuous when the number of cells increases, and is a problem that does not become apparent in a conventional battery pack composed of a small number of cells. For example, as an example of a battery pack composed of a small number of cells, a battery pack incorporating a battery set in which two battery cells are connected in series reaches 6 V (3 V per cell) after charging for a predetermined time. If not, even if it is only set as a battery life or a failure, when one cell is short-circuited, the voltage of the other cell is higher than the full charge voltage (for example, 4.2 V) of the cell. Therefore, it was possible to determine the failure of the battery cell simply by using only the entire voltage.

  As described above, in a battery pack having a large number of battery cells connected in series as used in an electric power tool, it is difficult to determine a battery life or a failure simply by determining the entire voltage.

  By the way, the battery pack for electric tools is configured to be detachable from the tool so that it can be used with various types of cordless electric tools in one battery pack. Lithium ion batteries have the potential to significantly shorten the battery life if an overdischarge condition occurs in some battery cells. Therefore, in battery packs composed of multiple cells, the voltage of all cells In general, when it is detected that one of them is in an overdischarged state, charging / discharging is generally stopped. In a system in which the battery pack and the cordless power tool are detachable as described above, there is a wide variety of methods for transmitting a signal notifying that the battery is overdischarged to the power tool via the terminal and cutting off the current in the power tool. Has been done.

  It is an object of the present invention to perform charging suitable for a battery pack as described above, particularly at least one of a plurality of cells in a system in which a battery pack used in an electric tool and the above-described tool can be attached and detached. The object is to provide a means for improving the problem of detecting that a battery cell is overdischarged.

  The charging device according to claim 1 for achieving the above object is a charging device for charging a battery pack as a drive source of a cordless power tool, and includes a plurality of secondary batteries built in the battery pack. Overdischarge signal receiving means for receiving from the battery pack an overdischarge signal indicating that at least one of the battery cells is in an overdischarged state, and when the overdischarge signal receiving means receives the overdischarge signal In addition, overdischarge state determination means for determining that at least one of the plurality of battery cells is in an overdischarge state, and charging current control means for controlling a charging current for charging the secondary battery, When the overdischarge state determination means determines that the overdischarge state is in the overdischarge state at the start of charging, the charging current control means performs charging with the first charging current for a predetermined time from the start of charging, and after the predetermined time has elapsed. If the over-discharge signal receiving means over-discharge state judging means has received the overdischarge signal is determined to be over-discharged state, the charging current control means is characterized by stopping the charge.

  According to such a configuration, when the battery pack is mounted on the cordless power tool, the charging device receives the overdischarge signal for informing that the secondary battery is in the overdischarge state from the battery pack side to the cordless power tool side. In the case where the overcharge signal is still received from the battery pack side after so-called precharge, the at least one of the secondary batteries is configured. Since it is determined that the battery cell has a life or failure and charging is stopped, it is possible to avoid accidentally charging a secondary battery including the battery cell having a life or failure.

  The charging device according to claim 2 is the charging device according to claim 1, wherein after the predetermined time has elapsed, the overdischarge state determination means determines that the secondary battery is not in an overdischarge state. The current control means switches to a second charging current larger than the first charging current and charges the secondary battery.

  According to such a configuration, if it is determined that there is no abnormality in the secondary battery as a result of precharging, charging is started in earnest with the second charging current.

  The charging device according to claim 3 is the charging device according to claim 1 or 2, wherein the overdischarge signal receiving means is electrically connected to a terminal provided for the battery pack to output an overdischarge signal to the cordless tool. It is a terminal connected to.

  According to such a configuration, since the overdischarge signal receiving means that can be connected to the overdischarge signal output terminal formed in the battery pack is also provided in the charging device, the overdischarge signal that is originally transmitted from the battery pack to the cordless electric tool is transmitted. Effective use also in the charging device can suppress power supply to the battery life or a failed secondary battery.

  The charging device according to claim 4 further includes battery voltage detection means for detecting a battery voltage output from the secondary battery in the charging device according to any one of claims 1 to 3, and the predetermined time is set. If it is determined that the overdischarge state determination means is in an overdischarge state even after the elapse of time and the battery voltage of the secondary battery detected by the battery voltage detection means does not exceed the predetermined battery voltage value, the charging current The control means is characterized by stopping charging.

  According to such a configuration, it is found that any one of a plurality of cells constituting the secondary battery has an abnormality, and at the same time, an abnormality is recognized in the secondary battery even when judged from the overall voltage of the secondary battery. In this case, since the charging is not performed, the secondary battery in an abnormal state can be more reliably removed from the charging target.

  The charging device according to claim 5 further includes battery voltage detection means for detecting a battery voltage output from the secondary battery in the charging device according to claim 4, wherein the charging current control means is the first charging current. If the battery voltage detected by the battery voltage detection means exceeds a predetermined voltage value during charging, the charging current control means has the first charging current larger than the first charging current even before the predetermined time has elapsed. The secondary battery is charged by switching to a charging current of 2.

  According to such a configuration, during the precharge period, when it is determined from the battery voltage that the secondary battery to be charged is normal, full charge is performed without waiting for the end of the precharge period. Since it carried out, it can advance a charge process rapidly, ascertaining that the secondary battery has not failed.

  A charging device according to a sixth aspect is the charging device according to any one of the first to fifth aspects, wherein the secondary battery is a lithium ion battery.

  The secondary battery built in the battery pack may be any secondary battery such as a nickel cadmium battery, a nickel hydride battery, or a lead storage battery, but a lithium ion battery is used for reasons such as high energy density. preferable.

  According to the present invention, in the charging system having a configuration in which the battery pack used in the electric tool and the above-described tool can be attached and detached, the tool side is notified that one of the plurality of cells is overdischarged. Therefore, it is possible to provide a charging device that can detect a life or failure of a battery cell and perform safe and reliable charging through a terminal used for the purpose.

An example of the outline | summary of a structure of the battery pack of this embodiment, a tool, and a charging device. An example of the outline of a structure of the circuit provided in the battery pack and the tool. An example of the outline of a structure of the circuit provided in the battery pack and the charging device. An example of the flowchart in the case of determining a battery failure using the whole voltage. An example of the flowchart in the case of determining a battery failure with the structure of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows an outline of the configuration of a battery pack, a tool, and a charging device according to the present embodiment. (A) is an explanatory view when the battery pack is mounted on a tool, and (b) is a battery. It is explanatory drawing in the case of mounting a pack in a charging device.

  The battery pack includes a battery set 1 composed of a plurality of battery cells. The battery pack 1 includes a charging plus terminal 2 for charging, a discharging plus terminal 3 for discharging, and a charging device side for determining the type of battery. The battery type identification terminal 4 provided, the temperature terminal 5 provided for the charging device side to detect the temperature of the battery, the minus terminal 6 for charging / discharging, and even one of the plurality of cells is below a predetermined voltage. And an overdischarge detection signal output terminal 7 is provided for outputting a signal when it is determined that the overdischarge has occurred. A circuit for determining the above-described overdischarge or the like is provided on the protective substrate 8. As described above, the battery pack includes the battery set 1, the various terminals 1 to 8, the protective substrate 8, and the exterior case (not shown) for housing these.

  1A shows a tool attaching / detaching portion with respect to the battery pack, and a tool terminal and a terminal holder 9 are formed in the housing 10 of the attaching / detaching portion. Although not shown, a motor or switch drive unit is disposed at the tip of the attachment / detachment unit. When the battery pack is mounted on the tool, the three terminals formed on the terminal holder 9 of the tool are electrically connected to the discharge plus terminal 3, the minus terminal 6 and the overdischarge detection signal output terminal 7 of the battery pack. Connected.

  In the battery pack, when it is detected that even one of the plurality of cells is in an overdischarge state with a voltage below a predetermined value, a signal is output via the overdischarge detection signal output terminal 7 described above, and the tool side The current is cut off in response to the signal.

  The lower part of (b) in FIG. 1 shows the attachment / detachment part of the charging device with respect to the battery pack. In the housing 13 of the attachment / detachment part, the charging terminal and terminal holder 11 and the battery pack when the battery pack is mounted A battery / charger fixing rail 12 for fixing is provided. In the charging device, a substrate and a circuit are installed in a housing (not shown).

  When the battery pack is mounted on the charging device, the five terminals formed on the terminal holder 11 of the charging device are the charging plus terminal 2, the battery type identification terminal 4, the temperature terminal 5, the minus terminal 6, And, it is electrically connected to the overdischarge detection signal output terminal 7.

  FIG. 2 shows a schematic configuration of a circuit provided in the battery pack and the tool. As described above, the battery pack and the tool are combined through the discharge plus terminal 3, the minus terminal 6, and the overdischarge detection signal output terminal 7. The configuration of the battery pack will be described below.

  In the battery pack, a battery set 1 in which battery cells 1a, 1b, 1c and 1d are connected in series, a protection IC 14 for monitoring the voltage of each battery cell constituting the battery set 1, and a shunt resistor 15 for current detection An overcharge signal transmission circuit 16 for transmitting an overcharge signal to the charging device side via the temperature terminal 5 when the protection IC 14 detects overcharge, and provided directly to the battery set 1 or in the vicinity of the battery set 1 The thermistor 17 for detecting the temperature of the battery set 1 is provided. The temperature information is transmitted to the charging device side via the temperature terminal 5.

  In the battery pack, an identification resistor 18 and a thermal protector 23 indicating a battery type that functions when charging the battery set 1 are provided. When the battery pack is mounted on the charging device, the battery type information is transmitted to the charging device via the battery type identification terminal 4. The thermal protector 23 is provided between the charging plus terminal 2 and the battery set 2, and when the battery set 1 is abnormal and the temperature of the battery set 1 reaches a predetermined value, the thermal protector 23 is turned off. It is comprised so that an electric current may be interrupted | blocked.

  Next, the configuration on the tool side will be described. A motor 19 is built in the tool, and the motor 19 is driven by operating a user trigger switch 20. An FET control circuit 22 for controlling the FET 21 and the FET 2121 is provided in order to cut off the current flowing through the motor 19. When the tool is used, if the protection IC 14 determines that even one cell in the battery set has a voltage equal to or lower than the predetermined value, it determines that the discharge is overdischarged and outputs an overdischarge signal. The signal is transmitted to the tool-side FET control circuit 22 via the overdischarge detection signal output terminal 7, and the FET control circuit 22 cuts off the current flowing through the motor 19 by turning off the FET 21.

  FIG. 3 shows an outline of the configuration of circuits provided in the battery pack and the charging device. The configuration of the battery pack shown in FIG. 3 is the same as the configuration of the battery pack shown in FIG. As described above, the battery pack and the charging device are combined through the charging plus terminal 2, the battery type identification terminal 4, the temperature terminal 5, the minus terminal 6, and the overdischarge detection signal output terminal 7.

  The charging device is provided with a power source 24 composed of a mine power source and an auxiliary power source, and the battery pack is charged by the power source 24. Further, the charging device includes a microcomputer 25 (hereinafter referred to as “microcomputer 25”) for performing various controls, a power supply stop means 26 for stopping charging, and an overdischarge detection signal output terminal 7. Overdischarge detection means 27 is provided for receiving an overdischarge signal to be transmitted and transmitting to the microcomputer 25 whether or not the battery is overdischarged.

  The protection IC 14 provided in the battery pack is configured to output a signal notifying that it is overcharged when it is determined that one of the cells is at a predetermined voltage or higher and is overcharged. Yes. The charging device further receives temperature information from the battery pack and a signal indicating that the battery is overcharged via the temperature terminal 5 and transmits the temperature and overcharge detection means 28 to the microcomputer 25, and from the battery pack. The battery type detecting means 29 for receiving the battery type information via the battery type identification terminal 4 and transmitting the information to the microcomputer 25 and the battery voltage detecting means 30 for detecting the battery voltage are provided.

  Even during charging, if the protection IC 14 determines that even one cell in the battery set 1 has a voltage equal to or lower than a predetermined value, it is determined that the battery is overdischarged and a predetermined signal is output. As described above, this signal is transmitted to the overdischarge detection means 27 on the charging device side via the overdischarge detection signal output terminal 7 and further to the microcomputer 25.

  Next, an example of processing for determining battery life or failure using the entire voltage will be described with reference to the flowchart shown in FIG.

  First, the charging device determines whether or not a battery pack is mounted (step 101). The battery pack mounting may be determined, for example, based on whether or not the battery type detecting means 29 and the microcomputer 25 recognize information transmitted through the battery type identification terminal 4 when the battery pack is mounted. If it is determined in step 101 that the battery pack is mounted, charging is started with the first charging current I1 (step 102). After the start of charging, the battery voltage detecting means 30 detects the battery voltage and determines whether or not a predetermined voltage has been reached (step 103). Here, a predetermined value is set to 30 V assuming a battery set 1 configured by connecting ten battery cells in series. If the voltage does not reach the predetermined level in step 103, the detection of the battery voltage is continued until a predetermined time has elapsed (step 104). If it is determined in step 103 that the predetermined time has passed in step 104 without detecting that the battery voltage is equal to or higher than the predetermined value, it is determined that the battery voltage is abnormal (step 105). If it is determined in step 103 that the battery voltage is equal to or higher than the predetermined value, the charging current is switched to the second charging current I2 (I2> I1).

  Thereafter, when full charge is determined (step 107), the charge is terminated (step 108). After charging, it is determined whether or not the battery pack has been removed (step 109). If it is determined that the battery pack has been removed, the process returns to step 101.

  In the control method as described above, for example, even when one cell is short-circuited in a series configuration of 10 cells, if the voltage of another cell rises to 30/9 = 3.33 V, it is determined to be abnormal. It will continue to charge without. If an attempt is made to detect an abnormality of a battery using only the whole voltage, it becomes more difficult to determine the abnormality as the number of batteries in series increases.

  Next, the battery life or failure determination process according to the present embodiment will be described with reference to FIG.

  First, the charging device determines whether or not a battery pack is mounted (step 201). The battery pack mounting may be determined, for example, based on whether or not the battery type detecting means and the microcomputer 25 recognize information transmitted through the battery type identification terminal 4 when the battery pack is mounted. If it is determined in step 101 that the battery pack is mounted, charging is started with the first charging current I1 (step 202). After the start of charging, whether or not the overdischarge detection circuit 27 has detected a signal transmitted via the overdischarge detection signal output terminal 7 during overdischarge (whether all cells are equal to or higher than a predetermined voltage value). A determination is made (step 203). The signal transmitted via the above-described overdischarge detection signal output terminal 7 is output from the protection IC 14 when even one of the cells is equal to or lower than a predetermined voltage. Here, if the threshold value is 3 V / cell or less, it is determined that overdischarge occurs and a signal is output. When the overdischarge detection circuit 27 detects an overdischarge signal in step 203 (when all cells have not reached the predetermined voltage value or more), the overdischarge detection signal is output until a predetermined time elapses (step 204). Continue detection. In step 203, an overdischarge signal has been detected (all cells have not reached the predetermined voltage value or more), and if a predetermined time has elapsed in step 204, it is determined that there is an abnormality and charging is terminated ( Step 205).

  If no overdischarge signal is detected in step 203 (when all cells have reached a predetermined voltage or higher), the charging current is switched to the second charging current I2 (I2> I1). Thereafter, when full charge is determined (step 207), charging is terminated (step 208). After the end of charging, it is determined whether or not the battery has been removed (step 209). If it is determined that the battery has been removed, the process returns to step 201.

  If the control method as described above is performed, if all the cells in the plurality of cells have not reached a predetermined voltage or more within a predetermined time, it is determined that there is an abnormality. In a 10-line configuration connected in series, if one cell is short-circuited, it can be determined that the battery has failed, and charging can be terminated. This control method is effective as the number of battery cells connected in series constituting the battery set increases.

  The power tool 1 according to the present invention is not limited to the above-described embodiment, and various improvements and modifications can be made within the scope described in the claims. For example, a step 301 for detecting the battery voltage by the battery voltage detecting means 30 and determining whether or not the detected battery voltage is equal to or higher than a predetermined battery voltage is inserted before the step 203 in the flowchart shown in FIG. If it is determined in step 301 that the battery voltage has not reached the predetermined battery voltage (step 301: NO), the process proceeds to a new step 302 for determining whether or not the same predetermined time as in step 204 has elapsed. Good. In step 302, if the predetermined time has not elapsed (step 302: NO), the process proceeds to step 203. If the predetermined time has elapsed (step 302: YES), the process proceeds to step 205, and the battery is abnormal. It is determined that there is, and charging is terminated. When it is determined in step 204 that the predetermined time has not elapsed (step 204: NO), the process returns to step 301.

  By doing in this way, since it is determined whether the battery is normal from a plurality of viewpoints of the total battery voltage and the cell voltage, a more reliable determination can be performed. More specifically, within the precharge period (within the time counted in step 301 or step 204), the battery voltage has increased until it exceeds a predetermined battery voltage value, and all the battery cells have a predetermined voltage value. For the first time in the above case, it is determined that the battery is normal and full-scale charging is started. Therefore, it is possible to avoid charging a battery that is less suitable for charging than in the past in that the state of the battery can be more reliably determined. Further, if it is found that there is no abnormality in the battery to be charged before the precharge period expires, the full charge can be started immediately by the current I2, so that the charging time can be shortened.

  Further, in the above-described embodiment, the embodiment in which a single terminal is provided for transmitting the overdischarge detection signal is illustrated, but the present invention is not limited to the illustrated embodiment, and the scope of the claims is defined. Configurations in which constituent elements are replaced or modified within the stated ranges are also included in the scope. For example, even a terminal shared with other signals is naturally applicable, and not only a configuration through a terminal to which electrical connection is made, but also non-contact communication means such as short-range wireless communication and optical communication It is obvious to those skilled in the art that the method is suitable for transmitting an overdischarge signal.

1 is a battery set, 2 is a charge plus terminal, 3 is a discharge plus terminal, 4 is a battery type identification terminal, 5 is a temperature terminal, 6 is a minus terminal, 7 is an overdischarge detection signal output terminal, 8 is a protective substrate, 9 is Tool terminal and terminal holder, 10 is a tool housing, 11 is a charging device terminal and terminal holder, 12 is a battery-charging device fixing rail, 13 is a charging device housing, 14 is a protection IC, and 15 is a shunt resistor for current detection. , 16 is an overcharge signal transmission means, 17 is a thermistor, 18 is an identification resistor, 19 is a motor, 20 is a trigger switch, 21 is an FET, 22 is an FET control means, 23 is a thermal protector, 24 is a power supply unit of the charging device, Reference numeral 25 denotes a microcomputer, 26 denotes power supply stopping means, 27 denotes overdischarge detection means, 28 denotes temperature and overcharge detection means, 29 denotes battery type detection means, 30 Battery voltage detection means.

Claims (6)

A charging device for charging a battery pack as a driving source of a cordless electric tool,
Overdischarge signal receiving means for receiving from the battery pack an overdischarge signal indicating that at least one of the plurality of battery cells constituting the secondary battery incorporated in the battery pack is in an overdischarged state. When,
An overdischarge state determining means for determining that at least one of the plurality of battery cells is in an overdischarged state when the overdischarge signal receiving means receives an overdischarge signal;
Charging current control means for controlling a charging current for charging the secondary battery;
Have
When the overdischarge state determination unit determines that the overdischarge state is in an overdischarge state at the start of charging, the charging current control unit performs charging with the first charging current for a predetermined time from the start of charging, and the predetermined time has elapsed. After that, if the overdischarge signal receiving means receives the overdischarge signal and the overdischarge state determining means determines that it is in the overdischarge state, the charging current control means stops charging. A charging device. If the overdischarge state determination means determines that the secondary battery is not in an overdischarge state after the predetermined time has elapsed, the charge current control means outputs a second current greater than the first charge current. The charging device according to claim 1, wherein the secondary battery is charged by switching to a charging current. The said overdischarge signal receiving means is a terminal electrically connected with the terminal provided in order for the said battery pack to output an overdischarge signal to a cordless tool, The Claim 1 or 2 characterized by the above-mentioned. Charging device. The battery further includes a battery voltage detecting means for detecting a battery voltage output from the secondary battery, the overdischarge state determining means is determined to be in an overdischarge state even after the predetermined time has elapsed, and 4. The charging current control unit stops charging when the battery voltage of the secondary battery detected by the battery voltage detection unit does not exceed a predetermined battery voltage value. 5. The charging device according to item. Battery voltage detecting means for detecting a battery voltage output from the secondary battery is further included, and the battery voltage detected by the battery voltage detecting means is predetermined while the charging current control means is charging with the first charging current. When the voltage value exceeds the predetermined charging time, the charging current control means switches to a second charging current larger than the first charging current to charge the secondary battery even before the predetermined time has elapsed. The charging device according to claim 1, wherein: The charging device according to claim 1, wherein the secondary battery is a lithium ion battery.

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