JP2018046618A - Charging system and charging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging system and a charging method that are capable of securely avoiding a trouble at the time of reverse connection.SOLUTION: A charging system 1 comprises: a polarity discrimination circuit 141 constituting detection means for detecting whether a connection state with a secondary battery 380 is normal connection or reverse connection; and a switch circuit 13 for opening/closing an electric path for charging the secondary battery 380. The switch circuit 13 is configured to shift from an open state to a closed state when the connection state detected by the polarity discrimination circuit 141 is normal connection and keep the open state when the connection state detected by the polarity discrimination circuit 141 is reverse connection.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a charging system for charging a secondary battery.

  Conventionally, an electric vehicle such as an AGV (Automatic Guided Vehicle) equipped with a secondary battery such as a nickel metal hydride battery is known. In an electric vehicle that operates with electric power stored in a secondary battery, it is necessary to connect a charger or the like to charge the secondary battery when the electric power is consumed. Many chargers have a power supply terminal and a ground-side terminal, and a battery positive electrode terminal is connected to the power supply terminal and a negative electrode terminal is connected to the ground-side terminal to perform a charging operation.

  During such a charging operation, the negative terminal of the battery is connected to the power supply terminal of the charger due to human error when connecting the charger, an electrical wiring error inside the electric vehicle, etc. The terminal is connected to the ground side terminal of the charger, and so-called reverse connection may occur. In the case of such reverse connection, abnormal current may flow from the battery and the charger may be damaged. Therefore, conventionally, a charger provided with a protection circuit that prevents an abnormal current from flowing from the battery to the charger has been proposed (see, for example, Patent Document 1).

JP 2009-118607 A

  However, the following problems remain even in the charger provided with the conventional protection circuit. In other words, if the generator circuit on the charging current supply side is not activated, the protection circuit works effectively to prevent the flow of abnormal current during reverse connection, while protection occurs when the generator circuit is activated. There is a problem that an excessive current flows into the charger side without the circuit effectively operating, and there is a possibility that trouble may occur in the rectifier diode and electronic components that constitute the control circuit of the charger.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a charging system and a charging method capable of reliably avoiding trouble at the time of reverse connection.

One aspect of the present invention is a charging system for a secondary battery,
Discrimination means for discriminating whether the connection state to the secondary battery is tangent or reverse;
Switch means for opening and closing an electrical path for charging the secondary battery,
The switch means switches from an open state to a closed state when it is determined by the determination means that the connection is a tangent,
When it is determined that the connection state is reversely connected by the determination unit, the charging system maintains the open state (Claim 1).

One aspect of the present invention is a method of charging a secondary battery,
When the connection state of the charging device to the secondary battery is determined to be tangent or reverse connection, when it is determined that the connection is tangent, the electrical path for charging the secondary battery is closed from the open state to the closed state. On the other hand, when it is determined that the connection state is reversely connected, the secondary battery charging method holds the path in an open state (Claim 5).

  In the charging system and the charging method of the present invention, in the case of reverse connection, the electrical path for charging the secondary battery is kept open. Therefore, even if reverse connection occurs, current does not flow from the secondary battery side. Therefore, according to the charging system and the charging method of the present invention, it is possible to avoid a trouble at the time of reverse connection with high reliability.

Explanatory drawing which shows the combination of the unmanned tow vehicle which mounts a battery, and a charger in Example 1. FIG. The perspective view of the unmanned tow vehicle which connects the conveyance trolley | bogie in Example 1. FIG. 1 is a block diagram of a charging system in Embodiment 1. FIG. FIG. 3 is an explanatory diagram of a charging circuit in the first embodiment. 2 is a block diagram of a charge control circuit in Embodiment 1. FIG. FIG. 3 is a time chart illustrating a temporal flow of a charging operation in the first embodiment. FIG. 3 is an explanatory diagram of another charging circuit in the first embodiment. The block diagram of the charger in a reference example.

The charging system of the present invention may include a measuring unit that measures a terminal voltage of the secondary battery before charging, and the terminal voltage may be set as a start condition of the charging operation that is equal to or higher than a predetermined threshold ( Claim 2).
When the terminal voltage of the secondary battery is less than the predetermined threshold value, there may be some trouble in the secondary battery. For such a secondary battery, it is preferable to avoid electrical connection.

The secondary battery is a nickel metal hydride battery, and constant current control may be executed to control the current supplied when charging the secondary battery to be constant (claims 3 and 6).
Since the nickel metal hydride battery is likely to be overcharged when constant voltage charging is performed, charging with constant current control is suitable. With constant current control, rapid charging can be performed with high safety, and the time required for charging can be shortened.

The charging may be terminated when the current for charging the secondary battery becomes equal to or less than a predetermined threshold during the execution of the constant current control.
In this case, overcharge can be avoided with high certainty, and performance deterioration of the secondary battery can be prevented.

The embodiment of the present invention will be specifically described with reference to the following examples.
Example 1
This example is an example related to the charging system 1 that charges a battery (secondary battery) 380 mounted on the unmanned towing vehicle 3. The contents will be described with reference to FIGS.

  As shown in FIGS. 1 and 2, the unmanned towing vehicle 3 is an AGV that connects a self-supporting transport cart 4 with a free wheel 48 and transports workpieces such as parts loaded on the transport cart 4 in a facility such as a factory. is there. The unmanned towing vehicle 3 includes a low-floor type vehicle body 30 that is thin in the height direction and long in the front-rear direction so as to be buried under the transport cart 4, and is connected to the transport cart 4 via a connecting pin 34 on the upper surface 303. The

  The unmanned towing vehicle 3 includes a drive unit (not shown) including a pair of drive wheels 33 arranged in a coaxial manner at two locations in the front-rear direction, and a battery 380 (FIG. 3) disposed at the rear of the vehicle body 30. (Refer to secondary battery.) Operates with the power stored in the battery. Charging the battery 380 can be performed using the charging terminal 38 provided on the side surface 302 of the vehicle body 30. Note that the battery 380 of this example is a nickel metal hydride battery.

  The charging terminal 38 is a terminal for connecting the charging plug 102 at the tip of the electric cord 101 extending from the charger 10 (see FIG. 1), and is connected to the positive terminal 38P connected to the positive side of the battery 380 and the negative terminal. And a negative electrode terminal 38M connected to the side. The charging plug 102 connected to the charging terminal 38 is provided with a power supply terminal 18P and a ground side terminal 18G (see FIG. 4).

  In charging the battery 380 using the charger 10, it is necessary to connect the power terminal 18P of the charging plug 102 to the positive terminal 38P on the unmanned tow truck 3 side and connect the ground terminal 18G to the negative terminal 38M. There is. In the unmanned tow truck 3, with respect to the connection structure of the charging plug 102 to the charging terminal 38, the power terminal 18P is in contact with the negative terminal 38M and the ground terminal 18G is in contact with the positive terminal 38P (reverse connection state). Safety is improved by providing a fail-safe structure (not shown) for mechanically preventing this.

Next, an electrical circuit configuration adopted by the charging system 1 of the present example including the charger 10 will be described.
First, the basic configuration of the charging system 1 of this example will be described with reference to the block diagram of FIG. In the charging system 1, a switch circuit (switch means) 13 whose initial state is an open state is interposed between the battery 380 and a charging power supply unit 12 that supplies power for charging the battery 380. .

  The switch circuit 13 is a circuit that electrically disconnects the battery 380 from the charger 10 in the initial open state, and electrically connects the charger 10 to the battery 380 in accordance with switching to the closed state. is there. The switch circuit 13 switches to a closed state in response to a charging circuit closing signal output from the control unit 14 including a polarity determining circuit (discriminating means) 141 that determines the connection polarity.

  Next, the above contents will be described in detail with reference to FIG. 4 showing a circuit configuration of the charger 10. The circuit of the charger 10 is configured around the control unit 14. The control unit 14 includes a voltage measurement circuit (measurement means) 142, a differential amplifier circuit 143, an error amplifier circuit 144, a charge end determination circuit 145, and the like in addition to the polarity determination circuit 141 described above. The control unit 14 is connected to a charging power supply unit 12, photocouplers 171 and 172, an N-channel MOS-FET 131 constituting the switch circuit 13, and the like.

  In the circuit configuration of the charger 10, an N-channel MOS-FET 131 is connected between the ground side terminal 18 </ b> G connected to the negative terminal 38 </ b> M of the battery 380 and GND (ground) in the case of positive connection (tangential connection state). A utilized switch circuit 13 is interposed. In addition, two photocouplers 171 and 172 that share the LED current limiting resistor 170 are interposed between the power supply terminal 18P connected to the positive terminal 38P of the battery 380 and the ground side terminal 18G in the positive connection. ing. The first photocoupler 171 is a photocoupler that is switched on with a positive connection and inputs a positive connection detection signal to the control unit 14. The second photocoupler 172 is a photocoupler that is turned on by reverse connection and inputs a reverse connection detection signal to the control unit 14.

  Only when the input of the positive connection detection signal is received, the control unit 14 outputs the charging circuit closing signal and switches the switch circuit 13 by the N-channel MOS-FET 131 to the closed state. When the switch circuit 13 is switched to the closed state, the ground side terminal 18G is grounded to GND, and the charging power supply unit 12 can supply the charging current to the battery 380.

  Thus, in the charging system 1, the first photocoupler 171 is switched ON by the voltage of the battery 380, and the switch circuit 13 is switched from the open state to the closed state to be in a chargeable state. On the other hand, when the battery 380 is not connected or when the battery 380 is reversely connected, the switch circuit 13 is kept open. When the switch circuit 13 is in the open state, the circuit on the charger 10 side is electrically disconnected from the battery 380, and the current of the battery 380 does not flow into the charger 10 side.

  When the switch circuit 13 is in the closed state, the voltage of the power supply terminal 18P is divided by the voltage dividing circuit 175 and input to the control unit 14 as a voltage signal. The voltage measurement circuit 142 of the control unit 14 measures the voltage of the battery 380 using this voltage signal. When the voltage of the battery 380 is equal to or higher than a predetermined threshold (18.0 V in this example) and lower than a predetermined charging target voltage (27.2 V in the present example, predetermined threshold), the control unit 14 A current control signal is output to activate the charging power supply unit 12. The charging power supply unit 12 is driven by constant current control by feedback control of a current signal by the current sensor 11 until the voltage of the power supply terminal 18P reaches a preset charging target voltage.

Next, (1) drooping type constant current control executed by the charger 10 during the charging operation, and (2) charging end determination for determining the end point of the charging operation will be described.
(1) Drooping type constant current control The charging operation by the charging system 1 is realized by the drooping type current control circuit illustrated in FIG. The drooping current control circuit includes a current sensor 11 that measures a charging current, a differential amplifier circuit 143 that amplifies a current signal output from the current sensor 11, and an error that amplifies a difference (error) with respect to a target current value of constant current control. The amplifier circuit 144 and the like are included. In the charging system 1 of this example, the target current value for constant current control is set to 100A.

  The current sensor 11 (FIGS. 4 and 5) generates a current signal having a voltage corresponding to the magnitude of the charging current (FIG. 6A). The differential amplifier circuit 143 amplifies the current signal output from the current sensor 11 with a predetermined amplification factor. The error amplifying circuit 144 is a circuit well known in the control system field called a so-called error amplifier, and amplifies an error with respect to a target current value among the measured current values represented by the output voltage of the differential amplifying circuit 143.

  The output signal of the error amplifier circuit 144 is input to the charging power supply unit 12 as a voltage control signal as shown in FIG. The power supply unit 12 for charging, which is a constant voltage output power supply, operates with the operating voltage controlled by the voltage control signal output from the error amplifier circuit 144, and is controlled to keep the charging current constant at 100A. Specifically, as shown in FIG. 5B, when the charging current exceeds 100A, the lowering control for suppressing the charging current is performed, and when the charging current is lower than 100A, the increasing control for increasing the charging current is performed.

(2) Charging end determination As the charging operation proceeds, the terminal voltage of the battery 380 gradually increases as shown in FIG. When this terminal voltage reaches the charging target voltage (time A in FIG. 6), the constant current control cannot be maintained, and the output of the voltage control signal of the error amplifier circuit 144 is stopped ((b) in FIG. 6). This voltage control signal is input to the charging power supply unit 12 and used for constant current control, and is also input to the charging end determination circuit 145. When the charge end determination circuit 145 determines that the output of the voltage control signal from the error amplifier circuit 144 is stopped, the charge end determination circuit 145 switches the power control signal input to the charging power supply unit 12 from ON to OFF ((d) in FIG. 4). The charging power supply unit 12 stops the output of the charging current in response to the switching of the power control signal to OFF, and the charging operation is thereby terminated.

  In the charging system 1 configured as described above, when the charger 10 is connected to the battery 380, first, whether the electrical path is switched to the closed state, is the normal connection state or the reverse connection state? Is determined. If it is in the normal connection state, the switch circuit 13 is controlled to switch the electrical path to the closed state and set a state in which charging can be started. On the other hand, in the reverse connection state, the circuit on the charger 10 side is not electrically connected to the battery 380.

  As described above, a fail-safe structure for preventing reverse connection due to human error is provided between the charging terminal 38 of the illustrated unmanned towing vehicle 3 and the charging plug 102 of the charger 10. ing. Therefore, there is almost no possibility that the mounting direction of the charging plug 102 with respect to the charging terminal 38 is reversed. However, if there is an error in the internal wiring of the charger 10 with respect to the charging plug 102 or the internal wiring of the unmanned tow truck 3 with respect to the charging terminal 38, an electrical reverse connection can occur. Even in such a case, according to the charging system 1 of this example, troubles caused by reverse connection can be avoided in advance.

  In the case of the charging system 1 that does not start the charging operation when the battery 380 is reversely connected, it is necessary to provide a diode or the like for preventing inflow of current at the time of reverse connection in the circuit on the unmanned tow truck 3 side that receives the charge. There is no. If the diode for the reverse connection can be eliminated, power loss due to the forward voltage drop of the diode can be eliminated. Since this power loss increases as the charging current increases, the effect of being able to eliminate the diode for the reverse connection becomes more prominent in a large-scale charging system that requires high power.

  The charging system 1 determines whether or not the terminal voltage of the battery 380 is equal to or higher than a predetermined threshold after setting the switch circuit 13 in a closed state, and starts a charging operation if the voltage is equal to or higher than the predetermined threshold. On the other hand, if the terminal voltage of battery 380 is an abnormal value less than a predetermined threshold, it is determined that some trouble may have occurred, and the charging operation is not started. Thereby, the seriousness of the trouble of the battery 380 can be avoided in advance, and the trouble on the side of the charger 10 that may occur due to the trouble on the side of the battery 380 can be prevented.

  The charging system 1 after starting the charging operation determines, with high accuracy, the state in which the battery 380 is close to full charge and cannot maintain constant current control by determining the output stop of the voltage control signal of the error amplifier circuit 144. . Then, the charger 10 stops the supply of the charging current in response to the output stop of the voltage control signal of the error amplifier circuit 144. The charging system 1 thus avoids overcharging of the battery 380 with high reliability by stopping the supply of the charging current and ending the charging operation.

  As described above, according to the charging system 1 of this example, even when the charger 10 is reversely connected to the battery 380, an excessive current of the battery 380 does not flow into the charger 10, and the charger side There is less risk of electrical trouble or battery 380 degradation. Further, in this charging system 1, since the supply of the charging current is stopped when the set voltage is reached by the constant current charging and the constant current control cannot be maintained, the battery 380 is less likely to be overcharged.

  In general, the battery 380, which is a nickel metal hydride battery, is likely to be overcharged when subjected to constant voltage charging, and is likely to rise in temperature or break. Care must be taken because such a temperature rise or damage is likely to occur even in a low current state. For nickel metal hydride batteries, not overcharging is effective in preventing deterioration.

  The charging system 1 of this example supplies a charging current by constant current control to the battery 380 to perform charging, and stops supplying the charging current when the constant current control cannot be maintained. The charging system 1 is a system that is less likely to cause overcharging of the battery 380 and is suitable for charging a nickel metal hydride battery. According to this charging system 1, there is little possibility of overcharging, and for example, rapid charging of about 5C (charging completed in 12 minutes) is possible.

  In this example, the switch circuit 13 using the N-channel MOS-FET 131 is illustrated, but the switch circuit may be configured using the P-channel MOS-FET. As shown in FIG. 7, a switch circuit 13 using an electromagnetic switch (contactor) 132 may be employed. In the switch circuit 13 illustrated in FIG. 4, the ON resistance of the N-channel MOS-FET 131 may be a problem. On the other hand, if the switch circuit 13 uses the electromagnetic switch 132 of FIG. 7, the ON resistance may be a problem. There is no.

In this example, the nickel-metal hydride battery is exemplified as the battery. However, any other secondary battery such as a lithium ion battery, a nickel cadmium battery, or a liquid circulation type battery may be used, and the battery can be widely applied.
The AGV has been exemplified as a battery-operated device. In addition, an electrically driven automobile such as an EV (Electric Vehicle) or a PHV (Plug-in Hybrid Vehicle), or a welfare vehicle (senior car, electric wheelchair) is required. ), An electric assist bicycle, or a rechargeable electric device such as an electric tool.

(Reference example)
For the purpose of comparison with the charging system of the first embodiment, a conventional type charger will be described with reference to FIG.
The circuit of the charger 90 shown in the figure is configured such that a rectifier diode 93 is interposed between the battery 380 to be charged and the power supply unit 92 for charging. The charging power supply unit 92 is configured to output a charging current via the output coil 920 after performing AC / DC conversion by a switching method.

  In the case of the charger 90, when the positive terminal 38P of the battery 380 is connected to the power supply terminal 98P and the negative terminal 38M of the battery 380 is connected to the ground side terminal 98G, the current from the battery 380 is blocked by the rectifier diode 93. Therefore, an excessive current does not flow into the circuit on the charger 90 side. On the other hand, when the battery 380 is reversely connected to the charger 90, the current from the battery 380 flows into the output coil 920 and the rectifier diode 93 without any limitation, and any of the components are damaged or the battery 380 Deterioration may occur.

  On the other hand, when the charger is connected to the battery, first, in the charging system according to the first embodiment that determines whether the battery is in the normal connection state or the reverse connection state, the switch circuit is opened in the reverse connection. As it is, do not electrically connect the charger to the battery. Therefore, even if a reverse connection state occurs, there is no possibility that an electrical trouble will occur in the charger due to the current from the battery.

  As described above, specific examples of the present invention have been described in detail as in the embodiments. However, these specific examples merely disclose an example of the technology included in the scope of claims. Needless to say, the scope of the claims should not be construed as limited by the configuration, numerical values, or the like of the specific examples. The scope of the claims includes techniques in which the specific examples are variously modified, changed, or appropriately combined using known techniques and knowledge of those skilled in the art.

DESCRIPTION OF SYMBOLS 1 Charging system 10 Charger 102 Charging plug 11 Current sensor 12 Charging power supply unit 13 Switch circuit 14 Control unit 141 Polarity determination circuit 142 Voltage measurement circuit 143 Differential amplification circuit 144 Error amplification circuit 145 Charge end determination circuit 171 and 172 Photocoupler 175 Voltage dividing circuit 18P Power supply terminal 18G Ground side terminal 3 Unmanned towing vehicle 38 Charging terminal 38P Positive electrode terminal 38M Negative electrode terminal 380 Battery 4 Carriage cart 90 Charger

Claims (6)

A rechargeable battery charging system,
Discrimination means for discriminating whether the connection state to the secondary battery is tangent or reverse;
Switch means for opening and closing an electrical path for charging the secondary battery,
The switch means switches from an open state to a closed state when it is determined by the determination means that the connection is a tangent,
A charging system configured to maintain an open state when it is determined that the connection state is reversely connected by the determination unit.   The charging system according to claim 1, further comprising: a measuring unit that measures a terminal voltage of the secondary battery before charging, wherein the terminal voltage is set to be a predetermined threshold value or more as a charging operation start condition.   3. The charging system according to claim 1, wherein the secondary battery is a nickel metal hydride battery, and performs constant current control for controlling the current supplied when charging the secondary battery to be constant.   The charging system according to claim 3, wherein the charging is terminated when a current for charging the secondary battery becomes equal to or less than a predetermined threshold during the execution of the constant current control. A method for charging a secondary battery,
When the connection state of the charging device to the secondary battery is determined to be tangent or reverse connection, when it is determined that the connection is tangent, the electrical path for charging the secondary battery is closed from the open state to the closed state. On the other hand, when it is determined that the connection state is reverse connection, the secondary battery charging method of holding the path in an open state.   6. The method of charging a secondary battery according to claim 5, wherein the secondary battery is a nickel metal hydride battery, and constant current control is performed to control the current supplied when charging the secondary battery to be constant.