JP4904729B2 - Cell voltage measuring device and fuel cell - Google Patents

Description

  The present invention relates to a cell voltage detection device for detecting the voltage of a cell or a group of cells constituting an assembled battery in which a plurality of cells such as fuel cells are connected in series, and particularly, disconnection of a connection line between the assembled battery and the cell voltage detection device. Alternatively, the present invention relates to a cell voltage detection device that can easily detect a connection failure and a fuel cell including the same.

  As a conventional battery voltage detector for an assembled battery, it has a detection terminal connected to each of both terminals of the cells constituting the assembled battery, and the detection terminals are short-circuited for a predetermined time via a switching element and a resistor. There is known a technique for detecting disconnection, contact failure, etc. between a battery cell and a cell voltage detection device by comparing the output voltage at the time of non-short circuit (for example, Patent Document 1).

Also, as a failure diagnosis technique of a conventional cell voltage detection device, the cell voltage of the fuel cell is detected, and when the cell voltage is below a predetermined value, the output current of the fuel cell is limited, and the cell voltage is still in the open voltage state. A technique for diagnosing a failure of the cell voltage detection device when the value is equal to or less than a predetermined value is known (Patent Document 2).
JP 2001-157367 A (page 6, FIG. 1) JP 2004-178899 A (page 4, FIG. 1)

  However, the device described in Patent Document 1 has a problem in that the circuit configuration becomes complicated because each transistor has a detection resistor between the voltage input terminals. There is also a problem that failure of the transistor cannot be detected.

  In addition, in the device described in Patent Document 2, it is necessary to limit the output current of the fuel cell in order to detect a failure. If the output current continues to be high when the vehicle is traveling, the failure is detected. There was a problem that could not be done.

In order to solve the above problems, the present invention provides a cell voltage measuring device for measuring a cell voltage of an assembled battery configured by connecting a plurality of cells in series, wherein each cell or a plurality of cells are connected in series. A plurality of input terminals to which a voltage for each cell group is input; a plurality of voltage measuring circuits for measuring a voltage between the input terminals; and the assembled battery and the input based on a voltage value measured by the voltage measuring circuit. A diagnostic device for determining the quality of connection with a terminal and the quality of each cell or each cell group, and a disconnection detection resistor for connecting between an input terminal serving as a ground potential of the cell voltage measuring device and another input terminal At least one disconnection detection resistor for connecting between the input terminals, and the diagnostic device calculates an average value of all measured voltage values or an average value of a part of the measured voltage values input to the diagnostic device. , Voltage measurement When one of the measured voltage values of the two cells or cell group adjacent output from the circuit is greater than a value obtained by multiplying a predetermined coefficient to the average value, is summarized in that the diagnosis of disconnection or contact failure of the connecting lines.

  According to the present invention, it is possible to detect a disconnection or contact failure of a connection line connecting a terminal of a fuel cell or a cell group and an input terminal of a cell voltage measuring device with a simple circuit configuration.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. The following examples are examples of a cell voltage measuring device that measures the cell voltage of the fuel cell stack. The cell voltage measuring device according to the present invention is a secondary battery such as a nickel metal hydride battery or a lithium ion battery. Needless to say, the present invention can be applied to the assembled battery.

  FIG. 1A is a schematic configuration diagram illustrating the configuration of a cell voltage detection device according to a first embodiment of the present invention, and FIG. 1B is a circuit diagram illustrating details of a voltage measurement circuit according to the first embodiment. In the first embodiment, the disconnection detection resistor is a disconnection detection resistor that connects between an input terminal serving as a ground potential of the cell voltage measurement device and another input terminal.

  The fuel cell stack 1 that is the object of cell voltage measurement has a total number ns of fuel cells or fuel cell groups. Symbols in the fuel cell stack 1 are defined as follows. ci (i = 1 to ns): a fuel cell or a group of fuel cells, ei (i = 1 to ns): a voltage value of the fuel cell or fuel cell group, pi (i = 0 to 0) ns): a terminal of a fuel cell or a group of fuel cells.

  The fuel cell stack 1 and the cell voltage measuring device 2 are connected by a connection line li (i = 0 to ns).

  The cell voltage measuring device 2 includes an input terminal ti (i = 0 to ns), a disconnection detecting resistor Ra10, a voltage measuring circuit Di (i = 1 to ns), and a diagnostic device 3. The voltage measuring circuit Di (i = 1 to ns) outputs the output voltage value Vi (i = 1 to ns) to the diagnostic device 3, respectively.

  As shown in FIG. 1B, each voltage measuring circuit Di (i = 1 to ns) includes an operational amplifier (op-amp) OPi (i = 1 to ns) and a resistor Rij (i = 1 to ns, j = 1 to 5), which are supplied with + V and −V power supply voltages. In common with FIGS. 1A and 1B, the reference potential of the circuit is the ground GND. Here, the resistance value of the resistor Rij (i = 1 to ns, j = 1 to 5) used in the voltage measuring circuit Di (i = 1 to ns) and the input impedance of the operational amplifier OPi (i = 1 to ns) are: The resistance values of all the disconnection detection resistors described below are sufficiently larger. In other words, the current flowing in and out of the input of the voltage measuring circuit Di (i = 1 to ns) is small enough to be ignored compared to the current flowing through the disconnection detection resistor.

  The voltage value ei of the fuel cell is connected to the input terminal ti from the connection line li and input to the cell voltage measuring device 2. The input voltage value ei of the fuel battery cell is output by the voltage measuring circuit Di as an output voltage value Vi with the ground GND as a reference potential.

  Here, in the voltage measuring circuit Di, the resistance value of the resistor Rij is determined such that an output voltage value Vi equal to the voltage difference between the two input terminals is output. The ground GND is connected to a terminal pi in the fuel cell stack 1 via a connection line l i and is equipotential with the ground GND of the cell voltage measuring device 2.

  The voltage of each cell or cell group of the fuel cell stack 1 is input to the voltage measuring circuit Di via the connection line li, and the output voltage value Vi is output from the respective voltage measuring circuit Di to the diagnostic device 3. The diagnostic device 3 calculates Vave which is the total average value of the voltages Vi or the average value of the plurality of voltages Vi, and based on the average value Vave and the input voltage Vi, whether the connection state of the connection line li is normal or disconnected. Judging.

As shown in FIG. 2, when the connection line lk on the side higher in potential than the connection line li that is equipotential to the ground GND of the reference potential is disconnected, the normal voltage output as shown in FIG. , The output voltages Vk + 1 and Vk of the cells kk + 1 and kk are far from the original cell voltage values ek and ek + 1 as shown in FIG.
Vk ≒ 0 ... Formula (1)
Vk + 1≈Σej = ei + 1 + ei + 2 +,..., + Ek + ek + 1 (2)
It is expressed by

As shown in FIG. 2, when the connection line lm having a lower potential than the connection line li that is equipotential to the ground GND of the reference potential is disconnected, the cell outputs from the normal voltage output as shown in FIG. The output voltages Vm + 1 and Vm of cm + 1 and cm are far from the original cell voltage values em and em + 1 as shown in FIG.
Vm.apprxeq..SIGMA.ej = em + em + 1 +,..., + Ei-1 + ei (3)
Vm + 1 ≒ 0 ... Formula (4)
It is expressed by

  FIG. 5 is a diagram for explaining a comparative example, (a) a configuration of a cell voltage detection device without a disconnection detection resistor, (b) an output voltage of a voltage measurement circuit in a normal state of the comparative example, and (c) a comparative example. The output voltage of the voltage measurement circuit at the time of disconnection of each is shown. The reference numerals in FIG. 5 are the same as those in FIG.

  As shown in FIG. 5 (a), when the connection line li that is equipotential with the ground GND of the reference potential is disconnected, the fuel cell stack 1 in the cell voltage measuring device 2 should be equipotential with the ground GND of the reference potential. The potential at the terminal pi becomes indefinite due to the disconnection of the connection line li.

  At this time, the voltages Vi and Vi + 1 output values close to the true voltage values ei and ei + 1 as shown in FIG. 5C from the normal voltage output as shown in FIG. 5B. There is.

  Therefore, in the first embodiment, as shown in FIG. 1A, the input terminals ti and ti + 1 are connected via the disconnection detection resistor Ra10.

As a result, as shown in FIG. 6A, when the connection line li is disconnected, the input terminal ti is substantially equipotential with the terminal pi + 1 of the fuel cell stack 1. Thus, from the normal voltage output as shown in FIG. 6 (b), the output voltages Vi and Vi + 1 of the voltage measuring circuit for the cells ci and ci + 1 become the voltage Vi at the time of disconnection shown in FIG. 6 (c). ≒ ei + ei + 1 ... Formula (5)
Vi + 1 ≒ 0 ... Formula (6)
The voltage expressed by can be output. Based on these changes in the output voltages Vi and Vi + 1, the diagnostic device 3 can easily detect that the connection line li is disconnected.

Here, regarding the voltage value measured by the cell voltage measuring device 2,
Vj> Vave × k0 (Formula (7))
Vj + 1> Vave × k0 (8)
When there is a voltage value satisfying Expression (7) or Expression (8), it is determined that the connection line lj is disconnected.

  In equations (7) and (8), k0 is a value satisfying 1 <k0 <2, and Vave is an average value of the cell voltage or cell group voltage calculated by equation (9).

Vave = ΣVj / ns (9)
Here, ΣVj is the sum of cell or cell group voltages, and ns is the number of cells or cell groups.

  In addition, the average value Vave of the cell voltages may be an average voltage value of two or more cells or cell groups instead of the average voltage value of all the cells or cell groups of the fuel cell stack 1.

  FIG. 7 is a diagram illustrating that the connection line li + 1 is disconnected in the first embodiment. At this time, the input voltage of the voltage measuring circuit Di + 1 for detecting the cell voltage between the input terminals ti and ti + 1 is almost 0 [V], and it is easily determined that the connection line li + 1 is disconnected. it can.

  Next, points to be noted when two disconnection detection resistors are connected to one input terminal will be described. FIG. 8 is a diagram illustrating a configuration of a modification of the first embodiment in which two disconnection detection resistors are connected to the same input terminal.

  As shown in FIG. 8, when two disconnection detection resistors Ra11 and Ra12 are connected to the same input terminal ti and the connection line li connected to the input terminal ti is disconnected, the output voltage Vi of the voltage measuring circuits Di and Di + 1. , Vi + 1 are voltages detected by the equations (10) and (11).

Vi≈Ra12 / (Ra11 + Ra12) × (ei + ei + 1) Equation (10)
Vi + 1≈Ra11 / (Ra11 + Ra12) × (ei + ei + 1) (11)
That is, there is an input terminal ti to which one end of each of the two disconnection detection resistors is connected. When the connection line li connected to the input terminal ti is disconnected, the potential of the input terminal ti is changed to each of the two disconnection detection resistors. It is determined by the potential of the other end and the resistance value of the disconnection detection resistor. Then, the divided voltages by the two disconnection detection resistors Ra11 and Ra12 are output to the output voltages Vi and Vi + 1 of the voltage measuring circuits Di and Di + 1 connected to the input terminal ti. For this reason, when the values of the two disconnection detection resistors Ra11 and Ra12 are equal and the other ends of the respective disconnection detection resistors are substantially equal in absolute value of the potential difference with respect to the potential of the input terminal ti at the normal time, and are opposite in polarity. Therefore, there is almost no change in the output voltage between normal and disconnected, and disconnection cannot be detected.

  As a countermeasure against this, if disconnection detection resistors Ra11 and Ra12 having different resistance values are used, the voltage dividing ratio is different, so that the value of equation (10) differs from the value of equation (11), and disconnection detection is possible. Become. For example, if the ratio of the maximum cell voltage to the minimum cell voltage under the same operating condition of the fuel cell is 1.2, the resistance ratio Ra11 / Ra12 of the disconnection detection resistors Ra11 and Ra12 exceeds the cell voltage ratio 1.2. If the disconnection detection resistors Ra11 and Ra12 are selected, it is possible to distinguish between fluctuations in the cell voltage and disconnection of the connection lines.

Ra11 / Ra12> 1.2 Formula (12)
According to the present embodiment described above, it is possible to detect a disconnection or poor contact of a connection line connecting a terminal of a fuel cell or a group of cells and an input terminal of a cell voltage measuring device with a simple circuit configuration. effective.

  Next, a second embodiment of the cell voltage measuring apparatus according to the present invention will be described. FIG. 9 is a schematic configuration diagram illustrating the configuration of the second embodiment. The feature of this embodiment is that a set of input terminals to which both terminals of the disconnection detection resistor are connected are not input to the same voltage measurement circuit but are input to different voltage measurement circuits. The second embodiment shown in FIG. 9 is different from the first embodiment shown in FIG. 1A only in the disconnection detection resistance, and the other configuration is the same as that of the first embodiment shown in FIG. Therefore, the same reference numerals are given to the same components, and redundant description is omitted.

  In FIG. 9, the disconnection detection resistor Ra11 is connected between the input terminals ti + 1 and ti-1, and the disconnection detection resistor Ra12 is connected between the input terminals ti and ti-3.

When the cell voltage measuring device 2 has a circuit configuration as shown in FIG. 1A of the first embodiment, if li is broken as shown in the connection diagram 6A, the equations (5) and (6) ), And when the connection line i i + 1 is disconnected as shown in FIG.
Vi + 1 ≈ 0 (13)
Vi + 2≈ei + 1 + ei + 2 (14)
The voltage expressed by is output.

When the power generation of the fuel cell stack 1 is in a transitional state and the voltage variation between cells or cell groups is large, there is a possibility of misdiagnosis when disconnection is determined under the condition shown by the equation (7) or (8). . Therefore, an input terminal whose output voltage does not significantly differ from that when the connection lines li and li + 1 are disconnected is connected to an input terminal separated by two or more and a disconnection detection resistor as shown in FIG. Connecting. As shown in FIG. 10, when the connection line li is disconnected, the input terminal ti becomes substantially equipotential with the cell terminal pi-3 via the disconnection detection resistor Ra12.
Vi ≒-(ei-1 + ei-2) Equation (15)
Vi + 1≈ei-2 + ei-1 + ei + ei + 1 Equation (16)
The voltage expressed by can be output.

As shown in FIG. 11, when the connection line li-1 is disconnected, the input terminal ti-1 becomes substantially equipotential with the cell terminal pi + 1 through the disconnection detection resistor Ra11, so that Vi-1≈ei-1 + Ei + ei + 1 Equation (17)
Vi≈−ei + 1 Equation (18)
The voltage expressed by can be output.

Further, as shown in FIG. 12, when the connection line l i + 1 is disconnected, the input terminal t i + 1 becomes almost equipotential with the cell terminal p i-1 through the disconnection detection resistor Ra11. (19)
Vi + 2≈ei + ei + 1 + ei + 2 Equation (20)
The voltage expressed by can be output.

here,
Vi + 1> Vave × k0 Formula (21)
When k0 is a value satisfying 2 <k0 <3 (22), it is determined that the connection line li is disconnected.

Also,
Vi + 2> Vave × k0 Formula (23)
When it is, it is determined that the connection line l i + 1 is disconnected.

Also,
Vi-1> Vave × k0 Formula (24)
If it is, it is determined that the connection line li-1 is disconnected.

  According to the present embodiment described above, when the connection line is disconnected, an abnormal value more than twice the average cell voltage or the average cell group voltage can be detected. Even when there is a large variation in cell voltage in a transient state, there is an effect that disconnection of connection lines or contact failure can be easily detected.

  Next, a third embodiment of the cell voltage detecting apparatus according to the present invention will be described with reference to FIGS. The third embodiment is an embodiment in which a plurality of voltage measurement circuits constituting the cell voltage measurement device are divided into a plurality (two in the third embodiment) of circuit modules.

  FIG. 13 is a schematic configuration diagram illustrating the configuration of the third embodiment. FIG. 14A is a detailed circuit diagram of the voltage measurement circuit DBi in the circuit module 5, and FIG. 14B is a voltage measurement circuit DAi in the circuit module 4. FIG.

  The cell voltage measuring device 2 in the present embodiment includes a plurality of input terminals ti (i = 0 to ns), a circuit module 4, a circuit module 5, and a diagnostic device 3. The circuit module 4 includes a + VA power source, a -VA power source, a DC / DC converter DCA that supplies a reference potential GND-A, and a voltage measurement circuit DAi. The circuit module 5 includes a + VB power supply, a -VB power supply, a DC / DC converter DCB that supplies a reference potential GND-B, and a voltage measurement circuit DBn. Other symbols are the same as those shown in the first embodiment, and are omitted.

  The circuit module 4 outputs the voltage value ei of the fuel cell input from the input terminal ti to the diagnostic circuit 3 as an output voltage value Vi with respect to the reference potential GND-A by the voltage measurement circuit DAi which is a differential amplifier. Each voltage measurement circuit DAi includes an operational amplifier OPi and a resistor Rij, as shown in FIG.

  Similarly, the circuit module 5 supplies the voltage value en of the fuel cell input from the input terminal tn to the diagnostic circuit 3 as an output voltage value Vn with respect to the reference potential GND-B by the voltage measurement circuit DBn which is a differential amplifier. Output. Each voltage measurement circuit DBi includes an operational amplifier OPi and a resistor Rij, as shown in FIG.

  As in the first embodiment, the voltage measurement circuits DAi and DBi determine the resistance value of the resistor Rij so that the output voltage value Vi is equal to the difference between the two input voltages.

  A positive power source + VA, a negative power source -VA, and a reference potential GND-A are supplied from the DC / DC converter DCA to the operational amplifier OPi constituting the voltage measuring circuit DAi included in the circuit module 4. A positive power source + VB, a negative power source -VB, and a reference potential GND-B are supplied from the DC / DC converter DCB to the operational amplifier OPi constituting the voltage measuring circuit DBi included in the circuit module 5.

  In FIG. 13, the input terminal tn having the lowest potential of the circuit module 5 and the input terminal tn-1 having the highest potential of the circuit module 4 are connected via a disconnection detection resistor Ra20.

  Here, since the disconnection detection method is the same as the method shown in the first embodiment, a description thereof will be omitted.

  Next, the reference potential and power supply voltage in this embodiment will be considered. The reference potential GND-A is different from the reference potential GND-B, and the reference potential GND-B is set higher than the reference potential GND-A in the polarity of the cell ci of the fuel cell stack 1 shown in FIG. .

  In the circuit module 4, if the plus power source + VA is about several [V] higher than the GND-A potential + e (ni), which is the maximum input voltage of the circuit module 4, the circuit module 4. The operational amplifiers OPi (i = 1 to ns) included in FIG. Similarly, the negative power source −VA is an operational amplifier included in the circuit module 4 if it is about several [V] lower than the potential −e × i of GND−A, which is the minimum input voltage of the circuit module 4. OPi (i = 1 to ns) is sufficiently operable.

  Similarly, in the circuit module 5, the positive power supply + VB is a number [with respect to the voltage of GND−B potential + e × (number of cells higher than GND-B), which is the maximum input voltage of the circuit module 5. If it is as high as V], the operational amplifier OPi (i = 1 to ns) included in the circuit module 5 is sufficiently operable. Similarly, the negative power supply −VB is a few [vs] with respect to the voltage of GND−B potential −e × (the cell from the GND−B cell to the cell cn + 1), which is the minimum input voltage of the circuit module 5. If V] is low, the operational amplifier OPi (i = 1 to ns) included in the circuit module 4 can operate sufficiently.

  From the above description regarding the positive and negative power supplies, + VA, -VA, + VB, and -VB, the power supplied to the individual operational amplifiers when divided into circuit modules as in the present embodiment, compared to when not divided. The absolute value of the voltage may be low. As the number of divisions increases, the effect of lowering the power supply voltage increases, and the cell voltage measuring device can be configured without using an operational amplifier having a higher withstand voltage than necessary.

  Further, according to this embodiment, when the cell voltage measuring device is composed of a plurality of circuit modules having individual power sources and reference potentials, disconnection or poor contact of connection lines input to both adjacent circuit modules can be simplified. It is possible to easily detect by a simple circuit configuration.

(A) The figure which shows the cell voltage measurement apparatus of Example 1, (b) The circuit diagram which shows the detail of the voltage measurement circuit in Example 1. FIG. It is a figure which shows that the connection lines lk and lm in Example 1 were disconnected. 5A is a diagram showing voltage outputs Vk and Vk + 1 at normal time in Example 1, and FIG. 5B is a diagram showing voltage outputs Vk and Vk + 1 at time of disconnection of connection line lk in Example 1. FIG. (A) The figure which shows voltage output Vm and Vm + 1 at the time of normal in Example 1, (b) The figure which shows voltage output Vm and Vm + 1 at the time of disconnection of the connection line lm in Example 1. (A) A diagram showing a cell voltage measuring device without a disconnection detection resistor of a comparative example, (b) a diagram showing voltage outputs Vi and Vi + 1 at normal time, (c) a voltage output Vi at disconnection of the connection line li And Vi + 1. (A) A diagram showing that the connection line li is broken in the first embodiment, (b) a diagram showing voltage outputs Vi and Vi + 1 when the connection line li is normal in the first embodiment, and (c) a voltage output when the connection line li is broken. It is a figure which shows Vi and Vi + 1. It is a figure which shows that connection line li + 1 was disconnected in Example 1. FIG. It is a figure which shows the circuit which connected two disconnection detection resistance to one input terminal. It is a figure which shows the cell voltage measuring apparatus of Example 2. FIG. It is a figure which shows that the connection line li in Example 2 was disconnected. It is a figure which shows that the connection line li-1 was disconnected in Example 2. FIG. It is a figure which shows that the connection line li + 1 was disconnected in Example 2. FIG. FIG. 6 is a diagram illustrating a cell voltage measurement device according to a third embodiment. (A) The figure which shows the voltage measurement circuit in the circuit module 5 of Example 3, (b) It is the figure which shows the voltage measurement circuit in the circuit module 4 of Example 3.

Explanation of symbols

1: Fuel cell stack 2: Cell voltage measuring device 3: Diagnostic device li (i = 0 to ns): Connection line ti (i = 0 to ns): Input terminal Di (i = 1 to ns): Voltage measuring circuit Ra10 : Disconnection detection resistor

Claims (5)

In the cell voltage measuring device for measuring the cell voltage of the assembled battery configured by connecting a plurality of cells in series,
A plurality of input terminals to which voltages for each cell group or a cell group in which a plurality of cells are connected in series are input;
A plurality of voltage measuring circuits for measuring a voltage between the input terminals;
Based on the voltage value measured by the voltage measurement circuit, a diagnostic device that determines whether the battery pack is connected to the input terminal and whether each cell or each cell group is good,
Including at least one disconnection detection resistor connecting between the input terminals including the disconnection detection resistor connecting between the input terminal serving as the ground potential of the cell voltage measuring device and the other input terminals ,
The diagnostic device calculates an average value of all measured voltage values or an average value of a part of measured voltage values input to the diagnostic device,
When one of measured voltage values of two adjacent cells or cell groups output from the voltage measuring circuit is larger than a value obtained by multiplying the average value by a predetermined coefficient, diagnosis of disconnection of a connection line or poor contact is made. A cell voltage measuring device.   The cell voltage measuring device according to claim 1, wherein the predetermined coefficient is set to a value equal to or greater than a value obtained by dividing a maximum cell voltage in the assembled battery by an average cell voltage. The cell voltage measuring device according to claim 1 or 2 , wherein both ends of the disconnection detecting resistor are connected to different voltage measuring circuits. The plurality of voltage measurement circuits are divided into a plurality of circuit modules each having an individual power source and a reference potential,
Each of the circuit modules measures voltages of different groups of cells connected in series in the assembled battery,
The input terminal to which the connection line drawn from the boundary between the different cell groups is connected is connected to the input terminal having the highest potential of the first circuit module and the input terminal having the lowest potential of the second circuit module,
An input terminal most potential high input or lowest potential of the circuit module, one of claims 1 to 3, characterized in that it has a disconnection detection resistor connected between the input terminals of different circuit modules 1 The cell voltage measuring device according to item. A fuel cell comprising the cell voltage measuring device according to any one of claims 1 to 4 .

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