JP2006228472A - Cooling system of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling system for a fuel cell with insulation resistance from a fuel cell stack secured and degradation of power generating efficiency prevented, even in case conductivity of the cooling liquid has risen. <P>SOLUTION: The system is provided with a fuel cell stack 2, a cooling liquid circulating piping 3 circulating cooling liquid (a) connected to the fuel cell stack 2, a heat exchanging means (a radiator 4) installed at the cooling liquid circulating piping 3, a first cooling liquid bypass piping 6 branched from the cooling liquid circulating piping 3 at downstream of the fuel cell stack 2 and connected to downstream of the heat exchanging means (the radiator 4) of a radius smaller than that of the cooling liquid circulating piping 3, an insulating valve 7 installed at the cooling liquid circulating piping 3 at downstream of the fuel cell stack 2, a charge releasing means (a ground 8) connected to the first cooling liquid bypass piping 6, and an ion removal means (an ion filter 9) installed at the first cooling liquid bypass piping 6. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell cooling system for cooling a fuel cell.

  A fuel cell is a device that generates electricity by reacting hydrogen gas and oxygen gas using hydrogen gas as fuel. Since a fuel cell generates heat with power generation, a cooling system for cooling the fuel cell is installed.

  The cooling system basically includes a coolant circulation pipe connected to the fuel cell stack and heat exchange means (for example, a radiator) installed in the coolant circulation pipe. In the cooling system, the coolant (for example, coolant) drained from the fuel cell stack circulates in the coolant circulation pipe, dissipates the heat in the coolant by the heat exchange means, and then recools the cooled coolant. It is introduced into the battery stack, and the temperature of the fuel cell stack is maintained at a specified operating temperature.

  As the coolant (cooling water) circulates in the coolant circulation pipe, it contains metal ions that dissolve from the metal parts of the fuel cell stack and the heat exchange means, so the conductivity of the coolant tends to increase. When the conductivity of the coolant increases, the potential decreases from the positive electrode of the fuel cell to the negative electrode of the fuel cell via the coolant circulation pipe, and as a result, the power generation efficiency of the fuel cell decreases.

  Therefore, a conventional cooling system is provided with a fuel cell and a fuel cell storage case that retains or insulates the fuel cell, and connects the fuel cell and the heat exchanging means through the wall of the fuel cell storage case. A liquid circulation pipe is formed. And a heat exchange means is installed in this coolant circulation pipe, and a pair of penetration parts which a coolant circulation pipe penetrates a fuel cell storage case are connected to the ground of a control device of a fuel cell (refer to patent documents 1). ). According to the present technology, a predetermined distance is secured from the fuel cell stack via the coolant circulation pipe, and then dropped to the ground to ensure insulation resistance.

In another conventional cooling system, resin insulation valves are installed in the coolant circulation pipes upstream and downstream of the fuel cell stack, and a bypass pipe that bypasses the heat exchange means is branched into the coolant circulation pipe. And connected (see Patent Document 2). According to the present technology, since the cooling water circulates in the bypass pipe by installing the insulation valve, the electricity flowing from the fuel cell stack is cut off to ensure the insulation resistance.
JP 2002-280039 A JP 2003-168462 A

  However, when the operation is resumed after the fuel cell operation has been stopped for a long period of time, a large amount of metal ions are dissolved in the coolant from the fuel cell stack, and the conductivity of the coolant is temporarily changed only when the fuel cell is started. The phenomenon of becoming higher was occurring.

If the coolant circulation pipe has a large diameter and the coolant circulation pipe distance from the fuel cell stack to the ground is short, the flow rate of the coolant circulating through the coolant circulation pipe increases.
When the conductivity of the cooling water increases, it is difficult to ensure insulation resistance. However, in the cooling system described in Patent Document 1, a pair of penetrations through which the coolant circulation pipe penetrates the fuel cell storage case is set as the ground position, and the length of the coolant circulation pipe is substantially the same as the inside of the fuel cell stack. The distance of the coolant circulation pipe from the fuel cell stack to the ground was short. For this reason, the potential of the fuel cell stack and the ground is lowered, insulation resistance cannot be ensured, and the power generation efficiency of the fuel cell is reduced.

  Further, in the cooling system described in Patent Document 2, the insulation valve is closed only when the fuel cell is stopped, and the coolant is circulated in the fuel cell stack through a bypass pipe that bypasses the heat exchange means to cut off electricity. It was. For this reason, during the start of the fuel cell, since electricity flows in the coolant circulation pipe, it is necessary to take measures such as installing an insulating cover separately. In addition, even if the insulation valve is closed and the electricity is cut off, there is a risk of electric shock when the vehicle is stopped and in an idling state, and there is a problem that it is difficult to inspect the car. .

  The present invention has been made to solve the above-described problems. That is, the fuel cell cooling system of the present invention has a fuel cell stack and a coolant circulation pipe that circulates a coolant connected to the fuel cell stack. And a diameter smaller than the diameter of the coolant circulation pipe connected to and branched from the coolant circulation pipe downstream of the fuel cell stack and connected to the downstream of the heat exchange means. The first coolant bypass pipe, the insulation valve installed in the coolant circulation pipe downstream of the fuel cell stack, the charge discharge means connected to the first coolant bypass pipe, and the first coolant bypass And an ion removing means installed in the pipe.

  According to the present invention, there is provided a fuel cell cooling system that can secure an insulation resistance from a fuel cell stack and prevent a decrease in power generation efficiency even when the conductivity of the coolant increases.

  Hereinafter, a fuel cell cooling system according to an embodiment of the present invention will be described with reference to the accompanying drawings.

First Embodiment FIG. 1 shows a basic configuration of a fuel cell cooling system 1 according to an embodiment of the present invention. In the fuel cell cooling system 1, a coolant circulation pipe 3 that circulates a coolant a as a coolant is connected to a fuel cell stack 2, and a radiator 4 that is a heat exchange means, a pump 5, and the like are connected to the coolant circulation pipe 3. Are sequentially installed. A first coolant bypass pipe 6 is branched and connected to the coolant circulation pipe 3 from the coolant circulation pipe 3 downstream of the fuel cell stack 2, and the coolant bypass pipe 6 is connected to the coolant circulation pipe downstream of the radiator 4. 3 is connected. The coolant bypass pipe 6 is formed from a pipe having a smaller diameter than the coolant circulation pipe 3. An insulating valve 7 is installed in the cooling water circulation pipe 3 downstream of the junction of the cooling liquid circulation pipe 3 and the cooling liquid bypass pipe 6. Are sequentially installed. Further, a ground 10 which is a charge discharging means is also installed in the coolant circulation pipe 3 upstream of the fuel cell stack 2.

  In the fuel cell cooling system 1, when the fuel cell is started after being left for a long period of time, the insulating valve 7 is closed and the cooling water a is circulated to the fuel cell stack 2 via the coolant bypass pipe 6. Note that when the fuel cell is started, it is not necessary to cool the cooling water a by the radiator 4 because the amount of heat generated by the fuel cell stack is small. Since the coolant bypass pipe 6 has a smaller diameter than the coolant circulation pipe 3, the flow rate of the coolant water a circulating through the coolant bypass pipe 3 is small. For this reason, even if the distance from the fuel cell stack 2 to the ground 8 is short, the insulation resistance value can be maintained at a high value. Electric charges are released by the ground 8 and ions in the cooling water a are removed by the ion filter 9, so that the temperature of the fuel cell stack 2 rises and the conductivity of the cooling water a can be lowered before normal operation is performed. it can.

  During normal operation of the fuel cell, the insulating valve 7 is opened, the coolant a is circulated through the coolant circulation pipe 3 to the radiator 4 and the pump 5, the electric charge is discharged by the ground 10, and the inside of the fuel cell stack 2. The cooling water a is introduced into the fuel cell stack 2 to cool the fuel cell stack 2. Then, the coolant bypass pipe 6 branched from the coolant circulation pipe 3 is connected with coolant water a having a small flow rate. The ions in the coolant water a are removed by the ion filter 9, and the coolant The conductivity of a is a low value.

  According to the embodiment of the present invention, when the fuel cell is started, the coolant a is circulated through the coolant bypass pipe 6 to reduce the conductivity of the coolant a, and then the coolant is supplied to the coolant circulation pipe 3. Since a is circulated, the insulation resistance from the fuel cell stack 2 to the earth 10 can be provided without providing an insulating cover even when the coolant a is passed through the coolant circulation pipe 3 during operation of the fuel cell. Can be secured.

  Further, according to the embodiment of the present invention, when the cooling water a passes through the ion filter 9, the conductivity of the cooling water a decreases. Therefore, the coolant circulation pipe 3 on the upstream side of the fuel cell stack 2 is provided with a large diameter pipe. Even in this case, the insulation resistance value can be lowered.

Second Embodiment FIG. 2 shows the configuration of a fuel cell cooling system according to an embodiment of the present invention. In addition, the same code | symbol is used for the structure same as the cooling system 1 of the fuel cell shown in FIG. 1, and the description is abbreviate | omitted. The fuel cell cooling system 11 includes a conductivity sensor 12 installed in the coolant circulation pipe 3 upstream of the junction of the coolant circulation pipe 3 and the coolant bypass pipe 6, and a control device 13. Then, the second coolant bypass pipe 14 is connected from the coolant circulation pipe 3 downstream of the pump 5, and the ground 15 that is a charge discharging means is installed in the coolant bypass pipe 14. An insulating valve 16 is installed in the coolant circulation pipe 3 upstream of the junction of the coolant bypass pipe 14 and the coolant circulation pipe 3.

  The control device 13 transmits a control signal for opening the insulation valves 7 and 16 when the conductivity of the cooling water a measured from the conductivity sensor 12 is lower than a specified value, and the cooling measured from the conductivity sensor 12. When the conductivity of the water a is higher than the specified value, a control signal for closing the insulating valves 7 and 16 is transmitted to control the flow of the cooling water a. Here, the specified value means the conductivity of the cooling water a that can ensure insulation resistance. Moreover, when the exchange efficiency of the ion filter 9 can be predicted, the purification time of the conductivity of the cooling water a can also be predicted in advance. For this reason, a predetermined time required for purification may be set in advance in the control device 13, and a control signal for controlling opening and closing of the insulating valve 7 may be transmitted when the predetermined time is reached.

  In the fuel cell cooling system 11, the conductivity of the cooling water a drained from the fuel cell stack 2 is measured by the conductivity sensor 12 when the fuel cell is started. The cooling water a at the start contains various metal ions, and it is determined that the conductivity of the cooling water a is higher than a specified value, and the control device 13 controls the insulating valves 7 and 16. A signal is transmitted. The insulating valves 7 and 16 are closed, and the cooling water a circulates through the coolant bypass pipe 6, charges are released by the ground 8, and ions are removed by the ion filter 9. Thereafter, the electric charge is released by the ground 15 via the coolant bypass pipe 14, and then the coolant a is introduced into the fuel cell stack 2. Further, when the conductivity of the coolant a drained from the fuel cell stack 2 is measured by the conductivity sensor 12, and it is determined that the conductivity of the coolant a is higher than a specified value, the insulation valves 7, 16 remains closed, and the cooling water a passes through the ion filter 9 and is introduced into the fuel cell stack 2.

  Thereafter, when the temperature of the fuel cell stack 2 rises and the conductivity of the coolant a discharged from the fuel cell stack 2 becomes lower than a specified value, the control device 13 controls the insulation valves 7 and 16. A signal is transmitted, both the insulation valves 7 and 16 are opened, the cooling water a circulates in the cooling water circulation pipe 3, and the cooling water a cools the fuel cell stack 2.

  In the fuel cell cooling system 11, when the elution amount of ions in the cooling water a is large and the ion filter 9 has a small capacity and low ion exchange efficiency, the cooling water a is supplied to the ion filter 9 only once. Only by passing water, ions in the cooling water a cannot be removed, and the conductivity of the cooling water a cannot be lowered. For this reason, in this embodiment, the cooling water a can be passed through the ion filter 9 a plurality of times to reduce the conductivity of the cooling water a, and further, the insulation resistance from the fuel cell stack 2 to the ground 16 is ensured. be able to.

  Further, in the present embodiment, since the conductivity sensor 12 is installed and the conductivity of the cooling water a is measured, the conductivity of the cooling water a is surely lowered, and then the coolant circulation pipe 3 is provided. Since the cooling water a is passed, the insulation resistance can be surely ensured.

3rd Embodiment The structure of the cooling system 17 of the fuel cell which concerns on other embodiment in this invention is shown in FIG. The same components as those of the fuel cell cooling systems 1 and 11 shown in FIGS. 1 and 2 are denoted by the same reference numerals, and the description thereof is omitted. In the fuel cell cooling system 17 according to the present embodiment, the ion filter 9 is not installed in the cooling water bypass pipe 6. Insulating covers are provided in a region from the upstream side of the insulating valve 7 to the downstream side of the insulating valve 16 in the coolant circulation pipe 3 and a region from the downstream side of the ground 8 of the coolant bypass pipe to the upstream side of the ground 15 of the coolant bypass pipe 14. 18 is covered.

  In this fuel cell cooling system 17, the ion filter 9 is not installed, so the conductivity of the cooling water a is always high.

  When starting the fuel cell with a small amount of heat generated in the fuel cell stack 2, the insulating valve 7 is closed and the cooling water a is circulated through the cooling water bypass pipe 6. At this time, the insulating valve 7 is closed, and electricity does not flow to the radiator 4 side. In addition, since electricity is in a grounded state, safety can be ensured even if it contacts the cooling water a in the coolant bypass pipe 6 by any chance.

  Thereafter, when the heat generation amount of the fuel cell stack 2 increases, the insulating valve 7 is opened, and the cooling water a is circulated through the coolant circulation pipe 3. At this time, the coolant a having a high conductivity flows through the coolant circulation pipe 3, but since the insulating cover 18 is provided, the insulation can be ensured.

  According to the present embodiment, since the insulation resistance can be secured even when the fuel cell is activated and stopped due to idling, vehicle inspection can be performed while the fuel cell is activated. Moreover, according to this Embodiment, since the insulation cover is coat | covered, safety | security can be ensured also during driving | running | working of a vehicle.

  In the first to third embodiments, pure water has been described as an example of the cooling liquid. However, it is of course possible to use a cooling liquid such as ethylene glycol or oil instead of pure water. .

Fourth Embodiment In the present embodiment, the pipe diameter of the coolant bypass pipe installed in the fuel cell cooling system shown in the first to third embodiments, and the length of the pipe from the fuel cell stack to the ground. (Hereinafter referred to as “pipe length”), the relationship between the conductivity and the insulation resistance value of the cooling water was examined.

  First, FIG. 4 shows a graph comparing the relationship between the pipe diameter of the coolant bypass pipe, the conductivity of the cooling water, and the insulation resistance value when the pipe length is 200 mm. As shown in FIG. 4, when the pipe length is the same as 200 mm, the insulation resistance value increases as the diameter of the coolant bypass pipe decreases. It is preferable to secure an insulation resistance value of at least about 50 kΩ or more. For this reason, as shown in FIG. 4, when tap water having a conductivity of about 100 μS / cm is used as the cooling water, the diameter of the coolant bypass pipe is preferably at least 25 mm, more preferably 15 mm or less. It is preferable to do. The electric conductivity of tap water is about 100 μS / cm, and when the tap water is purified by passing the tap water through the ion filter 9, the electric conductivity can be lowered to about 1 μS / cm.

  Next, FIG. 5 shows a graph comparing the relationship between the pipe length, the conductivity of the cooling water, and the insulation resistance value when the pipe diameter of the coolant bypass pipe is 15 mm. As shown in Fig. 5, when the pipe diameter of the coolant bypass pipe is reduced to 15 mm or less, the pipe length is shortened to 100 mm and the conductivity of the cooling water a rises to the level of tap water (approximately 100 μS / cm). Even so, an insulation resistance value of about 50 kΩ can be secured.

  Therefore, even if the distance from the fuel cell stack to the ground is short, such as when configuring within the fuel cell stack for convenience of layout, the pipe diameter of the coolant bypass pipe should be 15 mm or less. The specified insulation resistance value can be ensured. As a result, the fuel cell cooling system can be reduced in size and space can be reduced.

It is a figure which shows the basic composition of the cooling system of the fuel cell which concerns on 1st Embodiment in this invention. It is a figure which shows the structure of the cooling system of the fuel cell which concerns on 2nd Embodiment in this invention. It is a figure which shows the structure of the cooling system of the fuel cell which concerns on 3rd Embodiment in this invention. 5 is a graph comparing the relationship between the pipe diameter of the coolant bypass pipe, the conductivity of the cooling water, and the insulation resistance value when the pipe length is 200 mm. 6 is a graph comparing the relationship between the pipe length, the conductivity of the cooling water, and the insulation resistance value when the pipe diameter of the coolant bypass pipe is 15 mm.

Explanation of symbols

1 ... Fuel cell cooling system,
2 ... Fuel cell stack,
3 ... Cooling liquid circulation piping,
4. Radiator (heat exchange means),
5 ... pump,
6 ... 1st coolant bypass piping,
7… Insulation valve,
8, 10 ... Earth (charge discharging means),
9 ... Ion filter (ion removing means),
a… cooling water,

Claims (6)

A fuel cell stack;
A coolant circulation pipe for circulating the coolant connected to the fuel cell stack;
Heat exchange means installed in the coolant circulation pipe;
A first coolant bypass pipe branched from the coolant circulation pipe downstream of the fuel cell stack and connected downstream of the heat exchanging means and having a diameter smaller than the diameter of the coolant circulation pipe;
An insulation valve installed in the coolant circulation pipe downstream of the fuel cell stack;
Charge discharge means connected to the first coolant bypass pipe;
And a means for removing ions installed in the first coolant bypass pipe. A fuel cell stack;
A coolant circulation pipe for circulating the coolant connected to the fuel cell stack;
Heat exchange means installed in the coolant circulation pipe;
A first coolant bypass pipe branched from the coolant circulation pipe downstream of the fuel cell stack and connected downstream of the heat exchanging means and having a diameter smaller than the diameter of the coolant circulation pipe;
An insulation valve installed in the coolant circulation pipe downstream of the fuel cell stack;
Charge discharge means connected to the first coolant bypass pipe;
A fuel cell cooling system comprising: an insulating cover that covers an area excluding a junction of the coolant circulation pipe and the coolant bypass pipe from the fuel cell stack. Further, the coolant circulation pipe is branched and connected downstream from the junction of the coolant circulation pipe and the first coolant bypass pipe on the downstream side of the radiator, and is connected to the coolant circulation pipe upstream of the fuel cell stack. A connected second coolant bypass pipe;
An insulation valve installed on the coolant circulation pipe upstream of the confluence of the coolant circulation pipe and the second coolant bypass pipe;
Charge discharging means connected to the second coolant bypass pipe;
The fuel cell cooling system according to claim 1, wherein: Furthermore, a conductivity sensor installed upstream of the junction of the coolant circulation pipe and the coolant bypass pipe;
When the conductivity of the coolant measured from the conductivity sensor is lower than a specified value, a control signal for opening the insulating valve is transmitted, and the conductivity of the coolant measured from the conductivity sensor is lower than the specified value. A control device for transmitting a control signal for closing the insulation valve when
The fuel cell cooling system according to claim 1, wherein:   5. The fuel cell cooling system according to claim 1, wherein a diameter of each of the first coolant bypass pipe and the second coolant bypass pipe is 15 mm or less.   6. The fuel cell cooling system according to claim 1, wherein the coolant is coolant.

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