JP2006147342A - Fuel cell cooling system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correctly calculate a utilization rate of an ion exchange resin with a simple system constitution. <P>SOLUTION: A controller 10 switches a flow passage of cooling water to be branched into a bypass flow passage 6 before passing through an ion filter 4 and that after passing through the ion filter, measures the conductivity of the cooling water before passing through the ion filter 4 and that of the cooling water after passing through the ion filter 4, calculates a reduction rate of the conductivity depending on a result of the measurement, and calculates the utilization rate of the ion exchange resin depending on the result of above calculation. By the above, the utilization rate of the ion exchange resin can be correctly calculated with a simple system constitution. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell cooling system including an ion filter that removes ions eluted from a fuel cell system into cooling water.

In general, a fuel cell cooling system that cools a fuel cell by supplying cooling water to the fuel cell is known, and in such a system, cooling is performed from the system in order to prevent liquid junction reduction through the cooling water. The electrical insulation of the cooling water is maintained by adsorbing ions eluted in the water to the ion exchange resin inside the ion filter. By the way, the ion exchange resin inside the ion filter usually gradually loses the ion adsorption ability as it adsorbs ions eluted in the cooling water. Against this background, in conventional fuel cell cooling systems, a conductivity meter that measures the conductivity of the cooling water is provided in the cooling water flow path, and the usage rate of the ion exchange resin is calculated according to the decreasing rate of the cooling water conductivity. Alternatively, a conductivity meter is provided before and after the ion filter, and the usage rate of the ion exchange resin is calculated according to the change in the conductivity of the cooling water before and after passing through the ion filter (see, for example, Patent Document 1).
JP 2003-346845 A

  However, in general, the amount of ions eluted from the fuel cell system into the cooling water varies depending on various temperatures such as the temperature of parts constituting the system, the conductivity of the cooling water when contacting the parts, the cooling water temperature, and the cooling water flow rate. Depending on the factors, when the operating state of the system such as startup is in an unsteady state, the rate of decrease in the conductivity of the cooling water also becomes unsteady. Therefore, when the usage rate of the ion exchange resin is calculated according to the decreasing rate of the conductivity of the cooling water, the usage rate of the ion exchange resin cannot be calculated accurately. In addition, when a conductivity meter is provided before and after the ion filter and the usage rate of the ion exchange resin is calculated according to the change in conductivity of the cooling water before and after passing through the ion filter, it is necessary to provide a conductivity meter before and after the ion filter. This complicates the system configuration.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a fuel cell cooling system capable of accurately calculating the usage rate of an ion exchange resin with a simple system configuration. It is in.

  In order to solve the above-described problems, a fuel cell cooling system according to the present invention has a cooling water circulation passage for circulating cooling water in a fuel cell, an ion exchange resin inside, and the ion exchange resin in the cooling water. An ion filter for removing ions contained therein, provided on the upstream side of the ion filter, provided on the downstream side of the ion filter, an upstream bypass channel for diverting the cooling water before passing through the ion filter from the cooling water circulation channel, A downstream bypass channel that diverts the cooling water after passing through the ion filter from the cooling water circulation channel, a bypass channel that returns the cooling water divided from the cooling water circulation channel to the cooling water circulation channel, and a cooling that flows through the bypass channel A switching valve for switching water between the cooling water divided by the upstream bypass flow path and the cooling water divided by the downstream bypass flow path, and a bypass flow path And a bypass flow path between the cooling water before passing through the ion filter and the cooling water after passing through the ion filter by controlling the switching valve by measuring the conductivity of the cooling water flowing through the bypass flow path A controller that alternately switches the cooling water to be flown to the battery and compares the conductivity of the cooling water before and after passing through the ion filter using a conductivity meter.

  According to the fuel cell cooling system of the present invention, the cooling water to be diverted into the bypass flow path is alternately switched between the cooling water before passing through the ion filter and the cooling water after passing through the ion filter, and the cooling flowing through the bypass flow path is performed. Since the conductivity of the cooling water before and after passing through the ion filter is measured by measuring the water conductivity, the usage rate of the ion exchange resin can be accurately calculated with a simple system configuration.

  Hereinafter, the configuration and operation of the fuel cell cooling system according to the first and second embodiments of the present invention will be described with reference to the drawings.

  First, the configuration of the fuel cell cooling system according to the first embodiment of the present invention will be described.

[Configuration of fuel cell cooling system]
The fuel cell cooling system according to the first embodiment of the present invention is mounted on a vehicle and, as shown in FIG. 1, a fuel cell in which a plurality of fuel cells that generate power upon receipt of fuel gas and oxidant gas are stacked. A cooling water circulation channel 2 for circulating cooling water for cooling the stack 1, a cooling water pump 3 for pumping the cooling water to the fuel cell stack 1, and ions contained in the cooling water in the cooling water circulation channel 2 are removed. An ion filter 4 that performs cooling and a radiator 5 that cools the cooling water in the cooling water circulation passage 2 are provided as main components. Further, this fuel cell cooling system includes bypass flow paths 7a and 7b for diverting the cooling water before and after passing through the ion filter 4 to the upstream side of the cooling water pump 3 via the bypass flow path 6, and the bypass flow. Valves 8a and 8b for adjusting the flow rate of the cooling water diverted from the paths 7a and 7b to the bypass flow path 6, and a conductivity meter 9 for measuring the conductivity of the cooling water flowing in the cooling water flow path 6 are provided. Prepare. Although details will be described later, the bypass channels 6, 7a, 7b are for measuring the conductivity of the cooling water before and after passing through the ion filter 4, and therefore, the bypass channels 6, 7a, 7b. It is assumed that cooling water with a small flow rate that does not affect the pressure loss of the system flows. In the fuel cell cooling system having such a configuration, the controller 10 accurately calculates the usage rate of the ion exchange resin inside the ion filter 4 by executing the usage rate calculation process shown below. Hereinafter, with reference to the flowchart shown in FIG. 2, the operation of the controller 10 when executing the usage rate calculation process will be described.

[Usage calculation processing]
The flowchart shown in FIG. 2 starts when the fuel cell stack 1 is activated, and the usage rate calculation process proceeds to the process of step S1. Note that this usage rate calculation process is repeatedly executed every predetermined control period.

  In the process of step S1, the controller 10 controls the valves 8a and 8b to be in an open state and a closed state, respectively, so that a part of the cooling water before passing through the ion filter 4 is on the bypass flow path 7a and bypass flow path 6 side. To divert. Thereby, the process of step S1 is completed, and the calculation process proceeds to the process of step S2.

  In the process of step S2, the controller 10 measures the conductivity of the cooling water before passing through the ion filter 4 for a predetermined time such as several seconds by the conductivity meter 9, and calculates the average value C1 of the measured conductivity. Remember. Specifically, when the cooling water pump 3 circulates 20 [L] of cooling water at a flow rate of 120 [L / min] through the cooling water circulation passage 2, the controller 10 starts from time t <b> 1 shown in FIG. 3. Until t2 (in this case, about 3 [seconds]), the conductivity (conductivity In) of the cooling water before passing through the ion filter 4 is measured, and the average value C1 of the measured conductivity is calculated and stored. . Thereby, the process of step S2 is completed, and the calculation process proceeds to the process of step S3.

  In the process of step S3, the controller 10 estimates the flow rate of the cooling water flowing through the cooling water circulation passage 2 based on the rotation speed of the cooling water pump 3, and the cooling water passes through the ion filter 4 using the estimation result. The time required for this (ion filter passage time) is calculated. In the example shown in FIG. 3, it is assumed that the ion filter passage time is 4 [seconds]. Thereby, the process of step S3 is completed, and the calculation process proceeds to the process of step S4.

  In the process of step S4, the controller 10 determines whether or not the ion filter passage time calculated by the process of step S3 has elapsed since the start of measurement of the conductivity of the cooling water before passing the ion filter 4. And according to passage of ion filter passage time, controller 10 advances calculation processing to processing of Step S5.

  In the process of step S5, the controller 10 controls the valves 8a and 8b to be in a closed state and an open state, respectively, so that part of the cooling water after passing through the ion filter 4 is on the bypass flow path 7b and bypass flow path 6 side. To divert. Thereby, the process of step S5 is completed, and the calculation process proceeds to the process of step S6.

  In the process of step S6, the controller 10 measures the conductivity of the cooling water after passing through the ion filter 4 through the conductivity meter 9 for a predetermined time such as several seconds, and calculates the average value C2 of the measured conductivity. Calculate and store. Specifically, in the example illustrated in FIG. 3, the controller 10 performs the period from time t3 to time t4 when the ion filter passage time (4 [seconds]) has elapsed from time t1 (in this example, 3 [seconds]). Degree), the conductivity (conductivity out) of the cooling water after passing through the ion filter 4 is measured, and an average value C2 of the measured conductivity is calculated and stored. . Thereby, the process of step S6 is completed, and the calculation process proceeds to the process of step S7.

  In the process of step S7, the controller 10 calculates the reduction rate C2 / C1 of the conductivity of the cooling water using the average values C1 and C2 calculated by the processes of step S2 and step S6. In general, as shown in FIG. 4, the ion exchange resin has a characteristic that the decrease rate of the conductivity decreases as the usage rate (time) increases, so that the controller 10 is illustrated in FIG. 5. The ion exchange resin usage rate corresponding to the calculated reduction rate C2 / C1 is calculated with reference to a map in which the reduction rate decreases as the ion exchange resin usage rate increases. In the example shown in FIG. 3, the reduction rate is about 50 [%], so the controller 10 estimates the ion exchange resin usage rate to about 80 [%] with reference to the map shown in FIG. 5. Thereby, the process of step S7 is completed, and the calculation process proceeds to the process of step S8.

  In the process of step S8, the controller 10 determines whether or not the ion exchange resin usage rate calculated by the process of step S7 is a predetermined value (for example, 80%) or less. If the ion exchange resin usage rate is equal to or less than the predetermined value as a result of the determination, the controller 10 ends the series of calculation processes. On the other hand, when the ion exchange resin usage rate is not less than or equal to the predetermined value, the controller 10 instructs the user to replace the ion exchange resin as the process of step S9, and then the series of calculation processes ends.

  As is apparent from the above description, according to the fuel cell cooling system according to the first embodiment of the present invention, the controller 10 bypasses the cooling water before and after passing the ion filter 4. The cooling water to be diverted to 6 is switched, the conductivity of the cooling water before and after passing the ion filter 4 is measured using the conductivity meter 9, and the reduction rate of the conductivity is calculated based on the measurement result. Since the usage rate of the ion exchange resin is calculated based on this, the usage rate of the ion exchange resin can be accurately calculated with a simple system configuration.

  Next, the configuration of the fuel cell cooling system according to the second embodiment of the present invention will be described.

[Configuration of fuel cell cooling system]
As shown in FIG. 6, the fuel cell cooling system according to the second embodiment of the present invention includes cooling water in the cooling water circulation passage 2 in addition to the configuration of the fuel cell cooling system according to the first embodiment. A flow sensor 11 for detecting the flow rate is provided. And in the fuel cell cooling system which has such a structure, the controller 10 performs the usage rate calculation process shown below. Hereinafter, with reference to the flowchart shown in FIG. 7, the operation of the controller 10 when executing the usage rate calculation process will be described.

[Usage calculation processing]
The flowchart shown in FIG. 7 starts when the fuel cell stack 1 is activated, and the usage rate calculation process proceeds to the process of step S11. 7 are the same as the processes in steps S1, S2 and S5 to S9 shown in FIG. 2, and therefore the process in step S13 is executed below. Only the operation of the controller 10 at the time will be described.

  In the process of step S13, the controller 10 detects the flow rate of the cooling water flowing through the cooling water circulation channel 2 using the flow rate sensor 11, and the time required for the cooling water to pass through the ion filter 4 using the detection result. (Ion filter passage time) is calculated. Thereby, the process of step S13 is completed, and the calculation process proceeds to the process of step S14.

  As is clear from the above description, according to the fuel cell cooling system according to the second embodiment of the present invention, the controller 10 uses the flow sensor 11 to change the flow rate of the cooling water flowing through the cooling water circulation passage 2. Since the detection time is detected and the ion filter passage time is calculated, even when the pressure loss of the system fluctuates due to clogging of the ion filter 4 or the like, the cooling water flowing through the cooling water circulation passage 2 is detected. The flow rate can be accurately measured, and the ion filter passage time can be accurately calculated.

  As mentioned above, although the embodiment to which the invention made by the present inventor is applied has been described, the present invention is not limited by the description and the drawings that form part of the disclosure of the present invention according to this embodiment. That is, it should be added that other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the above embodiments are all included in the scope of the present invention.

It is a block diagram which shows the structure of the fuel cell cooling system used as the 1st Embodiment of this invention. It is a flowchart figure which shows the flow of the usage rate calculation process used as the 1st Embodiment of this invention. It is a figure which shows the mode of the change of the electrical conductivity of the cooling water before and behind the ion filter. It is a figure which shows the mode of the electrical conductivity change of the cooling water before and behind the ion filter accompanying the change of a usage rate. It is a map figure which shows the relationship between an ion exchange resin usage rate and a conductivity decreasing rate. It is a block diagram which shows the structure of the fuel cell cooling system used as the 2nd Embodiment of this invention. It is a flowchart figure which shows the flow of the usage rate calculation process used as the 2nd Embodiment of this invention.

Explanation of symbols

1: Fuel cell stack 2: Cooling water channel 3: Cooling water pump 4: Ion filter 5: Radiators 6, 7a, 7b: Bypass channels 8a, 8b: Valve 9: Conductivity meter 10: Controller 11: Flow sensor

Claims (4)

A coolant circulation path for circulating coolant in the fuel cell;
An ion filter having an ion exchange resin therein and removing ions contained in the cooling water by the ion exchange resin;
An upstream bypass channel that is provided upstream of the ion filter and diverts the cooling water before passing through the ion filter from the cooling water circulation channel;
A downstream bypass flow path that is provided on the downstream side of the ion filter and diverts the cooling water that has passed through the ion filter from the cooling water circulation flow path;
A bypass flow path for returning the cooling water diverted from the cooling water circulation flow path to the cooling water circulation flow path;
A switching valve that switches between cooling water flowing through the bypass flow path and cooling water branched by the upstream bypass flow path and cooling water branched from the downstream bypass flow path;
A conductivity meter that is provided in the bypass channel and measures the conductivity of the cooling water flowing in the bypass channel;
By controlling the switching valve, the cooling water flowing through the bypass channel is alternately switched between the cooling water before passing through the ion filter and the cooling water after passing through the ion filter, and the ion filter is used using the conductivity meter. A fuel cell cooling system comprising: a controller for comparing conductivity of cooling water before and after passing. The fuel cell cooling system according to claim 1,
The controller causes the cooling water before passing through the ion filter to flow through the bypass flow path, measures the conductivity of the cooling water before passing through the ion filter using the conductivity meter, and after the cooling water passes through the ion filter. Then, the cooling water after passing through the ion filter is allowed to flow through the bypass channel, and the conductivity of the cooling water after passing through the ion filter is measured using a conductivity meter, and the reduction rate of the conductivity before and after passing through the ion filter based on the measurement result And a usage rate of the ion exchange resin is calculated based on the calculated decrease rate. The fuel cell cooling system according to claim 2,
A circulation pump for circulating cooling water in the cooling water circulation channel is provided, and the controller estimates a flow rate of the cooling water in the cooling water circulation channel from an operation state of the circulation pump, and cools based on the estimation result. The time required for water to pass through the ion filter is calculated as the ion filter passage time. After passing the cooling water before passing the ion filter to the bypass flow path, A fuel cell cooling system, wherein cooling water is allowed to flow through the bypass channel. The fuel cell cooling system according to claim 2,
The flow rate sensor for measuring the flow rate of the cooling water in the cooling water circulation flow path is provided, and the controller uses the flow rate detected by the flow rate sensor to ionize the time required for the cooling water to pass through the ion filter. It is calculated as a filter passage time, and after passing the ion filter passage time after flowing the cooling water before passing the ion filter to the bypass passage, the cooling water after passing the ion filter is caused to flow to the bypass passage. Fuel cell cooling system.

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