Fuel cell ion exchanger and fuel cell system

An ion exchanger includes a lower casing, an upper casing, and a cartridge. The lower casing includes an upper opening and a circumferential wall, which includes an intake port and a discharge port. The upper casing includes a lid, which is arranged on the opening of the lower casing, and a cylinder, which extends downward from the lid and is accommodated in the circumferential wall. The cartridge, which is provided integrally with the inner side of the cylinder, accommodates an ion exchange resin. The cylinder includes a communication hole, through which the inner side of the cylinder is in communication with the intake port. The upper casing includes an accumulation limiting structure that limits the air remaining immediately below the lower surface of the lid in the upper casing after flowing into the cylinder together with coolant.

TECHNICAL FIELD

The present invention relates to an ion exchanger arranged in a coolant circuit of a fuel cell and a fuel cell system including the ion exchanger.

BACKGROUND ART

A fuel cell system includes a coolant circuit through which coolant flows to cool a fuel cell. The coolant circuit includes an ion exchanger that removes metal ions from the coolant by adsorbing the metal ions on an ion exchange resin (refer to, for example, Japanese Laid-Open Patent Publication No. 2013-233499).

The ion exchanger of the above patent document includes a case. The case includes an intake port, which draws coolant into the case, and a discharge port, which discharges coolant out of the case. A lid is arranged on an upper open end of the case. A cartridge, which is fixed to the lid, accommodates an ion exchange resin. A cylinder, which is accommodated in the case, is formed integrally with the lower surface of the lid. The cartridge is fixed to the inner circumferential surface of the cylinder in a removable manner. The cylinder includes a communication hole through which the inner side of the cylinder is in communication with an upper one of the intake port and the discharge port.

In the ion exchanger of the above patent document, when coolant is drawn through the intake port and into the case, the ion exchange resin adsorbs metal ions from the coolant as the coolant flows through the cartridge. The coolant from which the ions have been removed is discharged out of the case through the communication hole and the upper port.

In the ion exchanger of the above patent document, the cartridge is fixed to the lid. Thus, the lid and the cartridge are removed from the case simultaneously. Accordingly, when exchanging the cartridge, the intake port and a connection port do not have to be removed from a pipe of the coolant circuit. This facilitates the exchanging of cartridges.

However, the ion exchanger of the above patent document has a shortcoming in which the cylinder includes a void above the communication hole. Thus, air, which enters the cylinder together with the coolant, is apt to remain in the void, that is, immediately below the lower surface of the lid. The residual air is suddenly discharged from the ion exchanger to a coolant pipe. As a result, a large amount of air will flow into a pump arranged in the coolant circuit. This may cause a discharge failure of the pump such as cavitation. Further, when a large amount of air flows into the fuel cell, the fuel cell is cooled unevenly.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a fuel cell ion exchanger and a fuel cell system that restricts sudden discharge of a large amount of air into a coolant pipe of the fuel cell.

A fuel cell ion exchanger to achieve the above object is arranged in a coolant circuit for a fuel cell. The ion exchanger includes a lower casing, an upper casing, and a cartridge. The lower casing includes an upper opening, an intake port, and a discharge port. The discharge port is located in an upper portion of a circumferential wall. The upper casing includes a lid and a cylinder. The lid is arranged on the opening. The cylinder extends downward from the lid and is accommodated at an inner side of the circumferential wall. The cartridge is provided integrally with an inner side of the cylinder. The cartridge accommodates an ion exchange resin. The cylinder includes a communication hole, through which the inner side of the cylinder is in communication with the discharge port. The upper casing includes an accumulation limiting structure that limits air remaining immediately below a lower surface of the lid after entering the cylinder together with coolant.

Since such a structure limits the air remaining immediately below the lower surface of the lid in the upper casing, air in the cylinder is smoothly discharged out of the ion exchanger.

EMBODIMENTS OF THE INVENTION

One embodiment will now be described with reference toFIGS. 1 to 6. A fuel cell system of the present embodiment is installed in a vehicle.

As shown inFIG. 1, the fuel cell system is provided with a coolant circuit90that includes a pump91, which draws in and discharges coolant, a fuel cell92, and a heat exchanger93, which exchanges heat with ambient air to cool the coolant. The coolant circuit90includes a bypass94, which bypasses the heat exchanger93. An ion exchanger10, which adsorbs and removes ions from the coolant, is arranged in the bypass94. A three-way valve95is arranged at a downstream end of the bypass94.

As shown inFIGS. 2 and 6, the ion exchanger10includes a lower casing20, an upper casing30, and a cartridge40. The upper portion of the lower casing20includes an opening22. The lower portion of the lower casing20includes a bottom wall. The upper casing30includes a lid31, which is arranged on the opening22, and a cylinder35, which extends downward from the lid31. The cartridge40, which is provided integrally with the inner side of the cylinder35, accommodates an ion exchange resin42. The lower casing20, the upper casing30, and the cartridge40are formed from a hard resin material.

As shown inFIGS. 2 and 3, the lower casing20includes a tubular circumferential wall21. A tubular intake port25and a tubular discharge port26project from the lower portion and the upper portion of the circumferential wall21, respectively.

As shown by the broken line inFIG. 3, an upstream pipe51, which is located at the upstream side of the ion exchanger10in the bypass94, is connected to the intake port25. A downstream pipe52, which is located at the downstream side of the ion exchanger10in the bypass94, is connected to the discharge port26.

As shown inFIGS. 2, 3, and 6, a flange23is formed at the upper end of the circumferential wall21. As shown inFIGS. 2 and 4, the upper surface of the flange23includes an annular groove231, which receives a gasket12(refer toFIG. 6). Further, the flange23includes threaded holes24at the outer side of the annular groove231located at regular intervals in the circumferential direction.

As shown inFIGS. 2, 3, and 4, brackets27, which fix the lower casing20to a vehicle with bolts, are formed integrally with the circumferential wall21.

As shown inFIGS. 2, 4, and 6, the inner edge at the upper end of the circumferential wall21includes a first recess211and a second recess212that are opposed to each other. The first recess211is located at the same position as the discharge port26in the circumferential direction.

As shown inFIGS. 2, 3, 5, and 6, a flange32is formed on the outer edge of the upper end of the lid31. As shown inFIGS. 2 and 5, the flange32includes bolt holes33located at regular intervals in the circumferential direction.

As shown inFIGS. 5 and 6, the upper portion of the cylinder35includes a communication hole361. The outer circumferential surface of the cylinder35includes a tube36, which projects from the rim of the communication hole361toward the outer side. A projection37is formed on the outer circumferential surface of the cylinder35at the opposite side of the tube36.

As shown inFIG. 6, the tube36and the projection37of the upper casing30are fitted into the first recess211and the second recess212of the lower casing20, respectively. The upper end of the wall surface of the communication hole361is located at the same height as the lower surface of the lid31of the upper casing30. That is, the upper end of the wall surface of the communication hole361is flush with the lower surface of the lid31. Further, the inner diameter of the communication hole361and the inner diameter of the discharge port26are the same, and the communication hole361and the discharge port26are coaxial. Thus, when the cylinder35is accommodated in the circumferential wall21of the lower casing20, the inner space of the cylinder35is in communication with the discharge port26through the communication hole361.

As shown inFIG. 6, the inner circumferential surface of the cylinder35includes an internal thread38.

As shown inFIGS. 2 and 6, the cartridge40has the form of a tube. A mesh41is arranged in each of upper and lower openings of the cartridge40. The mesh41restricts the passage of the ion exchange resin42from the cartridge40and allows the passage of coolant and air.

As shown inFIG. 6, the outer circumferential surface of the cartridge40includes an external thread43. When the cartridge40is inserted from below into the cylinder35of the upper casing30, the external thread43of the cartridge40is engaged with the internal thread38of the upper casing30to fasten the cartridge40to the upper casing30in a removable manner.

When assembling the ion exchanger10, the cartridge40is first coupled to the cylinder35of the upper casing30. Then, the cylinder35of the upper casing30is inserted from above into the circumferential wall21of the lower casing20so that the upper surface of the flange23of the lower casing20comes into contact with the lower surface of the flange32of the upper casing30. Subsequently, as shown inFIG. 2, bolts11are inserted through the bolt holes33of the upper casing30and fastened to the threaded holes24of the lower casing20. This couples the lower casing20to the upper casing30as shown inFIG. 3.

In the ion exchanger10, when coolant is drawn into the lower casing20through the intake port25, the ion exchange resin42adsorbs metal ions from the coolant that passes through the cartridge40. The coolant from which the ions have been removed is discharged out of the lower casing20through the communication hole361and the discharge port26.

In the present embodiment, there is no void above the communication hole361in the cylinder35. Thus, when air flows into the cylinder35together with coolant, the upper casing30limits the air that remains immediately below the lower surface of the lid31. This smoothly discharges the air in the cylinder35out of the ion exchanger10through the communication hole361and the discharge port26. Accordingly, the sudden discharge of a large amount of air to the downstream pipe52is restricted.

The fuel cell ion exchanger and the fuel cell system have the following advantages.

(1) The cylinder35of the upper casing30includes the communication hole361, through which the inner space of the cylinder35is in communication with the discharge port26. The upper casing30includes an accumulation limiting structure that limits the air remaining immediately below the lower surface of the lid31in the upper casing30after flowing into the cylinder35together with coolant.

Since such a structure limits the air remaining immediately below the lower surface of the lid31in the upper casing30, air in the cylinder35is smoothly discharged out of the ion exchanger10. Thus, a sudden discharge of a large amount of air to the downstream pipe52is restricted. This reduces discharge failures of the pump91such as cavitation that would occur when a large amount of air flows into the pump91of the coolant circuit90. This also limits situations in which the fuel cell92is cooled unevenly when a large amount of air flows to the fuel cell92.

(2) Since the upper end of the wall surface of the communication hole361is located at the same height as the lower surface of the lid31of the upper casing30, there is no void above the communication hole361in the cylinder35. This limits the air remaining immediately below the lower surface of the lid31.

(3) The tube36, which includes the communication hole361, projects from the outer circumferential surface of the cylinder35of the upper casing30. The first recess211, which receives the tube36, is formed in the inner surface of the circumferential wall21of the lower casing20.

In such a structure, the tube36of the upper casing30is fitted into the first recess211of the lower casing20to connect the communication hole361and the discharge port26. Thus, there is no gap between the communication hole361and the discharge port26. This limits air leaking from between the communication hole361and the discharge port26and allows the air in the upper casing30to be discharged out of the ion exchanger10.

(4) The tube36and the projection37of the upper casing30are fitted into the first recess211and the second recess212of the lower casing20, respectively. This allows for simple and accurate positioning of the upper casing30in the circumferential direction relative to the lower casing20.

The projection37and the second recess212may be omitted.

The tube36may be omitted, and the communication hole361may be changed to a hole that extends through the cylinder35. In this case, the first recess211may be omitted.

As shown by the broken line inFIG. 6, the lower surface311of the lid31may be located at the same height as the upper end of the wall surface of the communication hole361at a portion adjacent to the communication hole361. Further, the lower surface311may become lower as the distance from the communication hole361increases, that is, toward the right as viewed inFIG. 6. In this case, air flows through the intake port25into the upper casing30and moves upward in the cylinder35. When the air reaches the lower surface311of the lid31, the air smoothly moves toward the communication hole361while guided by the lower surface311of the lid31, which becomes higher as the distance from the communication hole361decreases. Then, the air is discharged from the discharge port26to the downstream pipe52through the communication hole361. Accordingly, the air remaining immediately below the lower surface311of the lid31in the upper casing30is limited.