Fluid machine

Abstract

A fluid machine includes a motor and a motor housing. The motor housing defines a motor chamber for accommodating the motor. The motor chamber is filled with inert gas. A rotor rotates in accordance with rotation of the motor. A pump housing defines a pump chamber for accommodating the rotor. A dividing wall is located between the pump housing and the motor housing. The pump housing and the motor housing are attached to each other via the dividing wall. Therefore, water is prevented from being generated in the motor chamber even if fluid that contains hydrogen leaks from the pump chamber to the motor chamber.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a fluid machine that draws fluid into a pump chamber by rotation of a rotor and discharges the fluid out of the pump chamber through an outlet.

In a conventional fuel cell system that generates electric power using hydrogen gas and oxidizing gas as reactive gas, water is produced during generation of electric power. To discharge the generated water from the fuel cell, the hydrogen gas and the oxidizing gas are supplied to the fuel cell by an amount greater than a consumption amount required to generate electric power. Therefore, the hydrogen gas discharged from the fuel cell (so called hydrogen off-gas) includes unreacted hydrogen gas. Discharging the unreacted hydrogen gas deteriorates fuel economy of the fuel cell system. Therefore, the hydrogen off-gas is circulated and returned to the fuel cell to improve the fuel economy of the fuel cell system.

A fluid machine is used in the fuel cell system as means for forcibly circulating the hydrogen off-gas (see Japanese Laid-Open Patent Publication No. 2003-151592). That is, the fuel cell system of the above publication draws the hydrogen off-gas discharged from the fuel cell to the fluid machine via a condenser, which separates gas from liquid. The machine draws the hydrogen off-gas into a pump chamber and mixes the drawn hydrogen off-gas with new hydrogen gas supplied from a hydrogen tank. The hydrogen off-gas that is mixed with the new hydrogen gas is supplied to an anode of the fuel cell again. The ambient air, which serves as the oxidizing gas, is supplied to a cathode of the fuel cell via another fluid machine.

The fluid machine having such a function has been proposed in, for example, Japanese Laid-Open Patent Publication No. 2002-54587. The fluid machine of this Publication is an air pump that supplies air (oxidizing gas) to a fuel cell. The pump includes a motor housing and a pump housing, which are integrally attached to each other. The motor housing defines a motor chamber, which accommodates a motor. The pump housing defines a pump chamber, which accommodates a rotor, which rotates in accordance with rotation of the motor. The motor chamber and the pump chamber are separated by a bottom wall (dividing wall) of the motor housing through which a rotary shaft of the motor extends. A sealing material is provided at a portion of the bottom wall where the rotary shaft is inserted.

As described above, a fluid machine (hydrogen pump) for drawing hydrogen gas (hydrogen off-gas) and supplying it to the fuel cell is provided in the fuel cell system besides the fluid machine (air pump) for drawing air and supplying it to the fuel cell. In this case, the fluid machine (hydrogen pump) has substantially the same structure as the fluid machine (air pump) disclosed in Japanese Patent Publication No. 2002-54587 except that the fluid to be drawn and supplied is not air but hydrogen off-gas.

However, drawing and supplying hydrogen off-gas with the fluid machine disclosed in Japanese Patent Publication No. 2002-54587 arises the following problems. That is, since the hydrogen off-gas has characteristics to penetrate through metal, the hydrogen off-gas often penetrates through the bottom wall (dividing wall) of the motor housing, which separates the pump chamber from the motor chamber, and enters the motor chamber. Although a sealing material is provided at a portion of the bottom wall of the motor housing where the rotary shaft of the motor is inserted through, a slight gap exists to permit the rotary shaft to rotate. Therefore hydrogen off-gas moves from the pump chamber to the motor chamber through the slight gap.

In general, air is sealed in the motor chamber during assembly. Therefore, the oxygen contained in the air in the motor chamber and the hydrogen in the hydrogen off-gas that entered the motor chamber might react and generate water in the motor chamber. If water is generated as described above, members (such as a motor) in the motor chamber might be corroded. As a result, the performance of the fluid machine might deteriorate.

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide a fluid machine that prevents water from being generated in a motor chamber even if fluid that contains hydrogen leaks from a pump chamber to the motor chamber, and prevents the performance of the fluid machine from deteriorating.

To achieve the above-mentioned objective, the present invention provides a fluid machine. The machine includes a motor and a motor housing. The motor housing defines a motor chamber for accommodating the motor. The motor chamber is filled with inert gas. A rotor rotates in accordance with rotation of the motor. A pump housing defines a pump chamber for accommodating the rotor. A dividing wall is located between the pump housing and the motor housing. The pump housing and the motor housing are attached to each other via the dividing wall.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a plan cross-sectional view illustrating a hydrogen pump according to one embodiment of the present invention; and

FIG. 2 is a partially enlarged view of FIG. 1 explaining the state where hydrogen off-gas enters the motor chamber of the pump shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One embodiment of the present invention will now be described with reference to FIGS. 1 and 2.

FIG. 1 shows a hydrogen pump 10, which is one type of fluid machine used in a fuel cell system. That is, the fluid machine in this embodiment is a fluid pump for fluid including hydrogen. The hydrogen pump 10 of this embodiment is formed by a motor portion M and a pump portion P. The motor portion M includes a substantially cup-shaped motor housing 11, which has a closed first end (left end in FIG. 1) and an open second end (right end in FIG. 1), and a partition (dividing member) 12, which is coupled to the motor housing 11 to close the opening. The inner surface of the motor housing 11 and the inner surface of the partition 12 define a motor chamber 13. The motor chamber 13 is filled with inert gas (such as nitrogen) G.

The pump portion P includes a substantially oval cup-shaped pump housing 14, which has an open first end (left end in FIG. 1) and a bearing block (dividing member) 16, which is coupled to the pump housing 14 with bolts 15 to close the opening. The inner surface of the pump housing 14 and the inner surface of the bearing block 16 define a pump chamber 17. In this embodiment, the partition 12 and the bearing block 16 form a dividing wall. The motor housing 11 is open toward the dividing wall and the pump housing 14 is open toward the dividing wall. The dividing wall closes the motor housing 11 and the pump housing 14.

A substantially oval cup-shaped gear housing 18 is secured to a second end (right end in FIG. 1) of the pump housing 14 of the pump portion P with bolts (not shown). The gear housing 18 is smaller than the pump housing 14. The outer surface of the second end of the pump housing 14 and the inner surface of the gear housing 18 define a gear chamber 19. The outer surface of the partition 12 and the outer surface of the bearing block 16 are secured to each other with bolts (not shown) so that the motor portion M is integrated with the pump portion P. An O-ring 20 is arranged between the motor housing 11 and the partition 12, the pump housing 14 and the bearing block 16, the pump housing 14 and the gear housing 18, and the partition 12 and the bearing block 16 as a sealing member to keep the interior sealed from the outside.

A bearing 22 is located at a bottom portion 21 of the motor housing 11. The bearing 22 is coaxial with the motor housing 11 and faces the interior of the motor chamber 13. The bearing 22 rotatably supports a first end (left end in FIG. 1) of a drive shaft (rotary shaft) 23. A second end of the drive shaft 23 extends to the interior of the gear chamber 19 through a through hole 12a formed in the partition 12, a through hole 16a formed in the bearing block 16, and a through hole 24a formed in a bottom portion 24 of the pump housing 14.

The second end of the drive shaft 23 is rotatably supported by a bearing 25 located at the bottom portion 24 of the pump housing 14, and the middle portion of the drive shaft 23 is rotatably supported by a bearing 26 provided in the bearing block 16. A motor rotor 27 is secured to the drive shaft 23 in the motor chamber 13. A motor stator 28 is secured to the motor housing 11 such that the motor stator 28 is located on the outer circumferential side of the motor rotor 27. The motor rotor 27 and the motor stator 28 form an electric motor 29.

A driven shaft 30, which is parallel to the drive shaft 23, is located in the pump chamber 17 of the pump portion P. The ends of the driven shaft 30 are rotatably supported by a bearing 31 provided in the bottom portion 24 of the pump housing 14 and a bearing 32 provided in the bearing block 16. A two-blade drive rotor 33 and a two-blade driven rotor 34 are secured to the drive shaft 23 and the driven shaft 30 in the pump chamber 17, respectively. A second end (right end) of the driven shaft 30 extends to the interior of the gear chamber 19 through the bottom portion 24 of the pump housing 14 in the same manner as the second end (right end) of the drive shaft 23. A drive gear 35 secured to the second end of the drive shaft 23 and a driven gear 36 secured to the second end of the driven shaft 30 engage with each other in the gear chamber 19.

A seal ring (sealing material) 37 is located in the bearing block 16 next to the bearing 26 on the side facing the drive rotor 33 to seal the gap between the drive shaft 23 and the bearing block 16. The seal ring 37 is located between the inner surface of the through hole 16a and the drive shaft 23. In the same manner, a seal ring (sealing material) 37 is located in the bearing block 16 next to the bearing 32 on the side facing the driven rotor 34 to seal the gap between the driven shaft 30 and the bearing block 16. In this embodiment, a seal ring 37 is also located in the bottom portion 24 of the pump housing 14 next to the bearing 25 on the side facing the drive rotor 33 to seal the gap between the drive shaft 23 and the pump housing 14. In the same manner, a seal ring (sealing material) 37 is located in the bottom portion 24 of the pump housing 14 next to the bearing 31 on the side facing the driven rotor 34 to seal the gap between the driven shaft 30 and the pump housing 14.

The hydrogen pump 10 is placed such that an imaginary plane that includes the axes of the drive shaft 23 and the driven shaft 30 is horizontal. An inlet (not shown) is formed in the ceiling of the pump housing 14 of the pump portion P to draw hydrogen off-gas discharged from the fuel cell, which is not shown, into the pump chamber 17. An outlet 38 is formed in the bottom portion of the pump chamber 17 to discharge the hydrogen off-gas drawn by the rotation of the rotors 33, 34 from the pump chamber 17. Therefore, the hydrogen off-gas drawn into the pump chamber 17 from the inlet is discharged through the outlet 38 and supplied to the fuel cell again. As described above, the hydrogen pump 10 repeats drawing and supplying operation in which hydrogen off-gas is drawn into the pump chamber 17 and then discharged.

The operation of the hydrogen pump (fluid machine) 10 constituted as described above will now be described. The operation performed when hydrogen off-gas in the pump chamber 17 enters the motor chamber 13 will mainly be discussed below.

In a case where the hydrogen pump 10 repeats the drawing and supplying operation of hydrogen off-gas as described above, part of the hydrogen off-gas drawn into the pump chamber 17 from the inlet might enter the motor chamber 13 via the through hole 16a of the bearing block 16 and the through hole 12a of the partition 12 as shown in FIG. 2. That is, although the seal ring 37 is located in the through hole 16a of the bearing block 16, a slight gap is formed between the seal ring 37 and the drive shaft 23 to permit the drive shaft 23 to rotate.

A gap is also formed between the through hole 12a of the partition 12 and the circumferential surface of the drive shaft 23 to permit the drive shaft 23 to rotate. Therefore, the hydrogen off-gas drawn into the pump chamber 17 might enter the motor chamber 13 through the gaps. Since the hydrogen gas (hydrogen off-gas) has the characteristics to penetrate through metal, the hydrogen off-gas might penetrate through the bearing block 16 and the partition 12, which are made of metal material (for example, aluminum alloy), and enter the motor chamber 13.

However, in this embodiment, since the motor chamber 13 is filled with inert gas (nitrogen) G, that is, there is no residual air (oxidizing gas), the hydrogen off-gas that entered the motor chamber 13 does not generate water by a reaction with the air (oxidizing gas). Therefore, even if hydrogen off-gas enters the motor chamber 13, water is not generated by a reaction with air (oxidizing gas). Therefore, members such as electric motor 29 in the motor chamber 13 are prevented from corroding. As a result, the performance of the hydrogen pump 10 is prevented from deteriorating.

The inert gas (nitrogen) G in the motor chamber 13 is prevented from leaking into the pump chamber 17 by the seal ring 37 located in the through hole 16a of the bearing block 16. The O-rings 20, which function as the sealing members, prevent the inert gas (nitrogen) G from leaking outside from the contact portion between the motor housing 11 and the partition 12 and the contact portion between the partition 12 and the bearing block 16 passing through the through hole 12a of the partition 12. The O-rings 20 further prevent water from entering the motor chamber 13 from the contact portion between the motor housing 11 and the partition 12 and the contact portion between the partition 12 and the bearing block 16.

The preferred embodiment has the following advantages.

(1) Even if hydrogen off-gas enters the motor chamber 13 from the pump chamber 17, the motor chamber 13 is filled with inert gas (nitrogen) G, that is, there is no air (oxidizing gas). Therefore, water is not generated in the motor chamber 13 by a reaction between hydrogen and air. Accordingly, the members such as the electric motor 29 in the motor chamber 13 are prevented from being corroded by water, and the performance of the hydrogen pump 10 is reliably prevented from deteriorating.

(2) Since the diffusion velocity of nitrogen that fills the motor chamber 13 as the inert gas G is slower (about ⅓) than that of the air, the nitrogen does not leak from the motor chamber 13 easily. Therefore, the performance of the hydrogen pump 10 is maintained for a long period.

(3) The sealing material, which is the seal ring 37 in this embodiment, is located in the through hole 16a of the bearing block 16 through which the drive shaft 23 extends. Therefore, the seal ring 37 reliably prevents inert gas G in the motor chamber 13 from leaking into the pump chamber 17 through where (through hole 16a) the drive shaft 23 extends in the bearing block 16.

(4) The sealing member, which is the O-ring 20 in this embodiment, is located at the contact portion between the motor housing 11 and the partition 12. Therefore, the inert gas G in the motor chamber 13 is reliably prevented from leaking outside from the contact portion between the motor housing 11 and the partition 12. The O-ring 20 also prevents water from entering the motor chamber 13 via the contact portion from the outside.

(5) The sealing member, which is the O-ring 20 in this embodiment, is located at the contact portion between the partition 12 and the bearing block 16. Therefore, the inert gas G in the motor chamber 13 is reliably prevented from leaking outside from the contact portion between the partition 12 and the bearing block 16. The O-ring 20 also prevents water from entering the motor chamber 13 via the contact portion from the outside.

The invention may be embodied in the following forms.

In the preferred embodiment, the dividing wall is formed by the partition (dividing member) 12, which closes the opening of the motor housing 11, and the bearing block (dividing member) 16, which closes the opening of the pump housing 14. However, the dividing wall may be formed by only the bearing block 16. In this case, the bearing block 16 closes the opening of the motor housing 11 and the opening of the pump housing 14.

In the preferred embodiment, the O-ring 20 is used as the sealing member located at the contact portion between the motor housing 11 and the partition 12. However, the sealing member other than the O-ring 20 may be used as long as the sealing member prevents inert gas G from leaking outside via the contact portion and water from entering via the contact portion.

In the preferred embodiment, the sealing material, which is the seal ring 37, is located in the through hole 16a of the bearing block 16. However, the seal ring 37 may be located in the through hole 12a of the partition 12.

In the preferred embodiment, the motor chamber 13 is filled with the inert gas G, which is nitrogen. However, any inert gas other than nitrogen (for example, argon, helium, neon, xenon, and krypton) may be used as long as the inert gas does not react with hydrogen and generate water. The motor chamber 13 may be filled with mixed gas (for example, nitrogen and neon) that is the mixture of several types of inert gases G.

In the preferred embodiment, the present invention is embodied in the hydrogen pump 10, which circulates hydrogen gas (hydrogen off-gas) in the fuel cell system. However, the present invention may be embodied in any fluid machine (hydrogen pump) other than that used in the fuel cell system as long as the fluid machine draws and supplies fluid that includes hydrogen.

The present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.

Claims

1. A fluid machine, comprising:

a motor;

a motor housing, which defines a motor chamber for accommodating the motor, the motor chamber being filled with inert gas;

a rotor, which rotates in accordance with rotation of the motor;

a pump housing, which defines a pump chamber for accommodating the rotor; and

a dividing wall located between the pump housing and the motor housing, the pump housing and the motor housing being attached to each other via the dividing wall.

2. The fluid machine according to claim 1, wherein the inert gas is at least one of nitrogen, argon, helium, neon, xenon, and krypton.

3. The fluid machine according to claim 1, further comprising:

a rotary shaft, which transmits rotation of the motor to the rotor, the dividing wall has a through hole through which the rotary shaft extends; and

a sealing material located between the inner surface of the through hole and the rotary shaft.

4. The fluid machine according to claim 1, further comprising a sealing member located at a contact portion between the motor housing and the dividing wall.

5. The fluid machine according to claim 1, wherein the dividing wall includes a plurality of dividing members, which are piled on each other, and

a sealing member is located at least one of a portion between the adjacent dividing members, a portion between the motor housing and the adjacent dividing member, and a portion between the pump housing and the adjacent dividing member.

6. The fluid machine according to claim 1, wherein the motor housing is open toward the dividing wall and the pump housing is open toward the dividing wall, wherein the dividing wall closes the motor housing and the pump housing.

7. The fluid machine according to claim 1, wherein the fluid machine is a fluid pump for fluid including hydrogen.

8. The fluid machine according to claim 1, wherein the fluid machine is incorporated in a fuel cell system.

9. A fluid machine, comprising:

a motor;

a motor housing, which defines a motor chamber for accommodating the motor, the motor chamber being filled with inert gas;

a rotor, which rotates in accordance with rotation of the motor;

a pump housing, which defines a pump chamber for accommodating the rotor;

a dividing wall located between the pump housing and the motor housing, the pump housing and the motor housing being attached to each other via the dividing wall, and the motor housing is open toward the dividing wall and the pump housing is open toward the dividing wall, wherein the dividing wall closes the motor housing and the pump housing;

a rotary shaft, which transmits rotation of the motor to the rotor, the dividing wall has a through hole through which the rotary shaft extends; and

a sealing material located between the inner surface of the through hole and the rotary shaft.