CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Applications 2018-182435 and 2018-182436, both filed on Sep. 27, 2018, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to a valve device capable of limiting communication between a fluid introduction path and a fluid discharge path.

BACKGROUND DISCUSSION

In the related art, a fluid is used in various devices. Various valves are provided in a device in order to control flow of the fluid. As this kind of valve, for example, a list of references that indicate the source thereof is as follows.

JP 2017-166569A (Reference 1) discloses a flow rate control valve including a cylindrical housing having a plurality of communication holes through which a fluid flows, a spherical valve body accommodated in the housing and having a fluid inlet portion and a plurality of openings communicating with the respective communication holes in the housing, and a seal member which prevents leakage of the fluid between the housing and the valve body. In the flow rate control valve, the seal member is biased to the valve body side by a spring provided on the opposite side of the valve body.

JP 2012-145124A (Reference 2) discloses a valve including a rotor having a fan shape in a plan view, a cylindrical body in which the rotor is rotatably accommodated, a pair of ports for the inflow and the outflow of a fluid to and from the cylindrical body, and an annular seal member provided in close contact with the peripheral surface of the rotor. In this valve, the annular seal member is configured such that the axial length thereof is longer on the downstream side in the rotational direction than on the upstream side in the rotational direction of the rotor for making the ports from the opened state to the closed state. Further, the rotor is configured such that, when the rotor approaches the seal member, the radial length on the rotor side remote from the seal member is longer than the radial length on the rotor side close to the seal member. Thus, the seal member comes into contact with the rotor only when blocking the fluid, which prevents the wear of the seal member.

JP 2008-095811A (Reference 3) discloses a ball valve including a spherical valve body and a housing in which the valve body is accommodated, the housing being provided with an annular seat member. The valve body is configured so as not to come into contact with the seat member during rotation and is configured so as to come into contact with the seat member when blocking a flow path. In addition, a member (second shaft) capable of preventing the wear of the seat member is provided between the valve body and the seat member.

JP 2012-145154A (Reference 4) discloses a valve device including a valve body, a housing, and a seat member. In this valve device, the leakage of a fluid between the valve body and the housing is prevented by the seat member, and a seat member fixing unit is used to fix the seat member.

Further, in the related art, electrification of vehicles has been considered in order to reduce global environmental pollution due to exhaust gases of vehicles. As one example of such a vehicle, for example, there is one using a fuel cell as a power source as disclosed in JP 2018-018683A (Reference 5).

It is known that the power generation performance of a fuel cell provided in a fuel cell system disclosed in Reference 5 changes significantly due to the wet condition of a membrane in a fuel cell stack. Thus, in a technology disclosed in Reference 5, the air that has passed through a humidifier is supplied to the stack when the membrane is in a dry state, and the air that has bypassed the humidifier is supplied to the stack when the membrane is in a wet state. For this reason, a supply side on-off valve which controls the flow of air to the humidifier and a bypass supply path and an on-off valve which controls the flow of air to the bypass supply path are provided. Further, in order to prevent deterioration of the stack while the vehicle stops, each of the supply side on-off valve and the on-off valve needs to have a sealing function. The technology disclosed in Reference 5 has room for cost reduction, and it is conceivable to integrate a plurality of valves into one as one method of cost reduction (e.g., JP 2013-245738A (Reference 6) and JP 2018-080724A (Reference 7)).

A rotary type valve disclosed in Reference 6 is configured to include a rotor which opens and closes a flow path according to rotation and a casing in which the rotor is accommodated, and a casing opening serving as a fluid path is provided in the inner surface of the casing. A cylindrical seal member is provided in the casing opening so as to abut on the outer peripheral surface of the rotor.

A control valve disclosed in Reference 7 is configured to include a housing, a valve body accommodated in the housing, and a seal member provided between a communication hole in the housing and the outer peripheral surface of the valve body. The outer peripheral edge of the seal member is chamfered to prevent damage to the seal member.

The valve device disclosed in the above-described Reference 4 is configured to include the spherical valve body, the housing in which the valve body is accommodated, and the annular seat member inside the housing. When flowing a fluid, this is performed in a state where the valve body and the seat member are not in contact with each other.

The technology disclosed in Reference 1 is composed of the spherical valve body and the cylindrical housing, and there exists a location where the seal member is not supported. For this reason, the seal member may be deformed by the pressure difference between the upstream side and the downstream side of the flow rate control valve or the rotation of the valve body, thus failing in proper sealing.

The technology disclosed in Reference 2 is configured by exchanging the radial length of the fan-shaped rotor or the axial length of the seal member. For example, there is a possibility that the sealability of the seal member is significantly degraded when positional displacement occurs in the circumferential direction in the course of disposing the seal member.

The technology disclosed in Reference 3 causes cost increase since a separate member is used to prevent deformation of a seal member. In addition, since the seal member is fixed, the load on the seal member may greatly vary due to dimensional variation such as axial displacement of the valve body and the housing, and in such a case, variation in the rotational torque of the valve body also increases.

The technology disclosed in Reference 4 is excellent in anti-wear measures since the valve body and the seat member are not in contact with each other during the flow of a fluid, but are in contact with each other when the fluid does not flow. However, since the seat height is changed according to the rotor diameter, when the seat member is displaced in the circumferential direction, this greatly affects sealing performance.

Further, when sealing is performed by bringing the seal member into contact with the outer peripheral surface of the rotor as in the technology disclosed in Reference 6, displacement of the seal member in the circumferential direction greatly affects the sealability of the seal member, and the sealability is degraded even by slight displacement in the circumferential direction. Further, since a rubber seal is used as the seal member, sliding resistance is increased, which causes an increase in the size of a motor. Furthermore, since the rubber seal and the rotor are always in contact with each other when the sliding resistance is large, the wear of the seal member becomes remarkable.

In the technology disclosed in Reference 7, since the seal member always slides with respect to the rotor, there is a possibility that the wear of the seal member is increased as in the technology disclosed in Reference 2. Therefore, although it is conceivable to use a resin component having a small coefficient of friction, a resin may not provide the sealability required from the fuel cell system.

As described above, the technology of Reference 4 is excellent in anti-wear measures since the valve body and the seat member are not in contact with each other during the flow of a fluid, but are in contact with each other when the fluid does not flow. However, since the seat height is changed according to the rotor diameter, when the seat member is displaced in the circumferential direction, this greatly affects sealing performance.

Thus, a need exists for a valve device which is not susceptible to the drawback mentioned above.

SUMMARY

A feature of a valve device according to an aspect of this disclosure resides in that the valve device includes a housing having a cylindrical inner peripheral wall that defines a cylindrical space therein, a fluid introduction path formed in the housing to communicate with the cylindrical space at the inner peripheral wall, a plurality of fluid discharge paths formed in the housing to communicate with the cylindrical space at the inner peripheral wall, a valve body accommodated in the cylindrical space, the valve body being formed of a spherical body having therein a communication path that communicates the fluid introduction path with at least one of the plurality of fluid discharge paths, a valve body rotating mechanism configured to rotate the valve body about an axis of the cylindrical space as a rotation axis in the cylindrical space, a protrusion protruding from the inner peripheral wall of the housing toward the axis of the cylindrical space to surround at least a portion of an opening in the fluid introduction path at the inner peripheral wall of the housing, and a seal member provided on the protrusion and capable of abutting on the valve body.

