Pump having magnetic coupling mechanism

1. Field of the Invention

The present invention relates to a pump capable of effectively delivering a fluid by means of magnetic coupling action of a pair of magnets without leaking it to the outside when transferring a fluid ranged from high viscosity to low viscosity or a high viscous fluid under a high-pressure, more particularly to a pump having a magnetic coupling mechanism (no shaft sealing mechanism).

2. Description of the Related Art

In recent years, a market need for a pump in which a drive member such as a gear is driven by means of magnetic coupling action, i.e., a pump having a magnetic coupling mechanism tends to further increase. As a recent trend, a high-performance pump is becoming available as distinct from several tens of years ago, since the magnet industry as an essential technology thereof has been developed a high-performance magnet such as a neodymium-based magnet or the like.

In the pump industry, the most popular type of commercially available pump having such a magnetic coupling mechanism is a centrifugal type of pump. The centrifugal type of pump is suitable for transferring a fluid having low head, large volume and low viscosity in comparison to other types of pumps, and the magnetic coupling used in a centrifugal type pump is not required to have a large transferring capacity. It is therefore possible to design a magnetic coupling relatively compact in size with respect to the pump size, which also contributes to reduction in manufacturing cost.

In difference to the centrifugal type pump, it is only recently that, due to enhanced performance of a magnet used for magnetic couplings, gear pumps using a magnetic coupling become commercially practical and are being accepted in the market.

One of gear pumps having such a magnetic coupling mechanism is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 2006-052652.

In this gear pump, it is intended to provide a simplified transmission mechanism for transmitting rotational force to a gear and a sealing construction for preventing the leakage of a liquid to outside of a housing, and to attain size reduction thereof. More specifically, the gear pump includes a plurality of gears engaged with each other, a housing for accommodating the gears in a state of being hermetically sealed in isolation from the outside, a supply passage for feeding a fluid into the housing, and a discharge passage for delivering the fluid from the housing, and is configured such that at least one or more of the gears is a profile shifted spur gear, a magnetic member is attached to at least one or more of the gears, and a driving source is provided outside the housing, and when the driving source is energized, a rotational driving force is applied to the gears each provided with the magnetic member.

In Japanese Unexamined Patent Application Publication No. 2007-285270, a variable displacement pump is proposed in which a loss in power transmission from a drive shaft to a pump driving rotational body (or drive gear) hardly occurs even when the pump is driven at a low rotational speed. This variable displacement pump includes a pump housing, a drive shaft rotationally driven by an external driving source, and a pump driving rotational body rotationably installed in the pump housing, and is configured such that the pump driving rotational body is provided with a shaft hole in its center in order to allow the drive shaft to pass therethrough, and either of an inner peripheral wall portion partitioning the shaft hole or an outer peripheral portion of the drive shaft opposing the inner peripheral wall portion is formed of a permanent magnet, while the other portion is formed of a magnetic material.

Likewise, in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2007-531844, there is proposed a magnetically driven gear pump that includes a housing and a rotatable annular magnetic drive assembly, which is magnetically connected to an annular driven magnetic rotor assembly, but located spaced apart therefrom and is provided with an annular canister therebetween. The magnetically driven gear pump is configured such that, when the annular magnetic drive assembly starts to rotate, the annular driven magnetic rotor assembly rotates at a first shaft portion of a displaced static shaft, while a rotor gear drives an idler gear rotating at a second shaft portion of the displaced static shaft.

The above gear pumps are used for a variety of fluids, particularly used as a high-pressure generator in various ranges of rotation speeds in equipment for quantitative transfer or metering transfer of a high viscous fluid and for hydraulic power transfer.

In order to transfer a fluid having high viscosity under a high pressure, however, a large-sized magnetic coupling having a large torque transfer capacity is needed as a matter of course. That is, in the case when a fluid having high viscosity or high pressure is transferred by a gear pump, since a large load is applied to the gear pump, a so-called slipping phenomenon may occur in its magnetic coupling mechanism portion and thereby the torque of the external driving source may not be accurately transferred to the gear pump, which causes a critical problem in the gear pump that is desired to implement quantitative transfer or metering transfer.

Accordingly, when the specification of a gear pump requires the installation of a magnetic coupling having a large torque transfer capacity, the surface area of magnets should be increased to enhance the capacity of the magnetic coupling and as the result the apparatus size becomes large.

On the other hand, there is an attempt to utilize a more effective neodymium magnet, since the performance of a magnetic coupling much depends on the performance of a magnet and a high-performance magnetic coupling contributes to suppress increase in the coupling size. However, a rare metal such as neodymium is extremely expensive and is becoming difficult to obtain in recent years, so there is a need that a gear pump having a small-sized magnetic coupling, while still having a large torque transfer capacity would be provided.

The present invention addresses the above problems with the object of providing a pump having a magnetic coupling mechanism, the pump being able to produce a large transfer torque needed for heavy duty applications using a magnetic coupling having a relatively small transfer torque capacity without a fear of liquid leakage from a pump driving portion, and also having a simple construction and a high cost performance without using expensive material such as a rare metal.

In order to achieve the above object, a first aspect of the invention provides a pump having a magnetic coupling mechanism for driving a drive member of the pump by means of magnetic coupling action of an inner magnet and an outer magnet both constituting the magnetic coupling mechanism, wherein a reduction mechanism is intervened between the drive member of the pump and the magnetic coupling mechanism driven by an external driving source, and the drive member of the pump, the reduction mechanism and at least the inner magnet constituting the magnetic coupling mechanism are arranged in an enclosed housing.

A second aspect of the invention provides the pump having the magnetic coupling mechanism according to the first aspect of the invention, wherein the magnetic coupling mechanism includes a magnet portion having a bottomed cylindrical shape and constituting the enclosed housing, a rotor, on an outer peripheral portion of which the inner magnet is provided and in the central portion of which one end of a drive shaft for driving the reduction mechanism is connected, the rotor being disposed freely rotatably inside the magnet portion, and a cylindrical rotating member, on an inner peripheral portion of which the outer magnet is provided so as to oppose the inner magnet, the rotating member being disposed with keeping a predetermined gap with respect to the outer periphery of the magnet portion.

A third aspect of the invention provides the pump having the magnetic coupling mechanism according to the first aspect of the invention, wherein the pump is a gear pump.

Since a pump having a magnetic coupling mechanism of the present invention includes a reduction mechanism provided between a drive member of the pump and the magnetic coupling mechanism driven by an external driving source, even though the external driving power is small, the pump using a magnetic coupling having a relatively small torque transfer capacity is able to generate a torque required for pumping a fluid having high viscosity or under high pressure without slipping in the magnetic coupling.

Moreover, since the drive member of the pump, the reduction mechanism and an inner magnet, which constitutes the magnetic coupling mechanism, are accommodated in an enclosed housing, there is no fear of leakage of the fluid from the driving portion of the pump to the outside.

Furthermore, the pump having the magnetic coupling mechanism is able to deal with a fluid ranged from high viscosity to low viscosity under a high pressure without upsizing the magnetic coupling by selecting the reduction ratio of the reduction mechanism, and thereby it is possible to obtain a compact and easily manufactured pump.