Pumps – Condition responsive control of drive transmission or pump... – Having means to hold or resist movement of pumping element
Reexamination Certificate
2002-02-08
2004-01-20
Yu, Justine R. (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Having means to hold or resist movement of pumping element
C092S013000
Reexamination Certificate
active
06679684
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pump device.
2. Discussion of Related Art
JP-A-8-104214 discloses a pump device including a pump, an electric motor for driving the pump, and a pressure relief valve arranged to discharge a pressurized fluid delivered from the pump to a low-pressure reservoir when the delivery pressure of the pump (pressure of the pressurized fluid) exceeds a preset relief pressure. The pressure relief valve prevents an excessive rise of the delivery pressure of the pump, thereby protecting the electric motor from an overload.
In the pump device described in the above-identified publication, the pump is kept operated so as to maintain the delivery pressure at the present relief pressure, even after the delivery pressure has been raised to the present relief pressure. This continuous operation of the pump requires a comparatively large amount of consumption of an electric energy by the electric motor to drive the pump.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a pump device which is arranged to reduce the required amount of consumption of an electric energy. This object may be achieved according to any one of the following modes of the present invention, each of which numbered like the appended claims and depends from the other mode or modes, where appropriate, for easier understanding of technical features disclosed in the present application, and possible combinations of those features. However, it is to be understood that the invention is not limited to those technical features or combinations thereof, and that any one of a plurality of technical features described below with respect to any one mode of the invention may be a subject of the present invention, without the other technical feature or features being combined with that one feature.
(1) A pump device comprising a support member having a fitting recess, and a movable member which is reciprocated in said fitting recess to suck a working fluid, pressurize the fluid and deliver the pressurized fluid, the pump device comprising a movement restricting device operable to deform a wall at least partially defining the fitting recess of the support member, such that the wall is deformed toward the movable member, for restricting a reciprocating movement of the movable member in the fitting recess, at least when an amount of the pressurized fluid required to be delivered by the pump device is smaller than a nominal delivery amount of the pump device.
In the pump device according to the above mode (1) of this invention, the movement restricting device is operated, when the amount of the pressurized fluid required to be delivered by the pump device is smaller than the nominal delivery amount of the pump device, so that the wall of the support member which at least partially defines the fitting recess (such as a fitting hole or bore in a cylinder in a piston pump or a vane groove in a vane pump) is deformed toward the movable member, for restricting a reciprocating movement of the movable member in the fitting recess. For instance, the movement restricting device is arranged to inhibit or prevent the reciprocating movement of the movable member, reduce a speed of the movement, or reduce the reciprocating stroke of the movable member, when the pump device is not required to deliver the pressurized fluid. For example, the wall of the support member is elastically deformed toward the fitting recess, for zeroing the clearance between the movable member and the wall of the support member, and applying a pressing force from the wall to the movable member in a direction intersecting the direction of reciprocating movement of the movable member (e.g., in a direction perpendicular to the direction of movement). When a force of friction between the wall and the movable member which is produced on the basis of the pressing force becomes larger than a force by which the movable member is moved, the movement of the movable member is inhibited or prevented. Namely, the movable member is held stationary, with the wall held in pressing contact with the outer surface of the movable member. Alternatively, the wall of the support member is elastically deformed such that a portion of the wall projects toward the movable member, so that the projecting portion engages the movable member to limit a distance of movement of the movable member, for thereby reducing the reciprocating stroke of the movable member.
When the movement of the movable member in the fitting recess is inhibited, the pump device is not capable of delivering the pressurized fluid. In this case, the pressure of the fluid in a discharge port of the pump device in a pump chamber formed in front of the movable member is either lowered or maintained at a level before the movement is inhibited. Whether the fluid pressure is maintained or lowered depends upon a type of a fluid-operated device which is operated by the pressurized fluid delivered from the pump device, for instance. Where the fluid-operated device does not consume the pressurized fluid, the fluid pressure in the discharge port or pump chamber is maintained. Where the fluid-operated device consumes the pressurized fluid, the fluid pressure is lowered.
Where the reciprocating stroke of the movable member is reduced by the movement restricting device, the amount of the pressurized fluid delivered from the pump device during one reciprocation of the movable member is reduced. Accordingly, the rate of increase of the fluid pressure in the discharge port or pump chamber is reduced, or the fluid pressure is maintained or is lowered. Whether the rate of increase of the fluid pressure is reduced or the fluid pressure is maintained or lowered depends upon a relationship between the amount of consumption of the pressurized fluid by the fluid-operated device and the amount of the pressurized fluid delivered by the pump device.
In any case, an increase of the fluid pressure in the discharge port or pump chamber of the pump device can be restricted by the movement restricting device, so that the amount of electric energy required to move the movable member can be reduced. Further, a pressure relief valve provided in the conventional pump device is not essential, in the presence of the movement restricting device. However, the principle of the present invention does not exclude the provision of such a pressure relief valve for improving the operating safety of the pump device.
The movement restricting device may be arranged to deform either a portion or an entirety of the wall partially defining the fitting recess in the support member. Namely, the wall is required to be deformed such that the diameter of at least a portion of the wall (inside diameter of the fitting recess) is reduced to be smaller than the outside diameter of the movable member. Where the wall is deformed partially, the wall may have only one deformable portion or a plurality of deformable portions. For example, the wall has a deformable cylindrical portion which is deformed by the movement restricting device, in a direction intersecting the direction of movement of the movable member. However, the deformable portion is not limited to such a cylindrical portion of the wall.
Whether the pump device is required to deliver the pressurized fluid or not, that is, whether the movement restricting device should be operated or not, depends upon an operating condition of either the pump device per se or the fluid-operated device. For example, the movement restricting device is operated when it is not desirable to operate the pump device after the delivery pressure has reached a predetermined level, or when the fluid-operated device does not require the pressurized fluid whose pressure is higher than a predetermined level.
The principle of the present invention is applicable to a gas pump arranged to pressurize a gas, and a liquid pump arranged to pressurize a liquid. However, the present invention is more suitably applicable to the liquid pump, since a large press
Liu Han L
Toyota Jidosha & Kabushiki Kaisha
Yu Justine R.
LandOfFree
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