Patent Application
20080173362
1. Field of the Invention
The present invention relates to hydraulic reservoirs and, more particularly, to a hydraulic reservoir having a baffle.
2. Description of the Related Art
Many vehicles have hydraulic power assisted steering systems. Such systems typically include a reservoir. Hydraulic reservoirs are typically used to perform a number of functions such as holding a quantity of hydraulic fluid for supplying a hydraulic pump and conditioning the hydraulic fluid. The conditioning of the hydraulic fluid often involves cooling the fluid, deaerating the fluid and/or filtering the fluid. Increasing the volume of the hydraulic fluid held within the reservoir is one option for enhancing most of these reservoir functions. In modern motor vehicles, however, the available space in the engine compartment is often limited and it is generally desirable to minimize the weight of the vehicle, both factors which favor the use of smaller reservoirs. Various reservoir designs, including reservoirs with internal baffle structures have been developed in an effort to address these competing design criteria. While many known reservoir designs are adequate, they are not without limitations and drawbacks.
The manufacture of some reservoir designs is known to result in a relatively high variability in the deaeration performance of the reservoirs. An improved reservoir that is not subject to such high variability in performance and which is also relatively simple and inexpensive to manufacture is desirable.
The present invention provides a hydraulic reservoir that is relatively simple and inexpensive to manufacture and which provides enhanced performance characteristics.
The invention comprises, in one form thereof, a reservoir assembly for use with a hydraulic fluid. The reservoir assembly includes a reservoir housing defining a fluid chamber for holding the hydraulic fluid. The housing includes an inlet through which hydraulic fluid enters the fluid chamber and an outlet through which hydraulic fluid is discharged from the fluid chamber. A baffle member is disposed within the fluid chamber above the inlet and partitions the fluid chamber. The baffle member separates an upper zone of the fluid chamber positioned above the baffle member from an inlet zone of the fluid chamber positioned below the baffle member. The baffle member defines a central opening disposed radially inwardly of the reservoir housing which provides fluid communication between the inlet zone and the upper zone. The baffle member and the reservoir housing define a flow path wherein hydraulic fluid introduced into the fluid chamber through the inlet is substantially directed to flow circumferentially along a radially outer section of the inlet zone whereby air entrained in the hydraulic fluid collects in a central portion of the inlet zone proximate the central opening and is subsequently communicated to the upper zone thereby deaerating the fluid. The assembly further includes a means for forming a substantially fluid tight seal between the reservoir housing and the baffle member along an outer radial edge of the baffle member.
In some embodiments of the invention, the means for forming a substantially fluid tight seal between the reservoir housing and the baffle member takes the form of an axially extending flange disposed on the outer radial edge of the baffle member which is in a press-fit engagement with the reservoir housing. In other embodiments of the invention, the means for forming a substantially fluid tight seal may take the form of an O-ring member, a weld extending along the outer circumference of the baffle member and joining the baffle member to the reservoir housing, or an adhesive disposed between and joining the baffle member and reservoir housing.
The invention comprises, in another form thereof, a method of mass producing a reservoir assembly for use with hydraulic fluid. The method includes providing a plurality of reservoir housings wherein each of the reservoir housings define a fluid chamber for holding hydraulic fluid and include an inlet through which hydraulic fluid enters the fluid chamber and an outlet through which hydraulic fluid is discharged from the fluid chamber. The method also involves installing a baffle member in each of the reservoir housings. For each of the reservoir assemblies, the baffle member is disposed in the fluid chamber above the inlet, the baffle member partitioning the fluid chamber and thereby separating an upper zone of the fluid chamber positioned above the baffle member from an inlet zone of the fluid chamber positioned below the baffle member. The baffle member defines a central opening disposed radially inwardly of the reservoir housing and which provides fluid communication between the inlet zone and the upper zone. The baffle member and the reservoir housing define a flow path wherein fluid introduced into the fluid chamber through the inlet is substantially directed to flow circumferentially along a radially outer section of the inlet zone whereby air entrained in the hydraulic fluid collects in a central portion of the inlet zone proximate the central opening and is subsequently communicated to the upper zone thereby deaerating the hydraulic fluid. The method also includes forming a substantially fluid tight seal between the baffle member and the reservoir housing along the outer radial edge of the baffle member for substantially all of the plurality of reservoir housings.
An advantage of the present invention is that it provides a cost-efficient hydraulic reservoir design for reliably deaerating hydraulic fluid.
The above mentioned and other features of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplification set out herein illustrates an embodiment of the invention, in one form, the embodiment disclosed below is not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise form disclosed.
A reservoir housing 20 without a baffle member located therein is illustrated in
Hydraulic fluid enters fluid chamber 28 of reservoir 20 through inlet 30. A connector 32 in fluid communication with inlet 30 projects outwardly from housing 24. A hydraulic hose can be readily secured to connector 32 when installing reservoir 20 in a hydraulic system. Hydraulic fluid is discharged from fluid chamber 28 through outlet 34 which is positioned below inlet 30. Outlet 34 is located in the cut-away portion of housing 24 and a dashed outline is used to indicate the location of the outlet 34. A second connector (not shown) is in communication with outlet 34 and projects outwardly from housing 24 forming a substantially right angle with connector 32. The second connector is similar in structure to connector 32. Mounting studs 36 project from the bottom of reservoir housing 24 and are used to secure reservoir 20 in a vehicle.
In operation, inlet 30 is positioned so that hydraulic fluid enters housing 24 at a tangent to the axis of cylindrical fluid chamber 28. (Flow path line 31 in
It is known to inhibit the formation of such vortexes by the use of baffles. Two known examples of such baffles are illustrated in
When mass produced, it has been found that a significant number of baffle structures 40 will perform poorly. Observation of baffle structures 40 in use by the inventor of the present application indicates that an unacceptably high level of turbulence occurs on the upper surface of fluid in the reservoir (above upper baffle member 42) in the poorly performing reservoir assemblies. The inventor further realized that when manufacturing reservoir assemblies having a baffle structure 40, it is difficult to consistently provide a fluid tight seal between upper baffle member 42 and reservoir housing 24. The absence of such a fluid tight seal between upper baffle member 42 and reservoir housing 24 is thought to allow the rotary motion of fluid below baffle member 42 to be partially communicated to fluid above baffle member 44 resulting in the performance degrading turbulence.
Inlet 130 is positioned so that hydraulic fluid enters housing 124 along a line that defines a tangent with respect to a cylinder centered on axis 123 of reservoir housing 124. See flow path arrow 31 in
A baffle structure 60 is also positioned in fluid chamber 128 and is best understood with reference to
Baffle member 62 has a substantially planar disk portion 66 with a central opening 68 extending through disk portion 66 and an outer flange 70. Flange 70 extends around the outer circumference of disk portion 66 and projects in an axial direction. The use of flange 70 provides baffle member 66 with a relatively large radially outer surface 72. Connecting members 76 extend axially and join baffle member 62 with filter element 64. Baffle member 62, connecting members 76 and filter element support structure 78 are, in the illustrated embodiment, all integrally formed of a molded polymeric material.
Filter element support structure 78 includes an inner disk 84 to which connecting members 76 are joined. Inner disk 84 forms an impermeable barrier at the center of filter element 64. Supporting ribs 82 project radially outwardly from inner ring 84 and join inner ring 84 with outer ring 80. Mesh filter elements 84 extend across the fluid passageways formed between inner and outer rings 84, 80 and radially extending ribs 82.
Baffle structure 60 is installed in reservoir housing 124 before attaching top member 122. In the embodiment illustrated in
The press-fit engagement of polymeric flange 70 with the polymeric reservoir housing 124 is sufficiently tight to provide a fluid tight seal. By providing baffle member 62 with an axially projecting flange 70 on its outer circumference, the outer radial surface located of baffle member 62 is enlarged thereby providing a greater area for surfaces 72 and 174 to be engaged and thereby improving the sealing effect of this engagement. Moreover, the axial projecting nature of flange 70 provides flange 70 with less rigidity at its projecting edge allowing it to more easily conform to the interior surface 174 of reservoir housing 124.
The use of flange 70 on baffle structure 60 facilitates the mass production of reservoir assemblies 124 by providing a design wherein a plurality of reservoir assemblies 124 can be manufactured and substantially all of the plurality of reservoir assemblies 124 will include a substantially fluid tight seal between baffle member 62 and interior surface 174 of reservoir housing 124.
In the illustrated embodiment, flange 70 projects in a direction parallel to axis 123. In alternative embodiments, however, flange 70 could be provided with a slight flare so that it has an increasingly larger outer radius as it projects from disk portion 66. Such a flare would increase the interference fit between flange 70 and interior surface 174 at the projecting end of flange 70 which would be biased radially inwardly by interior surface 174 and thereby enhance the press-fit engagement of flange 70 with interior surface 124 and the fluid tight seal formed between flange 70 and interior surface 124.
The operation of reservoir assembly 120 will now be discussed. Hydraulic fluid enters fluid chamber 128 through inlet 130 substantially tangential with respect to a cylinder centered on axis 123 and within the inlet zone 128b between baffle member 62 and filter element 64. This fluid inflow sets up a rotating flow of fluid within fluid chamber 128 within inlet zone 128b. As a result of the rotating fluid flow, the lighter components of the fluid, most importantly entrained air, migrate toward central area 88 of inlet zone 128b located below and proximate central opening 68 in baffle member 62. The entrained air then migrates upwardly through opening 68 into the upper zone 128a where it enters the air filled head space above hydraulic fluid surface 138 thereby deaerating the hydraulic fluid. The fluid tight seal between flange 70 and interior surface 174 of reservoir housing 124 prevents the communication of fluid motion from inlet zone 128b to upper zone 128a along the outer circumference of fluid chamber 128 where the rotating fluid within inlet zone 128b has its greatest velocity. The fluid in the central area 88 of inlet zone 128b will have a smaller velocity and the presence of connecting members 76 partially partitions inlet zone 128b contributes to the reduced motion of fluid at the center of inlet zone 128b. With regard to the interaction of connecting members 76 and the fluid flow within inlet zone 128b, it is further noted that connecting members form portions of a circular arc centered on axis 123 to thereby minimize any turbulence that such members may produce in the rotating fluid. It is also noted that connecting members 76 have a radially outwardly projecting section at the top of each member 76 so that opening 68 and central zone 88 include not only that portion of inlet zone radially inwardly of connecting members 76 but also a small portion of inlet zone 128b positioned radially outwardly of the axially extending section of connecting members 76. Thus, entrained air can escape through opening 68 from central area 88 of the inlet zone 128b into the upper zone 128a without necessarily having to pass radially inwardly of connecting members 76.
Fluid must pass through mesh filter elements 86 to enter the lower zone 128c of fluid chamber 128 where outlet 134 is located. As the hydraulic system draws fluid from reservoir assembly 120, hydraulic fluid is discharged through outlet 134 drawing additional hydraulic fluid through filter elements 86.
In other embodiments, a fluid tight seal may be formed between the baffle member and the reservoir housing using methods instead of, or in addition to, the press-fit engagement of flange 70 and reservoir housing 124 described above. Several such alternative embodiments are illustrated in
In
While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles.
