JPH07208327A - Rotary type fluid pressure energy converter with shaft seal - Google Patents

Abstract

PURPOSE: To avoid shutting off of an engine during flight by preventing mixing of hydraulic fluid and blocking of a drain and providing a shaft seal system between a pump and a gear box. CONSTITUTION: An arclike chamber 56 is formed in a flangelike end member 22 of a pump, which has an annular shoulder 58 receiving a baffle 60 having a plate shape. The baffle 60 is engaged with a seal 62 arranged in a groove 64 provided in the end member 22 of the pump. The baffle 60 has a plurality of grooves 68 in the radial direction on its flat face, which form a passage P when they are arranged on the end member 22. When hydraulic fluid leaks across an inner seal 52, leaking hydraulic fluid passes the passage P formed by this groove and enters the arclike chamber 56. The hydraulic fluid collected in the chamber 56 is discharged out of an aircraft through a drip drain system of the aircraft. Consequently, it is possible to prevent mixing of hydraulic fluid which leaks across a seal of the pump and a gear box and has no interchangeability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary fluid pressure energy conversion device provided with a shaft seal, and more particularly to an improved shaft seal structure particularly useful for rotary hydraulic devices such as hydraulic pumps and hydraulic motors. Regarding

[0002]

2. Description of the Related Art A rotary hydraulic machine such as a motor and a pump usually has a housing, a rotary shaft extending from the housing for coupling with an external device, and hydraulic fluid leaking into and out of the housing along the shaft. To prevent
And a shaft seal surrounding the shaft within the housing.
Such seals traditionally include an annular resilient seal ring. In the event of a leak, hydraulic fluid will leak along the shaft in and out of the housing past the seals, resulting in loss of hydraulic fluid and potential contamination. When the pump is mounted on the gearbox of the transmission housing, the hydraulic fluid of the pump may leak into the interior of the transmission or the hydraulic fluid of the transmission may leak into the pump.

In US Pat. No. 5,199,718, a pair of annular elastic seal rings (with garter springs) are longitudinally spaced from each other on an axis. These pair of seal rings provide double protection against hydraulic fluid leakage along the shaft. A fluid passage extends from between these seals to the outside of the housing, and a pressure plug is provided at the outer end of the passage to prevent ingress of contaminants. The pressure of the hydraulic fluid leaking past the first seal is dependent on the holding pressure of the passage plug, for example 1 to 3 psi (6.9
To 21 kPa), hydraulic oil will drip from the housing and the seal will need to be repaired so that the plug will operate and be visible to the user.

In US Pat. No. 5,201,647, a rotary machine includes a housing, a shaft extending from the housing and held for rotation, a bearing carried by the housing and in sealing engagement with the shaft, and hydraulic fluid along the shaft. And a shaft seal to prevent leakage of the air. The shaft seal comprises an annular shell adapted to fit within the housing and is radially spaced from the shaft to enclose the shaft.
At least one, and preferably two, annular resilient seal rings are carried on the shell and extend radially inwardly from the shell for rotational sealing engagement with the shaft. A pressure relief valve is provided having at least one opening extending radially through the shell, and an annular band surrounds the shell outside the opening. The hydraulic fluid pressure forces the band away from the shell, allowing fluid to flow out of the shell and band through the shell opening, while the band moves through the opening and into the shell. And prevent ingress of pollutants and dust.

[0005]

The problem of leakage is a particular concern for aircraft. In the case of aircraft, leaks may result in the need to shut down the aircraft engine.

The hydraulic fluids used in aircraft hydraulic systems are not compatible with the hydraulic fluids used in the gearboxes that drive hydraulic pumps. Since the pump and gearbox are directly coupled, they form a cavity, and if they leak past the shaft seal of any device, the hydraulic fluid is drained into this cavity and mixed there . This cavity typically has a common outboard drain to allow hydraulic oil to drain,
Make sure that the cavity is not filled with hydraulic fluid.

However, when mixed at high temperatures (typical in the aircraft in which these devices are installed), these fluids form solids which can interfere with the outboard drain system. become. Once the drain system is blocked, hydraulic fluid will collect in the cavity. When the hydraulic oil level reaches the position of the gearbox shaft seal, the hydraulic oil enters the gearbox. This is because the gearbox shaft seal holds pressure in only one direction. The liquid level indicator detects a high level when a sufficient amount of hydraulic fluid has entered the gearbox. As part of the aircraft safety system, the engine (which drives its gearbox) is automatically shut off.

The root cause of this potential problem is leaking shaft seals on both the pump and gearbox. This is an industrially versatile problem and is generally considered a "weak link" in all rotary devices. The suboptimal design is to isolate the hydraulic oil, as the available technology for shaft seal design cannot guarantee zero leakage. It is also contemplated to make the hydraulic fluid in the gearbox the same as the hydraulic fluid. However, hydraulic system hydraulic fluids are inferior to gearbox hydraulic fluids, and vice versa.
According to the invention, baffles are provided on the end members of the pump to form a separate cavity between the pump and the gearbox. This prevents both hydraulic fluids from mixing in the event of a leak from the shaft seal. Each cavity also has its own outboard drain to ensure that these hydraulic fluids do not mix before exiting the outboard drain system. This ensures that the engine shuts down in flight due to high liquid levels in the gearbox as a result of leakage of the pump and gearbox shaft seals.

[0009] These guarantees are particularly relevant to the Federal Aviation Administration (Federa).
It is valuable for twin-engine aircraft seeking to obtain Extended Twin Engine Operations (ETOP) rating from Aviation Administration. This is because it eliminates one of the failure modes that results in engine shutdown during flight. In-flight engine shutoff is a more serious problem for aircraft with only two engines, unlike aircraft with three or four engines. This grading is
With normal operation, it allows longer distances on the aircraft. In the event of an emergency, the pilot
Routes must be planned so that they are always within the prescribed flight time from the airports that can be reached during the flight. ET
OP ratings increase this required flight time. The baffle configuration according to the present invention helps a twin-engine aircraft to achieve this class.

It is therefore an object of the present invention to provide a shaft seal system between the pump and the gearbox which eliminates hydraulic fluid mixing and drain blockage, thus avoiding engine shutdown during flight. .

[0011]

SUMMARY OF THE INVENTION In accordance with the present invention, a shaft seal system includes a baffle provided on an end member of a pump adjacent a gearbox and serving to define a hydraulic fluid chamber. The chamber has a passage between the baffle and the end member to allow leaked hydraulic fluid that has passed through the pump seal. The baffle interfaces with a seal contained in the end member of the pump. The baffle preferably carries an outer annular seal that engages the rotary pump shaft.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, the present invention relates to a rotary pump, here shown as a variable displacement pump.

Referring to FIG. 1, an axial piston pump has a housing 10 and a valve plate 14 including a suction port and a discharge port.

The drive shaft 16 includes a bearing 18 at one end of the housing 10 and a bearing 20 of an end member (mounting flange) 22.
Is rotatably supported in the housing 10. The housing 10 has an internal cavity 24 that receives a rotating pump assembly, including a rotatably mounted cylinder barrel 26. Cylinder barrel
The drive spline 16c connects the drive shaft 26 to the drive shaft 16 in a drivable manner.

The cylinder barrel 26 has a plurality of bores 30,
These bores are open at one end to receive piston 32. Each piston 32 is held in that position by a shoe plate 34.

Each shoe 38 has a yoke with an adjustable angle.
When the barrel 26 abuts against the shaft 40 and is rotated by the drive shaft 16, the piston shoe 38 follows the yoke 40 and the bore 30
Reciprocating motion of the piston 32 within occurs.

Each bore 30 has a port opposite its open end, which allows fluid communication between the valve plate 14 and the bore 30. Both the suction port (not shown) and the discharge port (not shown) are formed inside the valve plate 14.

The suction port and the discharge port are arranged so that the piston 32 is pushed away from the valve plate 14 when the piston 32 passes through the suction port and is pushed back to the valve plate 14 when passing through the discharge port. It is located in. These constant-volume pumps
For example, U.S. Pat. No. 5,230,274, and a variable displacement pump is shown in U.S. Pat. No. 3,643,550. The disclosures of both of these are incorporated herein by reference.

As further shown in FIG. 1, the pump includes a rotary impeller 50, which functions to raise the suction pressure as the piston is withdrawn from the valve plate 14 and thus the bore 30. To be filled with hydraulic oil.

The pump shaft 16 is formed by two partial shafts 16a, 16b and comprises an inner seal 52 and an outer seal 54. As shown in FIG. 2, the inner seal 52 and the outer seal 54 engage the partial shaft 16a and the outer partial shaft 16a.
The b extends axially outward to engage the drive spline of the gearbox.

In accordance with the present invention, the flanged end member 22 of the pump (FIG. 2) is formed with an arcuate chamber 56 which is shaped as a plate which is held in place by screws (not shown). An annular shoulder 58 for receiving a baffle 60 having The baffle 60 is the end member 22 of the pump.
It engages a seal 62 (FIG. 2) arranged in a groove 64 provided in (FIG. 4). The baffle 60 has a plurality of radial grooves 68 in its flat surface (FIG. 3) that when placed in the end member 22 form a passage P (FIG. 2). If a leak occurs over the inner seal 52, the leaked hydraulic oil enters the arcuate chamber 56 through the passage P defined by this groove. The hydraulic fluid collected in the chamber 56 is discharged outboard through the drip drain system of the aircraft. This prevents mixing of incompatible hydraulic fluids that have leaked past the pump and gearbox seals.

In the modification shown in FIG. 5, the outer seal 54 is omitted. The baffle 60a is modified so that it does not have a recess for the outer seal. In this configuration, the baffle 60a functions in substantially the same way, but a small amount of leakage may occur between the pump cavity and the gearbox cavity. Therefore, the hydraulic oils may be mixed. This configuration provides a viable alternative if the hydraulic fluids are compatible or compatible.

While the present invention has been shown as applicable to pumps having a rotary assembly of the axial piston type, the present invention is also shown in other types of pumps, such as US Pat. Nos. 3,451,346 and 4,505,654. It is also applicable to such vane pumps. The contents of these patents are incorporated herein by reference.

[0024]

Thus, according to the present invention, a shaft seal system between the pump and the gearbox is provided to eliminate hydraulic fluid mixing and drain blockage, thereby avoiding engine shut down during flight. it can.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a rotary pump embodying the present invention.

2 is a partial enlarged cross-sectional view of the pump shown in FIG. 1, shown with a gearbox interface.

FIG. 3 is a rear plan view of the baffle used in the pump.

FIG. 4 is an end view of the end member of the pump as viewed from the right side of FIG. 2 with the baffle removed.

FIG. 5 is a partial view of a modified form of rotary pump.

[Explanation of symbols]

 10 Housing 16 Drive shaft 16a, 16b Partial shaft 22 End member 26 Cylinder barrel 52 Inner seal 54 Outer seal 56 Chamber 60, 60a Baffle 68 Radial groove P passage

Claims (6)

[Claims] 1. A housing, a drive shaft rotatably supported within the housing, a rotary pump assembly in the housing for driving engagement with the shaft, an inner seal for engaging on the shaft, A partial axis of the shaft extending beyond the housing, a baffle provided on an end member of the housing, at least one chamber defined by the baffle and the end member, the baffle and the end member A fluid pressure energy conversion device defined by and including passage means extending between the seal and the chamber for passage of hydraulic fluid leaking past the inner seal into the chamber. 2. The baffle has a substantially flat surface,
The fluid pressure energy conversion device of claim 1, wherein said passage means comprises a generally radial groove in said baffle cooperating with said end member to define said passage means. 3. The baffle and the end member define a plurality of circumferentially spaced chambers.
Fluid pressure energy converter. 4. The baffle has a substantially flat surface,
4. The fluid pressure energy conversion device of claim 3, wherein said passage means comprises a plurality of generally radially circumferentially spaced grooves in said baffle which cooperate with said end member to define said passage means. 5. A fluid pressure energy conversion device according to any of claims 1 to 4 including an outer seal, said baffle retaining said outer seal. 6. The fluid pressure energy conversion device of claim 5, wherein the rotary pump assembly is of the axial piston type.