Information
-
Patent Grant
-
6652253
-
Patent Number
6,652,253
-
Date Filed
Monday, July 15, 200221 years ago
-
Date Issued
Tuesday, November 25, 200320 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 418 166
- 418 170
- 418 171
- 418 189
-
International Classifications
-
Abstract
An internal/external gear pump includes a wear plate disposed between the gear members and at least one sidewall of the pump. The wear plate has a recess formed therein having a substantially constant depth and width. The recess extends into the full mesh point between the gear members of the pump to provide a flow path from the full mesh point to an inlet side or suction port of the pump.
Description
TECHNICAL FIELD
This invention relates to positive displacement hydraulic pumps and, more particularly, to internal/external gear pumps.
BACKGROUND OF THE INVENTION
Internal/external gear pumps (IX pumps) have an internally toothed gear and an externally toothed gear, which are rotatably mounted in a housing. The externally toothed gear is usually the drive gear, and the internally toothed gear is usually the driven gear. These two gear members have offset rotatable axes and therefore have a single mesh point, which is opposite the maximum offset. When the two gear members are exiting the mesh points, the gear teeth remain engaged for approximately three or four teeth and then separate or are separating during that engagement and create a space between the rotating gear members which is filled with fluid such as hydraulic fluid from a reservoir through a suction port.
The rotation of the gears take the internal/external gears past a crescent or divider which separates the internally toothed member from the externally toothed member and seals flow trapped within the tooth spaces from returning to the inlet port. As the rotation continues, the toothed gear members are directed to come back into mesh, and as the space between the toothed gear members decreases, the fluid found therein is forced to exit through a pressure port. The gear members then, during this fluid exiting procedure, come back into mesh and start about three or four teeth before the full mesh point. There is one full mesh point during the gear rotation. At the full mesh point, the pump body and wear plate form a dam area.
This mesh point, along with the dam area in the body and wear plate, generally forms a boundary between the higher pressure fluid in the discharge port and the low pressure fluid in the intake port. As this mesh point passes across the dam, increasingly more area of the gears is exposed to high pressure building the forces exerted on the gears. The transition of the mesh point into the suction port exhausts the area previously exposed to high pressure, thus generating a force change on the gears which can result in transmission noise that is disturbing to the operator.
Internal/external pumps in the prior art have been known to employ metering grooves for both the inlet port and the discharge port. These metering grooves, however, cannot overlap within the full mesh point without creating excess leakage, which reduces the performance of the pump at its function of fluid transfer. Thus, this noise phenomenon can still occur within IX pumps. In certain environments, noise created by this event can be of concern to the operator. While those skilled in the art know that there is no performance problem, just a slight noise generation, it has still been a desire to eliminate the noise if at all possible.
It is also well known that those skilled in the art find the implementation of noise-reducing grooves difficult to manufacture. These grooves are of a graduated depth, that is, they are very narrow at the outermost point of their depth and they increase in depth as they approach the port with which they intercept. During manufacturing, it is difficult to control the dimensions of the depth and thus they are costly to produce within the pump body.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved internal/external gear pump having a noise control recess.
In one aspect of the present invention, the full mesh point of the IX pump is intercepted by a recess, which is communicated with the inlet port of the IX pump.
In another aspect of the present invention, the recess is positioned in a wear plate, which is disposed within a pump housing.
In yet another aspect of the present invention, the wear plate is sufficiently large to encompass the maximum portion of the pump housing covering both the internal/external gears as well as a portion of the outer flange of the housing.
In still another aspect of the present invention, the full mesh point is a dam area, which prevents fluid communication between the pressure port and the suction port.
In yet still another aspect of the present invention, the recess intersects the dam area at a location wherein the fluid communication is only between the dam area and the suction port.
In a further aspect of the present invention, the noise recess has a substantially constant width and depth.
DESCRIPTION OF THE DRAWINGS
FIG. 1
is an elevational view partly in section of a portion of a transmission mechanism having a hydraulic control pump.
FIG. 2
is view taken along line
2
—
2
of
FIG. 1
showing the internal components of the pump shown in FIG.
1
and incorporating the present invention.
FIG. 3
is an enlarged view of the area of the pump shown in the circle
3
of FIG.
2
.
FIG. 4
is a view taken along line
4
—
4
of FIG.
3
.
FIG. 5
is a view taken along line
5
—
5
of FIG.
4
.
DESCRIPTION OF AN EXEMPLARY EMBODIMENT
Referring to the drawings, wherein like characters represent the same or corresponding parts throughout the several views, there is seen in
FIG. 1
a transmission housing
10
to which is secured a pump
12
. The pump
12
has a body or housing
14
, which is secured to the housing
10
by a plurality of fasteners
16
. The transmission housing
10
also rotatably supports a shaft member
18
, which passes through the housing
10
and also through the housing
14
of the pump
12
.
As seen in
FIG. 2
, the pump
12
includes an externally toothed gear member
20
and an internally toothed gear member
22
. The gear member
20
has a plurality of teeth
24
formed on the outer periphery thereof, and the gear member
22
has a plurality of teeth
26
formed on the internal periphery thereof. The gear member
20
is rotatably connected with the shaft
18
such that when the shaft
18
rotates, the gear
20
also rotates. The gear
20
has a plurality of teeth
24
A through
24
F that are disposed in meshing relationship with teeth
26
A through
26
F. The tooth
24
C is fully engaged between the teeth
26
B and
26
C within a dam area
28
.
The gear
22
is rotatably supported in a recess
30
formed in the housing
14
. The gear
22
rotates about an axis
32
, which is offset from an axis
34
of the gear
20
and the shaft
18
. This offset is most noticeable at each position opposite the dam area
28
. The separation of the two gears is filled at least partially by a crescent member
36
, which is generally ensuing engagement with the teeth
24
of the gear
20
and the teeth
26
of the gear
22
.
As can be seen in
FIG. 2
, the teeth
24
separate from teeth
26
in an area
38
, and these teeth are also separated in an area
40
. The dam area
28
separates these areas
38
and
40
on one side and the crescent member
36
separates these areas
38
and
40
on the opposite side. The area
38
is an inlet or suction port area, and the area
40
is a discharge or pressure port. These ports are defined by the rotational direction of the gear
20
, which is in the direction of arrow
42
.
As the externally toothed gear
20
operates in the direction of arrow
42
, the internally toothed gear
22
is driven thereby. As seen in
FIG. 2
, these separate from the suction port
38
such that fluid is drawn from a reservoir, not shown, into the suction port
38
to fill the space between the teeth
24
and
26
. As the gear continues to rotate and the gear members reach the pressure port
40
, the teeth are coming into mesh such that the fluid found in this area is discharged from the pump to be supplied to a pressure control and other elements for a transmission. As the pump enters the dam area
28
, the teeth
24
and
26
come into a more complete meshing engagement such that in the dam area the tooth
24
C is fully engaged in the teeth
26
B and
26
C leaving a minimum clearance at the tips of the teeth.
The pump
12
has a wear plate
44
disposed between the transmission housing
10
and the gears
20
and
22
as well as the housing
14
. The wear plate
44
has an opening
46
for the inlet or suction port
38
and an opening
48
for the discharge or pressure port
40
. The wear plate
44
also has a recess
50
, which is interconnected with the suction port opening
46
.
As best seen in
FIGS. 4 and 5
, the recess
50
has a substantially constant width W and a substantially constant depth D. The recess
50
does have a rounded end
52
, which is in place for ease of manufacturing. As seen in
FIG. 2
, the recess
50
extends substantially halfway through the mesh point in the dam area
28
between the gear tooth
24
C and the gear teeth
26
D and
26
C.
Those skilled in the art will recognize that any fluid trapped between the teeth
24
C and
26
B and
26
C will be communicated with the recess
50
. This is best seen in the enlarged view of FIG.
3
. As the gears come into full mesh, the fluid trapped between the outer periphery
54
of the gear teeth
24
C and an inner periphery
56
of a space between gear teeth
26
B and
26
C will be compressed by this meshing engagement. Without the deployment of the recess
50
, the pressure in the fluid will become extremely high creating separating forces on the gears
20
and
22
. These forces would, of course, be employed by the bearings on which these gear members are supported. However, this increased pressure can produce a noise due to the increased engagement force.
Noise is also produced when the gear teeth begin to separate as shown with the engagement between the tooth
24
D and the space between the teeth
26
C and
26
D. When this occurs, the fluid is rapidly expanded into the inlet port
38
, again producing noise. The recess
50
intercepts this fluid between the peripheries
54
and
56
to prevent the increased pressure and simultaneously port the fluid to the inlet port
38
. This prevents the high-pressure generation and thereby eliminates the noise associated therewith.
The gear teeth
24
B,
26
B, and
26
A prevent excess fluid from the pressure port
40
from flowing into the inlet port
38
. It will also be noted that there are other gear teeth besides
26
A and
26
B which cooperate to prevent this backflow of fluid. Those skilled in the art will recognize if the mesh engagement between tooth
24
C and tooth
26
C progresses in the direction of rotation, the next set of meshing teeth
24
B,
26
B, and
26
A will rotate into full mesh at the dam area
28
, thereby providing a fluid connection between the recess
50
and an outer periphery
60
of tooth
24
B and an outer periphery
62
and the tooth space between the gear teeth
26
A and
26
B. Thus, the entering of meshing teeth into the dam area will continually revolve as the pump is operated.
While the pump is shown as having a single wear plate disposed between the transmission housing
10
and the pump housing
14
, it is also possible to put a wear plate within the cavity in the housing
14
in which the gears
20
and
22
are disposed therebetween and providing a recess on both sides of the dam area, which can improve the efficiency of the fluid flow between the meshing teeth.
The recess
50
is formed below a face
64
of the wear plate
44
. The recess
50
, as seen in
FIGS. 4 and 5
, has a constant width W and depth D which provide for simplicity and consistency in manufacture. The wear plate
44
is a thin member permitting the recess
50
to be formed in the face
64
by a coining or stamping process, which are well-known simple manufacturing expedients.
Obviously, modifications and variations are possible in light of the above disclosure. Therefore, it should be understood that the invention is only to be limited by the scope of the appended claims.
Claims
- 1. An internal/external gear pump comprising:an externally toothed gear member; an internally toothed gear member; an inlet port admitting fluid to said pump; an outlet port discharging fluid from said pump at an elevated pressure; said toothed gear members having a mesh area wherein the external and internal teeth enter into and retract from an intermeshing relationship, said internally toothed gear member and said externally toothed gear member having a full mesh position between said inlet port and said outlet port within the mesh area wherein one tooth of the externally toothed member is fully meshed in a space between two teeth of said internally toothed gear member defining a volume of trapped fluid; one side of said full mesh position axially defining an inlet portion of said pump and another side of said full mesh position defining a pressure portion of said pump; a sidewall disposed adjacent said gear members defining one closure wall for said pump; and a recess formed in said sidewall extending from said inlet port to a leading edge of said trapped volume in said full mesh position to establish a restricted flow path between said volume of trapped fluid and said inlet port.
- 2. The internal/external gear pump defined in claim 1 further comprising:said recess having a substantially constant depth and a substantially constant width.
- 3. The internal/external gear pump defined in claim 2 further wherein each tooth of said externally toothed gear member has an outer periphery that comes in close proximity to an outer periphery between adjacent teeth of said internally toothed gear member to form a closed chamber, within the mesh area, to both said input port and said output port and said closed chamber being vented to said inlet port by said recess.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
4767296 |
Satomoto et al. |
Aug 1988 |
A |
4897025 |
Negishi |
Jan 1990 |
A |
6089841 |
Meernik et al. |
Jul 2000 |
A |