Title: Parallel shaft reduction gear
Abstract: A parallel shaft reduction gear with a backstop mechanism superior in replacement and maintenance operations is provided. The parallel shaft reduction gear that is used in combination with a motor and equipped in a gear case with primary-stage shafts which are disposed axially parallel to an output shaft. The output shaft and the primary-stage shaft are rotatably supported by bearings on the motor side and on the opposite side of the motor side with respect to the gear case, respectively. The backstop mechanism that prevents reverse rotation of the output shaft is installed in any one of the output shaft and the primary-stage shaft on the axially outside of the corresponding opposite motor side bearing (lower side in the figure).
Patent Number: 6,845,857 Issued on 01/25/2005 to Matsuo, et al.
| Inventors:
|
Matsuo; Naoki (Kurashiki, JP);
Saiki; Kazunari (Kurashiki, JP)
|
| Assignee:
|
Sumitomo Heavy Industries, Ltd. (Tokyo, JP)
|
| Appl. No.:
|
423032 |
| Filed:
|
April 25, 2003 |
Foreign Application Priority Data
| Apr 26, 2002[JP] | 2002-126299 |
| Current U.S. Class: |
192/223; 74/411.5 |
| Intern'l Class: |
F16H 001/02; B60K041/26 |
| Field of Search: |
74/412 R,411.5,414
192/223,223.2
|
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Bonck; Rodney H.
Attorney, Agent or Firm: Squire, Sanders & Dempsey L.L.P.
Claims
What is claimed is:
1. A parallel shaft reduction gear used in combination with a motor,
comprising:
an output shaft;
at least one primary-stage shaft disposed in a gear case, the primary-stage
shaft being parallel to the output shaft;
a backstop mechanism for preventing reverse rotation of the output shaft;
an opposite motor side bearing for rotatably supporting an opposite motor
side of the output shaft, the opposite motor side being an opposite side
of a side on which the motor is attached to the gear case; and
an opposite motor side bearing for rotatably supporting an opposite motor
side of the primary-stage shaft; wherein
the backstop mechanism is installed in any one of the output shaft and the
primary-stage shaft at a position further from the motor than the
corresponding opposite motor side bearing of the shaft on which the
backstop mechanism is installed and, wherein
the corresponding opposite motor side bearing of the shaft equipped with
the backstop mechanism is assembled at a first position along a first axis
defined as being parallel to a longitudinal axis of the output shaft,
wherein an opposite motor side bearing of the other one of the shafts
which is parallel to the shaft equipped with the backstop mechanism is
located at a second position along the first axis, and wherein the first
position is closer to the motor than the second position.
2. A parallel shaft reduction gear used in combination with a motor,
comprising:
an output shaft;
at least one primary-stage shaft disposed in a gear case, the primary-stage
shaft being parallel to the output shaft;
a backstop mechanism for preventing reverse rotation of the output shaft;
an opposite motor side bearing for rotatable supporting an opposite motor
side of the output shaft, the opposite motor side being an opposite side
of a side on which the motor is attached to the gear case;
an opposite motor side bearing for rotatably supporting an opposite motor
side of the primary-stage shaft; and
an oil pump for circulating an oil in the parallel shaft reduction gear,
the oil pump being installed in the shaft equipped with the backstop
mechanism, wherein the backstop mechanism is disposed between the oil pump
and the corresponding opposite motor side bearing, wherein
the backstop mechanism is installed in any one of the output shaft and the
primary-stage shaft at a position further from the motor than the
corresponding opposite motor side bearing of the shaft on which the
backstop mechanism is installed.
3. The parallel shaft reduction gear according to claim 2, wherein the gear
has an installation face in a part of a face equipped with the oil pump,
and the oil pump is disposed axially inward than the installation face.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to parallel shaft reduction gears used in,
for example, cooling tower fan drives, and particularly to a parallel
shaft reduction gear equipped with a backstop mechanism for preventing
reverse rotation of the output shaft thereof.
2. Description of the Related Art
There are parallel shaft reduction gears each used together with a motor
and equipped with a backstop mechanism such as a one-way clutch for
preventing reverse rotation of the output shaft thereof.
FIG. 4 is a fragmentary enlarged view illustrating a sprag type one-way
clutch as an example of the backstop mechanism.
This one-way clutch 100 is a publicly-known mechanism, having cams 106 in
between an inner ring 102 and an outer ring 104. If the outer ring 104 is
secured to a casing (not shown), the rotation of the inner ring 102 is
limited to one direction (direction R in the figure), and the cams 106
prevent the reverse rotation of the inner ring 102.
If such a backstop mechanism capable of limiting the direction of rotation
is installed in one of the rotary shafts constituting the reduction gear,
the reverse rotation of the output shaft is prevented and only rotation of
the normal direction is transmitted to the target object to be driven.
Conventional parallel shaft reduction gears equipped with such a backstop
mechanism are, however, not designed to provide easy maintenance for the
backstop mechanism. For replacing/repairing the backstop mechanism, the
motor and other peripheral hardware must be all removed, and changeover
and maintenance are not easy to perform.
SUMMARY OF THE INVENTION
The present invention has been made to solve these problems, and one object
of the present invention is to provide a parallel shaft reduction gear
equipped with a backstop mechanism that is easy to replace and maintain.
The present invention provides a parallel shaft reduction gear that is used
in combination with a motor and has at least one primary-stage shaft
disposed axially parallel to an output shaft in a gear case. The output
shaft and the primary-stage shaft are rotatably supported by bearings on
the motor side and on the opposite side of the motor side with respect to
the gear case, respectively. A backstop mechanism for preventing reverse
rotation of the output shaft is installed in any one of the output shaft
and the primary-stage shaft on axially outside of the corresponding
opposite motor side bearing.
According to the invention, since the backstop mechanism is installed on
the opposite side of the motor beyond the bearing outwardly, the
installation/removal of the motor, which is rather time and labor
consuming, becomes unnecessary when replacing/repairing the backstop
mechanism. Thus, it is possible to provide a parallel shaft reduction gear
of which backstop mechanism is easy to replace and maintain.
If the reduction gear further includes an oil pump, which circulates oil in
the parallel shaft reduction gear, in the shaft equipped with the backstop
mechanism, and if the backstop mechanism is disposed between the oil pump
and the opposite motor side bearing, the backstop mechanism can be
replaced/repaired only by removing the oil pump that is easy to install
and remove.
If the backstop mechanism is installed in the shaft disposed most upstream
to the input side among a plurality of the primary-stage shafts (namely,
the input shaft), the backstop mechanism is installed in the shaft that
rotates at the lowest torque. Because the load applied to the backstop
mechanism from the rotary shaft is reduced, even a small backstop
mechanism can sufficiently prevent reverse rotation. Then the backstop
mechanism is downsized, and its production cost is reduced.
Furthermore, it is also preferable that the opposite motor side bearing of
the shaft equipped with the backstop mechanism is assembled inwardly than
the opposite motor side bearing of the other one of the shafts which is
parallel to the shaft equipped with the backstop mechanism. It is also
preferable that the gear case has an installation face in a part of a face
equipped with the oil pump, and the oil pump is disposed axially inward
than the installation face. Then, the backstop mechanism or the oil pump
need not project from the installation face of the parallel shaft
reduction gear, even when the backstop mechanism and the oil pump are
disposed in the shaft on the axially outside of the bearing on the
opposite side of the motor. Therefore, it becomes easy to carry and mount
the parallel shaft reduction gear.
If a small-diameter part is formed on the shaft equipped with the backstop
mechanism, which part is smaller than the inner diameter of the opposite
motor side bearing of the shaft and positioned on the axially outside of
the opposite motor side bearing, and if the backstop mechanism is
installed in this small-diameter part, the backstop mechanism can be
downsized without sacrificing the reverse rotation preventing function.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a sectional side view of a parallel shaft reduction gear
according to an embodiment of the invention;
FIG. 2 is an enlarged partial view of the vicinity of the backstop
mechanism of FIG. 1;
FIG. 3A is a front view of the backstop mechanism of FIG. 1, FIG. 3B is a
sectional view taken along the line IIIB--IIIB in FIG. 3A; and
FIG. 4 is an enlarged partial view of a sprag type one-way clutch.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now the preferred embodiments of the invention will be described with
reference to the accompanying drawings.
FIG. 1 is a sectional side view illustrating a parallel shaft reduction
gear 200 according to the embodiment of the invention.
The parallel shaft reduction gear 200 has an input shaft 204 (first
primary-stage shaft) coupled with the shaft of a motor (not shown), an
intermediate shaft 206 (second primary-stage shaft), and an output shaft
208.
The input shaft 204 is supported by a motor side bearing 220 (namely, one
of the bearings 220, 221 rotatably supporting the input shaft 204,
disposed on the side (upper side in FIG. 1) where the motor is installed),
and an opposite motor side bearing 221 disposed on the opposite side of
the motor side bearing 220 (lower side in FIG. 1). This input shaft 204
can rotate around a shaft center L1. Further, the input shaft 204 has a
first gear 210, an oil pump OP, and a backstop mechanism 202. The
peripheral structure of the backstop mechanism 202 will be described
later.
The intermediate shaft 206 is rotatably supported by a motor side bearing
222 and an opposite motor side bearing 223, and can rotate around a shaft
center L2 that is parallel to the shaft center L1 of the input shaft 204.
The intermediate shaft 206 has a large second gear 212 that meshes with
the first gear 210 assembled on the input shaft 204, and a third gear 214
which is smaller in diameter than that of the second gear 212.
The output shaft 208 is rotatably supported by a motor side bearing 224 and
an opposite motor side bearing 225, and can rotate around a shaft center
L3 that is parallel to the shaft center L1 of the input shaft 204. The
output shaft 208 has a fourth gear 216 that meshes with the third gear 214
assembled on the intermediate shaft 206.
These shafts (input shaft 204, intermediate shaft 206, and output shaft
208) and gears 210, 212, 214, and 216 are housed in a gear case 219 which
comprises an upper casing 217 and a lower casing 218.
The installation position S1 of the opposite motor side bearing 221 of the
input shaft 204 and the installation position S2 of the opposite motor
side bearing 223 of the intermediate shaft 206 are assembled inwardly in
the axial direction L1, L2, than a position S3 where the opposite motor
side bearing 225 of the output shaft 208 is seated (upper side in FIG. 1).
The lower casing 218 has a recess part 218b inward from the installation
face 218a of the parallel shaft reduction gear 200, according to the
positions S1, S2 of the opposite motor side bearings 221, 223. The
position S4 of the recess part 218b is axially inward than the position S5
of the installation face 218a. Furthermore, the installation position S6
of the oil pump OP is also inward in the axial direction than the position
S5 of the installation face 218a.
Now the backstop mechanism 202 is described in detail with reference to
FIGS. 2 and 3. FIG. 2 is an enlarged partial view illustrating the
vicinity of the backstop mechanism 202 of the parallel shaft reduction
gear 200 shown in FIG. 1. FIG. 3A is a front view of the backstop
mechanism 202, and FIG. 3B is a sectional view taken along the line
IIIB--IIIB in FIG. 3A.
The backstop mechanism 202 is disposed between the opposite motor side
bearing 221 of the input shaft 204 and the oil pump OP. The backstop
mechanism 202 is installed in a small-diameter part 204a on the lower end
side (lower side in FIG. 2) of the input shaft 204. More specifically, the
upper part 202h of the outer ring 202a of the backstop mechanism 202 is in
contact with a spacer 237 disposed under the opposite motor side bearing
221 of the input shaft 204. The lower part 2021 of the backstop mechanism
202 is in contact with an installation cover 234 of the oil pump OP. This
installation cover 234 is fastened with bolts 235 to the lower casing 218.
The movable part 236 of the oil pump OP is connected to the input shaft 204
with driver pins 232, while the fixed part 240 is fastened to the
installation cover 234 with bolts 239.
In this example, the backstop mechanism 202 is what is called the sprag
type, mainly comprises an outer ring 202a, an inner ring 202b, a snap ring
202c, and a cam 202d.
The outer ring 202a is in contact with the lower casing 218. The inner ring
202b is connected to the input shaft 204 with a key 238, and can rotate
together with the input shaft 204 around the shaft center L1.
A cam 202d is disposed between the outer ring 202a and the inner ring 202b.
The cam 202d works on the outer ring 202a to cause deformation there, so
that the outer ring 202a is fastened to the lower casing 218. The inner
ring 202b can rotate only in one direction (direction R1 in FIG. 3A)
against the fixed outer ring 202a, while cannot rotate in the opposite
direction (direction R2 in FIG. 3A).
Next the operation of the parallel shaft reduction gear 200 according to
the embodiment of the invention is explained.
As the motor rotates, the input shaft 204 connected to the motor shaft and
the first gear 210 on the input shaft 204 rotate around the shaft center
L1. As the first gear 210 rotates, the second gear 212 engaging with the
first gear 210 and the third gear 214 on the intermediate shaft 206 shared
with the second gear 212 rotate around the shaft center L2. As the third
gear 214 rotates, the fourth gear 216 engaging with the third gear 214 and
the output shaft 208 equipped with the fourth gear 216 rotate around the
shaft center L3. The output shaft 208 thereby transmits torque.
As the input shaft 204 rotates, the inner ring 202b of the backstop
mechanism 202 connected the input shaft 204 rotates together. Then the
rotation of the input shaft 204 is not limited because the inner ring 202b
is set to rotate in the normal direction (direction R1 in FIG. 3A) of the
input shaft 204. Therefore, the torque of the input shaft 204 is all
transmitted to the output shaft 208 via the intermediate shaft 206.
Meanwhile, if a rotational load is applied to the output shaft 208 in the
reverse direction from a device (not shown) to be driven, the torque is
conveyed to the input shaft 204 via the intermediate shaft 206. However,
since the inner ring 202b of the backstop mechanism 202 installed in the
input shaft 204 is configured not to rotate in the reverse direction
(direction R2 in FIG. 3A). As a result, the rotation of the input shaft
204 is restricted, and thereby the reverse rotations of the intermediate
shaft 206 and the output shaft 208 are prevented.
The oil pump OP connected to the input shaft 204 is driven by the rotation
of the input shaft 204 to circulate lubricating oil in the parallel shaft
reduction gear 200.
In general, the oil pump OP is required to be installed in the shaft that
rotates fastest (namely the input shaft 204) for higher operating
efficiency. This requirement may pose a problem to the backstop mechanism
202 of the embodiment. However, by installing the backstop mechanism 202
in between the oil pump OP and the opposite motor side bearing 221, a
sufficient amount of lubricating oil can be provided to the backstop
mechanism 202 which has a mechanically complex structure.
Furthermore, since the backstop mechanism 202 is installed on the axially
outside of the bearing 221 on the opposite side of the motor (lower side
in FIG. 1), the installation/removal of the motor, which is relatively
time and labor consuming, becomes unnecessary when replacing/repairing the
backstop mechanism 202. The backstop mechanism 202 can be
replaced/repaired only by removing the oil pump OP which is easy to remove
and install. Accordingly, a parallel shaft reduction gear 200 equipped
with a backstop mechanism 202 superior in replacement and maintenance
operations can be provided.
The backstop mechanism 202 is installed in the input shaft 204, which
exists most upstream to the input side in the primary-stage shafts (input
shaft 204 and intermediate shaft 206). In other words, the backstop
mechanism 202 is installed in the shaft (204) which can rotate with the
lowest torque. Then the load applied to the backstop mechanism 202 is
relatively low, and thus even a small backstop mechanism 202 can
sufficiently prevent reverse rotation. As a result, the reduction gear can
be downsized.
Furthermore, the opposite motor side bearing 221 of the input shaft 204 and
the opposite motor side bearing 223 of the intermediate shaft 206 are
assembled inwardly in the axial direction L1, L2 (upper side in FIG. 1)
than the opposite motor side bearing 225 of the output shaft 208. Then the
backstop mechanism 202 and the oil pump OP can be incorporated in a space
between the recess part 218b of the lower casing 218 and the installation
face 218a of the parallel shaft reduction gear 200. As a result, the
backstop mechanism 202 or oil pump OP does not project beyond the
installation face 218a, and it thus becomes easy to carry and mount the
parallel shaft reduction gear 200.
A small-diameter part 204a that is smaller than the inner diameter of the
opposite motor side bearing 221 is positioned on the axially outside of
the bearing 221, and the backstop, mechanism 202 is installed in this
small-diameter part 204a. Then the backstop mechanism 202 can be downsized
without loss of the reverse rotation preventing effect.
While the backstop mechanism 202 has been installed in the input shaft 204
in the embodiment, it may be installed in another shaft, for example, the
intermediate shaft 206. Additionally, its position for installation is not
limited to the space between the opposite motor side bearing and the oil
pump, as long as it is disposed on the axially outside of the opposite
motor side bearing.
According to the present invention, it is possible to provide a parallel
shaft reduction gear having a backstop mechanism superior in replacement
and maintenance operations.
*
