Rotary machine with cooling jacket including helical groove
An example rotary machine includes a motor including a rotor and a stator, and a cooling jacket disposed around the stator. The cooling jacket includes an inner body part being cylindrical and in contact with the stator, an outer body part being cylindrical and surrounding the inner body part, and a groove through which a cooling medium passes, the groove circling helically around an outer circumference of the inner body part at least once. The groove has a pair of side surfaces opposed in a direction of an axis of rotation of the rotor, and a bottom surface connected to each of the pair of side surfaces. Each of the pair of side surfaces is formed having a draft angle inclined away from each other, the draft angle inclined relative to a release direction orthogonal to the axis of rotation.
1. A rotary machine comprising:
a motor including a rotor and a stator; and
a cooling jacket disposed around the stator, wherein the cooling jacket includes:
a cylindrical inner body part in contact with the stator and comprising an outer circumferential surface that defines an outer diameter of the inner body part;
a cylindrical outer body part surrounding the inner body part; and
a helical groove formed in the outer circumferential surface of the inner body part and configured to transmit a cooling medium, the helical groove circling helically at an oblique angle around the inner body part a plurality of times,
wherein the helical groove includes a pair of side surfaces opposed to each other in a direction of an axis of rotation of the rotor and a bottom surface, the pair of side surfaces connected to and extending from the bottom surface of the helical groove to the outer circumferential surface of the inner body part,
wherein the inner body part has a virtual region being cylindrical about the axis of rotation, the virtual region having an outer diameter bounded by the bottom surface of the helical groove,
wherein each of the side surfaces is formed having a draft angle that is inclined away from each other, the draft angle determined relative to a direction orthogonal to the axis of rotation, and
wherein the draft angle is larger than the oblique angle of the helical groove and is derived using formula (1) under the condition of formula (2),
[
Formula
1
]
atan
[
(
D
1
-
D
2
)
/
2
tan
S
D
1
/
2
sin
{
acos
(
D
2
/
D
1
)
}
]
atan
(
P
π
D
1
)
>
1
[
Formula
2
]
(
1
)
(
D
1
-
D
2
)
tan
S
+
B
<
P
(
2
)
where S is the draft angle, D 1 is the outer diameter of the inner body part, D 2 is the outer diameter of the virtual region, P is an array pitch of the helical groove in the direction of the axis of rotation, and B is a width of the bottom surface in the direction of the axis of rotation.
2. The rotary machine according to claim 1 ,
wherein the bottom surface of the groove is substantially flat and extends in the direction of the axis of rotation.
3. The rotary machine according to claim 1 ,
wherein the draft angle is equal to or greater than approximately seven times the oblique angle of the helical groove, and
wherein the draft angle is equal to or less than 25°.
4. The rotary machine according to claim 1 , further comprising:
a rotating shaft that includes the rotor;
a compressor housing fixed to the cooling jacket; and
a compressor impeller accommodated inside the compressor housing and fixed to the rotating shaft.
5. The rotary machine according to claim 4 , further comprising a bearing located between the rotor and the compressor impeller.
6. The rotary machine according to claim 5 , wherein the inner body part includes a tubular portion holding the bearing.
7. The rotary machine according to claim 4 ,
wherein the inner body part includes an annular cover portion facing a coil end of the stator, and
wherein the outer body part includes an annular base portion contacting the annular cover portion and fixed to the compressor housing.
8. The rotary machine according to claim 7 ,
wherein the inner body part includes a tubular portion holding a second bearing supporting the rotating shaft, and
wherein the annular base portion is in contact with the annular cover portion.
9. The rotary machine according to claim 8 , wherein the outer body part further includes a cylindrical body portion surrounding the inner body part and a lid portion disposed opposite the annular base portion so as to block an opening of the cylindrical body portion.
10. The rotary machine according to claim 9 , wherein the lid portion includes a cylindrical bearing holding portion holding the second bearing, the second bearing supporting the rotating shaft.
11. A method for manufacturing the inner body part of the rotary machine according to claim 1 , the method comprising:
clamping a mold including at least one die, an inner surface of the die forming part of a helical projection circling helically at the oblique angle inside the mold, wherein the helical projection includes a pair of side surfaces, wherein each of the side surfaces of the helical projection is formed having a draft angle, the draft angle determined relative to a direction orthogonal to a longitudinal direction of the mold;
filling an inner cavity of the mold with molten metal;
solidifying the molten metal to form the inner body part of the rotary machine; and
separating the mold in the orthogonal direction, wherein the draft angle is equal to or greater than approximately seven times the oblique angle and equal to or less than 25° to facilitate a release of the inner body part from the die.
12. The method according to claim 11 ,
wherein the bottom surface of the groove is substantially flat and extends in the direction of the axis of rotation.
13. A rotary machine comprising:
a motor including a rotor and a stator; and
a cooling jacket disposed around the stator, wherein the cooling jacket includes:
a cylindrical inner body part in contact with the stator and comprising an outer circumferential surface that defines an outer diameter of the inner body part;
a cylindrical outer body part surrounding the inner body part; and
a V-shaped groove formed in the outer circumferential surface of the inner body part and configured to transmit a cooling medium, the V-shaped groove circling helically at an oblique angle around the inner body part a plurality of times,
wherein the V-shaped groove includes a pair of side surfaces opposed to each other in a direction of an axis of rotation of the rotor, and the pair of side surfaces are directly connected to each other at a bottom of the V-shaped groove,
wherein the pair of side surfaces extend from the bottom of the V-shaped groove to the outer circumferential surface of the inner body part,
wherein the inner body part has a virtual region being cylindrical about the axis of rotation, the virtual region having an outer diameter bounded by the bottom of the V-shaped groove,
wherein each of the side surfaces is formed having a draft angle that inclined away from each other, the draft angle determined relative to a direction orthogonal to the axis of rotation, and
wherein the draft angle is larger than the oblique angle of the V-shaped groove, and is derived using formula (1) under the condition of formula (3),
[
Formula
1
]
atan
[
(
D
1
-
D
2
)
/
2
tan
S
D
1
/
2
sin
{
acos
(
D
2
/
D
1
)
}
]
atan
(
P
π
D
1
)
>
1
[
Formula
3
]
(
1
)
(
D
1
-
D
2
)
tan
S
<
P
(
3
)
where S is the draft angle, D 1 is the outer diameter of the inner body part, D 2 is the outer diameter of the virtual region, and P is an array pitch of the V-shaped groove in the direction of the axis of rotation.
14. The rotary machine according to claim 13 , further comprising:
a rotating shaft that includes the rotor;
a compressor housing fixed to the cooling jacket;
a compressor impeller accommodated inside the compressor housing and fixed to the rotating shaft; and
a bearing that supports the rotating shaft and is located between the rotor and the compressor impeller.
15. The rotary machine according to claim 13 ,
wherein the draft angle is equal to or greater than approximately seven times the oblique angle of the V-shaped groove, and
wherein the draft angle is equal to or less than 25°.
16. A method for manufacturing the inner body part of the rotary machine according to claim 13 , the method comprising:
clamping a mold including at least one die, an inner surface of the die forming part of a helical projection circling helically at the oblique angle inside the mold, wherein the helical projection includes a pair of side surfaces, wherein each of the side surfaces of the helical projection is formed having a draft angle, the draft angle determined relative to a direction orthogonal to a longitudinal direction of the mold;
filling an inner cavity of the mold with molten metal;
solidifying the molten metal to form the inner body part of the rotary machine; and
separating the mold in the orthogonal direction, wherein the draft angle is equal to or greater than approximately seven times the oblique angle and equal to or less than 25° to facilitate a release of the inner body part from the die.