66 is connected to the other end of the circulation passage for the coolant described above. The coolant outlet 66 communicates with the groove 52.

The inner peripheral surface 50 is of the small-diameter tube portion 50 of the outer tube component 22 is fitted to the partial outer peripheral surface 28os-2 of the inner tube component 18. Within the inner peripheral surface 49 is of the large-diameter tube portion 49 of the outer tube component 22, a portion between the groove 52 and the groove 54 faces the outer peripheral surface 20os of the cooler 20. The inner peripheral surface 49 is of the large-diameter tube portion 49 of the outer tube component 22 and the outer peripheral surface 20os of the cooler 20 are separated from each other. Specifically, as shown in FIG. 3, the gap G is formed over the entire circumference between the inner peripheral surface 49 is of the large-diameter tube portion 49 of the outer tube component 22 and the outer peripheral surface 20os of the cooler 20. The dimension of the gap G in the radial direction of the housing 12 is set as appropriate.

On the other hand, as shown in FIG. 2, within the inner peripheral surface 49 is of the large-diameter tube portion 49 of the outer tube component 22, a portion closer to the second housing end portion 16 than the groove 52 is in close contact with the outer peripheral surface 26os of the large-diameter tube portion 26 of the inner tube component 18. The outer tube flange 56 provided with the outer tube sealing surface 56ss and the inner tube flange 32 provided with the inner tube sealing surface 32ss are fastened by fastening members such as bolts as described later.

[2-4. Passages for Coolant Inside Housing 12]

A coolant supply passage 68 is formed along the circumferential direction of the housing 12 by the wall surface of the groove 54 of the outer tube component 22 and the partial outer peripheral surface 28os-2 of the inner tube component 18. The shape of the coolant supply passage 68 is an annular shape centered on the axis A. The coolant supply passage 68 is located at the inflow end 46 of the coolant passage 44. That is, the coolant supply passage 68 is disposed at the first end portion 20a of the cooler 20. The coolant supply passage 68 communicates with the coolant inlet 64. Consequently, the coolant passage 44 of the cooler 20 communicates with the coolant inlet 64 via the coolant supply passage 68.

The coolant discharge passage 70 is formed along the circumferential direction of the housing 12 by the wall surface of the groove 52 of the outer tube component 22, the partial outer peripheral surface 28os-1 of the inner tube component 18, and the stepped surface 30 of the inner tube component 18. The shape of the coolant discharge passage 70 is an annular shape centered on the axis A. The coolant discharge passage 70 is located at the outflow end 48 of the coolant passage 44. That is, the coolant discharge passage 70 is disposed at the second end portion 20b of the cooler 20. The coolant discharge passage 70 communicates with the coolant outlet 66. Consequently, the coolant passage 44 of the cooler 20 communicates with the coolant outlet 66 via the coolant discharge passage 70.

The passages for the coolant (the coolant supply passage 68, the coolant passage 44 of the cooler 20, and the coolant discharge passage 70) formed inside the housing 12 are sealed by the O-ring 34 and the O-ring 36.

3. Method for Manufacturing Housing 12

FIG. 4 is a perspective view of the inner tube component 18 and the cooler 20. FIG. 5 is a perspective view of the inner tube component 18, the cooler 20, and the outer tube component 22. The housing 12 is manufactured generally through the following processes. First, each component is formed. Specifically, the inner tube component 18 is formed by forging. The cooler 20 is formed by the AM method. The outer tube component 22 is formed by casting.

As shown in FIG. 4, the thermal grease 72 is applied to the partial outer peripheral surface 28os-1 of the inner tube component 18. The inner peripheral surface 20 is of the cooler 20 is shrink-fitted to the partial outer peripheral surface 28os-1 of the inner tube component 18 to which the thermal grease 72 is applied. The O-ring 34 is mounted on the inner tube sealing surface 32ss of the inner tube component 18. The O-ring 36 is mounted on the partial outer peripheral surface 280s-2 of the inner tube component 18.

As shown in FIG. 5, the inner tube component 18 and the cooler 20 that have been integrated are inserted into the outer tube component 22. The inner peripheral surface 50 is of the small-diameter tube portion 50 of the outer tube component 22 is shrink-fitted to the partial outer peripheral surface 28os-2 of the inner tube component 18. The outer tube flange 56 is superposed on the inner tube flange 32.

A lid member (not shown) closes an opening formed in the first housing end portion 14 of the housing 12. The outer tube flange 56 and the inner tube flange 32 are superposed on each other. Further, the outer tube flange 56 and the inner tube flange 32 are fastened to an attachment object (not shown) by fastening members such as bolts. As a result, an opening formed in the second housing end portion 16 of the housing 12 is closed.

4. Flow of Coolant in Housing 12

The flow of the coolant in the housing 12 will be described with reference to FIG. 2. The coolant flows into the housing 12 from the coolant inlet 64. The coolant flows from the coolant inlet 64 to the coolant supply passage 68. The coolant flows into the coolant passage 44 of the cooler 20 from the inflow end 46 of the coolant passage 44 disposed in the coolant supply passage 68. The coolant flows through the coolant passage 44 from the inflow end 46 toward the outflow end 48. The coolant flows out to the coolant discharge passage 70 from the outflow end 48 disposed in the coolant discharge passage 70. The coolant flows through the coolant discharge passage 70 and flows out of the housing 12 from the coolant outlet 66.

5. Advantageous Effects Obtained by Housing 12 of Present Disclosure

In the housing 12 described above, the cooler 20 that defines the coolant passage 44 of the housing 12, the outer tube component 22 that constitutes the outer peripheral portion of the housing 12, and the inner tube component 18 that constitutes the inner peripheral portion of the housing 12 are constituted by separate components. Therefore, the cooler 20, the outer tube component 22, and the inner tube component 18 can be manufactured separately. For example, the outer tube component 22 and the inner tube component 18 can be manufactured by casting or forging which gives strength, and the cooling components (the ribs 74) can be manufactured by the AM method which can form a fine and complicated shape. Therefore, it is possible to provide the housing 12 having high strength and high cooling performance. That is, according to the above disclosure, it is possible to provide the suitable housing 12.

In the housing 12 described above, the cooler 20 is disposed between the outer tube component 22 and the inner tube component 18. As a result, the cooler 20 is protected by the outer tube component 22 and the inner tube component 18.

In the housing 12 described above, the gap G is formed between the inner peripheral surface 49 is of the large-diameter tube portion 49 of the outer tube component 22 and the outer peripheral surface 20os of the cooler 20. That is, the cooler 20 does not contact the outer tube component 22. Therefore, the external force acting on the outer tube component 22 is less likely to be transmitted to the cooler 20 accommodated in the outer tube component 22. Therefore, the cooler 20 is less likely to be damaged.

6. Internal Structure of Cooler 20

The internal structure of the cooler 20 provided in the housing 12 will be described below. As described above, the cooler 20 includes the inner peripheral tube portion 40 (base material) and the outer peripheral tube portion 42. The coolant passage 44 is disposed between the inner peripheral tube portion and the outer peripheral tube portion 42. As will be described later, the plurality of ribs 74 are disposed in the coolant passage 44. As will be described later, the plurality of ribs 74 generate turbulence in the coolant in the coolant passage 44, thereby improving the cooling performance of the cooler 20. Further, as will be described later, the plurality of ribs 74 increase the surface area of the cooler 20 that can be in contact with the coolant, thereby improving the cooling performance of the cooler 20. There are several possible modes of the arrangement and the posture of the ribs 74 in the coolant passage 44. Several modes of the cooler 20 in which the arrangements and the postures of the ribs 74 are different will be exemplified below.

[6-1. Cooler 20 of First Example]

FIGS. 6 to 8 are schematic views of the inside of the cooler 20 of a first example. Hereinafter, the axial direction of the cooler 20 is defined as a first direction (D1). Further, the circumferential direction of the cooler 20 is defined as a second direction (D2). The second direction (D2) intersects the first direction (D1). Further, the radial direction of the cooler 20 is defined as a third direction (D3). It should be noted that the outer peripheral tube portion 42 is not shown in FIGS. 6 and 8. Although the inner peripheral tube portion 40 and the outer peripheral tube portion 42 are shown as flat in FIGS. 6 to 8, the inner peripheral tube portion 40 and the outer peripheral tube portion 42 are actually curved along the circumferential direction of the cooler 20.

As shown in FIG. 6, the ribs 74 protrude from a main surface 40ms of the inner peripheral tube portion 40 toward the outer peripheral tube portion 42, and are connected to a main surface 42ms (see FIG. 7) of the outer peripheral tube portion 42 (see FIG. 7). In other words, the ribs 74 protrude from the main surface 42ms of the outer peripheral tube portion 42 toward the inner peripheral tube portion 40, and are connected to the main surface 40ms of the inner peripheral tube portion 40. Concerning the shape of the ribs 74, various shapes are conceivable. In the first example, the ribs 74 having a rectangular flat plate shape are illustrated. The ribs 74 are also referred to as fins.

In each of the ribs 74, a portion connected to the main surface 40ms of the inner peripheral tube portion 40 is referred to as a base end 76. In each of the ribs 74, a portion connected to the main surface 42ms of the outer peripheral tube portion 42 is referred to as a protruding end 78.

The plurality of ribs 74 are formed over the entire circumference of the cooler 20. The plurality of ribs 74 are divided into a plurality of rib groups 80. One rib group 80 includes a large number of ribs 74 arranged in the second direction (D2). The plurality of rib groups 80 are adjacent to each other in the first direction (D1). A gap is formed between two rib groups 80 adjacent to each other.

(Rib Group 80a)

In one rib group 80, the ribs 74 in a first posture and the ribs 74 in a second posture are alternately arranged in the second direction (D2). In this instance, for the sake of simplicity, the description will be made focusing on the three ribs 74 included in a rib group 80a. The three ribs 74 illustrated in the example are referred to as a rib 74a (first rib), a rib 74b (second rib), and a rib 74c (third rib). The rib 74b is located between the rib 74a and the rib 74c. Further, the rib 74b is adjacent to the rib 74a and adjacent to the rib 74c. The ribs 74a and 74c are the ribs 74 in the first posture. The rib 74b is the rib 74 in the second posture.

As shown in FIG. 7, a partial passage 82a (first partial passage), which is a part of the coolant passage 44, is defined by the rib 74a, the rib 74b, the inner peripheral tube portion 40, and the outer peripheral tube portion 42. A distance La1 between a base end 76a of the rib 74a and a base end 76b of the rib 74b in the second direction (D2) is larger than a distance La2 between a protruding end 78a of the rib 74a and a protruding end 78b of the rib 74b in the second direction (D2). In the present specification, the distance between the rib 74a and the rib 74b in the second direction (D2) is defined as a width of the partial passage 82a. The width of the partial passage 82a decreases as it is away from the inner peripheral tube portion 40. Therefore, in the partial passage 82a, a difference is generated between the flow velocity of the coolant flowing near the inner peripheral tube portion 40 and the flow velocity of the coolant flowing near the outer peripheral tube portion 42.

As shown in FIG. 7, a partial passage 82b (second partial passage), which is a part of the coolant passage 44, is defined by the rib 74b, the rib 74c, the inner peripheral tube portion 40, and the outer peripheral tube portion 42. A distance La3 between the base end 76b of the rib 74b and a base end 76c of the rib 74c in the second direction (D2) is smaller than a distance La4 between the protruding end 78b of the rib 74b and a protruding end 78c of the rib 74c in the second direction (D2). In the present specification, the distance between the rib 74b and the rib 74c in the second direction (D2) is defined as a width of the partial passage 82b. The width of the partial passage 82b increases as it is away from the inner peripheral tube portion 40. Therefore, in the partial passage 82b, a difference is generated between the flow velocity of the coolant flowing near the inner peripheral tube portion 40 and the flow velocity of the coolant flowing near the outer peripheral tube portion 42.

As shown in FIG. 6, at the position of each rib group 80, the partial passage 82a narrower near the outer peripheral tube portion 42 than near the inner peripheral tube portion 40, and the partial passage 82b wider near the outer peripheral tube portion 42 than near the inner peripheral tube portion 40, are alternately arranged in the second direction (D2). The rib 74 is interposed between the partial passage 82a and the partial passage 82b adjacent to each other.

(Rib Group 80b)

As shown in FIG. 6, the plurality of ribs 74 included in the rib groups 80 other than the rib group 80a are also arranged in the same manner as the plurality of ribs 74 included in the rib group 80a. For example, the plurality of ribs 74 included in a rib group 80b adjacent to the rib group 80a are also arranged in the same manner as the plurality of ribs 74 included in the rib group 80a. It should be noted that the partial passages 82a and 82b at the position of the rib group 80b are eccentric with respect to the partial passages 82a and 82b at the position of the rib group 80a. Here, the arrangement and the posture of the plurality of ribs 74 included in the two rib groups 80 will be described by taking three ribs 74 included in the rib group 80a and two ribs 74 included in the rib group 80b as an example. The two ribs 74 included in the rib group 80b are referred to as a rib 74d (fourth rib) and a rib 74e (fifth rib). The rib 74d is adjacent to the rib 74e. The rib 74d is the rib 74 in the second posture. The rib 74e is the rib 74 in the first posture.

As shown in FIG. 8, a space obtained by virtually extending the partial passage 82a toward the downstream of the coolant is referred to as a first extension space 84a. A space obtained by virtually extending the partial passage 82b toward the downstream of the coolant is referred to as a second extension space 84b. At least a portion of the rib 74d is located in the first extension space 84a. At least a portion of the rib 74e is located in the second extension space 84b.

As shown in FIG. 7, a distance La5 between a base end 76d of the rib 74d and a base end 76e of the rib 74e in the second direction (D2) is different from a distance La6 between a protruding end 78d of the rib 74d and a protruding end 78e of the rib 74e in the second direction (D2).

In FIGS. 6 to 8, the entire rib 74d is located in the first extension space 84a. In FIGS. 6 to 8, the posture of the rib 74d is the same as the posture of the rib 74b. In FIGS. 6 to 8, the entire rib 74e is located in the second extension space 84b. In FIGS. 6 to 8, the posture of the rib 74e is the same as the postures of the ribs 74a and 74c. In FIGS. 6 to 8, the distance La5 is smaller than the distance La6.

It should be noted that a first portion of the rib 74d may be located in the first extension space 84a, and a second portion of the rib 74d may be located in the second extension space 84b. Further, a first portion of the rib 74e may be located in the first extension space 84a, and a second portion of the rib 74e may be located in the second extension space 84b. Further, the posture of the rib 74d may be the same as the postures of the ribs 74a and 74c, and the posture of the rib 74e may be the same as the posture of the rib 74b. In this case, the distance La5 is larger than the distance La6.

As shown in FIG. 8, the partial passage 82b at the position of the rib group 80b is arranged across the first extension space 84a and the second extension space 84b. Similarly, the partial passage 82a at the position of the rib group 80b is arranged across the first extension space 84a and the second extension space 84b.

As shown in FIG. 9, the rib 74d divides the coolant flowing through the partial passage 82a at the position of the rib group 80a into two partial passages 82a and 82b at the position of the rib group 80b. The rib 74e divides the coolant flowing through the partial passage 82b at the position of the rib group 80a into two partial passages 82a and 82b at the position of the rib group 80b.

(Specific Example of Numerical Values Regarding Ribs 74)

FIG. 10 is an enlarged view of a pair of ribs 74 (the ribs 74a, 74c, and 74e in the first posture, and the ribs 74b and 74d in the second posture). The ribs 74a, 74c, and 74e in the first posture are different from the ribs 74b and 74d in the second posture in the direction in which they are inclined with respect to the main surface 40ms (the direction in which they protrude from the main surface 40ms). On the other hand, an inclination angle θ1 of the ribs 74a, 74c, and 74e with respect to the main surface 40ms of the inner peripheral tube portion 40 is the same as an inclination angle θ1 of the ribs 74b and 74d with respect to the main surface 40ms of the inner peripheral tube portion 40. By setting the inclination angle θ1 of the ribs 74 to 3 degrees or more, an appropriate flow velocity difference can be generated between the coolant flowing near the inner peripheral tube portion 40 and the coolant flowing near the outer peripheral tube portion 42 in the partial passages 82a and 82b. On the other hand, when the inclination angle θ1 of the ribs 74 exceeds 45 degrees, the cooling performance of the cooler 20 is significantly reduced. From the above, it is considered that the inclination angle θ1 of the ribs 74 with respect to the main surface 40ms of the inner peripheral tube portion 40 is preferably about 3 to 45 degrees.

From the viewpoint of increasing the surface area of the cooler 20 that can be in contact with the coolant, a thickness T1 of the ribs 74 is preferably thin. As the thickness T1 of the ribs 74 decreases, the number of the ribs 74 that can be formed in the cooler 20 increases. As the number of the ribs 74 increases, the surface area of the cooler 20 that can be in contact with the coolant increases. Therefore, the cooling performance of the cooler 20 is improved. When the thickness T1 of the ribs 74 exceeds 5 mm, the cooling performance of the cooler 20 is significantly reduced. According to the current AM method, the minimum formable thickness is about 0.2 mm. From the above, it is considered that the thickness T1 of the ribs 74 is preferably 0.2 mm or more and 5 mm or less.

From the viewpoint of increasing the surface area of the cooler 20 that can be in contact with the coolant, a separation distance Di1 between a pair of adjacent ribs 74 is preferably small. The separation distance Di1 is the smaller of the distances between the base ends 76 and between the protruding ends 78 of the pair of ribs 74. According to the current AM method, the minimum formable clearance is about 0.1 mm. Therefore, the lower limit of the separation distance Di1 between the pair of adjacent ribs 74 is about 0.1 mm.

(Advantageous Effects Obtained by Cooler 20 of First Example)

According to the first example, a flow velocity difference can be generated in the coolant in one passage (the partial passage 82a, 82b) sandwiched between a pair of ribs 74 adjacent to each other in the second direction (D2). Specifically, in one partial passage 82a, 82b, the flow velocity of the coolant can be changed for each position in the third direction (D3). In addition, in one rib group 80, the flow velocity of the coolant can be changed also between the partial passage 82a and the partial passage 82b adjacent to each other. By generating a flow velocity difference in the coolant flowing in the same direction, turbulence of the coolant is likely to be generated. When the turbulence is generated, the coolant is stirred. Then, unevenness of the temperature of the coolant in the coolant passage 44 is reduced. As a result, the cooling performance of the cooler 20 is improved. That is, according to the first example, it is possible to provide the suitable cooler 20.

According to the first example, the partial passage 82a and the partial passage 82b are alternately arranged in the second direction (D2). This complicates the flow of the coolant, and the turbulence of the coolant is more likely to occur. Therefore, the coolant is stirred, and the unevenness of the temperature of the coolant in the coolant passage 44 is reduced.

According to the first example, the coolant flowing through the partial passage 82a at the position of the rib group 80a is divided into the two partial passages 82a and 82b by the rib 74d at the position of the rib group 80b. Similarly, the coolant flowing through the partial passage 82b at the position of the rib group 80a is divided into the two partial passages 82a and 82b by the rib 74e at the position of the rib group 80b. This complicates the flow of the coolant, and the turbulence of the coolant is more likely to occur. Therefore, the coolant is stirred, and the unevenness of the temperature of the coolant in the coolant passage 44 is reduced.

[6-2. Cooler 20 of Second Example]

FIGS. 11 and 12 are schematic views of the inside of the cooler 20 of a second example. The following description will be focused on the difference between the cooler 20 of the second example and the cooler 20 of the first example. The cooler 20 of the first example and the cooler 20 of the second example are different from each other in the posture of ribs 174.

A portion of each rib 174 that is disposed closer to the inflow end 46 of the coolant passage 44 is referred to as an upstream side end portion 188. A portion of each rib 174 that is disposed closer to the outflow end 48 of the coolant passage 44 is referred to as a downstream side end portion 190.

(Rib Group 180a)

As shown in FIG. 11, in one rib group 180, the ribs 174 in a third posture and the ribs 174 in a fourth posture are alternately arranged in the second direction (D2). In this instance, for the sake of simplicity of description, the arrangement and the posture of the plurality of ribs 174 included in one rib group 180 will be described by taking three ribs 174 included in the rib group 180a as an example. The three ribs 174 illustrated in the example are referred to as a rib 174a, a rib 174b, and a rib 174c. The rib 174b is located between the rib 174a and the rib 174c. Further, the rib 174b is adjacent to the rib 174a and adjacent to the rib 174c. The ribs 174a and 174c are the ribs 174 in the third posture. The rib 174b is the rib 174 in the fourth posture.

As shown in FIG. 12, a partial passage 182a, which is a part of the coolant passage 44, is defined by the rib 174a, the rib 174b, the inner peripheral tube portion 40 (FIG. 2 or the like), and the outer peripheral tube portion 42 (FIG. 2 or the like). A distance Lb1 between an upstream side end portion 188a of the rib 174a and an upstream side end portion 188b of the rib 174b in the second direction (D2) is larger than a distance Lb2 between a downstream side end portion 190a of the rib 174a and a downstream side end portion 190b of the rib 174b in the second direction (D2). The width of the partial passage 182a decreases as it is away from the inflow end 46. Therefore, in the partial passage 182a, a difference is generated between the flow velocity of the coolant flowing near the inflow end 46 and the flow velocity of the coolant flowing near the outflow end 48.

As shown in FIG. 12, a partial passage 182b, which is a part of the coolant passage 44, is defined by the rib 174b, the rib 174c, the inner peripheral tube portion 40, and the outer peripheral tube portion 42. A distance Lb3 between the upstream side end portion 188b of the rib 174b and an upstream side end portion 188c of the rib 174c in the second direction (D2) is smaller than a distance Lb4 between the downstream side end portion 190b of the rib 174b and a downstream side end portion 190c of the rib 174c in the second direction (D2). The width of the partial passage 182b increases as it is away from the inflow end 46. Therefore, in the partial passage 182b, a difference is generated between the flow velocity of the coolant flowing near the inflow end 46 and the flow velocity of the coolant flowing near the outflow end 48.

As shown in FIG. 11, at the position of each rib group 180, the partial passage 182a wider near the inflow end 46 than near the outflow end 48, and the partial passage 182b narrower near the inflow end 46 than near the outflow end 48, are alternately arranged in the second direction (D2). The rib 174 is interposed between the partial passage 182a and the partial passage 182b adjacent to each other.

(Rib Group 180b)

As shown in FIG. 11, the plurality of ribs 174 included in the rib groups 180 other than the rib group 180a are also arranged in the same manner as the plurality of ribs 174 included in the rib group 180a. For example, the plurality of ribs 174 included in a rib group 180b adjacent to the rib group 180a are also arranged in the same manner as the plurality of ribs 174 included in the rib group 180a. It should be noted that the partial passages 182a and 182b at the position of the rib group 180b are eccentric with respect to the partial passages 182a and 182b at the position of the rib group 180a. Here, the arrangement and the posture of the plurality of ribs 174 included in the two rib groups 180 will be described by taking three ribs 174 included in the rib group 180a and two ribs 174 included in the rib group 180b as an example. The two ribs 174 included in the rib group 180b are referred to as a rib 174d and a rib 174e. The rib 174d is adjacent to the rib 174e. The rib 174d is the rib 174 in the third posture. The rib 174e is the rib 174 in the fourth posture.

As shown in FIG. 12, a space obtained by virtually extending the partial passage 182a toward the downstream of the coolant is referred to as a first extension space 184a. A space obtained by virtually extending the partial passage 182b toward the downstream of the coolant is referred to as a second extension space 184b. At least a portion of the rib 174d is located in the first extension space 184a. At least a portion of the rib 174e is located in the second extension space 184b. A distance Lb5 between an upstream side end portion 188d of the rib 174d and an upstream side end portion 188e of the rib 174e in the second direction (D2) is different from a distance Lb6 between a downstream side end portion 190d of the rib 174d and a downstream side end portion 190e of the rib 174e in the second direction (D2).

It should be noted that at least a portion of the rib 174d may be located in the second extension space 184b. Further, at least a portion of the rib 174e may be located in the first extension space 184a.

As shown in FIG. 12, the partial passage 182a at the position of the rib group 180b is arranged across the first extension space 184a and the second extension space 184b. Similarly, the partial passage 182b at the position of the rib group 180b is arranged across the first extension space 184a and the second extension space 184b.

As shown in FIG. 13, the rib 174d divides the coolant flowing through the partial passage 182a at the position of the rib group 180a into two partial passages 182a and 182b at the position of the rib group 180b. The rib 174e divides the coolant flowing through the partial passage 182b at the position of the rib group 180a into two partial passages 182a and 182b at the position of the rib group 180b.

(Specific Example of Numerical Values Regarding Ribs 174)

FIG. 14 is an enlarged view of the pair of ribs 174 (the ribs 174a, 174c, and 174d in the third posture, and the ribs 174b and 174e in the fourth posture). The ribs 174a, 174c, and 174d in the third posture are different from the ribs 174b and 174e in the fourth posture in the direction in which they extend from the inflow end 46 toward the outflow end 48. On the other hand, an inclination angle θ2 of the ribs 174a, 174c, and 174d with respect to an imaginary line B that is parallel to the axis A is the same as an inclination angle θ2 of the ribs 174b and 174e with respect to the imaginary line B. That is, the inclination angles θ2 of the ribs 174a to 174e with respect to the first direction (D1) are the same. By setting the inclination angle θ2 of the ribs 174 to 3 degrees or more, an appropriate flow velocity difference can be generated between the coolant flowing near the inflow end 46 and the coolant flowing near the outflow end 48 in the partial passages