Patent Description:
In recent years, as a semiconductor device for power conversion used for inverter control of a vehicle-mounted battery charger, electronic equipment typified by air-conditioners, air-conditioning equipment, personal computers, and the like, have been improved in performance, heating values of electronic components (a heat generating body) to be installed have been increased. It has been important to cool such electronic components. <CIT> discloses a cooling unit having the features of the preamble of claim <NUM>.

In electric vehicles and plug-in hybrid vehicles, a vehicle-mounted battery charger for charging a battery as a storage battery is installed. Usually, a vehicle-mounted battery charger is provided with a cooling unit to prevent components from being burned out due to a temperature rise during battery charging (see, for example, PTLs <NUM> and <NUM>). In particular, PTL <NUM> discloses a technique for joining a jacket main body as a metallic constituent member and a sealing body by friction stir welding, as a manufacturing method for maintaining water-tightness and air-tightness of a liquid-cooling type cooling unit.

Friction Stir Welding (FSW) is a method for solid-phase welding metal members to each other by moving a rotary tool along a butted portion of metal members while rotating the rotary tool, and by allowing the metal in the butted portion to plastically flow by frictional heat between the rotary tool and the metal members.

A cooling unit according to one aspect of the present disclosure includes:.

In a liquid-cooling jacket disclosed in PTL <NUM>, a jacket main body has a complicated shape, and, therefore is formed of, for example, an aluminum alloy casting material. On the other hand, a product having a relatively simple shape, for example, a sealing body is formed of an aluminum alloy expanded material.

In the case of manufacturing a liquid-cooling jacket by joining members of different types of aluminum alloys, it is common that the rigidity of the jacket main body is higher than that of the sealing body. In this case, when both members are joined by friction stir welding, a stirring pin as a rotating tool receives higher material resistance from the jacket main body than from the sealing body.

Consequently, if the size variation of the jacket main body and the sealing body increases due to, for example, the increase in size of the liquid-cooling jacket, and shape variation occurs, for example, a gap occurs in a butted portion, it becomes difficult to stir different materials in balance by the stirring pin, and a void may be generated in a plasticized region after joining. Herein, the plasticized region is a region in which stirring is carried out by pushing a rotary tool into the butted portion, and a region in which plastically flowing occurs in the peripheral edge by the stirring. In addition, a stress concentration portion is formed in the plasticized region when a water pressure is applied by cooling water flowing in the liquid-cooling jacket. If a void exists in the vicinity of the stress concentration portion, it may cause crack propagation, and the joining strength may be lowered.

An object of the present disclosure is to provide a cooling unit capable of securing the joining strength between a unit main body and a sealing body and having good reliability.

Hereinafter, exemplary embodiments of a cooling unit in accordance with the present disclosure are described with reference to drawings. Note here that the present disclosure is not limited to the below-mentioned exemplary embodiments.

<FIG> are perspective views each showing a configuration of cooling unit <NUM> in accordance with one exemplary embodiment. <FIG> shows a state of cooling unit <NUM> before joining in a exploded view, and <FIG> shows a state of cooling unit <NUM> during joining. <FIG> is a sectional view showing a joined state of cooling unit <NUM>.

As shown in <FIG>, cooling unit <NUM> includes unit main body <NUM> and sealing body <NUM>. Sealing body <NUM> is joined to unit main body <NUM> so as to close opening <NUM> of unit main body <NUM>, and thus, a sealed space in which cooling water flows is formed. Cooling unit <NUM> is provided in, for example, a vehicle-mounted battery charger, and prevents components from being burned out due to a temperature rise during battery charging. Although not shown, cooling unit <NUM> is provided with a circulation channel for allowing a cooling water to circulate in the sealed space.

Unit main body <NUM> is a box member having bottom portion <NUM> and peripheral wall portion <NUM> rising from a peripheral edge of bottom portion <NUM>. Unit main body <NUM> has, for example, a rectangular box shape in a plan view and having a rectangular opening <NUM>. Furthermore, unit main body <NUM> includes stepped portion <NUM> including stepped bottom surface <NUM> and stepped side surface <NUM> on the inner peripheral edge at an opening side of peripheral wall portion <NUM>. Stepped side surface <NUM> is formed so as to rise from stepped bottom surface <NUM> toward opening <NUM>.

Sealing body <NUM> is a flat plate member for closing opening <NUM> and has a size and shape corresponding to opening <NUM>. Sealing body <NUM> is placed on stepped bottom surface <NUM> in a state in which side surface <NUM> of sealing body <NUM> and stepped side surface <NUM> butt each other, and joined to unit main body <NUM> by friction stir welding. Plasticized region <NUM> is formed in a joined portion between unit main body <NUM> and sealing body <NUM>. Unit main body <NUM> is joined to sealing body <NUM> through plasticized region <NUM>. In the friction stir welding, rotary tool <NUM> for friction stir welding is used. Rotary tool <NUM> is formed of, for example, a tool steel, and includes columnar-shaped shoulder portion <NUM>, and stirring pin <NUM> protruding from the lower end surface of shoulder portion <NUM> (see, <FIG>).

according to the invention, void <NUM>, which is generated by friction stir welding, is formed in a unit main body <NUM> side from the center C of plasticized region <NUM>. Specifically, void <NUM> is formed inside peripheral wall portion <NUM> of unit main body <NUM>. That is to say, when cooling water flows and water pressure is applied to cooling unit <NUM>, stress concentration portion <NUM> is formed in a sealing body <NUM> side of plasticized region <NUM>. Void <NUM> is not present in the vicinity of stress concentration portion <NUM>. Therefore, it is possible to prevent crack from developing from void <NUM> as a starting point and deteriorating the joining strength. Plasticized region <NUM> has a length in a first direction along peripheral wall portion <NUM>, and has a width in a second direction perpendicular to the first direction. The center C of plasticized region <NUM> means the center of the width of plasticized region <NUM>.

Herein, even when void <NUM> is positioned in a unit main body <NUM> side from the center C of plasticized region <NUM>, mechanical strength of cooling unit <NUM> may be deteriorated depending on the size of void <NUM>. Thus, it is desirable that the size of void <NUM> be <NUM> or more and <NUM> or less in the direction perpendicular to stepped side surface <NUM> (direction in parallel to bottom portion <NUM>), or <NUM> or more and <NUM> or less in the direction perpendicular to stepped bottom surface <NUM> (direction perpendicular to bottom portion <NUM>). Thus, the mechanical strength of cooling unit <NUM> can be maintained.

The size of void <NUM> is controlled by the size of gap <NUM> formed between sealing body <NUM> and unit main body <NUM>, as well as rotational speed and movement speed of rotary tool <NUM>. For example, when the rotational speed and the movement speed of rotary tool <NUM> are constant, the size of void <NUM> depends on the size of gap <NUM>.

Furthermore, unit main body <NUM> and sealing body <NUM> are formed of, for example, an aluminum alloy. This can provide thermal conductivity and mechanical strength required for cooling unit <NUM>, and reduce the weight of cooling unit <NUM>.

In particular, a first aluminum alloy forming unit main body <NUM> is a material having higher rigidity than a second aluminum alloy forming sealing body <NUM>. Thus, durability of cooling unit <NUM> can be enhanced.

In addition, it is preferable that unit main body <NUM> is formed of an aluminum alloy casting material. Thus, castability, strength, machinability, and the like, of unit main body <NUM> can be enhanced. Furthermore, it is preferable that sealing body <NUM> is formed of an aluminum alloy expanded material. Thus, workability and thermal conductivity can be enhanced.

The above-described cooling unit <NUM> is manufactured by, for example, the following steps. <FIG> show manufacturing steps of cooling unit <NUM>. <FIG> show the mechanism in which void <NUM> is formed in cooling unit <NUM>.

Firstly, as a first step, as shown in <FIG>, unit main body <NUM> is processed to form stepped portion <NUM> at the inner peripheral edge of an opening <NUM> side of peripheral wall portion <NUM>.

Next, as a second step, as shown in <FIG>, sealing body <NUM> is placed on stepped bottom surface <NUM> in a state in which side surface <NUM> of sealing body <NUM> and stepped side surface <NUM> butt each other to form butted portion <NUM> between side surface <NUM> of sealing body <NUM> and stepped side surface <NUM>.

At this time, gap <NUM> is formed between stepped side surface <NUM> and side surface <NUM> of sealing body <NUM> by size variation between unit main body <NUM> and sealing body <NUM>. A width of gap <NUM> is <NUM> or more and <NUM> or less.

Next, as a third step, as shown in <FIG>, rotary tool <NUM> is pushed into butted portion <NUM>, and allowed to move along butted portion <NUM> while being rotated, and friction stir welding is carried out. Note here that positions of the start point and the end point of the friction stir welding need not be on butted portion <NUM>.

Specifically, as shown in <FIG>, a rotating direction R and a travel direction M of rotary tool <NUM> are set such that a unit main body <NUM> side is an advancing side (AS) in the rotating direction R of rotary tool <NUM>, and a sealing body <NUM> side is a retreating side (RS) in the rotating direction R of rotary tool <NUM>. Furthermore, as described below, the rotational speed and the movement speed of rotary tool <NUM> are set so that void <NUM> remains in unit main body <NUM>, and is formed in the peripheral wall portion, outside plasticized region <NUM>.

When rotary tool <NUM> is allowed to move along butted portion <NUM>, the rear part in the traveling direction M of the rotary tool <NUM> is filled by sealing body <NUM> in the retreating side flowing in the rotating direction R. At this time, gap <NUM> is formed between sealing body <NUM> and unit main body <NUM>, so that supply of materials become insufficient, and void <NUM> occurs in the rear part of rotary tool <NUM>.

Void <NUM> moves toward unit main body <NUM> as the advancing side by the rotation of rotary tool <NUM> as shown in <FIG>. Since centrifugal force is generated in void <NUM> as void <NUM> moves toward unit main body <NUM>, void <NUM> is gradually apart from rotary tool <NUM>. Then, the movement speed of void <NUM> becomes slow, and void <NUM> remains in unit main body <NUM> of the advancing side, and is formed outside plasticized region <NUM>.

After rotary tool <NUM> is rotated along butted portion <NUM> once, and then rotary tool <NUM> is pulled out. Thus, joining of unit body <NUM> and sealing body <NUM> is completed. Voids <NUM> are successively formed along the travel direction M of rotary tool <NUM>. A plurality of voids <NUM> may be formed intermittently along the travel direction M of rotary tool <NUM>. In the steps mentioned above, in cooling unit <NUM>, plasticized region <NUM> is formed along butted portion <NUM>. Furthermore, void <NUM> is formed in the peripheral wall of the unit main body <NUM>.

In this way, cooling unit <NUM> in accordance with one exemplary embodiment includes unit main body <NUM> including bottom portion <NUM> and peripheral wall portion <NUM> rising from a peripheral edge of bottom portion <NUM>, and sealing body <NUM> for sealing opening <NUM> of unit main body <NUM>. Unit main body <NUM> has stepped portion <NUM> including stepped bottom surface <NUM> and stepped side surface <NUM> rising from stepped bottom surface <NUM> toward opening <NUM> at the inner peripheral edge of peripheral wall portion <NUM>. Sealing body <NUM> is placed on stepped bottom surface <NUM> in a state in which side surface <NUM> of sealing body <NUM> and stepped side surface <NUM> butt each other. Furthermore, unit main body <NUM> is joined to sealing body <NUM> through plasticized region <NUM>, and void <NUM> is formed in the peripheral wall of the unit main body <NUM>.

Furthermore, the method for manufacturing cooling unit <NUM> includes a first step of processing unit main body <NUM> having bottom portion <NUM> and peripheral wall portion <NUM> rising from a peripheral edge of bottom portion <NUM> to form stepped portion <NUM> on the inner peripheral edge of peripheral wall portion <NUM>, stepped portion <NUM> including stepped bottom surface <NUM> and stepped side surface <NUM> rising from stepped bottom surface <NUM> toward opening <NUM> of unit main body <NUM> (see <FIG>); a second step of placing sealing body <NUM> for sealing opening <NUM> of unit main body <NUM> on stepped bottom surface <NUM> in a state in which side surface <NUM> of sealing body <NUM> and stepped side surface <NUM> butt each other to form butted portion <NUM> having a gap between side surface <NUM> of sealing body <NUM> and stepped side surface <NUM> (see <FIG>); and a third step of pushing rotary tool <NUM> into butted portion <NUM>, moving rotary tool <NUM> along butted portion <NUM> while rotary tool <NUM> being rotated (see <FIG>).

According to cooling unit <NUM> and the method for manufacturing cooling unit <NUM>, even if the cooling unit has a large size and a complicated structure, the joining strength between unit main body <NUM> and sealing body <NUM> can be secured and the reliability can be improved.

More specifically, even if the size variation of unit main body <NUM> and sealing body <NUM> increases due to the increase in size of cooling unit <NUM>, and the shape variation occurs, for example, a gap is generated in butted portion <NUM>, since void <NUM> is disposed in a place apart from stress concentration portion <NUM>, a crack can be prevented from developing from void <NUM> as a starting point, and joining strength can be secured.

As mentioned above, disclosure by the present inventors is specifically described based on the exemplary embodiments, but the present disclosure is not limited to the above-described exemplary embodiments, and can be modified without departing from the scope thereof.

For example, void <NUM> may be formed in any sites as long as it is formed in the peripheral wall portion of the unit main body <NUM>. As shown in <FIG>, void <NUM> may be formed inside plasticized region <NUM>. Also in this case, the same advantageous effect can be obtained as in cooling unit <NUM> described in the exemplary embodiment.

For example, in the friction stir welding step, by increasing the rotational speed or the movement speed of rotary tool <NUM>, void <NUM> can be positioned inside plasticized region <NUM>. In other words, when the rotational speed or the moving speed of rotary tool <NUM> is increased, followability when sealing body <NUM> at the retreating side flows and fills the rear part of rotary tool <NUM> is deteriorated, and the moving speed of void <NUM> becomes slower than the moving speed of rotary tool <NUM>. Therefore, void <NUM> does not move to unit main body <NUM> in the forward side and void <NUM> is formed inside plasticized region <NUM>.

It should be construed that the exemplary embodiments disclosed herein are illustrative in all pointes, and are not restrictive. The scope of the present disclosure is represented by the scope of the claims and not by the above description, and it is intended that all modifications within the sense and scope of the claims are involved in the scope of the present invention.

The present disclosure can provide a cooling unit capable of securing joining strength between a unit main body and a sealing body and having good reliability.

Claim 1:
A cooling unit comprising:
a unit main body (<NUM>) having a bottom portion (<NUM>) and a peripheral wall portion (<NUM>) rising from a peripheral edge of the bottom portion (<NUM>); and
a sealing body (<NUM>) for sealing an opening of the unit main body (<NUM>),
wherein the unit main body (<NUM>) is joined to the sealing body (<NUM>) through a plasticized region (<NUM>), and characterized in that
a void (<NUM>) is formed in the peripheral wall portion (<NUM>) of the unit main body (<NUM>).