Patent Description:
A ventilated brake disc comprising a pair of disc bodies that are spaced apart from each other is known as a brake disc for a disc brake gear. A ventilated brake disc having heat radiating pins is disclosed in <CIT>, for example.

Other examples of ventilated brake discs are shown in documents <CIT>, <CIT> and <CIT>.

It is required to facilitate an operation for fastening a pair of disc bodies to a wheel.

The present invention has been made in view of such circumstances. The object of the present invention is to provide a brake disc in which an operation for fastening a pair of disc bodies to a wheel is easy.

A brake disc according to the present invention comprises the features of claim <NUM>. Additionally a wheel with brake disc according to the present invention comprises the features according to claim <NUM>.

In the wheel with brake disc according to the present invention,.

In the wheel with brake disc according to the present invention,
the first positioning unit provided on one of the pair of disc bodies and the first positioning unit provided on the other may differ from each other in position, in a rotation axis direction of the wheel.

In the wheel with brake disc according to the present invention, the first positioning unit and the second positioning unit may form a bolt through-hole into which a bolt is inserted, the bolt being configured to penetrate the wheel and the pair of disc bodies to fasten the pair of disc bodies with the wheel therebetween.

In the wheel with brake disc according to the present invention,
at least one of the first positioning unit and the second positioning unit may have an inclined surface inclined in an insertion direction of the bolt.

In the wheel with brake disc according to the present invention,
a contact surface between the first positioning unit and the second positioning unit may define an angle <NUM>° or more and <NUM>° or less with respect to the rotation direction of the wheel.

The present invention can facilitate an operation for fastening a pair of disc bodies to a wheel.

An embodiment of the present invention is described in detail with reference to the drawings. <FIG> is a front view of a brake disc <NUM> seen from a rotation axis direction d2 described below, in a state where a pair of disc bodies <NUM> are fastened to a wheel <NUM>. In the example shown in <FIG>, the pair of disc bodies <NUM> are fastened to the wheel <NUM>, so that a wheel with brake disc <NUM> including the wheel <NUM> and the pair of disc bodies <NUM> is formed. <FIG> is a perspective view partially showing the brake disc <NUM> in a sector form, the brake disc <NUM> being cut along a broken line A and a broke line B in <FIG>.

In order to clarify a directional relationship among the drawings, a rotation direction d1 of the wheel <NUM>, a rotation axis direction d2 thereof, and a radial direction d3 thereof are shown by arrows in some drawings, which are directions common to the drawings. In the drawings showing components constituting the brake disc <NUM> and the wheel with brake disc <NUM>, a direction in which the wheel with brake disc <NUM> are formed, i.e., the pair of disc bodies <NUM> are fastened to the wheel <NUM> is shown.

The brake disc <NUM> according to this embodiment comprises a pair of disc bodies <NUM>. In the example shown in <FIG> and <FIG>, the pair of disc bodies <NUM> sandwich therebetween a wheel <NUM>. The pair of disc bodies <NUM> can be fastened by a fastening member <NUM> described below, with the wheel <NUM> therebetween. The pair of disc bodies <NUM> are fastened to each other with the wheel <NUM> therebetween, and are also fastened to the wheel <NUM>. In the example shown in <FIG> and <FIG>, the pair of disc bodies <NUM> are fastened to each other by a fastening member <NUM>, with the wheel <NUM> therebetween.

In a state where the pair of disc bodies <NUM> are fastened to the wheel <NUM>, the wheel <NUM> and the brake disc <NUM> are rotated in a rotation direction d1 about a rotation axis A1 which is shown by a point in <FIG> and by one-dot chain lines in <FIG>. A direction along which the rotation axis A1 extends is also referred to as rotation axis direction d2.

In the example shown in <FIG> and <FIG>, the fastening member <NUM> includes a bolt <NUM> that fastens the pair of disc bodies <NUM> to each other, with the wheel <NUM> therebetween. In particular, the fastening member <NUM> includes the bolt <NUM> having a head part 31a and a shaft part 31b extending from the head part 31a, and a nut <NUM> to be engaged with the shaft part 31b of the bolt <NUM>. The pair of disc bodies <NUM> can be fastened to each other by the bolt <NUM> and the nut <NUM> screwed to the shaft part 31b of the bolt <NUM>.

The wheel <NUM> and the pair of disc bodies <NUM> form bolt through-hole <NUM> penetrating through the wheel <NUM> and the pair of disc bodies <NUM>. The pair of disc bodies <NUM> are fastened to each other with the wheel <NUM> therebetween, by inserting the bolt <NUM> into the bolt through-hole <NUM>. In particular, the pair of disc bodies <NUM> can be fastened to each other with the wheel <NUM> therebetween, by inserting the bolt <NUM> through the bolt through-hole <NUM> and then by engaging the nut <NUM> with the shaft part 31b. In the example shown in <FIG> and <FIG>, the bolt through-hole <NUM> extend in the rotation axis direction d2.

The pair of disc bodies <NUM> are described. In this embodiment, the pair of disc bodies <NUM> have the same shape with each other. Herebelow, one of the pair of disc bodies <NUM>, which is shown on the front side in <FIG>, is referred to also as first disc body <NUM>. In addition, the other of the pair of disc bodies <NUM>, which is shown on the rear side in <FIG>, is referred to also as second disc body <NUM>. <FIG> is a perspective view of the first disc body <NUM> seen from the side of a contact surface 10b described below. <FIG> shows a portion corresponding to the portion of the first disc body <NUM> shown in <FIG>.

Each of the pair of disc bodies <NUM> has a substantially discoid shape having a hole in its center. In addition, each of the pair of disc bodies <NUM> has an inner surface 10a which is located on the wheel <NUM> side in a state where the disc bodies <NUM> are fastened to the wheel <NUM>, and a contact surface 10b located oppositely to the inner surface 10a as principal surfaces. The contact surface 10b contacts a brake pad, not shown, to brake the rotation of the wheel <NUM>. For example, a pair of brake pads are controlled by a brake caliper, not shown, to move toward and away from the respective contact surfaces 10b of the pair of disc bodies <NUM>. In this case, one of the pair of brake pads controlled by the brake caliper comes into contact with one contact surface 10b of the pair of disc bodies <NUM>, and the other of the pair of brake pads comes into contact with the other contact surface 10b of the pair of disc bodies <NUM>. Thus, the pair of brake pads apply a braking force caused by a frictional force to the pair of disc bodies <NUM>. Then, the braking force is transmitted from the pair of disc bodies <NUM> to the wheel <NUM>, so that the rotation of the wheel <NUM> is braked.

Each of the contact surfaces 10b of the pair of disc bodies <NUM> is provided with a through wall <NUM> forming a through-hole <NUM>. As shown in <FIG>, each of the contact surfaces 10b is provided with a plurality of the through walls <NUM> forming the through-holes <NUM>. As shown in <FIG>, in a state where the pair of disc bodies <NUM> are fastened to the wheel <NUM>, a plurality of the through-holes <NUM> formed in one (e.g., first disc body <NUM>) of the first disc bodies <NUM> and a plurality of the through-holes <NUM> formed in the other (e.g., second disc body <NUM>) of the pair of disc bodies <NUM> overlap with each other in the rotation axis direction d2. In addition, the through-holes <NUM> formed in the pair of disc bodies <NUM> also overlap below-described wheel through-holes <NUM> formed in the wheel <NUM> in the rotation axis direction d2. When the through-hole <NUM> of the one of the pair of disc bodies <NUM>, the wheel through-hole <NUM> of the wheel <NUM>, and the through-hole <NUM> of the other disc body <NUM> overlap with one another in the rotation axis direction d2, the bolt through-hole <NUM> is formed.

When the though holes <NUM> of the pair of disc bodies <NUM> overlap with each other in the rotation axis direction d2, the bolt through-hole <NUM> is formed. When the pair of disc bodies <NUM> are fastened to each other by means of the bolt <NUM> and the nut <NUM>, the through-hole <NUM> in which the nut <NUM> is disposed is referred to as first through-hole <NUM>. In addition, the through-hole <NUM> in which the head part 31a of the bolt <NUM> is disposed is referred to as second through-hole <NUM>.

<FIG> is an enlarged sectional view partially showing the pair of disc bodies <NUM> and the wheel <NUM> along a line C-C of <FIG>. In <FIG>, the fastening member <NUM> is shown not in a section but in a plan view seen from a direction perpendicular to the section. As shown in <FIG>, each through wall <NUM> has a shaft-part accommodation wall <NUM> that accommodates the shaft part 31b of the bolt <NUM>. The through wall <NUM>, which is located on the side where the nut <NUM> is disposed to form the first through-hole <NUM>, has the shaft-part accommodation wall <NUM> and a first larger-diameter wall <NUM>. A hole diameter w1 of a part of the first through-hole <NUM> where the first larger-diameter wall <NUM> is formed is larger than a hole diameter w2 of a part of the first through-hole <NUM> where the shaft-part accommodation wall <NUM> is formed. A part of the first larger-diameter wall <NUM> forms a restriction wall <NUM> described later. As shown in <FIG>, the restriction wall <NUM> functions as a nut accommodation wall <NUM> that accommodates the nut <NUM>, in a state where the pair of disc bodies <NUM> are fastened to the wheel <NUM>. The restriction wall <NUM> (nut accommodation wall <NUM>) restrict the rotation of the nut <NUM> disposed so as to be surrounded by the restriction wall <NUM>. In the example shown in <FIG>, the first through-hole <NUM> accommodates a part of the shaft part 31b of the bolt <NUM> so that the part is surrounded by the shaft-part accommodation wall <NUM>, and also accommodates the nut <NUM> so that the nut <NUM> is surrounded by the restriction wall <NUM> (nut accommodation wall <NUM>). The restriction wall <NUM> (nut accommodation wall <NUM>) and the shaft-part accommodation wall <NUM>, which form the first through-hole <NUM>, are continuously formed such that the restriction wall <NUM> (nut accommodation wall <NUM>) is located nearer than the shaft-part accommodation wall <NUM> to the contact surface 10b of the disc body <NUM> in which the first through-hole <NUM> is formed. Note that a hole diameter of a hole, such as the through-hole <NUM>, means a width of the hole in a perpendicular direction perpendicular to the direction along which the hole extends. When a width of the hole in the perpendicular direction is not constant, a hole diameter means a minimum width of the hole in the perpendicular direction.

The second through-hole <NUM> includes a shaft-part accommodation wall <NUM> and a second larger-diameter wall <NUM>. A hole diameter w3 of a part of the second through-hole <NUM> where the second larger-diameter wall <NUM> is formed is larger than a hole diameter w4 of a part of the second through-hole <NUM> where the shaft-part accommodation wall <NUM> is formed. A part of the second larger-diameter wall <NUM> forms a bolt restriction wall <NUM>. In the example shown in <FIG>, the second through-hole <NUM> accommodates a part of the shaft part 31b of the bolt <NUM> so that the part is surrounded by the shaft-part accommodation wall <NUM>, and also accommodates the head 31a of the bolt <NUM> so that the head 31a is surrounded by the bolt accommodation wall <NUM>. The bolt accommodation wall <NUM> and the shaft-accommodation wall <NUM>, which form the second through-hole <NUM>, are continuously formed such that the bolt accommodation wall <NUM> is located nearer than the shaft-part accommodation wall <NUM> to the contact surface 10b of the disc body <NUM> in which the second through-hole <NUM> is formed.

The restriction wall <NUM> is described. The through wall <NUM> provided on one of the pair of disc bodies <NUM> is partially provided with the restriction wall <NUM> that restricts the rotation of the nut <NUM>. The restriction wall <NUM> restricts the nut <NUM> from rotating together with the rotation of the bolt <NUM> when the pair of disc bodies <NUM> are fastened to the wheel <NUM>. When the pair of disc bodies <NUM> are fastened to the wheel <NUM>, the bolt <NUM> is rotated about an axis line A2 that passes a center of the shaft part 31b to extend in a direction along which the shaft part 31b extends. The restriction wall <NUM> restricts the rotation of the nut <NUM> such that the nut <NUM> is not rotated together with the rotation of the bolt <NUM> about the axis line A2. The shaft part 31b of the bolt <NUM> extends parallel to the rotation axis direction d2. In the example shown in <FIG>, each of the bolt through-holes <NUM> includes the first through-hole <NUM> formed in one of the pair of disc bodies <NUM>, and the second through-hole <NUM> formed in the other of the pair of disc bodies <NUM>. The restriction wall <NUM> is provided partially on the first larger-diameter wall <NUM> of the through wall <NUM> forming the first through-hole <NUM>.

An example of how the restriction wall <NUM> restricts the rotation of the nut <NUM> is described. When the pair of disc bodies <NUM> are fastened to the wheel <NUM> to make the brake disc <NUM> in this embodiment, the following operation is performed. The nut <NUM> is firstly disposed so as to be surrounded by the restriction wall <NUM> of the first through-hole <NUM> of the bolt through-hole <NUM>. Then, the shaft part 31b of the bolt <NUM> is inserted from the second through-hole <NUM>, and the bolt <NUM> is rotated with respect to the nut <NUM>. The nut <NUM> is engaged with the shaft part 31b by the above operation, so that the pair of disc bodies <NUM> are fastened to the wheel <NUM>.

The nut <NUM> has a polygonal columnar shape, for example. <FIG> is an enlarged front view showing the nut <NUM> and its environment of the front view of <FIG>. In the example shown in <FIG>, the nut <NUM> has a polygonal columnar shape, in particular, a hexagonal columnar shape, having a hole part 32a engageable with the shaft part 31b of the bolt <NUM>.

The restriction wall <NUM> of the first through-hole <NUM> in this embodiment is provided so as to be in surface-contact with at least one of side surfaces 32b of the polygonal columnar nut <NUM>. Since the side surface 32b of the nut <NUM> is in surface-contact with the restriction wall <NUM>, the nut <NUM> can be prevented from rotating together with the rotation of the bolt <NUM> when the bolt <NUM> is rotated with respect to the nut <NUM> so as to engage the nut <NUM> with the shaft part 31b.

Thus, the restriction walls <NUM> can prevent rotation of the nut <NUM> together with the rotation of the bolt <NUM>. In particular, when the restriction wall <NUM> is in surface-contact with at least one of the side surfaces 32b of the polygonal columnar nut <NUM>, the rotation of the nut <NUM> can be effectively prevented. In the example shown in <FIG>, the two side surfaces 32b of the hexagonal columnar nut <NUM> are in surface-contact with the restriction walls <NUM>.

In addition, as shown in <FIG>, a part of the first through-hole <NUM> where the restriction walls <NUM> are provided in the direction in which the shaft part 31b of the bolt <NUM> extends has a minimum width w15. The minimum width w15 is smaller than a maximum width w16 of the nut <NUM> in the direction in which the shaft part <NUM> of the bolt <NUM> extends. This structure also restricts the rotation of the nut <NUM>.

The restriction wall <NUM> (nut accommodation wall <NUM>) is located in the first through-hole <NUM> so as to be spaced apart from the contact surface 10b at a distance more than a maximum allowable wear amount of each of the pair of disc bodies <NUM>. The maximum allowable wear amount means a thickness of the disc body <NUM> in the rotation axis direction d2, which can be reduced because the contact surface 10b is worn by a brake pad that comes into contact therewith. In other words, in a state where the pair of disc bodies <NUM> are fastened to the wheel <NUM>, a distance w5 between the restriction wall <NUM> (nut accommodation wall <NUM>) which is a part for accommodating the nut <NUM> and the contact surface 10b of the disc body <NUM> in which the first through-hole <NUM> is formed is larger than the maximum allowable wear amount (see <FIG>). Thus, even when the disc body <NUM> is worn by the maximum allowable wear amount, the nut <NUM> can be prevented from contacting the brake pad.

In addition, in a state where the pair of disc bodies <NUM> are fastened to the wheel <NUM>, a distance w6 between the contact surface 10b of the disc body <NUM> in which the first through-hole <NUM> is formed and the shaft part 31b of the bolt <NUM> is larger than the maximum allowable wear amount (see <FIG>).

An example of a definition of the maximum allowable wear amount is described. In order thereto, suppose that the disc body <NUM> is formed of a layered body including a first layer forming the contact surface 10b, and a second layer stacked on the first layer oppositely to the side where the contact surface 10b is formed. The first layer is a layer that is allowed to be worn by the use of the brake disc <NUM>. The second layer is a layer that is not allowed to be worn by the use of the brake disc <NUM>. In this case, the maximum allowable wear amount can be defined as a thickness of the first layer in the rotation axis direction d2.

The maximum allowable wear amount can also be defined as the distance between the contact surface 10b and the position closest to the wheel <NUM> among the positions where the surface of the brake pad that comes into contact with the contact surface 10b can move according to specifications of the brake caliper comprising the brake pad.

In the example shown in <FIG>, when seen from the rotation axis direction d2, the restriction wall <NUM> has a profile including a pair of straight portions 432a that are parallel to each other, and a pair of curved portions 432b connecting the pair of straight portions 432a. Each of the pair of curved portions 432b is a substantially arcuate curved line. The restriction wall <NUM> having such a shape can be easily formed in the disc body <NUM> by the following method, for example. A hole is firstly formed in the disc body <NUM> such that a hole diameter of the hole corresponds to a hole diameter of a part in which the shaft-part accommodation wall <NUM> of the first through-hole <NUM> is formed. Then, an end mill is brought into contact with the contact surface 10b of the disc body <NUM> to form the first larger-diameter wall <NUM> including the restriction wall <NUM>. At this time, the aforementioned restriction wall <NUM>, which has a profile including a pair of straight portions 432a that are parallel to each other, and a pair of curved portions 432b connecting the pair of straight portions 432a, when seen from the rotation axis direction d2, can be formed by only an operation of bringing the end mill into contact with the contact surface 10b of the disc body <NUM> and moving it in only one direction.

The bolt accommodation wall <NUM> is described. In this embodiment, the restriction wall <NUM> is provided on a part of the through wall <NUM> provided in one of the pair of disc bodies <NUM>. The through wall <NUM>, which is provided in the other of the pair of disc bodies <NUM> and is not provided with the restriction wall <NUM>, is partially provided with the bolt accommodation wall <NUM> that rotatably accommodates the head part 31a of the bolt <NUM>. The through-hole <NUM> provided with the bolt accommodation wall <NUM> forms the second through-hole <NUM>. In the example shown in <FIG>, each of the bolt through-holes <NUM> includes the first through-hole <NUM> that is formed in one of the pair of disc bodies <NUM>, and the second through-hole <NUM> that is formed in the other of the pair of disc bodies <NUM>. The bolt accommodation wall <NUM> is provided on a part of the second larger-diameter wall <NUM> of the through wall <NUM> forming the second through-hole <NUM>. Thus, the bolt <NUM> can be rotated with respect to the nut <NUM> so as to engage the nut with the shaft part 31b, while the head part 31a of the bolt <NUM> can be accommodated in a space surrounded by the bolt accommodation wall <NUM>.

<FIG> is an enlarged front view showing the head part 31a of the bolt <NUM> and its environment of the front view of <FIG>. In the example shown in <FIG>, a hole diameter w7 of a part of the second through-hole <NUM> in which the bolt accommodation wall <NUM> is formed is equal to or larger than a dimension w8 of the head part 31a in a direction perpendicular to the direction in which the bolt <NUM> extends. Thus, in a state where the head part 31a is accommodated in a space surrounded by the bolt accommodation wall <NUM>, the bolt <NUM> can be rotated with respect to the nut <NUM>. In the example shown in <FIG>, the head part 31a has a circular profile seen from the rotation axis direction d2. A part of the second through-hole <NUM> in which the bolt accommodation wall <NUM> is formed is a circular hole. The hole diameter w7 of a part of the second through-hole <NUM> in which the bolt accommodation wall <NUM> is formed is equal to or larger than a diameter w8 of the head part 31a.

In a state where the pair of disc bodies <NUM> are fastened to the wheel <NUM>, a distance w9 between the contact surface 19b of the disc body <NUM> in which the second through-hole <NUM> is formed and the head 31a of the bolt <NUM> is larger than the maximum allowable wear amount (see <FIG>).

As shown in <FIG>, when seen from the rotation axis direction d2 of the wheel <NUM>, a shape of the first through-hole <NUM> and a shape of the second through-hole <NUM> differ from each other. For example, since a shape of the first larger-diameter wall <NUM> and a shape of the second larger-diameter wall <NUM> differ from each other, the shape of the first through-hole <NUM> and the shape of the second through-hole <NUM> are seen differently from each other, when seen from the rotation axis direction d2 of the wheel <NUM>. In this embodiment, as described above, the restriction wall <NUM> of the first larger-diameter wall <NUM> has a profile including a pair of the straight portions 432a and a pair of the curved portions 432b, when seen from the rotation axis direction d2. On the other hand, the bolt accommodation wall <NUM> of the second larger-diameter wall <NUM> has a circular profile when seen from the rotation axis direction d2. Thus, when seen from the rotation axis direction d2 of the wheel <NUM>, the first through-hole <NUM> and the second through-hole <NUM> can be distinguished from each other. As a result, in a below-described operation for fastening the pair of disc bodies <NUM> to the wheel <NUM>, it can be suppressed that an operator confuses the first through-hole <NUM> in which the nut <NUM> should accommodated, with the second through-hole <NUM> into which the bolt <NUM> should be inserted. In particular, as described later, there is a case in which there are preferred positions of the nut <NUM> and the bolt <NUM> from the viewpoint of balance in weight and fastening force of the wheel with brake disc <NUM>. In this case, it can be suppressed that the preferred positions of the nut <NUM> and the bolt <NUM> are damaged by an operator's mistake.

Positions of the first though hole <NUM> and the second through-hole <NUM> in the pair of disc bodies <NUM> are described. <FIG> is a view showing positions of the first through-holes <NUM> and the second through-holes <NUM> in the pair of disc bodies <NUM>. <FIG> shows the pair of disc bodies <NUM> that are seen from the contact surface 10b. In <FIG>, the shapes of the first through-hole <NUM>, the second through-hole <NUM> and the pair of disc bodies <NUM> are more simplified than those of <FIG>, etc., for the convenience of illustration of the positions of the first through-hole <NUM> and the second through-hole <NUM> and easy understanding.

As shown in <FIG>, a plurality of the first through-holes <NUM> and a plurality of the second through-holes <NUM> are formed in one (e.g., first disc body <NUM>) of the pair of disc bodies <NUM>. In addition, a plurality of the first through-holes <NUM> and a plurality of the second through-holes <NUM> are formed in the other (e.g., second disc body <NUM>) of the pair of disc bodies <NUM>. Thus, holes into which the holes into which the bolts <NUM> are inserted from the first disc <NUM> when the pair of disc bodies <NUM> are fastened to the wheel <NUM>, and holes into which the bolts <NUM> are inserted from the second disc body <NUM> when the pair of disc bodies <NUM> are fastened to the wheel <NUM> are both formed. This can make more equal the balance of a fastening force in the wheel with brake disc <NUM> formed by fastening.

As shown in <FIG>, the number of the first through-holes <NUM> formed in one (e.g., first disc body <NUM>) of the pair of disc bodies <NUM> and the number of the first through-holes <NUM> formed in the other (e.g., second disc body <NUM>) of the pair of disc bodies <NUM> are the same with each other. In addition, as shown in <FIG>, the number of the second through-holes <NUM> formed in one (e.g., first disc body <NUM>) of the pair of disc bodies <NUM> and the number of the second through-holes <NUM> formed in the other (e.g., second disc body <NUM>) of the pair of disc bodies <NUM> are the same with each other. This can offer the same effect. In the wheel with brake disc <NUM>, the number of the nuts <NUM> accommodated in one of the pair of disc bodies <NUM> and the number of the nuts <NUM> accommodated in the other of the pair of disc bodies <NUM> can be the same with each other. In addition, the number of the bolts <NUM> accommodated in one of the pair of disc bodies <NUM> and the number of the bolts <NUM> accommodated in the other of the pair of disc bodies <NUM> can be the same with each other. Thus, the weight of the wheel with brake disc <NUM> can be equalized on the side where one of the pair of disc bodies <NUM> is positioned, and on the side where the other is positioned. In particular, even when the weight of the nut <NUM> to be accommodated in the first through-hole <NUM> and the weight of the head part 31a of the bolt <NUM> to be accommodated in the second through-hole <NUM> differ from each other, the weight of the wheel with brake disc <NUM> can be made uniform. Thus, when the wheel with brake disc <NUM> is rotated, it can be suppressed that the rotation axis A1 becomes unstable because of the non-uniform weight.

In this embodiment, the first disc body <NUM> and the second disc body <NUM> have the six first through-holes <NUM> and the six second through-holes <NUM>, respectively. Accordingly, the first disc body <NUM> and the second disc body <NUM> respectively have the twelve through-holes <NUM>.

In addition, as shown in <FIG>, positions of the first through-holes <NUM> formed in one (e.g., first disc body <NUM>) of the pair of disc bodies <NUM> and the positions of the first through boles <NUM> formed in the other (e.g., second disc body <NUM>) of the pair of disc bodies <NUM> are the same with each other. In addition, positions of the second through-holes <NUM> formed in one (e.g., first disc body <NUM>) of the pair of disc bodies <NUM> and the positions of the second through boles <NUM> formed in the other (e.g., second disc body <NUM>) of the pair of disc bodies <NUM> are the same with each other. In this embodiment, the positions of the first through-holes <NUM> in the first disc body <NUM> and the positions of the first through-holes <NUM> in the second disc body <NUM> are the same with each other. In addition, the positions of the second through-holes <NUM> in the first disc body <NUM> and the positions of the second through-holes <NUM> in the second disc body <NUM> are the same with each other.

In this embodiment, the number and the positions of the first through-holes <NUM> and the number and the positions of the second through-holes <NUM> are the same with each other in the one and the other of the pair of disc bodies <NUM>. Thus, one and the other of the pair of disc bodies <NUM> have the same shape with each other. Since one and the other of the pair of disc bodies <NUM> have the same shape with each other, it is not necessary to manufacture one and the other of the pair of disc bodies <NUM> separately from each other. Thus, the productivity of the brake disc <NUM> is improved. In addition, there is no risk that an operator confuses one and the other of the pair of disc bodies <NUM>, during an operation for fastening the pair of disc bodies <NUM> to the wheel <NUM>, which is described later.

In order to fasten the pair of disc bodies <NUM> to the wheel <NUM>, it is necessary to overlap the first through-hole <NUM> formed in one of the pair of disc bodies <NUM> with the second through-hole <NUM> formed in the other of the pair of disc bodies <NUM> in the rotation axis direction d2, so as to form the bolt through-hole <NUM>. In order that the bolt through-hole <NUM> can be formed while the pair of disc bodies <NUM> is used, the disc bodies <NUM> to be used should satisfy the following condition. Firstly, a virtual disc body, which has a second through-hole <NUM> that is formed at a position where a first through-hole <NUM> is formed in a disc body <NUM> to be used, and a first through-hole <NUM> that is formed at a position where a second through-hole <NUM> is formed in the disc body <NUM> to be used is considered. If the disc body <NUM> to be used and the virtual disc body can be disposed symmetrically with their inner surfaces facing each other, the bolt through-hole <NUM> can be formed while one and the other of the pair of disc bodies <NUM> can have the same shape with each other.

As shown in <FIG>, the first through-holes <NUM> and the second through-holes <NUM> are provided rotationally symmetrically in one (e.g., first disc body <NUM>) of the pair of disc bodies <NUM>, when seen from the rotation axis direction d2 of the wheel <NUM>. In addition, the first through-holes <NUM> and the second through-holes <NUM> are provided rotationally symmetrically in the other (e.g., second disc body <NUM>) of the pair of disc bodies <NUM>, when seen from the rotation axis direction d2 of the wheel <NUM>. This offers the following effect. When the weight of the nut <NUM> and the weight of the head part 31a of the bolt <NUM> differ from each other, the nuts <NUM> and the head parts 31a of the bolts <NUM> can be provided rotationally symmetrically in one of the pair of disc bodies <NUM>, when seen from the rotation axis direction d2, in the wheel with brake disc <NUM>. In addition, the nuts <NUM> and the head parts 31a of the bolts <NUM> can be provided rotationally symmetrically in the other of the pair of disc bodies <NUM>, when seen from the rotation axis direction d2. Thus, it can be suppressed that, when the wheel with brake disc <NUM> is rotated, the rotation axis A1 becomes unstable because of uneven distribution of the nuts <NUM> and the head parts 31a of the bolt <NUM>.

In this embodiment, the first through-holes <NUM> and the second through-holes <NUM> are provided rotationally symmetrically in each of one and the other of the pair of disc bodies <NUM>, about the rotation axis A1 of the wheel <NUM>.

In addition, as shown in <FIG>, the through-holes <NUM> are equidistantly disposed in one (e.g., first disc body <NUM>) of the pair of disc bodies <NUM> on a circumference C1 about the rotation axis A1 of the wheel <NUM>. In addition, the through-holes <NUM> are equidistantly disposed in the other (e.g., second disc body <NUM>) of the pair of disc bodies <NUM> on a circumference C2 about the rotation axis A1 of the wheel <NUM>.

In addition, as shown in <FIG>, the first through-holes <NUM> and the second through-holes <NUM> are alternately formed in each of the pair of disc bodies <NUM> on the circumference about the rotation axis A1 of the wheel <NUM>. In the example shown in <FIG>, the through-holes <NUM> are disposed in one (e.g., first disc body <NUM>) of the pair of disc bodies <NUM> such that the first through-holes <NUM> and the second through-holes <NUM> are alternated on a circumference of a circle C1. In addition, the through-holes <NUM> are disposed in the other (e.g., second disc body <NUM>) of the pair of disc bodies <NUM> such that the first through-holes <NUM> and the second through-holes <NUM> are alternated on a circumference of a circle C2. This offers the following effect. When the weight of the nut <NUM> and the weight of the head part 31a of the bolt <NUM> differ from each other, the nuts <NUM> and the head parts 31a of the bolts <NUM> can be alternately disposed on the circumference of the circle C1 on one of the pair of disc bodies <NUM>, when seen from the rotation axis direction d2, in the wheel with brake disc <NUM>. In addition, the nuts <NUM> and the head parts 31a of the bolts <NUM> can be alternately disposed on the circumference of the circle C2 on the other of the pair of disc bodies <NUM>. Thus, it can be more effectively suppressed that, when the wheel with brake disc <NUM> is rotated, the rotation axis A1 becomes unstable because of uneven distribution of the nuts <NUM> and the head parts 31a of the bolt <NUM> in the rotation direction d1.

In the example shown in <FIG>, the circle C1, C2 passes through midpoints between an outer edge 10c and an inner edge 10d of each disc body <NUM> in a radial direction d3 perpendicular to the rotation axis direction d2. The first through-holes <NUM> and the second through-holes <NUM> are formed on the circle C1, C2 passing through the midpoints. This offers the following effect. There is a possibility that disc body <NUM> is warped by heat. In this case, when the disc body <NUM> is fastened at a position close to the inner edge 10d in the radial direction d3, the disc body <NUM> may be largely warped on the outer edge 10c side which is farther from the fastening position However, since the first through-holes <NUM> and the second through-holes <NUM> are formed on the circumference of the circle C1, C2 passing through the midpoints, the disc body <NUM> can be fastened to the wheel <NUM> on the circumference of the circle C1, C2 passing through the midpoints. Thus, the warp of the disc body <NUM> can be dispersed on the outer edge 10c side and on the inner edge 10d side to reduce the influence of the warp.

Note that the fact that the through-hole <NUM> is "disposed on the circumference" and that the through-hole <NUM> is "formed on the circumference" means that a part of the through-hole <NUM> is positioned on the circumference.

Next, the structure of the inner surface 10a side of the disc body <NUM> is described. <FIG> is a perspective view of the first disc body <NUM> seen from the inner surface 10af. <FIG> shows a part of the first disc body <NUM> which corresponds to the part shown in <FIG>. As shown in <FIG>, the brake disc <NUM> comprises a plurality of heat radiating members <NUM> provided on a principal surface of each of the pair of disc bodies <NUM> to project from the principal surface, and a first positioning unit <NUM> formed on each of the pair of disc bodies <NUM>.

The heat radiating members <NUM> are provided on the respective inner surfaces 10a of the pair of disc bodies <NUM> to project from the inner surface 10a. When the pair of disc bodies <NUM> are fastened to each other with the wheel <NUM> therebetween, the plurality of heat radiating members <NUM> sandwich the wheel <NUM>.

Due to the provision of the heat radiating members <NUM>, a contact area between the brake disc <NUM> and the atmosphere increases. Thus, frictional heat, which is generated by the friction caused when brake pads come into contact with the contact surfaces 10b of the pair of disc bodies <NUM>, is released to the atmosphere not only from the inner surfaces 10a and the contact surfaces 10b of the pair of disc bodies <NUM>, but also from the surfaces of the heat radiating members <NUM>. Thus, the pair of disc bodies <NUM> can be efficiently cooled.

In the example shown in <FIG>, the heat radiating member <NUM> has a pin-like shape. Each of the pin-like heat radiating members <NUM> extends along the rotation axis direction d2. In the example shown in <FIG>, the heat radiating member <NUM> has a substantially circular section when cut along a plane perpendicular to the rotation axis direction d2. The shape of a section of the pin-like heat radiating member <NUM>, which is cut along a plane perpendicular to the rotation axis direction d2, is not limited to a circular shape, and may be, for example, an oblong shape, a polygonal shape, or another shape. In addition, although not shown, the shape of the heat radiating member <NUM> is not limited to a pin-like shape. The heat radiating member <NUM> may have, for example, a fin-like shape, in other words, a substantially plate-like shape perpendicular to the inner surface 10a.

The first positioning unit <NUM> is described. The first positioning unit <NUM> is a constituent element that guides the pair of disc bodies <NUM> and the wheel <NUM> such that they are brought into contact with each other in an appropriate positional relationship, when the pair of disc bodies <NUM> are fastened to the wheels <NUM>. The first positioning units <NUM> are respectively formed on the pair of disc bodies <NUM>. When the pair of disc bodies <NUM> are fastened to the wheel <NUM>, the first positioning unit <NUM> is engaged with a below-described second positioning unit <NUM> of the wheel <NUM>. the first positioning unit <NUM> positions each of the pair of the disc bodies <NUM> with respect to the wheel <NUM> by being engaged with the second positioning unit <NUM>. In the example shown in <FIG>, the first positioning unit <NUM> has a projection-like shape projecting from the inner surface 10a. The first positioning unit <NUM> projects more than the plurality of heat radiating members <NUM> in a height direction of these heat radiating members <NUM>. In the example shown in <FIG>, the height direction of the heat radiating member <NUM> corresponds to the rotation axis direction d2. The first positioning unit <NUM> projects from the inner surface 10a along the rotation axis direction d2 more than the heat radiating members <NUM>.

In the example shown in <FIG>, the first positioning unit <NUM> includes a base part <NUM> having the same height as that of the heat radiating members <NUM> in the height direction of the heat radiating members <NUM>, and a first positioning projection <NUM> formed on a distal end surface 15a of the base part <NUM>. The first positioning projection <NUM> is a projection that projects from the distal end surface 15a of the base part <NUM> in the height direction of the heat radiating member <NUM>. The first positioning projection <NUM> is to be engaged with the below-described second positioning unit <NUM>. Since the first positioning projection <NUM> is provided on a part of the distal end surface 15a of the base part <NUM>, the first positioning projection <NUM> is thinner than the base part <NUM>. Since the first positioning unit <NUM> has the base part <NUM>, the first positioning unit <NUM> has a reliable strength, so that the first positioning unit <NUM> can be made difficult to break. In addition, the part of the first positioning unit <NUM> to be engaged with the second positioning unit <NUM> can have a shape and dimensions suitable for the engagement.

In the example shown in <FIG>, the base part <NUM> of the first positioning unit <NUM> has a thickness larger than that of the pin-like heat radiating member <NUM>. The first positioning projection <NUM> of the first positioning unit <NUM> also has a thickness larger than that of the pin-like heat radiating member <NUM>. A plurality of the first positioning units <NUM> are formed to be equidistantly disposed on a circumference about the rotation axis A1 of the wheel <NUM>. In this embodiment, each of the pair of disc bodies <NUM> have the three first positioning units <NUM>.

<FIG> is a view showing the first positioning unit <NUM> having the first positioning projection <NUM> seen from the rotation axis direction d2. According to the invention the first positioning projection <NUM> includes a side surface having a pair of flat surfaces 16a opposed to each other, and a pair of curved surfaces 16b connecting the pair of flat surfaces 16a. When observed from the rotation axis direction d2 as shown in <FIG>, each of the pair of curved surfaces 16b has a substantially arcuate profile.

Next, the wheel <NUM> is described. <FIG> is a perspective view showing the wheel <NUM> in this embodiment. <FIG> shows a part of the wheel <NUM> which corresponds to the part shown in <FIG>. The wheel <NUM> has a substantially discoid shape having a hole in its center. As shown in <FIG>, the wheel <NUM> has a first surface 20a and a second surface 20b. As shown in <FIG>, when the pair of disc bodies <NUM> are fastened to the wheel <NUM>, the first surface 20a of the wheel <NUM> is opposed to the inner surface 10a of the first disc body <NUM>, and the second surface 20b of the wheel <NUM> is opposed to the inner surface 10a of the second disc body <NUM>. The wheel <NUM> is a wheel for railway vehicle. In the example shown in <FIG>, when the wheel <NUM> is mounted on a railway vehicle, the first surface 20a is a surface that is positioned outside of the railway vehicle. When the wheel <NUM> is mounted on the railway vehicle, the second surface 20b is a surface that is positioned on the center side of the railway vehicle.

As shown in <FIG>, in a state where the pair of disc bodies <NUM> are fastened to the wheel <NUM>, a distal end 13a of the heat radiating member <NUM> and the distal end surface 15a of the base part <NUM> of the second disc body <NUM> are in contact with the second surface 20b. In addition, the distal end 13a of the heat radiating member <NUM> and the distal end surface 15a of the base part <NUM> of the first disc body <NUM> are in contact with the first surface 20a.

A wheel through-hole <NUM> penetrating from the first surface 20a up to the second surface 20b is formed in the wheel <NUM>. In a state where the pair of disc bodies <NUM> are fastened to the wheel <NUM>, the wheel through-hole <NUM> overlaps with the first through-hole <NUM> formed in one of the pair of disc bodies <NUM>, and the second through-hole <NUM> formed in the other of the pair of disc bodies <NUM>, in the rotation axis direction d2. Thus, the bolt through-hole <NUM> is formed by the wheel through-hole <NUM>, the first through-hole <NUM> and the second through-hole <NUM>. As shown in <FIG>, in a state where the pair of disc bodies <NUM> are fastened to the wheel <NUM>, the wheel through-hole <NUM> accommodates a part of the shaft part 31b of the bolt <NUM>.

The wheel <NUM> is provided with the second positioning unit <NUM> with which the aforementioned first positioning unit <NUM> is engaged. The second positioning unit <NUM> positions each of the pair of the disc bodies <NUM> with respect to the wheel <NUM> by being engaged with the first positioning unit <NUM>. In this embodiment, the second positioning unit <NUM> with which the first positioning unit <NUM> formed on the first disc body <NUM> is provided on the first surface 20a of the wheel <NUM>. In addition, the second positioning unit <NUM> with which the first positioning unit <NUM> formed on the second disc body <NUM> is provided on the second surface 20b of the wheel <NUM>. In each of the first surface 20a and the second surface 20b of wheel <NUM>, a plurality of the second positioning units <NUM> are equidistantly disposed on a circumference about the rotation axis A1 of the wheel <NUM>. The wheel <NUM> includes the three second positioning units <NUM> provided on the first surface 20a, and the three second positioning units <NUM> provided on the second surface 20b.

In this embodiment, as shown in <FIG>, the second positioning unit <NUM> has a second positioning recess <NUM> with which the first positioning projection <NUM> is engaged. In the example shown in <FIG>, the second positioning unit <NUM> has the second positioning recess <NUM> with which the first positioning unit <NUM> projecting from one surface of the disc body <NUM> is engaged. In the example shown in <FIG>, the second positioning unit <NUM> has the second positioning recess <NUM> recessed in the rotation axis direction d2.

<FIG> is a view showing the second positioning unit <NUM> having the second positioning recess <NUM>, when seen from the rotation axis direction d2. According to the invention the second positioning recess <NUM> includes a side surface having a pair of flat surfaces 22a parallel to each other, and a pair of curved surfaces 22b connecting the pair of flat surfaces 22a. When observed from the rotation axis direction d2 as shown in <FIG>, each of the pair of curved surfaces 22b has a substantially arcuate profile.

In a state where the first positioning unit <NUM> is engaged with the second positioning unit <NUM>, when the wheel <NUM> is relatively rotated with respect to the disc body <NUM> by a certain distance, the first positioning unit <NUM> and the second positioning unit <NUM> come into contact with each other. Thus, the relative rotation of the wheel <NUM> with respect to the disc body <NUM> by a certain distance or more can be prevented. When the wheel <NUM> is relatively rotated with respect to the disc body <NUM>, a surface of the first positioning unit <NUM> and a surface of the second positioning unit <NUM> may come into contact with each other. For example, when the wheel <NUM> is relatively rotated with respect to the disc body <NUM>, the first positioning unit <NUM> shown in <FIG> and the second positioning unit <NUM> shown in <FIG> come into contact with each other at their flat surface 16a and the flat surface 22a.

When the first positioning unit <NUM> and the second positioning unit <NUM> are in surface-contact with each other, a contact surface between the first positioning unit <NUM> and the second positioning unit <NUM> defines an angle between <NUM>° or more and <NUM>° or less with respect to the rotation direction d1 of the wheel <NUM>.

The angle defined by the contact surface with respect to the rotation direction d1 is determined as follows. When the wheel <NUM> is relatively rotated with respect to the disc body <NUM>, it is supposed that a contact surface between the second positioning unit <NUM> shown in <FIG> and the first positioning unit <NUM> is formed in an area 21a. In this case, a given circle C3 about the rotation axis A1 of the wheel <NUM> is drawn. Then, a tangent line L1 of the circle C3, which passes through an intersection point P1 of the circle C3 and the contact surface, is drawn. An angle θ1 defined between the tangent line L1 and the contact surface is determined as an angle defined by the contact surface with respect to the rotation direction d1.

An effect obtained by the fact that the contact surface between the first positioning unit <NUM> and the second positioning unit <NUM> defines an angle between <NUM>° or more and <NUM>° or less with respect to the rotation direction d1 of the wheel <NUM> is described. When a brake pad applies a braking force to the disc body <NUM>, the first positioning unit <NUM> and the second positioning unit <NUM> come into contact with each other, so that the braking force is transmitted from the disc body <NUM> to the wheel <NUM>. When the contact surface satisfies the above condition, the braking force acting in the direction opposite to the rotation direction d1 of the wheel <NUM> can be received by the contact surface defining an angle almost perpendicular to the direction of the braking force (angle between <NUM>° or more and <NUM>° or less). Thus, the braking force applied to the disc body <NUM> can be efficiently transmitted to the wheel <NUM> through the contact surface between the first positioning unit <NUM> and the second positioning unit <NUM>.

A positional relationship between the first positioning unit <NUM> / second positioning unit <NUM> and the bolt through-hole <NUM> is described. As shown in <FIG>, the first positioning unit <NUM> and the second positioning unit <NUM> form the bolt through-hole <NUM> composed of the through-hole <NUM> and the wheel through-hole <NUM>. The through-hole <NUM> is formed in the first positioning unit <NUM>, and the wheel through-hole <NUM> is formed in the second positioning unit <NUM>. In the example shown in <FIG>, the bolt through-hole <NUM> passes through a distal end surface 16c of the first positioning projection <NUM>.

<FIG> shows positions of the second positioning units <NUM> and the wheel through-holes <NUM>, when the first surface 20a of the wheel <NUM> is seen from the rotation axis direction d2. In <FIG>, the positions of the second positioning units <NUM> provided on the first surface 20a of the wheel <NUM> are shown by solid lines, and the positions of the second positioning units <NUM> provided on the second surface 20b of the wheel <NUM> are shown by one-dot chain lines. In a state where the pair of disc bodies <NUM> are fastened to the wheel <NUM>, the first positioning units <NUM> formed on the first disc body <NUM> are engaged with the second positioning units <NUM> provided on the first surface 20a of the wheel <NUM>, while the first positioning units <NUM> formed on the second disc body <NUM> are engaged with the second positioning units <NUM> provided on the second surface 20b of the wheel <NUM>.

<FIG> shows by broken lines positions at which the first through-holes <NUM> and the second through-holes <NUM> of the first disc <NUM> overlap with the wheel <NUM>, in a state where the pair of disc bodies <NUM> are fastened to the wheel <NUM>. Although not shown, the second through-hole <NUM> of the second disc <NUM> overlaps with a position of the wheel <NUM> which overlaps the first through-hole <NUM> of the first disc <NUM>. In addition, the first through-hole <NUM> of the second disc <NUM> overlaps with a position of the wheel <NUM> which overlaps with the second through-hole <NUM> of the first disc <NUM>.

In <FIG>, the shapes of the second positioning unit <NUM>, the wheel through-holes <NUM>, the first through-holes <NUM>, the second through-holes <NUM> and the wheel <NUM> are more simplified than those of <FIG>, <FIG>, etc., for the convenience of illustration of the positions of the second positioning unit <NUM>, the wheel through-holes <NUM>, the first through-hole <NUM> and the second through-hole <NUM> and easy understanding.

In this embodiment, as shown in <FIG>, the second positioning units <NUM> provided on the first surface 20a of the wheel <NUM> and the second positioning units <NUM> provided on the second surface 20b of the wheel <NUM> do not overlap with each other in the rotation axis direction d2. Thus, in a state where the pair of disc bodies <NUM> are fastened to the wheel <NUM> so that the wheel with brake disc <NUM> is formed, positions of the first positioning units <NUM> provided on one of the pair of disc bodies <NUM> and the first positioning units <NUM> provided on the other differ from each other in the rotation axis direction d2. In other words, in the wheel with brake disc <NUM>, the first positioning units <NUM> provided on one of the pair of disc bodies <NUM> and the first positioning units <NUM> provided on the other do not overlap with each other in the rotation axis direction d2. In the wheel with brake disc <NUM>, a position at which the first positioning unit <NUM> provided on one of the pair of disc bodies <NUM> is engaged with the second positioning unit <NUM>, and a position at which the first positioning unit <NUM> provided on the other of the pair of disc bodies <NUM> is engaged with the second positioning unit <NUM>, do not overlap with each other in the rotation axis direction d2.

An effect obtained by the fact that the positions of the first positioning unit <NUM> provided on one of the pair of disc bodies <NUM> and the first positioning unit <NUM> provided on the other differ from each other in the rotation axis direction d2 in the wheel with brake disc <NUM> is described. When a brake pad applies a braking force to the disc body <NUM>, the braking force is transmitted from the disc body <NUM> to the wheel <NUM> through the portion at which the first positioning unit <NUM> is engaged with the second positioning unit <NUM>. Since the positions of the first positioning unit <NUM> provided on one of the pair of disc bodies <NUM> and the first positioning unit <NUM> provided on the other differ from each other, a position at which the braking force is transmitted from one of the pair of disc bodies <NUM> to the wheel <NUM> and a position at which the braking force is transmitted from the other of the pair of disc bodies <NUM> to the wheel <NUM> also differ from each other in the rotation direction d1 of the wheel <NUM>. Thus, a load caused by the braking force onto the wheel <NUM> can be distributed in the rotation direction d1 of the wheel <NUM>.

Some of the bolt through-holes <NUM> are first bolt through-holes 40a each of which penetrates through a portion at which the first positioning unit <NUM> of one of the pair of disc bodies <NUM> is formed, and a portion at which the first positioning unit <NUM> of the other of the pair of disc bodies <NUM> is not formed. In addition, others of the bolt through-holes <NUM> are second bolt through-holes 40b each of which penetrates through portions at which no first positioning unit <NUM> of the pair of disc bodies <NUM> is formed. In <FIG>, in a state where the air of disc bodies <NUM> are fastened to the wheel <NUM> so that the wheel with brake disc <NUM> is formed, a position at which the first bolt through-hole 40a is formed is indicated by a symbol 40a for the sake of convenience, and a position at which the second bolt through-hole 40b is formed is indicated by a symbol 40b for the sake of convenience.

In this embodiment, as can be understood from <FIG>, <FIG> and <FIG>, the second through-hole <NUM> is formed in the first positioning unit <NUM> in both of the pair of disc bodies <NUM>. Namely, each of the first bolt through-holes 40a includes the second through-hole <NUM> which is formed at a portion of one of the pair of disc bodies <NUM>, at which the first positioning unit <NUM> is formed, and the first through-hole <NUM> which is formed at a position of the other of the pair of disc bodies <NUM>, at which the first positioning unit <NUM> is not formed. Each of the first through-hole <NUM> is formed at a portion of the disc body <NUM>, at which the first positioning unit <NUM> is not formed.

An effect obtained by the fact that the second through-hole <NUM> if formed in the first positioning unit <NUM> in both of the pair of disc bodies <NUM> is described. In this embodiment, one and the other of the pair of disc bodies <NUM> have the same shape with each other, from the viewpoint of improvement in manufacturability. On the other hand, as described above, the first through-hole <NUM> in which the nut <NUM> is to be accommodated, and the second through-hole <NUM> in which the head part 31a of the bolt <NUM> is to be accommodated differ from each other in shape. When the pair of disc bodies <NUM> are fastened to the wheel <NUM>, the first through-hole <NUM> formed in one of the pair of disc bodies <NUM> and the second through-hole <NUM> formed in the other of the pair of disc bodies <NUM> are firstly overlapped with each other, and then the bolt <NUM> and the nut <NUM> are used to fasten them. Suppose that the second through-holes <NUM> formed in one and the other of the pair of disc bodies <NUM> are overlapped with each other. In this case, the fastening is impossible by means of the second through-holes <NUM>. Thus, the pair of first disc bodies <NUM> and the wheel <NUM> are designed such that the second through-holes <NUM> overlap with each other upon fastening.

When the second through-hole <NUM> is formed in the first positioning unit <NUM> in both of the pair of disc bodies <NUM>, it is necessary that the second positioning units <NUM> of the wheel <NUM> are positioned such that the second through-holes <NUM> formed in the first positioning units <NUM> do not overlap with each other. To be specific, as described above, the second positioning unit <NUM> provided on the first surface 20a of the wheel <NUM> and the second positioning unit <NUM> provided on the second surface 20b of the wheel <NUM> are positioned so as not to overlap with each other in the rotation axis direction d2. Thus, in the wheel with brake disc <NUM> formed by engaging the first positioning units <NUM> of the pair of disc bodies <NUM> with the second positioning units <NUM> of the wheel <NUM>, the positions of the first positioning units <NUM> provided on one and the other of the pair of disc bodies <NUM> can be differed from each other. Namely, although one and the other of the pair of disc bodies <NUM> have the same shape with each other, the positions of the first positioning units <NUM> provided on one and the other pair of disc bodies <NUM> can be differed from each other in the wheel with brake disc <NUM>.

The following effect can be obtained by the fact that the through-hole <NUM> is formed in the first positioning unit <NUM> in both of the pair of disc bodies <NUM>, and that the second positioning unit <NUM> provided on the first surface 20a of the wheel <NUM> and the second positioning unit <NUM> provided on the second surface 20b of the wheel <NUM> are positioned so as not to overlap with each other in the rotation axis direction d2. Namely, when the pair of disc bodies <NUM> are fastened to the wheel <NUM>, the second through-holes <NUM> formed in the first positioning units <NUM> can be prevented from being overlapped with each other, by fastening the first positioning units <NUM> of the pair of disc bodies <NUM> to the second positioning units <NUM> of the wheel <NUM>.

As can be understood from <FIG> and <FIG>, some of the first bolt through-holes 40a each include the second through-hole <NUM> which is formed at a portion of the first disc body <NUM>, at which the first positioning unit <NUM> is formed, the wheel through-hole <NUM> which is formed at a portion of the wheel <NUM>, at which the second positioning unit <NUM> is provided on the first surface 20a and the second positioning unit <NUM> is not provided on the second surface 20b, and the first through-hole <NUM> which is formed at a portion of the second disc body <NUM>, at which the first positioning unit <NUM> is not formed. Others of the first bolt through-holes <NUM> each include the first through-hole <NUM> which is formed at a portion of the first disc <NUM>, at which the first positioning unit <NUM> is not formed, the wheel through-hole <NUM> which is formed at a portion of the wheel, at which the second positioning unit <NUM> is not provided on the first surface 20a and the second positioning unit <NUM> is provided on the second surface 20b, and the second through-hole <NUM> which is formed at a portion of the second disc <NUM>, at which the first positioning unit <NUM> is formed. The second bolt through-holes 40b each include the first through-hole <NUM> which is formed at a portion of the first disc <NUM>, at which the first positioning unit <NUM> is not formed, the wheel through-hole <NUM> which is formed at a portion of the wheel <NUM> at which no second positioning unit <NUM> is provided on the first surface 20a and the second surface 20b, and the second through-hole <NUM> which is formed at a portion of the second disc <NUM>, at which the first positioning unit <NUM> is not formed.

In this embodiment, as can be understood from <FIG>, the bolt through-holes <NUM> are comprised of three first bolt through-holes 40a each of which include the second through-hole <NUM> which is formed at a portion of the first disc body <NUM>, at which the first positioning unit <NUM> is formed, three first bolt through-holes 40a each of which include the second through-hole <NUM> which is formed at a portion of the second disc body <NUM>, at which the first positioning unit <NUM> is formed, and the six second bolt through-holes 40b.

The one-dot chain shown lines in <FIG> indicate the positions of the first positioning units <NUM> provided on the inner surface 10b of the disc body <NUM>. In the example shown in <FIG>, the second through-holes <NUM> are formed such that the second through-hole <NUM> which is formed at a portion of the disc body <NUM>, at which the first positioning unit <NUM> is formed, and the second through-hole <NUM> which is formed at a portion of the disc body <NUM>, at which the first positioning unit <NUM> is not formed, are alternated on the circumferences C1 and C2. In a state where the first pair of disc bodies <NUM> are fastened to the wheel <NUM>, as shown in <FIG>, the bolt through-holes <NUM> are disposed such that the first bolt through-holes 40a and the second bolt through-holes 40b are alternated about the rotation axis A1 of the wheel <NUM>.

In the example shown in <FIG>, a through-hole support <NUM> is formed on the inner surface 10a of each of the pair of disc bodies <NUM>. The second through-hole <NUM> each of which is formed at a portion of the disc body <NUM>, at which the first positioning unit <NUM> is formed, and the first through-hole <NUM> are respectively formed in the through-hole support <NUM>. The through-hole support <NUM> has a shape like a projection projecting from the inner surface. The through-hole support <NUM> has the same height as that of the heat radiating members <NUM> in the height direction of the heat radiating members <NUM>. In a state where the pair of disc bodies <NUM> are fastened to the wheel <NUM>, a distal end surface 17a of the through-hole support <NUM> is in contact with the wheel <NUM>. The through-hole support <NUM> has a thickness larger than that of the pin-like heat radiating member <NUM>.

Since the first through-hole <NUM> and the second through-hole <NUM> are each provided at a portion of the disc body <NUM>, at which the first positioning unit <NUM> or the through-hole support <NUM> are provided, the shaft part 31b of the bolt <NUM> inserted into the bolt through-hole <NUM> can be protected. The invention according to this embodiment can also be regarded as an invention in which the base part <NUM>, which protects the shaft part 31b of the bolt <NUM> similarly to the through-hole support <NUM>, is used as the first positioning unit <NUM>, so that the structure of the brake disc <NUM>, which is provided with the first positioning unit <NUM>, is simplified.

A method of manufacturing the wheel with brake disc <NUM> by fastening the pair of disc bodies <NUM> in this embodiment to the wheel <NUM> is described. <FIG> is a view showing an operation of fastening the pair of disc bodies <NUM> to the wheel <NUM>. <FIG> shows a fastening operation of a portion corresponding to the portion of the first disc body <NUM> shown in <FIG>.

In the fastening operation, as shown in <FIG>, the pair of disc bodies <NUM> are overlapped with the wheel <NUM>. At this time, the first disc body <NUM> is overlapped with the wheel <NUM> such that the first positioning unit <NUM> formed on the first disc body <NUM> and the second positioning unit <NUM> provided on the first surface 20a of the wheel <NUM> are overlapped with each other in the rotation axis direction d2. In addition, the second disc body <NUM> is overlapped with the wheel <NUM> such that the first positioning unit <NUM> formed on the second disc body <NUM> and the second positioning unit <NUM> provided on the second surface 20b of the wheel <NUM> are overlapped with each other in the rotation axis direction d2. At this time, since the through-hole <NUM> is formed in the first positioning unit <NUM>, an operator can overlap the pair of disc bodies <NUM> with the wheel <NUM> while visually checking the second positioning unit <NUM> of the wheel <NUM> through the through-hole <NUM>.

Then, as shown in <FIG>, the pair of disc bodies <NUM> are respectively brought close to the wheel <NUM> so that the first positioning unit <NUM> is engaged with the second positioning unit <NUM>. Thus, the pair of disc bodies <NUM> and the wheel <NUM> are aligned with each other. In the aligned state, the pair of disc bodies <NUM> and the wheel <NUM> are in contact with each other in an appropriate positional relationship in terms of fastening of the pair of disc bodies <NUM> to the wheel <NUM>. In the appropriate positional relationship, the first through-hole <NUM> formed in the first disc body <NUM>, the wheel through-hole <NUM> formed in the wheel <NUM>, and the second through-hole <NUM> formed in the second disc body <NUM> overlap with one another in the rotation axis direction d2, so as to allow insertion of the bolt <NUM>. In addition, the second through-hole <NUM> formed in the first disc body <NUM>, the wheel through-hole <NUM> formed in the wheel <NUM>, and the first through-hole <NUM> formed in the second disc body <NUM> overlap one another in the rotation axis direction d2, so as to allow insertion of the bolt <NUM>.

In this embodiment, the pair of disc bodies <NUM> and the wheel <NUM> can be aligned with each other by using the first positioning units <NUM> formed on the pair of disc bodies <NUM> and the second positioning units <NUM> provided on the wheel <NUM>. Thus, the alignment can be more easily performed than a case in which an alignment pin, which is engageable with the disc body <NUM> and the wheel <NUM> and is separated from the disc body <NUM> and the wheel <NUM>, is prepared and used for alignment. In particular, the wheel <NUM> for railway vehicle and the disc body <NUM> to be fastened to the wheel <NUM> for railway vehicle may be large. However, the present invention can facilitate the alignment of the large disc body <NUM> and the large wheel <NUM>.

Then, the nut <NUM> is disposed so as to be surrounded by the restriction wall <NUM> of the first through-hole <NUM>. Thereafter, the bolt <NUM> is inserted into the bolt through-hole <NUM> from the second through-hole <NUM>. When the distal end of the shaft part 31b of the bolt <NUM> comes into contact with the nut <NUM>, the bolt <NUM> is rotated with respect to the nut <NUM>. By these operations, the nut <NUM> is engaged with the shaft part 31b of the bolt <NUM>. Thus, as shown in <FIG> and <FIG>, the pair of disc bodies <NUM> are fastened to the wheel <NUM> so that the wheel with brake disc <NUM> is manufactured.

In this embodiment, the through wall <NUM> forming the through-hole <NUM> (first through-hole <NUM>) is partially provided with the restriction wall <NUM> that restricts the nut <NUM> from rotating together with the rotation of the bolt <NUM> when the pair of disc bodies <NUM> are fastened to the wheel <NUM>. Thus, after the nut <NUM> has been accommodated in a space surrounded by the restriction wall <NUM> and the bolt <NUM> has been inserted into the bolt through-hole <NUM>, an operator can perform the fastening operation without the need for fixing the nut <NUM> by holding it by hand, for example. In particular, the wheel <NUM> for railway vehicle and the disc body <NUM> to be fastened to the wheel <NUM> for railway vehicle may be large. However, the present invention can facilitate the alignment of the large disc body <NUM> and the large wheel <NUM>. For example, in the operation for fastening the large disc body <NUM> and the large wheel <NUM> to each other, when one operator inserts the bolt <NUM> and rotates it, it is not necessary for another operator to hold the nut <NUM>. Thus, the efficiency of the fastening operation can be improved.

In addition, in this embodiment, the bolt through-hole <NUM> is provided in the first positioning unit <NUM> and the second positioning unit <NUM>. Thus, the first positioning unit <NUM> is securely engaged with the second positioning unit <NUM> by fastening the pair of disc bodies <NUM> to the wheel <NUM> by using the bolt <NUM> passing through the bolt through-hole <NUM>. Thus, a braking force can be efficiently transmitted from the disc body <NUM> to the wheel <NUM> through the portion at which the first positioning unit <NUM> is engaged with the second positioning unit <NUM>.

Although one embodiment has been described above with reference to the specific example, but the aforementioned specific example is not intended to limit the one embodiment. The aforementioned one embodiment can be embodied differently, and can be variously omitted, replaced and change without departing from the scope thereof.

Modification examples are described herebelow with reference to the drawings. In the following description and the drawings used therein, the same symbols as those used for the corresponding parts in the aforementioned specific example are used for parts that can be formed similarly to the aforementioned specific example, and duplicate explanation is omitted.

In the aforementioned embodiment, the shape of the first through-hole <NUM> is described with reference to <FIG> and <FIG>. However, the shape of the first through-hole <NUM> is not limited thereto. <FIG> shows the first through-hole <NUM> in Modification Example <NUM>. <FIG> is an enlarged sectional view of the first through-hole <NUM> and its environment, when the disc body <NUM> having the first through-hole <NUM> with the nut accommodation wall <NUM> is cut along a plane parallel to a direction in which the first through-hole <NUM> extends. In <FIG>, the fastening member <NUM> disposed in the first through-hole <NUM> is shown in a plan view seen from a direction perpendicular to the section.

In the example shown in <FIG>, a hole diameter w10 of the first through-hole <NUM> in a contact surface 10b of the disc body <NUM> is smaller than a hole diameter w11 of a portion at which the nut accommodation wall <NUM> of the first through-hole <NUM> is formed. The portion at which the nut accommodation wall <NUM> is formed is a portion of a through wall <NUM>, with which the nut <NUM> is in contact, in a state where the pair of disc bodies <NUM> are fastened to the wheel <NUM>.

By applying a force to the nut <NUM> into the first through-hole <NUM>, the nut <NUM> can be accommodated in a space surrounded by the nut accommodation wall <NUM> of the first through-hole <NUM> shown in <FIG>. In the example shown in <FIG>, the hole diameter w10 of the opening of the first through-hole <NUM> in the contact surface 10b is smaller than the hole diameter w11 of a portion at which the nut accommodation walls <NUM> of the first through-hole <NUM> are formed. Thus, when the shaft part 31b of the bolt <NUM> is engaged with the nut <NUM> accommodated in a space surrounded by the nut accommodation wall <NUM>, it can be suppressed that the nut <NUM> is pressed by the bolt <NUM> so as to be detached from the first through-hole <NUM>.

In the aforementioned embodiment and the modification example, the shape of the first through-hole <NUM> is described with reference to <FIG>, <FIG> and <FIG>. However, the shape of the first through-hole <NUM> is not limited thereto. Not limited to the illustrated example, a shape having the restriction wall <NUM> capable of restricting the rotation of the nut <NUM> can be widely used as the shape of the first through-hole <NUM>. <FIG> shows the first through-hole <NUM> in Modification Example <NUM>. <FIG> is an enlarged sectional view of the first through-hole <NUM> and its environment, when the disc body <NUM> having the first through-hole is cut along a plane parallel to a direction in which the first through-hole <NUM> extends. <FIG> also shows the nut <NUM> disposed inside the first through-hole <NUM> in a plan view seen from a direction perpendicular to the section.

In the example shown in <FIG>, a hole diameter w12 of a part of the first through-hole <NUM>, at which the restriction wall <NUM> is formed, is smaller than a dimension w13 of the nut <NUM> in a direction orthogonal to a direction in which the bolt <NUM> with which the nut <NUM> is engaged extends. In this case, by applying a force to the nut <NUM> into a space surrounded by the restriction wall <NUM>, the nut <NUM> can be accommodated in a space surrounded by the restriction wall <NUM>. Since the nut <NUM> is pinched by the restriction wall <NUM>, the rotation of the nut <NUM> is restricted.

For example, the nut <NUM> has a columnar shape provided with a hole to be engaged with a shaft part 31b of the bolt <NUM>. A portion of the first through-hole <NUM>, at which the restriction walls <NUM> are formed, is a circular hole. The portion of the first through-hole <NUM>, at which the restriction walls <NUM> are formed, is formed such that its hole diameter w12 is smaller than the diameter w13 of the columnar nut <NUM>.

In the aforementioned embodiment and the respective modification examples, the example in which the first positioning unit <NUM> projects more than the plurality of heat radiating members <NUM> in the height direction of the heat radiating members <NUM>, and the second positioning unit <NUM> has the second positioning recess <NUM> to be engaged with the projecting first positioning unit <NUM> is shown. However, the shapes of the first positioning unit <NUM> and the second positioning unit <NUM> are not limited thereto. The shapes of the first positioning unit <NUM> and the second positioning unit <NUM> are not particularly limited, for example, as long as one of the first positioning unit <NUM> and the second positioning unit <NUM> has a projecting shape and the other has a recessed shape, and the one having the projecting shape and the other having the recessed shape can be engaged with each other.

<FIG> shows the first positioning unit <NUM> and the second positioning unit <NUM> in Modification Example <NUM>. <FIG> is an enlarged sectional view showing the first positioning unit <NUM> and the second positioning unit <NUM> and their environment, when the disc body <NUM> having the first positioning unit <NUM> and the wheel <NUM> having the second positioning unit <NUM> are cut along a plane parallel to a direction in which the bolt through-hole <NUM> extends.

In the example shown in <FIG>, the first positioning unit <NUM> is located nearer to a root part 13b of the heat radiating member <NUM> than a distal end 13a of the heat radiating member <NUM> in the height direction of the heat radiating members <NUM>. In the example shown in <FIG>, the first positioning unit <NUM> has a positioning surface 14c. The positioning surface 14c is located nearer to a root part 13b of the heat radiating member <NUM> than a distal end 13a of the heat radiating member <NUM> in the high direction of the heat radiating member <NUM>, and is opposed to the wheel <NUM>. In particular, the first positioning unit <NUM> has a base part <NUM> having the same height as that of the heat radiating member <NUM> in the height direction of the heat radiating member <NUM>, and a first positioning recess <NUM> formed in a distal end surface 15a of the base part <NUM>. In this case, a bottom surface of the first positioning recess <NUM> serves as the positioning surface 14c. In the example shown in <FIG>, the bolt through-hole <NUM> passes through the positioning surface 14c. In addition, in the example shown in <FIG>, the second positioning unit <NUM> has a second positioning projection <NUM> with which the first positioning unit <NUM> having the positioning surface 14c is engaged. In the example shown in <FIG>, the first positioning unit <NUM> has a recessed shape in the first positioning recess <NUM>. The second positioning unit <NUM> has a projecting shape in the second positioning projection <NUM>. In the example shown in <FIG>, the second positioning projection <NUM> is engaged with the first positioning recess <NUM>.

From the viewpoint of preventing the second positioning unit <NUM> having a projecting shape from being incorrectly engaged with a space between the heat radiating members <NUM> when the pair of disc bodies <NUM> and the wheel <NUM> are aligned, the second positioning unit <NUM> having a recessed shape is preferred to the second positioning unit <NUM> having a projecting shape. From the above viewpoint, it is preferable that the first positioning unit <NUM> projects more than the heat radiating members <NUM> in the height direction of the heat radiating members <NUM>, and that the second positioning unit <NUM> has the second positioning recess <NUM>.

In the aforementioned embodiment and the respective modification examples, the shapes of the first positioning unit <NUM> and the second positioning unit <NUM> are described with reference to <FIG>, <FIG>, <FIG> and <FIG>. However, the shapes of the first positioning unit <NUM> and the second positioning unit <NUM> are not limited thereto. <FIG> shows the first positioning unit <NUM> and the second positioning unit <NUM> in Modification Example <NUM>. <FIG> is an enlarged sectional view showing the first positioning unit <NUM> and the second positioning unit <NUM> and their environment, when the disc body <NUM> having the first positioning unit <NUM> and the wheel <NUM> having the second positioning unit <NUM> are cut along a plane parallel to a direction in which the bolt through-hole <NUM> extends.

In Modification Example <NUM>, at least one of the first positioning unit <NUM> and the second positioning unit <NUM> has an inclined surface 14b, 21b that is inclined along an insertion direction of the bolt <NUM>. In the example showing in <FIG>, the insertion direction of the bolt <NUM> is the same as the direction in which the bolt through-hole <NUM> extends, and thus is the same as the rotation axis direction d2. The first positioning unit <NUM> has the inclined surface 14b inclined with respect to the rotation axis direction d2. In addition, the second positioning unit <NUM> has the inclined surface 21b inclined with respect to the rotation axis direction d2.

One of the first positioning unit <NUM> and the second positioning unit <NUM>, which has a projecting shape, has an inclined surface that is inclined such that a width of the projecting shape narrows toward a distal end of the projecting shape. In addition, the other of the first positioning unit <NUM> and the second positioning unit <NUM>, which has a recessed shape, has an inclined surface that is inclined such that a width of the recessed shape narrows toward a bottom of the recessed shape. In the example shown in <FIG>, the first positioning unit <NUM> has the base part <NUM> and the first positioning projection <NUM>, and has a projecting shape in the first positioning projection <NUM>. A side surface of the first positioning projection <NUM> serves as the inclined surface 14b that is inclined such that a width of the first positioning projection <NUM> narrows towards the distal end surface 16c. In addition, in the example shown in <FIG>, the second positioning unit <NUM> has the second positioning recess <NUM>, and has a recessed shape in the second positioning recess <NUM>. A side surface of the second positioning recess <NUM> serves as the inclined surface 21b that is inclined such that a width of the second positioning recess <NUM> narrows toward the bottom.

Since at least one of the first positioning unit <NUM> and the second positioning unit <NUM> has the inclined surface 14b, 21b, the first positioning unit <NUM> can be easily engaged with the second positioning unit <NUM> along the inclined surface 14b, 21b. Thus, it is easy to engage the first positioning unit <NUM> with the second positioning unit <NUM>. In particular, the distal end of one of the first positioning unit <NUM> and the second positioning unit <NUM>, which has a projecting shape, can be easily inserted into the other having a recessed shape.

In the aforementioned embodiment and the respective modification examples, an example in which the second through-hole <NUM> is formed as the through-hole <NUM> in the first positioning unit <NUM> in both of the pair of disc bodies <NUM> is described. However, the positional relationship between the first positioning unit <NUM> and the through-hole <NUM> is not limited thereto. <FIG> is a view showing positional relationship between the first positioning unit <NUM> and the through-hole <NUM> in the pair of disc bodies <NUM> in Modification Example <NUM>. <FIG> shows the pair of disc bodies <NUM> seen from the contact surface 10b side, respectively. In <FIG>, the shapes of the first through-holes <NUM>, the second through-holes <NUM> and the pair of disc bodies <NUM> are simplified similarly to <FIG>, for the convenience of illustration of the positions of the first through-hole <NUM> and the second through-hole <NUM> and easy understanding. The one-dot chain lines shown in <FIG> indicate positions of the first positioning units <NUM> provided on the inner surface 10a of the disc body <NUM>.

In the example shown in <FIG>, the first through-hole <NUM> is formed in the first positioning unit <NUM> in both of the pair of disc bodies <NUM>. Also in this case, the same effect as the effect obtained by the case where the second through-hole <NUM> is formed in the first positioning unit <NUM> in both of the pair of disc bodies <NUM>, which is described above, can be obtained. The description about the position of the second through-hole <NUM> in the case where the second through-hole <NUM> is formed in the second through-hole, which is described above, is also applied to the position of the first through-hole <NUM> in the case where the first through-hole <NUM> is formed in the first positioning unit <NUM>, as long as they are not contradictory to each other.

In the aforementioned embodiment and the respective modification examples, an example in which the first through-holes <NUM> and the second through-holes <NUM> are formed in one of the pair of disc bodies <NUM>, and the first through-holes <NUM> and the second through-holes <NUM> are also formed in the other of the pair of disc bodies <NUM> is described. However, the positions of the first through-holes <NUM> and the second through-holes <NUM> are not limited thereto. <FIG> is a view showing the positions of the first through-holes and the second through-holes in the pair of disc bodies <NUM> in Modification Example <NUM>. <FIG> shows the pair of disc bodies <NUM> seen from the contact surface 10b side, respectively. In <FIG>, the shapes of the first through-holes <NUM>, the second through-holes <NUM> and the pair of disc bodies <NUM> are simplified similarly to <FIG> and <FIG>, for the convenience of illustration of the positions of the first through-hole <NUM> and the second through-hole <NUM> and easy understanding. The one-dot chain lines shown in <FIG> indicate positions of the first positioning units <NUM> provided on the inner surface 10a of the disc body <NUM>.

In the example shown in <FIG>, only the through-holes <NUM> as the through-holes <NUM> are formed in one of the pair of disc bodies <NUM>. In addition, only the second through-holes <NUM> as the through-hole <NUM> are formed in the other of the pair of disc bodies <NUM>. Namely, no second through-hole <NUM> is formed in the one of the pair of disc bodies <NUM>, and no first through-hole <NUM> is formed in the other of the pair of disc bodies <NUM>. Also in this case, the bolt through-hole <NUM> is formed by overlapping the first through-hole <NUM> formed in one of the pair of disc bodies <NUM> and the second through-hole <NUM> formed in the other in the rotation axis direction d2.

The pair of disc bodies <NUM> shown in <FIG> can be fastened to the wheel <NUM> in the following procedure. The nuts <NUM> are firstly accommodated in all the through-holes <NUM> (first through-holes <NUM>) in one of the pair of disc bodies <NUM>. Then, the bolts <NUM> are inserted from all the through-holes <NUM> (second through-holes <NUM>) in the other of the pair of disc bodies <NUM>, and the nuts <NUM> are engaged with the shaft parts 31b of the bolts <NUM>. As compared with the pair of disc bodies <NUM> shown in <FIG>, for example, the fastening procedure of the pair of disc bodies <NUM> shown in <FIG> is simple and easily understandable.

Some of the embodiments disclosed in the specification are composed of a plurality of components. These components can be integrated with one another. Conversely, one component can be divided into a plurality of components. Regardless of whether they are integrated or not, it is sufficient for them to achieve the object of the present invention.

Claim 1:
A brake disc (<NUM>) comprising a pair of disc bodies (<NUM>) each having, on a principal surface thereof,
a plurality of heat radiating members (<NUM>) projecting from the principal surface, the pair of disc bodies (<NUM>) being configured to sandwich therebetween a wheel (<NUM>) for railway vehicle with the heat radiating members (<NUM>), and the wheel (<NUM>) configured to being provided with a second positioning unit (<NUM>), wherein
each of the disc bodies (<NUM>) includes a first positioning unit (<NUM>) projecting more than the plurality of heat radiating members (<NUM>) in a height direction of the heat radiating members (<NUM>) or a first positioning unit (<NUM>) located nearer to a root part (13b) of the heat radiating member (<NUM>) than a distal end (13a) of the plurality of heat radiating members (<NUM>) in the height direction of the heat radiating members (<NUM>), wherein the first positioning unit (<NUM>) is configured to position each of the pair of the disc bodies (<NUM>) with respect to the wheel (<NUM>) by being engageable with the second positioning unit (<NUM>);
characterised in that
the first positioning unit (<NUM>) includes a side surface having a pair of flat surfaces (16a) opposed to each other, and a pair of curved surfaces (16b) connecting the pair of flat surfaces (16a).