Bumper beam assembly for vehicle

1. A bumper beam assembly for a vehicle comprising:

a back beam disposed inside a vehicle bumper, both distal ends of the back beam being oriented in a lateral direction of a main body of the vehicle;

crash boxes coupled to one side of the back beam, the crash boxes protruding from the both distal ends of the back beam toward the bumper; and

back beam stays integrally coupled to the other side of the back beam, the back beam stays protruding from the both distal ends of the back beam toward an inside of the vehicle, in a direction opposite to a direction in which the crash boxes protrude;

wherein the back beam includes:

back beam holes in the both distal ends thereof, the back beam holes being open toward the inside and an outside of the vehicle; and

base surfaces each formed in an inner circumference of the respective back beam holes, wherein each of the crash boxes are seated on and coupled to a corresponding base surface respectively;

wherein each of the back beam stays is connected to a corresponding base surface respectively;

wherein each of the back beam stays has a C-shaped cross section, with a portion thereof being connected to a respective one of the base surfaces; and

wherein the back beam stay is open in a direction toward the outside of the vehicle through the back beam hole but is closed in a direction toward the inside of the vehicle to form a crash-absorbing space defined therein.

2. The bumper beam assembly of claim 1 , wherein the back beam is bent such that a center portion thereof protrudes further toward an outside of the vehicle, in which the bumper is located, than the both distal ends thereof to which the crash boxes are coupled.

3. The bumper beam assembly of claim 1 , wherein the back beam has a C-shaped cross-section that is open toward the inside of the vehicle.

4. The bumper beam assembly of claim 1 , wherein each of the crash boxes is divided into a plurality of divided spaces by a plurality of vertical partitions and a plurality of horizontal partitions therein.

5. The bumper beam assembly of claim 1 , wherein each of the back beam stays is coupled to a side member, which forms a part of the main body of the vehicle.

6. The bumper beam assembly of claim 5 , wherein each of the back beam stays and the crash boxes are aligned along a longitudinal axis of the side member.

7. The bumper beam assembly of claim 1 , wherein the back beams and the back beam stays are made of glass mat reinforced thermoplastic, and the crash boxes are made of high density polyethylene.

8. The bumper beam assembly of claim 1 , wherein a cross-sectional thickness, a length of a protrusion toward the inside of the vehicle, an outer inclination angle and an inner inclination angle of each of the back beam stays satisfy 4 mm to 6 mm, 35 mm to 40 mm, 20° to 25°, and 30° to 35°, respectively, in order to minimize a degree to which a vehicle body panel intrudes into a space in the inside of the vehicle as well as an amount of crash energy that is transferred toward the main body of the vehicle through a side member.

9. The bumper beam assembly of claim 1 , wherein each of the crash boxes includes:

a base section, which is seated on and coupled to the respective base surfaces in order to cover a respective one of the back beam holes; and

an extension, which is integrally formed with the base section such that the extension extends beyond the back beam-hole toward the center section of the back beam along the one side of the back beam.