Abstract:
Disclosed herein is a drum type washing machine including a body, a tub arranged in the body, and a drum rotatably installed in the tub, and an inner surface of a rear wall of the has a flat portion along a rotating direction of the drum.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 2008-0088837, filed on Sep. 9, 2008 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Embodiments of the present invention relate to a drum type washing machine having an improved tub configuration. 
     2. Description of the Related Art 
     Generally, washing machines carry out washing, rinsing and dehydrating processes, to remove contaminants adhered to laundry using interaction of water and detergent. The washing machines may be classified into a cylindrical drum type, an agitator type, and a pulsator type, based on washing methods thereof. 
     In a drum type washing machine, structural strength of a tub may be important to support a load of laundry when the laundry is rotated at a high speed along with a drum. To enhance the strength of the tub, a rear wall of the tub has conventionally been fabricated with a complicated convex and concave inner surface. 
     SUMMARY 
     Therefore, it is an aspect of the present invention to provide a drum type washing machine, a tub of which has an improved configuration to reduce aerodynamic noise and bio-films and to enhance tub strength. 
     Additional aspects and/or advantages will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention. 
     The foregoing and/or other aspects of the present invention may be achieved by providing a drum type washing machine including a body, a tub arranged in the body, and a drum rotatably installed in the tub, and an inner surface of a rear wall of the tub has a flat portion in a rotating direction of the drum. 
     The drum type washing machine may further include a bearing housing insert-molded in the rear wall of the tub. 
     The inner surface of the rear wall of the tub may include a region corresponding to the bearing housing insert-molded in the rear wall of the tub, and the region may have no convex or concave portion in the rotating direction of the drum. 
     The inner surface of the rear wall of the tub may include a reinforcing portion extending in the rotating direction of the drum. The reinforcing portion may be formed at the outside of the region. An outer surface of the rear wall of the tub may include reinforcing ribs. The reinforcing ribs may include a plurality of straight ribs radially extending from a center of the tub. The tub may have a cylindrical shape, and the reinforcing ribs may include a plurality of concentric circular ribs having the same common center as that of the tub. A rear surface of the bearing housing may include reinforcing members having a shape corresponding to the reinforcing ribs of the tub. 
     The drum type washing machine may further include a shaft connected to the drum through a center of the rear wall of the tub and rotating the drum, and the inner surface of the rear wall of the tub may be gently curved upward from an outer rim of the tub to a center of the tub, thus being centrally raised. 
     The bearing housing may include a plurality of holes. 
     The foregoing and/or another aspects of the present invention are also achieved by providing a drum type washing machine including a tub having a rear wall, a drum rotatably arranged in the tub, and a bearing housing contained in the rear wall of the tub, and an inner surface of the rear wall of the tub includes a first region corresponding to the bearing housing, and a second region around the first region, and the first region is a planar region. 
     The rear wall of the tub may include a reinforcing portion formed in the second region. 
     The tub may have a cylindrical shape, and the reinforcing portion may protrude from the inner surface of the rear wall of the tub and extend in a circumferential direction of the rear wall of the tub. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a sectional view illustrating a drum type washing machine according to a first embodiment of the present invention; 
         FIG. 2  is an exploded perspective view of a tub provided in the drum type washing machine according to the embodiment of  FIG. 1 ; 
         FIG. 3  is a front perspective view of the tub provided in the drum type washing machine according to the embodiment of  FIG. 1 ; 
         FIG. 4  is a rear perspective view of the tub provided in the drum type washing machine according to the embodiment of  FIG. 1 ; 
         FIG. 5  is a front perspective view of a bearing housing provided in the drum type washing machine according to the embodiment of  FIG. 1 ; 
         FIG. 6  is a rear perspective view of the bearing housing provided in the drum type washing machine according to the embodiment of  FIG. 1 ; 
         FIG. 7  is a sectional view illustrating a drum type washing machine according to a second embodiment of the present invention; and 
         FIG. 8  is a partial sectional perspective view of a tub provided in the drum type washing machine according to the embodiment of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below to explain the present invention by referring to the figures. 
       FIG. 1  is a sectional view illustrating a drum type washing machine according to one embodiment of the present invention, and  FIG. 2  is an exploded perspective view of a tub provided in the drum type washing machine according to the embodiment of  FIG. 1 . 
     The drum type washing machine includes a cabinet  1  defining an external appearance of the drum type washing machine, a tub  2  installed in the cabinet  1  in a shock-absorbing manner using a damper  4 , a drum  3  rotatably disposed in the tub  2  and having dehydrating holes  3   b  perforated in a peripheral surface thereof, a shaft  5  connected to the drum  3  through the center of a rear wall  10  of the tub  2  and serving to rotate the drum  3 , a motor  6  mounted underneath the tub  2 , and a power transmission device  7  to transmit drive force of the motor  6  to the shaft  5 . 
     The power transmission device  7  includes a driving pulley  7   c  fixed to a rotating shaft  6   a  of the motor  6 , a driven pulley  7   a  fixed to the shaft  5 , and a belt  7   b  to link the driving pulley  7   c  and driven pulley  7   a  with each other. The driving pulley  7   c  takes the form of a hollow cylinder and is fixed to a distal end of the rotating shaft  6   a . The driven pulley  7   a  is fixed to a distal end of the shaft  5  penetrating the rear wall  10  of the tub  2 . 
     The tub  2  has a cylindrical shape and includes a front tub  2   a  and a rear tub  2   b  coupled to each other using bolts  2   d . The front tub  2   a  has an opening  2   c  for entrance and exit of laundry, and the shaft  5  penetrates through the rear tub  2   b . 
     An inner surface of the rear wall  10  of the tub  2  is gently curved upward from the outer rim to the center of the rear wall  10  of the tub  2 , thus being centrally raised. In addition, a rear wall  3   a  of the drum  3  is centrally raised to correspond to the inner surface of the rear wall  10  of the tub  2 . The center of the rear wall  10  of the tub  2  is raised to have an increased center thickness to stably support the shaft  5  that penetrates through the center of the rear wall  10  of the tub  2  and is affected by load of the drum  3 . 
     The inner surface of the rear wall  10  of the tub  2  is a smooth surface having no convex or concave portions in a rotating direction A of the drum  3 . In other words, the inner surface has flat portions. Specifically, since the inner surface of the rear wall  10  of the tub  2  has no convex or concave portion in a circumferential direction of the tub  2  corresponding to the rotating direction A of the drum  3 , air moving between the rear wall  3   a  of the drum  3  and the rear wall  10  of the tub  2  during high-speed dehydrating rotation of the drum  3  may cause only slight pressure variation. This results in reduced noise. Moreover, the smooth inner surface of the rear wall  10  of the tub  2  may restrict generation of contaminants due to wash water, such as bio-films, etc. 
     An outer surface of the rear wall  10  of the tub  2  is provided with reinforcing ribs  11  (see  FIG. 4 ). The reinforcing ribs  11  include a plurality of circular ribs  11   a  and a plurality of straight ribs  11   b  (see  FIG. 4 ). In the present embodiment, the reinforcing ribs  11  are provided at the outer surface of the rear wall  10  of the tub  2  to enhance structural strength of the tub  2 , instead of omitting a conventional convex and concave inner surface of the rear wall of the tub. 
     To further enhance the structural strength of the tub  2 , a metallic bearing housing  20  is formed in a shape corresponding to the rear wall  10  of the tub  2  and is insert-molded into the rear wall  10  of the tub  2 . 
     The bearing housing  20  is gently curved upward from the outer rim to the center of the bearing housing  20  thus being centrally raised, and is similar to the inner surface of the rear wall  10  of the tub  2 . A front surface of the bearing housing  20  is a smooth surface similar to the inner surface of the rear wall  10  of the tub  2 , and a rear surface of the bearing housing  20  is provided with reinforcing members  21  (see  FIG. 6 ) corresponding to the reinforcing ribs  11  of the tub  2 . The reinforcing members  21  of the bearing housing  20  include a plurality of circular members  21   a  and a plurality of straight members  21   b  (see  FIG. 6 ). 
       FIG. 3  is a front perspective view of the tub provided in the drum type washing machine according to the first embodiment of the present invention, and  FIG. 4  is a rear perspective view of the tub provided in the drum type washing machine according to the first embodiment of the present invention. 
     As shown in  FIG. 3 , the inner surface of the rear wall  10  of the tub  2  has no convex or concave portion in the circumferential direction of the tub  2  equal to the rotating direction A of the drum  3 , and entirely defines a smooth surface gently curved radially toward the center of the tub  2 . This configuration of the tub  2  is proposed not only to reduce pressure variation caused by air moving between the rear wall  3   a  of the drum  3  and the inner surface of the rear wall  10  of the tub  2  during high-speed dehydrating rotation of the drum  3 . This also achieves reduced aerodynamic noise, and still further stably supports the shaft  5  connected to the drum  3  through the center of the rear wall  10  of the tub  2 . 
     Therefore, as shown in  FIG. 4 , the reinforcing ribs  11  are provided at the outer surface of the rear wall  10  of the tub  2 , to assure the strength of the tub  2  despite the smooth inner surface of the rear wall  10  of the tub  2 . 
     The reinforcing ribs  11  include the plurality of concentric circular ribs  11   a  of different sizes having the same common center as the center of the rear wall  10  of the tub  2 , and the plurality of straight ribs  11   b  radially extending from the center of the rear wall  10  of the tub  2 . Providing the outer surface of the rear wall  10  of the tub  2  with the reinforcing ribs  11  may increase bending strength of the rear wall  10  of the tub  2 . 
       FIG. 5  is a front perspective view of the bearing housing provided in the drum type washing machine according to the first embodiment of the present invention, and  FIG. 6  is a rear perspective view of the bearing housing provided in the drum type washing machine according to the present embodiment. 
     Referring to  FIGS. 5 and 6 , the bearing housing  20  is formed of a metal, such as aluminum. The bearing housing  20  is formed in a shape corresponding to the rear wall  10  of the tub  2  and is insert-molded into the rear wall  10  of the tub  2 , in order to support the shaft  5  and also, to increase strength of the rear wall  10  of the tub  2 . 
     Accordingly, the front surface of the bearing housing  20  is a smooth surface having no convex or concave portions, similar to the rear wall  10  of the tub  2 , and the rear surface of the bearing housing  20  is formed with the reinforcing members  21  including the circular members  21   a  and the straight members  21   b . 
     The bearing housing  20  is centrally raised to correspond to the center of the rear wall  10  of the tub  2 . A plurality of holes  22  are circumferentially perforated in the bearing housing  20  between the circular members  21   a  and the straight members  21   b , to allow resin to be smoothly charged into the rear wall  10  of the tub  2  during insert-molding of the bearing housing  20 . 
       FIG. 7  is a sectional view illustrating a drum type washing machine according to a second embodiment of the present invention, and  FIG. 8  is a partial sectional perspective view of a tub provided in the drum type washing machine according to the embodiment of  FIG. 7 . 
     Hereinafter, a description of the same configurations as those of the drum type washing machine according to the first embodiment shown in  FIG. 1  will be omitted. 
     Referring to  FIGS. 7 and 8 , the drum type washing machine according to the present embodiment includes a cabinet  100  defining an external appearance of the drum type washing machine, a tub  102  installed in the cabinet  100  in a shock-absorbing manner using a damper  104 , a drum  103  rotatably disposed in the tub  102 , and a shaft  105  connected to the drum  103  through the center of a rear wall  110  of the tub  102  and serving to rotate the drum  103 . 
     An inner surface of the rear wall  110  of the tub  102  is gently curved thus being centrally raised, to stably support the shaft  105 . A bearing housing  120  is insert-molded into the rear wall  110  of the tub  102 , to reinforce the tub  102 . The bearing housing  120  is smaller than the rear wall  110  of the tub  102 , and is gently curved thus being centrally raised to correspond to the inner surface of the rear wall  110  of the tub  102 . 
     In a state wherein the bearing housing  120  is insert-molded in the rear wall  110  of the tub  102 , a region  112  of the inner surface of the rear wall  110  of the tub  102  corresponding to the bearing housing  120  may define a smooth region, whereas an outer rim region  113  of the inner surface not containing the bearing housing  120  may be formed with reinforcing portions  130  to reinforce the tub  102 . 
     The reinforcing portions  130  include a first reinforcing portion  130   a  and a second reinforcing portion  130   b , which extend lengthwise in a circumferential direction of the tub  102 . The first and second reinforcing portions  130   a  and  130   b  protrude forward from the inner surface of the rear wall  110  of the tub  102 , to have a semi-circular shape. 
     The reinforcing portions  130  reinforce the rear wall  110  of the tub  102 , more particularly, the outer rim region  113  of the rear wall  100  of the tub  102  which does not contain the bearing housing  120  and has a smaller thickness than the center of the rear wall  110  of the tub  102 . Thus, the tub  102  has a reinforced structure by the reinforcing portions  130  formed at the inner surface of the rear wall  110  and reinforcing ribs  111  including circular ribs  111   a  and straight ribs  111   b  formed at an outer surface of the rear wall  110  of the tub  102 . 
     The entire inner surface of the rear wall  110  of the tub  102  has a plan or slope having no convex or concave portions in the rotating direction A of the drum  103 . This is because the reinforcing portions  130  are formed in the circumferential direction of the tub  102  corresponding to the rotating direction A of the drum  103 . 
     Now, how the entire inner surface of the rear wall  110  of the tub  102  may be planar without any convex or concave portions in the rotating direction A of the drum  103  will be described with reference to  FIG. 8 . The reinforcing portions  130  naturally provide the outer rim region  113  of the tub  102  with a convex and concave portion with respect to a radial direction B of the tub  102 . 
     However, the reinforcing portions  130  protrude in the rotating direction A of the drum  103  from the outer rim region  113  of the tub  102  to have a predetermined semi-circular shape and therefore, define no convex or concave portions with respect to the rotating direction A of the drum  103 . Accordingly, the reinforcing portions  130  exert no resistance on the flow of air caused between a rear wall  103   a  of the drum  103  and the rear wall  110  of the tub  102  during rotation of the drum  103 . 
     Consequently, the reinforcing portions  130  further reinforce the tub  102  and also, reduce pressure variation due to the flow of air between the rear wall  103   a  of the drum  103  and the rear wall  110  of the tub  102 , thus achieving reduced aerodynamic noise. 
     As is apparent from the above description, a drum type washing machine according to the embodiments of the present invention may achieve reduced aerodynamic noise between a rear wall of a tub and a rear wall of a drum and enhanced structural strength of the tub while reducing generation of any contaminants, such as bio-films, at an inner surface of the rear wall of the tub. 
     Although a few embodiments have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.