DRUM TYPE WASHING MACHINE WITH LAUNDRY DRYING

FUNCTION Technical Field [1] The present invention relates to drum type washing machines, and more par¬ ticularly, to a drum type washing machine with a laundry drying function, in which a new flow passage structure is employed for improving a drying efficiency, and a drying performance. Background Art [2] In general, the drum type washing machine is an apparatus for washing laundry by rotating a drum with a driving force of a motor in a state detergent, washing water, and the laundry are introduced into the drum. The drum type washing machine has advantages in that damage to the laundry is small, entangling of the laundry is small, and a washing effect of pounding and rubbing can be made. [3] A related art drum type washing machine will be described in detail, with reference to FIG. 1. FIG. 1 illustrates a side section of a related art drum type washing machine, schematically. [4] Referring to FIG. 1, the related art drum type washing machine is provided with a cabinet 1 having a front opening for introduction of laundry, a door 2 mounted at the opening of the cabinet 1 for opening/closing the opening, a metal tub 3 in the cabinet 1 for holding washing water, a drum 4 rotatably mounted in the tub 3, and a motor unit 5 mounted on the tub 3, for providing driving force to the drum 4. [5] The door 2 has a glass 2a projected toward an opening of the tub 3. [6] There are hanging springs 6 between an inside of a top of the cabinet 1 and a top of an outside circumference of the tub 2, and, though not shown, there are dampers (not shown) between an inside of a bottom of the cabinet 1 and an underside of the outside circumference of the tub 2, for damping vibration of the tub 2 occurred during operation of the drum washing machine. [7] As the motor unit 5, an indirect coupling type is used mostly, in which the driving force is transmitted from a motor 5a to a washing shaft 5c via a belt 5b for rotating the drum 4. [8] In the meantime, there is a drying duct 7 in an upper portion of an inside of the cabinet 1. The drying duct 7 has a heater 7b and a fan 7a for producing hot air and forced blowing of the hot air. [9] One end of the drying duct 7 is connected to a gasket 8 connected between a cir¬ cumference of the front opening of the tub 3, and a circumference of the door at the front of the cabinet 1. [10] That is, the gasket 8 is mounted along a front inside circumference of the tub 3, and has a bellows shape for absorbing vibration of the tub 3. According to this, leakage of hot air through a connection of the drying duct 7 and the tub 3 is prevented. [11] The tub 3 has a condensing duct 9 connected to the drying duct 7. The condensing duct 9 has one end connected to an outside of the tub 3, and the other end connected to the drying duct 7. The condensing duct 9 has a water supply device 9a mounted thereon for supplying cooling water to condense, and remove moisture from air. [12] The drum type washing machine performs a washing cycle, a rinsing cycle, a spinning cycle, and a drying cycle. [13] The drying cycle of the drum type washing machine will be described. [14] Upon starting the drying cycle of the drum type washing machine, power is applied to the heater 7b on the drying duct 7. As the fan 7 a and the heater 7b are put into operation, the fan 7a blows hot air. [15] The hot air is guided by the drying duct 7, hits a sloped portion of the door glass 2a, and, therefrom, is introduced into an inside of the drum 4. [16] Then, the hot air heats laundry and vaporizes moisture from the laundry. In the instance, the drum 4 rotates slowly, to turn the laundry upside down, so that the laundry is exposed to the hot air uniformly, to help vaporization of the moisture. [17] The moisture vaporized thus is discharged through the condensing duct 9 carried by the air. In this instance, by spraying water from the water supply device 9a of the condensing duct 9, the moisture is removed from the air. The air having the moisture removed therefrom thus is introduced into the drying duct 7 again, and turned into hot air by the heater 7b and the fan 7a, and introduced into the drum 4 again, for performing drying of the laundry. [18] By repeating the foregoing process, the laundry is dried. [19] However, the related art drum type washing machine has problems in many aspects, such as the related art drum type washing machine has limitations in drying efficiency and drying performance because the related art drum type washing machine has a circulating structure in which the hot air is supplied to the inside of the drum through the connection portion of the drying duct at one side of an upper portion of the gasket, and discharged through a side of a front of the tub again. [20] First, because the air is discharged through the side of the front of the tub in a state the air supplied to the inside of the drum can not penetrate deep into the inside of the drum yet, drying of the laundry at the deep inside of the drum has not been adequate. Therefore, the related art flow passage structure has disadvantages of dropping the drying efficiency, and the drying performance. [21] Second, the gasket is liable to wear and tear because the gasket, which moves according to vibration of the tub, is connected to the drying duct which is fixedly secured, to require an expensive gasket 8 which has a relatively small thermal de¬ formation, to increase a production cost. [22] The vertical downward discharge of the hot air from the drying gasket 7 through the gasket causes the problem that the hot air fails the penetration deep into the inside of the drum, because the vertical downward direction is away from a direction of the shaft of the drum, and the hot air hits the door glass to have a resistance from the door glass. In order to overcome this problem, a fan with a large capacity is required. [23] Moreover, as described before, because the hot air is introduced into the drum 4 through the drying duct 7, and the gasket 8, and deflected at the sloped portion of the door glass 2a, the door 2 is heated unnecessarily. [24] In the meantime, the connection of the drying duct 7 to an outside circumference of upper side of the gasket 8, making the gasket 8 asymmetric between an upper side and a lower side of the gasket 8, causes the gasket to fail in balanced holding of a front of the tub 3. Disclosure of Invention Technical Problem [25] Accordingly, the present invention is directed to a drum type washing machine with a laundry drying function that substantially obviates one or more problems due to limitations and disadvantages of the related art. [26] An object of the present invention is to provide a drum type washing machine with a laundry drying function, which has a new improved flow passage structure for improving a drying efficiency and a drying performance. [27] Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. Technical Solution [28] To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a drum type washing machine having a laundry drying function includes a tub for receiving hot air through a front, and discharging the hot air through a rear, a drum rotatably mounted in the tub, a drying duct connected to a hot air inlet hole in the tub for guiding the hot air to a hot air inlet side of the tub, a heater for producing the hot air, and a fan for forced circulation of the hot air to a drum side, and a condensing duct for removing moisture from the hot air from the hot air outlet hole in a lower portion of the rear of the tub. [29] It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. Advantageous Effects [30] The drum type washing machine of the present invention having the drying system with a new flow passage structure has the following advantages. [31] First, the new drying system permits deep penetration of the air into an inside of the drum to dry all the laundry uniformly, to improve a drying efficiency, and a drying performance. [32] That is, the hot air, produced at the drying duct, is introduced into an upper portion of the drum, flows in a diagonal direction, and is discharged through a lower portion of a rear of the drum. According to this, the hot air penetrates deep into an inside of the drum, to improve a drying efficiency, and a drying performance. [33] Second, different from the related art drum type washing machine having a laundry drying function, the connection of the drying duct to the tub prevents the gasket from wear and tear. [34] The symmetric structure of the gasket in an upper side and a lower side enabled by the connection of the drying duct to the tub permits the gasket to absorb vibration of the tub, uniformly. [35] Next, different from the related art, as the hot air is introduced into the drum through the tub without passing through the gasket, the unnecessary heating of the door is prevented. [36] Fifth, the securing of the drying duct and the condensing duct to the tub permits to dispense with a separate gasket at the connection portion like the related art, and shortens an air flow passage of the ducts. [37] Sixth, the drying duct serves as a counterweight, to improve a balance of the tub. [38] Seventh, the hot air pass through holes are effectively arranged in the front of the drum taking strength of the drum, and a flow rate of the hot air introduced into the drum from the drying duct into account. Therefore, the flow rate of the hot air introduced into the drum can be maximized while the strength of the drum is maintained. [39] It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modi¬ fications and variations of this invention provided they come within the scope of the appended claims and their equivalents. Brief Description of the Drawings [40] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings; [41] FIG. 1 illustrates a side section of a related art drum type washing machine, schematically; [42] FIG. 2 illustrates a side section of a drum type washing machine in accordance with a preferred embodiment of the present invention; [43] FIG. 3 illustrates an exploded perspective view of key parts of FIG. 2; and [44] FIGS. 4 and 5 illustrate front views showing different embodiments of ar¬ rangements of hot air holes in a front of the drum in FIG. 2. Best Mode for Carrying Out the Invention [45] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. [46] FIG. 2 illustrates a side section of a drum type washing machine in accordance with a preferred embodiment of the present invention, FIG. 3 illustrates an exploded perspective view of key parts of FIG. 2, and FIGS. 4 and 5 illustrate front views showing different embodiments of arrangements of hot air holes in a front of the drum in FIG. 2. [47] Referring to FIGS. 2 and 3, the drum type washing machine in accordance with a preferred embodiment of the present invention includes a tub 20 in a cabinet 10 for holding washing water, having hot air inlet hole 20a in an upper portion of a front, and hot air outlet hole 20b in a lower portion of a rear, a drum 30 rotatably mounted in the tub 20, having a plurality of hot air pass through holes 30a of a predetermined array in a front, a drying duct 40 fixedly secured to an outside circumference of an upper portion of the tub 20, having a heater 41 and a fan 42 mounted therein for producing hot air, and one end connected to the hot air inlet holes in the tub 20 for supplying the hot air from the drying duct 40 to the drum 30, and a condensing duct 50 mounted in rear of the tub 20 such that one end thereof is connected to the hot air outlet hole 20b at the lower portion of the rear of the tub 20, and the other end thereof is connected to the drying duct 40, for removing moisture from the air discharged from the tub 20. [48] It is preferable that the tub 20 is a plastic injection molding, and the drum 30 is formed of stainless steel. [49] The hot air pass through holes 30a in the drum 30 are arranged in a radial direction, on the whole (see 4, and 5). [50] In more detail, referring to FIG. 4, the hot air pass through holes 30a in the front of the drum 30 are arranged in concentric circles in a circumferential direction as the holes go from an inner side to an outer side of the radial direction, with the hot air pass through holes 30a in each of the concentric circles are aligned in a line in the radial direction. [51] That is, referring to FIG. 4, the hot air pass through holes 30a in each of the concentric circles are arranged such that the hot air pass through holes 30a in each of the concentric circles are in the same line drawn outward from a center of the drum 30 in the radial direction. [52] Referring to FIG. 5, the hot air pass through holes 30a in the front of the drum 30 are arranged to form concentric circles in a circumferential direction as the hot air pass through holes 30a go from an inner side to an outer side in the radial direction, not in a radial line drawn outward from the center of the drum in the radial direction, but in a zigzag form along the radial line. [53] In the meantime, the drying duct 40 is fixedly secured to an outside of a top side of the tub 20 with fastening members, such as screws, with a heat shielding plate 43 between the tub 20 and the drying duct 40 for shielding transmission of heat from the drying duct 40 to the tub 20. [54] That is, the heat shielding plate 43 is fastened to the outside of the tub 20, and the drying duct 40 is fastened to the heat shielding plate 43 with fastening members, such as screws, in a state the heat shielding plate is secured to the tub. [55] In the meantime, even though it is preferable that the drum 30 is rotated by direct coupling type outer rotor type BLDC motor including a shaft 61 passed through the tub 20 and coupled to the drum 30, a rotor 62 coupled to a rear end portion of the shaft 61, and a stator 63 secured to a rear wall of the tub 20 so as to be positioned on an inner side of the rotor 62, the rotating system of the drum 30 is not limited to above. [56] There may be heat dissipation means, such as heat dissipation fins 44, on an upper surface of the drying duct 40 for increasing a heat dissipation area to prevent the upper surface of the drying duct from overheating. [57] The operation of the drum type washing machine having a laundry drying function of the present invention will be described. [58] The tub 20 has the hot air inlet hole 20a in the upper portion of the front of the tub 20, and the hot air outlet hole 20b in the lower portion of the rear of the tub 20, making the hot air to flow in a diagonal direction in the tub 30, enabling the hot air to reach deep into an inside of the drum uniformly throughout the drum to dry the laundry uniformly. [59] The hot air pass through holes 30a in the front surface of the drum 30, opposite to the hot air inlet hole 20a in the upper portion of the front of the tub 20, are arranged in concentric circles, in the same line drawn outward from a center of the drum 30 in the radial direction as shown in FIG. 4, or in a zigzag form along the radial direction as shown in FIG. 5. [60] That is, the hot air pass through holes in the front of the drum 30 are arranged such that a flow passage cross sectional area is the maximum while strength of the front of the drum 30 is not impaired. [61] The effective arrangement of the hot air pass through holes 30a throughout the entire front surface of the drum 30, such that the hot air inlet hole 20a and the hot air pass through holes 30a are in communication even if the drum 30 rotates, enables supply of the hot air to an inside of the drum 30 smoothly through the hot air pass through holes 30a in the front of the drum 30. [62] In the meantime, the heat shielding plate 43 under the drying duct 40 shields transmission of heat from the drying duct 40 to the tub 20. [63] Along with this, the drying duct 40 fixed to the outside surface of the tub with the heat shielding plate therebetween permits to dispense with the gasket at a connection portion of the drying duct 40 and the tub 20 for absorbing vibration. This is because the drying duct 40 fixed to the tub 20 moves together with the tub 20 when the tub 20 vibrates or shakes. [64] Of course, it is apparent that a person in this field of art knows that a sealing member may be mounted at the connection portion of the drying duct 40 and the tub 20 for preventing heat from leaking from the drying duct 40. [65] In the meantime, as the condensing duct 50 is secured to the rear of the tub 20 directly too, no gasket is required at a connection portion of the condensing duct 50 and the tub 20 for absorbing the vibration. [66] A drying process of the drum type washing machine having a laundry drying function will be described. [67] Upon starting the drying cycle of the drum type washing machine, power is applied both to the heater 41 in the drying duct 40 and the fan 42, to produce hot air. [68] The hot air produced thus in the drying duct 40 is introduced into the drum 30 through the hot air inlet hole 20a in the front of the tub 20 and the hot air pass through holes 30a in the front of the drum 30. [69] In this instance, because the hot air pass through holes 30a are arranged throughout the front surface of the drum so as to maximize the flow passage sectional area while strength of the front of the drum 30 is not impaired, and to position the hot air pass through holes 30a opposite to the hot air inlet hole 20a even if the drum 30 rotates, the hot air introduced into the inside of the tub 20 through the hot air inlet hole 20a can be introduced into an inside of the drum 30 directly without going around through other path. [70] Then, the hot air introduced into the drum 30 proceeds toward the hot air outlet hole 20b in the tub in a diagonal direction, and absorbs moisture from the laundry, thereby drying the laundry. [71] In this instance, since the drum rotates slowly to turn the laundry upside down, to expose the laundry to the hot air uniformly, the laundry drying efficiency is improved. [72] By rotating the drum 30 slowly, to turn the laundry upside down, and, in this state, raising the rotating speed of the drum 30 to a level at which the laundry does not separate from an inside surface of the drum 30, a time period of contact between the hot air introduced into the inside of the drum 30 and the laundry can be increased, adequately. [73] In the meantime, the hot air, finishing the drying, is discharged to the condensing duct 50 without temperature drop in a state the hot air contains the moisture, wherein, as the condensing duct 50 is connected to the lower portion of the rear of the tub 20 which is diagonal to the upper portion of the drum 30 into which the hot air is introduced, the air can be discharged out of the drum 30 more smoothly through the condensing duct 50. [74] That is, because, while the air at the hot air inlet hole in the front of the tub 20 is light and warm, the air at the hot air outlet hole 20b in the rear of the tub 20 is relatively heavy and cold, a flow passage structure of the present invention, in which the hot air inlet hole 20a is formed in the upper portion of the front of the tub 20 and the hot air outlet hole 20b is formed in a lower portion of the rear of the tub 20, meets to a natural air circulating principle. [75] Different from the related art, since the hot air is discharged in a state the hot air passes through the drum 30 completely, enabling the hot air to reach to the laundry at a deep place of the drum, the drum type washing machine of the present invention can improve the drying effect. [76] Moreover, the supply of cold water to the condensing duct 50 from the water supply device 51 for the moisture laden air introduced into the condensing duct 50 from the hot air outlet hole 20b enables removal of the moisture from the moisture laden air in the condensing duct 50 owing to a condensing action of the cold water. [77] The air dried at the condensing duct 50 is introduced into the drying duct 40 by the fan 42 in the drying duct 40, heated with the heater 41 in the drying duct 40, and introduced into the drum 30 by the fan 42, again. [78] By repeating above process, the laundry is dried. [79] In the meantime, different from the foregoing embodiment, the drying duct 40 and/ or the condensing duct 50 may be fixedly secured to the cabinet, while the drying duct 40 and/or the condensing duct 50 is connected to the tub 20. [80] That is, though not shown, in this case, most of configuration is identical to the foregoing embodiment except that the drying duct 40 and/or the condensing duct 50 is secured to the cabinet 10. [81] For an example, if the drying duct 40 is secured to the cabinet 10, there is a flexible gasket (not shown) at a connection portion of the drying duct 40 and the hot air inlet hole 20a in the tub 20, for preventing the connection portion suffering from damage or breakage of the connection due to vibration at the tub 20. [82] Of course, the configuration of the gasket on the drying duct 40 side is also applicable a case of the condensing duct 50 and the hot air outlet hole 20b in the tub 20, if the condensing duct 50 is secured to the cabinet 10. [83] In the meantime, though not shown, a plurality of hot air inlet holes 20a may be formed in the front of the tub 20, and a plurality of hot air outlet holes 20b may be formed in the rear of the tub 20, and, in correspondence to this change, the drying duct 40 is branched into a plurality of branches at an outlet side, for connection to the plurality of hot air inlet holes 20a in the tub, and the condensing duct 50 is branched into a plurality of branches at an inlet side, for connection to the plurality of hot air outlet holes 20b in the tub, for increasing a circulating rate of the hot air. [84] In the meantime, referring to FIG. 5, the hot air pass through holes 30a in the front of the drum 130 may be arranged to form concentric circles in a circumferential direction as the hot air pass through holes 30a go from an inner side to an outer side in the radial direction, in a zigzag form along the radial line, in other words, in a continuous arrangement of honeycomb type of hot air pass through holes 130a as shown in "A" part in FIG. 5. Industrial Applicability [85] The drum type washing machine of the present invention having the drying system with a new flow passage structure has significant industrial applicability.