washing machine

Abstract

To provide a washing machine capable of washing a washing tub effectively.SOLUTION: A washing machine 1 includes: a motor 6; a washing tub 8 having an outer tub 3 and an inner tub 4; a drain passage 15 connected to a drain port 3G of the outer tub 3; an overflow passage 17 connected to an overflow port 3E arranged at a position higher than the drain port 3G in the outer tub 3; a drain valve 16 for opening / closing the drain passage 15; a water supply valve 14 for supplying water in the washing tub 8; a water level detection part for detecting water level in the washing tub 8; and a microcomputer for executing a washing operation. In the washing operation, the microcomputer finishes a rinsing step in a state where the drain valve 16 is closed and water is stored in the washing tub 8, and in a tub washing step after the rinsing step, the microcomputer rotates the inner tub 4 by the motor 6 with the drain valve 16 closed, so as to ascend the water level in the washing tub 8 to a tub washing water level W3 which is equal to or higher than the overflow port 3E and lower than an opening 3D of the outer tub 3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a washing machine. [Background technology]

[0002] The washing machine described in the following Patent Document 1 includes a water tub with a drain outlet formed at the bottom, a drain hose connected to the drain outlet, a drain valve for opening and closing the drain hose, and a rotating tub housed in the water tub in a vertical shaft shape. The washing machine can execute a tub cleaning course for cleaning the water tub and the rotating tub. In the tub rotation cleaning process in the tub cleaning course, the drain valve is opened and the water is continuously drained from the water tub while the rotating tub is rotated. This causes the water in the water tub and the rotating tub to rise in a mortar shape to a water level where it will not overflow. The water tub and the rotating tub are cleaned by dehydration due to the centrifugal force at this time and by the water flow generated by the rotation of the rotating tub. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-2263 A Summary of the Invention [Problem to be solved by the invention]

[0004] Not only in the washing machine of Patent Document 1, but in the washing tub of a general washing machine, mold may grow as nutrients from biofilms made of detergent residue and dirt (hereinafter simply referred to as "dirt") remaining after a washing operation. Since biofilms often grow near the water surface of the water that accumulates in the washing tub during a washing operation, in order to prevent the growth of biofilms, that is, the growth of mold, it is necessary to remove dirt that is relatively high in the washing tub. However, when water is constantly drained from the lower drain during the tub rotation washing process as in Patent Document 1, the water level in the water tub and the spin tub does not easily reach the dirt even when the spin tub is rotated, so it is difficult to effectively remove this dirt with the water flow. In addition, the dirt that has been removed and taken in by the water flow may reattach to the water tub and the spin tub as the water level drops due to the drainage from the drain.

[0005] The present invention has been made against such a background, and has an object to provide a washing machine capable of effectively cleaning the washing tub. [Means for solving the problem]

[0006] The present invention relates to a washing tub having a motor that generates a driving force, an outer tub that is provided with a drain outlet, an overflow outlet located at a position higher than the drain outlet, and an opening located at a position higher than the overflow outlet and that stores water, an inner tub that is disposed within the outer tub and that is provided with a through hole for passing water between the outer tub and the inner tub and an inlet / outlet facing the opening, laundry is put in and taken out via the opening and the inlet / outlet, and that rotates by receiving the driving force of the motor, a drainage channel that is connected to the drain outlet and that drains water from the washing tub, an overflow channel that is connected to the overflow outlet and that guides water from the washing tub from the overflow outlet to the drainage channel, a drain valve that opens and closes the drainage channel, a water supply unit that supplies water into the washing tub, a water level detection unit that detects the water level in the washing tub, and a water supply system that detects the water level in the washing tub and a water supply system that detects the water level in the washing tub. A washing machine including a control unit which controls a water valve and the water supply unit and receives input of the detection results of the water level detection unit, and which executes a washing operation including a washing process in which the water supply unit supplies water into the washing tub to wash the laundry in the inner tub, a rinsing process in which the water supply unit supplies water into the washing tub after the washing process to rinse the laundry in the inner tub, and a tub cleaning process in which the washing tub is cleaned after the rinsing process, wherein the control unit closes the drain valve to end the rinsing process with water stored in the washing tub, and in the tub cleaning process, the control unit continues to rotate the inner tub with the drain valve closed, thereby raising the water level in the washing tub to a tub cleaning water level that is above the overflow outlet and lower than the opening.

[0007] In addition, the present invention is characterized in that, in the tub cleaning step, when the water level in the washing tub exceeds the tub cleaning water level, the control unit reduces the rotation speed of the motor.

[0008] The present invention is also characterized in that the control unit executes the tub cleaning process multiple times, and the control unit executes a drainage process at the end of at least the first tub cleaning process by opening the drain valve to drain a portion of the water in the washing tub, and the control unit sets the maximum rotation speed of the motor in the second or subsequent tub cleaning processes to be higher than the maximum rotation speed of the motor in the first tub cleaning process.

[0009] In the present invention, the control unit continues to rotate the motor during the drainage treatment.

[0010] The present invention is also characterized in that the washing machine includes a reception unit that receives a selection of the type of laundry, and when the laundry related to the selection received by the reception unit is a blanket, the control unit sets at least one of the maximum rotation speed of the motor in the tub cleaning process and the water level in the washing tub at the start of the tub cleaning process to be lower than in the case of laundry other than a blanket. Effect of the Invention

[0011] According to the present invention, in a washing machine having an outer tub and an inner tub in the outer tub, water supplied by a water supply unit flows between the outer tub and the inner tub through a through hole in the inner tub, and accumulates in the outer tub and the inner tub, i.e., the entire washing tub. When the drain valve opens the drainage path, the water in the washing tub is discharged from the drain outlet of the outer tub through the drainage path. When the water level in the washing tub rises to an overflow outlet located in the outer tub at a position higher than the drain outlet, the water on the water surface side, i.e., the upper side, in the washing tub is led from the overflow outlet through the overflow path to the drainage path and discharged through the drainage path. Laundry is put in and taken out of the inner tub through an opening located in the outer tub at a position higher than the overflow outlet and an inlet and outlet of the inner tub.

[0012] The control unit of the washing machine executes a tub cleaning process for cleaning the washing tub after the rinsing process as part of the washing operation. Specifically, the control unit closes the drain valve and ends the rinsing process with water stored in the washing tub, and in the subsequent tub cleaning process, the control unit continues to close the drain valve and rotates the inner tub by the motor with water stored in the washing tub, thereby raising the water level in the washing tub to a tub cleaning water level that is above the overflow port and lower than the opening of the outer tub by centrifugal force accompanying the rotation of the inner tub. When the inner tub is rotated without draining water in the middle, the water flow caused by the water that has risen to the tub cleaning water level in the washing tub reaches dirt that is at a height above the overflow port in the washing tub without leaking out of the opening. Therefore, dirt in the washing tub can be removed by such water flow and centrifugal force. The removed dirt is led to the drainage channel from the overflow port together with the water on the water surface side in the washing tub and discharged, so that the dirt can be prevented from reattaching to the washing tub. The washing tub can be effectively cleaned by such a tub cleaning process.

[0013] In addition, according to the present invention, during the tub cleaning process, when the water level in the washing tub exceeds the tub cleaning water level, the control unit reduces the motor rotation speed, thereby preventing the water in the washing tub from leaking out of the washing tub through the opening of the outer tub.

[0014] According to the present invention, when the tub cleaning step is performed multiple times, the control unit performs a drainage process at least at the end of the first tub cleaning step to drain part of the water in the washing tub. The control unit then sets the maximum rotation speed of the motor in the second and subsequent tub cleaning steps to be higher than the maximum rotation speed of the motor in the first tub cleaning step. In this case, in the second and subsequent tub cleaning steps, the small amount of water is pushed up higher by the centrifugal force caused by the high rotation of the inner tub, so that the tub cleaning water level is higher than the tub cleaning water level in the first tub cleaning step. Therefore, in the second and subsequent tub cleaning steps, among the dirt located at a height position above the overflow port in the washing tub, dirt near the opening can be removed without omission. By performing such multiple tub cleaning steps, the washing tub can be cleaned more effectively.

[0015] In addition, according to the present invention, the control unit continues to generate a water flow by continuing to rotate the motor during drainage treatment between multiple tub cleaning processes, so that dirt removed from the washing tub can be captured in the water flow, thereby preventing the dirt from re-adhering to the washing tub.

[0016] According to the present invention, when the laundry is a highly absorbent blanket, the control unit lowers at least one of the maximum motor rotation speed in the tub cleaning process and the water level in the washing tub at the start of the tub cleaning process, compared to the case of laundry other than a blanket. This prevents the water level in the washing tub from suddenly rising and leaking out of the washing tub through the opening of the outer tub during the tub cleaning process in the blanket washing operation. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic vertical cross-sectional view of a washing machine according to an embodiment of the present invention; [Diagram 2] 2 is a block diagram showing the electrical configuration of the washing machine. FIG. [Diagram 3] 4 is a flowchart showing a washing operation performed in the washing machine. [Figure 4] 10 is a flowchart showing a tub cleaning process in a washing operation. [Diagram 5] 11 is a time chart showing a plurality of tank cleaning steps that are performed in succession. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic vertical cross-sectional view of a washing machine 1 according to an embodiment of the present invention. The vertical direction in FIG. 1 is referred to as the vertical direction Z of the washing machine 1, and the upper side of the vertical direction Z is referred to as the upper side Z1 and the lower side is referred to as the lower side Z2. The washing machine 1 includes a housing 2 forming its outer shell, an outer tub 3 arranged in the housing 2, an inner tub 4 housed in the outer tub 3, a pulsator 5 as an example of a rotor arranged in the inner tub 4, a motor 6 that generates a driving force to rotate the inner tub 4 and the pulsator 5, and a clutch 7 as an example of a switching unit that switches the transmission destination of the driving force of the motor 6. The outer tub 3 and the inner tub 4 are collectively referred to as a washing tub 8.

[0019] The housing 2 is made of, for example, metal, and is formed in a box shape. An opening 2B that connects the inside and outside of the housing 2 is formed on a top surface 2A of the housing 2. A door 10 for opening and closing the opening 2B is provided on the top surface 2A. A display operation unit 11 constituted by a liquid crystal operation panel or the like is provided around the opening 2B on the top surface 2A. By operating the display operation unit 11, a user of the washing machine 1 can select operating conditions for the washing operation performed by the washing machine 1, and can instruct the washing machine 1 to start or stop the washing operation. Information for the user is displayed on the display operation unit 11.

[0020] The outer tank 3 is made of, for example, resin, and is formed in a cylindrical shape with a bottom. The outer tank 3 has a substantially cylindrical circumferential wall 3A arranged along the vertical direction Z, a bottom wall 3B that closes the hollow portion of the circumferential wall 3A from the lower side Z2, and a ring-shaped annular wall 3C that protrudes toward the center of the circumferential wall 3A along the upper edge of the circumferential wall 3A. An opening 3D that communicates with the hollow portion of the circumferential wall 3A from the upper side Z1 is provided on the inside of the annular wall 3C. The opening 3D is in a state of communicating with the opening 2B of the housing 2 from the lower side Z2 in opposition. The annular wall 3C may be provided with a door 12 that opens and closes the opening 3D. An overflow port 3E that penetrates the circumferential wall 3A in the radial direction is provided at the upper part of the circumferential wall 3A. The bottom wall 3B is formed in a disk shape extending substantially horizontally, and a through hole 3F that penetrates the bottom wall 3B is provided at the center of the bottom wall 3B. A drain outlet 3G is provided in the bottom wall 3B at a position avoiding the through hole 3F. In the outer tub 3, the overflow outlet 3E is disposed at a higher position than the drain outlet 3G, and the opening 3D is disposed at a higher position than the overflow outlet 3E.

[0021] A water supply passage 13 connected to a tap for tap water is connected to the annular wall 3C of the outer tub 3 from the upper side Z1. A water supply valve 14 is provided in the middle of the water supply passage 13. The water supply valve 14 is, for example, configured by an electromagnetic valve. A drain passage 15 is connected to the drain outlet 3G of the bottom wall 3B of the outer tub 3 from the lower side Z2. The drain passage 15 is drawn out to the outside of the washing machine 1, that is, to the outside of the machine. A drain valve 16 is provided in the middle of the drain passage 15. The drain valve 16 is opened and closed by, for example, a torque motor (not shown). The water supply valve 14, which is open and in the ON state, opens the middle of the water supply passage 13, thereby opening the entire water supply passage 13. The water supply valve 14, which is closed and in the OFF state, closes the middle of the water supply passage 13, thereby blocking the water supply passage 13 in the middle. The drain valve 16, which is open and in the ON state, opens the middle of the drain passage 15, thereby opening the entire drain passage 15. The drain valve 16, which is closed and in the OFF state, blocks the drainage channel 15 midway by closing the drainage channel 15 midway.

[0022] When the water supply valve 14 is opened with the drain valve 16 closed, water is supplied from the water supply passage 13 into the outer tub 3, so that water accumulates in the outer tub 3. The water supply passage 13 and the water supply valve 14 function as an example of a water supply unit that supplies water into the outer tub 3, i.e., into the washing tub 8. When the water supply valve 14 is closed, the water supply stops. When the drain valve 16 is opened, the water in the outer tub 3 is discharged from the drain outlet 3G through the drain passage 15 to the outside of the machine. The washing machine 1 further includes an overflow passage 17 having one end 17A connected to the overflow port 3E of the circumferential wall 3A and the other end 17B connected to a downstream portion of the drain passage 15 that is farther from the drain outlet 3G than the drain valve 16.

[0023] The inner tub 4 is made of metal, for example, and is formed into a cylindrical shape with a bottom that is one size smaller than the outer tub 3, and can accommodate laundry Q inside. The inner tub 4 is arranged coaxially inside the outer tub 3. The inner tub 4, when accommodated in the outer tub 3, can rotate around an axis J that forms its central axis and extends in the vertical direction Z. The washing machine 1 in which the inner tub 4, i.e., the washing tub 8 is arranged vertically is a vertical washing machine. The inner tub 4 has a substantially cylindrical circumferential wall 4A arranged along the vertical direction Z, a bottom wall 4B that closes the hollow portion of the circumferential wall 4A from the lower side Z2, and a ring-shaped annular wall 4C that protrudes toward the axis J along the upper edge of the circumferential wall 4A. The above-mentioned radial direction is the radial direction R based on the axis J.

[0024] The inner peripheral surface of the circumferential wall 4A is the inner peripheral surface of the inner tub 4. The circumferential wall 4A is surrounded by the circumferential wall 3A of the outer tub 3. The bottom wall 4B is provided at the lower end of the inner tub 4. The annular wall 4C faces the annular wall 3C of the outer tub 3 from the lower side Z2. An entrance / exit 4D is provided inside the annular wall 4C. The entrance / exit 4D is located at the upper end of the inner tub 4 and exposes the hollow part of the circumferential wall 4A to the upper side Z1. The entrance / exit 4D faces and communicates with the opening 3D of the outer tub 3 from the lower side Z2. A user puts laundry Q in and takes it out of the inner tub 4 from the upper side Z1 through the opened opening 2B, opening 3D, and entrance / exit 4D.

[0025] A plurality of through holes 4E are provided in the circumferential wall 4A and the bottom wall 4B of the inner tub 4, and the water in the outer tub 3 flows between the outer tub 3 and the inner tub 4 through the through holes 4E and is also stored in the inner tub 4. Therefore, the water is stored in the outer tub 3 and the inner tub 4, i.e., the entire washing tub 8, and the water level in the outer tub 3 and the water level in the inner tub 4 are the same. Note that the through holes 4E may not be provided in the circumferential wall 4A, but may be provided only in the bottom wall 4B.

[0026] The bottom wall 4B of the inner tank 4 is formed in a disk shape and extends approximately parallel to the bottom wall 3B of the outer tank 3 at a distance to the upper side Z1. A through hole 4F is provided in the bottom wall 4B at the circular center position coinciding with the axis J. A tubular support shaft 18 is provided in the bottom wall 4B, surrounding the through hole 4F and extending to the lower side Z2 along the axis J. The support shaft 18 is inserted into the through hole 3F of the bottom wall 3B of the outer tank 3, and the lower end of the support shaft 18 is located on the lower side Z2 of the bottom wall 3B.

[0027] The pulsator 5 is formed in a disk shape with the axis J as its center, and is disposed on the bottom wall 4B inside the inner tub 4. A plurality of radially arranged blades 5A are provided on the upper surface of the pulsator 5 facing the inlet / outlet 4D of the inner tub 4. The pulsator 5 is provided with a rotating shaft 19 extending from its center along the axis J to the lower side Z2. The rotating shaft 19 is inserted into the hollow portion of the support shaft 18, and the lower end of the rotating shaft 19 is located on the lower side Z2 than the bottom wall 3B of the outer tub 3.

[0028] The motor 6 is an electric motor such as an inverter motor. The motor 6 is disposed in the housing 2 on the lower side Z2 of the outer tub 3. The motor 6 has an output shaft 20 that rotates about an axis J, and outputs the generated driving force from the output shaft 20.

[0029] The clutch 7 is interposed between the lower end of each of the support shaft 18 and the rotating shaft 19 and the upper end of the output shaft 20 protruding from the motor 6 to the upper side Z1. The clutch 7 selectively transmits the driving force output from the output shaft 20 of the motor 6 to one or both of the support shaft 18 and the rotating shaft 19. When the driving force from the motor 6 is transmitted to the support shaft 18, the inner tub 4 receives the driving force of the motor 6 and rotates about the axis J. When the driving force from the motor 6 is transmitted to the rotating shaft 19, the pulsator 5 receives the driving force of the motor 6 and rotates about the axis J. A known electric transmission mechanism is used as the clutch 7. The above-mentioned torque motor (not shown) may operate the clutch 7.

[0030] 2 is a block diagram showing an electrical configuration of washing machine 1. Washing machine 1 includes a microcomputer 21 as an example of a water supply unit and a control unit. Microcomputer 21 includes, for example, a CPU 22, a memory 23 such as a ROM or a RAM, and a timer 24 for measuring time, and is built into housing 2 (see FIG. 1).

[0031] The motor 6, clutch 7, water supply valve 14, and drain valve 16 are electrically connected to the microcomputer 21 via, for example, a drive circuit 25, and the display operation unit 11 is also electrically connected to the microcomputer 21. The microcomputer 21 turns the motor 6 ON to drive it, and turns it OFF to stop it. The microcomputer 21 can also control the rotation direction of the motor 6. Therefore, the motor 6 can rotate forward and backward. The microcomputer 21 controls the clutch 7 to switch the transmission destination of the driving force of the motor 6 to one or both of the inner tub 4 and the pulsator 5. The microcomputer 21 controls the opening and closing, i.e., ON / OFF, of the water supply valve 14 and the drain valve 16. When a user operates the display operation unit 11 to select an operating condition, etc., the microcomputer 21 accepts the selection. The microcomputer 21 controls the display content of the display operation unit 11.

[0032] Washing machine 1 further includes a buzzer 26, a rotation speed reading device 27, and a water level detection unit 28, which are electrically connected to microcomputer 21. Microcomputer 21 notifies the user of the start and end of a washing operation by making buzzer 26 generate a predetermined sound.

[0033] The rotation speed reading device 27 is a device that reads the rotation speed of the motor 6, more precisely, the rotation speed of the output shaft 20 of the motor 6, and is composed of, for example, a Hall IC. The rotation speed read by the rotation speed reading device 27 is input to the microcomputer 21 in real time. The microcomputer 21 controls the motor 6 so that it rotates at a desired rotation speed by controlling the duty ratio of the voltage applied to the motor 6 based on the input rotation speed. Note that the rotation speeds of the inner tub 4 and the pulsator 5 may be the same as the rotation speed of the motor 6, or may be a value obtained by multiplying the rotation speed of the motor 6 by a predetermined constant such as the reduction ratio of the clutch 7.

[0034] Water level detection unit 28 is a water level sensor that detects the water level in outer tub 3, i.e., the water level in washing tub 8. One example of water level detection unit 28 is a pressure-type water level sensor that detects the water level in washing tub 8 based on the pressure inside washing tub 8. The surface of the water accumulated in washing tub 8 is not necessarily horizontal over the entire area, and water level detection unit 28 detects the water level of the highest part of the water surface as the water level in washing tub 8 at the current time. The water level in washing tub 8 at the current time, i.e., the detection result of water level detection unit 28, is input to microcomputer 21.

[0035] The microcomputer 21 controls the operation of the motor 6, the clutch 7, the water supply valve 14, and the drain valve 16 to perform a washing operation. The washing operation includes at least a washing process in which the water supply valve 14 is opened to supply water into the washing tub 8 to wash the laundry Q in the inner tub 4, a rinsing process in which the water supply valve 14 is opened after the washing process to supply water into the washing tub 8 to rinse the laundry Q in the inner tub 4, and a tub cleaning process in which the washing tub 8 is cleaned after the rinsing process. In this embodiment, the rinsing process is performed twice, the first rinsing process is referred to as the first rinsing process, and the second rinsing process is referred to as the second rinsing process. The washing operation in this embodiment also includes a dewatering process in which the inner tub 4 is rotated to dewater the laundry Q. The dewatering process includes an intermediate dewatering process performed during the washing operation and a final dewatering process performed at the end of the washing operation. The washing machine 1 may be a washing / drying machine that also performs a drying process in which the laundry Q is dried after the dewatering process.

[0036] When a user puts laundry Q into the inner tub 4 and instructs the start of a washing operation, the microcomputer 21 starts the washing operation. The user may put detergent into the inner tub 4 before or after putting in the laundry Q. Referring to the flow chart of FIG. 3, first, the microcomputer 21 detects the amount of laundry Q in the inner tub 4, that is, the load amount (step S1). As an example of load amount detection, the microcomputer 21 detects the load amount from the variation in the number of rotations of the motor 6 when the inner tub 4 is rotated steadily at a low speed. The microcomputer 21 determines the wash water level W1 (see FIG. 1), which is the water level to be supplied and stored in the washing tub 8, based on the load amount detected earlier. The relationship between the wash water level W1 and the load amount is obtained in advance by an experiment or the like and stored in the memory 23.

[0037] Then, as a water supply process as part of the washing step, microcomputer 21 continuously opens water supply valve 14 to supply water into washing tub 8 (step S2). Since drain valve 16 is closed, the water level in washing tub 8 rises. When the water level in washing tub 8 rises to the previously determined washing water level W1, microcomputer 21 closes water supply valve 14 to stop water supply. This ends the water supply process.

[0038] Next, in a state where water is stored in the washing tub 8, the microcomputer 21 executes the stirring process. Specifically, the microcomputer 21 switches the clutch 7 as necessary so that the driving force of the motor 6 is transmitted to the pulsator 5, and then drives the motor 6 to rotate the pulsator 5 (step S3). The pulsator 5 may rotate continuously in the same direction, but in this embodiment, the pulsator 5 is reversed so that the normal and reverse rotations are alternately repeated at intervals of 1 to 2 seconds by intermittent driving of the motor 6. In the stirring process, the laundry Q in the inner tub 4 is stirred and washed by the reversing pulsator 5. Note that the pulsator 5 may rotate even during the water supply process in step S2, which makes it easier for the detergent to dissolve in water. Dirt on the laundry Q is broken down by the detergent dissolved in water. When a predetermined stirring time has elapsed, the microcomputer 21 ends the stirring process. This ends the washing process.

[0039] After the washing step, the microcomputer 21 rotates the inner tub 4 at high speed with the drain valve 16 open as an intermediate spin-dry step (step S4). The laundry Q in the inner tub 4 is spin-dried by centrifugal force generated by this high-speed rotation. Water that seeps out of the laundry Q due to spin-drying is discharged outside the machine through the drain path 15. At the end of the intermediate spin-dry step, the microcomputer 21 switches the clutch 7 to stop the motor 6 so that the driving force of the motor 6 is not transmitted to the inner tub 4, and the inner tub 4 rotates by inertia. At the end of the intermediate spin-dry step, the microcomputer 21 closes the drain valve 16.

[0040] Next, the microcomputer 21 executes shower rinsing as the first rinsing step (step S5). Specifically, the microcomputer 21 supplies shower water into the inner tub 4 by intermittently opening the water supply valve 14 with the drain valve 16 closed. In this state, the microcomputer 21 rotates the inner tub 4 at a low speed, for example, 30 rpm, so that the shower water reaches every corner of the laundry Q. This allows the laundry Q in the inner tub 4 to be rinsed evenly. Thereafter, the microcomputer 21 executes the same intermediate spin-drying step as step S4 (step S6). Note that each intermediate spin-drying step may be regarded as a part of the processing in the immediately following rinsing step.

[0041] Next, the microcomputer 21 executes a second rinsing step. The contents of the second rinsing step are substantially the same as the washing step, except that no detergent is present. Specifically, the microcomputer 21 supplies water as in step S2 (step S7), and then agitates and rinses the laundry Q as in step S3 (step S8). After that, when a predetermined agitation time has elapsed, the microcomputer 21 closes the drain valve 16 and stops the motor 6 while water is stored in the washing tub 8, thereby completing the second rinsing step.

[0042] Next, the microcomputer 21 executes a tub cleaning step (step S9), and finally, the microcomputer 21 executes a final spin-drying step similar to the intermediate spin-drying step (step S10). However, the rotation conditions of the inner tub 4 may be different between the intermediate spin-drying step and the final spin-drying step, and in particular, the maximum rotation speed of the inner tub 4 in the final spin-drying step is higher than the maximum rotation speed of the inner tub 4 in the intermediate spin-drying step. The washing operation ends when the final spin-drying step is completed.

[0043] Next, the tub cleaning process of step S9 will be described with reference to the flow chart of FIG. 4. In the tub cleaning process, in addition to the washing water level W1 described above, there are an overflow water level W2 at the same height as the overflow outlet 3E of the outer tub 3, a tub cleaning water level W3 that is equal to or higher than the overflow water level W2 and lower than the opening 3D of the outer tub 3, and an abnormal water level W4 that is higher than the tub cleaning water level W3 (see FIG. 1). The overflow water level W2 is higher than the washing water level W1, and in this embodiment, is set at the same height as the lower end 3H of the overflow outlet 3E. The tub cleaning water level W3 does not have to be a constant water level, and may fluctuate between the overflow water level W2 and the abnormal water level W4. The abnormal water level W4 is set to be somewhat lower than the opening 3D of the outer tub 3. In addition, during the tub cleaning process, the water supply valve 14 is always closed.

[0044] At the beginning of the tub cleaning process, microcomputer 21 switches clutch 7 so that the driving force of motor 6 is transmitted to inner tub 4 (step S11). Next, microcomputer 21 checks the current water level in washing tub 8 (step S12). If the water level in washing tub 8 is equal to or higher than washing water level W1 (NO in step S12), microcomputer 21 opens drain valve 16 to drain the inner tub 4, thereby lowering the water level in washing tub 8 (step S13).

[0045] If the water level in the washing tub 8 is lower than the washing water level W1 (YES in step S12), at this timing t0, the microcomputer 21 operates the motor 6 while keeping the drain valve 16 closed to start the rotation of the inner tub 4 (step S14). Then, a vortex is generated in the washing tub 8 by the centrifugal force accompanying the rotation of the inner tub 4, and the water surface S in the washing tub 8 is curved in a U-shape so that the central part on the axis J side, i.e., the inner side in the radial direction R, is lower and the outer periphery on the outer side in the radial direction R is higher, as shown by the two-dot chain line in FIG. 1. As a result, the water level in the washing tub 8 rises to the tub cleaning water level W3, successively exceeding the washing water level W1 and the overflow water level W2. Then, the water on the water surface S side, i.e., the upper side Z1, in the washing tub 8 is led from the overflow port 3E through the overflow channel 17 to the drain channel 15, and is discharged outside the machine through the drain channel 15.

[0046] In the tub cleaning process, when the water level in the washing tub 8 exceeds the tub cleaning water level W3 and reaches the abnormal water level W4 (YES in step S15), the microcomputer 21 lowers the water level in the washing tub 8 by reducing the rotation speed of the motor 6 (step S16). This prevents the water in the washing tub 8 from leaking out of the washing tub 8 through the opening 3D of the outer tub 3.

[0047] In a state where the water level in the washing tub 8 is below the abnormal water level W4 (NO in step S15), when a predetermined time t1 has elapsed from the timing t0 at which the motor 6 started rotating in step S14 (YES in step S17), the microcomputer 21 checks the water level in the washing tub 8 (step S18). If the water level in the washing tub 8 is below the overflow water level W2 (YES in step S18), the microcomputer 21 increases the rotation speed of the motor 6 to raise the water level in the washing tub 8 (step S19). If the water level in the washing tub 8 is at the overflow water level W2 (NO in step S18), the microcomputer 21 maintains the rotation speed of the motor 6 to maintain the water level in the washing tub 8 at the overflow water level W2 (step S20).

[0048] The rotation speed of the motor 6 when the water level in the washing tub 8 is maintained at the overflow water level W2 is the maximum rotation speed during the tub cleaning process. The maximum rotation speed is set to a rotation speed lower than the resonance point of the washing machine 1, for example, 240 rpm or less. In this embodiment, the maximum rotation speed is 120 rpm when the water level in the washing tub 8 smoothly reaches the overflow water level W2, and the maximum rotation speed is 150 rpm when the rotation speed of the motor 6 is increased after the predetermined time t1 has elapsed (step S19). The maximum rotation speed is 70 rpm when the rotation speed of the motor 6 is decreased because the water level in the washing tub 8 reaches the abnormal water level W4 (step S16).

[0049] When the inner tub 4 is rotated without draining the water in this way, the water flow caused by the water that has risen to the tub cleaning water level W3 in the washing tub 8 reaches dirt at a height position above the lower end 3H of the overflow port 3E in the washing tub 8 without leaking out of the washing tub 8 from the opening 3D. The dirt at a height position above the lower end 3H is present on the upper part of the inner circumferential surface of the circumferential wall 3A of the outer tub 3 and on the upper part of the outer circumferential surface of the circumferential wall 4A of the inner tub 4. Therefore, such water flow and centrifugal force can remove dirt, especially dirt above the overflow port 3E, without leaking. The removed dirt is led to the drainage channel 15 through the overflow port 3E together with the water on the water surface S side in the washing tub 8 and discharged, so that the dirt can be prevented from reattaching to the washing tub 8. The washing tub 8 can be effectively cleaned by such a tub cleaning process. In addition, since the tub cleaning process is performed every time a washing operation is performed, the washing tub 8 can be maintained in a clean state for a long period of time.

[0050] A user can select the type of laundry Q by operating the display operation unit 11 prior to the start of a washing operation. The microcomputer 21 and the display operation unit 11 function as an example of a receiving unit to receive the selection of the type of laundry Q. When the laundry Q related to the selection received by the microcomputer 21 is a blanket, the microcomputer 21 lowers at least one of the maximum rotation speed of the motor 6 in the tub cleaning process and the water level in the washing tub 8 at the start of the tub cleaning process, i.e., the washing water level W1, to a level lower than that for laundry Q other than a blanket. This can prevent the water level in the washing tub 8 from suddenly rising to the abnormal water level W4 and leaking out of the washing tub 8 from the opening 3D of the outer tub 3 during the tub cleaning process in the washing operation for a blanket, which is a laundry Q with high water absorption.

[0051] When a predetermined time t2, for example, 10 to 20 seconds, has elapsed from the timing t0 at which motor 6 starts rotating in step S14 (YES in step S21), microcomputer 21 opens drain valve 16 to drain water from washing tub 8 as a drainage process at the end of the tub cleaning process (step S22). During the drainage process in step S22, microcomputer 21 continues to rotate motor 6 at, for example, 30 rpm. As a result, a water flow continues to be generated in washing tub 8 even during the drainage process, so that dirt removed from washing tub 8 can be captured in the water flow, thereby preventing the dirt from re-adhering to washing tub 8. Then, microcomputer 21 stops motor 6 (step S23) to end the tub cleaning process.

[0052] Microcomputer 21 may execute the tub cleaning process multiple times. Fig. 5 is a time chart when the tub cleaning process is executed twice. In the time chart of Fig. 5, the horizontal axis indicates elapsed time, and the vertical axis indicates, from the top, the water level in washing tub 8 detected by water level detection unit 28, the number of revolutions of motor 6, and the ON / OFF state of drain valve 16. Note that t0', t1', t2', W1', and W3' in the second tub cleaning process in Fig. 5 correspond to the above-mentioned t0, t1, t2, W1, and W3 in the first tub cleaning process, respectively.

[0053] Microcomputer 21 opens drain valve 16 to drain a portion of the water in washing tub 8 in the drain process (step S22) at least at the end of the first tub cleaning step. Then, microcomputer 21 sets the maximum rotation speed of motor 6 in the second and subsequent tub cleaning steps to be higher than the maximum rotation speed of motor 6 in the first tub cleaning step. As an example, the maximum rotation speed of motor 6 in the first tub cleaning step is 70 rpm, and the maximum rotation speed of motor 6 in the second and subsequent tub cleaning steps is 120 rpm.

[0054] In this case, in the second and subsequent tub cleaning steps, the small amount of water is pushed higher by the centrifugal force caused by the high speed rotation of the inner tub 4, so that the tub cleaning water level W3' becomes higher than the tub cleaning water level W3 in the first tub cleaning step. Therefore, in the second and subsequent tub cleaning steps, among the dirt in the washing tub 8 at a height position equal to or higher than the lower end 3H of the overflow port 3E, dirt close to the opening 3D can be completely removed. By carrying out such a plurality of tub cleaning steps, the washing tub 8 can be cleaned more effectively. In the drainage process (step S22) at the end of the last tub cleaning step, the water in the washing tub 8 is drained until the water level in the washing tub 8 becomes zero.

[0055] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the claims.

[0056] For example, in the embodiment described above, the axis J of the inner tub 4 in the washing machine 1 is arranged to extend vertically along the vertical direction Z (see FIG. 1), but the washing machine 1, which is a vertical washing machine, also includes a configuration in which the axis J is arranged to be slightly inclined with respect to the vertical direction Z. [Explanation of symbols]

[0057] 1. Washing machine 3 Outer tank 3D aperture 3E Overflow port 3G drain 4 Inner tank 4D entrance / exit 4E Through hole 6 Motor 8 Washing tub 11 Display operation section 13 Water supply channel 14 Water supply valve 15 Drainage Channel 16 Drain valve 17 Overflow channel 21 Microcomputer 28 Water level detector Q Laundry W3 Tank cleaning water level

Claims

1. A motor for generating a driving force; a washing tub having an outer tub provided with a drain outlet, an overflow outlet located at a position higher than the drain outlet, and an opening located at a position higher than the overflow outlet, and in which water is stored; an inner tub provided with a through hole for passing water between the outer tub and the inner tub, and an inlet / outlet facing the inlet / outlet, and disposed within the outer tub, laundry is put in and taken out through the inlet / outlet, and the inner tub rotates by receiving a driving force of the motor; A drainage channel connected to the drain outlet for discharging water from the washing tub; An overflow channel connected to the overflow outlet and directing water in the washing tub from the overflow outlet to the drainage channel; A drain valve that opens and closes the drainage path; A water supply unit that supplies water into the washing tub; A water level detection unit that detects a water level in the washing tub; a control unit that controls the motor, the drain valve, and the water supply unit, and receives a detection result from the water level detection unit, and executes a washing operation including a washing step in which the water supply unit supplies water into the washing tub to wash the laundry in the inner tub, a rinsing step in which the water supply unit supplies water into the washing tub up to a washing water level determined based on the amount of laundry in the inner tub after the washing step to rinse the laundry in the inner tub, and a tub cleaning step in which the washing tub is cleaned after the rinsing step, The control unit ends the rinsing process with the drain valve closed and water stored in the washing tub, and in the tub cleaning process, when the water level in the washing tub is equal to or higher than the washing water level, opens and closes the drain valve until the water level in the washing tub falls below the washing water level, and when the water level in the washing tub is below the washing water level and below the overflow outlet, the motor starts rotation of the inner tub with the drain valve still closed, thereby raising the water level in the washing tub to a tub cleaning water level that is equal to or higher than the overflow outlet and lower than the opening.

2. A motor for generating a driving force; a washing tub having an outer tub provided with a drain outlet, an overflow outlet located at a position higher than the drain outlet, and an opening located at a position higher than the overflow outlet, and in which water is stored; an inner tub provided with a through hole for passing water between the outer tub and the inner tub, and an inlet / outlet facing the inlet / outlet, and disposed within the outer tub, laundry is put in and taken out through the inlet / outlet, and the inner tub rotates by receiving a driving force of the motor; A drainage channel connected to the drain outlet for discharging water from the washing tub; An overflow channel connected to the overflow outlet and directing water in the washing tub from the overflow outlet to the drainage channel; A drain valve that opens and closes the drainage path; A water supply unit that supplies water into the washing tub; A water level detection unit that detects a water level in the washing tub; a control unit which controls the motor, the drain valve and the water supply unit and receives a detection result from the water level detection unit, and executes a washing operation including a washing process in which the water supply unit supplies water into the washing tub to wash the laundry in the inner tub, a rinsing process in which the water supply unit supplies water into the washing tub after the washing process to rinse the laundry in the inner tub, and a tub cleaning process in which the washing tub is cleaned after the rinsing process; a reception unit for receiving a selection of a type of laundry, The control unit closes the drain valve to end the rinsing step with water stored in the washing tub, and in the tub cleaning step, the water level in the washing tub is raised to a tub cleaning water level that is equal to or higher than the overflow port and lower than the opening by rotating the inner tub by the motor with the drain valve still closed, When the laundry related to the selection accepted by the accepting unit is a blanket, the control unit sets at least one of the maximum rotation speed of the motor in the tub cleaning process and the water level in the washing tub at the start of the tub cleaning process to a lower value than in the case of laundry other than a blanket.

3. The washing machine according to claim 1 or 2, wherein, in the tub cleaning step, when the water level in the washing tub exceeds the tub cleaning water level, the control unit reduces a rotation speed of the motor.

4. The control unit executes the tank cleaning process multiple times, The control unit executes a drainage process in which the drain valve is opened to drain a part of the water in the washing tub at least at the end of the first tub cleaning process, The washing machine according to any one of claims 1 to 3, wherein the control unit sets the maximum rotation speed of the motor in the second or subsequent tub cleaning steps to be higher than the maximum rotation speed of the motor in the first tub cleaning step.

5. The washing machine according to claim 4 , wherein the control unit continues to rotate the motor during the drainage process.

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