Drum-type washing machine

Abstract

To provide a drum-type washing machine enabling a set volume of water supplied into an outer tank to be properly discharged, even if a drum is being driven to rotate at relatively large rotational speed.SOLUTION: A drum-type washing machine according to the invention comprises: a drum that is rotatably accommodated inside an outer tank for storing water; a water level sensor to detect water level in the outer tank based on a water pressure applied from the water supplied into the outer tank; storage means to store stand-by time from start of water discharge in a state that the water level in the outer tank is a set water level until the water level reaches a stable zone in which output corresponding to the water level in the outer tank is properly output by the water level sensor; and control means to control water discharge from the outer tank. When discharging the water in a state in which the water level in the outer tank is the set water level while rotating the drum at specified rotational speed at which centrifugal force acting on laundry stored in the drum is equal to or higher than gravity acting on the laundry, the control means continues to discharge water from the outer tank from start of the water discharge into the outer tank until lapse of the stand-by time.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a drum-type washing machine installed in, for example, a coin-operated laundry facility. [Background technology]

[0002] Conventionally, drum-type washing machines (washing / drying machines) for washing laundry such as clothes include a housing, an outer tub (water tub) and drum (rotating tub) arranged within the housing, and a water supply channel and a drain channel connected to the outer tub (see, for example, Patent Document 1). Such drum-type washing machines have a piezoelectric sensor with a built-in diaphragm as a water level sensor (water level detection unit) that detects the water level in the outer tub. The water level sensor detects the water level in the outer tub by using a diaphragm to measure the water pressure that fluctuates with changes in the water level in the outer tub, and outputs an output corresponding to the water level supplied to the outer tub.

[0003] In a conventional drum-type washing machine, when water is supplied to the outer tub, the supply of water to the outer tub is started, and when the water level sensor detects that the water level in the outer tub has reached a preset water level, the supply of water to the outer tub is stopped. When water is drained from the outer tub, the drainage of the outer tub is started, and when the water level sensor detects that the water level in the outer tub has reached zero, the drainage from the outer tub is stopped. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-104227 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, for example, in a drum-type washing machine installed in a coin laundry, in addition to laundry such as clothes, futons such as mattresses may be washed. When washing a futon, if the drum is rotated at a relatively low rotation speed similar to that when washing clothes, the futon will lose its shape. Therefore, in order to prevent the futon from losing its shape, it is common to wash the futon after supplying water while rotating the drum at a relatively high rotation speed that keeps the futon attached to the inner peripheral surface of the drum, and then drain the water.

[0006] Here, how the output of the water level sensor changes when the water is drained from the outer tub while the drum is driven to rotate at a relatively low rotation speed and when the water is drained from the outer tub while the drum is driven to rotate at a relatively high rotation speed will be described with reference to Fig. 7. Fig. 7 shows a case where water is drained at a preset water level in the outer tub when the washing or rinsing cycle is performed.

[0007] First, when draining water from the outer tub while the drum is rotating at a relatively low rotation speed, as time passes from the start of draining and the water level in the outer tub gradually decreases, the output of the water level sensor changes in proportion to the water level in the outer tub, as shown in Figure 7(a). At that time, the output of the water level sensor always indicates the water level in the outer tub correctly after draining water from the outer tub has started. In this way, at a slow rotation speed such as when washing clothes, positive pressure acts on the water level sensor regardless of the amount of water, and the water level sensor can accurately measure the water level in the outer tub.

[0008] In contrast, if draining water from the outer tub while the drum is rotating at a relatively high rotation speed, even if the water level in the outer tub gradually decreases over time after draining begins, the output of the water level sensor will not indicate the water level in the outer tub until it reaches the critical water level, as shown in Figure 7(b) because the water flow in the outer tub becomes intense due to the high rotation speed of the drum, and normal pressure is no longer applied to the water level sensor (negative pressure acts on the water level sensor). However, after the water level in the outer tub decreases below the critical water level, the output of the water level sensor changes to be roughly proportional to the water level in the outer tub.

[0009] In a drum-type washing machine, if the water level sensor is unable to properly detect the water level in the outer tub when draining water from the outer tub, the water level sensor will erroneously detect that the water level in the outer tub has reached zero, and the set amount of water that had been supplied to the outer tub will not be properly drained.

[0010] In this way, in drum-type washing machines that use a water level sensor to detect the water level in the outer tub, there is a problem in that the water level sensor cannot accurately detect the water level when the drum is rotating at a high rotation speed and the water pressure is unstable.

[0011] Therefore, the present invention aims to provide a drum-type washing machine having a water level sensor that is capable of properly draining a set amount of water that has been supplied to the outer tub, even when the drum is rotated at a relatively high rotation speed. [Means for solving the problem]

[0012] A drum-type washing machine according to one aspect of the present invention comprises a drum rotatably accommodated inside an outer tub that stores water, a water level sensor that detects the water level in the outer tub based on the water pressure acting from water supplied into the outer tub, a memory means that starts draining water from a state in which the water level in the outer tub is at a set water level and stores a waiting time until the water level sensor reaches a stable region where an output corresponding to the water level in the outer tub is appropriately output by the water level sensor, and a control means that controls drainage from the outer tub, and is characterized in that when draining water from a state in which the water level in the outer tub is at the set water level while rotating the drum at a specified rotation speed at which the centrifugal force acting on the laundry stored in the drum is equal to or greater than the gravity acting on the laundry, the control means continues draining water from the outer tub from the time drainage into the outer tub begins until the waiting time has elapsed.

[0013] In this case, drainage is started when the water level in the outer tub is at a set water level, and a standby time is set in advance until the water level sensor reaches a stable region where an output corresponding to the water level in the outer tub is appropriately output, and drainage from the outer tub continues from when the water level in the outer tub is started when the water level in the outer tub is at the set water level until the standby time has elapsed. Therefore, in a drum-type washing machine having a water level sensor, even when the drum is rotated at a relatively high rotation speed, the set amount of water that was supplied to the outer tub can be appropriately drained.

[0014] It is preferable that the waiting time is set to a different value depending on the rotation speed of the drum.

[0015] In this case, since the water flow in the outer tub changes depending on the drum rotation speed, the waiting time until the water level sensor reaches a stable region where it properly outputs an output corresponding to the water level in the outer tub after drainage has started can be appropriately set.

[0016] The laundry is preferably a futon.

[0017] In this case, when washing a futon in a drum-type washing machine, even if the drum is rotated at a relatively high rotation speed, the set amount of water that was supplied to the outer tub can be properly drained.

[0018] The laundry is preferably a futon mattress.

[0019] In this case, even when the drum of a drum-type washing machine is rotating at a relatively high rotation speed that keeps the mattress stuck to the inner surface of the drum, the set amount of water that was supplied to the outer tub can be properly drained. Effect of the Invention

[0020] According to the drum type washing machine of the present invention, even when the drum is driven to rotate at a relatively high rotation speed, the set amount of water that has been supplied to the outer tub can be properly drained. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective view of a drum type washing machine 1 according to an embodiment of the present invention. [Diagram 2] 2 is a side cross-sectional view showing the configuration of the drum-type washing machine 1 of FIG. [Diagram 3] FIG. 1 is a control block diagram of a drum-type washing machine 1. [Figure 4] 4 is a diagram illustrating a change in the output of the water level sensor 20 during high speed rotation. FIG. [Diagram 5] 4 is a diagram illustrating a change in the output of the water level sensor 20 during high speed rotation. FIG. [Figure 6] 10 is a flowchart showing the procedure of a drainage operation in a standard washing course and a futon washing course in the drum type washing machine 1. [Figure 7] 5A and 5B are diagrams illustrating changes in the output of the water level sensor during low-speed rotation and high-speed rotation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, a drum type washing machine 1 according to an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view of the drum type washing machine 1 according to the embodiment of the present invention. Fig. 2 is a side cross-sectional view showing the configuration of the drum type washing machine 1 of Fig. 1.

[0023] 1 and 2, the drum type washing machine 1 of this embodiment has a box-shaped housing 2, an outer tub 3 having a substantially cylindrical inner circumferential surface is disposed inside the housing 2, and a drum 4 having a substantially cylindrical inner circumferential surface for accommodating laundry is supported inside the outer tub 3 by a main shaft 5 extending in the front-rear direction. The drum 4 is rotatable about a horizontal axis.

[0024] The front surface of the housing 2 is formed with an operating section 2a for a user to operate, and a clothes insertion opening 6 that faces an opening 4a formed at the front end of the drum 4. The housing 2 is provided with a door 8 for opening and closing the clothes insertion opening 6, which is opened and closed by the door 8, and laundry can be put in and taken out of the drum 4 when the door 8 is open.

[0025] A plurality of baffles 4b are provided on the inner peripheral surface of drum 4 so as to protrude into drum 4. Baffles 4b are protrusions for lifting up laundry contained in drum 4. For example, during the washing process, when drum 4 is rotated by the driving force of drive motor 11 (described later), the laundry containing water inside drum 4 is lifted by baffles 4b and falls naturally, which is called beating washing.

[0026] A large number of water passage holes 4c are drilled into the inner surface of the drum 4. Water supplied to the outer tub 3 during washing and rinsing flows into the drum 4 through the water passage holes 4c, and water expelled from the laundry inside the drum 4 during centrifugal dehydration is splashed toward the outer tub 3 through these water passage holes 4c.

[0027] A water level sensor 20 is attached to the lower end of the back surface of the outer tub 3 via a connection pipe 20a. The water level sensor 20 is connected to the inside of the outer tub 3 and is a sensor that detects the water level (water volume) in the outer tub 3 based on the water pressure acting according to the depth of the water supplied into the outer tub 3. For example, a piezoelectric sensor with a built-in diaphragm can be used as the water level sensor 20. In this case, the water level sensor 20 detects the water level in the outer tub 3 by measuring the water pressure that varies with the change in the water level in the outer tub 3 using the diaphragm, and outputs an output corresponding to the water level supplied into the outer tub 3.

[0028] The main shaft 5 is rotatably supported by a bearing 5a attached to the rear wall of the outer tub 3, and a main pulley 10 is attached to the tip of the main shaft 5 that protrudes further rearward. A drive motor 11 is installed at the bottom of the housing 2, and a motor pulley 12 is attached to the rotating shaft of the drive motor 11. The torque of the motor pulley 12 is transmitted to the main pulley 10 via a timing belt 16. As a result, when the drive motor 11 is driven, the drum 4 rotates around the main shaft 5.

[0029] A water supply pipe 30 with a water supply valve 30a installed midway is connected to the upper part of the rear wall of the outer tub 3, and when the water supply valve 30a is opened, water supplied from the outside is supplied to the outer tub 3 via the water supply pipe 30. A drain pipe 31 with a drain valve 31a installed midway is connected to a drain outlet installed at the bottom of the outer tub 3, and when the drain valve 31a is opened, the water in the outer tub 3 is discharged outside the machine through the drain pipe 31.

[0030] Fig. 3 is a control block diagram of the drum type washing machine 1. As shown in Fig. 3, the control unit 50 of the drum type washing machine 1 is composed of, for example, a microcomputer, and includes a CPU, a ROM in which a program for controlling the operation of the drum type washing machine 1 is stored, and a RAM in which data used when executing the program is temporarily stored. The operation of the drum type washing machine 1 is controlled by the control unit 50. The control unit 50 is connected to an operation unit 2a, a water level sensor 20, a water supply valve 30a, a drain valve 31a, and a drive motor 11.

[0031] In the drum type washing machine 1, the user can select between a standard washing course and a futon washing course (futon washing course) by operating the operation unit 2a of the housing 2. In the drum type washing machine 1, various operation courses can be selected by operating the operation unit 2a of the housing 2, but the following explanation will be given of the futon washing course.

[0032] The mattress cleaning course is used when washing a mattress, and the machine is operated in the following order: washing step, rinsing step, and spin-drying step. When a mattress is washed in the mattress cleaning course, the mattress is folded at its widthwise center line. Then, a folded portion is formed in the mattress along its longitudinal direction, and the width becomes approximately half of its original width. After that, the mattress is folded into a ring shape and inserted into the drum 4 so that it fits along the inner circumferential surface of the drum 4.

[0033] The control unit 50 has a storage unit 51 that stores various set values, and a drainage time measurement unit 52 .

[0034] The memory unit 51 stores the specified rotation speed (for standard washing) and set water level (for standard washing) of the drum 4 when the standard washing course is selected, the specified rotation speed (for washing the futon) and set water level (for washing the futon) of the drum 4 when the futon washing course is selected, the waiting time when the futon washing course is selected, etc.

[0035] (Standard rotation speed of drum 4) Specifically, the memory unit 51 stores, for example, 43 rpm as the specified rotation speed (for standard washing) of the drum 4 when the standard washing course is selected, and stores, for example, 90 rpm as the specified rotation speed (for washing the futon) of the drum 4 when the mattress washing course is selected. That is, when the standard washing course is selected, the drum 4 is rotated at 43 rpm when the washing step and the rinsing step are performed, and when the mattress washing course is selected, the drum 4 is rotated at 90 rpm when the washing step and the rinsing step are performed. That is, when the mattress washing course is selected, water is supplied to the outer tub 3 and drained from the outer tub 3 during the washing step and the rinsing step while the drum 4 is rotated at 90 rpm.

[0036] (Set water level) Specifically, the memory unit 51 stores, for example, 130 liters as the set water level (for standard washing) when the standard washing course is selected, and stores, for example, 180 liters as the set water level (for washing a futon) when the mattress washing course is selected. That is, when the standard washing course is selected, 130 liters of water is supplied to the outer tub 3 when the washing process and the rinsing process are performed. When the mattress washing course is selected, 180 liters of water is supplied to the outer tub 3 when the washing process and the rinsing process are performed. Note that the set water level is a water surface height (height from the bottom surface of the outer tub 3 to the water surface) that is set in advance, but in this embodiment, the amount of water supplied to the outer tub 3 until the water surface in the outer tub 3 reaches the set water level is set as the set water level.

[0037] Thus, in this embodiment, since the drum is driven at a relatively high rotation speed when washing bedding such as a futon compared to laundry such as clothes, the water inside the drum moves to the outer periphery of the drum by centrifugal force, and therefore the set water level (for washing the futon) in the futon washing course is set to a greater amount of water than the set water level (for standard washing) in the standard washing course.

[0038] (Waiting time for mattress cleaning course) In the drum washing machine 1, the change in the output of the water level sensor 20 when water is supplied into the outer tub 3 and when drainage is performed from the outer tub 3 while the drum 4 is rotating at a relatively high rotation speed of 90 rpm will be described with reference to FIGS. 4 and 5.

[0039] In FIG. 4, the change in the water level in the outer tub 3 when time has elapsed since the start of water supply is illustrated by a thin line, and the change in the output of the water level sensor 20 at that time is illustrated by a thick line. Note that the water supply rate (the amount of water supplied per unit time) supplied into the outer tub 3 is assumed to be constant.

[0040] When time has elapsed since the start of water supply and the water level in the outer tub 3 gradually increases linearly, until the water level in the outer tub 3 reaches the limit water level, the output of the water level sensor 20 changes linearly in proportion to the water level in the outer tub 3 as shown in FIG. 4. Thus, until the water level in the outer tub 3 reaches the limit water level, since the output of the water level sensor 20 changes in the same manner as the water level in the outer tub 3, the water level sensor 20 can appropriately detect the water level in the outer tub 3.

[0041] After that, when the water level in the outer tub 3 exceeds the limit water level, the output of the water level sensor 20 no longer changes linearly in proportion to the water level in the outer tub 3 as shown in FIG. 4. Thus, when the water level in the outer tub 3 exceeds the limit water level, the output of the water level sensor 20 changes differently from the water level in the outer tub 3, and the water level sensor 20 can no longer appropriately detect the water level in the outer tub 3.

[0042] In FIG. 5, the change in the water level in the outer tub 3 when time has elapsed since the start of drainage is illustrated by a thin line, and the change in the output of the water level sensor 20 at that time is illustrated by a thick line. Note that the drainage from the outer tub 3 starts from a state where the water level in the outer tub 3 is the set water level (for futon washing), and the drainage rate (the amount of drainage per unit time) drained from the outer tub 3 is assumed to be constant.

[0043] After a certain amount of time has passed since the start of drainage, even if the water level in the outer tub 3 gradually decreases linearly, until the water level in the outer tub 3 reaches the limit water level, the output of the water level sensor does not change linearly in proportion to the water level in the outer tub 3 as shown in FIG. 5. Thus, until the water level in the outer tub 3 reaches the limit water level, the output of the water level sensor 20 changes differently from the water level in the outer tub 3, and the water level sensor 20 cannot properly detect the water level in the outer tub 3.

[0044] After that, after the water level in the outer tub 3 reaches the limit water level, when the water level in the outer tub 3 gradually decreases linearly, as shown in FIG. 5, it changes linearly in approximate proportion to the water level in the outer tub 3. Thus, after the water level in the outer tub 3 reaches the limit water level, the output of the water level sensor 20 changes in the same way as the water level in the outer tub 3, so the water level sensor 20 can properly detect the water level in the outer tub 3.

[0045] In the present embodiment, the region where the water level in the outer tub 3 is from 0 to the limit water level is referred to as the "stable region", and the region where the water level in the outer tub 3 is higher than the limit water level is referred to as the "unstable region". That is, the "stable region" is the region where the water level sensor 20 properly outputs an output corresponding to the water level in the outer tub 3, and the "unstable region" is the region where the water level sensor 20 does not properly output an output corresponding to the water level in the outer tub 3.

[0046] Therefore, in the drum washing machine 1, in the "stable region", the water level in the outer tub 3 can be properly detected by the water level sensor 20, but in the "unstable region", the water level in the outer tub 3 cannot be detected by the water level sensor 20.

[0047] First, in the drum washing machine 1, the case of performing drainage at the end of the washing process in the standard washing course will be described.

[0048] When draining water at the end of a washing cycle in the standard wash course, draining water from the outer tub 3 is started when the water level in the outer tub 3 is at the set water level (for standard wash). In this case, if the water level sensor 20 detects that the water level in the outer tub 3 has reached 0 after draining has started, draining water from the outer tub 3 is stopped. When washing clothes in the standard wash course, the drum 4 rotates at a rotation speed (e.g., 43 rpm) at which the centrifugal force acting on the laundry contained in the drum 4 does not exceed the gravity acting on the laundry, and the output of the water level sensor 20 also decreases approximately in proportion to the decrease in the actual water level (see FIG. 7(a)), so the water level in the outer tub 3 can be accurately detected by the water level sensor 20.

[0049] Next, a case where drainage is performed at the end of the washing cycle in the mattress cleaning course in the drum type washing machine 1 will be described.

[0050] Similarly, when draining water at the end of the washing process in the mattress cleaning course, the water is drained from the outer tub 3 when the water level in the outer tub 3 is at the set water level (for mattress cleaning). However, in the mattress cleaning course, the drum 4 rotates at a rotation speed (for example, 90 rpm) at which the centrifugal force acting on the mattress housed in the drum 4 is equal to or greater than the gravity acting on the mattress. This causes a phenomenon in which the output of the water level sensor 20 is not proportional to the actual decrease in the water level, and the water level sensor 20 is unable to properly detect that the water level in the outer tub 3 has reached 0. The above phenomenon is believed to be caused by the fact that the water flow in the outer tub 3 becomes intense as the amount of water increases due to the high rotation speed of the drum 4, and normal pressure is not applied to the water level sensor 20 (negative pressure acts on the water level sensor 20). Therefore, even if the water level sensor 20 outputs an output indicating that the water level in the outer tub 3 has reached 0, it is not possible to know whether the water level in the outer tub 3 has actually reached 0, and therefore it is not possible to stop draining water from the outer tub 3.

[0051] Therefore, the inventor of the present invention found a method for continuing drainage from the outer tub 3 by conducting experiments in advance, in which the time from when the water level in the outer tub 3 is at a set water level (for cleaning a mattress) to when the water level reaches a "stable region" is set as a standby time, and drainage from the outer tub 3 is continued without determining that the water level in the outer tub 3 has reached 0 until the standby time has elapsed from the start of drainage. According to this method, in the "unstable region", in order to prevent drainage from being stopped due to a false detection that the water has run out even though there is water in the outer tub 3, a certain standby time is set with the drain valve 31a open, so that drainage can be ensured. This prevents the spin cycle from being performed with water in the outer tub 3, causing the drum 4 to rotate at high speed, and causing water leakage from the exhaust duct. Also, even in the mattress cleaning course in which the water level cannot be detected accurately by the water level sensor 20, accurate drainage can be performed by directly reusing the existing water level detection means (water level sensor) without using a new water level detection means.

[0052] When setting the standby time used in the mattress cleaning course, first, an experiment is carried out in advance with the drum type washing machine 1 to detect the shortest time from when the water level in the outer tub 3 is at the set water level (for cleaning the mattress) until the water level sensor 20 properly outputs an output corresponding to the water level in the outer tub 3 after drainage from the outer tub 3 begins, until the water level reaches a "stable region". After that, the standby time is set in advance to be the same as the shortest time or to be longer than the shortest time. In this embodiment, a case will be described in which the standby time is set to be longer than the shortest time.

[0053] The drain time measuring unit 52 is a so-called timer, and measures the drain time from the start of draining water from the outer tub 3. While the drain time measuring unit 52 is measuring the drain time, the rotation speed of the drum 4 is maintained at the specified rotation speed (for cleaning a futon mattress).

[0054] In this way, each time drainage is performed in the mattress cleaning course in the drum type washing machine 1, drainage continues at least until the standby time has elapsed after drainage from the outer tub 3 has started. After the standby time has elapsed, the water level in the outer tub 3 can be properly detected by the water level sensor 20, so drainage is stopped when the water level sensor 20 detects that the water level in the outer tub 3 has reached zero. That is, when drainage is performed at the end of the washing step in the mattress cleaning course in the drum type washing machine 1 and when drainage is performed at the end of the rinsing step in the mattress cleaning course, drainage continues from the start of drainage until the standby time has elapsed, and then drainage is stopped when the water level sensor 20 detects that the water level in the outer tub 3 has reached zero.

[0055] The drainage operation procedure for the standard washing course and the futon washing course in the drum type washing machine 1 will be described with reference to Fig. 6. Fig. 6 is a flow chart showing the drainage operation procedure for the standard washing course and the futon washing course in the drum type washing machine 1.

[0056] <Step S1> In step S1, the control unit 50 judges whether or not the mattress cleaning course has been selected. If the control unit 50 judges that the mattress cleaning course has been selected, the process proceeds to step S2. If the control unit 50 judges that the standard cleaning course has been selected, the process proceeds to step S8.

[0057] <Step S2> In step S2, the control unit 50 controls the drive motor 11 to rotate the drum 4 at a relatively high specified number of revolutions (for cleaning a futon mattress), and opens the water supply valve 30a to start supplying water to the outer tub 3. At this time, the control unit 50 closes the drain valve 31a, and the water supplied to the outer tub 3 is stored in the outer tub 3 and also stored in the drum 4 through the water passage hole 4c. After that, the cleaning operation is performed until the preset cleaning time has elapsed. When the cleaning operation is completed, the process proceeds to step S3.

[0058] <Step S3> In step S3, the control unit 50 controls the drive motor 11 so as to rotate the drum 4 at a specified number of revolutions (for cleaning a futon), and opens the drain valve 31a to start draining water from the outer tub 3.

[0059] <Step S4> In step S4, the control unit 50 starts drainage and at the same time, the drainage time measurement unit 52 measures the drainage time from when drainage from the outer tub 3 starts.

[0060] <Step S5> In step S5, the control unit 50 judges whether the drain time measured by the drain time measurement unit 52 has reached the standby time. If the control unit 50 judges that the drain time has reached the standby time, the process proceeds to step S6. In this way, in the mattress cleaning course, the water level sensor 20 cannot detect that the water level in the outer tub 3 has reached the stable region, so when the standby time has elapsed, the water level in the outer tub 3 is deemed to have reached the stable region.

[0061] <Step S6> In step S6, the control unit 50 determines whether or not the water level in the outer tub 3 has reached 0 based on the output of the water level sensor 20. If the control unit 50 determines that the water level in the outer tub 3 has reached 0, the process proceeds to step S7.

[0062] <Step S7> In step S7, the control unit 50 closes the drain valve 31a to stop draining water from the outer tub 3 because the water level in the outer tub 3 has reached 0.

[0063] <Step S8> In step S8, the control unit 50 controls the drive motor 11 to rotate the drum 4 at a specified number of revolutions (for standard washing), and opens the water supply valve 30a to start supplying water to the outer tub 3. At this time, the control unit 50 closes the drain valve 31a, so that the water supplied to the outer tub 3 is stored in the outer tub 3 and also stored in the drum 4 through the water passage hole 4c. Thereafter, the washing operation is performed until a preset washing time has elapsed. When the washing operation is completed, the process proceeds to step S9.

[0064] <Step S9> In step S9, the control unit 50 controls the drive motor 11 to rotate the drum 4 at a specified rotation speed (for standard washing), and opens the drain valve 31a to start draining water from the outer tub 3. After that, the process proceeds to step S6.

[0065] As described above, the drum type washing machine 1 of this embodiment has the drum 4 rotatably accommodated inside the outer tub 3 that stores water, the water level sensor 20 that detects the water level in the outer tub 3 based on the water pressure acting from the water supplied into the outer tub 3, a memory unit (memory means) 51 that starts draining water when the water level in the outer tub 3 is at a set water level and stores the standby time until the water level sensor 20 reaches a stable region where an output corresponding to the water level in the outer tub 3 is appropriately output by the water level sensor 20, and a control unit (control means) 50 that controls drainage from the outer tub 3. When draining water from a state in which the water level in the outer tub 3 is at the set water level while rotating the drum 4 at a specified rotation speed at which the centrifugal force acting on the mattress accommodated in the drum 4 is equal to or greater than the gravity acting on the mattress, the control unit 50 continues draining water from the outer tub 3 from the start of draining water into the outer tub 3 until the standby time has elapsed.

[0066] As a result, drainage is started when the water level in the outer tub 3 is at the set water level, and a standby time is set in advance until the water level sensor 20 reaches a stable region where an output corresponding to the water level in the outer tub 3 is appropriately output, and drainage from the outer tub 3 continues from when drainage into the outer tub 3 is started when the water level in the outer tub 3 is at the set water level until the standby time has elapsed. Therefore, in a drum type washing machine 1 having the water level sensor 20, the set amount of water that was supplied to the outer tub 3 can be appropriately drained even when the drum is rotated at a relatively high rotation speed.

[0067] In the drum type washing machine 1 of the present embodiment, the standby time is set to a different value depending on the rotation speed of the drum 4.

[0068] As a result, since the water flow in the outer tub 3 changes when the rotation speed of the drum 4 differs, the waiting time until the water level sensor 20 reaches a stable region where it properly outputs an output corresponding to the water level in the outer tub 3 after drainage has begun can be appropriately set.

[0069] In the drum type washing machine 1 of this embodiment, the laundry is a futon.

[0070] As a result, when washing a futon in the drum-type washing machine 1, even if the drum is rotated at a relatively high rotation speed, the set amount of water supplied to the outer tub 3 can be properly drained.

[0071] In the drum type washing machine 1 of this embodiment, the laundry is a futon mattress.

[0072] This allows the set amount of water that was supplied to the outer tub 3 to be properly drained even when the drum 4 in the drum-type washing machine 1 is rotating at a relatively high rotation speed that keeps the mattress stuck to the inner surface of the drum 4.

[0073] Although the embodiment of the present invention has been described above, the specific configuration of each part is not limited to the above-described embodiment.

[0074] For example, in the above embodiment, the set water level for the mattress cleaning course was 180 liters for both the washing and rinsing steps, but the set water level for the mattress cleaning course can be set individually for each washing or rinsing step.

[0075] In the above embodiment, when the mattress cleaning course is selected in the drum type washing machine 1, the drum 4 is rotated at a preset specified number of revolutions (for mattress cleaning), but this is not limited to the above. For example, when the specified number of revolutions (for mattress cleaning) when the mattress cleaning course is selected by the owner of the coin laundry shop can be changed for the drum type washing machine 1 installed in a coin laundry shop, a different value may be set for the waiting time according to the changed specified number of revolutions (for mattress cleaning). In this case, since the water flow in the outer tub 3 also changes when the number of revolutions of the drum 4 changes, the waiting time until the water level sensor 20 reaches a stable region where an output corresponding to the water level in the outer tub 3 is appropriately output can be appropriately set.

[0076] In the above embodiment, a value longer than the above-mentioned shortest time may be set as the standby time when the mattress cleaning course is selected in the drum type washing machine 1. For example, the standby time may be set to be the same as the above-mentioned shortest time or longer than the above-mentioned shortest time.

[0077] In the above embodiment, for example, a piezoelectric sensor with a built-in diaphragm is used as the water level sensor 20, but the present invention is not limited to this. The water level sensor 20 may be any sensor that detects the water level in the outer tub 3 based on the water pressure acting from the water supplied into the outer tub 3.

[0078] In the above embodiment, the drum type washing machine 1 has been described, but the present invention is not limited thereto. For example, the present invention can be applied to a drum type washing and drying machine. [Explanation of symbols]

[0079] 1. Drum type washing machine 3 Outer tank 4 Drums 20 Water level sensor 50 Control section (control means) 51 Storage unit (storage means) 52 Drainage time measuring section

Claims

1. A drum rotatably accommodated inside an outer tub that stores water; a water level sensor that detects a water level in the outer tub based on a water pressure acting from water supplied into the outer tub; a storage means for storing a standby time from when the water level in the outer tub is at a set water level and drainage is started until the water level sensor reaches a stable region where an output corresponding to the water level in the outer tub is appropriately output; A control means for controlling drainage from the outer tank, When draining water from a state in which the water level in the outer tub is at a set water level while rotating the drum at a specified rotation speed at which the centrifugal force acting on the laundry contained in the drum is equal to or greater than the gravity acting on the laundry, The control means continues draining water from the outer tub from when draining water into the outer tub starts until the standby time has elapsed.

2. 2. The drum type washing machine according to claim 1, wherein the standby time is set to a different value depending on the number of rotations of the drum.

3. 3. The drum type washing machine according to claim 1, wherein the laundry is a futon.

4. 3. The drum type washing machine according to claim 1, wherein the laundry is a futon mattress.

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