JP7627463B2 - washing machine - Google Patents

Description

The present invention relates to a washing machine.

Conventionally, in washing machines, a spin-drying process is carried out after the washing and rinsing processes. In the spin-drying process, the washing tub in which the laundry is stored, i.e., the washing and spin-drying tub or drum, rotates at high speed, and water is squeezed out of the laundry by centrifugal force generated in the washing tub. The water drained from the laundry is discharged into an outer tub that surrounds the washing tub, and is discharged outside the machine through a drainage channel consisting of a drain hose or the like (see, for example, Patent Document 1).

JP 2020-103419 A

If lint or other foreign matter accumulates in the drain hose, or if the drain hose is not properly installed outside the machine, drainage from the outer tub may deteriorate. If the spin cycle is performed in this state, the water discharged from the laundry will not be smoothly discharged from the outer tub, and as the washing tub speed increases to the specified spin speed, the rotating washing tub and the water accumulated at the bottom of the outer tub may come into contact, causing water bites, which may result in abnormal noises.

In addition, if the outer tub vibrates significantly when the washing tub speed is increased during the spin cycle, the water drained from the laundry will sway inside the outer tub and will not be discharged smoothly, which may result in water getting stuck in the washing tub.

The present invention was made in consideration of these problems, and aims to provide a washing machine that can reduce the occurrence of water bites in the washing tub during the spin-drying process.

A washing machine according to a first aspect of the present invention comprises an outer tub elastically supported within a housing, a drainage section for draining water from the outer tub, a washing tub rotatably arranged within the outer tub and containing laundry, a drive motor for driving the washing tub, a control section for controlling the drive motor to execute a spin-drying process for rotating the washing tub at a predetermined spin-drying speed, and a detection section including a pair of electrodes arranged in the space between a bottom portion of the outer tub and a bottom portion of the washing tub, detecting a current flowing between the pair of electrodes which changes depending on the water level in the outer tub, and outputting a detection signal indicating the magnitude of the detected current. Here, the control unit rotates the washing tub at a first detection rotation speed lower than the spin rotation speed while ramping up the rotation of the washing tub to the spin rotation speed, and during that time acquires the detection signal from the detection unit to detect the water level, and if it determines based on the detected water level that a poor drainage condition has occurred in which water is not being drained smoothly from the outer tub , it controls the drive motor to rotate the washing tub at the first detection rotation speed for a longer time than if the poor drainage condition does not occur, thereby slowing down the ramp-up of the rotation of the washing tub to the spin rotation speed.

Note that the "poor drainage state in which drainage from the outer tub is not performed smoothly" includes not only a state in which drainage from the outer tub is not performed smoothly at the time of the judgment, but also a state in which drainage from the outer tub is not performed smoothly when the rotation speed of the washing tub increases after the judgment.

According to the above configuration, when a drainage problem occurs, the drainage of water from the laundry is suppressed, so that the water is prevented from accumulating in the outer tub until it touches the bottom of the washing tub, and the occurrence of water sticking in the washing tub can be reduced. Furthermore, the occurrence of abnormal noise due to water sticking can also be reduced.
Furthermore, according to the above configuration, the time for which the washing tub is rotated at the first detection rotation speed is lengthened, so that when the water level in the outer tub is low, the rotation speed of the washing tub can be increased from the first detection rotation speed. Even if more water is discharged from the laundry due to the subsequent increase in rotation speed than at the first detection rotation speed, water is prevented from accumulating in the outer tub until it touches the bottom of the washing tub, thereby reducing the occurrence of water biting in the washing tub.

In addition, in the washing machine according to this aspect, the control unit determines whether or not the poor drainage state has occurred based on the magnitude of the detected water level.

If the drainage performance of the drainage section deteriorates and water does not drain smoothly from the outer tank, the water level in the outer tank will increase.

According to the above configuration, the control unit determines whether or not a poor drainage condition has occurred based on the water level detected by the detection unit, so that it is possible to detect the occurrence of a poor drainage condition caused by a deterioration in the drainage performance of the drainage unit.

In addition, in the washing machine according to this aspect, the control unit determines whether or not the poor drainage condition has occurred based on the magnitude of the detected fluctuation in the water level.

If the outer tank vibrates significantly, causing the water in the tank to sway and preventing smooth drainage, the large vibrations of the outer tank will cause large fluctuations in the water level in the tank.

According to the above configuration, the control unit determines whether or not a poor drainage condition has occurred based on the magnitude of the fluctuation in the water level detected by the detection unit, so that it is possible to detect the occurrence of a poor drainage condition caused by large vibrations in the outer tank.

A washing machine according to a second aspect of the present invention comprises an outer tub elastically supported within a housing, a drainage section for draining water from the outer tub, a washing tub rotatably arranged within the outer tub and containing laundry, a drive motor for driving the washing tub, a control section for controlling the drive motor to execute a spin-drying process for rotating the washing tub at a predetermined spin-drying speed, and a detection section including a pair of electrodes arranged in the space between a bottom portion of the outer tub and a bottom portion of the washing tub, detecting a current flowing between the pair of electrodes which changes depending on the water level in the outer tub, and outputting a detection signal indicating the magnitude of the detected current. The control unit rotates the washing tub at a first detection rotation speed lower than the spin-dry rotation speed while increasing the rotation speed of the washing tub to the spin-dry rotation speed, acquires the detection signal from the detection unit to detect the water level during the rotation, and when it determines that a poor drainage state in which drainage from the outer tub is not smoothly occurring based on the detected water level , controls the drive motor to make the time for rotating the washing tub at the first detection rotation speed longer than when the poor drainage state does not occur, or reduces the acceleration when increasing the rotation speed of the washing tub from the first detection rotation speed, thereby slowing down the increase in the rotation speed of the washing tub to the spin-dry rotation speed. A recess is formed in the bottom part of the outer tub, recessed from the inner surface of the bottom part, and the pair of electrodes protrude upward from the bottom surface of the recess. The control unit rotates the washing tub at a second detection rotation speed that is lower than the spin-drying rotation speed and higher than the first detection rotation speed, detects the water level using the detection unit during this rotation, and reduces the value of the spin-drying rotation speed if the detected water level is lower than a threshold value.

According to the above configuration, when the time for rotating the washing tub at the first detection rotation speed is extended, the rotation speed of the washing tub can be increased from the first detection rotation speed while the water level in the outer tub is low. Therefore, even if more water is discharged from the laundry due to the subsequent increase in rotation speed than at the first detection rotation speed, water is prevented from accumulating in the outer tub until it touches the bottom of the washing tub, and the occurrence of water biting in the washing tub can be reduced.

In addition, if the acceleration rate is reduced when increasing the rotation speed of the washing tub from the first detection rotation speed, less water is discharged from the laundry when the rotation speed increases from the first detection rotation speed, preventing water from accumulating in the outer tub until it touches the bottom of the washing tub, thereby reducing the occurrence of water biting in the washing tub.

According to the above configuration, some of the water discharged from the laundry into the outer tub accumulates in the recess while the rotation of the washing tub rises from the first detection rotation speed. If the outer tub vibrates significantly while the rotation of the washing tub rises from the first detection rotation speed and reaches the second detection rotation speed, the water accumulated in the recess is scattered and escapes from the recess, preventing water from remaining in the recess when the second detection rotation speed is reached.

The detection unit is configured so that a pair of electrodes protrude upward from the bottom surface of the recess, so that it can detect the water level in the recess. If the vibration of the outer tub is large enough to cause water to leak out of the recess and the water level detected by the detection unit at the second detection rotation speed falls below the threshold value, the value of the spin-dry rotation speed is lowered. This makes it possible to reduce the vibration of the outer tub when the washing tub rotates at the spin-dry rotation speed.

A washing machine according to a third aspect of the present invention comprises an outer tub elastically supported within a housing, a drainage section for draining water from the outer tub, a washing tub rotatably arranged within the outer tub and containing laundry, a drive motor for driving the washing tub, a control section for controlling the drive motor to execute a spin-drying process for rotating the washing tub at a predetermined spin-drying speed, and a detection section including a pair of electrodes arranged in the space between the bottom of the outer tub and the bottom of the washing tub, detecting a current flowing between the pair of electrodes which changes depending on the water level in the outer tub, and outputting a detection signal indicating the magnitude of the detected current. The control unit rotates the washing tub at a first detection rotation speed lower than the spin rotation speed while ramping up the rotation of the washing tub to the spin rotation speed, acquires the detection signal from the detection unit within a predetermined acquisition period to detect fluctuations in the water level within the acquisition period, and if it determines based on the magnitude of the detected water level fluctuation that a poor drainage condition in which water is not draining smoothly from the outer tub has occurred, it controls the drive motor so that the ramp-up of the rotation of the washing tub to the spin rotation speed is slower than if the poor drainage condition does not occur.
If the water in the outer tub sways due to large vibrations of the outer tub and cannot be discharged smoothly, the large vibrations of the outer tub will cause large fluctuations in the water level in the outer tub.
According to the above configuration, the control unit determines whether or not a poor drainage condition has occurred based on the magnitude of the water level fluctuation detected by the detection unit while the washing tub is rotating at the first detection rotation speed, so that it is possible to detect the occurrence of a poor drainage condition caused by large vibrations of the outer tub.
A washing machine according to a fourth aspect of the present invention comprises an outer tub elastically supported within a housing, a drainage section for draining water from the outer tub, a washing tub rotatably arranged within the outer tub and containing laundry, a drive motor for driving the washing tub, a control section for controlling the drive motor to execute a spin-drying process for rotating the washing tub at a predetermined spin-drying rotation speed, and a detection section including a light-emitting element and a light-receiving element located at a predetermined height from the bottom of the outer tub in the space between the bottom of the outer tub and the bottom of the washing tub, which detects the transmittance of light between the light-emitting element and the light-receiving element and outputs a detection signal according to the detected transmittance. Here, the control unit rotates the washing tub at a first detection rotation speed lower than the spin rotation speed while raising the washing tub up to the spin rotation speed, and during that time acquires the detection signal from the detection unit to detect whether water is present at the specified height, and if water is present at the specified height, controls the drive motor to rotate the washing tub at the first detection rotation speed for a longer time than when water is not present at the specified height, thereby slowing down the rise in rotation of the washing tub to the spin rotation speed .

According to the above configuration, when the water is not being smoothly discharged from the outer tub, the water discharge from the laundry is suppressed, so that the water is prevented from accumulating in the outer tub until it touches the bottom of the washing tub, and the occurrence of water pinching in the washing tub can be reduced. Furthermore, the occurrence of abnormal noise due to water pinching can also be reduced.
Furthermore, according to the above configuration, the time for which the washing tub is rotated at the first detection rotation speed is lengthened, so that when the water level in the outer tub is low, the rotation speed of the washing tub can be increased from the first detection rotation speed. Even if more water is discharged from the laundry due to the subsequent increase in rotation speed than at the first detection rotation speed, water is prevented from accumulating in the outer tub until it touches the bottom of the washing tub, thereby reducing the occurrence of water biting in the washing tub.

The present invention provides a washing machine that can reduce the occurrence of water bites in the washing tub during the spin-drying process.

The effects and significance of the present invention will become clearer from the description of the embodiments shown below. However, the following embodiment is merely an example of how the present invention can be put into practice, and the present invention is in no way limited to the embodiments described below.

FIG. 1 is a side cross-sectional view of a fully automatic washing machine according to a first embodiment. Fig. 2(a) is a plan cross-sectional view of the outer tub according to embodiment 1. Fig. 2(b) is a side cross-sectional view of the periphery of the water level detector in the outer tub, taken along line AA' in Fig. 2(a) according to embodiment 1. FIG. 3 is a block diagram showing a configuration of the fully automatic washing machine according to the first embodiment. FIG. 4 is a flowchart showing a control process by the control unit in the spin-drying process according to the first embodiment. FIG. 5 is a flowchart showing a water entrapment prevention control process according to the first embodiment. Fig. 6(a) is a flowchart showing a water level abnormality determination process included in the water bite prevention control process according to embodiment 1. Fig. 6(b) is a flowchart showing a reference value acquisition process for acquiring a reference value of a detection signal used in the water level abnormality determination process according to embodiment 1. FIG. 7 is a flowchart showing a vibration abnormality determination process included in the water bite prevention control process according to the first embodiment. FIG. 8 is a flowchart showing a water entrapment prevention control process according to the first modified example. 9A is a flowchart showing a water level detection process included in the water bite prevention control process according to the modified example 1. FIG. 9B is a flowchart showing a water level abnormality determination process included in the water bite prevention control process according to the modified example 1. FIG. 10 is a flowchart showing a water entrapment prevention control process according to the second modified example. FIG. 11 is a flowchart showing a control process by the control unit in the spin-drying process according to the third modified example. FIG. 12 is a flowchart showing a vibration prevention control process according to the third modified example. FIG. 13 is a side cross-sectional view of the periphery of the water level detector in the outer tub according to the second embodiment. FIG. 14 is a flowchart showing a water entrapment prevention control process according to the second embodiment.

Below, a fully automatic washing machine 1, which is one embodiment of the washing machine of the present invention, will be described with reference to the drawings.

<Embodiment 1>
FIG. 1 is a side cross-sectional view of a fully automatic washing machine 1 according to a first embodiment.

The fully automatic washing machine 1 has a housing 10 that forms the exterior. The housing 10 includes a rectangular cylindrical body 11 with open top and bottom faces, a top panel 12 that covers the top face of the body 11, and a foot stand 13 that supports the body 11. A laundry inlet 14 is formed in the top panel 12. The laundry inlet 14 is covered by an openable top lid 15.

Inside the housing 10, an outer tank 20 with an open top is elastically suspended and supported by four suspension rods 21 equipped with vibration isolation devices. The outer tank 20 has a substantially cylindrical peripheral surface portion 201 and a substantially disk-shaped bottom surface portion 202.

A washing and dehydrating tub 22 with an open top is placed inside the outer tub 20. The washing and dehydrating tub 22 has a substantially cylindrical peripheral surface portion 22a and a substantially disk-shaped bottom surface portion 22b, and rotates around a rotation axis extending in the vertical direction. A large number of dehydration holes 22c are formed around the entire circumference of the peripheral surface portion 22a of the washing and dehydrating tub 22. The washing and dehydrating tub 22 corresponds to the washing tub of the present invention.

A balance ring 23 is provided on the top of the washing/spinning tub 22. A pulsator 24 is rotatably arranged on the bottom of the washing/spinning tub 22. A number of blades 24a are provided radially on the surface of the pulsator 24.

On the outside of the bottom surface 202 of the outer tub 20, a drive unit 30 is arranged to generate torque to drive the washing and spin-drying tub 22 and the pulsator 24. The drive unit 30 includes a drive motor 31 and a transmission mechanism 32. The transmission mechanism 32 has a clutch mechanism 32a, and by switching operation using the clutch mechanism 32a, the torque of the drive motor 31 is transmitted only to the pulsator 24 to rotate only the pulsator 24 during the washing and rinsing processes, and the torque of the drive motor 31 is transmitted to the pulsator 24 and the washing and spin-drying tub 22 to rotate the pulsator 24 and the washing and spin-drying tub 22 together during the spin-drying process.

A drain outlet 203 is formed in the bottom surface 202 of the outer tub 20. The drain outlet 203 is connected to the drain section 40. The drain section 40 includes a drain valve 41 and a drain hose 42 connected to the drain valve 41. When the drain valve 41 is opened, the water stored in the washing and spin-drying tub 22 and the outer tub 20 is drained outside the machine through the drain hose 42.

A water supply unit 50 for supplying tap water into the washing and spin-drying tub 22, i.e., the outer tub 20, is disposed at the rear of the top panel 12. The water supply unit 50 has a water supply valve 51. The water inlet 51a of the water supply valve 51 is connected to a water faucet via a water supply hose. When the water supply valve 51 is opened, tap water from the water faucet flows through the water supply passage 52 and is supplied into the washing and spin-drying tub 22 from the water inlet 53.

Figure 2(a) is a plan cross-sectional view of the outer tank 20 according to the first embodiment. Figure 2(b) is a side cross-sectional view of the outer tank 20 around the water level detector 60 according to the first embodiment, taken along line A-A' in Figure 2(a).

The bottom surface 202 of the outer tub 20 is provided with a step 204 extending from the center toward the outer periphery, and the inner surface of the bottom surface 202 slopes downward from the right side of the step 204 in the direction of the dashed arrow in FIG. 2. On the left side of the step 204, where the inner surface of the bottom surface 202 is lowest, a drainage recess 205 is formed by recessing the bottom surface 202, and a drain outlet 203 is provided within the drainage recess 205. The inner surface of the bottom surface 202 of the outer tub 20 slopes downward from the center toward the outer periphery.

A cylindrical mounting hole 206 that protrudes slightly downward is formed in the bottom surface 202 of the outer tank 20 near the outer periphery and to the left of the drain recess 205, i.e., near the higher side of the inner surface of the bottom surface 202. An electrode-type conductivity sensor is attached to the mounting hole 206 from below as a water level detector 60. The water level detector 60 corresponds to the detection unit of the present invention.

The water level detector 60 has an upper part 60a having a cylindrical shape with an outer diameter smaller than that of the lower part 60b, and the upper part 60a is fitted into the mounting port 206. A gasket 210 is provided between the lower part 60b and the mounting port 206 to seal the water. The tip of the upper part 60a protrudes above the inner surface of the bottom part 202 and has a groove part 61 in the center. The bottom surface of the groove part 61 is lower than the inner surface of the bottom part 202 around the mounting port 206, and the part of the groove part 61 lower than the inner surface of the bottom part 202 becomes a residual water pocket 207 recessed from the inner surface of the bottom part 202. In this embodiment 1, the residual water pocket 207 is a square recess. The residual water pocket 207 may be a recess of any shape, such as a circle. The residual water pocket 207 corresponds to the recess of the present invention.

The water level detector 60 has a pair of electrodes 62 on two opposing side wall surfaces of the groove portion 61. The pair of electrodes 62 have a rectangular plate shape and are arranged in the space between the bottom portion 202 and the bottom portion 22b of the washing and spin-drying tub 22 so as to protrude upward from the bottom surface of the residual water pocket 207 in the bottom portion 202.

The water level detector 60 is used to detect the water level in the outer tub 20 in the control process of the spin-drying step described below. When water from the laundry is discharged from the outer tub 20 in the spin-drying step, some of the water passes through the water level detector 60 and accumulates in the residual water pocket 207. If water is not completely drained from the outer tub 20 and overflows from the drain recess 205, water may accumulate around the water level detector 60, higher than the top surface of the residual water pocket 207. When water accumulates at least in the residual water pocket 207, water is present between the pair of electrodes 62.

When detecting the water level in the outer tub 20, a voltage is applied to the pair of electrodes 62 in the water level detector 60. When water is present between the pair of electrodes 62, a current corresponding to the conductivity of the water flows between the electrodes. As the water level in the outer tub 20 rises and the water level between the pair of electrodes 62 increases, the surface area of the electrodes 62 in contact with the water increases, and therefore the current increases.

The water level detector 60 detects the water level between the pair of electrodes 62, i.e., the current flowing between the pair of electrodes 62, which changes depending on the water level in the outer tank 20, and outputs a detection signal indicating the magnitude of the detected current to the control unit 101. In this embodiment 1, the detection signal is a voltage signal, and in this case, the higher the water level in the outer tank 20, the larger the voltage value. The water level detector 60 can detect the water level in the outer tank 20 from the bottom surface of the residual water pocket 207, where the lower ends of the pair of electrodes 62 are located, to the position of the upper ends of the pair of electrodes 62.

Figure 3 is a block diagram showing the configuration of a fully automatic washing machine 1 according to the first embodiment.

In addition to the above-mentioned configuration, the fully automatic washing machine 1 includes a control unit 100. The control unit 100 includes a control unit 101, a memory unit 102, a motor drive unit 103, a clutch drive unit 104, a water supply drive unit 105, and a drain drive unit 106. The fully automatic washing machine 1 also includes an operation unit 110 and a water level sensor 120.

The operation unit 110 includes various operation buttons, such as a power button for turning on and off the power to the fully-automatic washing machine 1, a start/pause button for starting and pausing a washing operation, and a course selection button for selecting an arbitrary operation course from among a plurality of operation courses related to the washing operation. The operation unit 110 outputs an input signal to the control unit 101 according to the operation button operated by the user.

The water level sensor 120 is a diaphragm type water level sensor, and is connected via a hose to an air trap provided at the bottom of the outer tub 20. The water level sensor 120 detects the water level in the washing and spin-drying tub 22, i.e., the outer tub 20, by detecting the air pressure in the air trap, and outputs a water level signal corresponding to the detected water level to the control unit 101.

The motor drive unit 103 drives the drive motor 31 according to the control signal output from the control unit 101. The motor drive unit 103 includes a rotation sensor that detects the rotation speed of the drive motor 31, an inverter circuit, etc., and adjusts the drive power so that the drive motor 31 rotates at the rotation speed set by the control unit 101.

The clutch drive unit 104 drives the clutch mechanism 32a of the transmission mechanism unit 32 according to a control signal output from the control unit 101. The water supply drive unit 105 drives the water supply valve 51 according to a control signal from the control unit 101. The drain drive unit 106 drives the drain valve 41 according to a control signal from the control unit 101.

The memory unit 102 includes an EEPROM, a RAM, etc. The memory unit 102 stores programs for executing the washing operation of various operation courses. The memory unit 102 also stores various operating conditions used in the washing operation.

The control unit 101 includes a CPU and controls the motor drive unit 103, clutch drive unit 104, water supply drive unit 105, drain drive unit 106, etc., according to the program stored in the memory unit 102.

In the fully automatic washing machine 1, various washing operation courses are performed under the control of the control unit 101. In the washing operation, the washing process, intermediate spin-drying process, rinsing process, and final spin-drying process are performed in order. Depending on the washing course, the rinsing process may be performed twice, in which case the intermediate spin-drying process is performed after the first rinsing process.

Before the washing process, the laundry load is detected. In load detection, for example, after the laundry is put in and there is no water in the washing and spinning tub 22, the pulsator 24 rotates, and the load is determined based on the drive current of the drive motor 31 and the amount of inertial rotation until the drive motor 31 stops. The water level and time for the washing and rinsing processes are determined according to the detected load.

In the washing and rinsing processes, the pulsator 24 rotates to the right and left while water is stored in the washing and spin-drying tub 22. The rotation of the pulsator 24 generates a water flow in the washing and spin-drying tub 22. In the washing process, detergent is added to the washing and spin-drying tub 22, and the laundry is washed by the generated water flow and detergent. In the rinsing process, the laundry is rinsed by the generated water flow.

In the intermediate spin-drying process and the final spin-drying process, the washing and spin-drying tub 22 and the pulsator 24 rotate together at a high speed at a predetermined spin-drying speed. The laundry is spin-dried by the action of the centrifugal force generated in the washing and spin-drying tub 22. In the spin-drying process, the drain valve 41 is in an open state. The water squeezed out of the laundry is discharged into the outer tub 20 through the spin-drying hole 22c, and is discharged outside the machine through the drain outlet 203 and the drain hose 42.

The intermediate dehydration process and the final dehydration process are both dehydration processes, and hereafter, when there is no need to distinguish between them, they will simply be referred to as dehydration processes.

However, if foreign matter such as lint accumulates in the drain hose 42, or if the drain hose 42 is not properly installed outside the machine, the drainage from the outer tub 20 may deteriorate. If the spin cycle is performed in such a state, the water discharged from the laundry will not be smoothly discharged from the outer tub 20, and there is a risk that the rotating washing and spin-drying tub 22 will come into contact with the water accumulated at the bottom of the outer tub 20 while the rotation speed of the washing and spin-drying tub 22 is being increased to the spin rotation speed, resulting in so-called water bite, which may cause abnormal noise due to water bite.

In addition, if the outer tub 20 vibrates significantly when the rotation speed of the washing and spin-drying tub 22 is increased during the spin-drying process, the water drained from the laundry will sway inside the outer tub 20 and will not be discharged smoothly, which may cause water to get caught in the washing and spin-drying tub 22.

Therefore, in this embodiment 1, when the rotation speed of the washing and spin-drying tub 22 is increased during the spin-drying process, a water bite prevention control process is executed to prevent water bite from occurring in the washing and spin-drying tub 22.

Fig. 4 is a flowchart showing the control process by the control unit 101 in the spin-drying process according to the first embodiment. Fig. 5 is a flowchart showing the water-trapping prevention control process according to the first embodiment. Fig. 6(a) is a flowchart showing the water-level abnormality determination process included in the water-trapping prevention control process according to the first embodiment. Fig. 6(b) is a flowchart showing the reference value acquisition process for acquiring the reference value of the detection signal used in the water-level abnormality determination process according to the first embodiment. Fig. 7 is a flowchart showing the vibration abnormality determination process included in the water-trapping prevention control process according to the first embodiment.

Referring to FIG. 4, when the spin-drying process is started, the control unit 101 sets the target rotation speed of the washing and spin-drying tub 22 to the first rotation speed and starts the drive motor 31 (S101). The first rotation speed is set to a rotation speed slightly higher than the rotation speed at the so-called horizontal resonance point (e.g., 50 to 60 rpm) at which the washing and spin-drying tub 22 and the outer tub 20 vibrate significantly in the horizontal direction due to resonance, and is set to, for example, 120 rpm.

When the rotation speed of the washing and spin-drying tub 22 reaches the first rotation speed (S102: YES), the control unit 101 maintains the rotation speed of the washing and spin-drying tub 22 at the first rotation speed (S103) and waits for the first maintenance time to elapse from the start of the maintenance (S104). The first maintenance time is a period of several tens of seconds, for example 30 seconds, and is set before the spin-drying process depending on the load of laundry in the washing and spin-drying tub 22, etc. While the first maintenance time has elapsed, most of the amount of water that can be discharged can be squeezed out of the laundry by the centrifugal force acting at the first rotation speed.

When the first maintenance time has elapsed (S104: YES), the control unit 101 sets the target rotation speed to the second rotation speed and increases the rotation speed of the washing and spin-drying tub 22 (S105). The second rotation speed is set to a rotation speed slightly higher than the rotation speed at the so-called vertical resonance point (e.g., 200 to 220 rpm) at which the washing and spin-drying tub 22 and the outer tub 20 vibrate significantly in the vertical direction due to resonance, and is set to, for example, 240 rpm.

When the rotation speed of the washing and spin-drying tub 22 reaches the second rotation speed (S106: YES), the control unit 101 maintains the rotation speed of the washing and spin-drying tub 22 at the second rotation speed (S107) and waits for the second maintenance time to elapse from the start of the maintenance (S104). The second maintenance time is a time longer than the first maintenance time, for example, tens of seconds to about one minute, for example, 50 seconds, and is set before the spin-drying process depending on the load of laundry in the washing and spin-drying tub 22, etc. In addition, the second maintenance time can be extended by the water bite prevention control shown in FIG. 5. During the second maintenance time, most of the amount of water that can be discharged can be discharged from the laundry by the centrifugal force acting at the second rotation speed.

When the second maintenance time has elapsed (S108: YES), the control unit 101 sets the target rotation speed to the spin rotation speed and increases the rotation speed of the washing and spin-drying tub 22 (S109). The spin rotation speed is set to, for example, 800 rpm. The spin rotation speed of the final spin-drying process may be set higher than the spin rotation speed of the intermediate spin-drying processes.

As the second maintenance time approaches the end, the amount of water drained from the laundry decreases, but as the rotation speed of the washing and spin-drying tub 22 increases from the second rotation speed, the centrifugal force acting on the laundry increases, and more water can be drained from the laundry than at the second rotation speed.

When the rotation speed of the washing/spinning tub 22 reaches the spin rotation speed (S110: YES), the control unit 101 maintains the rotation speed of the washing/spinning tub 22 at the spin rotation speed (S111) and waits for the spin time to elapse from the start of the maintenance (S112). The spin time is a few minutes to a dozen minutes, and is set before the spin process depending on the load of laundry in the washing/spinning tub 22, etc.

When the spin-drying time has elapsed (S112: YES), the control unit 101 stops the drive motor 31 and stops the washing and spin-drying tub 22 (S113). This completes the spin-drying process.

Note that the first and second rotation speeds are rotation speeds in the low-speed region, and the dehydration rotation speed is the rotation speed in the high-speed region.

In parallel with the control process for the spin-drying process in FIG. 4, the control unit 101 executes the water-trapping prevention control process in FIG. 5.

Referring to FIG. 5, the control unit 101 monitors whether the rotation speed of the washing and spin-drying tub 22 has reached the second rotation speed (S201). The second rotation speed corresponds to the first detection rotation speed of the present invention.

When the rotation speed of the washing and spin-drying tub 22 reaches the second rotation speed (S201: YES), the control unit 101 operates the water level detector 60, i.e., applies a voltage to the pair of electrodes 62, and starts acquiring the detection signal, i.e., the voltage value, output from the water level detector 60 (S202). The detection signal is acquired at a predetermined sampling rate, for example, at intervals of 0.1 seconds.

When a predetermined acquisition time, for example 15 seconds, has elapsed since the start of acquisition of the detection signal (S203: YES), the control unit 101 stops the operation of the water level detector 60 and ends acquisition of the detection signal (S204). In this way, multiple detection signals are acquired.

Next, the control unit 101 executes the water level abnormality determination process of FIG. 6(a) (S205) and executes the vibration abnormality determination process of FIG. 7 (S206).

Referring to FIG. 6(a), the control unit 101 calculates the average value of the values of the acquired detection signals, i.e., the voltage values (S301). Next, the control unit 101 reads out the reference value of the detection signal from the storage unit 102 (S302). The reference value is acquired by the reference value acquisition process of FIG. 6(b).

The reference value acquisition process is executed at the end of the washing and rinsing steps, for example, between when the pulsator 24 stops operating and when draining starts. At this time, the pair of electrodes 62 of the water level detector 60 are entirely submerged in the water stored in the outer tub 20, and the value of the detection signal output from the water level detector 60 in this state, i.e., the voltage value, is set as the reference value. When the pair of electrodes 62 are entirely submerged, the detection signal does not change even if the water level changes. Therefore, the reference value is the value of the detection signal when the water level in the outer tub 20 is at the height of the upper ends of the pair of electrodes 62, i.e., the upper limit water level that the water level detector 60 can detect.

Referring to FIG. 6(b), the control unit 101 operates the water level detector 60 and starts acquiring a detection signal from the water level detector 60 (S401). The detection signal is acquired at a predetermined sampling rate, for example, at intervals of 0.1 seconds.

When a predetermined acquisition time, for example 15 seconds, has elapsed since the start of acquisition of the detection signal (S402: YES), the control unit 101 stops the operation of the water level detector 60 and ends acquisition of the detection signal (S403).

The control unit 101 calculates the average value of the multiple acquired detection signals (S404) and stores the calculated average value in the memory unit 102 as a reference value (S405).

The reference value obtained during the washing process is used during the spin-drying process after the washing process, and the reference value obtained during the rinsing process is used during the spin-drying process after the rinsing process.

Returning to FIG. 6(a), the control unit 101 calculates a water level judgment value by dividing the average value calculated in S301 by the reference value read out in S302 (S303). The water level judgment value is a value that expresses the water level in the outer tank 20 as a ratio to the upper limit water level that can be detected by the water level detector 60, and takes a value of 1 or less. In this way, the control unit 101 detects the water level in the outer tank 20 in the form of a water level judgment value from the detection signal obtained from the water level detector 60.

The current flowing through the pair of electrodes 62 differs depending on the conductivity of the water stored in the outer tub 20, even if the water level in the outer tub 20 is the same. The conductivity of the water in the outer tub 20 can change depending on the detergent and dirt components contained in the water. In this embodiment 1, as described above, by using the reference value obtained in the washing process or rinsing process immediately before when the same water as that in the spin-drying process was stored, the water level in the outer tub 20 can be detected with high accuracy without being influenced by differences in the conductivity of the water.

Next, the control unit 101 determines whether the water level determination value is greater than a predetermined water level threshold (S304). The water level threshold is set to a value of 0.9, for example.

When the drainage performance of the drain section 40 deteriorates due to the accumulation of foreign matter in the drain hose 42, causing poor drainage in which the outer tub 20 does not drain smoothly, the water drained from the laundry accumulates in the outer tub 20, and the water level in the outer tub 20 rises. This causes the water level judgment value to become greater than the water level threshold value.

When the control unit 101 determines that the water level determination value is greater than the water level threshold (S304: YES), it sets a water level abnormality (S305). In this way, the water level abnormality determination process ends.

Next, referring to FIG. 7, the control unit 101 divides the acquisition time, excluding the initial predetermined time, into a plurality of intervals (S501). If the acquisition time is 15 seconds, for example, a 12-second period from 3 seconds to 15 seconds is divided into six intervals of 2 seconds each.

Next, the control unit 101 calculates the difference between the minimum and maximum detection signals, i.e., the voltage values, acquired in each divided section (S502). When the outer tub 20 vibrates, the water in the outer tub 20 ripples, and the water level in the outer tub 20, i.e., the water level of the water present between the pair of electrodes 62, fluctuates. The difference value indicates the magnitude of the fluctuation in the water level.

The reason why the initial predetermined time of the acquisition time, for example, a time of less than 3 seconds, is excluded from the interval for calculating the difference value is that immediately after the water level detector 60 starts operating, the detection operation is unstable due to the influence of inrush current, etc., and the accuracy of the detection signal is low. Therefore, if acquisition of the detection signal starts after the detection operation of the water level detector 60 has stabilized, the initial predetermined time is not necessary.

Next, the control unit 101 sums the difference values of each section to obtain a vibration judgment value, which is the sum (S503). Then, the control unit 101 determines whether the vibration judgment value is greater than a predetermined vibration threshold value (S504).

If vibrations of such magnitude that drainage from the outer tank 20 is not performed smoothly occur in the outer tank 20, the fluctuations in the water level in the outer tank 20 become large, and the vibration judgment value becomes larger than the vibration threshold value.

When the control unit 101 determines that the vibration determination value is greater than the vibration threshold value (S504: YES), it sets a vibration abnormality (S505). In this way, the vibration abnormality determination process ends.

In addition, in S503, the average value of the difference values for each section may be calculated, and the average value may be set as the vibration judgment value. In this case, in the judgment in S504, the vibration threshold value is set to a value obtained by dividing the vibration threshold value when the sum value is the vibration judgment value by the total number of difference values, and substantially the same judgment is made as in S504 when the sum value is the vibration judgment value.

In this embodiment 1, a residual water pocket 207 is formed between the pair of electrodes 62, and water tends to accumulate there more easily than in the bottom surface portion 202 around the outer tub 20. When the outer tub 20 vibrates, rippling tends to occur between the pair of electrodes 62. This makes it easier to detect the magnitude of vibration of the outer tub 20.

Returning to FIG. 5, when the water level abnormality determination process in FIG. 6(a) and the vibration abnormality determination process in FIG. 7 are completed, the control unit 101 determines whether or not at least one of the water level abnormality and the vibration abnormality has been set as a result of these abnormality determination processes (S207).

When at least one of the abnormal settings is made (S207), the control unit 101 determines that a poor drainage condition has occurred in which the outer tub 20 is not draining water smoothly, and extends the second maintenance time during which the rotation speed of the washing and spin-drying tub 22 is maintained at the second rotation speed by a predetermined time, for example 10 seconds (S208).

As described above, the amount of water drained from the laundry decreases as the second maintenance time approaches the end. Therefore, even if a poor drainage state occurs, if the second maintenance time is extended, the rotation speed of the washing and spin-drying tub 22 can be increased from the second rotation speed with the water level in the outer tub 20 lower than when the second maintenance time is not extended. Therefore, even if the centrifugal force acting on the laundry increases and more water is drained from the laundry again, water is prevented from accumulating in the outer tub 20 until it comes into contact with the bottom portion 22b of the washing and spin-drying tub 22, and the occurrence of water biting in the washing and spin-drying tub 22 can be reduced.

Effects of First Embodiment
According to this embodiment 1, the fully automatic washing machine 1 includes a pair of electrodes 62 arranged in the space between the bottom portion 202 of the outer tub 20 and the bottom portion 22b of the washing and spin-drying tub 22, and is equipped with a water level detector 60 that detects the current flowing between the pair of electrodes 62, which changes depending on the water level in the outer tub 20, and outputs a detection signal indicating the magnitude of the detected current.The control unit 101 detects the water level in the outer tub 20 based on the detection signal from the water level detector 60 while the rotation of the washing and spin-drying tub 22 is being increased to the spin-drying rotation speed, and when it determines based on the detected water level that a poor drainage condition has occurred in which water is not being drained smoothly from the outer tub 20, it controls the drive motor 31 so that the increase in rotation of the washing and spin-drying tub 22 to the spin-drying rotation speed is slower than when a poor drainage condition does not occur.

This configuration prevents water from being discharged from the laundry when poor drainage occurs, preventing water from accumulating in the outer tub 20 until it touches the bottom surface 22b of the washing and spin-drying tub 22, reducing the occurrence of water pinching in the washing and spin-drying tub 22. Furthermore, the occurrence of abnormal noise caused by water pinching can also be reduced.

Furthermore, according to this embodiment 1, the control unit 101 rotates the washing and spin-drying tub 22 at a second rotation speed that is lower than the spin-drying rotation speed, and during that time, obtains a detection signal from the water level detector 60 to detect the water level in the outer tub 20, and controls the drive motor 31 so that when a poor drainage condition occurs, the washing and spin-drying tub 22 rotates at the second rotation speed for a longer time than when a poor drainage condition does not occur.

With this configuration, the rotation speed of the washing and dehydrating tub 22 can be increased from the second rotation speed when the water level in the outer tub 20 is low. Therefore, even if the subsequent increase in rotation speed causes more water to be discharged from the laundry than at the second rotation speed, water is prevented from accumulating in the outer tub 20 until it comes into contact with the bottom portion 22b of the washing and dehydrating tub 22, thereby reducing the occurrence of water biting in the washing and dehydrating tub 22.

Furthermore, if the drainage performance of the drainage section 40 deteriorates and water does not drain smoothly from the outer tub 20, the water level in the outer tub 20 will increase.

According to this embodiment 1, the control unit 101 executes the water level abnormality determination process shown in FIG. 6(a) to determine whether or not a poor drainage condition has occurred based on the magnitude of the water level detected by the water level detector 60, and thus can detect the occurrence of a poor drainage condition caused by a deterioration in the drainage performance of the drainage unit 40.

Furthermore, if the outer tub 20 vibrates strongly, causing the water in the outer tub 20 to sway and prevent smooth drainage, the strong vibration of the outer tub 20 will cause large fluctuations in the water level in the outer tub 20.

According to this embodiment 1, the control unit 101 executes the vibration abnormality determination process shown in FIG. 6(b) to determine whether or not a poor drainage condition has occurred based on the magnitude of the fluctuation in the water level detected by the water level detector 60, and thus can detect the occurrence of a poor drainage condition caused by large vibrations of the outer tank 20.

<Modification 1>
Fig. 8 is a flowchart showing the water bite prevention control process according to the modified example 1. Fig. 9(a) is a flowchart showing the water level detection process included in the water bite prevention control process according to the modified example 1. Fig. 9(b) is a flowchart showing the water level abnormality determination process included in the water bite prevention control process according to the modified example 1.

In the fully automatic washing machine 1 of the above-mentioned embodiment 1, as shown in FIG. 5 etc., in the water bite prevention control process, a determination is made as to whether or not a water level abnormality has occurred based on the water level in the outer tub 20 detected while the washing and spin-drying tub 22 is rotating at the second rotation speed.

In contrast, in the fully automatic washing machine 1 of this modified example 1, as shown in FIG. 8 etc., in the water bite prevention control process, a determination is made as to whether or not a water level abnormality has occurred based on the water level in the outer tub 20 detected while the washing and spinning tub 22 is rotating at the first rotation speed and the water level in the outer tub 20 detected while the washing and spinning tub 22 is rotating at the second rotation speed.

The following describes the changes made to the water entrapment prevention control process in the first embodiment.

Referring to FIG. 8, the control unit 101 monitors whether the rotation speed of the washing and spin-drying tub 22 has reached the first rotation speed (S211). When the rotation speed of the washing and spin-drying tub 22 has reached the first rotation speed (S211: YES), the control unit 101 executes the water level detection process of FIG. 9(a) (S212).

Referring to FIG. 9(a), the control unit 101 operates the water level detector 60 and starts acquiring a detection signal from the water level detector 60 (S311). The detection signal is acquired at a predetermined sampling rate, for example, at intervals of 0.1 seconds.

When a predetermined acquisition time, for example 15 seconds, has elapsed since the start of acquisition of the detection signal (S312: YES), the control unit 101 stops the operation of the water level detector 60 and ends acquisition of the detection signal (S313).

Next, the control unit 101 calculates the average value of the acquired detection signals (S314). Furthermore, the control unit 101 reads the reference value of the detection signal from the storage unit 102 (S315), and obtains a first judgment value by dividing the average value by the reference value (S316). The first judgment value is stored in the storage unit 102.

Returning to FIG. 8, after the rotation speed of the washing/drying tub 22 reaches the second rotation speed, when the control unit 101 finishes acquiring the detection signal from the water level detector 60 (S201 to S204), in S205, it executes the water level abnormality determination process of FIG. 9(b) instead of the water level abnormality determination process of FIG. 6(a).

Referring to FIG. 9(b), the control unit 101 calculates the average value of the acquired detection signals (S321). Furthermore, the control unit 101 reads the reference value of the detection signal from the storage unit 102 (S322), and calculates the second judgment value by dividing the average value by the reference value (S323).

Next, the control unit 101 reads the first judgment value from the storage unit 102 and adds it to the second judgment value to obtain a water level judgment value (S324). The control unit 101 then determines whether the water level judgment value is greater than a predetermined water level threshold (S325). The water level threshold is set to a value twice the water level threshold used in the water level abnormality judgment process of FIG. 6(a), for example, a value of 1.8.

When the control unit 101 determines that the water level judgment value is greater than the water level threshold (S325: YES), it sets a water level abnormality (S326).

In addition, in S324, the average value of the first judgment value and the second judgment value may be calculated, and the average value may be used as the water level judgment value. In this case, the water level threshold value for the judgment in S325 will be set to the same value as the water level threshold value for the judgment in S304 of FIG. 6(a), and substantially the same judgment will be made as in S325 when the sum value is the water level judgment value.

Furthermore, the first judgment value and the second judgment value may each be separately compared with a water level threshold value having the same value as the judgment in S304 of FIG. 6(a), and if either judgment value is greater than the water level threshold value, a water level abnormality may be set. Also, the value of the water level threshold value to be compared may be different between the first judgment value and the second judgment value.

According to this modified example 1, the water level abnormality is judged by taking into account the water level in the outer tub 20 when the laundry is being dewatered at the first rotation speed. This makes it possible to more accurately judge whether or not a drainage problem has occurred.

<Modification 2>
FIG. 10 is a flowchart showing a water entrapment prevention control process according to the second modified example.

In the fully automatic washing machine 1 of the above embodiment 1, as shown in FIG. 5, when at least one of the water level abnormality and the vibration abnormality is set in the water bite prevention control process, the second maintenance time is extended.

In contrast, in the fully automatic washing machine 1 of the present modified example 2, as shown in FIG. 10, when at least one of the water level abnormality and the vibration abnormality is set in the water bite prevention control process, the acceleration is reduced when increasing the rotation speed of the washing and spin-drying tub 22 from the second rotation speed.

In the water entrapment prevention control process of this modified example 2 shown in FIG. 10, the processes of S222 to S224 are executed instead of the process of S208 in the water entrapment prevention control process of the above-mentioned embodiment 1 shown in FIG. 5.

Referring to FIG. 10, in S207, the control unit 101 determines whether or not at least one of the water level abnormality and the vibration abnormality has been set. If no abnormality has been set (S207: NO), the control unit 101 sets the acceleration when increasing from the second rotation speed to the first acceleration, for example, 30 rpm/s (S221). As a result, in S109 of the control process in FIG. 4, the control unit 101 controls the drive motor 31 so that the rotation speed of the washing and spin-drying tub 22 increases to the spin-drying rotation speed at the first acceleration.

On the other hand, if at least one of the abnormality settings has been made (S207: YES), the control unit 101 sets the acceleration when increasing from the second rotation speed to a second acceleration smaller than the first acceleration, for example, 10 rpm/s (S222). As a result, in S109 of the control process in FIG. 4, the control unit 101 controls the drive motor 31 so that the rotation speed of the washing and spin-drying tub 22 increases at the second acceleration.

In this way, when there is poor drainage from the outer tub 20, the rotation of the washing and spin-drying tub 22 is started up more slowly from the second rotation speed than when there is no poor drainage, so that water is prevented from being discharged from the laundry during start-up. This prevents water from accumulating in the outer tub 20 until it comes into contact with the bottom surface 22b of the washing and spin-drying tub 22, and reduces the occurrence of water biting in the washing and spin-drying tub 22.

Then, the control unit 101 monitors whether the rotation speed of the washing and spin-drying tub 22 has reached the third rotation speed (S223). The third rotation speed is a rotation speed in the medium speed range that is higher than the second rotation speed and lower than the spin-drying rotation speed, and is set to, for example, 500 rpm.

By the time the rotation speed of the washing and spin-drying tub 22 reaches the third rotation speed, a lot of water has already been squeezed out of the laundry, so the amount of water coming out of the laundry is reduced. Therefore, even if the acceleration is increased, the occurrence of water biting in the washing and spin-drying tub 22 can be reduced.

Therefore, when the rotation speed of the washing/drying tub 22 reaches the third rotation speed (S223: YES), the control unit 101 sets the acceleration to the first acceleration (S224). As a result, in S109 of the control process in FIG. 4, the control unit 101 controls the drive motor 31 to increase the rotation speed to the spin-drying rotation speed at the first acceleration.

As described above, according to this modified example 2, if a poor drainage state occurs in which the outer tub 20 is not drained smoothly, the control unit 101 reduces the acceleration when increasing the rotation speed of the washing and spin-drying tub 22 from the second rotation speed. This reduces the amount of water drained from the laundry when the rotation speed increases from the second rotation speed, preventing water from accumulating in the outer tub 20 until it comes into contact with the bottom surface portion 22b of the washing and spin-drying tub 22, thereby reducing the occurrence of water biting in the washing and spin-drying tub 22.

In the above example, when the rotation speed of the washing/drying tub 22 reaches the third rotation speed, the acceleration is changed from the second acceleration to the first acceleration, which is greater than the second acceleration. However, the rotation of the washing/drying tub 22 may be increased to the spin rotation speed while maintaining the second acceleration. In this case, the time required to increase the rotation speed to the spin rotation speed will be longer, but the occurrence of water biting in the washing/drying tub 22 can be further reduced.

The configuration of this modified example 2 can also be applied to the configuration of modified example 1. In this case, the process of S208 in FIG. 8 is replaced with the processes of S221 to S224 in FIG. 10.

<Modification 3>
Fig. 11 is a flowchart showing a control process by the control unit 101 in the spin-drying process according to the modified example 3. Fig. 12 is a flowchart showing a vibration prevention control process according to the modified example 3.

In the fully automatic washing machine 1 of this modified example 3, the rotation speed of the washing and spin-drying tub 22 is temporarily maintained at the third rotation speed while being increased from the second rotation speed to the spin-drying rotation speed. Then, at the third rotation speed, a vibration prevention control process is executed to prevent vibration of the outer tub 20 based on the water level detected by the water level detector 60.

Referring to FIG. 11, when the second maintenance time has elapsed since the rotation speed of the washing and spin-drying tub 22 was maintained at the second rotation speed (S108: YES), the control unit 101 sets the target rotation speed to a third rotation speed, for example, 500 rpm, and increases the rotation speed of the washing and spin-drying tub 22 (S121).

When the rotation speed of the washing/drying tub 22 reaches the third rotation speed (S122: YES), the control unit 101 maintains the rotation speed of the washing/drying tub 22 at the third rotation speed (S123) and waits for the third maintenance time to elapse from the start of the maintenance (S124). The third maintenance time may be several tens of seconds.

When the third maintenance time has elapsed (S124: YES), the control unit 101 sets the target rotation speed to the spin-dry rotation speed and increases the rotation speed of the washing and spin-drying tub 22 (S109).

In parallel with the control process of FIG. 11, the control unit 101 executes the water entrapment prevention control process of FIG. 5 as well as the vibration prevention control process of FIG. 12.

Referring to FIG. 12, the control unit 101 monitors whether the rotation speed of the washing and spin-drying tub 22 has reached the third rotation speed (S601). The third rotation speed corresponds to the second detection rotation speed of the present invention.

When the rotation speed of the washing and spin-drying tub 22 reaches the third rotation speed (S601: YES), the control unit 101 operates the water level detector 60 and starts acquiring a detection signal from the water level detector 60 (S602). The detection signal is acquired at a predetermined sampling rate, for example, at intervals of 0.1 seconds.

When a predetermined acquisition time, for example 15 seconds, has elapsed since the start of acquisition of the detection signal (S603: YES), the control unit 101 stops the operation of the water level detector 60 and ends acquisition of the detection signal (S604).

Next, the control unit 101 calculates the average value of the multiple detection signals obtained (S605). Furthermore, the control unit 101 reads the reference value of the detection signal from the memory unit 102 (S606), and obtains a judgment value by dividing the average value by the reference value (S607). The judgment value is a value that indicates the water level in the outer tank 20 that exists between the pair of electrodes 62 of the water level detector 60.

Next, the control unit 101 determines whether the judgment value is smaller than a predetermined threshold value (S608). The threshold value is set to a value corresponding to a water level lower than the depth of the residual water pocket 207, for example, a value of 0.5.

In low-speed regions such as the second rotation speed, some of the water discharged from the laundry into the outer tub 20 accumulates in the residual water pocket 207. Normally, water remains in the residual water pocket 207 even when the rotation of the washing and spin-drying tub 22 is increased from the second rotation speed to the third rotation speed, which is a medium-speed region. However, if the outer tub 20 vibrates significantly while the rotation of the washing and spin-drying tub 22 is increased from the second rotation speed to the third rotation speed, water is likely to splash out of the residual water pocket 207, and water remaining in the residual water pocket 207 can be prevented.

When the outer tub 20 does not vibrate significantly and sufficient water remains in the remaining water pocket 207, the judgment value is equal to or greater than the threshold value. When the judgment value is equal to or greater than the threshold value (S608: NO), the control unit 101 sets the spin-drying rotation speed to the standard rotation speed, for example, 800 rpm (S609). As a result, in S111 of the control process in FIG. 11, the control unit 101 rotates the washing and spin-drying tub 22 at the standard rotation speed.

On the other hand, if the outer tub 20 vibrates significantly and water is discharged from the remaining water pocket 207, the judgment value becomes smaller than the threshold value. If the judgment value is smaller than the threshold value (S608: YES), the control unit 101 sets the spin-drying rotation speed to a low speed lower than the standard rotation speed, for example, 700 rpm (S610). As a result, in S111 of the control process in FIG. 11, the control unit 101 rotates the washing and spin-drying tub 22 at the low speed.

In this way, according to this modified example 3, when the rotation of the washing and spin-drying tub 22 is increased to the third rotation speed, i.e., the medium speed range, if it is detected that the outer tub 20 is vibrating significantly due to the water being discharged from the residual water pocket 207, the spin-drying rotation speed is lowered. Therefore, the vibration of the outer tub 20 when the washing and spin-drying tub 22 rotates at the spin-drying rotation speed can be reduced.

<Embodiment 2>
FIG. 13 is a side cross-sectional view of the periphery of the water level detector 70 in the outer tank 20 according to the second embodiment.

In the fully automatic washing machine 1 of this embodiment 2, a photosensor type water level detector 70 is disposed on the bottom surface 202 of the outer tub 20 instead of the water level detector 60. The other configurations of the fully automatic washing machine 1 are the same as those shown in the above embodiment 1. The water level detector 70 corresponds to the detection unit of the present invention.

As shown in FIG. 13, the water level detector 70 is attached from below to an attachment port 206 provided on the bottom surface 202 of the outer tank 20. The water level detector 70 has a cylindrical shape with an upper part 70a having a smaller outer diameter than the lower part 70b, and the upper part 70a is fitted into the attachment port 206. A gasket 210 is provided between the lower part 70b and the attachment port 206 to provide a water seal. The tip of the upper part 70a protrudes above the inner surface of the bottom surface 202 and has a groove 71 in the center.

A light-emitting element 72 and a light-receiving element 73 are arranged inside the tip of the water level detector 70, facing each other across a groove 71. A light-transmitting window 74 is provided in front of the light-emitting element 72 and the light-receiving element 73 on the two opposing side walls of the groove 71.

The light-emitting element 72 and the light-receiving element 73 are located at a predetermined height from the inner surface of the bottom surface 202 in the space between the bottom surface 202 of the outer tub 20 and the bottom surface 22b of the washing and spin-drying tub 22. Light emitted from the light-emitting element 72 is received by the light-receiving element 73. The amount of light received by the light-receiving element 73 varies depending on the light transmittance between the light-emitting element 72 and the light-receiving element 73. The water level detector 70 detects the light transmittance and outputs a detection signal according to the detected transmittance to the control unit 101. In this embodiment 2, the detection signal is a voltage signal.

When there is no water at the height of the light-emitting element 72 and the light-receiving element 73, the water level detector 70 detects the transmittance of air. When there is water at the height of the light-emitting element 72 and the light-receiving element 73, the water level detector 70 detects the transmittance of water.

Figure 14 is a flowchart showing the water entrapment prevention control process according to the second embodiment.

In this embodiment 2, similar to the above embodiment 1, in the dehydration process, the control unit 101 executes the control process shown in FIG. 5. Furthermore, in parallel with the control process shown in FIG. 5, the control unit 101 executes the water bite prevention control process shown in FIG. 14.

Referring to FIG. 14, when the rotation speed of the washing and spin-drying tub 22 reaches the second rotation speed (S701: YES), the control unit 101 operates the water level detector 70, i.e., causes the light-emitting element 72 to emit light, and starts acquiring a detection signal from the water level detector 60 (S702). The detection signal is acquired at a predetermined sampling rate, for example, at intervals of 0.1 seconds.

When a predetermined acquisition time, for example 15 seconds, has elapsed since the start of acquisition of the detection signal (S703: YES), the control unit 101 stops the operation of the water level detector 60 and ends acquisition of the detection signal (S704).

Next, the control unit 101 calculates the average value of the multiple acquired detection signals (S705). The average value of the detection signals indicates the light transmittance between the light-emitting element 72 and the light-receiving element 73 of the water level detector 70.

The control unit 101 determines whether the average value is within a predetermined range from the threshold value (S706). The threshold value is a value that indicates the transmittance of water stored in the outer tub 20 in the washing process or rinsing process immediately before the spin-drying process. That is, the control unit 101 operates the water level detector 70 for a predetermined time at the end of the washing process or rinsing process, for example, between the time when the pulsator 24 stops operating and the time when draining starts, to obtain a detection signal. The control unit 101 then calculates the average value of the obtained detection signals and determines the calculated average value as the threshold value.

When poor drainage occurs due to the accumulation of foreign matter in the drain hose 42, causing the outer tub 20 to be unable to drain water smoothly, the water drained from the laundry accumulates in the outer tub 20, causing the water level in the outer tub 20 to rise and resulting in water being present at the height of the light-emitting element 72 and the light-receiving element 73. As a result, the water level detector 70 detects the transmittance of the water, so that the average value of the detection signal falls within a predetermined range from the threshold value.

If the control unit 101 determines that the average value is within a predetermined range from the threshold value (S706: YES), it determines that a poor drainage condition is occurring and extends the second maintenance time by a predetermined time, for example, 10 seconds (S208).

In addition, the water level detector 70 may detect the air permeability when there is no water in the outer tub 20, such as immediately before the start of a washing operation, and the air permeability may be used as the threshold value. In this case, if it is determined in S706 that the average value is not within a predetermined range from the threshold value, the second maintenance time is extended in S707.

Furthermore, the control unit 101 may execute the same processes as S702 to S705 while rotating the washing and spin-drying tub 22 at the first rotation speed, and obtain an average value of the detection signal from the water level detector 70. In this case, the control unit 101 sums or averages the average value obtained at the first rotation speed and the average value obtained at the second rotation speed, and in S706, determines whether the sum or average value is within a predetermined range from a threshold value set for this value.

Furthermore, the water level detector 70 may be configured to have a pair of electrodes similar to those of the water level detector 60 next to the light emitting element 72 and the light receiving element 73, and to further output a detection signal corresponding to the current flowing between the electrodes. In this case, in the water bite prevention control process of FIG. 14, the control unit 101 obtains a detection signal corresponding to the current and performs the vibration abnormality determination process of FIG. 6(b). Then, when the control unit 101 determines in S706 that the average value is within a predetermined range from the threshold value or when a vibration abnormality is set in the vibration abnormality determination process, it extends the second maintenance time in S707. Furthermore, in this case, in the water bite prevention control process of FIG. 14, the control unit 101 may perform the water level abnormality determination process of FIG. 6(a) and extend the second maintenance time even when a water level abnormality is set in the water level abnormality determination process.

Furthermore, in this embodiment 2, similar to the above modification example 2, the processing of S707 in FIG. 14 may be replaced with the processing of S221 to S224 in FIG. 10, so that the acceleration when increasing the rotation speed from the second rotation speed is changed depending on the determination in S706.

<Effects of the Second Embodiment>
According to this embodiment 2, the fully automatic washing machine 1 includes a light-emitting element 72 and a light-receiving element 73 located at a predetermined height from the bottom portion 202 of the outer tub 20 in the space between the bottom portion 202 of the outer tub 20 and the bottom portion 22b of the washing and spin-drying tub 22, and is equipped with a water level detector 70 that detects the light transmittance between the light-emitting element 72 and the light-receiving element 73 and outputs a detection signal according to the detected transmittance, and the control unit 101 detects whether or not water is present at the predetermined height based on the detection signal from the water level detector 70 while the washing and spin-drying tub 22 is being brought up to the spin-drying rotation speed, and when water is present at the predetermined height, controls the drive motor 31 so that the start-up of the rotation of the washing and spin-drying tub 22 is slower than when water is not present at the predetermined height.

This configuration prevents water from being discharged from the laundry when poor drainage occurs, preventing water from accumulating in the outer tub 20 until it touches the bottom surface 22b of the washing and spin-drying tub 22, reducing the occurrence of water bite in the washing and spin-drying tub 22. Furthermore, the occurrence of abnormal noise caused by water bite can also be reduced.

<Other changes>
In the above-described first embodiment, both the water level abnormality determination process in Fig. 6(a) and the vibration abnormality determination process in Fig. 6(b) are executed in the water bite prevention control process in Fig. 5. However, only one of the water level abnormality determination process and the vibration abnormality determination process may be executed in the water bite prevention control process.

Furthermore, in the above-mentioned embodiment 1, a residual water pocket 207 is provided on the bottom surface 202 of the outer tank 20, and a pair of electrodes 62 of the water level detector 60 protrude upward from the bottom surface of the residual water pocket 207. However, a configuration in which the residual water pocket 207 is not provided on the bottom surface 202 of the outer tank 20 may be adopted. In this case, it is preferable to adopt a configuration in which the pair of electrodes 62 of the water level detector 60 protrude upward from the inner surface of the bottom surface 202.

Furthermore, the water level detector 60 of the above-mentioned embodiment 1 may also be used as a dirt detector that detects dirt on the water accumulated in the washing process by a change in the current flowing between the pair of electrodes 62. Similarly, the water level detector 70 of the above-mentioned embodiment 2 may also be used as a dirt detector that detects dirt on the water accumulated in the washing process by a change in the light transmittance between the light-emitting element 72 and the light-receiving element 73. Furthermore, a sensor equipped with a pair of electrodes, a light-emitting element, and a light-receiving element may be used as the water level detectors 60, 70, and in this case, this sensor may be used to detect dirt on the water in the washing process.

Furthermore, in the above-mentioned embodiments 1 and 2, an example in which the present invention is applied to a fully automatic washing machine 1 is shown. However, the present invention can also be applied to a fully automatic washer-dryer equipped with a clothes drying function. Furthermore, the present invention can also be applied to a drum-type washing machine and a drum-type washer-dryer that have a horizontal-axis drum as a washing tub.

In addition, various modifications of the embodiments of the present invention are possible within the scope of the technical ideas set forth in the claims.

1. Fully automatic washing machine (washing machine)
10. Housing
20 Outer tank
22 Washing and spin-drying tub (washing tub)
31 Drive motor
40 Drainage section
60 Water level detector (detection unit)
62 Electrode
70 Water level detector (detection unit)
72 Light emitting element
73 Light receiving element
101 Control unit
207 Residual water pocket (recess)

Claims (6)

an outer tank elastically supported within a housing;
A drainage section for draining water from the outer tank;
A washing tub that is rotatably disposed in the outer tub and that accommodates laundry;
A drive motor for driving the washing tub;
A control unit that controls the drive motor to execute a spin-drying process of rotating the washing tub at a predetermined spin-drying rotation speed;
A detection unit includes a pair of electrodes arranged in a space between a bottom surface of the outer tub and a bottom surface of the washing tub, detects a current flowing between the pair of electrodes that changes according to a water level in the outer tub, and outputs a detection signal indicating a magnitude of the detected current,
The control unit is
While the rotation of the washing tub is being increased to the spin-drying rotation speed, the washing tub is rotated at a first detection rotation speed which is lower than the spin-drying rotation speed, and the detection signal is obtained from the detection unit during the rotation to detect the water level;
When it is determined based on the detected water level that a poor drainage state in which drainage from the outer tub is not smoothly occurring is occurring , the drive motor is controlled to make the time for rotating the washing tub at the first detection rotation speed longer than when the poor drainage state is not occurring, thereby slowing down the start-up of rotation of the washing tub to the dehydration rotation speed.
A washing machine characterized by: an outer tank elastically supported within a housing;
A drainage section for draining water from the outer tank;
A washing tub that is rotatably disposed in the outer tub and that accommodates laundry;
A drive motor for driving the washing tub;
A control unit that controls the drive motor to execute a spin-drying process of rotating the washing tub at a predetermined spin-drying rotation speed;
A detection unit includes a pair of electrodes arranged in a space between a bottom surface of the outer tub and a bottom surface of the washing tub, detects a current flowing between the pair of electrodes that changes according to a water level in the outer tub, and outputs a detection signal indicating a magnitude of the detected current,
The control unit is
While the rotation of the washing tub is being increased to the spin-drying rotation speed, the washing tub is rotated at a first detection rotation speed which is lower than the spin-drying rotation speed, and the detection signal is obtained from the detection unit during the rotation to detect the water level;
When it is determined based on the detected water level that a poor drainage state in which drainage from the outer tub is not smoothly occurring has occurred, the drive motor is controlled to make the time for rotating the washing tub at the first detection rotation speed longer than when the poor drainage state does not occur, or to slow down the rise in rotation of the washing tub to the dehydration rotation speed by reducing the acceleration when increasing the rotation speed of the washing tub from the first detection rotation speed;
A recess is formed in the bottom surface of the outer tank, the recess being recessed from the inner surface of the bottom surface,
the pair of electrodes protrude upward from a bottom surface of the recess,
The control unit is
rotating the washing tub at a second detection rotation speed which is lower than the spin-drying rotation speed and higher than the first detection rotation speed, and detecting the water level by the detection unit during the second detection rotation speed;
When the detected water level is lower than a threshold value, the value of the spin-drying rotation speed is reduced.
A washing machine characterized by: The washing machine according to claim 1 or 2,
The control unit determines whether or not the poor drainage state occurs based on the detected water level .
A washing machine characterized by: In the washing machine according to any one of claims 1 to 3,
The control unit determines whether or not the poor drainage state occurs based on the magnitude of the detected fluctuation in the water level.
A washing machine characterized by: an outer tank elastically supported within a housing;
A drainage section for draining water from the outer tank;
A washing tub that is rotatably disposed in the outer tub and that accommodates laundry;
A drive motor for driving the washing tub;
A control unit that controls the drive motor to execute a spin-drying process of rotating the washing tub at a predetermined spin-drying rotation speed;
A detection unit includes a pair of electrodes arranged in a space between a bottom surface of the outer tub and a bottom surface of the washing tub, detects a current flowing between the pair of electrodes that changes according to a water level in the outer tub, and outputs a detection signal indicating a magnitude of the detected current,
The control unit is
While the rotation of the washing tub is being increased to the spin-drying rotation speed, the washing tub is rotated at a first detection rotation speed which is lower than the spin-drying rotation speed, and the detection signal is acquired from the detection unit within a predetermined acquisition period to detect the fluctuation of the water level within the acquisition period;
When it is determined based on the magnitude of the detected fluctuation in the water level that a poor drainage state in which drainage from the outer tub is not smoothly occurring is occurring, the drive motor is controlled so that the start-up of rotation of the washing tub up to the dehydration rotation speed is slower than when the poor drainage state is not occurring.
A washing machine characterized by: an outer tank elastically supported within a housing;
A drainage section for draining water from the outer tank;
A washing tub that is rotatably disposed in the outer tub and that accommodates laundry;
A drive motor for driving the washing tub;
A control unit that controls the drive motor to execute a spin-drying process of rotating the washing tub at a predetermined spin-drying rotation speed;
A detection unit includes a light emitting element and a light receiving element located at a predetermined height from the bottom of the outer tub in a space between the bottom of the outer tub and the bottom of the washing tub, detects the light transmittance between the light emitting element and the light receiving element, and outputs a detection signal according to the detected transmittance.
The control unit is
While the washing tub is being raised up to the spin-drying rotation speed, the washing tub is rotated at a first detection rotation speed lower than the spin-drying rotation speed, and during this time, the detection signal is obtained from the detection unit to detect whether water is present at the predetermined height;
When water is present at the predetermined height, the drive motor is controlled to rotate the washing tub at the first detection rotation speed for a longer time than when water is not present at the predetermined height, thereby slowing down the start-up of rotation of the washing tub to the dehydration rotation speed .
A washing machine characterized by:

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