JP2003071180A - Washing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a washing machine in which dehydration eccentricity can be simply computed and the rotation of a dehydration tub can be controlled. SOLUTION: A revolution speed sensor detecting the revolution speed of a dehydration tub and an acceleration sensor detecting the acceleration Ax (Fig. 5) in the radial direction of the dehydration tub are provided and the dehydration eccentricity of the dehydration tub is computed on the basis of the revolution speed detected by the revolution speed sensor and the acceleration Ax in the radial direction detected by the acceleration sensor, and the dehydration tub is controlled on the basis of the eccentricity computed. Since no complex computation is executed, the eccentricity of a dehydration tub can be simply computed, even using an inexpensive microcomputer (one-chip microcomputer).

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a washing machine that calculates the amount of dewatering eccentricity of a dewatering tub and controls the rotation of the dewatering tub. 2. Description of the Related Art During dehydration of a washing machine, if the laundry in the dehydration tub is uneven, large vibrations are generated when the tub is rotated. When the rotation speed increases, if this vibration is large, it is dangerous. Therefore, a mechanism for detecting the vibration and stopping the rotation of the dewatering tank is usually provided. To detect the deviation of the laundry in the dehydration tub, determine the eccentricity of the tub by measuring the frequency of contact of the tub with a switch installed at a place slightly away from the tub when the tub is rotated The method of doing is general. In addition, there is a method of detecting eccentricity of the tank using sensors such as an acceleration sensor. FIG. 1 shows a state in which an acceleration sensor is attached to an outer dehydration tub (which does not rotate here) for eccentricity detection. As the acceleration sensor, one capable of measuring two axes in the x direction and the y direction was used, and the acceleration sensor substrate was installed so that the radial direction was the x axis and the circumferential direction was the y axis. When you put laundry in the spin tub and rotate it, the vibration of the spin tub is transmitted to the outer tub,
An acceleration sensor detects a change in acceleration due to the vibration. FIG. 2 shows changes in the acceleration Ax in the x-axis direction and the acceleration Ay in the y-axis direction when the load is biased inside the dehydration tub and the dehydration tub is rotated at a constant speed. However, this acceleration sensor outputs the detected acceleration value as an analog signal in each of the x and y directions. The microcomputer reads the data by A / D conversion (10 bits 0 to 1023). The vertical axis in FIG. 2 is [measured acceleration A / D conversion value] −
[A / D conversion value of 0 (G)], that is, of from 0 (G)
Indicates the fset value. FIGS. 3 and 4 show Ax shown in FIG.
The result of Fourier transform of Ay is shown. Ax, A measured
Since y is the acceleration, the amount of eccentricity in each direction x,
In order to obtain y, it is necessary to perform integration as in the following equation. [0003] Therefore, in order to obtain the eccentricities x and y, the microcomputer must perform double numerical integration of Ax and Ay. However, a one-chip microcomputer usually used for controlling a washing machine has a low calculation speed, and it is difficult to sample acceleration measurement values at intervals of several msec and perform numerical integration. An object of the present invention is to provide a washing machine capable of easily calculating the amount of dewatering eccentricity of a dewatering tub and controlling the rotation of the dewatering tub. Means for Solving the Problems and Effects of the Invention The present invention for solving the problems includes a rotation speed sensor for detecting a rotation speed of a dewatering tub, and detecting a radial acceleration of the dehydration tub. An acceleration sensor is provided, and a dehydration eccentric amount of the dehydration tub is calculated based on the rotation speed detected by the rotation speed sensor and a radial acceleration detected by the acceleration sensor, and based on the calculated eccentric amount. And controlling the dehydration of the dehydration tub. [0007] Thereby, since complicated calculations are not performed,
Even if an inexpensive microcomputer (one-chip microcomputer) is used, the amount of eccentricity of the dewatering tank can be easily calculated (estimated), and dehydration control can be performed efficiently. [0008] In Fig. 3 and Fig. 4, the basic frequency 2Hz is the rotation frequency (the number of rotations per second) of the dewatering tank. Focusing on only the fundamental wave components of Ax and Ay, Approximately The locus of the above equation draws an ellipse. This equation is integrated to determine the deviation in each direction. [0011] The amount of eccentricity L is given by: In this case, the phase difference θ = π between Ax and Ay
When fixed to / 2, In this case, the force received in the radial direction x is larger than the force in the circumferential direction y. Thus, (If 0 <K <1>, then: L is a function of time, but the maximum value in the root is 1 when ωt = π / 2, regardless of the K value. Therefore, the estimated maximum value Lmax of the eccentric amount L is given by: ## EQU1 ## According to the above method, the eccentricity can be estimated by determining the amplitude P of Ax and the rotation speed ω of the dewatering tank. The rotation speed of the spin-drying tub can be measured by attaching a spin speed sensor such as a Hall IC to the motor for driving the spin-drying tub. CPU power is not required to perform numerical integration. If it is difficult to calculate P / ω / ω, if a Plimit data table for each rotation speed is prepared in the program, the function of stopping the tank rotation when the amount of eccentricity becomes large can be fulfilled. it can. (Creation of a data table indicating that the motor is stopped when the Ax amplitude P exceeds Plimit at this rotation speed) FIG.
Ax when accelerating to about 180 rpm is shown. Lmax will be obtained based on this figure. [Table 1] Until about 2 seconds in FIG. 5, the amount of eccentricity Lmax is considerably large, corresponding to the resonance rotational speed of the dewatering tank. After this rotational speed, Lmax rapidly decreases.
Thereafter, as the rotation speed increases, the amplitude P of Ax increases, but Lmax does not increase and the motor rotates stably. Then, the microcomputer controls the dehydration of the dehydration tub based on the eccentric amount thus obtained. The present invention is not limited to the embodiment described above, and various changes can be made within the scope of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a conventional washing machine in a state where an acceleration sensor is attached to an outer tub of a dehydration tub. FIG. 2 is a diagram showing a temporal change in a dehydration tub radial acceleration Ax and a dehydration tub circumferential acceleration Ay when an eccentric dehydration tub is rotated. FIG. 3 is a diagram showing a temporal change of a Fourier transform value of a dehydration tub radial acceleration Ax. FIG. 4 is a diagram illustrating a temporal change of a Fourier transform value of a dehydration tub circumferential acceleration Ay. FIG. 5 is a perspective view of a washing machine according to the present invention;
It is a figure which shows the time change of the dehydration tank radial direction acceleration Ax at the time of accelerating from 180 rpm to 180 rpm. [Description of symbols] Ax Dehydration tub radial acceleration Ay Dehydration tub circumferential acceleration

Claims (1)

Claims: 1. A rotation speed sensor for detecting a rotation speed of a dehydration tub, and an acceleration sensor for detecting acceleration in a radial direction of the dehydration tub, wherein the rotation detected by the rotation speed sensor is provided. Washing, wherein a dehydration eccentric amount of the dehydration tub is calculated based on a speed and a radial acceleration detected by the acceleration sensor, and dehydration control of the dehydration tub is performed based on the calculated eccentric amount. Machine.