Washing machine

Abstract

A washing machine includes a washing tub, a water tub, a drive unit, a feed-water unit, a drain unit, a water softening unit, a pH increasing unit, a pH decreasing unit, and a control unit. The water softening unit is disposed between the feed-water unit and the water tub, and is filled with a weak acid cation exchange material having weak acidic cation exchange groups with a pH from 7.5 to 14 at point of zero charge. The pH increasing unit increases the pH of washing water, and the pH decreasing unit decreases the pH of the washing water. The control unit performs the following operations: controlling the pH increasing unit to increase the pH of the washing water while the washing water is being fed; introducing the washing water with the increased pH to the water softening unit to decrease the hardness of the washing water; introducing the washing water with the decreased hardness to the washing tub; controlling, after the washing water is fed, the pH decreasing unit to decrease the pH of the washing water to a value of 5.5 to 7.0; and introducing the washing water with the decreased pH to the water softening unit.

Description

TECHNICAL FIELD[0001]The present invention relates to a washing machine equipped with a water softening device.BACKGROUND ART[0002]Washing machines generally use tap water, groundwater, or well water, and are greatly affected by the qualities of water used. In particular, hard water components such as calcium and magnesium deteriorate the detergency of surfactants, thereby adversely affecting the washing performance. Hard water does not dissolve detergent as readily as soft water, possibly causing any unit of a washing machine to be coated with detergent residue and turning moldy. Hard water also contains trace amounts of polyvalent metal ions, e.g., of iron, manganese, and aluminum, which can interact with detergent, thereby deteriorating the detergency of surfactants.[0003]To address this problem, commercially available detergents contain a water softening agent such as zeolite, which absorbs hard water components. Zeolite easily absorbs polyvalent ions, thereby providing some eff...

AI Technical Summary

Benefits of technology

[0018]A weak acid cation exchange material with a point of zero charge of 7.5 or more has high selectivity for H+ ions (acid), and is less likely to absorb cations other than H+ ions. As a result, the weak acid cation exchange material is readily regenerated to the H+ form. A general weak acid cation exchange resin containing carboxyl groups (COOH groups) as cation exchange groups has a point of zero charge of 5 to 6. The weak acid cation exchange material used in the washing machine of the present invention can be regenerated to the H form with water at a higher pH (about pH 7) than those ion exchange resins. A weak acid with a pH of 7 or so can be generated by various means without using a chemical agent or an electrolytic device. Thus, the washing machine is equipped with the water softening device that does not require using a special regenerant or performing electrolysis.

Problems solved by technology

In particular, hard water components such as calcium and magnesium deteriorate the detergency of surfactants, thereby adversely affecting the washing performance.

Hard water does not dissolve detergent as readily as soft water, possibly causing any unit of a washing machine to be coated with detergent residue and turning moldy.

Hard water also contains trace amounts of polyvalent metal ions, e.g., of iron, manganese, and aluminum, which can interact with detergent, thereby deteriorating the detergency of surfactants.

Zeolite, however, is used in a detergent dissolved in washing water, causing some of the hard water components and metal ions to be again dissolved in the washing water.

As a result, the above-described problem remains unsolved.

There is a concern, however, that using a large amount of detergent is not eco-friendly.

Moreover, there is no radical solution to the detergent residue in the washing machine.

This requires the user to take the trouble to frequently supply a regenerant such as salt to the cation exchange resin, against their desire to reduce the usage of detergent.

In addition, highly concentrated salt water may touch the skin of the user for any reason, and cause the user to get shocked.

When metal is used inside the washing machine or in its peripheral equipment such as the drain pipe, they may be corroded by highly concentrated salt water.

It is, however, not practical to mount an electrolytic device in domestic washing machines due to installation space limitations.

Since it cannot be expected that users periodically replace components of domestic washing machines, electrolysis may shorten the useful life of the resin and the water softening device.

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