EP2727510A2

EP2727510A2 - Dishwasher

Info

Publication number: EP2727510A2
Application number: EP13189800.9A
Authority: EP
Inventors: Fumihiko Sasahara; Masayoshi Uesaki
Original assignee: Panasonic Corp
Current assignee: Panasonic Corp
Priority date: 2012-11-06
Filing date: 2013-10-23
Publication date: 2014-05-07
Also published as: CN103799938A; TW201438653A; JP2014090946A

Abstract

The present invention includes a washing tub, a washing unit, a washing pump, a heating unit, a temperature detection unit, and a control unit. In the washing, the control unit performs: spraying the washing water by the washing unit while the washing water is heated by the heating unit, at a start time; when the temperature of the washing water reaches a first predetermined temperature, stopping the heating of the washing water for only a predetermined time and spraying the washing water. Thereafter, the control unit controls to perform spraying the washing water by the washing unit while the washing water is heated by the heating unit again, until the temperature of the washing water reaches a second predetermined temperature. This can achieve a dishwasher capable of sufficiently removing dirt dried and stuck on eating utensils and dirt stuck on cooking utensils during cooking.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a dishwasher for washing items to be washed, such as eating utensils, by spraying washing water thereto, and more specifically to a technique for washing dirt stuck on eating utensils, cooking utensils, and the like.

2. Background Art

Conventionally, as a general dishwasher, a dishwasher for washing eating utensils by spraying washing water from a washing nozzle toward the eating utensils while the washing water is heated has been proposed.
Hereinafter, a configuration of a general dishwasher is described using Fig. 3. Fig. 3 is a longitudinal sectional view of a conventional dishwasher.
As shown in Fig. 3, a conventional dishwasher includes at least washing tub 2, water supply valve 3, washing pump 5, washing nozzle 7, heater 8, dish basket 10, drainage pump 11, and the like. A front surface of a dishwasher main body is provided with door 1 which is opened and closed and through which eating utensils 9 are placed. Washing tub 2 is provided inside the dishwasher, and is configured to be supplied with water or hot water by water supply valve 3. Furthermore, a bottom part of washing tub 2 is provided with drainage port 4. Washing pump 5 is mounted such that it communicates with drainage port 4, and is driven by a motor.
Furthermore, drainage port 4 is equipped with garbage filter 6 for collecting garbage that has been washed off from eating utensils 9. Note here that the washing water refers to liquid to be used for washing and rinsing items to be washed, such as eating utensils 9 accommodated in washing tub 2.
Then, the washing water is sprayed from washing nozzle 7 and allowed to circulate inside washing tub 2 by washing pump 5.
Specifically, firstly, the washing water supplied into and stored in washing tub 2 is sucked into washing pump 5 through garbage filter 6. The sucked washing water is supplied to washing nozzle 7 provided on the inner bottom part of washing tub 2 by washing pump 5. The supplied washing water is sprayed from washing nozzle 7 toward eating utensils 9. After the washing water sprayed from washing nozzle 7 is used for washing eating utensils 9, it is circulated again in a passage returning again to drainage port 4. At this time, garbage dropped off from eating utensils 9 flows into garbage filter 6 together with the washing water. Then, garbage having a size that cannot pass through garbage filter 6 is collected by garbage filter 6.
Furthermore, heater 8 is disposed between washing nozzle 7 and the bottom part of washing tub 2, and heats the washing water. Specifically, heater 8 heats the washing water to such a high temperature as about 60°C at the time of washing.
Furthermore, dish basket 10 is configured such that eating utensils 9 are arranged in good order, and is disposed in the upper side of washing nozzle 7. Thus, the washing water can be efficiently sprayed to eating utensils 9 arranged in dish basket 10, so that washing of eating utensils 9 can be carried out efficiently.
Furthermore, drainage pump 11 sucks the washing water from drainage port 4 of washing tub 2, and discharges the washing water to the outside of the dishwasher via drainage hose 12.
A dishwasher having the above-mentioned configuration is disclosed in, for example, Japanese Patent Unexamined Publication No. 2000-316784 (hereinafter, referred to as "Patent Literature 1").
Hereinafter, an operation sequence of a general dishwasher is described briefly.
Firstly, a washing step of removing dirt attached to eating utensils 9 is carried out. Thereafter, a rinsing step of rinsing a detergent component or the like attached to eating utensils 9 with clean water is carried out two to three times.
Next, in order to finish washing of eating utensils 9 hygienically, a heating/rinsing step of rinsing with high-temperature clean water of 70-80°C is carried out.
Next, after the heating/rinsing step is carried out, washing water is discharged, and a drying step of drying eating utensils 9 is carried out. At this time, outside air is taken into washing tub 2 by air-blowing fan 13 provided in the lower part of washing tub 2. Then, after the taken outside air is heated to be warmed by heater 8, and allowed to flow among eating utensils 9. Thus, water droplets attached to eating utensils 9 are dried so as to dry eating utensils 9.
However, a conventional dishwasher is used, for example, for washing dirt that has been dried and stuck on eating utensils when several hours have passed after eating, and dirt stuck on cooking utensils during cooking, depending upon user's using states. In the cases where such eating utensils and cooking utensils are washed, even if they are washed by a dishwasher, dirt is not removed sufficiently.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned problems, a dishwasher of the present invention includes a washing tub for accommodating an item to be washed; a washing unit provided in the washing tub for spraying washing water to the item to be washed; a washing pump for forcedly feeding the washing water in the washing tub to the washing unit; a heating unit which is provided in the washing tub and heats the washing water; a temperature detection unit which is provided in a lower part of the washing tub and detects a temperature of the washing water; and a control unit for controlling a series of washing operations including at least washing, rinsing, and heating/rinsing. In the washing, at a start time, the control unit carries out spraying the washing water by the washing unit while the washing water is heated by the heating unit. When the temperature of the washing water reaches a first predetermined temperature, the control unit carries out stopping the heating of the washing water for only a predetermined time and spraying the washing water. Then, the control unit controls to carry out spraying the washing water by the washing unit while the washing water is heated by the heating unit, until the temperature of the washing water reaches a second predetermined temperature.
Thus, it is possible to sufficiently remove stuck dirt such as dirt dried and stuck on eating utensils after several hours have passed after eating, and dirt stuck on cooking utensils during cooking. As a result, a dishwasher having excellent washing performance can be achieved.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is a longitudinal sectional view of a dishwasher in accordance with an exemplary embodiment of the present invention.
Fig. 2 shows control sequences of a washing pump and a heater as well as temperature change of washing water in each step of the dishwasher in accordance with the exemplary embodiment.
Fig. 3 is a longitudinal sectional view of a conventional dishwasher.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the exemplary embodiment of the present invention is described with reference to drawings. Note here that the present invention is not construed to be limited by the exemplary embodiment.

(EXEMPLARY EMBODIMENT)

Hereinafter, a configuration of a dishwasher in the exemplary embodiment of the present invention is described with reference to Fig. 1.
Fig. 1 is a longitudinal sectional view of a dishwasher in accordance with an exemplary embodiment of the present invention. Fig. 2 shows control sequences of a washing pump and a heater as well as temperature change of washing water in each step of the dishwasher in accordance with the exemplary embodiment. Note here that the same reference is given to the same configuration as those of conventional dishwasher described with reference to Fig. 3 and the description thereof is omitted herein.
As shown in Fig. 1, the dishwasher of this exemplary embodiment include at least washing tub 2, washing pump 5, washing nozzle 7, heater 8, dish basket 10, drainage pump 11, thermistor 14, control unit 15, and the like. Washing tub 2 accommodates items to be washed, such as eating utensils 9 disposed in dish basket 10. Washing nozzle 7 is provided in washing tub 2 and functions as a washing unit that sprays washing water to the items to be washed such as eating utensils 9. Washing pump 5 forcedly feeds the washing water in washing tub 2 to washing nozzle 7. Heater 8 is provided in washing tub 2 and functions as a heater for heating the washing water. Thermistor 14 is provided outside in the lower part of washing tub 2, and functions as a temperature detection unit for detecting a temperature of the washing water.
Furthermore, control unit 15 controls a washing operation of the dishwasher based on detection information by, for example, thermistor 14 and input information input by a user from an input unit (not shown) according to program storing the control sequence. Specifically, control unit 15 controls washing pump 5, washing nozzle 7, heater 8, air-blowing fan 13, and the like. Thus, control unit 15 controls a series of washing operations including washing, rinsing, heating/rinsing, and drying, and thereby executes the washing operation of eating utensils 9.
Next, operations and effects in a washing step of the dishwasher, which is a point of this exemplary embodiment, are described using Fig. 2 with reference to Fig. 1.
Fig. 2 shows graphs showing control sequences of a washing pump and a heater as well as temperature change of washing water in each step of the dishwasher in accordance with the exemplary embodiment.
Firstly, as shown in Fig. 2, control unit 15 turns on heater 8 at the time when the washing step is started, and turns on washing pump 5. Then, a step of spraying the washing water forcedly fed by washing pump 5 from washing nozzle 7 is carried out while the washing water is heated by heater 8.
Next, when a temperature of the heated washing water reaches a first predetermined temperature, a step of stopping heating of the washing water is carried out while the washing water is sprayed for only a predetermined time.
Thereafter, heater 8 is turned on again, a step of spraying the washing water by washing nozzle 7 is executed while the washing water is heated.
Then, the above-mentioned step is carried out until the temperature of the washing water heated by heater 8 reaches a second predetermined temperature.
Next, when the temperature of the washing water reaches the second predetermined temperature, control unit 15 turns off heater 8 and washing pump 5.
As mentioned above, the washing step of the dishwasher of this exemplary embodiment is executed.
Note here that in the dishwasher of this exemplary embodiment, at the time when the washing step is started, when the temperature of the washing water is higher than the first predetermined temperature, heating of the washing water by heater 8 is not carried out from the start time. Then, control unit 15 carries out operation control in which the temperature of the washing water at the start time is made to be the first predetermined temperature.
Furthermore, in the dishwasher of this exemplary embodiment, when the temperature of the washing water decreases by only a predetermined temperature range (for example, 1.5°C) for the above-mentioned predetermined time, control unit 15 repeats ON/OFF operations of heater 8, and controls the temperature of the washing water. Thus, operation control is carried out such that the temperature of the washing water is maintained at the first predetermined temperature.
Hereinafter, operations and effects of the dishwasher of this exemplary embodiment are specifically described using Fig. 2 and with reference to Fig. 1.
Note here that a washing operation of the dishwasher of this exemplary embodiment includes at least the above-mentioned washing step, a rinsing step, a heating/rinsing step, and the like.
Firstly, when an operation of the dishwasher is started, control unit 15 opens water supply valve 3 to start supplying washing tub 2 with water.
Next, after water supplying is completed, the washing step is executed as shown in Fig. 2. Then, at the time when the washing step is started, washing pump 5 and heater 8 are electrified (turned on). Thus, while the washing water is heated by heater 8, a step of spraying washing water from washing nozzle 7 is carried out (hereinafter, the step is referred to as "step 1").
At this time, when it is detected by a temperature detection unit such as thermistor 14 that the temperature of the washing water reaches the first predetermined temperature (for example, about 40°C), heating of the washing water by heater 8 is stopped for only a predetermined time (for example, 5 minutes or more). At this time, a step of continuing to spray the washing water from washing nozzle 7 is carried out (hereinafter, the step is referred to as "step 2") while electrification of washing pump 5 is maintained.
It is desirable that the first predetermined temperature is made to be, for example, 40°C, which is, for example, a temperature at which an enzyme of detergent exclusively used for a dishwasher is activated and works most efficiently. The reason for this is because an enzyme generally includes protein as a main component, so that it is denatured and its activity is deteriorated at high temperatures. Thus, the first predetermined temperature is made to be about 40°C at which high activity of the enzyme and denaturation thereof due to high temperature are balanced. Thus, a detergent component penetrates into dirt of, for example, eating utensils, cooking utensils, or the like, reliability, such that the enzyme can be allowed to act on the dirt efficiently. Also with respect to dirt which is hardened and hardly removed efficiently when rapid heating is applied, when the temperature of about 40°C is maintained, a detergent component can be allowed to act on the dirt. When the first predetermined temperature is made to be, for example, about 40°C, the temperature is effective in washing of, for example, protein dirt by egg and starch dirt by rice. Furthermore, the predetermined time during which the first predetermined temperature is maintained is desirably about 5 minutes or more. Thus, an enzyme of detergent can be allowed to work effectively.
Next, as shown in Fig. 2, after the temperature of the washing water is maintained at the first predetermined temperature (for example, about 40°C) for a predetermined time (for example, 5 minutes or more), heater 8 is electrified (turned ON) again. Thus, while the washing water is heated, a step of spraying the washing water by washing nozzle 7 (hereinafter, the step is referred to as "step 3") is carried out until the temperature of the washing water reaches the second predetermined temperature (for example, 70 to 80°C). The second predetermined temperature is set to a temperature of 70 to 80°C, which are a higher temperature than the melting point of oil, that is, 40 to 50°C, in order to wash oil dirt or the like. Thus, for example, oil dirt can be dissolved in the washing water. As a result, dirt such as oil dirt can be easily removed.
Note here that in the washing of the above-mentioned step 3, the washing is ended at a time when the temperature of the washing water reaches the second predetermined temperature, but washing is not particularly limited to this example. For example, the washing of step 3 may be controlled to be ended by time control that is sufficient to reach the second predetermined temperature. That is to say, after the temperature of the washing water reaches the second predetermined temperature, a heating/rinsing step may be continued for a predetermined time. In this case, since heater 8 is turned off, the temperature of the washing water is gradually lowered from the second predetermined temperature. However, since the heating/rinsing step is carried out around the second predetermined temperature, high washing performance can be maintained.
Furthermore, this exemplary embodiment describes an example in which the first predetermined temperature is about 40°C, but the first predetermined temperature is not necessarily limited to this. For example, when a washing course exclusively for tough oily dirt is selected in a dishwasher, the first predetermined temperature may be set at 70 to 80°C. In this case, the temperature of the washing water is maintained to be a high temperature from the initial time of the washing step. Therefore, the tough oil dirt can be removed efficiently.
On the other hand, when the dishwasher is connected to an external hot water storage tank and a water heater, hot water of about 60°C is supplied to the inside of washing tub 2 immediately after water is supplied. At this time, when dirt such as dirt by egg is attached to eating utensils or the like, a surface of the dirt is rapidly hardened due to heat. Thus, a detergent component does not penetrate into the dirt. As a result, washing performance may be deteriorated.
Then, in the dishwasher of this exemplary embodiment, when the temperature of the washing water at the time when the washing step is started is higher than the first predetermined temperature, control unit 15 may control the temperature to be the first predetermined temperature by stopping heating of the washing water by heater 8 from the time when the washing step is started. Thus, deterioration of the washing performance can be prevented.
Furthermore, in this exemplary embodiment, when a large number of eating utensils and cooking utensils are set in the dishwasher, heat is deprived by the eating utensils and the cooking utensils, so that the temperature of the washing water is lowered. This makes it difficult to maintain the first predetermined temperature in step 2. As a result, action of the enzyme of the detergent is not effective, which may deteriorate washing performance.
Thus, in the dishwasher of this exemplary embodiment, when the temperature of the washing water decreases by a predetermined temperature range (for example, 1.5°C) for a predetermined time, control unit 15 repeats to turn heater 8 ON and OFF, and operation control of the temperature of the washing water may be maintained at the first predetermined temperature. Thus, even when a large number of eating utensils and cooking utensils are set, the first predetermined temperature can be maintained. As a result, it is possible to prevent deterioration of the activity of the detergent, and deterioration of washing performance that dirt is not easily removed.
As mentioned above, the washing step of the dishwasher of this exemplary embodiment is executed.
Next, as shown in Fig. 2, after the above-mentioned washing step is carried out, control unit 15 drains dirty washing water. Then, eating utensils 9 are rinsed with clean washing water that is newly supplied. The rinsing step is executed, for example, about two to three times.
Next, the heating/rinsing step of rising eating utensils 9 with high-temperature washing water (70 to 80°C) heated by heater 8 is carried out.
Next, the dishwasher of this exemplary embodiment may carry out a drying step (not shown), if necessary. Specifically, in the drying step, outside air is taken into washing tub 2 by air-blowing fan 13 shown in Fig. 1. Then, eating utensils 9 are dried by blowing hot air from the outside air that has been heated by heater 8. Thus, a drying step is executed.
Next, when the drying step is completed, the washing operation of the dishwasher is ended.
Note here that operations and effects of the steps such as a rinsing step, a heating/rinsing step, and a drying step are the same as those in a conventional general dishwasher, and therefore detail description is omitted.
As mentioned above, the washing operation of the dishwasher of this exemplary embodiment is executed.
Note here that the first predetermined temperature, the second predetermined temperature, and the predetermined time, which are described in this exemplary embodiment are not limited to the description of the above-mentioned exemplary embodiment. It is needless to say that setting of the first predetermined temperature, the second predetermined temperature, and the predetermined time may be changed depending upon various types of detergent, dirt, and the like. Thus, efficient and effective washing step or washing course can be achieved. For example, the second predetermined temperature may be set at about 40°C at which power of the enzyme of detergent can be effectively used. Thus, washing power by the enzyme of the detergent can be improved. Furthermore, since the washing water is not heated to a high temperature, energy-saving of the washing step or the washing course can be achieved.
That is to say, the dishwasher of this exemplary embodiment can effectively remove dirt dried and stuck on eating utensils after several hours have passed after eating, dirt stuck on cooking utensils during cooking by activating the enzyme of the detergent. As a result, it is possible to achieve the dishwasher that can effectively act on dirt that has not been able to be removed by a conventional dishwasher and can improve washing performance.
As described above, the dishwasher of the present invention includes a washing tub for accommodating an item to be washed; a washing unit provided in the washing tub for spraying washing water to the item to be washed; a washing pump for forcedly feeding the washing water in the washing tub to the washing unit; a heating unit provided in the washing tub and for heating the washing water; a temperature detection unit provided in the lower part of the washing tub and for detecting a temperature of the washing water; and a control unit for controlling a series of washing operations including at least a washing step, a rinsing step, and a heating/rinsing step. The control unit carries out a step of spraying the washing water by the washing unit while the washing water is heated by the heating unit at the start time of the washing step, and a step of stopping heating of the washing water for a predetermined time and spraying the washing water when the temperature of the washing water reaches the first predetermined temperature. Thereafter, the control unit may control such that the washing water is heated by a heating unit while the washing unit carries out the spraying step until the temperature of the washing water reaches the second predetermined temperature.
Thus, it is possible to sufficiently remove stuck dirt such as dirt dried and stuck on eating utensils after several hours have passed after eating, and dirt stuck on cooking utensils during cooking. As a result, a dishwasher having excellent washing performance can be achieved.
Furthermore, according to the dishwasher of the present invention, the first predetermined temperature may be set at a temperature at which an enzyme of detergent is activated.
Thus, a detergent component is allowed to permeate into dirt of eating utensils and cooking utensils reliably. As a result, by allowing the enzyme to act on dirt effectively, the dirt can be removed effectively. Furthermore, by maintaining the temperature at which the enzyme is activated with respect to dirt such as dirt by egg, which is hardened and is not easily removed, when rapid heat is applied.
Furthermore, according to the dishwasher of the present invention, the control unit may stop heating of washing water by a heating unit when the temperature of the washing water is higher than the first predetermined temperature at the time when the washing step is started, and carry out operation control with the washing water having the first predetermined temperature at the start time.
Thus, at the start time of operation, when hot water having a higher temperature than the first predetermined temperature is supplied as the washing water, it is possible to prevent deterioration of the washing performance with respect to dirt that is hardened and is not easily removed when rapid heat is applied.
Furthermore, according to the dishwasher of the present invention, when the temperature of the washing water is reduced from the first predetermined temperature to equal to or lower than a predetermined temperature range during a predetermined time, the control unit may carry out operation control such that the temperature of the washing water is maintained to the first predetermined temperature by repeating turn-on and turn-off of the heating unit.
Thus, when a large number of eating utensils and cooking utensils are set in a dishwasher, the temperature of the washing water is prevented from lowering, and the first predetermined temperature can be maintained. As a result, deterioration of the activation of the detergent can be suppressed, and deterioration of the washing performance can be prevented.

Claims

A dishwasher comprising:
a washing tub for accommodating an item to be washed;

a washing unit provided in the washing tub for spraying washing water to the item to be washed;

a washing pump for forcedly feeding the washing water in the washing tub to the washing unit;

a heating unit which is provided in the washing tub and heats the washing water;

a temperature detection unit which is provided in a lower part of the washing tub and detects a temperature of the washing water; and

a control unit for controlling a series of washing operations including at least washing, rinsing, and heating/rinsing,

wherein in the washing, the control unit controls to carry out:
spraying the washing water by the washing unit while the washing water is heated by the heating unit, at a start time;

stopping the heating of the washing water for only a predetermined time and spraying the washing water when the temperature of the washing water reaches a first predetermined temperature; and

then spraying the washing water by the washing unit while the washing water is heated by the heating unit until the temperature of the washing water reaches a second predetermined temperature.
The dishwasher of claim 1, wherein the first predetermined temperature is set at a temperature at which an enzyme of detergent is activated.
The dishwasher of claim 1, wherein the control unit stops heating of the washing water by the heating unit when the temperature of the washing water is higher than the first predetermined temperature at the start time of the washing, and carries out operation control with the washing water having the first predetermined temperature at the start time.
The dishwasher of claim 1, wherein when the temperature of the washing water is reduced from the first predetermined temperature to equal to or lower than a predetermined temperature range in the predetermined time, the control unit carries out operation control to maintain the temperature of the washing water at the first predetermined temperature by repeating turn-on and turn-off of the heating unit.