JP3212098B2 - Dishwasher - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dishwasher, and more particularly to a heater unit control suitable for maintaining stable performance.

[0002]

2. Description of the Related Art Conventionally, heating control of a heater unit of a dishwasher has been performed for the purpose of producing hot water at the time of washing. The temperature does not reach such a level as to affect the temperature. However, in the drying operation, the heating load is small because of the heating of the tank and the creation of the hot air, and the temperature rise which affects the components in the continuous operation is increased. The energization time is the reference voltage,
Since the temperature is fixed so as to correspond to the reference ambient temperature, the following problems have occurred.

First, as for the power supply voltage, as is well known, the input of the heater is proportional to the square of the fluctuation of the power supply voltage. Therefore, the fluctuation range of the heating value, that is, the temperature rise width around the heater unit. Is also very large.

[0004] Second, the ambient temperature at which the equipment is used. According to experiments, the temperature around the heater unit fluctuates almost in proportion to the ambient temperature.

[0005] For this reason, the intermittent energization time during drying is set with reference to a substantially central value. Therefore, for example, when operating at a voltage of 110% and an ambient temperature of 30 ° C.,
The overheat prevention device operates frequently, causing poor drying, or when the device is operated at 110% voltage, 0 ° C ambient temperature, and with some equipment failure, and is operated with continuous airflow without wind, the overheat prevention device operates. However, there was a risk that the equipment would be damaged by overheating.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to maintain stable performance under possible use environment conditions, and to quickly detect the temperature of a heater unit in the event of any equipment failure, An object of the present invention is to provide a dishwasher that operates safely to prevent overheating, eliminates the above-mentioned problems, and is excellent in reliability and safety.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to reduce the intermittent energization time to the heater unit in accordance with the power supply voltage and the ambient temperature so as to keep the calorific value constant under any use environment conditions. This can be achieved by controlling the automatic setting.

[0008]

[Operation] That is, the voltage is detected by the power supply voltage detection circuit, the outside air temperature is detected by the temperature sensor, and the intermittent energization time for controlling to a constant temperature, which is determined in advance by theory and experiment, is stored in the microcomputer table of the controller. In order to control the device by selecting and setting the intermittent energization time from the table according to the detected condition, the temperature is controlled to be constant.

[0009]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing the overall internal structure of a dishwasher according to the present invention, FIG. 2 is a plan view of a heater unit, FIG. 3 is a longitudinal sectional view of a heater unit, and FIG.
Is an enlarged vertical cross-sectional view of a device for preventing excessive temperature rise, and FIG. 5 is a block diagram showing a controller circuit.

In FIG. 1, reference numeral 1 denotes a main body of a dishwasher, which has a hinge 3 on its front surface and a door 3 which can be opened and closed forward as indicated by an arrow. Inside the door 3, a controller 4 for controlling washing, drying cycle operation such as water supply, heating, hot water circulation, drainage, air blowing, etc. of the dishwasher is installed. A display 5 for performing various displays instructed by 4 and an operation unit (not shown) are provided. On the inner surface of the door 3, a door inner wall 6 made of stainless steel is provided with a washing tank / drying tank (hereinafter referred to as a washing tank) 7 also made of stainless steel and a packing when the door 3 is closed. 8, the airtightness with the outside is maintained. An upper rail 9 and a lower rail 10 are formed in the washing tank 7 so that the upper basket 11 and the lower basket 12 can be easily moved to the front of the main body 1. The lower surface of the cleaning tank 7 has a plurality of small holes 13a in order to obtain a rotational force by receiving water pressure from a circulation pump (not shown),
A lower nozzle 16 having a spout 15 for guiding water to the upper nozzle 14 is rotatably mounted substantially at the center. Water from the spout 15 passes through a water guide pipe 17 fixed to a substantially central portion of the lower basket 12, and is spouted from a small hole 13b of the upper nozzle 14, and the upper nozzle rotates by the reaction. A heater unit 19 is fixed to a spherical portion 18 formed in a spherical shape on the lower surface of the cleaning tank 7. At the time of fixing, in order to efficiently transfer heat from the heater unit 19, a filler obtained by mixing aluminum powder with silicone resin, which is a heat-resistant member, is applied between the spherical portion 18 and the heater unit 19. You. In addition, a heater unit cover 20 is provided so that the heater unit 19 can be used as a ventilation path for drying, and
1, hot air is sent into the cleaning tank 7 from an air supply port 24 provided on the rear surface of the cleaning tank 7 through the air inlet 22, the duct (1) 23a, the heater unit cover 20, and the duct (2) 23b. ing. The outside is connected via an exhaust port (1) 25a and an exhaust port (2) 25b provided on the upper surface of the cleaning tank 7. Further, a temperature sensor 40 is provided at a lower portion of the main body 1 to detect an outside air temperature.

Referring to FIGS. 2, 3 and 4, the structure of the over-temperature prevention device mounted on the heater unit 19 will be described. The over-temperature rise prevention device comprises a fusing type thermal fuse 26 and an automatic reset type thermostat 27. In FIG. 4, a ring-shaped sheathed heater 28 is located substantially at the outer periphery of the heater unit 19, and is fixed by caulking to a heater base 29 made of an aluminum material so as to cover the surface of the sheathed heater 28. The temperature fuse 26 is located on the inner periphery of the sheath heater 28 and is directly attached to the heater unit 19 at the fuse mounting portion 31 of the fin 30 via an insulating tube. Further, the fin 30 is in close contact with a part of the sheath heater embedded portion 28a on the outer peripheral portion, and the heater unit 19 and the heater unit cover 20
It is located in the space formed between them. Fin 30
The thermostat 27 is directly fixed to the fin 30 with a screw at the front end flat portion. The operating temperature of the overheat prevention device will be described for the later description. Thermal fuse 2
6, the operating temperature of the thermostat 27 is set to approximately 150 ° C. The fins 30 are integrally formed and sandwich the thermal fuse 26 in the heater unit 19 and are fixed with screws. Further, in order to minimize the loss of heat transfer from the heater unit 19, the material of the fins 30 is a copper material. The fins 30 need to be galvanized in order to prevent electrolytic corrosion occurring at the junction between dissimilar metals. Further, a heat transfer paste made of a silicone material is interposed between the surface of the heater unit 19, the sheath heater embedding portion 28a, and the joint surface between the thermostat 27 and the fin 30, so as to eliminate the air layer as much as possible.

The control circuit of the controller will be described with reference to FIG. The controller includes a microcomputer 33, an oscillation circuit 34, a display circuit 35, a sensor circuit 36, and an operation circuit 3.
7, a power supply voltage detection circuit 38 and a drive circuit 39. The power supply voltage detection circuit 38 has a circuit constant set so that a voltage fluctuation of about 1.3% can be detected. Further, the microcomputer 33 has a table of intermittent energization time periods set in advance in consideration of the energization rate so as to keep the temperature of the heater unit 19 at the time of drying substantially constant in response to changes in voltage and temperature.

The electric control method of the heater unit 19 is as follows. In the case of heating with hot water at the time of cleaning, since the water temperature is raised to about 70 ° C. as early as possible, the heating load is large and the heater input is set to about 1 KW. And continuous heating. However, at the time of the drying operation, the blowing air volume is about 0.
Since the heating load is 5 m ³ / min and the heating load is small, it is necessary to perform an intermittent operation and control the temperature of the heater unit 19.
At the start of operation, for the purpose of improving the temperature rise characteristics, for example, initially, 20 seconds ON-45 seconds OFF are performed for 5 cycles, and then 9 seconds ON-45 seconds OFF are repeatedly performed until a fixed time. Controlling.

The operation of the dishwasher in the above configuration and control will be described with reference to a standard cycle operation. Tableware is placed in the upper basket 11 and the lower basket 12, detergent is introduced into a detergent inlet (not shown), the door 3 is closed, and operation is started by operating buttons. When the water is supplied to the specified water level, the heater unit 19 is energized, and at the same time, the cleaning pump motor (not shown) is operated. The pressurized water is sprayed from the small holes 13a of the lower nozzle 16 and the upper nozzle 14 at the same time,
It starts rotating under the reaction force of injection. The number of revolutions is about 20 revolutions per minute, and the washing water evenly hits the dishes in the washing tank 7 and the water temperature gradually rises.
And the action of detergent removes stains on dishes. In this state, the sheathed heater embedded portion 28a for heating to a specified water temperature
Is about 130 ° C under the conditions of 40 ° C outside temperature, operating voltage and 110% of rated value, assuming the worst conditions of normal use environment.
The temperature of the thermal fuse 26 and the temperature of the thermostat 27 are about 100 ° C., and unless an abnormality occurs, the OFF operation of the overheat prevention device does not occur. About 15 minutes after the start of operation, washing is completed and drained. Then, water is supplied again, and the rinsing operation is performed by the same control. After the rinsing, the drying operation starts after the drain operation.

The control of the heater unit 19 during the drying operation is as described above. By the blower 21, the inlet 2
When the air sucked from 3 passes through the space between the heater unit 19 and the heater unit cover 20, heat exchange with the heater unit 19 turns to 50-70 ° C. hot air and is introduced into the cleaning tank 7. The drying operation is performed while the evaporation of the water in the cleaning tank 7 is promoted by the warm air and the air is exhausted from the exhaust port (2) 25b.

When the operating condition of the dishwasher is, for example, operating at a rated voltage and normal temperature, the temperature of the sheathed heater embedded portion 28a is about 190 ° C., the temperature fuse 26 is about 150 ° C., and the thermostat The temperature of 27 also receives the heat of the sheathed heater embedded portion 28a via the fins 30, but is kept at 120 ° C. due to the cooling effect because it is effectively disposed in the ventilation passage. Also, the temperature rise around the heater unit 19 does not reach such a temperature as to damage each component. Further, for example, when the use environment conditions are 110% of the rated voltage and the outside air temperature is 40 ° C., the controller 4 detects the power supply voltage of 110% and the temperature of 40 ° C. At the start, control is performed so that ON for 15 seconds and OFF for 45 seconds are repeated for 5 cycles, and then ON for 7 seconds and OFF for 45 seconds are continued until completion. Therefore, the temperature around the heater unit 19 is almost the same as the rated condition.

As described above, in the normal operation state, even in a normally assumed bad condition, in the cycle operation, the overheat prevention device can be operated normally without operating, and the drying performance is at the same level. Can be maintained and stable performance can be provided. Table 1 shows an example of the intermittent energization time period corresponding to the voltage. As is clear from the example, the intermittent energization time is set so that the energization rate is low when the voltage is high and the energization rate is high when the voltage is low.

[0019]

[Table 1]

Next, any abnormality, for example, a clogged state of the filter 32 installed in the intake port 23 during the drying operation, stagnant circulating water due to foaming of the detergent during washing,
In such a case, the thermostat 27 of the overheating prevention device, if possible, is operated without damaging the equipment and before smoke or ignition occurs. It is necessary to cut off the power supply to the heater unit 19. Among these, FIG. 6 is a diagram comparing the temperature characteristics under the most severe conditions during continuous energization without wind and the operation of the thermostat 27 with the conventional system.
The horizontal axis indicates time, and the vertical axis indicates temperature. It can be seen that the temperature rise of the thermostat 27 is quick and the operation time is extremely short. The temperature of the sheath heater embedded portion 28a is also up to 260
° C, so that the occurrence of the above-mentioned problem can be prevented.

[0021]

As described above, according to the present invention, the cycle operation of the dishwasher can be smoothly completed under the conceivable use environment conditions, which is the original purpose, and stable performance can be obtained. For any malfunction of the equipment, the temperature of the heater unit is quickly detected, and the overheating prevention device can be operated safely without damaging the equipment, making dishwashing excellent in reliability and safety. Machine can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing the overall internal structure of a dishwasher.

FIG. 2 is a plan view of a heater unit.

FIG. 3 is a vertical sectional view of a heater unit.

FIG. 4 is an enlarged vertical cross-sectional view of a device for preventing excessive temperature rise.

FIG. 5 is a circuit block diagram of a controller.

FIG. 6 is a temperature characteristic diagram of the overheat prevention device.

[Explanation of symbols]

7 cleaning tank, 19 heater unit, 21 blower fan, 26 temperature fuse, 27 thermostat, 28
... sheath heater, 30 ... fins.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akihiro Takeuchi 1-1-1, Higashitaga-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Taga Engineering Co., Ltd. (72) Inventor Masaharu Kawai 1-1-1, Higashitaga-cho, Hitachi City, Ibaraki Prefecture No. 1 Hitachi, Ltd. Taga Plant (72) Inventor Kaoru Okano 1-1-1, Higashitaga-cho, Hitachi City, Ibaraki Pref. Hitachi, Ltd. Taga Plant (56) References JP-A 1-270839 (JP, A) JP-A-63-21029 (JP, A) JP-A-1-262832 (JP, A) JP-A-63-105733 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A47L 15/42 A47L 15/48 A47L 15/46

Claims (2)

(57) [Claims] A cleaning tank, a circulating pump, a blower fan, a heater unit, and a controller for controlling the energization of the heater unit are main components. During the hot water heating process during the cleaning operation, the heater unit is continuously energized to perform a drying operation. In a dishwasher that controls so that the heater unit is intermittently energized, power supply voltage fluctuations are detected, and even when the magnitude of the power supply voltage fluctuations is the same during the temperature rise cycle and the temperature maintenance cycle during the drying operation, A dishwasher characterized by controlling the duty ratio of intermittent power supply during a temperature rising cycle to be large. 2. The method according to claim 1, wherein the detection of the power supply voltage fluctuation is performed a plurality of times immediately before the start of the drying operation and thereafter a plurality of times until the end of the drying operation. A dishwasher characterized by being controlled so as to be as follows.