Process for controlling the operation of a dishwashing machine

Abstract

 The process controls the operation of a dishwashing machine comprising a washing tank (10) closed at the bottom by a sump (12) wherein a level sensor (14) is mounted, a washing pump (16) operated by an asynchronous electric motor (18) which makes water circulate in said tank (10), and a control unit (22). In such process, a reference value of the level of the water in the sump (12) is pre-established for the washing step and the rinsing step, respectively; the level sensor (14) measures continuously the actual value of the level of the water in the sump (12) during such steps; and the control unit (22) compares in each step the reference value and the actual value of the level of the water in the sump (12) and adjusts the rotation speed of the motor (18) in dependence on the difference existing between such values, as well as checks the operation capability of said sensor (14), by ascertaining that, during the water loading step, the measured value of the level of the water in the sump (12) continuously increases.

Description

[0001] The present invention refers to a process for controlling the operation of a dishwashing machine.

[0002] More specifically, the latter comprises a washing tank closed at the bottom by a sump wherein a level sensor is present, a washing pump actuated by an electric motor which makes water circulate in the aforesaid tank and a control unit.

[0003] It is known to control the actuation motor of a washing pump starting from the measurement of its rotation speed, which is carried out by a suitable instrument, or by varying its power supply frequency by means of an inverter device. Such control systems are reliable, but require the presence of dedicated components - such as a rotation speed measurer or an inverter - which cause the complexity and cost of the dishwashing machine to increase.

[0004] Object of the present invention is that of providing a process for controlling the operation of the actuation motor of the washing pump of a dishwashing machine which employs components that are in any case already present for performing other functions.

[0005] Such object is achieved due to a process in which:

• a reference value of the level of the water in the sump is pre-established for the washing step and the rinsing step, respectively,
• the level sensor measures continuously the actual value of the level of the water in the sump during said steps, and
• said control unit compares in each step the reference value and the actual value of the level of the water in the sump and adjusts the rotation speed of said motor in dependence on the difference existing between said values, as well as checks the operation capability of said sensor by ascertaining that, during the water loading step, the measured value of the level of the water in the sump continuously increases.

[0006] The control process of the invention is based on the use by a control unit of signals generated by a component which is in any case present, such as the level sensor, and that hence does not lead to additional costs. Consequently, the production of a dishwashing machine adapted to operate according to the process of the invention results more economical. In particular, being certain of the correct functioning of the level sensor, the latter can also be used for monitoring the attainment of a watch level which causes the immediate shutdown of the dishwashing machine, without requiring dedicated anti-overflow devices, and with consequent further cost savings.

[0007] Further advantages and characteristics of the present invention will be clearer from the following detailed description, carried out with reference to the enclosed drawings provided as a non-limiting example, in which:

the single figure is a schematic representation of the main components of a dishwashing machine in which the control process of the invention is implemented.

[0008] A dishwashing machine comprises a washing tank 10 closed at the bottom by a sump 12 in which a level sensor 14 is mounted. A washing pump 16 driven by an asynchronous electric motor 18 causes the circulation of the water in the tank 10, while a further pump 20 allows its external discharge.

[0009] The operation of the dishwashing machine is governed by a control unit 22. In particular, the level sensor 14 continuously measures the actual value of the water level in the sump 12 during the washing and rinsing steps, and transmits it to the control unit 22 which compares it with a reference value of the level of the water in the sump which is pre-established for each of such steps.

[0010] The control unit 22 can thus adjust the rotation speed of the motor 18 during the washing and rinsing steps in dependence on the difference existing between the actual value of the level of the water in the sump 12 and the pre-established reference value. In particular, the adjustment of the rotation speed of the motor 18 can be carried out by changing the power absorbed through the phase shutting method. For example, the maximum power supplied by the phase shutter and absorbed by the motor 18 can be established by the control unit 22 in dependence on the requirements of the washing step, and in particular it can be greater the more intense the washing action must be.

[0011] It is therefore critical, for the purpose of performing the adjustment process, that the pressure sensor 14 functions correctly. Consequently, the operation of the latter is previously advantageously verified by the control unit, by ascertaining that, in the water loading step, the value measured by the sensor 14 of the level of the water in the sump 12 continuously increases. In addition, in order to ensure the correct functioning of the sensor 14, the latter can be advantageously used also for monitoring the possibly rising of the water up to a watch level which causes the employment of emergency measures, such as the immediate shutdown of the dishwashing machine.

[0012] Naturally, without detriment to the principle of the invention, the embodiment details and embodiments can be widely varied with respect to that described as a mere example above, without departing from the claimed scope.

Claims

1. Process for controlling the operation of a dishwashing machine comprising a washing tank (10) closed at the bottom by a sump (12) wherein a level sensor (14) is mounted, a washing pump (16) operated by an asynchronous electric motor (18) which circulates water in said tank (10), and a control unit (22), in which process:

- a reference value of the level of the water in the sump (12) is pre-established for the washing step and the rinsing step, respectively,

- the level sensor (14) measures continuously the actual value of the level of the water in the sump (12) during said steps, and

- said control unit (22) compares in each step the reference value and the actual value of the level of the water in the sump (12) and adjusts the rotation speed of said motor (18) in dependence on the difference existing between said values, as well as checks the operation capability of said sensor (14) by ascertaining that, during the water loading step, the measured value of the level of the water in the sump (12) increases continuously.

2. Process according to claim 1, wherein the rotation speed of the motor (18) is adjusted by changing the power absorbed through the phase shutting method.

3. Process according to claim 2, wherein the maximum power absorbed is established by the control unit (22) in dependence on the requirements of the washing step.

Drawing