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Proportional Solenoid Valve (patent WO 2009/087465)

Introduction

We patented a proportional valve for gas and fluid mass flow control. The valve controls the mass flow of fluids using an electric signal. The principle of operation is based on flux shunting. 

The valve operates safely as it is normally closed (if the supply goes off, it shuts). Its uses are manifold, ranging from home appliances (gas kitchens, ovens, gas boilers) to automotive (fuel control) and industry.

We demonstrated that our valve can control the temperature of a gas oven as precisely as in an electric oven. Gas boilers are the main application for the valve, as it can control very precisely the gas flow, increasing efficiency and improving combustion at low loads.  Other devices on the merket require an additional electrovalve. 

Our electrovalve withstood all tests for kitchen devices. So it is also compliant with the international standards for gas ovens, etc. The patent is valid worldwide.


 

Linear Proportional Electrovalve

 

The position of the valve translator is commanded by an external current signal and is proportional to it. The translator is connected to a needle/nozzle system.   The proportionality is acheved even in open-loop control. Valve design is covered by patent WO 2009/087465 and its control by patent  BO2009A000491.  Figure 2 shows the experimental test rig of the electrovalve. A laser sensor was used to measure translator position. Heater cartridges are connected to a thermostat to modify the  temperature of a heat conducting sleeve. The valve has passed all tests contained in the standards Direttiva 90/396 , UNI EN 30-1-1,  UNI EN 30-1- 4, UNI EN 126, UNI EN 161, CEI EN 60730 – 1, UNI EN 298, UNI EN 549, UNI EN 297, EN 483  UNI EN ISO 228-1, UNI EN ISO 228-2,  UNI ISO 6952, UNI EN 549, UNI EN 126, UNI EN 161, UNI EN 297, UNI EN 298, UNI EN 483, CEI EN 60172 and can be certified thereof.

Fig.1 - Top-feed valve

 

Fig. 2 – Experimental test rig.

 

The next graph (Fig.3) shows the position of the translator as a function of the supply current. The graph is taken after the valve has been fed three for days with the maximum current at 110°C environment temperature, and after 500k cycles operation. The first 100kcycles have been carried out with 110°C environment temperature, the others with 25°C environment temperature.  The position was measured by a laser sensor micro-epsilon.  The scale of the position is mm, the current scale is A. The characteristic shows clearly the two end points. The ripple is due to the  supply technique used. The hysteresis can be further reduced through optimization. The reference ripple frequency and amplitude is a tradeoff between precision, noise and dynamical performance. As the ripple decays with the time, there is no ripple when the valve is at standstill. The optimal ripple depends on various parameters, among which translator inertia and friction values are the most important.

Currently, there are two versions of the valve: the smaller is suitable for a room temperature lower than 110°C and has a diameter of 30mm, the larger is suitable for temperatures above 110°C and its diameter is 38mm. The power consumption is 5W for the larger version. The valve is able to effective and fast control of a fluid flow. The valve has been tested with different kitchen burners including the oven burner.

 

Fig.3 Position vs.current of the proportional electrovalve.

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