| 摘要 |
Valve unit (1) for controlling the feed of a combustible gas to a burner apparatus, comprising: a device (6) for regulating the pressure of the gas at the outlet of the unit, including a valve seat (7) associated with a plug (8), and an operating means (14) for causing the plug to move relatively to the corresponding valve seat, to regulate the outlet feed pressure (Pu) by modulation, the operating means comprising at least one electromagnet of the proportional type; a control circuit of the pressure regulating device including a PWM signal generator generating a PWM voltage signal adapted to generate a current signal in the electromagnet in order to move the plug as a function of the magnitude of the current signal and thus determine the outlet pressure, the magnitude of the current being a function of the duty cycle of the PWM signal; the PWM signal having a frequency such that the operating means is subjected to a mechanical dither having a specified amplitude at least for a specified time interval; the PWM signal generator including means of controlling the duty cycle and means of controlling the frequency of the PWM signal, the duty cycle control means varying the duty cycle of the PWM signal with the variation of the desired outlet pressure, and the frequency control means being adapted to vary the frequency of the PWM signal as a function of the variation of the duty cycle so as to keep the amplitude of the dither substantially constant, independently from the variations of the duty cycle of the PWM signal. |
