# US 8,571,821 B2 · Method for determining the closing time of an electromagnetic fuel injector > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,571,821 B2 - Document ID: US8571821B2 - Status: Granted - Kind: B2 - Application number: 13/081,784 - Filed: 2011-04-07 - Published: 2011-10-13 - Granted: 2013-10-29 - Earliest claimed: 2010-04-07 - Assignees: Magneti Marelli S.p.A. - Applicants: Gabriele Serra; Marco Parotto; Saverio Armeni; Luigi Santamato; Romito Tricarico - Inventors: Gabriele Serra; Marco Parotto; Saverio Armeni; Luigi Santamato; Romito Tricarico - Web page: https://patentgrep.com/patent/US8571821B2 ## CPC - F02D 41/20: Output circuits, e.g. for controlling currents in command coils - F02D 2041/2055: {with means for determining actual opening or closing time} - F02M 51/061: {using electromagnetic operating means} - F02D: CONTROLLING COMBUSTION ENGINES (vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed B60K31/00; conjoint control of vehicle sub-units of different type or different function, road vehicle drive control systems for purposes other than the control of a single sub-unit B60W) - F02M: SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF ## Abstract A method for determining the closing time of an electromagnetic fuel injector including the steps of applying at a starting time of the injection a positive voltage to the coil of the electromagnetic actuator in order to circulate through the coil an electric current which causes the opening of an injection valve; applying at an ending time of the injection a negative voltage to the coil in order to annul the electric current flowing through the coil; detecting the trend over time of the voltage across the coil after the annulment of the electric current flowing through the coil; identifying a perturbation of the voltage across the coil; and recognizing the closing time of the injector that coincides with the time of the perturbation of the voltage. ## Claims ### Claim 1 A method for determining the closing time (t3) of an electromagnetic fuel injector (4), having a pin (23) movable between a closed position and an open position of an injection valve (15), and an electromagnetic actuator (14) equipped with a coil (16) and adapted to determine the displacement of the pin (23) between the closed position and the open position; the method including the steps of: applying at a starting time (t1) of the injection a positive voltage (v) to the coil (16) of the electromagnetic actuator (14) in order to circulate through the coil (16) an electric current (i) which causes the opening of the injection valve (15); applying at an ending time (t2) of the injection a negative voltage (v) to the coil (16) of the electromagnetic actuator (14) in order to annul the electric current (i) flowing through the coil (16); detecting the trend over time of the voltage (v) across the coil (16) of the electromagnetic actuator (14) when the voltage (v) is negative, after the annulment of the electric current (i) flowing through the coil (16) and until the annulment of the voltage (v); identifying a perturbation (P) of the voltage (v) across the coil (16) after the annulment of the electric current (i) flowing through the coil (16) by calculating the first derivative in time of the voltage (v) across the coil (16) after the annulment of the electric current (i) flowing through the coil (16); and recognizing the closing time (t3) of the injector (4) that coincides with the time (t3) of the perturbation (P) of the voltage (v) across the coil (16) after the annulment of the electric current (i) flowing through the coil (16); where the steps of identifying the perturbation (P) of the voltage (v) across the coil 16) further includes the steps of: calculating an absolute value of the first derivative in time of the voltage (v) across the coil (16); calculating an integral over time of the absolute value of the first derivative in time of the voltage (v) across the coil (16); and identifying the perturbation (P) when the absolute value of the integral over time of the first derivative in time of the voltage (v) across the coil (16) exceeds a second threshold value (S2). ### Claim 2 (depends on 1) The method as set forth in claim 1, wherein at the ending time (t2) of the injection the pin (23) has not yet reached a position of complete opening of the injection valve (15) and therefore the fuel injection occurs in the “ballistic zone”. ### Claim 3 (depends on 1) The method as set forth in claim 1, wherein the perturbation (P) of the voltage (v) across the coil (16) consists of a high frequency oscillation of the voltage (v) across the coil (16). ### Claim 4 (depends on 1) The method as set forth in claim 1, wherein the perturbation (P) of the voltage (v) across the coil (16) consists of an oscillation of the voltage (v) across the coil (16) having a frequency of about 70 kHz. ### Claim 5 (depends on 1) The method as set forth in claim 1, wherein the step of identifying the perturbation (P) of the voltage (v) across the coil (16) further includes the step of filtering the first derivative in time of the voltage (v) across the coil (16) by using a band-pass filter consisting of a low-pass filter and a high-pass filter. ### Claim 6 (depends on 5) The method as set forth in claim 5, wherein the band-pass filter has a bandwidth between 60 and 110 kHz. ### Claim 7 (depends on 1) The method as set forth in claim 1. wherein the step of identifying the perturbation (P) of the voltage (v) across the coil (16) further includes the step of applying preventively a moving average to the absolute value of the first derivative in time of the voltage (v) across the coil (16) before identifying the perturbation (P). ### Claim 8 (depends on 1) The method as set forth in claim 1, wherein the step of identifying the perturbation (P) of voltage (v) across the coil (16) further includes the step of normalizing the absolute value of the first derivative in time of the voltage (v) across the coil (16) before identifying the perturbation (P) such that after normalization the absolute value of first derivative in time of the voltage (v) across the coil (16) varies over a predefined standard interval. ### Claim 9 (depends on 1) The method as set forth in claim 1 further including the step of applying at the time (t3) of the perturbation (P) a predefined advance time to compensate the phase delay introduced by all filtering processes applied to the voltage (v) across the coil (16) for the purpose of identifying the perturbation (P) of voltage (v) across the coil (16). ### Claim 10 A method for determining the closing time (t3) of an electromagnetic fuel injector (4), having a pin (23) movable between a closed position and an open position of an injection valve (15), and an electromagnetic actuator (14) equipped with a coil (16) and adapted to determine the displacement of the pin (23) between the dosed position and the open position; the method including the steps of: applying, at a starting time (t1) of the injection a positive voltage (v) to the coil (16) of the electromagnetic actuator (14) in order to circulate through the coil (16) an electric current (i) which causes the opening of the injection valve (15); applying, at an ending time (t2) of the injection a negative voltage (v) to the coil (16) of the electromagnetic actuator (14) in order to annul the electric current (i) flowing through the coil (16); detecting the trend over time of the voltage (v) across the coil (16) of the electromagnetic actuator (14) when the voltage (v) is negative, after the annulment of the electric current (i) flowing through the coil (16) and until the annulment of the voltage (v); identifying a perturbation (P) of the voltage (v) across the coil (16) after the annulment of the electric current (i) flowing through the coil (16); recognizing the closing time (t3) of the injector (4) that coincides with the time (t3) of the perturbation (P) of the voltage (v) across the coil (16) after the annulment of the electric current (i) flowing through the coil (16); applying filtering processes to the voltage (v) across the coil (16); and applying at the time (t3) of the perturbation (P) a predefined advance time to compensate the phase delay introduced by all filtering processes applied to the voltage (v) across the coil (16) for the purpose of identifying the perturbation (P) of voltage (v) across the coil (16).