Abstract: A method of operating a fuel injector having a piezoelectric actuator operable by applying a drive pulse thereto, wherein the drive pulse has a frequency domain signature. The method includes i) determining at least one resonant frequency of an injector installation in which the injector is received, in use, and ii) modifying the drive pulse such that a maximum of the frequency domain signature thereof is remote from the determined resonant frequency of the injector installation.

Abstract: A method of detecting faults in an injector arrangement in an engine. The injector arrangement comprises at least one fuel injector having a piezoelectric actuator, and the method comprises: charging the piezoelectric actuator during a charge phase (tC); attempting to recharge the piezoelectric actuator during a test phase (tT) which commences after a time interval (?t) following the end of the charge phase (tC); sensing a current (IS) that flows through the piezoelectric actuator during the test phase (tT); and generating a short circuit fault signal if the sensed current (IS) reaches a first predetermined threshold current (ISC) which is indicative of a short circuit in the piezoelectric actuator.

Abstract: The invention relates to a method of estimating the temperature of a piezoelectric actuator body for controlling the operation of a fuel injector mounted within an engine housing and supplied with fuel from a high pressure fuel pump. The piezoelectric actuator body is housed within a volume of fuel. The method comprises determining a temperature (T—INJ IN, T—PUMP IN) of fuel upstream of the fuel volume, determining a temperature (T—CYL) of the engine housing, and estimating a temperature (T—STACK STEADY STATE; T—STACK DYNAMIC) of the piezoelectric actuator body based on the upstream temperature (T—INJ IN, T—PUMP IN) and the temperature (T—CYL) of the engine housing. By considering the heat transfer between the piezoelectric actuator body, the injector and fuel within the volume, and the heat transfer due to fuel flow through the volume for an injection, the temperature of the piezoelectric actuator body can be estimated by modelling or mapping.

Abstract: A method of detecting faults in an injector arrangement in an engine. The injector arrangement comprises at least one fuel injector having a piezoelectric actuator, and the method comprises: charging the piezoelectric actuator during a charge phase (tC); attempting to recharge the piezoelectric actuator during a test phase (tT) which commences after a time interval (?t) following the end of the charge phase (tC); sensing a current (IS) that flows through the piezoelectric actuator during the test phase (tT); and generating a short circuit fault signal if the sensed current (IS) reaches a first predetermined threshold current (ISC) which is indicative of a short circuit in the piezoelectric actuator.

Abstract: A method of operating a fuel injector having a piezoelectric actuator operable by applying a drive pulse thereto, wherein the drive pulse has a frequency domain signature. The method includes i) determining at least one resonant frequency of an injector installation in which the injector is received, in use, and ii) modifying the drive pulse such that a maximum of the frequency domain signature thereof is remote from the determined resonant frequency of the injector installation.

Abstract: The invention relates to a method of estimating the temperature of a piezoelectric actuator body for controlling the operation of a fuel injector mounted within an engine housing and supplied with fuel from a high pressure fuel pump. The piezoelectric actuator body is housed within a volume of fuel. The method comprises determining a temperature (T—INJ IN, T—PUMP IN) of fuel upstream of the fuel volume, determining a temperature (T—CYL) of the engine housing, and estimating a temperature (T—STACK STEADY STATE; T—STACK DYNAMIC) of the piezoelectric actuator body based on the upstream temperature (T—INJ IN, T—PUMP IN) and the temperature (T—CYL) of the engine housing. By considering the heat transfer between the piezoelectric actuator body, the injector and fuel within the volume, and the heat transfer due to fuel flow through the volume for an injection, the temperature of the piezoelectric actuator body can be estimated by modelling or mapping.

Abstract: An advance arrangement for use in controlling timing of fuel delivery by a fuel pump comprises an advance piston which is moveable within a first bore and which cooperates, in use, with a cam arrangement of a fuel pump to adjust the timing of fuel delivery by the pump, a surface associated with the advance piston being exposed to fuel pressure within an advance piston control chamber. The advance arrangement also includes a servo-piston which is slidable within a further bore provided in the advance piston to control the pressure of fuel within the advance piston control chamber, a surface associated with the servo-piston being exposed to fuel pressure within a servo control chamber.

Abstract: An advance arrangement for use in controlling timing of fuel delivery by a fuel pump comprises an advance piston which is moveable within a first bore and which cooperates, in use, with a cam arrangement of a fuel pump to adjust the timing of fuel delivery by the pump. A surface associated with the advance piston is exposed to fuel pressure within an advance piston control chamber. A light load piston is moveable relative to the advance piston against a spring load due to a light load control spring to adjust the timing under light load conditions. A temperature control valve is operable to control fuel pressure applied to the light load piston depending on engine temperature so as to permit adjustment of the timing depending on engine temperature.

Abstract: An advance arrangement for use in controlling timing of fuel delivery by a fuel pump comprises an advance piston which is moveable within a first bore and which cooperates, in use, with a cam arrangement of a fuel pump to adjust the timing of fuel delivery by the pump. A surface associated with the advance piston is exposed to fuel pressure within an advance piston control chamber. A light load piston is moveable relative to the advance piston against a spring load due to a light load control spring to adjust the timing under light load conditions. A temperature control valve is operable to control fuel pressure applied to the light load piston depending on engine temperature so as to permit adjustment of the timing depending on engine temperature.

Abstract: An advance arrangement for use in controlling timing of fuel delivery by a fuel pump comprises an advance piston which is moveable within a first bore and which cooperates, in use, with a cam arrangement of a fuel pump to adjust the timing of fuel delivery by the pump, a surface associated with the advance piston being exposed to fuel pressure within an advance piston control chamber. The advance arrangement also includes a servo-piston which is slidable within a further bore provided in the advance piston to control the pressure of fuel within the advance piston control chamber, a surface associated with the servo-piston being exposed to fuel pressure within a servo control chamber.