Denso Corporation

Yuta Mizuno

Fuminori Suzuki

A current control circuit controls a linear solenoid valve provided in an oil pressure circuit to feed back an output oil pressure. The current control circuit includes a PWM signal generation part, a target setting part, a duty ratio setting part and a vibration detection circuit. The target setting part sets a target current value, which is a target value of an excitation current of the linear solenoid valve and periodically varies with a predetermined dither amplitude and a dither period longer than a pulse period of the PWM signal. The self-excited vibration detection part calculates a phase difference between the target current value and an actual current value and detects a presence of self-excited vibration because of a resonance of a feedback of the output oil pressure and driving of the linear solenoid valve in the dither period when the phase difference decreases relative to an increase in the target current value or the phase difference increases relative to a decrease in the dither period.

Current control circuit

A load driving control apparatus calculates current slopes in an on-period and an off-period in one PWM cycle period, respectively, by using actual currents at a start time point and an end time point of the PWM cycle period as well as two sets of data, as data including a duty ratio corresponding to the actual current values. The data is so determined that the actual current data value of predetermined one of the start time point and the end time point is within a learning area. The duty ratio is calculated based on a difference between a target current value and the actual current value until calculation of the current slopes and is completed. The duty ratio is calculated based on the current slopes, the actual current value at start time point and a target current value after the calculation of the current slopes is completed. Since an actual current change characteristic is calculated based on the actual current values and the duty ratio is calculated based on the current change characteristic, robustness is enhanced.

Load driving control apparatus

An electronic control unit that is used in an automatic transmission to regulate oil circulation. The electronic control unit includes a switcher that supplies an electric current to a linear solenoid, a current detector that detects an actual electric current value of the solenoid, a target current calculator that calculates a target electric current value, a feedback controller that sets a duty ratio to match the actual electric current value to the target electric current value and to generate a Pulse Width Modulation (PWM) signal having the set duty ratio, and a corrector that determines whether a coupled oscillation has occurred by obtaining oil pressure information of the hydraulic circuit and to correct the PWM signal when determining that the vibration has occurred.

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Kariya, Japan

Yuta Mizuno