Denso Corporation

Nippon Soken, Inc.

Yasuhiro Fukagawa

Ken Tanaka

Tsutomu Nakamura

Masaru Touge

Youichirou Suzuki

Tomohisa Kishigami

Yasuyuki Sakakibara

Kenji Takeda

Eiji Takemoto

Masakiyo Horie

Takahisa Koyasu

Noboru Maeda

Noboru Nagase

Takeshi Nakamura

Hideo Naruse

Takamichi Kamiya

Tatsuya Kakehi

A slew rate regulation circuit varies a slew rate of a waveform of a voltage outputted to a DC motor through a N-channel MOSFET. The slew rate regulation circuit lowers a peak level by dispersing frequency components of switching noise, which develops in a frequency range higher than a frequency range determined by a carrier frequency.

Switching element driving device and method

When a transmission signal is detected as having been changed from a high level to a low level, two transmission lines are connected for only a predetermined time through a diode by a first transistor and a second transistor. The diode is arranged such that its forward direction is from a high-side transmission line to a low-side transmission line. The diode turns on, when a potential of the high-side transmission line becomes higher than that of the low-side transmission line by ringing and a potential difference therebetween exceeds a forward drop voltage of the diode. As a result, a peak wave level of a positive side in the ringing is limited to the forward drop voltage of the diode.

Differential communication device

A direct current motor includes an armature coil having at least three phase coils, a commutator having multiple commutator segments connected to the armature coil, a pair of brushes in slidable contact with the commutator to supply power to the phase coils through the commutator, a rotation shaft, and a ring varistor coaxially fixed to the rotation shaft and having a ring-shaped varistor body and multiple electrodes that are circumferentially arranged on a surface of the varistor body. Each commutator segment is connected to a corresponding electrode of the ring varistor. The electrodes of the ring varistor are paired to form electrode pairs. Each electrode pair includes any two of the electrodes. A capacitance of one electrode pair is different from a capacitance of another electrode pair.

Rotation sensor and direct current motor

A rotation detecting apparatus for detecting a rotational state of a direct-current motor includes a driving device, a control device, an energization detecting device, an alternating-current component detecting device, and a rotational state detecting device. An impedance between brushes of the motor changes periodically in accordance with rotation of the motor. The alternating-current component detecting device detects change of an alternating-current component of electric current that is supplied to the motor based on an electrical quantity. The change of the alternating-current component is caused by change of the impedance caused in accordance with the rotation. The rotational state detecting device detects at least one of a rotation angle, a rotational direction, and a rotational speed of the motor based on a detection result of the alternating-current component detecting device.

Rotation detecting apparatus and rotation detecting system

A power supply unit superimposes alternating-current voltage on direct-current voltage and applies it to a motor. As a result, when the motor is rotated, a current containing an alternating-current component flows. Further, the motor includes a capacitor connected in parallel with one phase coil. Owing to this capacitor, the impedance of the motor circuit between brushes is varied according to the rotation of the motor. Variation in impedance appears as variation in the amplitude of the alternating-current component in motor current. A signal processing unit extracts an alternating-current component from the motor current detected by the current detection unit and generates a rotation pulse corresponding to variation in the amplitude. A rotation angle detection unit detects the rotation angle of the motor based on this rotation pulse.

Rotation detector and direct-current motor

In a piezoelectric actuator control device for controlling operation of one or more piezoelectric actuators, when receiving a drive signal of a low level, a discharging switch is repeatedly turned on and off in order to discharge electric charge accumulated in the piezoelectric actuator. That is, the discharging switch is kept ON until a discharging current from a piezoelectric actuator reaches a peak threshold value Ip. When the discharging current reaches the peak threshold value Ip, the discharging switch is turned OFF and kept OFF until a discharging current from a piezoelectric actuator reaches a peak threshold value Ip. The device has a threshold value setting circuit for increasing the peak threshold value according to a discharging period of time.

Piezoelectric actuator drive device

In a driving device for a piezoelectric actuator, when a driving signal is input, a charging switch is repetitively turned on/off to charge and expand the piezoelectric actuator under the state that a discharging switch is turned off. Thereafter, when the input of the driving signal is stopped, the discharging switch is repetitively turned on/off under the state that the charging switch is turned off, thereby discharging and contracting the piezoelectric actuator. Particularly, during the charging period, the charging switch is turned on at a fixed period, and the charging switch is turned off when an integration value of current flowing in a charging circuit at the ON-time of the charging switch reaches a target charge amount.

Driving device for piezoelectric actuator

A piezo actuator drive circuit comprises a charging path for charging a piezo stack that can be driven by being charged and discharged, an arithmetic circuit for calculating the charging amount for the piezo stack, and a driving control circuit for comparing the calculated charging amount and a target charging amount and correcting the charging amount during the next charging process according to the difference between the compared charging amounts. A charging current flowing through the piezo stack and a charging voltage applied to it may be measured during a charging process. It is preferable that the calculated charging amount be the amount of energy that is the result of the time quadrature of the product of the measured current and voltage.

Growing community of inventors

Obu, Japan

Yasuhiro Fukagawa