Abstract: An assist control portion (61), upon detecting source power supply abnormality of a main electric power source (100), switches the characteristic of an assist map in which the steering torque Tx and the target current ias* are related to each other from an original assist characteristic to an abnormality-time assist characteristic. Therefore, the steering handle operation suddenly becomes heavy, thereby causing the driver to be aware of the abnormality. After that, the abnormality-time assist characteristic is altered so that the assist force relative to the steering torque further decline in accordance with declines in the actual amount of charge of the subsidiary electric power source (50) declines. Therefore, the steering handle operation gradually becomes heavier, thereby causing the driver to anticipate that the abnormality is further progressing.

Abstract: A subsidiary power supply (50), which is an electric power storage device, is connected in parallel to a circuit that connects a main power supply (100) to a motor drive circuit (30). A power supply control portion (62) controls a boosted voltage of a voltage-boosting circuit (40) so that an actual amount of charge in the subsidiary power supply (50) is equal to a target amount of charge. The target amount of charge is set to increase as deceleration of a vehicle increases.

Abstract: If the main electric power source has failed, an assist control portion shifts the characteristic of an assist map in which the steering torque and the target current are connected in a relation by one step of shift in a direction of increase of the steering torque each time a steering operation that satisfies a steering operation criterion condition is performed. This allows a driver to feel a decline in the steering assist force each time of performing steering operation and therefore become aware of the abnormality. Besides, an upper-limit current of the assist map may be reduced each time the steering operation that satisfies the steering operation criterion condition is performed. Besides, an upper-limit electric power of an electric motor may be reduced each time the steering operation that satisfies the steering operation criterion condition is performed.

Abstract: When a change in an output voltage of a main power supply is a decrease, and a degree of the decrease is larger than a reference value, a power supply control portion decreases a boosted voltage of a voltage-boosting circuit according to the degree of the decrease. When the change in the output voltage of the main power supply is an increase, and a degree of the increase is larger than the reference value, the power supply control portion increases the boosted voltage of the voltage-boosting circuit according to the degree of the increase.

Abstract: A vehicle steering device has an electric power abnormality detection portion that detects abnormality of the source power supply capability of an electric power source device, a vehicle speed detection portion that detects the vehicle speed, and a motor control portion that controls the driving of the electric motor on the basis of the steering torque detected by the steering torque detection portion. The motor control portion enhances the output restriction of the electric motor if the vehicle speed detected by the vehicle speed detection portion declines while the abnormality of the source power supply capability of the electric power source device is detected by the electric power abnormality detection portion.

Abstract: In a ring body of a stator, permanent magnets are arranged in alternate inter-pole magnetic path portions located between an even number of stator poles so that magnetic fields pointing in the circumferential direction of the ring body are generated. Coils are wound around alternate inter-pole magnetic path portions where permanent magnets are not provided so that magnetic fields that oppose the magnetic fields generated by the permanent magnets are generated. When electric power is not supplied to the coils, a ring-shaped magnetic circuit is formed by the permanent magnets, and therefore, magnetic flux does not leak to a rotor. When electric power is supplied to the coils, the magnetic flux of the magnetic fields of the permanent magnets and that of the coils combine with each other and flow from the stator poles to rotor poles of the rotor, whereby strong attraction force is obtained.

Abstract: In a power supply apparatus, a power supply circuit includes a primary power supply circuit including a high-voltage battery and a step-down circuit for stepping down the voltage of the high-voltage battery, and a secondary power supply circuit including a low-voltage battery and a step-up circuit for stepping up the voltage of the low-voltage battery. The primary power supply circuit and the secondary power supply circuit are connected in parallel. An output voltage of the secondary power supply circuit is set to be lower than an output voltage of the primary power supply circuit. When the output voltage of the primary power supply circuit becomes lower than a target voltage of the secondary power supply circuit, the voltage stepped-up by the step-up circuit is supplied to a motor drive circuit. Accordingly, power supply backup of an electric power steering apparatus can be performed at low cost.

Abstract: A power steering system, which is disposed in the forward part of a vehicle, allows an electric motor to boost the steering torque applied by a driver, and transmits the steering torque to wheels via a steering transmission mechanism. The power steering system includes an impact detection device that detects the impact of an object on a rack housing that houses a rack bar constituting the steering transmission mechanism to detect the impact on the power steering system more accurately.

Abstract: A power supply control section calculates a target charge/discharge current of a secondary power supply apparatus based on an actual charged amount and a target charged amount of the secondary power supply apparatus, and feedback-controls the stepped-up voltage of a step-up circuit such that an actual charge/discharge current detected by a secondary current sensor coincides with a target charge/discharge current. When the actual charged amount (1) is equal to or greater than the target charged amount, the target charge/discharge current is set to zero to prevent overcharging, and (2) is less than the target charged amount, a target charge current corresponding to a capacity margin of the step-up circuit is set to quickly charge the secondary power supply apparatus. When the output of the step-up circuit has no margin, the target charge/discharge current is set to zero.

Abstract: In a ring body of a stator, permanent magnets are arranged in alternate inter-pole magnetic path portions located between an even number of stator poles so that magnetic fields pointing in the circumferential direction of the ring body are generated. Coils are wound around alternate inter-pole magnetic path portions where permanent magnets are not provided so that magnetic fields that oppose the magnetic fields generated by the permanent magnets are generated. When electric power is not supplied to the coils, a ring-shaped magnetic circuit is formed by the permanent magnets, and therefore, magnetic flux does not leak to a rotor. When electric power is supplied to the coils, the magnetic flux of the magnetic fields of the permanent magnets and that of the coils combine with each other and flow from the stator poles to rotor poles of the rotor, whereby strong attraction force is obtained.

Abstract: When it is determined that a malfunction has occurred in a rotational angle sensor, an electronic control unit changes the control manner from the normal assist control to the sensorless assist control. In the sensorless assist control, an assist stop command unit receives the information concerning the motor rotational angular speed ?m from an angular speed conversion unit. Then, the motor rotational angular speed ?m is compared with the threshold value ?m1. If the motor rotational angular speed ?m is equal to or higher than the threshold value ?m1, an assist enabling signal is transmitted to a PWM voltage production unit to continue the power assist. On the other hand, if the motor rotational angular speed ?m is lower than the threshold value ?m1, a stop command signal is transmitted to the PWM voltage production unit to stop the power assist.

Abstract: In a power supply apparatus 40, a power supply circuit is formed by a primary power supply circuit 50 which includes a high-voltage battery 51 and a step-down circuit 55 for stepping down the voltage of the high-voltage battery 51, and a secondary power supply circuit 60 which includes a low-voltage battery 61 and a step-up circuit 70 for stepping up the voltage of the low-voltage battery 61. The primary power supply circuit 50 and the secondary power supply circuit 60 are connected in parallel. An output voltage of the secondary power supply circuit 60 is set to be lower than an output voltage of the primary power supply circuit 50. When the output voltage of the primary power supply circuit 50 becomes lower than a target voltage of the secondary power supply circuit 60, the voltage stepped-up by the step-up circuit 70 is supplied to a motor drive circuit 32. Accordingly, power supply backup of an electric power steering apparatus can be performed as low cost.

Abstract: A steering assist apparatus for a vehicle includes an electric motor for steering assist. Rotation output of the electric motor is reduced in speed by a ball-screw mechanism and converted to rectilinear motion, which is transmitted to a rack bar. An electronic control unit determines a target current value in accordance with a steering torque detected by a steering torque sensor and a vehicle speed detected by a vehicle speed sensor. While using an actual current value of the electric motor detected by a current sensor as a feedback, the electronic control unit controls the current flowing through the electric motor to be equal to the target current value. The electronic control unit changes the feedback gain of the feedback control in accordance with a steering angle detected by a steering angle sensor, to thereby suppress abnormal noise generated at a steering mechanism, without deteriorating steering feel.

Abstract: A power steering system, which is disposed in the forward part of a vehicle, allows an electric motor to boost the steering torque applied by a driver, and transmits the steering torque to wheels via a steering transmission mechanism. The power steering system includes an impact detection device that detects the impact of an object on a rack housing that houses a rack bar constituting the steering transmission mechanism to detect the impact on the power steering system more accurately.

Abstract: When it is determined that a malfunction has occurred in a rotational angle sensor, an electronic control unit changes the control manner from the normal assist control to the sensorless assist control. In the sensorless assist control, an assist stop command unit receives the information concerning the motor rotational angular speed ?m from an angular speed conversion unit. Then, the motor rotational angular speed ?m is compared with the threshold value ?m1. If the motor rotational angular speed ?m is equal to or higher than the threshold value ?m1, an assist enabling signal is transmitted to a PWM voltage production unit to continue the power assist. On the other hand, if the motor rotational angular speed ?m is lower than the threshold value ?m1, a stop command signal is transmitted to the PWM voltage production unit to stop the power assist.

Abstract: A semiconductor device has a semiconductor layer, and a first electrode (Schottky electrode or MIS electrode) and a second electrode (ohmic electrode) which are formed on the semiconductor layer apart from each other. The first electrode has a cross section in the shape of a polygon. A second electrode-side corner of the polygon has an interior angle of which an outward extension line of a bisector crosses the semiconductor layer or the second electrode. The interior angle of such a second electrode-side corner is larger than 90°.

Abstract: A heterojunction bipolar transistor comprising a collector layer of a first conductivity type, a base layer of a second conductivity type, and an emitter layer of the first conductivity type, which are formed on a semiconductor substrate in this order, and further a collector electrode directly or indirectly connected to the collector layer, a base electrode directly or indirectly connected to the base layer, and an emitter electrode directly or indirectly connected to the emitter layer, wherein a semiconductor protecting layer is formed on the base layer and extended outside an edge of the base layer, the base electrode is formed on the semiconductor protecting layer, and at least a region under the semiconductor protecting layer is filled with an organic insulator.

Abstract: A heterojunction bipolar transistor comprising a collector layer of a first conductivity type, a base layer of a second conductivity type, and an emitter layer of the first conductivity type, which are formed on a semiconductor substrate in this order, and further a collector electrode directly or indirectly connected to the collector layer, a base electrode directly or indirectly connected to the base layer, and an emitter electrode directly or indirectly connected to the emitter layer, wherein a semiconductor protecting layer is formed on the base layer and extended outside an edge of the base layer, the base electrode is formed on the semiconductor protecting layer, and at least a region under the semiconductor protecting layer is filled with an organic insulator.