Patents by Inventor Yoshiaki Ajima

Yoshiaki Ajima has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • System and method for driving synchronous motor
    Patent number: 7342378
    Abstract: A driving apparatus of a synchronous motor fixes all the switching devices of an inverter at OFF in accordance with a value of an all-OFF control pulse signal outputted by a pulse generator. A motor current keeps flowing through free wheel diodes for a predetermined period even after all the switching devices shift to the OFF state. Therefore, pulse generator changes an induced voltage detection signal to an H (high) level after the passage of the time in which a motor current drops down to zero. A terminal voltage of the motor is taken in to acquire an induced voltage and a rotor position is estimated.
    Type: Grant
    Filed: August 17, 2006
    Date of Patent: March 11, 2008
    Assignee: Hitachi, Ltd.
    Inventors: Kiyoshi Sakamoto, Tsunehiro Endo, Hidefumi Shirahama, Yoshiaki Ajima
  • System and method for driving synchronous motor
    Publication number: 20070120519
    Abstract: A driving apparatus of a synchronous motor fixes all the switching devices of an inverter at OFF in accordance with a value of an all-OFF control pulse signal outputted by a pulse generator. A motor current keeps flowing through free wheel diodes for a predetermined period even after all the switching devices shift to the OFF state. Therefore, pulse generator changes an induced voltage detection signal to an H (high) level after the passage of the time in which a motor current drops down to zero. A terminal voltage of the motor is taken in to acquire an induced voltage and a rotor position is estimated.
    Type: Application
    Filed: August 17, 2006
    Publication date: May 31, 2007
    Inventors: Kiyoshi Sakamoto, Tsunehiro Endo, Hidefumi Shirahama, Yoshiaki Ajima
  • Communication control device and a communication system using the same
    Patent number: 5999999
    Abstract: The communication control device allows a plurality of data items to be transferred to and from external devices, such as a CPU and a memory, via an external bus having a different data bus width in DMA (direct memory access) transfer mode. DMA transfer is controlled by the DMA controller provided in the communication control device. The DMA controller produces a signal indicating that a plurality of data items are continual.
    Type: Grant
    Filed: March 18, 1997
    Date of Patent: December 7, 1999
    Assignees: Hitachi, Ltd., Hitachi Engineering Co., Ltd, Hitachi Haramachi Electronics Co., Ltd.
    Inventors: Yoshiaki Homitsu, Hiroshi Ichige, Shigeo Kuboki, Yoshiaki Ajima, Yoshinori Atsuwata, Isao Saitoh, Satoko Iwama, Takamasa Fujinaga