Patents by Inventor Yoshifumi Kurokawa

Yoshifumi Kurokawa 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).

  • Publication number: 20170051792
    Abstract: In a yoke for a cross shaft universal joint, the forming direction of a through hole (17a) and a screw hole (18a) is inclined relative to the axes of circular holes (19a, 19a) formed in a pair of engaging arm parts (12, 12). And, by fastening a bolt (32) to thereby put first and second flange parts (14a, 15a) nearer to each other, mutually approaching forces are applied to the connecting arm parts (12, 12) in a direction inclined relative the axes of the circular holes (19a, 19a). Thus, cup bearings (29) incorporated in the circular holes (19a, 19a) are pressed against the end of a shaft part (28a) constituting a cross shaft (27), thereby enabling suppression of occurrence of shaking motion between the bearings incorporated in the circular holes and the end of the shaft part of the cross shaft supported rotatably by the bearings.
    Type: Application
    Filed: May 12, 2015
    Publication date: February 23, 2017
    Applicant: NSK LTD.
    Inventors: Takuma NAKAMURA, Yoshifumi KUROKAWA
  • Patent number: 9566998
    Abstract: Provided is construction and a manufacturing method of an inner shaft for an extendable and contractible shaft for which finishing for forming a synthetic resin coating layer 19a on the outer-circumferential surface of a male spline section 14b is performed, while at the same time an increase in weight thereof is suppressed. A concave groove 22 that extends in the axial direction is provided on the outer-circumferential surface of the male spline section in a state so as to be continuous in the axial direction with one male spline groove 23 of the male spline grooves 23 of the male spline section 14b. A portion of the concave groove 22 that is separated in the axial direction from the male spline section 14b is used to perform phase alignment of a cutting tool for performing a finishing process of a coating layer 19a and unevenness in the circumferential direction of the male spline section 14b.
    Type: Grant
    Filed: May 23, 2014
    Date of Patent: February 14, 2017
    Assignee: NSK LTD.
    Inventor: Yoshifumi Kurokawa
  • Publication number: 20160369849
    Abstract: A state where the connecting pin is laid across between at least one of the outer diameter side through-holes and the inner diameter side through-hole is maintained by an axial displacement of the connecting pin with respect to the outer diameter side through-hole and the inner diameter side through-hole being regulated based on an engagement between both edges of the connecting pin and a displacement-regulating portion which is a part of the yoke or the bolt.
    Type: Application
    Filed: January 9, 2015
    Publication date: December 22, 2016
    Applicant: NSK LTD.
    Inventor: Yoshifumi KUROKAWA
  • Publication number: 20160369835
    Abstract: The rolling surface of each ball and a radially outside surface of the inside guide plate are in contact with each other only at two circumferentially set-apart inside contact parts. The rolling surface of each ball and a radially inside surface of the outside guide plate are in contact with each other only at two circumferentially set-apart outside contact parts. At a state after the extensible rotation transmission shaft is assembled, at least the inner surface of the inner-side concave groove is elastically deformed more radially inwards than a state before the assembling, thereby preloading the respective balls.
    Type: Application
    Filed: July 2, 2015
    Publication date: December 22, 2016
    Applicant: NSK LTD.
    Inventor: Yoshifumi KUROKAWA
  • Publication number: 20160304111
    Abstract: A cylindrical buckling prevention member is fitted on a spring shaft portion of a torsion bar, and an outer peripheral surface of the buckling prevention member is positioned close to or in contact with an inner peripheral surface of a hollow output shaft. Accordingly, when one of a pair of coupling shaft portions, which are axially end portions of the torsion bar, to be coupled to a coupling hole of a counter-shaft later is press-fitted into the coupling hole of the counter-shaft, the spring shaft portion of the torsion bar can be prevented from buckling.
    Type: Application
    Filed: January 9, 2015
    Publication date: October 20, 2016
    Applicant: NSK LTD.
    Inventor: Yoshifumi KUROKAWA
  • Patent number: 9446782
    Abstract: Provided is a telescopic shaft having a coated section that reduces sliding resistance, with fluctuation of the sliding resistance according to sliding position of the telescopic shaft being reduced. A female shaft 16B is fitted onto a male shaft in a state of interference, and by causing the male shaft 16A to slide back-and-forth a specified number of times in the axial direction with respect to the female shaft 16B while applying, for example, a load in a direction that bends the male shaft 16A with respect to the female shaft 16B, friction heat is generated between side surfaces 411 of grooves 41 in the female shaft 16B and the coated section 61, which heats the coated section 61 and causes the coated section 61 to expand along the entire length in the axial direction of teeth 51 of the male shaft 16A. Therefore, the coated section 61 plastically deforms along the entire length in the axial direction of the teeth causing compressive strain to occur.
    Type: Grant
    Filed: June 25, 2012
    Date of Patent: September 20, 2016
    Assignee: NSK LTD.
    Inventors: Yoshifumi Kurokawa, Shin Mihara, Hiroyuki Hattori, Takuma Nakamura, Sho Inaki, Seiichi Moriyama, Yoshio Nakano
  • Patent number: 9422986
    Abstract: A telescopic shaft includes a male shaft having an outer circumference on which a plurality of protruding teeth are formed, and a female shaft having an inner circumference on which a plurality of tooth grooves are formed. The tooth grooves of the female shaft are fitted onto the protruding teeth of the male shaft such that the male shaft and the female shaft are relatively slidable in an axial direction and such that a rotational torque is transmittable between the male shaft and the female shaft. One of a curvature radius of a tooth surface of the protruding teeth and a curvature radius of a tooth surface of the tooth grooves is smaller than the other of the curvature radius of the tooth surface of the protruding teeth and the curvature radius of the tooth surface of the tooth grooves.
    Type: Grant
    Filed: October 24, 2012
    Date of Patent: August 23, 2016
    Assignee: NSK LTD.
    Inventor: Yoshifumi Kurokawa
  • Publication number: 20160186798
    Abstract: A telescopic shaft includes a male shaft having an outer circumference formed with a plurality of protruding teeth, and a female shaft having an inner circumference formed with a plurality of tooth grooves and fitted onto the male shaft. The protruding teeth and the tooth grooves are engaged such that the male shaft and the female shaft are relatively axially slidable and a rotational torque is transmittable between the male shaft and the female shaft. At least one of the male shaft and the female shaft is configured such that the radial rigidity of a portion of the at least one of the male shaft and the female shaft in an axial range of a region where the protruding teeth and the tooth grooves are engaged is lower than the radial rigidity of another portion of the at least one of the male shaft and the female shaft.
    Type: Application
    Filed: March 8, 2016
    Publication date: June 30, 2016
    Applicant: NSK LTD.
    Inventor: Yoshifumi KUROKAWA
  • Publication number: 20160153499
    Abstract: A rod-shaped element having an outer diameter, which is the same as an outer diameter of a completed rod part, has one axial end portion and the other axial end portion to which a base end portion of a bifurcated yoke is fixed. The one axial end portion is subject to plastic working for diametrically deforming an outer periphery of the one axial end portion. Thereby, the outer periphery of the one axial end portion is formed with a male spline part having a groove bottom diameter smaller than an outer diameter of a rod part and having a tooth tip diameter larger than the outer diameter of the rod part.
    Type: Application
    Filed: June 23, 2014
    Publication date: June 2, 2016
    Applicant: NSK LTD.
    Inventor: Yoshifumi KUROKAWA
  • Publication number: 20160153502
    Abstract: A pin is made of a synthetic resin having an appropriate thermal expansion rate and a low friction coefficient. At a state where respective members configuring a cross shaft universal joint are assembled, a tip portion of the pin is heated and softened, and one yoke is pivotally displaced relative to other yoke. Thereby, it is possible to set a fitting margin of the pin to a bottom inner surface of a bearing cup to an appropriate size and to adjust a shape of an end surface of the pin.
    Type: Application
    Filed: August 20, 2014
    Publication date: June 2, 2016
    Applicant: NSK LTD.
    Inventor: Yoshifumi KUROKAWA
  • Publication number: 20150210309
    Abstract: Provided is construction and a manufacturing method of an inner shaft for an extendable and contractible shaft for which finishing for forming a synthetic resin coating layer 19a on the outer-circumferential surface of a male spline section 14b can be performed easily, while at the same time an increase in weight thereof is suppressed. A concave groove 22 that extends in the axial direction is provided on the outer-circumferential surface of the male spline section in a state so as to be continuous in the axial direction with one male spline groove 23 of the male spline grooves 23 of the male spline section 14b. A portion of the concave groove 22 that is separated in the axial direction from the male spline section 14b is used to perform phase alignment of a cutting tool for performing a finishing process of a coating layer 19a and unevenness in the circumferential direction of the male spline section 14b.
    Type: Application
    Filed: May 23, 2014
    Publication date: July 30, 2015
    Inventor: Yoshifumi Kurokawa
  • Publication number: 20140200086
    Abstract: A telescopic shaft includes a male shaft having an outer circumference formed with a plurality of protruding teeth, and a female shaft having an inner circumference formed with a plurality of tooth grooves and fitted onto the male shaft. The protruding teeth and the tooth grooves are engaged such that the male shaft and the female shaft are relatively axially slidable and a rotational torque is transmittable between the male shaft and the female shaft. At least one of the male shaft and the female shaft is configured such that the radial rigidity of a portion of the at least one of the male shaft and the female shaft in an axial range of a region where the protruding teeth and the tooth grooves are engaged is lower than the radial rigidity of another portion of the at least one of the male shaft and the female shaft.
    Type: Application
    Filed: October 24, 2012
    Publication date: July 17, 2014
    Applicant: NSK LTD.
    Inventor: Yoshifumi Kurokawa
  • Publication number: 20140187339
    Abstract: A telescopic shaft includes a male shaft having an outer circumference on which a plurality of protruding teeth are formed, and a female shaft having an inner circumference on which a plurality of tooth grooves are formed. The tooth grooves of the female shaft are fitted onto the protruding teeth of the male shaft such that the male shaft and the female shaft are relatively slidable in an axial direction and such that a rotational torque is transmittable between the male shaft and the female shaft. One of a curvature radius of a tooth surface of the protruding teeth and a curvature radius of a tooth surface of the tooth grooves is smaller than the other of the curvature radius of the tooth surface of the protruding teeth and the curvature radius of the tooth surface of the tooth grooves.
    Type: Application
    Filed: October 24, 2012
    Publication date: July 3, 2014
    Applicant: NSK Ltd.
    Inventor: Yoshifumi Kurokawa
  • Publication number: 20140041194
    Abstract: Provided is a telescopic shaft having a coated section that reduces sliding resistance, with fluctuation of the sliding resistance according to sliding position of the telescopic shaft being reduced. A female shaft 16B is fitted onto a male shaft in a state of interference, and by causing the male shaft 16A to slide back-and-forth a specified number of times in the axial direction with respect to the female shaft 16B while applying, for example, a load in a direction that bends the male shaft 16A with respect to the female shaft 16B, friction heat is generated between side surfaces 411 of grooves 41 in the female shaft 16B and the coated section 61, which heats the coated section 61 and causes the coated section 61 to expand along the entire length in the axial direction of teeth 51 of the male shaft 16A. Therefore, the coated section 61 plastically deforms along the entire length in the axial direction of the teeth causing compressive strain to occur.
    Type: Application
    Filed: June 25, 2012
    Publication date: February 13, 2014
    Applicant: NSK LTD.
    Inventors: Yoshifumi Kurokawa, Shin Mihara, Hiroyuki Hattori, Takuma Nakamura, Sho Inaki, Seiichi Moriyama, Yoshio Nakano
  • Patent number: 7559266
    Abstract: This invention provides a telescopic shaft in which a backlash or a sliding resistance in a rotational direction is maintained to a predetermined value even when there are fabrication errors in a male shaft and a female shaft, and a preload is not reduced even when a sleeve is worn by a friction force in sliding, and a steering apparatus having the telescopic shaft. An inclined sleeve portion 712 is pressed by an elastic deformation of an urge sleeve portion 713, so that there is not backlash between a male shaft 12B and a female shaft 12A and a predetermined preload is applied. Although an outer periphery of the inclined sleeve portion 712 is worn by a friction in sliding, the inclined sleeve portion 712 is further pressed by an elastic force of the urge sleeve portion 713 by an amount of wearing the outer periphery of the inclined sleeve portion 712. Thus, a predetermined urge force is always operated to the inclined sleeve portion 71.
    Type: Grant
    Filed: June 27, 2007
    Date of Patent: July 14, 2009
    Assignee: NSK Ltd.
    Inventor: Yoshifumi Kurokawa
  • Publication number: 20080000316
    Abstract: This invention provides a telescopic shaft in which a backlash or a sliding resistance in a rotational direction is maintained to a predetermined value even when there are fabrication errors in a male shaft and a female shaft, and a preload is not reduced even when a sleeve is worn by a friction force in sliding, and a steering apparatus having the telescopic shaft. An inclined sleeve portion 712 is pressed by an elastic deformation of an urge sleeve portion 713, so that there is not backlash between a male shaft 12B and a female shaft 12A and a predetermined preload is applied. Although an outer periphery of the inclined sleeve portion 712 is worn by a friction in sliding, the inclined sleeve portion 712 is further pressed by an elastic force of the urge sleeve portion 713 by an amount of wearing the outer periphery of the inclined sleeve portion 712. Thus, a predetermined urge force is always operated to the inclined sleeve portion 71.
    Type: Application
    Filed: June 27, 2007
    Publication date: January 3, 2008
    Applicant: NSK LTD.
    Inventor: Yoshifumi KUROKAWA