Abstract: A vehicle speed estimation device of the embodiment includes an attitude angle estimator configured to estimate an attitude angle using an acceleration detected by an acceleration sensor and an angular speed detected by an angular speed sensor, which are attached to a vehicle, an angular speed corrector configured to correct the angular speed using the estimated attitude angle estimation value to calculate a corrected angular speed, a vector term calculator configured to calculate a gravity acceleration vector using the estimated attitude angle estimation value, a model configured to calculate an acceleration model value on the basis of a tire model using a steering angle of the vehicle and wheel speeds of wheels of the vehicle, and a vehicle speed estimator configured to estimate a vehicle speed of the vehicle using the corrected angular speed, the gravity acceleration vector, and the acceleration model value.

Abstract: A road-surface friction coefficient estimation device includes: a lateral acceleration calculator configured to calculate an acceleration in a lateral direction using a wheel speed detected by a wheel speed sensor mounted in a vehicle, a vehicle-body roll angular velocity detected by an angular velocity sensor mounted in the vehicle, and a vehicle-body lateral velocity and a yaw rate calculated from a geometric relationship; a coordinate converter configured to convert an acceleration detected by an acceleration sensor mounted in the vehicle to a measured acceleration in the lateral direction subjected to ground coordinate conversion; and a road-surface friction estimator configured to 10 estimate a road-surface friction coefficient using a road-surface friction model on the basis of the calculated acceleration in the lateral direction and the measured acceleration in the lateral direction.

Abstract: During conditions of use of a threaded joint comprising a box portion and a pin portion used to threadingly join oil well pipes, the stress acting on the outer surface of the box portion is prevented from exceeding the yield strength of the base metal of the joint, and the occurrence of stress corrosion in the joint portion is prevented. Specifically, the amount of thread interference T is controlled to be at most a specified value calculated as a function of the inner diameter D1 of the pin portion, the thread effective diameter D2 at the basic diameter position, the outer diameter D3 of the box portion, the internal pressure Pi, and the yield strength &sgr;y and Young's modulus E of the base metal. As a result, a threaded joint which is suitable for joining of oil well pipes can be provided.

Abstract: A tightening method for a special joint having unthreaded metal-to-metal sealing surfaces and unthreaded shoulder portions. By controlling the ratio of the tightening torque at the completion of tightening to the shouldering torque at the time when the unthreaded shoulder portions come into contact to be in the range of 1.25-20 and more preferably 1.4-10, sufficient gastightness can be guaranteed and plastic deformation due to overtightening can be prevented regardless of the type of pipe joint or the conditions of use. As a result, it can be widely utilized in the tightening of special joints used with oil well pipes even under the present state of increasingly severe oil well environments.

Abstract: The joint according to the invention relates to a sealed connection between metal pipes used for producing petroleum tubings or casings. This joint comprises a sleeve fitted with two threaded housings suitable for receiving the male ends of two pipes. The end faces thereof come to bear one against the other inside the sleeve. An annular convex tapering zone near the end face of each pipe bears in a sealing manner against an annular concave tapering zone of the sleeve. Shoulder stops 16 ensure the centering of each male end.