Abstract: A vehicle loads at least one of a plurality of upper units having space to store a person or an object on an under unit including a drive mechanism that rotates wheels in the vehicle. The vehicle includes an under unit including a drive mechanism that rotates wheels and the at least one of the plurality of upper units loaded on the under unit. The under unit includes a loading unit, on which the at least one of the plurality of upper units as described above can be loaded. Each of the plurality of upper units includes a joint that joins to a different upper unit that is adjacently loaded.

Abstract: A coil spring has a spring wire that is wound in a coil shape and whose sectional outer basic shape is circular and flat faces are formed between coil inner and outer diameter sections of a sectional outer shape of the spring wire, wherein a flattening T/W of the sectional outer shape with the flat faces in the coil axis direction is set so that a stress ratio is equal to or lower than a stress ratio of a coil spring whose sectional outer shape is circular.

Abstract: A coil spring has a spring wire wound in a coil shape having an outer diameter side portion and an inner diameter side portion on a peripheral shape in a cross section thereof, one of the outer diameter side portion and inner diameter side portion formed in a semi-circular shape expressed by x2+y2=b2, the other thereof formed in a non-circular shape with a long diameter “a” and a short diameter “b” expressed by (x/a)?+(y/b)?=1, and value of the “?” set in a range of 1.85 to 2.45, and contact faces provided between the inner diameter side portion and the outer diameter side portion on the peripheral shape in the cross section such that each contact face comes into contact with a contact face of an adjacent coil in an axial direction along an axis line of the coil spring.

Abstract: A stress distribution state is improved and a better design is realized. A coil spring 1 has a spring wire 3 that is wound in a coil shape and whose sectional outer basic shape is circular. Between coil inner and outer diameter sections 5 and 7 of a sectional outer shape of the spring wire 3, flat faces 9 and 11 are formed so that coil portions adjacent to each other in the direction of a coil axis 4 are stabilized when they are brought into contact with each other. A flattening T/W of the sectional outer shape with the flat faces 9 and 11 in the coil axis direction is set so that a stress ratio is equal to or lower than a stress ratio of a coil spring whose sectional outer shape is circular. The flat faces 9 and 11 stably receive load and shorten a solid length in a tightly compressed state. This is advantageous in designing a spring having a longer stroke and lower rigidity.

Abstract: A port is formed in a cylinder head of an engine. The port is opened and closed by a valve. A valve spring device is provided with a first spring and a second spring. The second spring is contained in a housing and held by a stopper in a manner such that it is compressed along an axis or subjected to a preload. The preload of the second spring is larger than an installation load of the first spring. An axial load acts on the springs. The valve spring device has load-deflection characteristics such that only the first spring deforms axially when the axial load is not larger than a predetermined value and that both the first and second springs deform axially when the axial is load exceeds the predetermined value.

Abstract: A coil spring has a spring wire wound in a coil shape having an outer diameter side portion and an inner diameter side portion on a peripheral shape in a cross section thereof, one of the outer diameter side portion and inner diameter side portion formed in a semi-circular shape expressed by x2+y2=b2, the other thereof formed in a non-circular shape with a long diameter “a” and a short diameter “b” expressed by (x/a)?+(y/b)?=1, and value of the “?” set in a range of 1.85 to 2.45, and contact faces provided between the inner diameter side portion and the outer diameter side portion on the peripheral shape in the cross section such that each contact face comes into contact with a contact face of an adjacent coil in an axial direction along an axis line of the coil spring.

Abstract: A port is formed in a cylinder head of an engine. The port is opened and closed by a valve. A valve spring device is provided with a first spring and a second spring. The second spring is contained in a housing and held by a stopper in a manner such that it is compressed along an axis or subjected to a preload. The preload of the second spring is larger than an installation load of the first spring. An axial load acts on the springs. The valve spring device has load-deflection characteristics such that only the first spring deforms axially when the axial load is not larger than a predetermined value and that both the first and second springs deform axially when the axial is load exceeds the predetermined value.

Abstract: By controlling the thickness of the nitrization layer formed on the surface, the coil spring made of spring steel may be made highly resistant to permanent set and fatigue. By carbonitriding the material of the coil spring to a depth of 20 to 50 .mu.m from the surface thereof so as to have an internal hardness of Hv 540 or higher, the coil spring can be made to endure 10.sup.7 cycles of repeated high stress without suffering any significant permanent set.